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Met Office UK Deterministic (UKV) Dataset

Overview

The Met Office UK Deterministic (UKV) dataset provides high-resolution weather forecasts for the UK region. This document details the dataset structure, variables, and their relevance to solar forecasting.

Dataset Structure

The dataset uses a Lambert Azimuthal Equal Area projection centered on the UK with:

  • Height: 970 pixels
  • Width: 1042 pixels
  • Grid Resolution: 2km
  • Temporal Resolution: 60 minutes
  • Forecast Range: 54 hours

Variables

Cloud Coverage Variables

These variables are critical for predicting solar irradiance attenuation:

  • high_type_cloud_area_fraction

    • Description: Fraction of high-altitude clouds
    • Units: 1 (fraction)
    • Impact: High clouds typically have less impact on solar radiation than lower clouds
    • Typical Range: 0-1

  • medium_type_cloud_area_fraction

    • Description: Fraction of medium-altitude clouds
    • Units: 1 (fraction)
    • Impact: Moderate impact on solar radiation
    • Typical Range: 0-1

  • low_type_cloud_area_fraction

    • Description: Fraction of low-altitude clouds
    • Units: 1 (fraction)
    • Impact: Most significant impact on solar radiation
    • Typical Range: 0-1

  • cloud_area_fraction

    • Description: Total cloud coverage
    • Units: 1 (fraction)
    • Impact: Overall indicator of solar radiation reduction
    • Typical Range: 0-1

Radiation Flux Variables

Direct measurements of solar radiation components:

  • surface_downwelling_shortwave_flux_in_air

    • Description: Total downward solar radiation at surface
    • Units: W m⁻²
    • Impact: Primary predictor for solar PV generation
    • Typical Range: 0-1000+ W/m²
    • Notes: Includes both direct and diffuse radiation

  • surface_downwelling_longwave_flux_in_air

    • Description: Thermal radiation from atmosphere
    • Units: W m⁻²
    • Impact: Affects panel temperature and efficiency
    • Typical Range: 200-500 W/m²

  • surface_downwelling_ultraviolet_flux_in_air

    • Description: UV component of solar radiation
    • Units: W m⁻²
    • Impact: Can affect panel degradation and specific PV technologies
    • Typical Range: 0-100 W/m²

Meteorological Variables

Environmental conditions affecting solar panel efficiency:

  • air_temperature

    • Description: Air temperature at 2m height
    • Units: K (Kelvin)
    • Impact: Panel efficiency decreases with temperature
    • Typical Range: 250-320K
    • Note: Convert to Celsius by subtracting 273.15

  • wind_speed

    • Description: Wind speed at surface level
    • Units: m s⁻¹
    • Impact: Affects panel cooling and efficiency
    • Typical Range: 0-30 m/s

  • wind_from_direction

    • Description: Wind direction at surface level
    • Units: degrees
    • Impact: Can influence panel temperature and local weather patterns
    • Range: 0-360°
    • Note: 0° is North, 90° is East

  • lwe_thickness_of_surface_snow_amount

    • Description: Snow depth in water equivalent
    • Units: m
    • Impact: Affects ground albedo and potential panel coverage
    • Typical Range: 0-1m

Coordinate System

The dataset uses Lambert Azimuthal Equal Area projection:

  • projection_x_coordinate

    • Description: X-axis grid coordinates
    • Units: m
    • Range: Covers UK extent

  • projection_y_coordinate

    • Description: Y-axis grid coordinates
    • Units: m
    • Range: Covers UK extent

Time Variables

Temporal information for forecasts:

  • forecast_period

    • Description: Time offset from reference
    • Type: timedelta64[ns]

  • forecast_reference_time

    • Description: Start time of forecast
    • Type: datetime64[ns]

  • time

    • Description: Valid time for forecast step
    • Type: datetime64[ns]

Usage in Solar Forecasting

Primary Predictors

  1. surface_downwelling_shortwave_flux_in_air: Direct indicator of solar energy availability
  2. cloud_area_fraction variables: Key for radiation attenuation
  3. air_temperature: Critical for panel efficiency calculations

Secondary Factors

  1. wind_speed: Panel cooling effects
  2. snow_amount: Ground reflectance and coverage
  3. UV flux: Specific panel technology considerations

Data Quality Considerations

  • Least significant digit information provided for each variable
  • Grid mapping information available in lambert_azimuthal_equal_area variable
  • All variables follow CF-1.7 conventions

Data Availability and Format

This dataset is hosted on Hugging Face at openclimatefix/met-office-uk-deterministic-solar.

File Format

  • Files are stored in .zarr.zip format
  • Each file represents a specific timestamp (e.g., 2023-01-16-00.zarr.zip)
  • Zarr format is optimized for:
    • Cloud storage access
    • Parallel I/O operations
    • Efficient chunked access to large arrays
    • Integration with data science tools (xarray, pandas, dask)

License

British Crown copyright 2022-2024, the Met Office, licensed under CC BY-SA.

Citation

Met Office UK Deterministic (UKV)2km on a 2-year rolling archive accessed from AWS Registry.