Engineering Papers⌕ Search

Engineering topics

Crutzen, P. J.

Publications and source records attributed to Crutzen, P. J..

At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2014

Global and Regional Impacts of HONO on the Chemical Composition of Clouds and Aerosols

Recently, realistic simulation of nitrous acid (HONO) based on the HONO / NOx ratio of 0.02 was found to have a significant impact on the global budgets of HOx (OH + HO2) and gas phase oxidation products in polluted regions, especially in winter when other photolytic sources are of minor importance. It has been reported that chemistry-transport models underestimate sulphate concentrations, mostly during winter. Here we show that simulating realistic HONO levels can significantly enhance aerosol sulphate (S(VI)) due to the increased formation of H2SO4. Even though in-cloud aqueous phase oxidation of dissolved SO2 (S(IV)) is the main source of S(VI), it appears that HONO related enhancement of H2O2 does not significantly affect sulphate because of the predominantly S(IV) limited conditions, except over eastern Asia. Nitrate is also increased via enhanced gaseous HNO3 formation and N2O5 hydrolysis on aerosol particles. Ammonium nitrate is enhanced in ammonia-rich regions but not under ammonia-limited conditions. Furthermore, particle number concentrations are also higher, accompanied by the transfer from hydrophobic to hydrophilic aerosol modes. This implies a significant impact on the particle lifetime and cloud nucleating properties. The HONO induced enhancements of all species studied are relatively strong in winter though negligible in summer. Simulating realistic HONO levels is found to improve the model measurement agreement of sulphate aerosols, most apparent over the US. Our results underscore the importance of HONO for the atmospheric oxidizing capacity and corroborate the central role of cloud chemical processing in S(IV) formation

Global and regional impacts↗
NASA NTRS2014

Global and Regional Impacts of HONO on the Chemical Composition of Clouds and Aerosols

Recently, realistic simulation of nitrous acid (HONO) based on the HONO/NO(sub x) ratio of 0.02 was found to have a significant impact on the global budgets of HO(sub x) (OH + HO2) and gas phase oxidation products in polluted regions, especially in winter when other photolytic sources are of minor importance. It has been reported that chemistry-transport models underestimate sulphate concentrations, mostly during winter. Here we show that simulating realistic HONO levels can significantly enhance aerosol sulphate (S(VI)) due to the increased formation of H2SO4. Even though in-cloud aqueous phase oxidation of dissolved SO2 (S(IV)) is the main source of S(VI), it appears that HONO related enhancement of H2O2 does not significantly affect sulphate because of the predominantly S(IV) limited conditions, except over eastern Asia. Nitrate is also increased via enhanced gaseous HNO3 formation and N2O5 hydrolysis on aerosol particles. Ammonium nitrate is enhanced in ammonia-rich regions but not under ammonia-limited conditions. Furthermore, particle number concentrations are also higher, accompanied by the transfer from hydrophobic to hydrophilic aerosol modes. This implies a significant impact on the particle lifetime and cloud nucleating properties. The HONO induced enhancements of all species studied are relatively strong in winter though negligible in summer. Simulating realistic HONO levels is found to improve the model measurement agreement of sulphate aerosols, most apparent over the US. Our results underscore the importance of HONO for the atmospheric oxidizing capacity and corroborate the central role of cloud chemical processing in S(IV) formation.

HONO↗
NASA NTRS2003

Tropospheric Ozone Over a Tropical Atlantic Station in the Northern Hemisphere: Paramaribo, Surinam (6 deg N, 55 deg W)

We present an analysis of 2.5 years of weekly ozone soundings conducted at a new monitoring station in Paramaribo, Surinam (6 deg N,55 deg W). This is currently one of only three ozone sounding stations in the northern hemisphere (NH) tropics, and the only one in the equatorial Atlantic region. Paramaribo is part of the Southern Hemisphere ADditional Ozone Sounding program (SHADOZ). Due to its position close to the equator, the Inter Tropical Convergence Zone (ITCZ) passes over Paramaribo twice per year, which results in a semi-annual seasonality of many parameters including relative humidity and ozone. The dataset from Paramaribo is used to: (1) evaluate ozone variability relative to precipitation, atmospheric circulation patterns and biomass burning; (2) contrast ozone at the NH equatorial Atlantic with that at nearby southern hemisphere (SH) stations Natal (6 deg S,35 deg W) and Ascension (8 deg S,14 deg W); (3) compare the seasonality of tropospheric ozone with a satellite-derived ozone product: Tropical Tropospheric Ozone Columns from the Modified Residual method (MR-TTOC). We find that Paramaribo is a distinctly Atlantic station. Despite its position north of the equator, it resembles nearby SH stations during most of the year. Transport patterns in the lower and middle troposphere during February and March differ from SH stations, which leads to a seasonality of ozone with two maxima. MR-TTOC over Paramaribo does not match the observed seasonality of ozone due to the use of a SH ozone sonde climatology in the MR method. The Paramaribo ozone record is used to suggest an improvement for northern hemisphere MR-TTOC retrievals. We conclude that station Paramaribo shows unique features in the region, and clearly adds new information to the existing SHADOZ record.

Peters, W.↗
NASA NTRS1994

Acetone in the atmosphere: Distribution, sources, and sinks

Acetone (CH3COCH3) was found to be the dominant nonmethane organic species present in the atmosphere sampled primarily over eastern Canada (0-6 km, 35 deg-65 deg N) during ABLE3B (July to August 1990). A concentration range of 357 to 2310 ppt (= 10(exp -12) v/v) with a mean value of 1140 +/- 413 ppt was measured. Under extremely clean conditions, generally involving Arctic flows, lowest (background) mixing ratios of 550 +/- 100 ppt were present in much of the troposphere studied. Correlations between atmospheric mixing ratios of acetone and select species such as C2H2, CO, C3H8, C2Cl4 and isoprene provided important clues to its possible sources and to the causes of its atmospheric variability. Biomass burning as a source of acetone has been identified for the first time. By using atmospheric data and three-dimensional photochemical models, a global acetone source of 40-60 Tg (= 10(exp 12) g)/yr is estimated to be present. Secondary formation from the atmospheric oxidation of precursor hydrocarbons (principally propane, isobutane, and isobutene) provides the single largest source (51%). The remainder is attributable to biomass burning (26%), direct biogenic emissions (21%), and primary anthropogenic emissions (3%). Atmospheric removal of acetone is estimated to be due to photolysis (64%), reaction with OH radicals (24%), and deposition (12%). Model calculations also suggest that acetone photolysis contributed significantly to PAN formation (100-200 ppt) in the middle and upper troposphere of the sampled region and may be important globally. While the source-sink equation appears to be roughly balanced, much more atmospheric and source data, especially from the southern hemisphere, are needed to reliably quantify the atmospheric budget of acetone.

Singh, H. B.↗
NASA NTRS1992

Atmospheric measurements of peroxyacetyl nitrate and other organic nitrates at high latitudes - Possible sources and sinks

Measurements of PAN and other reactive nitrogen species during the NASA Arctic Boundary Layer Expedition (ABLE 3A) are described, their north-south and east-west gradients in the free troposphere are characterized, and the sources and sinks of PAN and NO(y) are assessed. Large concentrations of PAN and NO(y) are present in the Arctic/sub-Arctic troposphere of the Northern Hemisphere during the summer. Mixing ratios of PAN and a variety of other molecules are more abundant in the free troposphere compared to the boundary layer. Coincident PAN and O3 atmospheric structures suggest that phenomena that define PAN also define the corresponding O3 behavior. Model calculations, correlations between NO(y) and anthropogenic tracers, and the compositions of NO(y) itself suggest that the Arctic/sub-Arctic reactive nitrogen measured during ABLE 3A is predominantly of anthropogenic origin with a minor component from the stratosphere.

Singh, H. B.↗
NASA NTRS1992

Relationship of peroxyacetyl nitrate to active and total odd nitrogen at northern high latitudes - Influence of reservoir species on NO(x) and O3

The partitioning of relative nitrogen in the Arctic and the sub-Arctic troposphere based on measurements conducted during the 1988 Arctic Boundary Layer Expedition (ABLE 3A) is described. The first set of comprehensive odd nitrogen and O3 measurements from the Arctic/sub-Arctic free troposphere shows that a highly aged air mass that has persisted under very cold conditions is present. A large fraction of the odd nitrogen appears to be present in the form of reservoir species such as PAN. Significant quantities of as yet unknown reactive nitrogen species, such as complex alkyl nitrates and pernitrates, are expected to be present. Together with PAN, these nitrate and pernitrate reservoir species could control the entire NO(x) availability of the high-latitude troposphere and in turn influence the O3 photochemistry of the region. The role of PAN in influencing the O3 reservoir is shown to be important and may be responsible for the increasing O3 temporal trend observed at high latitudes.

Singh, H. B.↗
NASA NTRS1992

Relationship of peroxyacetyl nitrate to active and total odd nitrogen at northern high latitudes: influence of reservoir species on NOx and O3

Measurements of peroxyacetyl nitrate (PAN), NO, NO2, HNO3, NOy (total odd nitrogen), and O3 were made in the high-latitude troposphere over North America and Greenland (35 degrees to 82 degrees N) during the Arctic Boundary Layer Expedition (ABLE 3A) (July-August 1988) throughout 0-to 6-km altitudes. These data are analyzed to quantitatively describe the relationships between various odd nitrogen species and assess their significance to global tropospheric chemistry. In the free troposphere, PAN was as much as 25 times more abundant than NOx. PAN to NOx ratio increased with increasing altitude and latitude. PAN was found to be the single most abundant reactive nitrogen species in the free troposphere and constituted a major fraction of NOy, PAN to NOy ratios were about 0.1 in the boundary layer and increased to 0.4 in the free troposphere. A 2-D global photochemical model with C1-C3 hydrocarbon chemistry is used to compare model predictions with measured results. A sizable portion (approximately 50%) of the gaseous reactive nitrogen budget is unaccounted for, and unknown organic nitrates and pernitrates are expected to be present. Model calculations (August 1, 70 degrees N) show that a major fraction of the observed NOx (50 to 70% of median) may find its source in the available PAN reservoir. PAN and the unknown reservoir species may have the potential to control virtually the entire NOx availability of the high latitude troposphere. It is predicted that the summer NOx and O3 mixing ratios in the Arctic/sub-Arctic troposphere would be considerably lower in the absence of the ubiquitous PAN reservoir. Conversely, this PAN reservoir may be responsible for the observed temporal increase in tropospheric O3 at high latitudes.

NASA Center ARC↗
NASA NTRS1991

A two-dimensional study of ethane and propane oxidation in the troposphere

The chemistry of ethane and propane is studied using a global two-dimensional 'zonally averaged' height- and latitude-dependent tropospheric model. The purpose of the study is to derive theoretical estimates of the seasonal and latitudinal distributions of a variety of intermediate organic compounds formed by the photochemical oxidation of C2H6 and C3H8. It is shown that C2H6 and C3H8 emitted at rates of 16 Tg C2H6/a and 23 Tg C3H8/a do not affect the overall photochemistry of the troposphere significantly. Major global effects on O3 and OH concentrations are suggested to be coming from the formation of peroxyacetyl nitrate by the interactions of NOx with other hydrocarbons with strong and spatially correlated anthropogenic or natural sources at the earth's surface. It is pointed out that attention should be given to organic nitrates produced by the oxidation of NMHC other than C2H6 and C3H8.

Kanakidou, M.↗
NASA NTRS1988

Modelling the Antarctic ozone hole

Researchers performed model calculations of the ozone depletions taking place in the Antarctic lower stratosphere. Making the assumption that odd nitrogen is frozen out on stratospheric haze particles, an analysis is given of how much homogeneous reactions can contribute to ozone loss during September-October. Comparisons with observations indicate the potential importance of reactions with HCl in the polar stratospheric cloud particles.

Crutzen, P. J.↗
NASA NTRS1988

Acute effects of a large bolide impact simulated by a global atmospheric circulation model

The goal is to use a global three-dimensional atmospheric circulation model developed for studies of atmospheric effects of nuclear war to examine the time evolution of atmospheric effects from a large bolide impact. The model allows for dust and NOx injection, atmospheric transport by winds, removal by precipitation, radiative transfer effects, stratospheric ozone chemistry, and nitric acid formation and deposition on a simulated Earth having realistic geography. Researchers assume a modest 2 km-diameter impactor of the type that could have formed the 32 km-diameter impact structure found near Manson, Iowa and dated at roughly 66 Ma. Such an impact would have created on the order of 5 x 10 to the 10th power metric tons of atmospheric dust (about 0.01 g cm(-2) if spread globally) and 1 x 10 to the 37th power molecules of NO, or two orders of magnitude more stratospheric NO than might be produced in a large nuclear war. Researchers ignore potential injections of CO2 and wildfire smoke, and assume the direct heating of the atmosphere by impact ejecta on a regional scale is not large compared to absorption of solar energy by dust. Researchers assume an impact site at 45 N in the interior of present day North America.

Thompson, Starley L.↗
NASA NTRS1983

A two-dimensional photochemical model of the atmosphere. I Chlorocarbon emissions and their effect on stratospheric ozone

A two-dimensional photochemical model is used to examine changes to the ozone layer caused by emissions of CFCl3, CF2Cl2, CH3CCl3 and CCl4. The influence of a possible secular increase in tropospheric methane up to 2 percent per year was found to be small, although it acts to mask decreases in total ozone caused by the chlorocarbons. Increasing NO(x) emissions caused by industralization also tend to mask decreases in total ozone and may have caused total ozone to increase by about 1 percent. The model-calculated ozone decreases are estimated to be about 3 percent by 1980. This estimate is higher than estimates by similar models, although it is noted that CCl4 and CH3CCl3 emissions are included in the model in addition to CFCl3 and CF2Cl2. This is significant because the model indicates that CCl4 has dominated the ozone depletions so far, and knowledge of the historical emission rate of CCl4 to the atmosphere is incomplete. There remain sufficient significant disagreements between theoretical and observed concentrations and variabilities, particularly for odd nitrogen and ClO, to caution against assigning too much confidence in the calculated ozone depletion.

Gidel, L. T.↗
NASA NTRS1983

The Delta band dissociation of nitric oxide - A potential mechanism for coupling thermospheric variations to the mesosphere and stratosphere

Depletion of solar radiation at discrete wavelengths by nitric oxide has a significant impact on the dissociation rate of this gas in the delta(0, 0) and delta(1, 0) bands. Inclusion of the opacity provided by a typical NO profile reduces the dissociation rate in the upper stratosphere to 50-75 pct of that predicted when the optical depth calculation omits this contribution. A substantial fraction of the NO column abundance as measured near the stratopause resides in the lower thermosphere where correlations of NO with solar and magnetic activity are well documented. Variations in the thermospheric NO abundance therefore modulate the radiation field at the precise wavelengths absorbed by this molecule in the mesosphere and upper stratosphere. Predicted changes in the dissociation rate arising from a varying thermospheric opacity exceed 8 pct throughout the mesosphere and reach 15 pct between 65 km and 95 km.

Frederick, J. E.↗
NASA NTRS1981

The effect of particle precipitation events on the neutral and ion chemistry of the middle atmosphere. II - Odd hydrogen

A one dimensional time-dependent model of the neutral and ion chemistry of the middle atmosphere has been used to examine the production of odd hydrogen (H, OH, and HO2) during charged particle precipitation. At altitudes above about 65 km, odd hydrogen production depends on the ionization rate, and the atomic oxygen and water vapor densities. Odd hydrogen production is shown to exhibit diurnal and other time dependent variations during such an event at these altitudes, and the assumption that two odd hydrogen particles are always produced per ionization is reexamined.

Solomon, S.↗
NASA NTRS1979

Actinometric measurements and theoretical calculations of j/O3/, the rate of photolysis of ozone to O/1D/

The paper presents an experimental technique which measures j/O3-O(1-D)/, the rate of solar photolysis of ozone to singlet oxygen atoms. It is shown that a flow actinometer carries dilute O3 in N2O into direct sunlight where the O(1D) formed reacts with N2O to form NO which chemiluminescence detects, with a time resolution of about one minute. Measurements indicate a photolysis rate of 1.2 (+ or - .2) x 10 to the -5/s for a cloudless sky, 45 deg zenith angle, 0.345 cm ozone column and zero albedo. Finally, ground level results compare with theoretical calculations based on the UV actinic flux as a function of ozone column and solar zenith angle.

Dickerson, R. R.↗
NASA NTRS1979

Observational and theoretical evidence in support of a significant in-situ photochemical source of tropospheric ozone

The latitudinal and seasonal variation of ozone in the troposphere is discussed. Of particular interest is the asymmetrical behavior of this gas with respect to the two hemispheres. These asymmetries, when coupled with a diagnostic photochemical model of the troposphere, lends support to the view that ozone cannot be viewed as an inert tracer of stratospheric origin. In the calculations it is noted that it is likely that the budgets of carbon monoxide and tropospheric ozone may be quite dependent on each other and the calculations are discussed in light of the uncertainty which currently exists about representative global tropospheric background concentrations of the nitrogen oxides. In addition, the seasonal variation of excess (C-14)O2 (a stratospheric tracer) is examined and compared with the seasonal ozone variation during the same period of observations at the same location and altitudes. The distinct maxima for ozone found during the summer in the lower troposphere are not present for the (C-14)O2 data. This finding likewise suggests that photochemical processes taking place in the troposphere are an important source term for tropospheric ozone.

Fishman, J.↗