AIRS

Frequently Asked Questions

Below are answers to questions users have asked about the AIRS data, data products, and algorithms.

AIRS Data User Registration
    Q.  What results when I register as an AIRS Data User?
 
General - Not a Product
    Q.  What is the impact of AIRS data on forecasting of weather disasters, and how are
weather and climate different?
    Q.  How does data collected through the AIRS program compare with data that
could be gathered using radio occultation?
    Q.  When people talk of the rising temperature of the earth, are they
talking about air temperature or surface temperature (skin or
meteorological)?
    Q.  Do you have images of the carbon dioxide distribution in the mid-
troposphere at different time periods in the 30,000-40,000 ft region
where jet planes fly?
    Q.  How do I find out when AIRS passes over a specific area?
    Q.  Where can I see mapped the data on methane concentration?
    Q.  1) How are "surface temperatures" determined for forrests and other
areas where the land is covered?
2) What is the accuracy of land surface measurements (+/- degrees C)
3) What is the effect of cloud cover on accuracy?
    Q.  When will the AIRS CO2 product be available?
    Q.  a) Which gases make up the whole of the Earths atmosphere?
b) What their respective percentage levels are?
c) Do these percentage levels vary with altitude?
d) Are any seasonal variations in these levels?
e) How much carbon dioxide is annually deposited into the atmosphere?
f) What percentage of (e) above is produced naturally?
g) How much carbon dioxide is absorbed/released by the worlds oceans?
h) Is (g) above is affected by the temperature of the oceans?
j) How much sulphur is present in the atmosphere?
    Q.  What is the definition of a sounder in the context of atmospheric
instruments?
    Q.  Since there is an increase in surface "brightening" and greenhouse gases
may be adding to the infra-red at the surface, have you been able to
subtract out the infra-red?
    Q.  Can I order AIRS maps, and do they cost anything?
    Q.  Has there been any correlation carried out for volcanic activity and
CO2 emissions during the course of the AIRS instrument operation?
 
How to Access Data
    Q.  Where can I find the AMSU-A (Advanced Microwave Sounding Unit on Aqua)
and HSB(Humidity Sounder for Brazil) data?
    Q.  How do I get an AIRS header file?
    Q.  I would like some information about the pressure, temperature, vorticity
(circulation), velocity etc. distrbution inside a hurricane. Do you have
such data available?

    Q.  How do I pull subsetted data files of all data products for the
lifetime of the mission?
    Q.  Are the AIRS L1A data (raw instrument counts, uncalibrated) available
to the public?
    Q.  How do I access AIRS Data
 
L1B AIRS Radiance Product (AIRIBRAD)
    Q.  Can I download an entire month of L1B AIRS radiance with channels
subsetting within only 1 request?
    Q.  Is a "simple" data download available for mean Earth radiance W/m2/um
covering the approximate wavelength range 3-60 microns?
    Q.  Is the new field spectral_clear_indicator a indicator for cloud-free FOV
in the new L1B AIRS product?
    Q.  Can you improve the meaurements of the temperature of the ground (earth)
by correcting any atmospheric disturbance? In other words, can AIRS get
better results than MODIS?
    Q.  How can I view AIRS Level 1B radiance files.
    Q.  Is there an application that I can use to read the subsetted AIRS L1B
radiance files?
    Q.  What are the frequencies of the individual AIRS IR channels?
    Q.  Is there access to either data files or documents illustrating typical
1D vertical weighting functions for AIRS channels.for nominal
temperature, absorption etc.?
    Q.  Is there a formula to calculate the exact size of the AIRS L1B field
of view?
 
L1B AMSU Radiance Product (AIRABRAD)
    Q.  Has the brightness temperature in the AMSU-A L1B product has been NADIR-
adjusted? If so is the error included in the product itself?
 
L2 Standard Product (AIRX2RET)
    Q.  Regarding "pressH2O" and "pressStd" values: Are these the bottom,
middle, or top of the layer?
    Q.  Is the resolution of AIRX2RET and AIRI2CCF 50km*50km or 45km*45km at
nadir? Is it larger away from nadir?
    Q.  There is a attribute field containing the time of observation in hours,
minutes and seconds in the HDF files. Does this time specification refer
to the local time zone?
    Q.  There have been changes in the retrieval processing from V4 to V5 which
affect the water vapor product. Is there documentation? I am currently
working with AIRS L2 water vapor products
    Q.  I am getting very big number for time. What is the unit of the time in
level 2 product. I would like to have yyyymmddhhmmss for each granule.
    Q.  There is supposed to be a 16 day repeat cycle to the data granules, but
lat-longs at day 1, day 9, day 17, don't match up. Why?
    Q.  Do you have any suggestions for users who desire moisture and
temperature profiles at the AIRS spatial resolution?
    Q.  Is the error estimate, emisIRStdErr, merely a sort of error bar or is
the estimated error actually this value? In that case, what is the sign
of the error? In the .hdf files that I have looked at, the value for
emisIRStdErr is always positive.
    Q.  Is there a tool that creates NetCDF files from HDF or is there a way to
get AIRS data in NetCDF format?
    Q.  The HSB data is not available since 2003 and there are L2 retreivals
that are processed without HSB. I notice that HSB was used in conjuction
with AMSU-A for the retrival of the first-guess moisture profile. I
wonder what sort of modification in the retrival algorithm was
undertaken after the loss of HSB?
    Q.  What is the algorithm employed for determination of AIRS surface
temperature?
    Q.  Is the surface air temperature retrieval algorithm the same as
temperature profile retrieval algorithm?
    Q.  what are the units and start of the time variable in the L2 product?
    Q.  How I can retrieve the granule starting (or ending) time from the name
of the granules?
 
L2 Support Product (AIRX2SUP)
    Q.  Is the totH2OStd quantity is the best moisture product to use for
performing integrated precipitable water comparisons between AIRS and
ground-based measurements?
    Q.  I would like to download L2SUP product. can you please tell me easy way
to download as i have limited speed broadband download connction.
 
L3 Product
    Q.  Why do I see a high-frequency oscillation in a histogram of the number
of occurances of a given value of water vapor in the 500-600mb layer of
Level 3 data when combining data over a time interval?
    Q.  Is there a way to get L3 CO2 product from AIRS ?
    Q.  Regarding the pressure levels for the relative humidity profiles. In V4,
the pressure level was the bottom of the layer for which the RH was
given. Someone mentioned to me today that that may have changed with
version 5.
    Q.  Why I do I find a number larger than 100 in RelHumid_A in AIRX3STM data
product? Relative humidity is usually less than 100 percent.
    Q.  I'm using the 1 deg gridded daily LEVEL 3 AIRS product. Is there a way
for me to simply approximate the average UTC time?
    Q.  How can I know the exact satellite overpass time for each pixel?
 
Quality Assurance
    Q.  I understand that water vapor is the largest GHG. Do we understand what
causes the fluctuations in water vapor? Has water vapor content been
increasing for the past 50 years?
 
Retrieval Algorithm
    Q.  How do I calculate brightness temperatures from AIRS L1B data?
    Q.  How do I get a copy of the AIRS retreival code?