Geoscience Reference
In-Depth Information
precipitation, leading to an increase in river discharge to the Arctic Ocean. Sea-
level pressure is expected to fall in the high latitudes, with compensating increases
in parts of the middle latitudes and subtropics, where precipitation amounts are
expected to decline. This follows because high pressures at the surface tend to be
accompanied by descending air motion unfavorable to condensation. Again, how-
ever, projections between different models vary greatly. Changes in precipitation
are particularly uncertain.
9.6
Regional Climate Models
There are many regional climate models in existence. Models of the 1990s to
early 2000s vintage were evaluated as through the Arctic Regional Climate Model
Comparison Project (ARCMIP), a coordinated set of simulations of the present-day
Arctic climate, focusing on the SHEBA year (October 1997-October 1998). This
year was chosen because of the availability of high quality data from the field camp
in the Beaufort and Chukchi seas, aircraft observations, as well as data from the
Barrow Arctic Radiation Monitoring site and remote sensing. Use was alsomade of
observations from the Mackenzie GEWEX study. At least seven modeling groups
participated. Like other MIPs, the simulations employed common initial and bound-
ary conditions for each model. Rinke et al. (
2005
) summarize performance biases
of the ARCMIP models for geopotential height, 2-m temperature, cloud cover, and
surface radiation fluxes. Results indicate that the model composite mean biases are
on the order of differences between different observations or data analyses. Echoing
the GCM comparisons, there is considerable scatter between the simulations for
individual models.
Regional climate models in wide use include:
Regional Atmospheric Climate Model (RACMO):
RACMO was developed by
the Royal Netherlands Meteorological Institute. It has a number of variations and
is constantly being improved. The Institute for Marine and Atmospheric Research
Utrecht integrated a multilayer snow routine into RACMO that treats snow grain
size growth, vertical heat conduction, firn densification, the percolation and refreez-
ing of meltwater, meltwater runoff, snow transport, and other processes, coupled to
the atmospheric part of RACMO. It has been widely used in studies of the surface
mass balance of the Greenland and Antarctic ice sheets (e.g., Ettema et al.,
2009
,
van den Berg et al.,
2011
).
Weather Research and Forecasting (WRF) model:
WRF was developed to
be a next-generation regional model that could be used for both research and oper-
ational weather forecasting. In part, WRF was intended as a replacement for the
fifth-generation Pennsylvania State University National Center for Atmospheric
Research, known as MM5. The WRF was originally developed for mid-latitude
applications, but - in modified form - it has been widely used in polar studies. In the
Arctic, WRF is the atmospheric component of the Regional Arctic Climate Model
