Environmental Engineering Reference
In-Depth Information
5. Questions and Answers
Douw Steyn
: Most of your simulated flows are thermally driven by surface
temperatures.
1.
Did you allow sea-surface-temperatures to evolve through the day?
2.
Did you allow sea-surface-temperatures to be spatially variable?
Answer
: At the beginning we used sea-surface-temperature (SST) from global
data as input to the model, kept fixed in time along the simulation. Next, we
tried fixed in time and space, and last - we let the SST evolve through the day.
With the last option we had some noticeable improvements in the lower part of
temperature profiles that could show the presence of the marine inversion.
Thank you for pointing out that issue.
Bill Physick
: My experience too has been that if the marine inversion is not in the
initial large-scale analysis, then the mesoscale model won't produce it. It is
virtually never in the large-scale analysis because the vertical resolution of the
analysis is too coarse. It is a frustrating problem.
Answer
: Indeed, we checked that and the synoptic grid did not reflect the presence
of the inversions, though in one profile there was a mild inversion based at 500
m (just at about the observed marine inversion base). We tried to assimilate
some of our measured profiles, in order to give the model the information about
the inversions, but so far it didn't have a major impact on the results of the
simulations.
Sven-Erik Gryning
: What is the explanation for the upper inversion at 2 km
height?
Answer
: All the upper air measurements of August campaign showed a persisting
inversion around 2-2.5 km height, which we related to subsidence. This
subsidence is supposedly due to upper air ridge above our area, and the Hadley
cell downward section located over our region in summertime. Again, this
inversion did not appear in the initial large-scale analysis.
