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>Mesoscale modeling of smoke transport over the Southeast Asian Maritime Continent: coupling of smoke direct radiative effect below and above the low-level clouds
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Mesoscale modeling of smoke transport over the Southeast Asian Maritime Continent: coupling of smoke direct radiative effect below and above the low-level clouds
The online-coupled Weather Research and Forecasting model with Chemistry (WRF-Chem) is used to simulate the direct and semi-direct radiative impacts of smoke particles over the Southeast Asian Maritime Continent (MC, 10° S–10° N, 90–150° E) during October 2006 when a significant El Ni?o event caused the highest biomass burning activity since 1997. With the use of an OC (organic carbon) / BC (black carbon) ratio of 10 in the smoke emission inventory, the baseline simulation shows that the clouds can reverse the negative smoke forcing in cloud-free conditions to a positive value. The net absorption of the atmosphere is largely enhanced when smoke resides above a cloud. This led to a warming effect at the top of the atmosphere (TOA) with a domain and monthly average forcing value of ~ 20 W m?2 over the islands of Borneo and Sumatra. Smoke-induced monthly average daytime heating (0.3 K) is largely confined above the low-level clouds, and results in a local convergence over the smoke source region. This heating-induced convergence transports more smoke particles above the planetary boundary layer height (PBLH), hence rendering a positive effect. This positive effect contrasts with a decrease in the cloud fraction resulting from the combined effects of smoke heating within the cloud layer and the more stable boundary layer; the latter can be considered as a negative effect in which a decrease of the cloud fraction weakens the heating by smoke particles above the clouds. During the nighttime, the elevated smoke layer lying above the clouds in the daytime is decoupled from the boundary layer, and the enhanced downdraft and shallower boundary layer lead to the accumulation of smoke particles near the surface. Because of monthly smoke radiative extinction, the amount of solar input at the surface is reduced by as much as 60 W m?2, which leads to a decrease in sensible heat, latent heat, 2 m air temperature, and PBLH by a maximum of 20 W m?2, 20 W m?2, 1 K, and 120 m, respectively. During daytime, the cloud changes over continents mostly occur over the islands of Sumatra and Borneo where the low-level cloud fraction decreases more than 10%. However, the change of local wind, including sea breeze, induced by the smoke direct radiative effect leads to more convergence over the Karimata Strait and the south coastal area of Kalimantan during both daytime and nighttime; consequently, the cloud fraction there is increased up to 20%. The sensitivities with different OC / BC ratios show the importance of the smoke single-scattering albedo for the smoke semi-direct effects. Lastly, a conceptual model is used to summarize the responses of clouds, smoke, temperature, and water vapor fields to the coupling of smoke direct effect below and above clouds over the Southeast Asian Maritime Continent.
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机译：使用化学（WRF-Chem）的在线耦合天气研究和预测模型（WRF-Chem）用于模拟烟雾颗粒对东南亚海洋大陆的直接和半直接辐射影响（MC，10°S-10°N，90- 150°E）在2006年10月期间，当一个重要的EL NI？O事件引起了1997年以来引起了最高的生物量燃烧活动。在烟雾排放库存中使用OC（有机碳）/ BC（黑碳）比例为10，基线仿真表明，云可以逆转摆脱无云条件的负烟雾到正值。当烟雾落在云上时，大气的净吸收大大提高。这导致了大气层（TOA）顶部的变暖效果，域名和月平均迫使价值〜20 W m？2在婆罗洲和苏门答腊岛上。烟雾诱导的月平均白天加热（0.3 k）主要被限制在低水平的云端上方，并导致烟雾源区的局部收敛。这种加热诱导的会聚在行星边界层高度（PBLH）上方传输更多的烟雾颗粒，因此呈现积极效果。这种正效应与云层内的烟雾加热的综合影响和更稳定的边界层的组合效果导致的云馏分的减少对比;后者可以被认为是负效应，其中云馏分的减少削弱了云层上方的烟雾颗粒的加热。在夜间期间，在白天在云层上方的升高的烟雾层与边界层分离，增强的下游和较浅的边界层导致表面附近的烟雾颗粒的积累。由于每月烟雾辐射灭火，表面的太阳能输入量减少多达60 W m？2，这导致明智的热量，潜热，2米空气温度和PBLH的降低20 W m？2,20Wm≤2,1k和120μm。白天期间，云在苏门答腊和婆罗洲的岛屿上发生变化，低水平云分数降低超过10％。然而，由烟雾直接辐射效果引起的当地风的变化，包括海风，在白天和夜间在卡里马坦南沿海地区的karimata海峡和南沿海地区的收敛程度有更多的收敛性;因此，云馏分增加到20％。具有不同OC / BC比率的敏感性表明烟雾单散射Albedo用于烟雾半直接效应的重要性。最后，概念模型用于总结云，烟雾，温度和水蒸气的响应，以至于东南亚海洋大陆的烟雾直接效应的耦合直接效应。
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