Detection and characterization of deep convective clouds over the Tibetan plateau and Asian Monsoon regions using hyperspectral infrared sounders

A novel method for detecting deep convective clouds based on the height of inverted hyperspectral infrared spectra near 9.6 μm, i.e., H-index, is presented. Verification to their cloud top heights using Single Field-of-View Retrieval Products (SiFSAP) and CERES products demonstrates that this method provide an effective way to detect the deep convective clouds, with the DCCs detected using H-index >3.5 K being mostly above 250 hPa, and DCCi2 detected by H-index >11.5 K mostly above 150 hPa. Further analysis of the spatiotemporal distribution of these two categories of DCCs and DCCi2 over the Tibetan Plateau (TP) and surrounding Asian Monsoon regions using 13 years of CrIS data (2013–2025) reveals: (1) Frequent DCCs occur over the Western Himalaya, Pakistan, Northwest India during summer, and western Himalayan DCCs are significantly more likely to intensify into DCCi2 compared to those over the TP, confirming previous findings of extreme deep convection along steep Himalayan slopes; (2) The occurrence of DCCs over the TP exhibits a strong correlation with ENSO cycles, with less DCCS during El Niño years (2015, 2019) and more DCCs during La Niña year (2022), and DCCs over the TP shows a decreasing trend: and (3) nighttime (∼1:30 am) DCCs are more frequent than daytime (∼1:30 pm) over the TP. Notably, frequent DCCs occurrence is found near Ya’an, Sichuan (the “Rain City”), particularly during summer nights. Frequent DCCs are also evident over the Bay of Bengal and South China Sea. From the annual cycle of DCCs, the maximum DCCs occurrence over the Western Himalaya and TP lags behind ocean regions by approximately 1 month, reflecting monsoon propagation dynamics. These results demonstrate the value of hyperspectral infrared data for studying DCCs over the TP and Asian Monsoon regions. This new method can be easily applied to other hyperspectral infrared sounders, such as AIRS and IASI, enabling DCC studies in other regions and facilitating climatological analysis using over 20 years of accumulated hyperspectral sounder data from AIRS, IASI and CrIS.