Environmental & Climate Sciences Department Seminar

Cloud feedbacks and an appropriate representation of clouds in climate models have long been one of the largest sources of uncertainty in predicting any potential future climate change. Although it is already a great challenge to derive true cloud fractions (CFs) from both active and passive remote sensing observations, it is even more difficult to infer their vertical distributions. Here we use the NASA CERES) Edition 4 cloud products in conjunction with the availability of ARM ground-based and NASA CloudSat-CALIPSO (CC) spaceborne radar-lidar observations over four ARM sites (SGP, ENA, TWP, and NSA) to answer two questions: Can spaceborne and ground-based radar-lidar combinations observe the same types and amounts of clouds? Are clouds detected and analyzed using passive satellite remote sensing comparable to these actively sensed clouds? From the long-term satellite-surface comparisons over these four sites, we found that ARM missed some optically thin high-level clouds at ARM SGP and ENA and even more at TWP, while CC missed some low-level clouds at NSA but identified more low-level clouds at SGP and ENA, even more at TWP. Passive sensors could not detect optically thin clouds, which is beyond their limitation. Based on the results, we conclude that true CFs can only be estimated from multiple instruments on various platforms. At the end of talk, we will present some comparisons between satellite observed and model simulated cloud properties.