排序方式： 共有42条查询结果，搜索用时 0 毫秒
41.
The estimation of surface evapotranspiration(ET) with satellite dataset is one of the main subjects in the understanding of climate change,disaster monitoring and the circulation of water vapor and energy in Tibet Autonomous Region(TAR).This research selects satellite images on January 11,April 6,July 31 and October 19 in 2010 as the representative of winter,spring,summer and autumn respectively,estimates the distribution of daily surface ET based on the surface energy balance system(SEBS) along with potential evapotranspiration(PET) and ET derived from Penman-Monteith(P-M) method.The results are obtained as follows.(1) The seasonal distribution of ET and PET basically decreases from the southeast part to the northwest part of TAR.Although ET and PET have similar spatial distributions,there are still some differences to estimate the extreme values especially the maximum value in the middle and southeastern parts of TAR.No matter what kind of methods we adopted,the maximum value of ET and PET always appears in summer,followed by autumn or spring while that in winter is the smallest.(2) In order to better understand the accuracy of SEBS model in the estimation of ET,we compared the ET from SEBS and the ET obtained from P-M method.Results show that the ET from SEBS could estimates the variation trend of actual ET,but it slightly underestimates or overestimates the value of ET as a whole,especially for those areas with thick forest.(3) The spatial distribution of Normalized Difference Vegetation Index(NDVI) exhibits a decreasing trend from the southeast part to the northwest part of TAR which displays remarkable consistency of distributions between ET and vegetation index.ET is well positively related to NDVI,minimum,mean,maximum air temperature and sunshine duration in different seasons while negatively related to precipitation,relative humidity and wind speed in summer. 相似文献
42.
本文利用西藏7个主要城镇2009年6~9月24h观测降水对T639、日本和德国三种数值预报模式降水产品进行了检验分析。结果表明:三种数值预报模式中,德国模式对晴雨预报准确率最高、空报率低。小雨量级上三种模式预报能力较强,偏差较小。三种数值预报模式对中雨量级预报能力明显减弱,预报量级明显偏小,其中德国和日本模式基本没有预报能力。综合三种数值预报模式降水对西藏北部那曲、东部林芝和昌都具有一定的参考意义。 相似文献