NCEP North American Regional Reanalysis (NARR)

The purpose of the National Centers for Environmental Prediction (NCEP) and National Center for Atmospheric Research (NCAR) North American Regional Reanalysis (NARR) is to create a long term set of consistent climate data on a regional scale on a North American domain. NARR is an improved long-term reanalysis of basic meteorological fields on a high resolution grid that, for the first time on any scale, includes precipitation. NARR assimilates a great deal of historical climate observational data using a 32 km version of the regional NCEP North American Mesoscale (NAM) model (formally the NCEP 1993 operational ETA model) and ETA data assimilation system (EDAS). The domain of analyses includes North and Central America as well as small parts of the UK, Eastern Asia and South America and the oceans in between. The period of the reanalyses is from October 1978 to the present and includes analyses made 8 times daily. Horizontal boundary conditions were derived from the NCEP/DOE Reanalysis, hereafter referred to as the Global Reanalysis (GR).

Much of the data are the same as used as in the NCAR/NCEP GR. The data include temperatures, winds, and moisture from radiosondes, as well as pressure data from surface observations. Also included in this data set are dropsondes, pibals, aircraft temperatures and winds, and cloud drift winds from geostationary satellites.

In addition to the above list, a major component of the NARR is the assimilation of precipitation. The precipitation data set comes from a variety of sources. The data over the continental United States comes from a 1/8-degree gauge data set analyzed using PRISM and a least-squares distance weighting algorithm. Over Canada and Mexico, the precipitation comes from 1-degree gauge data sets. Much of the rest of the domain's precipitation comes from CMAP (CPC [Climate Prediction Center] Merged Analysis of Precipitation), a merged combination of satellite and gauge precipitation.

Other data sets include winds and precipitable water from TOVS (TIROS [Television InfraRed Observations Satellite] Operational Vertical Sounder) satellite radiances, wind and moisture from hourly and 3-hourly surface stations, and ship and buoy data. Snow depth comes from the 512x512 Air Force snow data set. Sea-surface temperatures (SSTs) contain a 1-degree Reynolds data set, including the Great Lakes. Sea ice data comes from a satellite data set used for the GR. Canadian lake ice comes from the Canadian Ice Center.

This data set is encoded in WMO format GRIB version 1 using the NCEP GRIB table 131. The data are stored on a Lambert conformal grid (AWIPS grids 221) and efforts have been made to make the data GrADS compatible (http://grads.iges.org/grads).