无云情况下L波段微波辐射计快速大气校正方法

A rapid atmospheric correction model for L-band microwave radiometer under the cloudless condition

利用数值天气预报模式输出的大气温湿廓线数据与大气辐射传输模型计算了无云情况下全球海面大气在L波段的上行、下行辐射亮温及透射率,建立三个参数与大气水汽含量及海表气压的回归关系模型——辐射-水汽模型,利用该模型可快速计算大气辐射参数,对L波段微波辐射计进行大气校正.为了验证模型的实用性和可靠性,利用SSM/I卫星水汽含量数据和数值模式地表气压数据通过模型计算大气辐射参数,并与Aquarius卫星实测L波段微波辐射数据进行对比分析.结果表明:模型计算的辐射亮温比卫星观测数据偏低约0.335 K,但改正系统性偏差后的均方根误差仅0.086 K,且模型计算的大气透射率与卫星观测数据基本一致,说明利用该模型对L波段微波辐射计进行大气校正具有较高的可靠性,相比于传统利用大气辐射传输模型进行大气校正,该模型更为简单快速,输入参数更易获取,更适于工程应用.

Atmospheric correction is very important to the accurate retrieval of geophysical parameters from spaceborne L-band radiometers. In this paper, the L-band upwelling and downwelling radiation brightness temperature and transmittance above sea surface are calculated using the atmospheric radiation transfer model based on NCEP temperature and humidity profile data. A regression model, i.e., radiation-vapor model, is established to describe the relationship between the three atmospheric radiation parameters and the atmospheric water vapor content as well as the sea surface pressure.Using this model, the atmospheric radiation parameters can be calculated and used to correct the atmospheric effects in L-band microwave radiometer observation. In order to test the proposed model, the atmospheric radiation parameters are calculated by this model and compared with the SSM/I water vapor content data and the NCEP surface pressure data.Finally, the model outputs are compared with the Aquarius satellite data. Results indicate that the radiation brightness temperature calculated by the proposed model is lower than the Aquarius data about 0.335 K and the root-mean-square error between them is about 0.086 K after correcting the systematic errors. The atmospheric transmittance calculated by the proposed model agrees well with the Aquarius data. Besides, the proposed model uses fewer input data and is faster and more stable than other existing models.