基于风云三号卫星微波资料反演我国地表土壤湿度及其对比
投稿时间: 2015-09-01  最后修改时间: 2016-05-08  点此下载全文
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王国杰 南京信息工程大学 地理科学学院/气象灾害预报预警与评估协同创新中心, 江苏 南京 210044 gwang_nuist@163.com 
薛峰 南京信息工程大学 大气科学学院;江苏 南京 210044  
齐道日娜 南京信息工程大学 大气科学学院;江苏 南京 210044  
谭龑 南京信息工程大学 应用气象学院 生态气象环境中心;江苏 南京 210044  
娄丹 南京信息工程大学 地理科学学院/气象灾害预报预警与评估协同创新中心, 江苏 南京 210044  
刘毅 南京信息工程大学 地理科学学院/气象灾害预报预警与评估协同创新中心, 江苏 南京 210044  
基金项目:国家重点研发计划项目(2017YFA0603701);国家自然科学基金资助项目(41561124014;91337108;41375099)
中文摘要:土壤湿度是联系陆地水循环和能量循环的纽带,是地表最重要的水资源,也是一个重要的气象预报因子。基于风云三号卫星微波资料,采用能量辐射传输模型反演了我国逐日地表土壤湿度(FY-3B),并估算了其系统误差;然后,与中国气象局农业气象站观测资料和ERA-Interim、NCEP再分析资料进行了对比分析。研究结果表明,FY-3B土壤湿度呈由西北地区向东北和东南地区逐渐增加的空间分布特征,与农气站观测资料和两套再分析资料基本一致;其系统误差与植被覆盖度密切相关,我国西南部植被茂密的地区系统误差较大。FY-3B土壤湿度的季节性变化与农气站观测资料在全国范围有较好的一致性,总体表现为冬季土壤湿度较高,随着春季气温升高蒸散发增加,土壤湿度逐渐降低;夏天雨季来临,土壤湿度回升。然而,FY-3B土壤湿度与ERA-Interim和NCEP再分析资料在东北部分地区和长江流域以南呈很强的负相关,这主要是由于季节性干湿变化的不一致性所致;这表明,ERA-Interim和NCEP土壤湿度再分析资料在这些地区存在较大的不确定性。
中文关键词:土壤湿度  微波遥感  风云三号卫星  中国地区  对比分析
 
Soil moisture retrievals from FY-3B satellite microwave brightness and comparative analyses over China
Abstract:Soil moisture is a significant variable in environmental studies(e.g.,numerical weather prediction,modeling climate change,runoff prediction,drought monitoring,etc.).It is the most important terrestrial water resource for ecosystems.In addition,the soil moisture correlates terrestrial water and energy cycles,thus,this is an important predictor for hydro meteorological processes(e.g.,precipitation,drought,and heat waves).However,currently,soil moisture is not defined as a conventional component for meteorological monitoring.Therefore,several studies were carried out which often didn't contain the soil moisture observations over the globe.In recent years,the soil moisture retrieval using satellite remote sensing technology has been widely developed.Microwave remote sensing of soil moisture has received great attentions and has shown appropriate prospects due to a number of unique features(e.g.,its atmospheric transparency and sensitivity to surface soil moisture).The Fengyun-3B(FY-3B) satellite,which is managed by China Meteorological Administration(CMA),and FY-3B is the second satellite in the third Fengyun series,carrying a multi-frequency passive microwave radiometer on-board,the Microwave Radiation Imager(MWRI).Based on the brightness temperature observations of MWRI,we attempted to retrieve the land surface soil moisture for the period of July 2011 to July 2014 over China.This was done using a radiative transfer model as well as further estimations of the soil moisture's systematic errors.Next,the soil moisture retrievals are compared with in-situ soil moisture observations obtained from the CMA's agrometeorological monitoring network,in addition to the reanalyzed soil moisture data derived from ERA-Interim and National Centers for Environmental Prediction(NCEP) databases.The spatial distribution of FY-3B soil moisture appears increasing gradually from the northwest to the northeast and southeast of China,that agrees well with the in-situ observations as well as reanalysis soil moisture.The systematic errors of FY-3B retrievals are closely correlated with the vegetation density.Where it is densely become vegetated,the systematic errors are largest(e.g.,over the southwest of China),while the systematic errors are smaller where it is drier.In terms of the seasonal variations,FY-3B soil moisture agrees well with the in-situ agrometeorological observations.In most parts of the China territory,these two datasets confirm a positive correlation;it demonstrates that the FY-3B soil moisture captures the properties of temporal variations in China,generally representing that the soil moisture is relatively high in winter,while there is a decline in spring and summer seasons.However,soil moisture declining in Spring and Summer is not surprising the scholars due to the terrestrial water balance.In warm seasons,there are more precipitations than in cold seasons;however,evapo transpiration is largely increased in warm seasons due to the increasing the atmospheric demand of water vapor.Therefore,in warm seasons,water stored in soil becomes even less than that of in cold seasons.This agreement with in-situ observations demonstrates that the obtained FY-3B soil moisture is quite plausible in terms of temporal variations.However,FY-3B soil moisture shows a strong but negative correlation with ERA-Interim and NCEP reanalyzed soil moisture where soil is relatively wet,reaching-0.8~-0.5 in south of China as well as some parts of northeast of China,where the reanalyzed data are negatively correlated with in-situ observations as well.This negative correlation is mainly attributed to the differences in seasonal variations where the climate is relatively wet;in such regions,the reanalyzed soil moisture data shows a relatively dry winter and wet summer,in contract with that of the in-situ observations.Eventually,it can be concluded that the reanalyzed soil moisture data derived from ERA and the NCEP contain considerable uncertainties in wet climate regions;consequently,those data should be used with great caution.In terms of the temporal variations,the achieved FY-3B soil moisture observations are prior to the reanalyzed soil moisture data.
keywords:soil moisture  microwave remote sensing  Fengyun-3 satellite  China territory  ERA-Interim
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