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NCEP'S FILING PROCESS AND NAMING CONVENTIONS: BASIC- NCEP segregates the reports by data type and proximity to a synoptic time, and calls the group a data file. DATA TIME- NCEP accumulates and decodes the data from the GTS for a period that is roughly centered on synoptic times, plus or minus about one half of the interval between times. Please note that the observation type does not mean data value. It refers to the report type, or platform, such as land station, moving ship, etc. NCEP'S DATA FILE ORGANIZATION: NCEP's file organization (not the format) has varied over the years. We do not alter this. We have limited access software for BUFR - it requires the use of some software libraries that do not port to all computers. The tar file BUFRdecode_ADPsfc.tar located under the "Set Software" tab includes the libraries and fortran code that extracts basic atmospheric variables from the BUFR files and puts them into a simple text file. Information about the BUFR libraries, and sample code can be found at: NCEP BUFR lib. Definitions for BUFR MNEMONIC headers can be found at: NCEP BUFR MNEMONICS THE DATA: GENERAL- This data is not available as a database. We also remind users that the data consists only of the data which the stations reported over the GTS. Dropouts are not unusual, and we can not recover them. SPATIAL DATA COVERAGE-A plot of spatial data coverage derived from an individual report time can be found here. STATION IDENTIFICATIONS- generally, the 6-hourly and 3-hourly reports show WMO 5 digit numbers. See our combined list of U.S.A.F. catalogs. However, the hourly and 20 minute reports show alphabetic call signs like IKNO. Some of these are shown in the combined list. When users want to extract all the reports from a locale, it is more reliable to use a latitude-longitude "window", which will get both the WMO and call sign labeled reports. A slightly larger window will obtain neighboring station data that could be used when the desired station data is missing. SURFACE AIRWAYS- It appears that most of the northern hemisphere reports have been decoded by NCEP and included in this data. Note the station identifications paragraph above. CLOUDS- In recent years the presence of the cloud data fields has become unreliable. In 2000, before February 1, it appears that NCEP stopped decoding the cloud type data for the entire globe. We continue to investigate. PRECIPITATION- We are frequently asked about the availability of precipitation data, in this data set, outside of the U.S. NCEP routinely decodes the GTS precipitation data for all North American stations. NCEP does not decode the data for the remainder of the world. Knowledge of numerous decoding schemes are required to decode these data, and we have just a few of these on paper. NCEP operations considers these data to be climatological data, of little use for their models and forecasts. We understand that the NCEP's Climate Prediction Center (CPC) has been decoding these globally. Please refer to DS512.0, our global summary of day dataset, which is prepared by CPC. Note however that this dataset shows only daily totals. OTHER: Background information about the characteristics of this data may be found in An Introduction to Atmospheric and Oceanographic Datasets. There is general basic information in its Introduction. More specific information may be found in these chapter(s) or section(s): Surface Observations One should always be aware of Observational Data Problems. You may wish to refer to Other Sources of Data. |
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| Updated 22 July 2005 |
