improver.utilities.solar module

Utilites to find the relative position of the sun.

class improver.utilities.solar.DayNightMask[source]

Bases: object

Plugin Class to generate a daynight mask for the provided cube

__init__()[source]

Initial the DayNightMask Object

_create_daynight_mask(cube)[source]

Create blank daynight mask cube

Parameters:cube (iris.cube.Cube) – cube with the times and coordinates required for mask
Returns:Blank daynight mask cube. The resulting cube will be the same shape as the time, y, and x coordinate, other coordinates will be ignored although they might appear as attributes on the cube as it is extracted from the first slice.
Return type:daynight_mask (iris.cube.Cube)
_daynight_lat_lon_cube(mask_cube, day_of_year, utc_hour)[source]

Calculate the daynight mask for the provided Lat Lon cube

Parameters:
  • mask_cube (iris.cube.Cube) – daynight mask cube - data initially set to self.night
  • day_of_year (int) – day of the year 0 to 365, 0 = 1st January
  • utc_hour (float) – Hour in UTC
Returns:

daynight mask cube - daytime set to self.day
Return type:

mask_cube (iris.cube.Cube)
process(cube)[source]

Calculate the daynight mask for the provided cube. Note that only the hours and minutes of the dtval variable are used. To ensure consistent behaviour with changes of second or subsecond precision, the second component is added to the time object. This means that when the hours and minutes are used, we have correctly rounded to the nearest minute, e.g.:

dt(2017, 1, 1, 11, 59, 59) -- +59 --> dt(2017, 1, 1, 12, 0, 58)
dt(2017, 1, 1, 12, 0, 1)   -- +1  --> dt(2017, 1, 1, 12, 0, 2)
dt(2017, 1, 1, 12, 0, 30)  -- +30 --> dt(2017, 1, 1, 12, 1, 0)
Parameters:cube (iris.cube.Cube) – input cube
Returns:daynight mask cube, daytime set to self.day nighttime set to self.night. The resulting cube will be the same shape as the time, y, and x coordinate, other coordinates will be ignored although they might appear as attributes on the cube as it is extracted from the first slice.
Return type:daynight_mask (iris.cube.Cube)
improver.utilities.solar.calc_solar_declination(day_of_year)[source]

Calculate the Declination for the day of the year.

Calculation equivalent to the calculation defined in NOAA Earth System Reseach Lab Low Accuracy Equations https://www.esrl.noaa.gov/gmd/grad/solcalc/sollinks.html

Parameters:day_of_year (int) – Day of the year 0 to 365, 0 = 1st January
Returns:Declination in degrees.North-South
Return type:solar_declination (float)
improver.utilities.solar.calc_solar_elevation(latitudes, longitudes, day_of_year, utc_hour)[source]

Calculate the Solar elevation.

Parameters:
  • latitudes (float or numpy.array) – A single Latitude or array of Latitudes latitudes needs to be between -90.0 and 90.0
  • longitudes (float or numpy.array) – A single Longitude or array of Longitudes longitudes needs to be between 180.0 and -180.0
  • day_of_year (int) – Day of the year 0 to 365, 0 = 1st January
  • utc_hour (float) – Hour of the day in UTC in hours
Returns:

Solar elevation in degrees for each location.
Return type:

solar_elevation (float or numpy.array)
improver.utilities.solar.calc_solar_hour_angle(longitudes, day_of_year, utc_hour)[source]

Calculate the Solar Hour angle for each element of an array of longitudes.

Calculation equivalent to the calculation defined in NOAA Earth System Reseach Lab Low Accuracy Equations https://www.esrl.noaa.gov/gmd/grad/solcalc/sollinks.html

Parameters:
  • longitudes (float or numpy.array) – A single Longitude or array of Longitudes longitudes needs to be between 180.0 and -180.0 degrees
  • day_of_year (int) – Day of the year 0 to 365, 0 = 1st January
  • utc_hour (float) – Hour of the day in UTC
Returns:

solar_hour_angle (float or numpy.array)

Hour angles in degrees East-West
improver.utilities.solar.daynight_terminator(longitudes, day_of_year, utc_hour)[source]

Calculate the Latitude values of the daynight terminator for the given longitudes.

Parameters:
  • longitudes (numpy.array) – Array of longitudes. longitudes needs to be between 180.0 and -180.0 degrees
  • day_of_year (int) – Day of the year 0 to 365, 0 = 1st January
  • utc_hour (float) – Hour of the day in UTC
Returns:

latitudes of the daynight terminator
Return type:

latitudes (numpy.array)