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Sample records for absorption spectrometer doas

  1. Application of a long-path differential optical absorption spectrometer (LP-DOAS) on the measurements of NO(2), SO(2), O(3), and HNO(2) in Gwangju, Korea.

    PubMed

    Lee, Jeongsoon; Kim, Ki-Hyun; Kim, Young J; Lee, Jaihoon

    2008-03-01

    A differential optical absorption spectrometer (DOAS) technique has been applied to monitor airborne trace pollutants including NO(2), SO(2), O(3), and HNO(2) in the ultraviolet (UV) region (290-350 nm) over a 1.5 km beam path (two ways) during an intensive measurement campaign held at Gwangju, Korea (March 2002). Their mean mixing ratios (and standard deviations) were computed as 11.3 (8.8), 1.9 (1.7), 17.1 (19.3), and 0.5 (0.4)ppbv, respectively. As a means to evaluate the performance of the long-path DOAS (LP-DOAS) system with conventional point monitoring systems (PMS), correlation analysis was conducted between the two data sets. These data sets were then inspected to account for the influence of the environmental conditions on the correlation strength between the two systems, especially with respect to light level and wind speed. To facilitate the comparison, correlation analyses were conducted after dividing the data sets for those parameters into several classes. The strength of the correlations between DOAS and meteorological parameters was also examined to evaluate their effects on the DOAS performance. It was found that, among the four pollutant species, O(3) is the most sensitive to changes in meteorological conditions in relation with atmospheric mixing conditions. The overall results of our study indicate that open-path monitoring techniques can be used to effectively diagnose air quality and be substituted for the conventional point monitoring methods with the proper consideration of those parameters affecting the DOAS sensitivity (e.g., light level and wind speed). PMID:17335958

  2. Modular total absorption spectrometer

    NASA Astrophysics Data System (ADS)

    Karny, M.; Rykaczewski, K. P.; Fijałkowska, A.; Rasco, B. C.; Wolińska-Cichocka, M.; Grzywacz, R. K.; Goetz, K. C.; Miller, D.; Zganjar, E. F.

    2016-11-01

    The design and performance of the Modular Total Absorption Spectrometer built and commissioned at the Oak Ridge National Laboratory is presented. The active volume of the detector is approximately one ton of NaI(Tl), which results in very high full γ energy peak efficiency of 71% at 6 MeV and nearly flat efficiency of around 81.5% for low energy γ-rays between 300 keV and 1 MeV. In addition to the high peak efficiency, the modular construction of the detector permits the use of a γ-coincidence technique in data analysis as well as β-delayed neutron observation.

  3. Broadband microwave absorption spectrometer for liquid media

    SciTech Connect

    Mukherjee, P.; Gosnell, T.R.; Bigio, I.J.

    1988-12-01

    A broadband, continuous-sweep microwave spectrometer has been constructed for measurements of the absorption coefficient of aqueous solutions and other liquid media. The spectrometer makes use of the phase fluctuation optical heterodyne technique, which provides a direct measure of the microwave power deposited in the sample. Consequently, in contrast to the standard dielectrometric techniques that indirectly determine the absorption coefficient via separate measurements of the real and imaginary parts of the dielectric constant, this spectrometer directly measures the microwave absorption coefficient. Broadband spectra are obtained using a transmission line to couple microwave power into the liquid sample. The absorption spectrum for deionized water in the range 3--20 GHz is presented as an example and shows excellent agreement with calculated values of the absorption coefficient based on previously published dielectric data.

  4. Scanning imaging absorption spectrometer for atmospheric chartography

    NASA Technical Reports Server (NTRS)

    Burrows, John P.; Chance, Kelly V.

    1991-01-01

    The SCanning Imaging Absorption SpectroMeter for Atmospheric CHartographY is an instrument which measures backscattered, reflected, and transmitted light from the earth's atmosphere and surface. SCIAMACHY has eight spectral channels which observe simultaneously the spectral region between 240 and 1700 nm and selected windows between 1940 and 2400 nm. Each spectral channel contains a grating and linear diode array detector. SCIAMACHY observes the atmosphere in nadir, limb, and solar and lunar occultation viewing geometries.

  5. Two instruments based on differential optical absorption spectroscopy (DOAS) to measure accurate ammonia concentrations in the atmosphere

    NASA Astrophysics Data System (ADS)

    Volten, H.; Bergwerff, J. B.; Haaima, M.; Lolkema, D. E.; Berkhout, A. J. C.; van der Hoff, G. R.; Potma, C. J. M.; Wichink Kruit, R. J.; van Pul, W. A. J.; Swart, D. P. J.

    2011-08-01

    We present two Differential Optical Absorption Spectroscopy (DOAS) instruments built at RIVM, the RIVM DOAS and the miniDOAS. Both instruments provide virtually interference free measurements of NH3 concentrations in the atmosphere, since they measure over an open path, without suffering from inlet problems or interference problems by ammonium aerosols dissociating on tubes or filters. They measure concentrations up to at least 200 μg m-3, have a fast response, low maintenance demands, and a high up-time. The RIVM DOAS has a high accuracy of typically 0.15 μg m-3 for ammonia over 5-min averages and over a total light path of 100 m. The miniDOAS has been developed for application in measurement networks such as the Dutch National Air Quality Monitoring Network (LML). Compared to the RIVM DOAS it has a similar accuracy, but is significantly reduced in size, costs, and handling complexity. The RIVM DOAS and miniDOAS results showed excellent agreement (R2 = 0.996) during a field measurement campaign in Vredepeel, the Netherlands. This measurement site is located in an agricultural area and is characterized by highly variable, but on average high ammonia concentrations in the air. The RIVM-DOAS and miniDOAS results were compared to the results of the AMOR instrument, a continuous-flow wet denuder system, which is currently used in the LML. Averaged over longer time spans of typically a day the (mini)DOAS and AMOR results agree reasonably well, although an offset of the AMOR values compared to the (mini)DOAS results exists. On short time scales the (mini)DOAS shows a faster response and does not show the memory effects due to inlet tubing and transport of absorption fluids encountered by the AMOR. Due to its high accuracy, high uptime, low maintenance and its open path, the (mini)DOAS shows a good potential for flux measurements by using two (or more) systems in a gradient set-up and applying the aerodynamic gradient technique.

  6. Two instruments based on differential optical absorption spectroscopy (DOAS) to measure accurate ammonia concentrations in the atmosphere

    NASA Astrophysics Data System (ADS)

    Volten, H.; Bergwerff, J. B.; Haaima, M.; Lolkema, D. E.; Berkhout, A. J. C.; van der Hoff, G. R.; Potma, C. J. M.; Wichink Kruit, R. J.; van Pul, W. A. J.; Swart, D. P. J.

    2012-02-01

    We present two Differential Optical Absorption Spectroscopy (DOAS) instruments built at RIVM: the RIVM DOAS and the miniDOAS. Both instruments provide virtually interference-free measurements of NH3 concentrations in the atmosphere, since they measure over an open path, without suffering from inlet problems or interference problems by ammonium aerosols dissociating on tubes or filters. They measure concentrations up to at least 200 μg m-3, have a fast response, low maintenance demands, and a high up-time. The RIVM DOAS has a high accuracy of typically 0.15 μg m-3 for ammonia for 5-min averages and over a total light path of 100 m. The miniDOAS has been developed for application in measurement networks such as the Dutch National Air Quality Monitoring Network (LML). Compared to the RIVM DOAS it has a similar accuracy, but is significantly reduced in size, costs, and handling complexity. The RIVM DOAS and miniDOAS results showed excellent agreement (R2 = 0.996) during a field measurement campaign in Vredepeel, the Netherlands. This measurement site is located in an agricultural area and is characterized by highly variable, but on average high ammonia concentrations in the air. The RIVM-DOAS and miniDOAS results were compared to the results of the AMOR instrument, a continuous-flow wet denuder system, which is currently used in the LML. Averaged over longer time spans of typically a day, the (mini)DOAS and AMOR results agree reasonably well, although an offset of the AMOR values compared to the (mini)DOAS results exists. On short time scales, the (mini)DOAS shows a faster response and does not show the memory effects due to inlet tubing and transport of absorption fluids encountered by the AMOR. Due to its high accuracy, high uptime, low maintenance and its open path, the (mini)DOAS shows a good potential for flux measurements by using two (or more) systems in a gradient set-up and applying the aerodynamic gradient technique.

  7. Detection of water vapour absorption around 363nm in measured atmospheric absorption spectra and its effect on DOAS evaluations

    NASA Astrophysics Data System (ADS)

    Lampel, Johannes; Polyansky, Oleg. L.; Kyuberis, Alexandra A.; Zobov, Nikolai F.; Tennyson, Jonathan; Lodi, Lorenzo; Pöhler, Denis; Frieß, Udo; Platt, Ulrich; Beirle, Steffen; Wagner, Thomas

    2016-04-01

    Water vapour is known to absorb light from the microwave region to the blue part of the visible spectrum at a decreasing magnitude. Ab-initio approaches to model individual absorption lines of the gaseous water molecule predict absorption lines until its dissociation limit at 243 nm. We present first evidence of water vapour absorption at 363 nm from field measurements based on the POKAZATEL absorption line list by Polyansky et al. (2016) using data from Multi-Axis differential optical absorption spectroscopy (MAX-DOAS) and Longpath (LP)-DOAS measurements. The predicted absorptions contribute significantly to the observed optical depths with up to 2 × 10‑3. Their magnitude correlates well (R2 = 0.89) to simultaneously measured well-established water vapour absorptions in the blue spectral range from 452-499 nm, but is underestimated by a factor of 2.6 ± 0.6 in the ab-initio model. At a spectral resolution of 0.5nm this leads to a maximum absorption cross-section value of 5.4 × 10‑27 cm2/molec at 362.3nm. The results are independent of the employed cross-section data to compensate for the overlayed absorption of the oxygen dimer O4. The newly found absorption can have a significant impact on the spectral retrieval of absorbing trace-gas species in the spectral range around 363 nm. Its effect on the spectral analysis of O4, HONO and OClO are discussed.

  8. Ozone monitoring using differential optical absorption spectroscopy (DOAS) and UV photometry instruments in Sohar, Oman.

    PubMed

    Nawahda, Amin

    2015-08-01

    Ground level ozone (O3) concentrations were measured across Sohar highway in Oman during a four-month period from September to December 2014 by using an open-path deferential optical absorption spectroscopy (DOAS) instrument. The monthly average concentrations of O3 varied from 19.6 to 29.4 ppb. The measurements of O3 are compared with the measurements of a non-open-path UV photometry analyzer (UVP). The percent difference (PD) concept and linear regression methods were used to compare the readings of the two instruments. The findings show high correlation coefficients between the measurements of the DOAS and UVP instruments. The DOAS measurements of O3 are found to be less than those measured by the UVP instrument; the correlation coefficients between absolute PD values and meteorological parameters and PM2.5 were very low indicating a minor effect; therefore, titrations of O3 by traffic emissions and difference in elevation could be the reason for the difference in the measurements of the two instruments.

  9. Ozone monitoring using differential optical absorption spectroscopy (DOAS) and UV photometry instruments in Sohar, Oman.

    PubMed

    Nawahda, Amin

    2015-08-01

    Ground level ozone (O3) concentrations were measured across Sohar highway in Oman during a four-month period from September to December 2014 by using an open-path deferential optical absorption spectroscopy (DOAS) instrument. The monthly average concentrations of O3 varied from 19.6 to 29.4 ppb. The measurements of O3 are compared with the measurements of a non-open-path UV photometry analyzer (UVP). The percent difference (PD) concept and linear regression methods were used to compare the readings of the two instruments. The findings show high correlation coefficients between the measurements of the DOAS and UVP instruments. The DOAS measurements of O3 are found to be less than those measured by the UVP instrument; the correlation coefficients between absolute PD values and meteorological parameters and PM2.5 were very low indicating a minor effect; therefore, titrations of O3 by traffic emissions and difference in elevation could be the reason for the difference in the measurements of the two instruments. PMID:26138853

  10. Multi axis differential optical absorption spectroscopy (MAX-DOAS) of gas and aerosol distributions.

    PubMed

    Sinreich, R; Friess, U; Wagner, T; Platt, U

    2005-01-01

    We present and demonstrate a relatively simple algorithm, which converts a set of slant column density measurements of oxygen dimers (O4) and NO2 at several different elevation angles to determine the atmospheric aerosol extinction and the absolute concentration and mixing ratio of NO2 within the atmospheric boundary layer. In addition the height of the atmospheric boundary layer can usually be derived, also the technique can be readily extended to determine the concentration of several other trace gases including SO2, CH2O, or glyoxal. The algorithm is based on precise radiation transport modelling determination, taking into account the actual aerosol scenario as determined from the O4 measurements. The required hardware is simple encompassing essentially a miniature spectrometer, a small telescope, a pointing mechanism, and a Personal Computer (PC). Effectively the technique combines the simplicity of a passive MAX-DOAS observation with the capability of a much more complex active DOAS instrument to determine path-averaged, absolutely calibrated mixing ratios of atmospheric trace gases at relatively high accuracy.

  11. Multi axis differential optical absorption spectroscopy (MAX-DOAS) of gas and aerosol distributions.

    PubMed

    Sinreich, R; Friess, U; Wagner, T; Platt, U

    2005-01-01

    We present and demonstrate a relatively simple algorithm, which converts a set of slant column density measurements of oxygen dimers (O4) and NO2 at several different elevation angles to determine the atmospheric aerosol extinction and the absolute concentration and mixing ratio of NO2 within the atmospheric boundary layer. In addition the height of the atmospheric boundary layer can usually be derived, also the technique can be readily extended to determine the concentration of several other trace gases including SO2, CH2O, or glyoxal. The algorithm is based on precise radiation transport modelling determination, taking into account the actual aerosol scenario as determined from the O4 measurements. The required hardware is simple encompassing essentially a miniature spectrometer, a small telescope, a pointing mechanism, and a Personal Computer (PC). Effectively the technique combines the simplicity of a passive MAX-DOAS observation with the capability of a much more complex active DOAS instrument to determine path-averaged, absolutely calibrated mixing ratios of atmospheric trace gases at relatively high accuracy. PMID:16161782

  12. A wide spectral range photoacoustic aerosol absorption spectrometer.

    PubMed

    Haisch, C; Menzenbach, P; Bladt, H; Niessner, R

    2012-11-01

    A photoacoustic spectrometer for the measurement of aerosol absorption spectra, based on the excitation of a pulsed nanosecond optical parametrical oscillator (OPO), will be introduced. This spectrometer is working at ambient pressure and can be used to detect and characterize different classes of aerosols. The spectrometer features a spectral range of 410 to 2500 nm and a sensitivity of 2.5 × 10(-7) m(-1) at 550 nm. A full characterization of the system in the visible spectral range is demonstrated, and the potential of the system for near IR measurement is discussed. In the example of different kinds of soot particles, the performance of the spectrometer was assessed. As we demonstrate, it is possible to determine a specific optical absorption per particle by a combination of the new spectrometer with an aerosol particle counter. PMID:23035870

  13. A wide spectral range photoacoustic aerosol absorption spectrometer.

    PubMed

    Haisch, C; Menzenbach, P; Bladt, H; Niessner, R

    2012-11-01

    A photoacoustic spectrometer for the measurement of aerosol absorption spectra, based on the excitation of a pulsed nanosecond optical parametrical oscillator (OPO), will be introduced. This spectrometer is working at ambient pressure and can be used to detect and characterize different classes of aerosols. The spectrometer features a spectral range of 410 to 2500 nm and a sensitivity of 2.5 × 10(-7) m(-1) at 550 nm. A full characterization of the system in the visible spectral range is demonstrated, and the potential of the system for near IR measurement is discussed. In the example of different kinds of soot particles, the performance of the spectrometer was assessed. As we demonstrate, it is possible to determine a specific optical absorption per particle by a combination of the new spectrometer with an aerosol particle counter.

  14. Measurements of the absorption cross section of (13)CHO(13)CHO at visible wavelengths and application to DOAS retrievals.

    PubMed

    Goss, Natasha R; Waxman, Eleanor M; Coburn, Sean C; Koenig, Theodore K; Thalman, Ryan; Dommen, Josef; Hannigan, James W; Tyndall, Geoffrey S; Volkamer, Rainer

    2015-05-14

    The trace gas glyoxal (CHOCHO) forms from the atmospheric oxidation of hydrocarbons and is a precursor to secondary organic aerosol. We have measured the absorption cross section of disubstituted (13)CHO(13)CHO ((13)C glyoxal) at moderately high (1 cm(-1)) optical resolution between 21 280 and 23 260 cm(-1) (430-470 nm). The isotopic shifts in the position of absorption features were found to be largest near 455 nm (Δν = 14 cm(-1); Δλ = 0.29 nm), whereas no significant shifts were observed near 440 nm (Δν < 0.5 cm(-1); Δλ < 0.01 nm). These shifts are used to investigate the selective detection of (12)C glyoxal (natural isotope abundance) and (13)C glyoxal by in situ cavity enhanced differential optical absorption spectroscopy (CE-DOAS) in a series of sensitivity tests using synthetic spectra, and laboratory measurements of mixtures containing (12)C and (13)C glyoxal, nitrogen dioxide, and other interfering absorbers. We find the changes in apparent spectral band shapes remain significant at the moderately high optical resolution typical of CE-DOAS (0.55 nm fwhm). CE-DOAS allows for the selective online detection of both isotopes with detection limits of ∼200 pptv (1 pptv = 10(-12) volume mixing ratio), and sensitivity toward total glyoxal of few pptv. The (13)C absorption cross section is available for download from the Supporting Information. PMID:25551419

  15. Measurements of NO2, SO2, O3, benzene and toluene using differential optical absorption spectroscopy (DOAS) in Shanghai, China.

    PubMed

    Hao, Nan; Zhou, Bin; Chen, Dan; Sun, Yi; Gao, Song; Chen, Limin

    2006-01-01

    NO2, SO2, O3, benzene, and toluene were measured in Taopu industry park of Shanghai during the period June to August 2003 by differential optical absorption spectroscopy (DOAS) technique. The daily average concentrations of SO2, NO2, and O3 ranged from 5.7 ppb to 40 ppb, 22 ppb to 123 ppb, and 10.6 ppb to 23 ppb respectively. SO2 and NO2 concentrations were found to depend on wind direction. The diurnal variation of NO2 concentrations had two peaks due to traffic emission. Our DOAS measurements of NO2, SO2 and O3 were compared with the conventional measurement instruments (API automatic monitoring instrument). The concept of a percent difference (PD) and linear regression methods were employed to study the difference between DOAS and API instruments. The correlation analysis between PD values and meteorological parameters and analysis of abnormal higher absolute PD values indicated that the lower visibility induced the bad compatibility between the two systems. The results showed that both systems exhibited strong compatibility with good correlation, therefore the DOAS system is able to provide reliable information on distribution patterns of major air pollutants. Average benzene and toluene concentrations were 1.4 and 8.0 ppb respectively. PMID:16948427

  16. Differential optical absorption spectrometer for measurement of tropospheric pollutants

    NASA Astrophysics Data System (ADS)

    Evangelisti, F.; Baroncelli, A.; Bonasoni, P.; Giovanelli, G.; Ravegnani, F.

    1995-05-01

    Our institute has recently developed a differential optical absorption spectrometry system called the gas analyzer spectrometer correlating optical absorption differences (GASCOAD), which features as a detector a linear image sensor that uses an artificial light source for long-path tropospheric-pollution monitoring. The GASCOAD, its method of eliminating interference from background sky light, and subsequent spectral analysis are reported and discussed. The spectrometer was used from 7 to 22 February 1993 in Milan, a heavily polluted metropolitan area, to measure the concentrations of SO2, NO2, O3, and HNO2 averaged over a 1.7-km horizontal light path. The findings are reported and briefly discussed.

  17. Modular Total Absorption Spectrometer at the HRIBF (ORNL, Oak Ridge)

    SciTech Connect

    Wolińska-Cichocka, M.; Rykaczewski, K.P.; Fijałkowska, A.; Karny, M.; Grzywacz, R.K.; Gross, C.J.; Johnson, J.W.; Rasco, B.C.; Zganjar, E.F.

    2014-06-15

    The Modular Total Absorption Spectrometer (MTAS) array has been designed, constructed, characterized, and applied to the decay studies of {sup 238}U fission products at the Holifield Radioactive Ion Beam Facility (HRIBF) at Oak Ridge National Laboratory. A MTAS commissioning run was performed in January 2012 at the mass separator on-line to the HRIBF Tandem accelerator. Preliminary results of MTAS data confirm known decay patterns of {sup 142}Ba and {sup 142}La deduced from an earlier study using a total absorption spectrometer technique.

  18. Absorption spectrometer balloon flight and iodine investigations

    NASA Technical Reports Server (NTRS)

    1970-01-01

    A high altitude balloon flight experiment to determine the technical feasibility of employing absorption spectroscopy to measure SO2 and NO2 gases in the earth's atmosphere from above the atmospheric ozone layer is discussed. In addition to the balloon experiment the contract includes a ground-based survey of natural I emissions from geological sources and studies of the feasibility of mapping I2 from spacecraft. This report is divided into three major sections as follows: (1) the planning engineering and execution of the balloon experiment, (2) data reduction and analysis of the balloon data, and (3) the results of the I2 phase of the contract.

  19. Compact Femtosecond-Millisecond Transient Absorption Spectrometer

    NASA Astrophysics Data System (ADS)

    Carroll, Elizabeth; Hill, Melissa; Madsen, Dorte; Malley, Konstantin; Larsen, Delmar

    2008-03-01

    The measurement of population dynamics in biological, chemical, and solid-state samples occurring over 10-15-10^1 seconds requires a combination of transient absorption techniques, typically involving different laser systems and detection electronics (e.g. femtosecond transient absorption and nanosecond flash photolysis). The difficulty in exactly matching excitation conditions often prohibits connecting ultrafast and longer time measurements, particularly in samples exhibiting nonlinear kinetics. We present a simple solution to bridge the femtosecond and microsecond domains with an inexpensive modification of a kHz amplified Ti:Sapphire laser. By introducing a secondary pulse-picker between the laser oscillator (75 MHz) and amplifier, we can electronically delay unamplified 800-nm probe pulses in 13.3-ns steps. The 5-nJ pulses seed a photonic crystal fiber to produce a supercontinuum (450-1100 nm) for broadband probing. We demonstrate the system capability by resolving formation and decay dynamics, spanning 10 decades (10-14-10-4 s), of photoexcited solvated electrons in sinapic acid, and triplet states and quinonoid intermediates in Vitamin B6.

  20. NO2 column amounts from ground-based Pandora and MFDOAS spectrometers using the direct-sun DOAS technique: Intercomparisons and application to OMI validation

    NASA Astrophysics Data System (ADS)

    Herman, Jay; Cede, Alexander; Spinei, Elena; Mount, George; Tzortziou, Maria; Abuhassan, Nader

    2009-07-01

    Vertical column amounts of nitrogen dioxide, C(NO2), are derived from ground-based direct solar irradiance measurements using two new and independently developed spectrometer systems, Pandora (Goddard Space Flight Center) and MFDOAS (Washington State University). We discuss the advantages of C(NO2) retrievals based on Direct Sun - Differential Optical Absorption Spectroscopy (DS-DOAS). The C(NO2) data are presented from field campaigns using Pandora at Aristotle University (AUTH), Thessaloniki, Greece; a second field campaign involving both new instruments at Goddard Space Flight Center (GSFC), Greenbelt, Maryland; a Pandora time series from December 2006 to October 2008 at GSFC; and a MFDOAS time series for spring 2008 at Pacific Northwest National Laboratory (PNNL), Richland, Washington. Pandora and MFDOAS were compared at GFSC and found to closely agree, with both instruments having a clear-sky precision of 0.01 DU (1 DU = 2.67 × 1016 molecules/cm2) and a nominal accuracy of 0.1 DU. The high precision is obtained from careful laboratory characterization of the spectrometers (temperature sensitivity, slit function, pixel to pixel radiometric calibration, and wavelength calibration), and from sufficient measurement averaging to reduce instrument noise. The accuracy achieved depends on laboratory-measured absorption cross sections and on spectrometer laboratory and field calibration techniques used at each measurement site. The 0.01 DU precision is sufficient to track minute-by-minute changes in C(NO2) throughout each day with typical daytime values ranging from 0.2 to 2 DU. The MFDOAS instrument has better noise characteristics for a single measurement, which permits MFDOAS to operate at higher time resolution than Pandora for the same precision. Because Pandora and MFDOAS direct-sun measurements can be made in the presence of light to moderate clouds, but with reduced precision (˜0.2 DU for moderate cloud cover), a nearly continuous record can be obtained

  1. [Spectral calibration for space-borne differential optical absorption spectrometer].

    PubMed

    Zhou, Hai-Jin; Liu, Wen-Qing; Si, Fu-Qi; Zhao, Min-Jie; Jiang, Yu; Xue, Hui

    2012-11-01

    Space-borne differential optical absorption spectrometer is used for remote sensing of atmospheric trace gas global distribution. This instrument acquires high accuracy UV/Vis radiation scattered or reflected by air or earth surface, and can monitor distribution and variation of trace gases based on differential optical absorption spectrum algorithm. Spectral calibration is the premise and base of quantification of remote sensing data of the instrument, and the precision of calibration directly decides the level of development and application of the instrument. Considering the characteristic of large field, wide wavelength range, high spatial and spectral resolution of the space-borne differential optical absorption spectrometer, a spectral calibration method is presented, a calibration device was built, the equation of spectral calibration was calculated through peak searching and regression analysis, and finally the full field spectral calibration of the instrument was realized. The precision of spectral calibration was verified with Fraunhofer lines of solar light.

  2. Design and performance of a tunable diode laser absorption spectrometer for airborne formaldehyde measurements

    NASA Astrophysics Data System (ADS)

    Wert, B. P.; Fried, A.; Rauenbuehler, S.; Walega, J.; Henry, B.

    2003-06-01

    A tunable diode laser absorption spectrometer (TDLAS) was modified for high-precision and high-time-resolution formaldehyde (CH2O) measurements. This enhanced system was deployed in both the clean and polluted troposphere, as part of aircraft missions (TOPSE 2000, TexAQS 2000, and TRACE-P 2001) and ground-based missions (SOS 1999). Measurements of very constant ambient CH2O concentrations were used to determine instrument precisions, which were stable under normal operating conditions, with the exception of brief aircraft cabin pressure changes. Precisions of 15-50 pptv (1σ) were typically achieved for 1 min of averaging, corresponding to absorptions of 0.5-1.7 × 10-6, 3-5 times better than the previous version of the instrument (1998). Responsible modifications included improved temperature and pressure control of instrument components and the use of more stable optical mounts. During the TexAQS 2000 aircraft mission (polluted continental troposphere), measurements of 1 s time resolution were reported. Instrument accuracy was validated by calibration cross checks, interference tests, sample transmission tests, and field comparisons with a DOAS system.

  3. Elevated aerosol layers modify the O2-O2 absorption measured by ground-based MAX-DOAS

    NASA Astrophysics Data System (ADS)

    Ortega, Ivan; Berg, Larry K.; Ferrare, Richard A.; Hair, Johnathan W.; Hostetler, Chris A.; Volkamer, Rainer

    2016-06-01

    The oxygen collisional complex (O2-O2, or O4) is a greenhouse gas, and a calibration trace gas used to infer aerosol and cloud properties by Differential Optical Absorption Spectroscopy (DOAS). Recent reports suggest the need for an O4 correction factor (CFO4) when comparing simulated and measured O4 differential slant column densities (dSCD) by passive DOAS. We investigate the sensitivity of O4 dSCD simulations at ultraviolet (360 nm) and visible (477 nm) wavelengths towards separately measured aerosol extinction profiles. Measurements were conducted by the University of Colorado 2D-MAX-DOAS instrument and NASA's multispectral High Spectral Resolution Lidar (HSRL-2) during the Two Column Aerosol Project (TCAP) at Cape Cod, MA in July 2012. During two case study days with (1) high aerosol load (17 July, AOD~0.35 at 477 nm), and (2) near molecular scattering conditions (22 July, AOD<0.10 at 477 nm) the measured and calculated O4 dSCDs agreed within 6.4±0.4% (360 nm) and 4.7±0.6% (477 nm) if the HSRL-2 profiles were used as input to the calculations. However, if in the calculations the aerosol is confined to the surface layer (while keeping AOD constant) we find 0.53DOAS. Opportunities to identify and better characterize these elevated layers are also discussed.

  4. Field measurement of air pollutants near swine confined-animal feeding operations using UV DOAS and FTIR

    NASA Astrophysics Data System (ADS)

    Secrest, Cary D.

    2001-02-01

    12 This paper reports the results of ammonia measurements near two CAFOs. In September of 1999, measurements were conducted for 48 hours downwind of a large-scale CAFO using two open- path monitors; an ultra violet differential optical absorption spectrometer (UV DOAS), and a Fourier transform interferometer (FTIR). In March of 2000, measurements were conducted at a much smaller CAFO using UV DOAS. This paper describes the calibration of a UV DOAS, compares UV DOAS and FTIR measurements, describes the effects of wind and atmospheric stability on ambient ammonia concentration, and suggests potential applications for open-path monitors for assessing public health risk.

  5. SCIAMACHY—scanning imaging absorption spectrometer for atmospheric chartography

    NASA Astrophysics Data System (ADS)

    Burrows, J. P.; Hölzle, E.; Goede, A. P. H.; Visser, H.; Fricke, W.

    1995-04-01

    SCIAMACHY will perform global measurements of atmospheric trace gases in order to retrieve their global total column amounts as well as their stratospheric and tropospheric profiles. Aerosol abundances will be derived from observations of wavelength-dependent light scattering characteristics. Furthermore, the instrument will yield physical parameters of clouds, stratospheric temperature and pressure profiles; the latter being derived from Sun occultation measurements. SCIAMACHY observes the backscattered radiance over the wavelength range 240-2380 nm. Differential optical absorption spectrometry (DOAS) and back scattered u.v. (BUY) retrieval techniques are selected for the inversion of radiance. Ground scenes are scanned by a two-mirror scanning mechanism of high positioning accuracy. The instrument electronics, including subsystem controller and data electronics, mechanisms and thermal control electronics, allow SCIAMACHY to be operated autonomously. The instrument will be flown on the polar platform of the first European Polar Orbit Earth Observation Mission (POEM-1), now known as ENVISAT. It has been developed by the following industrial team: Dornier (prime-contractor, thermal control, instrument control); OHB (data electronics); SRON (detector modules and analogue electronics); TPD (optical unit).

  6. A decay total absorption spectrometer for DESPEC at FAIR

    NASA Astrophysics Data System (ADS)

    Tain, J. L.; Algora, A.; Agramunt, J.; Guadilla, V.; Jordan, M. D.; Montaner-Pizá, A.; Rubio, B.; Valencia, E.; Cano-Ott, D.; Gelletly, W.; Martinez, T.; Mendoza, E.; Podolyák, Zs.; Regan, P.; Simpson, J.; Smith, A. J.; Strachan, J.

    2015-12-01

    This paper presents the design of a total absorption γ-ray spectrometer for the determination of β-decay intensity distributions of exotic nuclear species at the focal plane of the FAIR-NUSTAR Super Fragment Separator. The spectrometer is a key instrument in the DESPEC experiment and the proposed implementation follows extensive design studies and prototype tests. Two options were contemplated, based on NaI(Tl) and LaBr3:Ce inorganic scintillation crystals respectively. Monte Carlo simulations and technical considerations determined the optimal configurations consisting of sixteen 15 × 15 × 25cm3 crystals for the NaI(Tl) option and one hundred and twenty-eight 5.5 × 5.5 × 11cm3 crystals for the LaBr3:Ce option. Minimization of dead material was crucial for maximizing the spectrometer full-energy peak efficiency. Module prototypes were build to verify constructional details and characterize their performance. The measured energy and timing resolution was found to agree rather well with estimates based on simulations of scintillation light transport and collection. The neutron sensitivity of the spectrometer, important when measuring β-delayed neutron emitters, was investigated by means of Monte Carlo simulations.

  7. Application of independent component analysis method in real-time spectral analysis of gaseous mixtures for acousto-optical spectrometers based on differential optical absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Fadeyev, A. V.; Pozhar, V. E.

    2012-10-01

    It is discussed the reliability problem of time-optimized method for remote optical spectral analysis of gas-polluted ambient air. The method based on differential optical absorption spectroscopy (DOAS) enables fragmentary spectrum registration (FSR) and is suitable for random-spectral-access (RSA) optical spectrometers like acousto-optical (AO) ones. Here, it is proposed the algorithm based on statistical method of independent component analysis (ICA) for estimation of a correctness of absorption spectral lines selection for FSR-method. Implementations of ICA method for RSA-based real-time adaptive systems are considered. Numerical simulations are presented with use of real spectra detected by the trace gas monitoring system GAOS based on AO spectrometer.

  8. Ground-based direct-sun DOAS and airborne MAX-DOAS measurements of the collision-induced oxygen complex, O2O2, absorption with significant pressure and temperature differences

    NASA Astrophysics Data System (ADS)

    Spinei, E.; Cede, A.; Herman, J.; Mount, G. H.; Eloranta, E.; Morley, B.; Baidar, S.; Dix, B.; Ortega, I.; Koenig, T.; Volkamer, R.

    2015-02-01

    The collision-induced O2 complex, O2O2, is a very important trace gas for understanding remote sensing measurements of aerosols, cloud properties and atmospheric trace gases. Many ground-based multi-axis differential optical absorption spectroscopy (MAX-DOAS) measurements of the O2O2 optical depth require correction factors of 0.75 ± 0.1 to reproduce radiative transfer modeling (RTM) results for a nearly pure Rayleigh atmosphere. One of the potential causes of this discrepancy is uncertainty in laboratory-measured O2O2 absorption cross section temperature and pressure dependencies due to difficulties in replicating atmospheric conditions in the laboratory environment. This paper presents ground-based direct-sun (DS) and airborne multi-axis (AMAX) DOAS measurements of O2O2 absorption optical depths under actual atmospheric conditions in two wavelength regions (335-390 and 435-490 nm). DS irradiance measurements were made by the Washington State University research-grade Multi-Function Differential Spectroscopy Instrument instrument from 2007 to 2014 at seven sites with significant pressure (778 to 1013 hPa) and O2O2 profile-weighted temperature (247 to 275 K) differences. Aircraft MAX-DOAS measurements were conducted by the University of Colorado (CU) AMAX-DOAS instrument on 29 January 2012 over the Southern Hemispheric subtropical Pacific Ocean. Scattered solar radiance spectra were collected at altitudes between 9 and 13.2 km, with O2O2 profile-weighted temperatures of 231 to 244 K and nearly pure Rayleigh scattering conditions. Due to the well-defined DS air-mass factors during ground-based measurements and extensively characterized atmospheric conditions during the aircraft AMAX-DOAS measurements, O2O2 "pseudo" absorption cross sections, σ, are derived from the observed optical depths and estimated O2O2 column densities. Vertical O2O2 columns are calculated from the atmospheric sounding temperature, pressure and specific humidity profiles. Based on the ground

  9. Retrieval of Stratospheric CH4 and CO2 Profiles from SCIAMACHY Solar Occultation Measurements with Onion Peeling DOAS

    NASA Astrophysics Data System (ADS)

    Noël, Stefan; Bramstedt, Klaus; Rozanov, Alexej; Bovensmann, Heinrich; Burrows, John P.

    2010-05-01

    A new retrieval method (called "Onion Peeling DOAS") has been developed to derive stratopheric profiles of atmospheric constituents from solar occultation measurements of the SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY). This method is intentionally kept simple and based on a combination of an onion peeling approach with a modified DOAS (Differential Optical Absorption Spectroscopy) fit. The method has already been successfully used to derive stratospheric water vapour profiles. However, the Onion Peeling DOAS method can also be applied to other atmospheric constituents. Here, we will present first retrieval results for methane (CH4) and carbon dioxide (CO2).

  10. Wavelength calibration of imaging spectrometer using atmospheric absorption features

    NASA Astrophysics Data System (ADS)

    Zhou, Jiankang; Chen, Yuheng; Chen, Xinhua; Ji, Yiqun; Shen, Weimin

    2012-11-01

    Imaging spectrometer is a promising remote sensing instrument widely used in many filed, such as hazard forecasting, environmental monitoring and so on. The reliability of the spectral data is the determination to the scientific communities. The wavelength position at the focal plane of the imaging spectrometer will change as the pressure and temperature vary, or the mechanical vibration. It is difficult for the onboard calibration instrument itself to keep the spectrum reference accuracy and it also occupies weight and the volume of the remote sensing platform. Because the spectral images suffer from the atmospheric effects, the carbon oxide, water vapor, oxygen and solar Fraunhofer line, the onboard wavelength calibration can be processed by the spectral images themselves. In this paper, wavelength calibration is based on the modeled and measured atmospheric absorption spectra. The modeled spectra constructed by the atmospheric radiative transfer code. The spectral angle is used to determine the best spectral similarity between the modeled spectra and measured spectra and estimates the wavelength position. The smile shape can be obtained when the matching process across all columns of the data. The present method is successful applied on the Hyperion data. The value of the wavelength shift is obtained by shape matching of oxygen absorption feature and the characteristics are comparable to that of the prelaunch measurements.

  11. Tropospheric ozone distributions measured with an airborne laser absorption spectrometer

    NASA Technical Reports Server (NTRS)

    Menzies, R. T.; Shumate, M. S.

    1978-01-01

    Measurements of tropospheric ozone have been made in the southern and middle California regions and over the Pacific Ocean during two series of flights in February and May 1977. The data were obtained by using a laser absorption spectrometer, a nadir-viewing instrument which remotely measures the ozone column abundance between ground level and aircraft altitude by interacting with ozone at specific wavelengths near 9.5 microns. The measurements indicate significantly lower ozone abundances above the Mojave Desert region as compared with farm, forest, and urban areas. The average tropospheric column density was found to be 0.0027 atm cm/km over the California region and 0.0035 atm cm/km over the Pacific Ocean region 1000-2000 km west of the coast of Mexico.

  12. Mapping of methane from Scanning Imaging Absorption Spectrometer for Atmospheric Cartography (SCIAMACHY)

    NASA Astrophysics Data System (ADS)

    Tan, K. C.; Lim, H. S.; MatJafri, M. Z.

    2012-11-01

    Among all the greenhouse gases, methane is the most dynamic and abundant greenhouse gas in the atmosphere. The global concentrations of atmospheric methane has increased more than doubled since pre-industrial times, with a current globally-averaged mixing ratio of ~ 1750 ppbv. Due to its high growth rate, methane brings significant effects on climate and atmospheric chemistry. There has a significant gap for variables between anthropogenic and natural sources and sinks of methane. Satellite observation of methane has been identified that it can provide the precise and accurate data globally, which sensitive to the small regional biases. We present measurements from Scanning Imaging Absorption Spectrometer for Atmospheric Cartography (SCIAMACHY) included on the European environmental satellite ENVISAT, launched on 1st of March 2002. Main objective of this study is to examine the methane distribution over Peninsular Malaysia using SCIAMACHY level-3 data. They are derived from the near-infrared nadir observations of the SCIAMACHY at the University of Bremen through scientific WFM-DOAS retrieval algorithm version 2.0.2.Maps of time averaged (yearly, tri-monthly) methane was generated and analyzed over Peninsular Malaysia for the year 2003 using PCI Geomatica 10.3 image processing software. The maps show dry-air column averaged mixing ratios of methane (denoted XCH4). It was retrieved using the interpolation technique. The concentration changes within boundary layer at all altitude levels are equally sensitive through the SCIAMACHY near-infrared nadir observations. Hence, we can make observation of methane at surface source region. The results successfully identify the area with highest and lowest concentration of methane at Peninsular Malaysia using SCIAMACHY data. Therefore, the study is suitable to examine the distribution of methane at tropical region.

  13. Light emitting diode cavity enhanced differential optical absorption spectroscopy (LED-CE-DOAS): a novel technique for monitoring atmospheric trace gases

    NASA Astrophysics Data System (ADS)

    Thalman, Ryan M.; Volkamer, Rainer M.

    2009-08-01

    The combination of Cavity Enhanced Absorption Spectroscopy (CEAS) with broad-band light sources (e.g. Light- Emitting Diodes, LEDs) lends itself to the application of cavity enhanced DOAS (CE-DOAS) to perform sensitive and selective point measurements of multiple trace gases with a single instrument. In contrast to other broad-band CEAS techniques, CE-DOAS relies only on the measurement of relative intensity changes, i.e., does not require knowledge of the light intensity in the absence of trace gases and aerosols (I0). We have built a prototype LED-CE-DOAS instrument in the blue spectral range (420-490nm) to measure nitrogen dioxide (NO2), glyoxal (CHOCHO), iodine monoxide (IO), water (H2O) and oxygen dimers (O4). Aerosol extinction is retrieved at two wavelengths by means of observing water and O4 and measuring pressure, temperature and relative humidity independently. The instrument components are presented, and the approach to measure aerosol extinction is demonstrated by means of a set of experiments where laboratory generated monodisperse aerosols are added to the cavity. The aerosol extinction cross section agrees well with Mie calculations, demonstrating that our setup enables measurements of the above gases in open cavity mode.

  14. Absolute calibration of the colour index and O4 absorption derived from Multi AXis (MAX-)DOAS measurements and their application to a standardised cloud classification algorithm

    NASA Astrophysics Data System (ADS)

    Wagner, Thomas; Beirle, Steffen; Remmers, Julia; Shaiganfar, Reza; Wang, Yang

    2016-09-01

    A method is developed for the calibration of the colour index (CI) and the O4 absorption derived from differential optical absorption spectroscopy (DOAS) measurements of scattered sunlight. The method is based on the comparison of measurements and radiative transfer simulations for well-defined atmospheric conditions and viewing geometries. Calibrated measurements of the CI and the O4 absorption are important for the detection and classification of clouds from MAX-DOAS observations. Such information is needed for the identification and correction of the cloud influence on Multi AXis (MAX-)DOAS profile inversion results, but might be also be of interest on their own, e.g. for meteorological applications. The calibration algorithm was successfully applied to measurements at two locations: Cabauw in the Netherlands and Wuxi in China. We used CI and O4 observations calibrated by the new method as input for our recently developed cloud classification scheme and also adapted the corresponding threshold values accordingly. For the observations at Cabauw, good agreement is found with the results of the original algorithm. Together with the calibration procedure of the CI and O4 absorption, the cloud classification scheme, which has been tuned to specific locations/conditions so far, can now be applied consistently to MAX-DOAS measurements at different locations. In addition to the new threshold values, further improvements were introduced to the cloud classification algorithm, namely a better description of the SZA (solar zenith angle) dependence of the threshold values and a new set of wavelengths for the determination of the CI. We also indicate specific areas for future research to further improve the cloud classification scheme.

  15. Direct sun and airborne MAX-DOAS measurements of the collision induced oxygen complex, O2O2 absorption with significant pressure and temperature differences

    NASA Astrophysics Data System (ADS)

    Spinei, E.; Cede, A.; Herman, J.; Mount, G. H.; Eloranta, E.; Morley, B.; Baidar, S.; Dix, B.; Ortega, I.; Koenig, T.; Volkamer, R.

    2014-09-01

    The collision induced O2 complex, O2O2, is a very important trace gas in remote sensing measurements of aerosol and cloud properties. Some ground based MAX-DOAS measurements of O2O2 slant column density require correction factors of 0.75 ± 0.1 to reproduce radiative transfer modeling (RTM) results for a near pure Rayleigh atmosphere. One of the potential causes of this discrepancy is believed to be uncertainty in laboratory measured O2O2 absorption cross section temperature and pressure dependence, due to difficulties in replicating atmospheric conditions in the laboratory environment. This paper presents direct-sun (DS) and airborne multi-axis (AMAX) DOAS measurements of O2O2 absorption optical depths under actual Earth atmospheric conditions in two wavelength regions (335-390 nm and 435-490 nm). DS irradiance measurements were made by the research grade MFDOAS instrument from 2007-2014 at seven sites with significant pressure (778-1013 hPa) and O2O2 profile weighted temperature (247-275 K) differences. Aircraft MAX-DOAS measurements were conducted by the University of Colorado AMAX-DOAS instrument on 29 January 2012 over the Southern Hemisphere subtropical Pacific Ocean. Scattered solar radiance spectra were collected at altitudes between 9 and 13.2 km, with O2O2 profile weighted temperatures of 231-244 K, and near pure Rayleigh scattering conditions. Due to the well defined DS air mass factors and extensively characterized atmospheric conditions during the AMAX-DOAS measurements, O2O2"pseudo" absorption cross sections, σ, are derived from the observed optical depths and estimated O2O2column densities. Vertical O2O2 columns are calculated from the atmospheric sounding temperature, pressure and specific humidity profiles. Based on the atmospheric DS observations, there is no pressure dependence of the O2O2 σ, within the measurement errors (3%). The two data sets are combined to derive peak σ temperature dependence of 360 and 477 nm absorption bands from 231

  16. Comparison of ground-based Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) and satellite DOAS measurements of NO2 distribution over Ulaanbaatar (Mongolia) during summer 2013

    NASA Astrophysics Data System (ADS)

    Böhnke, Sebastian; Behrendt, Thomas; Bruse, Michael; Meixner, Franz X.; Mamtimin, Buhalqem

    2014-05-01

    Cities are immense sources of air pollutants; however, emission inventories in many of them still are highly uncertain, particularly in developing countries. Ulaanbaatar is the most populous and polluted area in Mongolia. Tropospheric NO2 is proved to be harmful to both, the atmospheric environment and human health. It might be meaningful and important to observe pollutant concentrations in an area-integrated form (satellite observations) to create a sound data basis for air quality control measures. In our study, we preliminary present the results of both satellite and ground-based Differential Optical Absorption Spectroscopy (DOAS) measurements of vertical column densities (VCDs) of NO2 in Ulaanbaatar (urban area). As a ground validation tool, the MAX-DOAS measurements carried out in Ulaanbaatar (Mongolia) summer 2013 and are applied at 3 different sites in the west of Ulaanbaatar (106.73° E / 47.83° N), the city center (106.92° E / 47.92° N) and in the east (107.12° E / 47.87° N). Additionally, Automatic Weather Stations (AWS) have been set up and ozone was measured by UV absorption technique also at the 3 sites. Preliminary results show that the NO2 column densities increase during sunset and decrease after sunrise, which is most likely caused by a longer light path resulting from high solar zenith angles (SZA). The maximum DSCDs (Differential Slant Column Densities) are observed around sunset and sunrise (up to 10^17 molec cm-², mainly a measurement effect as stated above). The daily minima of the vertical column densities (VCD) appear in the morning and in the afternoon (DSCD ~2×10^15 molec cm-²) while, around noon, a second maximum can be observed (DSCD ~4×10^16 molec cm-²). Satellite data show mean VCDs of about 3×10^15 molec cm-² in July and a varying agreement with MAX-DOAS measurements.

  17. Retrieval of Greenhouse Gas Profiles from SCIMACHY Solar Occultation Measurements with Onion Peeling DOAS

    NASA Astrophysics Data System (ADS)

    Noel, Stefan; Bramstedt, Klaus; Reuter, Max; Rozanov, Alexei; Bovensmann, Heinrich; Burrows, John P.

    2010-12-01

    A new retrieval method (called 'Onion Peeling DOAS') has been developed to derive stratospheric profiles of atmospheric constituents from solar occultation measurements of the SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY). The method has already been successfully applied to water vapour. However, the Onion Peeling DOAS method can also be applied to other atmospheric constituents. Here, we summarise the results for stratospheric water vapour and present first results for other greenhouse gases, namely methane (CH4) and carbon dioxide (CO2).

  18. The use of NO2 absorption cross section temperature sensitivity to derive NO2 profile temperature and stratospheric/tropospheric column partitioning from visible direct sun DOAS measurements

    NASA Astrophysics Data System (ADS)

    Spinei, E.; Cede, A.; Swartz, W. H.; Herman, J.; Mount, G. H.

    2014-06-01

    This paper presents a TEmperature SEnsitivity Method (TESEM) to accurately calculate total vertical NO2 column, atmospheric slant NO2 profile-weighted temperature (T), and to separate stratospheric and tropospheric columns from direct-sun (DS) ground-based measurements using the retrieved T. TESEM is based on Differential Optical Absorption Spectroscopy (DOAS) fitting of the linear temperature-dependent NO2 absorption cross section, σ (T), regression model (Vandaele et al., 2003). The direct result of the DOAS spectral fitting retrieval is NO2 differential slant column density (Δ SCD) at the actual atmospheric NO2 T. Atmospheric NO2 T is determined from the DOAS fitting results after SCD in the reference spectrum is estimated using the Minimum Langley Extrapolation method (MLE). Since NO2 is mostly distributed between the lower troposphere and middle stratosphere and direct sun measurements have almost equal sensitivity to stratospheric and tropospheric absorption at solar zenith angles < 75° with a well known photon path, we assume that the retrieved total column NO2 T can be represented as a sum of the NO2 stratospheric and tropospheric Ts multiplied by the corresponding stratospheric and tropospheric fractions of the total SCDNO2. We use Global Modeling Initiative (GMI) chemistry-transport model (CTM) simulations to evaluate diurnal and seasonal variability of stratospheric and tropospheric NO2 T over two northern middle latitude sites in 2011. GMI simulations reveal that stratospheric NO2 T over northern middle latitudes can be estimated with an error of less than 3 K by the simulated temperature at 27 km from April to October. During November-March months the error can reach as high as 10 K. The tropospheric NO2 T can be approximated by the surface temperature within 3-5 K according to GMI simulations. Traditionally, either σ (NO2) is fitted at a single estimated NO2 T, or two predetermined (stratospheric and tropospheric) temperatures. Use of a single T

  19. DUVAS (derivative uv-absorption spectrometer): instrument description and operating manual

    SciTech Connect

    Hawthorne, A.R.; Dougherty, J.M.; Metcalfe, C.E.

    1980-11-01

    DUVAS is a real-time, field-portable spectrometer capable of monitoring a variety of aromatic organic vapors and inorganic gases at sub-ppM concentrations. The instrument is a prototype, microcomputer-controlled, derivative ultraviolet (UV) absorption spectrometer (DUVAS) developed primarily for area monitoring at coal conversion facilities, although other important occupational and environmental monitoring applications for compounds such as SO/sub 2/, NO/sub x/, NH/sub 3/, and HCHO are also being pursued.

  20. A Fourier transform spectrometer for visible and near ultra-violet measurements of atmospheric absorption

    NASA Technical Reports Server (NTRS)

    Parsons, C. L.; Gerlach, J. C.; Whitehurst, M.

    1982-01-01

    The development of a prototype, ground-based, Sun-pointed Michelson interferometric spectrometer is described. Its intended use is to measure the atmospheric amount of various gases which absorb in the near-infrared, visible, and near-ultraviolet portions of the electromagnetic spectrum. Preliminary spectra which contain the alpha, 0.8 micrometer, and rho sigma tau water vapor absorption bands in the near-infrared are presented to indicate the present capability of the system. Ultimately, the spectrometer can be used to explore the feasible applications of Fourier transform spectroscopy in the ultraviolet where grating spectrometers were used exclusively.

  1. Observation of the volcanic plume of Eyjafjallajökull over continental Europe by Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS)

    NASA Astrophysics Data System (ADS)

    Yilmaz, S.; Friess, U.; Kern, C.; Vogel, L.; Hoermann, C.; Wagner, T.; Platt, U.

    2010-12-01

    The recent eruption of Eyjafjallajökull Volcano (Iceland) and the emitted ash plume which disrupted commercial air traffic over Europe for an extended period of time has led to an exhaustive debate on how to improve our ability to quantitatively determine the ash load in the atmosphere as a function of time and geographical location in the aftermath of future eruptions. A combination of satellite remote sensing instruments detecting ash and SO2 and ground-based LIDAR stations can help constrain atmospheric transport and meteorology models used to predict ash dispersion. However, multi-axis Differential Optical Absorption Spectroscopy (MAX-DOAS) represents an additional and often neglected tool with considerable potential for the quantitative detection of elevated volcanic ash and SO2 plumes. It performs especially well during weather conditions in which satellites and LIDARs are impeded in their effectiveness, e.g. in the case of dense clouds above or below the plume, respectively. Here, the advantages and disadvantages of the DOAS technique are discussed, and its potential for monitoring of volcanic ash hazards explored. Results of ash and SO2 measurements of the Eyjafjallajökull plume as it passed over the city of Heidelberg, Germany are presented as an example of a positive detection of a highly diluted volcanic plume. SO2 was detected on several days with differential slant column densities (dSCD) of up to (3.33 ± 0.35) × 1017 molec/cm2. The occurrence of these high dSCDs is in good agreement with model predictions (FLEXPART), in-situ background (Schauinsland, Germany) and remote sensing measurements (GOME-2). For cloud free conditions, also the aerosol optical depth at 350 nm was retrieved from the MAX-DOAS measurements. The retrieved values of up to 1.31 ± 0.02 are in good agreement with Sun photometer measurements. Their relatively low cost and complementary nature in respect to other SO2/ash detection techniques makes multi-axis DOAS a promising

  2. A miniDOAS instrument optimised for ammonia field measurements

    NASA Astrophysics Data System (ADS)

    Sintermann, Jörg; Dietrich, Klaus; Häni, Christoph; Bell, Michael; Jocher, Markus; Neftel, Albrecht

    2016-06-01

    We present a differential optical absorption spectroscopy (DOAS) instrument, called "miniDOAS", optimised for optical open-path field-measurements of ambient ammonia (NH3) alongside nitrogen oxide (NO) and sulfur dioxide (SO2). The instrument is a further development of the miniDOAS presented by Volten et al. (2012). We use a temperature-controlled spectrometer, a deuterium light source and a modified optical arrangement. The system was set up in a robust, field-deployable, temperature-regulated housing. For the evaluation of light spectra we use a new high-pass filter routine based upon robust baseline extraction with local regression. Multiple linear regression including terms of an autoregressive-moving-average model is used to determine concentrations. For NH3 the random uncertainty is about 1.4 % of the concentration, and not better than 0.2 µg m-3. Potential biases for the slope of the calibration are given by the precision of the differential absorption cross sections (±3 %) and for the offset by the precision of the estimation of concentration offsets (cref) introduced by the reference spectrum Iref. Comparisons of miniDOAS measurements to those by NH3 acid trap devices showed good agreement. The miniDOAS can be flexibly used for a wide range of field trials, such as micrometeorological NH3 flux measurements with approaches based upon horizontal or vertical concentration differences. Results from such applications covering concentration dynamics of less than one up to several hundreds of µg m-3 are presented.

  3. Trace gas absorption spectroscopy using laser difference-frequency spectrometer for environmental application

    NASA Technical Reports Server (NTRS)

    Chen, W.; Cazier, F.; Boucher, D.; Tittel, F. K.; Davies, P. B.

    2001-01-01

    A widely tunable infrared spectrometer based on difference frequency generation (DFG) has been developed for organic trace gas detection by laser absorption spectroscopy. On-line measurements of concentration of various hydrocarbons, such as acetylene, benzene, and ethylene, were investigated using high-resolution DFG trace gas spectroscopy for highly sensitive detection.

  4. Search for molecular absorptions with the Fourier Transform Spectrometer

    NASA Technical Reports Server (NTRS)

    Knacke, Roger F.

    1995-01-01

    The objective of this research was a search for water molecules in the gas phase in molecular clouds. Water should be among the most abundant gases in the clouds and is of fundamental importance in gas chemistry, cloud cooling, shock wave chemistry, and gas-grain interactions of interstellar dust. Detection of water in Comet Halley in the 2.7 micron v(3) band in 1986 had shown that airborne H2O observations are feasible (ground-based observations of H2O are impossible because of the massive water content of the atmosphere). We planned to observe the v(3) band in interstellar clouds where a number of lines of this band should be in absorption. The search for H2O commenced in 1988 with a two flight program on the KAO. this resulted in a detection of interstellar H2O with S/N of 2-4 in the v(3) 1(01)-2(02) line at 3801.42/cm. A subsequent flight series of two flights in 1989 resulted in confirmation to the 3801.42/cm line detection and the detection of altogether four strong lines in the 000-001 v(3) vibration-rotation band of H2O.

  5. Airborne Carbon Dioxide Laser Absorption Spectrometer for IPDA Measurements of Tropospheric CO2: Recent Results

    NASA Technical Reports Server (NTRS)

    Spiers, Gary D.; Menzies, Robert T.

    2008-01-01

    The National Research Council's decadal survey on Earth Science and Applications from Space[1] recommended the Active Sensing of CO2 Emissions over Nights, Days, and Seasons (ASCENDS) mission for launch in 2013-2016 as a logical follow-on to the Orbiting Carbon Observatory (OCO) which is scheduled for launch in late 2008 [2]. The use of a laser absorption measurement technique provides the required ability to make day and night measurements of CO2 over all latitudes and seasons. As a demonstrator for an approach to meeting the instrument needs for the ASCENDS mission we have developed the airborne Carbon Dioxide Laser Absorption Spectrometer (CO2LAS) which uses the Integrated Path Differential Absorption (IPDA) Spectrometer [3] technique operating in the 2 micron wavelength region.. During 2006 a short engineering checkout flight of the CO2LAS was conducted and the results presented previously [4]. Several short flight campaigns were conducted during 2007 and we report results from these campaigns.

  6. Demonstration of a mid-infrared cavity enhanced absorption spectrometer for breath acetone detection.

    PubMed

    Ciaffoni, Luca; Hancock, Gus; Harrison, Jeremy J; van Helden, Jean-Pierre H; Langley, Cathryn E; Peverall, Robert; Ritchie, Grant A D; Wood, Simon

    2013-01-15

    A high-resolution absorption spectrum of gaseous acetone near 8.2 μm has been taken using both Fourier transform and quantum cascade laser (QCL)-based infrared spectrometers. Absolute absorption cross sections within the 1215-1222 cm(-1) range have been determined, and the spectral window around 1216.5 cm(-1) (σ = 3.4 × 10(-19) cm(2) molecule(-1)) has been chosen for monitoring trace acetone in exhaled breath. Acetone at sub parts-per-million (ppm) levels has been measured in a breath sample with a precision of 0.17 ppm (1σ) by utilizing a cavity enhanced absorption spectrometer constructed from the QCL source and a linear, low-volume, optical cavity. The use of a water vapor trap ensured the accuracy of the results, which have been corroborated by mass spectrometric measurements.

  7. Note: A flexible light emitting diode-based broadband transient-absorption spectrometer

    NASA Astrophysics Data System (ADS)

    Gottlieb, Sean M.; Corley, Scott C.; Madsen, Dorte; Larsen, Delmar S.

    2012-05-01

    This Note presents a simple and flexible ns-to-ms transient absorption spectrometer based on pulsed light emitting diode (LED) technology that can be incorporated into existing ultrafast transient absorption spectrometers or operate as a stand-alone instrument with fixed-wavelength laser sources. The LED probe pulses from this instrument exhibit excellent stability (˜0.5%) and are capable of producing high signal-to-noise long-time (>100 ns) transient absorption signals either in a broadband multiplexed (spanning 250 nm) or in tunable narrowband (20 ns) operation. The utility of the instrument is demonstrated by measuring the photoinduced ns-to-ms photodynamics of the red/green absorbing fourth GMP phosphodiesterase/adenylyl cyclase/FhlA domain of the NpR6012 locus of the nitrogen-fixing cyanobacterium Nostoc punctiforme.

  8. A compact DOAS instrument optimised for ammonia field-measurements

    NASA Astrophysics Data System (ADS)

    Neftel, Albrecht; Sintermann, Joerg; Dietrich, Klaus; Häni, Christoph; Jocher, Markus

    2016-04-01

    Accurate, high time-resolution measurements of NH3 in ambient air are still a challenge due to the stickiness of this molecule and its interactions with inlet or instrument surfaces. Differential optical absorption spectroscopy (DOAS) with open-path arrangement offers a contact-free in-situ approach to determine ambient NH3. We present a DOAS instrument, optimised for open-path field-measurements of ambient ammonia (NH3) alongside nitrogen oxide (NO) and sulphur dioxide (SO2). This device, operating in the UV range over paths of up to 100 m, is a further development of the miniDOAS presented by Volten et al. (2012). We use a temperature-controlled spectrometer, a deuterium light source and a modified optical arrangement. The system was set up in a robust, field-deployable, temperature-regulated housing. For the evaluation of light spectra a new high-pass filter routine based upon robust baseline extraction with local regression was used. In order to fit differential absorption cross-sections to the measurements, multiple linear regression is performed including terms of an autoregressive-moving-average model. In this presentation we discuss the influence of filter and fit procedure on the precision and accuracy of the system with examples of field measurements with artificial NH3 sources. Volten, H., Bergwerff, J. B., Haaima, M., Lolkema, D. E., Berkhout, A. J. C., van der Hoff, G. R., Potma, C. J. M., Wichink Kruit, R. J., van Pul, W. A. J. and Swart, D. P. J.: Two instruments based on differential optical absorption spectroscopy (DOAS) to measure accurate ammonia concentrations in the atmosphere, Atmospheric Meas. Tech., 5(2), 413-427, doi:10.5194/amt-5-413-2012, 2012.

  9. Characterization of fine resolution field spectrometers using solar Fraunhofer lines and atmospheric absorption features.

    PubMed

    Meroni, Michele; Busetto, Lorenzo; Guanter, Luis; Cogliati, Sergio; Crosta, Giovanni Franco; Migliavacca, Mirco; Panigada, Cinzia; Rossini, Micol; Colombo, Roberto

    2010-05-20

    The accurate spectral characterization of high-resolution spectrometers is required for correctly computing, interpreting, and comparing radiance and reflectance spectra acquired at different times or by different instruments. In this paper, we describe an algorithm for the spectral characterization of field spectrometer data using sharp atmospheric or solar absorption features present in the measured data. The algorithm retrieves systematic shifts in channel position and actual full width at half-maximum (FWHM) of the instrument by comparing data acquired during standard field spectroscopy measurement operations with a reference irradiance spectrum modeled with the MODTRAN4 radiative transfer code. Measurements from four different field spectrometers with spectral resolutions ranging from 0.05 to 3.5nm are processed and the results validated against laboratory calibration. An accurate retrieval of channel position and FWHM has been achieved, with an average error smaller than the instrument spectral sampling interval.

  10. Characterization of a new modular decay total absorption gamma-ray spectrometer (DTAS) for FAIR

    SciTech Connect

    Montaner Piza, A.; Tain, J. L.; Agramunt, J.; Algora, A.; Guadilla, V.; Marin, E.; Rice, S.; Rubio, B.

    2013-06-10

    Beta-decay studies are one of the main goals of the DEcay SPECtroscopy experiment (DESPEC) to be installed at the future Facility for Antiproton and Ion Research (FAIR). DESPEC aims at the study of nuclear structure of exotic nuclei. A new modular Decay Total Absorption gamma-ray Spectrometer (DTAS) is being built at IFIC and is specially adapted to studies at fragmentation facilities such as the Super Fragment Separator (Super-FRS) at FAIR. The designed spectrometer is composed of 16 identical NaI(Tl) scintillation crystals. This work focuses on the characterization of these independent modules, as an initial step for the characterization of the full spectrometer. Monte Carlo simulations have been performed in order to understand the detector response.

  11. Capillary absorption spectrometer and process for isotopic analysis of small samples

    DOEpatents

    Alexander, M. Lizabeth; Kelly, James F.; Sams, Robert L.; Moran, James J.; Newburn, Matthew K.; Blake, Thomas A.

    2016-03-29

    A capillary absorption spectrometer and process are described that provide highly sensitive and accurate stable absorption measurements of analytes in a sample gas that may include isotopologues of carbon and oxygen obtained from gas and biological samples. It further provides isotopic images of microbial communities that allow tracking of nutrients at the single cell level. It further targets naturally occurring variations in carbon and oxygen isotopes that avoids need for expensive isotopically labeled mixtures which allows study of samples taken from the field without modification. The method also permits sampling in vivo permitting real-time ambient studies of microbial communities.

  12. Performance of a high-resolution mid-IR optical-parametric-oscillator transient absorption spectrometer.

    PubMed

    Echebiri, Geraldine O; Smarte, Matthew D; Walters, Wendell W; Mullin, Amy S

    2014-06-16

    We report on a mid-IR optical parametric oscillator (OPO)-based high resolution transient absorption spectrometer for state-resolved collisional energy transfer. Transient Doppler-broadened line profiles at λ = 3.3 μm are reported for HCl R7 transitions following gas-phase collisions with vibrationally excited pyrazine. The instrument noise, analyzed as a function of IR wavelength across the absorption line, is as much as 10 times smaller than in diode laser-based measurements. The reduced noise is attributed to larger intensity IR light that has greater intensity stability, which in turn leads to reduced detector noise and better frequency locking for the OPO.

  13. Characterization of a Photoacoustic Aerosol Absorption Spectrometer for Aircraft-based Measurements

    NASA Astrophysics Data System (ADS)

    Mason, B. J.; Wagner, N. L.; Richardson, M.; Brock, C. A.; Murphy, D. M.; Adler, G.

    2015-12-01

    Atmospheric aerosol directly impacts the Earth's climate through extinction of incoming and outgoing radiation. The optical extinction is due to both scattering and absorption. In situ measurements of aerosol extinction and scattering are well established and have uncertainties less than 5%. However measurements of aerosol absorption typically have uncertainties of 20-30%. Development and characterization of more accurate and precise instrumentation for measurement of aerosol absorption will enable a deeper understand of significance and spatial distribution of black and brown carbon aerosol, the effect of atmospheric processes on aerosol optical properties, and influence of aerosol optical properties on direct radiative forcing. Here, we present a detailed characterization of a photoacoustic aerosol absorption spectrometer designed for deployment aboard research aircraft. The spectrometer operates at three colors across the visible spectrum and is calibrated in the field using ozone. The field calibration is validated in the laboratory using synthetic aerosol and simultaneous measurements of extinction and scattering. In addition, the sensitivity of the instrument is characterized under conditions typically encountered during aircraft sampling e.g. as a function of changing pressure. We will apply this instrument characterization to ambient aerosol absorption data collected during the SENEX and SEAC4RS aircraft based field campaigns.

  14. A split imaging spectrometer for temporally and spatially resolved titanium absorption spectroscopy.

    PubMed

    Hager, J D; Lanier, N E; Kline, J L; Flippo, K A; Bruns, H C; Schneider, M; Saculla, M; McCarville, T

    2014-11-01

    We present a temporally and a spatially resolved spectrometer for titanium x-ray absorption spectroscopy along 2 axial symmetric lines-of-sight. Each line-of-sight of the instrument uses an elliptical crystal to acquire both the 2p and 3p Ti absorption lines on a single, time gated channel of the instrument. The 2 axial symmetric lines-of-sight allow the 2p and 3p absorption features to be measured through the same point in space using both channels of the instrument. The spatially dependent material temperature can be inferred by observing the 2p and the 3p Ti absorption features. The data are recorded on a two strip framing camera with each strip collecting data from a single line-of-sight. The design is compatible for use at both the OMEGA laser and the National Ignition Facility. The spectrometer is intended to measure the material temperature behind a Marshak wave in a radiatively driven SiO2 foam with a Ti foam tracer. In this configuration, a broad band CsI backlighter will be used for a source and the Ti absorption spectrum measured. PMID:25430177

  15. A split imaging spectrometer for temporally and spatially resolved titanium absorption spectroscopy

    SciTech Connect

    Hager, J. D. Lanier, N. E.; Kline, J. L.; Flippo, K. A.; Bruns, H. C.; Schneider, M.; Saculla, M.; McCarville, T.

    2014-11-15

    We present a temporally and a spatially resolved spectrometer for titanium x-ray absorption spectroscopy along 2 axial symmetric lines-of-sight. Each line-of-sight of the instrument uses an elliptical crystal to acquire both the 2p and 3p Ti absorption lines on a single, time gated channel of the instrument. The 2 axial symmetric lines-of-sight allow the 2p and 3p absorption features to be measured through the same point in space using both channels of the instrument. The spatially dependent material temperature can be inferred by observing the 2p and the 3p Ti absorption features. The data are recorded on a two strip framing camera with each strip collecting data from a single line-of-sight. The design is compatible for use at both the OMEGA laser and the National Ignition Facility. The spectrometer is intended to measure the material temperature behind a Marshak wave in a radiatively driven SiO{sub 2} foam with a Ti foam tracer. In this configuration, a broad band CsI backlighter will be used for a source and the Ti absorption spectrum measured.

  16. Portable 4.6 Micrometers Laser Absorption Spectrometer for Carbon Monoxide Monitoring and Fire Detection

    NASA Technical Reports Server (NTRS)

    Briggs, Ryan M.; Frez, Clifford; Forouhar, Siamak; May, Randy D.; Ruff, Gary A.

    2013-01-01

    The air quality aboard manned spacecraft must be continuously monitored to ensure crew safety and identify equipment malfunctions. In particular, accurate real-time monitoring of carbon monoxide (CO) levels helps to prevent chronic exposure and can also provide early detection of combustion-related hazards. For long-duration missions, environmental monitoring grows in importance, but the mass and volume of monitoring instruments must be minimized. Furthermore, environmental analysis beyond low-Earth orbit must be performed in-situ, as sample return becomes impractical. Due to their small size, low power draw, and performance reliability, semiconductor-laser-based absorption spectrometers are viable candidates for this purpose. To reduce instrument form factor and complexity, the emission wavelength of the laser source should coincide with strong fundamental absorption lines of the target gases, which occur in the 3 to 5 micrometers wavelength range for most combustion products of interest, thereby reducing the absorption path length required for low-level concentration measurements. To address the needs of current and future NASA missions, we have developed a prototype absorption spectrometer using a semiconductor quantum cascade laser source operating near 4.6 micrometers that can be used to detect low concentrations of CO with a compact single-pass absorption cell. In this study, we present the design of the prototype instrument and report on measurements of CO emissions from the combustion of a variety of aerospace plastics.

  17. JPL Carbon Dioxide Laser Absorption Spectrometer Data Processing Results for the 2010 Flight Campaign

    NASA Technical Reports Server (NTRS)

    Jacob, Joseph C.; Spiers, Gary D.; Menzie, Robert T.; Christensen, Lance E.

    2011-01-01

    As a precursor to and validation of the core technology necessary for NASA's Active Sensing of CO2 Emissions over Nights, Days,and Seasons (ASCENDS) mission, we flew JPL's Carbon Dioxide Laser Absorption Spectrometer (CO2LAS) in a campaign of five flights onboard NASA's DC-8 Airborne Laboratory in July 2010. This is the latest in a series of annual flight campaigns that began in 2006, and our first on the DC-8 aircraft.

  18. Five-Channel Infrared Laser Absorption Spectrometer for Combustion Product Monitoring Aboard Manned Spacecraft

    NASA Technical Reports Server (NTRS)

    Briggs, Ryan M.; Frez, Clifford; Borgentun, Carl E.; Bagheri, Mahmood; Forouhar, Siamak; May, Randy D.

    2014-01-01

    Continuous combustion product monitoring aboard manned spacecraft can prevent chronic exposure to hazardous compounds and also provides early detection of combustion events. As future missions extend beyond low-Earth orbit, analysis of returned environmental samples becomes impractical and safety monitoring should be performed in situ. Here, we describe initial designs of a five-channel tunable laser absorption spectrometer to continuously monitor combustion products with the goal of minimal maintenance and calibration over long-duration missions. The instrument incorporates dedicated laser channels to simultaneously target strong mid-infrared absorption lines of CO, HCl, HCN, HF, and CO2. The availability of low-power-consumption semiconductor lasers operating in the 2 to 5 micron wavelength range affords the flexibility to select absorption lines for each gas with maximum interaction strength and minimal interference from other gases, which enables the design of a compact and mechanically robust spectrometer with low-level sensitivity. In this paper, we focus primarily on absorption line selection based on the availability of low-power single-mode semiconductor laser sources designed specifically for the target wavelength range.

  19. The hot DOA1 degenerate HZ 21 - A search for circumstellar/photospheric metals and peculiar absorption at He II

    NASA Technical Reports Server (NTRS)

    Fritz, M. L.; Leckenby, H.; Sion, E. M.; Vauclair, G.; Liebert, J.

    1990-01-01

    A high-resolution IUE spectrum of the hot DO1 degenerate HZ 21 was obtained by combining US1 + European 2 low-background observing shifts. The SWP image reveals a rich spectrum of interstellar absorption lines with an average velocity in the line of sight to HZ 21 of -30 km/s. However, there is no clear evidence of any highly or lowly ionized metal features which could be attributed to circumstellar, wind, or photospheric absorption. There is, however, a broad absorption trough at He II (1640) which was not unexpected, given the clear presence of He II (4686) absorption in this star's optical spectrum. The velocity width of He II (1640) appears consistent with photospheric absorption wings which appear to flank the geocoronal Ly-alpha emission feature. The He II (1640) feature reveals what appears to be a broad (310 km/s) emission reversal. Evidence is provided that the emission reversal is probably real.

  20. [Determination of sulfur in plant using a high-resolution continuum source atomic absorption spectrometer].

    PubMed

    Wang, Yu; Li, Jia-xi

    2009-05-01

    A method for the analysis of sulfur (S) in plant by molecular absorption of carbon monosulfide (CS) using a high-resolution continuum source atomic absorption spectrometer (CS AAS) with a fuel-rich air/acetylene flame has been devised. The strong CS absorption band was found around 258 nm. The half-widths of some absorption bands were of the order of picometers, the same as the common atomic absorption lines. The experimental procedure in this study provided optimized instrumental conditions (the ratio of acetylene to air, the burner height) and parameters, and researched the spectral interferences and chemical interferences. The influence of the organic solvents on the CS absorption signals and the different digestion procedures for the determination of sulfur were also investigated. The limit of detection achieved for sulfur was 14 mg x L(-1), using the CS wavelength of 257. 961 nm and a measurement time of 3 s. The accuracy and precision were verified by analysis of two plant standard reference materials. The major applications of this method have been used for the determination of sulfur in plant materials, such as leaves. Compared to the others, this method for the analysis of sulfur is rapid, easy and simple for sulfur determination in plant. PMID:19650504

  1. TRIPLE Q: a three channel quantum cascade laser absorption spectrometer for fast multiple species concentration measurements.

    PubMed

    Hübner, M; Welzel, S; Marinov, D; Guaitella, O; Glitsch, S; Rousseau, A; Röpcke, J

    2011-09-01

    A compact and transportable three channel quantum cascade laser system (TRIPLE Q) based on mid-infrared absorption spectroscopy has been developed for time-resolved plasma diagnostics. The TRIPLE Q spectrometer encompasses three independently controlled quantum cascade lasers (QCLs), which can be used for chemical sensing, particularly for gas phase analysis of plasmas. All three QCLs are operated in the intra-pulse mode with typical pulse lengths of the order of 150 ns. Using a multiplexed detection, a time resolution shorter than 1 μs can be achieved. Hence, the spectrometer is well suited to study kinetic processes of multiple infrared active compounds in reactive plasmas. A special data processing and analysis technique has been established to account for time jitter effects of the infrared emission of the QCLs. The performance of the TRIPLE Q system has been validated in pulsed direct current plasmas containing N(2)O/air and NO(2)/air.

  2. A low-cost portable fibre-optic spectrometer for atmospheric absorption studies

    NASA Astrophysics Data System (ADS)

    Bailey, J.

    2013-01-01

    A compact and portable solar absorption spectrometer based on fibre-optic Fabry-Perot technology has been built and tested. The instrument weighs only 4.2 kg and operates from 5 W of power from internal batteries. It provides spectroscopy over the range from 5980-6580 cm-1 (1.52-1.67 μm) at a resolution of 0.16 cm-1. The input to the spectrometer is via single-mode optical fibre from a solar tracking system. Spectral scanning is carried out with a piezoelectrically scanned fibre Fabry-Perot tunable filter. Software has been developed to calibrate the spectra in wavelength and relative flux. The signal to noise ratio in solar spectra is about 700 for a spectrum scanned at 200 milliseconds per spectral point. The techniques used should be capable of being adapted to a range of wavelengths and to higher or lower resolutions.

  3. Infrared absorption of gaseous CH2BrOO detected with a step-scan Fourier-transform absorption spectrometer.

    PubMed

    Huang, Yu-Hsuan; Lee, Yuan-Pern

    2014-10-28

    CH2BrOO radicals were produced upon irradiation, with an excimer laser at 248 nm, of a flowing mixture of CH2Br2 and O2. A step-scan Fourier-transform spectrometer coupled with a multipass absorption cell was employed to record temporally resolved infrared (IR) absorption spectra of reaction intermediates. Transient absorption with origins at 1276.1, 1088.3, 961.0, and 884.9 cm(-1) are assigned to ν4 (CH2-wagging), ν6 (O-O stretching), ν7 (CH2-rocking mixed with C-O stretching), and ν8 (C-O stretching mixed with CH2-rocking) modes of syn-CH2BrOO, respectively. The assignments were made according to the expected photochemistry and a comparison of observed vibrational wavenumbers, relative IR intensities, and rotational contours with those predicted with the B3LYP/aug-cc-pVTZ method. The rotational contours of ν7 and ν8 indicate that hot bands involving the torsional (ν12) mode are also present, with transitions 7(0)(1)12(v)(v) and 8(0)(1)12(v)(v), v = 1-10. The most intense band (ν4) of anti-CH2BrOO near 1277 cm(-1) might have a small contribution to the observed spectra. Our work provides information for directly probing gaseous CH2BrOO with IR spectroscopy, in either the atmosphere or laboratory experiments.

  4. Automated extraction of absorption features from Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) and Geophysical and Environmental Research Imaging Spectrometer (GERIS) data

    NASA Technical Reports Server (NTRS)

    Kruse, Fred A.; Calvin, Wendy M.; Seznec, Olivier

    1988-01-01

    Automated techniques were developed for the extraction and characterization of absorption features from reflectance spectra. The absorption feature extraction algorithms were successfully tested on laboratory, field, and aircraft imaging spectrometer data. A suite of laboratory spectra of the most common minerals was analyzed and absorption band characteristics tabulated. A prototype expert system was designed, implemented, and successfully tested to allow identification of minerals based on the extracted absorption band characteristics. AVIRIS spectra for a site in the northern Grapevine Mountains, Nevada, have been characterized and the minerals sericite (fine grained muscovite) and dolomite were identified. The minerals kaolinite, alunite, and buddingtonite were identified and mapped for a site at Cuprite, Nevada, using the feature extraction algorithms on the new Geophysical and Environmental Research 64 channel imaging spectrometer (GERIS) data. The feature extraction routines (written in FORTRAN and C) were interfaced to the expert system (written in PROLOG) to allow both efficient processing of numerical data and logical spectrum analysis.

  5. Supercontinuum based absorption spectrometer for cycle-resolved multiparameter measurements in a rapid compression machine.

    PubMed

    Werblinski, Thomas; Kleindienst, Stefan; Engelbrecht, Rainer; Zigan, Lars; Will, Stefan

    2016-06-10

    A broadband supercontinuum (SC) based absorption spectrometer capable of cycle-resolved multiparameter measurements at internal combustion (IC) engine conditions is presented. Three parameters, temperature, pressure and water mole fraction, were extracted from broadband near-infrared H2O absorption spectra, spanning the wavelength-range from 1340 to 1405.5 nm, which exhibits a large number of specific H2O transitions. The spectrometer is based on spatial domain detection and features a near-infrared line scan camera as a detector. Measurements were performed during a compression cycle of a rapid compression machine comprising a pressure and temperature range from 2.5 to 65 bar and 300 to 900 K, respectively. With the new spectrometer, we are for the first time, based on the authors' knowledge, able to perform measurements based on SC radiation over a complete compression and expansion stroke at measurement rates up to 50 kHz. A detailed overview is provided about the best match algorithm between theory and experiments, including parameters from two different spectral databases, namely the Barber-Tennyson database (BT2) and HITRAN2012. The results indicate that spectral broadening effects are not properly described by theory, especially at pressure levels exceeding 20 bar, which culminates in a clear underestimation of the derived pressure data by SC absorption spectroscopy. Nevertheless, temperature can be determined accurately by performing a three-parameter fit based on water mole fraction, temperature, and pressure. In contrast, making use of pressure transducer data as look-up values and varying only temperature and H2O mole fraction to find the best match leads to a clear overestimation of temperature at elevated pressures. PMID:27409013

  6. Supercontinuum based absorption spectrometer for cycle-resolved multiparameter measurements in a rapid compression machine.

    PubMed

    Werblinski, Thomas; Kleindienst, Stefan; Engelbrecht, Rainer; Zigan, Lars; Will, Stefan

    2016-06-10

    A broadband supercontinuum (SC) based absorption spectrometer capable of cycle-resolved multiparameter measurements at internal combustion (IC) engine conditions is presented. Three parameters, temperature, pressure and water mole fraction, were extracted from broadband near-infrared H2O absorption spectra, spanning the wavelength-range from 1340 to 1405.5 nm, which exhibits a large number of specific H2O transitions. The spectrometer is based on spatial domain detection and features a near-infrared line scan camera as a detector. Measurements were performed during a compression cycle of a rapid compression machine comprising a pressure and temperature range from 2.5 to 65 bar and 300 to 900 K, respectively. With the new spectrometer, we are for the first time, based on the authors' knowledge, able to perform measurements based on SC radiation over a complete compression and expansion stroke at measurement rates up to 50 kHz. A detailed overview is provided about the best match algorithm between theory and experiments, including parameters from two different spectral databases, namely the Barber-Tennyson database (BT2) and HITRAN2012. The results indicate that spectral broadening effects are not properly described by theory, especially at pressure levels exceeding 20 bar, which culminates in a clear underestimation of the derived pressure data by SC absorption spectroscopy. Nevertheless, temperature can be determined accurately by performing a three-parameter fit based on water mole fraction, temperature, and pressure. In contrast, making use of pressure transducer data as look-up values and varying only temperature and H2O mole fraction to find the best match leads to a clear overestimation of temperature at elevated pressures.

  7. First Results from the Modular Total Absorption Spectrometer at the HRIBF

    SciTech Connect

    Fijałkowska, A.; Karny, M.; Rykaczewski, K.P.; Wolińska-Cichocka, M.; Grzywacz, R.; Gross, C.J.; Johnson, J.W.; Rasco, B.C.; Zganjar, E.F.; Stracener, D.W.; Jost, C.; Goetz, K.C.; Goans, R.; Spejewski, E.; Cartegni, L.; Madurga, M.; Miernik, K.; Miller, D.; Padgett, S.W.; Paulauskas, S.V.; and others

    2014-06-15

    A Modular Total Absorption Spectrometer constructed at the Holifield Radioactive Ion Beam Facility has been applied to decay studies of over 20 {sup 238}U fission products. The measurements were focused on nuclei identified as important for decay heat analysis during a nuclear fuel cycle. Preliminary results on the average electromagnetic (EM) energy release in the β decay of {sup 89}Kr and {sup 139}Xe isotopes yielded values of 2446 keV and 1126 keV, respectively. It represents an increase of over 35% and 20%, respectively, when compared to the average EM energies deduced using the ENSDF database.

  8. First Results from the Modular Total Absorption Spectrometer at the HRIBF

    NASA Astrophysics Data System (ADS)

    Fijałkowska, A.; Karny, M.; Rykaczewski, K. P.; Wolińska-Cichocka, M.; Grzywacz, R.; Gross, C. J.; Johnson, J. W.; Rasco, B. C.; Zganjar, E. F.; Stracener, D. W.; Jost, C.; Goetz, K. C.; Goans, R.; Spejewski, E.; Cartegni, L.; Madurga, M.; Miernik, K.; Miller, D.; Padgett, S. W.; Paulauskas, S. V.; Al-Shudifat, M.; Hamilton, J. H.; Ramayya, A. V.

    2014-06-01

    A Modular Total Absorption Spectrometer constructed at the Holifield Radioactive Ion Beam Facility has been applied to decay studies of over 20 238U fission products. The measurements were focused on nuclei identified as important for decay heat analysis during a nuclear fuel cycle. Preliminary results on the average electromagnetic (EM) energy release in the β decay of 89Kr and 139Xe isotopes yielded values of 2446 keV and 1126 keV, respectively. It represents an increase of over 35% and 20%, respectively, when compared to the average EM energies deduced using the ENSDF database.

  9. Measurement of fission products β decay properties using a total absorption spectrometer

    NASA Astrophysics Data System (ADS)

    Zakari-Issoufou, A.-A.; Porta, A.; Fallot, M.; Algora, A.; Tain, J. L.; Valencia, E.; Rice, S.; Agramunt, J.; Äystö, J.; Bowry, M.; Bui, V. M.; Caballero-Folch, R.; Cano-Ott, D.; Eloma, V.; Estévez, E.; Farrelly, G. F.; Garcia, A.; Gelletly, W.; Gomez-Hornillos, M. B.; Gorlychev, V.; Hakala, J.; Jokinen, A.; Jordan, M. D.; Kankainen, A.; Kondev, F. G.; Martinez, T.; Mendoza, E.; Molina, F.; Moore, I.; Perez, A.; Podolyak, Zs.; Penttilä, H.; Regan, P. H.; Rissanen, J.; Rubio, B.; Weber, C.

    2013-12-01

    In a nuclear reactor, the β decay of fission fragments is at the origin of decay heat and antineutrino flux. These quantities are not well known while they are very important for reactor safety and for our understanding of neutrino physics. One reason for the discrepancies observed in the estimation of the decay heat and antineutrinos flux coming from reactors could be linked with the Pandemonium effect. New measurements have been performed at the JYFL facility of Jyväskylä with a Total Absorption Spectrometer (TAS) in order to circumvent this effect. An overview of the TAS technique and first results from the 2009 measurement campaign will be presented.

  10. Carbon Dioxide Laser Absorption Spectrometer (CO2LAS) Aircraft Measurements of CO2

    NASA Technical Reports Server (NTRS)

    Christensen, Lance E.; Spiers, Gary D.; Menzies, Robert T.; Jacob, Joseph C.; Hyon, Jason

    2011-01-01

    The Jet Propulsion Laboratory Carbon Dioxide Laser Absorption Spectrometer (CO2LAS) utilizes Integrated Path Differential Absorption (IPDA) at 2.05 microns to obtain CO2 column mixing ratios weighted heavily in the boundary layer. CO2LAS employs a coherent detection receiver and continuous-wave Th:Ho:YLF laser transmitters with output powers around 100 milliwatts. An offset frequency-locking scheme coupled to an absolute frequency reference enables the frequencies of the online and offline lasers to be held to within 200 kHz of desired values. We describe results from 2009 field campaigns when CO2LAS flew on the Twin Otter. We also describe spectroscopic studies aimed at uncovering potential biases in lidar CO2 retrievals at 2.05 microns.

  11. A broadband absorption spectrometer using light emitting diodes for ultrasensitive, in situ trace gas detection

    SciTech Connect

    Langridge, Justin M.; Shillings, Alexander J. L.; Jones, Roderic L.; Ball, Stephen M.

    2008-12-15

    A broadband absorption spectrometer has been developed for highly sensitive and target-selective in situ trace gas measurements. The instrument employs two distinct modes of operation: (i) broadband cavity enhanced absorption spectroscopy (BBCEAS) is used to quantify the concentration of gases in sample mixtures from their characteristic absorption features, and (ii) periodic measurements of the cavity mirrors' reflectivity are made using step-scan phase shift cavity ringdown spectroscopy (PSCRDS). The latter PSCRDS method provides a stand-alone alternative to the more usual method of determining mirror reflectivities by measuring BBCEAS absorption spectra for calibration samples of known composition. Moreover, the instrument's two modes of operation use light from the same light emitting diode transmitted through the cavity in the same optical alignment, hence minimizing the potential for systematic errors between mirror reflectivity determinations and concentration measurements. The ability of the instrument to quantify absorber concentrations is tested in instrument intercomparison exercises for NO{sub 2} (versus a laser broadband cavity ringdown spectrometer) and for H{sub 2}O (versus a commercial hygrometer). A method is also proposed for calculating effective absorption cross sections for fitting the differential structure in BBCEAS spectra due to strong, narrow absorption lines that are under-resolved and hence exhibit non-Beer-Lambert law behavior at the resolution of the BBCEAS measurements. This approach is tested on BBCEAS spectra of water vapor's 4v+{delta} absorption bands around 650 nm. The most immediate analytical application of the present instrument is in quantifying the concentration of reactive trace gases in the ambient atmosphere. The instrument's detection limits for NO{sub 3} as a function of integration time are considered in detail using an Allan variance analysis. Experiments under laboratory conditions produce a 1{sigma} detection limit

  12. A broadband absorption spectrometer using light emitting diodes for ultrasensitive, in situ trace gas detection

    NASA Astrophysics Data System (ADS)

    Langridge, Justin M.; Ball, Stephen M.; Shillings, Alexander J. L.; Jones, Roderic L.

    2008-12-01

    A broadband absorption spectrometer has been developed for highly sensitive and target-selective in situ trace gas measurements. The instrument employs two distinct modes of operation: (i) broadband cavity enhanced absorption spectroscopy (BBCEAS) is used to quantify the concentration of gases in sample mixtures from their characteristic absorption features, and (ii) periodic measurements of the cavity mirrors' reflectivity are made using step-scan phase shift cavity ringdown spectroscopy (PSCRDS). The latter PSCRDS method provides a stand-alone alternative to the more usual method of determining mirror reflectivities by measuring BBCEAS absorption spectra for calibration samples of known composition. Moreover, the instrument's two modes of operation use light from the same light emitting diode transmitted through the cavity in the same optical alignment, hence minimizing the potential for systematic errors between mirror reflectivity determinations and concentration measurements. The ability of the instrument to quantify absorber concentrations is tested in instrument intercomparison exercises for NO2 (versus a laser broadband cavity ringdown spectrometer) and for H2O (versus a commercial hygrometer). A method is also proposed for calculating effective absorption cross sections for fitting the differential structure in BBCEAS spectra due to strong, narrow absorption lines that are under-resolved and hence exhibit non-Beer-Lambert law behavior at the resolution of the BBCEAS measurements. This approach is tested on BBCEAS spectra of water vapor's 4v+δ absorption bands around 650 nm. The most immediate analytical application of the present instrument is in quantifying the concentration of reactive trace gases in the ambient atmosphere. The instrument's detection limits for NO3 as a function of integration time are considered in detail using an Allan variance analysis. Experiments under laboratory conditions produce a 1σ detection limit of 0.25 pptv for a 10 s

  13. A table-top femtosecond time-resolved soft x-ray transient absorption spectrometer

    SciTech Connect

    Leone, Stephen; Loh, Zhi-Heng; Khalil, Munira; Correa, Raoul E.; Leone, Stephen R.

    2008-05-21

    A laser-based, table-top instrument is constructed to perform femtosecond soft x-ray transient absorption spectroscopy. Ultrashort soft x-ray pulses produced via high-order harmonic generation of the amplified output of a femtosecond Ti:sapphire laser system are used to probe atomic core-level transient absorptions in atoms and molecules. The results provide chemically specific, time-resolved dynamics with sub-50-fs time resolution. In this setup, high-order harmonics generated in a Ne-filled capillary waveguide are refocused by a gold-coated toroidal mirror into the sample gas cell, where the soft x-ray light intersects with an optical pump pulse. The transmitted high-order harmonics are spectrally dispersed with a home-built soft x-ray spectrometer, which consists of a gold-coated toroidal mirror, a uniform-line spaced plane grating, and a soft x-ray CCD camera. The optical layout of the instrument, design of the soft x-ray spectrometer, and spatial and temporal characterization of the high-order harmonics are described. Examples of static and time-resolved photoabsorption spectra collected on this apparatus are presented.

  14. Aerosol absorption measurement at SWIR with water vapor interference using a differential photoacoustic spectrometer.

    PubMed

    Zhu, Wenyue; Liu, Qiang; Wu, Yi

    2015-09-01

    Atmospheric aerosol plays an important role in atmospheric radiation balance through absorbing and scattering the solar radiation, which changes local weather and global climate. Accurate measurement is highly requested to estimate the radiative effects and climate effects of atmospheric aerosol. Photoacoustic spectroscopy (PAS) technique, which observes the aerosols on their natural suspended state and is insensitive to light scattering, is commonly recognized as one of the best candidates to measure the optical absorption coefficient (OAC) of aerosols. In the present work, a method of measuring aerosol OAC at the wavelength where could also be absorbed by water vapor was proposed and corresponding measurements of the absorption properties of the atmospheric aerosol at the short wave infrared (SWIR, 1342 nm) wavelength were carried out. The spectrometer was made up of two high performance homemade photoacoustic cells. To improve the sensitivity, several methods were presented to control the noise derived from gas flow and vibration from the sampling pump. Calibration of the OAC and properties of the system were also studied in detail. Using the established PAS instrument, measurement of the optical absorption properties of the atmospheric aerosol were carried out in laboratory and field environment.

  15. Aerosol absorption measurement at SWIR with water vapor interference using a differential photoacoustic spectrometer.

    PubMed

    Zhu, Wenyue; Liu, Qiang; Wu, Yi

    2015-09-01

    Atmospheric aerosol plays an important role in atmospheric radiation balance through absorbing and scattering the solar radiation, which changes local weather and global climate. Accurate measurement is highly requested to estimate the radiative effects and climate effects of atmospheric aerosol. Photoacoustic spectroscopy (PAS) technique, which observes the aerosols on their natural suspended state and is insensitive to light scattering, is commonly recognized as one of the best candidates to measure the optical absorption coefficient (OAC) of aerosols. In the present work, a method of measuring aerosol OAC at the wavelength where could also be absorbed by water vapor was proposed and corresponding measurements of the absorption properties of the atmospheric aerosol at the short wave infrared (SWIR, 1342 nm) wavelength were carried out. The spectrometer was made up of two high performance homemade photoacoustic cells. To improve the sensitivity, several methods were presented to control the noise derived from gas flow and vibration from the sampling pump. Calibration of the OAC and properties of the system were also studied in detail. Using the established PAS instrument, measurement of the optical absorption properties of the atmospheric aerosol were carried out in laboratory and field environment. PMID:26368414

  16. [Research on the NO2 mean concentration measurement with target differential optical absorption spectroscopy technology].

    PubMed

    Liu, Jin; Si, Fu-Qi; Zhou, Hai-Jin; Zhao, Min-Jie; Dou, Ke; Liu, Wen-Qing

    2013-04-01

    A new monitoring method of NO2 concentration near ground with the target difference absorption spectrum technology (Target DOAS) is introduced in the present paper. This method is based on the passive difference absorption spectrum technology. The instrument collects solar reflection spectrum of remote objectives, such as wall of building and mountain, and a specific reference spectrum is chosen to subtract the influence of trace gases from the target to atmospheric top, then integrated concentration of NO2 along the path between the target and instrument can be calculated through the differential absorption spectra inversion algorithm. Since the distance between the instrument and target is given, the mean concentration of NO2 can be derived. With developed Target DOAS instrument, NO2 concentration measurement was carried out in Hefei. And comparison was made between the target DOAS and long path difference absorption spectrometer. Good consistency was presented, proving the feasibility of this method.

  17. [Research on the NO2 mean concentration measurement with target differential optical absorption spectroscopy technology].

    PubMed

    Liu, Jin; Si, Fu-Qi; Zhou, Hai-Jin; Zhao, Min-Jie; Dou, Ke; Liu, Wen-Qing

    2013-04-01

    A new monitoring method of NO2 concentration near ground with the target difference absorption spectrum technology (Target DOAS) is introduced in the present paper. This method is based on the passive difference absorption spectrum technology. The instrument collects solar reflection spectrum of remote objectives, such as wall of building and mountain, and a specific reference spectrum is chosen to subtract the influence of trace gases from the target to atmospheric top, then integrated concentration of NO2 along the path between the target and instrument can be calculated through the differential absorption spectra inversion algorithm. Since the distance between the instrument and target is given, the mean concentration of NO2 can be derived. With developed Target DOAS instrument, NO2 concentration measurement was carried out in Hefei. And comparison was made between the target DOAS and long path difference absorption spectrometer. Good consistency was presented, proving the feasibility of this method. PMID:23841393

  18. NOx emissions of various sources in Romania and the Rhein-Main region in Germany based on mobile MAX-DOAS measurements of NO2.

    NASA Astrophysics Data System (ADS)

    Riffel, Katharina; Sebastian, Donner; Shaiganfar, Reza; Wagner, Thomas; Dörner, Steffen

    2016-04-01

    The MAX DOAS-Method (Multi-AXis Differential Optical Absorption Spectroscopy) is used to analyze different trace gases (e.g. NO2, SO2, HCHO) at the same time and to determine the trace gas vertical column density (vertically integrated concentration). In summer 2015 we performed car-MAX-DOAS measurements in Romania during the AROMAT2 campaign. We encircled Bucharest at different weather situations and different times of the day. Afterwards the total NOx emissions were derived from the mobile MAX-DOAS observations in combination with wind data. In Germany we performed the same measurement procedure in fall/ winter/ spring 2015 /2016 by encircling the cities Mainz and Frankfurt. For the setting we mounted two MAX-DOAS instruments with different viewing directions (forward and backward) on the roof of a car. One instrument is a commercial mini MAX-DOAS that is built by the German company Hoffmann Messtechnik. The second one was built at the MPI in Mainz. This so-called Tube MAX-DOAS uses an AVANTES spectrometer with better optical characteristics than Hoffmann's mini MAX-DOAS. The advantage of two instruments working at the same time is (besides redundancy) that localized emission plumes can be measured from different directions at different locations. Thus, especially for emission plumes from power plants, tomographic methods can be applied to derive information about the plume altitude. Car-MAX-DOAS observations can cover large areas at a short time with reasonable resolution (depending on the speed of the car and the instruments integration time). Thus these measurements are well suited to validate satellites observations. This work will show the first AROMAT2 results of NOx emissions derived in Romania and in the Rhein-Main region, which is one of the most polluted area in Germany.

  19. A Near-Infrared Spectrometer to Measure Zodiacal Light Absorption Spectrum

    NASA Technical Reports Server (NTRS)

    Kutyrev, A. S.; Arendt, R.; Dwek, E.; Kimble, R.; Moseley, S. H.; Rapchun, D.; Silverberg, R. F.

    2010-01-01

    We have developed a high throughput infrared spectrometer for zodiacal light fraunhofer lines measurements. The instrument is based on a cryogenic dual silicon Fabry-Perot etalon which is designed to achieve high signal to noise Fraunhofer line profile measurements. Very large aperture silicon Fabry-Perot etalons and fast camera optics make these measurements possible. The results of the absorption line profile measurements will provide a model free measure of the zodiacal Light intensity in the near infrared. The knowledge of the zodiacal light brightness is crucial for accurate subtraction of zodiacal light foreground for accurate measure of the extragalactic background light after the subtraction of zodiacal light foreground. We present the final design of the instrument and the first results of its performance.

  20. Results of fission products β decay properties measurement performed with a total absorption spectrometer

    NASA Astrophysics Data System (ADS)

    Zakari-Issoufou, A.-A.; Porta, A.; Fallot, M.; Algora, A.; Tain, J. L.; Valencia, E.; Rice, S.; Agramunt, J.; Äystö, J.; Bowry, M.; Bui, V. M.; Caballero-Folch, R.; Cano-Ott, D.; Eloma, V.; Estévez, E.; Farrelly, G. F.; Garcia, A.; Gelletly, W.; Gomez-Hornillos, M. B.; Gorlychev, V.; Hakala, J.; Jokinen, A.; Jordan, M. D.; Kankainen, A.; Kondev, F. G.; Martinez, T.; Mendoza, E.; Molina, F.; Moore, I.; Perez, A.; Podolyak, Zs.; Penttilä, H.; Regan, P. H.; Rissanen, J.; Rubio, B.; Weber, C.

    2014-03-01

    β-decay properties of fission products are very important for applied reactor physics, for instance to estimate the decay heat released immediately after the reactor shutdown and to estimate the bar ν flux emitted. An accurate estimation of the decay heat and the bar ν emitted flux from reactors, are necessary for purposes such as reactors operation safety and non-proliferation. In order to improve the precision in the prediction for these quantities, the bias due to the Pandemonium effect affecting some important fission product data has to be corrected. New measurements of fission products β-decay, not sensitive to this effect, have been performed with a Total Absorption Spectrometer (TAS) at the JYFL facility of Jyväskylä. An overview of the TAS technique and first results from the 2009 campaign will be presented.

  1. Further developments of capillary absorption spectrometers using small hollow-waveguide fibers

    SciTech Connect

    Kelly, James F.; Sams, Robert L.; Blake, Thomas A.; Kriesel, Jason M.

    2014-05-01

    Our objective is to enhance quantification of stable carbon and oxygen isotope ratios to better than 1‰ relative isotope precision for sample sizes < 1 pico-mole. A newer variant Capillary Absorption Spectrometer (CAS) is described using a proprietary linear-taper hollow waveguide in conjunction with wavelength and frequency modulation techniques of tunable laser absorption spectrometry. Previous work used circular capillaries with uniform 1 mm ID to measure 13C/12C ratios with ≥ 20 pico-mole samples to ≤ 10 ppm (1‰ precision against standards) [1]. While performing fairly well, it generated residual modal noise due to multipath propagation in the hollow-waveguides (HWGs). This system has been utilized with laser ablation-catalytic combustion techniques to analyze small resolution (~ 25 μm spot diameter) laser ablation events on solids. Using smaller ID capillary waveguides could improve detection limits and spatial resolutions. Reducing an IR compatible hollow waveguide’s inner diameter (ID) to < 300 μm, reduces modal noise significantly for mid-IR operation, but feedback noise with high gain semiconductor lasers can become problematic. A proprietary linear-taper small waveguide (mean ID = 0.35 mm, L = 1 m) was tested to understand whether modal noise and optical feedback effects could be simultaneously reduced. We see better mode filtering and, significant reductions of feedback noise under favorable coupling of a multi-spatial mode QC laser to the smaller ID of the linear-tapered HWG. We demonstrate that better modal coupling operation is consistent with Liouville’s theorem, where greater suppression of feedback from spurious scatter within the HWG occurs by injecting the laser into the smaller ID port. Our progress on developing lighter weight, potentially fieldable alternatives to Isotope Ratio Mass Spectrometers (IRMS) with a small volume (≤ 0.1 cm3) CAS system will be discussed and compared to other competitive systems.

  2. Simulations of an airborne laser absorption spectrometer for atmospheric CO2 measurements

    NASA Astrophysics Data System (ADS)

    Lin, B.; Ismail, S.; Harrison, F. W.; Browell, E. V.; Dobler, J. T.; Refaat, T.; Kooi, S. A.

    2012-12-01

    Atmospheric column amount of carbon dioxide (CO2), a major greenhouse gas of the atmosphere, has significantly increased from a preindustrial value of about 280 parts per million (ppm) to more than 390 ppm at present. Our knowledge about the spatiotemporal change and variability of the greenhouse gas, however, is limited. Thus, a near-term space mission of the Active Sensing of CO2 Emissions over Nights, Days, and Seasons (ASCENDS) is crucial to increase our understanding of global sources and sinks of CO2. Currently, NASA Langley Research Center (LaRC) and ITT Exelis are jointly developing and testing an airborne laser absorption spectrometer (LAS) as a prototype instrument for the mission. To assess the space capability of accurate atmospheric CO2 measurements, accurate modeling of the instrument and practical evaluation of space applications are the keys for the success of the ASCENDS mission. This study discusses the simulations of the performance of the airborne instrument and its CO2 measurements. The LAS is a multi-wavelength spectrometer operating on a 1.57 um CO2 absorption line. The Intensity-Modulated Continuous-Wave (IM-CW) approach is implemented in the instrument. To reach accurate CO2 measurements, transmitted signals are monitored internally as reference channels. A model of this kind of instrument includes all major components of the spectrometer, such as modulation generator, fiber amplifier, telescope, detector, transimpedance amplifier, matched filter, and other signal processors. The characteristics of these components are based on actual laboratory tests, product specifications, and general understanding of the functionality of the components. For simulations of atmospheric CO2 measurements, environmental conditions related to surface reflection, atmospheric CO2 and H2O profiles, thin clouds, and aerosol layers, are introduced into the model. Furthermore, all major noise sources such as those from detectors, background radiation, speckle, and

  3. Total Absorption Gamma-ray Spectrometer (TAGS) Intensity Distributions from INL's Gamma-Ray Spectrometry Center

    DOE Data Explorer

    Greenwood, R. E.

    A 252Cf fission-product source and the INL on-line isotope separator were used to supply isotope-separated fission-product nuclides to a total absorption -ray spectrometer. This spectrometer consisted of a large (25.4-cm diameter x 30.5-cm long) NaI(Tl) detector with a 20.3-cm deep axial well in which is placed a 300-mm2 x 1.0-mm Si detector. The spectra from the NaI(Tl) detector are collected both in the singles mode and in coincidence with the B-events detected in the Si detector. Ideally, this detector would sum all the energy of the B- rays in each cascade following the population of daughter level by B- decay, so that the event could be directly associated with a particular daughter level. However, there are losses of energy from attenuation of the rays before they reach the detector, transmission of rays through the detector, escape of secondary photons from Compton scattering, escape of rays through the detector well, internal conversion, etc., and the measured spectra are thus more complicated than the ideal case and the analysis is more complex. Analysis methods have been developed to simulate all of these processes and thus provide a direct measure of the B- intensity distribution as a function of the excitation energy in the daughter nucleus. These data yield more accurate information on the B- distribution than conventional decay-scheme studies for complex decay schemes with large decay energies, because in the latter there are generally many unobserved and observed but unplaced rays. The TAGS data have been analyzed and published [R. E. Greenwood et al., Nucl Instr. and metho. A390(1997)] for 40 fission product-nuclides to determine the B- intensity distributions. [Copied from the TAGS page at http://www.inl.gov/gammaray/spectrometry/tags.shtml]. Those values are listed on this page for quick reference.

  4. A doubly curved elliptical crystal spectrometer for the study of localized x-ray absorption in hot plasmas

    SciTech Connect

    Cahill, Adam D. Hoyt, Cad L.; Pikuz, Sergei A.; Shelkovenko, Tania; Hammer, David A.

    2014-10-15

    X-ray absorption spectroscopy is a powerful tool for the diagnosis of plasmas over a wide range of both temperature and density. However, such a measurement is often limited to probing plasmas with temperatures well below that of the x-ray source in order to avoid object plasma emission lines from obscuring important features of the absorption spectrum. This has excluded many plasmas from being investigated by this technique. We have developed an x-ray spectrometer that provides the ability to record absorption spectra from higher temperature plasmas than the usual approach allows without the risk of data contamination by line radiation emitted by the plasma under study. This is accomplished using a doubly curved mica crystal which is bent both elliptically and cylindrically. We present here the foundational work in the design and development of this spectrometer along with initial results obtained with an aluminum x-pinch as the object plasma.

  5. An off Axis Cavity Enhanced Absorption Spectrometer and a Rapid Scan Spectrometer with a Room-Temperature External Cavity Quantum Cascade Laser

    NASA Astrophysics Data System (ADS)

    Liu, Xunchen; Kang, Cheolhwa; Xu, Yunjie

    2009-06-01

    Quantum cascade laser (QCL) is a new type of mid-infrared tunable diode lasers with superior output power and mode quality. Recent developments, such as room temperature operation, wide frequency tunability, and narrow line width, make QCLs an ideal light source for high resolution spectroscopy. Two slit jet infrared spectrometers, namely an off-axis cavity enhanced absorption (CEA) spectrometer and a rapid scan spectrometer with an astigmatic multi-pass cell assembly, have been coupled with a newly purchased room temperature tunable mod-hop-free QCL with a frequency coverage from 1592 cm^{-1} to 1698 cm^{-1} and a scan rate of 0.1 cm^{-1}/ms. Our aim is to utilize these two sensitive spectrometers, that are equipped with a molecular jet expansion, to investigate the chiral molecules-(water)_n clusters. To demonstrate the resolution and sensitivity achieved, the rovibrational transitions of the static N_2O gas and the bending rovibrational transitions of the Ar-water complex, a test system, at 1634 cm^{-1} have been measured. D. Hofstetter and J. Faist in High performance quantum cascade lasers and their applications, Vol.89 Springer-Verlag Berlin & Heidelberg, 2003, pp. 61-98. Y. Xu, X. Liu, Z. Su, R. M. Kulkarni, W. S. Tam, C. Kang, I. Leonov and L. D'Agostino, Proc. Spie, 2009, 722208 (1-11). M. J. Weida and D. J. Nesbitt, J. Chem. Phys. 1997, 106, 3078-3089.

  6. The 2014 ASCENDS Field Campaign - a Carbon Dioxide Laser Absorption Spectrometer Perspective

    NASA Astrophysics Data System (ADS)

    Spiers, G. D.; Menzies, R. T.; Jacob, J. C.; Geier, S.; Fregoso, S. F.

    2014-12-01

    NASA's ASCENDS mission has been flying several candidate lidar instruments on board the NASA DC-8 aircraft to obtain column integrated measurements of Carbon Dioxide. Each instrument uses a different approach to making the measurement and combined they have allowed for the informed development of the ASCENDS mission measurement requirements(1). The JPL developed Carbon Dioxide Laser Absorption Spectrometer, CO2LAS is one of these instruments. The CO2LAS measures the weighted, column averaged carbon dioxide between the aircraft and the ground using a continuous-wave heterodyne technique. The instrument operates at a 2.05 micron wavelength optimized for enhancing sensitivity to boundary layer carbon dioxide. Since the 2013 field campaign the instrument has undergone significant upgrades that improve the data collection efficiency and instrument stability and has recently been re-integrated onto the NASA DC-8 for the August 2014 ASCENDS field campaign. This presentation will summarize the instrument and algorithm improvements and review the 2014 field campaign flights and preliminary results. (1) Abshire, J.B. et al., "An overview of NASA's ASCENDS Mission lidar measurement requirements", submitted to 2014 Fall AGU Conference.

  7. Measurement of the Spectral Absorption of Liquid Water in Melting Snow With an Imaging Spectrometer

    NASA Technical Reports Server (NTRS)

    Green, Robert O.; Dozier, Jeff

    1995-01-01

    Melting of the snowpack is a critical parameter that drives aspects of the hydrology in regions of the Earth where snow accumulates seasonally. New techniques for measurement of snow melt over regional scales offer the potential to improve monitoring and modeling of snow-driven hydrological processes. In this paper we present the results of measuring the spectral absorption of liquid water in a melting snowpack with the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS). AVIRIS data were acquired over Mammoth Mountain, in east central California on 21 May 1994 at 18:35 UTC. The air temperature at 2926 m on Mammoth Mountain at site A was measured at 15-minute intervals during the day preceding the AVIRIS data acquisition. At this elevation. the air temperature did not drop below freezing the night of the May 20 and had risen to 6 degrees Celsius by the time of the overflight on May 21. These temperature conditions support the presence of melting snow at the surface as the AVIRIS data were acquired.

  8. ATLAS: Airborne Tunable Laser Absorption Spectrometer for stratospheric trace gas measurements

    NASA Technical Reports Server (NTRS)

    Loewenstein, Max; Podolske, James R.; Strahan, Susan E.

    1990-01-01

    The ATLAS instrument is an advanced technology diode laser based absorption spectrometer designed specifically for stratospheric tracer studies. This technique was used in the acquisition of N2O tracer data sets on the Airborne Antarctic Ozone Experiment and the Airborne Arctic Stratospheric Expedition. These data sets have proved valuable for comparison with atmospheric models, as well as in assisting in the interpretation of the entire ensemble of chemical and meteorological data acquired on these two field studies. The N2O dynamical tracer data set analysis revealed several ramifications concerning the polar atmosphere: the N2O/NO(y) correlation, which is used as a tool to study denitrification in the polar vertex; the N2O Southern Hemisphere morphology, showing subsidence in the winter polar vortex; and the value of the N2O measurements in the interpretation of ClO, O3, and NO(y) measurements and of the derived dynamical tracer, potential vorticity. Field studies also led to improved characterization of the instrument and to improved accuracy.

  9. Measurement of the spectral absorption of liquid water in melting snow with an imaging spectrometer

    NASA Technical Reports Server (NTRS)

    Green, Robert O.; Dozier, Jeff

    1995-01-01

    Melting of the snowpack is a critical parameter that drives aspects of the hydrology in regions of the earth where snow accumulates seasonally. New techniques for measurement of snow melt over regional scales offer the potential to improve monitoring and modeling of snow-driven hydrological processes. We present the results of measuring the spectral absorption of liquid water in a melting snowpack with the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS). AVIRIS data were acquired over Mammoth Mountain, in east central California on 21 May 1994 at 18:35 UTC. The air temperature at 2926 m on Mammoth Mountain at site A was measured at 15-minute intervals during the day preceding the AVIRIS data acquisition. At this elevation, the air temperature did not drop below freezing the night of May 20 and had risen to 6 degrees Celsius by the time of the overflight on May 21. These temperature conditions support the presence of melting snow at the surface as the AVIRIS data were acquired.

  10. First experiment with the NUSTAR/FAIR Decay Total Absorption γ -Ray Spectrometer (DTAS) at the IGISOL IV facility

    NASA Astrophysics Data System (ADS)

    Guadilla, V.; Algora, A.; Tain, J. L.; Agramunt, J.; Äystö, J.; Briz, J. A.; Cano-Ott, D.; Cucoanes, A.; Eronen, T.; Estienne, M.; Fallot, M.; Fraile, L. M.; Ganioglu, E.; Gelletly, W.; Gorelov, D.; Hakala, J.; Jokinen, A.; Jordan, D.; Kankainen, A.; Kolhinen, V.; Koponen, J.; Lebois, M.; Martinez, T.; Monserrate, M.; Montaner-Pizá, A.; Moore, I.; Nácher, E.; Orrigo, S.; Penttilä, H.; Podolyak, Zs.; Pohjalainen, I.; Porta, A.; Regan, P.; Reinikainen, J.; Reponen, M.; Rinta-Antila, S.; Rubio, B.; Rytkönen, K.; Shiba, T.; Sonnenschein, V.; Sonzogni, A. A.; Valencia, E.; Vedia, V.; Voss, A.; Wilson, J. N.; Zakari-Issoufou, A.-A.

    2016-06-01

    The new Decay Total Absorption Spectrometer (DTAS) has been commissioned with low energy radioactive beams at the upgraded IGISOL IV facility. The DTAS is a segmented detector composed of up to 18 NaI(Tl) crystals and it will be a key instrument in the DESPEC experiment at FAIR. In this document we report on the experimental setup and the first measurements performed with DTAS at IGISOL. The detector was characterized by means of MC simulations, and this allowed us to calculate the response function of the spectrometer and analyse the first cases of interest.

  11. A broadband cavity enhanced absorption spectrometer for aircraft measurements of glyoxal, methylglyoxal, nitrous acid, nitrogen dioxide, and water vapor

    NASA Astrophysics Data System (ADS)

    Min, K.-E.; Washenfelder, R. A.; Dubé, W. P.; Langford, A. O.; Edwards, P. M.; Zarzana, K. J.; Stutz, J.; Lu, K.; Rohrer, F.; Zhang, Y.; Brown, S. S.

    2016-02-01

    We describe a two-channel broadband cavity enhanced absorption spectrometer (BBCEAS) for aircraft measurements of glyoxal (CHOCHO), methylglyoxal (CH3COCHO), nitrous acid (HONO), nitrogen dioxide (NO2), and water (H2O). The instrument spans 361-389 and 438-468 nm, using two light-emitting diodes (LEDs) and a single grating spectrometer with a charge-coupled device (CCD) detector. Robust performance is achieved using a custom optical mounting system, high-power LEDs with electronic on/off modulation, high-reflectivity cavity mirrors, and materials that minimize analyte surface losses. We have successfully deployed this instrument during two aircraft and two ground-based field campaigns to date. The demonstrated precision (2σ) for retrievals of CHOCHO, HONO and NO2 are 34, 350, and 80 parts per trillion (pptv) in 5 s. The accuracy is 5.8, 9.0, and 5.0 %, limited mainly by the available absorption cross sections.

  12. A broadband cavity enhanced absorption spectrometer for aircraft measurements of glyoxal, methylglyoxal, nitrous acid, nitrogen dioxide, and water vapor

    NASA Astrophysics Data System (ADS)

    Min, K.-E.; Washenfelder, R. A.; Dubé, W. P.; Langford, A. O.; Edwards, P. M.; Zarzana, K. J.; Stutz, J.; Lu, K.; Rohrer, F.; Zhang, Y.; Brown, S. S.

    2015-10-01

    We describe a two-channel broadband cavity enhanced absorption spectrometer (BBCEAS) for aircraft measurements of glyoxal (CHOCHO), methylglyoxal (CH3COCHO), nitrous acid (HONO), nitrogen dioxide (NO2), and water (H2O). The instrument spans 361-389 and 438-468 nm, using two light emitting diodes (LEDs) and a grating spectrometer with a charge-coupled device (CCD) detector. Robust performance is achieved using a custom optical mounting system, high power LEDs with electronic on/off modulation, state-of-the-art cavity mirrors, and materials that minimize analyte surface losses. We have successfully deployed this instrument during two aircraft and two ground-based field campaigns to date. The demonstrated precision (2σ) for retrievals of CHOCHO, HONO and NO2 are 34, 350 and 80 pptv in 5 s. The accuracy is 5.8, 9.0 and 5.0 % limited mainly by the available absorption cross sections.

  13. DOAS, Radiant Cooling Revisited

    SciTech Connect

    Hastbacka, Mildred; Dieckmann, John; Bouza, Antonio

    2012-12-01

    The article discusses dedicated outdoor air systems (DOAS) and radiant cooling technologies. Both of these topics were covered in previous ASHRAE Journal columns. This article reviews the technologies and their increasing acceptance. The two steps that ASHRAE is taking to disseminate DOAS information to the design community, available energy savings and the market potential of radiant cooling systems are addressed as well.

  14. Eddy covariance carbonyl sulfide flux measurements with a quantum cascade laser absorption spectrometer

    NASA Astrophysics Data System (ADS)

    Gerdel, Katharina; Spielmann, Felix M.; Hammerle, Albin; Wohlfahrt, Georg

    2016-04-01

    Carbonyl sulfide (COS) is the most abundant sulfur containing trace gas present in the troposphere at concentrations of around 500 ppt. Recent interest in COS by the ecosystem-physiological community has been sparked by the fact that COS co-diffuses into plant leaves pretty much the same way as carbon dioxide (CO2) does, but in contrast to CO2, COS is not known to be emitted by plants. Thus uptake of COS by vegetation has the potential to be used as a tracer for canopy gross photosynthesis, which cannot be measured directly, however represents a key term in the global carbon cycle. Since a few years, quantum cascade laser absorption spectrometers (QCLAS) are commercially available with the precision, sensitivity and time response suitable for eddy covariance (EC) flux measurements. While there exist a handful of published reports on EC flux measurements in the recent literature, no rigorous investigation of the applicability of QCLAS for EC COS flux measurements has been carried out so far, nor have been EC processing and QA/QC steps developed for carbon dioxide and water vapor flux measurements within FLUXNET been assessed for COS. The aim of this study is to close this knowledge gap, to discuss critical steps in the post-processing chain of COS EC flux measurements and to devise best-practice guidelines for COS EC flux data processing. To this end we collected EC COS (and CO2, H2O and CO) flux measurements above a temperate mountain grassland in Austria over the vegetation period 2015 with a commercially available QCLAS. We discuss various aspects of EC data post-processing, in particular issues with the time-lag estimation between sonic anemometer and QCLAS signals and QCLAS time series detrending, as well as QA/QC, in particular flux detection limits, random flux uncertainty, the interaction of various processing steps with common EC QA/QC filters (e.g. detrending and stationarity tests), u*-filtering, etc.

  15. Total ozone column distribution over peninsular Malaysia from scanning imaging absorption spectrometer for atmospheric cartography (SCIAMACHY)

    NASA Astrophysics Data System (ADS)

    Tan, K. C.; Lim, H. S.; MatJafri, M. Z.

    2012-10-01

    Increasing of atmospheric ozone concentrations have received great attention around the whole because of its characteristic, in order to degrade air quality and brings hazard to human health and ecosystems. Ozone, one of the most pollutants source and brings a variety of adverse effects on plant life and human being. Continuous monitoring on ozone concentrations at atmosphere provide information and precautions for the high ozone level, which we need to be established. Satellite observation of ozone has been identified that it can provide the precise and accurate data globally, which sensitive to the small regional biases. We present measurements from Scanning Imaging Absorption Spectrometer for Atmospheric Cartography (SCIAMACHY) included on the European environmental satellite ENVISAT, launched on 1st of March 2002. Main objective of this study is to examine the ozone distribution over Peninsular Malaysia using SCIAMACHY level-2 of total ozone column WFMD version 1.0 with spatial resolution 1° x 1.25°. Maps of time averaged (yearly, tri-monthly) ozone was generated and analyzed over Peninsular Malaysia for the year 2003 using PCI Geomatica 10.3 image processing software. It was retrieved using the interpolation technique. The concentration changes within boundary layer at all altitude levels are equally sensitive through the SCIAMACHY nearinfrared nadir observations. Hence, we can make observation of ozone at surface source region. The results successfully identify the area with highest and lowest concentration of ozone at Peninsular Malaysia using SCIAMACHY data. Therefore, the study is suitable to examine the distribution of ozone at tropical region.

  16. Ground-based imaging differential optical absorption spectroscopy of atmospheric gases.

    PubMed

    Lohberger, Falko; Hönninger, Gerd; Platt, Ulrich

    2004-08-20

    We describe a compact remote-sensing instrument that permits spatially resolved mapping of atmospheric trace gases by passive differential optical absorption spectroscopy (DOAS) and present our first applications of imaging of the nitrogen dioxide contents of the exhaust plumes of two industrial emitters. DOAS permits the identification and quantification of various gases, e.g., NO2, SO2, and CH2O, from their specific narrowband (differential) absorption structures with high selectivity and sensitivity. With scattered sunlight as the light source, DOAS is used with an imaging spectrometer that is simultaneously acquiring spectral information on the incident light in one spatial dimension (column). The second spatial dimension is scanned by a moving mirror. PMID:15352396

  17. The use of NO2 absorption cross section temperature sensitivity to derive NO2 profile temperature and stratospheric-tropospheric column partitioning from visible direct-sun DOAS measurements

    NASA Astrophysics Data System (ADS)

    Spinei, E.; Cede, A.; Swartz, W. H.; Herman, J.; Mount, G. H.

    2014-12-01

    This paper presents a temperature sensitivity method (TESEM) to accurately calculate total vertical NO2 column, atmospheric slant NO2 profile-weighted temperature (T), and to separate stratospheric and tropospheric columns from direct-sun (DS), ground-based measurements using the retrieved T. TESEM is based on differential optical absorption spectroscopy (DOAS) fitting of the linear temperature-dependent NO2 absorption cross section, σ (T), regression model (Vandaele et al., 2003). Separation between stratospheric and tropospheric columns is based on the primarily bimodal vertical distribution of NO2 and an assumption that stratospheric effective temperature can be represented by temperature at 27 km ± 3 K, and tropospheric effective temperature is equal to surface temperature within 3-5 K. These assumptions were derived from the Global Modeling Initiative (GMI) chemistry-transport model (CTM) simulations over two northern midlatitude sites in 2011. TESEM was applied to the Washington State University Multi-Function DOAS instrument (MFDOAS) measurements at four midlatitude locations with low and moderate NO2 anthropogenic emissions: (1) the Jet Propulsion Laboratory's Table Mountain Facility (JPL-TMF), CA, USA (34.38° N/117.68° W); (2) Pullman, WA, USA (46.73° N/117.17° W); (3) Greenbelt, MD, USA (38.99° N/76.84° W); and (4) Cabauw, the Netherlands (51.97° N/4.93° E) during July 2007, June-July 2009, July-August and October 2011, November 2012-May 2013, respectively. NO2 T and total, stratospheric, and tropospheric NO2 vertical columns were determined over each site.

  18. Capillary Absorption Spectrometer for 13C Isotopic Composition of Pico to Subpico Molar Sample Quantities

    NASA Astrophysics Data System (ADS)

    Moran, J.; Kelly, J.; Sams, R.; Newburn, M.; Kreuzer, H.; Alexander, M.

    2011-12-01

    Quick incorporation of IR spectroscopy based isotope measurements into cutting edge research in biogeochemical cycling attests to the advantages of a spectroscopy versus mass spectrometry method for making some 13C measurements. The simple principles of optical spectroscopy allow field portability and provide a more robust general platform for isotope measurements. We present results with a new capillary absorption spectrometer (CAS) with the capability of reducing the sample size required for high precision isotopic measurements to the picomolar level and potentially the sub-picomolar level. This work was motivated by the minute sample size requirements for laser ablation isotopic studies of carbon cycling in microbial communities but has potential to be a valuable tool in other areas of biological and geological research. The CAS instrument utilizes a capillary waveguide as a sample chamber for interrogating CO2 via near IR laser absorption spectroscopy. The capillary's small volume (~ 0.5 mL) combined with propagation and interaction of the laser mode with the entire sample reduces sample size requirements to a fraction of that accessible with commercially available IR absorption including those with multi-pass or ring-down cavity systems. Using a continuous quantum cascade laser system to probe nearly adjacent rovibrational transitions of different isotopologues of CO2 near 2307 cm-1 permits sample measurement at low analyte pressures (as low as 2 Torr) for further sensitivity improvement. A novel method to reduce cw-fringing noise in the hollow waveguide is presented, which allows weak absorbance features to be studied at the few ppm level after averaging 1,000 scans in 10 seconds. Detection limits down to the 20 picomoles have been observed, a concentration of approximately 400 ppm at 2 Torr in the waveguide with precision and accuracy at or better than 1 %. Improvements in detection and signal averaging electronics and laser power and mode quality are

  19. Modeling the Performance of a Spaceborne Laser Absorption Spectrometer for Atmospheric CO2 Column Measurements

    NASA Astrophysics Data System (ADS)

    Lin, B.; Ismail, S.; Harrison, F. W.; Browell, E. V.; Nehrir, A. R.; Dobler, J. T.; Moore, B.; Refaat, T.; Kooi, S. A.

    2013-12-01

    Accurate global observations of atmospheric carbon dioxide (CO2) with a laser-based space mission, such as the NASA ASCENDS (Active Sensing of CO2 Emissions over Nights, Days, and Seasons) mission, are crucial to improving our understanding of global CO2 sources and sinks. This study focuses on modeling of the performance of a spaceborne laser absorption spectrometer (LAS) system for CO2 column measurements. The model accounts for all of the fundamental physics of the instrument subsystems and components and the influences of measurement environments. The characteristics of simulated LAS systems and their components are based on existing technologies and the implementation of operational systems. The modeled instrument is specifically assumed to be an Intensity-Modulated Continuous-Wave (IM-CW) LAS system like the Exelis airborne Multifunctional Fiber Laser Lidar (MFLL) operating in the 1.57 um CO2 absorption band. Environmental effects such as gas absorption, solar radiation, scattering of aerosols and thin clouds, atmospheric turbulence, and surface reflection are also considered in the model. The modeled results are presented statistically from simulation ensembles of multiple model runs to accurately represent the random nature of all of the noise sources and uncertainties related to the LAS instruments and the measurement environments. Model simulations demonstrate very good agreement when compared to prior airborne and ground based MFLL measurements. The model predicted lidar return powers for various calibrated surface targets show good agreement with those measured by the MFLL instrument during ground tests at NASA Langley Research Center in the summer of 2012. The difference between modeled and measured signal-to-noise ratios (SNR) of the LAS CO2 column optical depths (Tau_d) for the summer 2011 flight campaign on board the NASA DC-8 over Railroad Valley (RRV), NV is generally within 20%. The simulations for spaceborne Tau_d measurements over RRV indicate

  20. UV Scanner DOAS Data Retrieved Using A Modelled Reference Spectrum

    NASA Astrophysics Data System (ADS)

    Salerno, G. G.; Burton, M.; Caltabiano, T.; Randazzo, D.; Bruno, N.; Longo, V.; Oppenheimer, C.

    2007-12-01

    The difficulty of applying a real-time measured reference spectrum represents the main issue while using automatic Differential Optical Absorption Spectroscopy (DOAS) UV-Scanner networks for monitoring active volcanoes. Here we present the performance of a DOAS retrieval using a modelled reference spectrum derived from a high- resolution solar spectrum. Data analyzed were collected by the five UV scanners installed on Mt. Etna using three calibration cells (LC: low cell 3.2 e17; MC: middle cell 8.46 e17; and HC: high cell 9.98 e17 molecules/cm2) in order to collect calibrated clear-sky spectra (CCSS). We evaluated the errors affecting the CCSS retrievals examining the effects of seasonal variations, time of the day, changes of the telescope-viewing angle, and the modelled and real-measured instrumental line-shape function (ILS). For these purposes, between July 2006 and July 2007, 51 CCSS were recorded in different times of the day and different weather conditions using the LC and the MC, whereas the error associated with the variations of the telescope-viewing angle was evaluated on data collected in May 2007 using the LC and HC. This was estimated as the mean of each of 100 CCSS collected for every scanning angle. The modelled ILS function resolution was found empirically, while the real was measured experimentally using a mercury lamp. The absolute difference retrieved for the CCSS recorded in 12 months respect the true amounts of the calibration cells varied between ~ 1.15 e15 - 8.39 e16 molecules/cm2 for the LC and ~ 2.78 e15 - 1.75 e17 molecules/cm2 for the MC. These results revealed that the modelled reference spectrum did not affect significantly the DOAS performance. This was consistent with the absolute differences estimated for each scanning-angle variations (~ 1.15 e15 - 8.39 e16 molecules/cm2 for the LC and ~ 1.44 e15 - 2.52 e17 molecules/cm2 for the HC) respect to the true amounts. These results prove that UV-Scanner DOAS networks can work efficiently

  1. Laser Absorption spectrometer instrument for tomographic 2D-measurement of climate gas emission from soils

    NASA Astrophysics Data System (ADS)

    Seidel, Anne; Wagner, Steven; Dreizler, Andreas; Ebert, Volker

    2014-05-01

    One of the most intricate effects in climate modelling is the role of permafrost thawing during the global warming process. Soil that has formerly never totally lost its ice cover now emits climate gases due to melting processes[1]. For a better prediction of climate development and possible feedback mechanisms, insights into physical procedures (like e.g. gas emission from underground reservoirs) are required[2]. Therefore, a long-term quantification of greenhouse gas concentrations (and further on fluxes) is necessary and the related structures that are responsible for emission need to be identified. In particular the spatial heterogeneity of soils caused by soil internal structures (e.g. soil composition changes or surface cracks) or by surface modifications (e.g. by plant growth) generate considerable complexities and difficulties for local measurements, for example with soil chambers. For such situations, which often cannot be avoided, a spatially resolved 2D-measurement to identify and quantify the gas emission from the structured soil would be needed, to better understand the influence of the soil sub-structures on the emission behavior. Thus we designed a spatially scanning laser absorption spectrometer setup to determine a 2D-gas concentration map in the soil-air boundary layer. The setup is designed to cover the surfaces in the range of square meters in a horizontal plane above the soil to be investigated. Existing field instruments for gas concentration or flux measurements are based on point-wise measurements, so structure identification is very tedious or even impossible. For this reason, we have developed a tomographic in-situ instrument based on TDLAS ('tunable diode laser absorption spectroscopy') that delivers absolute gas concentration distributions of areas with 0.8m × 0.8m size, without any need for reference measurements with a calibration gas. It is a simple and robust device based on a combination of scanning mirrors and reflecting foils, so

  2. Retrieval and molecule sensitivity studies for the global ozone monitoring experiment and the scanning imaging absorption spectrometer for atmospheric chartography

    NASA Technical Reports Server (NTRS)

    Chance, Kelly V.; Burrows, John P.; Schneider, Wolfgang

    1991-01-01

    The Global Ozone Monitoring Experiment (GOME) and the SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY) are diode based spectrometers that will make atmospheric constituent and aerosol measurements from European satellite platforms beginning in the mid 1990's. GOME measures the atmosphere in the UV and visible in nadir scanning, while SCIAMACHY performs a combination of nadir, limb, and occultation measurements in the UV, visible, and infrared. A summary is presented of the sensitivity studies that were performed for SCIAMACHY measurements. As the GOME measurement capability is a subset of the SCIAMACHY measurement capability, the nadir, UV, and visible portion of the studies is shown to apply to GOME as well.

  3. Open-path Emission Factors Derived from DOAS and FTIR Measurements in the Mexico City Metropolitan Area

    NASA Astrophysics Data System (ADS)

    Flores, E.; Grutter, M.; Galle, B.; Mellqvist, J.; Samuelsson, J.; Knighton, B.; Jobson, B. T.; Volkamer, R.; Molina, L. T.; Molina, M. J.

    2004-12-01

    Mobile sources are responsible for about 50% of VOC (volatile organic compounds) and about 70% of NOx emissions in the Mexico City Metropolitan Area (MCMA). A novel approach has been developed to derive emission factors for mobile sources that are representative of the overall vehicle fleet, using collocated open-path Differential Optical Absorption Spectroscopy (DOAS) and Fourier Transform Infrared (FTIR) spectroscopic measurements. Measurements were recorded at two sites within the MCMA: (1) research-grade DOAS and FTIR systems were operated at the Mexican National Research and Training Center (CENICA) in Iztapalapa, (2) a research grade FTIR was operated at La Merced. In addition, point-sampling with a proton transfer reaction mass spectrometer (PTR-MS) was performed on the same location and the calibration standards for the PTR-MS and the DOAS instruments were cross-calibrated. The DOAS measured speciated aromatic hydrocarbons, including benzene, toluene, m-xylene, p-xylene, ethylbenzene (and mono-substituted alkylbenzenes), benzaldehyde, phenol, and p-cresol. The DOAS detection of aromatic hydrocarbons in the UV/vis spectral range between 250 to 310 nm suffers from the interference of molecular oxygen, and a novel approach is being presented that enables measurement of absolute concentrations of the above species. Further, HONO, NO2, SO2 and HCHO were measured at longer wavelengths. In combination with FTIR measurements of CO, CO2, NO, HCHO, ethylene, ethene, and total alkane, average emission factors for NOx, SO2 and numerous hydrocarbons were derived and scaled with fuel sales data to estimate total emissions of the vehicle fleet in the MCMA. The advantages and limitations of this low-cost emission inventory for mobile sources are decsribed.

  4. Multi-wavelength measurements of aerosol optical absorption coefficients using a photoacoustic spectrometer

    NASA Astrophysics Data System (ADS)

    Liu, Qiang; Huang, Hong-Hua; Wang, Yao; Wang, Gui-Shi; Cao, Zhen-Song; Liu, Kun; Chen, Wei-Dong; Gao, Xiao-Ming

    2014-06-01

    The atmospheric aerosol absorption capacity is a critical parameter determining its direct and indirect effects on climate. Accurate measurement is highly desired for the study of the radiative budget of the Earth. A multi-wavelength (405 nm, 532 nm, 780 nm) aerosol absorption meter based on photoacoustic spectroscopy (PAS) invovling a single cylindrical acoustic resonator is developed for measuring the aerosol optical absorption coefficients (OACs). A sensitivity of 1.3 Mm-1 (at 532 nm) is demonstrated. The aerosol absorption meter is successfully tested through measuring the OACs of atmospheric nigrosin and ambient aerosols in the suburbs of Hefei city. The absorption cross section and absorption Ångström exponent (AAE) for ambient aerosol are determined for characterizing the component of the ambient aerosol.

  5. A differential optical absorption spectroscopy method for retrieval from ground-based Fourier transform spectrometers measurements of the direct solar beam

    NASA Astrophysics Data System (ADS)

    Huo, Yanfeng; Duan, Minzheng; Tian, Wenshou; Min, Qilong

    2015-08-01

    A differential optical absorption spectroscopy (DOAS)-like algorithm is developed to retrieve the column-averaged dryair mole fraction of carbon dioxide from ground-based hyper-spectral measurements of the direct solar beam. Different to the spectral fitting method, which minimizes the difference between the observed and simulated spectra, the ratios of multiple channel-pairs—one weak and one strong absorption channel—are used to retrieve from measurements of the shortwave infrared (SWIR) band. Based on sensitivity tests, a super channel-pair is carefully selected to reduce the effects of solar lines, water vapor, air temperature, pressure, instrument noise, and frequency shift on retrieval errors. The new algorithm reduces computational cost and the retrievals are less sensitive to temperature and H2O uncertainty than the spectral fitting method. Multi-day Total Carbon Column Observing Network (TCCON) measurements under clear-sky conditions at two sites (Tsukuba and Bremen) are used to derive xxxx for the algorithm evaluation and validation. The DOAS-like results agree very well with those of the TCCON algorithm after correction of an airmass-dependent bias.

  6. Airborne Laser Absorption Spectrometer Measurements of CO2 Column Mixing Ratios: Source and Sink Detection in the Atmospheric Environment

    NASA Astrophysics Data System (ADS)

    Menzies, Robert T.; Spiers, Gary D.; Jacob, Joseph C.

    2016-06-01

    The JPL airborne Laser Absorption Spectrometer instrument has been flown several times in the 2007-2011 time frame for the purpose of measuring CO2 mixing ratios in the lower atmosphere. The four most recent flight campaigns were on the NASA DC-8 research aircraft, in support of the NASA ASCENDS (Active Sensing of CO2 Emissions over Nights, Days, and Seasons) mission formulation studies. This instrument operates in the 2.05-μm spectral region. The Integrated Path Differential Absorption (IPDA) method is used to retrieve weighted CO2 column mixing ratios. We present key features of the CO2LAS signal processing, data analysis, and the calibration/validation methodology. Results from flights in various U.S. locations during the past three years include observed mid-day CO2 drawdown in the Midwest, also cases of point-source and regional plume detection that enable the calculation of emission rates.

  7. Methods for Retrievals of CO2 Mixing Ratios from JPL Laser Absorption Spectrometer Flights During a Summer 2011 Campaign

    NASA Technical Reports Server (NTRS)

    Menzies, Robert T.; Spiers, Gary D.; Jacob, Joseph C.

    2013-01-01

    The JPL airborne Laser Absorption Spectrometer instrument has been flown several times in the 2007-2011 time frame for the purpose of measuring CO2 mixing ratios in the lower atmosphere. This instrument employs CW laser transmitters and coherent detection receivers in the 2.05- micro m spectral region. The Integrated Path Differential Absorption (IPDA) method is used to retrieve weighted CO2 column mixing ratios. We present key features of the evolving LAS signal processing and data analysis algorithms and the calibration/validation methodology. Results from 2011 flights in various U.S. locations include observed mid-day CO2 drawdown in the Midwest and high spatial resolution plume detection during a leg downwind of the Four Corners power plant in New Mexico.

  8. Airborne imaging spectrometer data of the Ruby Mountains, Montana: Mineral discrimination using relative absorption band-depth images

    USGS Publications Warehouse

    Crowley, J.K.; Brickey, D.W.; Rowan, L.C.

    1989-01-01

    Airborne imaging spectrometer data collected in the near-infrared (1.2-2.4 ??m) wavelength range were used to study the spectral expression of metamorphic minerals and rocks in the Ruby Mountains of southwestern Montana. The data were analyzed by using a new data enhancement procedure-the construction of relative absorption band-depth (RBD) images. RBD images, like bandratio images, are designed to detect diagnostic mineral absorption features, while minimizing reflectance variations related to topographic slope and albedo differences. To produce an RBD image, several data channels near an absorption band shoulder are summed and then divided by the sum of several channels located near the band minimum. RBD images are both highly specific and sensitive to the presence of particular mineral absorption features. Further, the technique does not distort or subdue spectral features as sometimes occurs when using other data normalization methods. By using RBD images, a number of rock and soil units were distinguished in the Ruby Mountains including weathered quartz - feldspar pegmatites, marbles of several compositions, and soils developed over poorly exposed mica schists. The RBD technique is especially well suited for detecting weak near-infrared spectral features produced by soils, which may permit improved mapping of subtle lithologic and structural details in semiarid terrains. The observation of soils rich in talc, an important industrial commodity in the study area, also indicates that RBD images may be useful for mineral exploration. ?? 1989.

  9. High energy resolution five-crystal spectrometer for high quality fluorescence and absorption measurements on an x-ray absorption spectroscopy beamline

    SciTech Connect

    Llorens, Isabelle; Lahera, Eric; Delnet, William; Proux, Olivier; Dermigny, Quentin; Gelebart, Frederic; Morand, Marc; Shukla, Abhay; Bardou, Nathalie; Ulrich, Olivier; and others

    2012-06-15

    Fluorescence detection is classically achieved with a solid state detector (SSD) on x-ray absorption spectroscopy (XAS) beamlines. This kind of detection however presents some limitations related to the limited energy resolution and saturation. Crystal analyzer spectrometers (CAS) based on a Johann-type geometry have been developed to overcome these limitations. We have tested and installed such a system on the BM30B/CRG-FAME XAS beamline at the ESRF dedicated to the structural investigation of very dilute systems in environmental, material and biological sciences. The spectrometer has been designed to be a mobile device for easy integration in multi-purpose hard x-ray synchrotron beamlines or even with a laboratory x-ray source. The CAS allows to collect x-ray photons from a large solid angle with five spherically bent crystals. It will cover a large energy range allowing to probe fluorescence lines characteristic of all the elements from Ca (Z = 20) to U (Z = 92). It provides an energy resolution of 1-2 eV. XAS spectroscopy is the main application of this device even if other spectroscopic techniques (RIXS, XES, XRS, etc.) can be also achieved with it. The performances of the CAS are illustrated by two experiments that are difficult or impossible to perform with SSD and the complementarity of the CAS vs SSD detectors is discussed.

  10. High energy resolution five-crystal spectrometer for high quality fluorescence and absorption measurements on an x-ray absorption spectroscopy beamline.

    PubMed

    Llorens, Isabelle; Lahera, Eric; Delnet, William; Proux, Olivier; Braillard, Aurélien; Hazemann, Jean-Louis; Prat, Alain; Testemale, Denis; Dermigny, Quentin; Gelebart, Frederic; Morand, Marc; Shukla, Abhay; Bardou, Nathalie; Ulrich, Olivier; Arnaud, Stéphan; Berar, Jean-François; Boudet, Nathalie; Caillot, Bernard; Chaurand, Perrine; Rose, Jérôme; Doelsch, Emmanuel; Martin, Philippe; Solari, Pier Lorenzo

    2012-06-01

    Fluorescence detection is classically achieved with a solid state detector (SSD) on x-ray absorption spectroscopy (XAS) beamlines. This kind of detection however presents some limitations related to the limited energy resolution and saturation. Crystal analyzer spectrometers (CAS) based on a Johann-type geometry have been developed to overcome these limitations. We have tested and installed such a system on the BM30B/CRG-FAME XAS beamline at the ESRF dedicated to the structural investigation of very dilute systems in environmental, material and biological sciences. The spectrometer has been designed to be a mobile device for easy integration in multi-purpose hard x-ray synchrotron beamlines or even with a laboratory x-ray source. The CAS allows to collect x-ray photons from a large solid angle with five spherically bent crystals. It will cover a large energy range allowing to probe fluorescence lines characteristic of all the elements from Ca (Z = 20) to U (Z = 92). It provides an energy resolution of 1-2 eV. XAS spectroscopy is the main application of this device even if other spectroscopic techniques (RIXS, XES, XRS, etc.) can be also achieved with it. The performances of the CAS are illustrated by two experiments that are difficult or impossible to perform with SSD and the complementarity of the CAS vs SSD detectors is discussed.

  11. Validation of OMI-TOMS and OMI-DOAS total ozone column using five Brewer spectroradiometers at the Iberian peninsula

    NASA Astrophysics Data System (ADS)

    Antón, M.; López, M.; Vilaplana, J. M.; Kroon, M.; McPeters, R.; Bañón, M.; Serrano, A.

    2009-07-01

    This article focuses on the comparison of the total ozone column data from the Ozone Monitoring Instrument (OMI) flying aboard the NASA EOS-Aura satellite platform with ground-based measurement recorded by Brewer spectroradiometers located at five Spanish remote sensing ground stations between January 2005 and December 2007. The satellite data are derived from two algorithms: OMI Total Ozone Mapping Spectrometer (OMI-TOMS) and OMI Differential Optical Absorption Spectroscopy (OMI-DOAS). The largest relative differences between these OMI total ozone column estimates reach 5% with a significant seasonal dependence. The agreement between OMI ozone data and Brewer measurements is excellent. Total ozone columns from OMI-TOMS are on average a mere 2.0% lower than Brewer data. For OMI-DOAS data the bias is a mere 1.4%. However, the relative difference between OMI-TOMS and Brewer measurements shows a notably lower seasonal dependence and variability than the differences between OMI-DOAS and ground-based data. For both OMI ozone data products these relative differences show significant dependence on the satellite ground pixel solar zenith angle for cloud-free cases as well as for cloudy conditions. However, the OMI ozone data products are shown to reveal opposite behavior with respect to the two antagonistic sky conditions. No significant dependency of the ground-based to satellite-based differences with respect to the satellite cross-track position is seen for either OMI retrieval algorithm.

  12. High resolution spectrometer for extended x-ray absorption fine structure measurements in the 6 keV to 15 keV energy range

    NASA Astrophysics Data System (ADS)

    Seely, J. F.; Hudson, L. T.; Henins, Albert; Feldman, U.

    2016-11-01

    A Cauchois transmission-crystal spectrometer has been developed with high crystal resolving power in the 6 keV-15 keV energy range and sufficient sensitivity to record single-shot spectra from the Lawrence Livermore National Laboratory (LLNL) Titan laser and other comparable or more energetic lasers. The spectrometer capabilities were tested by recording the W L transitions from a laboratory source and the extended x-ray absorption fine structure (EXAFS) spectrum through a Cu foil.

  13. Mass specific optical absorption coefficients of mineral dust components measured by a multi wavelength photoacoustic spectrometer

    NASA Astrophysics Data System (ADS)

    Utry, N.; Ajtai, T.; Pintér, M.; Tombácz, E.; Illés, E.; Bozóki, Z.; Szabó, G.

    2014-09-01

    Mass specific optical absorption coefficients of various mineral dust components including silicate clays (illite, kaolin and bentonite), oxides (quartz, hematite and rutile), and carbonate (limestone) were determined at wavelengths of 1064, 532, 355 and 266 nm. These values were calculated from aerosol optical absorption coefficients measured by a multi-wavelength photoacoustic (PA) instrument, the mass concentration and the number size distribution of the generated aerosol samples as well as the size transfer functions of the measuring instruments. These results are expected to have considerable importance in global radiative forcing calculations. They can also serve as reference for validating calculated wavelength dependent imaginary parts (κ) of complex refractive indices which up to now have been typically deduced from bulk phase measurements by using indirect measurement methods. Accordingly, the presented comparison of the measured and calculated aerosol optical absorption spectra revealed the strong need for standardized sample preparation and measurement methodology in case of bulk phase measurements.

  14. Intercomparison of stratospheric nitrogen dioxide columns retrieved from ground-based DOAS and FTIR and satellite DOAS instruments over the subtropical Izana station

    NASA Astrophysics Data System (ADS)

    Robles-Gonzalez, Cristina; Navarro-Comas, Mónica; Puentedura, Olga; Schneider, Matthias; Hase, Frank; Garcia, Omaira; Blumenstock, Thomas; Gil-Ojeda, Manuel

    2016-09-01

    A 13-year analysis (2000-2012) of the NO2 vertical column densities derived from ground-based (GB) instruments and satellites has been carried out over the Izaña NDACC (Network for the Detection of the Atmospheric Composition Change) subtropical site. Ground-based DOAS (differential optical absorption spectroscopy) and FTIR (Fourier transform infrared spectroscopy) instruments are intercompared to test mutual consistency and then used for validation of stratospheric NO2 from OMI (Ozone Monitoring Instrument) and SCIAMACHY (SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY). The intercomparison has been carried out taking into account the various differences existing in instruments, namely temporal coincidence, collocation, sensitivity, field of view, etc. The paper highlights the importance of considering an "effective solar zenith angle" instead of the actual one when comparing direct-sun instruments with zenith sky ones for a proper photochemical correction. Results show that NO2 vertical column densities mean relative difference between FTIR and DOAS instruments is 2.8 ± 10.7 % for a.m. data. Both instruments properly reproduce the NO2 seasonal and the interannual variation. Mean relative difference of the stratospheric NO2 derived from OMI and DOAS is -0.2 ± 8.7 % and from OMI and FTIR is -1.6 ± 6.7 %. SCIAMACHY mean relative difference is of 3.7 ± 11.7 and -5.7 ± 11.0 % for DOAS and FTIR, respectively. Note that the days used for the intercomparison are not the same for all the pairs of instruments since it depends on the availability of data. The discrepancies are found to be seasonally dependent with largest differences in winter and excellent agreement in the spring months (AMJ). A preliminary analysis of NO2 trends has been carried out with the available data series. Results show increases in stratospheric NO2 columns in all instruments but larger values in those that are GB than that expected by nitrous oxide oxidation. The

  15. Analysis of airborne imaging spectrometer data for the Ruby Mountains, Montana, by use of absorption-band-depth images

    NASA Technical Reports Server (NTRS)

    Brickey, David W.; Crowley, James K.; Rowan, Lawrence C.

    1987-01-01

    Airborne Imaging Spectrometer-1 (AIS-1) data were obtained for an area of amphibolite grade metamorphic rocks that have moderate rangeland vegetation cover. Although rock exposures are sparse and patchy at this site, soils are visible through the vegetation and typically comprise 20 to 30 percent of the surface area. Channel averaged low band depth images for diagnostic soil rock absorption bands. Sets of three such images were combined to produce color composite band depth images. This relative simple approach did not require extensive calibration efforts and was effective for discerning a number of spectrally distinctive rocks and soils, including soils having high talc concentrations. The results show that the high spectral and spatial resolution of AIS-1 and future sensors hold considerable promise for mapping mineral variations in soil, even in moderately vegetated areas.

  16. Mid-Ir Sub-Doppler Eresolution Spectrometer Using AN Enhanced-Cavity Absorption Cell Coupled with a Wide Beam

    NASA Astrophysics Data System (ADS)

    Abe, Masashi; Iwakuni, Kana; Okubo, Sho; Sasada, Hiroyuki

    2014-06-01

    We have introduced a wide-beam-coupled enhanced-cavity absorption cell (ECAC) into a 3-μ m difference-frequency generation spectrometer in order to reduce transit-time broadening of Lamb dips. It contains concave and convex mirrors with a curvature radius of ± 7 m separated by 37.5 cm, has a finesse of 770, and is coupled with a Gaussian beam having a 1/{e}^2 radius of 1.9 mm at beam waist. The spectrometer is applied to record sub-Doppler resolution spectra of the ν _3 band of CH_4 and the ν _1 and ν _4 bands of CH_3D, and the transit-time broadening is estimated 30 kHz for these molecules. The observed Lamb dips are about 80 kHz (HWHM) wide, which is one third of those recorded using another ECAC coupled with a 1/{e}^2 radius of 0.7 mm at the beam waist. Some A_1-A_2 splittings of the low J levels for CH_3D are first resolved, and the absolute transition frequencies are determined with a relative uncertainty of 10-9.

  17. Characterizing a Quantum Cascade Tunable Infrared Laser Differential Absorption Spectrometer (QC-TILDAS) for measurements of atmospheric ammonia

    NASA Astrophysics Data System (ADS)

    Ellis, R. A.; Murphy, J. G.; Pattey, E.; van Haarlem, R.; O'Brien, J. M.; Herndon, S. C.

    2010-03-01

    A compact, fast-response Quantum Cascade Tunable Infrared Laser Differential Absorption Spectrometer (QC-TILDAS) for measurements of ammonia (NH3) has been evaluated under both laboratory and field conditions. Absorption of radiation from a pulsed, thermoelectrically cooled QC laser occurs at reduced pressure in a 0.5 L multiple pass absorption cell with an effective path length of 76 m. Detection is achieved using a thermoelectrically-cooled Mercury Cadmium Telluride (HgCdTe) infrared detector. A novel sampling inlet was used, consisting of a short, heated, quartz tube with a hydrophobic coating to minimize the adsorption of NH3 to surfaces. The inlet contains a critical orifice that reduces the pressure, a virtual impactor for separation of particles, and additional ports for delivering NH3-free background air and calibration gas standards. The level of noise in this instrument has been found to be 0.23 ppb at 1 Hz. The sampling technique has been compared to the results of a conventional lead salt Tunable Diode Laser Absorption Spectrometer (TDLAS) during a laboratory intercomparison. The effect of humidity and heat on the surface interaction of NH3 with sample tubing was investigated at mixing ratios ranging from 30-1000 ppb. Humidity was seen to worsen the NH3 time response and considerable improvement was observed when using a heated sampling line. A field intercomparison of the QC-TILDAS with a modified Thermo 42CTL chemiluminescence-based analyzer was also performed at Environment Canada's Centre for Atmospheric Research Experiments (CARE) in the rural town of Egbert, ON between May-July 2008. Background tests and calibrations using two different permeation tube sources and an NH3 gas cylinder were regularly carried out throughout the study. Results indicate a very good correlation at 1 min time resolution (R2 = 0.93) between the two instruments at the beginning of the study, when regular background subtraction was applied to the QC-TILDAS. An overall good

  18. Characterizing a Quantum Cascade Tunable Infrared Laser Differential Absorption Spectrometer (QC-TILDAS) for measurements of atmospheric ammonia

    NASA Astrophysics Data System (ADS)

    Ellis, R. A.; Murphy, J. G.; Pattey, E.; van Haarlem, R.; O'Brien, J. M.; Herndon, S. C.

    2009-12-01

    A compact, fast-response Quantum Cascade Tunable Infrared Laser Differential Absorption Spectrometer (QC-TILDAS) for measurements of ammonia has been evaluated under both laboratory and field conditions. Absorption of radiation from a pulsed, thermoelectrically cooled QC laser occurs at reduced pressure in a 0.5 L multiple pass absorption cell with an effective path length of 76 m. Detection is achieved using a thermoelectrically cooled Mercury Cadmium Telluride (HgCdTe) infrared detector. A novel sampling inlet was used, consisting of a short, heated, quartz tube with a hydrophobic coating to minimize the adsorption of ammonia to surfaces. The inlet contains a critical orifice that reduces the pressure, a virtual impactor for separation of particles, and additional ports for delivering ammonia-free background air and calibration gas standards. This instrument has been found to have a detection limit of 0.23 ppb at 1 Hz. The sampling technique has been compared to the results of a conventional lead salt Tunable Diode Laser Absorption Spectrometer (TDLAS) during a laboratory intercomparison. The effect of humidity and heat on the surface interaction of ammonia with sample tubing was investigated at mixing ratios ranging from 30-1000 ppb. Humidity was seen to worsen the ammonia time response and considerable improvement was observed when using a heated sampling line. A field intercomparison of the QC-TILDAS with a modified Thermo 42CTL chemiluminescence based analyzer was also performed at Environment Canada's Centre for Atmospheric Research Experiments (CARE) in the rural town of Egbert, ON between May-July 2008. Background tests and calibrations using two different permeation tube sources and an ammonia gas cylinder were regularly carried out throughout the study. Results indicate a very good correlation with 1 min time resolution (R2=0.93) between the two instruments at the beginning of the study, when regular background subtraction was applied to the QC

  19. Multispectral imaging of tissue absorption and scattering using spatial frequency domain imaging and a computed-tomography imaging spectrometer

    NASA Astrophysics Data System (ADS)

    Weber, Jessie R.; Cuccia, David J.; Johnson, William R.; Bearman, Gregory H.; Durkin, Anthony J.; Hsu, Mike; Lin, Alexander; Binder, Devin K.; Wilson, Dan; Tromberg, Bruce J.

    2011-01-01

    We present an approach for rapidly and quantitatively mapping tissue absorption and scattering spectra in a wide-field, noncontact imaging geometry by combining multifrequency spatial frequency domain imaging (SFDI) with a computed-tomography imaging spectrometer (CTIS). SFDI overcomes the need to spatially scan a source, and is based on the projection and analysis of periodic structured illumination patterns. CTIS provides a throughput advantage by simultaneously diffracting multiple spectral images onto a single CCD chip to gather spectra at every pixel of the image, thus providing spatial and spectral information in a single snapshot. The spatial-spectral data set was acquired 30 times faster than with our wavelength-scanning liquid crystal tunable filter camera, even though it is not yet optimized for speed. Here we demonstrate that the combined SFDI-CTIS is capable of rapid, multispectral imaging of tissue absorption and scattering in a noncontact, nonscanning platform. The combined system was validated for 36 wavelengths between 650-1000 nm in tissue simulating phantoms over a range of tissue-like absorption and scattering properties. The average percent error for the range of absorption coefficients (μa) was less than 10% from 650-800 nm, and less than 20% from 800-1000 nm. The average percent error in reduced scattering coefficients (μs') was less than 5% from 650-700 nm and less than 3% from 700-1000 nm. The SFDI-CTIS platform was applied to a mouse model of brain injury in order to demonstrate the utility of this approach in characterizing spatially and spectrally varying tissue optical properties.

  20. Development of photovoltaic-driven MAX-DOAS system (Eco-MAXDOAS) and its evaluation using 4AZ-MAXDOAS system at Chiba, Japan

    NASA Astrophysics Data System (ADS)

    Kato, T.; Irie, H.

    2015-12-01

    It is recognized that the Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) technique is suitable for routine observations of atmospheric constituents as its setup is simple, power consumption is low, and fully automated long-term operation without absolute radiometric calibration is possible. In addition, it is also a powerful technique with abilities enabling simultaneous measurements of aerosols and their gaseous precursors, such as nitrogen dioxide (NO2) and sulfur dioxide (SO2). To exploit its further applications, we are have developed the photovoltaic-driven MAX-DOAS system, called Eco-MAXDOAS. By utilizing the Eco-MAXDOAS, we expect to make multi-component air quality observations possible in areas with problems on stable power supply. For this development, we removed a temperature controller to reduce the power consumption. Instead, a shutter was introduced just before the entrance slit of the spectrometer. With this modification, it was made possible to take dark count measurements more often than for the normal MAX-DOAS instrument by closing the shutter between observations at different elevation angles. We tested the Eco-MAXDOAS and found that the spectrometer temperature varied by less than ±0.3 degrees for 3 minutes interval of changing elevation angles. Using dark count data taken before and after scattered sun light observations, the Signal-to-Noise Ratio(SNR) was estimated to be about 10000. This supports that analysis for a differential absorption as small as 10-4 (0.01%) is possible. In addition, we compared the aerosol and NO2 data retrieved from Eco-MAXDOAS and MAX-DOAS observations, and we confirmed that the two retrieved values were usually almost the same but occasionally showed significant differences. To investigate the cause, we devised the 4AZ-MAXDOAS system, a set of 4 MAX-DOAS instruments directed toward different azimuth angels of north, south, east, and west. The observation with the 4AZ-MAXDOAS confirmed that the

  1. Application of DOAS Instruments for Trace Gas Measurements on Unmanned Aerial Systems

    NASA Astrophysics Data System (ADS)

    Horbanski, M.; Pöhler, D.; Mahr, T.; Wagner, T.; Platt, U.

    2012-04-01

    Unmanned Aerial Systems (UAS) are a new powerful tool for observations in the atmospheric boundary layer. Recent developments in measuring technology allow the construction of compact and sensitive active and passive DOAS instruments which can fit the space and weight constraints on Unmanned Aircraft Systems. This opens new possibilities for trace gas measurements in the lower troposphere, especially in areas which are not accessible to manned aviation e.g. volcanic plumes or which should be monitored regularly (e.g. industrial emissions of a stack). Two DOAS instruments for the APAESO platform of the Energy, Environment and Water Research Centre (EEWRC) at the Cyprus Institute are presented. Our first system is a passive DOAS for remote sensing applications which measures scattered sunlight and light reflected by the surface. It is equipped with telescopes for observations in downward (nadir) and horizontal (limb) viewing direction. Thus it allows determining height profiles and the spatial distribution of trace gases. For this the light is analysed by a compact spectrometer which covers the UV-blue range allowing to measure a broad variety of atmospheric trace gases (e.g. NO2, SO2, BrO, IO, H2O ...) and aerosol properties via O4 absorption. Additionally, the nadir direction is equipped with a system for the observation of surface properties. It will be used to measure and analyse reflection of different types of vegetation. The spectra will serve as reference spectra for satellite measurements to create global maps. The instrumental setup and the results of first test flights are shown. The second instrument which is currently under development is a Cavity Enhanced (CE-) DOAS for in situ measurements of NO3. In contrast to the passive DOAS it is able to perform night time measurements as it uses an active LED light source. This is important for studies of NO3 since it plays an important role in night time chemistry while it is rapidly photolysed during daytime

  2. NO2 and HCHO variability in Mexico City from MAX-DOAS measurements

    NASA Astrophysics Data System (ADS)

    Grutter, M.; Friedrich, M. M.; Rivera, C. I.; Arellano, E. J.; Stremme, W.

    2015-12-01

    Atmospheric studies in large cities are of great relevance since pollution affects air quality and human health. A network of Multi Axis Differential Optical Absorption Spectrometers (MAX-DOAS) has been established in strategic sites within the Mexico City metropolitan area. Four instruments are now in operation with the aim to study the variability and spatial distribution of key pollutants, providing results of O4, NO2 and HCHO slant column densities (SCD). A numerical code has been written to retrieve gas profiles of NO2 and HCHO using radiative transfer simulations. We present the first results of the variability of these trace gases which will bring new insight in the current knowledge of transport patterns, emissions as well as frequency and origin of extraordinary events. Results of the vertical column densities (VCD) valiability of NO2 and HCHO in Mexico City are presented. These studies are useful to validate current and future satellite observatopns such as OMI, TROPOMI and TEMPO.

  3. A prototype stationary Fourier transform spectrometer for near-infrared absorption spectroscopy.

    PubMed

    Li, Jinyang; Lu, Dan-feng; Qi, Zhi-mei

    2015-09-01

    A prototype stationary Fourier transform spectrometer (FTS) was constructed with a fiber-coupled lithium niobate (LiNbO3) waveguide Mach-Zehnder interferometer (MZI) for the purpose of rapid on-site spectroscopy of biological and chemical measurands. The MZI contains push-pull electrodes for electro-optic modulation, and its interferogram as a plot of intensity against voltage was obtained by scanning the modulating voltage from -60 to +60 V in 50 ms. The power spectrum of input signal was retrieved by Fourier transform processing of the interferogram combined with the wavelength dispersion of half-wave voltage determined for the MZI used. The prototype FTS operates in the single-mode wavelength range from 1200 to 1700 nm and allows for reproducible spectroscopy. A linear concentration dependence of the absorbance at λmax = 1451 nm for water in ethanolic solution was obtained using the prototype FTS. The near-infrared spectroscopy of solid samples was also implemented, and the different spectra obtained with different materials evidenced the chemical recognition capability of the prototype FTS. To make this prototype FTS practically applicable, work on improving its spectral resolution by increasing the maximum optical path length difference is in progress.

  4. Development Of A Supercontinuum Based Photoacoustic Aerosol Light Absorption And Albedo Spectrometer (PALAAS)

    NASA Astrophysics Data System (ADS)

    Arnold, Ian J.

    Aerosols are a major contributor to the global radiation budget because they modify the planetary albedo with their optical properties. These optical properties need to be measured and understood, ideally at multiple wavelengths. This thesis describes the ongoing development of a supercontinuum based multi-wavelength photoacoustic instrument to measure the light absorption and scattering coefficients of aerosols. Collimation techniques for supercontinuum sources using lens-based and off-axis parabolic mirror-based collimators were evaluated and it was determined that the off-axis mirror had superior collimation abilities for multi-spectral beams. A proof of concept supercontinuum-based photoacoustic instrument was developed using sequential measurements at multiple wavelengths. The instrument data were in good agreement with those from a commercial 3-wavelength photoacoustic instrument and the novel instrument had minimum detectable absorption and scattering coefficients of better than 4 Mm-1 and 21 Mm-1, respectively. The instrument however suffered from poor temporal resolution due to the sequential measurement and required the development of an aerosol delivery system to deliver a slowly varying aerosol concentration. In response, a spectral modulator has been developed to frequency encode different wavelength bands for simultaneous measurement with a photoacoustic instrumen.

  5. Light absorption coefficient measurement of SOA using a UV-Visible spectrometer connected with an integrating sphere

    NASA Astrophysics Data System (ADS)

    Zhong, Min; Jang, Myoseon

    2011-08-01

    A method for measuring an aerosol light absorption coefficient ( B a) has been developed using a conventional UV-visible spectrometer equipped with an integrating sphere covering a wide range of wavelengths (280-800 nm). The feasibility of the proposed method was evaluated in both the transmittance mode (TUV-IS) and the reflective mode (RUV-IS) using the reference aerosol known for the cross-sectional area. The aerosol was collected on a conventional filter and measured for B a values. The resulting RUV-IS method was applied to measure light absorption of secondary organic aerosol (SOA). SOA was produced through photooxidation of different precursor hydrocarbons such as toluene, d-limonene and α-pinene in the presence of NO x (60-70 ppb) and inorganic seed aerosol using a 2-m 3 indoor Teflon film chamber. Of the three precursor hydrocarbons, the B a value of toluene SOA (0.574 m 2 g -1 at 350 nm) was the highest compared with B a values for α-pinene SOA (0.029 m 2 g -1) and d-limonene SOA (0.038 m 2 g -1). When d-limonene SOA or toluene SOA was internally mixed with neutral [(NH 4) 2SO 4] or acidic inorganic seed (NH 4HSO 4:H 2SO 4 = 1:1 by mole), the SOA showed 2-3 times greater B a values at 350 nm than the SOA with no seed. Aerosol aging with a light source for this study reduced B a values of SOA (e.g., on average 10% for toluene SOA and 30% for d-limonene SOA within 4 h). Overall, weak absorption appeared for chamber-generated SOA over wavelengths ranging from 280 to 550 nm, which fall into the sunlight spectrum.

  6. High sensitivity liquid phase measurements using broadband cavity enhanced absorption spectroscopy (BBCEAS) featuring a low cost webcam based prism spectrometer.

    PubMed

    Qu, Zhechao; Engstrom, Julia; Wong, Donald; Islam, Meez; Kaminski, Clemens F

    2013-11-01

    Cavity enhanced techniques enable high sensitivity absorption measurements in the liquid phase but are typically more complex, and much more expensive, to perform than conventional absorption methods. The latter attributes have so far prevented a wide spread use of these methods in the analytical sciences. In this study we demonstrate a novel BBCEAS instrument that is sensitive, yet simple and economical to set up and operate. We use a prism spectrometer with a low cost webcam as the detector in conjunction with an optical cavity consisting of two R = 0.99 dielectric mirrors and a white light LED source for illumination. High sensitivity liquid phase measurements were made on samples contained in 1 cm quartz cuvettes placed at normal incidence to the light beam in the optical cavity. The cavity enhancement factor (CEF) with water as the solvent was determined directly by phase shift cavity ring down spectroscopy (PS-CRDS) and also by calibration with Rhodamine 6G solutions. Both methods yielded closely matching CEF values of ~60. The minimum detectable change in absorption (αmin) was determined to be 6.5 × 10(-5) cm(-1) at 527 nm and was limited only by the 8 bit resolution of the particular webcam detector used, thus offering scope for further improvement. The instrument was used to make representative measurements on dye solutions and in the determination of nitrite concentrations in a variation of the widely used Griess Assay. Limits of detection (LOD) were ~850 pM for Rhodamine 6G and 3.7 nM for nitrite, respectively. The sensitivity of the instrument compares favourably with previous cavity based liquid phase studies whilst being achieved at a small fraction of the cost hitherto reported, thus opening the door to widespread use in the community. Further means of improving sensitivity are discussed in the paper. PMID:24049768

  7. High sensitivity liquid phase measurements using broadband cavity enhanced absorption spectroscopy (BBCEAS) featuring a low cost webcam based prism spectrometer.

    PubMed

    Qu, Zhechao; Engstrom, Julia; Wong, Donald; Islam, Meez; Kaminski, Clemens F

    2013-11-01

    Cavity enhanced techniques enable high sensitivity absorption measurements in the liquid phase but are typically more complex, and much more expensive, to perform than conventional absorption methods. The latter attributes have so far prevented a wide spread use of these methods in the analytical sciences. In this study we demonstrate a novel BBCEAS instrument that is sensitive, yet simple and economical to set up and operate. We use a prism spectrometer with a low cost webcam as the detector in conjunction with an optical cavity consisting of two R = 0.99 dielectric mirrors and a white light LED source for illumination. High sensitivity liquid phase measurements were made on samples contained in 1 cm quartz cuvettes placed at normal incidence to the light beam in the optical cavity. The cavity enhancement factor (CEF) with water as the solvent was determined directly by phase shift cavity ring down spectroscopy (PS-CRDS) and also by calibration with Rhodamine 6G solutions. Both methods yielded closely matching CEF values of ~60. The minimum detectable change in absorption (αmin) was determined to be 6.5 × 10(-5) cm(-1) at 527 nm and was limited only by the 8 bit resolution of the particular webcam detector used, thus offering scope for further improvement. The instrument was used to make representative measurements on dye solutions and in the determination of nitrite concentrations in a variation of the widely used Griess Assay. Limits of detection (LOD) were ~850 pM for Rhodamine 6G and 3.7 nM for nitrite, respectively. The sensitivity of the instrument compares favourably with previous cavity based liquid phase studies whilst being achieved at a small fraction of the cost hitherto reported, thus opening the door to widespread use in the community. Further means of improving sensitivity are discussed in the paper.

  8. Water Vapour Profiles from SCIAMACHY Solar Occultation Measurements derived with Onion Peeling DOAS

    NASA Astrophysics Data System (ADS)

    Noël, S.; Bramstedt, K.; Rozanov, A.; Bovensmann, H.; Burrows, J. P.

    2009-04-01

    Water vapour is the most important greenhouse gas and plays a key role in atmospheric chemistry and transport. Most of the water vapour is located in the troposphere where it significantly contributes to weather and climate. Because the tropopause acts as a cold trap, the water vapour density in the stratosphere is significantly lower and decreases rapidly with increasing altitude. However, the amount of stratospheric water vapour plays an important role in the generation of Polar Stratospheric Clouds (PSCs), which in turn influence strongly the amount of ozone in polar regions. Trends in stratospheric water vapour are determined by methane oxidation, transport through the tropopause and by the Brewer-Dobson circulation. To seperate the various effects there is a clear need for global long term measurements of lower stratospheric water vapour, which can be provided by satellite measurements. A new retrieval method (called "Onion Peeling DOAS") has been developed to derive water vapour number density profiles from solar occultation measurements of the SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY). This method is intentionally kept simple and based on a combination of an onion peeling approach with a modified DOAS (Differential Optical Absorption Spectroscopy) fit in the wavelength region around 940 nm. The resulting water vapour profiles currently cover the altitude range 15-50 km. Here, first retrieval results and comparisons of the SCIAMACHY profiles with water vapour data provided by the Atmospheric Chemistry Explorer Fourier Transform Spectrometer (ACE-FTS) and model data of the European Centre for Medium Range Weather Forecasts (ECMWF) are shown.

  9. Airborne Measurements of Formaldehyde Employing a Tunable Diode Laser Absorption Spectrometer During TRACE-P

    NASA Technical Reports Server (NTRS)

    Fried, Alan; Drummond, James

    2003-01-01

    This final report summarizes the progress achieved over the entire 3-year proposal period including two extensions spanning 1 year. These activities include: 1) Preparation for and participation in the NASA 2001 TRACE-P campaign using our airborne tunable diode laser system to acquire measurements of formaldehyde (CH2O); 2) Comprehensive data analysis and data submittal to the NASA archive; 3) Follow up data interpretation working with NASA modelers to place our ambient CH2O measurements into a broader photochemical context; 4) Publication of numerous JGR papers using this data; 5) Extensive follow up laboratory tests on the selectivity and efficiency of our CH20 scrubbing system; and 6) An extensive follow up effort to assess and study the mechanical stability of our entire optical system, particularly the multipass absorption cell, with aircraft changes in cabin pressure.

  10. SO2 Emission from Active Volcanoes Measured Simultaneously by COSPEC and mini-DOAS

    NASA Astrophysics Data System (ADS)

    Barrancos, José; Roselló, José I.; Calvo, David; Padrón, Eleazar; Melián, Gladys; Hernández, Pedro A.; Pérez, Nemesio M.; Millán, Millán M.; Galle, Bo

    2008-01-01

    We measured SO2 emission rate from six volcanoes in Latin America (Santa Ana, El Salvador; San Cristóbal and Masaya, Nicaragua; Arenal and Poás, Costa Rica; Tungurahua and Sierra Negra, Ecuador) and from Mt. Etna, Italy, using two different remote sensing techniques: COSPEC (COrrelation SPECtrometer) and miniDOAS (miniaturized Differential Optical Absorption Spectroscopy). One of the goals of this study was to evaluate the differences in SO2 emission rates obtained by these two methods. The observed average SO2 emission rates measured during this study were 2688 t· d -1 from Tungurahua in July 2006, 2375 t· d -1 in September 2005 and 480 t· d -1 in February 2006 from Santa Ana, 1200 t· d -1 in May 2005 from Etna, 955 t· d -1 in March 2006 and 1165 t· d -1 in December 2006 from Masaya, 5400 t· d -1 of March 7, 2006 and 265 t· d -1 in March 2006 from San Cristobal, 113 t· d -1 in April 2006 from Arenal, 104 t· d -1 in April 2006 from Poás and 11 t· d -1 in July 2006 from Sierra Negra volcano. Most of the observed relative differences of SO2 emission measurements from COSPEC and miniDOAS were lower than 10%.

  11. Single snapshot DOA estimation

    NASA Astrophysics Data System (ADS)

    Häcker, P.; Yang, B.

    2010-10-01

    In array signal processing, direction of arrival (DOA) estimation has been studied for decades. Many algorithms have been proposed and their performance has been studied thoroughly. Yet, most of these works are focused on the asymptotic case of a large number of snapshots. In automotive radar applications like driver assistance systems, however, only a small number of snapshots of the radar sensor array or, in the worst case, a single snapshot is available for DOA estimation. In this paper, we investigate and compare different DOA estimators with respect to their single snapshot performance. The main focus is on the estimation accuracy and the angular resolution in multi-target scenarios including difficult situations like correlated targets and large target power differences. We will show that some algorithms lose their ability to resolve targets or do not work properly at all. Other sophisticated algorithms do not show a superior performance as expected. It turns out that the deterministic maximum likelihood estimator is a good choice under these hard conditions.

  12. Multipass optical absorption spectroscopy: a fast-scanning laser spectrometer for the in situ determination of atmospheric trace-gas components, in particular OH.

    PubMed

    Armerding, W; Spiekermann, M; Walter, J; Comes, F J

    1996-07-20

    The optical design of an absorption spectrometer for in situ measurements of atmospheric trace gases is reported. The light source is a rapidly tuned and power-stabilized dye-ring laser, which is frequency doubled by an intracavity BBO crystal. The second harmonic and the fundamental are used simultaneously for measurement of OH, SO(2), CH(2)O, and naphthalene in the UV and of NO(2) in the visible. The 1.2-km absorption path is folded within a 6-m White-cell-type multiple-reflection system with an open-path setup. The absorption sensitivity of the spectrometer is better than 1 part in 10(-5) under tropospheric conditions (integration time 1 min., signal-to-noise ratio 1).

  13. Comparison of aromatic hydrocarbon measurements made by PTR-MS, DOAS and GC-FID during the MCMA 2003 Field Experiment

    NASA Astrophysics Data System (ADS)

    Jobson, B. T.; Volkamer, R. A.; Velasco, E.; Allwine, G.; Westberg, H.; Lamb, B. K.; Alexander, M. L.; Berkowitz, C. M.; Molina, L. T.

    2010-02-01

    A comparison of aromatic hydrocarbon measurements is reported for the CENICA supersite in the district of Iztapalapa during the Mexico City Metropolitan Area field experiment in April 2003 (MCMA 2003). Data from three different measurement methods were compared: a Proton Transfer Reaction Mass Spectrometer (PTR-MS), long path measurements using a UV Differential Optical Absorption Spectrometer (DOAS), and Gas Chromatography-Flame Ionization analysis (GC-FID) of canister samples. The principle focus was on the comparison between PTR-MS and DOAS data. Lab tests established that the PTR-MS and DOAS calibrations were consistent for a suite of aromatic compounds including benzene, toluene, p-xylene, ethylbenzene, 1,2,4-trimethylbenzene, phenol and styrene. The point sampling measurements by the PTR-MS and GC-FID showed good correlations (r=0.6), and were in reasonable agreement for toluene, C2-alkylbenzenes and C3-alkylbenzenes. The PTR-MS benzene data were consistently high, indicating interference from ethylbenzene fragmentation for the 145 Td drift field intensity used in the experiment. Correlations between the open-path data measured at 16-m height over a 860-m path length (retroreflector in 430 m distance), and the point measurements collected at 37-m sampling height were best for benzene (r=0.61), and reasonably good for toluene, C2-alkylbenzenes, naphthalene, styrene, cresols and phenol (r>0.5). There was good agreement between DOAS and PTR-MS measurements of benzene after correction for the PTR-MS ethylbenzene interference. Mixing ratios measured by DOAS were on average a factor of 1.7 times greater than the PTR-MS data for toluene, C2-alkylbenzenes, naphthalene and styrene. The level of agreement for the toluene data displayed a modest dependence on wind direction, establishing that spatial gradients - horizontal, vertical, or both - in toluene mixing ratios were significant, and up to a factor of 2 despite the fact that all measurements were conducted above

  14. Comparison of Aromatic Hydrocarbon Measurements made by PTR-MS, DOAS and GC-FID during the MCMA 2003 Field Experiment

    SciTech Connect

    Jobson, Bertram T.; Volkamer, Rainer M.; Velasco, E.; Allwine, Gene; Westberg, Halvor H.; Lamb, Brian K.; Alexander, M. L.; Berkowitz, Carl M.; Molina, Luisa T.

    2010-02-15

    A comparison of aromatic hydrocarbon measurements is reported for the CENICA upersite in the district of Iztapalapa during the Mexico City Metropolitan Area field experiment in April 2003 (MCMA 2003). Data from three different measurement methods were compared: a Proton Transfer Reaction Mass Spectrometer (PTR-MS), long path measurements using a UV Differential Optical Absorption Spectrometer (DOAS), and Gas Chromatography-Flame Ionization analysis (GC-FID) of canister samples. The principle focus was on the comparison between PTR-MS and DOAS data. Lab tests established that the PTR-MS and DOAS calibrations were consistent for a suite of aromatic compounds including benzene, toluene, p-xylene, ethylbenzene, 1,2,4-trimethylbenzene, phenol and styrene. The point sampling measurements by the PTR-MS and GC-FID showed good correlations (r=0.6), and were in reasonable agreement for toluene, C₂-alkylbenzenes and C3-alkylbenzenes. The PTR-MS benzene data were consistently high, indicating interference from ethylbenzene fragmentation for the 145 Td drift field intensity used in the experiment. Correlations between the open-path data measured at 16-m height over a 860-m path length (retroreflector in 430m distance), and the point measurements collected at 37-m sampling height were best for benzene (r=0.61), and reasonably good for toluene, C2-alkylbenzenes, naphthalene, styrene, cresols and phenol (r>0.5). There was good agreement between DOAS and PTR-MS measurements of benzene after correction for the PTR-MS ethylbenzene interference. Mixing ratios easured by DOAS were on average a factor of 1.7 times greater than the PTR-MS data for toluene, C2-alkylbenzenes, naphthalene and styrene. The level of agreement for the toluene data displayed a modest dependence on wind direction, establishing that spatial gradients - horizontal, vertical, or both – in toluene mixing ratios were significant, and up to a factor of 2 despite the fact that all measurements were conducted above

  15. Airborne measurements of different trace gases during the AROMAT-2 campaign with an Avantes spectrometer

    NASA Astrophysics Data System (ADS)

    Bösch, Tim; Meier, Andreas; Schönhardt, Anja; Peters, Enno; Richter, Andreas; Ruhtz, Thomas; Burrows, John

    2016-04-01

    Differential Optical Absorption Spectroscopy (DOAS) is a well-known, versatile, and frequently used technique for the analysis of trace gases within the atmosphere. Although DOAS has been used for several decades, airborne DOAS has become more popular during the last years because of the possibility of measuring in high lateral resolutions with the help of imaging instruments. Here, we present results of the AROMAT-2 campaign in Romania in summer 2015. The introduced measurements were taken using a nadir viewing Avantes spectrometer on board of a Cessna aircraft which flew over Bucharest and the Turceni power plant in Romania. The instrument covers the wavelength region of 287 - 551nm at a spectral resolution of 0.13nm and has a temporal resolution of 0.5s, translating to about 450m in flight direction at 3000m flight attitude. The field of view of the instrument was set to 8.1 degrees, resulting in a pixel size across track of about 420m. Compared to the imaging DOAS instrument AirMAP which was also operated from the aircraft, the signal to noise ratio of the simple nadir viewing spectrometer is slightly better, which allows an analysis of less abundant species and interesting spectral features. The results show a day-to-day variation of NO2 over the city of Bucharest as well as spectral features over lakes in the city, which can be attributed to algae. Furthermore, we were able to measure large emission plumes of NO2 and SO2 over the Turceni power plant, which could be observed over long spatial distances. In addition, the results from the Avantes instrument were used for comparison with measurements of the imaging spectrometer AirMAP and good agreement was found, providing independent verification of the imager data.

  16. Intensity-Modulated Continuous-Wave Laser Absorption Spectrometer at 1.57 Micrometer for Atmospheric CO2 Measurements

    NASA Technical Reports Server (NTRS)

    Lin, Bing

    2014-01-01

    Understanding the earth's carbon cycle is essential for diagnosing current and predicting future climates, which requires precise global measurements of atmospheric CO2 through space missions. The Active Sensing of CO2 Emissions over Nights, Days, and Seasons (ASCENDS) space mission will provide accurate global atmospheric CO2 measurements to meet carbon science requirements. The joint team of NASA Langley Research Center and ITT Exelis, Inc. proposes to use the intensity-modulated, continuous-wave (IM-CW) laser absorption spectrometer (LAS) approach for the ASCENDS mission. Prototype LAS instruments have been developed and used to demonstrate the power, signal-to-noise ratio, precision and accuracy, spectral purity, and stability of the measurement and the instrument needed for atmospheric CO2 observations from space. The ranging capability from laser platform to ground surfaces or intermediate backscatter layers is achieved by transmitted range-encoded IM laser signals. Based on the prototype instruments and current lidar technologies, space LAS systems and their CO2 column measurements are analyzed. These studies exhibit a great potential of using IM-CW LAS system for the active space CO2 mission ASCENDS.

  17. Correlation study between suspended particulate matter and DOAS data

    NASA Astrophysics Data System (ADS)

    Si, Fuqi; Liu, Jianguo; Xie, Pinghua; Zhang, Yujun; Liu, Wenqing; Kuze, Hiroaki; Lagrosas, Nofel; Takeuchi, Nobuo

    2006-05-01

    Continuous data of aerosol optical thickness monitored using differential optical absorption spectroscopy (DOAS) are correlated with the concentration of ground-measured suspended particulate matter (SPM). A high correlation is found between the DOAS and the ground SPM data, making it possible to calculate the mass extinction efficiency of the aerosols in the atmosphere. It is found that the value of mean mass extinction efficiency (MEE) varies over a range of 2.6 13.7 m2 g-1, with smaller and larger values occurring for size distributions dominated by coarse and fine particles, respectively.

  18. Validation of the OMI-TOMS and OMI-DOAS total ozone column data using ground-based observations over China

    NASA Astrophysics Data System (ADS)

    Ma, Mingliang; Shi, Runhe; Gao, Wei

    2015-09-01

    This study evaluates the accuracy of total ozone column derived from Ozone Monitoring Instruments (OMI) with two algorithms: OMI Total Ozone Mapping Spectrometer (OMI-TOMS) and OMI Differential Optical Absorption Spectroscopy (OMI-DOAS), compared to ground-based Brewer and Dobson spectrophotometers located at eight China stations from July 2009 to December 2013, including Xianghe, Kunming, Mt.Waliguan, Lhasa, Taipei, Chengkung, Cape D'Aguilar and Longfengshan. Results showed that the agreement between OMI ozone data and ground-based measurements is excellent. Total ozone columns from both OMI-TOMS and OMI-DOAS data are on average about 1.5% lower than ground-based data. For both OMI ozone data products the SZA dependence of the mean relative differences (RD) between satellite data and the ground-based data is relative obvious when the SZA is larger than 50°. Similar to the SZA, the satellite view zenith angle (VZA) dependence of the mean relative differences (RD) between satellite and ground is relatively markedly when the VZA is smaller than 10° in eight stations. Finally, the dependence of the mean relative differences (RD) (-4.28% to 0.818%) between OMI-DOAS data and ground-based data for the total ozone column is remarkable. While for OMI-TOMS data the dependence is not obvious (the RD value varies from -3.30% to -0.676%).

  19. Development of a DOAS System for ToTAL-DOAS Applications with Temperature Control

    NASA Astrophysics Data System (ADS)

    Ramos, Javier A.; Frins, Erna

    2011-01-01

    The ToTAL -DOAS (Topographic Target Light s cattering - Differential optical Absorption Spectroscopy) is a novel atmospheric monitoring technique. The aim of our work has been enhancing a prototype, previously assembled within our research group, adding to it a temperature control and developing specific control software. The whole system offers the possibility of two dimension movement for spectra acquisition with a telescope of a field of view of approximately 0.03°, which let in signals in the near-UV and visible spectral range. The enhanced DOAS system is intended to be located on the roof of our faculty building to monitor SO2 and NO2 traces above the city of Montevideo. We are presenting the results of device's characterization.

  20. Double conical crystal x-ray spectrometer for high resolution ultrafast x-ray absorption near-edge spectroscopy of Al K edge

    SciTech Connect

    Levy, A.; Dorchies, F.; Fourment, C.; Harmand, M.; Hulin, S.; Santos, J. J.; Descamps, D.; Petit, S.; Bouillaud, R.

    2010-06-15

    An x-ray spectrometer devoted to dynamical studies of transient systems using the x-ray absorption fine spectroscopy technique is presented in this article. Using an ultrafast laser-induced x-ray source, this optical device based on a set of two potassium acid phthalate conical crystals allows the extraction of x-ray absorption near-edge spectroscopy structures following the Al absorption K edge. The proposed experimental protocol leads to a measurement of the absorption spectra free from any crystal reflectivity defaults and shot-to-shot x-ray spectral fluctuation. According to the detailed analysis of the experimental results, a spectral resolution of 0.7 eV rms and relative fluctuation lower than 1% rms are achieved, demonstrated to be limited by the statistics of photon counting on the x-ray detector.

  1. Comparing OMI-TOMS and OMI-DOAS total ozone column data

    NASA Astrophysics Data System (ADS)

    Kroon, M.; Veefkind, J. P.; Sneep, M.; McPeters, R. D.; Bhartia, P. K.; Levelt, P. F.

    2008-08-01

    The Ozone Monitoring Instrument (OMI) project team uses two total ozone retrieval algorithms in order to maintain the long-term record established with Total Ozone Mapping Spectrometer (TOMS) data as well as to improve the ozone column estimate using the hyperspectral capability of OMI. The purpose of this study is to assess where the algorithms produce comparable results and where the differences are significant. Starting with the same set of Earth reflectance data, the total ozone data used in this study have been derived using OMI-TOMS and OMI-Differential Optical Absorption Spectroscopy (DOAS) algorithms. OMI-TOMS is based on the TOMS version 8 algorithm that has been used to process TOMS data taken since November 1978. The OMI-DOAS retrieval algorithm was developed specifically for OMI. It takes advantage of the hyperspectral feature of the OMI instrument to reduce errors due to aerosols, clouds, surface, and sulfur dioxide from volcanic eruptions. The OMI-DOAS algorithm also has improved correction for cloud height. The mean differences in the ozone column derived from the two algorithms vary from 0 to 9 DU (0-3%), and their correlation coefficients vary between 0.89 and 0.99 with latitude and season. The largest differences occur in the polar regions and over clouds. Some of the differences are due to stray light, dark current, and other instrumental errors that have been corrected in the new version of the OMI radiance/irradiance data set (collection 3). Other differences are algorithmic. OMI-DOAS algorithmic errors identified through this analysis are also being corrected in collection 3 reprocessing. However, for consistency with the long-term TOMS record, OMI-TOMS collection 3 data will still be based on the TOMS V8 algorithm. Preliminary analysis shows much better agreement in the two total ozone data sets after reprocessing. Reprocessed collection 3 data from both algorithms will be available before the end of 2007. Continuing the TOMS total ozone

  2. Development of a cavity-enhanced absorption spectrometer for airborne measurements of CH4 and CO2

    NASA Astrophysics Data System (ADS)

    O'Shea, S. J.; Bauguitte, S. J.-B.; Gallagher, M. W.; Lowry, D.; Percival, C. J.

    2013-05-01

    High-resolution CH4 and CO2 measurements were made on board the FAAM BAe-146 UK (Facility for Airborne Atmospheric Measurements, British Aerospace-146) atmospheric research aircraft during a number of field campaigns. The system was based on an infrared spectrometer using the cavity-enhanced absorption spectroscopy technique. Correction functions to convert the mole fractions retrieved from the spectroscopy to dry-air mole fractions were derived using laboratory experiments and over a 3 month period showed good stability. Long-term performance of the system was monitored using WMO (World Meteorological Office) traceable calibration gases. During the first year of operation (29 flights) analysis of the system's in-flight calibrations suggest that its measurements are accurate to 1.28 ppb (1σ repeatability at 1 Hz = 2.48 ppb) for CH4 and 0.17 ppm (1σ repeatability at 1 Hz = 0.66 ppm) for CO2. The system was found to be robust, no major motion or altitude dependency could be detected in the measurements. An inter-comparison between whole-air samples that were analysed post-flight for CH4 and CO2 by cavity ring-down spectroscopy showed a mean difference between the two techniques of -2.4 ppb (1σ = 2.3 ppb) for CH4 and -0.22 ppm (1σ = 0.45 ppm) for CO2. In September 2012, the system was used to sample biomass-burning plumes in Brazil as part of the SAMBBA project (South AMerican Biomass Burning Analysis). From these and simultaneous CO measurements, emission factors for savannah fires were calculated. These were found to be 2.2 ± 0.2 g (kg dry matter)-1 for CH4 and 1710 ± 171 g (kg dry matter)-1 for CO2, which are in excellent agreement with previous estimates in the literature.

  3. A Capillary Absorption Spectrometer for Stable Carbon Isotope Ratio (13C/12C) Analysis in Very Small Samples

    SciTech Connect

    Kelly, James F.; Sams, Robert L.; Blake, Thomas A.; Newburn, Matthew K.; Moran, James J.; Alexander, M. L.; Kreuzer, Helen W.

    2012-02-06

    A capillary absorption spectrometer (CAS) suitable for IR laser isotope analysis of small CO{sub 2} samples is presented. The system employs a continuous-wave (cw) quantum cascade laser to study nearly adjacent rovibrational transitions of different isotopologues of CO{sub 2} near 2307 cm{sup -1} (4.34 {mu}m). This initial CAS system can achieve relative isotopic precision of about 10 ppm {sup 13}C, or {approx}1{per_thousand} (per mil in delta notation relative to Vienna Pee Dee Belemnite) with 20-100 picomoles of entrained sample within the hollow waveguide for CO{sub 2} concentrations {approx}400 to 750 ppm. Isotopic analyses of such gas fills in a 1-mm ID hollow waveguide of 0.8 m overall physical path length can be carried out down to {approx}2 Torr. Overall {sup 13}C/{sup 12}C ratios can be calibrated to {approx}2{per_thousand} accuracy with diluted CO{sub 2} standards. A novel, low-cost method to reduce cw-fringing noise resulting from multipath distortions in the hollow waveguide is presented, which allows weak absorbance features to be studied at the few ppm level (peak-to-rms) after 1,000 scans are co-added in {approx}10 sec. The CAS is meant to work directly with converted CO{sub 2} samples from a Laser Ablation-Catalytic-Combustion (LA CC) micro-sampler to provide {sup 13}C/{sup 12}C ratios of small biological isolates with spatial resolutions {approx}50 {mu}m.

  4. Modeling of intensity-modulated continuous-wave laser absorption spectrometer systems for atmospheric CO(2) column measurements.

    PubMed

    Lin, Bing; Ismail, Syed; Wallace Harrison, F; Browell, Edward V; Nehrir, Amin R; Dobler, Jeremy; Moore, Berrien; Refaat, Tamer; Kooi, Susan A

    2013-10-10

    The focus of this study is to model and validate the performance of intensity-modulated continuous-wave (IM-CW) CO(2) laser absorption spectrometer (LAS) systems and their CO(2) column measurements from airborne and satellite platforms. The model accounts for all fundamental physics of the instruments and their related CO(2) measurement environments, and the modeling results are presented statistically from simulation ensembles that include noise sources and uncertainties related to the LAS instruments and the measurement environments. The characteristics of simulated LAS systems are based on existing technologies and their implementation in existing systems. The modeled instruments are specifically assumed to be IM-CW LAS systems such as the Exelis' airborne multifunctional fiber laser lidar (MFLL) operating in the 1.57 μm CO(2) absorption band. Atmospheric effects due to variations in CO(2), solar radiation, and thin clouds, are also included in the model. Model results are shown to agree well with LAS atmospheric CO(2) measurement performance. For example, the relative bias errors of both MFLL simulated and measured CO(2) differential optical depths were found to agree to within a few tenths of a percent when compared to the in situ observations from the flight of 3 August 2011 over Railroad Valley (RRV), Nevada, during the summer 2011 flight campaign. In addition, the horizontal variations in the model CO(2) differential optical depths were also found to be consistent with those from MFLL measurements. In general, the modeled and measured signal-to-noise ratios (SNRs) of the CO(2) column differential optical depths (τd) agreed to within about 30%. Model simulations of a spaceborne IM-CW LAS system in a 390 km dawn/dusk orbit for CO(2) column measurements showed that with a total of 42 W of transmitted power for one offline and two different sideline channels (placed at different locations on the side of the CO(2) absorption line), the accuracy of the

  5. Spectroscopic Character and Spatial Distribution of Hydroxyl and Water Absorption Features Measured on the Lunar Surface by the Moon Mineralogy Mapper Imaging Spectrometer on Chandrayaan-1

    NASA Astrophysics Data System (ADS)

    Green, R. O.; Pieters, C. M.; Goswami, J.; Clark, R. N.; Annadurai, M.; Boardman, J. W.; Buratti, B. J.; Combe, J.; Dyar, M. D.; Head, J. W.; Hibbitts, C.; Hicks, M.; Isaacson, P.; Klima, R. L.; Kramer, G. Y.; Kumar, S.; Livo, K. E.; Lundeen, S.; Malaret, E.; McCord, T. B.; Mustard, J. F.; Nettles, J. W.; Petro, N. E.; Runyon, C. J.; Staid, M.; Sunshine, J. M.; Taylor, L. A.; Tompkins, S.; Varanasi, P.

    2009-12-01

    The Moon Mineralogy Mapper imaging spectrometer on Chandrayaan-1 has a broad spectral range from 430 to 3000 nm. By design, the range was specified to extend to 3000 nm to allow for possible detection of trace volatile compounds that possess absorption bands near 3000 nm. Soon after acquisition and calibration of a large fraction of the lunar surface in early February 2009, absorption features in the 2700 to 3000 nm region were detected over unexpectedly large regional areas. This extraordinary discovery has withstood extensive re-analysis and falsification efforts. We have concluded these absorption features are fundamentally present in the M3 measurements and are indicators of extensive hydroxyl and water-bearing materials occurring on the surface of the Moon. Based on current analyses, these absorption features appear strongest at high latitudes, but also occur in association with several fresh feldspathic craters. Interestingly, the distribution of these absorption features are not directly correlated with existing neutron spectrometer hydrogen abundance data for the sunlight surface. This may indicate that the formation and retention of hydroxyl and water is an active process largely restricted to the upper most surface. We present the detailed spectroscopic character of these absorption features in the 2700 to 3000 nm spectral region, including selected examples through all levels of measurement processing from raw data to calibrated apparent surface reflectance. In summary we show the measured strength and latitudinal distribution of the absorptions as well as selected localized occurrences in association with fresh feldspathic craters. The presence of hydroxyl and water bearing material over extensive regions of the lunar surface provides a new and unexpected source of volatiles. Options for harvesting these elements directly from the regolith may provide an alternate supply of volatiles for long term human exploration objectives.

  6. Vertical profiles of pollutant gases measured with passive DOAS in the Po Valley devoted to satellite and chemical model data comparison

    NASA Astrophysics Data System (ADS)

    Masieri, S.; Petritoli, A.; Kostadinov, I.; Bortoli, D.; Premuda, M.; Ravegnani, F.; Giovanelli, G.

    2009-04-01

    In the frame of QUITSAT Italian pilot project (Air QUality with InTegration of ground-based and SAtellite measurement and chemical Transport model), two field campaigns were made in S.Pietro Capofiume (44.65˚ N; 11.37˚ E) and Bologna (44.52˚ N; 11.34˚ E) to provide concentration of ground particular matter and gaseous pollutants, namely nitrogen dioxide (NO2), formaldehyde (HCHO), sulphur dioxide (SO2) and ozone (O3). The aim of the campaigns was to provide experimental data need for tests and improvement of algorithms developed for integration of satellite and ground-based data together with chemical transport model data in order to retrieve air quality in the QUITSAT domain. Ground based measurements were carried out within a network of in-situ analyser in the Po Valley and with a scanning multi-axis DOAS (Differential Optical Absorption Spectroscopy) spectrometer system developed at ISAC-CNR institute [1], in collaboration with Geophysics Center of Evora [2]. TropoGAS (TROPOspheric Gas Analyser Spectrometer) spectrometer permits active and passive DOAS measurements at the chosen angles: α =1,2,3,6,10,15,20,90 and another measurement was taken along the sun direction. A Xenon lamp installed at 1km of distance from spectrometer was used as a reference concentration measured in the same place, and these values shows good agreement with in-situ analyser concentration. Gas spectral absorption was evaluated with DOAS [3] algorithms from 430 to 500 nm in two different windows: first from 436 to 460 nm for NO2 retrieval; second from 460 to 500 nm for O4 (best line at 477 nm) and NO2. Air Mass Factor (AMF) was calculated using PROMSAR (PROcessing of Multi-Scattered Atmospheric Radiation) model [4], that is a backward Montecarlo Radiative Transfer Model (RTM). An apposite inversion method [5][6], was applied to retrieve profiles of the target gases from their Slant Column Densities (SCD), using advanced approaches involving measurement of the atmospheric O4

  7. Intercomparison of NO2 Slant Column Densities and Vertical Profiles Inferred from Balloon-borne Measurements of Solar Absorption Spectra in the IR and UV/vis

    NASA Astrophysics Data System (ADS)

    Butz, A.; Boesch, H.; Camy-Peyret, C.; Dorf, M.; Dufour, G.; Payan, S.; Weidner, F.; Pfeilsticker, K.

    2003-04-01

    During a series of LPMA/DOAS (Laboratoire de Physique Moléculaire et Applications/Differential Optical Absorption Spectroscopy) stratospheric balloon flights direct solar spectra in the UV/vis and near IR were simultaneously measured by the onboard installed Fourier Transform (LPMA) and two channel grating spectrometer (DOAS). The measurements were conducted in spring and summer at high and midlatitudes during ascent of the balloon into the stratosphere (30 - 40 km) and solar occultation at balloon float altitude. Here we present a direct intercomparison of the NO_2 slant column densities (SCDs) and vertical profiles retrieved from UV/vis-DOAS and IR-LPMA measurements for a wide range of geophysical conditions (ambient pressure and temperature and solar illumination). The comparison study thus allows us to verify the applied retrieval procedures, i.e., the underlying spectroscopic dataset as well as the inversion algorithms. First intercomparison studies showed a sizeable discrepancy between NO_2 inferred by LPMA in the IR and DOAS in the visible spectral range indicating deficiencies in the spectral retrieval techniques. After introducing a temperature correction scheme for the DOAS retrieval and a new LPMA MULTIFIT procedure which minimizes the correlations of the fitting parameters by performing the inversion simultaneously in several micro-windows, a reasonably good agreement between NO_2 inferred from both instruments is found.

  8. Comparison of aromatic hydrocarbon measurements made by PTR-MS, DOAS and GC-FID in Mexico City during the MCMA 2003 field experiment

    NASA Astrophysics Data System (ADS)

    Jobson, B. T.; Volkamer, R.; Velasco, E.; Allwine, G.; Westberg, H.; Lamb, B.; Alexander, M. L.; Berkowitz, C. M.; Molina, L. T.

    2009-09-01

    A comparison of aromatic hydrocarbon measurements is reported for the CENICA supersite in the district of Iztapalapa during the Mexico City Metropolitan Area field experiment in April 2003 (MCMA 2003). Data from three different measurement methods were compared, a proton transfer reaction mass spectrometer (PTR-MS), long path measurements using a UV differential optical absorption spectrometer (DOAS), and gas chromatography-flame ionization analysis (GC-FID) of canister samples. Lab tests established that the PTR-MS and DOAS calibrations were consistent for a suite of aromatic compounds including benzene, toluene, p-xylene, ethylbenzene, 1,2,4-trimethylbenzene, phenol, and styrene. The point sampling measurements by the PTR-MS and GC-FID showed good correlations (r=0.6), and were in reasonable agreement for toluene, C2-alkylbenzenes, and C3-alkylbenzenes. The PTR-MS benzene data were consistently high, indicating potential interference from fragmenting alkyl aromatics for the 145 Td drift field intensity used in the experiment. Correlations between the open-path data measured at 16-m height over a 860 m path length (retroreflector in 430 m distance), and the point measurements collected at 37-m sampling height were best for benzene (r=0.61), and reasonably good for toluene, C2-alkylbenzenes, naphthalene, styrene, cresols and phenol (r>0.5). While the DOAS data agreed within 20% with both point measurements for benzene, concentrations measured by DOAS were on average a factor of 1.7 times greater than the PTRMS data for toluene, C2-alkylbenzenes, naphthalene, and styrene. The level of agreement for the toluene data was a function of wind direction, establishing that spatial gradients - horizontal, vertical, or both - in VOC mixing ratios were significant, and up to a factor of 2 despite the fact that all measurements were conducted above roof level. Our analysis highlights a potential problem in defining a VOC sampling strategy that is meaningful for comparison with

  9. Monitoring vegetation using DOAS satellite observations

    NASA Astrophysics Data System (ADS)

    Eigemeier, Ellen; Beirle, Steffen; Marbach, Thierry; Platt, Ulrich; Wagner, Thomas

    2010-05-01

    Vegetation-cycles are of general interest for many applications. Be it for harvest-predictions, global monitoring of climate-change or as input to atmospheric models. From novel spectrally resolving UV/vis satellite instruments (like GOME or SCIAMACHY) the spectral signatures of different types of vegetation can be identified and analysed. Although the spatial resolution of GOME and SCIAMACHY observations is much coarser than those of conventional satellite instruments for vegetation monitoring, our data sets on different vegetation types add new and useful information, not obtainable from other sources. Common vegetation indices are based on the fact that the difference between Red and Near Infrared reflection is higher than in any other material on Earth's surface. This gives a very high degree of confidence for vegetation-detection. The spectrally resolving data from GOME and SCIAMACHY provide the chance to concentrate on finer spectral features throughout the red and near infrared spectrum. We look at these features using a technique known as Differential Optical Absorption Spectroscopy (DOAS). Although originally developed to retrieve information on trace gases, it can also be used to gain information on vegetation. Another advantage is that this method automatically corrects for atmospheric effects. This renders the vegetation-information easily comparable over long time-spans. In addition, high-frequency-structures from vegetation also effect the retrieval of tropospheric trace-gases and aerosols. To optimize vegetation monitoring with DOAS we produce spectrally resolved reference spectra from different vegetation types using our own instrumentation. We analyze the effect of different Pigments on high-frequency-structures of the DOAS Retrieval. Applying these results we investigate how well we can distinguish vegetation types from space.

  10. Monitoring vegetation using DOAS satellite observations

    NASA Astrophysics Data System (ADS)

    Eigemeier, E.; Beirle, S.; Marbach, T.; Platt, U.; Wagner, T.

    2009-12-01

    Vegetation-cycles are of general interest for many applications. Be it for harvest-predictions, global monitoring of climate-change or as input to atmospheric models. From novel spectrally resolving UV/vis satellite instruments (like GOME or SCIAMACHY) the spectral signatures of different types of vegetation can be identified and analysed. Although the spatial resolution of GOME and SCIAMACHY observations is much coarser than those of conventional satellite instruments for vegetation monitoring, our data sets on different vegetation types add new and useful information, not obtainable from other sources. Common vegetation indices are based on the fact that the difference between Red and Near Infrared reflection is higher than in any other material on Earth’s surface. This gives a very high degree of confidence for vegetation-detection. The spectrally resolving data from GOME and SCIAMACHY provide the chance to concentrate on finer spectral features throughout the red and near infrared spectrum. We look at these features using a technique known as Differential Optical Absorption Spectroscopy (DOAS). Although originally developed to retrieve information on trace gases, it can also be used to gain information on vegetation. Another advantage is that this method automatically corrects for atmospheric effects. This renders the vegetation-information easily comparable over long time-spans. In addition, high-frequency-structures from vegetation also effect the retrieval of tropospheric trace-gases and aerosols. To optimize vegetation monitoring with DOAS we produce spectrally resolved reference spectra from different vegetation types using our own instrumentation. We analyze the effect of different Pigments on high-frequency-structures of the DOAS Retrieval. Applying these results we investigate how well we can distinguish vegetation types from space.

  11. Tropospheric nitrogen dioxide column retrieval from ground-based zenith-sky DOAS observations

    NASA Astrophysics Data System (ADS)

    Tack, F.; Hendrick, F.; Goutail, F.; Fayt, C.; Merlaud, A.; Pinardi, G.; Hermans, C.; Pommereau, J.-P.; Van Roozendael, M.

    2015-06-01

    We present an algorithm for retrieving tropospheric nitrogen dioxide (NO2) vertical column densities (VCDs) from ground-based zenith-sky (ZS) measurements of scattered sunlight. The method is based on a four-step approach consisting of (1) the differential optical absorption spectroscopy (DOAS) analysis of ZS radiance spectra using a fixed reference spectrum corresponding to low NO2 absorption, (2) the determination of the residual amount in the reference spectrum using a Langley-plot-type method, (3) the removal of the stratospheric content from the daytime total measured slant column based on stratospheric VCDs measured at sunrise and sunset, and simulation of the rapid NO2 diurnal variation, (4) the retrieval of tropospheric VCDs by dividing the resulting tropospheric slant columns by appropriate air mass factors (AMFs). These steps are fully characterized and recommendations are given for each of them. The retrieval algorithm is applied on a ZS data set acquired with a multi-axis (MAX-) DOAS instrument during the Cabauw (51.97° N, 4.93° E, sea level) Intercomparison campaign for Nitrogen Dioxide measuring Instruments (CINDI) held from 10 June to 21 July 2009 in the Netherlands. A median value of 7.9 × 1015 molec cm-2 is found for the retrieved tropospheric NO2 VCDs, with maxima up to 6.0 × 1016 molec cm-2. The error budget assessment indicates that the overall error σTVCD on the column values is less than 28%. In the case of low tropospheric contribution, σTVCD is estimated to be around 39% and is dominated by uncertainties in the determination of the residual amount in the reference spectrum. For strong tropospheric pollution events, σTVCD drops to approximately 22% with the largest uncertainties on the determination of the stratospheric NO2 abundance and tropospheric AMFs. The tropospheric VCD amounts derived from ZS observations are compared to VCDs retrieved from off-axis and direct-sun measurements of the same MAX-DOAS instrument as well as to data

  12. Tropospheric nitrogen dioxide column retrieval from ground-based zenith-sky DOAS observations

    NASA Astrophysics Data System (ADS)

    Tack, F.; Hendrick, F.; Goutail, F.; Fayt, C.; Merlaud, A.; Pinardi, G.; Hermans, C.; Pommereau, J.-P.; Van Roozendael, M.

    2015-01-01

    We present an algorithm for retrieving tropospheric nitrogen dioxide (NO2) vertical column densities (VCDs) from ground-based zenith-sky (ZS) measurements of scattered sunlight. The method is based on a four-step approach consisting of (1) the Differential Optical Absorption Spectroscopy (DOAS) analysis of ZS radiance spectra using a fixed reference spectrum corresponding to low NO2 absorption, (2) the determination of the residual amount in the reference spectrum using a Langley-plot-type method, (3) the removal of the stratospheric content from the daytime total measured slant column based on stratospheric VCDs measured at sunrise and sunset, and simulation of the rapid NO2 diurnal variation, (4) the retrieval of tropospheric VCDs by dividing the resulting tropospheric slant columns by appropriate air mass factors (AMFs). These steps are fully characterized and recommendations are given for each of them. The retrieval algorithm is applied on a ZS dataset acquired with a Multi-AXis (MAX-) DOAS instrument during the Cabauw (51.97° N, 4.93° E, sea level) Intercomparison campaign for Nitrogen Dioxide measuring Instruments (CINDI) held from the 10 June to the 21 July 2009 in the Netherlands. A median value of 7.9 × 1015 molec cm-2 is found for the retrieved tropospheric NO2 VCDs, with maxima up to 6.0 × 1016 molec cm-2. The error budget assessment indicates that the overall error σTVCD on the column values is less than 28%. In case of low tropospheric contribution, σTVCD is estimated to be around 39% and is dominated by uncertainties in the determination of the residual amount in the reference spectrum. For strong tropospheric pollution events, σTVCD drops to approximately 22% with the largest uncertainties on the determination of the stratospheric NO2 abundance and tropospheric AMFs. The tropospheric VCD amounts derived from ZS observations are compared to VCDs retrieved from off-axis and direct-sun measurements of the same MAX-DOAS instrument as well as to

  13. Time-resolved near-edge x-ray absorption fine structure spectroscopy on photo-induced phase transitions using a tabletop soft-x-ray spectrometer

    NASA Astrophysics Data System (ADS)

    Grossmann, P.; Rajkovic, I.; Moré, R.; Norpoth, J.; Techert, S.; Jooss, C.; Mann, Klaus

    2012-05-01

    We present a table-top soft-x-ray spectrometer for the wavelength range λ = 1-5 nm based on a stable laser-driven x-ray source, making use of a gas-puff target. With this setup, optical light-pump/soft-x-ray probe near-edge x-ray absorption fine structure (NEXAFS) experiments with a temporal resolution of about 230 ps are feasible. Pump-probe NEXAFS measurements were carried out in the "water-window" region (2.28 nm-4.36 nm) on the manganite Pr0.7Ca0.3MnO3, investigating diminutive changes of the oxygen K edge that derive from an optically induced phase transition. The results show the practicability of the table-top soft-x-ray spectrometer on demanding investigations so far exclusively conducted at synchrotron radiation sources.

  14. A Compact Tunable Diode Laser Absorption Spectrometer to Monitor CO2 at 2.7 μm Wavelength in Hypersonic Flows

    PubMed Central

    Vallon, Raphäel; Soutadé, Jacques; Vérant, Jean-Luc; Meyers, Jason; Paris, Sébastien; Mohamed, Ajmal

    2010-01-01

    Since the beginning of the Mars planet exploration, the characterization of carbon dioxide hypersonic flows to simulate a spaceship’s Mars atmosphere entry conditions has been an important issue. We have developed a Tunable Diode Laser Absorption Spectrometer with a new room-temperature operating antimony-based distributed feedback laser (DFB) diode laser to characterize the velocity, the temperature and the density of such flows. This instrument has been tested during two measurement campaigns in a free piston tunnel cold hypersonic facility and in a high enthalpy arc jet wind tunnel. These tests also demonstrate the feasibility of mid-infrared fiber optics coupling of the spectrometer to a wind tunnel for integrated or local flow characterization with an optical probe placed in the flow. PMID:22219703

  15. A compact tunable diode laser absorption spectrometer to monitor CO2 at 2.7 μm wavelength in hypersonic flows.

    PubMed

    Vallon, Raphäel; Soutadé, Jacques; Vérant, Jean-Luc; Meyers, Jason; Paris, Sébastien; Mohamed, Ajmal

    2010-01-01

    Since the beginning of the Mars planet exploration, the characterization of carbon dioxide hypersonic flows to simulate a spaceship's Mars atmosphere entry conditions has been an important issue. We have developed a Tunable Diode Laser Absorption Spectrometer with a new room-temperature operating antimony-based distributed feedback laser (DFB) diode laser to characterize the velocity, the temperature and the density of such flows. This instrument has been tested during two measurement campaigns in a free piston tunnel cold hypersonic facility and in a high enthalpy arc jet wind tunnel. These tests also demonstrate the feasibility of mid-infrared fiber optics coupling of the spectrometer to a wind tunnel for integrated or local flow characterization with an optical probe placed in the flow.

  16. [Using Fourier transform to calculate gas concentration in DOAS].

    PubMed

    Liu, Qian-lin; Wang, Li-shi; Huang, Xin-jian; Wu, Yan-dan; Xiao, Ming-wei

    2008-12-01

    Being an analysis tool of high sensitivity, high resolution, multicomponents, real-time and fast monitoring, the differential optical absorption spectrometry (DOAS) is becoming a new method in atmosphere pollution monitoring. In the DOAS technique, many gases spectra have periodicity evidently, such as those from SO2, NO, NH3 and NO2. Aiming at three kinds of main air-polluted gases, i.e., SO2, NO and NO2 in atmosphere, the DOAS technique is used to monitor them, and Fourier transform is used to analyse the above-mentioned absorption spectra. Under the condition of Hanning Windows, Fourier transforma is used to process various gases spectra which have periodicity. In the process, the value of the characteristic frequency has a linearity relation to the gas concentration. So a new analysis method of DOAS is proposed, which is utilizing the relation between the value of the characteristic frequency and the gas concentration to deduce a linearity formula to calculate the gas concentration. So the value of the characteristic frequency can be used to get the gas concentration. For the gases with evident spectrum periodicity, such as SO2 and NO, this method is good. But for some gases with periodicity not evident, the error in the calculated concentration is beyond the allowable value. So in this method, the important process is frequency separation. It is also the main part in the future study. In a word, this method frees itself from the basic theory in the DOAS technique, cuts down on the process of the concentration calculation and the spectral analysis, and deserves further study. PMID:19248493

  17. Car MAX-DOAS measurements of the tropospheric Formaldehyde (HCHO) column around Bucharest (Romania) and in the Rhein-Main area (Germany)

    NASA Astrophysics Data System (ADS)

    Donner, Sebastian; Shaiganfar, Reza; Riffel, Katharina; Dörner, Steffen; Lampel, Johannes; Remmers, Julia; Wagner, Thomas

    2016-04-01

    The DOAS (differential optical absorption spectroscopy)-method analyses the absorptions of atmospheric trace gases in spectra of scattered sun light. It is an excellent way to determine the concentrations of different trace gases (e.g. NO2, SO2, HCHO…) simultaneously. MAX (Multi-AXis)-DOAS measurements observe scattered sun light under different elevation angles. From such measurements tropospheric vertical column densities (VCDs) or even vertical profiles of the measured trace gases and aerosols can be determined. We performed mobile MAX-DOAS measurements using two instruments on the roof of a car in summer 2015 in Romania during the AROMAT2 campaign and in the Winter/Spring 2016 in the Rhein-Main area (Germany). The latter is one of the densest populated areas in Germany. One instrument is a commercial Mini-MAX-DOAS instrument from the Hoffmann company, the other a self-built instrument using an AVANTES spectrometer with better optical characteristics. The instruments were looking in two different directions (one forward and one backward). Mobile MAX-DOAS measurements cover a quite large area in a short period of time. This enables to map existing gradients of concentrations of tropospheric trace gases, e.g. NO2 and HCHO. The results of those measurements then can be used to validate satellite measurements or can be compared to model results. In this study we focus on formaldehyde (HCHO). In small amounts it is emitted directly by industries and other anthropogenic and biogenic activities. Large amounts are mostly secondary produced. As it is an intermediate product of basic oxidation cycles of other hydrocarbons its concentrations are determined by the abundances of other hydrocarbons. Therefore it can be used as an indicator for volatile organic compounds (VOCs). Furthermore HCHO plays an important role in photochemical smog chemistry and tropospheric O3 chemistry. In this work we present the measurement setup and preliminary HCHO results of the AROMAT2

  18. Improvement of differential optical absorption spectroscopy with a multichannel scanning technique.

    PubMed

    Brauers, T; Hausmann, M; Brandenburger, U; Dorn, H P

    1995-07-20

    Differential optical absorption spectroscopy (DOAS) of atmospheric trace gases requires the detection of optical densities below 0.1%. Photodiode arrays are used more and more as detectors for DOAS because they allow one to record larger spectral intervals simultaneously. This type of optical multichannel analyzer (OMA), however, shows sensitivity differences among the individual photodiodes (pixels), which are of the order of 1%. To correct for this a sensitivity reference spectrum is usually recorded separately from the trace-gas measurements. Because of atmospheric turbulence the illumination of the detector while an atmospheric absorption spectrum is being recorded is different from the conditions during the reference measurement. As a result the sensitivity patterns do not exactly match, and the corrected spectra still show a residual structure that is due to the sensitivity difference. This effect usually limits the detection of optical densities to approximately 3 × 10(-4). A new method for the removal of the sensitivity pattern is presented in this paper: Scanning the spectrometer by small wavelength increments after each readout of the OMA allows one to separate the OMA-fixed pattern and the wavelength-fixed structures (absorption lines). The properties of the new method and its applicability are demonstrated with simulated spectra. Finally, first atmospheric measurements with a laser long-path instrument demonstrate a detection limit of 3 × 10(-5) of a DOAS experiment. PMID:21052280

  19. Development and metrological characterization of a tunable diode laser absorption spectroscopy (TDLAS) spectrometer for simultaneous absolute measurement of carbon dioxide and water vapor.

    PubMed

    Pogány, Andrea; Wagner, Steven; Werhahn, Olav; Ebert, Volker

    2015-01-01

    Simultaneous detection of two analytes, carbon dioxide (CO2) and water vapor (H2O), has been realized using tunable diode laser absorption spectroscopy (TDLAS) with a single distributed feedback diode laser at 2.7 μm. The dynamic range of the spectrometer is extended from the low parts per million to the percentage range using two gas cells, a single-pass cell with 0.77 m, and a Herriott-type multipass cell with 76 m path length. Absolute measurements were carried out, i.e., amount fractions of the analytes were calculated based on previously determined spectral line parameters, without the need for an instrument calibration using gas standards. A thorough metrological characterization of the spectrometer is presented. We discuss traceability of all parameters used for amount fraction determination and provide a comprehensive uncertainty assessment. Relative expanded uncertainties (k = 2, 95% confidence level) of the measured amount fractions are shown to be in the 2-3% range for both analytes. Minimum detectable amount fractions are 0.16 μmol/mol for CO2 and 1.1 μmol/mol for H2O for 76 m path length and 5 s averaging time. This corresponds to normalized detection limits of 27 μmol/mol m Hz(-1/2) for CO2 and 221 μmol/mol m Hz(-1/2) for H2O. Precision of the spectrometer, determined using Allan variance analysis, is 3.3 nmol/mol for CO2 and 21 nmol/mol for H2O. The spectrometer has been validated using reference gas mixtures with known CO2 and H2O amount fractions. An application example of the absolute TDLAS spectrometer as a reference instrument to validate other sensors is also presented.

  20. A new approach for the determination of sulphur in food samples by high-resolution continuum source flame atomic absorption spectrometer.

    PubMed

    Ozbek, N; Baysal, A

    2015-02-01

    The new approach for the determination of sulphur in foods was developed, and the sulphur concentrations of various fresh and dried food samples determined using a high-resolution continuum source flame atomic absorption spectrometer with an air/acetylene flame. The proposed method was optimised and the validated using standard reference materials, and certified values were found to be within the 95% confidence interval. The sulphur content of foods ranged from less than the LOD to 1.5mgg(-1). The method is accurate, fast, simple and sensitive.

  1. A Quantum Cascade Laser Absorption Spectrometer devoted to the in situ measurement of atmospheric N2O and CH4 emission fluxes.

    PubMed

    Mappé, I; Joly, L; Durry, G; Thomas, X; Decarpenterie, T; Cousin, J; Dumelie, N; Roth, E; Chakir, A; Grillon, P G

    2013-02-01

    This paper describes a Quantum Cascade Laser Absorption Spectrometer, called "QCLAS" that was developed to monitor in situ greenhouse gases like N2O and CH4, at high temporal resolution and with a high accuracy. The design of the laser sensor is reported as well as its performances in terms of precision error and field deployment capabilities. Finally, to demonstrate the efficiency and the robustness of QCLAS and its suitability for gas emission monitoring and for the determination of fluxes, we report the results from a field campaign, that took place in the Wallis and Futuna Islands in 2011, to investigate the impact of environmental intensive pig farming.

  2. Bromine Explosions In Smog Chamber Experiments: A comparison of Cavity-Enhanced (CE) and White-cell DOAS

    NASA Astrophysics Data System (ADS)

    Buxmann, J.; Hoch, D. J.; Sihler, H.; Pöhler, D.; Platt, U.; Bleicher, S.; Balzer, N.; Zetzsch, C.

    2011-12-01

    Reactive halogen species (RHS), such as Cl, Br or BrO, can significantly influence chemical processes in the troposphere, including the destruction of ozone, change in the chemical balance of hydrogen radicals (OH, HO2), increased deposition of toxic compounds (like mercury) with potential consequences for the global climate. Previous studies have shown that salt lakes can be significant sources for gaseous RHS. Environmental conditions such as salt composition, relative humidity (RH), pH, and temperature (T) can strongly influence reactive bromine levels, but are difficult to quantify in the field. Therefore, we conducted laboratory experiments by exposing NaCl salt containing 0.33% (by weight) NaBr to simulated sunlight in a Teflon smog-chamber under various conditions of RH and ozone concentrations. BrO levels were observed by a Differential-Optical-Absorption-Spectrometer (DOAS) in combination with a multi-reflection cell (White-cell). The concentrations of OH- and Cl- radicals were quantified by the radical clock method. We present the first direct observation of BrO from the "Bromine Explosion" (auto catalytic release of reactive bromine from salt surfaces - key to ozone destruction) in the laboratory above a simulated salt pan. The maximum BrO mixing ratio of 6419±71 ppt at 60% RH was observed to be one order of magnitude higher than at 37% RH and 2% RH. The release of RHS from the salt pan is possibly controlled by the thickness of the quasi liquid layer, covering the reactive surface of the halide crystals, as the layer thickness strongly depends on RH. Furthermore, a new cavity enhanced DOAS (CE-DOAS) instrument was designed and successfully used in chamber experiments. For the first time, such an instrument uses a spectral interval in the UV - wavelength range (325-365 nm) to identify BrO. We show a comparison of the CE-DOAS and White-cell DOAS instrument in a series of experiments, where e.g. a peak BrO mixing ratio up to 380 ppt within the first

  3. MAX-DOAS measurements of tropospheric NO2 over San Salvador: preliminary results

    NASA Astrophysics Data System (ADS)

    Alberti, Carlos; Wagner, Thomas

    2015-04-01

    We present the first Multi-AXis-Differential Optical Absorption Spectroscopy (MAX-DOAS) measurements at San Salvador. MAX-DOAS observes spectra of scattered sun light taken at different elevation angles. From the spectra the so called slant column density (SCD, the integrated trace gas concentration along the atmospheric light path) is derived. We quantify the dSCD of NO2 at different measurement conditions. From the measured NO2 SCDs we calculate the tropospheric vertical column density using the so called geometric approximation. The preliminary results of this MAX DOAS observations and the diurnal variation of the retrieved trace gas dSCDs will be presented. We also use the MAX-DOAS results for the validation of satellite observations.

  4. Total Ozone from the Ozone Monitoring System (OMI) using TOMS and DOAS Methods

    NASA Technical Reports Server (NTRS)

    Veefkind, J. P.; Bhartia, P. K.; Gleason, J.; deHaan, J. F.; Wellemeyer, C.; Levelt, P. F.

    2003-01-01

    The Ozone Monitoring Instrument (OMI) is the Dutch-Finnish contribution to NASA's EOS-Aura satellite scheduled for launch in January 2004. OMI is an imaging spectrometer that will measure the back-scattered Solar radiance in the wavelength range of 270 to 500 nm. The instrument provides near global coverage in one day with a spatial resolution of 13x24 square kilometers. OMI is a new instrument, with a heritage from TOMS, SBW, GOME, GOMOS and SCIAMACHY. OMI'S unique capabilities for measuring important trace gases and aerosols with a small footprint and daily global coverage, in conjunction with the other Aura instruments, will make a major contribution to our understanding of stratospheric and tropospheric chemistry and climate change. OMI will provide data continuity with the 23-year ozone record of TOMS. There are three ozone products planned for OMI: total column ozone, ozone profile and tropospheric column ozone. We are developing two different algorithms for total column ozone: one similar to the algorithm currently being used to process the TOMS data, and the other an improved version of the differential optical absorption spectroscopy (DOAS) method, which has been applied to GOME and SCIAMACHY data. The main reasons for starting with two algorithms for total ozone have to do with heritage and past experience; our long-term goal is to combine the two to develop a more accurate and reliable total ozone product for OMI. We will compare the performance of these two algorithms by applying both of them to the GOME data. We will examine where and how the results differ, and use the extensive TOMS-Dobson comparison studies to assess the performance of the DOAS algorithm.

  5. Comparison of ultraviolet absorbance, chemiluminescence, and DOAS instruments for ambient ozone monitoring.

    PubMed

    Williams, E J; Fehsenfeld, F C; Jobson, B T; Kuster, W C; Goldan, P D; Stutz, J; McClenny, W A

    2006-09-15

    This paper evaluates the accuracy of ozone measurements made by monitors that determine ozone concentrations in ambient air by UV absorption. These monitors are typically used to measure ozone for the purpose of establishing local compliance to air-quality standards. The study was predicated by the concern that commercially available UV absorbance O3 monitors may be subject to interference from volatile organic carbon (VOC) species that absorb light at 254 nm. To test for these and other effects, we compared simultaneous O3 measurements made by a commercial UV O3 monitor with an O3-NO chemiluminescence instrument, which is not subject to interference by VOC compounds. The comparisons were carried out in the summers of 1999 and 2000 at urban/industrial sites in Nashville and Houston, and in 2004 aboard a ship in the Gulf of Maine. In the two urban areas, we also compared the 03 measurements from these two methods with O3 measurements made by a long-path differential optical absorption spectrometer (DOAS). Our tests indicate that, with well-maintained monitors, there are no significant interferences even in areas with significant ambient concentrations of potentially interfering VOCs. PMID:17007137

  6. Improving Atmospheric Correction for Visible/Short Wave Infrared (VSWIR) Imaging Spectrometers with Iterative Fitting of Absorption By Three Phases of Water

    NASA Astrophysics Data System (ADS)

    Pennington, E. A.; Thompson, D. R.; Green, R. O.; Gao, B. C.

    2014-12-01

    Airborne imaging spectrometers like the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) offer valuable insight into the Earth's terrestrial and ocean ecosystems, mineralogy, and land use. Estimating surface reflectance requires accounting for atmospheric absorption, which is sensitive to the local abundance of water vapor. Analysts typically estimate water vapor concentrations using the depths of absorption features, which can be inaccurate by up to 50% over surface features containing liquid water or ice. This can bias the retrieved water vapor maps and create atmospheric artifacts in reflectance spectra. A new retrieval method offers significant accuracy improvements over plant canopies or ice by estimating the path lengths of all three phases of water simultaneously, adjusting absorptions to best fit the measurement over a broader spectral interval. This paper assesses the remaining sources of error for the three-phase retrieval technique. We analyze retrievals for synthetic data when the 940 and 1140 nm wavelength features are fitted, for initial vapor path estimates ranging from 0 to ±50% accuracy. These tests indicate that most error comes from inaccuracy in the initial path estimate used to obtain vapor absorption coefficients. We evaluate a modified algorithm that uses multiple iterations to refine this estimate. Error is found to approach a constant value, demonstrating improved robustness to initialization conditions. We also assess the new iterative method using corrected AVIRIS data over various environments. The iterative method yields significantly better water vapor maps, reducing spurious correlations between vegetation canopy water and vapor estimates. The new iterative method offers accuracy improvements over traditional Visible/Short Wave Infrared (VSWIR) atmospheric correction methods, at modest computational cost.

  7. Development of a space-borne spectrometer to monitor atmospheric ozone.

    PubMed

    Dobrolenskiy, Yury S; Ionov, Dmitry V; Korablev, Oleg I; Fedorova, Anna A; Zherebtsov, Evgeny A; Shatalov, Andrey E; Mantsevich, Sergey N; Belyaev, Denis A; Vyazovetskiy, Nikita A; Moiseev, Pavel P; Tchikov, Konstantin N; Krasavtsev, Valery M; Savushkin, Alexander V; Rumyantsev, Dmitry M; Kananykhin, Igor V; Viktorov, Alexey I; Kozyura, Alexey V; Moryakin, Sergey A; Poberovskii, Anatoly V

    2015-04-10

    A new compact satellite spectrometer dedicated to monitoring terrestrial atmospheric ozone (ozonometer) is in preparation for the Russian Geophysics Program. Four instruments at four satellites (Ionosphere) are intended to monitor the total ozone content by measuring spectra of scattered solar radiation in nadir. The spectrometer is based on the Rowland scheme with a concave holographic diffraction grating. It covers the near UV and visible range of the spectrum, 300-500 nm, with a spectral resolution of ∼0.3  nm. At present, a qualification model has been manufactured and tested. We introduce the description of the instrument and the results of laboratory and ground-based atmospheric calibrations. The ozone amount retrieved from atmospheric measurements using the differential optical absorption spectroscopy (DOAS) method is in good agreement with that measured by the collocated Brewer spectrophotometer and ozone monitoring instrument on board the Aura satellite. PMID:25967319

  8. A passive DOAS instrument for trace gas measurements on medium sized UAS: Instrumental design and first measurements.

    NASA Astrophysics Data System (ADS)

    Horbanski, Martin; Pöhler, Denis; Mahr, Tobias; Wagner, Thomas; Keleshis, Christos; Ioannou, Stelios; Lange, Manfred A.; Lelieveld, Jos; Platt, Ulrich

    2013-04-01

    Unmanned Aerial Systems (UAS) are a new powerful tool for observations in the atmospheric boundary layer. Recent developments in measuring technology allow the construction of compact and sensitive active and passive DOAS instruments which can fit the space and weight constraints on UAS. This opens new possibilities for trace gas measurements in the lower troposphere, especially in areas which are not accessible to manned aviation e.g. volcanic plumes or which should be monitored regularly (e.g. industrial emissions of a stack). We present a new developed passive DOAS instrument for the APAESO Platform of the Cyprus Institute, a medium size UAS. It is equipped with two telescopes for observations in downward (nadir) and horizontal (limb) viewing direction, respectively. Thus it allows determining height profiles and the horizontal distribution of trace gases. This is accomplished by analyzing the radiation collected by the telescopes with compact spectrometers, which cover the UV-blue spectral range allowing to measure a broad variety of atmospheric trace gases (e.g. NO2, SO2, BrO, IO, H2O ...) as well as aerosol properties via O4 absorption. Additionally, the nadir direction is equipped with a VIS-NIR spectrometer. It is used to measure reflection spectra of different types of vegetation. These will serve as references for satellite measurements to create global maps. First measurements on the APAESO platform were performed in October 2012 on Cyprus in a rural area south of Nicosia. The instrument is shown to work reliably and was able to detect NO2, H2O and O4 at atmospheric column densities. The instrumental design and first measurements will be presented and discussed.

  9. Intercomparison of MAX-DOAS NO2 retrieval algorithms

    NASA Astrophysics Data System (ADS)

    Peters, Enno; Pinardi, Gaia; Bösch, Tim; Wittrock, Folkard; Richter, Andreas; Burrows, John P.; Van Roozendael, Michel; Piters, Ankie; Wagner, Thomas; Drosoglou, Theano; Bais, Alkis; Wang, Shanshan; Saiz-Lopez, Alfonso

    2016-04-01

    Ground-based Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) measurements are a powerful method for monitoring of atmospheric composition in an automated way. The number of instruments and sites operated has been rapidly increasing over the last years. However, integrating the measurements from all these instruments into a consistent data set necessitates careful homogenization of measurements and data retrieval procedures. For this reason, several MAX-DOAS intercomparison campaigns have been carried out in the last years. Mostly, slant columns measured by different instruments and retrieved by different software were intercompared, i.e. observed differences were potentially caused by both, the instrument and/or the retrieval. In contrast, the approach presented here is a pure intercomparison of MAX-DOAS retrievals. In total, 16 international groups and institutes working in the field of MAX-DOAS participated. The work was performed as part of the EU-funded QA4ECV project. The intercomparison exercise is based on data recorded by the IUP-Bremen MAX-DOAS instrument during the MAD-CAT campaign (Multi-Axis DOAS comparison campaign for Aerosols and Trace gases), which was carried out at the Max-Planck-Institute of Chemistry in Mainz, Germany, in summer 2013. Each group participating in the exercise presented here performed MAX-DOAS fits using their own retrieval software but common input (IUP-Bremen spectra, same cross-sections, and same fit settings). The resulting slant columns show in general an excellent agreement (correlation coefficient > 99.9%). Surprisingly, the correlation is substantially smaller when using sequential Fraunhofer reference spectra instead of a noon reference indicating that groups calculate the sequential reference differently. Further differences were found to arise from treatment of the slit function and subsequent convolution of cross-sections as well as from wavelength calibration. The results indicate overall a high

  10. Real-time calibration of laser absorption spectrometer using spectral correlation performed with an in-line gas cell.

    PubMed

    Smith, Clinton J; Wang, Wen; Wysocki, Gerard

    2013-09-23

    A real-time drift correction and calibration method using spectral correlation based on a revolving in-line gas cell for laser-based spectroscopic trace-gas measurements has been developed and evaluated experimentally. This technique is relatively simple to implement in laser spectroscopy systems and assures long-term stability of trace-gas measurements by minimizing the effects of external sources of drift in real-time. Spectroscopic sensitivity sufficient for environmental monitoring and effective drift suppression has been achieved for long-term measurements of CO₂ with a quantum cascade laser based spectrometer.

  11. Use of a fast near-infrared spectrometer for absorption and emission measurements within the expanding blast wave of a high explosive

    NASA Astrophysics Data System (ADS)

    Koch, Jon D.; Carney, Joel; Lightstone, James; Piecuch, Scott

    2012-03-01

    We demonstrate the use of a fast InGaAs array and spectrometer to measure properties related to near-infrared absorption and emission (750 nm -1500 nm) following a high explosive detonation. Using a broadband light source and a rigid absorption gauge, gas temperatures are measured at a rate of 20 kHz for a period of several milliseconds behind the blast wave from a PETN, PBXN-5, and PBXN-113 detonations. The temperature and concentration of water vapor is determined by fitting experimental transmission spectra to a simulated database. Strong emission signatures obtained during the PETN breakout event (integrated over approximately the first 20 microseconds) indicate the presence of high energy nitrogen and oxygen atoms. Measurements from water absorption at a distance of 23 cm from the PETN charge indicate temperatures decaying from 1600 K to 600 K during the first few milliseconds, and measurements of non-ideal explosives with optically thick postdetonation environments are also demonstrated. These measurements are intended to aid the development of detonation and explosive simulations.

  12. Signal to Noise Ratio in Digital Lock-in Detection for Multiple Intensity-Modulated Signals in CO2 Laser Absorption Spectrometer

    NASA Astrophysics Data System (ADS)

    CHEN, S.; Lin, B.; Harrison, F. W.; Nehrir, A. R.; Campbell, J. F.; Refaat, T.; Abedin, N. M.; Obland, M. D.; Ismail, S.; Meadows, B. L.

    2013-12-01

    NASA Langley Research Center is investigating Intensity-Modulated, Continuous-Wave Laser Absorption Spectrometers (LASs) for the measurement of atmospheric carbon dioxide (CO2) column mixing ratio from both air- and space-borne platforms. The LAS system uses high-power fiber lasers/amplifiers in the 1.57-um CO2 absorption band and the 1.26-um O2 absorption band in the transmitters and simultaneous digital lock-in detection for the multiple intensity-modulated signals with different modulation waveforms , such as simple sinusoidal waves at different frequencies, associated with different wavelengths in the receivers. The Signal to Noise Ratio (SNR) of the simultaneous digital lock-in detection in the system is of interest for the system designs and the performance prediction of airborne and space-borne implementations in the future. This paper will discuss the properties of the signals and various noises in the LAS system, especially for the simultaneous digital lock-in detection with a single detector for the multiple intensity-modulated signals at different frequencies. The numerical simulation of the SNR for the simultaneous digital lock-in detection in terms of relative intensity of the multiple modulated signals and the integration time, and an initial experimental verification will be presented.

  13. Further advancement of differential optical absorption spectroscopy: theory of orthogonal optical absorption spectroscopy.

    PubMed

    Liudchik, Alexander M

    2014-08-10

    A modified version of the differential optical absorption spectroscopy (DOAS) method is presented. The technique is called orthogonal optical absorption spectroscopy (OOAS). A widespread variant of DOAS with smoothing of the registered spectrum and absorption cross sections being made employing a polynomial regression is a particular case of OOAS. The concept of OOAS provides a variety of new possibilities for constructing computational schemes and analyzing the influence of different error sources on calculated concentrations. PMID:25320931

  14. Development of a Near-Ir Cavity Enhanced Absorption Spectrometer for the Detection of Atmospheric Oxidation Products and Organoamines

    NASA Astrophysics Data System (ADS)

    Eddingsaas, Nathan C.; Jewell, Breanna; Thurnherr, Emily

    2014-06-01

    An estimated 10,000 to 100,000 different compounds have been measured in the atmosphere, each one undergoes many oxidation reactions that may or may not degrade air quality. To date, the fate of even some of the most abundant hydrocarbons in the atmosphere is poorly understood. One difficulty is the detection of atmospheric oxidation products that are very labile and decompose during analysis. To study labile species under atmospheric conditions, a highly sensitive, non-destructive technique is needed. Here we describe a near-IR incoherent broadband cavity enhanced absorption spectroscopy (IBBCEAS) setup that we are developing to meet this end. We have chosen to utilize the near-IR, where vibrational overtone absorptions are observed, due to the clean spectral windows and better spectral separation of absorption features. In one spectral window we can simultaneously and continuously monitor the composition of alcohols, hydroperoxides, and carboxylic acids in an air mass. In addition, we have used our CEAS setup to detect organoamines. The long effective path length of CEAS allows for low detection limits, even of the overtone absorption features, at ppb and ppt levels.

  15. Simple system for measuring tritium Ad/absorption using a 2. pi. counter and thermal desorption spectrometer

    SciTech Connect

    Miyake, H.; Matsuyama, M.; Watanabe, K. ); Cowgill, D.F. )

    1992-03-01

    In this paper, the authors develop a simple system using tritium tracer and thermal desorption techniques to measure the tritium adsorption and/or absorption on/in a material having typical surface conditions: namely, not cleaned surface. The tritium counting devices used were a 2{pi} counter and conventional proportional counter. With this system, the amounts of ad/absorption could be measured without exposing the samples to air after exposing them to tritium gas. The overall efficiency (F) of the 2{pi} counter was described at F = exp({minus}2.64h), where h is the distance from the sample to the detector. Ad/absorption measurements were carried out for several materials used for fabricating conventional vacuum systems. The results were, in the order of decreasing amounts of ad/absorption, as (fiber reinforced plastics(FRP)) {gt} (nickel(Ni), molybdenum disulfide(MoS{sub 2})) {gt} (stainless steel (SS304), iron(Fe), aluminum alloy(A2219)) {gt} (boron nitride(h-BN), silicon carbide (SiC), SS304 passivated by anodic oxidation layers(ASS) and that by boron nitride segregation layers (BSS)). The relative amounts were abut 100 for Ni and 0.1 for ASS and BSS, being normalized to Fe = 1.

  16. Direct determination of cadmium and copper in seawater using a transversely heated graphite furnace atomic absorption spectrometer with Zeeman-effect background corrector.

    PubMed

    Chan, M S; Huang, S D

    2000-02-01

    Methods for the direct determination of copper and cadmium in seawater were described using a graphite furnace atomic absorption spectrometer (GFAAS) equipped with a transversely heated graphite atomizer (THGA) and a longitudinal Zeeman effect background corrector. Ammonium nitrate was used as the chemical modifier to determine copper. The mixture of di-ammonium hydrogen phosphate and ammonium nitrate was used as the chemical modifier to determine cadmium. The matrix interference was removed completely so that a simple calibration curve method could be applied. This work is the first one with the capability of determining cadmium in unpolluted seawater directly with GFAAS using calibration curve based on simple aqueous standards. The accuracy of the methods was confirmed by analysis of three kinds of certified reference saline waters. The detection limits (LODs), with injection of a 20-mul aliquot of seawater sample, were 0.06 mug l(-1) for copper and 0.005 mug l(-1) for cadmium.

  17. In situ ozone data for evaluation of the laser absorption spectrometer ozone remote sensor: 1979 southeastern Virginia urban plume study summer field program

    NASA Technical Reports Server (NTRS)

    Gregory, G. L.; Mcdougal, D. S.; Mathis, J. J., Jr.

    1980-01-01

    Ozone data from the 1979 Southeastern Virginia Urban Study (SEV-UPS) field program are presented. The SEV-UPS was conducted for evaluation of an ozone remote sensor, the Laser Absorption Spectrometer. During the measurement program, remote-sensor evaluation was in two areas; (1) determination of the remote sensor's accuracy, repeatability, and operational characteristics, and (2) demonstration of the application of remotely sensed ozone data in air-quality studies. Data from six experiments designed to provide in situ ozone data for evaluation of the sensor in area 1, above, are presented. Experiments consisted of overflights of a test area with the remote sensor aircraft while in situ measurements with a second aircraft and selected surface stations provided correlative ozone data within the viewing area of the remote sensor.

  18. Monitoring vegetation using DOAS satellite observations

    NASA Astrophysics Data System (ADS)

    Eigemeier, E.; Beirle, S.; Marbach, T.; Platt, U.; Wagner, T.

    2009-04-01

    Vegetation-cycles are of general interest for many applications. Be it for harvest-predictions, global monitoring of climate-change or as input to atmospheric models. From novel spectrally resolving UV/vis satellite instruments (like GOME of SCIAMACHY) the spectral signatures of different types of vegetation can be identified and analysed. Although the spatial resolution of GOME and SCIAMACHY observations is much coarser than those of conventional satellite instruments for vegetation monitoring, our data sets on different vegetation types add new and useful information, not obtainable from other sources. Common Vegetation Indices use the fact that the difference between Red and Near Infrared reflection is higher than in any other material on Earth's surface. This gives a very high degree of confidence for vegetation-detection. The spectrally resolving data from GOME and SCIAMACHY provide the chance to concentrate on finer spectral features throughout the Red and Near Infrared spectrum. We look at these using a technique known as Differential Optical Absorption Spectroscopy (DOAS). Although originally developed to retrieve information on trace gases, it can also be used to gain information on vegetation. Another advantage is that this method automatically corrects for changes in the atmosphere. This renders the vegetation-information easily comparable over long time-spans. In addition, high-frequency-structures from vegetation also effect the retrieval of tropospheric trace-gases and aerosols. To optimize vegetation monitoring with DOAS we produce spectrally resolved reference spectra from different vegetation types. We investigate how well we will be able to distinguish vegetation types from space. This will also be valuable for monitoring global vegetation-cycles over long time spans. Preliminary results will be presented here.

  19. Multisnapshot Sparse Bayesian Learning for DOA

    NASA Astrophysics Data System (ADS)

    Gerstoft, Peter; Mecklenbrauker, Christoph F.; Xenaki, Angeliki; Nannuru, Santosh

    2016-10-01

    The directions of arrival (DOA) of plane waves are estimated from multi-snapshot sensor array data using Sparse Bayesian Learning (SBL). The prior source amplitudes is assumed independent zero-mean complex Gaussian distributed with hyperparameters the unknown variances (i.e. the source powers). For a complex Gaussian likelihood with hyperparameter the unknown noise variance, the corresponding Gaussian posterior distribution is derived. For a given number of DOAs, the hyperparameters are automatically selected by maximizing the evidence and promote sparse DOA estimates. The SBL scheme for DOA estimation is discussed and evaluated competitively against LASSO ($\\ell_1$-regularization), conventional beamforming, and MUSIC

  20. Stratospheric methane profiles from SCIAMACHY solar occultation measurements derived with onion peeling DOAS

    NASA Astrophysics Data System (ADS)

    Noël, S.; Bramstedt, K.; Rozanov, A.; Bovensmann, H.; Burrows, J. P.

    2011-11-01

    Stratospheric methane (CH4) profiles have been derived from solar occultation measurements of the SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY) on ENVISAT with an updated version of the Onion Peeling DOAS (ONPD) method. The SCIAMACHY solar occultation measurements cover the latitudinal range between about 50° N and 70° N. Currently, reasonable results are obtained between 20 and 40 km altitude. Comparisons with correlative ACE-FTS measurements show an average agreement within the expected accuracy of the ACE-FTS data of about 10%. To demonstrate the capability of SCIAMACHY solar occultation measurements in the context of greenhouse gas monitoring, time series of stratospheric CH4 profiles covering the period from 2003 to 2010 have been generated. The SCIAMACHY CH4 profile solar occultation temporal series shows a strong seasonal cycle. This is attributed to the variations in both time and space of the retrieved data set. At lower altitudes, the observed temporal variations are explained by variations of the tropopause height. The temporal data set is also impacted by variations of the size and duration of the polar vortex in the northern hemisphere. The data set provides unique information about CH4 changes in the stratosphere at mid to high latitudes.

  1. Stratospheric methane profiles from SCIAMACHY solar occultation measurements derived with onion peeling DOAS

    NASA Astrophysics Data System (ADS)

    Noël, S.; Bramstedt, K.; Rozanov, A.; Bovensmann, H.; Burrows, J. P.

    2011-07-01

    Stratospheric methane (CH4) profiles have been derived from solar occultation measurements of the SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY) on ENVISAT with an updated version of the Onion Peeling DOAS (ONPD) method. The SCIAMACHY solar occultation measurements cover the latitudinal range between about 50° N and 70° N. Currently, reasonable results are obtained between 20 and 40 km altitude. Comparisons with correlative ACE-FTS measurements show an average agreement within the expected accuracy of the ACE-FTS data of about 10 %. To demonstrate the capability of SCIAMACHY solar occultation measurements in the context of greenhouse gas monitoring, time series of stratospheric CH4 profiles covering the period from 2003 to 2010 have been generated. The SCIAMACHY CH4 profile solar occultation temporal series shows a strong seasonal cycle. This is attributed to the variations in both time and space of the retrieved data set. At lower altitudes, the observed temporal variations are explained by variations of the tropopause height. The temporal data set is also impacted by variations of the size and duration of the polar vortex in the northern hemisphere. The data set provides unique information about CH4 changes in the stratosphere at mid to high latitudes.

  2. [Determination of the retrieval arithmetic of aerosol size distribution measured by DOAS].

    PubMed

    Si, Fu-qi; Xie, Pin-hua; Liu, Jian-guo; Zhang, Yu-jun; Liu, Wen-qing; Hiroaki, Kuze; Nobuo, Takeuchi

    2008-10-01

    Atmospheric aerosol is not only an important factor for the change in global climate, but also a polluting matter. Moreover, aerosol plays a main role in chemical reaction of polluting gases. Determination of aerosol has become an important re- search in the study of atmospheric environment. Differential optical absorption spectroscopy (DOAS) is a very useful technique that allows quantitative measurement of atmospheric trace gas concentrations based on their fingerprint absorption. It also can be used to retrieve aerosol extinction coefficient. In the present work, the method of determination of aerosol size distribution measured by flash DOAS is described, and the arithmetic based on Monte-Carlo is the emphasis. By comparison with the concentration of PM10, visibility and Angstrom wavelength exponent, a good correlation can be found. Application of DOAS in aerosol field not only provides a novel method for aerosol detection, but also extends the field of application of DOAS technology. Especially, aerosol DOAS plays an important role in the study of atmospheric chemistry.

  3. [Determination of the retrieval arithmetic of aerosol size distribution measured by DOAS].

    PubMed

    Si, Fu-qi; Xie, Pin-hua; Liu, Jian-guo; Zhang, Yu-jun; Liu, Wen-qing; Hiroaki, Kuze; Nobuo, Takeuchi

    2008-10-01

    Atmospheric aerosol is not only an important factor for the change in global climate, but also a polluting matter. Moreover, aerosol plays a main role in chemical reaction of polluting gases. Determination of aerosol has become an important re- search in the study of atmospheric environment. Differential optical absorption spectroscopy (DOAS) is a very useful technique that allows quantitative measurement of atmospheric trace gas concentrations based on their fingerprint absorption. It also can be used to retrieve aerosol extinction coefficient. In the present work, the method of determination of aerosol size distribution measured by flash DOAS is described, and the arithmetic based on Monte-Carlo is the emphasis. By comparison with the concentration of PM10, visibility and Angstrom wavelength exponent, a good correlation can be found. Application of DOAS in aerosol field not only provides a novel method for aerosol detection, but also extends the field of application of DOAS technology. Especially, aerosol DOAS plays an important role in the study of atmospheric chemistry. PMID:19123420

  4. [MAX-DOAS Tomography Reconstruction for Gas Plume].

    PubMed

    Wei, Min-hong; Tong, Min-ming; Li, Su-wen; Xiao, Jian-yu

    2015-08-01

    In order to achieve precisely two-dimensional spatial distribution reconstruction of smoke plume, passive MAX-DOAS tomography is established, the measurement of the spatial distribution of the exhaust plume is implemented by more passive multi-axis differential absorption spectrum system. First, the multi-axis differential absorption spectrum system and its mechanism of inverse gas concentration are introduced in the paper. Then, algebra iterative algorithm is adopted to extract the information of the trace gas concentration in reconstruction simulation with different models and different scanning optical path, and the reconstruction program is designed. Then, the numerical simulation results are compared. Finally, a platform of multi-axis differential absorption optical tomography system is set up, a field campaign was carried out. The numerical simulation results show that the MAX-DOAS tomography can accurately reconstruct two-dimensional spatial distribution of plume model, the re- construction error of MAX-DOAS tomography with four light sources is about a third of the reconstruction error with double light sources, moreover, the reconstruction time is about a quarter of the reconstruction time of double light sources, and the reconstruction error of the twin peaks model is greater than that of the one peak model. Field test results show that the integral data of reconstruction image is consistent with the measured projection data of multi-axis differential absorption spectrum, the spatial distribution reconstruction of plume is in line with the actual situation. Studies have shown that the result of numerical simulation and field test results have consistency. PMID:26672304

  5. [MAX-DOAS Tomography Reconstruction for Gas Plume].

    PubMed

    Wei, Min-hong; Tong, Min-ming; Li, Su-wen; Xiao, Jian-yu

    2015-08-01

    In order to achieve precisely two-dimensional spatial distribution reconstruction of smoke plume, passive MAX-DOAS tomography is established, the measurement of the spatial distribution of the exhaust plume is implemented by more passive multi-axis differential absorption spectrum system. First, the multi-axis differential absorption spectrum system and its mechanism of inverse gas concentration are introduced in the paper. Then, algebra iterative algorithm is adopted to extract the information of the trace gas concentration in reconstruction simulation with different models and different scanning optical path, and the reconstruction program is designed. Then, the numerical simulation results are compared. Finally, a platform of multi-axis differential absorption optical tomography system is set up, a field campaign was carried out. The numerical simulation results show that the MAX-DOAS tomography can accurately reconstruct two-dimensional spatial distribution of plume model, the re- construction error of MAX-DOAS tomography with four light sources is about a third of the reconstruction error with double light sources, moreover, the reconstruction time is about a quarter of the reconstruction time of double light sources, and the reconstruction error of the twin peaks model is greater than that of the one peak model. Field test results show that the integral data of reconstruction image is consistent with the measured projection data of multi-axis differential absorption spectrum, the spatial distribution reconstruction of plume is in line with the actual situation. Studies have shown that the result of numerical simulation and field test results have consistency.

  6. DOAS evaluation of volcanic SO2 using a modeled background spectrum: Examples from the NOVAC stations at Nevado del Ruiz (Colombia) and Tungurahua (Ecuador)

    NASA Astrophysics Data System (ADS)

    Lübcke, Peter; Lampel, Johannes; Bobrowski, Nicole; Arellano, Santiago; Galle, Bo; Garzón, Gustavo; Hidalgo, Silvana; Vogel, Leif; Warnach, Simon; Platt, Ulrich

    2015-04-01

    SO2 emission rates are monitored using Differential Optical Absorption Spectroscopy (DOAS) in the UV at an increasing number of volcano observatories. The Network for Observation of Volcanic and Atmospheric Change (NOVAC) has currently installed 80 scanning DOAS instruments at 30 volcanoes world-wide. One important question for the evaluation of spectra using DOAS is the availability of background spectra that are not influenced by volcanic gas emissions. An SO2 contaminated background spectrum would lead to a negative offset of the retrieved SO2 column densities, and thus to an underestimation of the volcanic SO2 emission rate. In NOVAC this problem is approached by performing a scan, e.g. through a plane from one horizon to the other horizon, and defining the average of the 20% spectra with the lowest SO2 content as the zero-baseline value, which is assumed to be gas free. To verify this assumption we revisit the idea of evaluating spectra using the DOAS method with a modeled background spectrum based on a high-resolution solar atlas. One challenge when evaluating spectra with a modeled background spectrum is properly accounting for instrumental effects that are usually removed when calculating the measured optical density relative to a measured background spectrum. We present our approach to handle these instrumental effects, showing that we gain a similar fit quality to the method using a measured reference spectrum. For example, wavelength dependent structures in the spectrum due to the spectrometer (e.g., quantum efficiency of the detector and grating efficiency) were identified with help of a principal component analysis of an SO2 free subset of the residual spectra. These structures were included in a second iteration of the fit in order to improve the evaluation. We further discuss influences like strong ozone absorption and the instrument temperature on the quality of the SO2 fit using a modeled background spectrum. The new evaluation scheme was applied

  7. Development and application of a low-cost, portable DOAS system for stratospheric composition monitoring over the Argentinean Patagonia and Antarctic stations.

    NASA Astrophysics Data System (ADS)

    Raponi, Marcelo; Jiménez, Rodrigo; Ristori, Pablo; Wolfram, Elian; Tocho, Jorge; Quel, Eduardo

    2010-05-01

    challenge. Also, we present measurements carry out at the Marambio Antarctic Base (64° 14' S; 56° 37' W, 197 m asl) during the months of January - February of 2008, using the ERO-DOAS. The NO2 and O3 VCD are derived from solar spectra acquired during the twilights (zenithal angles between 87° - 92° ), using the DOAS (Differential Optical Absorption Spectroscopy) technique. The biggest contribution to these spectra comes from the stratosphere, atmosphere layer that we want to study. The analysis is carried out by solving the Beer-Lambert-Bouger (BLB) law for all the atmospheric absorbers and a quasi-continuous wavelength range. The algorithm minimizes the fitting residuals to the BLB law, having as unknown the slant column density of the species to determine. The effects of Rayleigh and Mie scattering, fluorescence and most of the Raman scattering are accounted for and subtracted out using a high-pass polynomial filter. We compare the data acquired by our DOAS system with co-located measurements performed with EVA, a visible absorption spectrometer operated by the Instituto Nacional de Técnica Aeroespacial (INTA), Spain. Additionally, a comparative study is presented among the ground-based signals and those obtained by the instrument OMI (AURA satellite). The bigger mistake sources associated with the comparison between AURA satellite observations and those carried out from earth are: a) NOx daily cycle, b) NO2 natural variability, and c) NO2 tropospheric sensibility. In the case of Marambio, it hasn't relevance since it is non polluted places and the tropospheric NO2 level is very low. We observe that the NO2 has a strong photochemical variability during the day. This variability is associated with the solar cycle, the NOx vertical distribution, the temperature in the high layers of the atmosphere and sometimes (in high latitudes) of other active species.

  8. Wavelength-Dependent Optical Absorption Properties of Artificial and Atmospheric Aerosol Measured by a Multi-Wavelength Photoacoustic Spectrometer

    NASA Astrophysics Data System (ADS)

    Utry, N.; Ajtai, T.; Pintér, M.; Bozóki, Z.; Szabó, G.

    2014-12-01

    Various aspects of the photoacoustic (PA) detection method are discussed from the point of view of developing it into a routine tool for measuring the wavelength-dependent optical absorption coefficient of artificial and atmospheric aerosol. The discussion includes the issues of calibration, cross-sensitivity to gaseous molecules, background PA signal subtraction, and size-dependent particle losses within the PA system. The results in this paper are based on a recently developed four-wavelength PA system, which has operational wavelengths in the near-infrared, in the visible, and in the ultraviolet. The measured spectra of artificial and atmospheric aerosol prove the outstanding applicability of the presented PA system.

  9. Inter-comparison of 2 microm Heterodyne Differential Absorption Lidar, Laser Diode Spectrometer, LICOR NDIR analyzer and flasks measurements of near-ground atmospheric CO2 mixing ratio.

    PubMed

    Gibert, Fabien; Joly, Lilian; Xuéref-Rémy, Irène; Schmidt, Martina; Royer, Adrien; Flamant, Pierre H; Ramonet, Michel; Parvitte, Bertrand; Durry, Georges; Zéninari, Virginie

    2009-01-01

    Remote sensing and in situ instruments are presented and compared in the same location for accurate CO(2) mixing ratio measurements in the atmosphere: (1) a 2.064 microm Heterodyne DIfferential Absorption Lidar (HDIAL), (2) a field deployable infrared Laser Diode Spectrometer (LDS) using new commercial diode laser technology at 2.68 microm, (3) LICOR NDIR analyzer and (4) flasks. LDS, LICOR and flasks measurements were made in the same location, LICOR and flasks being taken as reference. Horizontal HDIAL measurements of CO(2) absorption using aerosol backscatter signal are reported. Using new spectroscopic data in the 2 microm band and meteorological sensor measurements, a mean CO(2) mixing ratio is inferred by the HDIAL in a 1 km long path above the 15m height location of the CO(2) in situ sensors. We compare HDIAL and LDS measurements with the LICOR data for 30 min of time averaging. The mean standard deviation of the HDIAL and the LDS CO(2) mixing ratio results are 3.3 ppm and 0.89 ppm, respectively. The bias of the HDIAL and the LDS measurements are -0.54 ppm and -0.99 ppm, respectively. PMID:18718810

  10. Feasibility study on 1.6 μm continuous-wave modulation laser absorption spectrometer system for measurement of global CO2 concentration from a satellite.

    PubMed

    Kameyama, Shumpei; Imaki, Masaharu; Hirano, Yoshihito; Ueno, Shinichi; Kawakami, Shuji; Sakaizawa, Daisuke; Kimura, Toshiyoshi; Nakajima, Masakatsu

    2011-05-10

    A feasibility study is carried out on a 1.6 μm continuous-wave modulation laser absorption spectrometer system for measurement of global CO(2)concentration from a satellite. The studies are performed for wavelength selection and both systematic and random error analyses. The systematic error in the differential absorption optical depth (DAOD) is mainly caused by the temperature estimation error, surface pressure estimation error, altitude estimation error, and ON wavelength instability. The systematic errors caused by unwanted backscattering from background aerosols and dust aerosols can be reduced to less than 0.26% by using a modulation frequency of around 200 kHz, when backscatter coefficients of these unwanted backscattering have a simple profile on altitude. The influence of backscattering from cirrus clouds is much larger than that of dust aerosols. The transmission power required to reduce the random error in the DAOD to 0.26% is determined by the signal-to-noise ratio and the carrier-to-noise ratio calculations. For a satellite altitude of 400 km and receiving aperture diameter of 1 m, the required transmission power is approximately 18 W and 70 W when albedo is 0.31 and 0.08, respectively; the total measurement time in this case is 4 s, which corresponds to a horizontal resolution of 28 km.

  11. FTIR spectrometer with 30 m optical cell and its applications to the sensitive measurements of selective and nonselective absorption spectra

    NASA Astrophysics Data System (ADS)

    Ponomarev, Yu. N.; Solodov, A. A.; Solodov, A. M.; Petrova, T. M.; Naumenko, O. V.

    2016-07-01

    A description of the spectroscopic complex at V.E. Zuev Institute of Atmospheric Optics, SB RAS, operating in a wide spectral range with high threshold sensitivity to the absorption coefficient is presented. Measurements of weak lines and nonselective spectra of CO2 and H2O were performed based on the built setup. As new application of this setup, positions and intensities of 152 weak lines of H2O were measured between 2400 and 2560 cm-1 with threshold sensitivity of 8.6×10-10 cm-1, and compared with available calculated and experimental data. Essential deviations between the new intensity measurements and calculated data accepted in HITRAN 2012 and GEISA 2015 forthcoming release are found.

  12. The New MAX-DOAS Network in Mexico City for Trace Gas Detection

    NASA Astrophysics Data System (ADS)

    Arellano, E. J.; Krüger, A.; Rivera, C. I.; Stremme, W.; Friedrich, M. M.; Grutter, M.

    2014-12-01

    Atmospheric studies in large cities are of great relevance since pollution affects air quality and human health. We have designed and built instruments based on the Multi Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) technique and established a network in strategic sites within the Mexico City metropolitan area. Four instruments are now in operation with the aim to study the variability and spatial distribution of key pollutants, which will bring new insight in the current knowledge of transport patterns, emissions as well as frequency and origin of extraordinary events. The instruments measure UV/visible spectra of the sky at different elevation angles in the 280 nm to 510 nm wavelength region along one axis. Currently, 36 measurements constitute a full scan performed from west until East direction (-90 to +90°). The scanning unit, which is installed outdoors, holds a small telescope and the motor control unit. Light is transmitted via an optical fiber to the main box, which holds a compact USB spectrometer and the main control electronics. The spectrometer is accurately temperature controlled and all the spectra of each scan, together with elevation angle and other parameters, are recorded on a compact PC. Post processing of these data with the QDOAS software results in slant column densities (SCD) of the atmospheric gases. This information is then converted to vertical profiles through a process described in a companion presentation. Preliminary results will be presented for formaldehyde, fitted in the region 324-360 nm. The data obtained is useful for the comparison with satellite data for example OMI.

  13. DOAS measurements of tropospheric bromine oxide in mid-latitudes

    PubMed

    Hebestreit; Stutz; Rosen; Matveiv; Peleg; Luria; Platt

    1999-01-01

    Episodes of elevated bromine oxide (BrO) concentration are known to occur at high latitudes in the Arctic boundary layer and to lead to catalytic destruction of ozone at those latitudes; these events have not been observed at lower latitudes. With the use of differential optical absorption spectroscopy (DOAS), locally high BrO concentrations were observed at mid-latitudes at the Dead Sea, Israel, during spring 1997. Mixing ratios peaked daily at around 80 parts per trillion around noon and were correlated with low boundary-layer ozone mixing ratios.

  14. An automated on-line minicolumn preconcentration cold vapour atomic absorption spectrometer: application to determination of cadmium in water samples.

    PubMed

    Sahan, Serkan; Sahin, Uğur

    2012-01-15

    A method was developed for on-line solid phase preconcentration and cold vapour atomic absorption spectrometric determination of Cd(II) in aqueous samples. Lewatit Monoplus TP207 iminodiacetate chelating resin was used for the separation and preconcentration of Cd(II) ions at pH 4.0. The whole system was labmade. The influence of analytical parameters such as concentration of eluent and sodium tetrahydroborate solution, flow rate of eluent, sample, and Ar, and matrix ions were investigated. A preconcentration factor of 20 and a detection limit (3s(b)) of 2.1ngL(-1), along with a sampling frequency of 28h(-1) were achieved with 1.4min of sample loading time and with 2.8mL sample consumption. The relative standard deviation (R.S.D.) was 2.5% for 0.05μgL(-1) Cd(II) level. The developed method was used for Cd(II) analysis in water samples. The certified reference material (LGC6019) experimental results are in good agreement with the certified value.

  15. Multiple Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) observations of Bromine Monoxide (BrO) and ozone over the ice in Arctic and Sub Arctic in the winter, spring and summer of 2008 and 2009

    NASA Astrophysics Data System (ADS)

    Netcheva, Stoyka; Bottenheim, Jan; Bobrowski, Nicole; Staebler, Ralf; Chang, Rachel

    2010-05-01

    Ozone is frequently nearly completely removed from the marine boundary layer in the Polar Regions during the spring time every year. Those spring-time boundary layer ozone depletion events (ODE) are driven by reactive bromine liberated from saline surfaces. ODEs are usually found to be associated with enhanced BrO in the troposphere. ODEs and elevated BrO values over Polar Regions were recorded at ground coastal observation stations, through satellite observations and during a limited number of intensive measurements conducted on board research marine based and aircraft platforms. Improvements of the measurements, retrieval precision and spatial and temporal coverage have been made over the years. However, many questions about the processes remain unanswered including initiation and recycling mechanisms, the role of different surfaces and meteorological conditions for bromine release and recycling, and their vertical extent. Out On The Ice (OOTI) is a fully automated observatory designed to measure BrO, ozone and gaseous elemental mercury along with meteorological parameters in the cold remote Arctic environment. It was developed under OASIS-Canada ("Ocean Atmosphere Sea Ice and Snow interactions in Polar regions") framework to study air-surface interactions right above the sea ice surface. An overview of this work will be presented of the MAX-DOAS BrO and in-situ ozone measurements from four field campaigns selected for recurring elevated BrO values and frequent ozone depletion episodes. The characteristics of the surrounding surface and environmental variables such as temperature, solar radiation, winds speed and direction are combined with back trajectory analysis to improve our understanding on the factors affecting the presence and origin of BrO at specific locations.

  16. Signal-to-Noise Enhancement Techniques for Quantum Cascade Absorption Spectrometers Employing Optimal Filtering and Other Approaches

    SciTech Connect

    Disselkamp, Robert S.; Kelly, James F.; Sams, Robert L.; Anderson, Gordon A.

    2002-09-01

    Optical feedback to the laser source in tunable diode laser spectroscopy (TDLS) is known to create intensity modulation noise due to elatoning and optical feedback (i.e., multiplicative technical noise) that usually limits spectral signal-to-noise (S/N). The large technical noise often limits absorption spectroscopy to noise floors 100-fold greater than the Poisson shot noise limit due to fluctuations in the laser intensity. The high output powers generated from quantum cascade (QC) lasers, along with their high gain, makes these injection laser systems especially susceptible to technical noise. In this article we discuss a method of using optimal filtering to reduce technical noise. We have observed S/N enhancements ranging from {approx}20% to a factor of {approx}50. The degree to which optimal filtering will enhance S/N depends on the similarity between the Fourier components of the technical noise and those of the signal, with lower S/N enhancements observed for more similar Fourier decompositions of the signal and technical noise. We also examine the linearity of optimal filtered spectra for both time and intensity. This was accomplished by creating a synthetic spectrum for the species being studied (CH4, N2O, CO2, H2O in ambient air) utilizing line-positions and line-widths with an assumed Voight-profile from a previous database (HITRAN). Agreement better than 0.036% in wavenumber, and 1.64% in intensity (up to a 260-fold intensity ratio employed), was observed. Our results suggest that rapid ex post facto digital optimal filtering can be used to enhance S/N for routine trace gas detection.

  17. [Application of over sampling sigma-delta A/D in DOAS system].

    PubMed

    Li, Su-wen; Liu, Wen-qing; Xie, Pin-hua

    2006-12-01

    Differential optical absorption spectroscopy (DOAS) has become a widely used method to measure trace gases in the atmosphere. Concentration of trace gases is retrieved using least-squares fits of reference spectra to the measurement spectra. The measurement precision not only depends on the measurement precision of spectra and the noise of instrument and disturbing of other gases in measuring band, but suffers the influence of signal sampling and pre-processing. The present paper simply introduced DOAS measuring principle and the setup of instrument and put forward improving method-the technology of over sampling sigma- deltaA/D. Using the sigma-delta modulator structure to shape noises together with the over sampling technology can doubly restrain quantifying noises, which can improve the signal-to-noise ratio within the measuring band. So the measurement precision of DOAS system is improved with this technology. PMID:17361733

  18. Variation of the 3-μm absorption feature on Mars: observations over eastern Valles Marineris by the mariner 6 infrared spectrometer

    USGS Publications Warehouse

    Calvin, Wendy M.

    1997-01-01

    A new approach for calibration of the shortest wavelength channel (1.8 to 6.0 μm) of the Mariner 6 infrared spectrometer was derived. This calibration provides a new description of the instrument response function from 1.8 to 3.7 μm and accounts for the thermal contribution to the signal at longer wavelengths. This allows the two segments from 1.8 to 6 μm to be merged into a single spectrum. The broad water of hydration absorption spans these two segments and is examined in these merged spectra using a method of band integration. Unlike previous analyses which rely on ratios at two wavelengths, the integration method can assess the band strength independently from the albedo in the near infrared. Spectra taken over the eastern end of the Valles Marineris are examined for variations of the band-integrated value, and three distinct clusters are found. Within the estimated uncertainty, two clusters (both low and high albedo) have approximately the same integrated band depth. The third cluster (medium albedo) has an integrated band depth about 10% higher. This difference cannot be systematically attributed to either surface or atmospheric parameters and suggests variation in the amount of water either chemically or physically bound in surface materials. Approximately one-half of the high integrated band depth cluster is associated with chaotic terrain at the source of outflow channels, the other half occurs over lower inertia plains adjacent to chasmata. This suggests both surface physical properties and mineralogy as well as water in exchange with the atmosphere contribute to the 3-μm bound water absorption.

  19. Tomographic multiaxis-differential optical absorption spectroscopy observations of Sun-illuminated targets: a technique providing well-defined absorption paths in the boundary layer.

    PubMed

    Frins, Erna; Bobrowski, Nicole; Platt, Ulrich; Wagner, Thomas

    2006-08-20

    A novel experimental procedure to measure the near-surface distribution of atmospheric trace gases by using passive multiaxis differential absorption optical spectroscopy (MAX-DOAS) is proposed. The procedure consists of pointing the receiving telescope of the spectrometer to nonreflecting surfaces or to bright targets placed at known distances from the measuring device, which are illuminated by sunlight. We show that the partial trace gas absorptions between the top of the atmosphere and the target can be easily removed from the measured total absorption. Thus it is possible to derive the average concentration of trace gases such as NO(2), HCHO, SO(2), H(2)O, Glyoxal, BrO, and others along the line of sight between the instrument and the target similar to the well-known long-path DOAS observations (but with much less expense). If tomographic arrangements are used, even two- or three-dimensional trace gas distributions can be retrieved. The basic assumptions of the proposed method are confirmed by test measurements taken across the city of Heidelberg. PMID:16892129

  20. Vertical Profile Measurements of Formaldehyde and NO2 by means of the CU Airborne Multi-Axis DOAS instrument

    NASA Astrophysics Data System (ADS)

    Oetjen, H.; Baidar, S.; Coburn, S.; Ortega, I.; Dix, B. K.; Sinreich, R.; Volkamer, R.

    2010-12-01

    The University of Colorado airborne multi-axis differential optical absorption spectroscopy (CU AMAX-DOAS) instrument was operated on board the NOAA twin otter research aircraft to measure column abundances of reactive trace gases (e.g., NO2, formaldehyde, glyoxal, O4, BrO, and IO) during the CalNEx and CARES campaigns in California in May to July, 2010. Column observations of reactive trace gases provide means to bridge spatial scales between ground-based measurements, and satellite observations, and enable a more direct comparison with atmospheric models. However, the CU AMAX-DOAS features a novel telescope to collect scattered sunlight under discrete viewing angles providing the opportunity to obtain profile information of trace gases as well. This telescope was installed in a pylon pointing out of the side window of the aircraft and allows to flexibly scan most angles in front of the aircraft from the zenith to nadir geometry (only limited by the window openings in the pylon) as well as backwards down to about minus 20°. A motion compensation system is included to actively adjust the pointing of the telescope to compensate for aircraft angular movements in the vertical. Two spectrometers have been deployed covering wavelength ranges from 350-720 nm with a spectral resolution of ~2 nm full width at half maximum (FWHM) and 330-470 nm with 0.7 nm FWHM. The recorded spectra are analyzed with the well-known DOAS method to retrieve so-called slant column densities (SCDs) of absorbers. Sets of SCDs recorded at different viewing angles are converted into a vertical profile through experimentally constrained inverse modeling of radiative transfer. The angular scanning pattern of the telescope, as well as the flight plan was optimized to characterize the horizontal and vertical distribution of the trace gases. Especially, the variation of the flight altitude in combination with the scanning of different angles provides a powerful tool to obtain the detailed vertical

  1. β - γ and β-neutron- γ emission in mass A=137 Decay Chain Studied with the Modular Total Absorption Spectrometer (MTAS)

    NASA Astrophysics Data System (ADS)

    Rasco, Charles; Fijałkowska, Aleksandra; Karny, Marek; Rykaczewski, Krzysztof; Wolińska-Cichocka, Marzena; Grzywacz, Robert

    2013-10-01

    The Modular Total Absorption Spectrometer (MTAS) is a detector made up of 19 separate hexagon modules of NaI which results in over a ton of NaI in the MTAS detector. MTAS was designed to capture as much of the electromagnetic energy release in β-decays as possible. MTAS was constructed at the Holifield Radioactive Ion Beam Facility and measured over 20 decay products of 238U fission products in its inaugural measurement campaign in January 2012. The measurements were focused on nuclei identified as important for decay heat analysis of the nuclear fuel cycle. Silicon detectors placed at the center of MTAS to provide β triggers, make for extremely clean signals in MTAS. Preliminary results on the average electromagnetic energy release in the β decay of 137Xe and 137I isotopes will be presented. These isotopes are among the priority 1 cases listed by the NEA. The 137I also has a beta -neutron decay branch that is detected in MTAS. Neutron detection in a large NaI detector will also be discussed. This work was supported by the US DOE by award no. DE-FG02-96ER40978 and by US DOE, Office of Nuclear Physics.

  2. The development and evaluation of airborne in situ N2O and CH4 sampling using a quantum cascade laser absorption spectrometer (QCLAS)

    NASA Astrophysics Data System (ADS)

    Pitt, J. R.; Le Breton, M.; Allen, G.; Percival, C. J.; Gallagher, M. W.; Bauguitte, S. J.-B.; O'Shea, S. J.; Muller, J. B. A.; Zahniser, M. S.; Pyle, J.; Palmer, P. I.

    2016-01-01

    Spectroscopic measurements of atmospheric N2O and CH4 mole fractions were made on board the FAAM (Facility for Airborne Atmospheric Measurements) large atmospheric research aircraft. We present details of the mid-infrared quantum cascade laser absorption spectrometer (QCLAS, Aerodyne Research Inc., USA) employed, including its configuration for airborne sampling, and evaluate its performance over 17 flights conducted during summer 2014. Two different methods of correcting for the influence of water vapour on the spectroscopic retrievals are compared and evaluated. A new in-flight calibration procedure to account for the observed sensitivity of the instrument to ambient pressure changes is described, and its impact on instrument performance is assessed. Test flight data linking this sensitivity to changes in cabin pressure are presented. Total 1σ uncertainties of 2.47 ppb for CH4 and 0.54 ppb for N2O are derived. We report a mean difference in 1 Hz CH4 mole fraction of 2.05 ppb (1σ = 5.85 ppb) between in-flight measurements made using the QCLAS and simultaneous measurements using a previously characterised Fast Greenhouse Gas Analyser (FGGA, Los Gatos Research, USA). Finally, a potential case study for the estimation of a regional N2O flux using a mass balance technique is identified, and the method for calculating such an estimate is outlined.

  3. The development and evaluation of airborne in situ N2O and CH4 sampling using a Quantum Cascade Laser Absorption Spectrometer (QCLAS)

    NASA Astrophysics Data System (ADS)

    Pitt, J. R.; Le Breton, M. R.; Allen, G.; Percival, C.; Gallagher, M. W.; Bauguitte, S.; O'Shea, S.; Muller, J.; Zahniser, M. S.; Pyle, J. A.; Palmer, P. I.

    2015-12-01

    Spectroscopic measurements of atmospheric N2O and CH4 mole fractions were made on board the FAAM (Facility for Airborne Atmospheric Measurements) large Atmospheric Research Aircraft. We evaluate the performance of the mid-IR continuous wave Aerodyne Research Inc. Quantum Cascade Laser Absorption Spectrometer (QCLAS) employed over 17 flights conducted during summer 2014. Two different methods of correcting for the influence of water vapour on the spectroscopic retrievals are compared and evaluated. Test flight data demonstrating the sensitivity of the instrument to changes in cabin pressure is presented, and a new in-flight calibration procedure to account for this issue is described and assessed. Total 1σ uncertainties of 1.81 ppb for CH4 and 0.35 ppb for N2O are derived. We report a mean difference in 1 Hz CH4 mole fraction of 2.05 ppb (1σ = 5.85 ppb) between in-flight measurements made using the QCLAS and simultaneous measurements using a previously characterised Los Gatos Research Fast Greenhouse Gas Analyser (FGGA).

  4. The development and evaluation of airborne in situ N2O and CH4 sampling using a Quantum Cascade Laser Absorption Spectrometer (QCLAS)

    NASA Astrophysics Data System (ADS)

    Pitt, Joseph; Le Breton, Michael; Allen, Grant; Percival, Carl; Gallagher, Martin; Bauguitte, Stephane; O'Shea, Sebastian; Muller, Jennifer; Zahniser, Mark; Pyle, John; Palmer, Paul

    2016-04-01

    Spectroscopic measurements of atmospheric N2O and CH4 mole fractions were made on board the FAAM (Facility for Airborne Atmospheric Measurements) large Atmospheric Research Aircraft. We evaluate the performance of the mid-IR continuous wave Aerodyne Research Inc. Quantum Cascade Laser Absorption Spectrometer (QCLAS) employed over 17 flights conducted during summer 2014. Two different methods of correcting for the influence of water vapour on the spectroscopic retrievals are compared and evaluated. Test flight data demonstrating the sensitivity of the instrument to changes in cabin pressure is presented, and a new in-flight calibration procedure to account for this issue is described and assessed. Total 1σ uncertainties of 1.81 ppb for CH4 and 0.35 ppb for N2O are derived. We report a mean difference in 1 Hz CH4 mole fraction of 2.05 ppb (1σ = 5.85 ppb) between in-flight measurements made using the QCLAS and simultaneous measurements using a previously characterised Los Gatos Research Fast Greenhouse Gas Analyser (FGGA).

  5. The development and evaluation of airborne in situ N2O and CH4 sampling using a Quantum Cascade Laser Absorption Spectrometer (QCLAS)

    NASA Astrophysics Data System (ADS)

    Pitt, J. R.; Le Breton, M.; Allen, G.; Percival, C. J.; Gallagher, M. W.; Bauguitte, S. J.-B.; O'Shea, S. J.; Muller, J. B. A.; Zahniser, M. S.; Pyle, J.; Palmer, P. I.

    2015-08-01

    Spectroscopic measurements of atmospheric N2O and CH4 mole fractions were made on board the FAAM (Facility for Airborne Atmospheric Measurements) large Atmospheric Research Aircraft. We present details of the mid-IR Aerodyne Research Inc. Quantum Cascade Laser Absorption Spectrometer (QCLAS) employed, including its configuration for airborne sampling, and evaluate its performance over 17 flights conducted during summer 2014. Two different methods of correcting for the influence of water vapour on the spectroscopic retrievals are compared and evaluated. A new in-flight calibration procedure to account for the observed sensitivity of the instrument to ambient pressure changes is described, and its impact on instrument performance is assessed. Test flight data linking this sensitivity to changes in cabin pressure is presented. Total 1σ uncertainties of 1.81 ppb for CH4 and 0.35 ppb for N2O are derived. We report a mean difference in 1 Hz CH4 mole fraction of 2.05 ppb (1σ = 5.85 ppb) between in-flight measurements made using the QCLAS and simultaneous measurements using a previously characterised Los Gatos Research Fast Greenhouse Gas Analyser (FGGA). Finally, a potential case study for the estimation of a regional N2O flux using a mass balance technique is identified, and the method for calculating such an estimate is outlined.

  6. Validation opportunities of DOAS Network in Moscow Region

    NASA Astrophysics Data System (ADS)

    Borovski, Alexander; Postylyakov, Oleg; Elokhov, Alexander; Ivanov, Victor; Kanaya, Yugo

    A.M. Obukhov Institute of Atmospheric Physics (IAP) of Russian Academy of Science developed a network of atmosphere composition measurements by DOAS method. Measurements sites of the network are located in the centre of Moscow at IAP (55.74N, 37.62E) south-east part of the city at M.V. Lomonosov Moscow State University (55.70N 37.53E), and in background region at Zvenigorod Scientific Station of IAP (ZSS, 55.70N, 36.78E). Intensity of the scattered solar radiation is registered in ultra-violet and visible spectrum region. Three devices are mounted at ZSS: based on MDR-23 spectrometer (since 1990), JAMSTEC MAX-DOAS (since 2008), and based on ORIEL MS257 spectrometer (since 2008). ORIEL MS260i imaging spectrometers were mounted at city stations in 2010. Measurements are regular and continuous at all stations. Basing on performed measurements of spectral radiance, the vertical distribution at twilight, the total content and the integral content in the boundary layer (ABL) in daytime of NO2 are obtained. The quantities are obtained in clear sky and cloudy conditions. Besides that, the vertical distribution of aerosol and the total content (mainly contributed by ABL) of HCHO using MAX-DOAS are calculated. The HCHO total content is retrieved with error about 20 %. We analyzed the variability of the HCHO during clear sky conditions in 2010. The HCHO content is larger during east wind directions than during non-east wind directions. It can be associated with Moscow Megacity influence on air quality at Zvenigorod. The estimation of Moscow Megacity influence on HCHO abundance at Zvenigorod is around 2.5E14 mol/cm2 per 1 km length of trajectory path inside Moscow Ring Road. Our data show statistically significant positive temperature effect in HCHO for the background condition for temperatures from -5C to +33C. The temperature trend in HCHO data at ZSS is about (8.9±2.3)E14 mol/cm2/C. The increase of the HCHO VCD during increase of the air temperature can be explained by the

  7. Evaluation of MAX-DOAS aerosol retrievals by coincident observations using CRDS, lidar, and sky radiometer in Tsukuba, Japan

    NASA Astrophysics Data System (ADS)

    Irie, H.; Nakayama, T.; Shimizu, A.; Yamazaki, A.; Nagai, T.; Uchiyama, A.; Zaizen, Y.; Kagamitani, S.; Matsumi, Y.

    2015-01-01

    Coincident aerosol observations of Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS), Cavity Ring Down Spectroscopy (CRDS), lidar, and sky radiometer were conducted in Tsukuba, Japan on 5-18 October 2010. MAX-DOAS aerosol retrieval (for aerosol extinction coefficient and aerosol optical depth at 476 nm) was evaluated from the viewpoint of the need for a correction factor for oxygen collision complexes (O4 or O2-O2) absorption. The present study strongly supports this need, as systematic residuals at relatively high elevation angles (20 and 30°) were evident in MAX-DOAS profile retrievals conducted without the correction. However, adopting a single number for the correction factor (fO4 = 1.25) for all of the elevation angles led to systematic overestimation of near-surface aerosol extinction coefficients, as reported in the literature. To achieve agreement with all three observations, we limited the set of elevation angles to ≤ 10° and adopted an elevation-angle-dependent correction factor for practical profile retrievals with scattered light observations by a ground-based MAX-DOAS. With these modifications, we expect to minimize the possible effects of temperature-dependent O4 absorption cross section and uncertainty in DOAS fit on an aerosol profile retrieval, although more efforts are encouraged to quantitatively identify a physical explanation for the need of a correction factor.

  8. Evaluation of MAX-DOAS aerosol retrievals by coincident observations using CRDS, lidar, and sky radiometer inTsukuba, Japan

    NASA Astrophysics Data System (ADS)

    Irie, H.; Nakayama, T.; Shimizu, A.; Yamazaki, A.; Nagai, T.; Uchiyama, A.; Zaizen, Y.; Kagamitani, S.; Matsumi, Y.

    2015-07-01

    Coincident aerosol observations of multi-axis differential optical absorption spectroscopy (MAX-DOAS), cavity ring-down spectroscopy (CRDS), lidar, and sky radiometer were conducted in Tsukuba, Japan, on 5-18 October 2010. MAX-DOAS aerosol retrieval (for aerosol extinction coefficient and aerosol optical depth at 476 nm) was evaluated from the viewpoint of the need for a correction factor for oxygen collision complexes (O4 or O2-O2) absorption. The present study strongly supports this need, as systematic residuals at relatively high elevation angles (20 and 30°) were evident in MAX-DOAS profile retrievals conducted without the correction. However, adopting a single number for the correction factor (fO4 = 1.25) for all of the elevation angles led to systematic overestimation of near-surface aerosol extinction coefficients, as reported in the literature. To achieve agreement with all three observations, we limited the set of elevation angles to ≤10° and adopted an elevation-angle-dependent correction factor for practical profile retrievals with scattered light observations by a ground-based MAX-DOAS. With these modifications, we expect to minimize the possible effects of temperature-dependent O4 absorption cross section and uncertainty in DOAS fit on an aerosol profile retrieval, although more efforts are encouraged to quantitatively identify a physical explanation for the need of a correction factor.

  9. Monitoring of SO2 emissions from industry by passive DOAS

    NASA Astrophysics Data System (ADS)

    Li, Ang; Liu, Cheng; Xie, Pinhua; Liu, Jianguo; Qin, Min; Dou, Ke; Fang, Wu; Liu, Wenqing

    2005-05-01

    Sulfur dioxide is a highly toxic air contaminant that harms human health and damages the environment. It is easily converted to sulfuric acid which is the major component in acid rain and to sulfate particles. Coal-burning power plants are the main sources of SO2 pollution. It is necessary to evaluate the emissions from industry for emission reduction strategies. Passive DOAS method has been successfully applied in volcanic plume and atmosphere monitoring because of its advantage of relative simple system with no light source. Here we report the measurement of SO2 total flux from a chimney in plant area in Hefei city (China) with a compact passive DOAS system. The system consists of a small telescope pointing zenith direction and a fibre-coupled OceanOptics USB2000 spectrometer. In the measurement the system was mounted on a mobile platform moving under the plume approximately perpendicular to the plume transport direction and the spectra of the zenith direction were recorded. By combining the integrated gas concentration over the plume cross section with wind velocity data SO2 flux was estimated.

  10. Comparison of glyoxal, BrO, and IO vertical profiles derived from both ground-based and airborne MAX-DOAS measurements

    NASA Astrophysics Data System (ADS)

    Coburn, Sean; Volkamer, Rainer; Baidar, Sunil; Dix, Barbara; Koenig, Theodore; Ortega, Ivan; Sinreich, Roman; van Roozendael, Michel; Hendrick, Francois; Kinnison, Doug

    2015-04-01

    The information content of ground-based MAX-DOAS retrievals is assessed by collocated aircraft measurements for a ship MAX-DOAS setup over the Eastern tropical Pacific Ocean (TORERO RF17), and a mountain-top MAX-DOAS setup at Mauna Loa Observatory, Hawaii (CONTRAST RF17). During both case studies the CU airborne MAX-DOAS (AMAX-DOAS) instrument aboard the NSF/NCAR GV aircraft measured profiles of glyoxal, BrO, and IO with 12-20 degrees of freedom and up to 500 m vertical resolution. The TORERO field campaign took place in 2012, while CONTRAST in 2014; both campaigns covered the months of January and February. Additional measurements aboard the aircraft helped to provide information/validation of the AMAX-DOAS derived profiles, such as in-situ water vapor from the Vertical-Cavity Surface-Emitting Laser hygrometer (VCSEL), in-situ hydrocarbon measurements from the Trace Organic Gas Analyzer (TOGA), and aerosol information constrained by the Ultra High Sensitivity Aerosol Spectrometer (UHSAS). The AMAX-DOAS profiles are compared with ground-based MAX-DOAS inversions. The latter explores the effect of using either the measured differential slant column density (dSCD) or SCD as input to the optimal estimation inversion, where SCD = dSCD + SCD_ref. SCD_ref is the residual column amount of the trace gas contained within the reference spectrum. For the AMAX-DOAS data, the values of SCD_ref were actively minimized, while SCD_ref is usually unknown for ground-based MAX-DOAS retrievals. In absence of independent measurements to constrain SCD_ref, the current state-of-the-art with ground-based MAX-DOAS applications is to use dSCDs as input to the inversion. Here we assess the effect of uncertain SCD_ref for ground-based MAX-DOAS profiles in form of a sensitivity study. Additionally for the ground-based data, different methods are compared for the determination of SCD_ref: 1) the collocated aircraft profiles described above present the opportunity to forward calculate the SCD

  11. Impact of O2-Based Surface Pressure Uncertainties on Laser Absorption Spectrometer Retrievals of Column CO2 Mixing Ratios (XCO2)

    NASA Astrophysics Data System (ADS)

    Pernini, T.; Zaccheo, T. S.; Pernak, R.; Botos, C.; Browell, E. V.

    2015-12-01

    In this work we assess the overall impact of surface pressure uncertainties, derived from either laser-based O2 column measurements or numerical weather prediction (NWP) models, and water vapor uncertainties on laser-based retrievals of CO2 column mixing ratios (XCO2). Laser Absorption Spectrometer (LAS) estimates of column XCO2 can be derived from a combination of observed CO2 differential optical depths ( ) and measured/estimated values of temperature (T), pressure (P), and moisture (q) along the viewing path. XCO2 can be related to CO2 as (equation 1) where Δτother represents residual observed due to other species, is CO2 differential absorption cross section, psfc is surface pressure, q is local specific humidity and / represent the observation on/off-line wavelengths. The accuracy of retrieved XCO2 values depends on both the error characteristics of the observed and the ability to accurately characterize T, P, and q along the observed path. A radiative transfer (RT)-based simulation framework, combined with representative global upper-air observations and matched NWP profiles, was used to assess the impact of model differences in vertical T, vertical moisture, and surface P on estimates of column CO2 and O2concentrations. Additionally we characterize the impact of a combined XCO2 retrieval approach based on either O2 LAS measurements or NWP data, as well as the additional impact due to water vapor. These analyses focus on characterizing the errors for a combined retrieval approach for LAS CO2 measurements in the 1.57 and 2.05 μm regions and O2 measurements in the 0.76 and 1.27 μm. The results provide a set of signal-to-noise metrics that characterize the errors in retrieved XCO2 associated with uncertainties in knowledge of the atmospheric state, and provide a method for selecting optimal differential line pairs for both CO2 and O2 measurements to minimize the impact of this noise term.

  12. Column Path Length Measurements Using a Multi-Frequency, Intensity-Modulated Continuous-Wave (IM-CW) Laser Absorption Spectrometer

    NASA Astrophysics Data System (ADS)

    Harrison, F. W.; Lin, B.; Browell, E. V.; Dobler, J.; McGregor, D.; Kooi, S. A.; Collins, J. E.

    2012-12-01

    Accurate understanding of carbon balance in the environment is critical to projections of the future evolution of the Earth's climate. As a result, the NRC Decadal Survey (DS) of Earth Science and Applications from Space identified Active Sensing of CO2 Emissions over Nights, Days, and Seasons (ASCENDS) as a mid-term (Tier II) mission. The active space remote measurement of the column CO2 mixing ratio (XCO2) for the ASCENDS mission requires the simultaneous measurement of the CO2 and O2 number density and the column path length over which they are measured in order to derive the average XCO2 column. This paper presents methods for measuring the path lengths of the CO2 and O2 measurements that are inherent to the Multi-Functional Fiber Laser Lidar (MFLL), a laser absorption spectrometer (LAS) system under development for the ASCENDS mission. The MFLL is a multi-frequency intensity-modulated continuous-wave (IM-CW) LAS operating near 1.57 and 1.26 μm that uses a range-encoded modulation technique to minimize bias from thin clouds in the CO2 and O2 column measurements while simultaneously measuring the path length to the surface and to intervening cloud layers. This paper discusses the latest MFLL ground and flight test results. During these tests, range-encoded modulation techniques were demonstrated for path length measurements and the MFLL remote CO2 column measurements were evaluated against in situ CO2 measurements. This paper describes the encoding techniques employed, presents an approach for obtaining column path length measurements during CO2 retrievals, and presents the accuracy and precision of the technique. Measurement of path length meeting ASCENDS requirements of approximately 2-m precision were obtained in ground testing and demonstrated during flights over Railroad Valley, NV.

  13. Vegetation species composition and canopy architecture information expressed in leaf water absorption measured in the 1000 nm and 2200 spectral region by an imaging spectrometer

    NASA Technical Reports Server (NTRS)

    Green, Robert O.; Roberts, Dar A.

    1995-01-01

    Plant species composition and plant architectural attributes are critical parameters required for the measuring, monitoring, and modeling of terrestrial ecosystems. Remote sensing is commonly cited as an important tool for deriving vegetation properties at an appropriate scale for ecosystem studies, ranging from local to regional and even synoptic scales. Classical approaches rely on vegetation indices such as the normalized difference vegetation index (NDVI) to estimate biophysical parameters such as leaf area index or intercepted photosynthetically active radiation (IPAR). Another approach is to apply a variety of classification schemes to map vegetation and thus extrapolate fine-scale information about specific sites to larger areas of similar composition. Imaging spectrometry provides additional information that is not obtainable through broad-band sensors and that may provide improved inputs both to direct biophysical estimates as well as classification schemes. Some of this capability has been demonstrated through improved discrimination of vegetation, estimates of canopy biochemistry, and liquid water estimates from vegetation. We investigate further the potential of leaf water absorption estimated from Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) data as a means for discriminating vegetation types and deriving canopy architectural information. We expand our analysis to incorporate liquid water estimates from two spectral regions, the 1000-nm region and the 2200-nm region. The study was conducted in the vicinity of Jasper Ridge, California, which is located on the San Francisco peninsula to the west of the Stanford University campus. AVIRIS data were acquired over Jasper Ridge, CA, on June 2, 1992, at 19:31 UTC. Spectra from three sites in this image were analyzed. These data are from an area of healthy grass, oak woodland, and redwood forest, respectively. For these analyses, the AVIRIS-measured upwelling radiance spectra for the entire Jasper

  14. Spectrometer system using a modular echelle spectrograph and a laser-driven continuum source for simultaneous multi-element determination by graphite furnace absorption spectrometry

    NASA Astrophysics Data System (ADS)

    Geisler, Sebastian; Okruss, Michael; Becker-Ross, Helmut; Huang, Mao Dong; Esser, Norbert; Florek, Stefan

    2015-05-01

    A multi-element absorption spectrometer system has been developed based on a laser-driven xenon continuum source and a modular simultaneous echelle spectrograph (MOSES), which is characterized by a minimized number of optical components resulting in high optical throughput, high transmittance and high image quality. The main feature of the new optical design is the multifunction usage of a Littrow prism, which is attached on a rotation stage. It operates as an order-sorter for the echelle grating in a double-pass mode, as a fine positioning device moving the echelle spectrum on the detector, and as a forwarder to address different optical components, e.g., echelle gratings, in the setup. Using different prisms, which are mounted back to back on the rotation stage, a multitude of different spectroscopic modes like broad-range panorama observations, specific UV-VIS and NIR studies or high resolution zoom investigations of variable spectral channels can be realized. In the UV panorama mode applied in this work, MOSES has simultaneously detectable wavelength coverage from 193 nm to 390 nm with a spectral resolution λ/Δλ of 55,000 (3-pixel criterion). In the zoom mode the latter can be further increased by a factor of about two for a selectable section of the full wavelength range. The applicability and the analytical performance of the system were tested by simultaneous element determination in a graphite furnace, using eight different elements. Compared to an instrument operating in the optimized single line mode, the achieved analytical sensitivity using the panorama mode was typically a factor of two lower. Using the zoom mode for selected elements, comparable sensitivities were obtained. The results confirm the influence of the different spectral resolutions.

  15. Signal to Noise Ratio Estimation for a Space-borne Swept-Frequency Intensity-Modulated CO2 Laser Absorption Spectrometer

    NASA Astrophysics Data System (ADS)

    Chen, S.; Lin, B.; Petway, L. B.; Ismail, S.; Campbell, J. F.; Bai, Y.; Harrison, F. W.; Refaat, T. F.; Obland, M. D.; Meadows, B.; Browell, E. V.

    2014-12-01

    The Signal to Noise Ratio (SNR) in the digital lock-in detection for a space-borne swept-frequency Intensity-Modulated Continuous-Wave (IM-CW) CO2 Laser Absorption Spectrometer (LAS) has a direct influence on the accuracy of the CO2 measurement. According to the Maximum Likelihood Estimation (MLE) method, we have theoretically analyzed a linear swept-frequency sine wave signal in an additive high Gaussian-distributed noise with a constant variance, which is a good approximation for the detector-noise-limited system or the solar background noise dominated space-borne IM-CW CO2 LAS. The general MLE equations for the amplitude and the phase of the swept-frequency IM_CW signal have been generated and solved by a nonlinear optimization procedure. The variances of the amplitude and the phase have been obtained by using the Cramer-Rao lower bound, a lower bound on the variance of the estimated parameters. Under the large sampling numbers, the SNR, signal amplitude divided by the square-root of the amplitude variance, increases as the square-root of the total sampling numbers. Thousands of numerical simulations with randomly generated uniform distributed Gaussian noise were completed for the statistical verification of the estimation. The estimation has also been applied to a space-borne IM-CW CO2 LAS with typical parameters under averaged daytime solar background to confirm the feasibilities of the instrument design of the space-borne IM-CW CO2 LAS.

  16. Observation of atmospheric nitrous acid with DOAS in Beijing, China.

    PubMed

    Qin, Min; Xie, Pin-Hua; Liu, Wen-Qing; Li, Ang; Dou, Ke; Fang, Wu; Liu, Jian-Guo; Zhang, Wei-Jun

    2006-01-01

    Measurements of nitrous acid (HONO) and nitrogen dioxide (NO2) in Beijing City have been performed by means of a developed differential optical absorption spectroscopy (DOAS) system based on photodiode array (PDA), during the autumn of 2004. HONO and NO2 were simultaneously identified by their characteristic absorption bands in the spectral region between 337 nm and 372 nm with high sensibility and time resolution. The concentrations of HONO exhibit obviously diurnal variation with a nocturnal maximum and a daytime minimum. The highest HONO value up to 11.8 microg/m3 was observed during the night of 2/3 September. Possible sources of the observed HONO were discussed. Good correlation to NO2 indicates that NO2 is a main source component. The measurement also shows direct emission of HONO is an important source in strongly polluted urban area. PMID:20050551

  17. Light extinction by secondary organic aerosol: an intercomparison of three broadband cavity spectrometers

    NASA Astrophysics Data System (ADS)

    Varma, R. M.; Ball, S. M.; Brauers, T.; Dorn, H.-P.; Heitmann, U.; Jones, R. L.; Platt, U.; Pöhler, D.; Ruth, A. A.; Shillings, A. J. L.; Thieser, J.; Wahner, A.; Venables, D. S.

    2013-11-01

    Broadband optical cavity spectrometers are maturing as a technology for trace-gas detection, but only recently have they been used to retrieve the extinction coefficient of aerosols. Sensitive broadband extinction measurements allow explicit separation of gas and particle phase spectral contributions, as well as continuous spectral measurements of aerosol extinction in favourable cases. In this work, we report an intercomparison study of the aerosol extinction coefficients measured by three such instruments: a broadband cavity ring-down spectrometer (BBCRDS), a cavity-enhanced differential optical absorption spectrometer (CE-DOAS), and an incoherent broadband cavity-enhanced absorption spectrometer (IBBCEAS). Experiments were carried out in the SAPHIR atmospheric simulation chamber as part of the NO3Comp campaign to compare the measurement capabilities of NO3 and N2O5 instrumentation. Aerosol extinction coefficients between 655 and 690 nm are reported for secondary organic aerosols (SOA) formed by the NO3 oxidation of β-pinene under dry and humid conditions. Despite different measurement approaches and spectral analysis procedures, the three instruments retrieved aerosol extinction coefficients that were in close agreement. The refractive index of SOA formed from the β-pinene + NO3 reaction was 1.61, and was not measurably affected by the chamber humidity or by aging of the aerosol over several hours. This refractive index is significantly larger than SOA refractive indices observed in other studies of OH and ozone-initiated terpene oxidations, and may be caused by the large proportion of organic nitrates in the particle phase. In an experiment involving ammonium sulfate particles, the aerosol extinction coefficients as measured by IBBCEAS were found to be in reasonable agreement with those calculated using the Mie theory. The results of the study demonstrate the potential of broadband cavity spectrometers for determining the optical properties of aerosols.

  18. Light extinction by Secondary Organic Aerosol: an intercomparison of three broadband cavity spectrometers

    NASA Astrophysics Data System (ADS)

    Varma, R. M.; Ball, S. M.; Brauers, T.; Dorn, H.-P.; Heitmann, U.; Jones, R. L.; Platt, U.; Pöhler, D.; Ruth, A. A.; Shillings, A. J. L.; Thieser, J.; Wahner, A.; Venables, D. S.

    2013-07-01

    Broadband optical cavity spectrometers are maturing as a technology for trace gas detection, but only recently have they been used to retrieve the extinction coefficient of aerosols. Sensitive broadband extinction measurements allow explicit separation of gas and particle phase spectral contributions, as well as continuous spectral measurements of aerosol extinction in favourable cases. In this work, we report an intercomparison study of the aerosol extinction coefficients measured by three such instruments: a broadband cavity ring-down spectrometer (BBCRDS), a cavity-enhanced differential optical absorption spectrometer (CE-DOAS), and an incoherent broadband cavity-enhanced absorption spectrometer (IBBCEAS). Experiments were carried out in the SAPHIR atmospheric simulation chamber as part of the NO3Comp campaign to compare the measurement capabilities of NO3 and N2O5 instrumentation. Aerosol extinction coefficients between 655 and 690 nm are reported for secondary organic aerosols (SOA) formed by the NO3 oxidation of β-pinene under dry and humid conditions. Despite different measurement approaches and spectral analysis procedures, the three instruments retrieved aerosol extinction coefficients that were in close agreement. The refractive index of SOA formed from the β-pinene + NO3 reaction was 1.61, and was not measurably affected by the chamber humidity or by aging of the aerosol over several hours. This refractive index is significantly larger than SOA refractive indices observed in other studies of OH and ozone-initiated terpene oxidations, and may be caused by the large proportion of organic nitrates in the particle phase. In an experiment involving ammonium sulphate particles the aerosol extinction coefficients as measured by IBBCEAS were found to be in reasonable agreement with those calculated using Mie theory. The results of the study demonstrate the potential of broadband cavity spectrometers for determining the optical properties of aerosols.

  19. [Measurement of OH radicals in flame with high resolution differential optical absorption spectroscopy].

    PubMed

    Liu, Yu; Liu, Wen-Qing; Kan, Rui-Feng; Si, Fu-Qi; Xu, Zhen-Yu; Hu, Ren-Zhi; Xie, Pin-Hua

    2011-10-01

    The present paper describes a new developed high resolution differential optical absorption spectroscopy instrument used for the measurement of OH radicals in flame. The instrument consists of a Xenon lamp for light source; a double pass high resolution echelle spectrometer with a resolution of 3.3 pm; a multiple-reflection cell of 20 meter base length, in which the light reflects in the cell for 176 times, so the whole path length of light can achieve 3 520 meters. The OH radicals'6 absorption lines around 308 nm were simultaneously observed in the experiment. By using high resolution DOAS technology, the OH radicals in candles, kerosene lamp, and alcohol burner flames were monitored, and their concentrations were also inverted. PMID:22250529

  20. A Tale of Two Cities - HSI-DOAS Measurements of Air Quality

    NASA Astrophysics Data System (ADS)

    Graves, Rosemarie; Leigh, Roland; Anand, Jasdeep; McNally, Michael; Lawrence, James; Monks, Paul

    2013-04-01

    Differential Optical Absorption Spectroscopy is now commonly used as an air quality measuring system; primarily through the measurements of nitrogen dioxide (NO2) both as a ground-based and satellite technique. CityScan is a Hemispherical Scanning Imaging Differential Optical Absorption Spectrometer (HSI-DOAS) which has been optimised to measure concentrations of nitrogen dioxide. CityScan has a 95˚ field of view (FOV) between the zenith and 5˚ below the horizon. Across this FOV there are 128 resolved elements which are measured concurrently, the spectrometer is rotated azimuthally 1˚ per second providing full hemispherical coverage every 6 minutes. CityScan measures concentrations of nitrogen dioxide over specific lines of sight and due to the extensive field of view of the instrument this produces measurements which are representative over city-wide scales. Nitrogen dioxide is an important air pollutant which is produced in all combustion processes and can reduce lung function; especially in sensitised individuals. These instruments aim to bridge the gap in spatial scales between point source measurements of air quality and satellite measurements of air quality offering additional information on emissions, transport and the chemistry of nitrogen dioxide. More information regarding the CityScan technique can be found at http://www.leos.le.ac.uk/aq/index.html. CityScan has been deployed in both London and Bologna, Italy during 2012. The London deployment took place as part of the large NERC funded ClearfLo project in January and July/August. CityScan was deployed in Bologna in June as part of the large EU project PEGASOS. Analysis of both of these campaigns of data will be used to give unprecedented levels of spatial information to air quality measurements whilst also showing the difference in air quality between a relatively isolated mega city and a smaller city situated in a very polluted region; in this case the Po Valley. Results from multiple City

  1. Atmospheric aerosol characterization combining multi-wavelength Raman lidar and MAX-DOAS measurements in Gwanjgu

    NASA Astrophysics Data System (ADS)

    Chong, Jihyo; Shin, Dong Ho; Kim, Kwang Chul; Lee, Kwon-Ho; Shin, Sungkyun; Noh, Young M.; Müller, Detlef; Kim, Young J.

    2011-11-01

    Integrated approach has been adopted at the ADvanced Environmental Research Center (ADEMRC), Gwangju Institute of Science and Technology (GIST), Korea for effective monitoring of atmospheric aerosol. Various active and passive optical remote sensing techniques such as multi-wavelength (3β+2α+1δ) Raman LIDAR, sun-photometry, MAX-DOAS, and satellite retrieval have been utilized. This integrated monitoring system approach combined with in-situ surface measurement is to allow better characterization of physical and optical properties of atmospheric aerosol. Information on the vertical distribution and microphysical properties of atmospheric aerosol is important for understanding its transport characteristics as well as radiative effect. The GIST multi-wavelength (3β + 2α+1δ) Raman lidar system can measure vertical profiles of optical properties of atmospheric aerosols such as extinction coefficients at 355 and 532nm, particle backscatter coefficients at 355, 532 and 1064 nm, and depolarization ratio at 532nm. The incomplete overlap between the telescope field-of-view and beam divergence of the transmitting laser significantly affects lidar measurement, resulting in higher uncertainty near the surface where atmospheric aerosols of interest are concentrated. Differential Optical Absorption Spectroscopy (DOAS) technique is applied as a complementary tool for the detection of atmospheric aerosols near the surface. The passive Multi-Axis DOAS (MAX-DOAS) technique uses scattered sunlight as a light source from several viewing directions. Recently developed aerosol retrieval algorithm based on O4 slant column densities (SCDs) measured at UV and visible wavelengths has been utilized to derive aerosol information (e.g., aerosol optical depth (AOD) and aerosol extinction coefficients (AECs)) in the lower troposphere. The aerosol extinction coefficient at 356 nm was retrieved for the 0-1 and 1-2 km layers based on the MAX-DOAS measurements using the retrieval algorithm

  2. Measurements of ambient ammonia using a tunable diode laser absorption spectrometer: Characteristics of ambient ammonia emissions in an urban area of New York City

    NASA Astrophysics Data System (ADS)

    Li, Yongquan; Schwab, James J.; Demerjian, Kenneth L.

    2006-05-01

    A tunable diode laser absorption spectrometer (TDLAS) was deployed during the PMTACS-NY Supersite winter 2004 intensive field campaign at Queens College in New York City to measure the ambient gaseous ammonia. For the characterization of ammonia emissions from the mobile sources, a LI-7000 CO2/H2O analyzer was also collocated with the TDLAS to measure ambient CO2 and H2O vapor. The field measurements and laboratory calibration with certified ammonia standard have been used to evaluate the performance of the TDLAS system. High time resolved TDLAS ambient ammonia measurements performed at Queens College from 10 January to 6 February showed high variability, with NH3 concentrations ranging from below the detection limit (0.1 ppb) to maxima of 197.4 ppb and a mean value of 0.8 ppb over the entire campaign. Many high-frequency NH3 spikes spanning over a less than 1-min duration were observed during the high traffic periods. The occurrence of the NH3 spikes was closely correlated with observed CO2 spikes, a good marker of traffic exhaust. This correlation yielded an NH3 emission ratio of 0.12 ppbv/ppmv, which can be used to estimate an NH3 emission factor of 35.5 mg/km. The [NH3]/[CO2] ratios over the entire field study was also obtained and added into the best NH3 emission estimates. On a snowy day, no obvious drop of NH3 and CO2 concentrations was measured as the ambient H2O vapor increased. The observed dramatic decrease in the ambient NH3 and CO2 concentrations on a rainy day resulted from a quick air mass switch. Two similar bimodal diurnal patterns associated with the rush hour traffic were observed during school holidays and school days of Queens College, New York. More NH3 emissions from cold start vehicles might contribute to a higher peak in the late afternoon hours. Such observations suggest that the NH3 emissions from the traffic exhaust could be a major source of the ambient NH3 in urban areas.

  3. BrO/SO2 molar ratios from scanning DOAS measurements in the NOVAC network

    NASA Astrophysics Data System (ADS)

    Lübcke, P.; Bobrowski, N.; Arellano, S.; Galle, B.; Garzón, G.; Vogel, L.; Platt, U.

    2013-11-01

    The molar ratio of BrO to SO2 is, like other halogen/sulphur ratios, a~possible precursor for dynamic changes in the shallow part of a volcanic system. While the predictive significance of the BrO/SO2 ratio has not been well constrained yet, it has the major advantage that this ratio can be readily measured using the remote-sensing technique Differential Optical Absorption Spectroscopy (DOAS) in the UV. While BrO/SO2 ratios have been measured during several short-term field campaigns this article presents an algorithm that can be used to obtain long-term time series of BrO/SO2 ratios from the scanning DOAS instruments of the Network for Observation of Volcanic and Atmospheric Change (NOVAC) or comparable networks. Parameters of the DOAS retrieval of both trace gases are given and the influence of co-adding spectra on the retrieval error will be investigated. Difficulties in the evaluation of spectroscopic data from monitoring instruments in volcanic environments and possible solutions are discussed. The new algorithm is demonstrated by evaluating data from the NOVAC scanning DOAS systems at Nevado del Ruiz, Colombia encompassing almost four years of measurements between November 2009 and end of June 2013. This dataset shows variations of the BrO/SO2 ratio several weeks prior to the eruption on 30 June 2012.

  4. BrO/SO2 molar ratios from scanning DOAS measurements in the NOVAC network

    NASA Astrophysics Data System (ADS)

    Lübcke, P.; Bobrowski, N.; Arellano, S.; Galle, B.; Garzón, G.; Vogel, L.; Platt, U.

    2014-06-01

    The molar ratio of BrO to SO2 is, like other halogen/sulfur ratios, a possible precursor for dynamic changes in the shallow part of a volcanic system. While the predictive significance of the BrO/SO2 ratio has not been well constrained yet, it has the major advantage that this ratio can be readily measured using the remote-sensing technique differential optical absorption spectroscopy (DOAS) in the UV. While BrO/SO2 ratios have been measured during several short-term field campaigns, this article presents an algorithm that can be used to obtain long-term time series of BrO/SO2 ratios from the scanning DOAS instruments of the Network for Observation of Volcanic and Atmospheric Change (NOVAC) or comparable networks. Parameters of the DOAS retrieval of both trace gases are given. The influence of co-adding spectra on the retrieval error and influences of radiative transfer will be investigated. Difficulties in the evaluation of spectroscopic data from monitoring instruments in volcanic environments and possible solutions are discussed. The new algorithm is demonstrated by evaluating data from the NOVAC scanning DOAS systems at Nevado del Ruiz, Colombia, encompassing almost 4 years of measurements between November 2009 and end of June 2013. This data set shows variations of the BrO/SO2 ratio several weeks prior to the eruption on 30 June 2012.

  5. Scanning and mobile multi-axis DOAS measurements of SO2 and NO2 emissions from an electric power plant in Montevideo, Uruguay

    NASA Astrophysics Data System (ADS)

    Frins, E.; Bobrowski, N.; Osorio, M.; Casaballe, N.; Belsterli, G.; Wagner, T.; Platt, U.

    2014-12-01

    In March 2012 the emissions of NO2 and SO2 from a power station located on the east side of Montevideo Bay (34° 53‧ 10″ S, 56° 11‧ 49″ W) were quantified by simultaneously using mobile and scanning multi-axis differential optical absorption spectroscopy (in the following mobile DOAS and scanning DOAS, respectively). The facility produces electricity by means of two technologies: internal combustion motors and steam generators. The motors are powered with centrifuged heavy oil and produce a maximum power of 80 MW approximately. The steam generators produce approximately 305 MW and are powered with heavy fuel oil. We compare the emissions obtained from the measured slant column densities (mobile DOAS and scanning DOAS) with the emissions estimated from fuel mass balance. On one occasion it was possible to distinguish between the two types of sources, observing two plumes with different SO2 and NO2 emission rates. During the period of the campaign the mean SO2 emission flux was determined to be 0.36 (±0.12) kg s-1 and 0.26 (±0.09) kg s-1 retrieved from mobile and scanning DOAS respectively, while the calculated SO2 flux from the sulphur content of the fuel was 0.34 (±0.03) kg s-1. The average NO2 flux calculated from mobile DOAS was determined to be 11 (±3) × 10-3 kg s-1. Using the scanning DOAS approach a mean NO2 flux of 5.4 (±1.7) × 10-3 kg s-1 was obtained, which is significantly lower than by the mobile measurements. The differences between the results of mobile MAX-DOAS measurements and scanning DOAS measurements are most probably caused by the variability and the limited knowledge of the wind speed and direction.

  6. Intercomparison of aerosol extinction profiles retrieved from MAX-DOAS measurements

    NASA Astrophysics Data System (ADS)

    Frieß, U.; Klein Baltink, H.; Beirle, S.; Clémer, K.; Hendrick, F.; Henzing, B.; Irie, H.; de Leeuw, G.; Li, A.; Moerman, M. M.; van Roozendael, M.; Shaiganfar, R.; Wagner, T.; Wang, Y.; Xie, P.; Yilmaz, S.; Zieger, P.

    2016-07-01

    A first direct intercomparison of aerosol vertical profiles from Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) observations, performed during the Cabauw Intercomparison Campaign of Nitrogen Dioxide measuring Instruments (CINDI) in summer 2009, is presented. Five out of 14 participants of the CINDI campaign reported aerosol extinction profiles and aerosol optical thickness (AOT) as deduced from observations of differential slant column densities of the oxygen collision complex (O4) at different elevation angles. Aerosol extinction vertical profiles and AOT are compared to backscatter profiles from a ceilometer instrument and to sun photometer measurements, respectively. Furthermore, the near-surface aerosol extinction coefficient is compared to in situ measurements of a humidity-controlled nephelometer and dry aerosol absorption measurements. The participants of this intercomparison exercise use different approaches for the retrieval of aerosol information, including the retrieval of the full vertical profile using optimal estimation and a parametrised approach with a prescribed profile shape. Despite these large conceptual differences, and also differences in the wavelength of the observed O4 absorption band, good agreement in terms of the vertical structure of aerosols within the boundary layer is achieved between the aerosol extinction profiles retrieved by the different groups and the backscatter profiles observed by the ceilometer instrument. AOTs from MAX-DOAS and sun photometer show a good correlation (R>0.8), but all participants systematically underestimate the AOT. Substantial differences between the near-surface aerosol extinction from MAX-DOAS and from the humidified nephelometer remain largely unresolved.

  7. [Improving the temperature robustness of the DOAS based on two-dimensional correlation spectroscopy technology].

    PubMed

    Li, Hong-lian; Wei, Yong-jie; Lü, Chuan-ming; Chen, Wen-liang

    2013-09-01

    The accuracy of the measurement results will be influenced by the ambient temperature in the real-time monitoring based on Differential Optical Absorption Spectroscopy (DOAS). A novel method to improve the temperature robustness of DOAS technology is adopted by two-dimensional correlation spectroscopy technology. Two-dimensional correlation is used to analyse the SO2 absorption cross section at different temperatures. The diagonal slices of synchronization correlation spectroscopy which come from dynamic absorption cross section are obtained. The wavelength 300.5-310 nm is used as the preferred inversion wavelength range based on the slices. The field measurement results and reference value are compared. Results show that the 24-hour average measurement error is 22.5% at 290-310 nm and that at 300.5-310 nm is 9.9%. The correlation coefficients are 0.9496 and 0.7808, respectively. Two-dimensional correlation DOAS technology can be applied to enhance the robustness of temperature, and to improve the accuracy of the measurement results. PMID:24369636

  8. Monolithic spectrometer

    DOEpatents

    Rajic, S.; Egert, C.M.; Kahl, W.K.; Snyder, W.B. Jr.; Evans, B.M. III; Marlar, T.A.; Cunningham, J.P.

    1998-05-19

    A monolithic spectrometer is disclosed for use in spectroscopy. The spectrometer is a single body of translucent material with positioned surfaces for the transmission, reflection and spectral analysis of light rays. 6 figs.

  9. Monolithic spectrometer

    DOEpatents

    Rajic, Slobodan; Egert, Charles M.; Kahl, William K.; Snyder, Jr., William B.; Evans, III, Boyd M.; Marlar, Troy A.; Cunningham, Joseph P.

    1998-01-01

    A monolithic spectrometer is disclosed for use in spectroscopy. The spectrometer is a single body of translucent material with positioned surfaces for the transmission, reflection and spectral analysis of light rays.

  10. Multiple-invariance esprit for DOA estimation

    NASA Astrophysics Data System (ADS)

    Linczuk, Maciej

    2004-07-01

    We consider the problem of estimating the direction of arrival (DOA) of multiple sources in the presence of noise. First, we introduce a narrowband signal model disturbed by white, Gaussian noise. This signal is detected by Uniform Linear Antenna Array -- ULA. Next, we discuss some properties of this signal model and its cross correlation matrix. Using this properties we introduce SINGLE SHIFT INVARIANCE algorithm for DOA estimation: ESPRIT. Next, we describe an idea of MULTIPLE INVARIANCE algorithm based on MULTIPLE INVARIANCE ESPRIT. In the last section we examine some statistical properties of both algorithms: ESPRIT and MULTIPLE INVARIANCE ESPRIT.

  11. Simultaneous measurements of atmospheric pollutants and visibility with a Long-Path DOAS system in urban areas.

    PubMed

    Lee, Jeong Soon; Kim, Young J; Kuk, Bongjae; Geyer, Andreas; Platt, Ulrich

    2005-05-01

    In this paper, the applicability of a Long-Path Differential Optical Absorption Spectroscopy (LP-DOAS) system was checked for the feasibility of the simultaneous measurement of trace gases (such as 03, NO2, SO2, and HCHO) and atmospheric visibility (light extinction by aerosols) in Asian urban areas. Field studies show that an LP-DOAS system can simultaneously measure the key pollutants (such as O3, NO2, SO2, and HCHO) at detection limits in the ppb/sub-ppb range as well as the Mie extinction coefficient with an uncertainty of approximately 0.1 km(-1) at time resolution of a few minutes. It is thus concluded that the use of LP-DOAS system is feasible for simultaneous measurement of gaseous pollutants as well as an atmospheric extinction coefficient which is tightly bound to fine particulate concentration. PMID:15931992

  12. Methods-comparison measurements during the Carbonaceous-Species Methods Comparison Study, Glendora, California, August 1986: tunable-diode laser absorption spectrometer measurements of HCHO, H/sub 2/O/sub 2/ and HNO/sub 3/. Final report

    SciTech Connect

    Mackay, G.I.; Schiff, H.I.

    1987-10-21

    As part of the Carbonaceous-Species Methods Comparison Study at Citrus College, Glendora CA, on August 11-21, 1986, Unisearch Associates participated in methods evaluation studies for formaldehyde (HCHO), hydrogen peroxide (H/sub 2/O/sub 2/) and nitric acid (HNO/sub 3/). These three species play important roles in photochemistry of urban and rural air, and their measurements provide sensitive tests for current acid deposition and urban smog models. Two tunable diode laser absorption spectrometers (TDLAS) were used in the methods evaluation study.

  13. Airborne MAX-DOAS Measurements Over California: Testing the NASA OMI Tropospheric NO2 Product

    NASA Technical Reports Server (NTRS)

    Oetjen, Hilke; Baidar, Sunil; Krotkov, Nickolay A.; Lamsal, Lok N.; Lechner, Michael; Volkamer, Rainer

    2013-01-01

    Airborne Multi-AXis Differential Optical Absorption Spectroscopy (AMAX-DOAS) measurements of NO2 tropospheric vertical columns were performed over California for two months in summer 2010. The observations are compared to the NASA Ozone Monitoring Instrument (OMI) tropospheric vertical columns (data product v2.1) in two ways: (1) Median data were compared for the whole time period for selected boxes, and the agreement was found to be fair (R = 0.97, slope = 1.4 +/- 0.1, N= 10). (2) A comparison was performed on the mean of coincident AMAX-DOAS measurements within the area of the corresponding OMI pixels with the tropospheric NASA OMI NO2 assigned to that pixel. The effects of different data filters were assessed. Excellent agreement and a strong correlation (R = 0.85, slope = 1.05 +/- 0.09, N= 56) was found for (2) when the data were filtered to eliminate large pixels near the edge of the OMI orbit, the cloud radiance fraction was<50%, the OMI overpass occurred within 2 h of the AMAX-DOAS measurements, the flight altitude was>2 km, and a representative sample of the footprint was taken by the AMAX-DOAS instrument. The AMAX-DOAS and OMI data sets both show a reduction of NO2 tropospheric columns on weekends by 38 +/- 24% and 33 +/- 11%, respectively. The assumptions in the tropospheric satellite air mass factor simulations were tested using independent measurements of surface albedo, aerosol extinction, and NO2 profiles for Los Angeles for July 2010 indicating an uncertainty of 12%.

  14. Long-term measurements of trace gaseous pollutants over Beijing using Mini-MAX-DOAS instruments

    NASA Astrophysics Data System (ADS)

    Ma, Jianzhong; Jin, Junli; Shaiganfar, Reza; Wagner, Thomas

    2014-05-01

    Air quality in Beijing megacity has been of great concern in the atmospheric and environmental science community as well as public media. In addition to in situ measurements of ambient concentrations of air pollutants (e.g. NO2, SO2) near the ground, satellite data have also been used to analyze the long-term variation trend of urban pollution as well as the special emission control effect. However, the emission sources of pollutants in a megacity like Beijing are diverse and heterogeneously distributed in the urban canopy. Therefore, in situ surface measurement results may be quite different from one site to another depending on the representativeness of the chosen sites. Satellite measurements are found to have large biases in monitoring the air pollutant levels in a city due to both grid-smoothing and aerosol shielding effects. Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) is a passive remote sensing technology, which retrieves atmospheric trace gases by using scattered sun light from various elevation angles. Ground-based measurements by MAX-DOAS are especially sensitive to the tropospheric part of trace gas column, and can be used effectively to validate the satellite products for the troposphere. We have performed ground Mini-MAX-DOAS measurements at an urban site (39.95N, 116.32E) in Beijing since August 2008. The diurnal and seasonal variations of tropospheric NO2 vertical column densities were retrieved by analyzing the MAX-DOAS spectra obtained at this site. Such dataset were also used to validate the SCIMACHY and OMI satellite NO2 products for the period 2008-2009. Analyses of these MAX-DOAS spectra for SO2 and HCHO will be done in the near future to investigate the long-term variations of pollution level and character in Beijing over the past years.

  15. Inference of cloud altitude and optical properties from MAX-DOAS measurements

    NASA Astrophysics Data System (ADS)

    Nasse, Jan-Marcus; Zielcke, Johannes; Frieß, Udo; Lampel, Johannes; König-Langlo, Gert; Platt, Ulrich

    2015-04-01

    Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) is a widely used technique for the detection of atmospheric trace gases, e.g. NO2, SO2, BrO, HCHO, but also for the oxygen collision complex O4. The atmospheric distribution of the latter is proportional to the square of the molecular oxygen concentration and thus well known. By comparing measured O4 differential slant column densities (dSCDs) from MAX-DOAS measurements with modeled ones, information on aerosol distributions and optical properties, as well as on clouds can be obtained using an algorithm based on optimal estimation. Here the ability of MAX-DOAS observations to detect cloud altitude and cloud optical properties of different cloud covers based on measurements of O4 will be discussed. The analysis uses measurements made by a ship-borne instrument on two cruises of the German research vessel Polarstern to the Antarctic Weddell Sea from June to October 2013. During this time a broad range of cloud and aerosol conditions was encountered, in particular persistent low cloud cover with a high optical thickness. Aerosol and particle extinction profiles were retrieved with temporal resolutions of up to 15 minutes. For clouds at altitudes up to 2000 m the results show a very good agreement with co-located measurements of a commercial ceilometer and pictures from a cloud camera. Unless visibility was very poor due to fog, even rapid changes in cloud altitude or cover could be detected by MAX-DOAS. These results indicate that under homogeneous cloud cover an accurate retrieval of trace gas vertical profiles can be possible despite the strong influence of clouds on atmospheric light paths. We will discuss advantages and limitations of cloud detection with MAX-DOAS, implications for the subsequent retrieval of trace gas profiles and the possible use of external (ceilometer) data as a priori information for the profile retrieval algorithm.

  16. The effect of cloud screening on MAX-DOAS aerosol retrievals.

    NASA Astrophysics Data System (ADS)

    Gielen, Clio; Van Roozendael, Michel; Hendrik, Francois; Fayt, Caroline; Hermans, Christian; Pinardi, Gaia; De Backer, Hugo; De Bock, Veerle; Laffineur, Quentin; Vlemmix, Tim

    2014-05-01

    In recent years, ground-based multi-axis differential absorption spectroscopy (MAX-DOAS) has shown to be ideally suited for the retrieval of tropospheric trace gases and deriving information on the aerosol properties. These measurements are invaluable to our understanding of the physics and chemistry of the atmospheric system, and the impact on the Earth's climate. Unfortunately, MAX-DOAS measurements are often performed under strong non-clear-sky conditions, causing strong data quality degradation and uncertainties on the retrievals. Here we present the result of our cloud-screening method, using the colour index (CI), on aerosol retrievals from MAX-DOAS measurements (AOD and vertical profiles). We focus on two large data sets, from the Brussels and Beijing area. Using the CI we define 3 different sky conditions: bad (=full thick cloud cover/extreme aerosols), mediocre (=thin clouds/aerosols) and good (=clear sky). We also flag the presence of broken/scattered clouds. We further compare our cloud-screening method with results from cloud-cover fractions derived from thermic infrared measurements. In general, our method shows good results to qualify the sky and cloud conditions of MAX-DOAS measurements, without the need for other external cloud-detection systems. Removing data under bad-sky and broken-cloud conditions results in a strongly improved agreement, in both correlation and slope, between the MAX-DOAS aerosol retrievals and data from other instruments (e.g. AERONET, Brewer). With the improved AOD retrievals, the seasonal and diurnal variations of the aerosol content and vertical distribution at both sites can be investigated in further detail. By combining with additional information derived by other instruments (Brewer, lidar, ...) operated at the stations, we will further study the observed aerosol characteristics, and their influence on and by meteorological conditions such as clouds and/or the boundary layer height.

  17. First Results of Total Ozone from the Ozone Monitoring Instrument (OMI) using the DOAS Method

    NASA Astrophysics Data System (ADS)

    Veefkind, J. P.; de Haan, J. F.; Bhartia, P. K.; Yang, K.; Brinksma, E. J.; Kroon, M.; Levelt, P. F.

    2004-12-01

    The Ozone Monitoring Instrument (OMI) is one of four instruments on the NASA EOS-Aura satellite, that was successfully launched on July 15, 2004. OMI is an imaging spectrometer in the ultraviolet and visible part of the spectrum (270 to 500 nm) and was contributed to the Aura mission by The Netherlands and Finland. With its unprecedented spatial resolution of 13x24 km2 at nadir and daily global coverage, OMI promises highly interesting scientific results and will make a major contribution to our understanding of stratospheric and tropospheric chemistry and climate change. In this contribution we intend to present the first results of the OMI total ozone product derived using the DOAS technique. This product is one of two OMI total ozone products, the other product is based on the TOMS method. The DOAS implementation for OMI includes state-of-the-art features, such as improved methods for accounting for rotational Raman scattering and atmospheric temperature changes. These new features use the full spectral capabilities of the OMI instrument to derive the total ozone column. We anticipate to present global maps of ozone as well as results of initial validation with ground based observations. Also, we will compare with other satellite data products, such as derived from SCIAMACHY and TOMS. First comparisons between the two OMI total ozone products, derived using the DOAS and TOMS methods, will be presented. We intend to show (potential) users of the total ozone products the benefits of OMI's spatial resolution and daily global coverage.

  18. MAX-DOAS observations of the total atmospheric water vapour column and comparison with independent observations

    NASA Astrophysics Data System (ADS)

    Wagner, T.; Andreae, M. O.; Beirle, S.; Dörner, S.; Mies, K.; Shaiganfar, R.

    2013-01-01

    We developed an algorithm for the retrieval of the atmospheric water vapour column from Multi-AXis Differential Optical Absorption Spectroscopy (MAX-DOAS) observations in the yellow and red spectral range. The retrieval is based on the so-called geometric approximation and does not depend on explicit a priori information for individual observations, extensive radiative transfer simulations, or the construction of large look-up tables. Disturbances of the radiative transfer due to aerosols and clouds are simply corrected using the simultaneously measured absorptions of the oxygen dimer, O4. We applied our algorithm to MAX-DOAS observations made at the Max Planck Institute for Chemistry in Mainz, Germany, from March to August 2011, and compared the results to independent observations. Good agreement with Aerosol Robotic Network (AERONET) and European Centre for Medium-Range Weather Forecasting (ECMWF) H2O vertical column densities (VCDs) is found, while the agreement with satellite observations is less good, most probably caused by the shielding effect of clouds for the satellite observations. Good agreement is also found with near-surface in situ observations, and it was possible to derive average daily H2O scale heights (between 1.5 km and 3 km). MAX-DOAS measurements use cheap and simple instrumentation and can be run automatically. One important advantage of our algorithm is that the H2O VCD can be retrieved even under cloudy conditions (except clouds with very high optical thickness).

  19. MAX-DOAS observations of the total atmospheric water vapour column and comparison with independent observations

    NASA Astrophysics Data System (ADS)

    Wagner, T.; Andreae, M. O.; Beirle, S.; Dörner, S.; Mies, K.; Shaiganfar, R.

    2012-09-01

    We developed an algorithm for the retrieval of the atmospheric water vapour column from Multi-AXis Differential Optical Absorption Spectroscopy (MAX-DOAS) observations in the yellow and red spectral range. The retrieval is based on the so called geometric approximation and does not depend on a-priori information, extensive radiative transfer simulations, or the construction of large look-up tables. Disturbances of the radiative transfer due to aerosols and clouds are simply corrected using the simultaneously measured absorptions of the oxygen dimer, O4. We applied our algorithm to MAX-DOAS observations made at the Max Planck Institute for Chemistry in Mainz, Germany, from March to August 2011 and compared the results to independent observations. Good agreement with Aerosol Robotic Network (AERONET) and European Centre for Medium-Range Weather Forecasting (ECMWF) H2O vertical column densities (VCDs) is found, while the agreement with satellite observations is less good, most probably caused by the shielding effect of clouds for the satellite observations. Good agreement is also found with near-surface in-situ observations, and it was possible to derive average daily H2O layer heights (between 1.5 km and 3 km). MAX-DOAS measurements use cheap and simple instrumentation and can be run automatically. One important advantage of our algorithm is that the H2O VCD can be retrieved even under cloudy conditions (except clouds with very high optical thickness).

  20. [Air pollutants study by differential optical absorption spectroscopy with transmit-receive fibers].

    PubMed

    Wei, Yong-Jie; Geng, Xiao-Juan; Chen, Bo; Liu, Cui-Cui; Chen, Wen-Liang

    2013-10-01

    The differential optical absorption spectroscopy system is presented to monitor air pollutants, such as SO2, NO2, etc. The system employs a reflective telescope to collimate light source and focus absorbed light. A combined transmitting and receiving fiber bundle is set to the focus of a concave mirror. A Xenon lamp works as the light source. The light is coupled into the transmitting fiber, and then collimated by the reflective telescope system. After absorbed by the pollutants, the light is reflected by a pyramid mirror far away the telescope. Then the absorbed light is incident on the concave mirror the second time, and focused on the focal plane again. The receiving fiber induces the light which carries the information of the measured gas into a spectrometer. We can get the concentration of the pollutants by DOAS algorithm. Experimental results show that the proposed method can be adopted to measure some pollutants in air quality monitoring.

  1. [Air pollutants study by differential optical absorption spectroscopy with transmit-receive fibers].

    PubMed

    Wei, Yong-Jie; Geng, Xiao-Juan; Chen, Bo; Liu, Cui-Cui; Chen, Wen-Liang

    2013-10-01

    The differential optical absorption spectroscopy system is presented to monitor air pollutants, such as SO2, NO2, etc. The system employs a reflective telescope to collimate light source and focus absorbed light. A combined transmitting and receiving fiber bundle is set to the focus of a concave mirror. A Xenon lamp works as the light source. The light is coupled into the transmitting fiber, and then collimated by the reflective telescope system. After absorbed by the pollutants, the light is reflected by a pyramid mirror far away the telescope. Then the absorbed light is incident on the concave mirror the second time, and focused on the focal plane again. The receiving fiber induces the light which carries the information of the measured gas into a spectrometer. We can get the concentration of the pollutants by DOAS algorithm. Experimental results show that the proposed method can be adopted to measure some pollutants in air quality monitoring. PMID:24409736

  2. [Research on in-situ monitoring of SO2 concentration in the flue gases with DOAS method based on algorithm fusion].

    PubMed

    Tang, Guang-hua; Xu, Chuan-long; Shao, Li-tang; Yang, Dao-ye; Zhou, Bin; Wang, Shi-min

    2009-04-01

    Valuable achievements on differential optical absorption spectroscopy (DOAS) for monitoring atmospheric pollutants gas have been made in the past decades. Based on the idea of setting the threshold according to the maximum value, symbolized as OD'm, of differential optical density, the algorithm of traditional DOAS was combined with the DOAS algorithm based on the kalman filtering to improve the detection limit without losing measurement accuracy in the present article. Two algorithms have different inversion accuracy at the same ratio of signal to noise and the problem of inversion accuracy was well resolved by combining two algorithms at short light path length. Theoretical and experimental research on the concentration measurement of SO2 in the flue gases was carried out at the normal temperature and atmospheric pressure. The research results show that with the OD'm less than 0.0481, the measurement precision is very high for SO2 with the improved DOAS algorithm. The measurement lower limit of SO2 is less than 28.6 mg x m(-3) and the zero drift of the system is less than 2.9 mg x m(-3). If the OD'm is between 0.0481 and 0.9272, the measurement precision is high with the traditional DOAS algorithm. However, if the OD'm is more than 0.922, the errors of measurement results for both two DOAS algorithms are very large and the linearity correction must be performed.

  3. [Research on in-situ monitoring of SO2 concentration in the flue gases with DOAS method based on algorithm fusion].

    PubMed

    Tang, Guang-hua; Xu, Chuan-long; Shao, Li-tang; Yang, Dao-ye; Zhou, Bin; Wang, Shi-min

    2009-04-01

    Valuable achievements on differential optical absorption spectroscopy (DOAS) for monitoring atmospheric pollutants gas have been made in the past decades. Based on the idea of setting the threshold according to the maximum value, symbolized as OD'm, of differential optical density, the algorithm of traditional DOAS was combined with the DOAS algorithm based on the kalman filtering to improve the detection limit without losing measurement accuracy in the present article. Two algorithms have different inversion accuracy at the same ratio of signal to noise and the problem of inversion accuracy was well resolved by combining two algorithms at short light path length. Theoretical and experimental research on the concentration measurement of SO2 in the flue gases was carried out at the normal temperature and atmospheric pressure. The research results show that with the OD'm less than 0.0481, the measurement precision is very high for SO2 with the improved DOAS algorithm. The measurement lower limit of SO2 is less than 28.6 mg x m(-3) and the zero drift of the system is less than 2.9 mg x m(-3). If the OD'm is between 0.0481 and 0.9272, the measurement precision is high with the traditional DOAS algorithm. However, if the OD'm is more than 0.922, the errors of measurement results for both two DOAS algorithms are very large and the linearity correction must be performed. PMID:19626898

  4. Improvements in the DOAS Based Total Ozone Column Algorithm for OMI

    NASA Astrophysics Data System (ADS)

    de Haan, J. F.; Veefkind, J. P.; Valks, P.; Brinksma, E.; Levelt, P. F.

    2003-12-01

    The Ozone Monitoring Instrument is a nadir pointing imaging spectrometer with a wide swath (about 2600 km) that records reflected radiance spectra in the wavelength range 270-500 nm with a spectral resolution of about 0.5 nm. The high spatial resolution (13x24 km at nadir) makes it possible to obtain information on tropospheric ozone as problems due to (partly) cloudy pixels are reduced compared with instruments like GOME and SCIAMACHY. OMI is scheduled for launch early 2004 as part of the NASA EOS-Aura mission. To obtain accurate total ozone columns from OMI spectra an improved DOAS based algorithm is used as compared to the algorithm used in the operational processor for GOME and SCIAMACHY data. The following improvements have been implemented. First, the DOAS fit window is changed from 325-335 nm to 331.6 - 336.6 nm, making the retrieved columns less sensitive to the temperature and ozone profile. To further improve the accuracy we adopt a so-called empirical procedure to calculate air mass factors. In this procedure the DOAS method is applied to simulated spectra. These air mass factors are exact if the atmospheric model used in the calculations corresponds to the actual atmosphere. The third improvement is that the air mass factor is regarded as a function of the slant column density that results from the DOAS fit of a measured spectrum. These improvements have been implemented in the operational algorithm for OMI. We are currently investigating further improvements by handling rotational Raman scattering in a more advanced manner. In this poster presentation the improvements are discussed and some results based on GOME spectra will be presented.

  5. Correlation spectrometer

    DOEpatents

    Sinclair, Michael B.; Pfeifer, Kent B.; Flemming, Jeb H.; Jones, Gary D.; Tigges, Chris P.

    2010-04-13

    A correlation spectrometer can detect a large number of gaseous compounds, or chemical species, with a species-specific mask wheel. In this mode, the spectrometer is optimized for the direct measurement of individual target compounds. Additionally, the spectrometer can measure the transmission spectrum from a given sample of gas. In this mode, infrared light is passed through a gas sample and the infrared transmission signature of the gasses present is recorded and measured using Hadamard encoding techniques. The spectrometer can detect the transmission or emission spectra in any system where multiple species are present in a generally known volume.

  6. Inter-comparison of glyoxal retrievals from MAX-DOAS during the MAD-CAT campaign

    NASA Astrophysics Data System (ADS)

    Ortega, Ivan; Wagner, Thomas; Lampel, Johannes; van Roozendael, Michel; Richter, Andreas; Sinha, Vinayak; Xie, Pinhua; Volkamer, Rainer

    2015-04-01

    Over the past few years the smallest α-dicarbonyl compound glyoxal (CHOCHO) has received attention in order to inform relevant atmospheric chemistry processes such as oxidative capacity and secondary organic aerosol (SOA) formation. A method to detect glyoxal in the atmosphere is through the Differential Optical Absorption Spectroscopy (DOAS) applied to solar scattered light passive remote sensing measurements on different platforms, including ground based, aircrafts, and satellites. Although these measurements are often described still many questions about DOAS fitting parameters need to be investigated. We present results from a comprehensive Multi-AXis Differential Optical Absorption Spectroscopy (MAX-DOAS) comparison effort during the Multi Axis DOAS-Comparison campaign for Aerosols and Trace gases (MAD-CAT) held at the Max Planck institute for Chemistry in Mainz, Germany with an intensive operation period from June to August 2013. We evaluate the comparison for glyoxal differential Slant Column Densities (dSCD) from 6 different research groups during the MAD-CAT campaign. The data analysis is performed following three retrieval common settings. In general, good agreement between different groups is found, especially for days with low cloud coverage. Based on the diurnal variability of the glyoxal-to-formaldehyde ratio we identified that Mainz is influenced mostly by anthropogenic volatile organic compounds (AVOC) emission type. Also, for most of the days glyoxal was often clearly above the respective detection limits. We will present results of sensitivity studies in order to know influence of the wavelength window, dependence of the NO2 air mass factor, cross correlation with H2O, among others. Finally, synthetic spectra created with the SCIATRAN radiative transfer model using measurement related inputs are analysed and first results are presented.

  7. Remote sensing of atmospheric urban pollutants with DOAS in Castilla-La Mancha (Spain)

    NASA Astrophysics Data System (ADS)

    Saiz, A.; Poblete, F. J.; Mucientes, A. E.; Maigler, F. J.; Notario, A.; Martínez, E.; Albaladejo, J.

    Urban air pollution is one of the main environmental problems, owing to implications for public health and physical environment. In urban areas, the sources of atmospheric pollutants are distributed very inhomogeneously. Trace gas concentrations measured by conventional air quality monitoring stations are always influenced by small sources in their direct vicinity and surface effects like dry deposition and small-scale wind systems. Differential Optical Absorption Spectroscopy (DOAS) is a field-oriented monitoring technique that allows very fast and continuous measurements of different airborne pollutants along an open light path. Remote sensing techniques like DOAS can avoid the problems of local influences and surface effects, as DOAS can use light paths with range from several hundred of meters to several kilometres, thus the measured concentrations are averaged over the light path and barely influenced by small-scale variances. The technique is based on the fact that all trace gases absorb electromagnetic radiation in some part of the spectrum. If the radiation of the appropriate frequency is transmitted through the atmosphere the features of absorption of each molecule in that spectral region allow the identification and quantification of the gas concentrations. Up to date, only a few long term DOAS measurements of urban air pollution have been reported, and to the best of our knowledge, this study is the first one in the South of Spain. We present here some results obtained in a long term study performed in Ciudad Real and Puertollano, where the daily, weekly and seasonal variation of the concentrations of minor important tropospheric constituents as ozone, nitric oxide, nitrogen dioxide and sulphur dioxide, have been continuously monitored.

  8. Evaluating emissions of HCHO, HONO, NO2, and SO2 from point sources using portable Imaging DOAS

    NASA Astrophysics Data System (ADS)

    Pikelnaya, O.; Tsai, C.; Herndon, S. C.; Wood, E. C.; Fu, D.; Lefer, B. L.; Flynn, J. H.; Stutz, J.

    2011-12-01

    Our ability to quantitatively describe urban air pollution to a large extent depends on an accurate understanding of anthropogenic emissions. In areas with a high density of individual point sources of pollution, such as petrochemical facilities with multiple flares or regions with active commercial ship traffic, this is particularly challenging as access to facilities and ships is often restricted. Direct formaldehyde emissions from flares may play an important role for ozone chemistry, acting as an initial radical precursor and enhancing the degradation of co-emitted hydrocarbons. HONO is also recognized as an important OH source throughout the day. However, very little is known about direct HCHO and HONO emissions. Imaging Differential Optical Absorption Spectroscopy (I-DOAS), a relatively new remote sensing technique, provides an opportunity to investigate emissions from these sources from a distance, making this technique attractive for fence-line monitoring. In this presentation, we will describe I-DOAS measurements during the FLAIR campaign in the spring/summer of 2009. We performed measurements outside of various industrial facilities in the larger Houston area as well as in the Houston Ship Channel to visualize and quantify the emissions of HCHO, NO2, HONO, and SO2 from flares of petrochemical facilities and ship smoke stacks. We will present the column density images of pollutant plumes as well as fluxes from individual flares calculated from I-DOAS observations. Fluxes from individual flares and smoke stacks determined from the I-DOAS measurements vary widely in time and by the emission sources. We will also present HONO/NOx ratios in ship smoke stacks derived from the combination of I-DOAS and in-situ measurements, and discuss other trace gas ratios in plumes derived from the I-DOAS observations. Finally, we will show images of HCHO, NO2 and SO2 plumes from control burn forest fires observed in November of 2009 at Vandenberg Air Force Base, Santa Maria

  9. Multidimensional spectrometer

    DOEpatents

    Zanni, Martin Thomas; Damrauer, Niels H.

    2010-07-20

    A multidimensional spectrometer for the infrared, visible, and ultraviolet regions of the electromagnetic spectrum, and a method for making multidimensional spectroscopic measurements in the infrared, visible, and ultraviolet regions of the electromagnetic spectrum. The multidimensional spectrometer facilitates measurements of inter- and intra-molecular interactions.

  10. Space scannable LP-DOAS system

    NASA Astrophysics Data System (ADS)

    Li, Zhenbi; Liu, Wen Qing; Wang, Ya-Ping; Feng, Qi; Zheng, Xinming

    2003-06-01

    The DOAS technique is currently the developing trend and the main technique of online monitoring of tropospheric air quality measurements. In order to enlarge the scope of monitoring with only one set of instrument, we recently developed an multi-path LP-DOAS system in which we put several sets of retroreflectors at their own appointed remote places, each makes a measuring lightpath when the telescope aligns with it. In this way we can determine high spatial resolution and two or three-dimensional trace gas distributions of a larger region with the telescope as its center. We developed a stepping-motor-based mechanics-electrical device to drive the telescope. Under the control of a PC the telescope can automatically scan these retroreflectors one by one in continuous measure cycles.

  11. Hemispherical Scanning Imaging DOAS: Resolving nitrogen dioxide in the urban environment

    NASA Astrophysics Data System (ADS)

    Leigh, R. J.; Graves, R. R.; Lawrence, J.; Faloon, K.; Monks, P. S.

    2012-12-01

    Imaging DOAS techniques have been used for nitrogen dioxide and sulfer dioxide for a number of years. This presentation describes a novel system which images concentrations of nitrogen dioxide by scanning an imaging spectrometer 360 degrees azimuthally, covering a region from 5 degrees below the horizon, to the zenith. The instrument has been built at the University of Leicester (UK), on optical designs by Surrey Satellite Technologies Ltd, and incorporates an Offner relay with Schwarzchild fore-optics, in a rotating mount. The spectrometer offers high fidelity spectroscopic retrievals of nitrogen dioxide as a result of a reliable Gaussian line shape, zero smile and low chromatic aberration. The full hemispherical scanning provides complete coverage of nitrogen dioxide concentrations above approximately 5 ppbv in urban environments. Through the use of multiple instruments, the three-dimensional structure of nitrogen dioxide can be sampled and tomographically reconstructed, providing valuable information on nitrogen dioxide emissions and downwind exposure, in addition to new understanding of boundary layer dynamics through the use of nitrogen dioxide as a tracer. Furthermore, certain aerosol information can be retrieved through absolute intensity measurements in each azimuthal direction supplemented by traditional techniques of O4 spectroscopy. Such measurements provide a new tool for boundary layer measurement and monitoring at a time when air quality implications on human health and climate are under significant scrutiny. This presentation will describe the instrument and tomographic potential of this technique. First measurements were taken as part of the international PEGASOS campaign in Bologna, Italy. Results from these measurements will be shown, including imaging of enhanced NO2 in the Bologna urban boundary layer during a severe thunderstorm. A Hemispherical Scanning Imaging DOAS instrument operating in Bologna, Italy in June 2012. Visible in the background

  12. A All-Vacuum High Resolution Fourier Transform Spectrometer with Absorption Pathlengths up to 352 M: Acetylene Spectrum at 1.4-1.7 Microns.

    NASA Astrophysics Data System (ADS)

    Keppler, Karen Ann

    1995-01-01

    The spectra of acetylene (C_2H _2) and of water vapor have been recorded at room temperature with Doppler- or pressure -broadening-limited resolution at pathlengths up to 352m. The spectra were obtained with the combination of a FTIR (Fourier Transform Infrared) spectrometer, evacuated transfer optics, and a multipass cell of 4m base length. The measurements were performed at the Justus-Liebig-Universitat in Giessen, Germany, using the FTIR spectrometer at that university, the multipass cell assembled at The Ohio State University, and the vacuum transfer optics designed by the author. The regions in which the spectra were recorded are 5900-7150 cm^{-1} and 1850-6600 cm^{-1}. Calibration difficulties pertaining to the determination of the absolute accuracy of the data have been resolved, and molecular parameters have been extracted for the HCCH data. These calibration problems were not documented in earlier studies using high resolution Fourier transform spectrometers. For this reason, the dissertation addresses this matter in somewhat greater detail. This work contains a description of the technology used to obtain the data, and a description of the calibration of the spectra to make them suitable for future use as secondary wavenumber calibration standards. The bands detected for the first time in this study have been reported, and updated energy level diagrams for HCCH and H^{13}CCH have been included. The molecular parameters obtained from the HCCH spectra have been presented. The appendices include, among others, the basic observational data, a spectral map and associated wavenumber lists of HCCH, and a description of the weighting scheme developed by the author for Fourier Transform spectra.

  13. CEMS using hot wet extractive method based on DOAS

    NASA Astrophysics Data System (ADS)

    Sun, Bo; Zhang, Chi; Sun, Changku

    2011-11-01

    A continuous emission monitoring system (CEMS) using hot wet extractive method based on differential optical absorption spectroscopy (DOAS) is designed. The developed system is applied to retrieving the concentration of SO2 and NOx in flue gas on-site. The flue gas is carried along a heated sample line into the sample pool at a constant temperature above the dew point. In this case, the adverse impact of water vapor on measurement accuracy is reduced greatly, and the on-line calibration is implemented. And then the flue gas is discharged from the sample pool after the measuring process is complete. The on-site applicability of the system is enhanced by using Programmable Logic Controller (PLC) to control each valve in the system during the measuring and on-line calibration process. The concentration retrieving method used in the system is based on the partial least squares (PLS) regression nonlinear method. The relationship between the known concentration and the differential absorption feature gathered by the PLS nonlinear method can be figured out after the on-line calibration process. Then the concentration measurement of SO2 and NOx can be easily implemented according to the definite relationship. The concentration retrieving method can identify the information and noise effectively, which improves the measuring accuracy of the system. SO2 with four different concentrations are measured by the system under laboratory conditions. The results proved that the full-scale error of this system is less than 2%FS.

  14. Stratospheric NO2 Concentration Determined by DOAS Using Compact Spectrographs

    NASA Astrophysics Data System (ADS)

    Raponi, Marcelo M.; Wolfram, Elian; Rinaldi, Horacio; Rosales, Alejandro; Quel, Eduardo J.; Tocho, Jorge O.

    2008-04-01

    In this work we present the results for stratospheric NO2-total column concentration retrieved by DOAS (Differential Optical Absorption Spectroscopy) performed with compact spectrographs. The behavior for three different spectrographs (MonoSpec 27, Jarrell-Ash; HR4000, Ocean Optics and Mechelle 900, Multichannel Instruments) are analyzed making one intercomparison in the facilities of the LIDAR Division of CEILAP (CITEFA—CONICET), in Villa Martelli, Argentina (34.5° S, 58.5° W, 20 m amsl). The three instruments have a similar resolution (approximately 0.1 nm) but operate with different optical configurations and have optical sensors of different characteristics; two of them have cooling capability and the other one (HR4000) operates at room temperature. The NO2 concentration was obtained from spectral results at twilight using solar noon spectra as reference. In all cases zenithal diffuse irradiance was used. The NO2 absorption cross section given by S. Voigt and J. P. Burrows (University of Bremen—Institute of Environmental Physics) corresponding to 223 °K and 100 mbar is used. Results are compared with public data corresponding to ground-based device or to instruments mounted in satellites. These atmospheric soundings are of extreme importance to understand the roll that plays the stratospheric NO2 in the associated phenomena of destruction and formation of ozone in the low stratosphere at middle latitudes.

  15. The Use of a Microprocessor-Controlled, Video Output Atomic Absorption Spectrometer as an Educational Tool in a Two-Year Technical Curriculum.

    ERIC Educational Resources Information Center

    Kerfoot, Henry B.

    Based on instructional experiences at Charles County Community College, Maryland, this report examines the pedagogical advantage of teaching atomic absorption (AA) spectroscopy with an AA spectrophotometer that is equipped with a microprocessor and video output mechanism. The report first discusses the growing importance of AA spectroscopy in…

  16. Signal optimization, noise reduction, and systematic error compensation methods in long-path DOAS measurements

    NASA Astrophysics Data System (ADS)

    Simeone, Emilio; Donati, Alessandro

    1998-12-01

    The increment of the exploitable optical path represents one of the most important efforts in the differential optical absorption spectroscopy (DOAS) instruments improvement. The methods that allow long path measurements in the UV region are presented and discussed in this paper. These methods have been experimented in the new Italian DOAS instrument - SPOT - developed and manufactured by Kayser Italia. The system was equipped with a tele-controlled optical shuttle on the light source unit, allowing background radiation measurement. Wavelength absolute calibration of spectra by means of a collimated UV beam from a mercury lamp integrated in the telescope has been exploited. Besides, possible thermal effects on the dispersion coefficients of the holographic grating have been automatically compensated by means of a general non-linear fit during the spectral analysis session. Measurements in bistatic configuration have been performed in urban areas at 1300 m and 2200 m in three spectral windows from 245 to 380 nm. Measurements with these features are expected in the other spectral windows on path lengths ranging from about 5 to 10 km in urban areas. The DOAS technique can be used in field for very fast measurements in the 245-275 nm spectral range, on path lengths up to about 2500 m.

  17. SCINTILLATION SPECTROMETER

    DOEpatents

    Bell, P.R.; Francis, J.E.

    1960-06-21

    A portable scintillation spectrometer is described which is especially useful in radio-biological studies for determining the uptake and distribution of gamma -emitting substances in tissue. The spectrometer includes a collimator having a plurality of apertures that are hexagonal in cross section. Two crystals are provided: one is activated to respond to incident rays from the collimator; the other is not activated and shields the first from external radiation.

  18. Performance characteristics of a passively locked cavity-enhanced absorption spectrometer with wideband-tunable multimode near-infrared light source

    NASA Astrophysics Data System (ADS)

    Someya, Ryuta; Imamura, Takeshi; Okamoto, Tetsushi; Hatano, Hiroshi; Toyoshima, Naoko; Tei, Kazuyoku; Yamaguchi, Shigeru

    2016-03-01

    A trace material detection system was developed on the basis of cavity-enhanced absorption spectroscopy (CEAS) using a fiber-coupled passively locked external cavity diode laser (PLEC-DL) in the near-infrared (NIR) wavelength region. The oscillation range of an antireflection-coated diode laser (AR-DL) coupled into an external cavity could be simply selected with a narrowband bandpass filter (1 nm), resulting in a stable wavelength oscillation in the wideband tunability between 1640 and 1680 nm. The external cavity acts as a trace material sensor that exhibits excellent flexibility because it is free from the DL source and is carefully designed with mirrors having reflectivities of ca. 99.995 and 99.99%. Trace-level detection was successfully demonstrated with the developed sensor having a minimum detectable absorption coefficient of 2.4 × 10-8 cm-1, which corresponds to 0.15 ppm for CH4 concentration without interference from H2O absorption lines under atmospheric pressure.

  19. Mass-specific optical absorption coefficients and imaginary part of the complex refractive indices of mineral dust components measured by a multi-wavelength photoacoustic spectrometer

    NASA Astrophysics Data System (ADS)

    Utry, N.; Ajtai, T.; Pintér, M.; Tombácz, E.; Illés, E.; Bozóki, Z.; Szabó, G.

    2015-01-01

    Mass-specific optical absorption coefficients (MACs) and the imaginary part (κ) of the refractive indices of various mineral dust components including silicate clays (illite, kaolin and bentonite), oxides (quartz, hematite and rutile), and carbonate (limestone) were determined at the wavelengths of 1064, 532, 355 and 266 nm. The MAC values were calculated from aerosol optical absorption coefficients measured by a multi-wavelength photoacoustic (PA) instrument, the mass concentration and the number size distribution of the generated aerosol samples as well as the size transfer functions of the measuring instruments. Values of κ were calculated from the measured and particle-loss-corrected data by using a Mie-theory-based retrieval algorithm. The determined values could be used for comparisons with calculated wavelength-dependent κ values typically deduced from bulk-phase measurements by using indirect measurement methods. Accordingly, the presented comparison of the measured and calculated aerosol optical absorption spectra revealed the strong need for standardized sample preparation and measurement methodology in case of bulk-phase measurements.

  20. Vertical NO2 Profile measurements in Hong Kong using DOAS

    NASA Astrophysics Data System (ADS)

    Wenig, Mark; Bräu, Melanie; Zhu, Ying; Lipkowitsch, Ivo; Röttger, Clemens; Fat Lam, Yun

    2016-04-01

    In this presentation we describe our first measurements of vertical NO2 distributions in a street canyon in Hong Kong using different DOAS techniques. One approach is to use mobile cavity-enhanced DOAS (CE-DOAS) measurements on different floors of a high rise building to assemble a profile. In addition to this we use a ToTaL-DOAS (Topographic Target Light Scattering DOAS) approach to measure vertical and horizontal distributions of NO2 SCDs of the Hong Kong skyline including the building we used for the CE-DOAS measurements. As a third option to generate profile information, we use data from the Hong Kong Environmental Protection department (EPD) measurement stations. Each measurement location is at a different height and we used a concentration map we assembled using mobile CE-DOAS measurements which again had been corrected for diurnal variations using a continuously measuring LP-DOAS for horizontal extrapolation. We compare parameterized profiles from those three different methods and discuss how profile information can be used to make urban air quality monitoring more comparable.

  1. [Retrieval of NO2 total vertical columns by direct-sun differential optical absorption spectroscopy].

    PubMed

    Wang, Yang; Xie, Pin-hua; Li, Ang; Xu, Jin; Zeng, Yi; Si, Fu-qi; Wu, Feng-cheng

    2012-04-01

    An appropriate reference spectrum is essential for the direct-sun differential optical absorption spectroscopy (DS-DOAS). It depends on the real reference spectrum to retrieve the total vertical column density (VCD). The spectrum detected at the time with minimum sun zenith angle under the relative clear atmospheric condition in the measurement period was conventionally selected as the reference spectrum. Because there is still untracked NO2 absorption structure in the reference spectrum, the VCD retrieved based on the above spectrum is actually relative VCD, which results in larger error. To solve this problem, a new method was investigated. A convolution of extraterrestrial high-precision solar Fraunhofer spectrum and the instrumental function of the spectrometer was computed and chosen as the reference spectrum. The error induced by NO2 absorption structure in the reference spectrum was removed. Then the fitting error of slant column density (SCD) retrieved by this method was analyzed. The correlation between the absolute SCD and the differential slant column density (dSCD) was calculated. The result shows that the error of SCD retrieved by this new method is below 1.6 x 10(16) molecules x cm(-2) on March 7, 2011, while the error generated by the normal method is about 4.25 x 10(16) molecules x cm(-2). The new method decreased more than 62% error. In addition, the results throughout the day were compared to the troposphere VCD from MAX-DOAS and they are in good agreement. It indicates that the new method could effectively reduce the VCD error of the common way. PMID:22715747

  2. Cloud and aerosol classification for 2 1/2 years of MAX-DOAS observations in Wuxi (China) and comparison to independent data sets

    NASA Astrophysics Data System (ADS)

    Wang, Y.; Penning de Vries, M.; Xie, P. H.; Beirle, S.; Dörner, S.; Remmers, J.; Li, A.; Wagner, T.

    2015-05-01

    Multi-Axis-Differential Optical Absorption Spectroscopy (MAX-DOAS) observations of trace gases can be strongly influenced by clouds and aerosols. Thus it is important to identify clouds and characterise their properties. In a recent study Wagner et al. (2014) developed a cloud classification scheme based on the MAX-DOAS measurements themselves with which different "sky conditions" (e.g. clear sky, continuous clouds, broken clouds) can be distinguished. Here we apply this scheme to long term MAX-DOAS measurements from 2011 to 2013 in Wuxi, China (31.57° N, 120.31° E). The original algorithm has been modified, in particular in order to account for smaller solar zenith angles (SZA). Instrumental degradation is accounted for to avoid artificial trends of the cloud classification. We compared the results of the MAX-DOAS cloud classification scheme to several independent measurements: aerosol optical depth from a nearby AERONET station and from MODIS, visibility derived from a visibility meter; and various cloud parameters from different satellite instruments (MODIS, OMI, and GOME-2). The most important findings from these comparisons are: (1) most cases characterized as clear sky with low or high aerosol load were associated with the respective AOD ranges obtained by AERONET and MODIS, (2) the observed dependences of MAX-DOAS results on cloud optical thickness and effective cloud fraction from satellite indicate that the cloud classification scheme is sensitive to cloud (optical) properties, (3) separation of cloudy scenes by cloud pressure shows that the MAX-DOAS cloud classification scheme is also capable of detecting high clouds, (4) some clear sky conditions, especially with high aerosol load, classified from MAX-DOAS observations corresponding to the optically thin and low clouds derived by satellite observations probably indicate that the satellite cloud products contain valuable information on aerosols.

  3. Retrieval of cloud height from SCIAMACHY using oxygen absorption around 630nm

    NASA Astrophysics Data System (ADS)

    Grzegorski, Michael; Deutschmann, Tim; Platt, Ulrich; Wang, Ping; Wagner, Thomas

    2010-05-01

    The SCanning Imaging Absorption spectrometer for Atmospheric ChartographY (SCIAMACHY) on ENVISAT allows measurements of different atmospheric trace gases (e.g. O3, NO2, SO2, CH4, HCHO, CO, BrO, H2O, O2, O4) using the DOAS technique. The HICRU algorithm retrieves cloud height using the spectral analysis of the oxygen absorption around 630nm combined with results of the Monte-Carlo model TRACY-II and a new SCIAMACHY surface albedo database. The results are compared to: 1.) cloud height retrievals of other satellite instruments (MERIS, MODIS) 2.) ISCCP climatology 3.) SCIAMACHY cloud algorithms (SACURA, FRESCO+) 4.) LIDAR/RADAR measurements. For low clouds, the HICRU algorithm retrieves cloud heights more close to the the top, because of the assumption of an appropriate cloud model with a realistic estimation of the scattering inside the cloud. It is also demonstrated, that none the three SCIAMACHY cloud algorithms HICRU, SACURA and FRESCO+ is able to retrieve the top of high clouds because of principal characteristics of the retrieval methods based on oxygen absorption. But oxygen absorptions can provide important additional information on the vertical cloud structure and multiple cloud layers if the method is combined with cloud-top-retrieval using windows in the thermal infrared. An application of these concepts to the GOSAT instrument will be discussed.

  4. A new direct absorption tunable diode laser spectrometer for high precision measurement of water vapor in the upper troposphere and lower stratosphere

    NASA Astrophysics Data System (ADS)

    Sargent, M. R.; Sayres, D. S.; Smith, J. B.; Witinski, M.; Allen, N. T.; Demusz, J. N.; Rivero, M.; Tuozzolo, C.; Anderson, J. G.

    2013-07-01

    We present a new instrument for the measurement of water vapor in the upper troposphere and lower stratosphere (UT/LS), the Harvard Herriott Hygrometer (HHH). HHH employs a tunable diode near-IR laser to measure water vapor via direct absorption in a Herriott cell. The direct absorption technique provides a direct link between the depth of the observed absorption line and the measured water vapor concentration, which is calculated based on spectroscopic parameters in the HITRAN database. While several other tunable diode laser (TDL) instruments have been used to measure water vapor in the UT/LS, HHH is set apart by its use of an optical cell an order of magnitude smaller than those of other direct absorption TDLs in operation, allowing for a more compact, lightweight instrument. HHH is also unique in its integration into a common duct with the Harvard Lyman-α hygrometer, an independent photo-fragment fluorescence instrument which has been thoroughly validated over 19 years of flight measurements. The instrument was flown for the first time in the Mid-latitude Airborne Cirrus Properties Experiment (MACPEX) on NASA's WB-57 aircraft in spring, 2011, during which it demonstrated in-flight precision of 0.1 ppmv (1 s) with 1-sigma uncertainty of 5% ± 0.7 ppmv. Since the campaign, changes to the instrument have lead to improved accuracy of 5% ± 0.2 ppmv as demonstrated in the laboratory. During MACPEX, HHH successfully measured water vapor at concentrations from 3.5 to 600 ppmv in the upper troposphere and lower stratosphere. HHH and Lyman-α, measuring independently but under the same sampling conditions, agreed on average to within 1% at water vapor mixing ratios above 20 ppmv and to within 0.3 ppmv at lower mixing ratios. HHH also agreed with a number of other in situ water vapor instruments on the WB-57 to within their stated uncertainties, and to within 0.7 ppmv at low water. This agreement constitutes a significant improvement over past in situ comparisons, in

  5. A new direct absorption tunable diode laser spectrometer for high precision measurement of water vapor in the upper troposphere and lower stratosphere.

    PubMed

    Sargent, M R; Sayres, D S; Smith, J B; Witinski, M; Allen, N T; Demusz, J N; Rivero, M; Tuozzolo, C; Anderson, J G

    2013-07-01

    We present a new instrument for the measurement of water vapor in the upper troposphere and lower stratosphere (UT∕LS), the Harvard Herriott Hygrometer (HHH). HHH employs a tunable diode near-IR laser to measure water vapor via direct absorption in a Herriott cell. The direct absorption technique provides a direct link between the depth of the observed absorption line and the measured water vapor concentration, which is calculated based on spectroscopic parameters in the HITRAN database. While several other tunable diode laser (TDL) instruments have been used to measure water vapor in the UT∕LS, HHH is set apart by its use of an optical cell an order of magnitude smaller than those of other direct absorption TDLs in operation, allowing for a more compact, lightweight instrument. HHH is also unique in its integration into a common duct with the Harvard Lyman-α hygrometer, an independent photo-fragment fluorescence instrument which has been thoroughly validated over 19 years of flight measurements. The instrument was flown for the first time in the Mid-latitude Airborne Cirrus Properties Experiment (MACPEX) on NASA's WB-57 aircraft in spring, 2011, during which it demonstrated in-flight precision of 0.1 ppmv (1 s) with 1-sigma uncertainty of 5% ± 0.7 ppmv. Since the campaign, changes to the instrument have lead to improved accuracy of 5% ± 0.2 ppmv as demonstrated in the laboratory. During MACPEX, HHH successfully measured water vapor at concentrations from 3.5 to 600 ppmv in the upper troposphere and lower stratosphere. HHH and Lyman-α, measuring independently but under the same sampling conditions, agreed on average to within 1% at water vapor mixing ratios above 20 ppmv and to within 0.3 ppmv at lower mixing ratios. HHH also agreed with a number of other in situ water vapor instruments on the WB-57 to within their stated uncertainties, and to within 0.7 ppmv at low water. This agreement constitutes a significant improvement over past in situ comparisons

  6. JPL Fourier transform ultraviolet spectrometer

    NASA Technical Reports Server (NTRS)

    Cageao, R. P.; Friedl, R. R.; Sander, Stanley P.; Yung, Y. L.

    1994-01-01

    The Fourier Transform Ultraviolet Spectrometer (FTUVS) is a new high resolution interferometric spectrometer for multiple-species detection in the UV, visible and near-IR. As an OH sensor, measurements can be carried out by remote sensing (limb emission and column absorption), or in-situ sensing (long-path absorption or laser-induced fluorescence). As a high resolution detector in a high repetition rate (greater than 10 kHz) LIF system, OH fluorescence can be discriminated against non-resonant background emission and laser scatter, permitting (0, 0) excitation.

  7. A Vacuum Ultraviolet Absorption Array Spectrometer as a Selective Detector for Comprehensive Two-Dimensional Gas Chromatography: Concept and First Results.

    PubMed

    Gröger, Thomas; Gruber, Beate; Harrison, Dale; Saraji-Bozorgzad, Mohammad; Mthembu, Makhosazana; Sutherland, Aimée; Zimmermann, Ralf

    2016-03-15

    Fast and selective detectors are very interesting for comprehensive two-dimensional gas chromatography (GC × GC). This is particularly true if the detector system can provide additional spectroscopic information on the compound structure and/or functionality. Other than mass spectrometry (MS), only optical spectroscopic detectors are able to provide selective spectral information. However, until present the application of optical spectroscopy technologies as universal detectors for GC × GC has been restricted mainly due to physical limitations such as insufficient acquisition speed or high detection limits. A recently developed simultaneous-detection spectrometer working in the vacuum ultraviolet (VUV) region of 125-240 nm overcomes these limitations and meets all the criteria of a universal detector for GC × GC. Peak shape and chromatographic resolution is preserved and unique spectral information, complementary to mass spectrometry data, is gained. The power of this detector is quickly recognized as it has the ability to discriminate between isomeric compounds or difficult to separate structurally related isobaric species; thus, it provides additional selectivity. A further promising feature of this detector is the data analysis concept of spectral filtering, which is accomplished by targeting special electronic transitions that allows for a fast screening of GC × GC chromatograms for designated compound classes.

  8. A Vacuum Ultraviolet Absorption Array Spectrometer as a Selective Detector for Comprehensive Two-Dimensional Gas Chromatography: Concept and First Results.

    PubMed

    Gröger, Thomas; Gruber, Beate; Harrison, Dale; Saraji-Bozorgzad, Mohammad; Mthembu, Makhosazana; Sutherland, Aimée; Zimmermann, Ralf

    2016-03-15

    Fast and selective detectors are very interesting for comprehensive two-dimensional gas chromatography (GC × GC). This is particularly true if the detector system can provide additional spectroscopic information on the compound structure and/or functionality. Other than mass spectrometry (MS), only optical spectroscopic detectors are able to provide selective spectral information. However, until present the application of optical spectroscopy technologies as universal detectors for GC × GC has been restricted mainly due to physical limitations such as insufficient acquisition speed or high detection limits. A recently developed simultaneous-detection spectrometer working in the vacuum ultraviolet (VUV) region of 125-240 nm overcomes these limitations and meets all the criteria of a universal detector for GC × GC. Peak shape and chromatographic resolution is preserved and unique spectral information, complementary to mass spectrometry data, is gained. The power of this detector is quickly recognized as it has the ability to discriminate between isomeric compounds or difficult to separate structurally related isobaric species; thus, it provides additional selectivity. A further promising feature of this detector is the data analysis concept of spectral filtering, which is accomplished by targeting special electronic transitions that allows for a fast screening of GC × GC chromatograms for designated compound classes. PMID:26810390

  9. Lidar reflectance from snow at 2.05  μm wavelength as measured by the JPL Airborne Laser Absorption Spectrometer.

    PubMed

    Spiers, Gary D; Menzies, Robert T; Jacob, Joseph C

    2016-03-10

    We report airborne measurements of lidar directional reflectance (backscatter) from land surfaces at a wavelength in the 2.05 μm CO₂ absorption band, with emphasis on snow-covered surfaces in various natural environments. Lidar backscatter measurements using this instrument provide insight into the capabilities of lidar for both airborne and future global-scale CO₂ measurements from low Earth orbit pertinent to the NASA Active Sensing of CO₂ Emissions over Nights, Days, and Seasons mission. Lidar measurement capability is particularly useful when the use of solar scattering spectroscopy is not feasible for high-accuracy atmospheric CO₂ measurements. Consequently, performance in high-latitude and winter season environments is an emphasis. Snow-covered surfaces are known to be dark in the CO₂ band spectral regions. The quantitative backscatter data from these field measurements help to elucidate the range of backscatter values that can be expected in natural environments.

  10. Observations of tropospheric NO2 using ground based MAX-DOAS and OMI measurements during the Shanghai World Expo 2010

    NASA Astrophysics Data System (ADS)

    Chan, K. L.; Hartl, A.; Lam, Y. F.; Xie, P. H.; Liu, W. Q.; Cheung, H. M.; Lampel, J.; Pöhler, D.; Li, A.; Xu, J.; Zhou, H. J.; Ning, Z.; Wenig, M. O.

    2015-10-01

    During the Shanghai World Expo 2010 ground based Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) measurements of tropospheric nitrogen dioxide (NO2) were performed to investigate the effects of emission control measures during that time. In this study we measured NO2 using four identical MAX-DOAS instruments in Shanghai from April 2009 to November 2010. We combined our MAX-DOAS data, the Ozone Monitoring Instrument (OMI) satellite observations and meteorological information from the National Centers for Environmental Prediction final reanalysis data (NCEP FNL) in order to investigate the spatial distribution of NO2 over Shanghai and the effects of emission control measures during the Expo. In general, the comparison of cloud screened MAX-DOAS data and OMI observations are in good correlation (Pearson correlation coefficient between 0.67 and 0.93 for the four measurement stations). In addition, we compared the MAX-DOAS and OMI NO2 data from the Shanghai Expo in 2010 to the same time of the year in 2009. The results show that the NO2 columns were reduced up to ∼ 30% in the area of central Shanghai during the Expo but no significant reduction of NO2 levels was found in the nearby industrial area. The overall NO2 reduction from May, July and September 2010 ranged from 7.5% to 14.5%, which is comparable to observations in previous studies. Our results revealed that the NO2 reduction was mainly achieved by emission control policies on transportation sources in the city rather than the controls from nearby provinces.

  11. Spectrometer gun

    DOEpatents

    Waechter, D.A.; Wolf, M.A.; Umbarger, C.J.

    1981-11-03

    A hand-holdable, battery-operated, microprocessor-based spectrometer gun is described that includes a low-power matrix display and sufficient memory to permit both real-time observation and extended analysis of detected radiation pulses. Universality of the incorporated signal processing circuitry permits operation with various detectors having differing pulse detection and sensitivity parameters.

  12. Spectrometer gun

    DOEpatents

    Waechter, David A.; Wolf, Michael A.; Umbarger, C. John

    1985-01-01

    A hand-holdable, battery-operated, microprocessor-based spectrometer gun includes a low-power matrix display and sufficient memory to permit both real-time observation and extended analysis of detected radiation pulses. Universality of the incorporated signal processing circuitry permits operation with various detectors having differing pulse detection and sensitivity parameters.

  13. HISS spectrometer

    SciTech Connect

    Greiner, D.E.

    1984-11-01

    This talk describes the Heavy Ion Spectrometer System (HISS) facility at the Lawrence Berkeley Laboratory's Bevalac. Three completed experiments and their results are illustrated. The second half of the talk is a detailed discussion of the response of drift chambers to heavy ions. The limitations of trajectory measurement over a large range in incident particle charge are presented.

  14. Surface Plasmon Based Spectrometer

    NASA Astrophysics Data System (ADS)

    Wig, Andrew; Passian, Ali; Boudreaux, Philip; Ferrell, Tom

    2008-03-01

    A spectrometer that uses surface plasmon excitation in thin metal films to separate light into its component wavelengths is described. The use of surface plasmons as a dispersive medium sets this spectrometer apart from prism, grating, and interference based variants and allows for the miniaturization of this device. Theoretical and experimental results are presented for two different operation models. In the first case surface plasmon tunneling in the near field is used to provide transmission spectra of different broad band-pass, glass filters across the visible wavelength range with high stray-light rejection at low resolution as well as absorption spectra of chlorophyll extracted from a spinach leaf. The second model looks at the far field components of surface plasmon scattering.

  15. Moonlight DOAS for nighttime studies of volcanic plumes

    NASA Astrophysics Data System (ADS)

    Zielcke, Johannes; Bobrowski, Nicole; Vogel, Leif; Kern, Christoph; Platt, Ulrich

    2010-05-01

    Differential Optical Absorption Spectroscopy (DOAS) in the ultraviolet and visible wavelength region has become a widespread tool not only to study the chemistry of trace gases such as sulphur dioxide (SO2) and halogen oxides (e.g. BrO, ClO, OClO) in volcanic plumes, but also for volcano monitoring by observing SO2 fluxes. During daylight hours either direct or scattered sunlight can be used for measurements. At night other light sources have to be used, the two main possibilities being artificial ones and the moon. While artificial lighting has several important advantages, such as otherwise not available wavelength regions (e.g. deep UV) and a known light path, it is limited to measurements at the crater rim in most circumstances in volcanic environments, which is a potentially dangerous place, and limits the investigation of plume chemistry to the nearer source region. To study the composition of the plume further downwind at night, the moon is the only available source of light. Within the NOVAC (Network for Volcanic and Atmospheric Change) project, passive scanning DOAS instruments in the UV wavelength region were developed and deployed at several degassing volcanoes. We adapted these instruments, however, to track the moon and thus to conduct direct light measurements. As the speciation of bromine and other halogenic oxides relies on photodissociation of their respective elementary molecules, a discrepancy between day and nighttime chemistry is expected. While emissions during the day have been studied for some time now, little is known about the reactions occuring at night. We present direct moonlight measurements carried out at Mount Etna during November/December 2009. SO2 slant column densities (SCD) of up to 2 × 1018 molecules-cm2 were detected and spectra are analyzed for halogen compounds. The results are compared to direct sunlight measurements undertaken in the same period. Our maximum nighttime BrO-SO2 ratio is significantly lower than the ones

  16. Determination of lead in sea-water with a graphite furnace atomic absorption spectrometer and an improved automatic on-line pre-concentration system

    NASA Astrophysics Data System (ADS)

    Liu, Zhen-Shan; Huang, Shang-Da

    1995-03-01

    An improved automatic on-line pre-concentration system for graphite furnace atomic absorption spectrometry (GFAAS) for the determination of trace metals in sea-water was developed. This system was modified from a Perkin-Elmer AS-40 autosampler by mounting a silica gel C 18 microcolumn near the tip of the autosampler capillary. The pre-concentration procedure was performed by using a four-way distribution valve and controlled by a programmable controller. The pre-concentration system developed previously was improved by using a peristaltic pump to replace the reciprocating pumps, a newly designed tube bed adjuster to release the back-pressure in the pre-concentration system, and a better control program, such that on-line pre-concentration became more reliable and fully automatic. The chelating agent ammonium pyrolidinedithiocarbamate (APDC) and a miniature column packed with 5 mg of C 18 silica gel were used for pre-concentration. This system was tested by analyzing the lead content in reference standard sea-water samples. A sample volume of only 2 ml was required to determine lead in sea-water. The relative limit of detection of lead was 3.5 pg/ml.

  17. Ground-based demonstration of a CO2 remote sensor using a 1.57μm differential laser absorption spectrometer with direct detection

    NASA Astrophysics Data System (ADS)

    Sakaizawa, Daisuke; Kawakami, Shuji; Nakajima, Masakatsu; Sawa, Yosuke; Matsueda, Hidekazu

    2010-10-01

    A 1.57-μm laser remote sensor using differential absorption spectrometry is being developed as a candidate for the next space-based mission to observe atmospheric CO2 and/or other trace gases. The performance of the newly-developed active remote sensor has been evaluated for horizontal measurements and initial vertical measurements have been demonstrated. This study shows the results of in-house and field measurements to evaluate column-averaged CO2 mixing ratios. The in-house measurements demonstrated the instrumental response showing agreement within a correlation coefficient of 0.998 for a known CO2 density. Field measurements to evaluate horizontal and vertical column-averaged CO2 mixing ratio were made with a measured precision of 0.49% and 1.7%, respectively. The horizontal integration range was 2.1 km and the vertical range extended from the surface up to the cloud base at ~3 km with corresponding accumulation time of 25 min. Complementary measurements with a multi-positioned in-situ sensor along the observation path demonstrated that the mean horizontal column-averaged CO2 density agreed within the difference of 2.8 ppm of the atmospheric CO2 density.

  18. Gas-phase absorption cross sections of 24 monocyclic aromatic hydrocarbons in the UV and IR spectral ranges

    NASA Astrophysics Data System (ADS)

    Etzkorn, Thomas; Klotz, Björn; Sørensen, Søren; Patroescu, Iulia V.; Barnes, Ian; Becker, Karl H.; Platt, Ulrich

    Absorption cross sections of 24 volatile and non-volatile derivatives of benzene in the ultraviolet (UV) and the infrared (IR) regions of the electromagnetic spectrum have been determined using a 1080 l quartz cell. For the UV a 0.5 m Czerny-Turner spectrometer coupled with a photodiode array detector (spectral resolution 0.15 nm) was used. IR spectra were recorded with an FT-IR spectrometer (Bruker IFS-88, spectral resolution 1 cm -1). Absolute absorption cross sections and the instrument function are given for the UV, while for the IR, absorption cross sections and integrated band intensities are reported. The study focused primarily on the atmospherically relevant methylated benzenes (benzene, toluene, o-xylene, m-xylene, p-xylene, 1,2,4-trimethylbenzene, 1,3,5-trimethylbenzene, ethylbenzene, styrene) and their ring retaining oxidation products (benzaldehyde, o-tolualdehyde, m-tolualdehyde, p-tolualdehyde, phenol, o-cresol, m-cresol, p-cresol, 2,3-dimethylphenol, 2,4-dimethylphenol, 2,5-dimethylphenol, 2,6-dimethylphenol, 3,4-dimethylphenol, 3,5-dimethylphenol, 2,4,6-trimethylphenol and ( E,Z)- and ( E,E)-2,4-hexadienedial). The UV absorption cross sections reported here can be used for the evaluation of DOAS spectra (Differential Optical Absorption Spectroscopy) for measurements of the above compounds in the atmosphere and in reaction chambers, while the IR absorption cross sections will primarily be useful in laboratory studies on atmospheric chemistry, where FT-IR spectrometry is an important tool.

  19. Cloud and aerosol classification for 2.5 years of MAX-DOAS observations in Wuxi (China) and comparison to independent data sets

    NASA Astrophysics Data System (ADS)

    Wang, Y.; Penning de Vries, M.; Xie, P. H.; Beirle, S.; Dörner, S.; Remmers, J.; Li, A.; Wagner, T.

    2015-12-01

    Multi-axis differential optical absorption spectroscopy (MAX-DOAS) observations of trace gases can be strongly influenced by clouds and aerosols. Thus it is important to identify clouds and characterize their properties. In a recent study Wagner et al. (2014) developed a cloud classification scheme based on the MAX-DOAS measurements themselves with which different "sky conditions" (e.g., clear sky, continuous clouds, broken clouds) can be distinguished. Here we apply this scheme to long-term MAX-DOAS measurements from 2011 to 2013 in Wuxi, China (31.57° N, 120.31° E). The original algorithm has been adapted to the characteristics of the Wuxi instrument, and extended towards smaller solar zenith angles (SZA). Moreover, a method for the determination and correction of instrumental degradation is developed to avoid artificial trends of the cloud classification results. We compared the results of the MAX-DOAS cloud classification scheme to several independent measurements: aerosol optical depth from a nearby Aerosol Robotic Network (AERONET) station and from two Moderate Resolution Imaging Spectroradiometer (MODIS) instruments, visibility derived from a visibility meter and various cloud parameters from different satellite instruments (MODIS, the Ozone Monitoring Instrument (OMI) and the Global Ozone Monitoring Experiment (GOME-2)). Here it should be noted that no quantitative comparison between the MAX-DOAS results and the independent data sets is possible, because (a) not exactly the same quantities are measured, and (b) the spatial and temporal sampling is quite different. Thus our comparison is performed in a semi-quantitative way: the MAX-DOAS cloud classification results are studied as a function of the external quantities. The most important findings from these comparisons are as follows: (1) most cases characterized as clear sky with low or high aerosol load were associated with the respective aerosol optical depth (AOD) ranges obtained by AERONET and MODIS

  20. The impact of vibrational Raman scattering of air on DOAS measurements of atmospheric trace gases

    NASA Astrophysics Data System (ADS)

    Lampel, J.; Frieß, U.; Platt, U.

    2015-09-01

    In remote sensing applications, such as differential optical absorption spectroscopy (DOAS), atmospheric scattering processes need to be considered. After inelastic scattering on N2 and O2 molecules, the scattered photons occur as additional intensity at a different wavelength, effectively leading to "filling-in" of both solar Fraunhofer lines and absorptions of atmospheric constituents, if the inelastic scattering happens after the absorption. Measured spectra in passive DOAS applications are typically corrected for rotational Raman scattering (RRS), also called Ring effect, which represents the main contribution to inelastic scattering. Inelastic scattering can also occur in liquid water, and its influence on DOAS measurements has been observed over clear ocean water. In contrast to that, vibrational Raman scattering (VRS) of N2 and O2 has often been thought to be negligible, but it also contributes. Consequences of VRS are red-shifted Fraunhofer structures in scattered light spectra and filling-in of Fraunhofer lines, additional to RRS. At 393 nm, the spectral shift is 25 and 40 nm for VRS of O2 and N2, respectively. We describe how to calculate VRS correction spectra according to the Ring spectrum. We use the VRS correction spectra in the spectral range of 420-440 nm to determine the relative magnitude of the cross-sections of VRS of O2 and N2 and RRS of air. The effect of VRS is shown for the first time in spectral evaluations of Multi-Axis DOAS data from the SOPRAN M91 campaign and the MAD-CAT MAX-DOAS intercomparison campaign. The measurements yield in agreement with calculated scattering cross-sections that the observed VRS(N2) cross-section at 393 nm amounts to 2.3 ± 0.4 % of the cross-section of RRS at 433 nm under tropospheric conditions. The contribution of VRS(O2) is also found to be in agreement with calculated scattering cross-sections. It is concluded, that this phenomenon has to be included in the spectral evaluation of weak absorbers as it

  1. A two-laser beam technique for improving the sensitivity of low frequency open path tunable diode laser absorption spectrometer (OP-TDLAS) measurements

    NASA Astrophysics Data System (ADS)

    Mohammad, Isra'a. Lateef

    Open path tunable diode-laser absorption spectroscopy (OP-TDLAS) is a promising technique that is proposed for detecting low concentrations of possible biogenic gases on Mars. This technique determines the concentration of a gas by measuring the amount of laser light absorbed by molecules at a specific wavelength that is characteristic of those molecules. One of the major factors limiting sensitivity in the OP-TDLAS systems is noise. At low modulation frequencies, 1/f noise usually dominates. This 1/f noise is minimized in many spectroscopy systems by use of high frequency techniques. However, these methods use complex instruments that include reference cells and other devices for calibration, making them relatively large and bulky. We have built a spectroscopy system for space applications that requires small, low mass and low power instrumentation, making the high frequency techniques unsuitable. This work explores a new technique that uses a two-laser beam to reduce the affect of 1/f noise and increase the signal strength for measurements made at lower frequencies. The two lasers are excited at slightly different frequencies. An algorithm is used to estimate the total noise in the second harmonic from the combined spectra of both lasers. This noise is subtracted from the signal to give a more accurate measurement of gas concentration. The error in estimation of 1/f noise is negligible as it corresponds to noise level made at much higher frequencies. Experimental results using ammonia gas and two lasers operating at 500 and 510 Hz respectively shows that this technique reduces the effect of 1/f noise by 1/3 its normal value. Furthermore, the error in estimation of gas concentration is also reduced.

  2. A two-laser beam technique for improving the sensitivity of low frequency open path tunable diode laser absorption spectrometer (OP-TDLAS) measurements

    NASA Astrophysics Data System (ADS)

    Mohammad, Israa L.; Anderson, Gary T.; Chen, Youhua

    2013-09-01

    Open path tunable diode-laser absorption spectroscopy (OP-TDLAS) is a promising technique to detect low concentrations of possible biogenic gases on Mars. This technique finds the concentration of a gas by measuring the amount of laser light absorbed by gaseous molecules at a specific wavelength. One of the major factors limiting sensitivity in the TDLAS systems operating at low modulation frequencies is 1/f noise. 1/f noise is minimized in many spectroscopy systems by the use of high frequency modulation techniques. However, these techniques require complex instruments that include reference cells and other devices for calibration, making them relatively large and bulky. We are developing a spectroscopy system for space applications that requires small, low mass and low power instrumentation, making the high frequency techniques unsuitable. This paper explores a new technique using two-laser beam to reduce the affect of 1/f noise and increase the signal strength for measurements made at lower frequencies. The two lasers are excited at slightly different frequencies. An algorithm is used to estimate the noise in the second harmonic from the combined spectra of both lasers. This noise is subtracted from the signal to give a more accurate measurement of gas concentration. The error in estimation of 1/f noise is negligible as it corresponds to noise level made at much higher frequencies. Simulation results using ammonia gas and two lasers operating at 500 and 510 Hz respectively shows that this technique is able to decrease the error in estimation of gas concentration to 1/6 its normal value.

  3. Horizontal and temporal evolution of tropospheric NO2 in Vienna as inferred from car DOAS measurements

    NASA Astrophysics Data System (ADS)

    Schreier, Stefan F.; Richter, Andreas; Li, Zheng; Burrows, John P.

    2016-04-01

    Zenith-sky measurements were performed with a car DOAS (Differential Optical Absorption Spectroscopy) instrument to obtain tropospheric nitrogen dioxide (NO2) distributions within the metropolitan area of Vienna, Austria, on nine days in April, September, October, and November 2015. Several single car journeys having an approximate distance of 110 km and covering known emission sources of nitrogen oxides (NOx) as well as a background region north of Vienna were carried out. The spectral measurements are analyzed using the DOAS technique applying a nonlinear least-squares fitting algorithm. The obtained NO2 differential slant column densities (DSCDs) are based on the 425-490 nm fitting window and the inclusion of relevant high resolution absorption cross-sections. Tropospheric NO2 vertical column densities (VCDs) are extracted from the NO2 DSCDs by making assumptions on the diurnal variation of stratospheric NO2 VCDs and determining a tropospheric NO2 airmass factor. Additional meteorological (wind speed and wind direction) and air quality (surface NO2 concentrations) data from nearby measurement stations is used to interpret the horizontal and temporal evolution of NO2 pollution. Our results show that elevated NO2 pollution originating from rush-hour traffic over busy highways is transported along the Danube River to the Northwest of Vienna under certain meteorological conditions.

  4. Measurements of formaldehyde total content using DOAS technique: a new retrieval method for overcast

    NASA Astrophysics Data System (ADS)

    Postylyakov, Oleg; Borovski, Alexander

    2014-11-01

    Formaldehyde (HCHO) is a significant constituent of the atmospheric chemistry involved in a lot of chemical reactions, which principal global source is the intermediate oxidation of volatile organic compounds (VOCs). Taking into account that HCHO basically undergo by photolysis and reaction with hydroxyl radical within a few hours, isoprene together with other short-lived VOCs and direct HCHO emissions can cause local HCHO enhancement over certain areas, and, hence, cases with HCHO, that exceed some background level, can be examined as local pollution of the atmosphere by VOCs. HCHO has significant specific features in spectral structure of UV absorption cross-section to be measured using the differential optical absorption spectroscopy (DOAS) technique. Several retrieval algorithms applicable for DOAS measurements in cloudless were previously developed. A new algorithm applicable for overcast and cloudless sky and its error analysis is briefly presented in this paper. In case we know the cloud base height, but don't know cloud optical depth, the error of HCHO total content retrieval is about 10-20% for winter season, about 5% for summer season, and about 30-40% for transition season when the ABL is below the cloud base. In case we know both the cloud base height and cloud optical depth, the error is about 5-10% for winter season, less than 5% for summer season, and about 25-35% for transition season when the ABL is below the cloud base. The errors dramatically increase when clouds penetrate into ABL in both cases.

  5. [The effect of resolution on the measurement of carbon bisulfide by DOAS].

    PubMed

    Peng, Fu-Min; Lin, Yi-Hui; Xie, Pin-Hua; Wang, Jun-De; Zhang, Ying-Hua; Qin, Min; Liu, Wen-Qing; Li, Hai-Yang

    2008-11-01

    Featuring excellent response characteristics and detection sensitivity and with much lower operational cost, differential optical absorption spectroscopy (DOAS) can be a powerful tool to trace the concentration variation of carbon bisulfide (CS2), a kind of poisonous gas with bad smell. In the DOAS measurement, the accuracy of the carbon bisulfide results is determined by the selected spectral resolution. The present paper focuses on the effect of resolution on the detected characteristic absorption structure of CS2 and the variation in differential cross section of CS2 with the change in resolution, from which the effect of resolution on the detection limit of CS2 is deduced. In the end, the functional dependence of the ratio of signal to noise (S/N) on the resolution is reduced by studying the relationship between light intensity and resolution. And the optimized resolution is determined as 0. 41-0. 50 nm (FWHM) with the lowest S/N. The optimized resolution range can yield high sensitivity, good selectivity and a reasonable time resolution for the accurate qualitative and quantitative analysis of CS2 (the results of five different concentration cells show linear correlation with r = 0.999 9 and all the relative standard deviations are less than 0.3% with n = 10). In the end, the long time, real time and continuous monitoring of CS2 was carried out in the Fengtai District of Beijing, and a good result was obtained. PMID:19271469

  6. The Spectrometer

    NASA Astrophysics Data System (ADS)

    Greenslade, Thomas B.

    2012-03-01

    In the fall of 1999 I was shown an Ocean Optics spectrometer-in-the-computer at St. Patricks College at Maynooth, Ireland, and thought that I had seen heaven. Of course, it could not resolve the sodium D-lines (I had done that many years before with a homemade wire diffraction grating ), and I began to realize that inside was some familiar old technology. In this paper I would like to discuss its ancestors.

  7. The Spectrometer

    ERIC Educational Resources Information Center

    Greenslade, Thomas B., Jr.

    2012-01-01

    In the fall of 1999 I was shown an Ocean Optics spectrometer-in-the-computer at St. Patricks College at Maynooth, Ireland, and thought that I had seen heaven. Of course, it could not resolve the sodium D-lines (I had done that many years before with a homemade wire diffraction grating), and I began to realize that inside was some familiar old…

  8. Joint CFO and DOA estimation for multiuser OFDMA uplink

    NASA Astrophysics Data System (ADS)

    Zhang, Weile; Yin, Qinye; Gao, Feifei

    2012-12-01

    In this article, we develop a new subspace-based multiuser joint carrier frequency offset (CFO) and direction-of-arrival (DOA) estimation scheme for orthogonal frequency division multiple access uplink transmissions. We leverage multi-antenna at the receiver and consider that the signals transmitted by each user arrive at the receiving antenna array from multiple DOAs after bouncing from both surrounding and far scatterers. The rank reduction approach is then exploited to estimate the multiple CFOs and DOAs. Specifically, for each user, after the CFO estimation from one-dimensional search, its multiple DOAs can be obtained simultaneously via polynomial rooting. The proposed method supports generalized subcarrier assignment scheme and fully loaded transmissions. Both performance analysis and numerical results are provided to corroborate the proposed studies.

  9. Measurement of formaldehyde total content in troposphere using DOAS technique: improvements in version 1.3a of IAP retrieval algorithm

    NASA Astrophysics Data System (ADS)

    Postylyakov, O. V.; Borovski, A. N.

    2016-05-01

    Formaldehyde (HCHO) is a significant constituent of the atmospheric chemistry involved in a lot of chemical reactions. It is directly emitted by anthropogenic and biogenic sources and, more significantly, by production during oxidation of methane and other VOCs. So HCHO is used as an indicator of local pollution by VOCs. HCHO has a sufficiently large absorption cross-section in the UV spectral region to be detected by the technique of the differential optical absorption spectroscopy (DOAS). We present here new version 1.3a of the algorithm for retrieval of the HCHO total content in the troposphere from DOAS observations of the scattered solar radiation developed in A.M. Obukhov Institute of Atmospheric Physics (IAP). The new version has reduced retrieval error but negligible bias with respect to the previous versions. DOAS measurements of scattered solar radiation are performed at Zvenigorod Scientific Station (ZSS, 55°41'49''N, 36°46'29''E) located in 38 km west from Moscow Ring Road by a MAX-DOAS instrument since 2008. We provide preliminary results of the HCHO total content measurements in the troposphere observed in 2010-2012 obtained by the revised retrieval algorithm.

  10. Inter-comparison of MAX-DOAS Retrieved Vertical Profiles of Aerosol Extinction, SO2 and NO2 in the Alberta Oil Sands with LIDAR Data and GEM-MACH Air Quality Model.

    NASA Astrophysics Data System (ADS)

    Davis, Zoe; Friess, Udo; Strawbridge, Kevin; Whiteway, James; Aggarwal, Monika; Makar, Paul; Li, Shao-Meng; O'Brien, Jason; Baray, Sabour; Schnitzler, Elijah; Olfert, Jason S.; Osthoff, Hans D.; Lobo, Akshay; McLaren, Robert

    2016-04-01

    Understanding industrial emissions of trace gas pollutants in the Alberta oil sands is essential to maintaining air quality standards and informing public policy. Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) measurements of trace gases can improve knowledge of pollutant levels, vertical distribution and chemical transformation. During an intensive air measurement campaign to study emissions, transport, transformation and deposition of oil sands air pollutants from August to September of 2013, a MAX-DOAS instrument was deployed at a site north of Fort McMurray, Alberta to determine the vertical profiles of aerosol extinction, NO2 and SO2 through retrieval from the MAX-DOAS spectral measurements using an optimal estimation method. The large complement of data collected from multiple instruments deployed during this field campaign provides a unique opportunity to validate and characterize the performance of the MAX-DOAS vertical profile retrievals. Aerosol extinction profiles determined from two Light Detection and Ranging (LIDAR) instruments, one collocated and the other on a Twin Otter aircraft that flew over the site during the study, will be compared to the MAX-DOAS aerosol extinction profile retrievals. Vertical profiles of NO2 and SO2 retrieved from the MAX-DOAS measurements will be further compared with the composite vertical profiles measured from the flights of a second aircraft, the NRC-Convair 580, over the field site during the same measurement period. Finally, the MAX-DOAS retrieved tropospheric vertical column densities (VCDs) of SO2 and NO2 will be compared to the predicted VCDs from Environment and Climate Change Canada's Global Environmental Multi-scale - Modelling Air quality and Chemistry (GEM-MACH) air quality model over the grid cell containing the field site. Emission estimates of SO2 from the major oil mining facility Syncrude Mildred Lake using the MAX-DOAS VCD results, validated through the detailed characterization above

  11. An airborne amplitude-modulated 1.57 μm differential laser absorption spectrometer: simultaneous measurement of partial column-averaged dry air mixing ratio of CO2 and target range

    NASA Astrophysics Data System (ADS)

    Sakaizawa, D.; Kawakami, S.; Nakajima, M.; Tanaka, T.; Morino, I.; Uchino, O.

    2013-02-01

    Simultaneous measurements of the partial column-averaged dry air mixing ratio of CO2 (XCO2) and target range were demonstrated using airborne amplitude-modulated 1.57 μm differential laser absorption spectrometer (LAS). The LAS system is useful for discriminating between ground and cloud return signals and has a demonstrated ability to suppress the impact of integrated aerosol signals on atmospheric CO2 measurements. A high correlation coefficient (R) of 0.987 between XCO2 observed by LAS and XCO2 calculated from in situ measurements was obtained. The averaged difference in XCO2 obtained from LAS and validation data was within 1.5 ppm for all spiral measurements. An interesting vertical profile was observed for both XCO2LAS and XCO2val, in which lower altitude CO2 decreases compared to higher altitude CO2 attributed to the photosynthesis over grassland in the summer. In the case of an urban area where there are boundary-layer enhanced CO2 and aerosol in the winter, the difference of XCO2LAS to XCO2val is a negative bias of 1.5 ppm, and XCO2LAS is in agreement with XCO2val within the measurement precision of 2.4 ppm (1 SD).

  12. Performance Analysis of an Improved MUSIC DoA Estimator

    NASA Astrophysics Data System (ADS)

    Vallet, Pascal; Mestre, Xavier; Loubaton, Philippe

    2015-12-01

    This paper adresses the statistical performance of subspace DoA estimation using a sensor array, in the asymptotic regime where the number of samples and sensors both converge to infinity at the same rate. Improved subspace DoA estimators were derived (termed as G-MUSIC) in previous works, and were shown to be consistent and asymptotically Gaussian distributed in the case where the number of sources and their DoA remain fixed. In this case, which models widely spaced DoA scenarios, it is proved in the present paper that the traditional MUSIC method also provides DoA consistent estimates having the same asymptotic variances as the G-MUSIC estimates. The case of DoA that are spaced of the order of a beamwidth, which models closely spaced sources, is also considered. It is shown that G-MUSIC estimates are still able to consistently separate the sources, while it is no longer the case for the MUSIC ones. The asymptotic variances of G-MUSIC estimates are also evaluated.

  13. Ship-based MAX-DOAS measurements of nitrogen dioxide in the South China Sea

    NASA Astrophysics Data System (ADS)

    Schreier, Stefan F.; Peters, Enno; Richter, Andreas; Wittrock, Folkard; Burrows, John P.

    2014-05-01

    In November 2011, the SHIVA-Sonne campaign took place in the South China Sea in order to investigate the transport of very short-lived substances to the stratosphere for a better understanding of their role in ozone depletion. Among other instruments, a Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) instrument was placed on board the RV Sonne to measure scattered sunlight at different elevation angles. These measurements can be used for the retrieval of vertical columns of several trace gases (e.g. nitrogen dioxide (NO2), formaldehyde (HCHO), and iodine monoxide (IO)) by applying the DOAS method. In this study, we present tropospheric NO2 vertical columns (TVC NO2) retrieved from the MAX-DOAS measurements between 17 and 28 November 2011. During this period, the tropospheric NO2 levels were rather low (< 1 x 1015 molec cm-2) in the open sea most of the time. However, elevated NO2 levels (> 5 x 1015 molec cm-2) were observed when other large vessels navigated in the proximity of RV Sonne. Moreover, elevated levels of TVC NO2 (> 3 x 1015 molec cm-2) were also observed close to the coast of the island Borneo. The web-based version of the Hybrid Single Particle Lagrangian Integrated Trajectory Model (HYSPLIT) was used for the calculation of 24 h backward trajectories to better identify the sources of these elevated levels of TVC NO2. The analysis of the backward trajectories indicated that some cases with elevated tropospheric NO2 levels could be the result of NO2 transport from biomass burning and urban/industrial sources. In summary, the highest levels of TVC NO2 were found to be the result of the combustion process of large vessel engines. The contribution of biomass burning and urban/industrial sources to the tropospheric NO2 level in the South China Sea is rather low, at least during this part of the season.

  14. Photophoretic spectrometer

    SciTech Connect

    Arnold, S.; Amani, Y.; Orenstein, A.

    1980-09-01

    An instrument is described which measures the spectral dependence of the radiometric (photophoretic) force on a micron-sized particle in a static configuration. This spectrometer consists of a servo-stabilized Millikan chamber which can be used as a photophoretic balance over the spectral range from 200 nm to 1000 nm. Spectra may be taken in a vacuum as small as 10/sup -4/ torr. The action spectrum of the photophoretic force on a crystallite of CdS is used as an example. The pressure dependence of the force at 500 nm is consistant with a radiometric mechanism.

  15. MASS SPECTROMETER

    DOEpatents

    White, F.A.

    1960-08-23

    A mass spectrometer is designed with a first adjustable magnetic field for resolving an ion beam into beams of selected masses, a second adjustable magnetic field for further resolving the ion beam from the first field into beams of selected masses, a thin foil disposed in the path of the beam between the first and second magnets to dissociate molecular ions incident thereon, an electrostatic field for further resolving the ion beam from the second field into beams of selected masses, and a detector disposed adjacent to the electrostatic field to receive the ion beam.

  16. Long-term MAX-DOAS measurement of trace gases and aerosol in the Environmental Research Station Schneefernerhaus

    NASA Astrophysics Data System (ADS)

    Wang, Zhuoru; Hao, Nan; Hendrick, François; Van Roozendael, Michel; Holla, Robert; Valks, Pieter

    2016-04-01

    The Environmental Research Station Schneefernerhaus (Umwelt Forschungsstation Schneefernerhaus, UFS) is located immediately under the summit of Zugspitze (2962 m), the highest mountain of Germany, at a height of 2650 m. The UFS is a rare observation site in Germany with mostly clean and unpolluted air. It is ideal for both stratospheric composition measurements and trace gas measurements in the free-troposphere. It is optimal for detecting pollution events in the free-troposphere, which are indications of short- or long-range transport of air pollutants. A MAX-DOAS instrument has been working in the UFS since February 2011. With the zenith spectrum of each cycle used as the reference, the differential slant column densities (DSCDs) of trace gases are calculated from the spectra with Differential Optical Absorption Spectroscopy (DOAS) method. The DSCDs of both O4 and NO2 are calculated in two different wavelength intervals, 338-370 nm in the UV region and 440-490 nm in the VIS region. For HCHO and HONO, optimal fitting windows have been determined in the UV region. A retrieval algorithm, based on the radiative transfer model LIDORT and the optimal estimation technique, is used to provide information on the vertical profiles and vertical column densities (VCDs) of aerosol and trace gases. Meanwhile, zenith-sky radiance spectra during twilight hours are analyzed using DOAS method to derive the total vertical column densities (VCDs) of O3 and NO2. A zenith spectrum measured in the noon of a summer day was chosen as the reference spectrum. The slant column densities (SCDs) of O3 and NO2, which are the direct product of the DOAS analysis, are then converted into VCDs using the air mass factors (AMFs) derived by radiative transfer calculations. This work presents the results of the MAX-DOAS measurement in the UFS from 2012 to 2015, including aerosol (derived from O4 measurement), NO2, HCHO, and HONO, etc. The vertical profiles as well as the seasonal and diurnal variation

  17. Evaluation wavelength range mapping, a tool to optimize the evaluation window in differential absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Vogel, L.; Sihler, H.; Lampel, J.; Wagner, T.; Platt, U.

    2012-04-01

    Optical remote sensing via Differential Optical Absorption Spectroscopy (DOAS) has become a standard technique to assess various trace gases in the atmosphere. Measurement instruments are usually classified into active instruments applying an artificial light source and passive instruments using natural light sources, e.g., scattered or direct sunlight. Platforms range from ground based to satellites and trace gases are studied in all kinds of different environments. Naturally, the evaluation of gathered spectra needs to be tuned to each specific case and trace gas of interest due to the wide range of measurement conditions, atmospheric compositions and instruments used. A well chosen evaluation wavelength range is crucial to the DOAS technique. It should be as large as possible and include the largest differential absorption features of the trace gas of interest in order to maximize sensitivity. However, the differential optical densities of other absorbers should be minimized in order to prevent interferences between different absorption cross sections. Furthermore, instrumental specific features and wavelength dependent radiative transfer effects may have malicious effects and lead to erroneous values. Usually a compromise needs to be found depending on the conditions at hand. Evaluation wavelength range mapping is an easily applied tool to visualize wavelength depending evaluation features of DOAS and to find the optimal retrieval wavelength range. As an example, synthetic spectra are studied which simulate passive DOAS measurements of stratospheric bromine monoxide (BrO) by Zenith-DOAS and Multi-Axis DOAS (MAX-DOAS) measurements of BrO in volcanic plumes. The influence of the I0-effect and the Ring-effect on the respective retrievals are demonstrated. However, due to the general nature of the tool it is applicable to any DOAS measurement and the technique also allows to study any other wavelength dependent influences on retrieved trace gas columns.

  18. Development of 2-D-MAX-DOAS and retrievals of trace gases and aerosols optical properties

    NASA Astrophysics Data System (ADS)

    Ortega, Ivan

    Air pollution is a major problem worldwide that adversely a_ects human health, impacts ecosystems and climate. In the atmosphere, there are hundreds of important compounds participating in complex atmospheric reactions linked to air quality and climate. Aerosols are relevant because they modify the radiation balance, a_ect clouds, and thus Earth albedo. The amount of aerosol is often characterized by the vertical integral through the entire height of the atmosphere of the logarithm fraction of incident light that is extinguished called Aerosol Optical Depth (AOD). The AOD at 550 nm (AOD550) over land is 0.19 (multi annual global mean), and that over oceans is 0.13. About 43 % of the Earth surface shows AOD550 smaller than 0.1. There is a need for measurement techniques that are optimized to measure aerosol optical properties under low AOD conditions, sample spatial scales that resemble satellite ground-pixels and atmospheric models, and help integrate remote sensing and in-situ observations to obtain optical closure on the effects of aerosols and trace gases in our changing environment. In this work, I present the recent development of the University of Colorado two dimensional (2-D) Multi-AXis Differential Optical Absorption Spectroscopy (2-D-MAX-DOAS) instrument to measure the azimuth and altitude distribution of trace gases and aerosol optical properties simultaneously with a single instrument. The instrument measures solar scattered light from any direction in the sky, including direct sun light in the hyperspectral domain. In Chapter 2, I describe the capabilities of 2-D measurements in the context of retrievals of azimuth distributions of nitrogen dioxide (NO2), formaldehyde (HCHO), and glyoxal (CHOCHO), which are precursors for tropospheric O3 and aerosols. The measurements were carried out during the Multi-Axis DOAS Comparison campaign for Aerosols and Trace gases (MAD-CAT) campaign in Mainz, Germany and show the ability to bridge spatial scales to

  19. Study of the CH2I + O2 Reaction with a Step-Scan Fourier-Transform Infrared Absorption Spectrometer: Spectra of the Criegee Intermediate CH2OO and DIOXIRANE(?)

    NASA Astrophysics Data System (ADS)

    Huang, Yu-Hsuan; Lee, Yuan-Pern

    2014-06-01

    The Criegee intermediates are carbonyl oxides that play key roles in ozonolysis of unsaturated organic compounds. This mechanism was first proposed by Criegee in 1949, but the first direct observation of the simplest Criegee intermediate CH2OO in the gaseous phase has been reported only recently using photoionization mass spectrometry. Our group has reported the low-resolution IR spectra of CH2OO, produced from the reaction of CH2I + O2, with a second-generation step-scan Fourier-transfom IR absorption spectrometer. The spectral assignments were based on comparison of observed vibrational wavenumbers and rotational contours with theoretical predictions. Here, we report the IR absorption spectra of CH2OO at a resolution of 0.32 wn, showing partially rotationally-resolved structures. The origins of the νb{3}, νb{4}, νb{6}, and νb{8} vibrational modes of CH2OO are determined to be 1434.1, 1285.7, 909.2, and 847.3 wn, respectively. With the analysis of the vibration-rotational spectra, we provide a definitive assignment of these bands to CH2OO. The observed vibrational wavenumbers indicate a zwitterionic contribution to this singlet biradical showing a strengthened C-O bond and a weakened O-O bond. This zwitterionic character results to an extremely rapid self reaction via a cyclic dimer to form 2H2CO + O2 (1Δg). Another group of weak transient IR bands centered at 1231.5, 1213.3, and 899.8 wn are also observed. These bands might be contributed from dioxirane, which was postulated to be another important intermediate that might be isomerized from the Criegee intermediate in the reaction of O3 with 1-alkenes. O. Welz, J. D. Savee, D. L. Osborn, S. S.Vasu, C. J. Percival, D. E. Shallcross, and C. A. Taatjes, Science 335, 204 (2012). Y.-T. Su, Y.-H. Huang, H. A.Witek, and Y.-P. Lee, Science 340, 174 (2013).

  20. MAX-DOAS measurements of atmospheric trace gases in Ny-Ålesund

    NASA Astrophysics Data System (ADS)

    Wittrock, F.; Oetjen, H.; Richter, A.; Fietkau, S.; Medeke, T.; Rozanov, A.; Burrows, J. P.

    2003-12-01

    A new approach to derive tropospheric concentrations of some atmospheric trace gases from ground-based UV/vis measurements is described. The instrument, referred to as the MAX-DOAS, is based on the well-known UV/vis instruments, which use the sunlight scattered in the zenith sky as the light source and the method of Differential Optical Absorption Spectroscopy (DOAS) to derive column amounts of absorbers like ozone and nitrogen dioxide. Substantial enhancements have been applied to this standard setup to use different lines of sight near to the horizon as additional light sources (MAX - multi axis). Results from measurements at Ny-Ålesund (79° N, 12° E) are presented and interpreted with the full-spherical radiation transport model SCIATRAN. In particular, measurements of the oxygen dimer O4 which has a known column and vertical distribution in the atmosphere are used to evaluate the sensitivity of the retrieval to parameters such as multiple scattering, solar azimuth, surface albedo and refraction in the atmosphere and also to validate the radiative transport model. As a first application, measurements of NO2 emissions from a ship lying in Ny-Ålesund harbour are presented. The results of this study demonstrate the feasibility of long term UV/vis multi axis measurement that can be used to derive not only column amounts of different trace gases but also some information on the vertical location of these absorbers.

  1. Airborne multi-axis DOAS measurements of atmospheric trace gases on CARIBIC long-distance flights

    NASA Astrophysics Data System (ADS)

    Dix, B.; Brenninkmeijer, C. A. M.; Frieß, U.; Wagner, T.; Platt, U.

    2009-11-01

    A DOAS (Differential Optical Absorption Spectroscopy) instrument was implemented and operated onboard a long-distance passenger aircraft within the framework of the CARIBIC project (Civil Aircraft for the Regular Investigation of the atmosphere Based on an Instrument Container). The instrument was designed to keep weight, size and power consumption low and to comply with civil aviation regulations. It records spectra of scattered light from three viewing directions (nadir, 10° above and below horizon) using a miniaturized telescope system. The telescopes are integrated in the main pylon of the inlet system which is mounted at the belly of the aircraft. Fibre bundles transmit light from the telescopes to spectrograph-detector units inside the DOAS container instrument. The latter is part of the removable CARIBIC instrument container, which is installed monthly on the aircraft for a series of measurement flights. During 30 flight operations within three years, measurements of HCHO, HONO, NO2, BrO, O3 and the oxygen dimer O4 were conducted. All of these trace gases except BrO could be analysed with a 30 s time resolution. HONO was detected for the first time in a deep convective cloud over central Asia, while BrO, NO2 and O3 could be observed in tropopause fold regions. Biomass burning signatures over South America could be seen and measurements during ascent and descent provided information on boundary layer trace gas profiles (e.g. NO2 or HCHO).

  2. Airborne multi-axis DOAS measurements of atmospheric trace gases on CARIBIC long-distance flights

    NASA Astrophysics Data System (ADS)

    Dix, B.; Brenninkmeijer, C. A. M.; Frieß, U.; Wagner, T.; Platt, U.

    2009-02-01

    A DOAS (Differential Optical Absorption Spectroscopy) instrument was implemented and operated onboard a long-distance passenger aircraft within the framework of the CARIBIC project (Civil Aircraft for the Regular Investigation of the atmosphere Based on an Instrument Container). The instrument was designed to keep weight, size and power consumption low and to comply with civil aviation regulations. It records spectra of scattered light from three viewing directions (nadir, 10° above and below horizon) using a miniaturized telescope system. The telescopes are integrated in the main pylon of the inlet system which is mounted at the belly of the aircraft. Fibre bundles transmit light from the telescopes to spectrograph-detector units inside the DOAS container instrument. The latter is part of the removable CARIBIC instrument container, which is installed monthly on the aircraft for a series of measurement flights. During 30 flight operations within three years, measurements of HCHO, HONO, NO2, BrO, O3 and the oxygen dimer O4 were conducted. All of these trace gases except BrO could be analysed with a 30 s time resolution. HONO was detected for the first time in a deep convective cloud over central Asia. BrO, NO2 and O3 could be observed in tropopause fold regions, biomass burning signatures over South America could be seen and measurements during ascent and descent provided information on boundary layer trace gas profiles (e.g. NO2 or HCHO).

  3. Homogenization of UV-Visible NDACC spectrometers reprocessing for ozone and NO2

    NASA Astrophysics Data System (ADS)

    Pazmino, Andrea

    2010-05-01

    SAOZ is a ground-based UV-Visible zenith-sky spectrometer deployed since 1988 at a number of NDACC (Network for the Detection of Atmospheric Composition Change) stations at all latitudes on the globe. The instrument is providing ozone and NO2 total columns at sunrise and sunset using the Differential Optical Absorption Spectroscopy (DOAS) technique in the visible spectral range. SAOZ observations have been used extensively to validate various atmospheric chemistry satellite instruments such as nadir viewing TOMS, GOME, SCIAMACHY, OMI and GOME-2. The NDACC UV-Visible working group initiated a tentative homogenization of ozone and NO2 processing of all UV-Vis zenith sky spectrometers as one of its objectives. The first recommendation is concerning the total ozone retrieval. A significant change for the SAOZ network is the use of different cross-sections (O3, NO2, H2O, O4, and Ring calculations) and different spectral window fitting range, which leads to a recalculation of the slant columns. In addition, it is recommended to use a climatological air mass factor (AMF) instead of an annual AMF usually used in standard SAOZ processing. Here we present the results of comparisons between TOMS (since 1988), GOME (since 1995), SCIAMACHY (since 2002), OMI (since 2004), GOME-2 (since 2006) and SAOZ at all latitudes - tropics, mid-latitudes and Polar Regions - in both hemispheres. In the case of ozone, the NDACC recommendations resulted in a significant improvement of the differences between ground-based SAOZ and measurements from space. Preliminary results of NO2 SAOZ columns, using climatological AMF, are also presented and compared to different satellites, such as GOME, SCIAMACHY and OMI.

  4. Observations of atmospheric trace gases by MAX-DOAS in the coastal boundary layer over Jiaozhou Bay

    NASA Astrophysics Data System (ADS)

    Li, Xianxin; Wang, Zhangjun; Meng, Xiangqian; Zhou, Haijin; Du, Libin; Qu, Junle; Chen, Chao; An, Quan; Wu, Chengxuan; Wang, Xiufen

    2014-11-01

    Atmospheric trace gases exist in the atmosphere of the earth rarely. But the atmospheric trace gases play an important role in the global atmospheric environment and ecological balance by participating in the global atmospheric cycle. And many environmental problems are caused by the atmospheric trace gases such as photochemical smog, acid rain, greenhouse effect, ozone depletion, etc. So observations of atmospheric trace gases become very important. Multi Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) developed recently is a kind of promising passive remote sensing technology which can utilize scattered sunlight received from multiple viewing directions to derive vertical column density of lower tropospheric trace gases like ozone, sulfur dioxide and nitrogen dioxide. It has advantages of simple structure, stable running, passive remote sensing and real-time online monitoring automatically. A MAX-DOAS has been developed at Shandong Academy of Sciences Institute of Oceanographic Instrumentation (SDIOI) for remote measurements of lower tropospheric trace gases (NO2, SO2, and O3). In this paper, we mainly introduce the stucture of the instrument, calibration and results. Detailed performance analysis and calibration of the instrument were made at Qingdao. We present the results of NO2, SO2 and O3 vertical column density measured in the coastal boundary layer over Jiaozhou Bay. The diurnal variation and the daily average value comparison of vertical column density during a long-trem observation are presented. The vertical column density of NO2 and SO2 measured during Qingdao oil pipeline explosion on November 22, 2013 by MAX-DOAS is also presented. The vertical column density of NO2 reached to a high value after the explosion. Finally, the following job and the outlook for future possible improvements are given. Experimental calibration and results show that the developed MAX-DOAS system is reliable and credible.

  5. Underdetermined DOA Estimation Using MVDR-Weighted LASSO

    PubMed Central

    Salama, Amgad A.; Ahmad, M. Omair; Swamy, M. N. S.

    2016-01-01

    The direction of arrival (DOA) estimation problem is formulated in a compressive sensing (CS) framework, and an extended array aperture is presented to increase the number of degrees of freedom of the array. The ordinary least square adaptable least absolute shrinkage and selection operator (OLS A-LASSO) is applied for the first time for DOA estimation. Furthermore, a new LASSO algorithm, the minimum variance distortionless response (MVDR) A-LASSO, which solves the DOA problem in the CS framework, is presented. The proposed algorithm does not depend on the singular value decomposition nor on the orthogonality of the signal and the noise subspaces. Hence, the DOA estimation can be done without a priori knowledge of the number of sources. The proposed algorithm can estimate up to ((M2−2)/2+M−1)/2 sources using M sensors without any constraints or assumptions about the nature of the signal sources. Furthermore, the proposed algorithm exhibits performance that is superior compared to that of the classical DOA estimation methods, especially for low signal to noise ratios (SNR), spatially-closed sources and coherent scenarios. PMID:27657080

  6. Particle extinction measured at ambient conditions with differential optical absorption spectroscopy. 1. system setup and characterization.

    PubMed

    Müller, Thomas; Müller, Detlef; Dubois, René

    2005-03-20

    We describe an instrument for measuring the particle extinction coefficient at ambient conditions in the spectral range from 270 to 1000 nm. It is based on a differential optical absorption spectroscopy (DOAS) system, which was originally used for measuring trace-gas concentrations of atmospheric absorbers in the ultraviolet-visible wavelength range. One obtains the particle extinction spectrum by measuring the total atmospheric extinction and subtracting trace-gas absorption and Rayleigh scattering. The instrument consists of two nested Newton-type telescopes, which are simultaneously used for emitting and detecting light, and two arrays of retroreflectors at the ends of the two light paths. The design of this new instrument solves crucial problems usually encountered in the design of such instruments. The telescope is actively repositioned during the measurement cycle. Particle extinction is simultaneously measured at several wavelengths by the use of two grating spectrometers. Optical turbulence causes lateral movement of the spot of light in the receiver telescope. Monitoring of the return signals with a diode permits correction for this effect. Phase-sensitive detection efficiently suppresses background signals from the atmosphere as well as from the instrument itself. The performance of the instrument was tested during a measurement period of 3 months from January to March 2000. The instrument ran without significant interruption during that period. A mean accuracy of 0.032 km(-1) was found for the extinction coefficient for an 11-day period in March. PMID:15813269

  7. [Study on determination of plume velocity by passive differential optical absorption spectroscopy].

    PubMed

    Li, Ang; Xie, Pin-hua; Liu, Wen-qing; Liu, Jian-guo; Dou, Ke; Lin, Yi-hui

    2008-10-01

    Differential optical absorption spectroscopy (DOAS) technique has been used to measure various trace gases in the atmosphere by their strongly structured absorption of radiation in the UV and visible spectral range. Passive DOAS using the zenith scattered sunlight as the light source can obtain the continuous column density distribution of air pollutants (such as SO2 and NO2) by scanning the plume emitted from sources on a mobile platform, then with the plume velocity information the total emission value can be ultimately estimated. In practice it is hard to calculate the total emission because there is no efficient way to accurately get the plume velocity which is the most important parameter. Usually the wind speed near ground is used as the actual plume speed, which constitutes the greatest source of uncertainty in the passive DOAS measurements for the total emission calculation. A passive DOAS method for the determination of plume velocity of pollution source was studied in the present paper. Two passive DOAS systems were placed under the plume along the plume transmission direction to observed the scattered sunlight at one fixed sepasation angle, and then the plume velocity was derived from the time delay resulting from the plume moving a certain distance, and also the plume height needed in the plume velocity calculation was measured by the same two passive DOAS systems. Measurement of the plume emitted from a certain power plant was carried out by the two passive DOAS systems and the plume velocities of 3.6 and 5.4 m x s(-1) at two separate moments were derived. The comparison with the wind speed measured at the same time by the single theodolite wind observation method indicates that this optical remote sensing method based on passive DOAS can be used to determine the plume velocity by monitoring the total emission from sources.

  8. [Study on determination of plume velocity by passive differential optical absorption spectroscopy].

    PubMed

    Li, Ang; Xie, Pin-hua; Liu, Wen-qing; Liu, Jian-guo; Dou, Ke; Lin, Yi-hui

    2008-10-01

    Differential optical absorption spectroscopy (DOAS) technique has been used to measure various trace gases in the atmosphere by their strongly structured absorption of radiation in the UV and visible spectral range. Passive DOAS using the zenith scattered sunlight as the light source can obtain the continuous column density distribution of air pollutants (such as SO2 and NO2) by scanning the plume emitted from sources on a mobile platform, then with the plume velocity information the total emission value can be ultimately estimated. In practice it is hard to calculate the total emission because there is no efficient way to accurately get the plume velocity which is the most important parameter. Usually the wind speed near ground is used as the actual plume speed, which constitutes the greatest source of uncertainty in the passive DOAS measurements for the total emission calculation. A passive DOAS method for the determination of plume velocity of pollution source was studied in the present paper. Two passive DOAS systems were placed under the plume along the plume transmission direction to observed the scattered sunlight at one fixed sepasation angle, and then the plume velocity was derived from the time delay resulting from the plume moving a certain distance, and also the plume height needed in the plume velocity calculation was measured by the same two passive DOAS systems. Measurement of the plume emitted from a certain power plant was carried out by the two passive DOAS systems and the plume velocities of 3.6 and 5.4 m x s(-1) at two separate moments were derived. The comparison with the wind speed measured at the same time by the single theodolite wind observation method indicates that this optical remote sensing method based on passive DOAS can be used to determine the plume velocity by monitoring the total emission from sources. PMID:19123375

  9. [Retrieval of tropospheric NO2 by multi axis differential optical absorption spectroscopy].

    PubMed

    Xu, Jin; Xie, Pin-hua; Si, Fu-qi; Dou, Ke; Li, Ang; Liu, Yu; Liu, Wen-qing

    2010-09-01

    A method of retrieving NO2 in troposphere based on multi axis differential optical absorption spectroscopy (MAX-DOAS) was introduced. The differential slant column density (dSCD) of NO2 was evaluated by differential optical absorption spectroscopy (DOAS), removing the Fraunhofer structure and Ring effect. Combining the results of different observing directions, the tropospheric NO2 differential slant column density (deltaSCD) was evaluated, and the air mass factor (AMF) was calculated with the radiative transfer model SCIATRAN and the tropospheric NO2 vertical column density (VCD) was retrieved. To ensure the accuracy of the results, it was compared with the results of long path differential optical absorption spectroscopy (LP-DOAS), a good accordance was shown with the correlation coefficients of 0.94027 and 0.96924. PMID:21105419

  10. Ultra Compact Imaging Spectrometer (UCIS)

    NASA Astrophysics Data System (ADS)

    Blaney, Diana L.; Green, Robert; Mouroulis, Pantazis; Cable, Morgan; Ehlmann, Bethany; Haag, Justin; Lamborn, Andrew; McKinley, Ian; Rodriguez, Jose; van Gorp, Byron

    2016-10-01

    The Ultra Compact Imaging Spectrometer (UCIS) is a modular visible to short wavelength infrared imaging spectrometer architecture which could be adapted to a variety of mission concepts requiring low mass and low power. Imaging spectroscopy is an established technique to address complex questions of geologic evolution by mapping diagnostic absorption features due to minerals, organics, and volatiles throughout our solar system. At the core of UCIS is an Offner imaging spectrometer using M3 heritage and a miniature pulse tube cryo-cooler developed under the NASA Maturation of Instruments for Solar System Exploration (MatISSE) program to cool the focal plane array. The TRL 6 integrated spectrometer and cryo-cooler provide a basic imaging spectrometer capability that is used with a variety of fore optics to address lunar, mars, and small body science goals. Potential configurations include: remote sensing from small orbiters and flyby spacecraft; in situ panoramic imaging spectroscopy; and in situ micro-spectroscopy. A micro-spectroscopy front end is being developed using MatISSE funding with integration and testing planned this summer.

  11. Optical fiber interferometric spectrometer

    NASA Astrophysics Data System (ADS)

    Liu, Yong; Li, Baosheng; Liu, Yan; Zhai, Yufeng; Wang, An

    2006-02-01

    We design an optical fiber spectrometer based on optical fiber Mach-Zehnder interferometer. In optical fiber Fourier transform spectrometer spectra information is obtained by Fourier transform of interferogram, which recording intensity change vs. optical path difference. Optical path difference is generated by stretching one fiber arm which wound around fiber stretch drive by high power supply. Information from detector is linear with time rather than with optical path difference. In order to obtain high accuracy wavenumber, reference beam is used to control the optical path difference. Optical path difference is measured by reference laser interference fringe. Interferogram vs. optical path difference is resampled by Brault algorithm with information from reference beam and test beam. In the same condition, one-sided interferogram has higher resolution than that of two-sided interferogram. For one-sided interferogram, zero path difference position must be determined as accurately as possible, small shift will result in phase error. For practical experiment in laboratory, position shift is inevitable, so phase error correction must be considered. Zero order fringe is determined by curve fitting. Spectrum of light source is obtained from one-sided interferogram by Fourier cosine transform. A spectral resolution of about ~3.1 cm -1 is achieved. In practice, higher resolution is needed. This compact equipment will be used in emission spectra and absorption spectra, especially in infrared region.

  12. [Atmospheric HCHO gradient monitoring and analysis in Beijing City with a scanning DOAS system].

    PubMed

    Wang, Man-hua; Xie, Pin-hua; Qin, Min; Dou, Ke; Wang, Jie; Li, Ang; Xu, Jin; Shi, Peng; Wu, Feng-cheng

    2011-03-01

    Scanning differential optical absorption spectroscopy (DOAS) technique combined with meteorological tower was used for monitoring vertical profiles of SO2, NO2, O3, HCHO and HONO along three light paths in Beijing City during July 28, 2009 to August 13, 2009. As a result, the time series of concentrations and vertical gradient of HCHO as well as other gases were acquired. By analyzing the vertical distribution frequency characteristics of HCHO, data of other gases and meteorological data, it was concluded that the main source of HCHO is vehicles emissions around the measurement site. The photochemical reaction as the secondary source accounts for a significant proportion of the source of HCHO at certain times of day (around noon, for a few hours). PMID:21595241

  13. [Monitoring and analysis of air pollutants using DOAS in winter of Beijing].

    PubMed

    Zhu, Yan-wu; Fu, Qiang; Xie, Pin-hua; Liu, Wen-qing; Peng, Fu-min; Qin, Min; Lin, Yi-hui; Si, Fu-qi; Dou, Ke

    2009-05-01

    Based on the differential optical absorption spectroscopy (DOAS) technology, the measurement of air pollutants (SOz, NO2, HONO and HCHO) was performed continuously from Jan 19, 2007 to Feb 8, 2007 in Peking University campus. The typical diurnal variation characteristic of SO2 concentration, the main source and the meteorological factors that influence the pollutants were analyzed. The results indicated that the typical diurnal variation of SO2 concentration has the same shape as the letter "V" when wind speed was low, and in the afternoon the SO2 concentration was the lowest, while in other time it was high. Coal-burning made prominent contribution to the concentration of atmospheric various pollutants in the heating period of Beijing. Wind speed played a leading role and other meteorological factors also have some effect, which resulted from the influence of the meteorology on diffusion, transmission, elimination of air pollutants. PMID:19650497

  14. [The effect of spectral range on the measurement of ozone in the atmosphere by DOAS].

    PubMed

    Fu, Qiang; Peng, Fu-Min; Liu, Wen-Qing; Xie, Pin-Hua; Luo, Tao; Si, Fu-Qi; Li, Su-Wen

    2009-08-01

    Ozone (O3) often serves as the benchmark for the overall pollution level of a given airshed and it is critical that the measurement technique be accurate and precise, In the DOAS measurement, the accuracy of O3 concentration is determined by the selected spectral range. The present paper focuses on the effect of spectral range on the detected characteristic absorption structure of O3, and the variation of differential cross section of O3 with the change in spectral range and the source of interference in different spectral range. The effect of practical atmospheric light extinction on the light intensities of different spectral ranges was deduced; the effect of spectral range on the accuracy was determined by detecting the standard gases at different concentration and different spectral resolution. The optimized spectral range was determined for O3, which can yield high sensitivity, good selectivity and a reasonable time resolution for the accurate qualitative and quantitative analysis of O3. PMID:19839323

  15. [Ring effect and correction studies while retrieving trace gas concentration with passive DOAS].

    PubMed

    Zhang, Ying-Hua; Xie, Pin-Hua; Si, Fu-Qi; Peng, Fu-Min; Dou, Ke; Li, Su-Wen

    2009-02-01

    The method of retrieving the concentration of trace gases using of the diagnostic absorption of trace gases based on the scattered sunlight is called passive DOAS. It has been developed so fast in recent years because it remains simple and is prone to being combined with different platform. While retrieving the column density of trace gases with the scattered sunlight as light source, it will be affected strongly by solar Fraunhofer lines, which is also called Ring effect. It makes it hard to retrieve trace gases concentration and affects measurement precision, especially for lower concentration. The influence of Ring effect and its relation with solar zenith angle in stable day will be introduced in the present paper, and the modification will be provided so that different Ring spectrum is selected according to different solar zenith angle. The slant column density (SCD) of NO2 for 3 stable days was retrieved with this modification. It was proved that the modification is possible. PMID:19445217

  16. MAX-DOAS measurements of shipping emissions

    NASA Astrophysics Data System (ADS)

    Seyler, André; Wittrock, Folkard; Kattner, Lisa; Mathieu-Üffing, Barbara; Peters, Enno; Richter, Andreas; Schmolke, Stefan; Theobald, Norbert; Burrows, John P.

    2015-04-01

    Air pollution from ships contributes to overall air quality problems and it has direct health effects on the population in particular in coastal regions, and in harbor cities. In order to reduce the emissions the International Maritime Organisation (IMO) have tightened the regulations for air pollution. E.g. Sulfur Emission Control Areas (SECA) have been introduced where the sulfur content of marine fuel is limited. Recently, on the 1st of January 2015, the allowed sulfur content of marine fuels inside Sulfur Emission Control Areas has been significantly decreased from 1.0% to 0.1%. However, up to now there is no regular monitoring system available to verify that ships are complying with the new regulations. Furthermore measurements of reactive trace gases in marine environments are in general sparse. The project MeSMarT (Measurements of shipping emissions in the marine troposphere, www.mesmart.de) has been established as a cooperation between the University of Bremen and the German Bundesamt für Seeschifffahrt und Hydrographie (Federal Maritime and Hydrographic Agency) with support of the Helmholtz Research Centre Geesthacht to estimate the influence of ship emissions on the chemistry of the atmospheric boundary layer and to establish a monitoring system for main shipping routes. Here we present MAX-DOAS observations of NO2 and SO2 carried out from two permanent sites close to the Elbe river (Wedel, Germany) and on the island Neuwerk close to the mouths of Elbe and Weser river since the year 2013. Mixing ratios of both trace gases have been retrieved using different approaches (pure geometric and taking into account the radiative transfer) and compared to in situ observations (see Kattner et al., Monitoring shipping fuel sulfur content regulations with in-situ measurements of shipping emissions). Furthermore, simple approaches have been used to calculate emission factors of NOx and SO2 for single ships.

  17. Tropospheric nitrogen dioxide column retrieval based on ground-based zenith-sky DOAS observations

    NASA Astrophysics Data System (ADS)

    Tack, Frederik; Hendrick, Francois; Goutail, Florence; Fayt, Caroline; Merlaud, Alexis; Pinardi, Gaia; Pommereau, Jean-Pierre; Van Roozendael, Michel

    2014-05-01

    Nitrogen dioxide (NO2) is one of the most important chemically active trace gases in the troposphere. Listed as primary pollutant, it is also a key precursor in the formation of tropospheric ozone, aerosols, and acid rain, and can contribute locally to radiative forcing. The long-term monitoring of this species is therefore of great relevance. Here we present a new method to retrieve tropospheric NO2 vertical column amounts from ground-based zenith-sky measurements of scattered sunlight. It is based on a four-step approach consisting of (1) the DOAS analysis of zenith radiance spectra using a fixed reference spectrum corresponding to low tropospheric NO2 content, (2) the determination of the residual amount in the reference spectrum using a Langley-plot-type method, (3) the removal of the stratospheric content from the daytime total slant column using stratospheric vertical columns measured at twilight and simulated stratospheric NO2 diurnal variation, (4) estimation of the tropospheric vertical columns by dividing the resulting tropospheric slant columns by appropriate air mass factors. The retrieval algorithm is tested on a 2 month dataset acquired from June to July 2009 by the BIRA MAX-DOAS instrument in the framework of the Cabauw (51.97° N, 4.93° E) Intercomparison campaign for Nitrogen Dioxide measuring Instruments (CINDI). The tropospheric vertical column amounts derived from zenith-sky observations are compared to the vertical columns retrieved from the off-axis and direct-sun measurements of the same MAX-DOAS instrument as well as to data of a co-located SAOZ (Système d'Analyse par Observations Zénithales) spectrometer operated by LATMOS. First results show a good agreement between the different data sets with correlation coefficients and slopes close to or larger than 0.85. We observe that the main error sources arise from the uncertainties in the determination of the residual NO2 amount in the reference spectrum, the stratospheric NO2 abundance and

  18. Measurements of formaldehyde total content in troposphere using DOAS technique in Moscow Region

    NASA Astrophysics Data System (ADS)

    Borovski, A. N.; Dzhola, A. V.; Grechko, E. I.; Postylyakov, O. V.; Ivanov, V. A.; Kanaya, Y.

    2015-11-01

    Formaldehyde (HCHO) in the atmosphere is a product of oxidation of methane and other volatile organic compounds (VOCs), and so its content is an important index of air pollution by VOCs. HCHO has strong absorption cross-section in the UV spectral region and, hence, HCHO vertical column density (VCD) can be measured by remote optical methods including differential optical absorption spectroscopy (DOAS). Spectral measurements of scattered solar radiation are performed at Zvenigorod Scientific Station (ZSS, 55°41'49''N, 36°46'29''E) located in 38 km west from Moscow Ring Road by MAX-DOAS instrument since 2008. For analysis of the HCHO variability we selected spectra taken in cloud free conditions. Version 1.2 of retrieval algorithm is used. It uses information on the surface albedo and the height of the atmospheric boundary layer inferred from a model. Data screening using color index was implemented. The obtained data quantify the Moscow megapolis influence on air quality at Zvenigorod by comparison of HCHO VCD for east and west wind directions. HCHO VCD for east winds is grater one for west winds for 0.5×1016 mol×cm-2 in average. Strong dependence of HCHO VCD on air temperature is noticeable in our data for air temperatures from +5 to +35°C. In different conditions of the atmosphere gradient of the temperature effect is about 1.1-1.2×1015 mol×cm-2×°C-1. The increase of the formaldehyde content with the increase of the air temperature can be caused by the HCHO formation from non-methane biogenic volatile organic compounds for which more emission is expected at higher temperatures.

  19. [Study of retrieving formaldehyde with differential optical absorption spectroscopy].

    PubMed

    Li, Yu-Jin; Xie, Pin-Hua; Qin, Min; Qu, Xiao-Ying; Hu, Lin

    2009-01-01

    The present paper introduces the method of retrieving the concentration of HCHO with differential optical absorption spectroscopy (DOAS). The authors measured ambient HCHO in Beijing region with the help of differential optical absorption spectroscopy instrument made by ourself, and discussed numerous factors in retrieving the concentration of HCHO with differential optical absorption spectroscopy (DOAS), especially, the choice of HCHO wave band, how to avoid absorption of ambient SO2, NO2 and O3, and the influence of the Xenon lamp spectrum structure on the absorption of ambient HCHO. The authors achieved the HCHO concentration by simultaneously retrieving the concentrations of HCHO, SO2, NO2 and O3 with non-linear least square fitting method, avoiding the effect of choosing narrow wave of HCHO and the residual of SO2, NO2, O3 and the Xenon lamp spectrum structure in retrieving process to attain the concentration of HCHO, Finally the authors analyzed the origin of error in retrieving the concentration of HCHO with differential optical absorption spectroscopy (DOAS), and the total error is within 13.7% in this method. PMID:19385238

  20. Spatial and temporal variations in NO(2) distributions over Beijing, China measured by imaging differential optical absorption spectroscopy.

    PubMed

    Lee, Hanlim; Kim, Young J; Jung, Jinsang; Lee, Chulkyu; Heue, Klaus-Peter; Platt, Ulrich; Hu, Min; Zhu, Tong

    2009-04-01

    During the CAREBEIJING campaign in 2006, imaging differential optical absorption spectroscopy (I-DOAS) measurements were made from 08:00 to 16:00 on September 9 and 10 over Beijing, China. Detailed images of the near-surface NO(2) differential slant column density (DSCD) distribution over Beijing were obtained. Images with less than a 30-min temporal resolution showed both horizontal and vertical variations in NO(2) distributions. For DSCD to mixing ratio conversion, path length along the lines of I-DOAS lines of sight was estimated using the light-extinction coefficient and Angstrom exponent data obtained by a transmissometer and a sunphotometer, respectively. Mixing ratios measured by an in-situ NO(2) analyzer were compared with those estimated by the I-DOAS instrument. The obtained temporal and spatial variations in NO(2) distributions measured by I-DOAS for the two days are interpreted with consideration of the locations of the major NO(x) sources and local wind conditions. I-DOAS measurements have been applied in this study for estimating NO(2) distribution over an urban area with multiple and distributed emission sources. Results are obtained for estimated temporal and spatial NO(2) distributions over the urban atmosphere; demonstrating the capability of the I-DOAS technique. We discuss in this paper the use of I-DOAS measurements to estimate the NO(2) distribution over an urban area with multiple distributed emission sources. PMID:19111964

  1. Estimation of the efficiency of the hybrid LIDAR-DOAS system of lidar sensing of the polluted atmosphere using pulsed excilamps

    NASA Astrophysics Data System (ADS)

    Krekov, G. M.; Krekova, M. M.; Lisenko, A. A.; Sukhanov, A. Ya.; Erofeev, M. V.; Lomaev, M. I.; Tarasenko, V. F.

    2010-12-01

    Results of a closed numerical experiment on laser sensing of minor gas impurity concentrations in the tropospheric layer of the atmosphere based on new hybrid LIDAR-DOAS technique with a XeCl* excilamp used for a pulsed wideband radiation source are discussed. Quantitative estimates obtained using a new stochastic genetic search algorithm confirm that the suggested approach, expanding the possibilities of the classical Differential Optical Absorption Spectroscopy (DOAS) system to remote monitoring and localization of dangerous anthropogenic emissions of toxic gases up to the tropopause height, is promising. The necessity of estimating backscattered signals with high spectral resolution by solving the nonstationary radiative transfer equation calls for a significant modification of the statistical simulation algorithms. A combination of the Monte Carlo method with a genetic algorithm of solving inverse problems of reconstructing profiles of gaseous components in the troposphere enables exact quantitative prediction of the efficiency of new promising lidar systems of environmental monitoring to be provided.

  2. Mid infrared MEMS FTIR spectrometer

    NASA Astrophysics Data System (ADS)

    Erfan, Mazen; Sabry, Yasser M.; Mortada, Bassem; Sharaf, Khaled; Khalil, Diaa

    2016-03-01

    In this work we report, for the first time to the best of our knowledge, a bulk-micromachined wideband MEMS-based spectrometer covering both the NIR and the MIR ranges and working from 1200 nm to 4800 nm. The core engine of the spectrometer is a scanning Michelson interferometer micro-fabricated using deep reactive ion etching (DRIE) technology. The spectrum is obtained using the Fourier Transform techniques that allows covering a very wide spectral range limited by the detector responsivity. The moving mirror of the interferometer is driven by a relatively large stroke electrostatic comb-drive actuator. Zirconium fluoride (ZrF4) multimode optical fibers are used to connect light between the white light source and the interferometer input, as well as the interferometer output to a PbSe photoconductive detector. The recorded signal-to-noise ratio is 25 dB at the wavelength of 3350 nm. The spectrometer is successfully used in measuring the absorption spectra of methylene chloride, quartz glass and polystyrene film. The presented solution provides a low cost method for producing miniaturized spectrometers in the near-/mid-infrared.

  3. Vertical Profiles of SO2 and NO2 in the Alberta Oil Sands: MAX-DOAS Measurements and Comparison to in-situ Instrumentation

    NASA Astrophysics Data System (ADS)

    Davis, Zoe; Lobo, Akshay; McLaren, Robert

    2015-04-01

    Understanding the levels of industrially emitted gas pollutants in the Alberta oil sands is essential to making quality environmental management decisions but is currently limited due to scarcity of top-down quantification studies. Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) measurements of nitrogen dioxide (NO2) and sulfur dioxide (SO2) , important tropospheric trace gas pollutants, contributes to improved knowledge of these pollutants' levels, vertical distributions and chemical transformations. A mini-MAX-DOAS instrument measured spectra at multiple viewing elevation angles in order to retrieve NO2 and SO2 differential slant column densities (dSCDs) at an Environment Canada research site north of Fort McMurray, Alberta in the fall of 2013. For the first time in the oil sands, tropospheric vertical profiles of NO2 and SO2 were retrieved by applying the optimal estimation technique to the MAX-DOAS measurements. The DOAS fit retrievals of SO2 dSCDs were validated by comparison with retrievals obtained with a quartz calibration cell with known SO2 SCD placed in front of the MAX-DOAS telescope at multiple elevation angles on a clean day. Retrieved SO2 dSCDs varied significantly from the true value depending on the chosen wavelength fitting interval. At the lowest wavelength intervals, interference by stray light and O3 differential structures significantly reduced dSCDs and caused an elevation angle dependence. These results indicate that MAX-DOAS dSCD retrieval settings, particularly for weak absorbers with differential absorption structures in low-intensity spectral regions, must be chosen carefully in order to achieve the most accurate results. Tropospheric vertical column densities (VCDs) and vertical profile retrievals of NO2, SO2 and aerosol extinction during significant pollution events will be illustrated. Trace gas vertical profiles exhibited significant variability between days and at different times of day and were often spatially

  4. [Measurement of atmospheric NO3 radical with long path differential optical absorption spectroscopy based on red light emitting diodes].

    PubMed

    Li, Su-Wen; Liu, Wen-Qing; Wang, Jiang-Tao; Xie, Pin-Hua; Wang, Xu-De

    2013-02-01

    Nitrate radical (NO3) is the most important oxidant in the tropospheric nighttime chemistry. Due to its high reactivity and low atmospheric concentrations, modern red light emitting diodes (LEDs) was proposed as light source in long path differential optical absorption spectroscopy (LP-DOAS) to measure NO3 radical in the atmosphere. The spectral properties of Luxeon LXHL-MD1D LEDs were analyzed in the present paper. The principle of LEDs-DOAS system to measure nitrate radical was studied in this paper. The experimental setup and retrieval method of NO3 radical were discussed in this paper. The retrieved example of NO3 was given and the time series of NO3 concentrations was performed for a week. The results showed that the detection limits of LEDs-DOAS system were 12 ppt for atmospheric NO3 radical when the optical path of LEDs-DOAS system was 2.8 km. PMID:23697129

  5. Multibeam long-path differential optical absorption spectroscopy instrument: a device for simultaneous measurements along multiple light paths.

    PubMed

    Pundt, Irene; Mettendorf, Kai Uwe

    2005-08-10

    A novel long-path differential optical absorption spectroscopy (DOAS) apparatus for measuring tropospheric trace gases and the first results from its use are presented: We call it the multibeam instrument. It is the first active DOAS device that emits several light beams simultaneously through only one telescope and with only one lamp as a light source, allowing simultaneous measurement along multiple light paths. In contrast to conventional DOAS instruments, several small mirrors are positioned near the lamp, creating multiple virtual light sources that emit one light beam each in one specific direction. The possibility of error due to scattering between the light beams is negligible. The trace-gas detection limits of NO2, SO2, O3, and H2CO are similar to those of the traditional long-path DOAS instrument. PMID:16114540

  6. A Low-Complexity ESPRIT-Based DOA Estimation Method for Co-Prime Linear Arrays.

    PubMed

    Sun, Fenggang; Gao, Bin; Chen, Lizhen; Lan, Peng

    2016-01-01

    The problem of direction-of-arrival (DOA) estimation is investigated for co-prime array, where the co-prime array consists of two uniform sparse linear subarrays with extended inter-element spacing. For each sparse subarray, true DOAs are mapped into several equivalent angles impinging on the traditional uniform linear array with half-wavelength spacing. Then, by applying the estimation of signal parameters via rotational invariance technique (ESPRIT), the equivalent DOAs are estimated, and the candidate DOAs are recovered according to the relationship among equivalent and true DOAs. Finally, the true DOAs are estimated by combining the results of the two subarrays. The proposed method achieves a better complexity-performance tradeoff as compared to other existing methods. PMID:27571079

  7. A Low-Complexity ESPRIT-Based DOA Estimation Method for Co-Prime Linear Arrays

    PubMed Central

    Sun, Fenggang; Gao, Bin; Chen, Lizhen; Lan, Peng

    2016-01-01

    The problem of direction-of-arrival (DOA) estimation is investigated for co-prime array, where the co-prime array consists of two uniform sparse linear subarrays with extended inter-element spacing. For each sparse subarray, true DOAs are mapped into several equivalent angles impinging on the traditional uniform linear array with half-wavelength spacing. Then, by applying the estimation of signal parameters via rotational invariance technique (ESPRIT), the equivalent DOAs are estimated, and the candidate DOAs are recovered according to the relationship among equivalent and true DOAs. Finally, the true DOAs are estimated by combining the results of the two subarrays. The proposed method achieves a better complexity–performance tradeoff as compared to other existing methods. PMID:27571079

  8. Tropospheric Emission Spectrometer and Airborne Emission Spectrometer

    NASA Technical Reports Server (NTRS)

    Glavich, T.; Beer, R.

    1996-01-01

    The Tropospheric Emission Spectrometer (TES) is an instrument being developed for the NASA Earth Observing System Chemistry Platform. TES will measure the distribution of ozone and its precursors in the lower atmosphere. The Airborne Emission Spectrometer (AES) is an aircraft precursor to TES. Applicable descriptions are given of instrument design, technology challenges, implementation and operations for both.

  9. Development of aerosol retrieval algorithm for Geostationary Environmental Monitoring Spectrometer (GEMS)

    NASA Astrophysics Data System (ADS)

    Kim, Mijin; Kim, Jhoon; Park, Sang Seo; Jeong, Ukkyo; Ahn, Changwoo; Bhartia, Pawan. K.; Torres, Omar; Song, Chang-Keun; Han, Jin-Seok

    2014-05-01

    A scanning UV-Visible spectrometer, the GEMS (Geostationary Environment Monitoring Spectrometer) onboard the GEO-KOMPSAT2B (Geostationary Korea Multi-Purpose Satellite) is planned to be launched in geostationary orbit in 2018. The GEMS employs hyper-spectral imaging with 0.6 nm resolution to observe solar backscatter radiation in the UV and Visible range. In the UV range, the low surface contribution to the backscattered radiation and strong interaction between aerosol absorption and molecular scattering can be advantageous in retrieving aerosol optical properties such as aerosol optical depth (AOD) and single scattering albedo (SSA). This study presents a UV-VIS algorithm to retrieve AOD and SSA from GEMS. The algorithm is based on the general inversion method, which uses pre-calculated look-up table (LUT) with assumed aerosol properties and measurement condition. To calculate LUT, aerosol optical properties over Asia [70°E-145°E, 0°N-50°N] are obtained from AERONET inversion data (level 2.0) at 46 AERONET sites, and are applied to VLIDORT (spur, 2006). Because the backscattering radiance in UV-Visible range has significant sensitivity to radiance absorptivity and size distribution of loading aerosol, aerosol types are classified from AERONET inversion data by using aerosol classification method suggested in Lee et al. (2010). Then the LUTs are calculated with average optical properties for each aerosol type. The GEMS aerosol algorithm is tested with OMI level-1B dataset, a provisional data for GEMS measurement. The aerosol types for each measured scene are selected by using both of UVAI and VISAI, and AOD and SSA are simultaneously retrieved by comparing simulated radiance with selected aerosol type and the measured value. The AOD and SSA retrieved from GEMS aerosol algorithm are well matched with OMI products, although the retrieved AOD is slightly higher than OMI value. To detect cloud pixel, spatial standard deviation test of radiance is applied in the

  10. Compact Infrared Spectrometers

    NASA Technical Reports Server (NTRS)

    Mouroulis, Pantazis

    2009-01-01

    Concentric spectrometer forms are advantageous for constructing a variety of systems spanning the entire visible to infrared range. Spectrometer examples are given, including broadband or high resolution forms. Some issues associated with the Dyson catadioptric type are also discussed.

  11. Mars Airborne Prospecting Spectrometer

    NASA Astrophysics Data System (ADS)

    Steinkraus, J. M.; Wright, M. W.; Rheingans, B. E.; Steinkraus, D. E.; George, W. P.; Aljabri, A.; Hall, J. L.; Scott, D. C.

    2012-06-01

    One novel approach towards addressing the need for innovative instrumentation and investigation approaches is the integration of a suite of four spectrometer systems to form the Mars Airborne Prospecting Spectrometers (MAPS) for prospecting on Mars.

  12. A Modified Rife Algorithm for Off-Grid DOA Estimation Based on Sparse Representations.

    PubMed

    Chen, Tao; Wu, Huanxin; Guo, Limin; Liu, Lutao

    2015-01-01

    In this paper we address the problem of off-grid direction of arrival (DOA) estimation based on sparse representations in the situation of multiple measurement vectors (MMV). A novel sparse DOA estimation method which changes MMV problem to SMV is proposed. This method uses sparse representations based on weighted eigenvectors (SRBWEV) to deal with the MMV problem. MMV problem can be changed to single measurement vector (SMV) problem by using the linear combination of eigenvectors of array covariance matrix in signal subspace as a new SMV for sparse solution calculation. So the complexity of this proposed algorithm is smaller than other DOA estimation algorithms of MMV. Meanwhile, it can overcome the limitation of the conventional sparsity-based DOA estimation approaches that the unknown directions belong to a predefined discrete angular grid, so it can further improve the DOA estimation accuracy. The modified Rife algorithm for DOA estimation (MRife-DOA) is simulated based on SRBWEV algorithm. In this proposed algorithm, the largest and sub-largest inner products between the measurement vector or its residual and the atoms in the dictionary are utilized to further modify DOA estimation according to the principle of Rife algorithm and the basic idea of coarse-to-fine estimation. Finally, simulation experiments show that the proposed algorithm is effective and can reduce the DOA estimation error caused by grid effect with lower complexity. PMID:26610521

  13. A Modified Rife Algorithm for Off-Grid DOA Estimation Based on Sparse Representations

    PubMed Central

    Chen, Tao; Wu, Huanxin; Guo, Limin; Liu, Lutao

    2015-01-01

    In this paper we address the problem of off-grid direction of arrival (DOA) estimation based on sparse representations in the situation of multiple measurement vectors (MMV). A novel sparse DOA estimation method which changes MMV problem to SMV is proposed. This method uses sparse representations based on weighted eigenvectors (SRBWEV) to deal with the MMV problem. MMV problem can be changed to single measurement vector (SMV) problem by using the linear combination of eigenvectors of array covariance matrix in signal subspace as a new SMV for sparse solution calculation. So the complexity of this proposed algorithm is smaller than other DOA estimation algorithms of MMV. Meanwhile, it can overcome the limitation of the conventional sparsity-based DOA estimation approaches that the unknown directions belong to a predefined discrete angular grid, so it can further improve the DOA estimation accuracy. The modified Rife algorithm for DOA estimation (MRife-DOA) is simulated based on SRBWEV algorithm. In this proposed algorithm, the largest and sub-largest inner products between the measurement vector or its residual and the atoms in the dictionary are utilized to further modify DOA estimation according to the principle of Rife algorithm and the basic idea of coarse-to-fine estimation. Finally, simulation experiments show that the proposed algorithm is effective and can reduce the DOA estimation error caused by grid effect with lower complexity. PMID:26610521

  14. Ozone distributions over southern Lake Michigan: comparisons between ferry-based observations, shoreline-based DOAS observations and model forecasts

    NASA Astrophysics Data System (ADS)

    Cleary, P. A.; Fuhrman, N.; Schulz, L.; Schafer, J.; Fillingham, J.; Bootsma, H.; McQueen, J.; Tang, Y.; Langel, T.; McKeen, S.; Williams, E. J.; Brown, S. S.

    2015-05-01

    Air quality forecast models typically predict large summertime ozone abundances over water relative to land in the Great Lakes region. While each state bordering Lake Michigan has dedicated monitoring systems, offshore measurements have been sparse, mainly executed through specific short-term campaigns. This study examines ozone abundances over Lake Michigan as measured on the Lake Express ferry, by shoreline differential optical absorption spectroscopy (DOAS) observations in southeastern Wisconsin and as predicted by the Community Multiscale Air Quality (CMAQ) model. From 2008 to 2009 measurements of O3, SO2, NO2 and formaldehyde were made in the summertime by DOAS at a shoreline site in Kenosha, WI. From 2008 to 2010 measurements of ambient ozone were conducted on the Lake Express, a high-speed ferry that travels between Milwaukee, WI, and Muskegon, MI, up to six times daily from spring to fall. Ferry ozone observations over Lake Michigan were an average of 3.8 ppb higher than those measured at shoreline in Kenosha, with little dependence on position of the ferry or temperature and with greatest differences during evening and night. Concurrent 1-48 h forecasts from the CMAQ model in the upper Midwestern region surrounding Lake Michigan were compared to ferry ozone measurements, shoreline DOAS measurements and Environmental Protection Agency (EPA) station measurements. The bias of the model O3 forecast was computed and evaluated with respect to ferry-based measurements. Trends in the bias with respect to location and time of day were explored showing non-uniformity in model bias over the lake. Model ozone bias was consistently high over the lake in comparison to land-based measurements, with highest biases for 25-48 h after initialization.

  15. [Study on the measurement of ambient ammonia in urban area based on open-path DOAS technique].

    PubMed

    Wang, Jie; Xie, Pin-hua; Qin, Min; Ling, Liu-yi; Ye, Cong-lei; Liu, Jian-guo; Liu, Wen-qing

    2012-02-01

    As a key role in the acid-deposition and the generation of secondary particle matter (PM), measurement of the concentration of atmospheric ammonia in urban area has been attracting the scientists' interests nowadays. After studying the special absorption features of ammonia in short UV wavelength range, detailed concernful issues were put forward in the present paper. The decision of using xenon lamp as the light source was made after the evaluation of measurement of light spectroscopy. Retrieval wavelength band for NH3 was fixed from 204 to 214 nm and optimal method of deducting other interferential gases was also shown. A home-made open-path DOAS (OP-DOAS) system was set up for the measurement of the concentration of atmospheric NH3. The detection limit of such system was calculated with the typical noise level as low as 0.33 microg x m(-3) with the optical path 228 m. Through field experiment in Guangzhou city, such a system can be competent for the online and high time-resolution monitoring of the concentration of atmospheric ammonia. With a significant diurnal variation, the atmospheric ammonia changed from 0.83 to 3.11 microg x m(-3) with the mean value 1.59 microg x m(-3). The representative character of the diurnal variation is that the concentration of NH3 peaks during night while drops to bottom in the daytime. After the error analysis procedure, typical measurement accuracy of such OP-DOAS system was within 10%. PMID:22512193

  16. Sparse Bayesian Learning for DOA Estimation with Mutual Coupling

    PubMed Central

    Dai, Jisheng; Hu, Nan; Xu, Weichao; Chang, Chunqi

    2015-01-01

    Sparse Bayesian learning (SBL) has given renewed interest to the problem of direction-of-arrival (DOA) estimation. It is generally assumed that the measurement matrix in SBL is precisely known. Unfortunately, this assumption may be invalid in practice due to the imperfect manifold caused by unknown or misspecified mutual coupling. This paper describes a modified SBL method for joint estimation of DOAs and mutual coupling coefficients with uniform linear arrays (ULAs). Unlike the existing method that only uses stationary priors, our new approach utilizes a hierarchical form of the Student t prior to enforce the sparsity of the unknown signal more heavily. We also provide a distinct Bayesian inference for the expectation-maximization (EM) algorithm, which can update the mutual coupling coefficients more efficiently. Another difference is that our method uses an additional singular value decomposition (SVD) to reduce the computational complexity of the signal reconstruction process and the sensitivity to the measurement noise. PMID:26501284

  17. Sparse Bayesian learning for DOA estimation with mutual coupling.

    PubMed

    Dai, Jisheng; Hu, Nan; Xu, Weichao; Chang, Chunqi

    2015-01-01

    Sparse Bayesian learning (SBL) has given renewed interest to the problem of direction-of-arrival (DOA) estimation. It is generally assumed that the measurement matrix in SBL is precisely known. Unfortunately, this assumption may be invalid in practice due to the imperfect manifold caused by unknown or misspecified mutual coupling. This paper describes a modified SBL method for joint estimation of DOAs and mutual coupling coefficients with uniform linear arrays (ULAs). Unlike the existing method that only uses stationary priors, our new approach utilizes a hierarchical form of the Student t prior to enforce the sparsity of the unknown signal more heavily. We also provide a distinct Bayesian inference for the expectation-maximization (EM) algorithm, which can update the mutual coupling coefficients more efficiently. Another difference is that our method uses an additional singular value decomposition (SVD) to reduce the computational complexity of the signal reconstruction process and the sensitivity to the measurement noise. PMID:26501284

  18. Inter-Comparison of Nitrogen Dioxide Column Densities Retrieved by Ground-Based Max-Doas Under Different Instrumental Conditions Over Mainz

    NASA Astrophysics Data System (ADS)

    Bruchkouski, I.; Dziomin, V.; Ortega, I.; Volkamer, R.; Krasouski, A.

    2013-12-01

    This study is dedicated to the instrumental differences between ground-based MAX-DOAS measurement devices. Our MAX-DOAS instrument, which has been developed at the National Ozone Monitoring Research & Education Center of the Belarusian State University for the purpose of nitrogen dioxide and other atmospheric trace gases monitoring over Belarus, features a rotating mirror and a telescope directly connected to the spectrometer with a two-dimensional CCD detector. Using a mirror instead of an optical fibre makes it possible to change the field of view of the telescope, and the whole instrument is rather compact and all its components are placed outdoors in the open air. However, this makes it quite difficult to ensure a top-quality thermostabilization. In the course of the MAX-DOAS campaign, which took place in the Max Planck Institute for Chemistry in Mainz, Germany in summer of 2013, we had a great opportunity to compare our instrument with other devices of different types. In the present study we make a comparison of nitrogen dioxide slant column densities (SCDs) during several days obtained by our instrument with that measured by the device from the Department of Chemistry and Biochemistry, University of Colorado (Boulder), which has a thermostabilization level of about 0.01 degrees Celsius. We investigate the influence of the spectrometer parts thermostabilization on nitrogen dioxide SCDs retrieval. Furthermore, it was possible to modify the telescope field of view for our instrument from 0.005 to 1.3 degrees, so we performed nitrogen dioxide SCDs retrieval for different fields of view at the same angle of elevation. We analyze these measurement results and obtain an optimal field of view with the aim to achieve the highest possible signal to noise ratio.

  19. Doa1 is a MAD adaptor for Cdc48

    PubMed Central

    Zhang, Ting

    2016-01-01

    Dislocation of polypeptides from the mitochondrial outer membrane by the p97/Cdc48–Ufd1–Npl4 adenosine triphosphatase complex is essential for mitochondria-associated degradation and Parkin-mediated mitophagy. In this issue, Wu et al. (2016. J. Cell Biol. http://dx.doi.org/10.1083/jcb.201510098) identify Doa1 as a pivotal adaptor that recruits substrates to Cdc48 for processing. PMID:27044894

  20. Analysis of DOA estimation spatial resolution using MUSIC algorithm

    NASA Astrophysics Data System (ADS)

    Guo, Yue; Wang, Hongyuan; Luo, Bin

    2005-11-01

    This paper presents a performance analysis of the spatial resolution of the direction of arrival (DOA) estimates attained by the multiple signal classification (MUSIC) algorithm for uncorrelated sources. The confidence interval of estimation angle which is much more intuitionistic will be considered as the new evaluation standard for the spatial resolution. Then, based on the statistic method, the qualitative analysis reveals the factors influencing the performance of the MUSIC algorithm. At last, quantitative simulations prove the theoretical analysis result exactly.

  1. [Novel analysis algorithms for differential optical absorption spectroscopy for pollution monitoring].

    PubMed

    Zhang, Xue-Dian; Huang, Xian; Xu, Ke-Xin

    2007-11-01

    Differential optical absorption spectroscopy, or DOAS, is a widely used method to determine concentrations of atmospheric species. The principle of DOAS for measuring the concentration of air pollutants is presented in briefly. Using the linear relationship between the area of the measured differential absorbance curve and that of the differential absorption cross-section curve as taken from the literature, an alternative method for calculating the gas concentration on the basis of the proportionality between differential absorbance and differential absorption cross section of the gas under study was developed. The method can be used on its own for single-component analysis or as a complement to the standard technique in multi-component cases. The procedure can be used with differential absorption cross sections measured in the laboratory or taken from the literature. In addition, the method provides a criterion to discriminate between different species having absorption features in the same wavelength range.

  2. Measurement of tropospheric OH by laser long-path absorption spectroscopy

    NASA Technical Reports Server (NTRS)

    Kraft, Michael; Perner, D.

    1994-01-01

    OH-radicals are measured by laser long-path absorption spectroscopy. A tunable Nd:YAG/dye laser system provides broadbanded light at 308 nm. The beam is expanded to 0.3 m and pointed to an array of retroreflectors placed at a distance of 2800 m. The returning beam is separated from the outgoing beam and focused into a spectrometer of 0.3 pm resolution. A 1024 element diode array is used as a detector. The signal is digitized by a 14 bit analog to digital converter. The ultimate aim is a detection limit of 10(exp 5) molecules cm(exp -3) of OH. However the measurements in 1991 allowed only the recognition of OH absorptions corresponding to 3 x 10(exp 6) OH cm(exp -3) with a signal to noise ratio of two. Improvements of the instrument are under way. The advantages of the DOAS method are: the accuracy of detection is guaranteed because loss of OH radicals within the device is avoided, the rate of OH production by the device is negligible, and absorptions of other trace gases could be corrected for; and the calibration procedure for the device is fast and easy. The disadvantages of the system are: time resolution is about minutes because about ten spectra had to be added to keep the noise level down, the OH concentration is averaged along the whole light path, weight (500 kg) and size (4x4 m) of the device; and approximately 10 l/min of coolant and supply of 8 kW electrical power are necessary.

  3. Development and characterization of the CU ground MAX-DOAS instrument: lowering RMS noise and first measurements of BrO, IO, and CHOCHO near Pensacola, FL

    NASA Astrophysics Data System (ADS)

    Coburn, S.; Dix, B.; Sinreich, R.; Volkamer, R.

    2011-01-01

    We designed and assembled the University of Colorado Ground Multi AXis Differential Optical Absorption Spectroscopy (CU GMAX-DOAS) instrument to retrieve bromine oxide (BrO), iodine oxide (IO), formaldehyde (HCHO), glyoxal (CHOCHO), nitrogen dioxide (NO2) and the oxygen dimer O4 in the coastal atmosphere of the Gulf of Mexico. The detection sensitivity of DOAS measurements is directly proportional to the root mean square (RMS) of the residual spectrum that remains after all absorbers have been subtracted. Here we describe the CU GMAX-DOAS instrument and demonstrate that the hardware is capable of attaining RMS values of ~6 × 10-6 without apparent limitations other than photon shot noise. Laboratory tests revealed two factors that, in practice, limit the RMS: (1) detector non-linearity noise, RMSNLin, and (2) temperature fluctuations that cause variations in optical resolution (full width at half the maximum, FWHM, of atomic emission lines) and give rise to optical resolution noise, RMSFWHM. The non-linearity of our detector is low (~10-3) yet - unless actively controlled - is sufficiently large to create a RMSNLin limit of up to 1.4 × 10-4. The optical resolution is sensitive to temperature changes (0.03 detector pixels/°C at 334 nm), and temperature variations of 0.1 °C can cause residual RMSFWHM of ~1 × 10-4. Both factors were actively addressed in the design of the CU GMAX-DOAS instrument. The CU GMAX-DOAS was set up at a coastal site near Pensacola, FL, where we detected BrO, IO and CHOCHO in the marine boundary layer (MBL), with daytime average tropospheric vertical column densities, VCDs, of ~2 × 1013 molec cm-2, 8 × 1012 molec cm-2 and 4 × 1014 molec cm-2, respectively. HCHO and NO2 were also detected with typical MBL VCDs of 1 × 1016 and 3 × 1015. These are the first measurements of BrO, IO and CHOCHO over the Gulf of Mexico. The atmospheric implications of these observations for elevated mercury wet deposition rates in this area are briefly

  4. Comparison of OH concentration measurements by DOAS and LIF during SAPHIR chamber experiments at high OH reactivity and low NO concentration

    NASA Astrophysics Data System (ADS)

    Fuchs, H.; Dorn, H.-P.; Bachner, M.; Bohn, B.; Brauers, T.; Gomm, S.; Hofzumahaus, A.; Holland, F.; Nehr, S.; Rohrer, F.; Tillmann, R.; Wahner, A.

    2012-07-01

    During recent field campaigns, hydroxyl radical (OH) concentrations that were measured by laser-induced fluorescence (LIF) were up to a factor of ten larger than predicted by current chemical models for conditions of high OH reactivity and low NO concentration. These discrepancies, which were observed in forests and urban-influenced rural environments, are so far not entirely understood. In summer 2011, a series of experiments was carried out in the atmosphere simulation chamber SAPHIR in Jülich, Germany, in order to investigate the photochemical degradation of isoprene, methyl-vinyl ketone (MVK), methacrolein (MACR) and aromatic compounds by OH. Conditions were similar to those experienced during the PRIDE-PRD2006 campaign in the Pearl River Delta (PRD), China, in 2006, where a large difference between OH measurements and model predictions was found. During experiments in SAPHIR, OH was simultaneously detected by two independent instruments: LIF and differential optical absorption spectroscopy (DOAS). Because DOAS is an inherently calibration-free technique, DOAS measurements are regarded as a reference standard. The comparison of the two techniques was used to investigate potential artifacts in the LIF measurements for PRD-like conditions of OH reactivities of 10 to 30 s-1 and NO mixing ratios of 0.1 to 0.3 ppbv. The analysis of twenty experiment days shows good agreement. The linear regression of the combined data set (averaged to the DOAS time resolution, 2495 data points) yields a slope of 1.02 ± 0.01 with an intercept of (0.10 ± 0.03) × 106 cm-3 and a linear correlation coefficient of R2 = 0.86. This indicates that the sensitivity of the LIF instrument is well-defined by its calibration procedure. No hints for artifacts are observed for isoprene, MACR, and different aromatic compounds. LIF measurements were approximately 30-40% (median) larger than those by DOAS after MVK (20 ppbv) and toluene (90 ppbv) had been added. However, this discrepancy has a

  5. Comparison of OH concentration measurements by DOAS and LIF during SAPHIR chamber experiments at high OH reactivity and low NO concentration

    NASA Astrophysics Data System (ADS)

    Fuchs, H.; Dorn, H.-P.; Bachner, M.; Bohn, B.; Brauers, T.; Gomm, S.; Hofzumahaus, A.; Holland, F.; Nehr, S.; Rohrer, F.; Tillmann, R.; Wahner, A.

    2012-03-01

    During recent field campaigns, hydroxyl radical (OH) concentrations that were measured by laser-induced fluorescence (LIF) were up to a factor of ten larger than predicted by current chemical models for conditions of high OH reactivity and low NO concentration. These discrepancies, which were observed in forests and urban-influenced rural environments, are so far not entirely understood. In summer 2011, a series of experiments was carried out in the atmosphere simulation chamber SAPHIR in Jülich, Germany, in order to investigate the photochemical degradation of isoprene, methyl-vinyl ketone (MVK), methacrolein (MACR) and aromatic compounds by OH. Conditions were similar to those experienced during the PRIDE-PRD2006 campaign in the Pearl River Delta (PRD), China, in 2006, where a large difference between OH measurements and model predictions was found. During experiments in SAPHIR, OH was simultaneously detected by two independent instruments: LIF and differential optical absorption spectroscopy (DOAS). Because DOAS is an inherently calibration-free technique, DOAS measurements are regarded as a reference standard. The comparison of the two techniques was used to investigate potential artifacts in the LIF measurements for PRD-like conditions of OH reactivities of 10 to 30 s-1 and NO mixing ratios of 0.1 to 0.3 ppbv. The analysis of twenty experiment days shows good agreement. The linear regression of the combined data set (averaged to the DOAS time resolution, 2495 data points) yields a slope of 1.02 ± 0.01 with an intercept of (0.10 ± 0.03) ×106 cm-3 and a linear correlation coefficient of R2=0.86. This indicates that the sensitivity of the LIF instrument is well-defined by its calibration procedure. No hints for artifacts are observed for isoprene, MACR, and different aromatic compounds. LIF measurements were approximately 30-40% (median) larger than those by DOAS after MVK and toluene had been added. However, this discrepancy has a large uncertainty and

  6. A Channelization-Based DOA Estimation Method for Wideband Signals.

    PubMed

    Guo, Rui; Zhang, Yue; Lin, Qianqiang; Chen, Zengping

    2016-01-01

    In this paper, we propose a novel direction of arrival (DOA) estimation method for wideband signals with sensor arrays. The proposed method splits the wideband array output into multiple frequency sub-channels and estimates the signal parameters using a digital channelization receiver. Based on the output sub-channels, a channelization-based incoherent signal subspace method (Channelization-ISM) and a channelization-based test of orthogonality of projected subspaces method (Channelization-TOPS) are proposed. Channelization-ISM applies narrowband signal subspace methods on each sub-channel independently. Then the arithmetic mean or geometric mean of the estimated DOAs from each sub-channel gives the final result. Channelization-TOPS measures the orthogonality between the signal and the noise subspaces of the output sub-channels to estimate DOAs. The proposed channelization-based method isolates signals in different bandwidths reasonably and improves the output SNR. It outperforms the conventional ISM and TOPS methods on estimation accuracy and dynamic range, especially in real environments. Besides, the parallel processing architecture makes it easy to implement on hardware. A wideband digital array radar (DAR) using direct wideband radio frequency (RF) digitization is presented. Experiments carried out in a microwave anechoic chamber with the wideband DAR are presented to demonstrate the performance. The results verify the effectiveness of the proposed method. PMID:27384566

  7. A Channelization-Based DOA Estimation Method for Wideband Signals

    PubMed Central

    Guo, Rui; Zhang, Yue; Lin, Qianqiang; Chen, Zengping

    2016-01-01

    In this paper, we propose a novel direction of arrival (DOA) estimation method for wideband signals with sensor arrays. The proposed method splits the wideband array output into multiple frequency sub-channels and estimates the signal parameters using a digital channelization receiver. Based on the output sub-channels, a channelization-based incoherent signal subspace method (Channelization-ISM) and a channelization-based test of orthogonality of projected subspaces method (Channelization-TOPS) are proposed. Channelization-ISM applies narrowband signal subspace methods on each sub-channel independently. Then the arithmetic mean or geometric mean of the estimated DOAs from each sub-channel gives the final result. Channelization-TOPS measures the orthogonality between the signal and the noise subspaces of the output sub-channels to estimate DOAs. The proposed channelization-based method isolates signals in different bandwidths reasonably and improves the output SNR. It outperforms the conventional ISM and TOPS methods on estimation accuracy and dynamic range, especially in real environments. Besides, the parallel processing architecture makes it easy to implement on hardware. A wideband digital array radar (DAR) using direct wideband radio frequency (RF) digitization is presented. Experiments carried out in a microwave anechoic chamber with the wideband DAR are presented to demonstrate the performance. The results verify the effectiveness of the proposed method. PMID:27384566

  8. Simple Monte Carlo methods to estimate the spectra evaluation error in differential-optical-absorption spectroscopy.

    PubMed

    Hausmann, M; Brandenburger, U; Brauers, T; Dorn, H P

    1999-01-20

    Differential-optical-absorption spectroscopy (DOAS) permits the sensitive measurement of concentrations of trace gases in the atmosphere. DOAS is a technique of well-defined accuracy; however, the calculation of a statistically sound measurement precision is still an unsolved problem. Usually one evaluates DOAS spectra by performing least-squares fits of reference absorption spectra to the measured atmospheric absorption spectra. Inasmuch as the absorbance from atmospheric trace gases is usually very weak, with optical densities in the range from 10(-5) to 10(-3), interference caused by the occurrence of nonreproducible spectral artifacts often determines the detection limit and the measurement precision. These spectral artifacts bias the least-squares fitting result in two respects. First, spectral artifacts to some extent are falsely interpreted as real absorption, and second, spectral artifacts add nonstatistical noise to spectral residuals, which results in a significant misestimation of the least-squares fitting error. We introduce two new approaches to investigate the evaluation errors of DOAS spectra accurately. The first method, residual inspection by cyclic displacement, estimates the effect of false interpretation of the artifact structures. The second method applies a statistical bootstrap algorithm to estimate properly the error of fitting, even in cases when the condition of random and independent scatter of the residual signal is not fulfilled. Evaluation of simulated atmospheric measurement spectra shows that a combination of the results of both methods yields a good estimate of the spectra evaluation error to within an uncertainty of ~10%.

  9. Retrieval of absolute SO2 column amounts from scattered-light spectra - Implications for the evaluation of data from automated DOAS Networks

    NASA Astrophysics Data System (ADS)

    Lübcke, Peter; Lampel, Johannes; Arellano, Santiago; Bobrowski, Nicole; Dinger, Florian; Galle, Bo; Garzón, Gustavo; Hidalgo, Silvana; Chacón Ortiz, Zoraida; Vogel, Leif; Warnach, Simon; Platt, Ulrich

    2016-04-01

    Remote sensing of gas emissions is an important tool for monitoring volcanoes. The Network for Observation of Volcanic and Atmospheric Chance (NOVAC) comprises approximately 80 scanning Differential Optical Absorption Spectroscopy (DOAS) instruments installed at 30 volcanoes world-wide. The DOAS evaluation requires a Fraunhofer Reference Spectrum (FRS) that is free of the trace-gas of interest, however, for scanning DOAS instruments at volcanoes this requirement can be formulated in a weaker form. The spectra from one scan (e.g. from horizon to horizon) are evaluated using the DOAS approach employing one spectrum of the respective scan as FRS (for example a zenith-looking spectrum). Possible SO2 contamination of the FRS is corrected for by calculating an SO2 offset value for each scan that is then subtracted from the results of all encompassing. The SO2 offset can, for example, be defined as the average SO2 column density (CD) of the 20% of spectra with lowest SO2 content in one scan (the standard NOVAC method) or simply as the lowest SO2 CD that can be found in each scan. This approach is based on the assumption that at least one spectrum is recorded at a viewing direction with negligible absorption signature of volcanic SO2. We investigated an alternative approach for the DOAS evaluation using a modelled FRS which is based on a high-resolution Solar Atlas spectrum. We analyzed spectra from two volcanoes that are part of NOVAC - Nevado del Ruiz (Colombia) and Tungurahua (Ecuador) during January 2010-June 2012 and during January 2009- December 2011, respectively. Instrumental effects were identified with help of a Principal Component Analysis (PCA) of the residual structures of the DOAS evaluation. The major advantage of a retrieval based on a modelled FRS is that it yields absolute CDs of SO2 and other molecules included in the spectral retrieval. We investigated how frequently all viewing directions of each scan are contaminated with SO2. The results are compared

  10. A DOAS-like method for total column of CO2 from ground-based FTS measurements of the direct solar beam

    NASA Astrophysics Data System (ADS)

    Huo, Y. F.; Duan, M. Z.; Tian, W. S.

    2014-03-01

    A new algorithm, similar to that of DOAS method, is developed to retrieve the total column CO2 from the ground-based hyper-spectral measurements of direct solar beam. Other than spectrum fitting method, which is generally used in the optimal estimation algorithm, the radiances ratio at two wavelength named channel pair, where one is of weak and the other is of relatively strong absorption, is used to retrieve the total column CO2 in the Short Wave InfraRed(SWIR) band. Sensitivity studies show that this DOAS-like method is less dependent on the model parameters such as aerosols, water vapor, surface pressure, temperature, wavelength shift and signal noise, and the pairs of channels are carefully selected based on the sensitivity studies. To validate the algorithm, the FTS measurements located at Xi'Chong astronomical observatory are used to derive the total column CO2 amount, 272 pairs ratios are used in the retrieval and the results agree very well with that of GOSAT, which shows that the DOAS-like method could give reasonable value of XCO2.

  11. Accounting for surface reflectance in the derivation of vertical column densities of NO2 from airborne imaging DOAS

    NASA Astrophysics Data System (ADS)

    Meier, Andreas Carlos; Schönhardt, Anja; Richter, Andreas; Bösch, Tim; Seyler, André; Constantin, Daniel Eduard; Shaiganfar, Reza; Merlaud, Alexis; Ruhtz, Thomas; Wagner, Thomas; van Roozendael, Michel; Burrows, John. P.

    2016-04-01

    Nitrogen oxides, NOx (NOx = NO + NO2) play a key role in tropospheric chemistry. In addition to their directly harmful effects on the respiratory system of living organisms, they influence the levels of tropospheric ozone and contribute to acid rain and eutrophication of ecosystems. As they are produced in combustion processes, they can serve as an indicator for anthropogenic air pollution. In the late summers of 2014 and 2015, two extensive measurement campaigns were conducted in Romania by several European research institutes, with financial support from ESA. The AROMAT / AROMAT-2 campaigns (Airborne ROmanian Measurements of Aerosols and Trace gases) were dedicated to measurements of air quality parameters utilizing newly developed instrumentation at state-of-the-art. The experiences gained will help to calibrate and validate the measurements taken by the upcoming Sentinel-S5p mission scheduled for launch in 2016. The IUP Bremen contributed to these campaigns with its airborne imaging DOAS (Differential Optical Absorption Spectroscopy) instrument AirMAP (Airborne imaging DOAS instrument for Measurements of Atmospheric Pollution). AirMAP allows retrieving spatial distributions of trace gas columns densities in a stripe below the aircraft. The measurements have a high spatial resolution of approximately 30 x 80 m2 (along x across track) at a typical flight altitude of 3000 m. Supported by the instrumental setup and the large swath, gapless maps of trace gas distributions above a large city, like Bucharest or Berlin, can be acquired within a time window of approximately two hours. These properties make AirMAP a valuable tool for the validation of trace gas measurements from space. DOAS retrievals yield the density of absorbers integrated along the light path of the measurement. The light path is altered with a changing surface reflectance, leading to enhanced / reduced slant column densities of NO2 depending on surface properties. This effect must be considered in

  12. MAX-DOAS measurements of nitrogen dioxide at the high altitude sites Zugspitze (2964 m) and Pico Espejo (4765 m)

    NASA Astrophysics Data System (ADS)

    Schreier, Stefan F.; Richter, Andreas; Wittrock, Folkard; Burrows, John P.

    2015-04-01

    Spectral measurements at two mountain sites were performed with a MAX-DOAS (Multi AXis Differential Optical Absorption Spectroscopy) instrument from February to July 2003 (Zugspitze, Germany) and from March 2004 to November 2008 (Pico Espejo, Venezuela). Here, these measurements are used for the retrieval of slant column densities (SCDs) of nitrogen dioxide (NO2). While at the altitude of observations the NO2 levels are usually small, uplifting of anthropogenic emissions from the valley and in Venezuela also transport of emissions from biomass burning can lead to significant enhancements. Daily, weekly, and seasonal cycles of NO2 SCDs are shown for the two stations, linked to different meteorological conditions and compared between the two sites. In a next step, a preliminary approach to derive vertical column densities (VCDs) is presented. VCDs of NO2 from ground-based MAX-DOAS instruments provide useful information for the validation of satellite instruments such as SCIAMACHY, OMI, and GOME-2. Comparisons between ground-based and satellite-based NO2 VCDs are shown for selected periods.

  13. MAX-DOAS measurements of atmospheric trace gases in Ny-Ålesund - Radiative transfer studies and their application

    NASA Astrophysics Data System (ADS)

    Wittrock, F.; Oetjen, H.; Richter, A.; Fietkau, S.; Medeke, T.; Rozanov, A.; Burrows, J. P.

    2004-06-01

    A new approach to derive tropospheric concentrations of some atmospheric trace gases from ground-based UV/vis measurements is described. The instrument, referred to as the MAX-DOAS, is based on the well-known UV/vis instruments, which use the sunlight scattered in the zenith sky as the light source and the method of Differential Optical Absorption Spectroscopy (DOAS) to derive column amounts of absorbers like ozone and nitrogen dioxide. Substantial enhancements have been applied to this standard setup to use different lines of sight near to the horizon as additional light sources (MAX - multi axis). Results from measurements at Ny-Ålesund (79° N, 12° E) are presented and interpreted with the full-spherical radiative transfer model SCIATRAN. In particular, measurements of the oxygen dimer O4 which has a known column and vertical distribution in the atmosphere are used to evaluate the sensitivity of the retrieval to parameters such as multiple scattering, solar azimuth, surface albedo and refraction in the atmosphere and also to validate the radiative transfer model. As a first application, measurements of NO2 emissions from a ship lying in Ny-Ålesund harbour are presented. The results of this study demonstrate the feasibility of long term UV/vis multi axis measurement that can be used to derive not only column amounts of different trace gases but also some information on the vertical location of these absorbers.

  14. Operational MAX-DOAS Tropospheric Column Observations of NO2 used for Validation of OMI and SCIAMACHY

    NASA Astrophysics Data System (ADS)

    Vlemmix, T.; Piters, A. J. M.; Levelt, P. F.; Wang, P.; Stammes, P.

    2009-04-01

    Worldwide the number of observation sites where nitrogen dioxide (NO2) columns are monitored on an operational basis by atmospheric remote sensing is sparse. Few small networks exist so there is no global coverage which is essential for satellite validation. Since November 2007 multi axes differential optical absorption spectroscopy (MAX-DOAS) observations of NO2 are performed on an operational basis at the Royal Netherlands Meteorological Institute (KNMI). For this a Mini MAX-DOAS instrument is used. This poster will show the algorithm that is used to retrieve tropospheric vertical columns of NO2 which includes a correction for aerosols. Information on the aerosol optical thickness (AOT) and the height of the boundary layer is derived from O4 differential slant columns combined with observations of the radiation intensity at various viewing angles. The Doubling Adding KNMI (DAK) radiative transfer model is used to create a look up table for the AOT and boundary layer height retrieval. A comparison will be shown of retrieved AOT with CIMEL direct sun observations of AOT done at the CESAR site in Cabauw (25 kilometers from KNMI). Additionally we will show retrieved tropospheric vertical columns of NO2 in this highly polluted region throughout more than one year of observations. Finally a comparison is shown with satellite observations of SCIAMACHY and OMI. The results show the potential of this relatively low cost instrument for a global network of NO2 remote sensing sites.

  15. [MAX-DOAS measurements of NO2 column densities and vertical distribution at Ny-Alesund, Arctic during summer].

    PubMed

    Luo, Yu-Han; Sun, Li-Guang; Liu, Wen-Qing; Xie, Pin-Hua; Si, Fu-Qi; Zhou, Hai-Jin

    2012-09-01

    The multi-axis differential optical absorption spectroscopy (MAX-DOAS), one of the remote sensing techniques for trace gases measurements, is sensitive to the lower atmosphere by eliminating the influence of stratosphere retrieved from zenith-sky spectroscopy. Ground-based MAX-DOAS measurements were carried out to observe NO2 at Ny-Alesund, Arctic from 5th Jul to 1st Aug 2011. The differential slant column densities (DSCDs) of NO2 at four off-axis angles showed typical pattern of tropospheric absorbers. Based on the assumption that NO2 was well mixed in 0-1 km of the troposphere, the mean mixing ratio of NO2 during the measurement period was 1.023E11 molec x cm(-3). The fluctuation of NO2 might be related to the fossil fuel combustions and the photochemical reactions. The vertical distribution of NO2 at 0-3 km showed that NO2 was mainly originated from boundary layer of sea surface. PMID:23240391

  16. MAX-DOAS measurements and satellite validation of tropospheric NO2 and SO2 vertical column densities at a rural site of North China

    NASA Astrophysics Data System (ADS)

    Jin, Junli; Ma, Jianzhong; Lin, Weili; Zhao, Huarong; Shaiganfar, Reza; Beirle, Steffen; Wagner, Thomas

    2016-05-01

    North China (NC), namely Huabei in Chinese, is one of the most severely polluted regions in China, and the air pollution issues in this region have received a worldwide attention. We performed ground-based Multi Axis Differential Absorption Spectroscopy (MAX-DOAS) measurements at Gucheng, (39°08‧N, 115°40‧E), a rural site of North China about 110 km southwest of Beijing, from September 2008 to September 2010. The tropospheric vertical column densities (VCDs) of NO2 and SO2 were retrieved using the so-called geometric approximation. The results show that the tropospheric NO2 and SO2 VCDs over NC have nearly the same seasonal variation pattern, with the maximum in winter and minimum in summer, while their diurnal variations are different. We also compared the tropospheric NO2 and SO2 VCDs from our MAX-DOAS measurements with several products of corresponding OMI (Ozone Monitoring Instrument) satellite observations. While in summer good agreement is found, the satellite observations systematically underestimate the tropospheric NO2 in winter over the polluted rural area of NC, probably mostly due to the so called aerosol shielding effect. In contrast, for SO2 no such clear conclusion can be drawn, probably owing to the larger uncertainties from MAX-DOAS and in particular satellite retrievals. This indicates that improvements of the retrieval algorithm for MAX-DOAS and off-line corrections of satellite measurements for the tropospheric SO2 VCDs should be given more emphasis in the future.

  17. Four years of ground-based MAX-DOAS observations of aerosols, NO2, SO2 and HCHO in Wuxi, China

    NASA Astrophysics Data System (ADS)

    Wang, Yang; Lampel, Johannes; Wagner, Thomas; Li, Ang; Xie, Pinhua; Wu, Dexia; Beirle, Steffen

    2016-04-01

    Understanding the temporal variation and spatial distribution of the abundances of nitrogen dioxide (NO2), sulphur dioxide (SO2), formaldehyde (HCHO) and aerosols is necessary to study their role in tropospheric chemistry and to estimate their importance among anthropogenic emissions. To accomplish this, we operated a Multi AXis - Differential Optical Absorption Spectroscopy (MAX-DOAS) instrument from May 2011 to Nov 2014 in Wuxi, China. A new inversion algorithm PriAM (profile inversion algorithm of aerosol extinction and trace gas concentration) developed at AIOFM in cooperation with MPIC based on the optimal estimation algorithm is applied to obtain tropospheric profiles of trace gases and aerosols from the long-term observations. The performance of the inversion algorithm is evaluated by comparisons with other independent techniques for a period longer than one year. The cloud effect on the retrieved column densities, surface concentrations and profiles of the trace gases and aerosols is evaluated using of a cloud classification scheme based on the MAX-DOAS measurements themselves. From this study recommendations for the quality of the MAX-DOAS results for different cloud scenarios are given. Further, the MAX-DOAS results are used to characterize the seasonal, diurnal, and weekly variations of NO2, SO2, HCHO and aerosols. Systematic weekly variations are found for all the species, indicating a significant contribution of anthropogenic emissions to the observed abundances. The good correlations between the trace gases and aerosols, especially for HCHO, indicate a significant contribution of secondary aerosols from the precursors to the total aerosol load. We use the wind dependence of the pollutants to identify the dominating sources. High values are observed when the wind comes from the direction of industrial areas.

  18. Mapping the BrO/SO2 ratio in the plume of Popocatépetl, Mexico with Imaging-DOAS

    NASA Astrophysics Data System (ADS)

    Zielcke, Johannes; Luebcke, Peter; Vogel, Leif; Bobrowski, Nicole; Platt, Ulrich

    2015-04-01

    Differential Optical Absorption Spectroscopy (DOAS) in the ultraviolet and visible wavelength region has become a widespread tool, not only to study the chemistry of trace gases such as sulphur dioxide (SO2) and halogen oxides (e.g. BrO, OClO) in volcanic plumes. It can also be used for volcano monitoring by observing SO2 fluxes and the molar ratio of BrO to SO2, which is a possible precursor for dynamic changes in the shallow part of a volcanic system like other halogen/sulfur ratios. This acquisition of this ratio is convenient as it can be measured with comparatively simple UV DOAS instruments. Imaging-DOAS (IDOAS) utilizes the push-broom or whisk-broom technique to create a hyperspectral image of a section of the sky, then the DOAS evaluation is applied to each pixel to derive trace gas slant column densities (SCDs). Hereby images of the SO2 and BrO distribution can be created, allowing to study the chemistry in different parts of the plume. This is especially interesting for the case of BrO, which is produced in the atmosphere and not directly emitted by volcanoes. Here we present IDOAS measurements carried out at Popocatépetl volcano, Mexico, during April 2010 and 2011. SO2 SCDs of up to 2 - 1018 molecules cm-2 and BrO SCDs of up to 7 - 1013 molecules cm-2 were detected. The determined BrO/SO2 ratios range around 3 - 10-5, comparable to several other volcanoes in the Americas. An increase in the determined BrO/SO2 ratios with distance from the vent, i.e. plume age, can be observed.

  19. MAX-DOAS measurements and satellite validation of tropospheric NO2 and SO2 vertical column densities at a rural site of North China

    NASA Astrophysics Data System (ADS)

    Jin, Junli; Ma, Jianzhong; Lin, Weili; Zhao, Huarong; Shaiganfar, Reza; Beirle, Steffen; Wagner, Thomas

    2016-05-01

    North China (NC), namely Huabei in Chinese, is one of the most severely polluted regions in China, and the air pollution issues in this region have received a worldwide attention. We performed ground-based Multi Axis Differential Absorption Spectroscopy (MAX-DOAS) measurements at Gucheng, (39°08‧N, 115°40‧E), a rural site of North China about 110 km southwest of Beijing, from September 2008 to September 2010. The tropospheric vertical column densities (VCDs) of NO2 and SO2 were retrieved using the so-called geometric approximation. The results show that the tropospheric NO2 and SO2 VCDs over NC have nearly the same seasonal variation pattern, with the maximum in winter and minimum in summer, while their diurnal variations are different. We also compared the tropospheric NO2 and SO2 VCDs from our MAX-DOAS measurements with several products of corresponding OMI (Ozone Monitoring Instrument) satellite observations. While in summer good agreement is found, the satellite observations systematically underestimate the tropospheric NO2 in winter over the polluted rural area of NC, probably mostly due to the so called aerosol shielding effect. In contrast, for SO2 no such clear conclusion can be drawn, probably owing to the larger uncertainties from MAX-DOAS and in particular satellite retrievals. This indicates that improvements of the retrieval algorithm for MAX-DOAS and off-line corrections of satellite measurements for the tropospheric SO2 VCDs should be given more emphasis in the future.

  20. High Resolution Direction of Arrival (DOA) Estimation Based on Improved Orthogonal Matching Pursuit (OMP) Algorithm by Iterative Local Searching

    PubMed Central

    Wang, Wenyi; Wu, Renbiao

    2013-01-01

    DOA (Direction of Arrival) estimation is a major problem in array signal processing applications. Recently, compressive sensing algorithms, including convex relaxation algorithms and greedy algorithms, have been recognized as a kind of novel DOA estimation algorithm. However, the success of these algorithms is limited by the RIP (Restricted Isometry Property) condition or the mutual coherence of measurement matrix. In the DOA estimation problem, the columns of measurement matrix are steering vectors corresponding to different DOAs. Thus, it violates the mutual coherence condition. The situation gets worse when there are two sources from two adjacent DOAs. In this paper, an algorithm based on OMP (Orthogonal Matching Pursuit), called ILS-OMP (Iterative Local Searching-Orthogonal Matching Pursuit), is proposed to improve DOA resolution by Iterative Local Searching. Firstly, the conventional OMP algorithm is used to obtain initial estimated DOAs. Then, in each iteration, a local searching process for every estimated DOA is utilized to find a new DOA in a given DOA set to further decrease the residual. Additionally, the estimated DOAs are updated by substituting the initial DOA with the new one. The simulation results demonstrate the advantages of the proposed algorithm. PMID:23974150

  1. High resolution direction of arrival (DOA) estimation based on improved orthogonal matching pursuit (OMP) algorithm by iterative local searching.

    PubMed

    Wang, Wenyi; Wu, Renbiao

    2013-01-01

    DOA (Direction of Arrival) estimation is a major problem in array signal processing applications. Recently, compressive sensing algorithms, including convex relaxation algorithms and greedy algorithms, have been recognized as a kind of novel DOA estimation algorithm. However, the success of these algorithms is limited by the RIP (Restricted Isometry Property) condition or the mutual coherence of measurement matrix. In the DOA estimation problem, the columns of measurement matrix are steering vectors corresponding to different DOAs. Thus, it violates the mutual coherence condition. The situation gets worse when there are two sources from two adjacent DOAs. In this paper, an algorithm based on OMP (Orthogonal Matching Pursuit), called ILS-OMP (Iterative Local Searching-Orthogonal Matching Pursuit), is proposed to improve DOA resolution by Iterative Local Searching. Firstly, the conventional OMP algorithm is used to obtain initial estimated DOAs. Then, in each iteration, a local searching process for every estimated DOA is utilized to find a new DOA in a given DOA set to further decrease the residual. Additionally, the estimated DOAs are updated by substituting the initial DOA with the new one. The simulation results demonstrate the advantages of the proposed algorithm. PMID:23974150

  2. Airborne Measurements of Scattering and Absorption Coefficients in the Planetary Boundary Layer above the Po Valley, Italy, during the PEGASOS Campaigns

    NASA Astrophysics Data System (ADS)

    Rosati, B.; Weingartner, E.; Gysel, M.; Tillmann, R.; Mentel, T. F.; Decesari, S.; Marinoni, A.; Gobbi, G. P.; Fierli, F.; Cairo, F.; Bucci, S.; Zanatta, M.; Größ, J.; Baltensperger, U.

    2014-12-01

    Aerosol particles influence the Earth's radiation budget by interacting with the incoming sunlight. The chemical composition and size of aerosol particles determine their potential to scatter and absorb radiation as well as their capability to take up water (Zieger et al., 2011). If particles are hygroscopic their optical properties will be altered at enhanced relative humidities (RH) due to the increase in size and change in index of refraction. It is known that RH but also the chemical composition of aerosols change with altitude (Morgan et al., 2010) which makes it very important to investigate optical properties at different heights. Within the Pan-European Gas-Aerosols-climate interaction Study (PEGASOS) a set of instruments was installed on a Zeppelin to investigate changes of light scattering and absorption in the planetary boundary layer. In order to obtain the scattering properties, Mie calculations were performed for size distributions recorded with SMPS (scanning mobility particle sizer) and WELAS (optical size spectrometer). The index of refraction and the hygroscopicity of the aerosol particles were measured with the white-light humidified optical particle spectrometer (WHOPS). These measurements further allowed studying the RH-dependence of the optical properties. Moreover, a seven wavelength portable aethalometer was employed to determine the light absorption properties of the aerosol. In this work we will present vertical profiles of scattering and absorption coefficients measured during Zeppelin flights of the PEGASOS campaigns in Italy in 2012. Additionally comparisons with ground based measurements from nephelometers and aethalometers, as well as remote sensing results will be shown. W.T. Morgan et al., Enhancement of the aerosol direct radiative effect by semi-volatile aerosol components: Airborne measurements in North-Western Europe, Atmospheric Chemistry and Physics 10(2010), pp. 8151-8171.P. Zieger et al., Comparison of ambient aerosol

  3. Spherical grating spectrometers

    NASA Astrophysics Data System (ADS)

    O'Donoghue, Darragh; Clemens, J. Christopher

    2014-07-01

    We describe designs for spectrometers employing convex dispersers. The Offner spectrometer was the first such instrument; it has almost exclusively been employed on satellite platforms, and has had little impact on ground-based instruments. We have learned how to fabricate curved Volume Phase Holographic (VPH) gratings and, in contrast to the planar gratings of traditional spectrometers, describe how such devices can be used in optical/infrared spectrometers designed specifically for curved diffraction gratings. Volume Phase Holographic gratings are highly efficient compared to conventional surface relief gratings; they have become the disperser of choice in optical / NIR spectrometers. The advantage of spectrometers with curved VPH dispersers is the very small number of optical elements used (the simplest comprising a grating and a spherical mirror), as well as illumination of mirrors off axis, resulting in greater efficiency and reduction in size. We describe a "Half Offner" spectrometer, an even simpler version of the Offner spectrometer. We present an entirely novel design, the Spherical Transmission Grating Spectrometer (STGS), and discuss exemplary applications, including a design for a double-beam spectrometer without any requirement for a dichroic. This paradigm change in spectrometer design offers an alternative to all-refractive astronomical spectrometer designs, using expensive, fragile lens elements fabricated from CaF2 or even more exotic materials. The unobscured mirror layout avoids a major drawback of the previous generation of catadioptric spectrometer designs. We describe laboratory measurements of the efficiency and image quality of a curved VPH grating in a STGS design, demonstrating, simultaneously, efficiency comparable to planar VPH gratings along with good image quality. The stage is now set for construction of a prototype instrument with impressive performance.

  4. Inherent calibration of a blue LED-CE-DOAS instrument to measure iodine oxide, glyoxal, methyl glyoxal, nitrogen dioxide, water vapour and aerosol extinction in open cavity mode

    NASA Astrophysics Data System (ADS)

    Thalman, R.; Volkamer, R.

    2010-12-01

    The combination of Cavity Enhanced Absorption Spectroscopy (CEAS) with broad-band light sources (e.g. Light-Emitting Diodes, LEDs) lends itself to the application of cavity enhanced Differential Optical Absorption Spectroscopy (CE-DOAS) to perform sensitive and selective point measurements of multiple trace gases and aerosol extinction with a single instrument. In contrast to other broad-band CEAS techniques, CE-DOAS relies only on the measurement of relative intensity changes, i.e. does not require knowledge of the light intensity in the absence of trace gases and aerosols (I0). We have built a prototype LED-CE-DOAS instrument in the blue spectral range (420-490 nm) to measure nitrogen dioxide (NO2), glyoxal (CHOCHO), methyl glyoxal (CH3COCHO), iodine oxide (IO), water vapour (H2O) and oxygen dimers (O4). We demonstrate the first direct detection of methyl glyoxal, and the first CE-DOAS detection of CHOCHO and IO. The instrument is further inherently calibrated for light extinction from the cavity by observing O4 or H2O (at 477 nm and 443 nm) and measuring the pressure, relative humidity and temperature independently. This approach is demonstrated by experiments where laboratory aerosols of known size and refractive index were generated and their extinction measured. The measured extinctions were then compared to the theoretical extinctions calculated using Mie theory (3-7 × 10-7cm-1). Excellent agreement is found from both the O4 and H2O retrievals. This enables the first inherently calibrated CEAS measurement at blue wavelengths in open cavity mode, and eliminates the need for sampling lines to supply air to the cavity, i.e., keep the cavity enclosed and/or aerosol free. Measurements in open cavity mode are demonstrated for CHOCHO, CH3COCHO, NO2, H2O and aerosol extinction. Our prototype LED-CE-DOAS provides a low cost, yet research grade innovative instrument for applications in simulation chambers and in the open atmosphere.

  5. Inherent calibration of a novel LED-CE-DOAS instrument to measure iodine oxide, glyoxal, methyl glyoxal, nitrogen dioxide, water vapour and aerosol extinction in open cavity mode

    NASA Astrophysics Data System (ADS)

    Thalman, R.; Volkamer, R.

    2010-06-01

    The combination of Cavity Enhanced Absorption Spectroscopy (CEAS) with broad-band light sources (e.g. Light-Emitting Diodes, LEDs) lends itself to the application of cavity enhanced Differential Optical Absorption Spectroscopy (CE-DOAS) to perform sensitive and selective point measurements of multiple trace gases and aerosol extinction with a single instrument. In contrast to other broad-band CEAS techniques, CE-DOAS relies only on the measurement of relative intensity changes, i.e. does not require knowledge of the light intensity in the absence of trace gases and aerosols (I0). We have built a prototype LED-CE-DOAS instrument in the blue spectral range (420-490 nm) to measure nitrogen dioxide (NO2), glyoxal (CHOCHO), methyl glyoxal (CH3COCHO), iodine oxide (IO), water vapour (H2O) and oxygen dimers (O4). We demonstrate the first CEAS detection of methyl glyoxal, and the first CE-DOAS detection of CHOCHO and IO. A further innovation consists in the measurement of extinction losses from the cavity, e.g. due to aerosols, at two wavelengths by observing O4 (477 nm) and H2O (443 nm) and measuring the pressure, relative humidity and temperature independently. This approach is demonstrated by experiments where laboratory aerosols of known size and refractive index were generated and their extinction measured. The measured extinctions were then compared to the theoretical extinctions calculated using Mie theory (3-7×10-7 cm-1). Excellent agreement is found from both the O4 and H2O retrievals. This enables the first inherently calibrated CEAS measurement in open cavity mode (mirrors facing the open atmosphere), and eliminates the need for sampling lines to supply air to the cavity, and/or keep the cavity enclosed and aerosol free. Measurements in open cavity mode are demonstrated for CHOCHO, CH3COCHO, NO2, H2O and aerosol extinction at 477 nm and 443 nm. Our prototype LED-CE-DOAS provides a low cost, yet research grade innovative instrument for applications in simulation

  6. [Real-time forecasting model for monitoring pollutant with differential optical absorption spectroscopy].

    PubMed

    Li, Su-Wen; Liu, Wen-Qing; Xie, Pin-Hua; Wang, Feng-Sui; Yang, Yi-Jun

    2009-11-01

    For real-time and on-line monitoring DOAS (differential optical absorption spectroscopy) system, a model based on an improved Elman network for monitoring pollutant concentrations was proposed. In order to reduce the systematical complexity, the forecasting factors have been obtained based on the step-wise regression method. The forecasting factors were current concentrations, temperature and relative humidity, and wind speed and wind direction. The dynamic back propagation (BP) algorithm was used for creating training set. The experiment results show that the predicted value follows the real well. So the modified Elman network can meet the demand of DOAS system's real time forecasting.

  7. [Real-time forecasting model for monitoring pollutant with differential optical absorption spectroscopy].

    PubMed

    Li, Su-Wen; Liu, Wen-Qing; Xie, Pin-Hua; Wang, Feng-Sui; Yang, Yi-Jun

    2009-11-01

    For real-time and on-line monitoring DOAS (differential optical absorption spectroscopy) system, a model based on an improved Elman network for monitoring pollutant concentrations was proposed. In order to reduce the systematical complexity, the forecasting factors have been obtained based on the step-wise regression method. The forecasting factors were current concentrations, temperature and relative humidity, and wind speed and wind direction. The dynamic back propagation (BP) algorithm was used for creating training set. The experiment results show that the predicted value follows the real well. So the modified Elman network can meet the demand of DOAS system's real time forecasting. PMID:20101985

  8. Off-Grid DOA Estimation Based on Analysis of the Convexity of Maximum Likelihood Function

    NASA Astrophysics Data System (ADS)

    LIU, Liang; WEI, Ping; LIAO, Hong Shu

    Spatial compressive sensing (SCS) has recently been applied to direction-of-arrival (DOA) estimation owing to advantages over conventional ones. However the performance of compressive sensing (CS)-based estimation methods decreases when true DOAs are not exactly on the discretized sampling grid. We solve the off-grid DOA estimation problem using the deterministic maximum likelihood (DML) estimation method. In this work, we analyze the convexity of the DML function in the vicinity of the global solution. Especially under the condition of large array, we search for an approximately convex range around the ture DOAs to guarantee the DML function convex. Based on the convexity of the DML function, we propose a computationally efficient algorithm framework for off-grid DOA estimation. Numerical experiments show that the rough convex range accords well with the exact convex range of the DML function with large array and demonstrate the superior performance of the proposed methods in terms of accuracy, robustness and speed.

  9. [The retrieval of ozone column densities by passive differential optical absorption spectroscopy during summer at Zhongshan Station, Antarctic].

    PubMed

    Luo, Yu-Han; Liu, Wen-Qing; Bian, Lin-Gen; Lu, Chang-Gui; Xie, Pin-Hua; Si, Fu-Qi; Sun, Li-Guang

    2011-02-01

    Daily ozone column densities were monitored by Passive DOAS (differential optical absorption spectroscopy) from December 10th, 2008 to Feb 19th, 2009 at Zhongshan Station, Antarctic (69 degrees 22'24" S, 76 degrees 22'14" E). Considering the absorption of O3, OClO, NO2, O4, BrO and the Ring effect, ozone slant column densities were retrieved using the zenith scattered sunlight as the light source. The results showed that there was no obvious "ozone hole" during the monitoring period, but ozone VCD (vertical column density) had greatly changed within short time scale, especially in middle December and early February. The analysis of passive DOAS and Brewer measurements of ozone VCD showed good agreement with the correlative coefficient of 0.863, while satellite board OMI measurements with the correlative coefficient of 0.840, which confirmed the validity of the monitoring of Passive DOAS. PMID:21510403

  10. Retrieval of absolute SO2 column amounts from scattered-light spectra - Implications for the evaluation of data from automated DOAS Networks

    NASA Astrophysics Data System (ADS)

    Lübcke, Peter; Lampel, Johannes; Arellano, Santiago; Bobrowski, Nicole; Dinger, Florian; Galle, Bo; Garzón, Gustavo; Hidalgo, Silvana; Chacón Ortiz, Zoraida; Vogel, Leif; Warnach, Simon; Platt, Ulrich

    2016-04-01

    Remote sensing of gas emissions is an important tool for monitoring volcanoes. The Network for Observation of Volcanic and Atmospheric Chance (NOVAC) comprises approximately 80 scanning Differential Optical Absorption Spectroscopy (DOAS) instruments installed at 30 volcanoes world-wide. The DOAS evaluation requires a Fraunhofer Reference Spectrum (FRS) that is free of the trace-gas of interest, however, for scanning DOAS instruments at volcanoes this requirement can be formulated in a weaker form. The spectra from one scan (e.g. from horizon to horizon) are evaluated using the DOAS approach employing one spectrum of the respective scan as FRS (for example a zenith-looking spectrum). Possible SO2 contamination of the FRS is corrected for by calculating an SO2 offset value for each scan that is then subtracted from the results of all encompassing. The SO2 offset can, for example, be defined as the average SO2 column density (CD) of the 20% of spectra with lowest SO2 content in one scan (the standard NOVAC method) or simply as the lowest SO2 CD that can be found in each scan. This approach is based on the assumption that at least one spectrum is recorded at a viewing direction with negligible absorption signature of volcanic SO2. We investigated an alternative approach for the DOAS evaluation using a modelled FRS which is based on a high-resolution Solar Atlas spectrum. We analyzed spectra from two volcanoes that are part of NOVAC - Nevado del Ruiz (Colombia) and Tungurahua (Ecuador) during January 2010-June 2012 and during January 2009- December 2011, respectively. Instrumental effects were identified with help of a Principal Component Analysis (PCA) of the residual structures of the DOAS evaluation. The major advantage of a retrieval based on a modelled FRS is that it yields absolute CDs of SO2 and other molecules included in the spectral retrieval. We investigated how frequently all viewing directions of each scan are contaminated with SO2. The results are compared

  11. Active differential optical absorption spectroscopy for NO2 gas pollution using blue light emitting diodes

    NASA Astrophysics Data System (ADS)

    Aljalal, Abdulaziz; Gasmi, Khaled; Al-Basheer, Watheq

    2015-05-01

    Availability of high intensity light emitting diodes in the blue region offer excellent opportunity for using them in active Differential Optical Absorption Spectroscopy (DOAS) to detect air pollution. Their smooth and relatively broad spectral emissions as well as their long life make them almost ideal light sources for active DOAS. In this study, we report the usage of a blue light emitting diode in an active DOAS setup to measure traces of NO2 gas and achieving few parts per billion detection limit for a path length of 300 m. Details of the setup will be presented along with the effects on measurement accuracy due to shifts in the measured spectra calibration and due to using theoretical instrument Gaussian function instead of the measured instrument function.

  12. Can Nitrous Oxide be Measured Using Space Borne Ultraviolet Spectrometers?

    NASA Astrophysics Data System (ADS)

    Gonzalez Abad, G.; Wang, S.; García Nieto, D.; Benavent Oltra, N.; Anguas Ballesteros, M.; Serranía Alarcón, F.

    2015-12-01

    The photolysis of nitrous oxide (HONO) by longwave UV radiation has hydroxyl radicals (OH) and nitric oxide (NO) as products. Since HONO accumulates in the troposphere during the night hours it plays a major role in the production of OH in the early morning during the wake-up tropospheric photochemistry. Therefore HONO concentrations have strong implications for the formation of ozone (O3) and peroxyacyl nitrates (PANs) in the early hours of the morning. Given the diurnal variation of HONO concentration, measurements from space borne ultraviolet spectrometers have been unsuccessful. The upcoming geostationary instruments devoted to monitor air quality, including TEMPO, will open possibilities to systematically make early morning measurements of HONO. Here we present an observation experiment to analyze the feasibility of HONO measurements from geostationary instruments using a combination of chemical transport models, in situ DOAS measurements of HONO in Madrid and radiative transfer calculations.

  13. [Research on the influence of LED temperature shifts on differential optical absorption spectroscopy for measuring NO2].

    PubMed

    Ling, Liu-Yi; Xie, Pin-Hua; Qin, Min; Zheng, Ni-Na; Ye, Cong-Lei; Li, Ang; Hu, Ren-Zhi

    2012-11-01

    Influences of LEDs (without etalon structure and center wavelengths are respectively 370 nm (near-UV), 452 nm (blue) and 660 nm(red)) temperature shifts on differential optical absorption spectroscopy(DOAS) for measuring NO2 were studied. NO2 absorption spectra were formed using LED emitting spectra at 10 degrees C. The measured LED spectra at other temperatures were used as reference spectra of DOAS. Thus, NO2 differential optical densities under different LED temperature shifts were acquired and then NO2 differential cross-sections were fitted to the acquired differential optical densities. From fitting results, the linear relations of 0.995, 0.945 and 0.989 correlation between delta of fitting residual and near-UV, blue and red LEDs temperature shifts were found and their slopes are respectively 1.12 x 10(-3), 5.25 x 10(-5) and 7.45 x 10(-4) degrees C(-1). The fitting results show that the influence of temperature shifts of blue LED on DOAS retrieval is negligible and the temperature shifts of near-UV and red LED are impressible to DOAS measurement resulting in degradation of detection sensitivity. The retrieval results of blue LED with and without etalon with similar temperature properties were compared and showed that etalon of LED will greatly increase the influence of temperature shifts of LED on DOAS retrieval. PMID:23387143

  14. The Quadrupole Mass Spectrometer

    ERIC Educational Resources Information Center

    Matheson, E.; Harris, T. J.

    1969-01-01

    Describes the construction and operation of a quadrupole mass spectrometer for experiments in an advanced-teaching laboratory. Discusses the theory of operation of the spectrometer and the factors affecting the resolution. Some examples of mass spectra obtained with this instrument are presented and discussed. (LC)

  15. Observation of NO3 radicals by LP-DOAS during CAREBEIJING 2014

    NASA Astrophysics Data System (ADS)

    Lu, Xue; Qin, Min; Xie, Pinhua; Duan, Jun; Fang, Wu; Liu, Jianguo; Liu, Wenqing

    2016-04-01

    NO3 radical is a significant species during night, affecting the formation of secondary organic aerosol (SOA) in night. It is also the most pivotal oxidation in night, involved in the removal process of NOx and VOCs, which is directly related to atmosphere cleanliness. During the CAREBEIJING field campaign (June 5 - July 10, 2014), NO3 radical was measured with a long path differential optical absorption spectroscopy (LP-DOAS) at Wangdu Site (38.68°N; 115.18°E) in the north of China. In this poster, the principle and fitting analyses of LPDOAS were presented; a retrieval example and a time series of NO3 radicals' concentration with good continuity were showed. The detection limit (1σ) of NO3 with 3.4km optical path is 3.4ppt. The observed mean NO3 mixing ratios were 21 ppt. Under the assumption of steady state, the NO3 production rates were calculated averaging at 1.013ppb/h. The calculated NO3 lifetime has an average of 102.6 s. The correlation between the NO3 mixing ratio and its production rates is about 0.78, which indicates the importance of direct sinks. However, the slope of the logarithmic correlation between NO3 lifetime and NO2 mixing ratio is -0.44, revealing the removal of NO3 is not strongly dependent on the indirect loss process herein.

  16. Multipath Separation-Direction of Arrival (MS-DOA) with Genetic Search Algorithm for HF channels

    NASA Astrophysics Data System (ADS)

    Arikan, Feza; Koroglu, Ozan; Fidan, Serdar; Arikan, Orhan; Guldogan, Mehmet B.

    2009-09-01

    Direction-of-Arrival (DOA) defines the estimation of arrival angles of an electromagnetic wave impinging on a set of sensors. For dispersive and time-varying HF channels, where the propagating wave also suffers from the multipath phenomena, estimation of DOA is a very challenging problem. Multipath Separation-Direction of Arrival (MS-DOA), that is developed to estimate both the arrival angles in elevation and azimuth and the incoming signals at the output of the reference antenna with very high accuracy, proves itself as a strong alternative in DOA estimation for HF channels. In MS-DOA, a linear system of equations is formed using the coefficients of the basis vector for the array output vector, the incoming signal vector and the array manifold. The angles of arrival in elevation and azimuth are obtained as the maximizers of the sum of the magnitude squares of the projection of the signal coefficients on the column space of the array manifold. In this study, alternative Genetic Search Algorithms (GA) for the maximizers of the projection sum are investigated using simulated and experimental ionospheric channel data. It is observed that GA combined with MS-DOA is a powerful alternative in online DOA estimation and can be further developed according to the channel characteristics of a specific HF link.

  17. Joint estimation of TOA and DOA in IR-UWB system using a successive propagator method

    NASA Astrophysics Data System (ADS)

    Wang, Fangqiu; Zhang, Xiaofei; Wang, Chenghua; Zhou, Shengkui

    2015-10-01

    Impulse radio ultra-wideband (IR-UWB) ranging and positioning require accurate estimation of time-of-arrival (TOA) and direction-of-arrival (DOA). With receiver of two antennas, both of the TOA and DOA parameters can be estimated via two-dimensional (2D) propagator method (PM), in which the 2D spectral peak searching, however, renders much higher computational complexity. This paper proposes a successive PM algorithm for joint TOA and DOA estimation in IR-UWB system to avoid 2D spectral peak searching. The proposed algorithm firstly gets the initial TOA estimates in the two antennas from the propagation matrix, then utilises successively one-dimensional (1D) local searches to achieve the estimation of TOAs in the two antennas, and finally obtains the DOA estimates via the difference in the TOAs between the two antennas. The proposed algorithm, which only requires 1D local searches, can avoid the high computational cost in 2D-PM algorithm. Furthermore, the proposed algorithm can obtain automatically paired parameters and has better joint TOA and DOA estimation performance than conventional PM algorithm, estimation of signal parameters via rotational invariance techniques algorithm and matrix pencil algorithm. Meanwhile, it has very close parameter estimation to that of 2D-PM algorithm. We have also derived the mean square error of TOA and DOA estimation of the proposed algorithm and the Cramer-Rao bound of TOA and DOA estimation in this paper. The simulation results verify the usefulness of the proposed algorithm.

  18. Divergent Nod-Containing Bradyrhizobium sp. DOA9 with a Megaplasmid and its Host Range

    PubMed Central

    Teamtisong, Kamonluck; Songwattana, Pongpan; Noisangiam, Rujirek; Piromyou, Pongdet; Boonkerd, Nantakorn; Tittabutr, Panlada; Minamisawa, Kiwamu; Nantagij, Achara; Okazaki, Shin; Abe, Mikiko; Uchiumi, Toshiki; Teaumroong, Neung

    2014-01-01

    Bradyrhizobium sp. DOA9, a non-photosynthetic bacterial strain originally isolated from the root nodules of the legume Aeschynomene americana, is a divergent nod-containing strain. It exhibits a broad host range, being able to colonize and efficiently nodulate the roots of most plants from the Dalbergioid, Millettioid, and Robinioid tribes (7 species of Papilionoideae). In all cases, nodulation was determinate. The morphology and size of DOA9 bacteroids isolated from the nodules of various species of Papilionoideae were indistinguishable from the free-living form. However, they were spherical in Arachis hypogaea nodules. GusA-tagged DOA9 also colonized rice roots as endophytes. Since broad-host-range legume symbionts often carry multiple replicons in their genome, we analyzed the replicons for symbiosis genes by electrophoresis. DOA9 carried two replicons, a chromosome (cDOA9) and single megaplasmid (pDOA9) larger than 352 kb. The genes for nodulation (nodA, B, C) and nitrogen fixation (nifH) were localized on the megaplasmid. Southern blot hybridization revealed two copies of nodA on the megaplasmid, single copies of nodB and C on the megaplasmid, and one copy each of nifH on the chromosome and megaplasmid. These results suggested that Bradyrhizobium sp. DOA9 may have the unusual combination of a broad host range, bacteroid differentiation, and symbiosis-mediating replicons. PMID:25283477

  19. New concepts for the comparison of tropospheric NO2 column densities derived from car-MAX-DOAS observations, OMI satellite observations and the regional model CHIMERE during two MEGAPOLI campaigns in Paris 2009/10

    NASA Astrophysics Data System (ADS)

    Shaiganfar, R.; Beirle, S.; Petetin, H.; Zhang, Q.; Beekmann, M.; Wagner, T.

    2015-03-01

    We compare tropospheric column densities (vertically integrated concentrations) of NO2 from three data sets for the metropolitan area of Paris during two extensive measurement campaigns (25 days in summer 2009 and 29 days in winter 2010) within the European research project MEGAPOLI. The selected data sets comprise a regional chemical transport model (CHIMERE) as well as two observational data sets: ground based mobile Multi-AXis-Differential Optical Absorption Spectroscopy (car-MAX-DOAS) measurements and satellite measurements from the Ozone Monitoring Instrument (OMI). On most days, car-MAX-DOAS measurements were carried out along large circles (diameter ~35 km) around Paris. The car-MAX-DOAS results are compared to coincident data from CHIMERE and OMI. All three data sets have their specific strengths and weaknesses, especially with respect to their spatio-temporal resolution and coverage as well as their uncertainties. Thus we compare them in two different ways: first, we simply consider the original data sets. Second, we compare modified versions making synergistic use of the complementary information from different data sets. For example, profile information from the regional model is used to improve the satellite data, observations of the horizontal trace gas distribution are used to adjust the respective spatial patterns of the model simulations, or the model is used as a transfer tool to bridge the spatial scales between car-MAX-DOAS and satellite observations. Using the modified versions of the data sets, the comparison results substantially improve compared to the original versions. In general, good agreement between the data sets is found outside the emission plume, but inside the emission plumes the tropospheric NO2 VCDs are systematically underestimated by the CHIMERE model and the satellite observations (compared to the car-MAX-DOAS observations). One major result from our study is that for satellite validation close to strong emission sources (like

  20. New concepts for the comparison of tropospheric NO2 column densities derived from car-MAX-DOAS observations, OMI satellite observations and the regional model CHIMERE during two MEGAPOLI campaigns in Paris 2009/10

    NASA Astrophysics Data System (ADS)

    Shaiganfar, R.; Beirle, S.; Petetin, H.; Zhang, Q.; Beekmann, M.; Wagner, T.

    2015-07-01

    We compare tropospheric column densities (vertically integrated concentrations) of NO2 from three data sets for the metropolitan area of Paris during two extensive measurement campaigns (25 days in summer 2009 and 29 days in winter 2010) within the European research project MEGAPOLI. The selected data sets comprise a regional chemical transport model (CHIMERE) as well as two observational data sets: ground-based mobile Multi-AXis-Differential Optical Absorption Spectroscopy (car-MAX-DOAS) measurements and satellite measurements from the Ozone Monitoring Instrument (OMI). On most days, car-MAX-DOAS measurements were carried out along large circles (diameter ~ 35 km) around Paris. The car-MAX-DOAS results are compared to coincident data from CHIMERE and OMI. All three data sets have their specific strengths and weaknesses, especially with respect to their spatiotemporal resolution and coverage as well as their uncertainties. Thus we compare them in two different ways: first, we simply consider the original data sets. Second, we compare modified versions making synergistic use of the complementary information from different data sets. For example, profile information from the regional model is used to improve the satellite data, observations of the horizontal trace gas distribution are used to adjust the respective spatial patterns of the model simulations, or the model is used as a transfer tool to bridge the spatial scales between car-MAX-DOAS and satellite observations. Using the modified versions of the data sets, the comparison results substantially improve compared to the original versions. In general, good agreement between the data sets is found outside the emission plume, but inside the emission plumes the tropospheric NO2 vertical column densities (VCDs). are systematically underestimated by the CHIMERE model and the satellite observations (compared to the car-MAX-DOAS observations). One major result from our study is that for satellite validation close to

  1. Simulated Radiative Transfer DOAS - A new method for improving volcanic SO2 emissions retrievals from ground-based UV-spectroscopic measurements of scattered solar radiation

    NASA Astrophysics Data System (ADS)

    Kern, C.; Deutschmann, T.; Vogel, L.; Bobrowski, N.; Hoermann, C.; Werner, C. A.; Sutton, A. J.; Elias, T.

    2011-12-01

    Passive Differential Optical Absorption Spectroscopy (DOAS) has become a standard tool for measuring SO2 at volcanoes. More recently, ultra-violet (UV) cameras have also been applied to obtain 2D images of SO2-bearing plumes. Both techniques can be used to derive SO2 emission rates by measuring SO2 column densities, integrating these along the plume cross-section, and multiplying by the wind speed. Recent measurements and model studies have revealed that the dominating source of uncertainty in these techniques often originates from an inaccurate assessment of radiative transfer through the volcanic plume. The typical assumption that all detected radiation is scattered behind the volcanic plume and takes a straight path from there to the instrument is often incorrect. We recently showed that the straight path assumption can lead to column density errors of 50% or more in cases where plumes with high SO2 and aerosol concentrations are measured from several kilometers distance, or where the background atmosphere contains a large amount of scattering aerosols. Both under- and overestimation are possible depending on the atmospheric conditions and geometry during spectral acquisition. Simulated Radiative Transfer (SRT) DOAS is a new evaluation scheme that combines radiative transfer modeling with spectral analysis of passive DOAS measurements in the UV region to derive more accurate SO2 column densities than conventional DOAS retrievals, which in turn leads to considerably more accurate emission rates. A three-dimensional backward Monte Carlo radiative transfer model is used to simulate realistic light paths in and around the volcanic plume containing variable amounts of SO2 and aerosols. An inversion algorithm is then applied to derive the true SO2 column density. For fast processing of large datasets, a linearized algorithm based on lookup tables was developed and tested on a number of example datasets. In some cases, the information content of the spectral data is

  2. Variation of temporal and spatial patterns of NO2 in Beijing using mobile DOAS during the APEC in 2014 and the Victory Day Parade in 2015

    NASA Astrophysics Data System (ADS)

    Li, Ang; Xie, Pinhua; Wu, Fengcheng; Hu, Zhaokun; Xu, Jin; Qin, Min

    2016-04-01

    Recently Chinese cities have suffered severe haze events, especially in North China Plain (NCP). It has the characteristics of regional scale and complex components with high concentration level. In order to learn the haze formation, it is necessary to investigate temporal and spatial distribution of pollutants, emissions and pollution transport for better understanding of the impact of various sources on air quality. Control policies such as "odd-and-even license plate rule" were implemented by the Chinese government to restrict traffic and suspend factory production in Beijing and neighboring cities during the Asia-Pacific Economic Cooperation summit (APEC) in 2014 and Victory Parade in 2015. We use mobile differential optical absorption spectroscopy (DOAS) and multi-axis differential optical absorption spectroscopy (MAX-DOAS) to measure the variation of the spatial and temporal patterns of NO2 column densities from October 24, 2014 to December 31, 2014 and from August 25, 2015 to September 7, 2015. It is found that the NO2 column densities during the episode of control policies are significantly lower than those during other periods, and the emission flux of NO2 calculated by mobile DOAS is also lower than the results from other periods. There was a further 45.5% decline of the emission flux of NO2 in Beijing fifth ring road during the Victory Day Parade in 2015 than during APEC period. The low NO2 column densities that occur during the episode of control policies are affected by the control policies as well as meteorological conditions.

  3. A photoacoustic spectrometer for trace gas detection

    NASA Astrophysics Data System (ADS)

    Telles, E. M.; Bezerra, E.; Scalabrin, A.

    2005-06-01

    A high-resolution external laser photoacoustic spectrometer has been developed for trace gas detection with absorption transitions in coincidence with CO2 laser emission lines (9,2-10,9 μm: 920-1086 cm-1). The CO2 laser operates in 90 CW lines with power of up to 15 W. A PC-controlled step motor can tune the laser lines. The resonance frequency of first longitudinal mode of the photoacoustic cell is at 1600 Hz. The cell Q-factor and cell constant are measured close to 50 and 28 mVcmW-1, respectively. The spectrometer has been tested in preliminary studies to analyze the absorption transitions of ozone (O_3). The ethylene (C_2H_4) from papaya fruit is also investigated using N2 as carrier gas at a constant flow rate.

  4. Development of a Heated Closed Path NO2 CE-DOAS Instrument for the Detection of Halogen Nitrates

    NASA Astrophysics Data System (ADS)

    Herlyn, Lennard; Horbanski, Martin; Schmitt, Stefan; Pöhler, Denis; Kleinschmitt, Christoph; Platt, Ulrich

    2015-04-01

    Reactive halogen species (RHS) like bromine oxide (BrO) can catalytically destroy Ozone. Thus, they can play a major role in atmospheric chemistry even if only low concentrations are present. Former measurements of BrO and nitrogen dioxide (NO2) at the Dead Sea indicate the presence of bromine nitrate (BrONO2) as an important sink for BrO. BrONO2 is also assumed to play a key role in the heterogeneous, autocatalytic production of BrO on sea salt aerosols (bromine explosion). Therefore simultaneous measurements of BrO, NO2 and BrONO2 are urgently needed for a better understanding of halogen chemistry. However, a direct measurement of BrONO2 is difficult and for example with techniques like DOAS not possible since it only shows broad band absorption in the UV-VIS spectral range. We developed a new Cavity Enhanced DOAS instrument for indirect measurements of BrONO2. The instrument heats sample air to 140 °C to decompose BrONO2 into BrO and NO2 to an extent of over 95 %. The instrument then measures the total NO2, which is the sum of ambient NO2 and decomposed BrONO2. The concentration of the decomposed BrONO2 can then be retrieved by comparison with a simultaneous measurement of ambient NO2, using a conventional NO2 CE-DOAS instrument. At a time resolution of about 5 min the NO2 detection limit of the heated instrument was about 200 ppt , while the detection limit of the cold instrument was about 120 ppt. Thus, the detection limit for the excess NO2 is 230 ppt at 5 min time resolution. To achieve this accuracy a precise NO2 cross section at 140°C was needed. Temperature has a major influence on the intensity ratios between hot and cold NO2 bands due to the rotational temperature, collisional broadening and thermal Doppler broadening. Thus, this effect can not be neglected. However, so far no NO2 cross sections at these temperatures are available in literature yet. Thus, high resolution NO2 cross sections were recorded at different temperatures of up to 140 °C with

  5. High-resolution NO2 maps of Rotterdam and Zürich retrieved from the APEX imaging spectrometer

    NASA Astrophysics Data System (ADS)

    Kuhlmann, Gerrit; Hueni, Andreas; Brunner, Dominik

    2016-04-01

    In urban areas, nitrogen dioxide (NO_2) concentrations have high spatial and temporal variability making high-resolution NO2 maps an important tool for air pollution assessment and epidemiological studies. We retrieved high-resolution NO2 maps from the Airborne Prism Experiment (APEX) imaging spectrometer measured over Zürich on 30. August 2013 (11:24--12:05 UTC) and Rotterdam on 17. September 2014 (8:53--10:18 UTC). Our updated retrieval fits NO_2, O_3, O_4, H_2O and the Ring effect between 440 and 510 nm using Differential Optical Absorption Spectroscopy (DOAS). The radiance spectra were spectrally calibrated using a high-resolution solar reference spectrum to correct spectral shifts in across- and along-track direction. Air mass factors were computed using the SCIATRAN radiative transfer model. The retrieved NO2 maps have 50×50m2 resolution and cover an area of 10×26 km2 for Zürich and 10×50 km2 for Rotterdam. The maps show enhanced NO2 values in populated areas and at least three strong plumes from oil refineries in Rotterdam. A comparison with ground measurements in Rotterdam shows only weak correlation, because most of the NO2 is found in elevated plumes. In conclusion, airborne observations allow mapping of the NO2 distribution in urban areas providing a different perspective on urban air quality which cannot be acquired by ground-based observations. The obtained maps will be used for further analysis such as estimating NOX emissions from oil refineries and comparison with urban-scale chemistry transport modelling.

  6. The SAGE spectrometer

    NASA Astrophysics Data System (ADS)

    Pakarinen, J.; Papadakis, P.; Sorri, J.; Herzberg, R.-D.; Greenlees, P. T.; Butler, P. A.; Coleman-Smith, P. J.; Cox, D. M.; Cresswell, J. R.; Jones, P.; Julin, R.; Konki, J.; Lazarus, I. H.; Letts, S. C.; Mistry, A.; Page, R. D.; Parr, E.; Pucknell, V. F. E.; Rahkila, P.; Sampson, J.; Sandzelius, M.; Seddon, D. A.; Simpson, J.; Thornhill, J.; Wells, D.

    2014-03-01

    The SAGE spectrometer has been constructed for in-beam nuclear structure studies. SAGE combines a Ge-detector array and an electron spectrometer for detection of -rays and internal conversion electrons, respectively, and allows simultaneous observation of both electrons and -rays emitted from excited nuclei. SAGE is set up in the Accelerator Laboratory of the University of Jyväskylä and works in conjunction with the RITU gas-filled recoil separator and the GREAT focal-plane spectrometer allowing the use of the recoil-decay tagging method.

  7. Assessing the need for a O4 scaling factor for MAX-DOAS measurements during the MAD-CAT campaign in Mainz Germany, Summer 2013

    NASA Astrophysics Data System (ADS)

    Wagner, Thomas; Remmers, Julia; Shaiganfar, Reza; Lampel, Johannes; Wang, Yang; Beirle, Steffen; Dörner, Steffen

    2016-04-01

    MAX-DOAS measurements of the atmospheric absorption of the oxygen dimer O4 are often used to derive information about the tropospheric aerosol distribution. For that purpose measured absorptions are compared to results of a forward model based on radiative transfer simulations and assumptions about the atmospheric state. Many studies demonstrated good agreement of the derived aerosol results with independent observations. Nevertheless, in some studies also systematic differences between the measurements and the forward model were found. E.g. measured O4 absorptions on clear days were found to be even larger than the forward model results for an assumed aerosol-free atmosphere. These discrepancies motivated the use of a scaling factor for the retrieved O4 absorptions. Reported values of this scaling factor range from about 0.7 to 0.9. On the other hand, several studies found excellent agreement between measurements and forward model without the need of a scaling factor. So far, there is no convincing explanation for these conflicting findings. In this study we compare measurements and forward model results for two clear days during the MAD-CAT (Multi Axis DOAS - Comparison campaign of Aerosols and Trace gases) campaign in Mainz, Germany in Summer 2013. On these days the aerosol extinction profiles were well constraint by measurements of a ceilometer and a sun photometer. For almost all of these measurements (made in 4 azimuth directions) we find a systematic underestimation of the measured O4 absorptions by the forward model indicating the need for a scaling factor of about 0.65 to 0.9. We investigate several potential reasons for the observed discrepancy including the influence of the profiles of temperature, pressure and aerosol extinction as well as the aerosol optical properties.

  8. Imaging Fourier transform spectrometer

    SciTech Connect

    Bennett, C.L.

    1993-09-13

    This invention is comprised of an imaging Fourier transform spectrometer having a Fourier transform infrared spectrometer providing a series of images to a focal plane array camera. The focal plane array camera is clocked to a multiple of zero crossing occurrences as caused by a moving mirror of the Fourier transform infrared spectrometer and as detected by a laser detector such that the frame capture rate of the focal plane array camera corresponds to a multiple of the zero crossing rate of the Fourier transform infrared spectrometer. The images are transmitted to a computer for processing such that representations of the images as viewed in the light of an arbitrary spectral ``fingerprint`` pattern can be displayed on a monitor or otherwise stored and manipulated by the computer.

  9. Composite Spectrometer Prisms

    NASA Technical Reports Server (NTRS)

    Breckinridge, J. B.; Page, N. A.; Rodgers, J. M.

    1985-01-01

    Efficient linear dispersive element for spectrometer instruments achieved using several different glasses in multiple-element prism. Good results obtained in both two-and three-element prisms using variety of different glass materials.

  10. AUTOMATIC MASS SPECTROMETER

    DOEpatents

    Hanson, M.L.; Tabor, C.D. Jr.

    1961-12-01

    A mass spectrometer for analyzing the components of a gas is designed which is capable of continuous automatic operation such as analysis of samples of process gas from a continuous production system where the gas content may be changing. (AEC)

  11. A Simple Raman Spectrometer.

    ERIC Educational Resources Information Center

    Blond, J. P.; Boggett, D. M.

    1980-01-01

    Discusses some basic physical ideas about light scattering and describes a simple Raman spectrometer, a single prism monochromator and a multiplier detector. This discussion is intended for British undergraduate physics students. (HM)

  12. Fourier Transform Spectrometer System

    NASA Technical Reports Server (NTRS)

    Campbell, Joel F. (Inventor)

    2014-01-01

    A Fourier transform spectrometer (FTS) data acquisition system includes an FTS spectrometer that receives a spectral signal and a laser signal. The system further includes a wideband detector, which is in communication with the FTS spectrometer and receives the spectral signal and laser signal from the FTS spectrometer. The wideband detector produces a composite signal comprising the laser signal and the spectral signal. The system further comprises a converter in communication with the wideband detector to receive and digitize the composite signal. The system further includes a signal processing unit that receives the composite signal from the converter. The signal processing unit further filters the laser signal and the spectral signal from the composite signal and demodulates the laser signal, to produce velocity corrected spectral data.

  13. First comparison of OMI-DOAS total ozone using ground-based observations at a megacity site in East Asia: Causes of discrepancy and improvement in OMI-DOAS total ozone during summer

    NASA Astrophysics Data System (ADS)

    Hong, Hyunkee; Lee, Hanlim; Kim, Jhoon; Lee, Yun-Gon

    2014-08-01

    This study compares, for the first time, the total ozone columns derived from the Ozone Monitoring Instrument-Differential Optical Absorption Spectroscopy (OMI-DOAS algorithm) (TOCs-OMI) with those obtained from ground-based Brewer and Dobson spectrophotometers (TOCs-Ground) in Seoul, a megacity in northeast Asia, over the 3 years between 2008 and 2010. We found a seasonal mean underestimation of 2.68% (maximum 18.33% on a single day) in TOCs-OMI when compared with TOCs-Ground from Seoul, particularly during the summer seasons (June, July, and August) of our study period: 20 of the 30 days when this underestimation of TOCs-OMI was greatest occurred during the summer. The causes of such large underestimations in summer TOCs-OMI were investigated, and we found that the ghost column densities (GCDs) used in the current OMI-DOAS algorithm did not fully account for the tropospheric ozone amounts below the cloud top in Seoul, particularly during the summer season when surface ozone is enhanced due to active photochemical reactions. We propose the use of New TOCs-OMI based on New GCDs that were calculated using ozonesonde data for the limited number of days when such data were available. The mean bias errors (MBE) against the TOCs-Ground of the New TOCs-OMI and original TOCs-OMI were -0.60% and -2.16%, respectively, which demonstrates the greater accuracy of the New TOCs-OMI. To increase the amount of New TOCs-OMI data available for comparison with the TOCs-Ground data, the regression equation for the relationship between the ozonesonde data and OMI-DOAS cloud pressure data was used to increase the availability of New GCD data for each measurement date that TOCs-OMI data were available for. This procedure reduced the MBE of the original TOCs-OMI by 1.29%, 1.67%, and 1.29% in June, July, and August, respectively. The present study demonstrates that the underestimation of GCDs is one of the major causes of the underestimation of TOCs-OMI during the summer season and

  14. NO2 measurements in Hong Kong using LED based long path differential optical absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Chan, K. L.; Pöhler, D.; Kuhlmann, G.; Hartl, A.; Platt, U.; Wenig, M. O.

    2012-05-01

    In this study we present the first long term measurements of atmospheric nitrogen dioxide (NO2) using a LED based Long Path Differential Optical Absorption Spectroscopy (LP-DOAS) instrument. This instrument is measuring continuously in Hong Kong since December 2009, first in a setup with a 550 m absorption path and then with a 3820 m path at about 30 m to 50 m above street level. The instrument is using a high power blue light LED with peak intensity at 450 nm coupled into the telescope using a Y-fibre bundle. The LP-DOAS instrument measures NO2 levels in the Kowloon Tong and Mongkok district of Hong Kong and we compare the measurement results to mixing ratios reported by monitoring stations operated by the Hong Kong Environmental Protection Department in that area. Hourly averages of coinciding measurements are in reasonable agreement (R = 0.74). Furthermore, we used the long-term data set to validate the Ozone Monitoring Instrument (OMI) NO2 data product. Monthly averaged LP-DOAS and OMI measurements correlate well (R = 0.84) when comparing the data for the OMI overpass time. We analyzed weekly patterns in both data sets and found that the LP-DOAS detects a clear weekly cycle with a reduction on weekends during rush hour peaks, whereas OMI is not able to observe this weekly cycle due to its fix overpass time (13:30-14:30 LT - local time).

  15. Nitrogen dioxide monitoring with an automatic DOAS station at Terra Nova Bay, Antarctica

    NASA Astrophysics Data System (ADS)

    Ravegnani, Fabrizio; Kostadinov, Ivan K.; Giovanelli, Giorgio

    1998-08-01

    During the last few years UV-Vis spectrometers were developed at the FISBAT Institute and are used for application of differential optical absorption spectroscopy method to detect many atmospheric trace gases playing important roles in the stratospheric chemistry. After several test both in laboratory and in Antarctic region, one of the spectrometers, called GASCOD2/2, was modified in collaboration with ENEA for unattended and automatic measurement in extreme high-latitude environment. The instrument was installed in December 1995 in the Italian Station at Terra Nova Bay. The aim of this research is to study the dentrification processes during the formation of the so-called ozone hole over the Antarctic region. The preliminary results for the first year of nitrogen dioxide measurement are presented and discussed.

  16. Autonomous Long-Path DOAS Measurements of Tropospheric Trace Gases at Neumayer Station III, Antarctica: First Results

    NASA Astrophysics Data System (ADS)

    Nasse, Jan-Marcus; Frieß, Udo; Pöhler, Denis; Weller, Rolf; Platt, Ulrich

    2016-04-01

    Reactive Halogen Species (RHS, like IO, BrO, ClO, etc.) have an important impact on atmospheric chemistry. In Polar Regions, the role of halogen radical chemistry has been subject of intensive research for more than two decades. Among the most prominent effects of RHS on the Polar atmosphere are the change of the oxidative capacity of the troposphere including wide-spread and frequently virtually complete destruction of tropospheric ozone, in particular during springtime, as well as the oxidation and subsequent deposition of gaseous elemental mercury. The number of field observations and the understanding of the underlying processes varies greatly between bromine, iodine and chlorine compounds. While elevated BrO concentrations resulting from autocatalytic processes (the so-called bromine explosion mechanism) are frequently observed, the abundance and influence of iodine is still subject to discussions and available observations give no consistent picture. With only a few direct observations of chlorine compounds, such as ClO and OClO, the role of tropospheric chlorine chemistry remains poorly understood to date, despite strong evidence for its relevance. The lack of observations of chlorine radicals is mainly due to the challenging detection, particularly in the case of ClO. Scattered sunlight DOAS measurements, which are available from a number of Polar locations, are not sensitive for ClO, due to insufficient radiation intensity in the UV spectral region (<308nm) where this molecule is absorbing. Here we present the overall design and first results of a novel Long Path DOAS (Differential Optical Absorption Spectroscopy) instrument with an active light source suitable for the detection of ClO. It has been set up at the German Research Station Neumayer III in coastal Antarctica during the summer season 2015/16 and is planned to operate autonomously for at least one year. The instrument is able to detect - in addition to ClO - many trace gases absorbing in the UV

  17. Measurements of tropospheric NO2 in Romania using a zenith-sky mobile DOAS system and comparisons with satellite observations.

    PubMed

    Constantin, Daniel-Eduard; Merlaud, Alexis; Van Roozendael, Michel; Voiculescu, Mirela; Fayt, Caroline; Hendrick, François; Pinardi, Gaia; Georgescu, Lucian

    2013-01-01

    In this paper we present a new method for retrieving tropospheric NO2 Vertical Column Density (VCD) from zenith-sky Differential Optical Absorption Spectroscopy (DOAS) measurements using mobile observations. This method was used during three days in the summer of 2011 in Romania, being to our knowledge the first mobile DOAS measurements peformed in this country. The measurements were carried out over large and different areas using a mobile DOAS system installed in a car. We present here a step-by-step retrieval of tropospheric VCD using complementary observations from ground and space which take into account the stratospheric contribution, which is a step forward compared to other similar studies. The detailed error budget indicates that the typical uncertainty on the retrieved NO2tropospheric VCD is less than 25%. The resulting ground-based data set is compared to satellite measurements from the Ozone Monitoring Instrument (OMI) and the Global Ozone Monitoring Experiment-2 (GOME-2). For instance, on 18 July 2011, in an industrial area located at 47.03°N, 22.45°E, GOME-2 observes a tropospheric VCD value of (3.4 ± 1.9) × 1015 molec./cm2, while average mobile measurements in the same area give a value of (3.4 ± 0.7) × 10(15) molec./cm2. On 22 August 2011, around Ploiesti city (44.99°N, 26.1°E), the tropospheric VCD observed by satellites is (3.3 ± 1.9) × 10(15) molec./cm2 (GOME-2) and (3.2 ± 3.2) × 10(15) molec./cm2 (OMI), while average mobile measurements give (3.8 ± 0.8) × 10(15) molec./cm2. Average ground measurements over "clean areas", on 18 July 2011, give (2.5 ± 0.6) × 10(15) molec./cm2 while the satellite observes a value of (1.8 ± 1.3) × 10(15) molec./cm2. PMID:23519349

  18. Measurements of Tropospheric NO2 in Romania Using a Zenith-Sky Mobile DOAS System and Comparisons with Satellite Observations

    PubMed Central

    Constantin, Daniel-Eduard; Merlaud, Alexis; Van Roozendael, Michel; Voiculescu, Mirela; Fayt, Caroline; Hendrick, François; Pinardi, Gaia; Georgescu, Lucian

    2013-01-01

    In this paper we present a new method for retrieving tropospheric NO2 Vertical Column Density (VCD) from zenith-sky Differential Optical Absorption Spectroscopy (DOAS) measurements using mobile observations. This method was used during three days in the summer of 2011 in Romania, being to our knowledge the first mobile DOAS measurements peformed in this country. The measurements were carried out over large and different areas using a mobile DOAS system installed in a car. We present here a step-by-step retrieval of tropospheric VCD using complementary observations from ground and space which take into account the stratospheric contribution, which is a step forward compared to other similar studies. The detailed error budget indicates that the typical uncertainty on the retrieved NO2tropospheric VCD is less than 25%. The resulting ground-based data set is compared to satellite measurements from the Ozone Monitoring Instrument (OMI) and the Global Ozone Monitoring Experiment-2 (GOME-2). For instance, on 18 July 2011, in an industrial area located at 47.03°N, 22.45°E, GOME-2 observes a tropospheric VCD value of (3.4 ± 1.9) × 1015 molec./cm2, while average mobile measurements in the same area give a value of (3.4 ± 0.7) × 1015 molec./cm2. On 22 August 2011, around Ploiesti city (44.99°N, 26.1°E), the tropospheric VCD observed by satellites is (3.3 ± 1.9) × 1015 molec./cm2 (GOME-2) and (3.2 ± 3.2) × 1015 molec./cm2 (OMI), while average mobile measurements give (3.8 ± 0.8) × 1015 molec./cm2. Average ground measurements over “clean areas”, on 18 July 2011, give (2.5 ± 0.6) × 1015 molec./cm2 while the satellite observes a value of (1.8 ± 1.3) × 1015 molec./cm2. PMID:23519349

  19. NO2 DOAS Measurements of Traffic Emissions by Chasing Cars

    NASA Astrophysics Data System (ADS)

    Zhu, Ying; Lipkowitsch, Ivo; Chan, Ka Lok; Bräu, Melanie; Wenig, Mark

    2016-04-01

    On this poster we present NO2 measurements using a Cavity-Enhanced DOAS on a measurement bus which we used to chase other vehicles to measure their NO2 emissions. Emissions of nitrogen oxides from on-road vehicles have received highly attention recently due to the increasing trend of ambient NOx level. It is particularly important to identify and quantify the direct emission and secondary formation of NO2 contributed by traffic emissions, in order to study the impact to the local air quality. We sampled on-road emissions in different environments and different driving conditions (e.g. urban, highway, different speeds). We analyse the data set in terms of spatial and temporal variability to search for temporal and spatial patterns. We present mean values sorted for different vehicle types, distance to the target car and travelling speeds to provide an emission data base from this measurement study.

  20. CAST-10-2/DOA 2 Airfoil Studies Workshop Results

    NASA Technical Reports Server (NTRS)

    Ray, Edward J. (Compiler); Hill, Acquilla S. (Compiler)

    1989-01-01

    During the period of September 23 through 27, 1988, the Transonic Aerodynamics Division at the Langely Research Center hosted an International Workshop on CAST-10-2/DOA 2 Airfoil Studies. The CAST-10 studies were the outgrowth of several cooperative study agreements among the NASA, the NAE of Canada, the DLR of West Germany, and the ONERA of France. Both theoretical and experimental CAST-10 airfoil results that were obtained form an extensive series of tests and studies, were reviewed. These results provided an opportunity to make direct comparisons of adaptive wall test section (AWTS) results from the NASA 0.3-meter Transonic Cryogenic Tunnel and ONERA T-2 AWTS facilities with conventional ventilated wall wind tunnel results from the Canadian high Reynolds number two-dimensional test facility. Individual papers presented during the workshop are included.

  1. EEG data compression to monitor DoA in telemedicine.

    PubMed

    Palendeng, Mario E; Zhang, Qing; Pang, Chaoyi; Li, Yan

    2012-01-01

    Data compression techniques have been widely used to process and transmit huge amount of EEG data in real-time and remote EEG signal processing systems. In this paper we propose a lossy compression technique, F-shift, to compress EEG signals for remote depth of Anaesthesia (DoA) monitoring. Compared with traditional wavelet compression techniques, our method not only preserves valuable clinical information with high compression ratios, but also reduces high frequency noises in EEG signals. Moreover, our method has negligible compression overheads (less than 0.1 seconds), which can greatly benefit real-time EEG signal monitoring systems. Our extensive experiments demonstrate the efficiency and effectiveness of the proposed compression method.

  2. Multilaser Herriott Cell for Planetary Tunable Laser Spectrometers

    NASA Technical Reports Server (NTRS)

    Tarsitano, Christopher G.; Webster, Christopher R.

    2007-01-01

    Geometric optics and matrix methods are used to mathematically model multilaser Herriott cells for tunable laser absorption spectrometers for planetary missions. The Herriott cells presented accommodate several laser sources that follow independent optical paths but probe a single gas cell. Strategically placed output holes located in the far mirrors of the Herriott cells reduce the size of the spectrometers. A four-channel Herriott cell configuration is presented for the specific application as the sample cell of the tunable laser spectrometer instrument selected for the sample analysis at Mars analytical suite on the 2009 Mars Science Laboratory mission.

  3. Recurrent acute hemolytic transfusion reactions by antibodies against Doa antigens, not detected by cross-matching.

    PubMed

    Baumgarten, Ruben; van Gelder, Warry; van Wintershoven, Joyce; Maaskant-Van Wijk, Petra A; Beckers, Erik A M

    2006-02-01

    An 81-year-old male patient suffered from recurrent acute hemolytic transfusion reactions after transfusion with phenotyped cross-match-negative red blood cells (RBCs). Extensive posttransfusion workup eventually revealed Dombrock (a) (Do(a)) antibodies. Because commercially available cell panels do not allow for identification of anti-Do(a) and owing to the lack of Do(a) typing serum samples, selection of matched units of RBCs is dependent on negative cross-match results. In this case, selection of Do(a-) units by cross-matching failed, indicating that serologic methods were not reliable. A polymerase chain reaction with sequence-specific priming assay was used to detect DOA and DOB alleles, which encode Do(a) and Do(b) antigens, respectively. The patient was confirmed to be DOB/DOB by DNA sequencing. Furthermore, the involved mismatched units in each of the three hemolytic episodes were shown to be Do(a+). In the presenting case, DNA typing appeared to be superior to serologic methods in selecting matched RBC units in the presence of anti-Do(a). PMID:16441602

  4. Infrared absorption of methanol clusters (CH3OH)n with n = 2-6 recorded with a time-of-flight mass spectrometer using infrared depletion and vacuum-ultraviolet ionization.

    PubMed

    Han, Hui-Ling; Camacho, Cristopher; Witek, Henryk A; Lee, Yuan-Pern

    2011-04-14

    We investigated IR spectra in the CH- and OH-stretching regions of size-selected methanol clusters, (CH(3)OH)(n) with n = 2-6, in a pulsed supersonic jet by using the IR-VUV (vacuum-ultraviolet) ionization technique. VUV emission at 118 nm served as the source of ionization in a time-of-flight mass spectrometer. The tunable IR laser emission served as a source of predissociation or excitation before ionization. The variations of intensity of protonated methanol cluster ions (CH(3)OH)(n)H(+) and CH(3)OH(+) and (CH(3)OH)(2)(+) were monitored as the IR laser light was tuned across the range 2650-3750 cm(-1). Careful processing of these action spectra based on photoionization efficiencies and the production and loss of each cluster due to photodissociation yielded IR spectra of the size-selected clusters. Spectra of methanol clusters in the OH region have been extensively investigated; our results are consistent with previous reports, except that the band near 3675 cm(-1) is identified as being associated with the proton acceptor of (CH(3)OH)(2). Spectra in the CH region are new. In the region 2800-3050 cm(-1), bands near 2845, 2956, and 3007 cm(-1) for CH(3)OH split into 2823, 2849, 2934, 2955, 2984, and 3006 cm(-1) for (CH(3)OH)(2) that correspond to proton donor and proton acceptor, indicating that the methanol dimer has a preferred open-chain structure. In contrast, for (CH(3)OH)(3), the splitting diminishes and the bands near 2837, 2954, and 2987 cm(-1) become narrower, indicating a preferred cyclic structure. Anharmonic vibrational wavenumbers predicted for the methanol open-chain dimer and the cyclic trimer with the B3LYP∕VPT2∕ANO1 level of theory are consistent with experimental results. For the tetramer and pentamer, the spectral pattern similar to that of the trimer but with greater widths was observed, indicating that the most stable structures are also cyclic.

  5. Transport of gaseous NO2 and SO2 by MAX-DOAS in Beijing and surrounding area

    NASA Astrophysics Data System (ADS)

    Xu, Jin; Li, Ang; Xie, Pinhua; Liu, Jianguo; Liu, Wenqing

    2016-04-01

    With the development of industry and urbanization, regional pollution is increasing seriously, and the cross influence between cities is becoming more frequently. Multi Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) has been successfully applied in the remote sensing of gaseous pollutants during the past decade, it is based on scattered light of the sun, and can measure spectral in different directions, measure tropospheric and the whole atmospheric column densities of trace gases combining with radiative transfer model (RTM). This approach is very useful for the investigation of the main path of air pollution transportation. Fifteen MAX-DOAS stations which are in urban and in the path of pollution transport are set up in Beijing and surrounding area including Tianjin and Hebei province to observe the spatial and temporal distributions and regional transport of gaseous NO2 and SO2. The NO2 VCDs and profiles and SO2 VCDs are obtained. The results show that the NO2 column densities in urban are higher than surroundings, it shows that the NO2 in Beijing is mainly from the local; The SO2 column densities in other cities to the south of Beijing are obviously higher than in Beijing, so regional transport from the south of Hebei province will have a significant impact on Beijing. From the results of NO2 and SO2, the whole pollution process including incubation, generation, duration, and dispersion was observed. The vertical distribution show that NO2 concentration is mainly near the surface from 0 to 400m, and SO2 is higher in the transport process.

  6. Five Years of Ground-Based MAX-DOAS Observations of CHOCHO and HCHO in the Beijing Area

    NASA Astrophysics Data System (ADS)

    Hendrick, F.; Lerot, C.; De Smedt, I.; Stavrakou, T.; Fayt, C.; Gielen, C.; Hermans, C.; Muller, J. F.; Pinardi, G.; Van Roozendael, M.

    2015-12-01

    Glyoxal (CHOCHO) and formaldehyde (HCHO) are among the most important carbonyl compounds in the atmosphere. Given their short lifetime (typically a few hours) and since they are mainly produced by the oxidation of biogenic and anthropogenic volatile organic compounds (VOCs), they are very good proxy for detecting active VOCs chemistry which can be responsible for the formation of pollutants such as tropospheric ozone and secondary organic aerosols. Both CHOCHO and HCHO are also directly released by biomass burning and fossil fuel combustion. Measuring these species is therefore of major importance for air quality monitoring, especially given the scarcity of available observational data sets. In this presentation, CHOCHO and HCHO vertical profiles and corresponding column densities are retrieved from ground-based MAX-DOAS (Multi-AXis Differential Optical Absorption Spectroscopy) measurements in the Beijing city center and at the suburban site of Xianghe located at 60km East of Beijing. The periods covered by the observations are June 2008-April 2009 in Beijing and March 2010-December 2014 in Xianghe. We first investigate the capability of the MAX-DOAS technique to measure these species in such highly-polluted environment. Then the diurnal and seasonal cycles of CHOCHO and HCHO near-surface concentrations and vertical column densities as well as the corresponding CHOCHO/HCHO ratios (RGF) are examined on a long-term basis at both locations. This RGF ratio is often used as an indicator of changes in the atmospheric VOC mixture. Finally, these diurnal and seasonal cycles are further assessed using simulations from the 3D chemistry transport model IMAGES and observations from the OMI and GOME-2 satellite nadir sensors.

  7. Trace gas retrieval for limb DOAS under changing atmospheric conditions: The X-gas scaling method vs optimal estimation

    NASA Astrophysics Data System (ADS)

    Hueneke, Tilman; Grossmann, Katja; Knecht, Matthias; Raecke, Rasmus; Stutz, Jochen; Werner, Bodo; Pfeilsticker, Klaus

    2016-04-01

    Changing atmospheric conditions during DOAS measurements from fast moving aircraft platforms pose a challenge for trace gas retrievals. Traditional inversion techniques to retrieve trace gas concentrations from limb scattered UV/vis spectroscopy, like optimal estimation, require a-priori information on Mie extinction (e.g., aerosol concentration and cloud cover) and albedo, which determine the atmospheric radiative transfer. In contrast to satellite applications, cloud filters can not be applied because they would strongly reduce the usable amount of expensively gathered measurement data. In contrast to ground-based MAX-DOAS applications, an aerosol retrieval based on O4 is not able to constrain the radiative transfer in air-borne applications due to the rapidly decreasing amount of O4 with altitude. Furthermore, the assumption of a constant cloud cover is not valid for fast moving aircrafts, thus requiring 2D or even 3D treatment of the radiative transfer. Therefore, traditional techniques are not applicable for most of the data gathered by fast moving aircraft platforms. In order to circumvent these limitations, we have been developing the so-called X-gas scaling method. By utilising a proxy gas X (e.g. O3, O4, …), whose concentration is either a priori known or simultaneously in-situ measured as well as remotely measured, an effective absorption length for the target gas is inferred. In this presentation, we discuss the strengths and weaknesses of the novel approach along with some sample cases. A particular strength of the X-gas scaling method is its insensitivity towards the aerosol abundance and cloud cover as well as wavelength dependent effects, whereas its sensitivity towards the profiles of both gases requires a priori information on their shapes.

  8. [Studies on the remote measurement of the distribution of city gaseous pollutant by mobile passive differential optical absorption spectroscopy].

    PubMed

    Wu, Feng-cheng; Li, Ang; Xie, Pin-hua; Xu, Jin; Shi, Peng; Qin, Min; Wang, Man-hua; Wang, Jie; Zhang, Yong

    2011-03-01

    An optical remote sensing method based on passive differential optical absorption spectroscopy for the measurement of the distribution of city gaseous pollutant was studied. The passive DOAS system, which was installed in a car, successively measures the interested area (such as city, industrial area) and the column density was obtained by DOAS fitting process using the zenith scattered sunlight. The mobile DOAS was applied to measurement in Shenzhen City during the continuous six days and got the distribution of SO2, NO2 in this paper. It showed that the pollution in the west is higher than in the east. The average concentration in the west is 2.0 times higher than the eastern for SO2 and 3.6 times for NO2. And comparison of the values between mobile DOAS and the point instrument was carried out in Baguang site. There was an agreement between the two instruments, the correlation coefficient was 0.86 for SO2, while 0.57 for NO2. The results indicate that this optical remote sensing method based on passive DOAS is an effective means of rapidly determining the distribution of city gaseous pollutant. PMID:21595196

  9. Optimal spectral resolution for NO2 and SO2 retrieval by Geostationary Environmental Monitoring Spectrometer (GEMS)

    NASA Astrophysics Data System (ADS)

    Chong, J.; Kim, Y. J.; Scientific Team of DOAS

    2011-12-01

    Ministry of Environment, Korea is planning an environmental geostationary satellite program as a part of MP-GEOSAT (Multi-Purpose GEOstationary SATellite), which is scheduled to be launched in 2017 (Lee S. et al., 2010). It is supposed to be placed on an orbit of approximately 36,000 kilometers high directly over the equator, which revolves in the same direction the earth rotates. Its missions include meteorological, ocean monitoring, and environmental monitoring. Especially, Geostationary Environmental Monitoring Spectrometer (GEMS) is to provide atmospheric chemistry measurements of trace gases such as O3, NO2, SO2, HCHO, and aerosol in high temporal (every 1 hour) and spatial (30x30 km2) resolution over Asia, to monitor regional transport events such as transboundary pollution and Asian dust, and to enhance our understanding on interactions between atmospheric chemistry and meteorology. In order to determine the minimum required spectral resolution of GEMS, measurement accuracy has been estimated for different spectral resolutions based on the actual satellite data as well as model simulation data of very fine spectral resolution. Absorption spectra of SCIAMACHY level 2 data (http://www.temis.nl) with spectral resolution of 0.2nm and reconstructed spectra of broader spectral resolution; 0.4, 0.6, and 0.8nm have been utilized to assess the applicability for SO2 and NO2 retrievals over GEMS spatial coverage areas using the DOAS fitting method. The relative fitting error in SO2 retrieval of each spectral resolution over southern China was determined to be 45.1, 56.1, 99.7, and 187.3 %, respectively. The relative fitting errors in NO2 retrieval of each spectral resolution over northern India were 16.2, 24.6, 32.6, and 38.9 %, respectively. Since relative fitting error in SO2 retrieval increases as the spectra resolution increases, the optimal spectrum resolution was determined to be 0.4nm. On the other hand, since the relative fitting error in NO2 retrieval is below

  10. From slant column densities to trace gas profiles: Post processing data from the new MAX-DOAS network in Mexico City

    NASA Astrophysics Data System (ADS)

    Friedrich, M. M.; Stremme, W.; Rivera, C. I.; Arellano, E. J.; Grutter, M.

    2014-12-01

    The new MAX-DOAS network in Mexico City provides results of O4, HCHO and NO2 slant column densities (SCD). Here, we present a new numerical code developed to retrieve gas profiles of NO2 and HCHO using radiative transfer simulations. We present first results of such profiles from the MAX-DOAS station located at UNAM campus. The code works in two steps: First, the O4 slant column density information is used to retrieve an aerosol profile. As an a-priori aerosol profile, we use averaged ceilometer data measured at UNAM and scaled to the total optical depth provided by the Aeronet data base. In the second step, the retrieved aerosol profile information is used together with the trace gas (HCHO or NO2) SCDs to retrieve the trace gas profiles. The inversion is based on a gauss-newton iteration scheme and uses constrained least square fitting with either optimal estimation or Tihkonov regularization. For the latter, the regulation matrix is currently constructed from the discrete first derivative operator. The forward model uses the radiative transfer code VLIDORT. The inputs to VLIDORT are calculated using temperature and pressure information from daily radiosounde measurements and aerosol single scattering optical depths and asymmetry factors from the Aeronet data base for Mexico City. For the gas absorption cross sections we use the same values as were used for the SCD calculation from the recorded spectra using QDOAS. Besides demonstrating the functionality of the algorithm showing profile retrievals of simulated SCDs with added random noise, we present HCHO and NO2 profiles retrieved from SCDs calculated from the MAX-DOAS measurements at UNAM campus at selected days.

  11. Intercomparison of HONO SCDs and profiles from MAX-DOAS observations during the MAD-CAT campaign and comparison to chemical model simulations

    NASA Astrophysics Data System (ADS)

    Wang, Yang; Wagner, Thomas; Xie, Pinhua; Remmers, Julia; Li, Ang; Lampel, Johannes; Friess, Udo; Peters, Enno; Wittrock, Folkard; Richter, Andreas; Hilboll, Andreas; Volkamer, Rainer; Ortega, Ivan; Hendrick, Francois; Van Roozendael, Michel; Ma, Jianzhong; Jin, Junli; Su, Hang; Cheng, Yafang

    2015-04-01

    In order to promote the development of the passive DOAS technique and to improve the retrieval algorithms of trace gases and aerosols the Multi Axis DOAS - Comparison campaign for Aerosols and Trace gases (MAD-CAT) was held at the Max Planck Institute for Chemistry in Mainz, Germany from June to October 2013. MAX-DOAS (Multi-Axis Differential Optical Absorption Spectroscopy) instruments of various designs recorded UV-visible spectra of scattered sunlight at different elevation and azimuth angles. We present intercomparison results for slant column densities (SCDs) of nitrous acid (HONO) retrieved during this campaign by several research groups. Data analysis was performed in two steps, starting with the preferred settings of the individual groups, followed by an analysis using common retrieval settings. In general good agreement of the resulting HONO SCD sets was found. Furthermore, we performed various sensitivity analyses to improve and evaluate the uncertainties in the HONO SCD retrieval, such as the influence of the wavelength dependence of the NO2 air mass factor, the selection of the wavelength interval of the retrieval, the choice of the Fraunhofer reference spectrum, or the offset correction. Finally we compared the results from different kinds of inversion algorithms for the vertical profiles of trace gases and aerosols. The derived HONO profiles, VMR near surface and tropospheric vertical column densities are compared with each other and with the results of regional chemical model simulations. We found a high HONO VMR near surface of about 200 ppt, which is much higher than the typical daytime VMR of lower than 10 ppt at the early noon (around 9:30 local time), probably indicating a strong source of HONO. The strong vertical gradient in the profile of HONO VMR probably indicates the HONO source is close to the surface.

  12. Measurements of volcanic SO2 and CO2 fluxes by combined DOAS, Multi-GAS and FTIR observations: a case study from Turrialba and Telica volcanoes

    NASA Astrophysics Data System (ADS)

    Conde, Vladimir; Robidoux, Philippe; Avard, Geoffroy; Galle, Bo; Aiuppa, Alessandro; Muñoz, Angélica; Giudice, Gaetano

    2014-11-01

    Over the past few decades, substantial progress has been made to overcome the technical difficulties of continuously measuring volcanic SO2 emissions. However, measurements of CO2 emissions still present many difficulties, partly due to the lack of instruments that can directly measure CO2 emissions and partly due to its strong atmospheric background. In order to overcome these difficulties, a commonly taken approach is to combine differential optical absorption spectroscopy (DOAS) by using NOVAC scan-DOAS instruments for continuous measurements of crateric SO2 emissions, and electrochemical/NDIR multi-component gas analyser system (multi-GAS) instruments for measuring CO2/SO2 ratios of excerpts of the volcanic plume. This study aims to quantify the representativeness of excerpts of CO2/SO2 ratios measured by Multi-GAS as a fraction of the whole plume composition, by comparison with simultaneously measured CO2/SO2 ratios using cross-crater Fourier transform infrared spectroscopy (FTIR). Two study cases are presented: Telica volcano (Nicaragua), with a homogenous plume, quiescent degassing from a deep source and ambient temperature, and Turrialba volcano (Costa Rica), which has a non-homogeneous plume from three main sources with different compositions and temperatures. Our comparison shows that in our "easier case" (Telica), FTIR and Multi-GAS CO2/SO2 ratios agree within a factor about 3 %. In our "complicated case" (Turrialba), Multi-GAS and FTIR yield CO2/SO2 ratios differing by approximately 13-25 % at most. These results suggest that a fair estimation of volcanic CO2 emissions can be provided by the combination of DOAS and Multi-GAS instruments for volcanoes with similar degassing conditions as Telica or Turrialba. Based on the results of this comparison, we report that by the time our measurements were made, Telica and Turrialba were emitting approximately 100 and 1,000 t day-1 of CO2, respectively.

  13. Electron-proton spectrometer

    NASA Technical Reports Server (NTRS)

    Winckler, J. R.

    1973-01-01

    An electron-proton spectrometer was designed to measure the geomagnetically trapped radiation in a geostationary orbit at 6.6 earth radii in the outer radiation belt. This instrument is to be flown on the Applications Technology Satellite-F (ATS-F). The electron-proton spectrometer consists of two permanent magnet surface barrier detector arrays and associated electronics capable of selecting and detecting electrons in three energy ranges: (1) 30-50 keV, (2) 150-200 keV, and (3) 500 keV and protons in three energy ranges. The electron-proton spectrometer has the capability of measuring the fluxes of electrons and protons in various directions with respect to the magnetic field lines running through the satellite. One magnet detector array system is implemented to scan between EME north and south through west, sampling the directional flux in 15 steps. The other magnet-detector array system is fixed looking toward EME east.

  14. Compact Grism Spectrometer

    NASA Astrophysics Data System (ADS)

    Teare, S. W.

    2003-05-01

    Many observatories and instrument builders are retrofitting visible and near-infrared spectrometers into their existing imaging cameras. Camera designs that reimage the focal plane and have the optical filters located in a pseudo collimated beam are ideal candidates for the addition of a spectrometer. One device commonly used as the dispersing element for such spectrometers is a grism. The traditional grism is constructed from a prism that has had a diffraction grating applied on one surface. The objective of such a design is to use the prism wedge angle to select the desired "in-line" or "zero-deviation" wavelength that passes through on axis. The grating on the surface of the prism provides much of the dispersion for the spectrometer. A grism can also be used in a "constant-dispersion" design which provides an almost linear spatial scale across the spectrum. In this paper we provide an overview of the development of a grism spectrometer for use in a near infrared camera and demonstrate that a compact grism spectrometer can be developed on a very modest budget that can be afforded at almost any facility. The grism design was prototyped using visible light and then a final device was constructed which provides partial coverage in the near infrared I, J, H and K astronomical bands using the appropriate band pass filter for order sorting. The near infrared grism presented here provides a spectral resolution of about 650 and velocity resolution of about 450 km/s. The design of this grism relied on a computer code called Xspect, developed by the author, to determine the various critical parameters of the grism. This work was supported by a small equipment grant from NASA and administered by the AAS.

  15. The Apollo Alpha Spectrometer.

    NASA Technical Reports Server (NTRS)

    Jagoda, N.; Kubierschky, K.; Frank, R.; Carroll, J.

    1973-01-01

    Located in the Science Instrument Module of Apollo 15 and 16, the Alpha Particle Spectrometer was designed to detect and measure the energy of alpha particles emitted by the radon isotopes and their daughter products. The spectrometer sensor consisted of an array of totally depleted silicon surface barrier detectors. Biased amplifier and linear gate techniques were utilized to reduce resolution degradation, thereby permitting the use of a single 512 channel PHA. Sensor identification and in-flight radioactive calibration were incorporated to enhance data reduction.

  16. Comparison of imaging spectrometers

    SciTech Connect

    Bennett, C

    2000-01-09

    Realistic signal to noise performance estimates for the various types of instruments being considered for NGST are compared, based on the point source detection values quoted in the available ISIM final reports. The corresponding sensitivity of the various types of spectrometers operating in a full field imaging mode, for both emission line objects and broad spectral distribution objects, is computed and displayed. For the purpose of seeing the earliest galaxies, or the faintest possible emission line sources, the imaging Fourier transform spectrometer emerges superior to all others, by orders of magnitude in speed.

  17. Broad band waveguide spectrometer

    DOEpatents

    Goldman, Don S.

    1995-01-01

    A spectrometer for analyzing a sample of material utilizing a broad band source of electromagnetic radiation and a detector. The spectrometer employs a waveguide possessing an entry and an exit for the electromagnetic radiation emanating from the source. The waveguide further includes a surface between the entry and exit portions which permits interaction between the electromagnetic radiation passing through the wave guide and a sample material. A tapered portion forms a part of the entry of the wave guide and couples the electromagnetic radiation emanating from the source to the waveguide. The electromagnetic radiation passing from the exit of the waveguide is captured and directed to a detector for analysis.

  18. Genome Analysis of a Novel Bradyrhizobium sp. DOA9 Carrying a Symbiotic Plasmid

    PubMed Central

    Okazaki, Shin; Noisangiam, Rujirek; Okubo, Takashi; Kaneko, Takakazu; Oshima, Kenshiro; Hattori, Masahira; Teamtisong, Kamonluck; Songwattana, Pongpan; Tittabutr, Panlada; Boonkerd, Nantakorn; Saeki, Kazuhiko; Sato, Shusei; Uchiumi, Toshiki; Minamisawa, Kiwamu; Teaumroong, Neung

    2015-01-01

    Bradyrhizobium sp. DOA9 isolated from the legume Aeschynomene americana exhibited a broad host range and divergent nodulation (nod) genes compared with other members of the Bradyrhizobiaceae. Genome analysis of DOA9 revealed that its genome comprised a single chromosome of 7.1 Mbp and a plasmid of 0.7 Mbp. The chromosome showed highest similarity with that of the nod gene-harboring soybean symbiont B. japonicum USDA110, whereas the plasmid showed highest similarity with pBBta01 of the nod gene-lacking photosynthetic strain BTAi1, which nodulates Aeschynomene species. Unlike in other bradyrhizobia, the plasmid of DOA9 encodes genes related to symbiotic functions including nodulation, nitrogen fixation, and type III/IV protein secretion systems. The plasmid has also a lower GC content (60.1%) than the chromosome (64.4%). These features suggest that the plasmid could be the origin of the symbiosis island that is found in the genome of other bradyrhizobia. The nod genes of DOA9 exhibited low similarity with those of other strains. The nif gene cluster of DOA9 showed greatest similarity to those of photosynthetic bradyrhizobia. The type III/IV protein secretion systems of DOA9 are similar to those of nod gene-harboring B. elkanii and photosynthetic BTAi1. The DOA9 genome exhibited intermediate characteristics between nod gene-harboring bradyrhizobia and nod gene-lacking photosynthetic bradyrhizobia, thus providing the evidence for the evolution of the Bradyrhizobiaceae during ecological adaptation. Bradyrhizobium sp. DOA9 isolated from the legume Aeschynomene americana exhibited a broad host range and divergent nodulation (nod) genes compared with other members of the Bradyrhizobiaceae. Genome analysis of DOA9 revealed that its genome comprised a single chromosome of 7.1 Mbp and a plasmid of 0.7 Mbp. The chromosome showed highest similarity with that of the nod gene-harboring soybean symbiont B. japonicum USDA110, whereas the plasmid showed highest similarity with p

  19. Studies of dry acid deposition in the South Coast Air Basin: tunable diode laser absorption spectrometer measurements of HNO/sub 3/, HCHO and NO/sub 2/ and luminol NO/sub 2/ measurements in Claremont, California, September 1985. Final report, August 1985-July 1986

    SciTech Connect

    Mackay, G.I.; Schiff, H.I.; Mayne, L.K.; Harris, G.W.

    1986-07-01

    Two Tunable Diode Laser Absorption Spectrometer (TDLAS) systems were used to measure HNO/sub 3/. One system also measured formaldehyde (HCHO) atmosphere. Nitrogen dioxide (NO/sub 2/) was measured by the second TDLAS and by the LUMINOX, LMA-3 which is a new, small, simple and extremely sensitive instrument for NO/sub 2/ measurements. The importance of these measurements is the role that NO/sub 2/ plays as the direct precursor to gas phase HNO/sub 3/. Agreement between the HNO/sub 3/ measurements obtained by the 2 TDLAS systems were within the combined experimental errors. The diurnal behavior of the HNO/sub 3/ concentrations were quite regular with a maximum occuring between 15:00 and 18:00 each day. Maximum concentrations of 18 ppbv were observed on September 14th. HCHO exhibited similar behavior with the largest measured values of 14 ppbv occurring at 15:00 on the 13th. NO/sub 2/ showed somewhat more variable behaviour generally with two maxima, one in the afternoon and one about midnight. The TDLAS and LUMINOX were in good agreement with a few interesting exceptions.

  20. Mass Spectrometers in Space!

    NASA Technical Reports Server (NTRS)

    Brinckerhoff, William B.

    2012-01-01

    Exploration of our solar system over several decades has benefitted greatly from the sensitive chemical analyses offered by spaceflight mass spectrometers. When dealing with an unknown environment, the broadband detection capabilities of mass analyzers have proven extremely valuable in determining the composition and thereby the basic nature of space environments, including the outer reaches of Earth s atmosphere, interplanetary space, the Moon, and the planets and their satellites. Numerous mass analyzer types, including quadrupole, monopole, sector, ion trap, and time-of-flight have been incorporated in flight instruments and delivered robotically to a variety of planetary environments. All such instruments went through a rigorous process of application-specific development, often including significant miniaturization, testing, and qualification for the space environment. Upcoming missions to Mars and opportunities for missions to Venus, Europa, Saturn, Titan, asteroids, and comets provide new challenges for flight mass spectrometers that push to state of the art in fundamental analytical technique. The Sample Analysis at Mars (SAM) investigation on the recently-launch Mars Science Laboratory (MSL) rover mission incorporates a quadrupole analyzer to support direct evolved gas as well as gas chromatograph-based analysis of martian rocks and atmosphere, seeking signs of a past or present habitable environment. A next-generation linear ion trap mass spectrometer, using both electron impact and laser ionization, is being incorporated into the Mars Organic Molecule Analyzer (MOMA) instrument, which will be flown to Mars in 2018. These and other mass spectrometers and mission concepts at various stages of development will be described.

  1. Fourier Transform Spectrometer

    NASA Technical Reports Server (NTRS)

    1998-01-01

    Understanding the global atmospheric changes is difficult with today's current technology. However, with high resolution and nearly continuous observations from a satellite, it's possible to transform our understanding of the atmosphere. To enable the next generation of atmospheric science, a new class of orbiting atmospheric sensors is being developed. The foundation of this advanced concept is the Fourier Transform Spectrometer, or FTS.

  2. Estimates of free-tropospheric NO2 and HCHO mixing ratios derived from high-altitude mountain MAX-DOAS observations in the mid-latitudes and tropics

    NASA Astrophysics Data System (ADS)

    Schreier, S. F.; Richter, A.; Wittrock, F.; Burrows, J. P.

    2015-11-01

    In this study, mixing ratios of NO2 (XNO2) and HCHO (XHCHO) in the free troposphere are derived from two Multi-AXis Differential Optical Absorption Spectroscopy (MAX-DOAS) data sets collected at Zugspitze (2650 m a.s.l., Germany) and Pico Espejo (4765 m a.s.l., Venezuela). The estimation of NO2 and HCHO mixing ratios is based on the modified geometrical approach, which assumes a single-scattering geometry and a scattering point altitude close to the instrument. Firstly, the horizontal optical path length (hOPL) is obtained from O4 differential slant column densities (DSCDs) in the horizontal (0°) and vertical (90°) viewing directions. Secondly, XNO2 and XHCHO are estimated from the NO2 and HCHO DSCDs at the 0 and 90° viewing directions and averaged along the obtained hOPLs. As the MAX-DOAS instrument was performing measurements in the ultraviolet region, wavelength ranges of 346-372 and 338-357 nm are selected for the DOAS analysis to retrieve NO2 and HCHO DSCDs, respectively. In order to compare the measured O4 DSCDs and moreover to perform some sensitivity tests, the radiative transfer model SCIATRAN with adapted altitude settings for mountainous terrain is operated to simulate synthetic spectra, on which the DOAS analysis is also applied. The overall agreement between measured and synthetic O4 DSCDs is better for the higher Pico Espejo station than for Zugspitze. Further sensitivity analysis shows that a change in surface albedo (from 0.05 to 0.7) can influence the O4 DSCDs, with a larger absolute difference observed for the horizontal viewing direction. Consequently, the hOPL can vary by about 5 % throughout the season, for example when winter snow cover fully disappears in summer. Typical values of hOPLs during clear sky conditions are 19 km (14 km) at Zugspitze and 34 km (26.5 km) at Pico Espejo when using the 346-372 nm (338-357 nm) fitting window. The estimated monthly values of XNO2 (XHCHO), averaged over these hOPLs during clear sky conditions, are in

  3. Estimates of free-tropospheric NO2 and HCHO mixing ratios derived from high-altitude mountain MAX-DOAS observations at midlatitudes and in the tropics

    NASA Astrophysics Data System (ADS)

    Schreier, Stefan F.; Richter, Andreas; Wittrock, Folkard; Burrows, John P.

    2016-03-01

    In this study, mixing ratios of NO2 (XNO2) and HCHO (XHCHO) in the free troposphere are derived from two multi-axis differential optical absorption spectroscopy (MAX-DOAS) data sets collected at Zugspitze (2650 m a.s.l., Germany) and Pico Espejo (4765 m a.s.l., Venezuela). The estimation of NO2 and HCHO mixing ratios is based on the modified geometrical approach, which assumes a single-scattering geometry and a scattering point altitude close to the instrument altitude. Firstly, the horizontal optical path length (hOPL) is obtained from O4 differential slant column densities (DSCDs) in the horizontal (0°) and vertical (90°) viewing directions. Secondly, XNO2 and XHCHO are estimated from the NO2 and HCHO DSCDs at the 0° and 90° viewing directions and averaged along the obtained hOPLs. As the MAX-DOAS instrument was performing measurements in the ultraviolet region, wavelength ranges of 346-372 and 338-357 nm are selected for the DOAS analysis to retrieve NO2 and HCHO DSCDs, respectively. In order to compare the measured O4 DSCDs and moreover to perform some sensitivity tests, the radiative transfer model SCIATRAN with adapted altitude settings for mountainous terrain is operated to simulate synthetic spectra, on which the DOAS analysis is also applied. The overall agreement between measured and synthetic O4 DSCDs is better for the higher Pico Espejo station than for Zugspitze. Further sensitivity analysis shows that a change in surface albedo (from 0.05 to 0.7) can influence the O4 DSCDs, with a larger absolute difference observed for the horizontal viewing direction. Consequently, the hOPL can vary by about 5 % throughout the season, for example when winter snow cover fully disappears in summer. Typical values of hOPLs during clear-sky conditions are 19 km (14 km) at Zugspitze and 34 km (26.5 km) at Pico Espejo when using the 346-372 (338-357 nm) fitting window. The estimated monthly values of XNO2 (XHCHO), averaged over these hOPLs during clear-sky conditions

  4. Temporal variations of aerosol, glyoxal, and formaldehyde at urban sites of Japan as observed by MAX-DOAS based on detailed error analysis

    NASA Astrophysics Data System (ADS)

    Irie, H.; Chin, S.; Ni, W.; Nakayama, T.; Shimizu, A.; Yamazaki, A.; Nagai, T.; Takamura, T.; Khatri, P.

    2014-12-01

    The degradation of volatile organic compounds (VOCs) results in the formation of ozone (O3) and secondary organic aerosols (SOA) in the troposphere. This process consists of the oxidation of VOCs by hydroxyl radical (OH), O3, and nitrate radical (NO3). Detailed understanding of the VOC degradation mechanism is challenged by the co-existence of vast variety of VOC species in the atmosphere. However, investigations on ubiquitous oxidation intermediates, e.g., formaldehyde (HCHO) and glyoxal (CHOCHO), can help us improve the current knowledge of the VOC sources and degradation pathways. We installed one ground-based Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) system in Meteorological Research Institute (MRI) located at Tsukuba, Japan (36.06N, 130.13E) in June 2010. In addition, two more systems were installed in Chiba University at Chiba, Japan (35.63N, 140.10E) in June and December 2012, respectively. Since then, we have retrieved lower-tropospheric vertical profile information for eight components; aerosol extinction coefficients at two wavelengths, 357 and 476 nm, and NO2, HCHO, CHOCHO, H2O, SO2, and O3 concentrations. For a detailed evaluation for the aerosol retrieval, which is a key step in the MAX-DOAS eight-component retrieval, simultaneous aerosol observations with the Cavity Ring-Down Spectroscopy (CRDS), lidar, and sky radiometer were conducted at Tsukuba on October 5-18, 2010. At Chiba, in addition to the comparison with sky radiometer data, a self-consistency test was performed by comparing results obtained from two MAX-DOAS systems operated at the same place. Through these detailed evaluations, our retrieval method was improved significantly, attaining excellent agreement with CRDS, lidar, and sky radiometer data. On the basis of these efforts, we find clear seasonal and diurnal temporal variations in HCHO and CHOCHO concentrations and their ratios (RGF) retrieved from MAX-DOAS systems. Using NO2 retrieved together with HCHO and

  5. Sulfur dioxide vertical column DOAS retrievals from the Ozone Monitoring Instrument: Global observations and comparison to ground-based and satellite data

    NASA Astrophysics Data System (ADS)

    Theys, N.; De Smedt, I.; Gent, J.; Danckaert, T.; Wang, T.; Hendrick, F.; Stavrakou, T.; Bauduin, S.; Clarisse, L.; Li, C.; Krotkov, N.; Yu, H.; Brenot, H.; Van Roozendael, M.

    2015-03-01

    We present a new data set of sulfur dioxide (SO2) vertical columns from observations of the Ozone Monitoring Instrument (OMI)/AURA instrument between 2004 and 2013. The retrieval algorithm used is an advanced Differential Optical Absorption Spectroscopy (DOAS) scheme combined with radiative transfer calculation. It is developed in preparation for the operational processing of SO2 data product for the upcoming TROPOspheric Monitoring Instrument/Sentinel 5 Precursor mission. We evaluate the SO2 column results with those inferred from other satellite retrievals such as Infrared Atmospheric Sounding Interferometer and OMI (Linear Fit and Principal Component Analysis algorithms). A general good agreement between the different data sets is found for both volcanic and anthropogenic SO2 emission scenarios. We show that our algorithm produces SO2 columns with low noise and is able to provide accurate estimates of SO2. This conclusion is supported by important validation results over the heavily polluted site of Xianghe (China). Nearly 4 years of OMI and ground-based multiaxis DOAS SO2 columns are compared, and an excellent match is found. We also highlight the improved performance of the algorithm in capturing weak SO2 sources by detecting shipping SO2 emissions in long-term averaged data, an unreported measurement from space.

  6. Simultaneous balloon-borne measurements of the key inorganic bromine species BrO and BrONO2 in the stratosphere: DOAS and MIPAS-B evaluation

    NASA Astrophysics Data System (ADS)

    Kazarski, Sebastian; Maucher, Guido; Ebersoldt, Andreas; Butz, André; Friedl-Vallon, Felix; Höpfner, Michael; Kleinert, Anne; Nordmeyer, Hans; Oelhaf, Hermann; Pfeilsticker, Klaus; Sinnhuber, Björn-Martin; Wetzel, Gerald; Orphal, Johannes

    2015-04-01

    Inorganic bromine contributes to a loss of stratospheric ozone of about 25 - 30%. Past studies have demonstrated several uncertainties in the photochemistry of stratospheric bromine, especially by considering the three body reaction (kBrONO2) BrO + NO2 + M → BrONO2 + M, and the photolysis frequencies of BrONO2 (jBrONO2). Hence, an improved knowledge of the ratio jBrONO2/kBrONO2 is crucial to better assess the bromine-related loss of ozone as well as the total amount of bromine in the stratosphere. Here, we report on the first simultaneous balloon-borne measurements of NO2, BrO, and BrONO2 in the stratosphere, performed over Timmins (Ontario, 49 °N, Canada) on Sept., 7th and 8th, 2014. During the flight the targeted species were monitored by remote sensing in the UV, visible and mid-IR spectral ranges by Differential Optical Absorption Spectroscopy (DOAS) and Michelson Interferometer for Passive Atmospheric Sounding (MIPAS-B), respectively. The analysis and interpretation of the measurements involves radiative transfer as well as photochemical modelling. Major features of the applied techniques are reported and first results of the DOAS as well as MIPAS-B evaluation are discussed. Further investigations address inter-comparisons of the retrieved NO2, BrO, and O3 concentrations and volume mixing ratios, to demonstrate validations of both evaluation methods.

  7. Case studies on summertime measurements of O3, NO2, and SO2 with a DOAS system in an urban semi-industrial region in Athens, Greece.

    PubMed

    Psiloglou, Betaasil E; Larissi, Ioanna K; Petrakis, Muichael; Paliatsos, Athanasios G; Antoniou, Alphantonis; Viras, Loisos G

    2013-09-01

    The objective of this study is to analyze the concentrations of SO2, NO2, and O3 measured by a Differential Optical Absorption Spectroscopy (DOAS) system that was operating at the campus of Technological Education Institute of Piraeus during 2008 and 2009 warm periods (July to September) in relation to the prevailing meteorological conditions. The DOAS system was operating in a particularly polluted area of the West part of Attica basin on a continuous basis, measuring the concentration levels of the main pollutants (O3, NO2, and SO2) as well as aromatic hydrocarbon substances (benzene, toluene, and xylene). According to the analysis, the SO2 concentration levels at this measuring site are rather high and this may be attributed to the characteristics of this measuring site. Proximity of roadways and local circulation are just some of the factors that can affect the concentration levels of monitoring of pollutant concentrations such as NO2 and surface ozone. The results provide evidence for the occurrence of an atmospheric phenomenon that produces higher ozone concentrations during weekends despite lower concentrations of ozone precursors. This phenomenon is known as the weekend effect. PMID:23430070

  8. Long term seasonal variation of stratospheric BrO and NO2 from ground based Zenith Sky DOAS observations at Kiruna, Sweden

    NASA Astrophysics Data System (ADS)

    Gu, Myojeong; Enell, Carl-Fredrik; Pukite, Janis; Kühl, Sven; Platt, Ulrich; Raffalski, Uwe; Wagner, Thomas

    2013-04-01

    Stratospheric BrO and NO2 have an important influence on the stratospheric ozone depletion. Several studies have proved the performance of field measurements of stratospheric trace gases. In particular, ground-based zenith-sky Differential Optical Absorption Spectroscopy (DOAS) has successfully monitored BrO and other trace gases related to stratospheric ozone chemistry such as O3, NO2 and OClO. In this study, we investigated the characteristics of stratospheric BrO and NO2 in polar region using zenith-sky DOAS. The instrument was conducted on the Swedish Institute for Space Physics in Kiruna (Sweden, 68.84°N, 20.41°E) since 1996. We present the seasonal variation of BrO and NO2 for the period 1997-2009 and focus on their averaged seasonal trends with respect to different years. The retrieved NO2 and BrO columns are also compared to ECMWF analysis data for investigating the dependence of the NO2 and BrO enhancements on meteorological parameters like stratospheric temperatures, potential vorticity, and PSC area. Also, the NO2 column densities are compared with OMI satellite data. Recently, the instrument was equipped with a new detector which ensures continuous operation in the future. Being one of the longest measurements of spectroscopic measurements of trace gases in the Arctic, the Kiruna observation will contribute to a better understanding of the impacts of stratospheric trace gases and insights of their chemical reactions.

  9. Determination of the NO2 concentration and its distribution with different DOAS techniques - a study in the metropolitan area of Hong Kong

    NASA Astrophysics Data System (ADS)

    Horbanski, M.; Chan, K. L.; Pöhler, D.; Wenig, M. O.; Platt, U.

    2012-04-01

    In Hong Kong, like in other urban areas, nitrogen dioxide (NO2) emissions still remain one of the most problematic pollutions. Even though a lot of effort has already been made towards their reduction, concentrations are often much above the recommended limits. Therefore, the Hong Kong Environmental Protection Department continuously monitors the NO2 concentration levels. These stations only give in-situ information at a few fixed locations, which are unable to capture the strong spatial gradients that are present in urban areas. These gradients are mainly caused by differences in automobile traffic, the population densities and industries that are found in the individual city areas. The gradients are further enhanced by street canyon effects. Hence, it can be assumed that there are areas with much higher pollution compared to the values at the official measuring sites. At present the uncertainties about the spatial NO2 distribution place a limitation on the assessment of health risks and on the quality of chemical model calculations. We applied a new Cavity Enhanced (CE-) DOAS instrument to car based measurements in the city of Hong Kong for eight days in December 2010. Measurements on mobile platforms like cars give the opportunity to create a map of the NO2 for a whole city area with high spatial resolution. The CE-DOAS instrument is distinguished by its compact and robust setup. It directly measures NO2 by its optical absorption and therefore it does not have interferences with other trace gas species like O3 or NOy. This is a great advantage over other NO2 instruments (e.g. solid state detectors or chemiluminescence instruments which have such known problems). For our measurements a van travels along carefully selected tracks to give a representative coverage of the area of interest. The mobile measurements are corrected for the varying meteorological conditions and traffic variations during the different measurements by comparing them to a fixed measurement

  10. The CU ground MAX-DOAS instrument: characterization of RMS noise limitations and first measurements near Pensacola, FL of BrO, IO, and CHOCHO

    NASA Astrophysics Data System (ADS)

    Coburn, S.; Dix, B.; Sinreich, R.; Volkamer, R.

    2011-11-01

    We designed and assembled the University of Colorado Ground Multi AXis Differential Optical Absorption Spectroscopy (CU GMAX-DOAS) instrument to retrieve bromine oxide (BrO), iodine oxide (IO), formaldehyde (HCHO), glyoxal (CHOCHO), nitrogen dioxide (NO2) and the oxygen dimer (O4) in the coastal atmosphere of the Gulf of Mexico. The detection sensitivity of DOAS measurements is proportional to the root mean square (RMS) of the residual spectrum that remains after all absorbers have been subtracted. Here we describe the CU GMAX-DOAS instrument and demonstrate that the hardware is capable of attaining RMS of ∼6 × 10-6 from solar stray light noise tests using high photon count spectra (compatible within a factor of two with photon shot noise). Laboratory tests revealed two critical instrument properties that, in practice, can limit the RMS: (1) detector non-linearity noise, RMSNLin, and (2) temperature fluctuations that cause variations in optical resolution (full width at half the maximum, FWHM, of atomic emission lines) and give rise to optical resolution noise, RMSFWHM. The non-linearity of our detector is low (∼10-2) yet - unless actively controlled - is sufficiently large to create RMSNLin of up to 2 × 10-4. The optical resolution is sensitive to temperature changes (0.03 detector pixels °C-1 at 334 nm), and temperature variations of 0.1°C can cause RMSFWHM of ~1 × 10-4. Both factors were actively addressed in the design of the CU GMAX-DOAS instrument. With an integration time of 60 s the instrument can reach RMS noise of 3 × 10-5, and typical RMS in field measurements ranged from 6 × 10-5 to 1.4 × 10-4. The CU GMAX-DOAS was set up at a coastal site near Pensacola, Florida, where we detected BrO, IO and CHOCHO in the marine boundary layer (MBL), with daytime average tropospheric vertical column densities (average of data above the detection limit), VCDs, of ∼2 × 1013 molec cm-2, 8 × 1012 molec cm-2 and 4 × 1014 molec cm-2, respectively

  11. Acousto-optic differential optical absorption spectroscopy for atmospheric measurement of nitrogen dioxide in Hong Kong.

    PubMed

    Cheng, Andrew Y S; Chan, M H

    2004-12-01

    Measurement of the atmospheric concentration of nitrogen dioxide (NO(2)) pollutant was demonstrated by differential optical absorption spectroscopy (DOAS) using a visible acousto-optic tunable filter. In a traditional spectral scanning DOAS system for atmospheric concentration monitoring, a highly stable light source is required. When the light intensity fluctuates during scanning, the concentration retrieval will be inaccurate. In order to reduce the error due to intensity fluctuations, a modified DOAS system has been developed by introducing a broadband light intensity monitoring channel. Using the measured intensity of the broadband channel as the intensity of the light source, the spectrum can be de-biased and the residual intensity variation will primarily result from atmospheric extinction. In addition, by employing the lock-in detection technique, the background light interference is also removed in the modified DOAS system. The atmospheric NO(2) concentration measurement was performed at the campus of City University of Hong Kong, and the results were compared with the concentration reported from a nearby monitoring station in Sham Shui Po, operated by the Hong Kong Environmental Protection Department.

  12. An efficient central DOA tracking algorithm for multiple incoherently distributed sources

    NASA Astrophysics Data System (ADS)

    Hassen, Sonia Ben; Samet, Abdelaziz

    2015-12-01

    In this paper, we develop a new tracking method for the direction of arrival (DOA) parameters assuming multiple incoherently distributed (ID) sources. The new approach is based on a simple covariance fitting optimization technique exploiting the central and noncentral moments of the source angular power densities to estimate the central DOAs. The current estimates are treated as measurements provided to the Kalman filter that model the dynamic property of directional changes for the moving sources. Then, the covariance-fitting-based algorithm and the Kalman filtering theory are combined to formulate an adaptive tracking algorithm. Our algorithm is compared to the fast approximated power iteration-total least square-estimation of signal parameters via rotational invariance technique (FAPI-TLS-ESPRIT) algorithm using the TLS-ESPRIT method and the subspace updating via FAPI-algorithm. It will be shown that the proposed algorithm offers an excellent DOA tracking performance and outperforms the FAPI-TLS-ESPRIT method especially at low signal-to-noise ratio (SNR) values. Moreover, the performances of the two methods increase as the SNR values increase. This increase is more prominent with the FAPI-TLS-ESPRIT method. However, their performances degrade when the number of sources increases. It will be also proved that our method depends on the form of the angular distribution function when tracking the central DOAs. Finally, it will be shown that the more the sources are spaced, the more the proposed method can exactly track the DOAs.

  13. The yeast ERAD-C ubiquitin ligase Doa10 recognizes an intramembrane degron

    PubMed Central

    Habeck, Gregor; Ebner, Felix A.; Shimada-Kreft, Hiroko

    2015-01-01

    Aberrant endoplasmic reticulum (ER) proteins are eliminated by ER-associated degradation (ERAD). This process involves protein retrotranslocation into the cytosol, ubiquitylation, and proteasomal degradation. ERAD substrates are classified into three categories based on the location of their degradation signal/degron: ERAD-L (lumen), ERAD-M (membrane), and ERAD-C (cytosol) substrates. In Saccharomyces cerevisiae, the membrane proteins Hrd1 and Doa10 are the predominant ERAD ubiquitin-protein ligases (E3s). The current notion is that ERAD-L and ERAD-M substrates are exclusively handled by Hrd1, whereas ERAD-C substrates are recognized by Doa10. In this paper, we identify the transmembrane (TM) protein Sec61 β-subunit homologue 2 (Sbh2) as a Doa10 substrate. Sbh2 is part of the trimeric Ssh1 complex involved in protein translocation. Unassembled Sbh2 is rapidly degraded in a Doa10-dependent manner. Intriguingly, the degron maps to the Sbh2 TM region. Thus, in contrast to the prevailing view, Doa10 (and presumably its human orthologue) has the capacity for recognizing intramembrane degrons, expanding its spectrum of substrates. PMID:25918226

  14. Multiple-Diode-Laser Gas-Detection Spectrometer

    NASA Technical Reports Server (NTRS)

    Webster, Christopher R.; Beer, Reinhard; Sander, Stanley P.

    1988-01-01

    Small concentrations of selected gases measured automatically. Proposed multiple-laser-diode spectrometer part of system for measuring automatically concentrations of selected gases at part-per-billion level. Array of laser/photodetector pairs measure infrared absorption spectrum of atmosphere along probing laser beams. Adaptable to terrestrial uses as monitoring pollution or control of industrial processes.

  15. Analysis of aircraft spectrometer data with logarithmic residuals

    NASA Technical Reports Server (NTRS)

    Green, A. A.; Craig, M. D.

    1985-01-01

    Spectra from airborne systems must be analyzed in terms of their mineral-related absorption features. Methods for removing backgrounds and extracting these features one at a time from reflectance spectra are discussed. Methods for converting radiance spectra into a form similar to reflectance spectra so that the feature extraction procedures can be implemented on aircraft spectrometer data are also discussed.

  16. [Studies on the determination of the flux of gaseous pollutant from an area by passive differential optical absorption spectroscopy].

    PubMed

    Li, Ang; Xie, Pin-Hua; Liu, Wen-Qing; Liu, Jian-Guo; Dou, Ke

    2009-01-01

    An optical remote sensing method based on passive differential optical absorption spectroscopy (DOAS) for the determination of the flux of SO2 or other gaseous pollutants from an area (such as industrial area, city) which includes many different atmospheric pollution sources was studied in the present paper. Passive DOAS using the zenith scattered sunlight as the light source provides the column density (the integrated concentration of atmospheric absorbers along the light path) and has been successfully applied to the determination of the flux of gaseous pollutants emitted from the volcano or point source. Passive DOAS instrument installed in a car scanned the plume emitted from an area by circling around the area in this paper. Column density of each selected gaseous pollutant was retrieved from zenith scattered sunlight spectra collected by the instrument by spectral analysis method of passive DOAS in their particular absorption spectral range respectively. Combined with the meteorological (wind field) information during the period of measurement, the net flux value of gaseous pollutant from this area during the measurement could be estimated. DOAS method used to obtain the column density of gaseous pollutant in the section plane of the plume emitted from source and the method of net flux calculation of gaseous pollutant from a certain area are described. Also a passive DOAS instrument was developed and installed in a car to scan the gaseous pollutants from the area surrounded by the 5th Ring Road in Beijing city during a field campaign in the summer of 2005. The SO2 net flux 1.13 x 10(4) kg x h(-1) and NO2 net flux 9.3 x 10(3) kg x h(-1) from this area were derived separately after the passive DOAS measured the entire ring road and the wind data were roughly estimated from wind profile radar. The results indicate that this optical remote sensing method based on passive DOAS can be used to rapidly determine the flux of gaseous pollutant (such as SO2, NO2

  17. [Studies on the determination of the flux of gaseous pollutant from an area by passive differential optical absorption spectroscopy].

    PubMed

    Li, Ang; Xie, Pin-Hua; Liu, Wen-Qing; Liu, Jian-Guo; Dou, Ke

    2009-01-01

    An optical remote sensing method based on passive differential optical absorption spectroscopy (DOAS) for the determination of the flux of SO2 or other gaseous pollutants from an area (such as industrial area, city) which includes many different atmospheric pollution sources was studied in the present paper. Passive DOAS using the zenith scattered sunlight as the light source provides the column density (the integrated concentration of atmospheric absorbers along the light path) and has been successfully applied to the determination of the flux of gaseous pollutants emitted from the volcano or point source. Passive DOAS instrument installed in a car scanned the plume emitted from an area by circling around the area in this paper. Column density of each selected gaseous pollutant was retrieved from zenith scattered sunlight spectra collected by the instrument by spectral analysis method of passive DOAS in their particular absorption spectral range respectively. Combined with the meteorological (wind field) information during the period of measurement, the net flux value of gaseous pollutant from this area during the measurement could be estimated. DOAS method used to obtain the column density of gaseous pollutant in the section plane of the plume emitted from source and the method of net flux calculation of gaseous pollutant from a certain area are described. Also a passive DOAS instrument was developed and installed in a car to scan the gaseous pollutants from the area surrounded by the 5th Ring Road in Beijing city during a field campaign in the summer of 2005. The SO2 net flux 1.13 x 10(4) kg x h(-1) and NO2 net flux 9.3 x 10(3) kg x h(-1) from this area were derived separately after the passive DOAS measured the entire ring road and the wind data were roughly estimated from wind profile radar. The results indicate that this optical remote sensing method based on passive DOAS can be used to rapidly determine the flux of gaseous pollutant (such as SO2, NO2

  18. Single-snapshot DOA estimation by using Compressed Sensing

    NASA Astrophysics Data System (ADS)

    Fortunati, Stefano; Grasso, Raffaele; Gini, Fulvio; Greco, Maria S.; LePage, Kevin

    2014-12-01

    This paper deals with the problem of estimating the directions of arrival (DOA) of multiple source signals from a single observation vector of an array data. In particular, four estimation algorithms based on the theory of compressed sensing (CS), i.e., the classical ℓ 1 minimization (or Least Absolute Shrinkage and Selection Operator, LASSO), the fast smooth ℓ 0 minimization, and the Sparse Iterative Covariance-Based Estimator, SPICE and the Iterative Adaptive Approach for Amplitude and Phase Estimation, IAA-APES algorithms, are analyzed, and their statistical properties are investigated and compared with the classical Fourier beamformer (FB) in different simulated scenarios. We show that unlike the classical FB, a CS-based beamformer (CSB) has some desirable properties typical of the adaptive algorithms (e.g., Capon and MUSIC) even in the single snapshot case. Particular attention is devoted to the super-resolution property. Theoretical arguments and simulation analysis provide evidence that a CS-based beamformer can achieve resolution beyond the classical Rayleigh limit. Finally, the theoretical findings are validated by processing a real sonar dataset.

  19. Measurement reduction for mutual coupling calibration in DOA estimation

    NASA Astrophysics Data System (ADS)

    Aksoy, Taylan; Tuncer, T. Engin

    2012-01-01

    Mutual coupling is an important source of error in antenna arrays that should be compensated for super resolution direction-of-arrival (DOA) algorithms, such as Multiple Signal Classification (MUSIC) algorithm. A crucial step in array calibration is the determination of the mutual coupling coefficients for the antenna array. In this paper, a system theoretic approach is presented for the mutual coupling characterization of antenna arrays. The comprehension and implementation of this approach is simple leading to further advantages in calibration measurement reduction. In this context, a measurement reduction method for antenna arrays with omni-directional and identical elements is proposed which is based on the symmetry planes in the array geometry. The proposed method significantly decreases the number of measurements during the calibration process. This method is evaluated using different array types whose responses and the mutual coupling characteristics are obtained through numerical electromagnetic simulations. It is shown that a single calibration measurement is sufficient for uniform circular arrays. Certain important and interesting characteristics observed during the experiments are outlined.

  20. Airborne measurements of NO2 shipping emissions using imaging DOAS

    NASA Astrophysics Data System (ADS)

    Meier, Andreas C.; Schönhardt, Anja; Richter, Andreas; Seyler, André; Ruhtz, Thomas; Lindemann, Carsten; Wittrock, Folkard; Burrows, John P.

    2014-05-01

    NOx (NO and NO2) play a key role in tropospheric chemistry and affect human health and the environment. Shipping emissions contribute substantially to the global emissions of anthropogenic NOx. Due to globalization and increased trade volume, the relative importance emissions from ships gain even more importance. The Airborne imaging DOAS instrument for Measurements of Atmospheric Pollution (AirMAP), developed at IUP Bremen, has been used to perform measurements of NO2 in the visible spectral range. The observations allow the determination of spatial distributions of column densities of NO2 below the aircraft. Airborne measurements were performed over Northern Germany and adjacent coastal waters during the NOSE (NO2 from Shipping Emissions) campaign in August 2013. The focus of the campaign activities was on shipping emissions, but NO2 over cities and power plants has been measured as well. The measurements have a spatial resolution below the order of 100 × 30 m2, and they reveal the large spatial variability of NO2 and the evolution of NO2 plumes behind point sources. Shipping lanes as well as plumes of individual ships are detected by the AirMAP instrument. In this study, first results from the NOSE campaign are presented for selected measurement areas.

  1. Long term NO2 measurements in Hong Kong using LED based Long Path Differential Optical Absorption Spectroscopy

    NASA Astrophysics Data System (ADS)

    Chan, K. L.; Pöhler, D.; Kuhlmann, G.; Hartl, A.; Platt, U.; Wenig, M. O.

    2011-11-01

    In this study we present the first long term measurements of atmospheric nitrogen dioxide (NO2) using a LED based Long Path Differential Optical Absorption Spectroscopy (LP-DOAS) instrument. This instrument is measuring continuously in Hong Kong since December 2009, first in a setup with a 550 m absorption path and then with a 3820 m path at about 30 m to 50 m above street level. The instrument is using a high power blue light LED with peak intensity at 450 nm coupled into the telescope using a Y-fibre bundle. The LP-DOAS instrument measures NO2 concentrations in the Kowloon Tong and Mong Kok district of Hong Kong and we compare the measurement results to concentrations reported by monitoring stations operated by the Hong Kong Environmental Protection Department in that area. Hourly averages of coinciding measurements are in reasonable agreement (R = 0.74). Furthermore, we used the long-term data set to validate the Ozone Monitoring Instrument (OMI) NO2 data product. Monthly averaged LP-DOAS and OMI measurements correlate well (R = 0.84) when comparing the data for the OMI overpass time. We analyzed weekly patterns in both data sets and found that the LP-DOAS detects a clear weekly cycle with a reduction on weekends during rush hour peaks, whereas OMI is not able to observe this weekly cycle due to its fix overpass time.

  2. Tropospheric and Airborne Emission Spectrometers

    NASA Technical Reports Server (NTRS)

    Glavich, Thomas; Beer, Reinhard

    1996-01-01

    X This paper describes the development of two related instruments, the Tropospheric Emission Spectrometer (TES) and the Airborne Emission Spectrometer (AES). Both instruments are infrared imaging Fourier Transform Spectrometers, used for measuring the state of the lower atmosphere, and in particular the measurement of ozone and ozone sources and sinks.

  3. Photoacoustic Soot Spectrometer (PASS) Instrument Handbook

    SciTech Connect

    Dubey, M; Springston, S; Koontz, A; Aiken, A

    2013-01-17

    The photoacoustic soot spectrometer (PASS) measures light absorption by aerosol particles. As the particles pass through a laser beam, the absorbed energy heats the particles and in turn the surrounding air, which sets off a pressure wave that can be detected by a microphone. The PASS instruments deployed by ARM can also simultaneously measure the scattered laser light at three wavelengths and therefore provide a direct measure of the single-scattering albedo. The Operator Manual for the PASS-3100 is included here with the permission of Droplet Measurement Technologies, the instrument’s manufacturer.

  4. Joint Estimation of 2D-DOA and Frequency Based on Space-Time Matrix and Conformal Array

    PubMed Central

    Wan, Liang-Tian; Liu, Lu-Tao; Si, Wei-Jian; Tian, Zuo-Xi

    2013-01-01

    Each element in the conformal array has a different pattern, which leads to the performance deterioration of the conventional high resolution direction-of-arrival (DOA) algorithms. In this paper, a joint frequency and two-dimension DOA (2D-DOA) estimation algorithm for conformal array are proposed. The delay correlation function is used to suppress noise. Both spatial and time sampling are utilized to construct the spatial-time matrix. The frequency and 2D-DOA estimation are accomplished based on parallel factor (PARAFAC) analysis without spectral peak searching and parameter pairing. The proposed algorithm needs only four guiding elements with precise positions to estimate frequency and 2D-DOA. Other instrumental elements can be arranged flexibly on the surface of the carrier. Simulation results demonstrate the effectiveness of the proposed algorithm. PMID:24453856

  5. Alpha Magnetic Spectrometer

    NASA Astrophysics Data System (ADS)

    Ting, Samuel

    2012-07-01

    The Alpha Magnetic Spectrometer (AMS) is a precision particle physics magnetic spectrometer designed to measure electrons, positrons, gamma rays and various nuclei and anti-nuclei from the cosmos up to TeV energy ranges. AMS weighs 7.5 tons and measures 5 meters by 4 meters by 3 meters. It contains 300,000 channels of electronics and 650 onboard microprocessors. It was delivered to the International Space Station onboard space shuttle Endeavour and installed on May 19, 2011. Since that time, more than 14 billion cosmic ray events have been collected. All the detectors function properly. At this moment, we are actively engaged in data analysis. AMS is an international collaboration involving 16 countries and 60 institutes. It took 16 years to construct and test. AMS is the only major physical science experiment on the International Space Station and will continue to collect data over the entire lifetime of the Space Station (10-20 years).

  6. Imaging Fourier Transform Spectrometer

    SciTech Connect

    Bennett, C.L.; Carter, M.R.; Fields, D.J.; Hernandez, J.

    1993-04-14

    The operating principles of an Imaging Fourier Transform Spectrometer (IFTS) are discussed. The advantages and disadvantages of such instruments with respect to alternative imaging spectrometers are discussed. The primary advantages of the IFTS are the capacity to acquire more than an order of magnitude more spectral channels than alternative systems with more than an order of magnitude greater etendue than for alternative systems. The primary disadvantage of IFTS, or FTS in general, is the sensitivity to temporal fluctuations, either random or periodic. Data from the IRIFTS (ir IFTS) prototype instrument, sensitive in the infrared, are presented having a spectral sensitivity of 0.01 absorbance units, a spectral resolution of 6 cm{sup {minus}1} over the range 0 to 7899 cm{sup {minus}1}, and a spatial resolution of 2.5 mr.

  7. FAST NEUTRON SPECTROMETER

    DOEpatents

    Davis, F.J.; Hurst, G.S.; Reinhardt, P.W.

    1959-08-18

    An improved proton recoil spectrometer for determining the energy spectrum of a fast neutron beam is described. Instead of discriminating against and thereby"throwing away" the many recoil protons other than those traveling parallel to the neutron beam axis as do conventional spectrometers, this device utilizes protons scattered over a very wide solid angle. An ovoidal gas-filled recoil chamber is coated on the inside with a scintillator. The ovoidal shape of the sensitive portion of the wall defining the chamber conforms to the envelope of the range of the proton recoils from the radiator disposed within the chamber. A photomultiplier monitors the output of the scintillator, and a counter counts the pulses caused by protons of energy just sufficient to reach the scintillator.

  8. Miniaturized Ion Mobility Spectrometer

    NASA Technical Reports Server (NTRS)

    Kaye, William J. (Inventor); Stimac, Robert M. (Inventor)

    2015-01-01

    By utilizing the combination of a unique electronic ion injection control circuit in conjunction with a particularly designed drift cell construction, the instantly disclosed ion mobility spectrometer achieves increased levels of sensitivity, while achieving significant reductions in size and weight. The instant IMS is of a much simpler and easy to manufacture design, rugged and hermetically sealed, capable of operation at high temperatures to at least 250.degree. C., and is uniquely sensitive, particularly to explosive chemicals.

  9. Rapid scanning mass spectrometer

    SciTech Connect

    Leckey, J.H.; Boeckmann, M.D.

    1996-11-25

    Mass spectrometers and residual gas analyzers (RGA) are used in a variety of applications for analysis of volatile and semi-volatile materials. Analysis is performed by detecting fragments of gas molecules, based on their mass to charge ratio, which are generated in the mass spectrometer. When used as a detector for a gas chromatograph, they function as a means to quantitatively identify isolated volatile species which have been separated from other species via the gas chromatograph. Vacuum Technology, Inc., (VTI) produces a magnetic sector mass spectrometer/RGA which is used in many industrial and laboratory environments. In order to increase the utility of this instrument, it is desirable to increase the mass scanning speed, thereby increasing the number of applications for which it is suited. This project performed the following three upgrades on the computer interface. (1) A new electrometer was designed and built to process the signal from the detector. This new electrometer is more sensitive, over 10 times faster, and over 100 times more stable than the electrometer it will replace. (2) The controller EPROM was reprogrammed with new firmware. This firmware acts as an operating system for the interface and is used to shuttle communications between the PC and the AEROVAC mass spectrometer. (3) The voltage regulator which causes the ion selector voltage to ramp to allow ions of selected mass to be sequentially detected was redesigned and prototyped. The redesigned voltage regulator can be ramped up or down more than 100 times faster than the existing regulator. These changes were incorporated into a prototype unit and preliminary performance testing conducted. Results indicated that scanning speed was significantly increased over the unmodified version.

  10. DOA estimation for monostatic MIMO radar based on unitary root-MUSIC

    NASA Astrophysics Data System (ADS)

    Wang, Wei; Wang, Xianpeng; Li, Xin; Song, Hongru

    2013-11-01

    Direction of arrival (DOA) estimation is an important issue for monostatic MIMO radar. A DOA estimation method for monostatic MIMO radar based on unitary root-MUSIC is presented in this article. In the presented method, a reduced-dimension matrix is first utilised to transform the high dimension of received signal data into low dimension one. Then, a low-dimension real-value covariance matrix is obtained by forward-backward (FB) averaging and unitary transformation. The DOA of targets can be achieved by unitary root-MUSIC. Due to the FB averaging of received signal data and the eigendecomposition of the real-valued matrix covariance, the proposed method owns better angle estimation performance and lower computational complexity. The simulation results of the proposed method are presented and the performances are investigated and discussed.

  11. The Influence of Random Element Displacement on DOA Estimates Obtained with (Khatri–Rao-)Root-MUSIC

    PubMed Central

    Inghelbrecht, Veronique; Verhaevert, Jo; van Hecke, Tanja; Rogier, Hendrik

    2014-01-01

    Although a wide range of direction of arrival (DOA) estimation algorithms has been described for a diverse range of array configurations, no specific stochastic analysis framework has been established to assess the probability density function of the error on DOA estimates due to random errors in the array geometry. Therefore, we propose a stochastic collocation method that relies on a generalized polynomial chaos expansion to connect the statistical distribution of random position errors to the resulting distribution of the DOA estimates. We apply this technique to the conventional root-MUSIC and the Khatri-Rao-root-MUSIC methods. According to Monte-Carlo simulations, this novel approach yields a speedup by a factor of more than 100 in terms of CPU-time for a one-dimensional case and by a factor of 56 for a two-dimensional case. PMID:25393783

  12. Real-Valued Covariance Vector Sparsity-Inducing DOA Estimation for Monostatic MIMO Radar.

    PubMed

    Wang, Xianpeng; Wang, Wei; Li, Xin; Liu, Jing

    2015-11-10

    In this paper, a real-valued covariance vector sparsity-inducing method for direction of arrival (DOA) estimation is proposed in monostatic multiple-input multiple-output (MIMO) radar. Exploiting the special configuration of monostatic MIMO radar, low-dimensional real-valued received data can be obtained by using the reduced-dimensional transformation and unitary transformation technique. Then, based on the Khatri-Rao product, a real-valued sparse representation framework of the covariance vector is formulated to estimate DOA. Compared to the existing sparsity-inducing DOA estimation methods, the proposed method provides better angle estimation performance and lower computational complexity. Simulation results verify the effectiveness and advantage of the proposed method.

  13. Sparsity-Aware DOA Estimation Scheme for Noncircular Source in MIMO Radar.

    PubMed

    Wang, Xianpeng; Wang, Wei; Li, Xin; Liu, Qi; Liu, Jing

    2016-04-14

    In this paper, a novel sparsity-aware direction of arrival (DOA) estimation scheme for a noncircular source is proposed in multiple-input multiple-output (MIMO) radar. In the proposed method, the reduced-dimensional transformation technique is adopted to eliminate the redundant elements. Then, exploiting the noncircularity of signals, a joint sparsity-aware scheme based on the reweighted l1 norm penalty is formulated for DOA estimation, in which the diagonal elements of the weight matrix are the coefficients of the noncircular MUSIC-like (NC MUSIC-like) spectrum. Compared to the existing l1 norm penalty-based methods, the proposed scheme provides higher angular resolution and better DOA estimation performance. Results from numerical experiments are used to show the effectiveness of our proposed method.

  14. Sparsity-Aware DOA Estimation Scheme for Noncircular Source in MIMO Radar

    PubMed Central

    Wang, Xianpeng; Wang, Wei; Li, Xin; Liu, Qi; Liu, Jing

    2016-01-01

    In this paper, a novel sparsity-aware direction of arrival (DOA) estimation scheme for a noncircular source is proposed in multiple-input multiple-output (MIMO) radar. In the proposed method, the reduced-dimensional transformation technique is adopted to eliminate the redundant elements. Then, exploiting the noncircularity of signals, a joint sparsity-aware scheme based on the reweighted l1 norm penalty is formulated for DOA estimation, in which the diagonal elements of the weight matrix are the coefficients of the noncircular MUSIC-like (NC MUSIC-like) spectrum. Compared to the existing l1 norm penalty-based methods, the proposed scheme provides higher angular resolution and better DOA estimation performance. Results from numerical experiments are used to show the effectiveness of our proposed method. PMID:27089345

  15. Real-Valued Covariance Vector Sparsity-Inducing DOA Estimation for Monostatic MIMO Radar

    PubMed Central

    Wang, Xianpeng; Wang, Wei; Li, Xin; Liu, Jing

    2015-01-01

    In this paper, a real-valued covariance vector sparsity-inducing method for direction of arrival (DOA) estimation is proposed in monostatic multiple-input multiple-output (MIMO) radar. Exploiting the special configuration of monostatic MIMO radar, low-dimensional real-valued received data can be obtained by using the reduced-dimensional transformation and unitary transformation technique. Then, based on the Khatri–Rao product, a real-valued sparse representation framework of the covariance vector is formulated to estimate DOA. Compared to the existing sparsity-inducing DOA estimation methods, the proposed method provides better angle estimation performance and lower computational complexity. Simulation results verify the effectiveness and advantage of the proposed method. PMID:26569241

  16. DOA Estimation under Unknown Mutual Coupling and Multipath with Improved Effective Array Aperture

    PubMed Central

    Wang, Yuexian; Trinkle, Matthew; Ng, Brian W.-H.

    2015-01-01

    Subspace-based high-resolution direction of arrival (DOA) estimation significantly deteriorates under array manifold perturbation and rank deficiency of the covariance matrix due to mutual coupling and multipath propagation, respectively. In this correspondence, the unknown mutual coupling can be circumvented by the proposed method without any passive or active calibration process, and the DOA of the coherent signals can be accurately estimated accordingly. With a newly constructed matrix, the deficient rank can be restored, and the effective array aperture can be extended compared with conventional spatial smoothing. The proposed method achieves a good robustness and DOA estimation accuracy with unknown mutual coupling. The simulation results demonstrate the validity and efficiency of the proposed method. PMID:26670235

  17. Off-Grid DOA Estimation Using Alternating Block Coordinate Descent in Compressed Sensing

    PubMed Central

    Si, Weijian; Qu, Xinggen; Qu, Zhiyu

    2015-01-01

    This paper presents a novel off-grid direction of arrival (DOA) estimation method to achieve the superior performance in compressed sensing (CS), in which DOA estimation problem is cast as a sparse reconstruction. By minimizing the mixed k-l norm, the proposed method can reconstruct the sparse source and estimate grid error caused by mismatch. An iterative process that minimizes the mixed k-l norm alternately over two sparse vectors is employed so that the nonconvex problem is solved by alternating convex optimization. In order to yield the better reconstruction properties, the block sparse source is exploited for off-grid DOA estimation. A block selection criterion is engaged to reduce the computational complexity. In addition, the proposed method is proved to have the global convergence. Simulation results show that the proposed method has the superior performance in comparisons to existing methods. PMID:26343658

  18. X-ray Spectrometer

    NASA Technical Reports Server (NTRS)

    Porter, F. Scott

    2004-01-01

    The X-ray Spectrometer (XRS) instrument is a revolutionary non-dispersive spectrometer that will form the basis for the Astro-E2 observatory to be launched in 2005. We have recently installed a flight spare X R S microcalorimeter spectrometer at the EBIT-I facility at LLNL replacing the XRS from the earlier Astro-E mission and providing twice the resolution. The X R S microcalorimeter is an x-ray detector that senses the heat deposited by the incident photon. It achieves a high energy resolution by operating at 0.06K and by carefully controlling the heat capacity and thermal conductance. The XRS/EBIT instrument has 32 pixels in a square geometry and achieves an energy resolution of 6 eV at 6 keV, with a bandpass from 0.1 to 12 keV (or more at higher operating temperature). The instrument allows detailed studies of the x-ray line emission of laboratory plasmas. The XRS/EBIT also provides an extensive calibration "library" for the Astro-E2 observatory.

  19. Capon-based single-snapshot DOA estimation in monostatic MIMO radar

    NASA Astrophysics Data System (ADS)

    Hassanien, Aboulnasr; Amin, Moeness G.; Zhang, Yimin D.; Ahmad, Fauzia

    2015-05-01

    We consider the problem of single snapshot direction-of-arrival (DOA) estimation of multiple targets in monostatic multiple-input multiple-output (MIMO) radar. When only a single snapshot is used, the sample covariance matrix of the data becomes non-invertible and, therefore, does not permit application of Capon-based DOA estimation techniques. On the other hand, low-resolution techniques, such as the conventional beamformer, suffer from biased estimation and fail to resolve closely spaced sources. In this paper, we propose a new Capon-based method for DOA estimation in MIMO radar using a single radar pulse. Assuming that the angular locations of the sources are known a priori to be located within a certain spatial sector, we employ multiple transmit beams to focus the transmit energy of multiple orthogonal waveforms within the desired sector. The transmit weight vectors are carefully designed such that they have the same transmit power distribution pattern. As compared to the standard MIMO radar, the proposed approach enables transmitting an arbitrary number of orthogonal waveforms. By using matched-filtering at the receiver, the data associated with each beam is extracted yielding a virtual data snapshot. The total number of virtual snapshots is equal to the number of transmit beams. By choosing the number of transmit beams to be larger than the number of receive elements, it becomes possible to form a full-rank sample covariance matrix. The Capon beamformer is then applied to estimate the DOAs of the targets of interest. The proposed method is shown to have improved DOA estimation performance as compared to conventional single-snapshot DOA estimation methods.

  20. Mass spectrometers: instrumentation

    NASA Astrophysics Data System (ADS)

    Cooks, R. G.; Hoke, S. H., II; Morand, K. L.; Lammert, S. A.

    1992-09-01

    Developments in mass spectrometry instrumentation over the past three years are reviewed. The subject is characterized by an enormous diversity of designs, a high degree of competition between different laboratories working with either different or similar techniques and by extremely rapid progress in improving analytical performance. Instruments can be grouped into genealogical charts based on their physical and conceptual interrelationships. This is illustrated using mass analyzers of different types. The time course of development of particular instrumental concepts is illustrated in terms of the s-curves typical of cell growth. Examples are given of instruments which are at the exponential, linear and mature growth stages. The prime examples used are respectively: (i) hybrid instruments designed to study reactive collisions of ions with surfaces: (ii) the Paul ion trap; and (iii) the triple quadrupole mass spectrometer. In the area of ion/surface collisions, reactive collisions such as hydrogen radical abstraction from the surface by the impinging ion are studied. They are shown to depend upon the chemical nature of the surface through the use of experiments which utilize self-assembled monolayers as surfaces. The internal energy deposited during surface-induced dissociation upon collision with different surfaces in a BEEQ instrument is also discussed. Attention is also given to a second area of emerging instrumentation, namely technology which allows mass spectrometers to be used for on-line monitoring of fluid streams. A summary of recent improvements in the performance of the rapidly developing quadrupole ion trap instrument illustrates this stage of instrument development. Improvements in resolution and mass range and their application to the characterization of biomolecules are described. The interaction of theory with experiment is illustrated through the role of simulations of ion motion in the ion trap. It is emphasized that mature instruments play a

  1. Joint Estimation of Time-Frequency Signature and DOA Based on STFD for Multicomponent Chirp Signals

    PubMed Central

    Zhao, Ziyue; Liu, Congfeng

    2014-01-01

    In the study of the joint estimation of time-frequency signature and direction of arrival (DOA) for multicomponent chirp signals, an estimation method based on spatial time-frequency distributions (STFDs) is proposed in this paper. Firstly, array signal model for multicomponent chirp signals is presented and then array processing is applied in time-frequency analysis to mitigate cross-terms. According to the results of the array processing, Hough transform is performed and the estimation of time-frequency signature is obtained. Subsequently, subspace method for DOA estimation based on STFD matrix is achieved. Simulation results demonstrate the validity of the proposed method. PMID:27382610

  2. Comb-locked Lamb-dip spectrometer.

    PubMed

    Gatti, Davide; Gotti, Riccardo; Gambetta, Alessio; Belmonte, Michele; Galzerano, Gianluca; Laporta, Paolo; Marangoni, Marco

    2016-01-01

    Overcoming the Doppler broadening limit is a cornerstone of precision spectroscopy. Nevertheless, the achievement of a Doppler-free regime is severely hampered by the need of high field intensities to saturate absorption transitions and of a high signal-to-noise ratio to detect tiny Lamb-dip features. Here we present a novel comb-assisted spectrometer ensuring over a broad range from 1.5 to 1.63 μm intra-cavity field enhancement up to 1.5 kW/cm(2), which is suitable for saturation of transitions with extremely weak electric dipole moments. Referencing to an optical frequency comb allows the spectrometer to operate with kHz-level frequency accuracy, while an extremely tight locking of the probe laser to the enhancement cavity enables a 10(-11) cm(-1) absorption sensitivity to be reached over 200 s in a purely dc direct-detection-mode at the cavity output. The particularly simple and robust detection and operating scheme, together with the wide tunability available, makes the system suitable to explore thousands of lines of several molecules never observed so far in a Doppler-free regime. As a demonstration, Lamb-dip spectroscopy is performed on the P(15) line of the 01120-00000 band of acetylene, featuring a line-strength below 10(-23) cm/mol and an Einstein coefficient of 5 mHz, among the weakest ever observed. PMID:27263858

  3. Comb-locked Lamb-dip spectrometer.

    PubMed

    Gatti, Davide; Gotti, Riccardo; Gambetta, Alessio; Belmonte, Michele; Galzerano, Gianluca; Laporta, Paolo; Marangoni, Marco

    2016-06-06

    Overcoming the Doppler broadening limit is a cornerstone of precision spectroscopy. Nevertheless, the achievement of a Doppler-free regime is severely hampered by the need of high field intensities to saturate absorption transitions and of a high signal-to-noise ratio to detect tiny Lamb-dip features. Here we present a novel comb-assisted spectrometer ensuring over a broad range from 1.5 to 1.63 μm intra-cavity field enhancement up to 1.5 kW/cm(2), which is suitable for saturation of transitions with extremely weak electric dipole moments. Referencing to an optical frequency comb allows the spectrometer to operate with kHz-level frequency accuracy, while an extremely tight locking of the probe laser to the enhancement cavity enables a 10(-11) cm(-1) absorption sensitivity to be reached over 200 s in a purely dc direct-detection-mode at the cavity output. The particularly simple and robust detection and operating scheme, together with the wide tunability available, makes the system suitable to explore thousands of lines of several molecules never observed so far in a Doppler-free regime. As a demonstration, Lamb-dip spectroscopy is performed on the P(15) line of the 01120-00000 band of acetylene, featuring a line-strength below 10(-23) cm/mol and an Einstein coefficient of 5 mHz, among the weakest ever observed.

  4. Comb-locked Lamb-dip spectrometer

    PubMed Central

    Gatti, Davide; Gotti, Riccardo; Gambetta, Alessio; Belmonte, Michele; Galzerano, Gianluca; Laporta, Paolo; Marangoni, Marco

    2016-01-01

    Overcoming the Doppler broadening limit is a cornerstone of precision spectroscopy. Nevertheless, the achievement of a Doppler-free regime is severely hampered by the need of high field intensities to saturate absorption transitions and of a high signal-to-noise ratio to detect tiny Lamb-dip features. Here we present a novel comb-assisted spectrometer ensuring over a broad range from 1.5 to 1.63 μm intra-cavity field enhancement up to 1.5 kW/cm2, which is suitable for saturation of transitions with extremely weak electric dipole moments. Referencing to an optical frequency comb allows the spectrometer to operate with kHz-level frequency accuracy, while an extremely tight locking of the probe laser to the enhancement cavity enables a 10−11 cm−1 absorption sensitivity to be reached over 200 s in a purely dc direct-detection-mode at the cavity output. The particularly simple and robust detection and operating scheme, together with the wide tunability available, makes the system suitable to explore thousands of lines of several molecules never observed so far in a Doppler-free regime. As a demonstration, Lamb-dip spectroscopy is performed on the P(15) line of the 01120-00000 band of acetylene, featuring a line-strength below 10−23 cm/mol and an Einstein coefficient of 5 mHz, among the weakest ever observed. PMID:27263858

  5. Comb-locked Lamb-dip spectrometer

    NASA Astrophysics Data System (ADS)

    Gatti, Davide; Gotti, Riccardo; Gambetta, Alessio; Belmonte, Michele; Galzerano, Gianluca; Laporta, Paolo; Marangoni, Marco

    2016-06-01

    Overcoming the Doppler broadening limit is a cornerstone of precision spectroscopy. Nevertheless, the achievement of a Doppler-free regime is severely hampered by the need of high field intensities to saturate absorption transitions and of a high signal-to-noise ratio to detect tiny Lamb-dip features. Here we present a novel comb-assisted spectrometer ensuring over a broad range from 1.5 to 1.63 μm intra-cavity field enhancement up to 1.5 kW/cm2, which is suitable for saturation of transitions with extremely weak electric dipole moments. Referencing to an optical frequency comb allows the spectrometer to operate with kHz-level frequency accuracy, while an extremely tight locking of the probe laser to the enhancement cavity enables a 10‑11 cm‑1 absorption sensitivity to be reached over 200 s in a purely dc direct-detection-mode at the cavity output. The particularly simple and robust detection and operating scheme, together with the wide tunability available, makes the system suitable to explore thousands of lines of several molecules never observed so far in a Doppler-free regime. As a demonstration, Lamb-dip spectroscopy is performed on the P(15) line of the 01120-00000 band of acetylene, featuring a line-strength below 10‑23 cm/mol and an Einstein coefficient of 5 mHz, among the weakest ever observed.

  6. MASS SPECTROMETER LEAK

    DOEpatents

    Shields, W.R.

    1960-10-18

    An improved valve is described for precisely regulating the flow of a sample fluid to be analyzed, such as in a mass spectrometer, where a gas sample is allowed to "leak" into an evacuated region at a very low, controlled rate. The flow regulating valve controls minute flow of gases by allowing the gas to diffuse between two mating surfaces. The structure of the valve is such as to prevent the corrosive feed gas from contacting the bellows which is employed in the operation of the valve, thus preventing deterioration of the bellows.

  7. Automated transportable mass spectrometer

    NASA Astrophysics Data System (ADS)

    Echo, M. W.

    1981-09-01

    The need was identified for a mass spectrometer (MS) which can be conveniently transported among several facilities for rapid verification of the isotopic composition of special nuclear material. This requirement for a light weight, transportable MS for U and Pu mass analysis was met by deleting the gas chromograph (GC) portions of a Hewlett-Packard Model 5992 Quadrupole GCMS and substituting a vacuum lock sample entry system. A programmable power supply and vacuum gauge were added and circuitry modifications were made to enable use of the supplied software.

  8. Gas Chromatic Mass Spectrometer

    NASA Technical Reports Server (NTRS)

    Wey, Chowen

    1995-01-01

    Gas chromatograph/mass spectrometer (GC/MS) used to measure and identify combustion species present in trace concentration. Advanced extractive diagnostic method measures to parts per billion (PPB), as well as differentiates between different types of hydrocarbons. Applicable for petrochemical, waste incinerator, diesel transporation, and electric utility companies in accurately monitoring types of hydrocarbon emissions generated by fuel combustion, in order to meet stricter environmental requirements. Other potential applications include manufacturing processes requiring precise detection of toxic gaseous chemicals, biomedical applications requiring precise identification of accumulative gaseous species, and gas utility operations requiring high-sensitivity leak detection.

  9. Metrology for terahertz time-domain spectrometers

    NASA Astrophysics Data System (ADS)

    Molloy, John F.; Naftaly, Mira

    2015-12-01

    In recent years the terahertz time-domain spectrometer (THz TDS) [1] has emerged as a key measurement device for spectroscopic investigations in the frequency range of 0.1-5 THz. To date, almost every type of material has been studied using THz TDS, including semiconductors, ceramics, polymers, metal films, liquid crystals, glasses, pharmaceuticals, DNA molecules, proteins, gases, composites, foams, oils, and many others. Measurements with a TDS are made in the time domain; conversion from the time domain data to a frequency spectrum is achieved by applying the Fourier Transform, calculated numerically using the Fast Fourier Transform (FFT) algorithm. As in many other types of spectrometer, THz TDS requires that the sample data be referenced to similarly acquired data with no sample present. Unlike frequency-domain spectrometers which detect light intensity and measure absorption spectra, a TDS records both amplitude and phase information, and therefore yields both the absorption coefficient and the refractive index of the sample material. The analysis of the data from THz TDS relies on the assumptions that: a) the frequency scale is accurate; b) the measurement of THz field amplitude is linear; and c) that the presence of the sample does not affect the performance characteristics of the instrument. The frequency scale of a THz TDS is derived from the displacement of the delay line; via FFT, positioning errors may give rise to frequency errors that are difficult to quantify. The measurement of the field amplitude in a THz TDS is required to be linear with a dynamic range of the order of 10 000. And attention must be given to the sample positioning and handling in order to avoid sample-related errors.

  10. IR spectrometers for Venus and Mars measurements

    NASA Astrophysics Data System (ADS)

    Drummond, Rachel; Neefs, Eddy; Vandaele, Ann C.

    2012-07-01

    The SOIR spectrometer [1] is an infra-red spectrometer that has performed over 500 solar occultation measurements of the Venus atmosphere, profiling major and minor constituents and studying aerosol absorption, temperature and pressure effects. NOMAD is a 3-channel spectrometer for Mars occultation, limb and nadir measurements. 2 channels are infra-red, the other UV-visible. We will present the technology that enables SOIR and NOMAD to get to parts per billion mixing ratio sensitivities for trace atmospheric components and highlight the improvements made to the SOIR design to enable nadir viewing with NOMAD. Key components include the Acousto-Optical Tunable Filter with radio frequency driver that allows these spectrometers to select the wavelength domain under observation with no need for mechanical moving parts. It also allows background measurements because it is opaque when no RF is applied. The grating with 4 grooves/mm is a very hard to manufacture optical component, and suppliers were very difficult to find. The detector-cooler combination (working at 90K) is from Sofradir/Ricor and the model on board Venus Express is still working after 6 years in space (more on/off cycles that ON hour lifetime problem). The detector MCT mix is slightly altered for nadir observation, in order to reduce thermal background noise and the nadir channel spectrometer is cooled down to 173K by a large V-groove radiator. All the optical components have been enlarged to maximise signal throughput and the slit (that determines spatial and spectral resolution) has also been increased. The spacecraft attitude control system switches from yaw steering for nadir to inertial pointing for solar occultations. 1. Nevejans, D., E. Neefs, E. Van Ransbeeck, S. Berkenbosch, R. Clairquin, L. De Vos, W. Moelans, S. Glorieux, A. Baeke, O. Korablev, I. Vinogradov, Y. Kalinnikov, B. Bach, J.P. Dubois, and E. Villard, Compact high-resolution space-borne echelle grating spectrometer with AOTF based on

  11. Resonant ultrasound spectrometer

    DOEpatents

    Migliori, Albert; Visscher, William M.; Fisk, Zachary

    1990-01-01

    An ultrasound resonant spectrometer determines the resonant frequency spectrum of a rectangular parallelepiped sample of a high dissipation material over an expected resonant response frequency range. A sample holder structure grips corners of the sample between piezoelectric drive and receive transducers. Each transducer is mounted on a membrane for only weakly coupling the transducer to the holder structure and operatively contacts a material effective to remove system resonant responses at the transducer from the expected response range. i.e., either a material such as diamond to move the response frequencies above the range or a damping powder to preclude response within the range. A square-law detector amplifier receives the response signal and retransmits the signal on an isolated shield of connecting cabling to remove cabling capacitive effects. The amplifier also provides a substantially frequency independently voltage divider with the receive transducer. The spectrometer is extremely sensitive to enable low amplitude resonance to be detected for use in calculating the elastic constants of the high dissipation sample.

  12. Measurements of stratospheric composition using a star pointing spectrometer

    NASA Technical Reports Server (NTRS)

    Fish, Deb J.; Jones, Rod L.; Freshwater, Ray A.; Roscoe, Howard K.; Oldham, Derek J.

    1994-01-01

    Measurements of stratospheric composition have been made with a novel star-pointing spectrometer. The instrument consists of a telescope that focuses light from stars, planets, or the moon onto a spectrometer and two dimensional CCD array detector. Atmospheric absorptions can be measured, from which atmospheric columns of several gases can be determined. The instrument was deployed in Abisko, 69 deg N, during the European Arctic Stratospheric Ozone Experiment (EASOE). The instrument has the potential for measuring O3, OClO, NO2, and NO3. In this paper, a method for the retrieval of vertical columns is described, and some examples of ozone measurements given.

  13. Chip scale broadly tunable laser for laser spectrometer

    NASA Astrophysics Data System (ADS)

    Chao, Tien-Hsin; Lu, Thomas; Davis, Scott R.; Anderson, Michael H.

    2016-04-01

    We are developing an innovative Tunable Laser Spectrometer (TLS) that is compact, broad tuning range (> 200 nm) enabled by an innovative chip-scale (a waveguide based architecture), non-mechanical (voltage- controlled tuning), Waveguide External-cavity Semiconductor Laser (WECSL). This WECSL based TLS, with broad tuning range, will enable the simultaneous measurement of multiple gases abundances in Martian and other planetary atmospheres, adsorbed to soil; and bound to rocks. This monolithic, robust, integrated-optic Tunable Laser Absorption Spectrometer (TLS) will operate in the near infrared and infrared spectral bands. The system architecture, principles of operation and applications of the TLS will be reported in this paper.

  14. Investigation of the formaldehyde differential absorption cross section at high and low spectral resolution in the simulation chamber SAPHIR

    NASA Astrophysics Data System (ADS)

    Brauers, T.; Bossmeyer, J.; Dorn, H.-P.; Schlosser, E.; Tillmann, R.; Wegener, R.; Wahner, A.

    2007-07-01

    The results from a simulation chamber study on the formaldehyde (HCHO) absorption cross section in the UV spectral region are presented. We performed 4 experiments at ambient HCHO concentrations with simultaneous measurements of two DOAS instruments in the atmosphere simulation chamber SAPHIR in Jülich. The two instruments differ in their spectral resolution, one working at 0.2 nm (broad-band, BB-DOAS), the other at 2.7 pm (high-resolution, HR-DOAS). Both instruments use dedicated multi reflection cells to achieve long light path lengths of 960 m and 2240 m, respectively, inside the chamber. During two experiments HCHO was injected into the clean chamber by thermolysis of well defined amounts of para-formaldehyde reaching mixing rations of 30 ppbV at maximum. The HCHO concentration calculated from the injection and the chamber volume agrees with the BB-DOAS measured value when the absorption cross section of Meller and Moortgat (2000) and the temperature coefficient of Cantrell (1990) were used for data evaluation. In two further experiments we produced HCHO in-situ from the ozone + ethene reaction which was intended to provide an independent way of HCHO calibration through the measurements of ozone and ethene. However, we found an unexpected deviation from the current understanding of the ozone + ethene reaction when CO was added to suppress possible oxidation of ethene by OH radicals. The reaction of the Criegee intermediate with CO could be 240 times slower than currently assumed. Based on the BB-DOAS measurements we could deduce a high-resolution cross section for HCHO which was not measured directly so far.

  15. Fourier Transform Spectrometer

    NASA Technical Reports Server (NTRS)

    1998-01-01

    The FTS is a compact interferometer with the capability to passively sense the Earth's surface and atmosperic radiation emissions and absorptions. It's a powerful, yet highly versatile instrument, being developed by technologists at NASA Langley Research Center, in partnership with other NASA centers, universities and industry.Using advanced materials, the FTS will be more compact and much lighter than current interferometers.

  16. Airborne DOAS observations of tropospheric NO2 using an UltraLight Trike and flux calculation

    NASA Astrophysics Data System (ADS)

    Constantin, Daniel-Eduard; Voiculescu, Mirela; Merlaud, Alexis; Dragomir, Carmelia; Georgescu, Lucian; Hendrick, Francois; Van Roozendael, Michel

    2016-04-01

    In this paper we present airborne DOAS observations of tropospheric NO2 using an Ultralight Trike (ULT) and associated flux calculation. The instrument onboard the ULT was developed for measuring the tropospheric NO2 Vertical Column Density (VCD). Measurements were performed for several days during 2011-2014, in a region SE of Romania, over the cities of Galati (45.43°N, 28.03°E) and Braila (45.26°N, 27.95°E). Measurements of the NO2 column in the same area were performed using car-DOAS observations. The correlation between the tropospheric NO2 VCD from airborne and mobile ground-based DOAS observations was used to validate the airborne observations. A specific AMF for each case was calculated using the radiative transfer model (RTM) UVspec/DISORT. We present also a comparison between SCDstrato derived from DOMINO (Dutch OMI NO2) and the SCDstrato obtained from ground and airborne measurements. Due to the mobility and flexibility of the ULT flights, this aerial platform provides a promising tool for satellite validation, especially for space observations by high resolution sensors such as the future TROPOMI instrument. A key added value of the ULT-DOAS, illustrated in this work, is the capacity to investigate the spatial variability of NO2 inside the horizontal extent of satellite pixels, e.g. above plant exhaust plumes.

  17. Extended reactance domain algorithms for DoA estimation onto an ESPAR antennas

    NASA Astrophysics Data System (ADS)

    Harabi, F.; Akkar, S.; Gharsallah, A.

    2016-07-01

    Based on an extended reactance domain (RD) covariance matrix, this article proposes new alternatives for directions of arrival (DoAs) estimation of narrowband sources through an electronically steerable parasitic array radiator (ESPAR) antennas. Because of the centro symmetry of the classic ESPAR antennas, an unitary transformation is applied to the collected data that allow an important reduction in both computational cost and processing time and, also, an enhancement of the resolution capabilities of the proposed algorithms. Moreover, this article proposes a new approach for eigenvalues estimation through only some linear operations. The developed DoAs estimation algorithms based on this new approach has illustrated a good behaviour with less calculation cost and processing time as compared to other schemes based on the classic eigenvalues approach. The conducted simulations demonstrate that high-precision and high-resolution DoAs estimation can be reached especially in very closely sources situation and low sources power as compared to the RD-MUSIC algorithm and the RD-PM algorithm. The asymptotic behaviours of the proposed DoAs estimators are analysed in various scenarios and compared with the Cramer-Rao bound (CRB). The conducted simulations testify the high-resolution of the developed algorithms and prove the efficiently of the proposed approach.

  18. SCIAMACHY WFM-DOAS XCO2: reduction of scattering related errors

    NASA Astrophysics Data System (ADS)

    Heymann, J.; Bovensmann, H.; Buchwitz, M.; Burrows, J. P.; Deutscher, N. M.; Notholt, J.; Rettinger, M.; Reuter, M.; Schneising, O.; Sussmann, R.; Warneke, T.

    2012-10-01

    Global observations of column-averaged dry air mole fractions of carbon dioxide (CO2), denoted by XCO2 , retrieved from SCIAMACHY on-board ENVISAT can provide important and missing global information on the distribution and magnitude of regional CO2 surface fluxes. This application has challenging precision and accuracy requirements. In a previous publication (Heymann et al., 2012), it has been shown by analysing seven years of SCIAMACHY WFM-DOAS XCO2 (WFMDv2.1) that unaccounted thin cirrus clouds can result in significant errors. In order to enhance the quality of the SCIAMACHY XCO2 data product, we have developed a new version of the retrieval algorithm (WFMDv2.2), which is described in this manuscript. It is based on an improved cloud filtering and correction method using the 1.4 μm strong water vapour absorption and 0.76 μm O2-A bands. The new algorithm has been used to generate a SCIAMACHY XCO2 data set covering the years 2003-2009. The new XCO2 data set has been validated using ground-based observations from the Total Carbon Column Observing Network (TCCON). The validation shows a significant improvement of the new product (v2.2) in comparison to the previous product (v2.1). For example, the standard deviation of the difference to TCCON at Darwin, Australia, has been reduced from 4 ppm to 2 ppm. The monthly regional-scale scatter of the data (defined as the mean intra-monthly standard deviation of all quality filtered XCO2 retrievals within a radius of 350 km around various locations) has also been reduced, typically by a factor of about 1.5. Overall, the validation of the new WFMDv2.2 XCO2 data product can be summarised by a single measurement precision of 3.8 ppm, an estimated regional-scale (radius of 500 km) precision of monthly averages of 1.6 ppm and an estimated regional-scale relative accuracy of 0.8 ppm. In addition to the comparison with the limited number of TCCON sites, we also present a comparison with NOAA's global CO2 modelling and

  19. SCIAMACHY WFM-DOAS XCO2: reduction of scattering related errors

    NASA Astrophysics Data System (ADS)

    Heymann, J.; Bovensmann, H.; Buchwitz, M.; Burrows, J. P.; Deutscher, N. M.; Notholt, J.; Rettinger, M.; Reuter, M.; Schneising, O.; Sussmann, R.; Warneke, T.

    2012-06-01

    Global observations of column-averaged dry air mole fractions of carbon dioxide (CO2), denoted by XCO2, retrieved from passive remote sensing instruments on Earth orbiting satellites can provide important and missing global information on the distribution and magnitude of regional CO2 surface fluxes. This application has challenging precision and accuracy requirements. SCIAMACHY on-board ENVISAT is the first satellite instrument, which measures the upwelling electromagnetic radiation in the near and short wave infrared at an adequate spectral and spatial resolution to yield near-surface sensitive XCO2. In a previous publication (Heymann et al., 2012), it has been shown by analysing seven years of SCIAMACHY WFM-DOAS XCO2 (WFMDv2.1) that unaccounted thin cirrus clouds can result in significant errors. In order to enhance the quality of the SCIAMACHY XCO2 data product, we have developed a new version of the retrieval algorithm (WFMDv2.2), which is described in this manuscript. It is based on an improved cloud filtering and correction method using the 1.4 μm strong water vapour absorption and 0.76 μm O2-A bands. The new algorithm has been used to generate a SCIAMACHY XCO2 data set covering the years 2003-2009. The new XCO2 data set has been validated using ground-based observations from the Total Carbon Column Observing Network (TCCON). The validation shows a significant improvement of the new product (v2.2) in comparison to the previous product (v2.1). For example, the standard deviation of the difference to TCCON at Darwin, Australia, has been reduced from 4 ppm to 2 ppm. The monthly regional-scale scatter of the data (defined as the mean inner monthly standard deviation of all quality filtered XCO2 retrievals within a radius of 350 km around various locations) has also been reduced, typically by a factor of about 1.5. Overall, the validation of the new WFMDv2.2 XCO2 data product can be summarised by a single measurement precision of 3.8 ppm, an estimated regional

  20. Aircraft-borne DOAS limb observations of iodine monoxide around Borneo

    NASA Astrophysics Data System (ADS)

    Großmann, Katja; Hossaini, Ryan; Mantle, Hannah; Chipperfield, Martyn; Wittrock, Folkard; Peters, Enno; Lampel, Johannes; Walker, Hannah; Heard, Dwayne; Krystofiak, Gisèle; Catoire, Valéry; Dorf, Marcel; Werner, Bodo; Pfeilsticker, Klaus

    2015-04-01

    Iodine monoxide (IO) has a major impact on the photochemistry of the troposphere. It can for example catalytically destroy ozone, influence the atmospheric oxidation capacity by changing the partitioning of the HOx and NOx species, or contribute to the formation of ultrafine particles. Information regarding the vertical distribution of IO is still sparse since only few vertical profiles of IO exist for the troposphere. Spectroscopic measurements were carried out from aboard the research aircraft DLR-Falcon during the SHIVA (Stratospheric ozone: Halogen Impacts in a Varying Atmosphere) campaign at Malaysian Borneo in November and December 2011 to study the abundance and transport of trace gases in the lower atmosphere. Sixteen research flights were performed covering legs near the surface in the marine boundary layer (MBL) as well as in the free troposphere (FT) up to an altitude of 13 km. The spectroscopic measurements were evaluated using the Differential Optical Absorption Spectroscopy (DOAS) technique in limb geometry, which supports observations of UV/visible absorbing trace gases, such as O4, BrO, IO, NO2, HCHO, CHOCHO, HONO and H2O, and altitude information was gained via the O4 scaling technique and/or full inversion. The inferred vertical profiles of IO showed mixing ratios of 0.5-1.5 ppt in the MBL, which decreased to 0.1-0.3 ppt in the FT. Occasionally, the IO observed in the FT of the marine environment coincided with elevated amounts of CO, but no IO was observed over land, neither in the boundary layer, nor in the FT. This behavior strongly indicated that the major sources for IO were organic and inorganic precursor molecules emitted from the ocean, which during daytime rapidly formed a sizable amount of IO in the MBL that was occasionally transported into the FT where efficient loss processes for IO must exist. The inferred vertical profiles of IO are compared to simulations using the global 3-D chemistry transport model TOMCAT including recent fluxes

  1. Retrieval of aerosol optical and micro-physical properties with 2D-MAX-DOAS

    NASA Astrophysics Data System (ADS)

    Ortega, Ivan; Coburn, Sean; Hostetler, Chris; Ferrare, Rich; Hair, Johnathan; Kassianov, Evgueni; Barnard, James; Berg, Larry; Schmid, Beat; Tomlinson, Jason; Hodges, Gary; Lantz, Kathy; Wagner, Thomas; Volkamer, Rainer

    2015-04-01

    Recent retrievals of 2 dimensional (2D) Multi-AXis Differential Optical Absorption Spectroscopy (2D-MAX-DOAS) have highlighted its importance in order to infer diurnal horizontal in-homogeneities around the measurement site. In this work, we expand the capabilities of 2D measurements in order to estimate simultaneously aerosol optical and micro-physical properties. Specifically, we present a retrieval method to obtain: (1) aerosol optical thickness (AOT) in the boundary layer (BL) and free troposphere (FT) and (2) the effective complex refractive index and the effective radius of the aerosol column size distribution. The retrieval method to obtain AOT is based on an iterative comparison of measured normalized radiances, oxygen collision pair (O4), and absolute Raman Scattering Probability (RSP) with the forward model calculations derived with the radiative transfer model McArtim based on defined aerosol extinction profiles. Once the aerosol load is determined we use multiple scattering phase functions and single scattering albedo (SSA) obtained with Mie calculations which then constrain the RTM to forward model solar almucantar normalized radiances. The simulated almucantar normalized radiances are then compared to the measured normalized radiances. The best-fit, determined by minimizing the root mean square, retrieves the complex refractive index, and effective radius. We apply the retrieval approach described above to measurements carried out during the 2012 intensive operation period of the Two Column Aerosol Project (TCAP) held on Cape Cod, MA, USA. Results are presented for two ideal case studies with both large and small aerosol loading and similar air mass outflow from the northeast coast of the US over the West Atlantic Ocean. The aerosol optical properties are compared with several independent instruments, including the NASA Langley airborne High Spectral Resolution Lidar (HSRL-2) for highly resolved extinction profiles during the overpasses, and with the

  2. Investigation of NO2 vertical distribution from satellite data by using two NO2 DOAS retrievals

    NASA Astrophysics Data System (ADS)

    Behrens, Lisa K.; Hilboll, Andreas; Richter, Andreas; Peters, Enno; Burrows, John P.

    2016-04-01

    NO2 is an important indicator for air pollution from anthropogenic as well as natural sources. NOx emission sources and their horizontal distribution are well known from satellite measurements. In contrast, knowledge of the vertical NO2 distribution is only limited. To address this issue we developed a new NO2 differential optical absorption spectroscopy (DOAS) retrieval in the UV spectral range for satellite observations from the GOME-2 instrument on board EUMETSAT's MetOp-A satellite. This new UV NO2 retrieval is compared to a common NO2 retrieval in the visible spectral range. Here we show that by using retrievals in the UV and visible, sensitivity to the vertical distribution of NO2 can be achieved in satellite measurements. Box air mass factor calculations show that sensitivity below 9km is clearly higher in the visible spectral range whereas above 9km, the sensitivity is somewhat higher in the UV range. Due to the higher sensitivity of the visible spectral range closer to the ground, the NO2 slant columns derived from the visible spectral range are mostly higher than in the UV spectral range. Nevertheless, our new NO2 retrieval and the common NO2 retrieval from the visible spectral range show a similar horizontal distribution. In both spectral ranges, well known NO2 signals over highly polluted areas, e.g., China or biomass burning areas like Africa south of the equator can be observed. However in some areas, NO2 signals clearly visible in the visible spectral range cannot be detected in the UV spectral range, such as in Africa north of the equator over the biomass burning regions. From the differences in NO2 slant columns, we can gain insight into the vertical distribution of NO2. By using air mass factors, slant columns can be converted into vertical columns. For air mass factor calculations, an a priori NO2 profile is needed from model simulations, here the MACC2 interim reanalysis fields. If the model simulates the NO2 profile with correct height

  3. ISS Update: Alpha Magnetic Spectrometer

    NASA Video Gallery

    NASA Public Affairs Officer Kelly Humphries interviews Trent Martin, Johnson Space Center project manager for the Alpha Magnetic Spectrometer (AMS) aboard the International Space Station. Questions...

  4. Particle extinction measured at ambient conditions with differential optical absorption spectroscopy. 2. Closure study.

    PubMed

    Müller, Thomas; Müller, Detlef; Dubois, René

    2006-04-01

    Spectral particle extinction coefficients of atmospheric aerosols were measured with, to the best of our knowledge, a newly designed differential optical absorption spectroscopy (DOAS) instrument. A closure study was carried out on the basis of optical and microphysical aerosol properties obtained from nephelometer, particle soot/absorption photometer, hygroscopic tandem differential mobility analyzer, twin differential mobility particle sizer, aerodynamic particle sizer, and Berner impactors. The data were collected at the urban site of Leipzig during a period of 10 days in March 2000. The performance test also includes a comparison of the optical properties measured with DOAS to particle optical properties calculated with a Mie-scattering code. The computations take into account dry and ambient particle conditions. Under dry particle conditions the linear regression and the correlation coefficient for particle extinction are 0.95 and 0.90, respectively. At ambient conditions these parameters are 0.89 and 0.97, respectively. An inversion algorithm was used to retrieve microphysical particle properties from the extinction coefficients measured with DOAS. We found excellent agreement within the retrieval uncertainties.

  5. UV differential optical absorption method for measuring sulf