Analysis Of Temporal-spatial Characteristics Of Haze In China Based On Satellite Remote Sensing Data

In this paper, firstly, the temporal characteristics of haze days occurred in China in1981-2010were analyzed based on weather phenomena record, visibility and relative humidity data of ground-based observations. Combined with meteorological data, weather features in haze days and the correlation between the number of haze day and meteorological factors were calculated. Secondly, based on MODIS and CALIOP/CALIPSO satellite data, characteristics of aerosol spatial distribution and type in haze were identified. Last, study of three typical cases was done, occurred in eastern northwest of China in March2013, in northeast of China in October2013and in eastern of China in December2013separately. The main conclusions are as follows:(1) The frequency of haze days in China decreased before1990s and increased from1991to2005, and then decreased again after2005. Haze days occurred in winter were most frequent then followed in fall and spring. There was high incidence of haze-day in January, February, November and December, and the low incidence from June to September.(2) In general, the distribution of haze days in eastern and southern China is more than that in western and northeastern. Haze-day in north of the main haze region was greater than that in south in spring and summer, and in southern China haze occurred more in autumn and winter. Haze in south Yunnan often occurred in spring, but it appeared in summer in north Heilongjiang and Inner Mongolia.(3) Haze events usually happened under calm weather when the blocking high or zonal circulation in the high-altitude. When there is a groove or low pressure in high-altitude and the ground were controlled by low pressure system, the haze eased. When the cold weather comes with winds and rain, haze is over. In the process of haze, visibility is reduced, lowering the temperature, wind speed is small, temperature inversion exist near-surface and atmospheric stratification is stable.(4) The monthly average number of haze days is negatively correlated with precipitation, air temperature and vapor pressure and significantly are positively correlated with pressure. But there are different correlations with wind speed and relative humidity in different regional. The haze days in northern cities have greater correlation with temperatures than in southern cities, while they have less correlation with precipitation than in the southern. Overall, the effects of precipitation and wind speed of haze were not significant.(5) The distribution of AOD in haze days had a low center in the south and a high center in the north. The values of AOD in most parts of northern China ranged from0.6to0.8, while in the northeast and northwest regions AOD values were from0.3to0.4, and in the South were generally from0.5to0.6. In Northwest, Northeast China, Inner Mongolia, Qinghai-Tibet Plateau and the Yunnan-Guizhou Plateau AOD values were low, while in North China, in the Yangtze River region and the Sichuan Basin AOD values were high.(6) The depolarization ratio of the most particles during haze days in Northwest is less than40%and the color ratio less than0.8. The composition was mainly fine particles of spherical or near spherical during haze days. The depolarization ratio of most of particles in North China during the haze days is less than60%, and the color ratio of most of fine particles is smaller than1.0. Most regular and irregular coarse particles distributed in surface layer, and more regular medium-sized particles were in high-level. The depolarization ratio of the most of the particles during the haze days in the southern is less than50%, the color ratio of particles under4km is mostly about1.0to1.6, and the particles are coarser, while the color ratio of particles above4km is mostly about0.8to1.4. Compared with the northwest area and north China, the distribution of aerosol during haze days in the southern region was more obvious, and scattering ability weakened with the altitude increasing, while the fine spherical particles reduced.(7) The classification results of aerosol on the east and west by using the Level2data of satellite of CALIPSO displays that the main ingredient of aerosol during haze days is dust aerosol, and the minor ingredients is continental aerosol and smoke aerosol. The proportion of dust aerosol in the western region is higher than the eastern region, while the proportion of continental aerosols in eastern is higher than in the western region. When by using MODIS data products for the eastern region the classification of the aerosol during haze days shows that dust and the mixed aerosol are the main component of haze days, the urban/industrial type, dust and mixed aerosols type of haze days are more than sunny days.