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Midlatitude Eddies, Storm-Track Diffusivity, and Poleward Moisture Transport in Warm Climates

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  • 1 Department of Meteorology, and Bert Bolin Centre for Climate Research, Stockholm University, Stockholm, Sweden
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Abstract

Recent work using both simplified and comprehensive GCMs has shown that poleward moisture transport across midlatitudes follows Clausius–Clapeyron scaling at temperatures close to modern, but that it reaches a maximum at sufficiently elevated temperatures and then decreases with further warming. This study explores the reasons for this nonmonotonic behavior using a sequence of NCAR Community Atmosphere Model, version 3 (CAM3) simulations in an aquaplanet configuration spanning a broad range of climates. No significant change is found in the scale, structure, or organization of midlatitude eddies across these simulations. Instead, the high-temperature decrease in poleward moisture transport is attributed to the combined effect of decreasing eddy velocities and contracting mixing lengths. The contraction in mixing length is, in turn, a consequence of the decreasing eddy velocities in combination with constant eddy decorrelation time scales.

Corresponding author address: Rodrigo Caballero, Department of Meteorology, Stockholm University, 106 91 Stockholm, Sweden. E-mail: rodrigo@misu.su.se

Abstract

Recent work using both simplified and comprehensive GCMs has shown that poleward moisture transport across midlatitudes follows Clausius–Clapeyron scaling at temperatures close to modern, but that it reaches a maximum at sufficiently elevated temperatures and then decreases with further warming. This study explores the reasons for this nonmonotonic behavior using a sequence of NCAR Community Atmosphere Model, version 3 (CAM3) simulations in an aquaplanet configuration spanning a broad range of climates. No significant change is found in the scale, structure, or organization of midlatitude eddies across these simulations. Instead, the high-temperature decrease in poleward moisture transport is attributed to the combined effect of decreasing eddy velocities and contracting mixing lengths. The contraction in mixing length is, in turn, a consequence of the decreasing eddy velocities in combination with constant eddy decorrelation time scales.

Corresponding author address: Rodrigo Caballero, Department of Meteorology, Stockholm University, 106 91 Stockholm, Sweden. E-mail: rodrigo@misu.su.se
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