MD Files - Basic Concepts

McIDAS Learning Guide
Version 2015

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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:

ISFC (international surface hourly observations)
IRAB (international RAOB (radiosonde) mandatory levels)
IRSG (international RAOB (radiosonde) significant levels)
ISHP (ship and buoy observations)
PIRP (AIREP and PIREP reports)
SYN (international surface synoptic observations)
GFSMOS (real-time GFS MOS)
NAMMOS (real-time NAM MOS)
NGMMOS (real-time NGM MOS)

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.

**Note: On 25 January 2005 the North American Mesoscale forecast model (NAM) replaced the ETA model, creating a new schema, NAMMOS. In addition, NGMMOS, which is the same as DCFO14, was created at the same time to follow the more logical naming convention of the other MOS schemas (GFSMOS and NAMMOS). References to older models (like NGM and ETA) are still found in the Learning Guide because it has many examples from the 1993 "Storm of the Century" and those models were operational at that time.

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:

a scaling factor, for example 2, meaning temperatures are stored in Kelvin * 10**2
the units in which the values are stored, for example Kelvin

SSEC's Real-time Point Data

The table below lists real-time point data that SSEC receives and the associated dataset names.

Schema	ADDE Dataset

PIRP	RTPTSRC/AIRCRAFT
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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