Coupled and Stand-alone Regional Climate Modeling of Intensive Storms in
Western Canada
Abstract
A coupled atmospheric-hydrologic system models the complex interactions
between the land surface and the atmospheric boundary layer, and the
water-energy cycle from groundwater across the land surface to the top
of the atmosphere. A regional climate model called WRF (Weather Research
Forecasting) was coupled with a land surface scheme (Noah) to simulate
intensive storms in central Alberta, Canada. Accounting for the
land-atmosphere feedback enhances the predictability of the fine-tuned
WRF-Noah system. Soil moisture, vegetation, and land surface temperature
influence latent and sensible heat fluxes, and modulate both thermal and
dynamical characteristics of land and lower atmosphere. WRF was set up
in a two-way, three-domain nested framework so that the output of the
outermost domain (D1) was used to run the second domain (D2) and the
output of D2 was used to run the innermost domain (D3). In two-way
nesting, D3 and D2 provide the feedback to their outer domains (D2 and
D1), respectively. D3 was set at a 3-km resolution adequate to simulate
convective storms. WRF-Noah was forced with climate outputs from Global
Climate Models (GCMs) for the baseline period 1980–2005. A
quantile-quantile bias correction method and a regional frequency
analysis were applied to develop intensity-duration-frequency (IDF)
curves from precipitation simulated by WRF-Noah. The simulated baseline
precipitation of central Alberta agreed well with observed rain gauge
data of Edmonton. The 5th‐generation NCAR mesoscale atmospheric model
(MM5) was also set up in a 3-domain, but one-way nesting configuration.
As expected, after bias correction, precipitation simulated by MM5 was
less accurate than that simulated by WRF-Noah. For storms of short
durations and return periods of more than 25 years, both MM5 driven by
SRES climate scenarios of CMIP3 and WRF-Noah driven by RCP climate
scenarios of CMIP5 projected storm intensities in central Alberta to
increase from the base period to the 2050s, and to the 2080s.