Responses of the Summertime Subtropical Anticyclones to Global Warming

Abstract

Subtropical anticyclones dominate the subtropical ocean basins in summer. Using the multimodel output from phase 5 of the Coupled Model Intercomparison Project (CMIP5), the future changes of the subtropical anticyclones as a response to global warming are investigated, based on the changes in subsidence, low-level divergence, and rotational wind. The subtropical anticyclones over the North Pacific, South Atlantic, and south Indian Ocean are projected to become weaker, whereas the North Atlantic subtropical anticyclone (NASA) intensifies, and the South Pacific subtropical anticyclone (SPSA) shows uncertainty but is likely to intensify. Diagnostic analyses and idealized simulations suggest that the projected changes in the subtropical anticyclones are well explained by the combined effect of increased tropospheric static stability and changes in diabatic heating. Increased static stability acts to reduce the intensity of all the subtropical anticyclones, through the positive mean advection of stratification change (MASC) over the subsidence regions of the subtropical anticyclones. The pattern of change in diabatic heating is dominated by latent heating associated with changes in precipitation, which is enhanced over the western North Pacific under the “richest get richer” mechanism but is reduced over subtropical North Atlantic and South Pacific due to a local minimum of SST warming amplitude. The change in the diabatic heating pattern substantially enhances the subtropical anticyclones over the North Atlantic and South Pacific but weakens the North Pacific subtropical anticyclone.

Impacts of Subtropical Highs on Summertime Precipitation in North America

“…Li, Li, and Kushnir () and Li et al () also reported westward shifts of the NASH from preindustrial conditions to the 21st century. He et al () reported strengthening of the NASH and weakening of the NPSH in CMIP5 models, and our results replicate this for both CMIP5 and CESM‐LENS, though in CMIP5 the spread is very large.…”

“…Changes in the positions and strengths of the subtropical highs are in fact anticipated as a result of global warming. Global climate model projections for the 21st century show a strengthening and westward shift of the North Atlantic subtropical high (NASH) with increasing greenhouse gas concentrations (He et al, ; Li et al, ; Li et al, ; Li et al, ), while projected trends in the North Pacific subtropical high (NPSH) are inconsistent across studies (He et al, ; Li, Li, Ting, & Liu, ). Variability in the NASH location has been linked to temperature and precipitation variability in the southeastern U.S. in observational data (Bishop et al, ; Katz et al, ; Li et al, ; Li, Li, & Kushnir, ), and changes in the strength of the subtropical highs can also impact precipitation in North America by changing winds and therefore moisture advection (Kushnir et al, ; Wei et al, ).…”

Future Changes in Seasonality of the North Pacific and North Atlantic Subtropical Highs

“…These two studies only focused on the zonally asymmetric component of the NPSH and NASH. He et al () investigated the total response of the subtropical highs to global warming and found that the NPSH will weaken, while the NASH will strengthen in the future. To date, relative contributions of the zonal mean and zonally asymmetric components to the response of the NPSH and NASH to warming have not been carefully examined.…”

Assessing Climate Change Impacts on Human‐Perceived Temperature Extremes and Underlying Uncertainties

“…The position and intensity of WNPSH play a major role in the formation of the East Asia's climate by influencing the moisture transport from ocean and affecting the wind speed and temperature (He, Lin, et al, ). In the context of climate warming, many studies indicate that an enhanced WNPSH could lead to an enhanced southerly wind and a significant increase in the moisture transport (precipitation) over the high‐latitude areas of China in summer (He et al, ; He, Wu, et al, ; He & Zhou, ). The climate warming could lead to a weakened WNPSH and result in a weakened southerly wind and an increase in the cyclone weather over the low‐latitude areas in winter (Lin et al, ).…”