Research-Environment modeling

 

Influence of the Indian summer monsoon on aerosol loadings in East Asia

 
 

    The spatial and temporal variations of aerosol loading over eastern Asia during July are examined in conjunction with the intensity of the Indian summer monsoon. Two contrasting years, 2002 and 2003, which represent weak and active Indian summer monsoon events, respectively, are selected with a focus on a subregion in southern East Asia (SR; 23<C32<N, 105<C120<E) and a subregion in northern East Asia (NR; 35<C44<N, 115<C130<E). It is shown that the interannual variation of July mean wind intensity is a major factor in regulating the midsummer spatial pattern of aerosols over eastern Asia when the Indian monsoon index is anomalously large. The aerosol optical depth (AOD) anomalies in the NR and SR are positive and negative, respectively, during an active monsoon year, whereas the opposite is observed during a weak monsoon year. These results help us to understand the impact of Indian summer monsoon on aerosol loadings at a larger spatial scale in East Asia (Liu et al. 2011).

    To examine the physical processes behind the relationship between AOD and Indian summer monsoon intensity, the regional coupled climate-chemistry/aerosol model (RegCM3) is used to investigate the difference in the spatial distribution of aerosol optical depth (AOD) between a strong summer monsoon year (SSMY, July 2003) and a weak summer monsoon year (WSMY, July 2002) under the actual- and same-emission scenarios in the same subregions as in Liu et al. (2011). It is shown that the intensity of the Asian summer monsoon is primarily responsible for the AOD spatial distribution anomaly in mid-summer over East Asia. Specifically, the AOD over southern China, upwind of the Asian summer monsoon, is greater in WSMY than in SSMY, but the opposite is observed for the AOD downwind over North China and the Korean Peninsula. The present modeling results are consistent with the analyses based on the MODIS products, NCAR/DOE wind fields, and air parcel movements according to the 7-day trajectories of air parcels determined by the Hybrid Single-Particle Lagrangian Integrated Trajectory model (Yan et al. 2011).

 

Liu X.D., L.B. Yan, P. Yang, Z.-Y. Yin, and G.R. North, 2011: Influence of Indian summer monsoon on aerosol loading in East Asia, Journal of Applied Meteorology and Climatology, 50(3), 523-533.

Yan Libin, Xiaodong Liu, P. Yang, Z.-Y. Yin, and G.R. North, 2011: "Study of the impact of summer monsoon circulation on spatial distributions of aerosols in East Asia based on numerical simulations" (under review)