Water vapour profiles by ground-based FTIR spectroscopy: study for an optimised retrieval and its validation

[摘要] The sensitivity of ground-based instruments measuring in theinfrared with respect to tropospheric water vapour content isgenerally limited to the lower and middle troposphere. The largevertical gradients and variabilities avoid a better sensitivityfor the upper troposphere/lower stratosphere (UT/LS) region. Inthis work an optimised retrieval is presented and it isdemonstrated that compared to a commonly applied method, itimproves the performance of the FTIR technique. The reasons forthis improvement and the possible deficiencies of the method arediscussed. Only by applying the method proposed here and usingmeasurements performed at mountain observatories can water vapourvariabilities in the UT/LS be detected in a self-consistentmanner. The precision, expressed as noise to signal ratio, isestimated at 45%. In the middle and lower troposphere,precisions of 22% are achieved. These estimations areconfirmed by a comparison of retrieval results based on real FTIRmeasurements with coinciding measurements of synopticalmeteorological radiosondes.

[学科分类] 大气科学