Bases: scikits.hydroclimpy.lib.evaporation.SolarInformation
Computes the Potential EvapoTranspiration (PET) through different models.
The class instance stores the information (temperatures series, solar radiaitons, altitude...) required to calculate the PET for one given site over several dates with different models.
The PET estimated with a given model is the output of the instance method corresponding to the model. Thus, it is very easy to compare PETs estimated with different models.
Parameters:  tmin : TimeSeries
tmax : TimeSeries
latitude : float
z : float
Kt : {None, float}, optional


Methods
Droogers  
Hamon  
Hansen  
Hargreaves  
Kharrufa  
Makkink  
PenmanMonteith  
PenmanMonteithASCE  
PriestleyTaylor  
Thornthwaite  
Turc  
apx_solar_radiations  
clearsky_solar_radiations  
frac_day_of_year  
net_lw_radiations  
set_atmospheric_pressure  
solar_radiations_from_sunshinehours  
solar_radiations_from_temperatures  
vapor_pressure_from_dewpoint  
vapor_pressure_from_humidity 
Because the PotentialEvapoTranspiration class is a subclass of SolarInformation, it inherits all its attributes (freq, latitude, extraterrestrial_solar_radiations...). In addition, the class has its own attributes:
Empirical coefficient for the estimation of solar radiations from temperatures. A value of 0.171 is used by default.
If set to None, is computed from , the temperature range, as .
Slope of the vapor pressuretemperature relationship, as
where is average air temperature [].
Returns the vapor pressure at saturation [kPa]. The saturated vapor pressure for the time step is calculated as the average of the saturated vapor pressures corresponding to the minimum and maximum temperatures for the time step.
The relationship between saturated vapor pressure and temperature is:
Returns the solar radiations [MJ.m^{2}.d^{1}] approximated from temperatures, as:
where is an empirical parameter. By default, . Otherwise, is estimated from the temperature range as .
Parameters:  Kt : {None, float}, optional


Computes the net longwave radiation [MJ.m^{2}.d^{1}] as a function of temperatures:
where [MJ.K^{4}.m^{2}.d^{1}] is the StefanBolztmann constant, the actual vapor pressure, the actual incoming solar radiation, the incoming clearsky solar radiation. The temperatures are expressed in [K]
Parameters:  ea : float
solar_radiations : TimeSeries


Returns the vapor pressure [kPa] calculated from relative humidity.
The relative humidity is the ratio of the vapor pressure on the vapor pressure at saturation at the same temperature.
If maximum and minimum relative humidities ( and ) are available, the vapor pressure is calculated as
If is unavailable, the previous equation simplifies in
If only the average relative humidity is available, is estimated with:
Parameters:  RHmin : None, TimeSeries
RHmax : None, TimeSeries
RHmean : None, TimeSeries


Returns the vapor pressure [kPa] calculated from the dew point temperature, :
If the dew point temperature is None, it is approximated by the minimum air temperature .
Parameters:  tdew : None, TimeSeries


Sets the atmospheric pressure.
If P is None, it is calculated from [101.3 kPa], the average atmospheric pressure at sea level.
Parameters:  P : TimeSeries
z0 : {0., float} optional
tmean : {20., float} optional


References
Burman et al., 1987
The evaporation module provides different models for the computation of reference evapotranspiration. These models are available as methods of the PotentialEvapoTranspiration class.