1. General Model Information

Name: SWELTER - Synthetic Weather Estimator for Land use and Terrestrial Ecosystem Research.

Acronym: SWELTER


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

Contact:

Dr. S.P. Evans.
Forest Research
Alice Holt Lodge
Farnham
Surrey GU10 4LH
UNITED KINGDOM.
Phone: +44 (0)1420 22255
Fax: +44 (0)1420 23563
email: sam.evans@forestry.gsi.gov.uk
Homepage: http://www.forestresearch.gov.uk/website/forestresearch.nsf/ByUnique/INFD-62GECE

Author(s):

Abstract:

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 model:

Model parentage:

Source of the Abstract CAMASE, Register of Agro-Ecosystem Models


II. Technical Information

II.1 Executables:

Operating System(s): PC 486.
Contract necessary:
Costs: : To be confirmed.
Comments:

II.2 Source-code:

Programming Language(s): Visual preparation.

II.3 Manuals:



II.4 Data:



III. Mathematical Information


III.1 Mathematics


III.2 Quantities

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.

III.2.1 Input

Temperature, windspeed (mean, standard deviation, 1st order autocorrelation), precipitation (total/month, number of rain days), altitude, latitude, slope, aspect. Input check in model: Yes.

III.2.2 Output


Basic spatial unit: m2.
Time interval of simulation: Hour or day.

IV. References


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

Parentage:
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

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