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utils

buck_vapor_pressure(temperature_c: xr.Dataset) -> xr.Dataset

Approximate vapor pressure of water.

https://en.wikipedia.org/wiki/Arden_Buck_equation https://journals.ametsoc.org/view/journals/apme/20/12/1520-0450_1981_020_1527_nefcvp_2_0_co_2.xml

Parameters

temperature_c Temperature in Celsius

Returns

xr.Dataset Vapor pressure in hPa

Source code in src/climate_data/generate/utils.py 
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def buck_vapor_pressure(temperature_c: xr.Dataset) -> xr.Dataset:
    """Approximate vapor pressure of water.

    https://en.wikipedia.org/wiki/Arden_Buck_equation
    https://journals.ametsoc.org/view/journals/apme/20/12/1520-0450_1981_020_1527_nefcvp_2_0_co_2.xml

    Parameters
    ----------
    temperature_c
        Temperature in Celsius

    Returns
    -------
    xr.Dataset
        Vapor pressure in hPa
    """
    over_water = 6.1121 * np.exp(
        (18.678 - temperature_c / 234.5) * (temperature_c / (257.14 + temperature_c))
    )
    over_ice = 6.1115 * np.exp(
        (23.036 - temperature_c / 333.7) * (temperature_c / (279.82 + temperature_c))
    )
    vp = xr.where(temperature_c > 0, over_water, over_ice)  # type: ignore[no-untyped-call]
    return vp  # type: ignore[no-any-return]

identity(ds: xr.Dataset) -> xr.Dataset

Identity transformation

Source code in src/climate_data/generate/utils.py 
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def identity(ds: xr.Dataset) -> xr.Dataset:
    """Identity transformation"""
    return ds

interpolate_to_target_latlon(ds: xr.Dataset, method: str = 'nearest', target_lon: xr.DataArray = cdc.TARGET_LONGITUDE, target_lat: xr.DataArray = cdc.TARGET_LATITUDE) -> xr.Dataset

Interpolate a dataset to a target latitude and longitude grid.

Parameters

ds Dataset to interpolate method Interpolation method target_lon Target longitude grid target_lat Target latitude grid

Returns

xr.Dataset Interpolated dataset

Source code in src/climate_data/generate/utils.py 
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def interpolate_to_target_latlon(
    ds: xr.Dataset,
    method: str = "nearest",
    target_lon: xr.DataArray = cdc.TARGET_LONGITUDE,
    target_lat: xr.DataArray = cdc.TARGET_LATITUDE,
) -> xr.Dataset:
    """Interpolate a dataset to a target latitude and longitude grid.

    Parameters
    ----------
    ds
        Dataset to interpolate
    method
        Interpolation method
    target_lon
        Target longitude grid
    target_lat
        Target latitude grid

    Returns
    -------
    xr.Dataset
        Interpolated dataset
    """
    return (
        ds.interp(longitude=target_lon, latitude=target_lat, method=method)  # type: ignore[arg-type]
        .interpolate_na(dim="longitude", method="nearest", fill_value="extrapolate")
        .sortby("latitude")
        .interpolate_na(dim="latitude", method="nearest", fill_value="extrapolate")
        .sortby("latitude", ascending=False)
    )

kelvin_to_celsius(temperature_k: xr.Dataset) -> xr.Dataset

Convert temperature from Kelvin to Celsius

Parameters

temperature_k Temperature in Kelvin

Returns

xr.Dataset Temperature in Celsius

Source code in src/climate_data/generate/utils.py 
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def kelvin_to_celsius(temperature_k: xr.Dataset) -> xr.Dataset:
    """Convert temperature from Kelvin to Celsius

    Parameters
    ----------
    temperature_k
        Temperature in Kelvin

    Returns
    -------
    xr.Dataset
        Temperature in Celsius
    """
    return temperature_k - 273.15

meter_to_millimeter(rainfall_m: xr.Dataset) -> xr.Dataset

Convert rainfall from meters to millimeters

Parameters

rainfall_m Rainfall in meters

Returns

xr.Dataset Rainfall in millimeters

Source code in src/climate_data/generate/utils.py 
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def meter_to_millimeter(rainfall_m: xr.Dataset) -> xr.Dataset:
    """Convert rainfall from meters to millimeters

    Parameters
    ----------
    rainfall_m
        Rainfall in meters

    Returns
    -------
    xr.Dataset
        Rainfall in millimeters
    """
    return 1000 * rainfall_m

precipitation_flux_to_rainfall(precipitation_flux: xr.Dataset) -> xr.Dataset

Convert precipitation flux to rainfall

Parameters

precipitation_flux Precipitation flux in kg m-2 s-1

Returns

xr.Dataset Rainfall in mm/day

Source code in src/climate_data/generate/utils.py 
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def precipitation_flux_to_rainfall(precipitation_flux: xr.Dataset) -> xr.Dataset:
    """Convert precipitation flux to rainfall

    Parameters
    ----------
    precipitation_flux
        Precipitation flux in kg m-2 s-1

    Returns
    -------
    xr.Dataset
        Rainfall in mm/day
    """
    seconds_per_day = 86400
    mm_per_kg_m2 = 1
    return seconds_per_day * mm_per_kg_m2 * precipitation_flux

rh_percent(temperature_c: xr.Dataset, dewpoint_temperature_c: xr.Dataset) -> xr.Dataset

Calculate relative humidity from temperature and dewpoint temperature.

Parameters

temperature_c Temperature in Celsius dewpoint_temperature_c Dewpoint temperature in Celsius

Returns

xr.Dataset Relative humidity as a percentage

Source code in src/climate_data/generate/utils.py 
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def rh_percent(
    temperature_c: xr.Dataset, dewpoint_temperature_c: xr.Dataset
) -> xr.Dataset:
    """Calculate relative humidity from temperature and dewpoint temperature.

    Parameters
    ----------
    temperature_c
        Temperature in Celsius
    dewpoint_temperature_c
        Dewpoint temperature in Celsius

    Returns
    -------
    xr.Dataset
        Relative humidity as a percentage
    """
    # saturation vapour pressure
    svp = buck_vapor_pressure(temperature_c)
    # actual vapour pressure
    vp = buck_vapor_pressure(dewpoint_temperature_c)
    return 100 * vp / svp

scale_wind_speed_height(wind_speed_10m: xr.Dataset) -> xr.Dataset

Scaling wind speed from a height of 10 meters to a height of 2 meters

Reference: Bröde et al. (2012) https://doi.org/10.1007/s00484-011-0454-1

Parameters

wind_speed_10m The 10m wind speed [m/s]. May be signed (ie a velocity component)

Returns

xr.DataSet The 2m wind speed [m/s]. May be signed (ie a velocity component)

Source code in src/climate_data/generate/utils.py 
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def scale_wind_speed_height(wind_speed_10m: xr.Dataset) -> xr.Dataset:
    """Scaling wind speed from a height of 10 meters to a height of 2 meters

    Reference: Bröde et al. (2012)
    https://doi.org/10.1007/s00484-011-0454-1

    Parameters
    ----------
    wind_speed_10m
        The 10m wind speed [m/s]. May be signed (ie a velocity component)

    Returns
    -------
    xr.DataSet
        The 2m wind speed [m/s]. May be signed (ie a velocity component)
    """
    scale_factor = np.log10(2 / 0.01) / np.log10(10 / 0.01)
    return scale_factor * wind_speed_10m  # type: ignore[no-any-return]

vector_magnitude(x: xr.Dataset, y: xr.Dataset) -> xr.Dataset

Calculate the magnitude of a vector.

Source code in src/climate_data/generate/utils.py 
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def vector_magnitude(x: xr.Dataset, y: xr.Dataset) -> xr.Dataset:
    """Calculate the magnitude of a vector."""
    return np.sqrt(x**2 + y**2)  # type: ignore[return-value]