基于MODIS资料的陕西水云特征研究

Investigation of Characteristics of Water Cloud for Shaanxi Based on MODIS Data

陕西位于西北内陆地区,是中国气候的敏感区,为准确认识其上空的水云特征,利用MODIS的MYD06二级云产品数据,对陕西水云的概率分布、云顶高度、粒子有效半径、光学厚度进行了统计分析.结果表明:(1)水云概率分布显示出单峰结构,峰值出现在11月,5月出现概率最低.水云在秋季出现概率最高,春季出现概率最低.(2) 7月和9月水云云顶高度的概率分布会产生显著的变化,7月和8月的分布形态与其余各月有显著差别.水云云顶高度平均最大值出现在春季的4～5月,最小值出现在冬季的12～2月.(3)水云的粒子有效半径在10月～次年5月,分布形态相似,6～9月分布形态与之明显不同.水云粒子尺度平均最大值出现在夏季的6～8月,最小值出现在秋季的11月.(4)光学厚度在0～5之间的水云在10月～次年5月,出现概率最高,峰值出现在12～2月;6～9月光学厚度在5～10之间的水云出现概率最高,峰值出现在7～8月.水云光学厚度最大值出现在秋季的9～11月,最小值出现在夏季的7～8月.

Shaanxi Province is the climate sensitive region of China, locating at northwest inland. The probability distribution of water cloud, cloud-top height, optical thickness and the effective radius of cloud are analyzed by using MYD06-L2 of MODIS cloud product to understand the property of water cloud over Shaanxi. The results were concluded as follows:(1) Single peak was obtained for probability distribution pattern of water cloud and reached the top at November, while the lowest at May. Moreover, the maximum and minimum appearance probabilities were observed at autumn and spring.(2) The probability distribution of water cloud-top height produced significant change in July and September, and from April to May, the water could-top height mean value reached the maximum and from December to February the minimum mean value appeared, and specially that of July and August showed distinct form.(3) It was found that the probability distributions of the effective radius of cloud particle are similar from October to May the next year, while obvious differences existed from June to September. The maximum and minimum average appeared from June to August and in November, respectively.(4) The water cloud with optical thickness ranging 0~5, had a higher probability from October to May the next year and reached the top from December to February the next year. Yet, water cloud with optical thickness ranging 5~10 performed different. The higher probability existed from May to October, and reached the top from July to August. Additionally, the maximum and minimum of optical thickness occure from September to November and July to August, respectively.