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Direct radiative forcing of various aerosol species over East Asia with a
coupled Regional Climate/Chemistry model
Zhiwei Han
Key Laboratory of Regional Climate-Environment for East Asia (RCE-TEA),Institute of Atmospheric Physics (IAP),
Chinese Academy of Sciences (CAS), Beijing 100029, China. hzw@mail.iap.ac.cn
The Regional Integrated Environmental Model System
(RIEMS) was developed at RCE-TEA, IAP/CAS and has
been utilized to predict regional climate in East Asia (Fu et
al., 2005). RIEMS was further developed recently by
incorporating tropospheric chemistry and aerosol processes
to explore potential impacts of anthropogenic agents (O 3 ,
aerosols etc) on regional climate over East Asia where
intense human activity and continuous economic growth
occur. Gas phase chemical mechanism is represented by CB-
IV mechanism, ISSOROPIA has been used to calculate
physical state and composition of inorganic aerosols. Black
carbon, organic carbon (both primary and secondary), soil
dust and sea salt aerosols are also included in RIEMS based
on previous works on aerosols (Han et al., 2004; Han et al.,
2008).
The time period of this study is March, 2006, with the study
domain covering most of the East Asia (85-145ºE, 15-55ºN).
The reanalysis data, four times a day with 1º×1º resolution
are derived from National Centers for Environmental
Prediction (NCEP) to provide initial and boundary
conditions for RIEMS. The Lambert projection was used,
with horizontal resolution of 60 km, and 16 levels from the
surface to 100 mb. Emission inventories of SO 2 , NO x , CO,
NMVOC, BC and OC are from Streets et al. (2003) and
interpolated to RIEMS projection.
Figure 1a-1d shows the model predicted monthly mean
surface direct radiative forcing (DRF) by sulfate, BC, OC,
soil dust and sea salt aerosols, respectively. Strong cooling
by sulfate at the surface (< -10 W m -2 ) occurred over large
areas of east China, with a maximum of < -20 W m -2 around
Chongqing city in Sichuan Province. DRF by sulfate at the
top of the atmosphere (TOA) is negative (not shown) and
almost the same as the DRF at the surface. BC and OC
aerosols exert cooling effects at the surface, with maximum
values being -10 W m -2 and -2 W m -2 over the regions
similar to that of sulfate. Soil dust aerosol cause negative
forcing at the surface, showing cooling effect predicted
mainly over the northwestern China and parts of the eastern
China, as a result of dust deflation in arid regions and
subsequent southeastward transport. The sign of DRF at
TOA by soil dust is geographically dependent, either
negative or positive. The maximum surface cooling by soil
dust can be larger than -10 W m -2 , implying the potentially
important climatic impact of Asian soil dust in springtime.
The total surface forcing by all the five aerosols (Figure 1e)
predicted with an assumption of external mixture is negative
in the study domain, with strong cooling of ~ -30 W m -2
occurring over the middle reaches of the Yangtze River.
Korean peninsula exhibits moderate cooling of -6 ~ -3 W m -
2 , and the predicted DRF over Japan is generally in a range
of -6 ~ 0 W m -2 .
Figure 1 The predicted monthly mean surface DRF
by (a) sulfate, (b) BC, (c) OC, (d) soil dust, (e) sea
salt (f) external mixture of the aerosols
References
(d) (e) (f)
Fu Congbin et al., Regional Climate Model
Intercomparison Project for Asia, Bulletin of
American Meteorological Society, 86(2),257-266.
2005.
Han, Zhiwei et al., Model study on particle size
segregation and deposition during Asian dust events
in March 2002, Journal of Geophysical Research,
109,D19205, doi: 10.1029 /2004jd004920. 2004
Han Zhiwei et al.,. Regional modeling of organic aerosols
over China in summertime. Journal of Geophysical
Research, 113, D11202, doi:10.1029/2007JD009436.
2008.
Streets, D.G. et al., An inventory of gaseous and primary
emissions in Asia in the year 2000. Journal of
Geophysical Research 108 (D21), 8809,
doi:10.1029/2002JD003093. 2003.