新论文介绍:Simulation of dust aerosol radiative feedback using the GMOD:2. Dust-climate interactions

[发布日期: 2014-12-30 浏览量 750]

  We examine equilibrium climate responses to the shortwave and/or longwave direct radiative effect of mineral dust aerosol using the Global transport Model of Dust (GMOD) embedded within a general circulation model (GCM). The presence of mineral dust aerosol in the atmosphere is estimated to exert global mean shortwave and longwave radiative forcings (RF) of -0.25 W m-2 and +0.27 W m-2, respectively, at the top of the atmosphere (TOA) and -1.95 W m-2 and +0.61 W m-2 at the surface. Climatic effect of dust is simulated using two different approaches. In the first approach, monthly mean fields of dust simulated a priori are used in the radiative transfer module of the GCM to drive climate change, with levels of dust fixed during the climate integration (denoted as simulation FIXDST). In the second approach, dust aerosol interacts online with meteorology through the dust cycle and its direct radiative effect (denoted as simulation CPLD). With both longwave and shortwave RF of dust, predicted changes in global and annual mean surface air temperature and air temperature at 200 hPa are zero and +0.12 K, respectively, in FIXDST, and -0.06 K and +0.05 K in the CPLD simulation. The stronger cooling in CPLD than in FIXDST is a result of a 13% higher dust burden in CPLD with dust-climate interactions. Although dust longwave radiative effect is predicted to offset a large portion of its shortwave effect on a global and annual mean basis, dust shortwave effect dominates during the daytime, and the longwave effect prevails at night, which is found to be very important for predictions of temperature. For example, over the Sahara Desert, the changes in annual mean, annual mean daytime, and annual mean nighttime surface air temperature are predicted to be +0.32 K, -0.11 K, and +0.68 K, respectively, in the FIXDST simulation. The longwave and shortwave radiative effects of dust are predicted to have different impacts on the dust cycle in CPLD simulation; the solar radiative effect reduces dust emissions by increasing surface humidity and by reducing surface wind speed, while the thermal effect increases dust uplift through opposite changes in the meteorological parameters.