Current Issue

• Relationship between Surface Sensible Heating over the Qinghai-Xizang Plateau and Precipitation in the Eastern Part of Northwest China in Spring
• ZHOU Junqian;LIU Xin;LI Weiping;ZHU Lingjing;WU Hui
• 2016 Vol. 35 (4): 845-853.  DOI:10.7522/j.issn.1000-0534.2015.00053
• Abstract ( ) PDF (6201KB) ( )
• To study the relationship between spring surface heat abnormal field over the Qinghai-Xizang Plateau and the precipitation in eastern part of Northwest China, in-situ surface heat flux data on four representative sites to analysis the change characteristics of atmospheric boundary layer of the Qinghai-Xizang Plateau, then the relationship between spring surface sensible heat over the Qinghai-Xizang Plateau and spring rainfall in the eastern part of Northwest China at interannual time scale was studied by using JRA-55 and NCEP reanalysis data and site observation of rainfall in the eastern part of Northwest China, research results indicate that: (1) The sensible heat flux contributes more than the latent heat flux and is the main part of the surface diabatic heating field over the Qinghai-Xizang Plateau in spring. (2) There is a negative correlation between the rainfall anomalies of the eastern part of Northwest China and the surface sensible heat anomalies over the Qinghai-Xizang Plateau; (3)Stronger surface sensible heating over the Qinghai-Xizang Plateau in spring leads to weaker upward movement of the vertical circulation over the Qinghai-Xizang Plateau and its surrounding areas in the same season and vice versa; (4) Composite analysis of relative vorticity, geopotential height, wind and water vapor flux divergence in the eastern part of Northwest China shows that when the inter-annual anomalies of spring surface sensible heating on the Qinghai-Xizang Plateau is positive, there is positive anomaly of vorticity in the upper troposphere and negative vorticity in the middle and lower troposphere in the studied areas, airflows exit convergence movement on the higher level and sinking motion on the lower levels, weakening the moisture convergence from lower to higher level, resulting in the decrease of spring rainfall in the eastern part of Northwest China.

• Gravity Wave Characteristics in Two Summer Heavy Rainfall in the Qinghai-Xizang Plateau
• WU Di;WANG Chenghai;HE Guangbi
• 2016 Vol. 35 (4): 854-864.  DOI:10.7522/j.issn.1000-0534.2015.00066
• Abstract ( ) PDF (31813KB) ( )
• For a more comprehensive understanding the impact of mesoscale gravity waves on the occurrence and development of heavy rain over Qinghai-Xizang Plateau, two heavy rainfall events in the eastern part of Tibetan Plateau are simulated by using the mesoscale model WRF (V3.5.1), the gravity wave characteristics and the connection between the heavy rainfall events are investigated. The results show that the simulation results well reproduce the two heavy rainfall process, the propagation characteristics of wave were represented by the alternative movement of vertical velocity and divergence respectively, and the ascending movement is closely associated with the development of precipitation. The analysis of the Richardson number show that vertical shear instability at 5 km to 6 km appears before the waves occur, with the signal of waves intensifying, the vertical shear start to weaken. It is shown that the gravity wave can extract energy from the unstable airflow of vertical shear. Vertical shear and Richardson number can be as an indicator of the heavy rainfall forecast in the downstream. The mesoscale gravity waves in two heavy rains were identified by using the Morlet wavelet method, the gravity waves which have longer wavelength are generated early and disappear late, and which plays an major role in reinforcing the precipitation processes. All above indicate that development of mesoscale gravity wave is one of the dynamic mechanisms resulting in heavy rain and plays an important role in the process of summer heavy rain in the eastern part of Tibetan Plateau. The gravity wave analysis contributes to our understanding of the heavy rain process in the region, and improves prediction ability of the Tibetan Plateau area precipitation.

• Analysis of Durative Rainstorm Characteristics Occurred in the Ambient Area of Qinghai-Xizang Plateau
• HE Guangbi;ZENG Bo;YU Shuhua;ZHANG Hongjiao;CHEN Yongren
• 2016 Vol. 35 (4): 865-874.  DOI:10.7522/j.issn.1000-0534.2015.00081
• Abstract ( ) PDF (5366KB) ( )
• Durative rainstorm is the main cause bringing about disasters such as flood, landslip and mud-rock flow. Southwestern China and southeast of the Qinghai-Xizang Plateau is one of the districts where the annual averaged rainfall duration is the longest, and also summer averaged rainfall duration is the longest. The artical is aimed at local and regional durative rainstorm over the Qinghai-Xizang Plateau and its surrounding areas. First rainfall duration standards are given, then the characteristics of two kinds of durative rainstorm, and the relation between regional durative rainstorm and the activities of the plateau low systems are analyzed. Based on the precipitation data provided by National Meteorological Information Center, historical weather charts and NCEP 1°×1° reanalysis data, the statistical and synoptical method are used to analyze the characteristics of persistence rainstorm and the plateau low systems going with the rainstorm over the Plateau and its surrounding areas during the period of 1961-2011. The result shows that local persistence rainstorm usually lasts for 3~4 days over the Plateau and its surrounding areas, the longest rainstorm occurs in Wuhan, Hubei province, it lasts for 10 days. The occurrence of rainstorm in the surrounding areas of plateau is lower than it over the plateau, there are 4 high frequency occurrence center of rainstorm, the frequency of rainstorm is highest in Bomi, Xizang province, the rainstorm occurs 15 times. The high frequency of rainstorm from western to mid-eastern Sichuan has the widest range. The other two high frequency area are southern Yunnan and mid-eastern Hubei. The regional persistence rainstorm in the east of Plateau lasts for 3 days, it occurs frequently in July, since 21 century, the center of rainstorm has the tendency of moving eastward. Usually, the persistence rainstorm is accompanied by the Plateau low systems of the Qinghai-Xizang Plateau vortex, Qinghai-Xizang Plateau shear line and the southwest vortex which is the most important effect system.

• Contrast on Anusplin and Cokriging Meteorological Spatial Interpolation in Southeastern Margin of Qinghai-Xizang Plateau
• TAN Jianbo;LI Ainong;LEI Guangbin
• 2016 Vol. 35 (4): 875-886.  DOI:10.7522/j.issn.1000-0534.2015.00037
• Abstract ( ) PDF (4944KB) ( )
• Meteorological data is the essential data of ecological, resources, environment, global change and other research areas. However, the meteorological in Mountain are rare and complex than in plain. And acquiring precise spatial grid meteorological data has been a difficult task in this area. Anusplin and Cokriging interpolation method are one of the most common method that considering terrain’impacts during the Meteorological Spatial Interpolation. To ensure which one is more suit for complex area, we take the most complex mountain area (the Southeastern margin of the Qinghai-Xizang Plateau) as study area to compare the two methods. Based on Anusplin and Cokriging meteorological spatial interpolation method separately, combined with the terrain data and 96 meteorological stations in the southeastern margin of the Qinghai-Xizang Plateau region, 250 m resolution average temperature and total precipitation interpolated surfaces in 2010 was obtained. With the cross-validation method comparison method, the interpolation accuracy of Anusplin and Cokriging was compared, and the spatial distribution of errors was analyzed. Applying relevant information, accurate of the two methods in local area where the result of interpolation are quite different was qualitatively analyzed. Through this, the method which is more suit for this area is sought out and the applicability of Anusplin in this area was assessed. The results showed that, Anusplin interpolation outperformed Cokriging. In the comparing of mean square error(RMSE) of the interpolation of temperature and precipitation, Anusplin temperature is only 0.82℃ and Cokriging is 1.45℃, the RMSE of precipitation of the two methodes are consistent, but Anusplin are superior to Cokriging in the highly heterogeneous area. Therefore Anusplin can achieve better results than Cokriging, indicating that Anusplin is suit for the interpolation in Southeastern Margin of Qinghai-Xizang Plateau.

• Assessment on Accuracy of GlobAlbedo over the Northern Qinghai-Xizang Plateau
• CHEN Aijun;ZHOU Chan;BIAN Lingen;LIU Yujie
• 2016 Vol. 35 (4): 887-894.  DOI:10.7522/j.issn.1000-0534.2015.00097
• Abstract ( ) PDF (1930KB) ( )
• Retrieved with the combined data from multiple satellites, the GlobAlbedo provides the global land surface albedo (LSA) product, and it is delivered by the European Space Agency (ESA). To evaluate the accuracy of the GlobAlbedo and advance its application in the study of the earth-atmosphere interaction over the Qinghai-Xizang Plateau, the ground-observed solar shortwave radiation data from BJ and XDT stations, located over the Northern Qinghai-Xizang Plateau, were used to make comparison with the GlobAlbedo. Besides, the comparison was also made between the GlobAlbedo and the Moderate Resolution Imaging Spectroradiometer LSA product MCD43B3. Results revealed that: The shortwave band (0.3~5.0 μm) land surface albedos from the GlobAlbedo in 1 km resolution were totally in rather well agreement with the ground-observed land surface albedo, but their accuracy were significantly influenced by the snow fraction (SF). The root-mean-square errors (RMSEs) between the actual land surface albedos from GlobAlbedo and the high-quality ground-observed land surface albedos fell in between 0.0100 and 0.0218 when the SF was less than 0.1, and the accuracy of GlobAlbedo could meet the requirements of the land surface process and climate models. Otherwise, they fell in between 0.0252 and 0.1461 and there were some uncertainty in the accuracy of GlobAlbedo. When compared with MCD43B3, the GlobAlbedo has a slightly better accuracy than MCD43B3. The RMSEs between the actual land surface albedos from GlobAlbedo and the high-quality ground-observed land surface albedos fell in between 0.0195 and 0.0959, while those between the actual land surface albedos from MCD43B3 and the high-quality ground-observed albedos fell in between 0.0273 and 0.1269.

• Predictability to the Winter Temperature over the Qinghai-Xizang Plateau based on ECC
• CHEN Xiaoyang;YOU Qinglong;RUAN Neng
• 2016 Vol. 35 (4): 895-907.  DOI:10.7522/j.issn.1000-0534.2015.00057
• Abstract ( ) PDF (2660KB) ( )
• Eurasian continent surface temperature (EA), Northeastern hemisphere 500 hPa geopotential height(NH), sea surface temperature over the tropical Indian Ocean (TI) and sea surface temperature over the Western Pacific (WP) were considered as predictors at 9, 6 and 3months lead times. The Barnett-Preisendorfer canonical correlation analysis (BP-CCA) was used to establish statistical downscaling models between four predictors and the winter temperature over the Qinghai-Xizang Plateau (QXP), and the most skillful period of each predictor was selected as the critical period. Then one year out cross validation and ensemble canonical correlation (ECC) was applied to evaluate the practical model prediction ability. The independent sample test was used to estimate the predictability of interannual variation with a longer time scale. The main resultsare as follows:(1) The spatial patterns of how different predictors influence the QXP are well recognized by BP-CCA. The predictability of EA was reflected by the positive feedback of temperature-snow-albedo. The NH pattern shows a cyclonic anomaly and the East Asia trough is relative weak, which prevents the cold air from high latitudes. TI reveals the impact of canonical Indian Ocean Dipole (IOD) on temperature over the QXP, more moisture was brought to the QXP region. WP controls the winter temperature over the QXP by changing the position of subtropical high. (2) Correlation coefficient between predictand and observation, in the cross validation and independent sample test, are about 0.5 and 0.3 respectively. This indicates that all the four predictors have a good predictable skill to the winter temperature over the QXP. (3) The ECC method synthesizes different predictable information from all the four predictors, which increase the correlation coefficient to 0.7 in the eastern QXP. It means that ECC can give a more reliable and stable prediction.

• Relations of Cloud Amount to Asymmetric Diurnal Temperature Change in Central and Eastern Qinghai-Xizang Plateau
• WANG Yi;BO Yue;WANG Chenghai
• 2016 Vol. 35 (4): 908-919.  DOI:10.7522/j.issn.1000-0534.2015.00033
• Abstract ( ) PDF (3628KB) ( )
• By using ISCCP data and observation station data, the variations of cloud amount and cloud types are investigated in Central and Eastern Qinghai-Xizang Plateau (QXP) from 1984 to 2009; and the relationship between daily maximum/minimum temperature and cloud amount are analyzed. The results show that the diurnal variations of cloud amount at low-mid-level in QXP appears obviously unimodal types, but the diurnal variations of high-cloud amounts are not obviously. The warming rates of daily maximum/minimum temperature in TP are different, i.e, so called asymmetric diurnal temperature change. Diurnal/nocturnal cloud amount and daily maximum/minimum temperature have a distinct relation over Central and Eastern QXP, which have a positive feedback mechanism. The asymmetric temperature change reduces the difference of temperature between land and atmosphere in the morning, then the convection weakens, which may cause cloud amounts decreasing after sunrise. It will lead to much more solar shortwave radiation reaches the ground and the faster process of air warming in the morning. The decreasing of low-mid-cloud amounts and increasing of high-cloud amounts at noon increase the solar radiation of reaches the ground and causes a warmer daily maximum temperature. Cloud amounts of total cloud increase at dusk except cirrus, which slows down the decreasing rate of temperature after sunset, which benefits to increase the daily minimum temperature.

• Convergence Line Frontogenesis Type Rainstorm in Early Summer in the Eastern Section of the Yunnan-Guizhou Plateau
• YANG Xiuzhuang;DU Xiaoling;WU Guhui;WANG Chao
• 2016 Vol. 35 (4): 920-933.  DOI:10.7522/j.issn.1000-0534.2015.00008
• Abstract ( ) PDF (12990KB) ( )
• The convergence line frontogenesis is one of the causes of the rainstorm in the Eastern Section of the Yunnan-Guizhou Plateau, a typical Convergence Line Frontogenesis Type Rainstorm weather was analyzed which was happened from 11 to 12 May 2012, using 1°×1° reanalysis data of the NCEP/NCAR, sounding data and TBB data of FY-2E. The results show that it is a really typical Convergence Lines Frontogenesis Type Rainstorm in Guizhou, Coupling between mesoscale convergence line and shear line at low-level is the main reason for the development of convection. The mesoscale convective systems triggered due to convection move from west to east as a mesoscale clouds in the Satellite Images. The atmospheric stratification is unstable with high-temperature and high humidity in the process of the typical rainstorm all the time. The strong southwest airflow on 700 hPa and 850 hPa provides a better moisture transport condition for heavy rain produced.Positive vorticity and convergence are maintained on low-levels, negative vorticity and convergence divergence are maintained on high-levels. Frontogenesis function reveals the phenomenon of frontogenesis is existed obviously between the ground and 800 hPa, gradually decreases with height. horizontal divergence term F2 is main power factor causing Frontogenesis on the surface, the horizontal divergence term F2 and horizontal deformation term F3 have a significant positive contribution causing Frontogenesis on 850 hPa. Using theory of air blocks and method of kinematics to analyze convection, the trigger mechanism of convection is related of LFC, horizontal convergence intensity of synoptic-scale environmental field, convergence vertical height, convergence duration.

• Interdecadal Variation of Springtime Southern Branch Trough and Its Relationship with Precipitation and Atmospheric Circulation
• ZHANG Yongli;FAN Guangzhou;ZHU Keyun;YUAN Dongsheng;HUA Wei;WANG Bingyun
• 2016 Vol. 35 (4): 934-945.  DOI:10.7522/j.issn.1000-0534.2014.00157
• Abstract ( ) PDF (5998KB) ( )
• The Springtime Southern Branch Trough (SSBT) is generated by the dynamic forcing of the Qinghai-Xizang Plateau, which own abnormal interdecadal variability, and which may be closely related to the anomaly of precipitation in China. The intensity and east/west position of the SSBT and the pertinence between these are analyzed and the corresponding interdecadal variation of precipitation and atmospheric circulation in China, whose interdecadal variation in last 65 years are discussed as well, using the monthly average of reanalyzed data from NCEP/NCAR, combined with monthly precipitation data of 596 observation stations provided, and by employing the methods such as mutation inspection, composition analysis, etc. The results of the analysis indicate that the intensity and position of SSBT is characterized by interdecadal variability, its intensity have a weak mutation process in the late 1970s, and its position was sudden changed from east to west in the early 1990s. And the mutation before(after) the intensity of SSBT is, the stronger (weaker) the SSBT is, while the mutation before(after) the position is, the easter (wester) the SSBT leans, and the precipitation of the Yellow River basin, the middle and lower parts of the Yangtze River and its northern/southern areas increases (decreases), while it apparently drops (rises) in Qinghai-Xizang Plateau and its surrounding area, by using before and after the period of the intensity and position of SSBT. Besides, the relationship between mutation before/after the period of intensity/position and atmospheric circulation, vertical movement, water vapor is also very significant, which explains the reason for the difference of precipitation in China. Then on the base of these, the concept frame of interdecadal relationship with precipitation and atmospheric circulation in SSBT is summarized. These results are helpful to better provide more scientific basis for how and why the spring climate change and climate prediction of China.

• Statistics Characteristics and the Abnormal Development of Flow Pattern of the Southwest Vortex in Recent 61 Summer Half Years
• YE Yao;LI Guoping
• 2016 Vol. 35 (4): 946-954.  DOI:10.7522/j.issn.1000-0534.2015.00073
• Abstract ( ) PDF (4208KB) ( )
• Based on the NCEP/NCAR reanalysis data, we analysis the interannual variability of southwest vortex frequency in the summer half years (May to October) from 1954 to 2014, and discuss the climate characteristics in southwest vortex anomaly years emphatically. The result shows that the number of the southwest vortex annual average time is 43 in the summer half year from 1954 to 2014, June is the most powerful month of the southwest vortex, and the weakest month is August. The years with more southwest vortex are 1954, 1955, 1956, 1963, 1964, 1997, 1998, 2005, 2007 and 2009. The years with less southwest vortex are 1960, 1961, 1962, 1972, 1974, 1975, 1981, 1982, 1988 and 2014. This statistical results have a good corresponding wih the history extreme weather. The southwest wind and the anomaly of convergence flow are strong in the key area of southwest vortex, and the cyclonic shear and the monsoon circulation with low latitude increase in the multiple years of southwest vortex, these characteristics are advantaged to the development of southwest vortex, with a large number of positive angular momentum transporting into the key area of southwest vortex with a fluctuant change. Meanwhile, the water vapor flux of the key area from the Indian Ocean increases, which is advantageous to precipitation. During the southwest vortex less years, the monsoon circulation of low latitude weakened, and the meridional wind present a north wind anomaly and the anomaly of divergence flow are strong in the key area, these characteristics are disadvantaged to the development of southwest vortex with a weakened transporting of positive angular momentum in the key area. The key area water vapor flux which comes from the Indian Ocean decreases, these are disadvantageous to precipitation. Thus, in addition to the terrain and the heating effect, the water vapor and the angular momentum transporting which are brought by westerlies and monsoon circulation are also the important factors for the development of southwest vortex. Finally, to be sure, as be a preliminary statistics of southwest vortex, we used the reanalysis data with 2.5°×2.5° resolution. The data with different resolution has an influence of the statistics of southwest vortex. So using the proper resolution reanalysis data is an important point for the statistics of southwest vortex in the future. And this study also shows that: in the year with more southwest vortex, the angular momentum and the water vapor flux of the key area increase and in downstream region of the key area, the angular momentum and the water vapor flux decrease. In the year with less southwest vortex, the angular momentum and the water vapor flux of the key area decrease and the angular momentum and the water vapor flux increase in downstream region of the key area. This kind of reverse phase change needs to be further study.

• Regional Differences of Land Extreme Precipitation and Temperature Changes under Climate Change Condition
• CHEN Jiao;ZHANG Yaocun
• 2016 Vol. 35 (4): 955-968.  DOI:10.7522/j.issn.1000-0534.2015.00075
• Abstract ( ) PDF (17125KB) ( )
• Trend distribution of the extreme precipitation and temperature events under climate change condition in 1901-2012 and regional differences of extreme events' frequency in the relatively warmer or colder periods are analyzed by defining the 10th or 90th percentile as the threshold of extreme events for each grid based on the CRU TS 3.22 datasets, focusing on the accelerated warming period from mid-late 1970's to late 1990's and the global warming hiatus (1998-2012). The results show that the frequencies of the extreme severe precipitation events and the extreme high temperature events increase while the frequencies of the extreme low temperature events decrease under significant global warming condition in the last 112 years. Frequency distribution of summer extreme severe precipitation events in the accelerated warming period is similar to that in 1956-1976 and high values are in North American mid-high latitudes, South America and Eurasian low latitudes. North American mid-high latitudes become low-value areas while frequencies in Eurasian mid latitudes increase in the warming hiatus. High values of frequency of winter extreme severe precipitation events are in northern South America, Eurasia and western Oceania while North America and southern Africa become low-value areas in the global-warming hiatus. Frequencies of the extreme high temperature events increase in warmer periods and mid-eastern Eurasian areas have high values in winter in the accelerated warming period. The feature of the extreme low temperature events is opposite to the extreme high temperature events but the frequency in Eurasian mid latitudes in the relatively warmer period of 1931-1955 is higher than the coldest period of 1901-1930 and the relatively colder period of 1956-1976. Frequencies of the extreme low temperature events increase obviously in northwestern Oceania in summer and winter and Eurasian mid-high latitudes in winter in the warming hiatus compared to that in the accelerated warming period. These results reveal the regional differences of land extreme precipitation and temperature changes in different periods, and the possible mechanisms still need further study.

• Impact of Boundary Layer Parameterization Scheme on the Diurnal Variation of Precipitation in Central Eastern China
• XU Jianyu;LIU Yu
• 2016 Vol. 35 (4): 969-978.  DOI:10.7522/j.issn.1000-0534.2015.00078
• Abstract ( ) PDF (13947KB) ( )
• The planetary boundary layer (PBL) is an important part of the numerical weather prediction model. Previous sensitive studies of the PBL schemes are mainly focused on the typical typhoon or heavy rainfall cases, but it is not clear how the PBL schemes impact the diurnal variation of precipitation in the operational model. Based on the operational central China regional mesoscale model WRF3D, sensitivity experiments have been made in July 2012 by using two PBL schemes named MYJ and ACM2 respectively. Then the impact of different schemes on the diurnal variation of precipitation in central eastern China has been studied by comparing the forecasted precipitation with the high-resolution observation provided by the National Meteorological Information Center. Furthermore, because of WRF3D is not a cloud-resolving model due to the limit of computing resources, the interaction of implicit and explicit precipitation processes should also be studied by deeply diagnosing the model outputs. The result showed that the precipitation forecasts by both schemes can reflect the double peaks observed in central eastern China to a certain extent. For the early morning precipitation peak, the difference between these two forecasts is little. But the difference in the late afternoon peak is distinct. Specifically, the late afternoon peak forecasted by the MYJ scheme is 4h ahead of the observation with an exaggerated amplitude, while it is only 1h ahead and the amplitude is reasonable by using the ACM2 scheme. In general, the diurnal variation of precipitation forecasted by ACM2 is more close to the observation. Dividing the forecasted precipitation into the implicit and explicit part, it shows that the late afternoon precipitation peak is mainly composed of the implicit one. In addition, the area-averaged implicit (explicit) precipitation forecasted by the MYJ scheme is more (less) than ACM2 at all times. Furthermore, detailed analysis of the high-resolution model outputs shows that, the over-predicted implicit precipitation by the MYJ scheme is mainly due to its own local closure, making the lower troposphere too wet, resulting in the larger CAPE and slightly smaller CIN appear some time earlier, and eventually triggering the KF cumulus parameterization scheme to produce the heavier and earlier implicit precipitation compared with ACM2. On the other hand, there is energy competition between the processes of implicit and explicit precipitation, inducing the much less hydrometeors forecasted by the MYJ scheme and leading to the less explicit precipitation compared with ACM2. It is concluded that there's important impact of the PBL schemes on the forecasted diurnal variation of precipitation in central eastern China. This result is intended to provide a reliable basis for the optimization of the PBL scheme in WRF3D.

• Surface Temperature and Precipitation Variation of Pastoral Transitional Zone in Northern China during 1964-2013
• ZHAO Wei;WEI Zhigang;ZHENG Zhiyuan;DONG Wenjie
• 2016 Vol. 35 (4): 979-988.  DOI:10.7522/j.issn.1000-0534.2015.00079
• Abstract ( ) PDF (8176KB) ( )
• This study analyzed the spatial-temporal change of historical temperature and precipitation in pastoral transitional zone in Northern China, based on observational temperature and precipitation grid datasets during 1964-2013 from Chinese Meteorology Administration (CMA). The climate division was made using rotated empirical orthogonal function (REOF) in the meantime. The result shows that: (1) The whole pastoral transitional zone in Northern China can be divided into 4 regions which can be simply named the west region, the central region, the southern section of the east region, and the northern section of the east region, respectively. (2) In general, the pastoral transitional zone in Northern China had experienced a significant warming during 1964-2013 which was mainly attributed to the warming of winter and larger increase of minimum temperature rather than the increase of maximum temperature. The pastoral transitional zone in Northern China had also experienced a slightly decrease of precipitation (13 mm less during 1964-2013), and it was largely because the summer precipitation had declined the most in this period. (3) Focused on sub-regions, the temperature of the central region in pastoral transitional zone increased the most in the period of 1964-2013 among 4 sub-regions. As for the precipitation, annual precipitation in western north region decreased in the last 50 years mostly because of the decrease of spring precipitation in local. Meanwhile, the annual precipitation in central region and the southern section of the east region had decreased as well, but differently, it can be mainly attributed to the summer precipitation's decline. Moreover, the annual precipitation increased in the northern section of the east region, and the spring precipitation contributed it the most. (4) The pastoral transitional zone in Northern China has experienced a warming hiatus resembling to the global warming hiatus since late 1990s, only the temperature has declined more, meaning that the declining trend of temperature in pastoral transitional zone is more obvious.

• Validation and Evaluation of Cloud and Precipitation Forecast Performance by Different Moist Physical Processes Schemes in GRPAES_GFS Model
• MA Zhanshan;LIU Qijun;QIN Yanyan
• 2016 Vol. 35 (4): 989-1003.  DOI:10.7522/j.issn.1000-0534.2015.00063
• Abstract ( ) PDF (10483KB) ( )
• Cumulus convection schemes and cloud microphysical schemes are the most important moist physical processes in numerical weather model, which have significant effects on cloud and precipitation forecast performance. Cloud and precipitation forecast performances by different combinations between the above precipitation processes parameterization schemes in GRAPES_GFS model have been diagnosed and validated using CMAP precipitation observation data and MODIS, MLS and CloudSat satellite data. The results show that: (1) The distinction of cloud microphysical schemes is a predominant reason for precipitation forecast difference at mid-high latitude areas. There is a sequence of SI > NCEP3 > NCEP5 according to the precipitation intensity of order. While the distinction of cumulus convection schemes is the main reason for those at low latitude areas. (2) There is more grid-scale precipitation of SI and NCEP3 schemes than that of NCEP5 scheme at middle latitude areas. Compared with SAS and KF scheme, BM scheme is prone to causing more grid-scale precipitation with its combinations partner cloud scheme. (3) There is obviously more convection precipitation of BM scheme than those of SAS and KF schemes. The convection precipitation magnitude of SAS scheme and KF scheme is very approximate at mid-high latitude areas, nevertheless, that of SAS scheme is the least among the three convection schemes at low latitude areas. (4) The cloud top temperature of NCEP5 is in good agreement with MODIS satellite data, while those of NCEP3 scheme and SI scheme are warmer than MODIS. There is a sequence of SAS < BM < KF from cold to warm for their cloud top temperature. (5) The integration cloud water content of NCEP5 is closest to MODIS observation and there are significantly less for the two simple ice microphysical schemes, especially for SI scheme. KF scheme has an obvious better performance for integration cloud water prediction than those of SAS and BM scheme. (6) There are all negative biases of cirrus cloud compared with MLS observation for three combinations. The comprehensive mixed phase cloud scheme NCEP5 has an slightly advantage with cirrus cloud forecast than that of simple ice phase scheme. (7) In terms of global average, the combination KF convection scheme and NCEP5 cloud scheme have better performances for cloud and precipitation forecast among all these precipitation processes parameterization schemes.

• Relationship between the Convective Boundary Layer and Residual Layer over Badain Jaran Desert in Summer
• ZHAO Cailing;LYU Shihua;HAN Bo;AO Yinhuan;LI Zhaoguo;ZHANG Shaobo
• 2016 Vol. 35 (4): 1004-1014.  DOI:10.7522/j.issn.1000-0534.2015.00080
• Abstract ( ) PDF (5299KB) ( )
• The characteristics and influencing factors of convective boundary layer height development of the Badain Jaran Desert were analyzed based on the observation data of July 2012 and WRF model. The result shows that: (1) Over the Badain Jaran desert, a convective boundary layer (CBL) that deeper than 4000 m has been observed on July 2012. It is also found that there was a nearly neutral residual layer in the morning before a deep CBL which was approximate 4000 m can be formed in the afternoon. When there was no residual layer in the morning as in 7 July, although the surface sensible heat flux was still intensive, the maximum depth of CBL on that day was only 1900 m. (2) The simulated maximum depth of CBL in different day varies much even the surface sensible heat flux changes little. After comparing the spatial distribution and temporal variation, it is found that the lapse rate within the residual layer owns not only a stronger time correlation but also a more significant pattern correlation with the CBL depth than the surface sensible heat flux. The maximum spatial correlation coefficient between the lapse rate within the residual layer and CBL height is -0.51. (3) Observations and simulated results show that the stratification status in the residual layer can directly affect the CBL development efficiency which is forced by sensible hear flux, and then affect the maximum CBL depth. Therefore, this study suggests that in addition to the sensible heat flux, the stratification status in the residual layer also plays an essential role for the development of CBL in the Badain Jaran desert in summer.

• Linkages between Pacific Interdecadal Oscillation and the Interdecadal Change of Summertime Thunderstorm Days in Jiangsu
• CHEN Shengjie;SUN Yan;HAN Guirong
• 2016 Vol. 35 (4): 1015-1026.  DOI:10.7522/j.issn.1000-0534.2015.00025
• Abstract ( ) PDF (4616KB) ( )
• The monthly Pacific Decadal Oscillation index (PDOI), NCEP/NCAR monthly reanalysis dataset, and thunderstorm days data recorded by 13 stations in Jiangsu for the period of 1961-2012 are used to investigate the relationships between PDO and summer thunderstorm days (STDs) in Jiangsu and the possible cause. The results show that spring PDOI and STD in Jiangsu both are characterized by interdecadal variations, and they are just out of the phase. Before the mid-1970s and since 2006, PDO was in the negative phases and STDs in Jiangsu were more than the climatic average. However from the mid-late-1970s to early in the 21th Century, PDO was in its warm phase, and thunderstorm poorly happened in Jiangsu in summer. During the cold phase of PDO, there are extensive negative anomalies of both sea level pressure and 500 hPa height over the Eurasian continent and western Pacific in summer. Associated with this, the Asian low pressure behave stronger, the polar vortex in troposphere tends to move towards the Asian region, and the trough to the north of the Qinghai-Xizang Plateau in central Asian is intensified. Moreover, the western Pacific subtropical high is weaker and eastward than the normal. The India-Burma trough strengthens obviously. In the control of the anomalous circulation, there is anomalously stronger transport of water vapor from the southwest at the low level of the troposphere over the Yangtze-Huaihe region. The mid-level air over Jiangsu turns to be drier while the low-level turns to be wetter, which contribute to unstable air layer and strong convective activity. It is also found that the anomalous low-level convergence and the anomalous upper-level divergence is observed, accompanied by ascending anomalies over Jiangsu. Meanwhile the vertical wind shear is abnormally enhanced in the lower troposphere when PDO is in its cold phase. All of this contributes to the development of thunderstorm in summer. And it is vice versa during the PDO warm phase. As a stably strong signal of interdecadal climate variability, the anomalous circulation associated PDO phenomena provides important environment and meteorological conditions for some kind of meso- and small-scale system events such as thunderstorm.

• Validation of Total Cloud Amount in 2007 Derived by NOAA/AVHRR
• LIU Jian;YANG Xiaofeng;CUI Peng
• 2016 Vol. 35 (4): 1027-1038.  DOI:10.7522/j.issn.1000-0534.2015.00029
• Abstract ( ) PDF (17458KB) ( )
• Based on recalibration and accurate re-location of NOAA/AVHRR data, long term total cloud amount were calculated by improved cloud detection and radiation calculation method. The study satellite data came from National Satellite meteorological Center. The long term total cloud amount is daily data and has 0.01°×0.01° spatial resolution. Based on 2007 data, NOAA/AVHRR calculated total cloud amount were validated using MODIS cloud products and synoptic observations. Compared with synoptic observations, NOAA/AVHRR derived total cloud amount shows the same cloud distribution character in China. The value of total cloud amounts estimated from NOAA/AVHRR is smaller than synoptic observations. These results are the same as Europe research conclusions. There are a lot of reasons to cause biases. One of reasons may come from the observation ability of NOAA/AVHRR. Compared with surface observation, accurate rate of AVHRR's cloud detection get 77.12%. It is higher than MODIS's 74.34%. At the same time, NOAA/AVHRR has lower false rate and higher loss rate than MODIS. NOAA/AVHRR used added snow detection to improve the accuracy of cloud detection so that NOAA AVHRR has lower false rate, especially in winter time over high latitude area. Because MODIS has more channels to detect cloud than NOAA/AVHRR, especially for cirrus, MODIS has lower loss rate than NOAA/AVHRR. EOF method was used to analyze the cloud amount distribution properties of AVHRR calculated, MODIS product and surface observations. The results show that the first EOF eigenvector can represent the distribution of three kinds of cloud amount. Compared with MODIS, either the time coefficient or spatial distribution of AVHRR calculated cloud amount is closer to surface observation, especially in winter time. In order to analyze the spatial relationship between satellite observation and surface observation, SVD method was used. AVHRR or MODIS data was set as left vector field. Surface observation was set as right vector. The SVD analysis results show that both AVHRR and MODIS have good relationship with surface observation. The first five correlation coefficients of AVHRR are 0.95, 0.95, 0.94, 0.92 and 0.88. They are all higher than corresponding MODIS's (0.89, 0.91, 0.90, 0.88 and 0.74). At the same time, the first SVD mode time correlation coefficient of AVHRR is 0.96, which is higher than MODIS's 0.76. AVHRR has lower discrete degree of curve fitting than MODIS. Two suit data show that AVHRR derived cloud amount has better match degree with surface observation than MODIS cloud amount.

• Comparison of Two Different Satellite Precipitation Data in Sichuan from May to August in 2013
• YANG Xing;WANG Yongqian;LIU Zhihong
• 2016 Vol. 35 (4): 1039-1049.  DOI:10.7522/j.issn.1000-0534.2015.00060
• Abstract ( ) PDF (2461KB) ( )
• This research chooses two satellites' precipitation products which are the newly CMORPH version1.0 and TRMM3B42 V6, using these two products to estimate the precipitation and events of precipitation in Sichuan province from May to August 2013 under three different temporal resolution which are 3 hours, daily and monthly. Using gauge data's location to choose the corresponding nearest data of satellite products, this method is different from before those which to resample and interpolate the pixel data, in this way the error may decline. This research chooses correlation coefficient to study the effect synchronous of precipitation algorithms, BIAS to study precipitation algorithm's systematical error and degree of correlation, RMSE to study the deviation of precipitation algorithm. Finding that both of the two products have bad synchrony with gauge data and can't reflect the precipitation information under 3 hours temporal resolution, but TRMM3B42 V6 has less systematic error and corresponds with gauge data better than CMORPH. For both of the two products are origin from different satellite data, each of these initial data may has its own error, so the error may still exist after merging them to the new product; The initial satellite data consist geosynchronous data, the shortage of geosynchronous satellite data is the period, if the period is long or short enough, the satellite may get the wrong data, these two reasons may cause the error of the final precipitation products. Both of the two products' synchrony are increasing when the temporal resolution comes to daily, TRMM3B42 V6's bias is less than CMORPH, it corresponds with gauge data better than CMORPH and has better synchrony with gauge data. TRMM3B42 V6 underestimates the precipitation and CMORPH overestimates the precipitation under monthly temporal scale, and TRMM3B42 V6 has higher correlation with gauge data than CMORPH, because CMORPH has use infrared data to get motion vector, and convective cloud can influent the brightness temperature of the cloud, when it overestimates brightness temperature of the top cloud will cause precipitation's overestimation. As for estimating the events of precipitation, this research uses three coefficients to analysis this issue, and they are: probability of detection (PD), frequency of hit (FH) and Heidke skill score (HSS). Form these three coefficients can know that CMORPH is better than TRMM3B42 V6 at detecting the events of precipitation.

• Characteristics and Reasons of Local Chang of Precipitation over Shaanxi during 1960-2012
• PENG Yan;WANG Zhao;DONG Yan;DONG Zipeng;LI Xingmin;CHEN Chuang
• 2016 Vol. 35 (4): 1050-1059.  DOI:10.7522/j.issn.1000-0534.2015.00023
• Abstract ( ) PDF (6145KB) ( )
• Based on observational data (82 meteorological stations) of rain frequency and amount from 1960 to 2012,the variation of total rainfall and frequency of annual and rain season(from June to September)during 1960-2012 were analyzed. And the variation of atmospheric perceptible water over Shaanxi, the effect of aerosol on precipitation was also discussed based on NCEP/NCAR reanalysis data (2.5°×2.5°) and MODIS C05 aerosol product.The result shows that the trend of annual rainfall and annual rain frequency decreased, while in rain seasons, there was an increase of total rainfall and a decrease of rain frequency. This phenomenon indicated thatrainfall intensity was enhanced and rainfalls highly concentrate in rain season. For annual and rain season,thelight rainfall and rain frequencywas slightly dropped.Whilein rain season, theamount and frequencyof moderate and heavy rain (≥10mm) was obviously increased (about 75.6% to total observation station). The variation of atmospheric perceptible water over Shaanxi provinceindicatedthatthe drop of annual rainfall may great related with the decrease of atmospheric perceptible water from 1960 to 2012, but opposite to the rainfall increasein rain season.Furthermore,the variation of aerosol optical depth (AOD) showed that there was a heavy aerosol loading and increasing tendency in AOD over Guanzhong, Hanzhong and Ankangbasin of Shaanxi province because of human activities during the last few decades, just the same regions of increase of rainfall in rain seasons. And the main aerosol type gradually shifted to the urban industrial type in Shaanxi. Studies showed that in some conditions high AOD may favor the precipitation.Therelationship of AOD and rainfall variabilityin Rain seasons showed that in Shaanxiprovince when AOD≥0.4 and rainfall≥10mm, the increased of AOD will invigorate the rain events.In general, the increase of rain events and rainfall concentrate in rain season was highly related with the increase of AOD over Shaanxi province.

• Structure and Mechanism Analysis of An Extratropical Cyclone on A Cyclonic Track
• XIONG Qiufen;GOU Shang;ZHANG Xin
• 2016 Vol. 35 (4): 1060-1072.  DOI:10.7522/j.issn.1000-0534.2015.00063
• Abstract ( ) PDF (16202KB) ( )
• The extratropical cyclone is the low vortex in the mid-latitude region associated with the baroclinic polar front. It is an important weather system that could reault in heavyrain, snowstorm, sandstorm, strong wind and storm tide on the sea. For a comprehensive understanding of structure and mechanism analysis of an extratropical cyclone, the analysis of the intensity, background, potential vorticity and advection of the extratropical cyclone on a cyclonic track that occurred from 6 to 10 June 2014 was done using conventional observations, NCEP 1°×1° reanalysis data and water vapor images from FY-2E. The result showed that: (1) The extratropical cyclone was deepening slowly, but it moved cyclonically on a curve path. The moving circle in the low troposphere is larger than that in the high troposphere, it stopped deepening when the center of the surface cyclone coincided with the center of the upper-level low vortex. (2) The extratropical cyclone with a cyclonic track was caused by the adjustment on 500 hPa in circulation of the ridge in Lake Baikal and Xinjiang which had developed during cyclogenesis, then the ridge in Okhotsk, Japan was strengthened while the surface cyclone had begun deepening. (3) The positive relativity vorticity tilted westward with height. The positive relativity vorticity in the lower layer of the troposphere was the first to enlarge, then the positive relativity vorticities in the entire troposphere were strengthened while the development of the surface cyclone. The front zone were intensified during the extratropical cyclone deepening, and it was weakening while the positive relative vorticities at different levels were vertically overlapped. (4) When the upper-level dry air with high potential vorticity was descending into moisture area, the upper-level positive vorticity advection resulted in convergence in the lower layer of the troposphere and development of surface low. (5) It was also found by quasi-geostrophic theory that warm advection and strong positive vorticity advection with upward vertical velocity in the middle troposphere intensified the surface cyclone, and the surface low moved into the regions of warm advection and differential vorticity advection between the upper level and low level downstream. The baroclinic instability with thermal advection is main mechanism of the formation and development of the extratropical cyclone.

• Spatio-Temporal Distribution of Aerosol and Weather Characteristics during Haze over the Eastern Northwest China
• YAN Jiaolong;ZHANG Wu;SHAN Yunpeng;LIU Dan
• 2016 Vol. 35 (4): 1073-1086.  DOI:10.7522/j.issn.1000-0534.2015.00028
• Abstract ( ) PDF (17440KB) ( )
• More frequency of haze events during recent ten years, caused more and more concern, it is hard to get the comprehensive information only with the ground-based observation.Based on CALIOP/CALIPSO satellite remote sensing data and ground-based routine observations,annual variation of haze events and the vertical spatial distribution characteristics of aerosol optical properties during haze event occurred in the eastern Northwest China(ENWC)was analyzed, to have a deeper understanding of haze events. Taking the haze events occurredin ENWC in March and November 2013 as examples,the aerosol particle shape and size distribution,weathersituation and meteorological elements during haze events were analyzed. The results show that, the frequency ofhaze events in ENWC decreased from 1981 to 2000 firstly and then increased obviously in early 21th century.Haze events occurred most frequently in December,November and January. When haze events occurred, the majority impact area in the troposphere is from 2 km to 4 km above the surface,the aerosol backscatter coefficientranged from 0.8×10^-3~2.5×10^-3 km^-1·sr^-1,and the backscatter coefficient decreased firstly with altitude andthen increased gradually. Aerosols volume depolarization ratio was mostly less than 20% in the area,whichmeans most part of aerosols were regular particles. The irregular particles were suspending under 4 km above thesurface the aerosol irregularities were weaken with the increasing of altitude. The value of Color ratio was below 0.8 in the area and centered at 0.0~0.4 between 8 and 12 km in height. Haze events could easily occur when thehigh-altitude and the surface are separately controlled by high-pressure system and uniform pressure,and there istemperature inversion near surface. This work provides advanced method for haze research and may contribute to the improvement on the prediction accuracy of heavy polluted weather.

• Performance Evaluation of Three-Dimensional Variation Assimilation Retrieval of Wind Field
• WANG Yanchun;WANG Hongyan;LIU Liping
• 2016 Vol. 35 (4): 1087-1101.  DOI:10.7522/j.issn.1000-0534.2015.00022
• Abstract ( ) PDF (21115KB) ( )
• In order to study the capacity, the applicability in different weather systems and the potential applications in business work of 3DVAR, three dual-Doppler radar systems corresponding three different weather systems as tropical storms, squall line and stratiform cloud precipitationare built by 6 Doppler weather radars which are Guangzhou radar, Shenzhen radar, Haikou radar, Zhanjiang radar, Longyan radar and Xiamen radar. The wind structure retrieved from dual-Doppler radar is used as ‘the true value’ to evaluate the performance of 3DVAR from the wind structure, AE, RMSE and COR. The results show that the wind structures retrieved from 3DVAR while using two radars dovetail nicely with the basic characteristics of various types of weather and could reproduce the convergence line in the low levels in a squall line and cyclonic circulation in a tropical storm. By comparing the wind retrieved from 3DVAR using single radar's data and that using two radars' data, it is indicated that While using one radar, it could not show wind structures of severe weather systems well and the retrieval performance of convergence line in the squall line and cyclonic circulation in the tropical storm is both poor. It could not only greatly reduce the error of wind direction but also improve the quality of tangential wind while using two radars' data. The results of error analysis indicate that the retrieval performance of wind speed and wind direction is reliable. The retrieval performance of stratiform clouds precipitation is superior to that of squall line and tropical storm.

• Comparison of the Mixing Layer Height Determination Methods using Lidar and Microwave Radiometer
• YANG Fuyan;ZHANG Ning;ZHU Liangfang;ZHU Yan
• 2016 Vol. 35 (4): 1102-1111.  DOI:10.7522/j.issn.1000-0534.2015.00045
• Abstract ( ) PDF (5668KB) ( )
• Methods for determining the mixing layer height based on a lidar and a microwave radiometer were compared during four sunny days (on 4, 7, 18 January and 4 February, 2010) in Suzhou. The observed mixing layer height varied between 300 m and 1500 m. The gradient method, the standard deviation method and the wavelet method were applied to extracting the mixing layer height from the lidar. Results showed that the three methods can determine the mixing layer height well and have a good agreement among them, the differences mainly occurred during the development and disappearance of the mixing layer, results by the gradient method and the wavelet method show little difference, while the standard deviation method results are slightly higher than others. The results determined by the temperature gradient method using microwave radiometer data were compared with the results determined using the lidar observations; there was a good correlation between the results and the correlation coefficient was 0.76. The results from the lidar were higher than these from microwave observations. The difference between the two observation devices was because of the different detection principles, especially in the development and dissipation stage of the boundary layer.

• Quality Control of Dual PRF Velocity Data for Doppler Weather Radars
• XIAO Yanjiao;WAN Yufa;WANG Zhibin
• 2016 Vol. 35 (4): 1112-1122.  DOI:10.7522/j.issn.1000-0534.2015.00039
• Abstract ( ) PDF (10501KB) ( )
• The dual pulse repetition frequency (dual PRF) technique is available to extend the unambiguous velocity interval of Doppler weather radar, but the velocity data are typically contaminated by discrete outliers in large areas of high quality data. The quality control is needed before using the radial velocity data. The radial velocity data from CINRAD-SA, SC, CC and CD type Doppler weather radar running in dual PRF mode have been analyzed quantitatively through calculating the deviations of each radial velocity from its local median velocity. On this basis, a three-step postprocessing algorithm is proposed. First of all, the dual PRF velocity data are filtered based on the size to remove the isolated noise. Secondly, aliased velocity data that fall outside of the extended unambiguous velocity interval are unfolded using local continuity constraints. And lastly, using the known error characteristics of the dual PRF velocity data, velocity outliers are corrected in an efficient way. The algorithm has been tested using dual PRF velocity data from CINRAD-SA, SC, CD and CC type Doppler weather radars. The results of dual PRF velocity data analysis show the vast majority of the analyzed points obeys local continuity with hardly any deviation or small deviation from the local median velocity, the fraction of outliers are centered at different velocity deviations which roughly match the unambiguous intervals of the low PRF and high PRF measurements. The results of the algorithm testing show that it can correct effectively aliased velocities and discrete outliers caused by dual PRF mode. After quality control using this algorithm, high quality velocity data with changeless spatial resolution are produced.

• Characteristics of Charge Sources Retrieved from the Multi-Station ynchronous Electric Field Change Measurements of Negative Return-Strokes
• WU Zhijun;QIE Xiushu;WANG Dongfang
• 2016 Vol. 35 (4): 1123-1134.  DOI:10.7522/j.issn.1000-0534.2015.00070
• Abstract ( ) PDF (7105KB) ( )
• Using the measurements from slow and fast antenna of 7 stations synchronized by GPS during a thunderstorm which passed over Beijing Lightning NETwork (BLNET) on 9 August 2011, the magnitude and location of charge neutralized by 127 return strokes of 51 negative cloud-to-ground (CG) lightning flashes are fitted by using nonlinear least-squares fitting algorithm after Monte Carlo data processing and correction in advance. The fitting results were analyzed from several aspects shown as below. (1) For the charge sources neutralized by the strokes in one multi-stroke negative CG lightning, the horizontal distribution range Le and the vertical distribution range ΔHe was 13.0±9.3 km and 2.1±1.7 km respectively, and the ratio Le/ΔHe was 61.2±278.5. As the vertical range ΔHe increased, the horizontal range Le and the ratio Le/ΔHe decreased. (2) When the thunderstorm evolved from developing stage into mature stage, the maximum height of the stroke charge sources raised up gradually. When the thunderstorm evolved into dissipating stage, the maximum height of the stroke charge sources significantly became less than before. Throughout this period, the minimum height of the stroke charge sources kept around 5 km and the horizontal locations moved from northwest to southeast while the thunderstorm moved in the same direction. (3) The superposition of the charge sources and the radar echo showed the charge sources of negative return-stroke were mainly concentrated inside the cloud region with radar reflectivity higher than 25 dBZ. The charge sources with height more than 7 km accounted for 34% of the total and were concentrated inside updrafts of convection, while the charge sources with height less than 7 km were about 66% and located both inside and outside updrafts of convection.