Numerical Simulation Of Aerosol In The Atmosphere And Snow

As a key climate forcing factor, aerosol can change the Earth-Atmosphere radiation budget and alter the size and residence time of cloud deoplets, and have prefound impacts on the global climate, hydrologic cycle and ecosystem balance. So, it is very important significance to process the aerosol in the atmosphere and snow with complex aerosol processes and interaction. To better understanding the aerosol in Earth system, the aerosol modeling has been development. In this study, the Weather Research and Forecasting model with Chemistry(WRF-Chem) is updated and used to study the black carbon and dust and their radiative forcing in seasonal snow and the trans-Pacific transport and evolution of aerosols. The main conclusions are summarized as follows:(1) A fully coupled meteorology-chemistry model(WRF-Chem) has been configured to conduct quasi-global simulation for the 5 years of 2010-2014 and evaluated with multiple observation datasets for first time. The simulation over the trans-Pacific transport region is evaluated using various reanalysis and observational datasets for meteorological fields and aerosol properties. In general, precipitation and winds are well simulated by the model. The simulation captures the overall spatial and seasonal variability of satellite retrieved aerosol optical depth(AOD) and absorbing AOD(AAOD) over the Pacific that is determined by the outflows of pollutants and dust and the emissions of marine aerosols. The assessment of simulated extinction Angstrom exponent(EAE) indicates that the model generally reproduces the variability of aerosol size distributions. In addition, the vertical profile of aerosol extinction and its seasonality over the Pacific that are dominated by marine aerosols near the surface and the outflow of pollutants and dust above 4 km are also well simulated. The difference between the simulation and satellite retrievals can be mainly attributed to model biases in estimating marine aerosol emissions as well as the satellite sampling and retrieval uncertainties. Compared with the surface measurements over the western U.S., the model reproduces the observed magnitude and seasonality of dust, sulfate, and nitrate surface concentrations, but significantly underestimates the peak surface concentrations of carbonaceous aerosol likely due to model biases in the spatial and temporal variability of biomass burning emissions and secondary organic aerosol(SOA) production. A sensitivity simulation shows that the trans-Pacific transported dust, sulfate, and nitrate can make significant contribution to surface concentrations over the rural areas of the western U.S., while the peaks of carbonaceous aerosol surface concentrations are dominated by the North American emissions. Both the retrievals and simulation show small annual variability of aerosol characteristics for 2010-2014 averaged over three Pacific sub-regions. The evaluation in this study demonstrates that the WRF-Chem quasi-global simulation can be used for investigating trans-Pacific transport of aerosols and providing reasonable inflow chemical boundaries for the western U.S. to further understand the impact of transported pollutants on the regional air quality and climate with high-resolution nested regional modeling.(2) A state-of-the-art regional model, WRF-Chem, is coupled with the SNICAR model that includes the most sophisticated representation of snow metamorphism processes available for climate study. The coupled model is used to simulate the black carbon(BC) and dust concentrations and their radiative forcing in seasonal snow over North China in January-February of 2010, with extensive field measurements used to evaluate the model performance. In general, the model simulated spatial variability of BC and dust mass concentrations in the top snow layer(hereafter BCS and DSTS, respectively) are quantitatively or qualitatively consistent with observations. The model generally moderately underestimates BCS in the clean regions but significantly overestimates BCS in some polluted regions. Most model results fall into the uncertainty ranges of observations. The simulated BCS and DSTS are highest with >5000 ng g-1 and up to 5 mg g-1, respectively, over the source regions and reduce to <50 ng g-1 and <1 μg g-1, respectively, in the remote regions. BCS and DSTS introduce a similar magnitude of radiative warming(~ +10 W m-2) in the snowpack, which is comparable to the magnitude of surface radiative cooling due to BC and dust in the atmosphere. This study represents an effort in using a regional modeling framework to simulate BC and dust and their direct radiative forcing in snowpack. Although a variety of observational datasets have been used to attribute model biases, some uncertainties in the results remain, which highlights the need for more observations, particularly concurrent measurements of atmospheric and snow aerosols and the deposition fluxes of aerosols, in future campaigns.(3) The WRF-Chem, couped with the SNICAR model, is used to simulate the aerosol in snow and armosphere with the conducted quasi-global simulation. In this study, we focus on the East Asia and Europe. The results show that the BC and Dust direct radiative forcing at the surface show seasonal variation, and the maximum value is in spring; but the BC and Dust direct radiative forcing in snow shows that the maximum value is in winter. In the East Asia, The snow water equivalent is effect by the aerosol in the atmosphere through the albedo and the surface radiation changed. But the snow water equivalent is effect by the precipitation under zero degree in Europe. The aerosol in snow and atmosphere can change the surface temperature by changing the surface radiation, the latent heating and sensible heating. The aerosol in the atmosphere can increase the latent heating and sensible heating and decrease the surface radiation. In the East Asia, the aerosol in snow can cause the surface temperature increasing, mainly through increased the surface radiation; in the Europe, the surface temperature is effect by the latent heating, sensible heating and the surface radiation.