Diagrams for Compound Extremes Over Polar Ice Sheets and Ex-Polar Lands (IMAGE)
Caption
Regarding the ex-polar lands, compound hot-dry extremes prevail due to active land–atmosphere interactions. Specifically, a mid-tropospheric ridge initiates descending motions, creating clear-sky conditions downstream. The resultant excessive short-wave heating of the land surface depletes soil moisture through enhanced evaporation. A dryer land heats more quickly, and the associated excessive sensible heating warms the air above and further strengthens the existing mid-tropospheric ridge, establishing a positive feedback during an extreme hot-dry event.
While over polar ice sheet, compound warm-wet extremes are mostly “externally” driven by intruding lower latitude moist air through long-range advective transport. The brought-in moisture creates clouds and precipitation, and the clouds, together with moisture, lead to much enhanced downward thermal radiative energy fluxes that cause substantial warming at the surface.
Credit
Ran Yang
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Citation is required when using this material. Citation: Yang R, Hu X, Cai M, Deng Y, Clem KR, Yang S, Xu L, Yang Q. A Paradigm Shift of Compound Extremes over Polar Ice Sheets. Ocean-Land-Atmos. Res. 2024; 3: Article 0040. https://doi. org/10.34133/olar.0040
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