Cloud Volume Changes over the Pacific for 11 years Observed by CALIPSO-CloudSat or MODIS Observations

LASP Science Seminars

Cloud Volume Changes over the Pacific for 11 years Observed by CALIPSO-CloudSat or MODIS Observations

Seung-Hee Ham
(Science Systems and Applications Inc.)
September 29, 2022
4:00 PM MT/MST

The two active sensors belong to NASA A-train mission, i.e., Cloud Aerosol Lidar with Orthogonal Polarization (CALIOP) lidar aboard Cloud Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) and Cloud Profiling Radar (CPR) radar aboard CloudSat have provided detailed information about the cloud structures. In this study, we combine CALIPSO and CloudSat (CALCS) active sensor measurements to examine cloud volume changes over the Pacific and compare the results with Moderate Resolution Imaging Spectroradiometer (MODIS) passive measurements. It is shown that CALCS and MODIS capture similar features of cloud volumes related to El Niño–Southern Oscillation (ENSO) events. Over the eastern Pacific during the El Niño season, increased relative humidity (RH) anomalies caused the increase of mid and high cloud volumes. However, MODIS often misses thin cirrus cloud changes in high altitudes and mid-level clouds are overestimated. As a result, the correlation between RH and cloud volume anomalies is higher when CALCS observations are used, compared to MODIS. Both MODIS and CALCS low cloud anomalies are well explained by estimated inversion strength (EIS) and sea surface temperature (SST) anomalies. However, larger fluctuations are noted in MODIS low cloud anomalies, partly due to the overlapping cloud effects in passive measurements. Also, the cloud base heights of mid and high-level clouds are underestimated by MODIS retrievals, causing smaller impacts on the low troposphere cloud amounts. However, CALCS measurements indicate that cloud base heights of mid/high-level clouds are often below 3 km, and the changes of mid/high clouds are largely compensated with low-level cloud changes.

 

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