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Precipitation Responses to Radiative Effects of Ice Clouds: A Cloud-Resolving Modeling Study of a Pre-Summer Torrential Precipitation Event


doi: 10.1007/s00376-016-5218-8

  • The precipitation responses to the radiative effects of ice clouds are investigated through analysis of five-day and horizontally averaged data from 2D cumulus ensemble model experiments of a pre-summer torrential precipitation event. The exclusion of the radiative effects of ice clouds lowered the precipitation rate through a substantial reduction in the decrease of hydrometeors when the radiative effects of water clouds were switched on, whereas it increased the precipitation rate through hydrometeor change from an increase to a decrease when the radiative effects of ice clouds were turned off. The weakened hydrometeor decrease was associated with the enhanced longwave radiative cooling mainly through the decreases in the melting of non-precipitating ice to non-precipitating water. The hydrometeor change from an increase to a decrease corresponded to the strengthened longwave radiative cooling in the upper troposphere through the weakened collection of non-precipitating water by precipitation water.
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    Chou M.-D., D. P. Kratz, and W. Ridgway, 1991: Infrared radiation parameterizations in numerical climate models. J.Climate, 4, 424- 437.10.1175/1520-0442(1991)0042.0.CO;203545b339ec55c925a7bf8cf9be57de1http%3A%2F%2Fadsabs.harvard.edu%2Fabs%2F1991JCli....4..424Chttp://adsabs.harvard.edu/abs/1991JCli....4..424CAbstract Parameterizations for infrared radiation (IR) in clear atmosphere can be made fast and accurate by grouping spectral regions with similar radiative properties, and by separating the low pressure region of the atmosphere from the high pressure region. Various approaches are presented in this study to parameterizing the broadband transmission functions for use in numerical climate models. For water vapor and carbon dioxide (CO2) bands, the transmission functions are parameterized separately for the middle atmosphere (0.01鈥30 mb) and for the region below. In the middle atmosphere where the dependence of absorption on pressure and temperature is not strong, the diffuse transmission functions are derived from that at a reference pressure and temperature. In the lower stratosphere and the troposphere, the spectra are grouped into band-center regions and band-wing regions. One-parameter scaling is applied to approximate a nonhomogeneous path with an equivalent homogeneous path, and the diffuse transmitt...
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    Gao S. T., F. Ping, X. F. Li, and W.-K. Tao, 2004: A convective vorticity vector associated with tropical convection: A two-dimensional cloud-resolving modeling study. J. Geophys. Res., 109,D14106, doi: 10.1029/2004JD004807.10.1029/2004JD004807a947fa8d401b3ca338394633653f20bahttp%3A%2F%2Fonlinelibrary.wiley.com%2Fdoi%2F10.1029%2F2004JD004807%2Fcitedbyhttp://onlinelibrary.wiley.com/doi/10.1029/2004JD004807/citedbyAlthough dry/moist potential vorticity ((? ·63θ)/ρ) is a useful physical quantity for meteorological analysis, it cannot be applied to the analysis of two-dimensional (2-D) simulations. A new vorticity vector (? ×63θ)/ρ (convective vorticity vector (CVV)) is introduced in this study to analyze 2-D cloud-resolving simulation data associated with 2-D tropical convection. The cloud model is forced by the vertical velocity, zonal wind, horizontal advection, and sea surface temperature obtained from the Tropical Ocean-Global Atmosphere (TOGA) Coupled Ocean-Atmosphere Response Experiment (COARE) and is integrated for a selected 10-day period. The CVV has zonal and vertical components in the 2-D x-z frame. Analysis of zonally averaged and mass-integrated quantities shows that the correlation coefficient between the vertical component of the CVV and the sum of the cloud hydrometeor mixing ratios is 0.81, whereas the correlation coefficient between the zonal component and the sum of the mixing ratios is only 0.18. This indicates that the vertical component of the CVV is closely associated with tropical convection. The tendency equation for the vertical component of the CVV is derived and the zonally averaged and mass-integrated tendency budgets are analyzed. The tendency of the vertical component of the CVV is determined by the interaction between the vorticity and the zonal gradient of cloud heating. The results demonstrate that the vertical component of the CVV is a cloud-linked parameter and can be used to study tropical convection.
    Gao S. T., X. P. Cui, Y. S. Zhou, and X. F. Li, 2005: Surface rainfall processes as simulated in a cloud-resolving model. J. Geophys. Res., 110,D10202, doi: 10.1029/2004JD005467.10.1029/2004JD005467683671c9eded03a9c7df7d4005f6922chttp%3A%2F%2Fonlinelibrary.wiley.com%2Fdoi%2F10.1029%2F2004JD005467%2Fabstracthttp://onlinelibrary.wiley.com/doi/10.1029/2004JD005467/abstract[1] Surface rain rate can be simply formulated with the sum of moisture and cloud sources/sinks. In this study the moisture sink comprises the local moisture change, moisture convergence (with an imposed vertical velocity), and surface evaporation, whereas the cloud source/sink comprises the local hydrometeor change since the cyclic boundary condition leads to zero hydrometeor convergence. The sources/sinks and their contributions to the surface rain rate are examined based on hourly zonal mean simulation data from a two-dimensional cloud-resolving model. The model is forced by the large-scale vertical velocity, zonal wind, and horizontal advections obtained from Tropical Ocean Global Atmosphere Coupled Ocean-Atmosphere Response Experiment (TOGA COARE). Although variation in the moisture sink largely accounts for much of the variation in the surface rain rate, the cloud source/sink may modify the surface rain rate significantly. The magnitude of the cloud source/sink increases when the zonal mean surface rain rate increases from 0 to 1 mm h
    Gao S. T., X. P. Cui, and X. F. Li, 2009: A modeling study of diurnal rainfall variations during the 21-day period of TOGA COARE. Adv. Atmos. Sci.,26, 895-905, doi: 10.1007/ s00376-009-8123-6.10.1007/s00376-009-8123-64f40c92f0c4ae81fdc368cfaa357c441http%3A%2F%2Fd.wanfangdata.com.cn%2FPeriodical_dqkxjz-e200905007.aspxhttp://d.wanfangdata.com.cn/Periodical_dqkxjz-e200905007.aspx
    Gray W. M., R. W. Jacobson Jr., 1977: Diurnal variation of deep cumulus convection. Mon. Wea. Rev., 105, 1171- 1188.10.1175/1520-0493(1977)1052.0.CO;2625462aec00c5dd43ded75cdc6060671http%3A%2F%2Fadsabs.harvard.edu%2Fabs%2F1977MWRv..105.1171Ghttp://adsabs.harvard.edu/abs/1977MWRv..105.1171GAbstract This paper presents observational evidence in support of the existence of a large diurnal cycle (one daily maximum and one daily minimum) of oceanic, tropical, deep cumulus convection. The more intense the deep convection and the more associated it is with organized weather systems, the more evident is a diurnal cycle with a maximum in the morning. At many places heavy rainfall is 2鈥3 times greater in the morning than in the late afternoon-evening. Many land stations also show morning maxima of heavy rainfall. The GATE observations show a similar diurnal range in heavy rainfall, but the time of maximum occurrence is in the afternoon. This occurrence is 6鈥7 h later than in most other oceanic regions and is probably a result of downwind influences from Africa and the fact that the GATE heavy rainfall was often associated with squall lines. Diurnal variations in low-level, layered and total cloudiness show a much smaller range. The variability of deep convection and heavy rainfall is not readily observable from those satellite pictures which cannot well resolve individual convective cells nor is it easily obtained from surface observations of the percent of sky coverage which are heavily weighted to the presence of low-level and layered clouds. A comparison of previous observational studies is made. It is hypothesized that the diurnal cycle in deep convection with a morning maximum is associated with organized weather disturbances. This diurnal cycle likely results from day versus night variations in tropospheric radiational cooling between the weather system and its surrounding cloud-free region.
    Krueger S. K., Q. Fu, K. N. Liou, and H.-N. S. Chin, 1995: Improvements of an ice-phase microphysics parameterization for use in numerical simulations of tropical convection. J. Appl. Meteor., 34, 281- 287.10.1175/1520-0450-34.1.281f0bd8c8e6b1ee6b687ebd97f75b97f4bhttp%3A%2F%2Fadsabs.harvard.edu%2Fabs%2F1995JApMe..34..281Khttp://adsabs.harvard.edu/abs/1995JApMe..34..281KAbstract It is important to properly simulate the extent and ice water content of tropical anvil clouds in numerical models that explicitly include cloud formation because of the significant effects that these clouds have on the radiation budget. For this reason, a commonly used bulk ice-phase microphysics parameterization was modified to more realistically simulate some of the microphysical processes that occur in tropical anvil clouds. Cloud ice growth by the Bergeron process and the associated formation of snow were revised. The characteristics of graupel were also modified in accord with a previous study. Numerical simulations of a tropical squall line demonstrate that the amount of cloud ice and the extent of anvil clouds are increased to more realistic values by the first two changes.
    Li X. F., S. T. Gao, 2011: Precipitation Modeling and Quantitative Analysis. Springer,240 pp.10.1007/978-94-007-2381-84452ac6969801ac04671982209dc5aachttp%3A%2F%2Fagris.fao.org%2Fagris-search%2Fsearch.do%3FrecordID%3DUS201300004078http://agris.fao.org/agris-search/search.do?recordID=US201300004078The book examines surface rainfall processes through cloud-resolving modeling and quantitative analysis of surface rainfall budget and summarizes modeling and analysis results in recent seven years. The book shows validation of precipitation modeling against observations and derives a set of diagnostic precipitation equations. The book provides detailed discussions of the applications of precipitation equations to the examination of effects of sea surface temperature, vertical wind shear, radiation, and ice clouds on torrential rainfall processes in the tropics and mid-latitudes, and to the studies of sensitivity of precipitation modeling to uncertainty of the initial conditions and to the estimate of precipitation efficiency. The book can be used as a text book for graduate students and will be beneficial to researchers and forecasters for precipitation process studies and operational forecasts.搂Xiaofan Li is a physical scientist at the Center for Satellite Applications and Research, National Environmental Satellite, Data, and Information Service, National Oceanic and Atmospheric Administration, Camp Springs, Maryland, USA. He has a doctorate in meteorology from the University of Hawaii at Manoa, Honolulu, USA and a master s degree in meteorology from Nanjing University of Information Science and Technology, Nanjing, China.搂Shouting Gao is a professor at the Laboratory of Cloud-Precipitation Physics and Severe Storm, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, China. He has a doctorate and a master s degree in meteorology from the Institute of Atmospheric Physics, Beijing, China.
    Li X. F., X. Y. Shen, 2013: Rain microphysical budget in the tropical deep convective regime: A 2-D cloud-resolving modeling study. J. Meteor. Soc.Japan, 91, 801- 815.10.2151/jmsj.2013-6069c42d6d25f1bffde2e8e5a9ae60b0c94http%3A%2F%2Fci.nii.ac.jp%2Fnaid%2F40019929933http://ci.nii.ac.jp/naid/40019929933The rain microphysical budget associated with precipitation in the tropical deep convective regime is investigated through the analysis of grid-scale data from a 1.5-km-mesh two-dimensional cloud-resolving model simulation forced by large-scale forcing from tropical ocean global atmosphere coupled-ocean atmosphere response experiment. The rain grids are partitioned into several types based on the rain microphysical budget, and relationships between rainfall types and vertical profiles of vertical momentum, water vapor, and cloud hydrometeors are examined. Over 67% of the total rainfall is associated with the net rain source, in which the collection of cloud water by rain is greater than the melting of precipitation ice to rain in the presence of upward motions throughout the troposphere. Over 26% of the total rainfall is related to downward motions in the lower troposphere, leading to the melting of precipitation ice as a major term in the production of precipitation. About 15% of the total rainfall corresponds to dynamic hydrometeor advection only.
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    Li X. F., C.-H. Sui, and K.-M. Lau, 2002: Dominant cloud microphysical processes in a tropical oceanic convective system: A 2D cloud resolving modeling study. Mon. Wea. Rev., 130, 2481- 2491.36ee71232d9d31c1cf466d3b85b35f76http%3A%2F%2Fadsabs.harvard.edu%2Fcgi-bin%2Fnph-data_query%3Fbibcode%3D2002MWRv..130.2481L%26db_key%3DPHY%26link_type%3DEJOURNALhttp://xueshu.baidu.com/s?wd=paperuri%3A%28a53bd1acd783752acb63f8e80a252a52%29&filter=sc_long_sign&tn=SE_xueshusource_2kduw22v&sc_vurl=http%3A%2F%2Fadsabs.harvard.edu%2Fcgi-bin%2Fnph-data_query%3Fbibcode%3D2002MWRv..130.2481L%26db_key%3DPHY%26link_type%3DEJOURNAL&ie=utf-8&sc_us=12405316899339171360
    Li X. F., X. Y. Shen, and J. Liu, 2011: A partitioning analysis of tropical rainfall based on cloud budget. Atmos. Res., 102, 444- 451.48223bb2acc5a2dcf34e726c0d48a513http%3A%2F%2Fwww.sciencedirect.com%2Fscience%2Farticle%2Fpii%2FS016980951100295X%3F_rdoc%3D7%26_fmt%3Dhigh%26_origin%3Dbrowse%26_srch%3DhubEid%281-s2.0-S0169809511X0011X%29%26_docanchor%3D%26_ct%3D8%26_refLink%3DY%26_zone%3Drslt_list_item%26md5%3D14e7284a3006ae876b8acf57f0d64f52http://xueshu.baidu.com/s?wd=paperuri%3A%28b7b077cb8d2d3df5f0f5365299f78b1b%29&filter=sc_long_sign&tn=SE_xueshusource_2kduw22v&sc_vurl=http%3A%2F%2Fwww.sciencedirect.com%2Fscience%2Farticle%2Fpii%2FS016980951100295X%3F_rdoc%3D7%26_fmt%3Dhigh%26_origin%3Dbrowse%26_srch%3DhubEid%281-s2.0-S0169809511X0011X%29%26_docanchor%3D%26_ct%3D8%26_refLink%3DY%26_zone%3Drslt_list_item%26md5%3D14e7284a3006ae876b8acf57f0d64f52&ie=utf-8&sc_us=6952376337920794662
    Li X. F., G. Q. Zhai, S. T. Gao, and X. Y. Shen, 2014: A new convective-stratiform precipitation rate separation scheme. Atmos. Sci. Lett., 15, 245- 251.
    Li X. F., P. J. Zhu, G. Q. Zhai, R. Liu, X. Y. Shen, W. Huang, and D. H. Wang, 2016: Testing parameterization schemes for simulating depositional growth of ice crystal using Koenig and Takahashi parameters: A pre-summer rainfall case study over southern China. Atmos. Sci. Lett.,17, 3-12, doi: 10.1002/asl.591.10.1002/asl.591eded01fd80ad8aedb27a754f56cee5afhttp%3A%2F%2Fonlinelibrary.wiley.com%2Fdoi%2F10.1002%2Fasl.591%2Ffullhttp://onlinelibrary.wiley.com/doi/10.1002/asl.591/fullAbstract Top of page Abstract 1Introduction 2Model and experiments 3Results 4Summary Acknowledgements References In this study, the three (Hsie, Krueger and Zeng) schemes that parameterize depositional growth of ice crystal are tested using Koenig and Takahashi parameters in modeling China pre-summer torrential rainfall event. The Krueger scheme with the Takahashi parameter produces the closest simulations to the observations because it increases cloud ice and snow in the upper troposphere. The increased ice hydrometeor enhances and suppresses infrared radiative cooling above and below 12 km, respectively. The suppressed infrared cooling reduces net condensation while the enhanced infrared cooling suppresses hydrometeor loss through the reduction in melting of ice hydrometeor.
    Lilly D. K., 1988: Cirrus outflow dynamics. J. Atmos. Sci., 45, 1594- 1605.10.1175/1520-0469(1988)045<1594:COD>2.0.CO;22a220f7f-3269-42d5-9bf1-cfdcacafed90b4a2cd37f1a9f88133d751140bb8e426http%3A%2F%2Fadsabs.harvard.edu%2Fabs%2F1988JAtS...45.1594Lrefpaperuri:(24c18935cb1713524dbd556cf3895ae6)http://adsabs.harvard.edu/abs/1988JAtS...45.1594LCirrus outflow from deep convection are analyzed as dynamically and thermodynamically active systems. The initial outflow is considered as an analog to wake collapse, in which a neutrally buoyant flow intrusion is flattened and stretched by its stratified environment, and the initially isotropic turbulence within it is converted to other forms. The early spread of the outflow is predicted on the basis of analytic and numerical calculations by Dugan et al. Strong radiative heat flux curvature then leads to maintenance or regeneration of buoyant turbulence in the collapsed outflow plume. Mixed layer analysis allow predictions of entrainment rates. In the case of strong net radiative heating, the mixed layer model predicts an encroachment condition, in which the upper boundary attains nearly the same temperature as the environment and grows into it rapidly. This tendency is countered by bodily ascent of the warm mesoscale plumes, the rate of which is predicted with the aid of a theory of drag on a flat plate in a stratified fluid. It is found that narrow plumes rise rapidly enough that their mean temperature is not much different from the environment, and their tops may be cold enough to contribute to drying of the lower stratosphere. Wider plumes follow the mixed layer analysis and develop a substantial temperature excess and an encroaching upper boundary condition. The critical width is estimated to be of order 150 km. The effect of cirrus precipitation represents an unknown limitation to this analysis.
    Lin Y.-L., R. D. Farley, and H. D. Orville, 1983: Bulk parameterization of the snow field in a cloud model. J. Climate Appl. Meteor., 22, 1065- 1092.10.1175/1520-0450(1983)022<1065:BPOTSF>2.0.CO;29190891c3775ec6ca868fe681504eba0http%3A%2F%2Fadsabs.harvard.edu%2Fabs%2F1983japme..22.1065lhttp://adsabs.harvard.edu/abs/1983japme..22.1065lA two-dimensional, time-dependent cloud model has been used to simulate a moderate intensity thunderstorm for the High Plains region. Six forms of water substance (water vapor, cloud water, cloud ice, rain, snow and hail, i.e., graupel) are simulated. The model utilizes the `bulk water' microphysical parameterization technique to represent the precipitation fields which are all assumed to follow exponential size distribution functions. Autoconversion concepts are used to parameterize the collision-coalescence and collision-aggregation processes. Accretion processes involving the various forms of liquid and solid hydrometeors are simulated in this model. The transformation of cloud ice to snow through autoconversion (aggregation) and Bergeron process and subsequent accretional growth or aggregation to form hail are simulated. Hail is also produced by various contact mechanisms and via probabilistic freezing of raindrops. Evaporation (sublimation) is considered for all precipitation particles outside the cloud. The melting of hail and snow are included in the model. Wet and dry growth of hail and shedding of rain from hail are simulated.The simulations show that the inclusion of snow has improved the realism of the results compared to a model without snow. The formation of virga from cloud anvils is now modeled. Addition of the snow field has resulted in the inclusion of more diverse and physically sound mechanisms for initiating the hail field, yielding greater potential for distinguishing dominant embryo types characteristically different from warm- and cold-based clouds.
    Liu J., X. Y. Shen, and X. F. Li, 2014: Radiative effects of water clouds on heat, cloud microphysical and surface rainfall budgets associated with pre-summer torrential rainfall. Terrestrial, Atmospheric and Oceanic Sciences, 25, 39- 48.10.3319/TAO.2013.08.02.01(A)6e58d3503240ff23f053f77ae4c34232http%3A%2F%2Fconnection.ebscohost.com%2Fc%2Farticles%2F94091125%2Fradiative-effects-water-clouds-heat-cloud-microphysical-surface-rainfall-budgets-associated-pre-summer-torrential-rainfallhttp://connection.ebscohost.com/c/articles/94091125/radiative-effects-water-clouds-heat-cloud-microphysical-surface-rainfall-budgets-associated-pre-summer-torrential-rainfallThis study investigates thermal, cloud microphysical and surface-rainfall responses to the radiative effects of water clouds by analyzing two pairs of two-dimensional cloud-resolving model sensitivity experiments of a pre-summer heavy rainfall event. In the presence of the radiative effects of ice clouds, exclusion of the radiative effects of water clouds reduces the model domain mean rain rate through the mean hydrometeor increase, which is associated with the decreases in the melting of graupel and cloud ice caused by enhanced local atmospheric cooling. In the absence of the radiative effects of ice clouds, removal of the radiative effects of water clouds increases model domain mean rain rate via the enhancements in the mean net condensation and the mean hydrometeor loss. The enhanced mean net condensation and increased mean latent heat are related to the strengthened mean infrared radiative cooling in the lower troposphere. The increased mean hydrometeor loss associated with the reduction in the melting of graupel is caused by the enhanced local atmospheric cooling.
    Rutledge S. A., P. V. Hobbs, 1983: The mesoscale and microscale structure and organization of clouds and precipitation in midlatitude cyclones. Part VIII: A model for the "seeder-feeder" process in warm-frontal rainbands. J. Atmos. Sci., 40, 1185- 1206.190349a4f106b0dcb21fdedd82392d0ahttp%3A%2F%2Fadsabs.harvard.edu%2Fcgi-bin%2Fnph-data_query%3Fbibcode%3D1983JAtS...40.1185R%26db_key%3DPHY%26link_type%3DABSTRACT%26high%3D02314http://xueshu.baidu.com/s?wd=paperuri%3A%28786d88b8781324b0be4dbf25f892342c%29&filter=sc_long_sign&tn=SE_xueshusource_2kduw22v&sc_vurl=http%3A%2F%2Fadsabs.harvard.edu%2Fcgi-bin%2Fnph-data_query%3Fbibcode%3D1983JAtS...40.1185R%26db_key%3DPHY%26link_type%3DABSTRACT%26high%3D02314&ie=utf-8&sc_us=9754303940089065557
    Rutledge S. A., P. V. Hobbs, 1984: The mesoscale and microscale structure and organization of clouds and precipitation in midlatitude cyclones. Part XII: A diagnostic modeling study of precipitation development in narrow cold-frontal rainbands. J. Atmos. Sci., 41, 2949- 2972.
    Shen X. Y., Y. Wang, N. Zhang, and X. F. Li, 2010: Precipitation and cloud statistics in the deep tropical convective regime. J. Geophys. Res., 115,D24205, doi: 10.1029/2010JD014481.10.1029/2010JD01448120e0b38fe034a038594b48daf01946e7http%3A%2F%2Fonlinelibrary.wiley.com%2Fdoi%2F10.1029%2F2010JD014481%2Ffullhttp://onlinelibrary.wiley.com/doi/10.1029/2010JD014481/fullPrecipitation and cloud statistics in the deep tropical convective regime is investigated through the analysis of grid-scale data from a two-dimensional, cloud-resolving model simulation. The model is forced by large-scale vertical velocity, zonal wind, horizontal advection, and sea surface temperature observed and derived from the Tropical Ocean Global Atmosphere Coupled Ocean Atmosphere Response Experiment. The analysis is conducted by categorizing the grid-scale data into eight rainfall types based on precipitation processes: Water vapor convergence, local vapor change, and hydrometeor change/convergence. Among the eight rainfall types, the rainfall with local atmospheric drying, water vapor divergence, and hydrometeor loss/convergence has the largest contribution (30.8%) to the total rainfall because of large rainfall coverage (35.3%). The hydrometeor loss is mainly caused by water clouds through precipitation and the evaporation of rain. For the three other rainfall types with water vapor divergence, each rainfall type contributes to the total rainfall by less than 5%. Of the total rainfall, 61% is attributed to the four rainfall types with water vapor convergence. Although the rainfall with local atmospheric drying, water vapor convergence, and hydrometeor loss/convergence shows the largest surface rain rate (27.8 mm h), it only accounts for a small part (10%) of the total rainfall due to its small rainfall coverage (1.2%). For the three other rainfall types with water vapor convergence, each rainfall type contributes to the total rainfall by 14-19%. The grid-scale precipitation statistics are significantly different from the model domain mean precipitation statistics found by Shen et al. (2010), suggesting a spatial-scale dependence of precipitation statistics.
    Shen X. Y., Y. Wang, and X. F. Li, 2011a: Radiative effects of water clouds on rainfall responses to the large-scale forcing during pre-summer heavy rainfall over southern China. Atmos. Res., 99, 120- 128.10.1016/j.atmosres.2010.09.011af931b2ad30f4cbfe1301085587a7a6fhttp%3A%2F%2Fwww.sciencedirect.com%2Fscience%2Farticle%2Fpii%2FS0169809510002498http://www.sciencedirect.com/science/article/pii/S0169809510002498Water clouds are an essential ingredient of precipitation systems and their radiative effects may significantly impact rainfall processes. This study investigates radiative effects of water clouds on rainfall using a two-dimensional cloud-resolving model simulation of a pre-summer heavy rainfall event over southern China from 3 to 8 June 2008, forced with large-scale data from NCEP/GDAS. During the onset phase, the exclusion of radiative effects of water clouds increased the mean rain rate through the mean hydrometeor change from loss to gain in the presence of radiative effects of ice clouds, whereas it increased the mean rain rate through the increases in the mean net condensation and mean hydrometeor loss in the absence of radiative effects of ice clouds. During the development phase, the removal of radiative effects of water clouds enhanced the mean rainfall through the mean hydrometeor change from gain to loss. During the mature phase, the elimination of radiative effects of water clouds weakened the mean rainfall through the decreased mean net condensation. The exclusion of radiative effects of ice clouds enhanced the decrease in the mean rainfall. During the decay phase, the removal of radiative effects of water clouds increased the mean rainfall through the enhanced net condensation.
    Shen X. Y., Y. Wang, and X. F. Li, 2011b: Effects of vertical wind shear and cloud radiative processes on responses of rainfall to the large-scale forcing during pre-summer heavy rainfall over southern China. Quart. J. Roy. Meteor. Soc., 137, 236- 249.10.1002/qj.735626136d7a885d5037b4b3d383f4c0426http%3A%2F%2Fonlinelibrary.wiley.com%2Fdoi%2F10.1002%2Fqj.735%2Ffullhttp://onlinelibrary.wiley.com/doi/10.1002/qj.735/fullAbstract Top of page Abstract 1.Introduction 2.Model and experiments 3.Results 4.Summary Acknowledgements Appendix. Surface rainfall, heat and kinetic energy budgets, and convectivetratiform rainfall partitioning method References The pre-summer heavy rainfall over southern China during 38 June 2008 is simulated using a two-dimensional cloud-resolving model. The model is integrated with imposed zonally uniform vertical velocity, zonal wind, horizontal temperature and vapour advection from National Centers for Environmental Prediction (NCEP)/Global Data Assimilation System (GDAS) data. The effects of vertical wind shear and cloud radiative processes on the response of rainfall to large-scale forcing are analysed through the comparison of two sensitivity experiments with the control experiment. One sensitivity experiment excludes the large-scale vertical wind shear and the other excludes the cloud radiative effects. During the decay phase of convection, the increase in model domain-mean surface rain-rate resulting from the exclusion of vertical wind shear is associated with the slowdown in the decrease of perturbation kinetic energy due to the exclusion of barotropic conversion from mean kinetic energy to perturbation kinetic energy. The increase in domain-mean rain-rate from the exclusion of cloud radiative effects is related to the enhancement of condensation and associated latent heat as a result of strengthened radiative cooling. The increase in the domain-mean surface rain-rate is mainly associated with the increase of convective rainfall, which is in turn related to the local atmospheric change from moistening to drying. During the onset and mature phases of convection, the domain-mean surface rain-rates are generally insensitive to vertical wind shear and cloud radiative effects whereas convective and stratiform rain-rates are sensitive to vertical wind shear and cloud radiative effects. The decrease in convective rain-rate and the increase in stratiform rain-rate are primarily associated with the enhanced transport of hydrometeor concentration from convective regions to raining stratiform regions. Copyright 漏 2011 Royal Meteorological Society
    Shen X. Y., N. Zhang, and X. F. Li, 2011c: Effects of large-scale forcing and ice clouds on pre-summer heavy rainfall over southern China in June 2008: A partitioning analysis based on surface rainfall budget. Atmos. Res., 101, 155- 163.10.1016/j.atmosres.2011.02.001ae2fabbf9a039b2fcc69be895766795chttp%3A%2F%2Fwww.sciencedirect.com%2Fscience%2Farticle%2Fpii%2FS016980951100038Xhttp://www.sciencedirect.com/science/article/pii/S016980951100038XThe effects of large-scale forcing and ice clouds on rainfall are studied by analyzing a series of sensitivity experiments of a pre-summer heavy rainfall event over southern China from 3 to 8 June 2008. The analysis is conducted categorizing grid-scale rainfall simulation data into eight rainfall types based on different rainfall processes. The rainfall with water vapor divergence and local atmospheric drying and hydrometeor loss/convergence (TfM) has the largest contribution to total rainfall during the development of rainfall when the imposed large-scale forcing produces water vapor convergence. TfM and the rainfall with water vapor convergence and local atmospheric moistening and hydrometeor loss/convergence (tFM) have the largest contributors to total rainfall during the decay phase when the imposed large-scale forcing generates water vapor divergence. TfM becomes the largest contributor during the decay phase when the exclusion of ice clouds decreases tFM and increases TfM. The removal of ice clouds enhances the contribution of the rainfall with water vapor convergence to total rainfall during the life span of the rainfall event.
    Shen X. Y., J. Liu, and X. F. Li, 2012: Torrential rainfall responses to ice microphysical processes during pre-summer heavy rainfall over southern China. Adv. Atmos. Sci.,29, 493-500, doi: 10.1007/s00376-011-1122-4.10.1007/s00376-011-1122-4c69cac865aa439824ad2f931b5cd4a40http%3A%2F%2Fwww.cnki.com.cn%2FArticle%2FCJFDTotal-DQJZ201203008.htmhttp://d.wanfangdata.com.cn/Periodical_dqkxjz-e201203007.aspxIn this study, the effects of key ice microphysical processes on the pre-summer heavy rainfall over southern China during 3鈥8 June 2008 were investigated. A series of two-dimensional sensitivity cloud-resolving model simulations were forced with zonally uniform vertical velocity, zonal wind, horizontal temperature, and water vapor advection data from the National Centers for Environmental Prediction (NCEP)/Global Data Assimilation System (GDAS). The effects of key ice microphysical processes on the responses of rainfall to large-scale forcing were analyzed by comparing two sensitivity experiments with a control experiment. In one sensitivity experiment, ice crystal radius, associated with depositional growth of snow from cloud ice, was reduced from 100 碌m in the control experiment to 50 碌m, and in the other sensitivity experiment the efficiency of the growth of graupel from the accretion of snow was reduced to 50% from 100% in the control experiment. The results show that the domain-mean rainfall responses to these ice microphysical processes are stronger during the decay phase than during the onset and mature phases. During the decay phase, the increased mean rain rate resulting from the decrease in ice crystal radius is associated with the enhanced mean local atmospheric drying, the increased mean local hydrometeor loss, and the suppressed mean water vapor divergence. The increased mean rain rate caused by the reduction in accretion efficiency is related to the reduced mean water vapor divergence and the enhanced mean local hydrometeor loss.
    Shen X. Y., W. Huang, T. Qing, W. Y. Huang, and X. F. Li, 2014: A modified scheme that parameterizes depositional growth of ice crystal: A modeling study of pre-summer torrential rainfall case over southern China. Atmos. Res., 138, 293- 300.10.1016/j.atmosres.2013.11.020b47ec6acfb088752133a505f86ca31dchttp%3A%2F%2Fwww.sciencedirect.com%2Fscience%2Farticle%2Fpii%2FS0169809513003438http://www.sciencedirect.com/science/article/pii/S0169809513003438Depositional growth of cloud ice is estimated and its parameterization schemes are compared through the two-dimensional cloud-resolving modeling analysis of pre-summer heavy rainfall over southern China. Hsie et al. (1980) and Krueger et al. (1995) developed parameterization schemes to calculate depositional growth of cloud ice by estimating the growth timescale under the assumption that the ice crystal concentration is independent of crystal size. A new scheme is proposed by Zeng et al. (2008) under the assumption that the ice crystal concentration is proportional to the mass of ice crystal. Hsie's and Krueger's schemes produce small amount of cloud ice similar to what Zeng's scheme with low ice crystal concentration does. When ice crystal concentration is increased to a high value in Zeng's scheme, the simulation generates anomalous depositional growth of cloud ice and thus anomalous area expansion of stratiform rainfall. Zeng's scheme is modified by changing radius of base ice crystal from 0 to 40 渭m in the calculation of depositional growth of cloud ice. The modified scheme with high ice crystal concentration greatly reduces growth of cloud ice and thus fractional coverage of stratiform rainfall.
    Soong S. T., Y. Ogura, 1980: Response of tradewind cumuli to large-scale processes. J. Atmos. Sci., 37, 2035- 2050.10.1175/1520-0469(1980)0372.0.CO;29df5cf9ce9c81877f465d04443834769http%3A%2F%2Fadsabs.harvard.edu%2Fabs%2F1980jats...37.2035shttp://adsabs.harvard.edu/abs/1980jats...37.2035sThe two-dimensional slab-symmetric numerical cloud model used by Soong and Ogura (1973) for studying the evolution of an isolated cumulus cloud is extended to investigate the statistical properties of cumulus clouds which would be generated under a given large-scale forcing composed of the horizontal advection of temperature and water vapor mixing ratio, vertical velocity, sea surface temperature and radiative cooling. Random disturbances of small amplitude are introduced into the model at low levels to provide random motion for cloud formation.The model is applied to a case of suppressed weather conditions during BOMEX for the period 22-23 June 1969 when a nearly steady state prevailed. The composited temperature and mixing ratio profiles of these two days are used as initial conditions and the time-independent large-scale forcing terms estimated from the observations are applied to the model. The result of numerical integration shows that a number of small clouds start developing after 1 h. Some of them decay quickly, but some of them develop and reach the tradewind inversion. After a few hours of simulation, the vertical profiles of the horizontally averaged temperature and moisture are found to deviate only slightly from the observed profiles, indicating that the large-scale effect and the feedback effects of clouds on temperature and mixing ratio reach an equilibrium state. The three major components of the cloud feedback effect, i.e., condensation, evaporation and vertical fluxes associated with the clouds, are determined from the model output. The vertical profiles of vertical heat and moisture fluxes in the subcloud layer in the model are found to be in general agreement with the observations.Sensitivity tests of the model are made for different magnitudes of the large-scale vertical velocity. The most striking result is that the temperature and humidity in the cloud layer below the inversion do not change significantly in spite of a relatively large variation in height and intensity of the trade-wind inversion. This may indicate that cumulus clouds respond quickly to the large-scale forcing and adjust their own transport properties to maintain the observed large-scale thermodynamic fields whose variation has a much longer time scale. Sensitivity tests on varying sea surface temperature indicate that a 卤1掳C change in the sea surface temperature does not change the height of the inversion significantly during a 6 h simulation period. Another simulation shows that a tradewind inversion can develop rapidly from an initial sounding without an inversion if the large-scale downward motion is fairly large.
    Soong S. T., W.-K. Tao, 1980: Response of deep tropical cumulus clouds to mesoscale processes. J. Atmos. Sci., 37, 2016- 2034.10.1175/1520-0469(1980)0372.0.CO;29cb2afe5e74b2575cdebc09c8082d7bfhttp%3A%2F%2Fadsabs.harvard.edu%2Fabs%2F1980JAtS...37.2016Shttp://adsabs.harvard.edu/abs/1980JAtS...37.2016SAbstract The two-dimensional cloud ensemble model developed by Soong and Ogura (1980) is used to simulate the response of deep clouds to mesoscale lifting using data obtained in the Global Atmospheric Research Program (GARP) Atlantic Tropical Experiment (GATE). The input to the model includes the mesoscale vertical velocity, horizontal advections of temperature and mixing ratio of water vapor, radiative cooling and sea surface temperature. The cloud ensemble feedback effects due to the condensation and evaporation of cloud liquid drops and vertical fluxes of heat and moisture are determined by the model. The simulated upward mass flux inside the model clouds is about three times the mass flux due to mesoscale lifting. The downward mass flux inside clouds is also large, leaving a small downward mass flux in the cloud-free area. The major portion of the heat flux is produced by the updraft inside clouds. On the other hand, the moisture fluxes due to both updraft and downdraft are important. In the cloud-fre...
    Sui C.-H., K.-M. Lau, W.-K. Tao, and J. Simpson, 1994: The tropical water and energy cycles in a cumulus ensemble model. Part I: Equilibrium climate. J. Atmos. Sci., 51, 711- 728.10.1175/1520-0469(1994)0512.0.CO;23414b4ea-d2e5-4f06-8a8f-c2835e9691b6a7958b5cd9ee7bdad3cc249f75c81921http%3A%2F%2Fconnection.ebscohost.com%2Fc%2Farticles%2F9502021220%2Ftropical-water-energy-cycles-cumulus-ensemble-modelrefpaperuri:(aeda55ca1d3ca0325ab997993d1e6dac)http://connection.ebscohost.com/c/articles/9502021220/tropical-water-energy-cycles-cumulus-ensemble-modelPresents a study of the tropical water cycles and its role in the climate system using a cumulus ensemble model to compliment general circulation models (GCM). Measurements of radiative transfer in clouds; Convective-radiative equilibrium response; Ensemble mean distributions; Heat budget measurements.
    Sui C.-H., K.-M. Lau, Y. N. Takayabu, and D. A. Short, 1997: Diurnal variations in tropical oceanic cumulus convection during TOGA COARE. J. Atmos. Sci., 54, 639- 655.10.1175/1520-0469(1997)0542.0.CO;26e2940b8a9c57a212c9b3059f906d072http%3A%2F%2Fadsabs.harvard.edu%2Fabs%2F1997JAtS...54..639Shttp://adsabs.harvard.edu/abs/1997JAtS...54..639SDiurnal variations in atmospheric convection, dynamic/thermodynamic fields, and heat/moisture budgets over the equatorial Pacific warm pool region are analyzed based on data collected from different observation platforms during the Intensive Observation Period of the Tropical Ocean Global Atmosphere Coupled Ocean-Atmosphere Response Experiment (TOGA COARE). Results reveal that the diurnal variations in rainfall/convection over the TOGA COARE region can be classified into three distinct stages: warm morning cumulus, afternoon convective showers, and nocturnal convective systems. Afternoon rainfall comes mostly from convective cells, but the nocturnal rainfall is derived from deeper convective cells and large areas of stratiform clouds. Results further show that afternoon convective showers are more evident in the large-scale undisturbed periods when the diurnal SST cycle is strong, but the nocturnal convective systems and morning cumulus are more enhanced in the disturbed periods when more moisture is available. The primary cause of the nocturnal rainfall maximum is suggested to be associated with more (less) available precipitable water in the night (day) due to the diurnal radiative cooling/heating cycle and the resultant change in tropospheric relative humidity.
    Sui C.-H., X. Li, and K.-M. Lau, 1998: Radiative-convective processes in simulated diurnal variations of tropical oceanic convection. J. Atmos. Sci., 55, 2345- 2359.10.1175/1520-0469(1998)055<2345:RCPISD>2.0.CO;21411852efc72d4d0590d48cde966d9b1http%3A%2F%2Fadsabs.harvard.edu%2Fabs%2F1998JAtS...55.2345Shttp://adsabs.harvard.edu/abs/1998JAtS...55.2345SThis paper presents an analysis of the diurnal variation of tropical oceanic convection and its associated energy cycle as simulated by an anelastic cumulus ensemble model. The model includes subgrid turbulence, cloud microphysics, and radiative transfer processes. In two experiments designed to simulate the diurnal cycles in large-scale disturbed (Al) and undisturbed conditions (A4) over the tropical western Pacific warm pool, the model produces diurnal variations that are in general agreement with observations. In Al, a time-independent SST and mean ascending motion are prescribed in the model. The model generates a diurnal cycle with positive (negative) rainfall anomalies during the night (day), and the maximum (minimum) rainfall near 0200 (1300-1400) local time. In A4, a diurnally varying SST is prescribed in the model and the domain-averaged vertical velocity is constrained to be zero. The simulated diurnal variations still have a nocturnal rainfall maximum but with a weaker magnitude and a secondary peak in the afternoon. The model is then used to investigate the radiative effects of clouds that has been suggested as the cause of the nocturnal rainfall maximum by many studies. Two experiments (A2 and A3) are performed with the model, in which a time-independent SST is prescribed and the domain-averaged vertical velocity is constrained to be zero. The only difference between the two experiments is that the cloud-radiation interaction is suppressed in A3. The results show that despite the significant difference in total cloudiness/rainfall due to the difference in mean vertical motion between A2 and Al, and the difference in cloud-radiative forcing between A2 and A3, the simulated diurnal cycles in all three experiments show a dominant nocturnal rainfall maximum. The results support the suggestion by Sui et al. that the nocturnal rainfall maximum is related to more (less) available precipitable water in the night (day) due to the diurnal radiative cooling/heating cycle.
    Tao W.-K., J. Simpson, 1993: Goddard Cumulus Ensemble model. Part I: Model description. Terrestrial, Atmospheric & Oceanic Sciences, 4, 35- 72.d3e37b10-a816-43b4-9d09-2e383b22f60e23bfa0079035695c3e9fec77a70e2026http%3A%2F%2Fwww.airitilibrary.com%2FPublication%2FalDetailedMesh%3Fdocid%3D10170839-199303-4-1-35-71-arefpaperuri:(83924efdd356c29b2cd3a405472fe3e4)http://www.airitilibrary.com/Publication/alDetailedMesh?docid=10170839-199303-4-1-35-71-aDuring the past two decades, convective scale models have advanced sufficiently to study the dynamic and microphysical processes associated with mesoscale convective systems. The basic features of these models are that they are non-hydrostatic and include a good representation of microphysical processes. The Goddard Cumulus Ensemble (GCE) model has been extensively applied to study cloud-environment interactions, cloud interaction and mergers, air-sea interaction, cloud draft structure and trace gas transport. The GCE model has improved significantly during the past decade. For example, ice-microphysical processes, and solar and infrared radiative transfer processes have been included. These model improvements allow the GCE model to study cloud-radiation interaction, cloud-radiation-climate relations and to develop rain retrieval algorithms for Tropical Rainfall Measuring Mission (TRMM). In Part , a full description of the GCE model is presented, as well as several sensitivity tests associated with its assumptions. In Part (Simpson and Tao, 1993), we will review GCE model applications to cloud precipitating processes and to the Tropical Rainfall Measuring Mission (TRMM), a joint U. S.-Japan satellite project to measure rain and latent heat release over the global tropics.
    Tao, W.-K, J. Simpson, M. McCumber, 1989: An ice-water saturation adjustment. Mon. Wea. Rev., 117, 231- 235.10.1175/1520-0493(1989)1172.0.CO;2f63023e797f1af11a34c8d3827de62d4http%3A%2F%2Fciteseer.ist.psu.edu%2Fshowciting%3Fcid%3D8707393http://citeseer.ist.psu.edu/showciting?cid=8707393CiteSeerX - Scientific documents that cite the following paper: An ice–water saturation adjustment
    Tao W.-K., J. Simpson, C.-H. Sui, B. Ferrier, S. Lang, J. Scala, M.-D. Chou, and K. Pickering, 1993: Heating, moisture, and water budgets of tropical and midlatitude squall lines: Comparisons and sensitivity to longwave radiation. J. Atmos. Sci., 50, 673- 690.10.1175/1520-0469(1993)0502.0.CO;2ff40b1899e906634a1719ad696835378http%3A%2F%2Fadsabs.harvard.edu%2Fabs%2F1993JAtS...50..673Thttp://adsabs.harvard.edu/abs/1993JAtS...50..673TAbstract A two-dimensional, time-dependent, and nonhydrostatic numerical cloud model is used to estimate the heating (Q1, moisture (Q2), and water budgets in the convective and stratiform regions for a tropical and a midlatitude squall line (EMEX and PRE-STORM). The model is anelastic and includes a parameterized three-class ice-phase microphysical scheme and longwave radiative transfer processes. A quantitative estimate of the impact of the longwave radiative cooling on the total surface precipitation as well as on the development and structure of these two squall lines is presented. It was found that the vertical eddy moisture fluxes are a major contribution to the model-derived Q2 budgets in both squall cases. A distinct midlevel minimum in the Q2 profile for the EMEX case is due to vertical eddy transport in the convective region. On the other hand, the contribution to the Q1 budget by the cloud-scale fluxes is minor for the EMEX case. In contrast, the vertical eddy heat flux is relatively important f...
    Wang D. H., X. F. Li, W.-K. Tao, Y. Liu, and H. G. Zhou, 2009a: Torrential rainfall processes associated with a landfall of severe tropical storm Bilis (2006): A two-dimensional cloud-resolving modeling study. Atmos. Res., 91, 94- 104.10.1016/j.atmosres.2008.07.005807d9876e38a3abee40cf3c38810fe73http%3A%2F%2Fwww.sciencedirect.com%2Fscience%2Farticle%2Fpii%2FS0169809508001592http://www.sciencedirect.com/science/article/pii/S0169809508001592Torrential rainfall processes associated with a landfall of Typhoon Bilis (2006) are investigated using a two-dimensional cloud-resolving model simulation. The model is integrated for 6days with imposed zonally-uniform vertical velocity, zonal wind, horizontal temperature and vapor advection from NCEP/GDAS data. The simulation is validated with observations in terms of surface rain rate and reflectivity. The simulated stratiform clouds cover 89% of the simulation domain that leads to dominant stratiform rainfall on 15 July 2006. The convective clouds develop to cover 29% of the simulation domain that yields dominant convective rainfall whereas the stratiform clouds shrink to 46% on 16 July 2006. The domain-mean simulation shows that the increase of domain-mean surface rain rate from 15 to 16 July 2006 mainly results from local atmospheric moistening on 15 July and local atmospheric drying on 16 July although water vapor convergence rates in the two days are similar.
    Wang D. H., X. F. Li, W.-K. Tao, and Y. Wang, 2009b: Effects of vertical wind shear on convective development during a landfall of severe tropical storm Bilis (2006). Atmos. Res., 94, 270- 275.10.1016/j.atmosres.2009.06.0047d32d6574c188b582b06eb1d9a15e190http%3A%2F%2Fwww.sciencedirect.com%2Fscience%2Farticle%2Fpii%2FS016980950900177Xhttp://www.sciencedirect.com/science/article/pii/S016980950900177XEffects of vertical wind shear on convective development during the landfall of tropical storm Bilis (2006) are investigated with a pair of sensitivity experiments using a two-dimensional cloud-resolving model. The validated simulation data from Wang et al. [Wang, D., Li, X., Tao, W.-K., Liu, Y., Zhou, H., 2009: Torrential rainfall processes associated with a landfall of severe tropical storm Bilis (2006): A two-dimensional cloud-resolving modeling study. Atmos. Res., 91, 94鈥104.] are used as the control experiment. The difference between the control and sensitivity experiments is that vertically varying zonal winds in the control experiment are replaced by their mass-weighted means in the sensitivity experiment. The imposed vertical velocity with ascending motion in the upper troposphere and descending motion in the lower troposphere is responsible for dominant stratiform rainfall on 15 July. The vertical wind shear does not have important impacts on development of stratiform rainfall. One day later, imposed upward motion extends to the lower troposphere. The inclusion of negative vertical wind shear produces well-organized convection and strong convective rainfall because it causes kinetic energy transfer from large-scale forcing to perturbation circulations.
    Wang D. H., X. F. Li, and W.-K. Tao, 2010a: Responses of vertical structures in convective and stratiform regions to large-scale forcing during the landfall of severe tropical storm Bilis (2006). Adv. Atmos. Sci.,27, 33-46, doi: 10.1007/s00376-009-8139-y.10.1007/s00376-009-8139-y0247e7c207f6be04e6ee5f93a5bbb3f8http%3A%2F%2Fd.wanfangdata.com.cn%2FPeriodical_dqkxjz-e201001003.aspxhttp://d.wanfangdata.com.cn/Periodical_dqkxjz-e201001003.aspxThe responses of vertical structures, in convective and stratiform regions, to the large-scale forcing during the landfall of tropical storm Bilis (2006) are investigated using the data from a two-dimensional cloud-resolving model simulation. An imposed large-scale forcing with upward motion in the mid and upper troposphere and downward motion in the lower troposphere on 15 July suppresses convective clouds, which leads to 65100% coverage of raining stratiform clouds over the entire model domain. The imposed forcing extends upward motion to the lower troposphere during 16–17 July, which leads to an enhancement of convective clouds and suppression of raining stratiform clouds. The switch of large-scale lower-tropospheric vertical velocity from weak downward motion on 15 July to moderate upward motion during 16–17 July produces a much broader distribution of the vertical velocity, water vapor and hydrometeor fluxes, perturbation specific humidity, and total hydrometeor mixing ratio during 16–17 July than those on 15 July in the analysis of contoured frequency-altitude diagrams. Further analysis of the water vapor budget reveals that local atmospheric moistening is mainly caused by the enhancement of evaporation of rain associated with downward motion on 15 July, whereas local atmospheric drying is mainly determined by the advective drying associated with downward motion over raining stratiform regions and by the net condensation associated with upward motion over convective regions during 16–17 July.
    Wang Y., X. Y. Shen, and X. F. Li, 2010b: Microphysical and radiative effects of ice clouds on responses of rainfall to the large-scale forcing during pre-summer heavy rainfall over southern China. Atmos. Res., 97, 35- 46.10.1016/j.atmosres.2010.03.0058d83f45c485378920fda2426afe916a2http%3A%2F%2Fwww.sciencedirect.com%2Fscience%2Farticle%2Fpii%2FS0169809510000542http://www.sciencedirect.com/science/article/pii/S0169809510000542Ice clouds are an important part of precipitation systems and their microphysical and radiative effects may significantly impact rainfall simulations. This study investigates these effects using a two-dimensional cloud-resolving model simulation of a pre-summer heavy rainfall event over southern China from 3-8 June 2008, forced with NCEP/GDAS data. The microphysical and radiative effects of ice clouds on rainfall responses to the large-scale forcing during pre-summer heavy rainfall over southern China are analyzed by comparing the control experiment and two sensitivity experiments with the exclusion of ice radiative effects and with the total exclusion of ice microphysics (the exclusion of both ice radiative and microphysical effects), respectively. During the development phase, the total exclusion of ice microphysics decreased the model domain mean surface rain rate primarily by suppressing the convective rain rate through the exclusion of ice radiative effects on 4 June 2008 and by reducing the stratiform rain rate through the exclusion of ice microphysical effects on 5 June. During the peak phase on 6 June, the mean rain rate significantly increased from the previous day. The reduction in the mean rain rate by the total exclusion of ice microphysics continued from the previous day due to the continuous decrease in the stratiform rain rate caused by the exclusion of ice microphysical effects. During the decay phase on 7 June, the total exclusion of ice microphysics increased the mean rain rate by enhancing convective rainfall through the exclusion of ice microphysical effects. These results indicate that the microphysical and radiative effects of ice clouds play equally important roles in pre-summer heavy rainfall events.
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Manuscript received: 20 October 2015
Manuscript revised: 09 February 2016
Manuscript accepted: 24 February 2016
通讯作者: 陈斌, bchen63@163.com
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    沈阳化工大学材料科学与工程学院 沈阳 110142

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Precipitation Responses to Radiative Effects of Ice Clouds: A Cloud-Resolving Modeling Study of a Pre-Summer Torrential Precipitation Event

  • 1. Key Laboratory of Meteorological Disaster, Ministry of Education/Joint International Research Laboratory of Climate and Environment Change/Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters, Nanjing University of Information Science and Technology, Nanjing, Jiangsu 210044, China
  • 2. Changzhou Meteorological Bureau, Changzhou, Jiangsu 213022, China
  • 3. Inner Mongolia Meteorological Service Center, Hohhot, Inner Mongolia 010051, China

Abstract: The precipitation responses to the radiative effects of ice clouds are investigated through analysis of five-day and horizontally averaged data from 2D cumulus ensemble model experiments of a pre-summer torrential precipitation event. The exclusion of the radiative effects of ice clouds lowered the precipitation rate through a substantial reduction in the decrease of hydrometeors when the radiative effects of water clouds were switched on, whereas it increased the precipitation rate through hydrometeor change from an increase to a decrease when the radiative effects of ice clouds were turned off. The weakened hydrometeor decrease was associated with the enhanced longwave radiative cooling mainly through the decreases in the melting of non-precipitating ice to non-precipitating water. The hydrometeor change from an increase to a decrease corresponded to the strengthened longwave radiative cooling in the upper troposphere through the weakened collection of non-precipitating water by precipitation water.

1. Introduction
  • Solar shortwave radiative heating and infrared longwave radiative cooling are crucial to the thermal balance and vertical stratification during the development of precipitation systems. The radiative difference between cloudy and cloud-free areas leads to a nocturnal precipitation peak through the enhancement of secondary circulation (Gray and Jacobson, 1977). Cloud radiative processes affect the unstable vertical temperature structure associated with upper-tropospheric stratiform clouds (Lilly, 1988) and the destabilization of the environment (Dudhia, 1989). (Tao et al., 1993) conducted cloud-resolving model experiments and found that the longwave radiative cooling enhanced precipitation in both the tropics and midlatitudes. Sui et al. (1997, 1998), (Gao et al., 2009) and (Gao and Li, 2010) showed that the nocturnal temperature decrease induced by the infrared radiative cooling lowers the saturation mixing ratio and increases condensation, which produces the nocturnal precipitation peak.

    Recently, (Shen et al., 2011b) showed that the exclusion of radiation enhances the daily and horizontally averaged precipitation rate during the onset and dissipation phases, but it weakens the average precipitation rate during the peak phase. (Wang et al., 2010b) found that the removal of the radiative effects of ice clouds lowers the average precipitation rate during the onset and development phases, whereas it increases the average precipitation rate during the peak and dissipation phases. (Shen et al., 2011a) revealed that the elimination of the radiative effects of water clouds lowers the average precipitation rate during the peak phase but increases it during the dissipation phase. (Liu et al., 2014) further studied the responses of five-day and horizontally averaged heat, cloud microphysical and surface precipitation budgets to the radiative effects of water clouds. When the radiative effects of ice clouds were switched on, the exclusion of the radiative effects of water clouds lowered the horizontally averaged precipitation rate through decreases in the melting of ice crystals caused by enhanced local atmospheric cooling. When the radiative effects of ice clouds were switched off, the removal of the radiative effects of water clouds increased the average precipitation rate through the strengthened net condensation and the reduction in the melting of ice crystals related to enhanced lower-tropospheric longwave radiative cooling.

    (Wang et al., 2010b) studied the precipitation responses to the radiative effects of ice clouds only when the radiative effects of water clouds were turned on. But what would the precipitation responses be to the radiative effects of ice clouds when the radiative effects of water clouds are switched on and off, respectively? How do the radiative effects of ice clouds affect cloud microphysics and the precipitation rate? The objective of this study is to examine the cloud microphysical and thermal responses to the radiative effects of ice clouds, and this is approached by analyzing model-simulated data averaged over five days and the model domain. The difference in the average precipitation rate caused by the exclusion of the radiative effects of ice clouds is explained by the difference in the vertical profiles of the averaged heat through analysis of the difference in the averaged cloud microphysical budget. The model and experiments are briefly described in section 2. The results are presented in section 3, and summarized in section 4.

2. Model and experiments
  • Before convection started in this torrential rainfall event, the western Pacific subtropical high extended westward and southwesterly winds were intensified. Warm and humid air transported by the southwesterly winds converged with cold air from the north over southern China. A trough moved into southern China to trigger squall-line convection, which led to torrential rainfall with a maximum rain amount of 482.2 mm in Yangjiang, Guangdong, on 6 June 2008. The model was integrated from 0200 LST 3 June to 0200 LST 8 June 2008 in the control experiment (P). The control simulation was validated with available observational data, including rain gauge (Wang et al., 2010b) and temperature and specific humidity data from GDAS (Shen et al., 2011b). The control experiment and associated sensitivity experiments have been used to study various physical processes associated with the development of precipitation systems. For example, the precipitation responses to vertical wind shear and cloud radiative processes (Shen et al., 2011b) and ice (Wang et al., 2010b, Shen et al., 2011c) and water (Shen et al., 2011a, 2012; Liu et al., 2014) clouds, and the improvement of the simulated depositional growth of ice crystals (Shen et al., 2014; Li et al., 2016).

    The model used in this study is the modified 2D cumulus ensemble model (Soong and Ogura, 1980; Soong and Tao, 1980; Tao and Simpson, 1993; Sui et al., 1994, 1998; Li et al., 1999, 2002). The prognostic equations of specific humidity and five cloud species (cloud water, raindrops, cloud ice, snow and graupel) have their source/sink terms from cloud microphysical schemes (Lin et al., 1983; Rutledge and Hobbs, 1983, 1984; Tao et al., 1989; Krueger et al., 1995). The prognostic equation of potential temperature has its source/sink terms from radiation schemes (Chou et al., 1991, 1998; Chou and Suarez, 1994), and the release of latent heat from cloud microphysical schemes. Details on the model, physical package and parameters can be found in (Gao and Li, 2008) and (Li and Gao, 2011). A description of the large-scale forcing, including vertical velocity and zonal wind, can be found in Shen et al. (2011b, Fig. 1). Such a model setup has been used to successfully simulate and study the tropical precipitation rate during TOGA COARE (Gao et al., 2004, 2005; Shen et al., 2010; Li and Gao, 2011, 2013, 2014) and for severe tropical storm Bilis in 2006 (Wang et al., 2009a, b, 2010a).

    Three sensitivity experiments (PNWR, PNIR and PNCR) were conducted, identical to P except that water, ice and total (both water and ice) hydrometeor mixing ratios were set to zero when radiation was computed. The difference between PNIR and P (i.e., PNIR-P) is analyzed to study the precipitation responses to the radiative effects of ice clouds when the radiative effects of water clouds are switched on. The difference between PNCR and PNWR (i.e., PNCR-PNWR) is analyzed to study the precipitation responses to the radiative effects of ice clouds when the radiative effects of water clouds are turned off.

3. Results
  • The exclusion of the radiative effects of ice clouds lowered the five-day and horizontally averaged pre-summer precipitation rate from P to PNIR when the radiative effects of water clouds were switched on, but it increased the average precipitation rate from PNWR to PNCR when the radiative effects of water clouds were turned off (Table 1). To examine the cloud processes responsible for the surface precipitation rate (P S), the cloud budget is analyzed. The cloud budget is expressed by \begin{equation} P_{\rm S}=Q_{\rm NC}+Q_{\rm CM} , (1)\end{equation} where Q NC is the net condensation and Q CM is hydrometeor change due to cyclic lateral boundaries in the model.

    Figure 1.  Vertical profiles of the differences between (a) PNIR and P (PNIR$-$P) and (b) PNCR and PNWR (PNCR$-$PNWR) for local temperature change (black), condensational heating (red), convergence of vertical heat flux (green), vertical temperature advection (blue), and radiation (orange), averaged over 5 days and the model domain. Units: $^\circ$C d$^-1$.

    When the radiative effects of water clouds were switched on, the reduction in the average precipitation rate from P to PNIR caused by the exclusion of the radiative effects of ice clouds was associated with the slowdown in the averaged decrease of hydrometeors from P to PNIR (Table 1). When the radiative effects of water clouds were switched off, the increase in the average precipitation rate from PNWR to PNCR resulting from the removal of the radiative effects of ice clouds corresponded to the average hydrometeor change from an increase in PNWR to a decrease in PNCR. The averaged hydrometeor change (Q CM) can be further broken down into the averaged hydrometeor change in cloud water (Q CMC), raindrops (Q CMR), cloud ice (Q CMI), snow (Q CMS) and graupel (Q CMG): \begin{equation} Q_{\rm CM}=Q_{\rm CMC}+Q_{\rm CMR}+Q_{\rm CMI}+Q_{\rm CMS}+Q_{\rm CMG} . (2)\end{equation}

    When the radiative effects of water clouds were switched on, the reduction in the averaged decrease of hydrometeors from P to PNIR caused by the elimination of the radiative effects of ice clouds resulted from the increase in the averaged cloud-water gain, the averaged cloud-ice change from a loss in P to a gain in PNIR, and the reduction in the averaged graupel loss (Fig. 1). The increase in the averaged cloud-water gain from P to PNIR was associated with the slowdown in the collection of cloud water by rain (P RACW) from P to PNIR (Table 2a). The averaged cloud-ice change from a loss in P to a gain in PNIR was related to the decrease in the averaged melting of cloud ice to cloud water (P IMLT) (Table 2b). The reduction in the averaged graupel loss corresponded to the enhancement in the averaged accretion of cloud water by graupel (P GACW) from P to PNIR (Table 2c).

    Thus, the decrease in averaged hydrometeors from P to PNIR was associated with the slowdown in the averaged collection of cloud water by rain and the averaged P IMLT, as well as the enhancement in the averaged P GACW, which may be related to the decrease in air temperature.

    To demonstrate the relationship between the reduced hydrometeor decrease and falling temperature, the averaged heat budget is analyzed. Following (Li et al., 1999), the horizontally averaged heat budget can be expressed by \begin{equation} \label{eq1} \dfrac{\partial\overline{T}}{\partial t}=\dfrac{\overline{Q} _{\rm cn}}{c_p}+\dfrac{\overline{Q}_{\rm R}}{c_p}-\dfrac{\pi}{\overline{\rho}} \dfrac{\partial(\overline{\rho}\overline{w'\theta'})}{\partial z}-\pi\overline{w}_{\rm o}\dfrac{\partial\overline{\theta}}{\partial z}- \overline{u}_{\rm o}\dfrac{\partial\overline{T}_{\rm o}}{\partial x} . (3)\end{equation} where T and θ are the air temperature and potential temperature, respectively; u and w are the zonal wind and vertical velocity, respectively; ρ is air density that is the function of height only; π=(p/p0)\kappa with \(\kappa=R/c_p\); R is the gas constant; p is pressure and p0=1000 hPa; cp is the specific heat of dry air at constant pressure; Q cn is the net latent heat release through phase changes among different cloud species; Q R is the radiative heating rate due to the convergence of net flux of solar and infrared radiative fluxes; over bar is area mean; subscript "o" denotes imposed large-scale forcing.

    The strengthened averaged local atmospheric cooling from P to PNIR (Fig. 1a) was mainly associated with the enhanced averaged longwave radiative coolingcaused by the exclusion of the radiative effects of ice clouds (Fig. 2a). The weakened averaged heat divergence corresponded to the enhanced averaged longwave radiative cooling. The release in the averaged latent heat was weakened above 7 km, whereas it was generally enhanced below 7 km.

    When the radiative effects of water clouds were turned off, the averaged hydrometeors changed from an increase in PNWR to a decrease in PNCR, caused by the removal of the radiative effects of ice clouds, was associated with the averaged raindrop change from an increase in PNWR to a decrease in PNCR (Table 1). The averaged raindrop change from an increase in PNWR to a decrease in PNCR corresponded to the reduction in the averaged P RACW (Table 3), which may have been caused by the decrease in air temperature. This can be demonstrated by the vertical profiles of the differences in the averaged heat budgets between PNCR and PNWR in Fig. 1b, where the enhanced averaged local atmospheric cooling occurs mainly in the upper troposphere. The intensified averaged local atmospheric cooling from PNWR to PNCR corresponded to the strengthened averaged longwave radiative cooling (Fig. 2b). The enhanced averaged local atmospheric cooling was stronger in the upper troposphere than in the mid and lower troposphere, though the averaged longwave radiative cooling was weaker in the upper troposphere than in the mid and lower troposphere. In the mid and lower troposphere, the enhanced averaged longwave radiative cooling was largely cancelled out by the increases in the release of the averaged latent heat and the convergence of vertical heat flux.

    Figure 2.  Vertical profiles of the differences between (a) PNIR and P (PNIR$-$P) and (b) PNCR and PNWR (PNCR$-$PNWR) for radiation (orange) and its components of solar radiative heating (red) and infrared radiative cooling (blue), averaged over five days and the model domain. Units: $^\circ$C d$^-1$.

4. Summary
  • The responses of pre-summer precipitation to the radiative effects of ice clouds were examined using a 2D cumulus ensemble model in this study. The cloud budgets and vertical profiles of heat budgets were analyzed to study the linkage between the precipitation rate and radiation using the model simulation data averaged over five days and the model domain. The major results can be summarized as follows:

    When the radiative effects of water clouds were switched on, the removal of the radiative effects of ice clouds lowered the precipitation rate through a suppression of the hydrometeor decrease. The weakened hydrometeor decrease was associated with the decreases in the averaged P RACW and the averaged P IMLT, as well as the enhancement in the averaged P GACW, which corresponded to the strengthened averaged local atmospheric cooling associated with the enhanced averaged longwave radiative cooling.

    When the radiative effects of water clouds were turned off, the exclusion of the radiative effects of water clouds increased the precipitation rate through hydrometeor change from an increase to a decrease. The hydrometeor change was associated with the reduction in the averaged P RACW caused by the strengthened averaged longwave radiative cooling in the upper troposphere.

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