Climate Forecast System (CFS Radiative Fluxes)

Aerodynamic conductance measures the efficiency of turbulent exchange of heat and moisture between the surface and atmosphere. It depends on wind speed, stability, and surface roughness and is used in surface energy balance and evapotranspiration calculations.

• Units: m/s.
• Higher values indicate stronger surface-atmosphere coupling and faster exchange.

Surface albedo is the fraction of incoming shortwave radiation reflected by the surface. Higher albedo means less solar energy absorbed and a cooler surface.

• Units: percent.
• Important for snow and ice feedbacks and surface energy balance.

Clear‑sky UV‑B downward flux is UV‑B radiation at the surface without cloud effects. It is used for UV exposure estimates.

• Units: W/m².

Plant canopy surface water is liquid water intercepted by vegetation. It represents interception storage and evaporation potential.

• Units: kg/m^2.

Convective precipitation rate is the intensity of precipitation produced by convection. It highlights storm‑driven rainfall rates.

• Units: kg/m²/s.
• Accumulations represent water-equivalent depth over the output interval; rates describe intensity.

Categorical indicator of rain occurrence at the surface during the output period. Useful as a yes/no mask for rain.

• Units: flag.
• Use with accumulation or rate fields for intensity.

Downward longwave (thermal) flux represents incoming energy at the surface. Clear-sky versions remove cloud effects to isolate the atmospheric background.

• Units: W/m².
• Shortwave affects surface heating; longwave affects radiative cooling.

Clear‑sky downward shortwave flux is broadband solar energy at the surface without cloud effects.

• Units: W m-2.

Upward longwave (thermal) flux represents outgoing energy at the surface. Clear-sky versions remove cloud effects to isolate the atmospheric background.

• Units: W/m².
• Shortwave affects surface heating; longwave affects radiative cooling.

Upward shortwave (solar) flux represents outgoing energy at the surface. Clear-sky versions remove cloud effects to isolate the atmospheric background.

• Units: W/m².

Cloud work function is an energy measure used by convection schemes to diagnose convective potential. Larger values generally indicate a more favorable environment for deep convection.

• Units: J/kg.
• Cloud fraction influences surface radiation and temperature.

Downward longwave (thermal) flux represents incoming energy at the surface. It is a key driver of surface heating and cooling.

• Units: W/m^2.
• Shortwave affects surface heating; longwave affects radiative cooling.

Downward radiative flux represents incoming energy at the surface. It is a key driver of surface heating and cooling.

• Units: W/m^2.
• Shortwave affects surface heating; longwave affects radiative cooling.

Downward UV‑B solar flux is the UV‑B portion of incoming sunlight at the surface. It is used for UV exposure and health guidance.

• Units: W/m².

Direct evaporation from bare soil is the latent heat flux associated with moisture evaporating from exposed soil surfaces.

• Units: W/m^2.
• Soil state affects evapotranspiration and boundary-layer moisture.

Canopy evaporation represents water stored on vegetation surfaces that evaporates back to the atmosphere. It affects rainfall interception losses.

• Units: kg/m².

Friction velocity (u*) is a measure of near‑surface shear stress. It is commonly used in turbulence, dust, and air‑sea exchange calculations.

• Units: m/s.

Ground heat flux is the conductive heat exchange between the surface and the subsurface. It is a key term in the surface energy balance.

• Units: W/m^2.

Geopotential height is the altitude of a pressure surface in the atmosphere. It is the primary field for identifying ridges, troughs, and large‑scale flow patterns.

• Units: gpm.

Boundary layer height marks the depth of the turbulent surface-influenced layer. It affects mixing, dispersion, and surface fluxes.

• Units: m.

Ice cover is the proportion of the grid cell covered by ice. It is used as a surface-state mask for sea ice and related cryosphere diagnostics.

• Units: Proportion.

Ice thickness is the physical thickness of sea or lake ice. It is important for marine navigation and heat exchange.

• Units: m.

Land cover is a land/sea mask where 0 indicates sea and 1 indicates land. It is used to separate land and ocean surface processes.

• Units: Proportion.

Latent heat net flux represents energy exchange due to evaporation/condensation at the surface. It links moisture and energy budgets.

• Units: W/m^2.

Near‑infrared beam downward solar flux is the direct (beam) NIR component reaching the surface. It represents unscattered sunlight.

• Units: W/m².

Near‑infrared diffuse downward solar flux is the scattered NIR component reaching the surface. It dominates under hazy or cloudy skies.

• Units: W/m².

Potential evaporation rate is the potential latent heat flux for evaporation under an assumed unlimited water supply.

• Units: W/m^2.

Precipitation rate is the total intensity of precipitation over the period. It combines convective and stratiform contributions.

• Units: kg/(m^2 s).
• Accumulations represent water-equivalent depth over the output interval; rates describe intensity.

Pressure is the atmospheric pressure at the specified level. It is a fundamental mass-field variable for dynamics and thermodynamics.

• Units: Pa.

Precipitable water is the total column water vapor from the surface to the top of the atmosphere. It is a key moisture indicator.

• Units: kg/m^2.

Maximum specific humidity is the peak water‑vapor mixing ratio during the period. It highlights the moistest conditions.

• Units: kg/kg.
• Higher values indicate more atmospheric moisture and greater cloud or precip potential.

Minimum specific humidity is the lowest water‑vapor mixing ratio during the period. It highlights the driest conditions.

• Units: kg/kg.
• Higher values indicate more atmospheric moisture and greater cloud or precip potential.

Snow sublimation is the loss of snow directly to water vapor. It reduces snowpack without melting and can be important in dry, windy conditions.

• Units: kg/m².
• Accumulations represent water-equivalent depth over the output interval; rates describe intensity.

Surface roughness length is the effective height of surface obstacles that control drag. It strongly influences near-surface wind, turbulence, and exchange fluxes.

• Units: m.

Surface exchange coefficient is the bulk transfer coefficient used to compute turbulent heat and moisture fluxes. It depends on stability and roughness.

• Units: dimensionless.

Sensible heat net flux is turbulent heat exchange driven by temperature differences. It affects near‑surface temperature and stability.

• Units: W/m^2.

Surface slope type is the land-surface slope classification used by the model for runoff and drainage behavior.

• Units: Index.
• Soil state affects evapotranspiration and boundary-layer moisture.

Snow depth is the physical thickness of the snowpack. It is distinct from snow water equivalent, which measures water content.

• Units: m.

Snow phase change heat flux is the energy used for melting or freezing snow. It links radiation and snowpack evolution.

• Units: W m-2.
• Accumulations represent water-equivalent depth over the output interval; rates describe intensity.

Snow cover is the fraction of the grid cell covered by snow. It helps interpret albedo, runoff timing, and surface energy balance.

• Units: percent.

Liquid volumetric soil moisture (non-frozen) is the liquid portion of soil water expressed as a proportion of soil volume, excluding soil ice.

• Units: Proportion.
• Soil state affects evapotranspiration and boundary-layer moisture.

Soil moisture content is the amount of water stored in the soil layer or column represented by the product.

• Units: kg/m^2.
• Soil state affects evapotranspiration and boundary-layer moisture.

Volumetric soil moisture is the fraction of soil volume occupied by water. It is commonly used in hydrology and drought monitoring.

• Units: Fraction.
• Soil state affects evapotranspiration and boundary-layer moisture.

Soil type class used by the land-surface model. It controls infiltration, drainage, and heat/moisture storage, and strongly affects runoff and evapotranspiration.

• Units: code.

Specific humidity is the mass of water vapor per mass of air at the specified level. It is central to moisture transport.

• Units: kg/kg.
• Higher values indicate more atmospheric moisture and greater cloud or precip potential.

Snowfall water equivalent is the liquid water content of new snowfall during the period. It is used for snow totals and hydrology.

• Units: kg/m².
• Accumulations represent water-equivalent depth over the output interval; rates describe intensity.

Storm surface runoff represents overland flow generated by rainfall or snowmelt. It responds quickly to heavy precipitation.

• Units: kg/m^2.

Total cloud cover is the fraction of the grid cell covered by clouds at any level. It influences radiation, temperature, and visibility.

• Units: percent.
• Cloud fraction influences surface radiation and temperature.

Maximum temperature is the highest temperature reached during the output period. It is commonly used for heat stress and daily extremes.

• Units: K.

Minimum temperature is the lowest temperature reached during the output period. It is commonly used for frost and cold-stress assessment.

• Units: K.

Air temperature is the thermal state of the atmosphere at the specified level. It influences density, stability, and energy exchange.

• Units: K.

Transpiration rate is the flux of water vapor from vegetation to the atmosphere. It links plant activity to surface energy balance and humidity.

• Units: kg/m²/s.

Zonal gravity wave stress is the east-west component of momentum flux from unresolved gravity waves. It affects large-scale circulation and jet dynamics.

• Units: N/m².

Momentum flux, u‑component is the east‑west surface stress exerted by the atmosphere. It drives boundary-layer dynamics.

• Units: N/m².

U‑component of wind is the east‑west component of the horizontal wind. Combine with v for speed and direction.

• Units: m/s.
• Combine u and v components to compute speed and direction.

Upward longwave (thermal) flux represents outgoing energy at the surface. It is a key driver of surface heating and cooling.

• Units: W/m^2.
• Shortwave affects surface heating; longwave affects radiative cooling.

Upward radiative flux represents outgoing energy at the surface. It is a key driver of surface heating and cooling.

• Units: W/m^2.
• Shortwave affects surface heating; longwave affects radiative cooling.

Meridional gravity wave stress is the north-south component of momentum flux from unresolved gravity waves. It affects large-scale circulation and jet dynamics.

• Units: N/m².

Visible beam downward solar flux is the direct visible sunlight at the surface. It is important for illumination and solar energy.

• Units: W m-2.

Visible diffuse downward solar flux is the scattered visible light at the surface. It increases under clouds or aerosol loading.

• Units: W m-2.

Vegetation fraction is the portion of the grid cell covered by vegetation. It affects albedo, roughness, and evapotranspiration.

• Units: percent.

Momentum flux, v‑component is the north‑south surface stress exerted by the atmosphere. It drives boundary-layer dynamics.

• Units: N/m².

V‑component of wind is the north‑south component of the horizontal wind. Combine with u for speed and direction.

• Units: m/s.
• Combine u and v components to compute speed and direction.

Categorical land-use/vegetation class. It is used to set roughness, albedo, canopy properties, and other surface-exchange parameters.

• Units: code.

Water runoff is the amount of water leaving the land surface as runoff during the period. It is useful for hydrology, flooding, and land-surface diagnostics.

• Units: kg/m^2.

Snow water equivalent (SWE) is the total liquid water stored in the snowpack. It integrates depth and density of existing snow.

• Units: kg/m^2.
• Accumulations represent water-equivalent depth over the output interval; rates describe intensity.