Verification and Case Studies for Urban Effects in HIRLAM Numerical Weather Forecasting - Meteorological and Air Quality Models for Urban Areas - page 133

(a) (b)

(c) (d)

Fig. 14.3 Difference plots (between outputs of the DMI-HIRLAM control and urbanized runs
using (a,c) R+AHF - anthropogenic heat flux and rouhgness and (b,d) BEP modifications of the
ISBA land-surface scheme) for the (a,b) air temperature at 2 m and (c,d) wind velocity at 10 m on
1st August 2004 at 06 UTC (See also Colour Plate 14 on page 177)

wind velocities reached a maximum of more than 3.5 m s − 1 during daytime and
depending on the dominant wind direction. The wind velocity difference is the low-
est (less than 0.1 m s − 1 ) during the evening and night hours. For temperature, this
“urban pattern” is also well defined, but similarly has small area coverage too. The
highest difference is 1.3 ºC in the morning. It varies through the day reaching a
minimum during late evening hours. Such behaviour might be related to BEP where
more attention is given to the dynamical than the thermal, because the anthropogenic
heat flux contribution is not included (except for building wall heat transfer).

14.3.3 Overall Urbanized NWP Performance

Evaluation of the HIRLAM NWP models (two resolutions) has been conducted
through analysis of meteorological parameters for the diurnal variations of the
average air temperature, wind velocity, and relative humidity. This evaluation was
performed also with a focus on only on six urban/suburban meteorological stations
of the Copenhagen metropolitan area. As an example, the diurnal variability for
00 UTC forecasts for the relative humidity and wind velocity at 10 m is shown in