Contributions to regional precipitation change and its polar-amplified pattern under warming

Abstract

In response to increased greenhouse-gas concentrations, climate models predict that the polar regions will experience the largest relative change in precipitation, where a substantial absolute increase in precipitation coincides with small precipitation rates in the present-day climate. The reasons for this amplification, however, are still debated. Here, we use an atmospheric energy budget to decompose regional precipitation change from climate models under greenhouse-gas forcing into contributions from atmospheric radiative feedbacks, dry-static energy flux divergence changes, and surface sensible heat flux changes. The polar-amplified relative precipitation change is shown to be a consequence of the Planck feedback, which, when combined with larger polar warming, favors substantial atmospheric radiative cooling that balances increases in latent heat release from precipitation. Changes in the dry-static energy flux divergence contribute modestly to the polar-amplified pattern. Additional contributions to the polar-amplified response come, in the Arctic, from the cloud feedback and, in the Antarctic, from both the cloud and water vapor feedbacks. The primary contributor to the intermodel spread in the relative precipitation change in the polar region is also the Planck feedback, with the lapse rate feedback and dry-static energy flux divergence changes playing secondary roles. For all regions, there are strong covariances between radiative feedbacks and changes in the dry-static energy flux divergence that impact the intermodel spread. These results imply that constraining regional precipitation change, particularly in the polar regions, will require constraining not only individual feedbacks but also the covariances between radiative feedbacks and atmospheric energy transport.

Factors Contributing to Historical and Future Trends in Arctic Precipitation

“…(1) (Bonan et al, 2023;Dagan & Stier, 2020;Muller & O'Gorman, 2011;Pithan & Jung, 2021;Yukimoto et al, 2022), where L is the latent heat of evaporation (2.5 × 10 6 J/kg), P is precipitation (kg/m 2 /s), ∇ H DSE is the horizontal divergence of the column-integrated DSE (W/m 2 ), and F SH is the surface sensible heat flux (W/m 2 , upward positive). The downward surface sensible heat flux corresponds to the DSE vertical divergence.…”

“…Recently, the factors that alter the Arctic hydrological cycle have also been discussed from the perspective of energetics (Bonan et al, 2023;Pithan & Jung, 2021), suggesting that changes in the radiative cooling of the atmosphere are essential factors in the "Arctic amplification" of precipitation changes. However, the drivers of…”

“…In the Arctic, the absolute amount of water vapor is small and its contribution to longwave cooling is relatively small; however, its effect on shortwave (nearinfrared) heating is significant. Bonan et al (2023) decomposed changes in radiative cooling in response to warming into Planck feedback, temperature lapse-rate feedback, water vapor feedback, and albedo feedback. They argued that the polar amplification of relative precipitation change mainly results from Planck feedback.…”

“…These include enhanced radiative cooling (responding locally to increased air temperature) and reduced heat transport from lower latitudes due to greater temperature increases at higher latitudes. Future precipitation will change in proportion to the temperature change while maintaining consistent fractional contributions across different scenarios.Recently, the factors that alter the Arctic hydrological cycle have also been discussed from the perspective of energetics (Bonan et al, 2023;Pithan & Jung, 2021), suggesting that changes in the radiative cooling of the atmosphere are essential factors in the "Arctic amplification" of precipitation changes. However, the drivers of…”

Factors Driving Past Trends in Arctic Precipitation and Their Future Changes

“…Recently, the factors that alter the Arctic hydrological cycle have also been discussed from the perspective of energetics (Pithan and Jung, 2021;Bonan et al, 2023), suggesting that changes in the radiative cooling of the atmosphere are essential factors in the "Arctic amplification" of precipitation changes. However, the drivers of past changes in Arctic precipitation remain unclear.…”