美国加州大学Duan, Suqin Q.团队近日取得一项新成果。他们发现，潮湿的热浪由于干燥空气的夹带而加剧，从而限制了深层对流。该研究于2024年7月25日发表于国际一流学术期刊《自然—地球科学》杂志上。

在这里，研究人员使用再分析数据、进行耦合模式比对项目第6阶段的输出和模式夹带扰动实验，结果显示，在较低的自由对流层(大约在地表以上1-3km)中，不饱和空气的夹带限制了深层对流，从而允许更高的近地表湿热。因此，具有大规模沉降和干燥低层自由对流层的地区，如毗邻炎热和干旱土地的沿海地区，特别容易受到潮湿热浪的影响。

即使在北印度平原、东南亚和南美洲内陆等对流区域，低自由对流层的干燥度也强烈影响地表最高湿球温度。随着气候变暖，低自由度对流层空气的干燥度(相对于饱和度)增加，这使得极端湿热的增加幅度更大，进一步提高了潮湿热浪的可能性。

据了解，热带和亚热带的潮湿热浪对社会构成重大风险，但人们对控制其强度的动力尚未完全了解。由炎热潮湿的近地表空气产生的深层对流被认为限制了潮湿热浪的强度。

附：英文原文

Title: Moist heatwaves intensified by entrainment of dry air that limits deep convection

Author: Duan, Suqin Q., Ahmed, Fiaz, Neelin, J. David

Issue&Volume: 2024-07-25

Abstract: Moist heatwaves in the tropics and subtropics pose substantial risks to society, yet the dynamics governing their intensity are not fully understood. The onset of deep convection arising from hot, moist near-surface air has been thought to limit the magnitude of moist heatwaves. Here we use reanalysis data, output from the Coupled Model Intercomparison Project Phase 6 and model entrainment perturbation experiments to show that entrainment of unsaturated air in the lower-free troposphere (roughly 1–3km above the surface) limits deep convection, thereby allowing much higher near-surface moist heat. Regions with large-scale subsidence and a dry lower-free troposphere, such as coastal areas adjacent to hot and arid land, are thus particularly susceptible to moist heatwaves. Even in convective regions such as the northern Indian Plain, Southeast Asia and interior South America, the lower-free tropospheric dryness strongly affects the maximum surface wet-bulb temperature. As the climate warms, the dryness (relative to saturation) of the lower-free tropospheric air increases and this allows for a larger increase of extreme moist heat, further elevating the likelihood of moist heatwaves.

DOI: 10.1038/s41561-024-01498-y

Source: https://www.nature.com/articles/s41561-024-01498-y