Synonyms: 
Ozone
O3 Column

O3 Photometer - UAS (NOAA)

Ozone (O3) in the lower stratosphere (LS) is responsible for absorbing much of the biologically damaging ultraviolet (UV) radiation from the sunlight, and thus plays a critical role in protecting Earth's environment. By absorbing UV light, O3 heats the surrounding air, leading to the vertical stratification and dynamic stability that define the stratosphere. Halogen species from anthropogenic compounds such as CFCs can cause significant damage to the O3 layer in the LS and have led to the formation of the Antarctic ozone hole. Accurate measurement of O3 in the LS is the first step toward understanding and protecting stratospheric O3. The UAS Ozone Photometer was designed specifically for autonomous, precise, and accurate O3 measurements in the upper troposphere and lower stratosphere (UT/LS) onboard the NASA Global Hawk Unmanned Aircraft System (GH UAS) and other high altitude research platforms such as the ER-2 and WB-57. With a data rate of 2 Hz, the instrument can provide high-time-resolution, detailed information for studies of O3 photochemistry, radiation balance, stratosphere-troposphere exchange, and air parcel mixing in the UT/LS. Furthermore, its accurate data are useful for satellite retrieval validation.  Contacts: Troy Thornberry, Ru-Shan Gao

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O3 Photometer (NOAA)

Ozone (O3) in the lower stratosphere (LS) is responsible for absorbing much of the biologically damaging ultraviolet (UV) radiation from the sunlight, and thus plays a critical role in protecting Earth's environment. By absorbing UV light, O3 heats the surrounding air, leading to the vertical stratification and dynamic stability that define the stratosphere. Manmade halogen compounds, such as CFCs, cause significant damage to the O3 layer in the LS and lead to the formation of the Antarctic ozone hole. Accurate measurement of O3 in the LS is the first step toward understanding and protecting stratospheric O3. The Ozone Photometer was designed specifically for autonomous, precise, and accurate O3 measurements in the upper troposphere and lower stratosphere (UT/LS). Flown for thousands of hours onboard the NASA ER-2, NASA WB-57, and NSF GV high-altitude aircraft, this instrument has played a key role in improving our understanding of O3 photochemistry in the UT/LS. Furthermore, its accurate data has been used, and continues to be highly sought after, for satellite validation, and studies of radiation balance, stratosphere-troposphere exchange, and air parcel mixing. Contacts: Ru-Shan Gao, David Fahey, Troy Thornberry, Laurel Watts, Steve Ciciora

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Gulfstream V - NSF, WB-57 - JSC, Global Hawk - AFRC
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Ozonesondes (NOAA)

NOAA Ozonesonde payloads include an Electrochemical Concentration Cell (ECC) ozonesonde, and a radiosonde to telemeter data to the ground and provide in situ measurements of temperature, pressure, relative humidity (surface to upper troposphere), and GPS coordinates. Sounding data typically reach an altitude of 28 km.

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Balloon
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Balloonsondes (NOAA)

NOAA Balloonsonde payloads include a NOAA Frost Point Hygrometer (FPH), an Electrochemical Concentration Cell (ECC) ozonesonde, and a radiosonde to telemeter data to the ground and provide in situ measurements of temperature, pressure, relative humidity (surface to upper troposphere), and GPS coordinates. Sounding data typically reach an altitude of 28 km.

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Balloon
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Direct beam Irradiance Airborne Spectrometer

A solar tracking Direct beam Irradiance Airborne Spectrometer (DIAS) is used for calculation of line of sight ozone and wavelength dependent aerosol optical depths.

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Fourier Transform Infrared Spectrometer

The absorption of infrared solar radiation along a slant path to the sun is recorded from 2 to 15 micrometers. Six spectral filters are used to cover the region from 2-15 microns. An interferogram is recorded in about 10 seconds. Interferograms are transformed to produce spectra. Column amounts are retrieved by fitting the observed spectra using the non-linear least squares fitting code SFIT2 that employs an Optimal Estimation retrieval algorithm.

The major chlorine reservoirs (HCl and ClONO2), the important nitrogen-containing gases in the stratosphere (N2O, NO, NO2, and HNO3), stratospheric and tropospheric tracers (HF, CH4, C2H6, H2O, CO2), a major source CFC (CF2Cl2) and ozone may be routinely retrieved.

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Langley In Situ Fast-Response Ozone Measurements

• Technique: Chemluminescent reaction of ozone with nitric oxide
• Dynamic Range: 0.6 - 1600 ppb
• Accuracy: 5% or 2 ppb
• Precision: 2% or 0.6 ppb
• Response: 2-3 Hz; recorded at 6 Hz, reported at 1 Hz, faster data on request
• Spatial Resolution: <10 m vertical (aircraft spiral), 200 m horizontal (at 400 kts)

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Airborne Submillimeter Radiometer

The ASUR (Airborne SUbmillimeter Radiometer) is an airborne radiometer measuring the thermal emission of trace gases in the stratosphere (in an altitude range between 15 and 50 km). The instrument detects the radiation in a frequency range between 604.3 and 662.3 GHz. This corresponds to wavelengths of about 0.45-0.5 mm. In this frequency range a major part of the radiation is absorbed by atmospheric water vapor. As most of the water vapor is found in the troposphere (in the Arctic up to 8 km, in the tropics up to 16 km altitude) the instrument is operated on board of an aircraft flying at an altitude of 10-12 km, such that a major part of the water vapor absorption is avoided. Using appropriate inversion techniques vertical profiles from 15 to over 50 km altitude can be retrieved with a vertical resolution of typically 6 km and 12 km in the lower and upper stratosphere, respectively.

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Submillimeter Limb Sounder

The Submillimeterwave Limb Sounder (SLS) is a heterodyne radiometer measuring thermal emission spectra near 640 GHz (for detection of ClO, HCl, and O3) and 604 GHz. (for detection of HNO3 and N2O) designed for use on high altitude balloons and aircraft. The instrument consists of five subsystems:

-optics which define the instrument field of view (FOV)
-radiometer front-ends which down converts incoming radiance signals
-intermediate frequency (IF) stage which selects and frequency shifts signal bands
-spectrometers which frequency resolve and detect the incoming power spectrum
-command and data handling which controls the instrument and transmits data to the ground

Limb scanning is accomplished by a flat mirror (~20 cm diameter) connected to a stepper motor (0.2 steps) and 14 bit position encoder. This mirror is also used for gain and zero calibration by viewing an absorber target located below the mirror and upward at 47° elevation angle to view the cold sky. A set of three off-axis parabolic reflectors form the instrument field of view (0.35 full width at half maximum) and couple limb radiance to the mixer input waveguide. These reflectors are oversized (~30 dB edge taper) to minimize side lobes in the FOV. Pointing and beam shape were verified by scanning the instrument FOV across the emission from a 600 GHz transmitter (multiplied output of a Gunn oscillator) located in the receiver optical far-field.

The radiometer front-end is an uncooled second harmonic mixer using a waveguide mounted Schottky diode. The radiometer is operated double side band (DSB), i.e., spectral features occurring symmetrically above and below the effective local oscillator frequency (637.050 GHz) appear together in the IF output spectrum. The diode is pumped at a 318.525 GHz. This source is generated by a tripled 106.175 GHz phase-locked InP Gunn oscillator and wave guide coupled to the mixer block. The mixer produces an IF output spectrum of 10.5 to 13 GHz, which corresponds to signals at the mixer input at 647.5 GHz to 650.0 GHz (in the radiometer upper side band) and 626.5 GHz to 624.1 GHz ( in the lower side band). The design of the 604 GHz radiometer system is similar to 637 GHz system but operates at a lower IF frequency of 2 to 3 GHz.

Diagram of the SLS frequency down-conversion scheme. RF signals enter the signal flow path through mixer feeds at the left of the diagram. At the right side, the signal flow enters a set of UARS MLS-type filterbank spectrometers where bands are further spectrally resolved, power detected, and digitized.

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Balloon, ER-2 - AFRC
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Dual-Beam UV-Absorption Ozone Photometer

The NOAA-O3 instrument consists of a mercury lamp, two sample chambers that can be periodically scrubbed of ozone, and two detectors that measure the 254-nm radiation transmitted through the chamber. The ozone absorption cross-section at this wavelength is accurately known; hence, the ozone number density can be easily calculated. Since the two absorption chambers are identical, virtually continuous measurements of ozone are made by alternating the ambient air sample and ozone scrubbed sample between the two chambers. At a one-second data collection rate, the minimum detectable concentration of ozone (one standard deviation) is 1.5 x 10 10 molecules/cm 3 (0.6ppbv at STP).

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