基于MOD16监测陕西省地表蒸散变化

基于MOD16数据产品结合气象数据,统计分析了陕西省2000-2013年地表蒸散的时空分布特征,研究表明MOD16蒸散产品能够满足陕西省地表蒸散时空分布研究的要求,结果对陕西省水资源的有效利用具有重要的理论和实践意义。主要结论:(1) 2000-2013年蒸散(ET)、潜在蒸散(PET)年际波动不大,全省ET平均值在490 mm左右, PET平均值在1550 mm左右,年平均ET与PET的差距说明陕西省较为干旱缺水。全省ET、PET的年内变化都呈单峰分布趋势,两者变化存在差异, 6月两者差距最大,此时最为缺水。(2)陕西省不同区域蒸散有明显的空间分布差异,陕西南部水分较为充足,而在陕西北部较为缺水。陕西中西部区域干旱有所缓解,中东部区域干旱加重。(3)各功能区年平均ET与PET大小顺序正好相反,干旱程度顺序为防风治沙工程区>陕北退耕还林区>渭北退耕还林区>关中农业生产区>陕北天然林保护区>陕南退耕还林区>陕南天然林保护区。各功能区年内ET月平均变化差异明显,可分为三类,单峰型、波动型、双峰型。(4)蒸散的时空变化与气候特点,特别是水热条件的时空变化有很高的相关关系,而与植被的分布和生长状况也紧密相关。

Surveying variations of evapotranspiration in Shaanxi Province Using MOD16 products

Evapotranspiration(ET) from the land surface is a crucial component of water and energy balance. Understanding of spatiotemporal variation of regional evapotranspiration is of highly valuable to management of water resources and effective promotion of ecological services in Shaanxi Province. Under the support of ArcGIS spatial analysis module, this paper mainly aims at MODIS evapotranspiration data set(MOD16)combined with meteorological datasets to conduct a systematic research on the spatial and temporal characteristics in Shaanxi Province during 2000-2013 and to explore changes of evapotranspiration characteristics in the different functional areas according to the ecological environment features in Shaanxi Province. By calculating the correlation coefficient between MOD16 potential evapotranspiration(PET) and pan evaporation at the beginning of the study, the result indicated that MOD16 products are more applicable for the analysis of spatio-temporal variations of evapotranspiration in Shaanxi Province. Then the statistical analysis of the spatial and temporal distribution of MOD16 products showed as follows:(1)Interannual fluctuations of ET and PET were not significant during 2000-2013. The 13-year mean ET was 490 mm. The 13-year mean PET was 1550 mm. The big gap of ET and PET showed that the land surface was drought in Shaanxi Province. The seasonal variation of ET or PET showed a unimodal pattern. The biggest difference between ET or PET in May was about 145 mm, indicated that the land surface was the thirstiest.(2)The spatial distribution of the ET and PET had obvious regional characteristics. The spatial distribution of ET from south to north decreasing, while PET was increased from south to north. The opposite distribution indicated that the surface moisture was adequately in the south but not enough in the north. By computing trends of the ET and PET, it found that the drought was easing in the midwest Shaanxi but worsening in the mideast during 2000-2013.(3)The intensity orders of ET and PET in each functional area were in opposite directions. Therefore, the order of drought intensity was I(the Controlling Desert Area) > Ⅱ(the Retuning Farmland to Forest in North Area) > Ⅲ(the Retuning Farmland to Forest in Weibei Area) > VⅡ(the Farmland in Guanzhong Area) > V(the Natural Forest in North Area) > IV(the Retuning Farmland to Forest in South Area) > VI(the Natural Forest in South Area). The seasonal variations of ET in each functional area were different, and it can be divided into three types including unimodal type, wave type and bimodal type. The unimodal type had two functional area including IV and VI. The wave type had four functional area including I, Ⅱ, Ⅲ and V. The bimodal type had VⅡ.(4)In addition, with the correlation analysis to meteorological factors and vegetation characteristics, the spatio-temporal variation of evapotranspiration was closely related with climate characteristics especially water-heat conditions and vegetation distribution and growth state.