HIRS Cloud-cleared Version 2 Products


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 and NOAA-16..  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 2001. Version 2 extends the data from December 1999 to December 2001.

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. The second version data were created the summer of 2002. Version 2 provides an all-sky data set containing cloud-top retrievals using the CO2 slicing method of Wylie and Menzel. Orbit statistic files have additional statistics on the skewness and kurtosis of each orbit.

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.channel.OB

These files containing statistical information about each HIRS orbit, satellite and channel.  The parameters include mean, maximum, minimum,standard deviation, skewness and kurtosis of brightness temperature, number of observations, number of ITPP bad data, and number of bad data as determined by additional quality control.  There are about 220 orbital files with total data volume of about 355 Mb.


Swath products

File format for clear-sky data

File name format = instrument.satellite.year.day.version.CS

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 90 Gbytes.  These pixel data have a 55 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.
 
VARIABLE DATA TYPE DESCRIPTION  SCALE & OFFSET
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
isf byte spare NA
iref byte reflectance iref=reflectance*100
itb int*2(19) channels 1-19 brightness temperatures (Kelvin) itb=(TB-100.)*100

File format for all-sky data

File name format = instrument.satellite.year.day.hour.angle.C2

These data give all the all-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 380 Gbytes.  These pixel data have a 55 byte record structure.  We have Fortran and IDL code that reads these data.  
 
VARIABLE DATA TYPE DESCRIPTION  SCALE & OFFSET
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
iref byte reflectance iref=reflectance*100
itb int*2(19) 7 channels 4-8,10,12 brightness temperatures (Kelvin) itb=(TB-100.)*100
ipct int*2 Pressure at cloud top (Mb) NA
iem byte IR emissivity of cloud (%) NA
itc INT*2 Temperature of cloud top (K) itc=(TEMPERATURE-100.)*100.
itsfc INT*2 Surface temperature used in CO2 slicing routine(K) itsfc=(TEMPERATURE-100.)*100.
idelrad INT*2 (4) Radiance (clear) - Radiance (cloud) for HIRS channels 4-7 NA
iclear INT*2 Temperature of cloud top (K) itb=(TEMPERATURE-100.)*100.
ipctrto INT*2 (5) The cloud height solutions for the CO2 pairs + window NA
iused byte Flag indicates which ratio was used NA

Tape format

Data received on tape media are organized into monthly tar files. Tapes are organized by afternoon and morning satellites.  Each tar file on tape contains all the available scan line data files for that month.  A listing of the entire clear-sky and all-sky swath archive on DLT are given in the following table.
Satellite & Date File Name Data type
TN,N7,N9,N11: all; N14:1/95-6/96HIRS_CS_tape1.A.dltclear sky
N14:7/96-12/01; N16:3/01-12/01HIRS_CS_tape2.A.dltclear sky
N6,N8,N10,N12,N15: allHIRS_CS_tape1.M.dltclear sky
N6:7/79-4/83; N8:4/83-8/83 HIRS_C2_tape1.M.dltall-sky
N8:9/83-5/84; HIRS_C2_tape2.M.dltall-sky
HIRS_C2_tape3.M.dltall-sky
HIRS_C2_tape4.M.dltall-sky
HIRS_C2_tape5.M.dltall-sky
TN:11/78-1/81; N7:7/81-10/83HIRS_C2_tape1.A.dltall-sky
N7:11/83-1/85; N9:1/85-12/87HIRS_C2_tape2.A.dltall-sky
N9:1/88-10/88; HIRS_C2_tape3.A.dltall-sky
HIRS_C2_tape4.A.dltall-sky
HIRS_C2_tape5.A.dltall-sky
HIRS_C2_tape6.A.dltall-sky

 


Grid products

File format

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


Data Problems

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