Rapid Refresh Forecast System Pressure Levels

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

• Units: 1/s.

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.

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.

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.

Graupel accumulation represents the water-equivalent amount of graupel in the column. It helps diagnose convective microphysics.

• Units: kg/kg.

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.

Ice water mixing ratio is the mass of ice-phase hydrometeors per mass of air. It indicates ice cloud content.

• Units: kg/kg.

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

• Units: kg/(m^2 s).

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.

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

• Units: K.

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.

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.

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.

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.

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.

Stream function is a flow potential whose contours follow non-divergent flow. It is used to visualize rotational components of the wind field.

• Units: m2 s-1.

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

• Units: K.

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.

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.