GRID files

GRID files are post-processed data produced from FITACF files, in which the fitted data products are placed on a magnetic latitude/longitude grid of equal-area cells spanning 1 degree of magnetic latitude. They may contain data from one radar or from multiple radars. For more information, see the make_grid tutorial.

Naming Convention

The community standard for naming GRID files containing data from only one radar is:

YYYYMMDD.<3-letter abbreviation>.grd

When the gridded data from multiple radars have been combined, the files are named as:

YYYYMMDD.north.grd

YYYYMMDD.south.grd

In both cases, the grid files contain 24-hours of data.

Scalar Fields

The following times refer to the start and end of the integration period.

Field name	Units	Data Type	Description
start.year	None	short	Start Year
start.month	None	short	Start Month number (not padded)
start.day	None	short	Start Day (not padded)
start.hour	hrs	short	Start Hour
start.minute	min	short	Start Minute
start.second	s	short	Start Seconds
end.year	None	short	End Year
end.month	None	short	End Month (not padded)
end.day	None	short	End Day (not padded)
end.hour	hrs	short	End Hour
end.minute	min	short	End Minute
end.second	s	short	End Seconds

Vector Fields

In the table below, numstid is the number of radars included in that grid record, and numv is the total number of gridded velocity vectors.

Field name	Units	Dimensionality	Data Type	Description
stid	None	[numstid]	short	A list of numeric station IDs that provided data for the record
channel	None	[numstid]	short	A list of channel numbers associated with the station id
nvec	None	[numstid]	short	Number of velocity vectors for each station
freq	kHz	[numstid]	float	Transmitted frequency for each radar
major.revision	None	[numstid]	short	Major make_grid version number
minor.revision	None	[numstid]	short	Minor make_grid version number
program.id	None	[numstid]	short	Control program ID
noise.mean	None	[numstid]	float	Mean sky noise
noise.sd	None	[numstid]	float	Sky noise standard deviation
gsct	None	[numstid]	short	Groundscatter flag
v.min	m/s	[numstid]	float	Minimum velocity threshold
v.max	m/s	[numstid]	float	Velocity maximum threshold
p.min	None	[numstid]	float	Power minimum threshold
p.max	None	[numstid]	float	Power maximum threshold
w.min	m/s	[numstid]	float	Spectral width minimum threshold
w.max	m/s	[numstid]	float	Spectral width maximum threshold
ve.min	m/s	[numstid]	float	Velocity error minimum threshold
ve.max	m/s	[numstid]	float	Velocity error maximum threshold
vector.mlat	degrees	[numv]	float	Magnetic Latitude
vector.mlon	degrees	[numv]	float	Magnetic Longitude
vector.kvect	degrees	[numv]	float	Magnetic Azimuth
vector.srng	km	[numv]	float	Slant range
vector.stid	None	[numv]	short	Station identifier
vector.channel	None	[numv]	short	Channel number
vector.index	None	[numv]	int	Grid cell index
vector.vel.median	m/s	[numv]	float	Weighted mean velocity magnitude
vector.vel.sd	m/s	[numv]	float	Velocity standard deviation
vector.pwr.median	dB	[numv]	float	Weighted mean power
vector.pwr.sd	dB	[numv]	float	Power standard deviation
vector.wdt.median	m/s	[numv]	float	Weighted mean spectral width
vector.wdt.sd	m/s	[numv]	float	Standard deviation of spectral width