Optical and Physical Characteristics of Aerosol Vertical Layers over Northeastern China

Hao Li,Chun Zhang,Luqman Atique,Ge Han,Md Arfan Ali,Zhongfeng Qiu,Miao Zhang,Ziyue Zhang,Muhammad Bilal,Bo Su,Minxia Wang

doi:10.3390/atmos11050501

Abstract

The optical and physical characteristics of the aerosol vertical layers over Northeastern China (NEC) are investigated using the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) Level 2 layer products from 2007 to 2014. To better examine the spatial and temporal variations in the characteristics of aerosols over NEC, the region is divided into three parts (Heilongjiang province, Jilin province, and Liaoning province) to analyze the inter-annual and seasonal variations of nine selected aerosol parameters in each part during night and day times. The results reveal that the values of aerosol optical depth (AOD) increase year by year, over the whole NEC, being relatively high over the Liaoning (LN) province; this might be induced by higher levels of economic development and agricultural activity. The highest AOD values appear in summer, which is plausibly related to the temperate monsoon climate in NEC. Higher AOD values exist during the daytime than at night; this is intuitively the result of higher daytime anthropogenic activities. The base altitude of the lowest aerosol layer (BAL) and the top altitude of the highest aerosol layer (TAH) varied significantly due to the topography of NEC. The number of aerosol layers (N) is relatively large over LN, which might be caused by a relatively stronger atmospheric convection over this landscape. The thickness of the lowest aerosol layer (TLL) bore little relationship with the topography of NEC. The AOD proportion of the lowest aerosol layer (PAODL) is high (0.70 to 0.85 for the entire NEC), indicating that aerosols are mainly concentrated in the lowest layer of the atmosphere. The volume depolarization ratio of the lowest aerosol layer (VDRL) is large during spring and winter due to the presence of dust aerosols. The color ratio of the lowest aerosol layer (CRL) is large during the day due to relatively more human activities taking place than at night. Moreover, there is a significantly positive linear correlation between N and TAH, and a negative logarithm correlation between N and PAODL over NEC. The results of this study could provide researchers and the government departments with detailed and certain optical and physical information about aerosol layers over NEC, to help in the treatment of air pollution over NEC.

Highlights

Atmospheric aerosols have scattering and absorption effects on solar radiation, which can significantly change the solar radiation energy reaching the surface, affecting the radiation budget of the whole earth-atmosphere system and, in turn, causing climate and environmental changes [1,2,3,4,5,6].The optical and physical characteristics of atmospheric aerosols are key factors in the objective evaluation of aerosol radiation forcing and climate effects [7,8,9]
Annual mean values of AODA were analyzed over Northeastern China (NEC) Heilongjiang province (HLJ), Jilin province (JL), and Liaoning province (LN) (Figures 2a and 3a)
0.35, night: 0.25 to 0.30) followed by JL and HLJ. It can be seen from the spatial distribution maps (Figures 4 and 5) that there is a banded high-value center in the annual mean AODA distribution, which is mainly composed of Dalian, Shenyang, Changchun, and Harbin cities, and runs from northeast to southwest

Summary

Introduction

The optical and physical characteristics of atmospheric aerosols are key factors in the objective evaluation of aerosol radiation forcing and climate effects [7,8,9]. Observation of the optical and physical characteristics of atmospheric aerosols has become a research hotspot in the field of atmospheric environment and climate change [10,11,12,13,14]. With more frequent haze pollution episodes occurring over most areas of China in recent years, the study of aerosol properties was first conducted over economically developed areas, such as Beijing-Tianjin-Hebei, the Yangtze River. Due to a fast-developing economy and urban-scale expansion in NEC, energy consumption has increased rapidly, leading to frequent air pollution events [17,18]

Methods

Results

Conclusion