SCIAMACHY临边散射探测的切高校正及敏感性研究

Tangent height correction and sensitivity studies from SCIAMACHY limb scattering detection

针对临边紫外—可见光散射探测仪器在指向过程中由于失准等原因产生的切线高度偏移,提出一种基于UV窄波段的切线高度反演THRUNB(Tangent Height Retrieved by UV Narrow Bands)方法用于校正SCIAMACHY临边辐射切线高度。THRUNB方法通过分析多个紫外波段的临边辐射廓线形状和工程指向信息对切高修正的影响,提出窄波段(300—305 nm)和新的工程切高(43、46、49、52和55 km)使测量矢量即保持较全灵敏度又减少维数。同时采用最优估计算法结合SCIATRAN模型,从临边辐射反演切高偏差。实验结果表明THRUNB法比TRUE(Tangent height Retrieved by UV-B Exploitation)方法进行切高校正的平均精度提高了45%,而算法的运行时间减少了20%。与ESA提供的SCIAMACHY L1B切高信息相比,切高校正的平均偏差小于150 m,说明该方法可以有效减少仪器指向信息错误引起的切高偏差。与Bremen大学提供的SCIAMACHY v3.5的臭氧廓线产品相比,切高校正后的臭氧廓线反演平均误差在13—38 km范围内小于10%;而未校正的臭氧廓线反演误差在该范围内高达22%,说明切高校正能够提高后期大气痕量气体廓线反演的准确度。同时,研究了大气压强、温度和臭氧廓线对切线高度反演的影响,实验结果表明有效的臭氧和中性密度廓线是切线高度校正的关键。

A tangent height retrieved by UV narrow bands(THRUNB)method is proposed to correct the tangent height from SCIAMACHY limb instrument to solve the tangent height offset caused by misalignment and other reasons in the pointing process of limb UV-VIS scattering detection instrument.In this method,a narrow band(300—305 nm)and a new engineering tangent height sequence(43,46,49,52,and 55 km)are proposed to maintain measurement vectors that are more sensitive and with less dimension by analyzing the influence of the limb radiance profile shape and engineering pointing information of multiple UV bands on the tangent height correction.At the same time,the optimal estimation algorithm combined with SCIATRAN model is used to retrieve the tangent height deviation from the limb radiance.The experimental results show that the average accuracy of tangent height correction by the THRUNB method is improved by 45%,and the running time of the algorithm is reduced by 20%,compared with TRUE(tangent height retrieved by UV-B exploitation)method.Compared with SCIAMACHY L1B tangent height data provided by ESA,the average deviation of tangent height is less than 150 m.Compared with the SCIAMACHY v3.5 ozone profile product provided by University of Bremen,the average relative error of the retrieved ozone profile with tangent height correction is less than 10%in the range of 13—38 km,and the average relative error without tangent height correction is as high as 22%in the same range.At the same time,the effects of atmospheric pressure,temperature,and ozone profile on tangent height retrieved are investigated.The experimental results show that the influence of pressure and ozone on TH retrieval is positively correlated,whereas the temperature is negatively correlated.The ozone profile has the greatest influence on TH retrieval,followed by pressure and temperature.The THRUNB method can effectively reduce the tangent height offset caused by the instrument pointing information error.The accuracy of the retrieved atmospheric trace gas profile can be improved by correcting tangent height.The effective ozone and neutral density profiles are very important for tangent height correction.