Seasonal and Semi‐Diurnal Variations in Cloud‐Phase Characteristics Over the Southern Himalayas and Adjacent Regions as Observed by the Himawari‐8 Satellite

Abstract

Investigated in this study are the seasonal and semi‐diurnal variations of the cloud‐phase climatology over the southern Himalayas and adjacent regions by using 5 years of Himawari‐8 cloud‐product data (2016–2020). The four selected regions from south to north are the Gangetic Plains (I), Himalayan foothills (II), southern slope of the Himalayas (III), and the Himalayan–Tibetan Plateau region (IV), respectively. Results showed that the cloud frequency of cloud gradually increases from region I via II to III, then sharply decreases as the altitude increases up to IV. Ice‐phase clouds occurs more frequently over regions I/II (III/IV) during boreal summer (winter), while water‐phase cloud has a higher frequency over region III/IV (I/II) in summer (winter), respectively. All of the different cloud phases have a clear seasonal cycle. Furthermore, the semi‐diurnal variation shows that water‐phase clouds tends to have an occurrence frequency peak around noon (in the later afternoon) over regions I/II/III in summer (winter), whereas over region IV it only occurs more in the morning in both seasons. Ice‐phase cloud generally occurs more in the late afternoon in both boreal summer and winter, especially over region IV. Further analysis showed that the differences in the cloud‐phase characteristics over the southern Himalayas and adjacent regions are likely related to the interactions of the synoptic‐scale circulation, the topography, and the water vapor transport.

Cloud characteristics over the Yunnan–Guizhou plateau as observed by MODIS and Himawari‐8

“…To cover as many observation samples as possible, all three daytime datasets in warm and cold season were used in this study. Because the H8 has a better view over southwestern China during 0210 UTC (Shang et al, 2018; Yu et al, 2022), the hourly data of clouds in both the H8_Japan and H8_Zhuge cloud products were used to examine the cloud characteristics over the YGP and its surrounding area in this period. As members of the A‐Train constellation, MODIS passes over the YGP region at approximately 0630 UTC in the daytime.…”

“…As polar‐orbiting satellite‐based sensor (e.g., Moderate Resolution Imaging Spectroradiometer [MODIS]) cloud products have been widely used to study the distribution of cloud cover, cloud‐top heights and optical thickness (King et al, 2013; Marchand et al, 2010), for example, the cloud cover over the Mongolian Plateau is higher in summer and the spatial distribution of high/middle/low clouds are obviously variable (Bao et al, 2018); and the largest cloud cover difference between afternoon and morning is found over the Tibetan Plateau (TP) (Zhao et al, 2019). The cloud products obtained from the geostationary satellite Himawari‐8 (H8) can be used to analyse the continuous changes in cloud properties over a target area (Shang et al, 2018; Yang et al, 2022; Yu et al, 2022; Zhao et al, 2023; Zhuge et al, 2021). Yang et al (2020) used the H8 cloud data to investigate the cloud properties over the four study regions in China; they found both cloud cover and cloud types show clear seasonal and diurnal variation over the TP.…”