Who to Contact

Dr. Wilbert R. Skinner
University of Michigan
Space Physics Research Laboratory
Department of Atmospheric, Oceanic, and Space Sciences
2455 Hayward Street
Ann Arbor, MI 48109-2143
734.647.3960
734.763.7130 fax
wskinner@umich.edu
 
or

Alan Marshall
University of Michigan
Space Physics Research Laboratory
Department of Atmospheric, Oceanic, and Space Sciences
2455 Hayward Street
Ann Arbor, MI 48109-2143
(734) 763-6223
(734) 763-7130 fax
armarsh@umich.edu
 

Filenames and Types

An in-depth description of the file formats can be obtained from the CDHF by those who are qualified users there (by asking for the HRDI level 3a Standard Formatted Data Units (SFDU) information). The same information is also available from the DAAC as part of a data request, or by printing the detailed information below (see 'full format description'). There are two general types of level 3a files for HRDI, L3AL files, and L3AT files.

The format of the level 3a data files is the same for each of the instruments on the UARS spacecraft, to ease use and intercomparison. These files are produced at standard latitude (for L3AL files) or time (for L3AT files) points. The latitude points are every 4 degrees along the spacecraft track, while the time points are every spacecraft minute (about 65 seconds). At each point, a single profile (series of measurements at different altitudes above a point on the Earth's surface) is interpolated from the lower level results, and written to the level 3a file. For HRDI data, this profile is available on either an altitude or a pressure grid. The standard altitude grid is:

5 to 60 km every 5 km, 63 to 120 km every 3 km, and 125 to 400 km every 5 km
while the standard pressure grid levels are:
p(i) = 1000.0 * (10**(-i/6))), where i=0,1,...35 (in millibars) (1000mb, 681.29mb, ..., 1.468e-3mb)
The file naming convention for these files is (capital letters represent fixed letters, while lower case letters indicate where changes can be made):
HRDI_Llev_Ssubtype_Ddayn.Vvers_Ccn_PROD
where:
lev = 3AL (for latitude gridded data)
= 3AT (for time gridded data)
subtype = MERWIN_A (for meridional winds, on an altitude grid)
= MERWIN_P (for meridional winds, on a pressure grid)
= ZONWIN_A (for zonal winds, on an altitude grid)
= ZONWIN_P (for zonal winds, on a pressure grid)
dayn = the UARS day number (four digits, it is the number of days since launch, 12-September-1991 being 0001)
vers = the version of the data file, in this case 0010
cn = the cycle number of the file, usually 01 or 02

Simplified Format Description

It is important to note that the L3A files (both types) are written using an algorithm which saves space by only writing out the part of the standard array which the instrument has collected data over. Thus the altitudes (or pressures) of the HRDI data must be determined using the data header information 'start_index', which holds the index number of the lowest index actually used in the file. Thus if the "start_index" value is 3, the lowest altitude reported for that L3AT file is 15 km.

Full Format Description

HRDI Level 3a Data Quality