TITLE:
Assessment of the 2006-2012 Climatological Fields and Mesoscale Features from Regional Downscaling of CESM Data by WRF-Chem over Southeast Alaska
AUTHORS:
Nicole Mölders, Cindy L. Bruyère, Scott Gende, Michael A. Pirhalla
KEYWORDS:
Evaluation, Regional Climate Modeling, Downscaling, Southeast Alaska, WRF-Chem, CESM
JOURNAL NAME:
Atmospheric and Climate Sciences,
Vol.4 No.4,
September
25,
2014
ABSTRACT: This
case study examined how well downscaling of Community Earth System Model (CESM)
data can reproduce climatological conditions relevant for summer (JJA) air quality
in Glacier Bay National Park. Climatology was determined from the
meteorological results obtained by the Weather Research and Forecasting model
inline coupled with chemistry (WRF-chem) when driven with CESM data of 2006-2012.
The climatology of this experiment (EXP) was evaluated by climatology from
gridded blended sea-wind speeds, CRU data, and 42 surface meteorology sites.
The quality relative to known performance was assessed by comparison to climatology determined from WRF-chem
control simulations driven with FNL analysis data (CON) in forecast mode.
Compared to observations, the thermodynamic and dynamic performances of EXP
showed similar shortcomings (dampened diurnal temperature range, overestimation
of wind speed over land) as CON. Over water EXP wind-speed climatology JJA bias
(simulated minus observed) was -0.7 m/s. With respect to the CRU data EXP
biases in JJA 2m temperature, diurnal temperature range, relative humidity and
accumulated precipitation were -1.1 K, -4.9 K, 13%,
and 110 mm, respectively. The slightly warmer atmosphere in EXP compensated for
deficiencies in the cloud schemes leading to better results for the number of
wet days and accumulated precipitation than in CON. Downscaling captured known
mesoscale responses important for regional climate in a similar way as CON.
When using CESM forcing, lateral boundary effects expanded spatially farther into the domain
than known for forcing by analysis data. Overall, climatologies obtained
from downscaling for Southeast Alaska had similar skill than those derived from
forecasts driven by analysis data.