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徐文静, 吕达仁. 2023. 基于静止卫星探测的夏季青藏高原云分布及其日变化分析[J]. 气候与环境研究, 28(3): 229−241. doi: 10.3878/j.issn.1006-9585.2022.21050
引用本文: 徐文静, 吕达仁. 2023. 基于静止卫星探测的夏季青藏高原云分布及其日变化分析[J]. 气候与环境研究, 28(3): 229−241. doi: 10.3878/j.issn.1006-9585.2022.21050
XU Wenjing, LÜ Daren. 2023. Analysis of Cloud Distribution and its Diurnal Variation over the Tibetan Plateau in Summer Based on Geostationary Satellite Data [J]. Climatic and Environmental Research (in Chinese), 28 (3): 229−241. doi: 10.3878/j.issn.1006-9585.2022.21050
Citation: XU Wenjing, LÜ Daren. 2023. Analysis of Cloud Distribution and its Diurnal Variation over the Tibetan Plateau in Summer Based on Geostationary Satellite Data [J]. Climatic and Environmental Research (in Chinese), 28 (3): 229−241. doi: 10.3878/j.issn.1006-9585.2022.21050

基于静止卫星探测的夏季青藏高原云分布及其日变化分析

Analysis of Cloud Distribution and its Diurnal Variation over the Tibetan Plateau in Summer Based on Geostationary Satellite Data

  • 摘要: 我国新一代静止气象卫星首颗卫星风云四号先进成像仪AGRI(Advanced Geosynchronous Radiation Imager)具有更多的观测波段、更高的光谱分辨率和更高的时空分辨率,能够以较小的卫星天顶角获取完整的青藏高原观测图像,但尚未开发利用青藏高原地区的风云四号卫星云产品开展相关研究。本文基于FY-4A/AGRI提供的青藏高原地区像元级云图像,研究分析夏季青藏高原地区云分布及其日变化的特征和规律。研究发现高原南部和东南部区域云出现频率远高于高原其他地区;高原地区云频具有明显的昼夜变化,最高云频发生在12:00(当地时间,下同),最低云频出现在04:00;高原南部地区云频具有日出后增长速度最快、增长幅度最大、最先达到最高值的特征;当高原云频在当地正午达到最大值时,极高云频沿主要山脉分布,具有明显的地形依赖特征;云顶最大频率高度超过12 km的区域集中在雅鲁藏布江河谷及其北侧,念青唐古拉山脉附近,以及横断山脉东界以西地区;云顶最大频率高度日变化与云频的日变化存在显著不同。本文同时就青藏高原复杂地形对云分布和日变化的强烈影响进行了讨论。

     

    Abstract: The Tibetan Plateau (TP) has a significant impact on the climate at the continental to global scale. During summer, the diurnal variation of clouds over the TP not only affects local convection and precipitation processes but also is closely related to floods in the Yangtze River basin of China, the Asian summer monsoon, and the large-scale climate regime in the Northern Hemisphere. Therefore, understanding the bulk characteristics of clouds over the TP is essential to study cloud-climate feedback and their impact on climate change and dynamics. Due to its remote geographical location, satellite cloud retrievals are highly relied upon for studying the TP. Recent satellite observations have revealed many unique features and roles of clouds over the TP. However, sun-synchronous satellites with low temporal resolution can only capture cloud characteristics twice a day, which is insufficient to understand the diurnal variations of clouds that vary spatially and temporally, especially during summer. The Fengyun-4A (FY-4A) is the first satellite of the new generation of Chinese geostationary meteorological satellites. The Advanced Geosynchronous Radiation Imager (AGRI) on board FY-4A has higher radiation, spectrum, and spatial resolution with shortened revisit time, which provides an opportunity to monitor clouds and their daily cycle with a new level of ability. Although FY-4A/AGRI has the capability to provide a complete image of the TP with smaller viewing zenith angles, cloud retrievals over the TP derived from FY-4A have not yet been exploited and utilized. In this study, pixel-level cloud retrievals obtained from FY-4A/AGRI are used to investigate and analyze the occurrence distribution and diurnal variation patterns of clouds over the TP during summer. The results show that clouds occur most frequently over the south and southeast of the TP all day long, and the TP has an obvious diurnal cycle. Cloud frequencies are highest at noon and lowest at 4 a.m., with peak cloud frequencies distributed along major mountains, showing terrain-dependent characteristics. Cloud tops with a most probable height of more than 12 km are concentrated in the Yarlung Zangbo River Valley and its northern side, near the Nyainqentanglha Mountain Range, the vicinity of Nyainqentangula Mountains, and the west of the eastern boundary of Hengduan Mountains. The diurnal cycle of cloud heights shows an apparent delay against that of cloud occurrence frequencies. This study also discusses the strong topographic influences on the spatiotemporal distribution patterns of clouds over the TP.

     

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