资源环境科技发展态势分析平台

This study examines the climatology of cloud phase over Southeast Asia (SEA) based on A-Train satellite observations. Using the combined CloudSat-CALIPSO (CC) data, five main cloud groups are investigated: ice-only, ice-above-liquid, liquid-only, ice-above-mixed, and mixed-only clouds that have annual mean frequencies of 28.6 %, 20.1 %, 16.0 %, 9.3 %, and 6.7 %, respectively. Liquid-only clouds tend to occur in relatively cold, dry, and stable lower troposphere. The other four cloud groups appear more frequently in relatively warm, humid, and unstable conditions, and their seasonal distributions move with the Asian monsoon and the Intertropical Convergence Zone (ITCZ). Liquid clouds are found to be highly inhomogeneous based on the heterogeneity index (H-sigma) from Aqua Moderate Resolution Imaging Spectroradiometer (MODIS), while ice-only and mixed-only clouds are often very smooth. Ice-above-liquid clouds are more heterogeneous than ice-only clouds owing to ice clouds being optically thin. We demonstrate that the distribution of clear-sky H-sigma has a long tail towards heterogeneous values that are caused by undetected sub-pixel cloud within both CC and MODIS datasets. The reflectance at 0.645 mu m (R-0.645) and brightness temperature at 11 mu m (BT11) of CC ice-only, liquid-only, and ice-above-liquid clouds show peak frequencies near that of clear sky (R-0.645 similar to 0.02; BT11 similar to 294 K), which explains why up to 30 % of these CC cloud groups are classified as clear by MODIS. In contrast, mixed-only clouds are thick (average top similar to 13 km), bright (average R-0.645 similar to 0.6), and cold (average BT11 similar to 234 K). Cloud phase comparison between CC and MODIS reveals only modest agreement, with the best agreement (73 %) occurring between CC ice-above-mixed and MODIS ice clouds. The intraseasonal and interannual behaviors of the all-sky H-sigma and spectral signatures follow that of cloud phase and vary with the Madden-Julian oscillation (MJO) and the El Nino-Southern Oscillation (ENSO) phases.