Seasonal variations in aerosol optical properties over China

Yuesi Wang,Bryce L Nordgren,Lili Wang,Hongbin Chen,Shigong Wang,Zhanqing Li,Pucai Wang,Yang Sun,Wei Min Hao,Jinyuan Xin

doi:10.1029/2010jd015376

Abstract

[1] Seasonal variations in background aerosol optical depth (AOD) and aerosol type are investigated over various ecosystems in China based upon three years' worth of meteorological data and data collected by the Chinese Sun Hazemeter Network. In most parts of China, AODs are at a maximum in spring or summer and at a minimum in autumn or winter. Minimum values (0.10∼0.20) of annual mean AOD at 500 nm are found in the Qinghai-Tibetan Plateau, the remote northeast corner of China, the northern forest ecosystems and Hainan Island. Annual mean AOD ranges from 0.25 to 0.30 over desert and oasis areas, as well as the desertification grasslands in northern China; the annual mean AOD over the Loess Plateau is moderately high at 0.36. Regions where the highest density of agricultural and industrial activities are located and where anthropogenic sulphate aerosol and soil aerosol emissions are consistently high throughout the whole year (e.g., the central-eastern, southern and eastern coastal regions of China) experience annual mean AODs ranging from 0.50∼0.80. Remarkable seasonal changes in the main types of aerosol over northern China (characterized by the Angstrom exponent, α) are seen. Due to biomass and fossil fuel burning from extensive agricultural practices in northern rural areas, concentrations of smoke and soot aerosols rise dramatically during autumn and winter (high α), while the main types of aerosol during spring and summer are dust and soil aerosols (low α). Over southeastern Asia, biomass burning during the spring leads to increases in smoke and soot emissions. Over the Tibetan Plateau and Hainan Island where the atmosphere is pristine, the main types of aerosol are dust and sea salt, respectively.

Highlights

[2] Under the aegis of the East Asian Study of Tropospheric Aerosols – an International Regional Experiment (EAST‐AIRE) [Li et al, 2007b], the Chinese Sun Hazemeter Network (CSHNET) was successfully implemented to obtain spatial and temporal distributions of aerosol optical properties in China [Xin et al, 2006, 2007]
[4] There are a handful of international aerosol experiments that have already taken place in the east Asian region surrounding and inside China, such as the Asian‐Pacific Regional Aerosol Characterization Experiment (ACE‐Asia) [Huebert et al, 2003], the NASA Global Tropospheric Experiment Transport and Chemical Evolution Over the Pacific (TRACE‐P) [Christopher and TRACE‐P Science Team, 2003], the Asian Atmospheric Particle Environment (APEX) [Nakajima et al, 2003], the Atmospheric Brown Clouds‐East Asian Regional Experiment (EAREX) [Nakajima et al 2007], the East Asian Study of Tropospheric Aerosols – an International Regional Experiment (EAST‐AIRE) [Li et al, 2007b] and the East Asian Studies of Tropospheric Aerosols and their Impact on Regional Climate (EAST‐AIRC) [Li et al, 2011]
Eck et al [2005] and Kim et al [2007] discussed seasonal variations of columnar aerosol optical properties over eastern Asia determined from multiyear AERONET measurements

Summary

Introduction

[2] Under the aegis of the East Asian Study of Tropospheric Aerosols – an International Regional Experiment (EAST‐AIRE) [Li et al, 2007b], the Chinese Sun Hazemeter Network (CSHNET) was successfully implemented to obtain spatial and temporal distributions of aerosol optical properties in China [Xin et al, 2006, 2007]. [3] China is situated in the eastern part of Asia, on the west coast of the Pacific Ocean. [4] There are a handful of international aerosol experiments that have already taken place in the east Asian region surrounding and inside China, such as the Asian‐Pacific Regional Aerosol Characterization Experiment (ACE‐Asia) [Huebert et al, 2003], the NASA Global Tropospheric Experiment Transport and Chemical Evolution Over the Pacific (TRACE‐P) [Christopher and TRACE‐P Science Team, 2003], the Asian Atmospheric Particle Environment (APEX) [Nakajima et al, 2003], the Atmospheric Brown Clouds‐East Asian Regional Experiment (EAREX) [Nakajima et al 2007], the East Asian Study of Tropospheric Aerosols – an International Regional Experiment (EAST‐AIRE) [Li et al, 2007b] and the East Asian Studies of Tropospheric Aerosols and their Impact on Regional Climate (EAST‐AIRC) [Li et al, 2011]. There is a similar trend in the distribution of aerosol optical depths (AODS), their quantitative comparability is poor, due to a lack of systemic ground‐based network measurements, as well as systemic errors in satellite retrievals products [Liang et al, 2006; Wang et al, 2007; Li et al, 2007a; Liu et al, 2010]

Data and Methodology

Results and Discussion

Conclusions