Scilab Function
Last update : 23/8/2006
c_ETP - Function to generate potential evapotranspiraton time series
Calling Sequence
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[ETP] = c_ETP(NbVal,TimeSteps,Latitude,TM,DateStart)
Parameters
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NbVal
: Number of value in the returne time serie (ex. NbVal = 100 > return 100 ETP values).
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TimeSteps
: Length of the time step expressed in hour. TimeSteps must vary within [1/1440 (1 minute) .. 24].
There must be an integer number of timestep in 24 hours (ex. TimeSteps=5 is not allowed).
Ex : for a 6 hourly time-series, TimeSteps = 6.
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Latitude
: Latitude (in radians) of the point to which the potential evapotranspiration values are assigned.
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TM
: Mean monthly temperatures (matrix [12x1]).
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DateStart
: Date of the first value generated (format YYYYMMDDhhmm, ex: DateStart = 199001010000, the ETP time series will start on the first of January 1990).
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ETP
: Potential evapotranspiration generated (matrix [NbValx1]).
Description
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CAUTION : The evapotranspiration values are inter-annual values. The time series is identical every year.
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WARNING : This function is written in C language and interfaced with SCILAB (HYDROGR.dll).
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The function adjusts a Fourrier transform on the monthly temperature values and apply the formula proposed by Morton (see bibliography) based on temperature and latitude).
Examples
// Mean monthly temperature
T = [0.687;0.498;2.774;6.086;10.565;13.702;16.159;15.585;12.619;8.486;3.300;0.778];
// Generation of ETP daily time series (2000 days), latitude = 45deg, start = 1/1/1980
E = c_ETP(2000,24,%pi/4,T,198001010000);
// Graph
plot2d(c_CONVDATE(0,198001010000)+(0:1999),E,style=-1);
// Date on the x axis
a=gca(); a.auto_ticks=['off','on']; [tck tck_txt]=SERIEDATE(198001010000,c_CONVDATE(1,c_CONVDATE(0,198001010000)+2000),'a',1); // Axe des dates (dates ici au format 36893.567)
XTICKS=tlist(['ticks','locations','labels'],tck,tck_txt);a.x_ticks=XTICKS;xgrid(2);xtitle('PE with the Morton formula','date','PE (mm)')
See Also
c_GR4J
,
Authors
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Julien Lerat (transcription of fortran code written by Claude Michel)
CEMAGREF Antony, HBAN Unit, julien.lerat@cemagref.fr
Bibliography
Oudin, L., C. Michel, et al. (2005). "Which potential evapotranspiration input for a lumped rainfall-runoff model?: Part 1--Can rainfall-runoff models effectively handle detailed potential evapotranspiration inputs?" Journal of Hydrology 303(1-4): 275-289
Bibliography
Oudin, L., F. Hervieu, et al. (2005). "Which potential evapotranspiration input for a lumped rainfall-runoff model?: Part 2--Towards a simple and efficient potential evapotranspiration model for rainfall-runoff modelling." Journal of Hydrology 303(1-4): 290-306.
Bibliography
Morton, F. I. (1983). "OPERATIONAL ESTIMATES OF AREAL EVAPOTRANSPIRATION AND THEIR SIGNIFICANCE TO THE SCIENCE AND PRACTICE OF HYDROLOGY." Journal of Hydrology 66(1-4): 1-76.