Identifying the seas of clouds around Mt. Lu based on FY-4A satellite observations: Formation and sustenance

The characteristics, recognition and formation of seas of clouds (SOC) around Mt. Lu are studied based on FY-4A observations and other data. From 2019 to 2021, 19 events of SOCs are recorded in the dataset, including 12 traditional SOCs (TSOC) and 7 small-scale SOCs with cloud waterfalls over Mt. Lu (SSOC). The FY-4A visible-channel cloud image can identify the area and development of TSOC but cannot capture the detailed structure of SSOC. The L2 cloud-top-height product of FY-4A can be used for the recognition of TSOC around Mt. Lu but cannot be used for the recognition except of SSOC. Normally the wake phenomena of SOC (WSOC) occur on islands over the sea, but three WSOC events are found in Mt. Lu, although it is located in the land. The WSOC in Mt. Lu exhibits a comma-type cloud pattern with regular fluctuations but without continuous vortexes. The formation of the WSOC in Mt. Lu is mainly caused by the isolated ellipse shape of Mt. Lu, the northernly low-level jet, and the temperature inversion layer below the mountain top. Besides, for most SOC events, Mt. Lu is under the control of high-pressure systems and located in high-humidity region, where the synoptic-scale subsidence inversion layer and sufficient moisture could play an important role in the forming and maintenance of SOCs over Mt. Lu.