1. General Model Information
Name: SWELTER - Synthetic Weather Estimator for Land use and Terrestrial Ecosystem Research.
Main medium: air
Main subject: meteorology, hydrology
Organization level: landscape
Type of model: Markov chain, static-algebraic equations
Main application: research, simulation/optimisation tool
Keywords: weather generator, land use, ecosystem research
Dr. S.P. Evans.
Alice Holt Lodge
Surrey GU10 4LH
Phone: +44 (0)1420 22255
Fax: +44 (0)1420 23563
SWELTER is stochastic-deterministic weather generator for use in research
on ecosystem dynamics and the effects of climate variability. Monthly
insrumental weather data for mean temperature, precipitation and wind speed
are inputted into a first-order Markov chain, coupled to an autocorrelation
intensity factor, to generate daily- or hourly-scale estimates of mean,
maximum and minimum temperature and wind speed. The same approach is used
in a two-state domain to estimate the mean amount of precipitation on a
rain day. Algorithms are outlined to estimate precipitation intensity and
duration, and relative humidity. Total, direct and diffuse solar radiation
are approximated using a spherical geometry approach, corrected for altitude
and latitude. The model is validated from 15 sites within the European
Union, and are representative of a range of climates. All predicted values
were within the 95% confidence interval of the instrumental data. Ranking
carried out to indicate the model's predictive ability, based on statistical
appraisal of results, shows fair to good predictions for 6 variables
[mean, minimum and maximum temperature, precipitation, solar radiation,
relative humidity and wind speed], and poor predictions for precipitation
duration. Sensitivity analysis has shown that values for the SD and the
1st order autocorrelation can be substituted by constants. This reduces
the input data requirements. Use of the model in ecosystem research may
represent a suitable alternative to the acquisition of instrumental
meteorological daily-scale data within the geographical area of the
European Union, since it is able to generate good quality synthetic daily
values for a range of climate parameters, derived from more widely
available monthly scale instrumental series.
Purpose of the
Source of the Abstract
CAMASE, Register of Agro-Ecosystem Models
II. Technical Information
Operating System(s): PC 486.
Costs: : To be confirmed.
Programming Language(s): Visual preparation.
III. Mathematical Information
Rate variables: Daylength, extra-terrestrial radiation, terrestrial radiation (direct & diffuse) [2 methods], solar angle, minimum temperature, maximum temperature, mean temperature, relative humidity, atmospheric pressure, cloudiness, saturated vapour pressure, rainfall amount, rainfall duration, rainfall intensity, windspeed, evapotranspiration according to Penman-Monteith, Feddes et al. & Doorenbos-Kassam equations.
State variables: Altitude, latitude, slope, aspect.
Temperature, windspeed (mean, standard deviation, 1st order autocorrelation), precipitation (total/month, number of rain days), altitude, latitude, slope, aspect. Input check in model: Yes.
Basic spatial unit: m2.
Time interval of simulation: Hour or day.
Evans S.P. (1997). The potential use of weather generators in palaeoclimatic and palaeoecological research: the SWELTER (Synthetic Weather Estimator for Land use and Terrestrial Ecosystem Research) model.
Italian Journal of Quaternary Sciences, (Il Quaternario), 9: 643-648.
V. Further information in the World-Wide-Web
VI. Additional remarks
Last review of this document by: T. Gabele: Dec 15 1997
Status of the document:
last modified by
Joachim Benz Mon Dec 12 17:20:37 CET 2005