Ice Cloud Distribution and Seasonal Migration over Land Area of China Based on MODIS Data

Ice clouds have an important impact on the global climate, and ice cloud features vary with convection and weather system. Mid-latitude ice clouds originate from the convective cloud system and the atmospheric circulation in the atmosphere, but the understanding on the formation of ice crystals in clouds is still lacking. Non-spherical ice crystal particles have also posed a great challenge to the accurate calculation of the ice cloud in the climate model. Due to limitations of aircraft observation and remote sensing, the observation of ice clouds depends mainly on satellite remote sensing. Based on moderate resolution imaging spectrometer (MODIS) cloud product level-3 data (MOD08_M3), the probability distribution of ice cloud, ice cloud optical thickness, ice cloud effective radius and ice water path over China from November 2011 to October 2016 are analyzed, and the distribution and seasonal migration are discussed. The horizontal distribution and trend of ice cloud attributes in different seasons are studied emphatically. Main conclusions are as follows. The occurrence probability of ice clouds is higher in the northeastern part of the Qinghai-Tibet Plateau during winter, spring and autumn, mainly due to the warm and humid air raised by the northeast slope of the Qinghai-Tibet Plateau. The occurrence probability of ice clouds in low latitudes in summer is related to monsoon and the intertropical convergence zone. The overall occurrence probability of ice clouds is on the rise, especially in the summer of 2016. The horizontal distribution of effective radius of ice cloud is increasing from southwest to northeast, mainly due to the difference of temperature distribution. Through the year, the effective low radius of the ice particles appears in the southwest region, and the high value appears in the northeastern region during the winter, spring and autumn, and appears in Xinjiang area during summer. The ice cloud effective particle radius is larger in high latitudes than in low latitudes, and the overall seasonal variation is not obvious. The horizontal distribution and seasonal changes of ice cloud thickness and ice water path are roughly the same, showing the downward trend from southeast to northwest. The large value of ice cloud optical thickness and ice water path are mainly in the southern region. The minimum value appears in the northern part of Xinjiang, which is mainly related to the air vapor content and the East Asian Monsoon. The ice cloud optical thickness and ice water path are larger in monsoon area than in non-monsoon zone. There is little difference in the distribution of ice thickness between ice age and ice water, and large value areas are in the southern region. Seasonal changes in northwest, northern and the Qinghai-Tibet Plateau regions are relatively significant.