Studies On Determining Atmospheric Boundary Layer Height From COSMIC Radio Occultation Data And Selecting Channels For Hyperspectral Infrared Instruments

This thesis includes two parts.The first part is the study on determining the atmospheric boundary layer height with COSMIC occultation data,and the second part is the study on the channel selection algorithm for hyperspectral infrared instruments.In the first part,this paper presents a new method to estimate the height of atmospheric boundary layer(ABL)by using COSMIC radio occultation bending angle data: using the numerical differentiation method combined with the regularization technique,the first derivative of BA profiles is retrieved,and the height at which the first derivative of BA has the global minimum is defined to be the ABL height.And a sharpness parameter is introduced to reflect the reliability of estimated ABL heights.To validate the new method,the author applied it to 4 months of COSMIC BA data(January,April,July,and October in 2008),and the estimated ABL top heights are compared with two kinds of ABL heights from COSMIC data products and with the heights determined by finite difference method upon the refractivity data.Results show that there will be lower uncertainties between different methods as the sharpness parameter increases and for the cases with large differences,our method can detect thinner and lower ABL tops and provide a reference ABL tops when cases are usually excluded in the quality control process.In the second part,this paper uses relative entropy to measure the information content in an observation,and this index is applied to the channel selection process of hyperspectral instruments for the first time.Relative entropy can be decomposed into the information content defined by Shannon entropy difference and degree of freedom for signal,that is,it contains the information of the jacobian matrix,background error,observation error and mean field at the same time,which can be used to generate different channel schemes in different areas.Given the characteristics of relative entropy,this paper designs an iteration process for channel selection and the channel selection scheme for the atmospheric infrared sounder is proposed.Then the channel selection results for retrieving water vapor and temperature in tropical region,mid-latitude area in summer and winter,sub-arctic area in summer and winter are given respectively.Results show that there are differences in the channel choices in different seasons and regions.Comparing with 324 channels used by AIRS,similar inversion results can be achieved with fewer channels.The order of information redundancy observed in different regions is: sub-arctic > mid latitude > tropical,And in different seasons is: Winter > summer.