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- Author or Editor: R. D. Hart x
- Journal of Applied Meteorology and Climatology x
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Abstract
Maine stratus clouds were simultaneously observed by nadir Nd:YAG lidar measurements and in situ cloud physics measurements. A procedure was applied to derive the two-dimensional vertical cross section of the liquid water from within the cloud top lidar observations. A comparison to direct in-cloud liquid water observations gave good results. The liquid water retrieval was limited to an effective optical of 1.5. The true cloud optical thickness was also obtained from the retrieval procedure to a corresponding limit of 3.8. The optical thickness of the observed marine stratus clouds was predominantly below 3.0.
Abstract
Maine stratus clouds were simultaneously observed by nadir Nd:YAG lidar measurements and in situ cloud physics measurements. A procedure was applied to derive the two-dimensional vertical cross section of the liquid water from within the cloud top lidar observations. A comparison to direct in-cloud liquid water observations gave good results. The liquid water retrieval was limited to an effective optical of 1.5. The true cloud optical thickness was also obtained from the retrieval procedure to a corresponding limit of 3.8. The optical thickness of the observed marine stratus clouds was predominantly below 3.0.
Abstract
Simultaneous measurements with the millimeter-wave imaging radiometer (MIR), cloud lidar system (CLS), and the MODIS airborne simulator (MAS) were made aboard the NASA ER-2 aircraft over the western Pacific Ocean on 17–18 January 1993. These measurements were used to study the effects of clouds on water vapor profile retrievals based on millimeter-wave radiometer measurements. The CLS backscatter measurements (at 0.532 and 1.064 μm) provided information on the heights and a detailed structure of cloud layers; the types of clouds could be positively identified. All 12 MAS channels (0.6–13 μm) essentially respond to all types of clouds, while the six MIR channels (89–220 GHz) show little sensitivity to cirrus clouds. The radiances from the 12-μm and 0.875-μm channels of the MAS and the 89-GHz channel of the MIR were used to gauge the performance of the retrieval of water vapor profiles from the MIR observations under cloudy conditions. It was found that, for cirrus and absorptive (liquid) clouds, better than 80% of the retrieval was convergent when one of the three criteria was satisfied; that is, the radiance at 0.875 μm is less than 100 W cm−3 sr−1, or the brightness at 12 μm is greater than 260 K, or brightness at 89 GHz is less than 270 K (equivalent to cloud liquid water of less than 0.04 g cm−2). The range of these radiances for convergent retrieval increases markedly when the condition for convergent retrieval was somewhat relaxed. The algorithm of water vapor profiling from the MIR measurements could not perform adequately over the areas of storm-related clouds that scatter radiation at millimeter wavelengths.
Abstract
Simultaneous measurements with the millimeter-wave imaging radiometer (MIR), cloud lidar system (CLS), and the MODIS airborne simulator (MAS) were made aboard the NASA ER-2 aircraft over the western Pacific Ocean on 17–18 January 1993. These measurements were used to study the effects of clouds on water vapor profile retrievals based on millimeter-wave radiometer measurements. The CLS backscatter measurements (at 0.532 and 1.064 μm) provided information on the heights and a detailed structure of cloud layers; the types of clouds could be positively identified. All 12 MAS channels (0.6–13 μm) essentially respond to all types of clouds, while the six MIR channels (89–220 GHz) show little sensitivity to cirrus clouds. The radiances from the 12-μm and 0.875-μm channels of the MAS and the 89-GHz channel of the MIR were used to gauge the performance of the retrieval of water vapor profiles from the MIR observations under cloudy conditions. It was found that, for cirrus and absorptive (liquid) clouds, better than 80% of the retrieval was convergent when one of the three criteria was satisfied; that is, the radiance at 0.875 μm is less than 100 W cm−3 sr−1, or the brightness at 12 μm is greater than 260 K, or brightness at 89 GHz is less than 270 K (equivalent to cloud liquid water of less than 0.04 g cm−2). The range of these radiances for convergent retrieval increases markedly when the condition for convergent retrieval was somewhat relaxed. The algorithm of water vapor profiling from the MIR measurements could not perform adequately over the areas of storm-related clouds that scatter radiation at millimeter wavelengths.
