Guo J.,Chinese Academy of Meteorological Sciences |
Guo J.,University of Maryland University College |
Zhai P.,Chinese Academy of Meteorological Sciences |
Wu L.,Henan Climate Center |
And 7 more authors.
International Journal of Climatology | Year: 2014
Some new features concerning the diurnal variation of precipitation over the Tibetan Plateau (TP) are revealed from rainfall data acquired by a network of rain gauge stations and estimated by the Climate Precipitation Center Morphing (CMORPH) technique collected during the summer of 2010 and 2011. Maxima in precipitation amount and frequency are associated with the afternoon-to-evening precipitation regime at approximately 60% of the stations in the network. CMORPH data also capture this pattern, but miss the late morning peak that occurs at some stations. The timing of maximum occurrence agrees well with the diurnal cycle of synoptic conditions favouring the development of precipitation over this area. There is no distinct west-to-east propagation of the diurnal cycle, implying that the diurnal cycle is more driven by local effects than by large-scale circulation. It turns out that the diurnal cycle in precipitation frequency depends largely on topography and landscape. The geographical transition in precipitation peak time is distinct from hilly regions (daytime peak) towards lakes and valleys (evening-to-nocturnal peaks). Stations located in mountainous regions (valleys) tend to experience more precipitation in either late morning or early afternoon (late afternoon or evening). Overall, precipitation amount shows a similar topographic dependence, as does the precipitation frequency, suggesting that local-scale effects, such as the mountain valley circulation effect, has a great impact on the diurnal variation in precipitation when large-scale dynamical processes are weak. A possible mechanism for the non-uniform diurnal cycle of precipitation over the TP is proposed. The major conclusion is that plateau-scale synoptic systems, as well as local circulation systems caused by the complex topography, should be taken into account when determining the diurnal variation in precipitation over the TP. © 2013 Royal Meteorological Society.
Guo J.-P.,Chinese Academy of Meteorological Sciences |
Zhang X.-Y.,Chinese Academy of Meteorological Sciences |
Wu Y.-R.,Beijing Normal University |
Wu Y.-R.,CAS Institute of Remote Sensing Applications |
And 6 more authors.
Atmospheric Environment | Year: 2011
This paper analyzes TOMS AOD at 500 nm (1980-2001), along with MODIS data (2000-2008) at 550 nm to investigate variations at one-degree grid over eight typical regions in China and the trends in AODs, temporally and spatially. In contrast to recently reported global decrease in AOD over global ocean beginning around 1990, we find there virtually exists no apparent AOD transition in China for that: firstly no notable upward tendencies in AOD during 1980-1992 for the relative low value (+0.001/decade), then during 1996-2001 a discernible ascending tendency with larger magnitude at 0.01/decade, and finally, since 2000, a weak upward trend with +0.004/decade. The large increases during 1996-2001 are presumably consequences of large increases in industrial activities and bear a strong resemblance to the long-term decreasing observations of incident solar radiation and cloud cover in China. Specifically, in late 1990's, only in Taklimakan Desert a negative trend with a maximum magnitude of -0.04/decade is detected. However, over regions such as Jingjinji and Pearl River Delta influenced by industrial activities, positive tendencies at +0.01/decade are observed. Seasonal patterns in the AOD regional long-term trend are evident. AODs exhibit generally similar seasonality and the summer dominates higher AOD value than the autumn. In particular, during the period 1980-2001, all the eight regions except Taklimakan Desert witness the maximum aerosols in winter while there is not such seasonality during the period 2000-2008. Geographically, we also document spatial patterns of AOD variations over China. Results reveal that no apparent upward trends in AOD (about 15% per decade) are observed in 1980's, while beginning 1990 till 2008, both data (TOMS and MODIS) are indicative of a significant AOD increase across China, especially in 1990's it is indeed the case, roughly in accordance with the overall trends at regional scale. © 2011 Elsevier Ltd.
Bian D.,Tibet Institute of Plateau Atmospheric and Environmental Science Research |
Bian B.,Tibet Institute of Plateau Atmospheric and Environmental Science Research |
La B.,Tibet Institute of Plateau Atmospheric and Environmental Science Research |
Wang C.,Tibet Institute of Plateau Atmospheric and Environmental Science Research |
Chen T.,Tibet Institute of Plateau Atmospheric and Environmental Science Research
Acta Geographica Sinica | Year: 2010
An analysis is made about the response of Selin Co lake area change to climate change, based on RS, GIS and modern climate statistical methods with the aid of TM and CBERS remote sensing data from 1980-2008 as well as temperature, precipitation, the amount of evaporation, the biggest depth of frozen soil from 1975-2008 at the stations such as Shenzha, Bange and Anduo etc. Based on the digitized 1:100,000 topographic map in 1975 and through analyses of remote sensing data after the 1980s, it is found that water levels of Selin Co, Co'e and Yagen Co lakes present a distinct expanding trend in the past 30 years. In 2008, the water level areas of the above three lakes are 2196.23 km2, 279.24 km2, 103.07 km2, and they increase by 574.46 km2, 11.59 km2 and 68.13 km2 respectively compared to 1975. Moreover, Selin Co expands at a rate of 20%, with an average of 420 km2/10a, thus it has become the largest salty inland lake, exceeding the area of Nam Co lake in Tibet during the period 1999-2008. The main reasons for lake area expansion is the increase in snow/ice meting water under the background of global warming, followed by the increase of precipitation, decrease of the evaporation and degradation of permafrost.