snowfall_annual_maxima.py

import numpy as np


class SafranSnowfall(object):
    """"
    Hypothesis:

    -How to count how much snowfall in one hour ?
        I take the average between the rhythm of snowfall per second between the start and the end
        and multiply that by 60 x 60 which corresponds to the number of seconds in one hour

    -How do how I define the limit of a day ?
        From the start, i.e. in August at 4am something like that,then if I add a 24H duration, I arrive to the next day

    -How do you aggregate several days ?
        We aggregate all the N consecutive days into a value x_i, then we take the max
        (but here the problem might be that the x_i are not idnependent, they are highly dependent one from another)
    """

    def __init__(self, dataset):
        self.dataset = dataset
        # Corresponding starting times
        # start_datetime = datetime(year=year, month=8, day=1, hour=6)
        # start_times = np.array(dataset.variables['time'])[:-1]

        # Compute the daily snowfall in kg/m2
        snowfall_rates = np.array(dataset.variables['Snowf'])
        mean_snowfall_rates = 0.5 * (snowfall_rates[:-1] + snowfall_rates[1:])
        hourly_snowfall = 60 * 60 * mean_snowfall_rates
        # Transform the snowfall amount into a dataframe
        nb_days = len(hourly_snowfall) // 24
        self.daily_snowfall = [sum(hourly_snowfall[24 * i:24 * (i+1)]) for i in range(nb_days)]

    def annual_snowfall(self, nb_days_of_snowfall=1):
        # Aggregate the daily snowfall by the number of consecutive days
        shifted_list = [self.daily_snowfall[i:] for i in range(nb_days_of_snowfall)]
        # First element of shifted_list is of length n, Second element of length n-1, Third element n-2....
        # The zip is done with respect to the shortest list
        snowfall_in_consecutive_days = [sum(e) for e in zip(*shifted_list)]
        # Return the maximum of the aggregated list
        # The returned array is of size n-nb_days+1 x nb_massif
        return np.array(snowfall_in_consecutive_days)