Contribution of the North Atlantic subtropical high to regional climate model (RCM) skill in simulating southeastern United States summer precipitation
Abstract
© 2014, Springer-Verlag Berlin Heidelberg.This study assesses the skill of advanced
regional climate models (RCMs) in simulating southeastern United States (SE US) summer
precipitation and explores the physical mechanisms responsible for the simulation
skill at a process level. Analysis of the RCM output for the North American Regional
Climate Change Assessment Program indicates that the RCM simulations of summer precipitation
show the largest biases and a remarkable spread over the SE US compared to other regions
in the contiguous US. The causes of such a spread are investigated by performing simulations
using the Weather Research and Forecasting (WRF) model, a next-generation RCM developed
by the US National Center for Atmospheric Research. The results show that the simulated
biases in SE US summer precipitation are due mainly to the misrepresentation of the
modeled North Atlantic subtropical high (NASH) western ridge. In the WRF simulations,
the NASH western ridge shifts 7° northwestward when compared to that in the reanalysis
ensemble, leading to a dry bias in the simulated summer precipitation according to
the relationship between the NASH western ridge and summer precipitation over the
southeast. Experiments utilizing the four dimensional data assimilation technique
further suggest that the improved representation of the circulation patterns (i.e.,
wind fields) associated with the NASH western ridge substantially reduces the bias
in the simulated SE US summer precipitation. Our analysis of circulation dynamics
indicates that the NASH western ridge in the WRF simulations is significantly influenced
by the simulated planetary boundary layer (PBL) processes over the Gulf of Mexico.
Specifically, a decrease (increase) in the simulated PBL height tends to stabilize
(destabilize) the lower troposphere over the Gulf of Mexico, and thus inhibits (favors)
the onset and/or development of convection. Such changes in tropical convection induce
a tropical–extratropical teleconnection pattern, which modulates the circulation along
the NASH western ridge in the WRF simulations and contributes to the modeled precipitation
biases over the SE US. In conclusion, our study demonstrates that the NASH western
ridge is an important factor responsible for the RCM skill in simulating SE US summer
precipitation. Furthermore, the improvements in the PBL parameterizations for the
Gulf of Mexico might help advance RCM skill in representing the NASH western ridge
circulation and summer precipitation over the SE US.
Type
Journal articlePermalink
https://hdl.handle.net/10161/9177Published Version (Please cite this version)
10.1007/s00382-014-2352-9Publication Info
Li, L; Li, W; & Jin, J (2015). Contribution of the North Atlantic subtropical high to regional climate model (RCM)
skill in simulating southeastern United States summer precipitation. Climate Dynamics, 45(1-2). pp. 477-491. 10.1007/s00382-014-2352-9. Retrieved from https://hdl.handle.net/10161/9177.This is constructed from limited available data and may be imprecise. To cite this
article, please review & use the official citation provided by the journal.
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Show full item recordScholars@Duke
Wenhong Li
Associate Professor of Climate
Dr. Li's research interests focus primarily on climate dynamics, land-atmosphere interaction,
hydroclimatology, and climate modeling. Her current research is to understand how
the hydrological cycle changes in the current and future climate and their impacts
on the ecosystems, subtropical high variability and change, unforced global temperature variability,
and climate and health issues.

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