Is Hadley Cell Expanding?

Abstract

This review provides a comprehensive coverage of changes of the Hadley Cell extent and their impacts on the weather, climate, and society. The theories predicting the Hadley Cell width are introduced as a background for the understanding of the circulation changes and the metrics used for detection. A variety of metrics derived from various data sources have been used to quantify the Hadley Cell width. These metrics can be classified as dynamical, hydrological, thermal, and chemical metrics, based on the properties of the variables used. The dynamical metrics have faster trends than those based on thermal or hydrological metrics, with the values exceeding 1 degree per decade. The hydrological metric edge poleward trends were found a slightly faster expansion in the Northern Hemisphere than its southern counterpart. The chemical metrics show a poleward trend of more than 1 degree per decade in both hemispheres. We also suggest a few reasons for the discrepancy among trends in Hadley Cell expansion found in previous studies. Multiple forcings have been found responsible for the expansion, which seems to be more attributed to the natural variability than anthropogenic forcing. Validation of the scaling theories by the trends in Hadley Cell width suggests that theories considering the extratropical factor would be better models for predicting the Hadley Cell width changes. The Hadley Cell has an impact on different atmospheric processes on varying spatio-temporal scales, ranging from weather to climate, and finally on society. The remaining questions regarding Hadley Cell climate are briefly summarized at the end.

Relationship between the hadley circulation and tropical SST meridional structures under different thermal conditions in the indo-pacific warm pool

“…Moreover, as concluded in previous studies, the variations of HC are closely associated with the distribution of meridional structure of the tropic SST (Feng and Li, 2013;Guo and Tan, 2018;Sun et al, 2018). Different meridional structures of SST, like the asymmetric structure and symmetric structure along the equator, can generate great impacts on the HC at different temporal-spatial scales, indicating the response ratio of the asymmetric (symmetric) structure of the HC to asymmetric (symmetric) structure of SST varied with different thermal conditions (Feng et al, 2016;Xian et al, 2021).…”

“…In addition, the enhanced variations of HC in the boreal winter have also been ascribed to the strengthened asymmetric mode of ENSO during the last decades . Moreover, the possible impacts of SST warming on the HC variations have been studied, and it is found that the global SST warming is conducive to the enhancement of the predominant mode of the HC's seasonal variability (Zhou and Wang, 2006;Ma and Li, 2008;Zhou et al, 2020;Xian et al, 2021). Meanwhile, the variations of thermal conditions over the IPWP also greatly impact the connection between the HC and the tropic SST, especially after 1980 (Feng et al, 2018).…”

Meridional Heat Transport in the DeepMIP Eocene ensemble: non-CO2 and CO2 effects

“…There are several metrics to quantitively analyze the Hadley cell, its edge and its circulation strenght. We choose to use the average meridional streamfunction Ψ (Xian et al, 2021) to quantify its intensity, which is defined as :…”

Meridional Heat Transport in the DeepMIP Eocene ensemble: non-CO2 and CO2 effects

“…There are several metrics to quantitively analyze the Hadley cell, its edge and its circulation. We choose to use the average meridional streamfunction Ψ (Xian et al, 2021) to quantify its intensity, which is defined as :…”