NARCCAP data is organized into groups based on its spatial and temporal structure: 2-D vs 3-D, daily vs 3-hourly, etc. The groups are listed in the table below. Each variable name links to the corresponding description in the CF Standard Name Table.
| Table 1: Daily fields (2-D) | ||||
|---|---|---|---|---|
| Var. | Long Name | Units | Notes | |
| sic | Daily average Sea-ice Fraction | 1 | ||
| spdmax | Maximum Daily 10-Meter Wind Speed | m s-1 | ||
| tasmax | Maximum Daily Surface Air Temperature | K | ||
| tasmin | Minimum Daily Surface Air Temperature | K | ||
| Table 2: Primary 3-hourly surface fields (2-D) | ||||
| Var. | Long Name | Units | Notes | |
| huss | Surface Specific Humidity | kg kg-1 | instantaneous | |
| pr | Precipitation | kg m-2 s-1 | average | |
| ps | Surface Pressure | Pa | instantaneous | |
| rsds | Surface Downwelling Shortwave Radiation | W m-2 | average, positive down | |
| tas | Surface Air Temperature | K | instantaneous | |
| uas | Zonal Surface Wind Speed | m s-1 | instantaneous, positive east | |
| vas | Meridional Surface Wind Speed | m s-1 | instantaneous, positive north | |
| Table 3: Additional 3-hourly fields (2-D) | ||||
| Var. | Long Name | Units | Notes | |
| clt | Total Cloud Fraction | 1 | average | |
| evps | Surface Evaporation of Condensed Water | kg m-2 s-1 | average | |
| hfls | Surface Latent Heat Flux | W m-2 | average, positive up | |
| hfss | Surface Sensible Heat Flux | W m-2 | average, positive up | |
| mrfso | Soil Frozen Water Content | kg m-2 | instantaneous | |
| mrro | Surface and Subsurface Runoff | kg m-2 s-1 | average | |
| mrros | Surface Runoff | kg m-2 s-1 | average | |
| mrso | Total Soil Moisture Content | kg m-2 | instantaneous | |
| prc | Convective Precipitation | kg m-2 s-1 | average | |
| prw | Precipitable Water | kg m-2 | instantaneous | |
| psl | Sea Level Pressure | Pa | instantaneous | |
| rlds | Surface Downwelling Longwave Radiation | W m-2 | average, positive down | |
| rlus | Surface Upwelling Longwave Radiation | W m-2 | average, positive up | |
| rlut | Outgoing Longwave Radiation | W m-2 | average, positive up | |
| rsdt | TOA Incident Shortwave Radiation | W m-2 | average, positive down | |
| rsus | Surface Upwelling Shortwave Radiation | W m-2 | average, positive up | |
| rsut | TOA Reflected Shortwave Radiation | W m-2 | average, positive up | |
| snd | Snow Depth | m | instantaneous | |
| snm | Snow Melt | kg m-2 s-1 | average | |
| tauu | Surface Downward Flux of Eastward Momentum | Pa | average, positive down | |
| tauv | Surface Downward Flux of Northward Momentum | Pa | average, positive down | |
| ts | Surface (skin) Temperature | K | instantaneous | |
| zg500 | 500 hPa Geopotential Height | m | instantaneous | |
| zmla | Atmospheric Boundary Layer Thickness | m | instantaneous | |
| Table 4: Fixed/static surface fields (2-D) | ||||
| Var. | Long Name | Units | Notes | |
| landtyp | Land-Cover Type | - | ||
| lat | Latitude of Grid Points | deg. N | ||
| lon | Longitude of Grid Points | deg. E | ||
| mrsofc | Capacity of Soil to Store Water | kg m-2 | ||
| orog | Surface Altitude | m | ||
| rootd | Root Depth | m | ||
| sftlf | Land Area Fraction | 1 | land/ocean | |
| Table 5: Atmospheric fields (3-D) | ||||
| Var. | Long Name | Units | Notes | |
| cli | Cloud Ice Fraction of Layer | 1 | instantaneous | |
| clw | Cloud Liquid Water Fraction of Layer | 1 | instantaneous | |
| hus | Specific Humidity | kg kg-1 | instantaneous | |
| ta | Temperature | K | instantaneous | |
| ua | Zonal Wind Component | m s-1 | instantaneous | |
| va | Meridional Wind Component | m s-1 | instantaneous | |
| wa | Vertical Wind Component | m s-1 | instantaneous | |
Notes:
The "screen height" or "reference height" is 1.5-2 m above the surface.
Quantities that can be used for storage terms in budgets are instantaneous values. Quantities that are fluxes in budgets are average values for the 3-hr period prior to the reporting time.
3-hourly values (Tables 2, 3, & 5) are reported at 03 UTC, 06 UTC, … 24 UTC. (UTC stands for Universal Coordinated Time; it is equivalent to GMT, Greenwich Mean Time, in this context.)
The "day" for daily min/max values (Table 1) is from 06 UTC - 06 UTC, with the date stamp referring to the beginning time.
Minimum and maximum daily temperatures [tasmax, tasmin] are recorded from instantaneous screen height temperatures sampled every time step during the course of the day.
Winds [uas, vas] are true west-east and south-north winds, i.e., rotated from the model's grid to the earth's longitudinal and latitudinal directions.
Surface air temperature [tas] and specific humidity [huss] are recorded from screen height values, 2 meters above the surface.
Surface winds [uas, vas] are recorded from "anemometer level" values, 10 meters above the surface.
Units for precipitation [pr] and surface pressure [ps] are MKS, following CF standards. See below for unit conversion.
Snow depth [snd] is snow-water equivalent and is the average depth over the entire grid box, even if the model allows snow to cover a fraction of the grid box.
Land-cover type [landtyp] is a vegetation index linked to a table supplying land-cover descriptions.
3-D fields are provided every 25 hPa from 1050 hPa to 25 hPa.
Note that according to the CF conventions, ice and liquid cloud water [cli, clw] are each reported as a ratio: (cloud-water mass)/(mass of gas+condensed constituents), i.e., more like specific humidity than mixing ratio.
Precipitation and other water fluxes are given in MKS units of kg/m^2/s. This is an instantaneous flux rate averaged over the previous 3 hours. This can be converted to more familiar units as follows:
Water has a density of 1 gram per cubic centimeter, so 1 kg of water forms a cube 1000 cubic cm in volume. Distributed evenly over 1 square meter, this forms a layer 1 mm in depth. Multiply by 10800 seconds in a 3-hour period to get total mm of precipitation per 3 hour timestep.
Similarly, soil moisture and related variables given in kg/m^2 can be converted to the more familiar cm by simply dividing by 10.