Source code for salishsea_tools.unit_conversions

# coding=utf-8

# Copyright 2013-2016 The Salish Sea MEOPAR contributors
# and The University of British Columbia

# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at

#    http://www.apache.org/licenses/LICENSE-2.0

# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

"""Salish Sea NEMO model unit conversion functions and constants.
"""
from __future__ import division

import numpy as np

# For convenience we import the TEOS-10 salinity conversion factors
# and functions so that they can be used from either here or the
# :py:mod:`salishsea_tools.teos_tools` module
from salishsea_tools.teos_tools import (
    PSU_TEOS,
    TEOS_PSU,
    psu_teos,
    teos_psu,
)


__all__ = [
    'PSU_TEOS', 'TEOS_PSU', 'psu_teos', 'teos_psu',
    'M_PER_S__KM_PER_HR', 'M_PER_S__KNOTS', 'mps_kph', 'mps_knots',
    'wind_to_from', 'bearing_heading',
    'humanize_time_of_day',
]


#: Conversion factor from m/s to km/hr
M_PER_S__KM_PER_HR = 3600 / 1000
#: Conversion factor from m/s to knots
M_PER_S__KNOTS = 3600 / 1852
#: Conversion factor from knots to m/s
KNOTS__M_PER_S = 1852 / 3600


[docs]def mps_kph(m_per_s): """Convert speed from m/s to km/hr. :kbd:`m_per_s` may be either a scalar number or a :py:class:`numpy.ndarray` object, and the return value will be of the same type. :arg m_per_s: Speed in m/s to convert. :returns: Speed in km/hr. """ return m_per_s * M_PER_S__KM_PER_HR
[docs]def mps_knots(m_per_s): """Convert speed from m/s to knots. :kbd:`m_per_s` may be either a scalar number or a :py:class:`numpy.ndarray` object, and the return value will be of the same type. :arg m_per_s: Speed in m/s to convert. :returns: Speed in knots. """ return m_per_s * M_PER_S__KNOTS
def knots_mps(knots): """Convert speed from knots to m/s. :kbd:`knots` may be either a scalar number or a :py:class:`numpy.ndarray` object, and the return value will be of the same type. :arg knots: Speed in knots to convert. :returns: Speed in m/s. """ return knots * KNOTS__M_PER_S
[docs]def wind_to_from(wind_to): """Convert wind bearing from "physics" compass "to" direction to "human"compass "from" direction. "Physics" compass has zero at the east and bearing angles increase in the counter-clockwise direction. "Human" compass has zero at the north and bearing angles increase in the clockwise direction. Example: 0° on the physics compass indicates air flow to the east which is called a west (270°) wind on the human compass. :kbd:`wind_to` may be either a scalar number or a :py:class:`numpy.ndarray` object, and the return value will be of the same type. :arg wind_to: Bearing on physics (to) compass to convert. :returns: Bearing on human (from) compass. """ try: # Scalar value case return 270 - wind_to if wind_to <= 270 else 270 - wind_to + 360 except ValueError: # N-dimensional array case mask_le_270, mask_gt_270 = wind_to <= 270, wind_to > 270 wind_from = np.array(wind_to, copy=True) wind_from[mask_le_270] = 270 - wind_to[mask_le_270] wind_from[mask_gt_270] = 270 - wind_to[mask_gt_270] + 360 return wind_from
[docs]def bearing_heading( bearing, headings=( 'N', 'NNE', 'NE', 'ENE', 'E', 'ESE', 'SE', 'SSE', 'S', 'SSW', 'SW', 'WSW', 'W', 'WNW', 'NW', 'NNW', 'N'), ): """Convert a compass bearing to a heading. :arg float bearing: The compass bearing to convert. :arg sequence headings: A sequence of headings to convert the bearing to. The default is the 16 compass points that divide the compass into 22.5° segments. :returns: Compass heading. :rtype: str """ return headings[int(round(bearing * (len(headings) - 1) / 360, 0))]
[docs]def humanize_time_of_day(date_time): """Return a "humanized" time of day string like "early Monday afternoon" that corresponds to :kbd:`date_time`. We use the same terminology as is used in the Environment Canada weather forecasts: https://www.ec.gc.ca/meteo-weather/default.asp?lang=En&n=10220A6B-1#c4 :arg date_time: Date/time to humanize. :type date_time: :py:class:`arrow.Arrow` :returns: Humanized time of day and day name; e.g. early Monday afternoon :rtype: str """ day_of_week = date_time.format('dddd') if date_time.hour < 6: part_of_day = '' early_late = 'overnight' elif date_time.hour < 12: part_of_day = 'morning' early_late = 'early' if date_time.hour < 9 else 'late' elif 12 <= date_time.hour < 18: part_of_day = 'afternoon' early_late = 'early' if date_time.hour < 15 else 'late' else: part_of_day = 'evening' early_late = 'early' if date_time.hour < 21 else 'late' return ' '.join((early_late, day_of_week, part_of_day)).rstrip()