EAQUATE An International Experiment For Hyperspectral Atmospheric Sounding Validation BY J. P. TAYLOR, W. L SMITH, V. CUOMO, A. M. LARAR, D. K. ZHOU, C. SERIO, T. MAESTRI, R. RIZZI, S. NEWMAN, P. ANTONELLI, S. MANGO, P. DI GIROLAMO, F. ESPOSITO, G. GRIECO, D. SUMMA, R. RESTIERI, G. MASIELLO, F. ROMANO, G. PAPPALARDO, G. PAVESE, L. MONA, A. AMODEO, AND G. PISANI The validation of advanced infrared sounding satellites requires a diverse set of coordinated synergistic observations utilizing ground based and^airbome instrumentation. The European Aqua Thermodynamic Experi- hyperspectral sounding instruments, modeled after ment (EQUATE) was held in September 2004 the experimental Geosynchronous Imaging Fourier in both Italy and the United Kingdom to vali- Transform Spectrometer (GIFTS), are being planned date data from the Atmospheric Infrared Sounder for implementation during the next decade. (AIRS) instrument on the Earth Observing System The focus of this initial experiment was placed (EOS) Aqua satellite. It also aimed to demonstrate on the validation of the AIRS instrument on the how combinations of ground-based and airborne EOS Aqua satellite. During EAQUATE, the Proteus systems are useful for validating hyperspectral sat- aircraft, carrying five separate remote sensing ellite sounding observations from satellites due for instruments [the NPOESS Airborne Sounder launch through this decade. The era of hyperspectral Testbed-Interferometer (NAST-I), NAST-Microwave atmospheric sounding began with the launch of the (NAST-M), Scanning High-Resolution Infrared AIRS experiment of the EOS Aqua satellite during Sounder (S-HIS), Far-Infrared Sensor for Cirrus May 2002. Following AIRS, the Infrared Atmospheric (FIRSC), and Microscale Measurement of Atmospheric Sounding Interferometer (IASI) was launched Pollution Sensor (micro-MAPS)], was stationed in aboard the Meteorological Operational (METOP) Naples, Italy, from 4 to 11 September and in Cranfield polar-orbiting satellite in October 2006, and the United Kingdom, from 11 to 19 September 2004. Cross-Track Infrared Sounder (CrIS) instrument is During the Italian portion of the campaign, Proteus to be orbited aboard the National Polar-Orbiting underflew Aqua in coordination with ground-based Environmental Satellite System (NPOESS) Prepatory remote sensing measurements, including several Project (NPP) operational series of polar orbiters in Raman lidar water vapor and temperature profilers late 2009. Operational geostationary satellite imaging and radiosondes, provided by • |CA|I M|TE0|0|JDGIC# L SCJCIETY Unauthenticated | Downloaded 10/09/21 05:34 AM UTC the Istituto di Metodologie per l'Analisi Ambientale (IMAA), the Dipartimento di Ingegneria e Fisica delFAmbiente (DIFA), the University of Basilicata in Potenza, and the Univer- sity of Naples (UNINA), in Napoli, Italy. During the U.K. portion of the campaign, the Proteus underflights of Aqua were coordinated with the U.K. Facility for Airborne Atmospheric Measurements (FAAM) BAel46-301 aircraft, which flew a large payload of in situ measurement instru- FIG. I. The Proteus aircraft showing instrumentation fitted during ments, including dropsondes EAQUATE. and remote-sensing instru- ments [e.g., the Airborne Research Interferometer Oceanic and Atmospheric Administration (NOAA)- Evaluation System (ARIES) interferometer spec- National Aeronautics and Space Administration trometer], useful for validating the Aqua satellite (NASA) Integrated Program Office (IPO) for the observations. A brief description of the instrumen- NPOESS carried five separate radiometers. The tation used in the EAQUATE campaign is given in Proteus generally maintained a flight altitude in "Instrumentation," followed by a description of some the range of 15-17 km, depending upon flight of the results from "The Italian phase" and "The U.K. duration, when underflying the Aqua satellite and phase." The "Conclusions" discuss the merits of cali- overflying the IMAA/DIFA ground sites and the bration and validation of satellite instruments and the FAAM BAel46-301 aircraft measurements. required synergy of different observing systems. The results presented in this paper often rely on FAAM BAel46-30l (Met Office and NERC). The complex retrieval theory. A good review of a range FAAM BAel46-301 (Fig. 2) is jointly funded by the of the retrieval techniques used here is presented in Met Office and the Natural Environment Research Zhou et al. (2006) and Amato et al. (2002). Council (NERC). Capable of operating between 15 m and 10.5 km, the aircraft can carry a scientific INSTRUMENTATION. Full details of the key payload of 4,000 kg. For the EAQUATE campaign instrumentation used in the EAQUATE campaign the scientific payload consisted of a combination of is given in Table 1. spectrometers for measuring the radiation from the visible to the microwave region of the electromagnetic Proteus (IPO). The Proteus aircraft (Fig. 1), sponsored spectrum plus an array of instrumentation to char- by the Department of Defense (DoD)-National acterize the troposphere both in terms of thermody- AFFILIATIONS: TAYLOR AND NEWMAN—Met Office, Exeter, Devon, Interuniversitario per le Scienze fisiche della Materia, United Kingdom; SMITH—Hampton University, Hampton, Virginia, University of Naples, Napoli, Italy and University of Wisconsin—Madison, Madison, Wisconsin; CORRESPONDING AUTHOR: Dr. Jonathan P. Taylor, CUOMO, ROMANO, PAPPALARDO, PAVESE, MONA, AND AMODEO—Istituto Met Office, FitzRoy Road, Exeter, Devon, EXI 3PB, United di Metodologie per l'Analisi Ambientale, CNR, Tito Scalo, Italy; Kingdom LARAR AND ZHOU—NASA Langley Research Center, Hampton, E-mail: [email protected] Virginia; SERIO, DI GIROLAMO, ESPOSITO, GRIECO, SUMMA, RESTIERI, The abstract for this article can be found in this issue, following the AND MASIELLO—Dipartimento di Ingegneria e Fisica dell'Ambiente, table of contents. University of Basilicata, Potenza, Italy; MAESTRI AND RIZZI—Physics DOI: 10.1175/BAMS-89-2-203 Department, Alma Mater Studiorum, University of Bologna, Bologna, Italy; ANTONELLI—Mediterranean Agency for Remote In final form 6 July 2007 Sensing, Benevento, Italy; MANGO—NPOESS Integrated Program ©2008 American Meteorological Society Office, Silver Spring, Maryland; PISANI—Consorzio Nazionale 204 | BAFISr FEBRUARY 2008 Unauthenticated | Downloaded 10/09/21 05:34 AM UTC namical variables like temperature and water vapor, cold space and hot calibration targets are provided by and also particulates in the form of aerosols and a 360° rotation of the scan mirror every 2.67 s. The cloud particles. The main focus of the work during AIRS radiance measurement accuracy and its ability EAQUATE was cloud-free atmospheres, but one to achieve the 1-K/l-km sounding accuracy objective flight in cirrus clouds was conducted under an Aqua are to be validated using the EAQUATE surface and overpass. During the EAQUATE flights dropsondes airborne datasets. were launched to give vertical profiles of temperature and water vapor. During satellite overpasses up to THE ITALIAN PHASE. The Italian phase of 14 sondes were launched in quick succession, giving the EAQUATE measurement campaign took place high levels of spatial detail. In addition to the ther- between 6 and 10 September 2004. modynamic measurements, the BAel46-301 made Figure 3 shows the times for all measurements; continuous measurements of carbon monoxide and note that two flights of the Proteus aircraft were ozone concentrations and also measured aerosol and coincident with Aqua overpasses. cloud particle size, shape, and concentration. The Proteus aircraft flew legs at high altitudes along the line of the Aqua overpasses at 0101 UTC Ground based (IMAAIDIFAIUNINA). A wide range of 8 September and 0056 UTC 10 September (Fig 4). instrumentation was used during EAQUATE mea- The numbers of overpasses of the ground sites by the surement campaign: ground based, airborne, and Proteus aircraft are given in the figures. satelliteborne. During the Italian phase of the experiment, the NAST-I, AIRS retrieval validation. The NAST-I instru- ground-based instrumentation was located at three ment on Proteus covers the entire spectral range different sites located in southern Italy. These systems of AIRS at greater resolution, allowing the direct were operated continuously throughout the Proteus comparison of radiances and level-2 products, like airborne measurement period, which included the temperature and water vapor. During the night of Aqua overpass times. 9-10 September 2004 the Proteus aircraft flew a flight track over southern Italy that was coincident with Aqua AIRS (NASA). The AIRS instrument flying aboard the AIRS overpass at 0056 UTC 10 September. The the EOS Aqua polar-orbiting satellite is the first space- aircraft track passed over the Potenza site, allowing borne spectrometer designed to meet the 1-K/l-km for a direct comparison of the satellite, aircraft, sounding accuracy objective of future operational satel- and ground-based profile information (Fig. 4). The lite sounders by measuring the infrared spectrum quasi NAST team of scientists has developed an inversion continuously from 3.7 to 15.4 ^m, with high spectral scheme. Detailed NAST-I physically based empirical resolution (v/Sv = 1200/1). The sensitivity requirements, orthogonal function (EOF) regression and simulta- expressed as noise-equivalent differential temperature neous matrix inversion (i.e., nonlinear multivariable (NEDT), referred to a 250-K target temperature and physical iteration) can be found