Impacts of reducing scattering and absorbing aerosols on the temporal extent and intensity of South Asian summer monsoon and East Asian summer monsoon
Impacts of reducing scattering and absorbing aerosols on the temporal extent and intensity of South Asian summer monsoon and East Asian summer monsoon
复制标题
DOI：
10.5194/acp-23-8341-2023
复制
发表时间：
2023-07
影响因子：
6.3
通讯作者：
Chenwei Fang;J. Haywood;Junyi Liang;B. Johnson;Ying Chen;Bin Zhu
中科院分区：
文献类型：
--
作者：
Chenwei Fang;J. Haywood;Junyi Liang;B. Johnson;Ying Chen;Bin Zhu
抽象。预计气溶胶排放量的绝大多数减少将在不久的将来发生;然而，对人口稠密的亚洲季风区上空大规模环流的相关影响仍然不确定。使用最先进的英国地球系统模式版本1（UKESM 1），本研究探讨了南亚夏季风和东亚夏季风（SASM和EASM，分别）的碳气溶胶和SO2的人为排放的理想化减少的响应。分析的重点是在季风的时间范围和降水强度的变化减少散射（SCT）或吸收（ABS）气溶胶或减少两者。对于SCT，前季风季节海陆热力对比和海平面气压梯度的早期转换，以及后季风季节对流层变暖导致的后期转换，使季风爆发提前，但撤退延迟，从而导致南亚和东亚夏季雨季的延长。对流层上层亚洲急流的北移导致印度北方和中国东部对流层水汽辐合和低层上升异常。陆地变暖引起的南亚高压的加强也是亚洲地区动力不稳定的原因之一。这些变化增强了这些地区在北方夏季的雨季。减少吸收气溶胶的作用在相反的意义上，使亚洲的雨季缩短和减弱，由于对海陆对比度，亚洲急流位移和南亚高压强度的相反影响。随着SCT和ABS气溶胶一起减少，季风系统加强，因为整体影响主要是气溶胶散射效应，导致季风降水和850 hPa环流加强。虽然气溶胶散射和吸收在辐射收支中起着不同的作用，但它们对季风降水的影响几乎是线性增加的。具体而言，季风相关的大尺度响应的模式，从减少SCT和ABS一起是类似的线性总和单独减少SCT或ABS的单独效果，这是尽管固有的非线性的大气系统。ABS和SCT气溶胶排放减少迫使亚洲雨季的相反调整表明，针对诸如使气候变暖的黑碳排放等因素的排放控制与针对总体气溶胶排放的排放控制有不同的反应。
Abstract. The vast majority of reductions in aerosol emissions are projected to take place in the near future; however, associated impacts on the large-scale circulation over the populated Asian monsoon region remain uncertain. Using the state-of-the-art UK Earth System Model version 1 (UKESM1), this study examines the response of the South Asian summer monsoon and East Asian summer monsoon (SASM and EASM, respectively) to idealized reductions in anthropogenic emissions of carbonaceous aerosols and SO2. The analysis focuses on changes in the monsoon temporal extent and intensity of precipitation following decreases in either scattering (SCT) or absorbing (ABS) aerosols or decreases in both. For SCT, the combination of the early transition of land–sea thermal contrast and sea level pressure gradient during the pre-monsoon season, together with the late transition in the post-monsoon season associated with the tropospheric warming, advances the monsoon onset but delays its withdrawal, which leads to an extension of the summer rainy season across South Asia and East Asia. The northward shift of the upper-tropospheric Asian jet forced by the SCT reduction causes the anomalous convergence of tropospheric moisture and low-level ascent over northern India and eastern China. The intensification of the South Asian high (SAH) due to the warming over land also contributes to the dynamic instability over Asia. These changes enhance the rainy season of these regions in boreal summer. Reductions in absorbing aerosol act in the opposite sense, making the Asia's rainy season shorter and weaker due to the opposite impacts on land–sea contrast, Asian jet displacement and SAH intensity. With reductions in both SCT and ABS aerosol together the monsoon systems intensify, as the overall impact is dominated by aerosol scattering effects and results in the strengthening of monsoon precipitation and 850 hPa circulation. Although aerosol scattering and absorption play quite different roles in the radiation budget, their effects on the monsoon precipitation seem to add almost linearly. Specifically, the patterns of monsoon-related large-scale responses from reducing both SCT and ABS together are similar to the linear summation of separate effect of reducing SCT or ABS alone; this is despite the inherent nonlinearity of the atmospheric systems. The opposing adjustments of Asian rainy season forced by the ABS and SCT aerosol emission reductions suggest that emission controls that target factors like emissions of black carbon that warm the climate would have a different response to those that target overall aerosol emissions.