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- Title
Shortwave Radiative Flux Variability Through the Lens of the Pacific Decadal Oscillation.
- Authors
Chtirkova, Boriana; Folini, Doris; Ferreira Correa, Lucas; Wild, Martin
- Abstract
The variability of the shortwave radiative fluxes at the surface and top of atmosphere (TOA) is examined in a pre‐industrial modeling setup using the Pacific Decadal Oscillation (PDO) as a possible pacemaker of atmospheric decadal‐scale variability. Within models from the Coupled Model Intercomparison Project—Phase 6, downwelling shortwave radiation at the surface, the net shortwave fluxes at the surface and TOA, as well as cloud radiative effects show remarkably similar patterns associated with the PDO. Through ensemble simulations designed with a pure PDO pattern in the North Pacific only, we show that the PDO relates to about 20%–40% of the unforced year‐to‐year variability of these shortwave fluxes over the Northern Hemispheric continents. The sea surface temperature imprint on shortwave‐flux variability over land is larger for spatially aggregated time series as compared to smaller areas, due to the blurring effect of small‐scale atmospheric noise. The surface and TOA radiative flux anomalies associated with the PDO index range of [−1.64; 1.64] are estimated to reach up to ±6 Wm−2 for North America, ∓3 Wm−2 for India and ±2 Wm−2 for Europe. We hypothesize that the redistribution of clouds in response to a North Pacific PDO anomaly can impact the South Pacific and North Atlantic SSTs. Plain Language Summary: We investigate how solar radiation at Earth's surface and the top of the atmosphere, which are mainly controlled by cloudiness, can vary over decades as a response to a horseshoe pattern typical for the North Pacific sea surface temperatures (SSTs)—the Pacific Decadal Oscillation (PDO). We use idealized climate model simulations to show that about a third of the year‐to‐year changes in solar radiation over the Northern Hemispheric continents are related to this phenomenon. These changes are more noticeable when looking at large areas rather than small ones, as high frequency smaller scale atmospheric variations can obscure the bigger picture. By keeping the PDO fixed to a constant negative value, implying below average cold sea surface temperatures off the western coast of North America and warmer than average temperatures toward Japan, we show that North America and Europe exhibit a reduction in cloudiness, while clouds increase in India. The same with an opposite sign is true for a positive PDO anomaly. These changes in cloud patterns might further affect SSTs in the South Pacific and North Atlantic oceans. Key Points: The Pacific Decadal Oscillation (PDO) is a prominent pacemaker for variability, accounting for about 1/3 of the shortwave flux year‐to‐year variability over NH continentsA negative PDO anomaly leads to a reduction in atmospheric shortwave reflectivity (clouds) in North America and Europe and an increase in IndiaThe redistribution of clouds in response to a North Pacific PDO anomaly might influence SSTs in the South Pacific and North Atlantic
- Subjects
NORTH America; OCEAN temperature; SURFACE of the earth; OSCILLATIONS; ATMOSPHERICS; SOLAR radiation; TERRESTRIAL radiation; COASTS; ATMOSPHERIC ammonia
- Publication
Journal of Geophysical Research. Atmospheres, 2024, Vol 129, Issue 11, p1
- ISSN
2169-897X
- Publication type
Article
- DOI
10.1029/2023JD040520