Plateau Meteorology

Current Issue

28 October 2016, Volume 35 Issue 5   
  • Analysis on Interdecadal Correlation between Solar Activity and Snow Depth over the Qinghai-Xizang Plateau and East Asian Atmospheric Circulation inWinter
  • SONG Yan;LI Zhicai;XIAO Ziniu;ZHANG Jing;LI Hongyi;ZHU Yuxiang
  • 2016 Vol. 35 (5): 1135-1147.  DOI:10.7522/j.issn.1000-0534.2015.00059
  • Abstract ( ) PDF (4863KB) ( )
  • The sun is the main energy source of the earth's climate system. Recognizing the influence of the solar activity on the earth's climate system will improve the climate prediction accuracy. On the basis of knowing the solar activity rules on short term and long term time scales, more further studies about the response of components of the climate system to the solar activity is necessary. These studies proved that the solar activity is an important factor to change the climate system. Because previous studies show that the present global warming belongs to reasonable extent of climate system's fluctuations, it is necessary to explore the natural factor's role further. There still has larger space for investigating the influence of solar activity on climate system, also, some unknown fields have not been involved. Snow depth over the Qinghai-Xizang Plateau is one of the key physical factors affecting climate system, however, relationship between snow and the solar activity is still not accessed. Solar radio flux (SRF), solar sunspot number (SSN) and total solar irradiance (TSI) are commonly used parameters of solar activity, which have different physical meanings. For the first time, this paper reveals the interdecadal correlation between solar activity and winter snow depth over the Qinghai-Xizang Plateau and the typical circulation pattern over the East Asia, that is the Arctic Oscillation and the East Asian winter monsoon. In the future, in-depth study on the influence of solar activity on the climate system will be done, and the physical process and physical mechanism will be further revealed in the later work. Arctic Oscillation and East Asian winter monsoon have obvious relation to the snow depth over the Qinghai-Xizang Plateau and solar activity, and the interdecadal correlations between them are discussed in this paper. Some researches about the solar activity and the East Asian winter monsoon on interdecadal time scales (longer than 11 years cycle period) is very rare. This paper studies the interdecadal correlation between the solar activity and the East Asian winter monsoon and discusses the interdecadal correlation between the winter snow depth over the Qinghai-Xizang Plateau and Arctic Oscillation and East Asian winter monsoon. The results show that on interdecadal time scale, over 11 years solar cycle, the sun modulated the change of winter snow depth over the Qinghai-Xizang Plateau and East Asian atmospheric circulation ahead. At the fourth 11-years lag year, through Monte-Carlo test method, the correlation coefficient between snow depth and SRF is 0.8013, which passes 0.05 significant level. Our study also exposes that winter snow depth over the Qinghai-Xiang Plateau has significant contemporary and lag correlation with Arctic Oscillation and the East Asian winter monsoon on long time scale.
  • Relationship Between the Qinghai-Xizang Plateau Monsoon and the Atmospheric Heat Source/Sink
  • ZENG Yuchan;FAN Guangzhou;LAI Xin;HUA Wei;ZHANG Yongli
  • 2016 Vol. 35 (5): 1148-1156.  DOI:10.7522/j.issn.1000-0534.2015.00093
  • Abstract ( ) PDF (3030KB) ( )
  • Qinghai-Xizang Plateau as a risen heat source may have a significant impact on Asian and the global climate, especially plays an important role for the outbreak of monsoon. It exists a self-contained climate of pressure system on the Tibet Plateau, which is an independent winds formed under the heat of Plateau. Therefore, the thermal effects of the Qinghai-Xizang plateau would have been affected on the plateau monsoon. In order to further understand the relationship between the Qinghai-Xizang plateau monsoon and the atmospheric heat source/sink, using the daily and monthly reanalysis data of the NCEP/NCAR from 1948 to 2013 to analyze the relationship between the change date of plateau atmosphere heating source collection and the plateau monsoon, and the strength of those two. The results show that during the past 66 years, the average monthly plateau heat source is obvious seasonal variations. The strongest heat collection occurs in January and the strongest heat source in July. The heat collection turns into heat source approximately in April, while the heat source turn into the heat collection in October. The heat collection turns into heat source approximately in 15 pentad, while the heat source turn into the heat collection roughly among 58 pentad. Compared with the summer monsoon establishment date, the change from heat sink to heat source is about 3 pentad earlier than that of summer monsoon, and the transition from heat source to heat sink is about 1 pentad ahead of end date. The relationship between thermal effects with the intensity of the summer plateau monsoon presents a positive correlation. When the atmospheric heat source is strong, the plateau summer monsoon is strong. When the atmospheric heat source is weak, the plateau summer monsoon is weak. In the stronger heat source years, convergence is strong in the plateau body, yet divergence becomes strong in the plateau around. In the weak heat source years, convergence is weak in the plateau body, yet divergence becomes weak in the plateau around. The atmospheric thermal gradient between the plateau and around indicates an apparent seasonal change as well. The atmospheric thermal gradient between the plateau and around positively correlates with the plateau monsoon in July, in detail, the effect of the plateau summer monsoon would be stronger as the thermal gradient becomes bigger and the effect of the plateau summer monsoon would be weaker as the thermal gradient becomes smaller.
  • Evaluation and Projections of Permafrost on the Qinghai-Xizang Plateau by CMIP5 Coupled Climate Models
  • CHANG Yan;LYU Shihua;LUO Siqiong;WU Jing;LI Ruiqing;LI Suosuo
  • 2016 Vol. 35 (5): 1157-1168.  DOI:10.7522/j.issn.1000-0534.2015.00090
  • Abstract ( ) PDF (4718KB) ( )
  • As an important forcing factor of the land surface, permafrost is very sensitive indicator of climate change. The freeze-thaw process is directly involved in local energy and water cycles, and in turn affects weather and climate. In this study, using the multi-model results from the fifth phase of the Coupled Model Intercomparison Project (CMIP5), we computed the near-surface permafrost area on the Qinghai-Xizang Plateau (QXP) via surface frost index (SFI) method, and assessed the ability of models to simulate the related climate variables and present-day (1986-2005) permafrost, by comparing with the reanalysis products and the frozen soil map of the QXP. Based on this assessment, the climate models were aggregated by arithmetic mean to project the changes of permafrost on the QXP under the four different Representative Concentration Pathways (RCPs). The results show that the CMIP5 coupled models have some simulation capabilities for permafrost on the QXP. The simulated present-day near surface permafrost distribution is similar to the plateau frozen soil map, with the annual average of permafrost area of 127.5×104 km2 (1986-2005). The prediction results by multi-model ensemble mean indicate that the permafrost appear a degradation tendency on the QXP, especially on the eastern, southern and the edges of northern plateau. The permafrost will shrink from the edges to the north-west inner part of the QXP, and most probably exist only in the northwestern regions by 2099. Using the SFI method, the rate of the permafrost area change under RCP2.6, RCP4.5, RCP6.0 and RCP8.5 scenarios are-2.2×104 km2·(10a)-1, -5.9×104 km2·(10a)-1, -5.4×104 km2·(10a)-1 and -10.0×104 km2·(10a)-1, respectively. In the next 50 years, the permafrost area will decrease about 23.9×104 km2 (20.8%), 33.5×104 km2 (27.7%), 25.6×104 km2 (21.1%) and 43.5×104 km2 (35.3%) under RCP2.6, RCP4.5, RCP6.0 and RCP8.5, respectively. The average values of permafrost area in the last period of 21st century are about 91.4×104 km2 (RCP2.6), 70.9×104 km2 (RCP4.5), 72.8×104 km2 (RCP6.0) and 41.7×104 km2 (RCP8.5). Although there are large ranges in degree of degradation for different scenarios, the linearity of relationship exist between the permafrost area and the surface air temperature.
  • Simulation of the Effect of Qinghai-Xizang Plateau Anomalous Heating on the Downstream Flow from May to August by RegCM4.0
  • XU Xiaoyu;WANG Yafei
  • 2016 Vol. 35 (5): 1169-1181.  DOI:10.7522/j.issn.1000-0534.2015.00058
  • Abstract ( ) PDF (7906KB) ( )
  • The effect of the Qinghai-Xizang Plateau anomalous heating on the downstream atmospheric circulation is explored from May to August by using the Regional Climate Model Version 4.0, and a series of numerical experiments are performed with three different kinds of anomalous heating rates over the plateau for each month. The results are: (1) After 12 days when the atmosphere over the plateau is heated with the rate of 4 K·d-1 in May, the geopotential height anomaly on 500 hPa is positive near the Okhotsk Sea and negative in Northeast China and to the south of the Kamchatka Peninsula, forming a suspected wave train; however, it turns to be a dipole pattern on 200 hPa, with positive in the west and negative in the east. When it comes to June, the construction of this wave train becomes more evident, with a complete wave like the Okhotsk-Japan (OKJ) pattern appearing on 200 hPa, which includes a positive anomaly over the plateau, a negative anomaly to the south of Lake Baikal, a positive anomaly around the Okhotsk Sea and a negative anomaly to the east of Japan. The negative geopotential height anomaly on 500 hPa over the plateau indicates the baroclinic effect of this anomalous heating. (2) There are no similar wave structures on both 200 hPa and 500 hPa during other months. In July, the geopotential height anomaly is always negative from Mongolia to the Okhotsk Sea and to the east of Japan on both 200 hPa and 500 hPa. In August, the geopotential height anomaly turns to be positive off the east coast of Japan, and the negative anomaly near the Okhotsk Sea remains to be unchanged. (3) Sensitivity experiments of different anomalous heating rates show that, with the strengthening of anomalous heating over the plateau, the geopotential height anomalies tend to be almost proportionally increased at each point along the wave track on 200 hPa in June. (4) In addition, the analysis of ray tracing shows that the ray paths in May are similar to those in June, and the simulation route lies between the ray paths with zonal wavenumber 3 and 4, nearer to the one with zonal wavenumber 4. However, in July and August, the ray paths with three different kinds of zonal wavenumber are close to each other, which are very different from those in May and June.
  • Multi-Scale Variation of the Summer Rainfall over Sichuan-Chongqing Basin in Recent 50 Years
  • WANG Chunxue;MA Zhenfeng;QIN Ningsheng;ZHANG Shunqian;DENG Biao
  • 2016 Vol. 35 (5): 1191-1199.  DOI:10.7522/j.issn.1000-0534.2015.00094
  • Abstract ( ) PDF (3464KB) ( )
  • In the past research, there are many studies on the characteristics of the summer precipitation in Sichuan-Chongqing basin, but most of them are separately discussed in terms of its annual or inter annual variation characteristics and its possible mechanism. The analysis of the characteristics of the seasonal variation is relatively less. Therefore, in this paper the characteristics of the seasonal interannual and decadal variation will be studied systematically and deeply from different time scales. The daily precipitation data from 1961 to 2010 of 24 meteorological stations are used in this paper. Use the same period monthly mean 500 hPa, 100 hPa height field and 1000~300 hPa zonal wind and humidity field reanalysis data. Two methods are used in this article. MTM-SVD method is a multivariable frequency domain decomposition technique proposed by Park and Mann. The empirical orthogonal function expansion technique was introduced into the study of atmospheric science by Lorenz in the middle of 1950 s. The results show that the main mode of summer precipitation in Sichuan-Chongqing Basin is the East-west reverse distribution pattern. MTM-SVD analysis points out that the seasonal changes of summer rainfall at Sichuan-Chongqing Basin mainly reflected the oscillation of Quasi-33 day. The seasonal typical cycle performed the evolution between the distribution of east-west reverse and the north-south. Its interannual variation mainly showed Quasi-2 years cycle, which spatial distribution is consistent with that primary mode. In the aspects of decadal variations, the summer precipitation has decreasing trend in the western basin but growing trend in the eastern basin. The results of sliding t test indicated that the summer rainfall appeared two distinct mutations in 1979 and 1987. Synthetic analysis shows that corresponding to the abnormally northeastward South Asia high (SAH), the West Pacific subtropical high (WPSH) inclines to more northward, while the warm-humid air from the Bay of Bengal is blocked in the west basin which leading to more precipitation in west basin than the east basin. The southwestward SAH and the southward WPSH always accompanies more rainfall in the east basin than the west. In this paper, the fact of the multi scale variation of the precipitation in the basin is analyzed, and the general circulation background of the typical year is given too. The impact factors for different time scale characteristics are not the same. The characteristics of precipitation intraseasonal oscillation signal may affected by the plateau vortex and MJO. Interannual time scale signal is mainly affected by the Indian Ocean dipole, the thermal status of Tibetan Plateau external forcing, decadal scale change should be considering the factor of solar activities, etc., which are worth further study.
  • Up-Scaling Research for Soil Moisture inYellow River Source Region
  • CHEN Jinlei;WEN Jun;TIAN Hui
  • 2016 Vol. 35 (5): 1212-1223.  DOI:10.7522/j.issn.1000-0534.2015.00100
  • Abstract ( ) PDF (5601KB) ( )
  • The minimal Number of Required Sites (NRS) for regional soil moisture estimating under the certain accuracy requirements, and the representativeness of sites are studied by using the soil moisture data derive from "Maqu soil moisture observation network in Yellow River source region of the Northwest Institute of Eco-Environment and Resources, Chinese Academy Sciences"from July 2011 to August 2012. In addition, the best upscaling method which suitable for network has been selected by evaluating four commonly used methods. The results show that: (1) Under the accuracies R≥0.99, RMSD≤0.02 m3·m-3, NRS at both 5 and 10 cm depth is 10. (2) Representativeness of the sites have been validated by time stability analyses, time sliding correlation analyses and optimal combination of sites. NST01 is the most representative site at 5 cm depth for the first two methods, and CST05 and NST02 are the most representative sites at 10 cm depth. The optimum combination sites at 5 cm depth are NST01, NST02, and NST07. NST05, NST08, and NST13 are the best group at 10 cm depth. (3) Linear fitting is the best up-scaling method."Single site"obtained by OCS has the greatest up-scaling effect, and time sliding correlation analyses takes the second place. (4) The linear fitting equations are used to estimate the variation of regional soil moisture during 3 July 2013 to 3 July 2014, when a large number of observed soil moisture data are lost.
  • Characteristics of Micrometeorology and Energy Transfer in the Surface Layer over the Zhangye Oasis-Desert Area
  • ZHANG Fen;LIU Shaomin;XU Ziwei;WANG Jiemin;ZHU Zhongli
  • 2016 Vol. 35 (5): 1233-1247.  DOI:10.7522/j.issn.1000-0534.2015.00071
  • Abstract ( ) PDF (10820KB) ( )
  • Based on dataset of'The Multi-Scale Observation Experiment on Evapotranspiration over heterogeneous land surfaces of the Heihe Water Allied Telemetry Experimental Research (HiWATER-MUSOEXE)-flux observation matrix'conducted in the Zhangye oasis-desert area in 2012, the variation characteristics of micrometeorology and energy fluxes were analyzed combing synchronous airborne and satellite remote sensing image. The results showed that: (1) The oasis exhibited significant'oasis effect'with the phenomena of cold, wet, wind barrier, and enhancing rain while comparing to desert. The interaction process of different scales occurred in the internal oasis and between oasis and desert under different weather background. The temperature inversion and humidity increasing were found in the oasis when advection occurred, and the humidity also increased in the nearby desert at the same time. There was a phase lag of air temperature after the irrigations in oasis. The precipitation in oasis was greater than that in the desert. The soil moisture in oasis was greater than that in desert, and it was controlled by irrigations in oasis, but it was controlled by precipitation in desert. (2) The daily cycles and magnitude of incoming shortwave radiation were similar in the oasis and desert. The incoming longwave radiation in oasis was greater than that in desert. The outgoing shortwave/longwave radiation in desert were obviously greater than that in oasis, and the net radiation was relatively small. (3) The latent heat flux in oasis was significantly greater than that in desert, whereas the soil heat flux and sensible heat flux in oasis were lower. The energy transfer of oasis was dominated by latent heat flux, while it was dominated by sensible heat flux in desert. The phenomenons of negative sensible heat flux, large latent heat flux even over the net radiation were observed in sunny afternoon in the oasis. Due to the discrepancy of wind field and the water vapor and heat conditions in oasis and desert, the occurrence time and intensity of advection was different at each site in oasis.
  • Conceptual Models of Short-Time Heavy Rainfall in the East of Northwest China
  • BAI Xiaoping;WANG Shigong;ZHAO Lu;SHANG Kezheng;LIU Xiaotan;MING Rujun
  • 2016 Vol. 35 (5): 1248-1256.  DOI:10.7522/j.issn.1000-0534.2015.00102
  • Abstract ( ) PDF (2080KB) ( )
  • To study the temporal, spatial and climatic characteristics of short-time heavy rainfall in the east of Northwest China, by using the NCEP/NCAR 1° ×1° reanalysis data during 2001-2011 to classify the weather circulation situation which influences the east of Northwest China, focusing on the time and circulation state when the short-time heavy rainfall happens, together with the energy theory, four synoptic scale concept models is established including low vortex type, low trough type, cut the variant and southwest airflow type. The results show that the regional short-time heavy rainfall events in the east of Northwest China weather type have obvious seasonal characteristics and regional features. Temporally, in late spring and early summer as well as autumn, the short-time heavy rainfall is featured by low trough type while in middle summer, southwest airflow type and two high variant take the dominant role. Spatially, the Gobi desert is mainly home to short-time heavy rainfall of low trough type, the northeast Qinghai Tibet plateau slope zone is given priority to with southwest airflow type of short-time heavy rainfall, the loss plateau and the south of Qinling area is the most of southwest airflow type and low trough type.
  • Effects of Parameterized Physical Processes of WRF Model on Simulation of Rainstorm in Jiuquan, Gansu Province
  • WANG Tiantian;GAO Xiaoqing;YIN Xianzhi;WANG Yanfeng;WANG Rong
  • 2016 Vol. 35 (5): 1257-1269.  DOI:10.7522/j.issn.1000-0534.2015.00096
  • Abstract ( ) PDF (4593KB) ( )
  • In order to investigate the influence of various parameterization schemes in different physical processes on rainstorm simulation, the numerical simulation and a series of sensitive experiments are carried out to the typical heavy rainstorm in Jiuquan of Gansu province on June 4-5 2012 by using the Weather Research and Forecasting Model (WRFV3.2) with a series of cumulus parameterization scheme and microphysics scheme combination. The study is performed by using the meteorological observational data and the FNL 1°×1° six hours reanalyzed data. Comparison and analysis research of different scheme combinations'simulating effect is given in this paper, and the contrastive analysis is made with precipitation and rainfall area. The results show that, WRF has a strong simulating ability for precipitation and flow field variation as well as has a good capacity to predict the mesoscale weather systems. The extended directions of rainstorm belts has been simulated accurately by all the scheme combinations, but the positions of the heavy rainfall centers souther than the reality. The sensitivity of microphysics schemes to the rainfall simulation was significantly higher than that of cumulus parameterization schemes. The simulations were closer to the reality with 18 km fine horizontal resolution. In general, Betts-Miller-Janjic and WRF-Single-Moment-5-class (BMJ-WSM5) schemes performed better. ETS skill score confirmed that as well. WRF can also well simulate physical quantity fields of this rainstorm. The diagnostic analyses of vertical speed, vorticity, divergence, and the rain mixing ratio are carried out, then, the role of the cumulus parameterization schemes and microphysical schemes in rainstorm forecast can be better understood. These sesults will be beneficial for finding out the causes for rainstorm.
  • Summer Prediction of Moisture Transport in the Middle and Lower Reaches of the Yangtze River in BCC_CSM Mode
  • WANG Xujia;ZHENG Zhihai;GU Bohui;ZHAO Yuheng
  • 2016 Vol. 35 (5): 1270-1279.  DOI:10.7522/j.issn.1000-0534.2015.00092
  • Abstract ( ) PDF (5436KB) ( )
  • Based on hindcast datasets of the Beijing Climate Centre climate system model and NCEP reanalysis datasets, using correlation analysis, composite analysis and others, firstly, the summer atmospheric moisture content and the characteristics of moisture transport in the middle and lower reaches of the Yangtze River are analyzed, and the relationship between rainfall and the summer monsoon are discussed. Secondly, the pattern of moisture transport simulation capabilities are evaluated, and possible reasons for the model error are analyzed. Results shows that: (1) summer precipitation in the Yangtze River has a close relationship with the East Asian summer monsoon, and the East Asian summer monsoon affects mainly through the moisture transport in Yangtze River to influence precipitation, moisture transport is therefore an important hub contact between precipitation and water origin; (2) there is a cyclonic bias of atmospheric water vapor transportation in low latitude of Yangtze River, which led to atmospheric moisture content of the Yangtze River decrease, this is an important reason for the precipitation simulation of below normal level in this region, negative biases simulation centers distributed between 20°N-40°N, while low latitudes is a positive deviation distribution. Further studies shows that the simulation of the deviation of the Yangtze River moisture transport mainly caused by an analog deviation the summer monsoon, and the simulation of the weak monsoon is better than the simulation of strong monsoon.
  • Relationship between Summer Monsoon Changes in East Asia and Abnormal Summer Rainfall in North China
  • HAO Lisheng;DING Yihui;MIN Jinzhong
  • 2016 Vol. 35 (5): 1280-1289.  DOI:10.7522/j.issn.1000-0534.2015.00085
  • Abstract ( ) PDF (4434KB) ( )
  • To find out the causes of abnormal summer rainfall in North China and to improve climate prediction technologies, a comprehensive analysis on the relationship between East Asian summer monsoon and summer precipitation in North China is carried out in this paper by defining the index of East Asian summer monsoon with the meridional wind field and based on such data as summer precipitation in North China and general atmospheric circulation reanalyzed by NCEP/NCAR. The results of the analysis indicate that:1) North China has more summer rainfall during strong East Asian summer monsoon years but less summer rainfall during weak East Asian summer monsoon years. An opposite case also exists. The spatial distribution pattern of more (less) rainfall in East Asian strong summer monsoon years is significantly different from that of more (less) rainfall in weak East Asian summer monsoon years. (2) Irrespective of strong or weak East Asian summer monsoon years, the circulation conditions contributing to more summer rainfall in North China are sufficient water vapor sources (strong summer monsoon years:abnormal water vapor carried by southwest wind; weak summer monsoon years:abnormal water vapor carried by southeast wind) and good dynamic conditions (with convergence circulation at 850 hPa in North China, prominent zonal circulation at 500 hPa at middle latitude, and more low-pressure trough transit in North China). (3) The circulation pattern related to less summer rainfall in North China is significantly different:No effective dynamic conditions (with divergence circulation at 850 hPa in North China, prominent meridional circulation at 500 hPa at middle latitude, and less low-pressure trough transit in North China) are created both in strong summer monsoon years with sufficient water vapor sources (abnormal southwest wind) and weak summer monsoon years with insufficient water vapor sources (abnormal northerly wind). (4) Although there are sufficient water vapor sources in strong East Asian summer monsoon years, the summer rainfall differs a lot in different years in North China due to diverse dynamic conditions. If the dynamic conditions are good, North China will have abnormally more summer rainfall; otherwise, it will also have abnormally less summer rainfall. (5) In weak East Asian monsoon years, water vapor carried by southwest wind is reduced significantly, so North China will have abnormally less summer rainfall if there is lack of water vapor supplement from other paths and the dynamic conditions are poor. Although water vapor carried by southwest wind is reduced significantly in weak summer monsoon years, sometimes there are also sufficient water vapor sources in North China if more water vapor is carried by southeast wind. At the same time, if the dynamic conditions are good, North China may also have abnormally more summer rainfall, as the case during 2011 2013. In terms of the prediction of summer rainfall in North China, it cannot be simply considered that North China will have more summer rainfall in case of strong East Asian summer monsoon or will have less summer rainfall in case of weak East Asian summer monsoon, as the intensity change of East Asian summer monsoon only suggests different water vapor conditions. The summer rainfall in North China can only be well predicted after the dynamic conditions are also considered.
  • Relationship between Atmospheric Ozone and Polar Vortex Intensity in the Mid-High Latitude over the Northern Hemisphere in Winter
  • LI Chengchao;GUO Shichang;YI Qi;LI Haifeng
  • 2016 Vol. 35 (5): 1290-1297.  DOI:10.7522/j.issn.1000-0534.2015.00026
  • Abstract ( ) PDF (2144KB) ( )
  • In order to fully understand the relationship between atmospheric ozone in the mid-high latitude over the Northern Hemisphere (NH) and the polar vortex intensity (PVI) in winter, according to the correlation method and E-P flux method, the relationship between them are analyzed (the four key regions included Arctic, East Asia, North America and Western Europe are taken as samples) and their influence mechanism have been studied based on ECMWF reanalysis data during January 1979 to December 2011. The results show as following. Firstly, there was a significant negative correlation between the total amount of ozone and PVI in the stratosphere of the Arctic in winter. Secondly, in the years whose average PVI values were bigger (smaller), the total amount of ozone in the polar and North America area decreased (increased) significantly. Thirdly, when PVI was weaker, the vortex-motion heat flux to the stratosphere was stronger, and there was an enhanced convergence of E-P flux divergence in the mid-high latitude, which resulted in residual circulation increasing and led to shifting high concentration ozone from the mid-low latitude areas to mid-high latitude areas, as a result, the ozone increased in high latitude areas. Finally, the vortex-motion heat flux in the stratosphere over the mid-high latitude areas had an increasing trend form 1979 to 2011, leading to the increase of temperature in the north pole, which resulted in the inhibition of heterogeneous reaction to increase the total amount of ozone in north pole region in the end.
  • Variation of Kunming Quasi-Stationary Front and Its Effect Analysis in Winter during 1970-2009
  • ZHANG Jinghua;ZHANG Wancheng;ZHENG Jianmeng;MA Tao
  • 2016 Vol. 35 (5): 1298-1306.  DOI:10.7522/j.issn.1000-0534.2015.00042
  • Abstract ( ) PDF (2350KB) ( )
  • Using the daily ground routine observation data and 74 kinds of circulation index data provided by the China climate center from 1970 to 2009, the characteristics of the Kunming quasi-stationary front in winter and the relationships among the Kunming stationary front activities and cloudy days, precipitation days, and drought variation in Guiyang, Kunming and Zhanyi stations are analyzed. The results show that the Kunming stationary front activity number is decreasing, and the sphere of influence by it has marked change from 1970 to 2009. The numbers affected by the Kunming quasi-stationary front is the most in Guiyang, the second is in the area between Zhanyi and Kunming, the last is in Kunming. The numbers of influence Kunming and Guiyang by the Kunming quasi-stationary front is a decreasing trend, and is unchanged in Zhanyi, but increased in winter of 2000 and 2008. With the decreasing of the Kunming stationary front in winter appearance in Kunming, the cloudy days are decreasing in Yunnan. The trend of cloudy days was consistent with the variation of Kunming quasi-stationary front. The time affected by the Kunming quasi-stationary front was positively correlated with precipitation days, and negative correlated with drought days. Kunming precipitation in winter reduction and drought increase are related to the significant reduction of stationary front influence. The influences of the different weather system on the location of Kunming quasi-stationary front are not the same. The west ridge of the Western Pacific subtropical high was the best related to the range of stationary front activities, and it was positively correlated with the numbers of influence Yunnan by the stationary front, but was negatively correlated with the consistent time of the stationary front influence on Guizhou. When the Western Pacific Subtropical High keeps in the west, the stationary front affected on Yunnan happen less. When the Western Pacific Subtropical High retreats in the east, the stationary front affected on Yunnan happen more. In addition, the time of the stationary front located in Yunnan was negatively correlated with the Southern Branch Trough (SBT), the area and intensity of subtropical high, Asian zonal index and Eurasian zonal circulation, and was positively correlated with the activities of Asian polar vortex area. The time of the stationary front located in Guizhou was positively correlated with the area of theWestern Pacific subtropical high and the SBT strength.
  • Influence Mechanism Analysis of Snow Caused by Two Central Asian Vortexes in West of Southern Xinjiang in 2011
  • ZHANG Yunhui;YU bixin;TAN Yanmei;YU Yan
  • 2016 Vol. 35 (5): 1307-1316.  DOI:10.7522/j.issn.1000-0534.2015.00065
  • Abstract ( ) PDF (7650KB) ( )
  • The snowstorm forecast of Southern West Xinjiang has always been a difficult point. The Central Asian Vortexes are the important systems producing the heavy snow or rainfall over Southern West Xinjiang. Different vortexes traverse routes made different snow or rainfall scope and intensity. Taking the snowstorm during 5th to 9th (Remembered as 1205 process) and the weak snow with better advantages during 17th to 22nd (Remembered as 1217 process) on December 2011 in Southern West Xinjiang as examples, the reason of the differences between the two was discussed to promote prediction capability. Based on the data of conventional observation data, T639, NECP/NCAR reanalysis data and FY-2D satellite, the mechanisms differences between the two cases caused by Central Asian vortexes were analyzed comparatively. The results showed that Central Asian Vortexes are scale weather system with regional characteristics, deep and fairly positive pressure. Two cases had in common were several points, both with positive vortices in the whole layer of the vortexes, upward motion in the front of that and convergence areas below 400 hPa. Also, the water vapor was both provided by the southwesterly airstream in the front of the vortexes at 500 hPa, with same water vapor budget of more input in the western and southern boundary and more output in the northern boundary. Although, the climatic background, location, strength, structure, holding time and water vapor transports of the vortexes in the two cases were similar as mentioned above, there was something different as well, such as the large scale circulation backgrounds where the vortexes formed, the vortexes tracks, the configurations of high and low altitude and the mechanisms of moisture convergence. In the case 1205 process, under the circulation of northern ridge and southern vortex, the vortex moved toward northeast at 500 hPa while easterly jet established over the basin at 850 hPa, inserting cold air from the east at the surface. The warm moisture of the mid-layer had been butting up the cold moisture of the low-layer, the good cooperation of which made it snow heavy in Southern West Xinjiang. Nevertheless, in the case 1217 process, the vortex broke away from the polar front frontal zone and moved toward south to the Central Asian, moving in the north path. The water vapor, provided by the southwesterly airstream in the front of the vortexes, was abundant, but there's no easterly wind over the basin at 850 hPa and the cold air at the surface climbed over the hill to the basin from Southern West Xinjiang, with the mechanisms of moisture convergence lacked.
  • Formation Mechanisms of A Regional Rainstorm under the Stable Atmospheric Stratification
  • LIU Yong;YUAN Yuan;PAN Liujie;XU Juanjuan
  • 2016 Vol. 35 (5): 1317-1326.  DOI:10.7522/j.issn.1000-0534.2015.00030
  • Abstract ( ) PDF (4429KB) ( )
  • The course of a regional rainstorm from 5 to 6 September 2011 in the middle of Shannxi province is integrated analyzed by using the routine meteorological observation data, surface hourly precipitation, physical quantity field, radar and satellite cloud imagery data. The result shows that the regional rainstorm appears in continuous rain which covers central and southern Shaanxi, with characteristics of weak precipitation intensity, long duration and not much local. It is a steady precipitation. This strong precipitation occurred under the condition of stable atmospheric stratification convection; Lower and elevated CAPE are both 0 J·kg-1. By analyzing conditional symmetric instability conditions, it finds that vertical movement of the early precipitation comes from the forced fronts and conditional symmetric instability condition., while the vertical movement lately mainly comes from forced fronts. The cold air form the east area in low level not only plays the role of rising cold wedge, but also enhanced the atmospheric baroclinicity and frontal zone at lower level. Above all, they are conducive to the generation of heavy rain. It is confirmed by satellite cloud imagery and radar echo that strong precipitation is formed by the weak convective cloud belt or stratiform cloud; Low level flush water vapor condition, strong frontal zone and vapor convergence are the main course of the rainstorm.
  • Modeling Analysis of a Severe Autumn/Winter Drought in Eastern China by using Regional Atmospheric Modeling System (RAMS)
  • MENG Chunchun;MA Yaoming;MA Weiqiang;GOU Peng;BAI Yang
  • 2016 Vol. 35 (5): 1327-1338.  DOI:10.7522/j.issn.1000-0534.2015.00082
  • Abstract ( ) PDF (6983KB) ( )
  • To testify RAMS'performance on drought events, the simulation of 2008/2009 severe autumn/winter drought event over eastern China was conducted in this study. The RAMS outputs were compared with European Centre for Medium-Range Weather Forecasts (ERA-interim) Reanalysis data and Global Summary of Day (GSOD) observation data respectively. The ERA-interim reanalysis data showed that most parts of the north China were controlled by northwest wind which was accompanied by cold air, the warm and moist air from South Sea is so weak to meet with cold air from the northern region, therefore forming a circulation which is unfavorable for precipitation over Eastern China, and the downward motion and low relative humidity prevailed over the drought area which intensified the drought. RAMS has proven to be capable of reproducing the aforementioned general atmospheric circulation, and RAMS captured the distribution features of the rainfall and air temperature over China authentically. Meanwhile, compared with GSOD observations, RAMS showed good performance on the simulation of precipitation and air temperature time variations over the drought area, both the square of correlation coefficient between simulations and observations of precipitation and that of air temperature reached above 0.8. Although the performance of RAMS on this drought simulation is fairly accurate, the spatial resolution of RAMS simulation needs enhancement and large amount of drought simulations should be completed and contrasted to draw a conclusive evaluation of RAMS capability.
  • Analysis on Variation Characteristics and Differences of the Climate Drying Degree between South and North of China
  • ZHANG Hongli;ZHANG Qiang;LIU Qian;YAN Pengcheng
  • 2016 Vol. 35 (5): 1339-1351.  DOI:10.7522/j.issn.1000-0534.2015.00099
  • Abstract ( ) PDF (7923KB) ( )
  • With global warming, droughts have become one of the most serious environmental problems. There are different degrees of drought tendency in some regions of China in recent years. Precipitation and Potential evaporation are selected from the high resolution data of Climatic Research Unit (CRU) to calculate drought index during 1961-2012 in China, and the aridity index is calculated by the ratio of potential evaporation to precipitation to study the aridity difference between north and south China. By separating eastern China into two regions (north and south) and using the linear trend estimation, Morlet wavelet analysis and other methods, variations in droughts and the differences between the dry and wet seasons north and the south of eastern China are analyzed. It shows that: (1) Eastern China is drying during past 112 years, and the trend is more obvious after twentieth Century 60's. The increasing trend of aridity in northern China is faster than that in the south, and the differences between aridity in north and south China expand with time. An increasing aridity is accompanying an increasing temperature, so it can be concluded that the effect of increasing temperature on the potential evaporation intensifies the degree of drought. (2) In addition, sudden turn of drought and flood also increase, which may carry greater challenges for climatic prediction and drying disaster risk. There is a accelerate transformation of 20 years and 2 years in aridity index both over north and south china, and the quasi biennial phenomenon also accelerate after twentieth Century 60 years, but the transition process always is mild in south. (3) There are also differences in the dry and wet season in eastern China. Inter-annual and decadal amplitude of variation in dry season is significantly higher than that in wet season. Compared with the wet season, spatial consistency change is better in dry season. Besides, the time of dry and wet have changed in recent years. The dry season delays while the wet season comes ahead in eastern China, which suggests that both the dry and wet seasons last longer. (4) In addition, in the last half a century, both the dry and wet seasons in north China show a significant trend of drought, but there are not the similar features in south China.
  • Analysis of Extreme Temperature Changes in China based on the Homogeneity-Adjusted Data
  • WANG Dai;YOU Qinglong;JIANG Zhihong;WU Wenbo;JIAO Yang
  • 2016 Vol. 35 (5): 1352-1363.  DOI:10.7522/j.issn.1000-0534.2016.00019
  • Abstract ( ) PDF (4917KB) ( )
  • Based on homogeneity-adjusted and quality-control daily maximum, minimum and mean temperature data of 693 meteorological stations in China from 1961 to 2014, then divided the area of China into several regions due to the spatial variability of extreme temperature, and analyzed the change characteristic of 11 extreme temperature indices (were defined by World Meteorological Organization) by linear trend and cumulative departure methods. The result shows that an increasing trend occurs on extreme high temperature indices (including extra-maximum air temperature, summer days, warm nights, warm days, a continuous warm stage and the growing season length) in all regions, while extreme low temperature indices (including extra-minimum air temperature, frost days, cold nights, cold days and continuous cold stage) present a decreasing trend, except for extraminimum air temperature, which shows a trend of increase. Among them, the degree of change of extreme temperature indices in night is the greatest (increase of warm nights and decrease of cold nights are the most significant). Furthermore, in most of regions of each index have an obvious trend turning. The turning time of extreme high temperature indices is nearly in 1995 to 1998, while extreme low temperature indices is nearly in 1985 to 1986 and 1995. Extreme high temperature indices show a decreasing/increasing trend before/after turning, but extreme low temperature indices are adverse, except for extra-maximum air temperature that is increased/decreased before/after turning. There is a significant correlation between all extreme indices with average temperature nearly in all regions. The correlation between the threshold indices with average temperature is the most significant.
  • Study of Systematic Bias Corrected Method in CMIP5 Decadal Experiments of BCC_CSM1.1 Climate Model on Tropical SST
  • GAO Feng;WU Tongwen;XIN Xiaoge
  • 2016 Vol. 35 (5): 1364-1375.  DOI:10.7522/j.issn.1000-0534.2015.00083
  • Abstract ( ) PDF (9788KB) ( )
  • The decadal prediction component of CMIP5 experiment aims at improving our understanding of physical climate system and ability to predict its evolution in the near term. These decadal simulations make it possible and meaningful to assess model skill in forecasting climate under the observed ocean initial conditions. In this study, the decadal hindcast and prediction experiment carried out by BCC_CSM1.1 climate model for CMIP5 was used to evaluate the model's prediction capability of SST in tropical area. Using a model bias correcting method, we corrected the raw model simulation results and examined whether this method can improve the model's hindcast performance in tropical SST. By analyzing the decadal experiment which is conducted every 5 years from 1960 to 1990, results show as following:in spite of initiation with observation SST was taken into account in the decadal hindcast experiments, the model still underperforms in simulating the realistic SST evolution. The relationship between different groups of the experiments and the observation only show consistent positive correlation in western Pacific and the tropical North Atlantic Ocean area, while hindcast skills of corrected model simulation are improved significantly in the global ocean area, particularly in the southern Indian and tropical Pacific Ocean area. In the tropical western Pacific, the space correlation efficient between corrected model simulation and observation is above 0.8 in all the 120 months after the predicted time. The corrected model simulations can reproduce the mode of the Pacific SST in the observation. Therefore, the bias correcting method in the present study is important and useful for reducing the systematic bias and conducting the climate prediction of tropical SST on time-scales.
  • Application of A Comprehensive Analysis Method on Hourly Surface Air Temperature Interpolation over A Complex Terrain Region
  • CHEN Feng;DONG Meiying;JI Chunxiao
  • 2016 Vol. 35 (5): 1376-1388.  DOI:10.7522/j.issn.1000-0534.2015.00095
  • Abstract ( ) PDF (16465KB) ( )
  • Generating accurate and fine gridded meteorological data becomes one of the final goals in meteorological modernization, which is the key fact in doing researches in meteorology, hydrology, and ecology sciences. How to convert the information from local observations into the whole region is getting more and more attention from scientists in meteorology, hydrology, geography, ecology and so on. In practical application, interpolation method is usually used to achieve the grid data of the problem. To obtain accurate and fine gridded meteorology information, a new interpolation method named Comprehensive Analysis method (IN) is used to reproduce the gridded 2 m temperature dataset based on the high resolution numerical prediction, digital elevation model, and surface observation data over a complex terrain region. This method divides the model prediction error into the error of modeling the weather system and the error of describing the topography, and then uses the observation data to revise these two parts separately. Four steps are used in the revising:Firstly, the numerical model predicting temperature is used as the first guess field in the reanalysis grid system; Secondly, the first guess value and the corresponding error are obtained on the observation site; Thirdly, this error is interpolated to the reanalysis grid system; Finally, the gridded error is added into the first guess field to obtain the final temperature field. The inter-comparison is mode among the Inverse Distance Weighting (IW), Ordinary Kriging (KR), Gradient Inverse Distance Weighting (IG) and IN based on the hourly observed scattered station 2 m temperature data over Zhejiang province and its surround area. The results show that the IN method produces the best result, follows the IG, IW, and KR. The IG and IN have greater abilities on reproduce the temperature over high altitude area than the IW and KR. The IN can produce a normal and reasonable temperature field over the no data area, which shows a stronger ability on no data interpolation. The interpolation accuracy increases with the number of sites increase, and no improvements appear when the number of sites reaches 1000 in IN and 1600 in other three methods.
  • Planetary Wave Activity and Its Impact on Different Types of SSW Events
  • XU Luyang;CHEN Quanliang
  • 2016 Vol. 35 (5): 1389-1400.  DOI:10.7522/j.issn.1000-0534.2015.00051
  • Abstract ( ) PDF (4463KB) ( )
  • Based on the criteria of WMO (World Meteorological Organization), 52 SSW (stratospheric sudden warming) events during 1957-2002 were firstly classified into two types:31 major warming and 21 minor warming events, then 31 major warming events were divided into 20 vortex displacement events and 11 vortex splitting events according to their forms of vortex. Using the ERA-40 daily reanalysis data from ECMWF, composition analysis was used to study these three types of SSW events from 1957 to 2002, including 20 vortex displacement major warming, 11 vortex splitting major warming and 21 minor warming events. The changes of stratosphere of these three were studied, and the anomalies of lower stratospheric planetary wave-number 1, wave-number 2 and the corresponding EP fluxes during the sudden warming period were also interviewed in detail. The results showed that the vortex displacement major warming offsets its low temperature center and the vortex, and reverses wind field of high latitude from westerly to easterly wind. The vortex splitting type splits its low temperature center and the vortex, and reverses wind field of high latitude into easterly wind as well as the vortex displacement event. Minor warming events only offsets its low temperature center, the vortex and wind field of high latitude remain stable. For all these three SSW types, the amplitude of wave-number 1 anomalously increases before the sudden warming and the amplitude of wave-number 1 reaches its climax when the warming occurs, but the climax reaching date and the degree of amplitude increase is different according to the different types. The vortex displacement events and minor warming events remain its climax of amplitude of wave-number 1 for approximately 6~8 days, while the vortex splitting type decreases its amplitude of wave number 1 when the warming occurs. As to the wave-number 2, the vortex displacement type and minor warming events are alike, the amplitudes increase before the sudden warming, and then decrease when the warming began. The vortex splitting type increases its amplitude of wave number 2 after the warming begins. The EP flux of wave-number 1 and wave-number 2 were also calculated and analyzed. The minor warming type and vortex displacement type both have strong upward wave-number 1 EP flux, but the vortex displacement type is stronger, these strongly uploaded EP fluxed of wave number 1 causes the strong increase of the amplitudes of wave number 1. However, the upward wave-number 2 EP flux of these two types is much weaker. For the vortex splitting type, the upward wavenumber 2 EP flux is quite strong, which leads to the increase of the amplitude of wave number 2.
  • Analysis on Contribution of Edge Conglutination between Particles in Cloud to Radar Brightness Band
  • WANG Meng;WANG Zhenhui;WANG Yun;DONG Huijie
  • 2016 Vol. 35 (5): 1401-1408.  DOI:10.7522/j.issn.1000-0534.2015.00054
  • Abstract ( ) PDF (1382KB) ( )
  • Taking two small, spherical particles for example, the backscattering cross-section as a whole during the stage of edge conglutination between them would be greatest as compared with that before they contact with each other and that after they fuse and coalesce into a single spherical particle, especially the conglutination and coalescence process starts from two small, spherical ice particles. The paper studies the contribution of this phenomenon to radar bright band. DDA is used to calculate DDA, the backscattering cross-section of the edge-conglutinated particles. It has been found that DDA in case the conglutination is along the direction of radar wave polarization may be 1.5 times greater than mie, the backscattering cross-section of the equal volume, spherical particle at a certain size though the ratio may decrease to even less than 1 and fluctuate as the particle size increases because of resonance for large particles. Introducing'probability of edge conglutination'as a parameter to depict the effect of edge conglutination and applying the parameter into simulating radar bright band, it has been shown that, for a normal intense cloud echo such as 5874 mm6·m-3 (37.69 dBZ), radar reflectivity factor can increase by 2.57 times in case the conglutination percentage=33%, increase by 3.29 times in case p=50%, and increase by 5.59 times in case p=100%, respectively, while the increase is only increase by 2.40 times if the conglutination is not considered. Therefore, conglutination on the edge of two spherical particles along radar wave polarization direction can effectively increase the radar reflectivity factor and greatly benefit the formation of bright band.

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