Environmental Research Letters (Jan 2023)
Global trends in atmospheric layer thickness since 1940 and relationships with tropical and extratropical climate forcing
Abstract
Global warming necessitates continual insights into changing atmospheric temperatures to enhance climate change monitoring and prediction. The thickness of an atmospheric layer serves as an effective proxy for the average temperature of that layer, playing a pivotal role in weather forecasting, understanding atmospheric dynamics, and detecting shifts in extreme weather conditions. This study investigates the global trends in thickness of the layer between 1000 hPa and 500 hPa, from 1940 to the present and evaluates the impact of tropical and extra-tropical climate modes on these trends. Our findings reveal a consistent, statistically significant positive trend in atmospheric layer thickness. However, the magnitude of this trend varies both regionally and seasonally. The most substantial absolute changes are observed in the high latitudes during their respective winter seasons; however, when considering global changes relative to each location’s unique historical variability, the most pronounced increase occurs in the tropics, specifically over central Africa, with a standard deviation increase of up to 0.03 σ yr ^−1 . Based on the relative changes, the thickness over the Southern Hemisphere’s high-latitude landmasses is increasing at a faster pace during its winter compared to the Northern Hemisphere during its winter. Furthermore, our analysis of the impact of dominant tropical and extra-tropical climate modes revealed a strong correlation ( R ∼ 0.9) between sea surface temperature changes in the Pacific warm pool region and the global average thickness. This relationship accounts for about 76% to 78% variance of the inter-annual variability in thickness. Consequently, we identify the increase in sea surface temperature in the Indo-Pacific warm pool as a significant controller of the rate and magnitude of atmospheric layer thickness changes globally. This underscores the crucial role of oceanic-atmospheric interactions in driving global climate variations and extremes.
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