CloudSat inferred contrasting monsoon intra-seasonal variation in the cloud vertical structure over Indian regions

Abstract

Earlier studies reported the contrasting cloud properties over central India during intraseasonal oscillation of the Indian summer monsoon (ISM). This intraseasonal ISM variation in the cloud vertical structure (VSC) over different parts of India is yet to be explored. To fill this gap area, VSC derived from nine years of CloudSat measurements over geographically different but having homogenous ISM rainfall Indian regions are selected for the study. We investigated VSC, types of clouds, and microphysical properties during the intra-seasonal variation of ISM. Significant contrast was found in the mid-tropospheric cloud region during the ISM spells. Analysis of cloud types shows significant intra-seasonal variability with the presence or absence of mixed-phase clouds (As, Ns, and Ac). In ISM (active and break) spells, the core monsoon regions (CI, CE, WI) share similar VSC features (complete or void mid-levels). Hence, microphysical properties follow similar characteristics except for ice water content which differs profusely among them. Over these regions, ten times higher ice effective radius during active days indicates dominating ice process compared to break days. Larger-sized ice hydrometeors (> 25 μm) are present at 5–6 km, which shows good interrelation with the ISM active and break spells above freezing level, and its size decreases with altitude. Whereas no difference in VSC is found during different ISM spells over the eastern part of India (WB and EI) except in the ice microphysical parameters, which are more dominant during break days. Further, irregular and discontinuous VSC over North and South India (NI and SI) could be due to their pertinent geographical conditions. Suppression of cloud processes at mid-tropospheric altitude is one of the most important reasons behind reduced precipitation over the core ISM regions. Mid-tropospheric drying is a remarkable sign of ISM break, which is the main source of suppressed convection and cloud activity over the core ISM region. This CloudSat study brought robust composite cloud vertical structure for the ISM intra-seasonal variability of cloud over different regions of India to improve the understanding of cloud-related processes and then increase the predictive capabilities of large-scale models.