Aircraft-Borne Measurements    

/gif/alias.gif (27765 bytes)     ALIAS (Aircraft Laser Infrared Absorption Spectrometer) measures the abundance of HCl (hydrochloric acid), N2O (nitrous oxide), CH4 (methane), and CO (carbon monoxide) in the stratosphere and troposphere aboard the NASA ER-2 high-altitude aircraft.  The instrument measures the absorption by target molecules of light generate by a high-resolution, four-channel scanning tunable diode laser.  Measurements obtained during six ozone field campaigns have provided new understanding regarding how volcanic aerosols and polar stratospheric clouds initiate ozone depletion.  Click Here for the ALIAS Homepage
/jpeg/unir_dc8.jpg (104708 bytes)     The Laser Hygrometer measures the abundance of H2O (water vapor) aboard the NASA DC-8, ER-2, and WB-57 aircrafts.  The instrument measures the absorption of infrared light generated by a tunable diode laser as the light passes through a pair of external mirrors mounted in a manner that allows for multiple passes of the light beams.  The measurements have been used to study the composition of polar stratospheric clouds and the affect of aerosols on Earth's climate.  Click Here for the Laser Hygrometer Homepage
/gif/mtpdc8.gif (125311 bytes)     MTP (Microwave Temperature Profiler) measures the vertical profile of temperature from the NASA DC-8, ER-2, and WB-57 research aircrafts.  The instrument measures the emission of microwave energy by atmospheric oxygen using a radiometer capable of scanning both frequency and elevation.  Measurements obtained during numerous tropospheric ozone and stratospheric ozone field campaigns have provided new insight into how air air is exchanged between the troposphere and stratosphere and how perturbations in stratospheric temperature due to high-elevation mountains affect the growth of polar stratospheric clouds.  Click Here for the MTP Homepage

/jpeg/radiometer.jpg (144406 bytes)     The Sea Surface Temperature Radiometer (SSTR) obtains measurements of ocean surface temperature as well as the intensity of upwelling infrared radiation.  Theinstrument is a high precision radiometer that uses four optical band passes covering the spectral range from 850 to 1000 cm-1 as well as a broad spectral filter with an effective bandwidth of 873 to 1013 cm-1.  Data have been used in a number of field campaigns to better understand radiative transfer processes in the lower troposphere and the processes that regulate sea-surface temperature, improving model predictions of climate change. 

/jpeg/ssr.jpg (59617 bytes)     The Solar Spectral Radiometer (SSR) measures the intensity of solar radiation at many different directions within Earth's atmosphere.  This compact (9 cm diameter), light weight (less than 1 kg) instrument incorporates micro-thermopile detectors in a housing similar to commercial pyranometers and obtains fast response (75 ms) measurements over a large spectral range (200 to 2700 nm).  Data have been used to better understand radiative transfer processes in Earth's atmosphere, improving model predictions of climate change.
/jpeg/wisp.jpg (36317 bytes)    WISP (Water Isotope Spectrometer) is a new instrument designed to measure the isotopic abundance of water vapor in the upper troposphere and lower stratosphere from NASA's WB-57 aircraft.  The absorption of laser light due to closely space absorption features of the target molecules is monitored as the light traverses back and forth within an
open-path Herriott cell suspended beneath the aircraft.  The measurements will be used to better understand the microphysical processes that regulate the water vapor abundance of the middle atmosphere, which is critical for assessing the sensitivity of stratospheric ozone to climate change and the strength of the "water vapor feedback" that may exacerbate surface warming due to rising concentrations of greenhouse gases.  Click Here for the WISP Homepage

Balloon-Borne Measurements

/jpeg/aliasii.jpg (263038 bytes)     ALIAS II (Aircraft Laser Infrared Absorption Spectrometer) measures the abundance of stratospheric HCl (hydrochloric acid), N2O (nitrous oxide), CH4 (methane), and CO2 (carbon dioxide) aboard the NASA OMS in situ balloon gondola.  The instrument measures the absorption by target molecules of light generated by a high-resolution, four-channel scanning tunable diode laser.  Measurements obtained during flights from New Mexico, Alaska, Brazil, and Sweden have been used to constrain the exchange rate of air from different regions of the stratosphere, which is essential for the development of more realistic models of stratospheric transport.  Click Here for the ALIAS II Homepage

/jpeg/filos.jpg (131055 bytes)     FILOS (Far-Infrared Limb Observing Spectrometer) measures the concentration of the hydroxyl radical (OH).  The instrument is a Fabry-Perot interferometer that detects infrared radiation at the very precise wavelengths characteristic of emission by OH.  The observations have been used to study the photochemistry of upper stratospheric ozone; a second instrument currently under development will measure OH using heterodyne techniques with increased sensitivity and will be used to validate measurements of OH to be obtained by the new MLS instrument aboard the EOS Aura platform. 
     The balloon-based MkIV measures the distribution of stratospheric ozone and several dozen other gases aboard the NASA OMS remote balloon gondola.  The instrument measures the absorption of sunlight by atmospheric molecules using a high-resolution Fourier transform spectrometer that operates in solar occultation mode.  Measurements obtained during flights New Mexico, Texas, Alaska, and Sweden have been used to show that the decomposition of CFCs is the primary source of stratospheric chlorine and have improved our understanding of how volcanic aerosols and polar stratospheric clouds lead to enhanced ozone depletion by chlorine in the lower stratosphere.  Click Here for the MkIV Homepage

/jpeg/sls1.jpg (57034 bytes)     The SLS (Submillimeterwave limb sounder) measures the distribution of stratospheric ClO (chlorine monoxide), HCl (hydrochloric acid), N2O (nitrous oxide), CF2CL2 (CFC-12), and O3 (ozone) from the NASA OMS remote balloon gondola and from a European gondola.  The instrument measures energy emitted in the microwave by atmospheric gases using a high resolution heterodyne radiometer-spectrometer.  Measurements obtained during numerous flights from Sweden have helped establish that chlorine from industrial-CFCs leads to the depletion of Arctic ozone during winter and spring.

/jpeg/uvozone1.jpg (25922 bytes)     The UV-Ozone instrument measures the concentration of ozone aboard the NASA OMS remote and in situ balloon gondolas.  The instrument measures the absorption of UV light generated by a mercury lamp.  Measurements obtained during flights from New Mexico, Texas, Alaska, Brazil, and Sweden have played an integral role in numerous studies of stratospheric photochemistry and dynamics. Click Here for the UV-Ozone Homepage

Ground-Based Measurements

/gif/laser.gif (23755 bytes)     The LIDAR system measures profiles of ozone, temperature, and aerosols from the Table Mountain (34.38 N) research facility near JPL and from the Mauna Loa, Hawaii (19.54 N) observatory.  The measurements are obtained by analyzing laser light that is reflected from the atmosphere into a collection telescope.  The data have been used to study the effects of volcanoes on ozone and to help validate satellite observations of ozone and aerosols.  Click Here for the LIDAR Homepage
/jpeg/ground.jpg (353786 bytes)     The ground-based MkIV measures the total column abundance of O3, the dynamical tracer HF (hydrogen fluoride), other halogen species such as HCl (hydrogen chloride) and ClNO3 (chlorine nitrate), and numerous other gases from a variety of locations.  Physically, this is the same instrument that also flies on the NASA OMS remote balloon gondola and operates using solar absorption spectrometry.  Measurements obtained during the National Ozone Expedition (NOZE) experiment from Antarctica in 1986 were used to show, along with data from other instruments, that the Antarctic ozone hole is caused by chlorine resulting from the decomposition of CFCs.  The measurements continue to play an important role in isolating the effects of chemistry and dynamics on ozone during field experiments such as the recent SOLVE Arctic ozone field campaign.  Click Here for the MkIV Homepage
/gif/UVvis.gif (95678 bytes)     The AVUS (Atmospheric Visible-UV Spectroscopy)  instruments measure the vertical column abundance of OH (hyroxyl), NO2 (nitrogen dioxide), NO3 (nitrate radical), BrO (bromine monoxide) and O3(ozone) from Table Mountain (34.38 N) research facility near JPL.  The two instruments currently in operation measure the absorption of sun light by atmospheric gases based on small fluctuations in the intensity of light at extremely high spectral resolution.   The data currently contribute to an international program designed to measure long-term changes in the global atmosphere called the "Network for Detection of Stratospheric Change"; in the future, the data will also be used as part of the validation effort for the SAGE III and OMI satellite instruments.  Click Here for the AVUS Homepage

Space-Based Measurements

/jpeg/atmos.jpg (176760 bytes)     ATMOS (Atmospheric Trace Molecule Spectroscopy Experiment) has measured the distribution of stratospheric ozone and several dozen other gases for about two-week intervals during four flights on the NASA Space Shuttle between 1985 and 1994.  The instrument measures the absorption of sunlight by atmospheric molecules using a high-resolution Fourier transform spectrometer that operates in solar occultation mode.  The four shuttle missions have played a key role in quantifying the link between industrial-CFCs and ozone depletion.  Click Here for the ATMOS Homepage
/jpeg/airs1.jpg (296347 bytes)     The AIRS (Atmospheric Infrared Sounder) will measure profiles of temperature, humidity and total precipitable water as well as cloud properties (fractional coverage, height, and temperature) and surface temperature.  The instrument, which will fly onboard NASAs Earth Observing System Aqua spacecraft that is scheduled for launch in December 2000, consists of of a high spectral resolution spectrometer that measures upwelling thermal radiation in the visible and near-infrared.  The primary purposes of the mission will be to improve our understanding of the the global energy and water cycles, to monitor climate variations and trends, and to improve numerical weather predictions and model forecasts of climate change.  Measurements of tropopause height and water vapor in the upper troposphere and lowermost stratosphere will be important for quantifying the sensitivity of stratospheric ozone to climate change.  Click Here for the AIRS Homepage
/gif/mls_photo1.gif (216698 bytes)     The MLS (Microwave Limb Sounder) instrument has been measuring the abundance of stratospheric ozone, ClO, and related species from NASA's Upper Atmosphere Research Satellite (UARS) since early January 1991.  The instrument measures energy emitted in the microwave by atmospheric gases using millimeter-wavelength heterodyne receivers.  Measurements from MLS have been crucial in establishing that the Antarctic ozone hole, as well as significant depletion of Arctic ozone during winter and spring, is caused by industrially produced CFCs.  An advanced MLS instrument currently being built for the NASA EOS Aura satellite will measure key molecules critical for understanding global change in Earth's upper troposphere, stratosphere, and mesosphere.  Click Here for the MLS Homepage
/jpeg/tes.jpg (488210 bytes)     The TES (Tropospheric Emission Spectrometer) instrument will measure the distribution of ozone and other trace gases in Earth's troposphere from NASA's EOS Aura satellite.  The instrument measures energy emitted in the infrared using using a high-resolution Fourier transform spectrometer that can operate in either down looking (nadir) or side looking (limb) mode.  The TES observations will be used to generate a three-dimensional observational database important for quantifying the effects of human activity on tropospheric ozone on a global scale, troposphere-biosphere interactions, and troposphere-stratosphere exchange.  Click Here for the TES Homepage 

Revised: 28 August 2000


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Author: Ross J. Salawitch
Page Design: Aaron B. Milam