Plateau Meteorology

Current Issue

28 December 2004, Volume 23 Issue 6   
  • Mechanism of Hail Formation on the Northeast Border of Qinghai-Xizang Plateau and Its Neighbourhood
  • KANG Feng-qin;ZHANG Qiang;MA Sheng-ping;QIAO Yan-jun;GUO Xue-liang
  • 2004 Vol. 23 (6): 749-757. 
  • Abstract ( ) PDF (491KB) ( )
  • As a study background of the shear wave moving eastward inducing hailstorm frequently on the northeastern border of Qinghai-Xizang Plateau and its neighbourhood, the formation and growth of hails are simulatedusing a 3D cloud model with hail-bin microphysics developed by Institute of Atmospheric Physics, Chinese Academy of Sciences and the large scale circulations information obtained from MM5V3 model.The results show that: (1) the space distribution and positioning of temperature, the vertical airflow, the horizontal wind zero line region and 5 categories of hail and 5 hydrometeors meet the needs of the "cave channels"(CC), the water contents of hail are large;(2) the smallice particles( D<1 mm), graupel and hail embryos (1 mm< D<5 mm) and small hailstones (5 mm < D<10 mm) show another high water content region over -30~-50℃ altitudeat the initial stage of hail formation.Between them there is a clear low water content space, which means there are two different hail's formation Mechanisms;(3) as thehail and rainfall, the downwind is forming.On the region of cave channels, the downwind occurs too, here still is the center of high hail water content, even all upwind turn to downwind on the CC region.The simulated results present a detailed CC mechanism, even the downwind on CC region, reveal "CC" in the hail cloud is effective region of formation and growth of hail.
  • Analysis and Satellite Monitor of A Developing Process of Hail Cloud
  • ZHANG Jie;LI Wen-li;KANG Feng-qin;QU Yong-xing;SONG Xu-ying
  • 2004 Vol. 23 (6): 758-763. 
  • Abstract ( ) PDF (323KB) ( )
  • Weather process, energy conversion and reflectance character of a hail cloud in visible and middle infrared bands are analyzed by using the satellite, radar and some observed data including surface and upper air, aiming at a convection process of regional hail generanting on September 21, 2003.The result showed that, accompanying the exchange of atmospheric energy, the convective cool cloud cells in areas of Lake Qinghai to the east move toward the precess of east to combined warm clouds brought by the warm tongue in westsouth of Qinghaihu on the same day, which formed hail and rainstorm weather.The reason is that there are a instability atmosphere layer and effect of surface heated.1 The cloud developed peak at 17:00, at that time, the lowest temperature of cloud top is -44℃, critical temperature of hail generant is -39.2℃, critical bright-temperature is 221K.(2) Horizontal gradient of temperature of hail cloud is between 20~35℃/50km, it means that character of hail intensity is with hail and without disaster.3 The effective radius of cloud particle is larger and optical thickness of aerosol is large, which were reflected by CH1 and CH3 reflectance.
  • Radar Climatic Characteristics of Severe Convective Cloud in Yongdeng, Gansu
  • QU Yong-xing;ZHANG Qiang;KANG Feng-qin
  • 2004 Vol. 23 (6): 773-780. 
  • Abstract ( ) PDF (353KB) ( )
  • Using the 19-year radar echo data in disaster area of Yongdeng, Gansu, the relation between the forming of severe convective echo and distributing characteristics with special topography characteristics of Yongdeng, Gansu, the large-scale weather background and its corresponding to severe convective echo moving, height, intensity and echo spectrum are analyzed.The results show that (1) the special topography cause the air flow blocking and make it to turn back and converge, then vertical motion violently quicken, and making the convective cloud developed very quickly, which is the critical factor of the forming and distribution of convective cloud.(2) the weather pattern at high level and the convective cloud construction restrict radar echo moving and echo basic characteristic.(3) the echo spectrum of hail cloud show that convective activity of hail storm is exuberant state in general, the severe echo height and its temperature are important conditions for the formation of hail cloud.(4) the change of hail storm echo intensity depends on the case intensity of hail storm.
  • Characteristics of Water Requirement and Supply of Main Crops in Gansu Province
  • YANG Xing-guo;LIU Hong-yi;FU Zhao;MA Peng-li;WANG Run-yuan;YANG Qi-guo
  • 2004 Vol. 23 (6): 821-827. 
  • Abstract ( ) PDF (333KB) ( )
  • The crop water requirements (CWR) of wheat and corn are calculated by utilizing the FAO Penman-Monteith equation (FAO-PM) and the spatial-temporal characteristics of CWR and water supply(WS) in different climatic regions of Gansu province were analyzed as well.The result shows that the CWR increases from south-east to north-west and the maximum value(515 mm) is at Anxi and Dunhuang regions, the minimum value(282 mm) is at Hui- and Cheng-county basins.The distribution of daily CWR is the typical curve with one peak value during the growth period of crop.Because of the climatic change, CWR occurred the undulated decreasing tendency.For the rainfed agriculture regions, the characteristics of the calculated CWR are closely to the observation after taking into consideration the water supply of soil water.Although CWR of corn is more than that of wheat, the difference between CWR and WS of corn is less than that of wheat because the key and maximum water requirement dates of CWR for corn are coincide with the rainy periods.For the irrigated culture region, the total quantity of surface water resource is able to meet the amount of CWR, but the water resource supplying to ecological environment is also exhausted.Therefore, the self-contradictory of water requirement and supply is more serious.
  • Experimental Study on Surface Energy Balance over Loess Plateau of Middle Part Gansu in Summer
  • YANG Xing-guo;ZHANG Qiang;WANG Run-yuan;MA Peng-li;YANG Qi-guo;LIU Hong-yi
  • 2004 Vol. 23 (6): 828-834. 
  • Abstract ( ) PDF (293KB) ( )
  • The surface energy flux characteristic of Loess Plateau in middle part of Gansu is analyzed based on the experimental energy flux data observed over Dingxi Arid Meteorology and Ecological Environment Experimental Stations in June~August 2003.The result shows that the net radiation is mainly used up field evapotranspiration either in spring wheat field or in bare field on fine or cloudy days, which lead to the rate of latent flux to net radiation is higher at bare field than that at spring wheat one because of the rainfall increasing.The diurnal temperature variations of the surface and soil show the approximately sine curve on clear and cloudy days either at the surface or 5 cm and 10 cm depths, but the anti-phase variation on the weak extent at 20 cm depths, even no diurnal variation under 50 cm.Furthermore, the cloud and precipitation can bring about great influence on surface radiation and energy balance in semi-arid region.The Bowen rate is increasing after sunrise and the maximum value occurs at midday time and under zero with large fluctuation during night.Meanwhile the Bowen rate in spring wheat field is bigger than one in bare one and the both maximum values are 1.01 and 0.75 respectively.
  • Climate Features and Formation Causes of Autumn Rain over Southwest China
  • BAI Hu-zhi;DONG Wen-jie
  • 2004 Vol. 23 (6): 884-889. 
  • Abstract ( ) PDF (337KB) ( )
  • On the basis of analying the climatic characterstics of autumn rain over Southwest China, the autumn rain index was designed by using the autumn precipitation and rain day numbers, meanwhile, the decompositions of EOF and REOF technique were carried out, and the main effective factors about autumn rain were analyzed.The results showed that the first mode indicates the precipitation trend to the north and to the south over the mid-and-upper reaches of Changjiang River is just oposite.The second load eigenvector fields reflectes the consistency of precipitation over Southwest China.The six climatic zones of autumn rain over Southwest China were respectively divided by REOF technique.The trend of climatic change indicated that there is more rain comparatively over Southwest China in autumn in the periods of from 1960's to early 1970's and 1980's, and for less rain in the periods of mid-and-late 1970's, from middle 1980's to late 1990's, however the autumn rain appeared obviouslyin early 21 st centurytoo.Western Pacific subtropical high, trough located at India and Burma, and Baikal trough were the main influence systems of autumn rain over southwest China.If the Baikal trough and India-Burma trough were well-developed and west Pacific subtropical high were strengthened, which would be favorable for more rain over Southwest China in autumn, on the contrary, if the condition was overturned, and then which would resulted in rainless.
  • Climatic Characteristics of Qinghai-Xizang Plateau and Its Surrounding
  • BAI Hu-zhi;DONG Wen-jie;MA Zhen-feng
  • 2004 Vol. 23 (6): 890-897. 
  • Abstract ( ) PDF (443KB) ( )
  • The relationship between the climatic characteristic over Qinghai-Xizang Palteau and Chinese abnormal climate is studied by using the temperature and precipitation data of 710 stations (72 stations in Qinghai-Xizang Plateau).The results show that the areas of more rain days can be divided into five areas, namely the South China, South China-Southeast of Qinghai-Xizang Plateau, Qinghai-Xizang Plateau and West China, and the more rain areas more than 5 rain days in each decad move from east to west of China.The annual precipitation feature in Southeast of Qinghai-Xizang Plateau are double peak values, and in Northeast, for single peak value, but there are obvious "Plateau rainy period", summer drought and autumn rainfall in Northwest of Qinghai-Xizang Plateau.The analysis of teleconnetion in Linzhi shows that the correlation coefficient between the winter temperature in Linzhi and the one at the same period in Qinghai-Xizang Plateau is positive, and the other regions are negative.The correlation coefficient between summer precipitation in Linzhi and the one at the same period in South of Qinghai-Xizang Plateau and in the mid-and-lower reaches of Changjiang River is positive, and in North of Qinghai-Xizang Plateau, for negative.The correlation between winter temperature at Linzhi and summer precipitation of regions from Yellow River to Changjiang River is negative.
  • Climatic Change Characteristics of Precipitation in Gansu Province in Recent 40 years
  • LIN Shu;LU Deng-rong
  • 2004 Vol. 23 (6): 898-904. 
  • Abstract ( ) PDF (328KB) ( )
  • Using the day-by-day precipitation data at 59 stations in Gansu province from 1960 to 2003, the climatic change characteristics of yearly precipitation and rain days in Gansu in four seasons are studied.The results show that the spatial distribution patterns of multi-yearly mean precipitation in Gansu is similar to that of the rain days.The trend coefficients of yearly precipition in Gansu Corridor and Baiyin are positive, others are negative.The trend coefficients of yearly rain days in most of parts of Gansu Corridor are positive, others are negative.The linear trend estimate value of precipitation shows that the zero line of linear trend value of yearly precipitaion basically takes Yellow River as the boundary, the precipitaion of Gansu Corridor is increasing, others are decreasing, and especially the decrease of precipitaion in Hui and Kang county basins is very obvious.The rain days in west Gansu Corridor, Linxia and Gannan are increasing, and those of in the mid and southeast parts of Gansu are decreasing.The rain days increase, The precipitaion will be increased too in areas, and vice versa.The yearly rain days and precipitation in Gansu in 1990's are low values, but the both rise up in the beginning of 21 century.The sudden change of precipitaion in Gansu is in middle of 1990's, and that for the rain days in Gansu Corridor is in the late of 1960's, in the area to the east of Yellow River, in the late of 1970's and middle of 1990's.Both the precipitation and rain days in Gansu in winter and autum have the province-wide increasing and decreasing trends in past 40 years respectively.But for changes of the precipitation and rain days in Gansu in spring or summer show the feature on the regional scale.
  • Study on Precipitation Variability in Last 100 Years and Trend Prediction in Northeast Asia in Future 10~15 Years
  • ZHANG Cun-jie;LI Dong-liang;WANG Xiao-ping
  • 2004 Vol. 23 (6): 919-929. 
  • Abstract ( ) PDF (581KB) ( )
  • The reliability of CRU05 precipitation dataset constructed by Climatic Research Unit of University of East Anglia of United Kingdom is examined using the precipitation data of twenty two observation stations in north of China.Comparing with the same data, this new dataset has higher spatial and-longer temporal resolutions than other similar datasets, which has high quality in the East China in last 100 years and in the west of China in last 70 years.We use this dataset to analysis the precipitation variability in Northeast Asia, it is found that there are 3, 10 and 30 year prominent oscillation periods.Interannual and interdecadal oscillation periods play an important role in the drought and rainy periods in the last 100 years.the precipitation of Northeast Asia was divided into ten regions, including (I) middle Asia and north of Xinjiang, (II) north China and east of Northwest China, (III) north and middle of Mongolia, (IV) Hexi Corridor and west of Mongolia, (V) east of Heilongjiang river, (VI) west of Daxing'anling Mountain, (VII) north of Middle Asia, (VIII) south of Xinjiang and Chaidamu basin, (IX) south of Northeast China, and (X) north of Altai Mountain.It was found that the arid and semi-arid areas in North of China are not isolated, and connected with the arid areas of Mongolia and Middle Asia.In addition, basing on the analysis of prominent oscillation periods, the trends of precipitation in north of China in the future 10~15 years were discussed.
  • Effects of ENSO Cycle on the Summer Climate Anomaly over Northwest China
  • LI Yao-hui;LI Dong-liang
  • 2004 Vol. 23 (6): 930-935. 
  • Abstract ( ) PDF (300KB) ( )
  • The anomaly features of summer rainfall and temperature in Northwest China during the ENSO cycle are analysed by using the data of Shaanxi, Gansu, Ningxia, Qinghai and Xinjiang from the period of 1960-1996.The results show that the characters of summer climate anomaly in Northwest China are quite different in different phases of ENSO.During the devoloped years of ElNiño, rainfall is deficient and temperature is higher over the most of areas of Northwest China, especially on the east side of Qinghai-Xizang Plateau(QXP), which is easy to occur drought, but in Xingjiang the low temperature and more rain are the dominant.In the next years of ElNiño or La Niña years, Xingjiang and region on the east side of Qinghai-Xizang Plateau are wet and low temperature, but the features of climatic anomaly in the La Niña year are more remarkable.The summer rainfall anomaly features in Northwest China are more clear in the developed years of ElNiño than in the next years of El Niño and La Niña year, but the features of temperater anomaly are opposite too.No matter whether it is rainfall anomaly or temperature anomaly, the summer climate on the northeast side of the QXP is the most sensitive region to the ENSO effct over Northwest China.

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