Constructing suitable meteorological drought indicators is an important foundation for drought monitoring and drought evaluation services. Based on the daily average temperature and precipitation of 155 national meteorological stations in Sichuan Province from 1997 to 2021, as well as the crop area data of each county (city or district), the modified meteorological drought composite index (MCI_m) is formed by improving the seasonal adjustment coefficient of the meteorological drought composite index (MCI). The regional drought process identification method was revised according to annual drought disaster area and annual effective irrigation area and 51 regional drought processes in Sichuan Province were identified in the past years. The temporal and spatial distribution characteristics of regional drought processes in Sichuan Province were analyzed by using empirical orthogonal function (EOF), rotated empirical orthogonal function (REOF) and Morlet wavelet analysis. The results show that the evolution results of the durative day, average intensity, average impact area and comprehensive intensity index of the regional drought processes in Sichuan Province decrease initially, followed by increase, but then again decrease. The average annual cumulative days of regional drought process in the basin area were more than those in the mountains area around the basin, and those in the mountains area around the basin were more than those in western Sichuan Plateau and Panxi area. The spatial pattern of annual accumulated MCI_m anomaly decomposed by EOF was consistent in Sichuan Province and was also opposite in the northern and southern parts of Sichuan. Sichuan Province can be divided into six drought climatic areas. The annual cumulative MCI_m periodic change from 2009 to 2015 was more obvious than that from 2001 to 2008 in each area. The identified regional drought processes according to improved regional drought process identification method are in good agreement with the drought disaster situation and could better reflect the actual situation of drought in Sichuan Province more accurately.

By using thelatest data obtainedfromthe 80 m observingtowerformeteorolo~calfactors detectinginthe hinterland ofTaldi·makan Desert。the evolution characteristics of the wind velocity，temperature an d humidity profiles near the surface layer there on a cloudy day(A 1 2，2006)were analyzed in detail，and these profiles were compared with those ofthe typical sunshiny day there．Re·suits are as follows：(1)On cloudy day，the value of wind speed is increasing with height at night but its change doesn’t obey the loga·rithmic law，it grows at a faster rate；in the daytime the wind spe ed is small，the distributions of wind velocity profiles above and below 10 m near the surface layer are rather diferent at each o~ervational time；(2)Observed temperature profiles on cloudy day age classi·fled into four types：radiation coling at night。transition from night to daytime in early morning，insolation in the daytime，transition from daytime to night，respectively，they are similar to those of sunshiny day；(3)There is a minimum in spec~c humidity profiles，a·beve the height where the minimum appears the specie humidity rises with height increase and appears a”moisture inversion”phe·nomenon，and below that height the specific humidity rises with height decrease．

Desertific;ation is one of the most serious ec;ologic;al} social and economic; problems in arid and semi一arid regions in the con-
temporary world.  Based on referring to a large amount of literature we have narrated and(ommented the concept of desertification in
detail and its  connotation from time spac content  landscape  development tendency and results of sandy desertification in this arti-
cle and have particularly outlined the domestic and foreign desertific;ation monitoring appraisal target system}graduation and its distri-
bution in the world. On one of the focal arguments point of the(auses of desertification} we have synthesized various viewpoints and fi-
nally summarized as natural reason and artificial reason such as drought climate, gale and unreasonable human being's”six excesses"
activities.  Simultaneously controlling methods, basic  we have outlined the interaction ways of desertific;ation and some
Between global warming and desertification. In the end， the preventing and questions like these have also been summarized systemically