The Atmospheric Infrared Sounder (AIRS) on the EOS Aqua spacecraft provides accurate and consistent measurements of midtropospheric carbon dioxide (CO2) with global monthly coverage. The data are widely used for studies of vertical transport of CO2 due to large-scale dynamics (e.g., ENSO, MJO, and the Walker Circulation). The purpose of this paper is to characterize the response of CO2 in the midtroposphere, at the altitudes where AIRS is most sensitive, to geophysical changes at the surface across the globe. Our findings confirm that surface factors, as well as weather and climate patterns, impact the global variability of midtropospheric CO2 as observed by AIRS. Despite a phase lag and a reduction in the seasonal amplitude observed in AIRS CO2 relative to surface CO2 measurements in the Northern Hemisphere, a significant correlation is observed between regional variability of CO2 from AIRS and Moderate Resolution Imaging Spectroradiometer (MODIS)-derived Gross Primary Productivity at the surface, primarily in the high-latitude boreal forests during the peak of the growing season (July). A video of global AIRS CO2 and MODIS vegetation index clearly shows the seasonal drawdown of CO2 from the midtroposphere over highly vegetated areas in the northern latitudes. In the Southern Hemisphere, we see higher amplitude in the seasonal cycle, with the phase leading that of the surface. Both are indicative of interhemispheric transport.
The Atmospheric Infrared Sounder (AIRS) is a hyperspectral infrared instrument on the Earth Observing System (EOS)
Aqua Spacecraft, launched on May 4, 2002 into a near polar sun-synchronous orbit. AIRS has 2378 infrared channels
ranging from 3.7 μm to 15.4 μm and a 13.5 km footprint at nadir. AIRS, in conjunction with the Advanced Microwave
Sounding Unit (AMSU), produces temperature profiles with 1K/km accuracy on a global scale, as well as water vapor
profiles and trace gas amounts for CO2, CO, SO2, O3 and CH4. AIRS CO2 climatologies have been shown to be useful
for identifying anomalies associated with geophysical events such as El Niño-Southern Oscillation or Madden–Julian
oscillation. In this study, monthly representations of mid-tropospheric CO2 are constructed from 10 years of AIRS
Version 5 monthly Level 3 data. We compare the AIRS mid-tropospheric CO2 representations to ground-based
measurements from the Scripps and National Oceanic and Atmospheric Administration Climate Modeling and
Diagnostics Laboratory (NOAA CMDL) ground networks to better understand the phase lag of the CO2 seasonal cycle
between the surface and middle troposphere. Results show only a small phase lag in the tropics that grows to
approximately two months in the northern latitudes.
The Atmospheric Infrared Sounder (AIRS) on NASA's Earth Observing System Aqua spacecraft was launched in May
of 2002 and acquires hyperspectral infrared spectra used to generate a wide range of atmospheric products including
temperature, water vapor, and trace gas species including carbon dioxide. Here we present monthly representations of
global concentrations of mid-tropospheric carbon dioxide produced from 8 years of data obtained by AIRS between the
years of 2003 and 2010. We define them as "representations" rather than "climatologies" to reflect that the files are
produced over a relatively short time period and represent summaries of the Level 3 data. Finally, they have not yet been
independently validated. The representations have a horizontal resolution of 2.0° × 2.5° (Latitude × Longitude) and
faithfully reproduce the original 8 years of monthly L3 CO2 concentrations with a standard deviation of 1.48 ppm and
less than 2% outliers. The representations are intended for use in studies of the global general circulation of CO2 and
identification of anomalies in CO2 typically associated with atmospheric transport. The seasonal variability and trend
found in the AIRS CO2 data are discussed.
We apply the method of Vanishing Partial Derivatives (VPD) to AIRS spectra to retrieve daily the global distribution of
CO2 at a nadir geospatial resolution of 90 km x 90 km without requiring a first-guess input beyond the global average.
Our retrievals utilize the 15 μm band radiances, a complex spectral region. This method may be of value in other
applications, in which spectral signatures of multiple species are not well isolated spectrally from one another.
The AIRS instrument was launched in May 2002 into a polar sun-synchronous orbit onboard the EOS Aqua Spacecraft. Since then we have released three versions of the AIRS data product to the scientific community. AIRS, in conjunction with the Advanced Microwave Sounding Unit (AMSU), produces temperature profiles with 1K/km accuracy on a global scale, as well as water vapor profiles and trace gas amounts. The first version of software, Version 2.0 was available to scientists shortly after launch with Version 3.0 released to the public in June 2003. Like all AIRS product releases, all products are accessible to the public in order to have the best user feedback on issues that appear in the data. Fortunately the products have had exceptional accuracy and stability. This paper presents the improvement between AIRS Version 4.0 and Version 5.0 products and shows examples of the new products available in Version 5.0.
The Atmospheric Infrared Sounder (AIRS) sounding suite, launched in 2002, is the most advanced atmospheric
sounding system to date, with measurement accuracies far surpassing those of current operational weather satellites.
From its sun-synchronous polar orbit, the AIRS system provides more than 300,000 all-weather soundings covering
more than 90% of the globe every 24 hours. Usage of AIRS data products, available to all through the archive system
operated by NASA, is spreading throughout the atmospheric and climate research community. An ongoing validation
effort has confirmed that the system is very accurate and stable and is close to meeting the goal of providing global
temperature soundings with an accuracy of 1 K per 1-km layer and water vapor soundings with an accuracy of 20%
throughout the troposphere, surpassing the accuracy of radiosondes. This unprecedented data set is currently used for
operational weather prediction in a number of countries, yielding significant positive impact on forecast accuracy and
range. It is also enabling more detailed investigations of current issues in atmospheric and climate research. In addition
to the basic soundings related to the hydrologic cycle, AIRS also measures a number of trace gases, the latest such
product being the global distribution of carbon dioxide. We discuss some examples of recent research with AIRS data.
The Earth Science and Meteorological communities are taking great interest in a new instrument released by NASA. The Atmospheric Infrared Sounder (AIRS), launched on the EOS Aqua Spacecraft on May 4, 2002, is a high spectral resolution infrared imaging spectrometer with over 2300 distinct infrared wavelengths ranging from 3.7 μm to 15.4 μm. AIRS is unique in that it provides the highest infrared spectral resolution to date while also providing coverage of over 95% of the Earth's surface every day at 15 km spatial resolution. The AIRS project is currently managed by NASA's Jet Propulsion Laboratory in Pasadena, California1. The AIRS is providing a wealth of scientific data to the Earth Science community including upper atmospheric water vapor and atmospheric composition on key greenhouse gases. It is also improving weather forecasting and the studies of processes affecting climate and weather.
The Atmospheric Infrared Sounder (AIRS), Advanced Microwave Sounding Unit (AMSU), and Humidity Sounder from Brazil (HSB) are three instruments onboard the Earth Observing System (EOS) Aqua Spacecraft. Together, they form the Aqua Infrared and Microwave Sounding Suite (AIMSS). This paper discusses the science objectives and the status of the instruments and their data products one year after launch. All instruments went through a successful activation and calibration and have produced exceptional, calibrated, Level 1B data products. The Level 1B Product Generation Executables (PGEs) have been given to NOAA and the GSFC DAAC for production and distribution of data products. After nine months of operations, the HSB instrument experienced an electrical failure of the scanner. Despite the loss of HSB, early validation results have shown the AIRS and AMSU are producing very good temperature profiles.
We describe preliminary comparisons of AIRS/AMU/HSB retrieved geophysical products with correlative data sets to constrain retrieval uncertainties. The results are relevant to the 70% of oceanic retrieval footprints within the latitude range from 40S to 40N where infrared retrievals are completed. Comparisons are further limited to those retrievals whose sea surface temperatures (SST) agree with forecast model SST to within ±3 K. We present here comparisons with forecast model assimilations and dedicated radiosondes. Retrieved cloud cleared radiances and those calculated from weather forecast model output agree within 0.5 to 3 K, depending on cloud amount. Retrieved sea surface temperatures at night are compared against model output, with a resulting difference of 0.94 ± 0.95 K (a result skewed by the ±3 K selection criterion). Retrieved temperature profiles are compared with model output, and with dedicated radiosondes. Temperature profile uncertainties vary from about 1.3 K just above the surface to less than 1 K in the troposphere. Total water vapor is compared against dedicated radiosondes. Under dry conditions retrieved total water vapor agrees with radiosonde total water to within 10%, with small biases. The current retrieval algorithm generates temperature profiles meeting the 1 K per km requirement of the AIRS system.