Aerosol and monsoon climate interactions over Asia

Abstract

The increasing severity of droughts/floods and worsening air quality from increasing aerosols in Asia monsoon regions are the two gravest threats facing over 60% of the world population living in Asian monsoon regions. These dual threats have fueled a large body of research in the last decade on the roles of aerosols in impacting Asian monsoon weather and climate. This paper provides a comprehensive review of studies on Asian aerosols, monsoons, and their interactions. The Asian monsoon region is a primary source of emissions of diverse species of aerosols from both anthropogenic and natural origins. The distributions of aerosol loading are strongly influenced by distinct weather and climatic regimes, which are, in turn, modulated by aerosol effects. On a continental scale, aerosols reduce surface insolation and weaken the land-ocean thermal contrast, thus inhibiting the development of monsoons. Locally, aerosol radiative effects alter the thermodynamic stability and convective potential of the lower atmosphere leading to reduced temperatures, increased atmospheric stability, and weakened wind and atmospheric circulations. The atmospheric thermodynamic state, which determines the formation of clouds, convection, and precipitation, may also be altered by aerosols serving as cloud condensation nuclei or ice nuclei. Absorbing aerosols such as black carbon and desert dust in Asian monsoon regions may also induce dynamical feedback processes, leading to a strengthening of the early monsoon and affecting the subsequent evolution of the monsoon. Many mechanisms have been put forth regarding how aerosols modulate the amplitude, frequency, intensity, and phase of different monsoon climate variables. A wide range of theoretical, observational, and modeling findings on the Asian monsoon, aerosols, and their interactions are synthesized. A new paradigm is proposed on investigating aerosol-monsoon interactions, in which natural aerosols such as desert dust, black carbon from biomass burning, and biogenic aerosols from vegetation are considered integral components of an intrinsic aerosol-monsoon climate system, subject to external forcing of global warming, anthropogenic aerosols, and land use and change. Future research on aerosol-monsoon interactions calls for an integrated approach and international collaborations based on long-term sustained observations, process measurements, and improved models, as well as using observations to constrain model simulations and projections.

Changes in terrestrial near-surface wind speed and their possible causes: an overview

“…Other forcing mechanisms, such as changes in atmospheric aerosol (AA) emissions and greenhouse gas (GHG) concentrations, may therefore also play a role. Changes in these factors can alter the boundary layer characteristics, which can in turn affect the atmospheric stability and the SWS (Ramanathan et al 2005;Bichet et al 2012;Zhang et al 2016b;Li et al 2016). The absorbing and scattering properties of aerosol particles are known to increase atmospheric stability by reducing the amount of solar radiation reaching the ground, and an increase in the atmospheric stability due to aerosols can reduce vertical turbulent exchange, thereby reducing the vertical flux of horizontal momentum.…”

In situ measurements of desert dust particles above the western Mediterranean Sea with the balloon-borne Light Optical Aerosol Counter/sizer (LOAC) during the ChArMEx campaign of summer 2013

“…Buat-Ménard and Chesselet, 1979;Martin et al, 1991;Swap et al, 1992;Duce, 1995;Alpert et al, 1998;Mahowald et al, 2009Mahowald et al, , 2011Maher et al, 2010;Liu et al, 2011;Choobari et al, 2014;Li et al, 2016). Desert dust aerosol is of particular interest in the Mediterranean region where it is (i) frequently observed in high concentrations in the troposphere; (ii) is a major component of surface PM 10 Rea et al, 2015), aerosol optical depth (Moulin et al, 1998;Gkikkas et al, 2013;Nabat et al, 2013), atmospheric deposition (Pye, 1992;Vincent et al, 2016); and (iii) affecting the regional air quality (Querol et al, 2009); atmospheric thermodynamics (e.g.…”

Isotopic composition of daily precipitation along the southern foothills of the Himalayas: impact of marine and continental sources of atmospheric moisture

“…Gadgil, 2003;Allen and Armstrong, 2012). The warming of the Tibetan Plateau relative to the Indian Ocean, which results in low pressure over Asia and higher pressure over the Indian Ocean (Overpeck et al, 1996), pulls moisture from Southeast Asia and the Bay of Bengal and transports it north-westward (Hren et al, 2009;Li et al, 2016). There is an east-west gradient in monsoonal influence across the Himalayas with the central Himalayas receiving up to 80 % of its annual precipitation during the monsoon months according to some estimates (Bookhagen and Burbank, 2010;Lang and Barros, 2004).…”