Photosynthesis Reduction Factor (PRFT)

Photosynthesis Reduction Factor (PRFT) is a quadratic equation¹ is used to calculate the temperature reduction factor that affects photosynthesis (Ritchie et al., 1998):

\(\ PRFT = 1 - 0.0025 * (T_{day} - T_{opt})^2\)

Code for PRFT:

PythonR

def calcPRFT(TDay, TOpt=18):
    ''' Estimate Photosynthesis reduction factor (PRFT)

        Parameters:
            TDay (float): Number or array of Day Temperatures
            TOpt (float): Optimum Temperature. Default value 18

        Returns: 
            (float): A number or array of PRFT

    '''
    PRFT = 0
    if (TDay > 0):
        PRFT = 1 - 0.0025 * (TDay - TOpt) ** 2
    return PRFT

# -----------------------------------------------------------------
# The code below, allows run calculations faster using a NDVIA GPU 
# or available CPU cores to run in parallel.
# -----------------------------------------------------------------

@guvectorize([(float64[:], float64[:], float64[:])], '(n), ()->(n)')
def PRFT_gu(Tday, Topt, res):
    for i in range(Tday.shape[0]):
        res[i] = 1 - 0.0025*(Tday[i]-Topt[0])**2 if Tday[i] > 0.0 else 0.0

@numba.vectorize([float64(float64, float64)])
def getPRFT(Tday, Topt): 
    prft = 1 - 0.0025*(Tday-Topt)**2 if Tday > 0.0 else 0.0
    return prft

@numba.jit(parallel=True)
def apply_PRFT(Tday, Topt=18):
    n = len(Tday)
    result = np.zeros(n, dtype="float64")
    for i in range(n):
        result[i] = getPRFT(Tday[i], Topt)
    return result

def calculatePRFT(Tday, Topt=18):
    ''' Estimate Photosynthesis reduction factor (PRFT) in parallel.

        Parameters:
            Tday (float): Number or array of Day Temperatures
            Topt (float): Optimum Temperature. Default value 18

        Returns: 
            (float): A number or array of PRFT

    '''
    if (Tday is None):
        print("Day Temperature parameter is not valid")
        return
    result = []
    try:
        result = apply_PRFT(Tday, Topt)
    except:
        print("Error calculating photosynthesis reduction factor (PRFT)")

    return result #pd.Series(result, index=w.index, name="PRFT") int(GDD)

Check the API reference to know how to use it.

# Function to calculate the Photosynthetic Reduction Factor (PRFT)
calculatePRFT <- function(Tday, Topt){
    prft <- 0
    if (Tday > 0){
        prft <- 1.0 - 0.0025*(Tday-Topt)^2
    }
    return(prft)
}

calculatePRFT_wrap <- function(Tday, Topt){
    prft <- vector("numeric", length (Tday)) 
    for (i in 1:length(Tday)) {
        prft[[i]] <- calculatePRFT(Tday=Tday[[i]], Topt)
    }
    return(prft)
}

The whole R code can be found in the Github repository at Rcode folder.

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1. hyperbola with two parameters ↩