一次沙尘天气过程中沙尘气溶胶对辐射的影响

摘要

Dust aerosols play an important role in radiation budget.Aerosol-radiation interactions during dust storms were studied by implementing dust emission scheme by Shao (2004)(hereinafter referred to as Shao 2004 scheme)in Weather Research and Forecas-ting with Chemistry (WRF/Chem).Downward short wave radiation flux at ground surface was reduced by an average of42.51%,with hourly average range from -3.30 to -49.46 W·m-2,and the instantaneous maximum was -162.67 W·m-2.Dust aerosol radiation emission enhanced the downward long wave radiation flux at ground surface,with hourly average range from 17.49 to 50.49 W·m-2 , and the instantaneous maximum was 99.17 W·m-2.The downward long wave radiation flux at ground surface was reduced in the region with PM10 concentrations ranging from 10 to 20 mg·m-3 ,and the reduced radiation was reserved in the atmosphere and kept the air warm.Daytime dust aerosols mainly enhanced the outgoing radiation flux at the top of atmosphere (TOA),while nighttime they-mainly reduced outgoing radiation flux at TOA.The outgoing radiation flux at TOA ranged from -25.29 to +28.83 W·m-2,with an instantaneous maximum of 87.22 W·m-2.%沙尘气溶胶对辐射有显著影响，利用耦合了Shao2004起沙参数化方案的WRF／Chem（大气／化学全耦合模式），模拟分析了沙尘天气过程中沙尘气溶胶对辐射的影响。结果发现沙尘气溶胶可以导致地面向下的短波辐射通量减小42．51％，平均减小－3．30～－49．46 W·m－2，最大可达－162．67 W·m－2；沙尘气溶胶可以通过自身向外发射长波辐射，导致地面向下的长波辐射通量增大，地面向下的长波辐射通量平均增加为17．49～50．49 W·m－2，最大可达99．17 W·m－2。当PM10浓度为10～20 mg·m－3，沙尘气溶胶能够减小地面向下的长波辐射通量，即沙尘气溶胶在该地区对大气具有“保温”作用；白天沙尘气溶胶主要增加大气层顶向上的长波辐射通量，夜间则减少大气层顶向上的长波辐射通量，大气层顶向外的长波辐射通量平均变化为－25．29～28．83 W·m－2，最大可达87．22 W·m－2。