Environmental Engineering Reference
In-Depth Information
cal layers. The lateral boundary values are received from ECMWF every 6 h. The
system is run on NEC-SX6 DMI supercomputer, and the produced model output
files are archived on the mass storage system. The current operational DMI fore-
casting model includes the digital filtering initialization, semi-Lagrangian advec-
tion scheme, and a set of physical parameterizations such as Savijaervi radiation,
STRACO condensation, CBR turbulence scheme, and ISBA land surface scheme.
Several specific tests and verification of the DMI-HIRLAM-U01/I01 models
(Fig. 14.1b) for high resolution (Mahura et al., 2005) and urbanization (Baklanov
et al., 2006b; Mahura et al., 2006) were conducted within the FUMAPEX project
(Baklanov et al., 2005, 2006a). For these models the preparation of land-use clas-
sification based on CORINE dataset (CORINE, 2000) and climate generation files
had a resolution of 1.4 km. These on-going research activities are part of the DMI-
Enviro-HIRLAM model developments and tests (Mahura et al., 2008).
14.2.2 Approach Based on Improved Urban Roughness
and Anthropogenic Fluxes
The simple NWP urbanisation includes modifications of the Interaction Soil Bio-
sphere Atmosphere (ISBA) land surface scheme based on the original proposed by
Noilhan and Planton (1989) and updated and used by the DMI-HIRLAM model.
The changes include modifications of the urban roughness, anthropogenic heat flux
and albedo parameters in grid cells of modelling domains where the urban class is
present. The urban roughness changes by up to 2 m when the urban class becomes
100% of a grid-cell. The anthropogenic heat flux is modified similarly, with a max-
imum value which ranges from 10 to 200 Wm 2 . Albedo for the summer varies
by factor of two (0.2-0.4) relative to the winter because of snow coverage. This
approach is the cheapest way to simulate in operational forecast applications and
NWP models with low vertical resolution (i.e. the first computational vertical level
is higher than 20 m).
In our study, the urban related modifications of the ISBA land surface scheme
are evaluated. Over the grid cells of the modelling domain where, at least, a small
fraction of urban related class was presented, the roughness was modified to reflect
the urban area presence. The anthropogenic heat fluxes were also added for the
same grid cells. A combined contribution of these two features into the formation
of airflow over the urban areas was incorporated into the land surface scheme of the
model, where the model domain covers the entire territory of Denmark.
14.2.3 Building Effect Parameterization
The Building Effect Parameterization (BEP) module includes the urban sub-layer
parameterisation based on the drag term in the main equations suggested by Martilli
et al. (2002) with modifications for implementation into NWP models and several
further improvements (Hamdi and Shayes, 2007). The aim of the urban sub-layer
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