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Sensitivity of the WRF model to land use and lake representation in a convection-resolving domain

Conference: Swiss Climate Summer School 2017
Year: 2017
Contribution type: Poster
PDF file: 2017_lavin_poster_SCSS2017.pdf

The EURO-Med-CORDEX Flagship Pilot Study (FPS) on Convection Permitting
climate modelling (CPCM) is an initiative which aims at investigating
convective-scale events, their processes and changes in key regions (initially, the
Alps) of Europe and the Mediterranean using high horizontal resolution models.
As a contribution to FPS CPCM, in this work we evaluate the sensitivity of the
simulated climate to land use and lake surface temperature representation.
The work is carried out using the Weather Research and Forecasting (WRF)
modelling system, version 3.8.1, configured to use the WRF Single moment
5-class microphysics scheme, Yonsei University (YSU) non-local closure PBL
scheme, Rapid Radiative Transfer Model (RRTMG) radiation scheme and the
Global/Regional Integrated Modelling System (GRIMS) scheme for shallow
convection. The model is coupled to the Noah land surface model. The Alpine
region is covered by a high resolution (0.0275o regular on a rotated lon-lat grid,
~3 km), convection-resolving domain, nested into the standard 0.11o
EURO-CORDEX domain. In the latter, we used a Kain-Fritsch mass flux scheme
to represent convective processes. All sensitivity simulations were forced by the
ERA-Interim reanalysis.
In order to investigate the sensitivity of the model to the land use distribution, a
widely used dataset provided with WRF (based on USGS) was replaced with a
newer, more detailed data set (based on CORINE), which has been re-mapped
to keep the same land use categories of the former (Pineda et al., 2004), thus
testing only the sensitivity to the new soil distribution. The differences between
both datasets (Figure 1a vs 1b) consist mainly on an increase of urban areas and
croplands, due to changes over time (1993 vs. 2012). In addition, some
differences are produced by corrections on some categories, such as areas with
changes between evergreen and deciduous forests.

Figure 1: a) Land use categories from the USGS data set over the Alpine
domain. b) as (a) but for CORINE re-mapped to USGS types.

At high resolution in this area, lakes represent an important surface coupling
process. None of the lakes in the alpine area are resolved by ERA-Interim,
therefore, lake surface temperature needs to be carefully initialized and, ideally,
dynamically represented by a lake model (Mallard et al., 2015). In this work we
test the effect of two alternatives to SST nearest neighbour interpolation:
initialization using daily-average surface air temperature and a model
representing a more complex lake dynamics.
Acknowledgement: this work is supported by the Spanish government through
grant BES-2016-078158 and MINECO/FEDER co-funded projects MULTI-SDM
(CGL2015-66583-R) and INSIGNIA (CGL2016-79210-R).