WRF Variables¶

Coordinate types¶

Variables are stored with coordinates appropriate to their type:

Surface variables: (time, height_Xm, y, x) -- named height coordinate (e.g. height_0m, height_2m, height_10m)
Level-interpolated variables: (time, height, y, x) or (time, pressure, y, x)
Soil variables: (time, depth, y, x)

When a surface variable shares a cfdb name with a 3D level-interpolated variable (e.g., T2 and T both map to air_temp), the surface variant is suffixed with its height (e.g., air_temp_2m) to avoid conflicts.

Surface variables¶

Fixed height above ground, stored as (time, height_Xm, y, x):

Key	cfdb Name	Height	Source Vars	Transform
`T2`	`air_temp`	2 m	T2	direct
`PSFC`	`surface_pressure`	0 m	PSFC	direct
`Q2`	`mixing_ratio`	2 m	Q2	direct
`Q2_SH`	`specific_humidity`	2 m	Q2	mixing ratio to SH
`RH2`	`relative_humidity`	2 m	T2, Q2, PSFC	Bolton (1980)
`TD2`	`dew_temp`	2 m	Q2, PSFC	inverse Bolton
`RAIN`	`precip`	0 m	RAINNC, RAINC	accumulation increment
`WIND10`	`wind_speed`	10 m	U10, V10	wind rotation
`WIND_DIR10`	`wind_direction`	10 m	U10, V10	wind rotation
`U10`	`u_wind`	10 m	U10, V10	wind rotation
`V10`	`v_wind`	10 m	U10, V10	wind rotation
`TSK`	`soil_temp`	0 m	TSK	direct
`SWDOWN`	`shortwave_radiation`	0 m	SWDOWN	direct
`GLW`	`longwave_radiation`	0 m	GLW	direct
`SNOWH`	`snow_depth`	0 m	SNOWH	direct
`HGT`	`terrain_height`	0 m	HGT	direct
`SLP`	`mslp`	0 m	PSFC, T2, HGT	hypsometric reduction
`XLAND`	`land_sea_mask`	0 m	XLAND	1/2 to 1/0 conversion
`SEAICE_VAR`	`sea_ice`	0 m	SEAICE	direct
`SST_VAR`	`sea_surface_temp`	0 m	SST	direct
`SNOW_VAR`	`snow_water_equiv`	0 m	SNOW	direct

3D level-interpolated variables¶

Interpolated to user-specified target_levels on height or pressure coordinate:

Key	cfdb Name	Source Vars	Transform
`T`	`air_temp`	T, P, PB, PH, PHB	potential to actual temperature
`WIND`	`wind_speed`	U, V, PH, PHB	unstagger + rotation
`WIND_DIR`	`wind_direction`	U, V, PH, PHB	unstagger + rotation
`U`	`u_wind`	U, V, PH, PHB	unstagger + rotation
`V`	`v_wind`	U, V, PH, PHB	unstagger + rotation
`QVAPOR`	`mixing_ratio`	QVAPOR, PH, PHB	level interpolation
`Q_SH`	`specific_humidity`	QVAPOR, PH, PHB	mixing ratio to specific humidity
`RH`	`relative_humidity`	T, P, PB, QVAPOR, PH, PHB	Bolton (1980)
`TD`	`dew_temp`	QVAPOR, P, PB, PH, PHB	inverse Bolton
`GHT`	`geopotential_height`	PH, PHB	unstagger z, /9.81
`W`	`vertical_velocity`	W, PH, PHB	unstagger z

Soil variables¶

Stored on a depth coordinate derived from WRF's DZS (soil layer thicknesses):

Key	cfdb Name	Source Vars	Transform
`SMOIS`	`soil_moisture`	SMOIS	direct (per layer)
`TSLB`	`soil_layer_temp`	TSLB	direct (per layer)