Date of Award

1-1-2018

Language

English

Document Type

Master's Thesis

Degree Name

Master of Science (MS)

College/School/Department

Department of Atmospheric and Environmental Sciences

Content Description

1 online resource (ii, x, 50 pages) : illustrations (some color)

Dissertation/Thesis Chair

Brian E.J. Rose

Committee Members

Andrea L. Lang

Keywords

Sudden Stratospheric Warmings, Energy budget (Geophysics), Atmospherics, Stratospheric circulation, Tropospheric circulation

Subject Categories

Atmospheric Sciences | Climate

Abstract

The flux of moist static energy (MSE) across 70°N and 65°S plays a key role in the energy budget and climate of the polar regions. This flux, which provides respectively 98 W m⁻² and 91 W m⁻² heating of the northern and southern polar caps, is usually studied from a vertically integrated perspective. Its vertical structure is examined using the NASA-MERRA-2 reanalysis to compute monthly fluxes of sensible, latent and potential energy across 70°N and 65°S for the period 1980-2016. The flux is bimodal, with peaks in the lower troposphere and in the middle stratosphere, and is near zero at the tropopause. Distinctly different seasonal cycles are found for the stratospheric and tropospheric components. At 70°N, the fraction of the total integrated MSE flux occurring in the stratosphere is 20% during winter and only 7% during summer. Interannual variability of the stratospheric flux is intimately connected to major sudden stratospheric warming (SSW) events. Months in which SSWs are observed feature both an increased total flux and a larger fraction occurring in the stratosphere. The relationship between the tropospheric and stratospheric fluxes are explored through lead-lag correlations. The strongest correlation (+0.31) is found with the troposphere leading the stratosphere by 1 month. This positive correlation appears to be enhanced during SSWs. Correlations between the MSE flux and polar cap mean temperatures are strongest in the lower-mid troposphere when lagging the surface temperatures. The vertical structure as well as how the structure changes given an instantaneous doubling of CO2 were examined in the CESM in slab ocean model mode. A similar bimodel structure across 70°N and 65°S were found. In the 2xCO2 run, the integrated MSE flux anomaly is weakly poleward, with increases mainly in the free troposphere at 70°N and 65°S.

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