The HIRS cloud-cleared products were developed from the HIRS 1B data set.   The International TOVS Processing Package (ITPP) was used to calibrate the raw counts into brightness temperature for TIROS-N, NOAA-6, -7,-8,-9,-10,-11,-12,-14 and ATOVS and AVHRR processing package (AAPP) was used for processing NOAA-15..  A modified ISCCP approach was used for cloud-clearing and multiple channel regression was developed for limb correction.  We currently have data available for each satellite starting in November 1978 and ending December 1999.

The first processing stage conducted in the spring 2000 used a cloud detection method and limb correction algorithm so to produce a clear-sky scan line and gridded data sets.

Details of the products derived from our process are given below.  File name formats are given for each product and the file name key is provided.  Software for reading the satellite-view and gridded products can accessed via anonymous ftp.  Data and software requests can be made to Darren.L.Jackson@noaa.gov.

Orbital statistics

File name format  = instrument.satellite.year.channel.LG

These files containing statistical information about each HIRS orbit, satellite and channel.  The parameters include mean, maximum, minimum and standard deviation of brightness temperature, number of observations, number of ITPP bad data, and number of bad data as determined by additional quality control.  There are approximately 1000 orbital log files using a total of 250 Mbytes.

Scan line products

File format

File name format = instrument.satellite.year.day

These data give all the clear-sky HIRS observations at the resolution of the satellite observations.  Data are stored in daily files that consume about 4-5 Mbytes each.  The entire HIRS clear-sky satellite view archive is approximately 60 Gbytes.  These pixel data have a 56 byte record structure.  We have Fortran and IDL code that reads these data and applies limb correction.  Addition coefficient files are need for the limb correction.
itime int*4 GMT time in seconds from start of day itime=time*100
ilon int*2 longitude in degrees (0  to 359.99; GM eastward) ilon=(lon-180)*100
ilat int*2 latitude in degrees (-90 to 90)  ilat=lat*100
iline int*2 line number(1-1100) NA
isp byte scan position (1-56) NA
iszen int*2 solar zenith angle in degrees (0-90) iszen=angle*100
ialt int*2 satellite altitude in km ialt=altitude*10
iqc  byte spare NA
isf byte spare NA
iref byte reflectance iref=reflectance*100
itb int*2(19) channels 1-19 brightness temperatures (Kelvin) itb=(TB-100.)*100

I/O information

IDL and Fortran code exist for reading the scan line data files.  Code includes regression coefficient data files for limb correction algorithm.  Regression coefficient data files are available along with verification data set to ensure proper use of the data.

Tape format

Data received on tape media are organized into monthly tar files.  Each tar file on tape contains all the available scan line data files for that month.  A listing of the entire scan line data archive on DLT are in files HIRS_sl_dec78-nov92.dlt and HIRS_sl_dec92-dec99.dlt.

Grid products

File format

File name format = instrument.satellite.year.timeaverage.resolution.type.

All gridded data are INT*2 with array arrangement of  LON x LAT X CHN.   LON and LAT are determined by resolution.  Latitudes only range from 70N-70S.  Channel array element is 20 representing each HIRS channel.  Data were created on PC, so byte swapping might be an issue.  The mean fields are scaled and offset (MEAN = INT2/100. + 100.) while the standard deviation fields were only scaled (STD = INT2/100.).  Count values do not need modification.  Missing values are -99 AFTER offset and scale are applied. First grid box (1,1) is located at (0.5E,69.5S).  Longitudes move eastward.  All data values for channels 1-19 are brightness temperatures expressed in Kelvin.  Channel 20 is reflectance with values between 0 and 1.

I/O information

IDL and Fortran code exist for reading the grid files.

Tape format

Data received on tape media are organized into monthly tar files.  Each tar file on tape contains all the available grid files for that month.  A listing of the entire monthly-mean grid archive on DLT are in files HIRS_MONTHLY.dlt and HIRS_PENTAD.dlt.

The following table identifies all of the available grid products. (Monthly and Pentad grid products table)

Data Problems

There are several known problems with HIRS 1b Version 1 data. Last modified: Tue Aug 14 10:36:58 MDT 2001