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China University (2013)

Retrievals And Analysis Of Precipitable Water Vapor And Aerosol Optical Properties Over Semi-arid Area Of Northwestern China

Li X

Titre : Retrievals And Analysis Of Precipitable Water Vapor And Aerosol Optical Properties Over Semi-arid Area Of Northwestern China

Auteur : Li X

Grade : Doctoral Dissertation 2013

Université : China University

Résumé partiel
Water vapor and aerosol are the major atmospheric components, both of them modulate the radiative energy balance of Earth-atmosphere system and influence human activeites. Water vapor, as the highest concentrations of greenhouse gases in the atmosphere, is the important factor in climate change research for its positive feedback. With the intensification of human activities, more and more aerosols are emitted into the atmosphere, which play a crucial role in the global and regional climate change by the direct, indirect and semi-direct effect, and cause severe damage to environment and human health. The region of northwest China located in the climate-sensitive band represents the typical arid and semi-arid climate ozone with most serious area of water scarcity, so the analysis of aerosol optical properties and water vapor in this region shows theoretical and practical significance to the research of climate change and human activities. We have developed the retrieval algorithm of pricipitable water vapor (PWV) and aerosol optical depth using the Multifilter Rotating Shadowband Radiometer (MFRSR), which has been deployed at the Semi-Arid Climate and Environment Observatory of Lanzhou University (SACOL), SACOL city station (Lanzhou university campus) and Zhangye mobile facility during the China-US joint dust field campaign from April to June2008. PWV from MFRSR is analyzed and compared with other ground-based remote sensing instruments. To evaluate and validate the accuracy of satellite PWV retrieval, the comparisons between PWV retrievals from satellite and MFRSR are implemented, basing on which a corrected method for satellite products is proposed. Aerosol optical properties as well as its dependence on air mass long-distance transport are analyzed using aerosol optical depth (AOD) retrieved by MFRSR combined with Mie theory and HYSPLIT model.PWV is retrieved from water vapor absorption channel from MFRSR based on the law of radiation extinction, LBLRTM for simulating the relationship between water vapor transmission and water vapor content and Gaussian extrapolation of daily calibration constant. PWV retrieved from MFRSR at SACOL shows a seasonal variation, with the average value of0.72±0.53cm and75%of PWV values smaller than1.07cm during the observation period. The results of comparisons show a remarkable agreement between MFRSR and sunphotometer with correlation coefficient of0.99and root mean square difference (RMSD) of0.09cm, and correlation coefficient of0.97and RMSD of0.14cm between MFRSR and microwave radiometer, which verifies the accuracy and reliability of MFRSR PWV retrieval. To evaluate PWV products from MODIS and AIRS, we use the PWV from MFRSR to compare with MODIS near-IR and AIRS PWV over northwest China. The results suggest that an overestimation of MODIS increases with PWV value, and a systematic underestimation of AIRS PWV retrieval relative to MFRSR.

Mots clés : MFRSR, Precipitable water vapor, Aerosol, Optical depth, Retrieval method, Satellite, Backward trajectories, Classification

Présentation (Globethesis)

Page publiée le 21 avril 2013, mise à jour le 10 janvier 2018