Environmental Engineering Reference
In-Depth Information
Positive values indicate that the atmospheric layer between 10 and 200 m is stable,
negative values indicates that the layer is unstable, values around 0 indicates
neutral conditions of this layer (Stull 1988). We see that the ptg profile by MM5
and WRF is in good agreement with the observations. In general the potential
temperature gradient by WRF is better than by MM5.
Fig. 1.
Vertical potential temperature gradient profiles between 10 and 200 m by WRF, MM5 for
the Linate airport, together with the observations for 0.00, 06.00, 12.00 and 18.00 h for the whole
year
Secondly, we analyze the impact of using MM5 and WRF on calculated
PM10 and O
3
concentrations. In general CHIMERE/MM5 and CHIMERE/WRF
underestimate the PM10 concentrations for January. The difference in PM10
concentrations for January between CHIMERE/MM5 and CHIMERE/WRF is
around a factor 1.6 (PM10 higher for CHIMERE/MM5), see
Fig. 2.
This difference
and the larger underestimation in PM10 concentrations by CHIMERE/WRF are
related to the differences in heat fluxes and the resulting PBL heights calculated
by WRF. In general the PBL height by WRF meteorology is a factor 2.8 higher at
noon in January than calculated by MM5. This study showed that the difference in
microphysics scheme has an impact on the profile of cloud liquid water (CLW)
calculated by the meteorological driver and therefore on the production of SO
4
aerosol.
A sensitivity analysis shows that changing the Noah Land Surface Model (LSM)
for the 5-layer soil temperature model, the calculated monthly mean PM10 con-
centrations increase by 30%, due to the change in the heat fluxes and the resulting
PBL heights, see Fig. 2c. For June, PM10 calculated concentrations by CHIMERE/
MM5 and CHIMERE/WRF are similar and agree with the observations. Calculated
O
3
values for June are in general overestimated by a factor 1.3 by CHIMERE/MM5
and CHIMRE/WRF.
