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At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS2005

HNO3, N2O5 and CIONO2 Enhancements after the October-November 2003 Solar Proton Events

The large solar storm in October-November 2003 produced enormous amounts of high-energy protons which reached the Earth and penetrated into the middle atmosphere in the polar regions. At this time, the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) on board the Environmental Satellite (ENVISAT) was observing the atmosphere in the 6-68 km altitude range. MIPAS observed significant enhancements of the NO(y) components HNO3, N2O5 and CIONO2 in the Northern polar stratosphere after the intense solar proton events. Two distinct HNO3 enhancements were observed. An instantaneous increase of 1-2 ppbv was observed immediately after the SPEs and is attributed to gas-phase chemistry: NO2 + OH + M yields HNO3 + M, accelerated by SPE-produced excess OH. A very large second increase of 1- 5 ppbv started around 10 November and lasted until the end of December. It is attributed to NO(x) (NO+NO2) produced in the mesosphere during the major SPEs in late October/early November and then transported downwards during November and December, partially converted to N2O5 in the upper stratosphere, which finally formed HNO3 via ion cluster reactions. N2O5 was observed to increase by 0.1-0.4 ppbv 1-3 days after the major SPEs and reached down to 30 km altitude. A second, more pronounced N2O5 enhancement of up to 1.2 ppbv at 40 km appeared about 12-13 days after the major SPEs. With a delay of 1-2 days after the major SPEs CIONO2 increased by up to 0.4 ppbv (40%) at 32 km altitude. NO(y) enhancements in the Southern hemisphere were generally less pronounced.

Lopez-Puertas, M.↗
NASA NTRS1975

Laboratory studies of infrared absorption by NO2 and HNO3

Data concerning the quantitative absorption in the 11 and 22 micron region by HNO3 were obtained. Results are presented indicating the temperature dependence of these bands of HNO3 vapor. The 21.8 micron absorption bands of HNO3 vapor at 40 C are discussed along with the integrated intensity and line parameters for the 6.2 micron band of NO2.

Murcray, D. G.↗
NASA NTRS1993

CLAES observations of ClONO2 and HNO3 in the Antarctic stratosphere, between June 15 and September 17, 1992

The Cryogenic Array Etalon Spectrometer (CLAES) on the NASA Upper Atmosphere Research Satellite (UARS) began viewing the stratosphere in October 1991. This paper presents preliminary retrievals of ClONO2 and HNO3 from the CLAES measurements for selected days in June, July, August, and September of 1992 for the Southern Hemisphere. The data shows that by July 10, lower stratospheric ClONO2 and HNO3 have developed high 'collar' regions surrounding the polar vortex, and low values inside the vortex. This general structure is sustained through September 17, although the ClONO2 values inside the vortex increase significantly by this date. The data suggests that substantial sequestration of gaseous HNO3 in polar stratospheric clouds occurs in the early winter Antarctic stratosphere, accompanied by the conversion of ClONO2 to reactive chlorine through heterogeneous processes on the PSCs.

Roche, A. E.↗
NASA NTRS1994

Temperature dependent absorption cross-sections of HNO3 and N2O5

Absorption cross-sections for HNO3 and N2O5 have been measured in the wavelength region 220-450 nm, using a dual beam diode array spectrometer with a spectral resolution of 0.3 nm. The results for both compounds are in good agreement with recommended values at room temperature. However, the cross-sections of both HNO3 and N2O5 show a marked reduction with decreasing temperature in the range 295-233 K. The calculated photolysis rate of HNO3 at the low temperatures and high solar zenith angles characteristic of the polar winter and spring is significantly lower than previously estimated.

Rattigan, Oliver V.↗
NASA NTRS1994

Balloon profiles of stratospheric NO2 and HNO3 for testing the heterogeneous hydrolysis of N2O5 on sulfate aerosols

Simultaneous in situ measurements of stratospheric NO2, HNO3, HCl, and CH4 from 34 to 24 km were made in August 1992 from Palestine, Texas, using the Balloon-borne Laser In-Situ Sensor (BLISS) tunable diode laser spectrometer. Although the measurements of NO2, HNO3, and NO2/HNO3 agree well with gas-phase model calculations near 34 km where Stratospheric Aerosol and Gas Experiment (SAGE) 2 data show little sulfate aerosol, this is not true at the lower altitudes where SAGE 2 shows high aerosol loadings. At 24 km the BLISS NO2 and HNO3 measurements are 70% lower and 50% higher, respectively, than the gas phase model predictions, with a measured NO2/HNO3 ratio 5 times smaller. When the heterogeneous hydrolysis of N2O5 and ClONO2 on sulfate aerosol of surface area densities matching the SAGE 2 measurements is added to the model, good agreement with the BLISS measurements is found over the whole altitude range.

Webster, C. R.↗
NASA NTRS1998

Retrieval of HCl and HNO3 Profiles from Ground-Based FTIR Data Using SFIT2

A recently developed algorithm, SFIT2, is used to assess profile information available in ground-based FTIR measurements of HCl and HNO3 and to analyze spectra recorded at Lauder, New Zealand, and Arrival Heights, Antarctica. It is shown that the altitude range of HCI retrievals may be extended by using multiple spectral lines. A preliminary analysis of a five year record of HNO3 at Lauder shows that the Pinatubo aerosol caused a large increase of HNO3 in a layer at about 20-30 km while having little effect at lower altitude.

Connor, Brian↗
NASA NTRS1978

Stratospheric NO and HNO3 observations in the Northern Hemisphere for three seasons

NO, HNO3, and O3 levels and air temperature were measured as a function of latitude in the 18 to 21 km region of the stratosphere, and the sum of odd nitrogen, equal to NO + NO2 + HNO3, was calculated and compared with model predictions. (NO2 values were inferred from photochemical equilibrium characteristics.) The data show that NO measurements generally exhibit good agreement with model predictions for low and midlatitudes but poor agreement at high latitudes. The experimental sum of odd nitrogen mixing ratios and model predictions agree within a factor of 2-1/2 or better at both 20 and 40 deg N, and show excellent agreement for latitudinal dependence.

Loewenstein, M.↗
NASA NTRS1984

Stratospheric HNO3 quantification from line-by-line nonlinear least-squares analysis of high-resolution balloon-borne solar absorption spectra in the 870/cm region

Line parameters for the nu(5) and 2nu(9) bands and associated hot bands of HNO3 have been calculated and compared with laboratory spectra, and the results are presented. Spectral intervals near 870/cm for which best agreement was obtained are used to quantitatively analyze HNO3 absorption features in 0.02/cm resolution stratospheric solar absorption spectra.

Goldman, A.↗
NASA NTRS1985

Stratospheric H2O and HNO3 profiles derived from solar occultation measurements

Compact two-channel radiometers for solar occultation experiments have been constructed in order to measure stratospheric trace gases. The instruments can be used as filter- or correlation-type radiometers, depending on the trace gas under investigation. Within the LIMS correlative measurement program, balloon flights were performed with a payload of up to four of these two-channel radiometers. From the filter-type measurements, profiles of the trace gases H2O and HNO3 are inferred for the height region between the tropopause and the balloon float level. The data evaluation also includes a comprehensive analysis of the error sources and their effect on the accuracy of the trace gas profiles. The derived H2O and HNO3 profiles are assessed against the observations of other authors and are discussed in the light of the trace gas distributions calcualted from photochemical models.

Fischer, H.↗
NASA NTRS1986

Condensation of HNO3 and HCl in the winter polar stratospheres

Nitric acid and hydrochloric acid vapors may condense in the winter polar stratospheres. Nitric acid clouds, unlike water ice clouds, would form at the temperatures at which polar stratospheric clouds (PSCs) are observed and would have optical depths of the magnitude observed suggesting that HNO3 is a dominant component of PSCs. ClO, N2O5 and ClNO3 may react on cloud particle surfaces yielding additional HNO3, HCl, and HOCL. In the vicinity of PSCs these reactions could deplete the stratosphere of photochemically active NO(x) species. The sedimentation of PSCs may remove these materials from the stratosphere. The loss of vapor phase NO(x) might allow halogen-based chemistry to create the ozone hole.

Toon, Owen B.↗
NASA NTRS1989

In situ stratospheric measurements of HNO3 and HCl near 30 km using the balloon-borne laser in situ sensor tunable diode laser spectrometer

In situ stratospheric measurements of the concentrations of the reservoir species HNO3 and HCl made during two flights of the high-resolution (0.0005/cm) balloon-borne laser in situ sensor instrument from Palestine, Texas, are reported. A measured HNO3 volume mixing ratio of 4.3 parts per billion by volume (ppbv) at 31 km altitude is about 1 ppbv larger than previously reported measurements at 32 deg N. An HCl mixing ratio of 1.6 ppbv at 29 km is in agreement with values obtained from earlier remote sensing techniques within the experimental uncertainties. Upper limits at 31 km of 0.4 ppbv for H2O2 and 0.2 ppbv for HOCl are also derived from analyses of spectra recorded near 1252/cm.

May, R. D.↗
NASA NTRS1993

Modified HNO3 seasonality in volcanic layers of a polar ice core - Snow-pack effect or photochemical perturbation?

Changes in atmospheric HNO3 chemistry following the Laki (1783), Tambora (1815), and Katmai (1912) volcanic eruptions are presently investigated in view of a central Greenland ice core's chemical composition. Attention is given to the concentration of several cations and anions, using ion chromatography. Following the eruptions, the ratio of winter to summer depositions of NO3(-) was significantly higher than during nonvolcanic periods. While this may be due to ice pack effects, it is proposed that large concentrations of the stratospheric H2SO4 particles ejected by the volcanoes favored HNO3 removal during Arctic winter.

Laj, Paolo↗
NASA NTRS1994

Identification of the HNO3 3 nu(sub 9) - nu(sub 9) band Q branch in stratospheric solar occultation spectra

The spectroscopic identification for the HNO3 3 nu(sub 9) - nu(sub 9) band Q branch at 830.4/cm is reported based on 0.01/cm resolution solar occultation spectra of the lower stratosphere recorded by the Atmospheric Trace Molecule Spectroscopy (ATMOS) Fourier transform spectrometer and a recent analysis of this band. Least-squares fits to 0.0025/cm resolution laboratory spectra in the Q branch region indicate an integrated intensity of 0.529 x 10(exp -18)/cm/mol/sq cm at 296 K for this weak band. Stratospheric HNO3 retrievals derived from the ATMOS data are consistent with this value within its estimated uncertainty of about +/- 30%. A set of spectroscopic line parameters suitable for atmospheric studies has been generated.

Perrin, A.↗
NASA NTRS1994

HNO3 profiles obtained during the EASOE campaign

A small cryogenically cooled spectrometer system designed to obtain atmospheric emission spectra in the 7.5 micrometer to 13.0 micrometer region was flown piggyback on 9 balloon flights from ESRANGE (67.9 deg N, 21.2 deg E) during the European Arctic Stratospheric Ozone Experiment (EASOE) campaign. Initial analysis of the spectra obtained has been concentrated on obtaining HNO3 profiles for the various flights. HNO3 profiles for 17 December 1991, 9 January 1992, 22 January 1992, 5 February 1992 and 14 March 1992 are presented.

Murcray, F. J.↗
NASA NTRS2001

Participation of HNO3 CIMS Instrument in the Sage III Ozone Loss and Validation Experiment (SOLVE)

This project was part of a larger SOLVE project led by Paul Wennberg at California Institute of Technology. The work completed on this project included participating in the installation and preflight testing of a new chemical ionization mass spectrometer for measuring gas and particle phase nitric acid on the ER-2. The investigators subsequently participated in SOLVE where additional instrument improvements were made and a substantial data set was generated. The two Georgia Tech investigators that participated in this work (Fred Eisele and Dave Tanner) had previously been responsible for much of the design and construction of the ion source and mass spectrometer which would be used to measure HNO3 in SOLVE, with Caltech focusing on inlets, calibration, gas supplies/pumping computer control, and overall integration. Thus, a similar focus remained during the SOLVE measurements though all investigators worked on most if not all aspects of the instrument at some point in the mission. Some of the more interesting results from the study included measurements of nitric acid on what are thought to be 5-20 microns diameter individual particles which could supply a local mechanism for HNO3 removal, Nitric acid measurements on SOLVE were completed as a collaborative effort with a great deal of overlap between this project and the larger parent project led by Paul Wennberg. As such, the instrumentation used, its operation, and the resulting measurements are far more fully discussed in the attached report (appendix A) which describes the joint SOLVE nitric acid measurement effort.

Eisele, F. L.↗
NASA NTRS2008

Observations and Modeling of Composition of Upper Troposphere/Lower Stratosphere (UTILS): Isentropic Mixing Events and Morphology of HNO3 as Observed by HIRDLS and Comparison with Results from Global Modeling Initiative

isentropic exchange of air masses between the tropical upper troposphere and mid-latitude lowermost stratosphere (the so-called "middle world") is an important pathway for stratospheric-tropospheric exchange. A seasonal, global view of this process has been difficult to obtain, in part due to the lack of the vertical resolution in satellite observations needed to capture the laminar character of these events. Ozone observations at a resolution of about 1 km from the High Resolution Dynamic Limb Sounder (HIRDLS) on NASA's Aura satellite show instances of these intrusions. Such intrusions should also be observable in HN03 observations; however, the abundances of nitric acid could be additionally controlled by chemical processes or incorporation and removal into ice clouds. We present a systematic examination of the HIRDLS data on O3 and HNO3 to determine the seasonal and spatial characteristics of the distribution of isentropic intrusions. At the same time, we compare the observed distributions with those calculated by the Global Modeling Initiative combined tropospheric-stratospheric model, which has a vertical resolution of about I km. This Chemical Transport Model (CTM) is driven by meteorological fields obtained from the GEOS-4 system of NASA/Goddard Global Modeling and Assimilation Office (GMAO), for the Aura time period, at a vertical resolution of about 1 km. Such comparison brings out the successes and limitations of the model in representing isentropic stratospheric-tropospheric exchange, and the different processes controlling HNO3 in the UTAS.

Rodriquez, J. M.↗