According to many scholars’studies on the Northwest China，this article summed up the ecological environment，climate hange features and trends in the Northwest China．Due to some coupling relationship existing between climate，environmental change nd sandstorm frequency，the paper briefly described some climatic factors influencing dust storm frequency，and combined with the elevant arguments to explore the climate and environment changes how to impact on occurrence and development of sandstorm in Northwest China．Many researches show that the development of dust storms is directly affected by the wind，precipitation and status of underlying surface，etc．The frequency and intensity of dust storms are closely related to the natural conditions and climate of sandstorm ources，and gale is a bigger influence factor under certain underlying surface condition．The increase of precipitation has a certain inhibitory effect on sandstorm，the temperature has the indirect effect through atmospheric circulation on duststorm，and soil moisture’s nfluence on sandstorm by changing the vegetation cover，surface condition．
Sandstorm is a severe weather phenomenon in China．Locating in the northeast of Hexi corridor，Minqin is surrounded by deserts，under the bad natural environment，it is becoming one of the most sandstorm outbreak areas in China．Based on the longterm sandstorm observation in this region，the interannual rule of sandstorm breakout was studied．Results show that the general trend of sandstorm outbreak was reduced，and for a certain period it had the oscillation with peak or trough．The outbreak of sandstorm had 5 or 15 years periodic change，and in different seasons it has a slightly difference．Using NECP/NCAR data，the 500 hPa height field in spring of typical years was analyzed，and we found a height field feature that has a close realtionship with sandstorm breakout in Min-qin area．Near the Obama hyjal lake and Balkhash Lake there was a high value system and a low value system，they may appear at same time or alone．When Minqin is controlled by high value system in spring，sandstorm will reduce，but when controlled by the low value system，sandstorm will be more in Minqin．
Soil heat flux plays an important role in energy flux exchange between land and atmosphere, especially in arid and semi-arid region. Based on soil heat flux at Zhangye National Climate Observatory, the diurnal variation of soil heat flux and the relationship between that and radiation flux are analyzed under different weather conditions for clear, cloudy and rainy day.The results show that the soil accepted heat from the air on clear day, on the contrary, the output heat of soil exceeded the input on cloudy and rainy day. In addition, most values of soil heat flux are negative in autumn and winter season, and positive in spring and summer .
Based on five - layer wind speed, air temperature, humidity and vapor p ressure of the gradient tower of Zhangye National Climate Observatory built in 2007 from Sep tember 2007 to August 2008, the percentage of missing value was calculated, and the climate characteristics of Zhangye in different seasons were also analyzed. The reliability of data from the gradient towerwas checked by comparing with some other observational stations.
The spatial distribution ofwater resource shortage in China is summed up from the p ractical condition and sustaining devel2 opment angles. The actuality and trend ofwater resource are reviewed, the characteristic ofwater cycle and water resource utilization in arid region ofNorthwest China are analyzed. And research advances on water cycle and effective utilization ofwater resource in arid re2 gion are summarized, the scientific countermeasures about effective utilization of water resource in arid region are p reliminarily dis2 cussed. Finally, some important scientific issues aboutwater cycle and effective utilization ofwater resource in arid region ofNorthwest China are put forward.
By using global reanalysis data from NCEP /NCAR, the durative of a floating dust overBeijing during 7 - 10 in Ap ril of 2006 was analyzed. Itwas found that the impact systems of the floating dustweatherwereWest Siberia cold eddy, Okhotsk warm high and Tibetan Plateau high ridge at the level of 500 hPa; the dry - cold air at the level of 700 hPa transferred to Beijing ceaselessly, and the cold advection and baroclinic instabilitywere strong, the gale and dust storm occurred in the strong cold advection area; the weak instability stratification in surface layer and mid - low level in the south ofNorth China resulted in weak ascending air flow, then transported dust particles to Beijing depending on the easterlywind in front of the surface low p- ressure. Because of the neutral or instability condition atmid - low level over Beijing, the dust particleswere difficult to go down, and the floating dustweather lasted for four days.
The status quo of disasters caused by sand—dust storm in Northern China Was analyzed，and the spatial distribu6on，develo-ping trend，as well as origin，source and moving path of san d—dust storm were reviewed respectively．Th e agronomy approaches to sand—dust storm disasters reduction were suggested，and mechan ism for sand—dust storm prevention under the ground of global cli-mate change Was discussed mainly．It Was pointed out that the farming structure adjustment should apply to global climate change to prevent worsening of sand—dust storm in Northern China，an d the way to improve sustainable development of agriculture in arid and semi—arid regions Was put forward，namely combining the environment and the needs of social development in Northern China，making use of climate change law，adopting agricultural control measures through reasonable spatial—temporal farming distribution，exerting the environment preservation function of conservation tilage and winter crop extending northward．
Some researches on the creeping environmental problems in recent years in International Center for Creeping Environmental Problems of Lanzhou were reviewed，including definition，significance，Cases and countermeasures on creeping environment，and rela-tionships among human activities，global warming and creeping environment．
Based on the re - analyzed grid data of NCEP，the observed precipitation of 31 stations in southeast Gansu，and the 15 ～ 40 cm ground temperature data of 4 representative stations from 1960 to 2001，86 primarily selected factors were designed with 11 kinds of physical quantities，the forecasted area was divided into 3 districts of east，south and west，weather circulation was classified as 4 patterns，3 primary and 12 two - stage discriminant functions of rainstorms in southeast Gansu were obtained through discriminant analysis approach，and the dynamic statistical PP forecast model is composed of these functions. The results of examining in return indicate that in the situation of 90% ～93% rainstorm days included by positive examples，excluding rate of forecast mistake reaches 63% ～68%；The two - stage dynamic discriminant in east and south districts is good，the forecast skill is basically above 60%，of which for the composite flow patterns in east district it can reach above 80%，and it is not good in west district on the whole，but relatively to actual forecast level of rainstorms，12 functions have certain reference value. The examination conducted by using observed data from 2004 to 2005 July shows that the model forecast skill can reach 39. 3%；Through experimental running，applying 12 and 36 hours forecasting data of T213，the model explanation has good reflection to the rainstorm occurred in southeast Gansu from June 30 to July 2，2005，two aspects both show that the model has practical value
The operational flow，prediction effects and some problems occurring in the prediction of GRAPES-SDM which is running in IAM are summarized. The results account for that the prediction ability of the model is good，but there are some problems needed to be improved further.
Based on the data of 10℃initial dates and upper air temperature of 39 stations in Cansu loess plateau from 1971 to 2004 the(limatic; feature and(irc;ulation background of 10℃initial dates were analyzed in the paper meanwhile the(limatic; prediction method WHS eSCabhShed f01' the I'epl'eSentatlVe SCatlOn Of Xlfeng. 1}eSn1tS S1lOW that thel'e al'e 3 earlier and 3 later areas where the dally mean tempel'atm'e SCeadlly OVPI' 10℃，which are located in Beidao} Lanzhou} Jingc;huan} and Huajialing} Dongxiang} Minxian} respec;trvely; and the earliest 10℃initial date is April 14 in Beidao} the latest date is June 5 in Huajialing; and 10℃initial date ocurged later in Dingxi and Lingxia, earlier in Tianshui} Pingliang} Qingyang and Baiyin. The、hanging trend of the day when the mean temperature steadily over 10℃in Cansu loess parts of the region in 1980s it is earlier in the north plateau has been earlier and earlier since 1990s} and it is part and later in the south part. 500 hPa } 700 hPa height later f;ellls in 1970s in are(ontrolled by the ridge of high pressure from the north part of Qinghai一Xizang plateau to Xinjiang} and temperature fields、ontrolled by the broad temperature ridge there and OLR flow fields(ontrolled by positive anomalies on 10℃initial date in earlier years; on the(ontrary, 500 hPa} 700 hPa height fields a1.e influenced by the deep trough over Tarim Basin temperature 10T:initial fields affected by the broad temperatune trough over Xinjiang} and OLR flow fields influenced by negative anomalies on late in later years
based on the mean daily temperature data in spring from 1961 to 2000，using empirical orthogonal function complex empirical orthogonal function(CE<)F)，fractal dimension，and wavclet analysis methods, the spatial and temporal evolvement of spring cold weather intensity in Chinese loess plateau was analyzed in this paper. Results show that the spring cold weather intensity decreased approximately from north to south, and also there was a gradient from cast to west;the linear decreasing rate of the spring cold weather intensity in the middle of the plateau was bigger than that in the peripheral，and the changing tendency was remarkable in March and April;there was periodic oscillation of the spring cold weather intensity change，which were about 2一}I a in March，3一} a in April，2一} a and 6 a in May, respectively. 'hhe spring cold weather in- tensity was weakest in 1990x. "hhe strongest period of spring cold weather in March，April and May, and the distribution was different in each month. "hhe spring cold weather intensity change in April had a transition in 1980，and then it decreased obvi- ously. 'hhe fractal dimension increased gradually from March to May, the changing complex degree of the spring cold weather intensity increased at the same time. "hhe big amplitude area of spring cold weather was in the center of the plateau. "hhe change information flew to cast in the west and southwest in the cast of the plateau.
Abstract:A model simulation of“2002.3”sandstorm by nonhydrostatic mesoscale model MM5 is analyzed in an effort to study the mechanism of the sandstorm.The diagnosis of convective momentum transport (CMT) shows that, at every level,the maximum bud- get residualXof the horizontal momentum is located behind the trough,whichXstrengthened the northwest cold air flow to south. The angle between Xand Vwas smaller than 90°behind the trough,that means accelerated northwest cold air flow to south and it is in favor of deepening the trough and moves to southeast. At the level of 300hPa, kinetic ener- gy transferEhad clear belt distribution, and the maximum centers ofEwas mainly located on the each side of upper Jet, that showed the upper Jet played a very important role in kinetic energy transfer. The distribution character of vorticity and divergency is consistent with the trough that trigged the sandstorm.Model trajectories analyses indicated that there was airstream in the trough at the upper level of 300hPa, and it flow to southeast at the level of 500hPa, there exist mountain-plain circulation to the north of the Plateau. The sand transport routing can be determined by superimposing the sand concentration over the trajectories, theoretically, but the forecasting of the trajectories is difficult at now.
The reasons of sandstorm occurring frequently in spring in Hexi corridor were analyzed .we found special geographical locadon .particular topography and physiognomy and arid climatic background are the main reasons. The number of sandstorm occurring in Hexi corridor has decreased since 1955 in general ,most in 1970 s'.least in 1990 s'.The results show that the occurring of sandstorm in Hexi corridor connects with winter monsoon of East Asia .and has吨h correlation with SST of Middle East Pacific in prophase autumn and winter. When the SST was higher .the winter monsoon of East Asia would be weaker .the number of sand storm occurring in Hexi corridor would be less than usual. On the contrary .it would be more.
In this paper .the characteristics of }atial distribution and temporal evolvement for winter temperature abnormality in Northwest China are researched饰using the methods of EOF and REOF with the winter temperature data of 89 observation stations about 40 years over ham.Gansu .Ningxia .Qinghai and Xinjiang provinces. Some significative conclusions are found.
