## 2011 Vol. 28, No. 5

Display Method:
2011, 28(5): 985-996. doi: 10.1007/s00376-010-0045-9
Abstract:
The ozone budget inside the middle stratospheric polar vortex (24--36 km) during the 2002--2003 Arctic winter is studied by analyzing Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) satellite data. A comprehensive global chemical transport model (Model for Ozone and Related Chemical Tracers, MOZART-3) is used to analyze the observed variation in polar vortex ozone during the stratospheric sudden warming (SSW) events. Both MIPAS measurement and MOZART-3 calculation show that a pronounced increase (26--28 DU) in the polar vortex ozone due to the SSW events. Due to the weakening of the polar vortex, the exchange of ozone mass across the edge of the polar vortex increases substantially and amounts to about 3.0107 kg according to MOZART-3 calculation. The enhanced downward transport offsets about 80% of polar vortex ozone mass increase by horizontal transport. A passive ozone'' experiment shows that only ～55% of the vertical ozone mass flux in February and March can be attributed to the variation in vertical transport. It is also shown that the enhanced downward ozone above ～32 km should be attributed to the springtime photochemical ozone production. Due to the increase of air temperature, the NOx reaction rate increases by 40%--80% during the SSW events. As a result, NOx catalytic cycle causes another 44% decrease in polar vortex ozone compared to the net ozone changes due to dynamical transport. It is also shown that the largest change in polar vortex ozone is due to horizontal advection by planetary waves in January 2003.
2011, 28(5): 997-1010. doi: 10.1007/s00376-011-0120-x
Abstract:
This study investigated the impact of different verification-area designs on the sensitive areas identified using the conditional nonlinear optimal perturbation (CNOP) method for tropical cyclone targeted observations. The sensitive areas identified using the first singular vector (FSV) method, which is the linear approximation of CNOP, were also investigated for comparison. By analyzing the validity of the sensitive areas, the proper design of a verification area was developed. Tropical cyclone Rananim, which occurred in August 2004 in the northwest Pacific Ocean, was studied. Two sets of verification areas were designed; one changed position, and the other changed both size and position. The CNOP and its identified sensitive areas were found to be less sensitive to small variations of the verification areas than those of the FSV and its sensitive areas. With larger variations of the verification area, the CNOP and the FSV as well as their identified sensitive areas changed substantially. In terms of reducing forecast errors in the verification area, the CNOP-identified sensitive areas were more beneficial than those identified using FSV. The design of the verification area is important for cyclone prediction. The verification area should be designed with a proper size according to the possible locations of the cyclone obtained from the ensemble forecast results. In addition, the development trend of the cyclone analyzed from its dynamic mechanisms was another reference. When the general position of the verification area was determined, a small variation in size or position had little influence on the results of CNOP.
2011, 28(5): 1011-1022. doi: 10.1007/s00376-010-9211-3
Abstract:
Using radiosonde temperatures of 92 selected stations in China, the uncertainties in homogenization processes caused by different reference series, including nighttime temperature, the NCEP (National Centers for Environmental Prediction) and ERA-40 (European Centre for Medium-Range Weather Forecasts) forecasting background, are examined via a two-phase regression approach. Although the results showed limited consistency in the temporal and spatial distribution of identified break points (BPs) in the context of metadata events of instrument model change and correction method, significant uncertainties still existed in BP identification, adjustment, and impact on the estimated trend. Reanalysis reference series generally led to more BP identification in homogenization. However, those differences were parts of global climatic shifts, which may have confused the BP calculations. Discontinuities also existed in the reanalysis series due to changes in the satellite input. The adjustment values deduced from the reanalysis series ranged widely and were larger than those from the nighttime series and, therefore, impacted the estimated temperature trend.
2011, 28(5): 1023-1029. doi: 10.1007/s00376-010-0080-6
Abstract:
Based on the daily maximum surface air temperature records from an updated homogenized temperature dataset for 549 Chinese stations during 1960--2008, we reveal that there is an abrupt increase in the number of days with high temperature extremes (HTEs, an HTE day is defined when the maximum temperature exceeds the 95th percentile of the daily maximum temperature distributions) across China in the mid-1990s. Before this regime shift, the average number of HTE days is about 2.9 d yr-1 during the period from the 1970s to the early 1990s, while it rocketed to about 7.2 d yr-1 after the mid-1990s. We show that the significant HTE day increase occurs uniformly across the whole of China after the regime shift. The observational evidence raises the possibility that this change in HTE days is associated with global-scale warming as well as circulation adjustment. Possible causes for the abrupt change in the HTE days are discussed, and the circulation adjustment is suggested to play a crucial role in the increase in HTE days in this region.
2011, 28(5): 1030-1038. doi: 10.1007/s00376-010-0150-9
Abstract:
Annual precipitation, evaporation, and calculated accumulation from reanalysis model outputs have been investigated for the Greenland Ice Sheet (GrIS), based on the common period of 1989--2001. The ERA-40 and ERA-interim reanalysis data showed better agreement with observations than do NCEP-1 and NCEP-2 reanalyses. Further, ERA-interim showed the closest spatial distribution of accumulation to the observation. Concerning temporal variations, ERA-interim showed the best correlation with precipitation observations at five synoptic stations, and the best correlation with in itu measurements of accumulation at nine ice core sites. The mean annual precipitation averaged over the whole GrIS from ERA-interim (363 mm yr-1) and mean annual accumulation (319 mm yr-1) are very close to the observations. The validation of accumulation calculated from reanalysis data against ice-core measurements suggests that further improvements to reanalysis models are needed.
2011, 28(5): 1039-1048. doi: 10.1007/s00376-010-0093-1
[Abstract](557) [PDF 541KB](1004)
Abstract:
The climatological characteristics and interdecadal variability of the water vapor transport and budget over the Yellow River-Huaihe River valleys (YH1) and the Yangtze River-Huaihe River valleys (YH2) of East China were investigated in this study, using the NCEP/NCAR monthly mean reanalysis datasets from 1979 to 2009. Changes in the water vapor transport pattern occurred during the late 1990s over YH1 (YH2) that corresponded with the recent interdecadal changes in the eastern China summer precipitation pattern. The net moisture influx in the YH1 increased and the net moisture influx in the YH2 decreased during 2000--2009 in comparison to 1979--1999. Detailed features in the moisture flux and transport changes across the four boundaries were explored. The altered water vapor transport over the two domains can be principally attributed to the additive effects of the changes in the confluent southwesterly moisture flow by the Indian summer monsoon and East Asian summer monsoon (related with the eastward recession of the western Pacific subtropical high). The altered water vapor transport over YH1 was also partly caused by the weakened midlatitude westerlies.
2011, 28(5): 1049-1055. doi: 10.1007/s00376-011-0122-8
Abstract:
A statistical dynamic model for forecasting Chinese landfall of tropical cyclones (CLTCs) was developed based on the empirical relationship between the observed CLTC variability and the hindcast atmospheric circulations from the Pusan National University coupled general circulation model (PNU-CGCM). In the last 31 years, CLTCs have shown strong year-to-year variability, with a maximum frequency in 1994 and a minimum frequency in 1987. Such features were well forecasted by the model. A cross-validation test showed that the correlation between the observed index and the forecasted CLTC index was high, with a coefficient of 0.71. The relative error percentage (16.3%) and root-mean-square error (1.07) were low. Therefore the coupled model performs well in terms of forecasting CLTCs; the model has potential for dynamic forecasting of landfall of tropical cyclones.
2011, 28(5): 1056-1066. doi: 10.1007/s00376-010-0050-z
Abstract:
In this study, a new parameter optimization method was used to investigate the expansion of conditional nonlinear optimal perturbation (CNOP) in a land surface model (LSM) using long-term enhanced field observations at Tongyu station in Jilin Province, China, combined with a sophisticated LSM (common land model, CoLM). Tongyu station is a reference site of the international Coordinated Energy and Water Cycle Observations Project (CEOP) that has studied semiarid regions that have undergone desertification, salination, and degradation since late 1960s. In this study, three key land-surface parameters, namely, soil color, proportion of sand or clay in soil, and leaf-area index were chosen as parameters to be optimized. Our study comprised three experiments: First, a single-parameter optimization was performed, while the second and third experiments performed triple- and six-parameter optimizations, respectively. Notable improvements in simulating sensible heat flux (SH), latent heat flux (LH), soil temperature (TS), and moisture (MS) at shallow layers were achieved using the optimized parameters. The multiple-parameter optimization experiments performed better than the single-parameter experminent. All results demonstrate that the CNOP method can be used to optimize expanded parameters in an LSM. Moreover, clear mathematical meaning, simple design structure, and rapid computability give this method great potential for further application to parameter optimization in LSMs.
2011, 28(5): 1067-1076. doi: 10.1007/s00376-011-0113-9
Abstract:
A genetic algorithm was used to optimize the parameters of the two-dimensional Storm Surge/Tide Operational Model (STORM) to improve sea level predictions. The genetic algorithm was applied to nine typhoons that affected the Korean Peninsula during 2005--2007. The following model parameters were used: the bottom drag coefficient, the background horizontal diffusivity, Smagorinski's horizontal viscosity, and the sea level pressure scaling. Generally, the simulation results using the optimized, mean, and median parameter values improved sea level predictions. The four estimated parameters improved the sea level prediction by 76% and 54% in the bias and root mean square error for Typhoon Kalmaegi (0807) in 2008, respectively. One-month simulations of February and August 2008 were also improved using the estimated parameters. This study demonstrates that parameter optimization on STORM can improve sea level prediction.
2011, 28(5): 1077-1098. doi: 10.1007/s00376-010-0039-7
Abstract:
This study investigates the capability of the dynamic downscaling method (DDM) in an East Asian climate study for June 1998 using the fifth-generation Pennsylvania State University--National Center for Atmospheric Research non-hydrostatic Mesoscale Model (MM5). Sensitivity experiments show that MM5 results at upper atmospheric levels cannot match reanalyses data, but the results show consistent improvement in simulating moisture transport at low levels. The downscaling ability for precipitation is regionally dependent. During the monsoon season over the Yangtze River basin and the pre-monsoon season over North China, the DDM cannot match observed precipitation. Over Northwest China and the Tibetan Plateau (TP), where there is high topography, the DDM shows better performance than reanalyses. Simulated monsoon evolution processes over East Asia, however, are much closer to observational data than reanalyses. The convection scheme has a substantial impact on extreme rainfall over the Yangtze River basin and the pre-monsoon over North China, but only a marginal contribution for Northwest China and the TP. Land surface parameterizations affect the locations and pattern of rainfall bands. The 10-day re-initialization in this study shows some improvement in simulated precipitation over some sub-regions but with no obvious improvement in circulation. The setting of the location of lateral boundaries (LLB) westward improves performance of the DDM. Including the entire TP in the western model domain improves the DDM performance in simulating precipitation in most sub-regions. In addition, a seasonal simulation demonstrates that the DDM can also obtain consistent results, as in the June case, even when another two months consist of no strong climate/weather events.
2011, 28(5): 1099-1108. doi: 10.1007/s00376-010-0031-2
Abstract:
Both water vapor and heat processes play key roles in producing surface rainfall. While the water vapor effects of sea surface temperature and cloud radiative and microphysical processes on surface rainfall have been investigated in previous studies, the thermal effects on rainfall are analyzed in this study using a series of two-dimensional equilibrium cloud-resolving model experiments forced by zonally-uniform, constant, large-scale zonal wind and zero large-scale vertical velocity. The analysis of thermally-related surface rainfall budget reveals that the model domain mean surface rain rate is primarily associated with the mean infrared cooling rate. Convective rainfall and transport of hydrometeor concentration from convective regions to raining stratiform regions corresponds to the heat divergence over convective regions, whereas stratiform rainfall corresponds to the transport of hydrometeor concentration from convective regions and heat divergence over raining stratiform regions. The heat divergence over convective regions is mainly balanced by the heat convergence over rainfall-free regions, which is, in turn, offset by the radiative cooling over rainfall-free regions. The sensitivity experiments of rainfall to the effects of sea surface temperature and cloud radiative and microphysical processes show that the sea surface temperature and cloud processes affect convective rainfall through the changes in infrared cooling rate over rainfall-free regions and transport rate of heat from convective regions to rainfall-free regions.
2011, 28(5): 1109-1117. doi: 10.1007/s00376-010-0129-6
Abstract:
Global ocean temperature has been rising since the late 1970s at a speed unprecedented during the past century of recordkeeping. This accelerated warming has profound impacts not only on the marine ecosystem and oceanic carbon uptake but also on the global water cycle and climate. During this rapid warming period, the tropical Pacific displays a pronounced La Nina-like trend, characterized by an intensification of west--east SST gradient and of atmospheric zonal overturning circulation, namely the Walker circulation. This La Nina-like trend differs from the El Nino-like trend in warm climate projected by most climate models, and cannot be explained by responses of the global water cycle to warm climate. The results of this study indicate that the intensification of the zonal SST gradient and the Walker circulation are associated with recent strengthening of the upper-ocean meridional overturning circulation.
2011, 28(5): 1118-1128. doi: 10.1007/s00376-010-0128-7
Abstract:
Changes of the frequency of precipitation extremes (the number of days with daily precipitation exceeding the 90th percentile of a daily climatology, referred to as R90N) in summer (June--August) over the mid-lower reaches of the Yangtze River are analyzed based on daily observations during 1961--2007. The first singular value decomposition (SVD) mode of R90N is linked to an ENSO-like mode of the sea surface temperature anomalies (SSTA) in the previous winter. Responses of different grades of precipitation events to the climatic mode are compared. It is notable that the frequency of summer precipitation extremes is significantly related with the SSTA in the Pacific, while those of light and moderate precipitation are not. It is suggested that the previously well-recognized impact of ENSO on summer rainfall along the Yangtze River is essentially due to a response in summer precipitation extremes in the region, in association with the East Asia-Pacific (EAP) teleconnection pattern. A negative relationship is found between the East Asian Summer Monsoon (EASM) and precipitation extremes over the mid-lower reaches of the Yangtze River. In contrast, light rainfall processes are independent from the SST and EASM variations.
2011, 28(5): 1129-1142. doi: 10.1007/s00376-010-0131-z
Abstract:
A terrestrial biogeochemical model (CASACNP) was coupled to a land surface model (the Common Land Model, CoLM) to simulate the dynamics of carbon substrate in soil and its limitation on soil respiration. The combined model, CoLM{\_}CASACNP, was able to predict long-term carbon sources and sinks that CoLM alone could not. The coupled model was tested using measurements of belowground respiration and surface fluxes from two forest ecosystems. The combined model simulated reasonably well the diurnal and seasonal variations of net ecosystem carbon exchange, as well as seasonal variation in the soil respiration rate of both the forest sites chosen for this study. However, the agreement between model simulations and actual measurements was poorer under dry conditions. The model should be tested against more measurements before being applied globally to investigate the feedbacks between the carbon cycle and climate change.
2011, 28(5): 1143-1158. doi: 10.1007/s00376-010-0060-x
Abstract:
A real case study for the transformation of Tropical Storm (TS) Haima (2004) into an extratropical cyclone (EC) is carried out numerically since, after landfall, Haima (2004) (as an EC) brought severe weather to a large area (from the south to the north) in China during 13--16 September 2004. With the linear diagnostic model (derived in a previous study) for the tangentially-averaged radial-vertical circulation within vortices moving on the spherical Earth, Haima's (2004) life cycle is reconstructed noticeably well. Therefore, the major contributor could be identified confidently for Haima's (2004) extratropical transition based on the diagnostic model outputs. The quantitative comparison shows that up to a 90% contribution to the inner-region updraft and a 55% contribution to the upper-layer outflow come from latent heating during Haima's (2004) TS stage. Up to a 90% contribution to the inner-region updraft and nearly a 100% contribution to the upper-layer outflow come from the upper-layer eddy angular momentum advection (EAMA) during Haima's (2004) EC stage. Representing the asymmetric structure of the storm, the predominantly positive contribution of the upper-layer EAMA to Haima's (2004) transformation is closely associated with the S-shaped westerlies in the upper layer with two jets. One jet in the cyclonic-curvature area carries cyclonic angular momentum into the storm, and the other jet in the anticyclonic-curvature area carries anticyclonic angular momentum out of the storm. Consequently, the newly-increased cyclonic tangential wind is deflected by the Coriolis force to the right to form the upper-layer outflow accompanied by the central-area rising motion, leading to Haima's (2004) extratropical transition after its landfall.
2011, 28(5): 1159-1176. doi: 10.1007/s00376-010-0170-5
Abstract:
An analysis was conducted on the evolutional process of a mesoscale convective vortex (MCV) and associated heavy rainfall in the Dabie Mountain area on 21--22 June 2008, as well as their structural characteristics in different stages, by using the mesoscale reanalysis data with 3 km and 1 h resolution generated by the Local Analysis and Prediction System (LAPS) in the Southern China Heavy Rainfall Experiment. The results showed that the latent heat released by convection in the midtroposphere was the main energy source for the development of a low-level vortex. There was a positive feedback interaction between the convection and the vortex, and the evolution of the MCV was closely related to the strength of the positive interaction. The most typical characteristics of the thermal structure in different stages were that, there was a relatively thin diabatic heating layer in the midtroposphere in the formative stage; the thickness of diabatic heating layer significantly increased in the mature stage; and it almost disappeared in the decay stage. The characteristics of the dynamic structure were that, in the formative stage, there was no anticyclonic circulation at the high level; in the mature stage, an anticyclonic circulation with strong divergence was formed at the high level; in the decay stage, the anticyclonic circulation was damaged and the high-level atmosphere was in a disordered state of turbulence. Finally, the structural schematics of the MCV in the formative and mature stage were established respectively.
2011, 28(5): 1177-1183. doi: 10.1007/s00376-011-0020-0
Abstract:
Based on hourly precipitation data in eastern China in the warm season during 1961--2000, spatial distributions of frequency for 20 mm h-1 and 50 mm h-1 precipitation were analyzed, and the criteria of short-duration rainfall events and severe rainfall events are discussed. Furthermore, the percentile method was used to define local hourly extreme precipitation; based on this, diurnal variations and trends in extreme precipitation were further studied. The results of this study show that, over Yunnan, South China, North China, and Northeast China, the most frequent extreme precipitation events occur most frequently in late afternoon and/or early evening. In the Guizhou Plateau and the Sichuan Basin, the maximum frequency of extreme precipitation events occurs in the late night and/or early morning. And in the western Sichuan Plateau, the maximum frequency occurs in the middle of the night. The frequency of extreme precipitation (based on hourly rainfall measurements) has increased in most parts of eastern China, especially in Northeast China and the middle and lower reaches of the Yangtze River, but precipitation has decreased significantly in North China in the past 50 years. In addition, stations in the Guizhou Plateau and the middle and lower reaches of the Yangtze River exhibit significant increasing trends in hourly precipitation extremes during the nighttime more than during the daytime.
2011, 28(5): 1184-1200. doi: 10.1007/s00376-010-0087-z
Abstract:
The Chinese Academy of Meteorological Sciences (CAMS) two-moment bulk microphysics scheme was adopted in this study to investigate the representation of cloud and precipitation processes under different environmental conditions. The scheme predicts the mixing ratio of water vapor as well as the mixing ratios and number concentrations of cloud droplets, rain, ice, snow, and graupel. A new parameterization approach to simulate heterogeneous droplet activation was developed in this scheme. Furthermore, the improved CAMS scheme was coupled with the Weather Research and Forecasting model (WRF v3.1), which made it possible to simulate the microphysics of clouds and precipitation as well as the cloud--aerosol interactions in selected atmospheric condition. The rain event occurring on 27--28 December 2008 in eastern China was simulated using the CAMS scheme and three sophisticated microphysics schemes in the WRF model. Results showed that the simulated 36-h accumulated precipitations were generally agreed with observation data, and the CAMS scheme performed well in the southern area of the nested domain. The radar reflectivity, the averaged precipitation intensity, and the hydrometeor mixing ratios simulated by the CAMS scheme were generally consistent with those from other microphysics schemes. The hydrometeor number concentrations simulated by the CAMS scheme were also close to the experiential values in stratus clouds. The model results suggest that the CAMS scheme performs reasonably well in describing the microphysics of clouds and precipitation in the mesoscale WRF model.
2011, 28(5): 1201-1214. doi: 10.1007/s00376-011-0127-3
Abstract:
In this study, monthly NCEP/NCAR reanalysis data and NOAA ERSST as well as observed precipitation data from 160 stations in China were used to investigate coupled modes affecting the rainfall over China and sea surface temperature (SST) in the Pacific during boreal summertime based on singular value decomposition (SVD) method. The SVD analysis revealed three remarkable coupled modes: rainfall over North China associated with an ENSO-like SST pattern (ENSO--NC), rainfall over the Yangtze River valley associated with SST anomalies in the western tropical Pacific (WTP--YRV), and rainfall over the Yellow River loop valley associated with tropical Pacific meridional mode-like SST pattern (TPMM--YRLV). These coupled SVD modes appear robust and closely correlated with the single field. Furthermore, the covariabilities among of the three coupled modes have different characteristics at the decadal time scale. In addition, the possible atmospheric teleconnections of the coupled rainfall and SST modes were discussed. For the ENSO--NC mode, anomalous low-pressure and high-pressure over the Asian continent induces moisture divergence over North China and reduces summer rainfall there. For the WTP--YRV mode, East Asia--Pacific teleconnection induces moisture convergence over the Yangtze River valley and enhances the summer rainfall there. The TPMM SST and the summer rainfall anomalies over the YRVL are linked by a circumglobal, wave-train-like, atmospheric teleconnection.
2011, 28(5): 1215-1232. doi: 10.1007/s00376-010-0054-8
Abstract:
The A. M. Obukhov Institute of Atmospheric Physics, Russian Academy of Sciences (IAP RAS) climate model (CM) of intermediate complexity is extended by a spatially explicit terrestrial carbon cycle module. Numerical experiments with the IAP RAS CM are performed forced by the reconstructions of anthropogenic and natural forcings for the 16th to the 20th centuries and by combined SRES (Special Report on Emission Scenarios) A2--LUH (Land Use Harmonization) anthropogenic scenarios for the 21st century. Hereby, the impact of uncertainty in land--use scenarios on results of simulations with a coupled climate--carbon cycle model is tested. The simulations of the model realistically reproduced historical changes in carbon cycle characteristics. In the IAP RAS CM, climate warming reproduced in the 20th and 21st centuries enhanced terrestrial net primary production but terrestrial carbon uptake was suppressed due to an overcompensating increase in soil respiration. Around year 2100, the simulations the model forced by different land use scenarios diverged markedly, by about 70 Pg (C) in terms of biomass and soil carbon stock but they differed only by about 10 ppmv in terms of atmospheric carbon dioxide content.