摘要 : Passive satellite retrievals using conventional CO_2absorption techniques tend tosystematically underestimate the upper transmissive cloud top heights (CTHs). Thesetechniques are based on single-layer assumptions that the upper cl... 展开 Passive satellite retrievals using conventional CO_2absorption techniques tend tosystematically underestimate the upper transmissive cloud top heights (CTHs). Thesetechniques are based on single-layer assumptions that the upper cloud occupies ageometrically thin layer above a cloud-free surface. This study presents a new modifiedCO_2absorption technique (MCO2AT) to improve the inference of transmissive CTHsin the upper troposphere above 600 hPa. The MCO2AT employs an iterative algorithmthat starts with a single-layer CO_2absorption technique (SCO2AT) followed by aniterative procedure to retrieve an enhanced upper CTH based on inferred effectivebackground radiances. Both techniques are applied to the 10.7 and 13.3 μm channeldata of the Twelfth Geostationary Operational Environmental Satellite (GOES 12)imager and their retrievals of upper tropospheric CTHs are compared with two activesensing products: the ground-based Active Remotely Sensed Cloud Location (ARSCL)products from the Atmospheric Radiation Measurement Program (ARM) SouthernGreat Plains (SGP) site and the satellite-based Cloud Aerosol Lidar With OrthogonalPolarization (CALIOP) products. On average, the CTHs from MCO2AT and SCO2ATare lower than those from both of the active sensors by ~1 and 2.4 km, respectively,possibly due to the different sensitivities and spatial resolutions between passive andactive sensors. Preliminary validation of the new modified method is encouraging,especially the improvements for upper transmissive clouds in geometrically thick and/ormultilayered cloud situations. The development of the modified method is particularlyuseful for sensors like the GOES 12, Meteosat-9, and others, which carry only oneCO2 absorption channel at ~13.3 μm. 收起