| Absorbing aerosol-radiation interaction and the feedbacks between meteorological processes and aerosol cycle have been proven to be significant in climate change,weather and air quality.In order to investigate absorbing aerosols' radiative effect and its interaction with the planetary boundary layer in China,we made long-term statistical analysis by employing "Observation minus reanalysis" method as well as conducting numerical simulations of episodes resulted from dust and biomass burning respectively by using online coupled model WRF-Chem(Weather Research and Forecasting-Chemistry).And the main conclusions were as following:(1)The temperature difference between radiosonde and Final Operational Global Analysis(FNL)showed similarity in vertical distribution and annual variation with CALIPSO detected polluted dust which was a mixture of dust and smoke.Air Pollution Index(API)correlated positively with the difference between observation and FNL at 850 hPa,while negatively with that at 1000 hPa.That was to say,aerosol concentration related with upper warming and lower cooling.The increased API strengthened the planetary boundary layer(PBL)stability,which further caused deterioration of air quality of the next day,resulting in a positive feedback loop between absorbing aerosol and PBL structure,during which air pollutants accumulated.(2)Radiative forcing of dust aerosol and the radiative feedbacks on the planetary boundary layer(PBL)in North China during a typical Asian dust storm in the early April of 2011 was investigated by an online coupled meteorology-chemistry-aerosol model WRF-Chem.Dust-induced daily mean radiative forcing(RF)at the ground surface and in the atmosphere were estimated to be-21.1 W·m-2 and 12.7 W·m-2,respectively,over Gobi desert,and-13.1 W.m-2 and 4.8 W·m-2,respectively,in downwind region over the North China Plain(NCP).Comparatively,radiative perturbation on short-wave radiation was approximately twice that on long-wave radiation in magnitude.In the daytime,when solar radiation dominated,the surface cooling and atmospheric heating due to dust increased PBL stability,leading to reductions of PBL height(PBLH)of about 90 m and decreases in wind speed up to 0.4 m·s-1.On the contrary,the radiative forcing in terrestrial radiation caused an opposite response at night,especially in the downwind region.Although dust emission was repressed by weakened wind speed during daytime,the elevated PBLH along with larger deflation at night lifted more dust particles to higher altitude(by up to 75 m in average),which prolonged dust residence time in the atmosphere and further intensified dust loading in downwind areas.(3)The interaction of meteorological characteristics,energy budget with biomass burning aerosols(with a considerable portion of black carbon)over Yangtze River Delta has been investigated,by analyzing the observation at the site of the Stations for Observing Regional Processes of the Earth System(SORPES)and conducting WRF-Chem simulation.The results indicated that heavy load of aerosols resulted in a decrease in the solar radiation with a net radiation loss of up to-443W·m-2 in the daytime,while a reduction of the outgoing longwave radiation at night by a dome effect as well(weaker in magnitude than daytime).Weakened latent fluxes and sensible fluxes were observed along with a changed Bowen ratio.It was speculated that aerosols reduced the net radiation and caused a decrease in air temperature near surface and an increase in upper air,which stabilized the PBL and depressed the vertical exchange and led to an aggravation in aerosol concentration in turn.Taking aerosol radiative feedbacks into consideration notably narrowed gaps between model simulation with corresponding observations in energy balance and meteorology factors,suggesting a significant importance of absorbing aerosol-radiation interaction in numerical weather prediction. |
PDF Full Text Request