Influence of dust aerosols on eastern Pacific tropical cyclone intensity

The thermodynamic state of the tropical atmosphere plays an important role in the development of tropical cyclone (TC) intensity. This study reports new results that demonstrate a negative association between eastern Pacific TC intensity in offshore regions and dust aerosol optical depth (AOD) for the years 1980–2019. At the same time, a negative response of cloud water in the lower troposphere to dust AOD is reported by analyzing MERRA-2 reanalysis data and GCM simulations from CMIP6. This response can be explained by the dust semi-direct effect, in which dust aerosols absorb solar radiation, promoting the evaporation of clouds. In principle, this aerosol-driven vaporization modification could affect the enthalpy of the air surrounding a TC. Using potential intensity theory, the authors demonstrate that change in TC intensity related to dust AOD conditions is a consequence of the anomalous enthalpy of the air surrounding a TC caused by the dust semi-direct effect.

熱帶地區大氣的熱力學狀態對颱風的發展起著重要作用.本項研究結果表明, 東太平洋颱風強度與沙塵AOD之間存在一定的負相關.同時, MERRA-2再分析資料和CMIP6的GCM模擬的分析結果, 都表明了低層大氣中雲對沙塵AOD的負回應.沙塵顆粒物的准直接輻射效應可以解釋上述回應:沙塵顆粒物吸收太陽輻射, 並用此熱量促進雲層蒸發.理論上, 這種氣溶膠驅動的汽化作用會影響颱風周圍空氣的焓.根據颱風的潛在強度理論, 與沙塵相關的颱風強度變化, 實則是沙塵的准直接輻射效應引起的颱風周圍空氣焓值變化的結果.