Engineering topics

Kumer, John B.

Publications and source records attributed to Kumer, John B..

6 records

NASA NTRS1999

Nitrogen Species in the Post-Pinatubo Stratosphere: Model Analysis Utilizing UARS Measurements

We present an analysis of the impact of heterogeneous chemistry on the partitioning of nitrogen species measured by the Upper Atmosphere Research Satellite (UARS) instruments. The UARS measurements utilized include N2O, HNO3, and ClONO2 from the cryogenic limb array etalon spectrometer (CLAES), version 7 (v.7), and temperature, methane, ozone, H2O, HCl, NO and NO2 from the halogen occultation experiment (HALOE), version 18. The analysis is carried out for the UARS data obtained between January 1992 and September 1994 in the 100- to 1-mbar (approx. 17-47 km) altitude range and over 10 deg latitude bins from 70 deg S to 70 deg N. The spatiotemporal evolution of aerosol surface area density (SAD) is adopted from analysis of the Stratospheric Aerosol and Gas Experiment (SAGE) II data. A diurnal steady state photochemical box model, constrained by the temperature, ozone, H2O, CH4, aerosol SAD, and columns of O2 and O3 above the point of interest, has been used as the main tool to analyze these data. Total inorganic nitrogen (NOY) is obtained by three different methods: (1) as a sum of the UARS-measured NO, NO2, HNO3, and ClONO2; (2) from the N2O-NOY correlation; and (3) from the CH4-NOY correlation. To validate our current understanding of stratospheric heterogeneous chemistry for post-Pinatubo conditions, the model-calculated monthly averaged NO(x)/NO(y) ratios and the NO, NO2, and HNO3 profiles are compared with the UARS-derived data. In general, the UARS-constrained box model captures the main features of nitrogen species partitioning in the post-Pinatubo years, such as recovery of NO(x) after the eruption, their seasonal variability and vertical profiles. However, the model underestimates the NO2 content, particularly in the 30- to 7-mbar (approx. 23-32 km) range. Comparisons of the calculated temporal behavior of the partial columns of NO2 and HNO3 and ground-based measurements at 45 deg S and 45 deg N are also presented. Our analysis indicates that ground-based and HALOE v.18 measurements of the NO2 vertical columns are consistent within the range of their uncertainties and are systematically higher (up to 50%) than the model results at midlatitudes in both hemispheres. Reasonable agreement is obtained for HNO3 columns at 45 deg S, suggesting some problems with nitrogen species partitioning in the model. Outstanding uncertainties are discussed.

Danilin, Michael Y.↗

NASA NTRS1999

Nitrogen Species in the Post-Pinatubo Stratosphere: Model Analysis Utilizing UARS Measurements

We present an analysis of the impact of heterogeneous chemistry on the partitioning of nitrogen species measured by the Upper Atmosphere Research Satellite (UARS) instruments. The UARS measurements utilized include N2O, HNO3, and ClONO2 from the cryogenic limb array etalon spectrometer (CLAES), version 7 (v.7), and temperature, methane, ozone, H2O, HCl, NO and NO2 from the halogen occultation experiment (HALOE), version 18. The analysis is carried out for the UARS data obtained between January 1992 and September 1994 in the 100-to 1-mbar (approx. 17-47 km) altitude range and over 10 degrees latitude bins from 70 S to 70 N. The spatiotemporal evolution of aerosol surface area density (SAD) is adopted from analysis of the Stratospheric Aerosol and Gas Experiment (SAGE) II data. A diurnal steady state photochemical box model, constrained by the temperature, ozone, H2O, CH4, aerosol SAD, and columns of O2 and O3 above the point of interest, has been used as the main tool to analyze these data. Total inorganic nitrogen (NOy) is obtained by three different methods: (1) as a sum of the UARS-measured NO, NO2, HNO3, and ClONO2; (2) from the N2O-NOy correlation, and (3) from the CH4-NOy correlation. To validate our current understanding of stratospheric heterogeneous chemistry for post-Pinatubo conditions, the model-calculated monthly averaged NOx/NOy ratios and the NO, NO2, and HNO3 profiles are compared with the UARS-derived data. In general, the UARS-constrained box model captures the main features of nitrogen species partitioning in the post-Pinatubo years, such as recovery of NOx after the eruption, their seasonal variability and vertical profiles. However, the model underestimates the NO2 content, particularly in the 30- to 7-mbar (approx.23-32 km) range. Comparisons of the calculated temporal behavior of the partial columns of NO2 and HNO3 and ground-based measurements at 45 S and 45 N are also presented. Our analysis indicates that ground-based and HALOE v.18 measurements of the NO2 vertical columns are consistent within the range of their uncertainties and are systematically higher (up to 50%) than the model results at midlatitudes in both hemispheres. Reasonable agreement is obtained for HNO3 columns at 45 S, suggesting some problems with nitrogen species partitioning in the model. Outstanding uncertainties are discussed.

Danilin, Michael Y.↗

NASA NTRS1992

Cryogenic limb array etalon spectrometer (CLAES) - Experiment description and initial results

The primary objective of the CLAES experiment is to measure the altitude profiles of temperature and of a series of minor and trace species important to stratospheric ozone layer photochemistry and radiative structure. Ways in which the species to be measured by CLAES are distributed among the broad categories of source, radical, and reservoir species involved in ozone production and loss are illustrated. CLAES requires high spectral resolution and high radiometric sensitivity to isolate and accurately measure weak emissions from trace species such as HCl and NO against intense backgrounds from abundant emitters such as CO2, H2O, and O3. Spectroscopy is performed by tilt scanning one of the four solid etalons between 0 and 23 deg in conjunction with one or more of the nine selectable discrete interference filters.

Roche, Aidan E.↗

NASA NTRS1991

Cryogenic Limb Array Etalon Spectrometer (CLAES) - Experiment description

The CLAES measurement concept, instrument design, and performance are presented, and the scientific capabilities and measurement modes are discussed. The CLAES experiment involves remote measurement of earth-limb emission spectra. Characteristic vibration-rotation line spectral radiances are obtained between 3.5 and 13 microns and inverted through an iterative relaxation process to yield pressure, temperature, and species mixing ratio. The UARS limb-viewing instruments, including CLAES, combined with the 57-deg orbit inclination, allow for measurements to 80-deg latitudes. CLAES requires high spectral resolution and high radiometric sensitivity to isolate and accurately measure weak emissions from trace species such as HCl and NO against intense backgrounds from abundant emitters such as CO2, H2O, and O3. Accuracy and precision of retrieved quantities, observational modes, and calibration modes are also discussed.

Roche, Aidan E.↗

NASA NTRS1989

Cryogenic Limb Array Etalon Spectrometer (CLAES) - Experiment overview

The Cryogenic Limb Array Etalon Spectrometer (CLAES) is one of a complement of instruments on the NASA Upper Atmosphere Research Satellite which is expected to study atmospheric photochemistry, energy input, and dynamics following a 1991 launch. CLAES measures stratospheric altitude profiles of temperature, pressure, O3, H2O, CH4, N2O, NO, NO2, N2O5, HNO3, ClONO2, HCl, CFC-11, and CFC-12. These data are obtained typically between 10 and 60 km, with 2.5-km vertical resolution and 500-km horizontal grid size. Coverage is obtained between latitudes 80 deg north and south, thereby providing substantial coverage of the Antarctic spring polar ozone-hole region. CLAES derives the listed geophysical parameters from measurement of earth-limb spectral emissions between 3.5 and 13 microns. Brief discussions of the measurement concept, instrument design, and performance are presented, followed by a more detailed discussion of scientific capabilities and measurement modes.

Roche, Aidan E.↗

NASA NTRS1987

Nonlocal thermodynamic equilibrium effects in stratospheric NO and implications for infrared remote sensing

It is shown that the vibrational state population of stratospheric nitric oxide (NO) could be substantially different from that expected on the basis of LTE. Deviations from LTE may arise because stratospheric NO can be photochemically produced from NO2 with several vibrational quanta. Model calculations suggest that the population of NO(v = 1) could be some 30 percent above that expected from LTE at 30 km, with smaller enhancements above and below. Substantially larger enhancements are predicted for NO(v = 2). This result is shown to have important implications for NO determination by remote sensing of IR emission. Data needed for the quantification of these effects are enumerated.

Kaye, Jack A.↗