Abstract
We examine the 2002 Yakutsk wildfire event and simulate the impacts of smoke aerosols on local radiative energy budget, using the WRF-Chem-SMOKE model. When comparing satellite retrievals (the Surface Radiation Budget (SRB) dataset) with model simulations, we found that the agreement is generally good, except for the regions where the model predicts too few clouds or SRB misclassifies strong smoke plumes as clouds. We also found that the smoke-induced changes in upward shortwave fluxes at top of atmosphere (TOA) vary under different burning and meteorological conditions. In the first period of the fire season (9–12 August), smoke particles cause a warming effect around 3 W/m2, mainly through functioning as ice nuclei, which deplete the cloud water amount in the frontal system. At the beginning of the second period of the fire season (19–20 August), large amounts of pre-existing smoke particles cause a strong cooling effect of −8 W/m2. This is offset by the warming effect caused by relatively small amounts of cloud condensation nuclei increases, which promotes the rain formation and depletes the cloud water amount. After the cloud decks are well mixed with smoke plumes (21–22 August), the first indirect and direct effects of smoke together lead to a cooling of −10 W/m2. These results highlight the importance of meso-scale modeling efforts in estimating the smoke-induced changes in the radiative energy budget over high latitudes.
Highlights
Smoke aerosols emitted from wildfires in Siberia, Russia, can significantly affect the radiative energy budget over Europe and high latitude regions [1,2,3], directly via scattering and absorbing solar radiation [4,5], and indirectly via altering cloud properties and the albedo [6,7]
During FP1, In the beginning of FP2, the domain was under the influence of the strong blocking high-pressure relatively small amounts of smoke particles were swirled into a relatively strong frontal system system
Comparing the SWTOA ↑ modeled by smoke aerosols considered (SMOKE) and CLEAN against the SRB dataset on 20 and 21 August, we find that the SMOKE case performs much better than the CLEAN case in simulating the SWTOA ↑ associated with the cloud deck around the western edge of the blocking high-pressure system
Summary
Smoke aerosols emitted from wildfires in Siberia, Russia, can significantly affect the radiative energy budget over Europe and high latitude regions [1,2,3], directly via scattering and absorbing solar radiation (the direct effect) [4,5], and indirectly via altering cloud properties and the albedo (the indirect effect) [6,7]. The climate modeling results in [8] demonstrate that, over Siberia, the direct and indirect effects of smoke aerosols are as high as +1 W/m2 and −3 to −5 W/m2 , respectively. It should be noted that, during the fire season in Siberia, smoke aerosols mainly interact with convective clouds associated with extratropical cyclones [9]. It is very challenging, if not impossible, for climate models to properly simulate the dynamics and thermodynamic characteristics of cyclones, because of the hydrostatic assumption and the relatively large grid spacing. These studies focused on the most intense fire periods (a few days), and reported the daily averaged direct radiative effect of BB (biomass burning) aerosols as high as 70–150 W/m2
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