NCEP ADP ETA/NAM Upper Air Observation Subsets are composed of a regional synoptic set of upper air reports centered over North America, operationally collected by the National Centers for Environmental Prediction (NCEP). These include radiosondes, pibals and aircraft reports from the Global Telecommunications System (GTS) and satellite data from the National Environmental Satellite Data and Information Service (NESDIS). The reports can include pressure, geopotential height, temperature, dewpoint depression, wind direction and speed. Data may be available at up to 20 mandatory levels from 1000mb to 1mb, plus a few significant levels. Report time intervals range from 3 hourly to 12 hourly. These data are the primary input to the (EDAS)/NAM Data Assimilation System (NDAS starting Jan. 23, 2005). DS351.0 provides global data coverage over the same time period.

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