Alternative small scale meteorology input to a chemical transport ...

CHAPTER 4. RESULTS AND DISCUSSIONS
4.1. Comparison of meteorological data
The meteorological data that is provided to CMAQ, undergoes preprocessing in
MCIP. An investigation of possible ways to process CALMET data in MCIP was made. The
results revealed two options, summarized below:
(i) MCIP can accept meteorological parameters, such as air temperature, pressure,
density and wind fields, and can diagnose atmospheric characteristics necessary for CMAQ,
such as PBL scales and surface layer fluxes.
(ii) MCIP can be redesigned to accept from CALMET not only the basic
meteorological parameters mentioned above, but also surface layer and PBL characteristics
available from CALMET instead of re-diagnosing them.
The first option was explored with the assumption that the temperature of earth’s
surface (ground temperature) is the same as the temperature of the air just above it. After
processing the meteorological data and running CMAQ with it, the results showed a high
sensitivity of MCIP to ground temperature. Ground temperature appears to be a critical
parameter for computation of all PBL and surface layer characteristics. MCIP uses the
difference between surface air temperature and ground temperature to compute practically all
surface layer parameters. Therefore, alternative ways need to be investigated further for proper
modeling of ground temperature.
The second option allows the use of additional CALMET data directly in MCIP. This
32