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Theoretical background on pwsFWI: Difference between revisions
Theoretical background on pwsFWI (view source)
Revision as of 14:57, 13 April 2021
, 14:57, 13 April 2021→Humidity – the science
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<math>P_{Sat}\ {{=}}\ {A} \times {e}^{\frac{{B}\times{T}} {({C}\ +\ {T})} }</math> | <math>P_{Sat}\ {{=}}\ {A} \times {e}^{\frac{{B}\times{T}} {({C}\ +\ {T})} }</math> | ||
Where A = 6.112, B= 17.62 and C= 243.12 are the coefficients of the August-Roche-Magnus equation as found in the Guide to Meteorological Instruments and Methods <ref>[https://www.wmo.int/pages/prog/www/IMOP/CIMO-Guide.html Guide to Meteorological Instruments and Methods of Observation (WMO-No. 8, CIMO Guide)], In Chapter 4. Measurement Of Humidity, Annex 4.B. Formulae For The Computation Of Measures Of Humidity.</ref> | Where A = 6.112, B= 17.62 and C= 243.12 are the coefficients of the August-Roche-Magnus equation as found in the Guide to Meteorological Instruments and Methods <ref>[https://www.wmo.int/pages/prog/www/IMOP/CIMO-Guide.html Guide to Meteorological Instruments and Methods of Observation (WMO-No. 8, CIMO Guide)], In Chapter 4. Measurement Of Humidity, Annex 4.B. Formulae For The Computation Of Measures Of Humidity.</ref>. P<sub>sat</sub> in hPa and T in °C. The coefficients are slightly different from the ones found in the [https://en.wikipedia.org/wiki/Vapour_pressure_of_water#Approximation_formulas Wikipedia]. | ||
With this estimator for P<sub>Sat</sub> we can work straight on to an FWI for personal weather stations (which from here on I will call pwsFWI or rough pwsFWI). | With this estimator for P<sub>Sat</sub> we can work straight on to an FWI for personal weather stations (which from here on I will call pwsFWI or rough pwsFWI). | ||
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<math>{pwsFWI}\ {{=}}\ {VPD} \times {Windspeed}</math> | <math>{pwsFWI}\ {{=}}\ {VPD} \times {Windspeed}</math> | ||
The VPD must be seen as the largest driving factor in evaporation and as such in the drying of the fuel(s). For the Meteorological variables in the calculation per day, the daily high or total (T, Wind, Rain) or daily low (RH) values are taken. | The VPD must be seen as the largest driving factor in evaporation and as such in the drying of the fuel(s). For the Meteorological variables in the calculation per day, the daily high or total (T, Wind, Rain) or daily low (RH) values are taken. | ||
== Some reasoning == | == Some reasoning == | ||