To better understand the dust storm (hereafter DS) inducing circulation in the China-Mongolia (CM) DS activity area,the spring mean circulation features and differences on lower levels in three subregions of the CM DS area for the majorandminor-DS years have,as a whole (not partly),been analyzed,utilizing the National Centers for Environmental Prediction and the National Center for Atmospheric Research (NCEP/NCAR) reanalyzed gridded data,the observed DS frequency data in the CM area,and the composite analysis method.The main conclusions are as follows:(1) Judging from the differences in the DS-inducing systems,dust origins,paths of invading cold air,and main DS-strike areas,the whole CM DS area is roughly divided into the three subre-gions:the East-,Middleand West-CM subregions (in this paper,referred to as E-,M-,and W-CM).(2) In major DSs during spring over the E-CM,the middleand lower-level troughs or cyclones over the Japan Sea and northeastern China (NEC) domi-nate.The invading cold air along the northeastern (NE) or north by east (NE) path often causes the DS in the E-CM region.But nearly the opposite is true inminor DS during spring in E-CM.(3) In the major DS during spring over the M-CM region,the Mongolian troughs or cyclones are the main DS-inducing systems.The strong invading cold air along the northwestern (NW)or north by west (Nw) path causes the DSs in the M-CM region.(4) In the major DSs during spring over the W-CM region,the South Xinjiang heat lows prevail,the intruding cold air has a western path,and creates the DSs in South Xinjiang.(5) In the past 50 years,the DSs over the M-CM region have had the most severe impact on the preceding three subregions of the CM DS area.Overall,DS activities over all of three regions of the CM area decreased in the past (particularly,over Mand W-CM regions since the mid-1980s.But there existed a short and sudden increasing in E-CM in the years 2000-2002.(6) It is circulation changes and desertification evolutions that cause the yearly and decadal changes of DS in
MinHong Song 1,ZhengAn Qian 1,Ying Cai 1,ChungMing Liu 2 1.Cold and Arid Regions Environmental and Engineering Research Institute,Chinese Academy of Sciences,Lanzhou Gansu 730000,China.2.Department of Atmospheric Sciences,Taiwan University,Taipei 106,China.
Estimation of large-scale land surface temperature from satellite images is of great importance for the study of climate change. This is especially true for the most challenging areas, such as the Tibetan Plateau （TP）. In this paper, two split window algorithms （SWAs）, one for the NOAA’s Advanced Very High Resolu-tion Radiometer （AVHRR）, and the other for the Moderate Resolution Imaging Spectroradiometer （MODIS）, were applied to retrieve land surface temperature （LST） over the TP simultaneously. AVHRR and MODIS data from 17 January, 14 April, 23 July, and 16 October 2003 were selected as the cases for winter, spring, summer, and autumn, respectively. Firstly, two key parameters （emissivity and water vapor content） were calculated at the pixel scale. Then, the derived LST was compared with in situ measurements from the Coordinated Enhanced Observing Period （CEOP） Asia-Australia Monsoon Project （CAMP） on the TP （CAMP/Tibet） area. They were in good accordance with each other, with an average percentage error （PE） of 10.5% for AVHRR data and 8.3% for MODIS data, meaning the adopted SWAs were applicable in the TP area. The derived LST also showed a wide range and a clear seasonal difference. The results from AVHRR were also in agreement with MODIS, with the latter usually displaying a higher level of accuracy.
The regional heat flux exchange between heterogeneous landscapes and the nearby surface layer （SL） is a key issue in the study of land-atmosphere interactions over arid areas such as the Heihe River basin in northwestern China and in high elevation areas such as the Tibetan Plateau. Based on analysis of the land surface heterogeneity and its effects on the overlying air flow, the use of SL observations, atmospheric boundary layer （ABL） observations, and satellite remote sensing （RS） measurements along with three parameterization methodologies （here, termed as the RS, tile, and blending approaches） have been proposed to estimate the surface heat flux densities over heterogeneous landscapes. The tile and blending approaches have also been implemented during HEIhe basin Field Experiment （HEIFE）, the Coordinated Enhanced Observing Period （CEOP） Asia-Australia Monsoon Project on the Tibetan Plateau （CAMP/Tibet）, the Arid Environment Comprehensive Monitoring Plan ＇95 （AECMP＇95）, and the DunHuang Experiment （DHEX）. The results showed that these two proposed parameterization methodologies can be accurately used over heterogeneous land surfaces.
