A53D-01 INVITED 13:40h
An Overview of SAGE III Validation Activities
The Stratospheric Aerosol and Gas Experiment (SAGE) III satellite mission was launched in December 2001 to provide continued solar occultation measurements of aerosols, ozone, water vapor, and other trace species needed to assess changes to atmospheric composition. The instrument has an advanced design from its predecessors that also permits measurements during lunar occultation events and with a limb scattering mode. The validation effort for this mission has focused primarily on two different approaches. The first emphases matched comparisons between SAGE III and other satellite instruments (e.g., SAGE II, POAM III, and HALOE) and ozonesondes to determine relative biases and precision. The second approach utilizes comprehensive aircraft, balloon, and rocket measurements obtained during the SAGE III Ozone Loss and Validation Experiment (SOLVE) II and Validation of International Satellites and Study of Ozone Loss (VINTERSOL) field experiments in January-February 2003. These data have been used to provide correlative measurements not available from other satellite data sets and to augment match comparisons. Of considerable value is the rich set of aircraft observations from SOLVE II/VINTERSOL that were specifically designed to acquire insight into basic assumptions with the retrieval technique (e.g. constituent homogeneity along the satellite-sun line-of-sight) and assess the quality of spectroscopic information with atmospheric observations (e.g., ozone cross sections in the Wulf band region). This talk will highlight comparison findings for the SAGE III Version 3 dataset from both of these approaches.
A53D-02 INVITED 14:00h
Validation Program for the Atmospheric Chemistry Experiment (ACE): Overview and Initial Results
The Atmospheric Chemistry Experiment (ACE) is a Canadian scientific satellite mission designed to make remote sensing measurements of the Earth's atmosphere. The SCISAT-1 satellite, carrying the ACE payload, was successfully launched into a 650 km altitude, 74 degree inclination orbit on August 12, 2003. The primary instrument on-board SCISAT-1 is a high-resolution (0.02 cm-1) Fourier Transform Spectrometer (ACE-FTS) operating between 750 and 4100 cm-1. It also contains two filtered imagers to measure atmospheric extinction due to clouds and aerosols at 0.525 and 1.02 microns. The secondary instrument is a dual UV-visible-NIR spectrograph called MAESTRO which extends the wavelength coverage to the 280-1000 nm spectral region. Both instruments use solar occultation to obtain profiles of atmospheric trace gas species, temperature and pressure. The ACE Validation Program was developed to validate the level 2 profile results from the ACE mission. The program involves comparisons with results from experiments such as satellite-based instruments, balloon and aircraft campaigns and ground-based observations. The validation process is to be undertaken in two phases. Initial comparisons are primarily being made with results from satellite-based instruments. Throughout the life of the mission there will be ongoing comparisons to ground-, balloon-, and aircraft-based experiments as well as satellite data. A group of validation experiment teams from around the world has been assembled to collaborate on the ACE validation program. The plans for validation of the ACE level 2 data products will be outlined and initial validation comparison results will be presented.
http://www.ace.uwaterloo.ca
A53D-03 14:20h
Aerosol Properties From Multi-angle Satellite Imaging
The MISR Aerosol Product is reaching maturity, the result of a multi-faceted validation effort. The MISR product provides, in addition to aerosol optical depth (AOT), information about particle size, shape, and single-scattering albedo (SSA). Particle micro-physical property retrievals are much more difficult to validate than AOT; there are significant uncertainties in aerosol size, and especially shape and SSA, as obtained from surface-based sun photometers, whereas instrumented aircraft must fly complex patterns to adequately sample all the aerosol layers in the entire column seen simultaneously by MISR. In addition to AOT, size, and SSA constraints from numerous AERONET surface monitoring sites, the MISR particle property validation effort relies on coincident satellite and field observations made as part of the PRIDE, SAFARI-2000, ACE-Asia, CLAMS, CRYSTAL-FACE, and INTEX-NA campaigns. We developed a technique for creating environmental snapshots from multiple, near-simultaneous in situ and surface measurements, which amount to full-column optical models of the ocean surface and atmosphere viewed by the satellite. The implementation sheds light on the complementary nature of satellite and in situ aerosol observations, and provides validation events for a range of clean, dusty, polluted, maritime and continental cases. In addition to showing statistical summaries of MISR-AERONET inter-comparisons, we will present examples where we bring together detailed field observations, offering stronger, quantitative constraints on the satellite aerosol retrievals. This work is performed at the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration.
http://www-misr.jpl.nasa.gov
A53D-04 14:40h
Comparison of Tropical GPS Radio Occultation Temperature and Water Vapor Retrievals with Ground-based Lidar and Radiosonde
An intercomparison of temperature and water vapor soundings from CHAMP and SAC-C GPS radio occultations with coincident ground-based lidar measurements by the Aerospace Transportable Lidar System (ATLS) and ancillary radiosondes is presented. GPS occultations provide globally distributed high vertical resolution, horizontally averaged soundings of atmospheric refractivity. Stratospheric and upper tropospheric temperature and lower tropospheric water vapor can be obtained from refractivity. Imperfect ionospheric corrections and assumptions of mesosphere and upper stratosphere (~35-80 km) temperatures can result in unphysical oscillations in the upper regions of the GPS occultation temperature profile. Results from a recent January lidar campaign conducted in Hawaii during which lidar and GPS occultation detected significant medium to large-scale stratospheric wave activity are analyzed. An upper bound for physically significant temperature oscillations, atmospheric gravity waves, is deduced. Comparisons of water vapor are complicated by both its high temporal and spatial variability and the ambiguity in measuring water vapor and temperature with the GPS occultation method. However, we show that the vertical structure of water vapor in radiosonde, lidar and GPS occultation is in reasonable agreement.
A53D-05 14:55h
Intercomparison of long-term changes in middle atmospheric water vapor as measured by HALOE, POAM, and the Water Vapor Mm-wave Spectrometer (WVMS) instruments
We present 12 years of coincident water vapor measurements from the HALogen Occultation Experiment (HALOE) and several ground-based Water Vapor Mm-wave Spectrometer (WVMS) instruments which observe from 40-80km. The WVMS instruments at Lauder, New Zealand (45.0S, 169.7E) and Table Mountain, California (34.4N, 242.3E) both confirmed the large increase in water vapor observed globally by HALOE from 1991-1996 (2%/year). From 1996 to the present the WVMS instruments at Lauder, New Zealand and Mauna Loa, Hawaii (19.5N, 204.4E) and HALOE have shown no clear trend in the upper stratosphere and mesosphere. Since measurements near the peak of the water vapor mixing ratio are not significantly affected by the vertical transport rate, the absence of any observed trend at these altitudes indicates (with some delay in time) that there was no long-term trend in water vapor entering the stratosphere. We will discuss the uncertainty in the observed long-term variations given measurements from several independent instruments, including the newly reintroduced WVMS Table Mountain instrument, which has been operating since November, 2003. We will also show how the 0.3 ppmv (4% of the water vapor at 60km) decrease in lower stratospheric water vapor observed since 2001 by HALOE and the Polar Ozone and Aerosol Measurement (POAM) III instrument have affected upper stratospheric measurements. Finally, we will also discuss how these effects compare to the large changes in middle atmospheric water vapor observed in the upper stratosphere/lower mesosphere in the early 1990s.
http://wvms.nrl.navy.mil
A53D-06 15:10h
Retrieval of Trace Gas Profiles From Low-Resolution Emission Radiometers Flown on Four MANTRA Balloon Missions
Results are presented for two infrared emission radiometers flown on the MANTRA (Middle Atmosphere Nitrogen TRend Assessment) balloon missions. Four MANTRA campaigns have culminated in balloon launches in the late summer of 1998, 2000, 2002, and 2004 from Vanscoy, Canada ($52\deg$N, $107\deg$W). Raw radiance measurements collected during each balloon ascent are analyzed using a forward estimation technique to simultaneously recover multiple trace gas profiles from the low-resolution spectral measurements of atmospheric radiance. The technique uses detailed atmosphere and instrument models and a least-mean-squares minimization technique to iterate best-fit volume mixing ratios for several gas species, based on atmospheric emission data taken in the 800-1250 cm$^{-1}$ atmospheric window at an instrument resolution of approximately 20 cm$^{-1}$. The primary trace gas measured by this instrument is nitric acid. Relevant retrieved profiles are compared with those obtained from infrared solar occultation spectra recorded by high-resolution Fourier transform spectrometers also flown on the 1998, 2002, and 2004 missions. These results are also compared with available data from the Sub-Millimetre Radiometer (SMR) on Odin and from the ACE-FTS on Scisat-1, as well as with general nitric acid climatologies based on observations by the Microwave Limb Sounder instrument onboard the Upper Atmosphere Research Satellite.
http://www.atmosp.physics.utoronto.ca/MANTRA
A53D-07 15:25h
Measurements of Trace Gas (NO2, SO2, HCHO, O3) Amounts, Aerosol Properties, and UV Irradiance for Aura Validation Using Overlapping Spectral Measurements from Four Different Instruments
Aura validation measurements of NO2, SO2, HCHO, O3, aerosol properties, and UV irradiance are discussed based on a closure experiment using a coordinated suite of four ground-based instruments currently operating at Goddard Space Flight Center (GSFC). The instrument cluster will be operated at GSFC and the data compared with results from AURA overflights. After the initial AURA comparisons, we plan to move the instrument suite to other sites for participation in AURA aircraft campaigns and to sites that measure in extremely polluted and extremely clean environments. The four instruments are 1) a uniquely improved double Brewer spectrometer, 2) a modified UV Multifilter Rotating Radiometer (UV-MFRSR), 3) a CIMEL sun and sky photometer, and 4) an aerosol Micropulse Lidar (MPL). O3, NO2, HCHO, and SO2 column amounts will be measured by using the improved double Brewer spectrometer in direct-sun mode. A new "bootstrap" solar irradiance method has enabled the Brewer spectrometer to detect NO2, HCHO, and SO2 with a sensitivity of approximately 0.4 DU. Clean-site solar irradiance data from Mauna Loa will improve the sensitivity. O3 and UV irradiances will be measured by both the Brewer spectrometer and UV-MFRSR providing overlapping ground-based data and validation for Aura observations. Aerosol properties will be measured by three instruments (Brewer, CIMEL, and UV-MFRSR), providing particle size, optical depth, and absorption optical thickness (single scattering albedo) as a function of wavelength in the combined UV-Visible spectral range (305nm - 1020nm). The extension of these properties into the UV range will be used to validate aerosol UV-VIS absorption optical thickness measurements from the Aura-OMI spectrometer.