Source: Dr. Ken Mitchell of NCEP's Environmental Modeling Center (NECP/EMC) and Dr. Jin Huang of NECP's Climate Prediction Center (NCEP/CPC). NCEP is the National Centers for Environmental Protection.

The hourly forcing data are obtained by converting Global 6-hourly Reanalysis data from Gaussian grid to hourly data on LDAS 1/8th degree grid. The process involves interpolation in time and space, elevation
correction (for air temperature, specific humidity, downward long-wave radiation and surface pressure), zenith angle correction for downward solar radiation, and fine tuning for air temperature using Reanalysis
6-hourly Tmax and Tmin.  Please note that:

1) the radiation values are downward, not net values;
2) The global Reanalysis algorithms did not ingest surface station observations of temperature, himidity or winds. The only exception is station surface pressure.

The data is organized by one file per year/station (the lat/lon is listed at the top of the data) and is listed hourly (0Z to 23Z) every day. There are 7 variables:
1) Tair:  Air temperature (K);
2) Psfc:  Surface Pressure (Pa);
3) DSWR:  Downward solar radiation (W/m**2);
4) DLWR:  Downward long-wave radiation (W/m**2);
5) SPFH:  Specific humidity (Kg/Kg);
6) U:     U wind speed (m/s) (positive means from west to east);
7) V:     V wind speed (m/s) (positive means from south to north).
 

  ftp://ftp.ncep.noaa.gov/pub/cpc/wd51jh/DMIP (link now inactive)