The Jet Propulsion Laboratory (JPL) is best known for planetary exploration but is also heavily involved in Earth science and has in recent years become one of the premier centers for atmospheric science related to infrared and microwave satellite sounders such as the Atmospheric Infrared Sounder (AIRS), the Advanced Microwave Sounding Unit (AMSU) and the Advanced Technology Microwave Sounder (ATMS), as well as aircraft based microwave sounders such as the High Altitude MMIC Sounding Radiometer (HAMSR) and the development of future sounders such as an infrared CubeSat system (CIRAS) and a geostationary microwave sounder (GeoSTAR). We give a brief overview of these sensors and focus on the development and assessment of sounder data products, which include vertical profiles of temperature and water vapor, cloud and surface parameters, and in the case of infrared sounders also trace gas estimates and for microwave sounders precipitation as well. The baseline AIRS data product “retrieval system” was developed by the AIRS science team and has been undergoing continuous maintenance and upgrade in close collaboration with the sounder team at JPL. To support that process, the JPL team has developed a broad range of assessment tools and techniques, which can be applied to data from other sounders as well and can range from simple “sanity check” analysis to thorough “validation” analysis. An example of the less complex testing is the preliminary assessment of products generated by new retrieval systems operating on data from the Cross-track Infrared Sounder (CrIS) and the Advanced Technology Microwave Sounder (ATMS) flying on the Suomi NPP and JPSS satellites. These retrieval systems are developed by individual investigators funded by NASA research grants and are delivered to a Sounder “Science Investigator Processing System” (SIPS) located at JPL for integration, testing and delivery to a NASA data processing center and eventual release to the public, but only limited resources are available to the SIPS for the assessment, which therefore must be relatively superficial. An example of thorough assessment is the quantification of the impact on AIRS products of the failure of the AMSU-A2 microwave sounder 2 years ago. The baseline AIRS retrieval system used initially data from the companion microwave sounders, the Humidity Sounder for Brazil (HSB), AMSU-A1 and AMSU-A2, to provide a “first guess” and support “cloud clearing”. As these instruments suddenly failed (HSB) or gradually deteriorated (AMSU), some effort was devoted to develop a version that did not depend on microwave data. It was considered somewhat inferior to the baseline system and was kept in reserve and therefore not fully assessed. When AMSU-A2 failed, this AIRS-only system became the primary version, and a substantial effort was undertaken to fully assess its performance. We discuss details of that assessment. These capabilities have resulted from substantial investments NASA has made over the years in support of AIRS and can now be applied to next-generation systems as well.
The Atmospheric Infrared Sounder (AIRS) and companion instrument, the Advanced Microwave Sounding Unit
(AMSU) on the NASA Earth Observing System Aqua spacecraft are facility instruments designed to support
measurements of atmospheric temperature, water vapor and a wide range of atmospheric constituents in support of
weather forecasting and scientific research in climate and atmospheric chemistry. This paper is an update to the science
highlights from a paper by the authors released last year and also looks back at the lessons learned and future needs of
the scientific community. These lessons not only include requirements on the measurements, but scientific shortfalls as
well. Results from the NASA Science Community Workshop in IR and MW Sounders relating to AIRS and AMSU
requirements and concerns are covered and reflect much of what has been learned and what is needed for future
atmospheric sounding from Low Earth Orbit.
KEYWORDS: Clouds, Temperature metrology, Climatology, Gases, Space operations, Data centers, Data processing, Carbon dioxide, Infrared radiation, Microwave radiation
The Atmospheric Infrared Sounder (AIRS) on the EOS Aqua Spacecraft was launched in May of 2002. The AIRS
Sounding Suit, AIRS along with AMSU-A and HSB, were designed to measure the atmospheric temperature and water
vapor profiles, the surface and the cloud parameters for climate research and for improvement in weather forecast. Over
the last 8+ years AIRS has been operating extremely stable, far surpassing original design life of 4 - 5 years. Many
exciting research papers on climate have been published with AIRS data. The AIRS data are assimilated by most NWP
centers and have shown considerable improvement in forecast skill. We will describe the current status of the
instruments as well as the new activity on the data processing software.
The Atmospheric Infrared Sounder (AIRS) on the EOS Aqua Spacecraft was launched on May 4, 2002. Early in the
mission, the AIRS instrument demonstrated its value to the weather forecasting community with better than 6 hours of
improvement on the 5 day forecast. Now with over eight years of consistent and stable data from AIRS, scientists are
able to examine processes governing weather and climate and look at seasonal and interannual trends from the AIRS
data with high statistical confidence. Naturally, long-term climate trends require a longer data set, but indications are
that the Aqua spacecraft and the AIRS instrument should last beyond 2018. This paper briefly describes the AIRS data
products and presents some of the most significant findings involving the use of AIRS data in the areas of weather
forecast improvement, climate processes and model validation, cloud and polar processes, and atmospheric composition
(chemistry and dust).
The wide range of products available from AIRS have made it invaluable as a tool for operational weather forecasting
and climate modeling. AIRS has improved the 5 day forecast by 6 hours in the NCEP operational system and
researchers have identified further improvement potential by assimilation of more channels and footprints. AIRS data
have been used to validate the distribution and transport of water vapor and greenhouse gases in climate models,
resulting in the identification of significant errors in the handling of these quantities. We present the AIRS Version 5
products and their accuracies and reference key papers involving their use. We also touch briefly on the limitations of
AIRS due to its coarse spatial resolution, particularly in achieving boundary layer sensitivity.
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.
This study will present results of an effort to validate the accuracy of the cloud-cleared radiance products of the Atmospheric Infrared Sounder (AIRS) using observations from a variety of aircraft based sensors. The AIRS cloud-clear radiances are a product of the Level 2 ground processing software developed by the NASA AIRS science team. The cloud-clear radiance represents an estimate of the infrared upwelling spectrum at the top of the atmosphere for a cloud free atmosphere. This study concentrates on observations collected during the Pacific THORpex experiment, conducted in February-March 2003. NASA ER-2 aircraft based observations from the Scanning-High Resolution Interferometer Sounder (S-HIS) and the MODIS Airborne Simulator (MAS) are used in this validation effort.
The Atmospheric Infrared Sounder (AIRS) was launched in May 2002. Along with two companion microwave sensors, it forms the AIRS Sounding Suite. This system is the most advanced atmospheric sounding system to date, with measurement accuracies far surpassing those available on current weather satellites. The data products are calibrated radiances from all three sensors and a number of derived geophysical parameters, including vertical temperature and humidity profiles, surface temperature, cloud fraction, cloud top pressure, and ozone burden. These products are generated under cloudy as well as clear conditions. An ongoing calibration/validation effort has confirmed that the system is very accurate and stable, and most of the geophysical parameters have been validated. AIRS is in some cases more accurate than any other source and can therefore be difficult to validate, but this offers interesting new research opportunities. The applications for the AIRS products range from numerical weather prediction to atmospheric research - where the AIRS water vapor products near the surface and in the mid to upper troposphere will make it possible to characterize and model phenomena that are key for short-term atmospheric processes, such as weather patterns, to long-term processes, such as interannual cycles (e.g., El Niño) and climate change.
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.
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.
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