The GEM Model Location Time Series is one of the model output data sets provided in the Southern Great Plains - 1997 (SGP97). The full GEM MOLTS data set covers most of North America (up to 252 locations). MOLTS are hourly time series output at selected locations that contain values for various surface parameters and `sounding' profiles at GEM model levels and are derived from the GEM model output. The MOLTS output files were converted into Joint Office for Science Support (JOSS) Quality Control Format (QCF), the same format used for atmospheric rawinsonde soundings processed by JOSS. The MOLTS output provided by JOSS on-line includes only the initial analysis output (i.e. no forecast MOLTS) and only state parameters (pressure, altitude, temperature, humidity, and wind). The full output, including the forecast MOLTS and all output parameters, in its original format (Binary Universal Form for the Representation of meteorological data, or BUFR) is available from the National Center for Atmospheric Research (NCAR)/Scientific Computing Division. The Atmospheric Environment Service/Canadian Meteorological Centre (AES/CMC) operates the GEM model with a resolution of 35 km and 28 vertical levels. The GEM analysis and forecast fields are generated every 12 hours at 0000 and 1200 UTC daily. MOLTS are hourly vertical profile and surface time series derived from the GEM model output. The complete MOLTS output includes 13 informational items, 27 parameters for each level and 28 parameters at the surface. Output are available each hour beginning at the initial analysis (the only output available from JOSS) and ending at the 36 hour forecast. JOSS converts the raw format (BUFR) files into JOSS QCF format which is the same format used for atmospheric sounding data such as National Weather Service (NWS) soundings. JOSS calculated the total wind speed and direction from the u and v wind components. JOSS calculated the mixing ratio from the specific humidity (Pruppacher and Klett 1980) and the dew point from the mixing ratio (Wallace and Hobbs 1977). Then the relative humidity was calculated from the dew point (Bolton 1980). JOSS did not conduct any quality control on this output. The header records (15 total records) contain output type, project ID, the location of the nearest station to the MOLTS location (this can be a rawinsonde station, an Atmospheric Radiation Measurement (ARM)/Cloud and Radiation Testbed (CART) station, a wind profiler station, a surface station, or just the nearest town), the location of the MOLTS output, and the valid time for the MOLTS output. The five header lines contain information identifying the sounding, and have a rigidly defined form. The following 6 header lines are used for auxiliary information and comments about the sounding, and they vary significantly from dataset to dataset. The last 3 header records contain header information for the data columns. Line 13 holds the field names, line 14 the field units, and line 15 contains dashes ('-' characters) delineating the extent of the field.