Estimate of radiative forcing of Asian biomass‐burning aerosols during the period of TRACE‐P

Abstract

[1] The regional radiative impact of biomass-burning aerosols in Asia is estimated using the new and detailed emission data during the experimental period of Transport and Chemical Evolution over the Pacific (TRACE-P) in March 2001. Integration of the USA National Oceanic and Atmospheric Administration (NOAA) Hybrid Single-Particle 10 Lagrangian Integrated Transport model (HYSPLIT) and a solar radiative transfer model (CLIRAD-SW) allow us to simulate the spatial and temporal distributions of black carbon (BC) and organic carbon (OC) aerosols from biomass burning in the South Asian region. It also allows us to estimate further their aerosol optical properties and radiative forcing. We find that an anticyclone over Bay of Bengal dominates the transport of pollutants of the South Asian region. The monthly mean surface concentration of OC and BC is 1.1 mg m À3 in this region. Western Myanmar has the maximum value, with the concentration reaching 12.5 mg m À3 . The monthly mean clear-sky direct shortwave radiative forcing ranges from À1.9 to 0.4 W m À2 at the top of the atmosphere and from À0.5 to À12.0 W m À2 at surface, resulting in an increase of the atmospheric heating rate from 0.01 to 0.3°C day À1. Owing to the spatial distributions of the aerosol optical depth ratio (OC/BC) and the surface albedo, there is a strong gradient of heating rate near the source regions, which may modify local circulations.

Modelling of long-range transport of Southeast Asia biomass-burning aerosols to Taiwan and their radiative forcings over East Asia

“…Similarly, the ratio obtained from an emission inventory compiled by U.S. EPA (2005) during open biomass burning was 4.7. Wang et al (2007) also reported an OC/BC ratio of 6.5Á8.0 over Indochina, India and South Asia. Figure 15 shows the average DRF of aerosols at the top of atmosphere (TOA), ground surface (SFC) and in the atmosphere (ATM).…”

“…The primary biomass-burning carbon aerosols (BC and OC) play important roles in the radiation budget. Wang et al (2007) indicated that solar absorption by BC within the atmospheric, which increases the radiative heating rate, leads to a significant reduction in solar radiation reaching the surface. On the other hand, OC enhances the reflected solar radiation at the TOA, leading to a cooling effect due to reduced incoming solar radiation to the atmosphere and ground surface.…”

Observing and understanding the Southeast Asian aerosol system by remote sensing: An initial review and analysis for the Seven Southeast Asian Studies (7SEAS) program

“…Smoke that is transported aloft and over the mountain ranges of Burma and Laos is caught in the free tropospheric westerlies, and transported over northern Vietnam into the Pacific Ocean (Tang et al, 2003a,b;Satake et al, 2004;Verma et al, 2008;Lin et al, 2009;Reid et al, 2009) or from Burma (Myanmar) into the Southeastern Tibetan Plateau (Engling et al, 2011). Plumes are frequently shown in these papers to reach as far as Taiwan, including the free troposphere receptor site on Lulin Mountain (Wang et al, 2007;Wai et al, 2008;Lin et al, 2009), southern Japan (Tang et al, 2003a,b;Satake et al, 2004) and Hawaii ). Aircraft observations near Europe even identified one exceptionally large IC pollution and smoke event that had traversed 2/3 of the globe (Stohl et al, 2007).…”

“…However, before aerosol radiative forcing can be calculated, reliable values of radiative fluxes are needed. There are several approaches for estimating the reflected shortwave and the emitted longwave radiative fluxes at the top of atmosphere including radiative transfer (Davison et al, 2004;Remer and Kaufman, 2006;Wang et al, 2007;Rajeev et al, 2008) and observational approaches (Christopher et al, 2006). Radiative transfer techniques use narrow-band measurements such as MODIS to infer broadband fluxes, and require numerous assumptions about wavelength dependent surface and aerosol properties.…”

“…For major events, total top of atmosphere forcing is on the order of −50 Wm 2 (Davison et al, 2004;Rajeev et al, 2008;Feng and Christopher, 2013-this issue). Further down wind in biomass burning receptor sites such as at Mt Lulin, top of atmosphere fluxes range from 0.4 to −1.9 W m 2 (Wang et al, 2007). When averaged over the domain, the low clear sky fraction of SEA results in a diurnally averaged cloud-free aerosol forcing values for this region of around −6Wm −2 (Feng and Christopher, 2013-this issue).…”