NAM CONUS Nest

Best (4-layer) lifted index uses parcels from the lowest four model layers to assess stability at 500 hPa. More negative values indicate greater instability.

• Units: K.
• Often used alongside CAPE and CIN in convective forecasting.

Absolute vorticity combines relative vorticity and planetary vorticity from Earth's rotation. It highlights rotation and dynamical forcing in the flow.

• Units: 1/s.

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.

Accumulated precipitation represents the total water-equivalent amount of rain and snow during the output period. It is a primary field for hydrologic impacts and event totals.

• Units: kg/m^2.
• Use with the model time interval to interpret totals and compare to gauges.

Baseflow‑groundwater runoff represents subsurface drainage from soil into streams. It is a slower component of runoff.

• Units: kg/m^2.

Blackadar's mixing length scale is the turbulence length scale used by boundary-layer physics to limit the size of turbulent eddies. It directly affects the exchange coefficients that control momentum, heat, and moisture mixing near the surface and through the planetary boundary layer.

• Units: m.
• This is mainly a model-physics diagnostic rather than a directly observed atmospheric variable.

Brightness temperature is the blackbody temperature that would emit the observed radiance in a spectral channel. It is used for satellite and cloud diagnostics.

• Units: K.

Convective Available Potential Energy (CAPE) quantifies buoyant energy available to rising air parcels. Larger values generally imply stronger potential updrafts and greater convective intensity.

• Units: J/kg.
• Often used with CIN and lifting mechanisms to assess thunderstorm potential.

Cloud condensation represents the conversion of water vapor to cloud water in the model microphysics. It helps diagnose cloud formation and latent heating.

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

Drag coefficient represents the aerodynamic resistance between the surface and the atmosphere. It controls surface stress and is used in momentum and heat flux calculations.

• Units: dimensionless.

Categorical indicator of freezing rain occurrence at the surface during the output period.

• Units: flag.
• Useful as a mask for icing or glaze hazards.

Cloud ice is the ice-phase condensate carried in cloud, as distinct from falling snow or graupel. In NAM it is mainly used for cloud microphysics, icing diagnostics, and simulated satellite or radiation calculations.

• Units: kg/m^2.
• Compare it with cloud water, snow, and rime factor to distinguish suspended ice from precipitating frozen hydrometeors.

Categorical indicator of ice pellet (sleet) occurrence at the surface during the output period.

• Units: flag.
• Use with precipitation fields to gauge intensity.

Convective Inhibition (CIN) measures the energy barrier that must be overcome to initiate convection. More negative values indicate a stronger cap that can suppress storms.

• Units: J/kg.
• When CIN is weak and CAPE is high, convection is more likely.

Cloud water mixing ratio is the mass of liquid cloud droplets per mass of air. It describes in‑cloud liquid water content.

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

Cloud liquid water mixing ratio emphasizes the liquid phase of cloud water. It is used in microphysics and fog diagnostics.

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

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

• Units: kg/m^2.

Percent frozen precipitation indicates the fraction of total precipitation that is falling in frozen form. It helps distinguish mixed-phase and winter precipitation impacts.

• Units: percent.
• Higher values indicate a larger frozen contribution to the total precipitation.

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.

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

• Units: W m-2.

Categorical indicator of snow occurrence at the surface during the output period.

• Units: flag.
• Use alongside snowfall/snow-water-equivalent fields.

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.

Dew point temperature is the temperature at which the air becomes saturated. It is a direct measure of moisture content.

• Units: K.
• When dew point is close to air temperature, fog or low cloud potential increases.

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.

Geometric vertical velocity (dz/dt) is the vertical speed of air in height coordinates. Positive values indicate rising motion and negative values sinking motion.

• Units: m/s.

Evaporation is the amount of water transferred back to the atmosphere over the period carried by the GRIB message. It is a core land-atmosphere flux used in hydrology, soil-moisture budgeting, and surface energy-balance work.

• Units: kg/m^2.
• For accumulated fields, interpret it over the forecast interval in the message rather than as an instantaneous rate.

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.

Wind gust is the peak short-duration wind speed. It captures brief, hazardous bursts that can exceed sustained winds.

• Units: m/s.

High cloud cover is the fraction of the grid cell covered by clouds in the upper troposphere. It affects longwave radiation and aviation.

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

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.

Haines Index combines atmospheric stability and dryness to estimate the potential for large fire growth. Higher values indicate a more favorable environment for extreme fire behavior.

• Units: Numeric.
• Typically used in wildfire forecasting and risk monitoring.

Storm-relative helicity measures the potential for streamwise vorticity to be ingested by a storm updraft. Higher values suggest a greater likelihood of rotating updrafts.

• Units: m^2/s^2.
• Commonly evaluated in the lowest 1 to 3 km layer.

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.

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.

Low cloud cover is the fraction of the grid cell covered by low clouds. It strongly affects visibility, fog potential, and surface temperatures.

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

Lifted Index compares a lifted parcel's temperature to the environment at 500 hPa. More negative values indicate greater instability and thunderstorm potential.

• Units: K.
• Values near zero indicate neutral stability.

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

• Units: W/m^2.

Large-scale condensate heating rate is the temperature tendency caused by resolved condensation and deposition outside the deep convection parameterization. It isolates diabatic heating tied to stratiform cloud and precipitation processes.

• Units: K/s.
• Use it with CNVHR, SWHR, and LWHR when you need to partition total diabatic heating by physical source.

Lightning is a dimensionless model diagnostic in these NOAA mesoscale inventories. Higher values indicate greater modeled lightning or convective electrical activity.

• Units: non-dim.

Long-wave radiative heating rate is the temperature tendency caused by thermal infrared radiation. Negative values commonly indicate radiative cooling, while positive values indicate net long-wave warming at that level.

• Units: K/s.
• Pair it with SWHR to separate shortwave and longwave radiative tendencies.

Hourly maximum downward vertical velocity in the lowest 400 hPa highlights the strongest subsidence within the lower troposphere during the hour.

• Units: m/s.

Hourly maximum simulated reflectivity at 1 km AGL captures the strongest modeled reflectivity near the surface. It is used to identify peak convective intensity and heavy precipitation cores.

• Units: dBZ.

Maximum relative humidity is the highest RH reached during the period. It can indicate peak cloud or fog potential.

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

Hourly maximum upward vertical velocity in the lowest 400 hPa highlights the strongest updrafts within the lower troposphere during the hour.

• Units: m/s.

Maximum u‑component of wind is the strongest east‑west flow during the period. It helps identify peak wind directions.

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

Maximum v‑component of wind is the strongest north‑south flow during the period.

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

Mid-level cloud cover is the fraction of the grid cell covered by clouds in the middle troposphere. It influences both shortwave and longwave radiation.

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

Moisture convergence is the horizontal convergence of water vapor transport. Areas of convergence favor rising motion and precipitation development.

• Units: kg/(m^2 s).

Horizontal moisture divergence measures the divergence of the horizontal moisture field in model tendency units. It is used to diagnose where the resolved flow is exporting moisture or concentrating it into convergence zones that favor cloud and precipitation development.

• Units: kg/kg/s.
• Negative values indicate moisture convergence; positive values indicate moisture divergence.

Minimum relative humidity is the lowest RH reached during the period. It is used in fire‑weather and drying assessments.

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

Hourly minimum updraft helicity is the lowest helicity value during the hour. It provides a lower bound on rotating updraft potential.

• Units: m2/s2.

Mean sea level pressure (ETA reduction) is MSLP computed using the ETA model reduction method. It is used for synoptic analysis.

• Units: Pa.

Moisture availability represents how much moisture is available at the surface for evaporation. It is used in land-surface and fire-weather diagnostics.

• Units: percent.

Maximum snow albedo is the highest reflectivity of the snow surface during the period. Higher values indicate fresher, brighter snow.

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

Hourly maximum updraft helicity (2–5 km AGL) highlights the strongest rotating updrafts during the hour.

• Units: m2/s2.

Convective precipitation is water-equivalent accumulation produced by convective processes during the output period. It highlights thunderstorm-driven rainfall.

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

Potential evaporation is the amount of water that could evaporate if sufficient moisture were available. It reflects atmospheric demand.

• Units: kg/m^2.

Parcel lifted index compares a lifted parcel temperature to the environment at 500 hPa. More negative values indicate greater instability and thunderstorm potential.

• Units: K.
• More negative values indicate greater instability.

Pressure of the level from which the parcel was lifted indicates the parcel source level used for stability indices. It helps interpret lifted index and CAPE products.

• Units: Pa.

Soil porosity is the fraction of soil volume that is pore space. It governs storage and drainage capacity.

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

Potential temperature is the temperature a parcel would have if brought dry‑adiabatically to a reference pressure. It is used for stability.

• Units: K.

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.

Pressure reduced to mean sea level is MSLP computed from surface pressure and temperature. It is used to locate highs and lows.

• 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.

Humidity parameter in canopy conductance is the dimensionless stress function that applies the effect of air humidity to vegetation canopy conductance. It is used in land-surface evapotranspiration calculations to reduce or enhance stomatal opening under dry or humid air.

• Units: Fraction.
• Interpret it as one factor in the canopy conductance formulation alongside the solar, temperature, and soil-moisture terms.

Solar parameter in canopy conductance is the dimensionless radiation response term in the canopy conductance formulation. It modulates stomatal conductance and transpiration according to available solar energy.

• Units: Fraction.
• Use it with RCT, RCQ, and RCSOL to see which environmental factor is limiting canopy conductance.

Soil moisture parameter in canopy conductance is the dimensionless soil-water stress term used in the canopy conductance formulation. It reduces canopy conductance and transpiration when root-zone moisture is limiting.

• Units: Fraction.
• Use it with RCS, RCT, and RCQ to identify whether evapotranspiration is being constrained most strongly by soil moisture, light, temperature, or humidity.

Temperature parameter in canopy conductance is the dimensionless temperature response term in the canopy conductance formulation. It represents how close conditions are to the vegetation's preferred temperature range for transpiration.

• Units: Fraction.
• Use it with RCS, RCQ, and RCSOL to separate the temperature effect from other canopy-conductance controls.

Composite reflectivity is the maximum reflectivity in the column. It is a standard radar‑style field for identifying convective cores and precipitation intensity.

• Units: dBZ.

Reflectivity is a radar‑style measure of hydrometeor concentration at a given level. Higher values generally correspond to heavier precipitation.

• Units: dBZ.

Echo top height is the altitude of the highest reflectivity in the column. It is a proxy for storm depth and convective vigor.

• Units: m.

Relative humidity describes how close the air is to saturation at the specified level. High values favor cloud formation.

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

Rime factor is a dimensionless microphysics diagnostic that describes the degree of riming on frozen hydrometeors. It is useful for distinguishing lightly rimed ice from graupel-like or heavily rimed particles in winter-weather and icing analysis.

• Units: non-dim.
• Interpret it with cloud ice, snow, and rain fields when diagnosing mixed-phase precipitation structure.

Number of soil layers is a static model metadata field describing the soil discretization.

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

Minimum stomatal resistance is a vegetation parameter controlling transpiration efficiency. Lower values allow stronger evapotranspiration under favorable conditions.

• Units: s m-1.

Rain water mixing ratio is the mass of rainwater per mass of air. It describes rain content within the column.

• Units: kg/kg.
• 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.

Direct evaporation cease (soil moisture) is the threshold below which bare-soil evaporation is shut off in the land-surface model.

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

Transpiration stress-onset (soil moisture) is the threshold at which plants begin to experience moisture stress in the land-surface model.

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

Snow-free albedo is the background land-surface reflectivity with snow cover removed. It is used by the radiation scheme to represent how much incoming solar radiation the underlying surface would reflect in the absence of snow.

• Units: %.
• Use it with snow cover or snow albedo fields when you need to separate the land-surface background from the current snowpack effect.

Snow mixing ratio is the mass of snow particles per mass of air. It describes suspended snow content relevant to microphysics and precipitation.

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

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 melt represents water released by melting snowpack during the period. It is a key driver of runoff and flooding.

• Units: kg/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.