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- Title
Contributions of Local Land‒Atmosphere Coupling and Mesoscale Atmospheric Circulation to the 2013 Extreme Flash Drought and Heatwave Compound Event Over Southwest China.
- Authors
Fu, Kaiqi; Wang, Kaicun
- Abstract
The flash drought and heat wave compound event of the 2013 summer in Southwest China was exceptional, with profound socio‒economic impacts. Existing studies have captured the signal of this compound event; however, its causes are still poorly understood. In this study, we utilized a high‐resolution index to examine the life cycle of this compound event from 1980 to 2020 and quantified the relative contributions of land‒atmosphere coupling and mesoscale atmospheric circulation using the air parcel backward tracking method. It was found that the dry soil caused by the precipitation deficit further inhibited precipitation and caused the soil to become even drier, which then led to the development of the flash drought. The dry soil induced a substantial increase in the land‒atmosphere sensible heat flux and a rise in the near‐surface air temperature. During this process, the strength of land‒atmosphere coupling was 2.5 standard deviations higher than the mean value of the climate, playing an integral role in the near‐surface air temperature increase, accounting for 55.9% of the maximum temperature changes. The mesoscale atmospheric circulation contributed 44.1%, of which horizontal advection accounted for 41.1%, while vertical advection only accounted for 3.0%. The western Pacific subtropical high expanded westward, accompanied by the northward‐moving westerly jet stream, which prevented cold air from accessing the Southwest China, and abnormal subsidence interfered with precipitation formation. Furthermore, the control of an abnormally high‐pressure system over the region led to a decrease in cloud cover, allowing more surface incident solar radiation and contributing to the increase in the near‐surface air temperature. Plain Language Summary: Compound events are increasingly likely to occur in the context of global warming. In 2013, a compound event of flash drought and heat wave occurred in Southwest China with severe impacts on the economy and society. However, the cause of this compound event remains uncertain. This study utilized a high‐resolution index to identify the occurrence process of this compound event. Additionally, the air parcel backward tracking method was employed to isolate and quantify the impacts of land‒atmosphere coupling and mesoscale atmospheric circulation. The study concluded that a precipitation deficit led to dry soil, further hindering precipitation, resulting in even drier soil. As a result, the sensible heat flux increased, elevating the near‐surface air temperature. During this process, the land‒atmosphere coupling intensity was 2.5 standard deviations greater than the climatological average, contributing to 55.9% of the change in maximum temperature, while mesoscale circulation contributed to 44.1% (horizontal advection accounted for 41.1%, while vertical advection only accounted for 3.0%). The westward extension of the western Pacific subtropical high, the northward movement of the westerly jet, and the abnormal high‐pressure system reduced precipitation and increased solar radiation reaching the surface, which led to a rise in the near‐surface temperature. Key Points: The land‐atmosphere coupling strength for this compound event was 2.5 standard deviations higher than the mean value of the climateLand‒atmosphere coupling contributed 55.9% and mesoscale circulation contributed 44.1% to the maximum temperature change during this eventStrong land‐atmosphere coupling induced this compound event, while horizontal advection contributed to its demise
- Subjects
CHINA; ATMOSPHERIC circulation; HEAT waves (Meteorology); CLOUDINESS; ATMOSPHERIC temperature; DROUGHTS; LAND-atmosphere interactions; ATMOSPHERE
- Publication
Journal of Geophysical Research. Atmospheres, 2023, Vol 128, Issue 21, p1
- ISSN
2169-897X
- Publication type
Article
- DOI
10.1029/2023JD039406