Abstract:
The "HIRDLS/Aura Level 2 Geophysical Parameters" data product (HIRDLS2) contains an entire day's worth of Level-2 vertical profiles of O3, HNO3, H2O, CFC-11, CFC-12, N2O, NO2, N2O5, ClONO2, temperature, geopotential height, and aerosol extinction at 12.1 and 8.3 microns, as well as cloud top pressure. The HIRDLS2 data are provided on 24 levels per decade of pressure corresponding to about 1 km
... vertical resolution. The vertical range of the data depends on the measured species. The current and final version of this product is 7. Of the original targeted species, only CH4 was not retrieved in this version.
The data are stored in the version 5 Hierarchical Data Format for the Earth Observing System (HDF-EOS5), which is an extension of the HDF5 format. Each file contains a single swath object with one day of data (measured species and species precision), geolocation fields (e.g. time, latitude, longitude, pressure), and swath attributes, along with file level metadata. Each file contains approximately 5600 profile scans. Time stamps are in TAI-93 format (seconds since January 1, 1993) as well as in seconds since start of day. Arrays with missing data are set to a constant fill value (-999.0).
The High Resolution Dynamics Limb Sounder (HIRDLS) aboard the EOS Aura spacecraft was launched July 15, 2004. The instrument was designed to scan the Earth limb at multiple azimuth angles, measuring infrared emissions in 21 channels ranging from 6.12 to 17.76 microns in the upper troposphere, stratosphere and mesosphere. On July 30, 2004 when the instrument was switched on, it was discovered that a piece of plastic film was blocking most of the HIRDLS scanning mirror. Only a small portion of the mirror at the far azimuth scan (away from the sun side) was clear for making observations of the Earth's atmosphere. Several attempts to remove the blockage were unsuccessful. This obstruction resulted in limited data coverage between -64 and +82 degrees latitude, and thus excluded observations over the Antarctic region. The first reliable data are from January 29, 2005, earlier data from January 21 to 28 are of substandard quality and are not included in version 7. From January 3 to March 17, 2008 the chopper frequency became erratic, and data for these days should be used with caution. The HIRDLS instrument remained operational until March 17, 2008 when the chopper stalled.
Parameters contained in the data files include the following:
Variable Name|Description|Units
O3|Ozone (O3) Volume Mixing Ratio|mol/mol
HNO3|Nitric Acid (HNO3) Volume Mixing Ratio|mol/mol
CFC11|CFC-11 (CFCl3) Volume Mixing Ratio|mol/mol
CFC12|CFC-12 (CF2Cl2) Volume Mixing Ratio|mol/mol
ClONO2|Chlorine Nitrate (ClONO2) Volume Mixing Ratio|mol/mol
N2O|Nitrous Oxide (N2O) Volume Mixing Ratio|mol/mol
N2O5|Dinitrogen Pentoxide (N2O5) Volume Mixing Ratio|mol/mol
NO2|Nitrogen Dioxide (NO2) Volume Mixing Ratio|mol/mol
H2O|Water Vapor (H2O) Volume Mixing Ratio|mol/mol
Temperature|Temperature Profile|K
CloudTopPressure|Pressure of Top of Clouds|hPa
8.3MicronExtinction|Aerosol Extinction at 8.3 Microns|1/km
12.1MicronExtinction|Aerosol Extinction at 12.1 Microns|1/km
GPH|Smoothed Geopotential Height|m
RawGPH|Raw Geopotential Height|m
End of parameter information 
