for siting and exposure of in situ meteorological sensors in simple terrain
are as follows:
for wind speed and wind direction should be located over level, open terrain
at a height of 10 m above ground level and at a distance at least ten times
the height of nearby obstructions. For elevated releases, additional
measurements should be made at stack top or 100 m, whichever is lower.
Monitoring requirements for stacks 200 m and above should be determined in
consultation with the appropriate EPA Regional Office.
sensors should be located at 2 m. Probe placement for temperature difference
measurements depend on the application. For use in estimating surface layer
stability, the measurement should be made between 20z0 and 100z0 ; the same
recommendation applies to temperature difference measurements for use in
estimating the P-G stability category using the solar radiation delta-T
method. For use in estimating stable plume rise, temperature difference
measurements should be made across the plume rise layer, a minimum
separation of 50 m is recommended for this application. Temperature sensors
should be shielded to protect them from thermal radiation and any
significant heat sources or sinks.
used for measuring incoming (solar) radiation should be located with an
unrestricted view of the sky in all directions during all seasons. Sensor
height is not critical for pyranometers; a tall platform or rooftop is an
acceptable location. Net radiometers should be mounted about 1 m above
recommendations applicable to siting and exposure of meteorological
instruments in complex terrain are not possible. Generally, one should begin
the process by conducting a screening analysis to determine, among other
things, what terrain features are likely to be important; the screening
analysis should also identify potential worse case meteorological
conditions. This information should then be used to design a monitoring plan
for the specific application.
siting considerations also apply to coastal and urban sites. Multiple sites,
though often desirable, may not always be possible in these situations. In
general, site selection for meteorological monitoring in support of
regulatory modeling applications in coastal and urban locations should be
conducted in consultation with the appropriate EPA Regional Office.
the recommendations in this section cannot be achieved, then alternate
should be developed in
consultation with the appropriate EPA Regional Office. Approval of site.
selection for meteorological monitoring should be obtained from the
permit granting authority prior to installation of any equipment.
3. SITING AND EXPOSURE
3.1.1 Objectives for Siting
3.1.2 Factors to Consider
3.2 Simple Terrain Locations
3.2.1 Speed and Wind Direction
3.2.2 Temperature, Temperature
Difference, and Humidity
3.3 Complex Terrain Locations
3.3.1 Wind Speed
3.3.2 Wind Direction
3.3.3 Temperature Difference
3.4 Coastal Locations
3.5 Urban Locations