基于CALIOP资料的中国及周边地区云出现概率时空分布特征分析

云垂直结构是影响大气辐射的重要参数，其时空分布是影响全球气候变化的关键组成部分.本文利用星载激光雷达CALIOP的1 km云层产品，计算了中国及周边地区（0-55°N，70-140°E）云的出现概率，对不同地区、不同季节、不同高度单层云的出现概率做了对比分析.结果表明：云的出现概率表现出明显的地区差异，蒙古高原和印度半岛北部少云，热带海域和中国南方多云，多数地区夜间云出现概率略高于白天；除蒙古高原和印度半岛北部以外，多数地区单层云比多层云更常见；多数地区高云占单层云的比例最大，而中国大陆南部单层的中云较常见，西太平洋北部海域常被单层的低云覆盖；夏秋两季云出现概率普遍大于春冬两季，尤其印度半岛北部的云主要出现在夏季；蒙古高原和印度半岛北部单层云少于多层云，冬季尤其明显，而中国西南地区东部全年单层云更常见；夏季单层的高云占全年单层云的比例最大，青藏高原部分地区超过35%，这与其地形特征和夏季对流活动旺盛有关.

A CALIOP-Based Study of the Spatial and Temporal Features of the Frequency of Cloud Occurrence Over China and Its Surrounding Areas

This paper considers cloud vertical structure, which is an important parameter affecting atmospheric radiation, and whose spatial and temporal distribution is a key component of global climate change. The occurrence of clouds over China and its surrounding areas (0-55°N, 70-140°E) has been calculated based on the cloud layer products from CALIOP (the cloud-aerosol lidar with orthogonal polarization) at 1 km resolution. Cloud occurrence in different regions and seasons, and at different heights has been compared and analyzed. The results show significant regional differences in the frequency of cloud occurrence. Fewer clouds are found over the Mongolian Plateau and the northern Indian Peninsula, with more clouds appearing over the tropical seas and southern China. Cloud cover at night is slightly higher than during the day. Single-layer clouds are more common than multi-layer clouds in most areas, except the Mongolian Plateau and the northern Indian Peninsula. In most areas, high-level cloud accounts for the largest proportion of single-layer clouds; however, mid-level clouds are more common in southern China, and the northern parts of the western Pacific are often covered by low clouds. The occurrence of clouds in summer and autumn is generally greater than in spring and winter, especially over the northern Indian Peninsula, where clouds are most frequent in summer. Single-layer clouds over the Mongolian Plateau and the northern Indian Peninsula occur less frequently than multi-layer clouds, especially in winter. Furthermore, single-layer clouds are common over the eastern part of southwest China all year round. Over parts of the Tibetan Plateau in summer, high clouds account for the largest proportion (>35%) of annual single-layer clouds, as a result of topography and enhanced summer convection.