McIDAS Learning Guide
Version 2006

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MD Files - Basic Concepts

MD files normally contain observational data for a specific time period, for example, a day or an entire year. MD files store the data in individual records for a specific location at a specific time. Each MD file contains individual records. A record contains observational data for a latitude and longitude at a specific time. For example, one record may include measurements of temperature, dew point, wind speed, wind direction, and sea level pressure at 15 UTC for Houston, TX. A single MD file may contain thousands of records.

MD files use the naming convention MDXXnnnn where nnnn is a four-digit number. For example, MDXX0013 is the file name for MD file 13. Most McIDAS commands use only the MD file number. However, you must use the MDXX prefix with the DMAP command or when using Unix commands to copy, move, or delete MD files.

MD file Schemas

McIDAS stores MD files according to unique templates called schemas. SSEC receives real-time data for these nine schemas:

MD files in the ISFC, IRAB, SYN, and GFSMOS schemas are arranged in a table of rows and columns as shown in the ISFC example below. Time and day information common to all records in the row appears in the row header. Similarly, a column header designates common information according to location. Therefore, all the records along a particular row represent the same time and all the records down a particular column are reports from the same location.

MD files in the IRSG, ISHP, and PIRP schemas have row headers, but not column headers because the reporting location changes.

**As of January 25, 2005 the North American Mesoscale forecast model (NAM) has replaced the ETA model, creating a new schema, NAMMOS. In addition, NGMMOS, which is the same as DCFO14, was created to follow the more logical naming convention of the other MOS schemas (GFSMOS and NAMMOS). In order to use the new datasets, your server, or any remote server you are pointing at must be updated to McIDAS-X 2005. Older servers can still use the ETAMOS and FO14 schemas, but will need to use the TYPE= keyword with the MOSRPT command. See the McIDAS User's Guide for more information on schemas.

The individual data values within the MD file are stored according to the parameters of a schema. Examples of parameters within the ISFC schema are temperature, dew point, and cloud cover. Parameters are used for searching and plotting the MD file data. For each parameter, the schema provides:

SSEC's Real-time Point Data

The table below lists the real-time point data that SSEC receives and the associated dataset names.
Schema ADDE Dataset
PIRP RTPTSRC/AIRCRAFT
NAMMOS RTPTSRC/ETAMOS
NGMMOS RTPTSRC/FOUS14
GFSMOS RTPTSRC/GFSMOS
NAMMOS RTPTSRC/NAMMOS
NGMMOS RTPTSRC/NGMMOS
ISFC RTPTSRC/SFCHOURLY
ISHP RTPTSRC/SHIPBUOY
SYN RTPTSRC/SYNOPTIC
IRAB RTPTSRC/UPPERMAND
IRSG RTPTSRC/UPPERSIG

SSEC's History Data

SSEC has history data for the following schemas and years.
Schema Years
ISFC 1976 to present
IRAB/IRSG 1977 to present
ISHP 1985 to present
SYN 1991 to present

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