Classification and characteristic analysis of the clouds and dust in a dust-carrying precipitation process based on multi-source remote sensing observations

Abstract

A dust-carrying precipitation event that took place on May 11, 2020 in North China was observed by remote sensing methods including a micropulse lidar (MPL), millimeter-wavelength cloud radar (MMCR) and microwave radiometer from Yanjiaping (YJP) Station, which is the center of the transmission path of this dust storm, and it is the only super station capable of vertical observation of aerosols, clouds and precipitation in North China. The study researched the macro and microphysical characteristics of clouds and sand dust, as well as the possible impact of sand dust on clouds. It is found that dust has a great influence on the CBH measurement of ceilometer but little on the MMCR. The normalized relative backscatter (NRB) and depolarization ratio (DR) of the MPL were comparatively analyzed in terms of the mass concentration of PM10, revealing that the mass concentration of PM10 is linearly positively correlated to the NRB, with the correlation coefficient up to 0.9273. It was also discovered that the 100 μg/m3 is a critical point for the mass concentration of dust particles, and when the PM10 was greater than 100 μg/m3, the DR would fluctuate within a narrow range of 0.32–0.38. A classification method that could be used to distinguish among clear sky, non-dust aerosols, clouds, dust, and cloud-dust mixing zones was proposed. Based on the classification results, the immersion freezing process that might occur in the cloud-dust mixing area was analyzed using Z-LDR and V-SW by reference to the vertical distribution of temperature and humidity.