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2014 Vol. 31, No. 4

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A Decadal Shift of Summer Surface Air Temperature over Northeast Asia around the Mid-1990s
CHEN Wei, and LU Riyu
2014, 31(4): 735-742. doi: 10.1007/s00376-013-3154-4
This study identifies a decadal shift of summer surface air temperature (SAT) over Northeast Asia, including southeastern parts of Russia, Mongolia and northern China, around the mid-1990s. The results suggest that the SAT over the Northeast Asia experienced a significant warming after 1994 relative to that before 1993. This decadal shift also extends to northern China, and leads to a warmer summer over Northeast China and North China after the mid-1990s. The decadal warming over Northeast Asia is found to concur with the enhancement of South China rainfall around the mid-1990s. On the one hand, both the Northeast Asian SAT and South China rainfall exhibit this mid-1990s decadal shift only in summer, but not in other seasons. On the other hand, both the Northeast Asian SAT and South China rainfall exhibit this mid-1990s decadal shift not only in the summer seasonal mean, but also in each month of summer (June, July and August). Furthermore, the decadal warming is found to result from an anticyclonic anomaly over Northeast Asia, which can be interpreted as the response to the increased precipitation over South China, according to previous numerical results. Thus, we conclude that the warming shift of summer Northeast Asian SAT around the mid-1990s was a remote response to the increased precipitation over South China.
Model Simulations of Mesoscale Eddies and Deep Convection in the Labrador Sea
2014, 31(4): 743-754. doi: 10.1007/s00376-013-3107-y
Deep convection in the Labrador Sea is confined within a small region in the southwest part of the basin. The strength of deep convection in this region is related to the local atmospheric and ocean characteristics, which favor processes of deep convection preconditioning and intense air-sea exchange during the winter season. In this study, we explored the effect of eddy-induced flux transport on the stratification of the Labrador Sea and the properties of deep convection. Simulations from an eddy-resolving ocean model are presented for the Labrador Sea. The general circulation was well simulated by the model, including the seasonal cycle of the deep Labrador Current. The simulated distribution of the surface eddy kinetic energy was also close to that derived from Topex-Poseidon satellite altimeter data, but with smaller magnitude. The energy transfer diagnostics indicated that Irminger rings are generated by both baroclinic and barotropic processes; however, when they propagate into the interior basin, the barotropic process also disperses them by converting the eddy energy to the mean flow. In contrast to eddy-permitting simulations, deep convection in the Labrador Sea was better represented in the eddy-resolving model regarding their lateral position. Further analysis indicated that the improvement might be due to the lateral eddy flux associated with the resolved Irminger rings in the eddy-resolving model, which contributes to a realistic position of the isopycnal dome in the Labrador Sea and correspondingly a realistic site of deep convection.
The Summer Snow Cover Anomaly over the Tibetan Plateau and Its Association with Simultaneous Precipitation over the Mei-yu-Baiu region
LIU Ge, WU Renguang, ZHANG Yuanzhi, and NAN Sulan
2014, 31(4): 755-764. doi: 10.1007/s00376-013-3183-z
The summer snow anomalies over the Tibetan Plateau (TP) and their effects on climate variability are often overlooked, possibly due to the fact that some datasets cannot properly capture summer snow cover over high terrain. The satellite-derived Equal-Area Scalable Earth grid (EASE-grid) dataset shows that snow still exists in summer in the western part and along the southern flank of the TP. Analysis demonstrates that the summer snow cover area proportion (SCAP) over the TP has a significant positive correlation with simultaneous precipitation over the mei-yu-baiu (MB) region on the interannual time scale. The close relationship between the summer SCAP and summer precipitation over the MB region could not be simply considered as a simultaneous response to the Silk Road pattern and the SST anomalies in the tropical Indian Ocean and tropical central-eastern Pacific. The SCAP anomaly has an independent effect and may directly modulate the land surface heating and, consequently, vertical motion over the western TP, and concurrently induce anomalous vertical motion over the North Indian Ocean via a meridional vertical circulation. Through a zonal vertical circulation over the tropics and a Kelvin wave-type response, anomalous vertical motion over the North Indian Ocean may result in an anomalous high over the western North Pacific and modulate the convective activity in the western Pacific warm pool, which stimulates the East Asia-Pacific (EAP) pattern and eventually affects summer precipitation over the MB region.
Regional-scale Surface Air Temperature and East Asian Summer Monsoon Changes during the Last Millennium Simulated by the FGOALS-gl Climate System Model
MAN Wenmin, and ZHOU Tianjun
2014, 31(4): 765-778. doi: 10.1007/s00376-013-3123-y
The spatial patterns and regional-scale surface air temperature (SAT) changes during the last millennium, as well as the variability of the East Asian summer monsoon (EASM) were simulated with a low-resolution version of Flexible Global Ocean-Atmosphere-Land-Sea-ice (FGOALS-gl) model. The model was driven by both natural and anthropogenic forcing agents. Major features of the simulated past millennial Northern Hemisphere (NH) mean SAT variations, including the Medieval Climate Anomaly (MCA), the Little Ice Age (LIA) and the 20th Century Warming (20CW), were generally consistent with the reconstructions. The simulated MCA showed a global cooling pattern with reference to the 1961-90 mean conditions, indicating the 20CW to be unprecedented over the last millennium in the simulation. The LIA was characterized by pronounced coldness over the continental extratropical NH in both the reconstruction and the simulation. The simulated global mean SAT difference between the MCA and LIA was 0.14C, with enhanced warming over high-latitude NH continental regions. Consistencies between the simulation and the reconstruction on regional scales were lower than those on hemispheric scales. The major features agreed well between the simulated and reconstructed SAT variations over the Chinese domain, despite some inconsistency in details among different reconstructions. The EASM circulation during the MCA was stronger than that during the LIA The corresponding rainfall anomalies exhibited excessive rainfall in the north but deficient rainfall in the south. Both the zonal and meridional thermal contrast were enhanced during the MCA. This temperature anomaly pattern favored a stronger monsoon circulation.
Predictability of Winter Rainfall in South China as Demonstrated by the Coupled Models of ENSEMBLES
Se-Hwan YANG, LI Chaofan, and LU Riyu
2014, 31(4): 779-786. doi: 10.1007/s00376-013-3172-2
Winter rainfall over South China shows strong interannual variability, which accounts for about half of the total winter rainfall over South China. This study investigated the predictability of winter (December-January-February; DJF) rainfall over South China using the retrospective forecasts of five state-of-the-art coupled models included in the ENSEMBLES project for the period 1961-2006. It was found that the ENSEMBLES models predicted the interannual variation of rainfall over South China well, with the correlation coefficient between the observed/station-averaged rainfall and predicted/area-averaged rainfall being 0.46. In particular, above-normal South China rainfall was better predicted, and the correlation coefficient between the predicted and observed anomalies was 0.64 for these wetter winters. In addition, the models captured well the main features of SST and atmospheric circulation anomalies related to South China rainfall variation in the observation. It was further found that South China rainfall, when predicted according to predicted DJF Nio 3.4 index and the ENSO-South China rainfall relationship, shows a prediction skill almost as high as that directly predicted, indicating that ENSO is the source for the predictability of South China rainfall.
Effects of NOx and VOCs from Five Emission Sources on Summer Surface O3 over the Beijing-Tianjin-Hebei Region
QU Yu, AN Junling, LI Jian, CHEN Yong, LI Ying, LIU Xingang, and HU Min
2014, 31(4): 787-800. doi: 10.1007/s00376-013-3132-x
The impacts of emissions from industry, power plant, transportation, residential, and biogenic sources on daily maximum surface ozone (O3DM) over the Beijing-Tianjin-Hebei (BTH) region in North China in the summer of 2007 were examined in a modeling study. The modeling system consisted of the Weather Research and Forecasting (WRF) model and the photochemical dispersion model, CAMx. The factor separation technique (FST) was used to quantify the effect of individual emission source types and the synergistic interactions among two or more types. Additionally, the effectiveness of emission reduction scenarios was explored. The industry, power plant, and transportation emission source types were found to be the most important in terms of their individual effects on O3DM. The key contributor to high surface O3 was power plant emissions, with a peak individual effect of 40 ppbv in the southwestern BTH area. The individual effect from the biogenic emission category was quite low. The synergistic effects from the combinations of each pair of anthropogenic emission types suppressed O3 formation, while the synergistic effects for combinations of three were favorable for O3 formation when the industrial and power plant emission source types coexisted. The quadruple synergistic effects were positive only with the combination of power plant, transportation, residential, and biogenic sources, while the quintuple synergistic effect showed only minor impacts on O3DM concentrations. A 30% reduction in industrial and transportation sources produced the most effective impacts on O3 concentrations, with a maximum decrease of 20 ppbv. These results suggested that the synergistic impacts among emission source types should be considered when formulating emission control strategies for O3 reduction. Electronic Supplementary Material: Supplementary material (the monthly H2O2/HNO3 ratios Figs. S1-S5) is available online at
The Natural Oscillation of Two Types of ENSO Events Based on Analyses of CMIP5 Model Control Runs
XU Kang, SU Jingzhi, and ZHU Congwen
2014, 31(4): 801-813. doi: 10.1007/s00376-013-3153-5
The eastern- and central-Pacific El Ni?o-Southern Oscillation (EP- and CP-ENSO) have been found to be dominant in the tropical Pacific Ocean, and are characterized by interannual and decadal oscillation, respectively. In the present study, we defined the EP- and CP-ENSO modes by singular value decomposition (SVD) between SST and sea level pressure (SLP) anomalous fields. We evaluated the natural features of these two types of ENSO modes as simulated by the pre-industrial control runs of 20 models involved in phase five of the Coupled Model Intercomparison Project (CMIP5). The results suggested that all the models show good skill in simulating the SST and SLP anomaly dipolar structures for the EP-ENSO mode, but only 12 exhibit good performance in simulating the tripolar CP-ENSO modes. Wavelet analysis suggested that the ensemble principal components in these 12 models exhibit an interannual and multi-decadal oscillation related to the EP- and CP-ENSO, respectively. Since there are no changes in external forcing in the pre-industrial control runs, such a result implies that the decadal oscillation of CP-ENSO is possibly a result of natural climate variability rather than external forcing.
Comparison of the Observation Capability of an X-band Phased-array Radar with an X-band Doppler Radar and S-band Operational Radar
WU Chong, and LIU Liping
2014, 31(4): 814-824. doi: 10.1007/s00376-013-3072-5
An X-band phased-array meteorological radar (XPAR) was developed in China and will be installed in an airplane to observe precipitation systems for research purposes. In order to examine the observational capability of the XPAR and to test the operating mode and calibration before installation in the airplane, a mobile X-band Doppler radar (XDR) and XPAR were installed at the same site to observe convective precipitation events. Nearby S-band operational radar (SA) data were also collected to examine the reflectivity bias of XPAR. An algorithm for quantitative analysis of reflectivity and velocity differences and radar sensitivity of XPAR is presented. The reflectivity and velocity biases of XPAR are examined with SA and XDR. Reflectivity sensitivities, the horizontal and vertical structures of reflectivity by the three radars are compared and analyzed. The results indicated that while the XPRA with different operating modes can capture the main characteristic of 3D structures of precipitation, and the averaged reflectivity differences between XPAR and XDR, and XDR and SA, were 0.4 dB and 6.6 dB on 13 July and -4.5 dB and 5.1 dB on 2 August 2012, respectively. The minimum observed reflectivities at a range of 50 km for XPAR, XDR and SA were about 15.4 dBZ, 13.5 dBZ and -3.5 dBZ, respectively. The bias of velocity between XPAR and XDR was negligible. This study provides a possible method for the quantitative comparison of the XPAR data, as well as the sensitivity of reflectivity, calibration, gain and bias introduced by pulse compression.
Applications of Wavelet Analysis in Differential Propagation Phase Shift Data De-noising
HU Zhiqun, and LIU Liping
2014, 31(4): 825-835. doi: 10.1007/s00376-013-3095-y
Using numerical simulation data of the forward differential propagation shift (DP) of polarimetric radar, the principle and performing steps of noise reduction by wavelet analysis are introduced in detail. Profiting from the multiscale analysis, various types of noises can be identified according to their characteristics in different scales, and suppressed in different resolutions by a penalty threshold strategy through which a fixed threshold value is applied, a default threshold strategy through which the threshold value is determined by the noise intensity, or a DP penalty threshold strategy through which a special value is designed for DP de-noising. Then, a hard- or soft-threshold function, depending on the de-noising purpose, is selected to reconstruct the signal. Combining the three noise suppression strategies and the two signal reconstruction functions, and without loss of generality, two schemes are presented to verify the de-noising effect by dbN wavelets: (1) the penalty threshold strategy with the soft threshold function scheme (PSS); (2) the DP penalty threshold strategy with the soft threshold function scheme (PPSS). Furthermore, the wavelet de-noising is compared with the mean, median, Kalman, and finite impulse response (FIR) methods with simulation data and two actual cases. The results suggest that both of the two schemes perform well, especially when DP data are simultaneously polluted by various scales and types of noises. A slight difference is that the PSS method can retain more detail, and the PPSS can smooth the signal more successfully.
CMIP5/AMIP GCM Simulations of East Asian Summer Monsoon
FENG Jinming, WEI Ting, DONG Wenjie, WU Qizhong, and WANG Yongli
2014, 31(4): 836-850. doi: 10.1007/s00376-013-3131-y
The East Asian summer monsoon (EASM) is a distinctive component of the Asian climate system and critically influences the economy and society of the region. To understand the ability of AGCMs in capturing the major features of EASM, 10 models that participated in Coupled Model Intercomparison Project/Atmospheric Model Intercomparison Project (CMIP5/AMIP), which used observational SST and sea ice to drive AGCMs during the period 1979-2008, were evaluated by comparing with observations and AMIP II simulations. The results indicated that the multi-model ensemble (MME) of CMIP5/AMIP captures the main characteristics of precipitation and monsoon circulation, and shows the best skill in EASM simulation, better than the AMIP II MME. As for the Meiyu/Changma/Baiyu rainbelt, the intensity of rainfall is underestimated in all the models. The biases are caused by a weak western Pacific subtropical high (WPSH) and accompanying eastward southwesterly winds in group I models, and by a too strong and west-extended WPSH as well as westerly winds in group II models. Considerable systematic errors exist in the simulated seasonal migration of rainfall, and the notable northward jumps and rainfall persistence remain a challenge for all the models. However, the CMIP5/AMIP MME is skillful in simulating the western North Pacific monsoon index (WNPMI).
Planetary Wave Reflection and Its Impact on Tropospheric Cold Weather over Asia during January 2008
Debashis NATH, CHEN Wen, WANG Lin, and MA Yin
2014, 31(4): 851-862. doi: 10.1007/s00376-013-3195-8
Reflection of stratospheric planetary waves and its impact on tropospheric cold weather over Asia during January 2008 were investigated by applying two dimensional Eliassen-Palm (EP) flux and three-dimensional Plumb wave activity fluxes. The planetary wave propagation can clearly be seen in the longitude-height and latitude-height sections of the Plumb wave activity flux and EP flux, respectively, when the stratospheric basic state is partially reflective. Primarily, a wave packet emanating from Baffin Island/coast of Labrador propagated eastward, equatorward and was reflected over Central Eurasia and parts of China, which in turn triggered the advection of cold wind from the northern part of the boreal forest regions and Siberia to the subtropics. The wide region of Central Eurasia and China experienced extreme cold weather during the second ten days of January 2008, whereas the extraordinary persistence of the event might have occurred due to an anomalous blocking high in the Urals-Siberia region.
The Southern Annular Mode (SAM) in PMIP2 Simulations of the Last Glacial Maximum
Seong-Joong KIM, LÜ Junmei, and Baek-Min KIM
2014, 31(4): 863-878. doi: 10.1007/s00376-013-3179-8
The increasing trend of the Southern Annular Mode (SAM) in recent decades has influenced climate change in the Southern Hemisphere (SH). How the SAM will respond increased greenhouse gas concentrations in the future remains uncertain. Understanding the variability of the SAM in the past under a colder climate such as during the Last Glacial Maximum (LGM) might provide some understanding of the response of the SAM under a future warmer climate. We analyzed the changes in the SAM during the LGM in comparison to pre-industrial (PI) simulations using five coupled ocean-atmosphere models (CCSM, FGOALS, IPSL, MIROC, HadCM) from the second phase of the Paleoclimate Modelling Intercomparison Project (PMIP2). In CCSM, MIROC, IPSL, and FGOALS, the variability of the simulated SAM appears to be reduced in the LGM compared to the PI simulations, with a decrease in the standard deviation of the SAM index. Overall, four out of the five models suggest a weaker SAM amplitude in the LGM consistent with a weaker SH polar vortex and westerly winds found in some proxy records and model analyses. The weakening of the SAM in the LGM was associated with an increase in the vertical propagation of Rossby waves in southern high latitudes.
Retrieval of Aerosol Optical Properties over a Vegetation Surface Using Multi-angular, Multi-spectral, and Polarized data
WANG Han, SUN Xiaobing, SUN Bin, LIANG Tianquan, LI Cuili, and HONG Jin
2014, 31(4): 879-887. doi: 10.1007/s00376-013-3100-5
An algorithm to retrieve aerosol optical properties using multi-angular, multi-spectral, and polarized data without a priori knowledge of the land surface was developed. In the algorithm, the surface polarized reflectance was estimated by eliminating the atmospheric scattering from measured polarized reflectance at 1640 nm. A lookup table (LUT) and an iterative method were adopted in the algorithm to retrieve the aerosol optical thickness (AOT, at 665 nm) and theAngstrom exponent (computed between the AOTs at 665 and 865 nm). Experiments were performed in Tianjin to verify the algorithm. Data were provided by a newly developed airborne instrument, the Advanced Atmosphere Multi-angle Polarization Radiometer (AMPR). The AMPR measurements over the target field agreed well with the nearby ground-based sun photometer. An algorithm based on Research Scanning Polarimeter (RSP) measurements was introduced to validate the observational measurements along a flight path over Tianjin. The retrievals were consistent between the two algorithms. The AMPR algorithm shows potential in retrieving aerosol optical properties over a vegetation surface.
Effects of Meridional Sea Surface Temperature Changes on Stratospheric Temperature and Circulation
HU Dingzhu, TIAN Wenshou, XIE Fei, SHU Jianchuan, and Sandip DHOMSE
2014, 31(4): 888-900. doi: 10.1007/s00376-013-3152-6
Using a state-of-the-art chemistry-climate model, we analyzed the atmospheric responses to increases in sea surface temperature (SST). The results showed that increases in SST and the SST meridional gradient could intensify the subtropical westerly jets and significantly weaken the northern polar vortex. In the model runs, global uniform SST increases produced a more significant impact on the southern stratosphere than the northern stratosphere, while SST gradient increases produced a more significant impact on the northern stratosphere. The asymmetric responses of the northern and southern polar stratosphere to SST meridional gradient changes were found to be mainly due to different wave properties and transmissions in the northern and southern atmosphere.~Although SST increases may give rise to stronger waves, the results showed that the effect of SST increases on the vertical propagation of tropospheric waves into the stratosphere will vary with height and latitude and be sensitive to SST meridional gradient changes. Both uniform and non-uniform SST increases accelerated the large-scale Brewer-Dobson circulation (BDC), but the gradient increases of SST between 60?S and 60?N resulted in younger mean age-of-air in the stratosphere and a larger increase in tropical upwelling, with a much higher tropopause than from a global uniform 1.0 K SST increase.
A Case Study of Mesoscale Convective Band (MCB) Development and Evolution along a Quasi-stationary Front
Daeun JEONG, Ki-Hong MIN, Gyuwon LEE, and Kyung-Eak KIM
2014, 31(4): 901-915. doi: 10.1007/s00376-013-3089-9
This paper presents a case study of mesoscale convective band (MCB) development along a quasi-stationary front over the Seoul metropolitan area. The MCB, which initiated on 1500 UTC 20 September 2010 and ended on 1400 UTC 21 September 2010, produced a total precipitation amount of 259.5 mm. The MCB development occurred during a period of tropopause folding in the upper level and moisture advection with a low-level jet. The analyses show that the evolution of the MCB can be classified into five periods: (1) the cell-forming period, when convection initiated; (2) the frontogenetic period, when the stationary front formed over the Korean peninsula; (3) the quasi-stationary period, when the convective band remained over Seoul for 3 h; (4) the mature period, when the cloud cover was largest and the precipitation rate was greater than 90 mm h-1; and (5) the dissipating period, when the MCB diminished and disappeared. The synoptic, thermodynamic, and dynamic analyses show that the MCB maintained its longevity by a tilted updraft, which headed towards a positive PV anomaly. Precipitation was concentrated under this area, where a tilted ascending southwesterly converged with a tilted ascending northeasterly, at the axis of cyclonic rotation. The formation of the convective cell was attributed in part by tropopause folding, which enhanced the cyclonic vorticity at the surface, and by the low-level convergence of warm moist air and upper-level divergence. The southwesterly flow ascended in a region with high moisture content and strong relative vorticity that maintained the development of an MCB along the quasi-stationary front.
Boreal Winter Rainfall Anomaly over the Tropical Indo-Pacific and Its Effect on Northern Hemisphere Atmospheric Circulation in CMIP5 Models
WANG Hai, and LIU Qinyu
2014, 31(4): 916-925. doi: 10.1007/s00376-013-3174-0
Experimental outputs of 11 Atmospheric Model Intercomparison Project (AMIP) models from phase 5 of the Coupled Model Intercomparison Project (CMIP5) are analyzed to assess the atmospheric circulation anomaly over Northern Hemisphere induced by the anomalous rainfall over tropical Pacific and Indian Ocean during boreal winter. The analysis shows that the main features of the interannual variation of tropical rainfall anomalies, especially over the Central Pacific (CP) (5S5N, 175E135W) and Indo-western Pacific (IWP) (20S20N, 110150E) are well captured in all the CMIP5/AMIP models. For the IWP and western Indian Ocean (WIO) (10S10N, 4575E), the anomalous rainfall is weaker in the 11 CMIP5/AMIP models than in the observation. During El Nio/La Nia mature phases in boreal winter, consistent with observations, there are geopotential height anomalies known as the Pacific North American (PNA) pattern and Indo-western Pacific and East Asia (IWPEA) pattern in the upper troposphere, and the northwestern Pacific anticyclone (cyclone) (NWPA) in the lower troposphere in the models. Comparison between the models and observations shows that the ability to simulate the PNA and NWPA pattern depends on the ability to simulate the anomalous rainfall over the CP, while the ability to simulate the IWPEA pattern is related to the ability to simulate the rainfall anomaly in the IWP and WIO, as the SST anomaly is same in AMIP experiments. It is found that the tropical rainfall anomaly is important in modeling the impact of the tropical Indo-Pacific Ocean on the extratropical atmospheric circulation anomaly.
Application of Aircraft Observations over Beijing in Cloud Microphysical Property Retrievals from CloudSat
WANG Lei, LI Chengcai, YAO Zhigang, ZHAO Zengliang, HAN Zhigang, and WEI Qiang
2014, 31(4): 926-937. doi: 10.1007/s00376-013-3156-2
Cloud microphysical property retrievals from the active microwave instrument on a satellite require the cloud droplet size distribution obtained from aircraft observations as a priori data in the iteration procedure. The cloud lognormal size distributions derived from 12 flights over Beijing, China, in 2008-09 were characterized to evaluate and improve regional CloudSat cloud water content retrievals. We present the distribution parameters of stratiform cloud droplet (diameter 500 m and 1500 m) and discuss the effect of large particles on distribution parameter fitting. Based on three retrieval schemes with different lognormal size distribution parameters, the vertical distribution of cloud liquid and ice water content were derived and then compared with the aircraft observations. The results showed that the liquid water content (LWC) retrievals from large particle size distributions were more consistent with the vertical distribution of cloud water content profiles derived from in situ data on 25 September 2006. We then applied two schemes with different a priori data derived from flight data to CloudSat overpasses in northern China during April-October in 2008 and 2009. The CloudSat cloud water path (CWP) retrievals were compared with Moderate Resolution Imaging Spectroradiometer (MODIS) liquid water path (LWP) data. The results indicated that considering a priori data including large particle size information can significantly improve the consistency between the CloudSat CWP and MODIS CWP. These results strongly suggest that it is necessary to consider particles with diameters greater than 50 m in CloudSat LWC retrievals.
Development and Preliminary Evaluation of a Double-cell Ozonesonde
ZHANG Jinqiang, XUAN Yuejian, YAN Xiaolu, LIU Mingyuan, TIAN Hongmin, XIA Xiang'ao, PANG Li, and ZHENG Xiangdong
2014, 31(4): 938-947. doi: 10.1007/s00376-013-3104-1
Ozonesondes are widely used to obtain ozone concentration profiles from the surface to the upper atmosphere. A kind of double-cell ozonesonde has been developed at the Institute of Atmospheric Physics (IAP), Chinese Academy of Sciences (named the IAP ozonesonde) based on previous experience over the past 20 years of developing the singlecell GPSO3 ozonesonde. The IAP ozonesonde is of the Electrochemical Concentration Cell (ECC) type. A detailed description of the IAP ozonesonde is firstly provided in the present paper, followed by a presentation of results from a series of launches carried out to evaluate its performance. The analysis involved comparing its observations with measurements from the GPSO3 and ECC ozonesondes (Model type ENSCI-Z) as well as a Brewer spectrophotometer. The results showed that the IAP ozonesonde is a vast improvement over the GPSO3 ozonesonde, able to capture vertical ozone structures very well and in good agreement with ECC ozonesonde measurements. The average difference in the ozone partial pressure between the IAP and ECC ozonesondes was 0.3 mPa from the surface to 2.5 km, close to zero from 2.5 to 9 km and generally less than 1 mPa for layers higher than 9 km. The apparent deviation is likely caused by a decreasing pump flow rate in the IAP ozonesonde which needs further improvement. The total ozone amounts measured by the IAP ozonesonde profiles were highly comparable with the Brewer data with a relative difference of 6%. The development of the IAP ozonesonde and its strong performance will surely accelerate the process of conventional observations of ozone profiles over China in the near future as well as provide more data for ozone research in general.
Transition from the Southern Mode of the Mei-yu Front Cloud System to Other Leading Modes
QIN Danyu, LI Bo, and HUANG Yong
2014, 31(4): 948-961. doi: 10.1007/s00376-013-3045-8
Based on normalized six-hourly black body temperature (TBB) data of three geostationary meteorological satellites, the leading modes of the mei-yu cloud system between 1998 and 2008 were extracted by the Empirical Orthogonal Function (EOF) method, and the transition processes from the first typical leading mode to other leading modes were discussed and compared. The analysis shows that, when the southern mode (EOF1) transforms to the northeastern mode (EOF3), in the mid-troposphere, a low trough develops and moves southeastward over central and eastern China. The circulation pattern is characterized by two highs and one low in the lower troposphere. A belt of low pressure is sandwiched between the weak high over central and western China and the strong western North Pacific subtropical high (WNPSH). Cold air moves southward along the northerly flow behind the low, and meets the warm and moist air between the WNPSH and the forepart of the low trough, which leads to continuous convection. At the same time, the central extent of the WNPSH increases while its ridge extends westward. In addition, transitions from the southern mode to the dual centers mode and the tropical-low-influenced mode were found to be atypical, and so no common points could be concluded. Furthermore, the choice of threshold value can affect the number of samples discussed.
Precipitation Pattern of the Mid-Holocene Simulated by a High-Resolution Regional Climate Model
YU Entao, WANG Tao, GAO Yongqi, and XIANG Weiling
2014, 31(4): 962-971. doi: 10.1007/s00376-013-3178-9
Early proxy-based studies suggested that there potentially occurred a southern drought/northern flood'' (SDNF) over East China in the mid-Holocene (from roughly 7000 to 5000 years before present). In this study, we used both global and regional atmospheric circulation models to demonstrate that the SDNFnamely, the precipitation increases over North China and decreases over the the lower reaches of the Yangtze River Valleycould have taken place in the mid-Holocene. We found that the SDNF in the mid-Holocene was likely caused by the lower SST in the Pacific. The lowered SST and the higher air temperature over mainland China increased the land-sea thermal contrast and, as a result, strengthened the East Asian summer monsoon and enhanced the precipitation over North China.
Eddy Kinetic Energy Study of the Snowstorm over Southern China in January 2008
ZUO Qunjie, GAO Shouting, and LÜ Daren
2014, 31(4): 972-984. doi: 10.1007/s00376-013-3122-z
The energetics of the third stage of a snowstorm over China was analyzed using ECWMF data. The analysis of the energy budget for the Middle East trough and the western Pacific trough that developed toward China on 25-28 January 2008 showed the advection of the geopotential by the ageostrophic wind to be both a crucial source and the primary sink of the eddy kinetic energy centers associated with the troughs. The magnitudes of the energy conversion terms, interaction kinetic energy conversion and baroclinic conversion, were too small to explain the development of the energy centers and the jet streaks. The energy centers gained energy at their entrance regions via the convergence of the ageostrophic geopotential fluxes, and then lost energy at their exit regions by the same fluxes. At the entrance regions, the fluxes converged, increasing the geopotential gradient, which generated a stronger geostrophic wind and higher kinetic energy, resulting in an ascending motion in this area. When the troughs moved to China, the ascending motion caused by the convergence of the fluxes at entrance region intensified the snowstorms over central and southern China.
The Role of Atmospheric Teleconnection in the Subtropical Thermal Forcing on the Equatorial Pacific
WANG Lu, and YANG Haijun
2014, 31(4): 985-994. doi: 10.1007/s00376-013-3173-1
The equatorial response to subtropical Pacific forcing was studied in a coupled climate model. The forcings in the western, central and eastern subtropical Pacific all caused a significant response in the equatorial thermocline, with comparable magnitudes. This work highlights the key role of air-sea coupling in the subtropical impact on the equatorial thermocline, instead of only the role of the oceanic tunnel''. The suggested mechanism is that the cyclonic (anticyclonic) circulation in the atmosphere caused by the subtropical surface warming (cooling) can generate an anomalous upwelling (downwelling) in the interior region. At the same time, an anomalous downwelling (upwelling) occurs at the equatorward flank of the forcing, which produces anomalous thermocline warming (cooling), propagating equatorward and resulting in warming (cooling) in the equatorial thermocline. This is an indirect process that is much faster than the oceanic tunnel'' mechanism in the subtropical impact on the equator.