Abstract
Abstract. Particulate solar absorption is a critical factor in determining the value and even sign of the direct radiative forcing of aerosols. The heating to the atmosphere and cooling to the Earth's surface caused by this absorption are hypothesized to have significant climate impacts. We find that anthropogenic aerosols play an important role around the globe in total particulate absorption of solar radiation. The global-average anthropogenic fraction in total aerosol absorbing optical depth exceeds 65% in all seasons. Combining the potentially highest dust absorption with the lowest anthropogenic absorption within our model range, this fraction would still exceed 47% in most seasons except for boreal spring (36%) when dust abundance reaches its peak. Nevertheless, dust aerosol is still a critical absorbing constituent over places including North Africa, the entire tropical Atlantic, and during boreal spring in most part of Eurasian continent. The equality in absorbing solar radiation of dust and anthropogenic aerosols appears to be particularly important over Indian subcontinent and nearby regions as well as North Africa.
Highlights
Light-absorbing aerosols heat the atmosphere while cooling the Earth’s surface
When combining contributions from dust and anthropogenic aerosols, the highest AAOD values in all seasons appear over North Africa, spatially extending into the tropical Atlantic Oceans
In order to examine the relative importance of dust and anthropogenic aerosols in solar absorption, we have derived the distributions of fractional contribution of anthropogenic AAOD in the total AAOD during various seasons (Fig. 3, the upper panels)
Summary
Light-absorbing aerosols heat the atmosphere while cooling the Earth’s surface. They contribute a positive component to the total direct radiative forcing (DRF) of all aerosols at the top of the atmosphere (TOA). It has been suggested that the solar absorption by BC could significantly alter the distribution of precipitation over the tropical Intertropical Convergence Zone (ITCZ), ranging from the Pacific, Atlantic, to Indian Oceans as well as the Indian summer monsoon regions (e.g. Chung and Ramanathan, 2003; Wang, 2004, 2007; Robert and Jones, 2004; Chung and Seinfeld, 2005; Lau and Kim, 2006; Ramanathan et al, 2007; Meehl et al, 2008). Modeling studies have indicated that the climate sensitivity to radiative forcing of absorbing aerosols is different than that of relatively well-mixed greenhouse gases
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