Mountain Climate Simulator
Entry ID: MTCLIM
Abstract: MT-CLIM is a computer program that uses observations of daily maximum
temperature, minimum temperature, and precipitation from one location (the
"base") to estimate the temperature, precipitation, radiation, and humidity at
another location (the "site"). The base and the site can be at different
elevations, and can have different slopes and aspects. Better results are
obtained when the base and ... site are relatively close to one another (at the
bottom and the top of a valley, for example).
Temperature estimates at the site are based on the base temperatures and a
user-supplied temperature lapse rate. Separate lapse rates can be supplied for
daily maximum and minimum temperature. Precipitation estimates at the site are
based on the daily record of precipitation from the base, and a user-specified
ratio of annual total precipitation between the site and the base.
The estimation of radiation and humidity are more complex, since these
parameters are not assumed to be measured at the base station. Humidity
estimates are based on the observation that daily minimum temperature is
usually very close to dewpoint temperature. The MT-CLIM algorithm includes
corrections to this assumption for arid climates. Radiation estimates are based
on the observation that the diurnal temperature range (from minimum temperature
to maximum temperature) is closely related to the daily average atmospheric
transmittance. In conjunction with information about the latitude, elevation,
slope, and aspect of the site, this relationship can be used to estimate daily
total radiation with a typical error range of +/- 15%.
Some of the limitations of MT-CLIM are the use of a single base station for
observations and the need for the user to specify the temperature and
precipitation relationships with elevation. We have developed an expanded
version of the MT-CLIM logic, called Daymet, that uses observations from a
large number of base stations.
(Summary adapted from
Bristow, K.L., and G.S. Campbell, 1984. On the relationship
between incoming solar radiation and daily maximum and minimum
temperature. Agricultural and Forest Meteorology, 31:159-166.
Running, S.W., R.R. Nemani, and R.D. Hungerford,
1987. Extrapolation of synoptic meteorological data in
mountainous terrain and its use for simulating forest
evaporation and photosynthesis. Canadian Journal of Forest
Glassy, J.M., and S.W. Running, 1994. Validating diurnal
climatology of the MT-CLIM model across a climatic gradient in
Oregon. Ecological Applications, 4(2):248-257.
Kimball, J.S., S.W. Running, and R. Nemani, 1997. An improved
method for estimating surface humidity from daily minimum
temperature. Agricultural and Forest Meteorology, 85:87-98.
Thornton, P.E., and S.W. Running, 1999. An improved algorithm
for estimating incident daily solar radiation from measurements
of temperature, humidity, and precipitation. Agricultural and
Forest Meteorology, 93:211-228.
Creation and Review Dates