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Aaron Donohoe

Senior Research Scientist

Email

adonohoe@apl.washington.edu

Phone

206-616-3471

Department Affiliation

Polar Science Center

Education

B.A. Physics, Bowdoin College, 2003

Ph.D. Atmospheric Sciences, University of Washington, 2011

Publications

2000-present and while at APL-UW

Radiative and dynamic controls on atmospheric heat transport over different planetary rotation rates

Cox, T., K.C. Armour, G.H. Roe, A. Donohoe, and D.M.W. Frierson, "Radiative and dynamic controls on atmospheric heat transport over different planetary rotation rates," J. Clim., EOR, doi:10.1175/JCLI-D-20-0533.1, 2021.

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8 Feb 2021

Atmospheric heat transport is an important piece of our climate system, yet we lack a complete theory for its magnitude or changes. Atmospheric dynamics and radiation play different roles in controlling the total atmospheric heat transport (AHT) and its partitioning into components associated with eddies and mean meridional circulations. This work focuses on two specific controls: a radiative one, atmospheric radiative temperature tendencies; and a dynamic one, planetary rotation rate. We use an idealized grey radiation model to employ a novel framework to lock the radiative temperature tendency and total AHT to climatological values, even while the rotation rate is varied. This setup allows for a systematic study of the effects of radiative tendency and rotation rate on AHT. We find that rotation rate controls the latitudinal extent of the Hadley cell and the heat transport efficiency of eddies. Both rotation rate and radiative tendency influence the strength of the Hadley cell and the strength of equator-pole energy differences that are important for AHT by eddies. These two controls do not always operate independently and can reinforce or dampen each other. In addition, we examine how individual AHT components, which vary with latitude, sum to a total AHT that varies smoothly with latitude. At slow rotation rates the mean meridional circulation is most important in ensuring total AHT varies smoothly with latitude, while eddies are most important at rotation rates similar to, and faster than, the Earth's.

Mechanisms of tropical precipitation biases in climate models

Kim, H., S.M. Kang, K. Takahashi, A. Donohoe, and A.G. Pendergrass, "Mechanisms of tropical precipitation biases in climate models," Clim. Dyn., EOR, doi:10.1007/s00382-020-05325-z, 2020.

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27 Oct 2020

We investigate the possible causes for inter-model spread in tropical zonal-mean precipitation pattern, which is divided into hemispherically symmetric and anti-symmetric modes via empirical orthogonal function analysis. The symmetric pattern characterizes the leading mode and is tightly related to the seasonal amplitude of maximum precipitation position. The energetic constraints link the symmetric pattern to the seasonal amplitude in cross-equatorial atmospheric energy transport AET0 and the annual-mean equatorial net energy input NEI0. Decomposition of AET0 into the energetics variables indicates that the inter-model spread in symmetric precipitation pattern is correlated with the inter-model spread in clear-sky atmospheric shortwave absorption, which most likely arises due to differences in radiative transfer parameterizations rather than water vapor patterns. Among the components that consist NEI0, the inter-model spread in symmetric precipitation pattern is mostly associated with the inter-model spread in net surface energy flux in the equatorial region, which is modulated by the strength of cooling by equatorial upwelling. Our results provide clues to understand the mechanism of tropical precipitation bias, thereby providing guidance for model improvements.

Robust longitudinally variable responses of the ITCZ to a myriad of climate forcings

Atwood, A.R., A. Donohoe, D.S. Battisti, X. Liu, and F.S.R. Pausata, "Robust longitudinally variable responses of the ITCZ to a myriad of climate forcings," Geophys. Res. Lett., 47, doi:10.1029/2020GL088833, 2020.

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16 Sep 2020

We evaluate the longitudinal variation in meridional shifts of the tropical rainbelt in response to natural and anthropogenic forcings using a large suite of coupled climate model simulations. We find that the energetic framework of the zonal mean Hadley cell is generally not useful for characterizing shifts of the rainbelt at regional scales, regardless of the characteristics of the forcing. Forcings with large hemispheric asymmetry such as extratropical volcanic forcing, meltwater forcing, and the Last Glacial Maximum give rise to robust zonal mean shifts of the rainbelt; however, the direction and magnitude of the shift vary strongly as a function of longitude. Even the Pacific rainband does not shift uniformly under any forcing considered. Forcings with weak hemispheric asymmetry such as CO2 and mid‐Holocene forcing give rise to zonal mean shifts that are small or absent, but the rainbelt does shift regionally in coherent ways across models that may have important dynamical consequences.

More Publications

Acoustics Air-Sea Interaction & Remote Sensing Center for Environmental & Information Systems Center for Industrial & Medical Ultrasound Electronic & Photonic Systems Ocean Engineering Ocean Physics Polar Science Center
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