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Study on Dust Aerosol and Its Indirect Climatic Effect Over China

Author: ShenFanHui
Tutor: WangTiJian
School: Nanjing University
Course: Atmospheric Physics and Atmospheric Environment
Keywords: China Dust aerosol Radiative forcing Climate effect Dust model
CLC: X513
Type: Master's thesis
Year: 2011
Downloads: 3
Quote: 0
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Abstract


Dust aerosol named mineral aerosol, is one of the most important aerosol components in atmosphere. It also has disregarded effect in climate system. Dust can absorb and scatter solar radiation to change the balance of region climate. Dust can act as cloud condensation nuclei (CCN) to alter cloud albedo, cloud precipitation, and cloud life time, hence affect atmospheric circulation and hydrologic cycle. Additionally, giant dust aerosol can act as giant cloud condensation nuclei (GCCN) to change the cloud precipitation, and to change the solar radiation, cloud liquid water and surface temperature. Beside this, dust aerosol can act as ice nuclei (IN) to affect the cold cloud, it can increase the cold cloud optical depth. All of these climate effects of dust aerosol can change the atmospheric circulation and hydrologic cycle. Here we use the model (RegCCMS) couple of atmospheric chemistry model and regional climate model to simulate the temporal and spatial variations of dust aerosol surface concentration, column burden, and dust optical depth; then estimating dust aerosol effect on climate change, including first and second indirect radiative forcing and its climate responses, also we use the model to estimate the climate responses of dust acting as GCCN and IN.The simulated results show that the high concentration of dust aerosol loading in the northwest region of China, in Xinjiang, Mongolia and Gansu province, but Sichuan, Chongqing and Qinghai also have the high concentration. The highest concentration and column burden in March, April, and May are2200μg/m3,2700u g/m3,3500μg/m3and2400mg/m2、4000mg/m2、6000mg/m2.The soluble part of the dust aerosol can act as CCN, it makes the increasing of cloud droplet number concentration about30m"3, the decreasing of cloud droplet size0.18μm under the condition with fixed cloud water and lower auto-conversion rate from cloud water to rain water. Simulated the first indirect forcing are the same at top of troposphere and surface, the indirect forcing of the three month are-1.26W· m-2,-2.0W· m-2,-2.69W· m-2. The decreasing of surface temperature and precipitation are-0.025K、-0.0334K、-0.04K and-0.0018mm· d-1,-0.018mm· d-1,-0.05mm· d-1. The second indirect effect focus on the auto-conversion, it makes the decreasing of the auto-conversion about2.473×10-9Kg/Kg/s, then the cloud fraction would increase, increasing about1.92%, which makes the cloud liquid water increasing about0.417g/m-2, and the net absorb solar radiation would decrease about5.1W/m2, the decreasing of surface temperature and precipitation are0.64K and0.2mm/day. But in dust aerosol there has giant particles, which can act as GCCN, which is benefit for the collision and coalescence of CCN, and then increase the auto-conversion about8.25×10-12Kg/Kg/s and precipitation. So the increasing of net absorb solar radiation is about2.89W/m2, which caused the increasing of surface temperature and precipitation, they are0.56K and0.13mm/day. Then increase the surface specific humidity, is about0.17g/Kg.The dust aerosol can transport to the high level about3-4km, and the dissoluble particles can act as IN, which can increase the number concentration of ice crystals, then decreased the ice nuclei radii. As a result, the ice cloud optical depth increased about0.021, and the net absorb solar radiation decreased17.0W/m2, which made the decreasing of surface temperature and precipitation about0.84K and0.22mm/day.

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CLC: > Environmental science, safety science > Environmental pollution and its prevention > Atmospheric pollution and its control > Particulate pollutants
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