Abstract
A neural-network algorithm that uses CALIPSO lidar measurements to infer droplet effective radius, extinction coefficient, liquid-water content, and droplet number concentration for water clouds is described and assessed. These results are verified against values inferred from High-Spectral-Resolution Lidar (HSRL) and Research Scanning Polarimeter (RSP) measurements made on an aircraft that flew under CALIPSO. The global cloud microphysical properties are derived from 14+ years of CALIPSO lidar measurements, and the droplet sizes are compared to corresponding values inferred from MODIS passive imagery. This new product will provide constraints to improve modeling of Earth’s water cycle and cloud-climate interactions.
Highlights
CALIPSO Lidar measurements provide the first ever direct measurements of the global distribution of water-cloud extinction coefficients from space
Additional information from aircraft measurements and collocated MODIS, AMSR-E and other A-Train satellite measurements will be analyzed for future algorithm improvements
The original contributions presented in the study are included in the article/supplementary material, further inquiries can be directed to the corresponding author
Summary
CALIPSO Lidar measurements provide the first ever direct measurements of the global distribution of water-cloud extinction coefficients from space. In this paper we describe the retrieval algorithm for estimating microphysical properties of water clouds (e.g., extinction coefficient, effective drop size, liquid water content, and droplet number concentration) from 14 + years of global lidar measurements acquired by NASA’s CALIPSO satellite. The effective color ratio from the CALIPSO measurements (right panels of Figure 2) is 25% higher compared with the single-scattering color ratio and is consistent with theoretical calculations Other information, such as cloud temperature, estimated from CALIPSO cloud-height measurements, can provide extra information about the effective variance of the droplet size distribution. The water-cloud effective radii determined from the RSP measurements (blue line in the middle panel of Figure 11) agree better with CALIPSO’s Re estimates derived with the lidar ratio method (green and red line) within uniform clouds.
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