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1.
Surface NO and NO2 mixing ratios were measured aboard the research vessel Polarstern during the mission ANT VII/1 from 24 September to 5 October 1988. The measurements were taken along the meridian at 30° W in the Atlantic region covering latitudes between 30° N and 30° S. The average mixing ratios were about 12 pptv NO/30 pptv NO2 in the Northern Hemisphere and about 7 pptv NO/22 pptv NO2 in the Southern. Elevated mixing ratios of 20 pptv NO/70 pptv NO2 were found at 12° N (probably due to air masses originating from the surface of West Africa) and in the region of the ITCZ between 8° N and 5° N. Because of probable contamination by the ship, the measured mixing ratios mostly represent upper limits.  相似文献   

2.
A latitudinal profile (30° W, from 30° N to 30° S) of mixing ratios of nitric acid and particulate nitrate was determined on the Atlantic Ocean during the Polarstern cruise ANT VII/1 from Bremerhaven, Germany, to Rio Grande, Brazil. The detection of HNO3 was performed simultaneously by laser-photolysis fragment-fluorescence (LPFF) and by nylon filter packs. The detection limit was about 30 pptv for a signal accumulation time of 1 h for LPFF and about 5 pptv for the filters at a collection time of 4 h. In general, the mixing ratios of HNO3 in the Northern Hemisphere were found to be significantly higher than those in the Southern Hemisphere. The Atlantic background concentrations frequently varied between 80 pptv and the detection limit. Larger deviations from this trend were found for the more northern latitudes and for episodes like crossings of exhaust plumes from ships or from continental pollutions sources.  相似文献   

3.
In summer, atmospheric ozone was measured from an aircraft platform simultaneously with nitric oxide (NO), oxides of nitrogen (NO y ), and water vapor over the Pacific Ocean in east Asia from 34° N to 19° N along the longitude of 138±3°E. NO y was measured with the aid of a ferrous sulfate converter. The altitude covered was from 0.5 to 5 km. A good correlation in the smoothed meridional distributions between ozone and NO y was seen. In particular, north of 25° N, ozone and NO y mixing ratios were considerably higher than those observed in tropical marine air south of 25° N. NO y and O3 reached a minimum of 50 pptv and 4 ppbv respectively in the boundary layer at a latitude of 20° N. The NO concentration between 2 and 5 km at the same latitude was 30 pptv. The profiles of ozone and water vapor mixing ratios were highly anti-correlated between 25° N and 20° N. In contrast, it was much poorer at the latitude of 33° N, suggesting a net photochemical production of ozone there.  相似文献   

4.
Hydrogen peroxide, one of the key compounds in multiphase atmospheric chemistry, was measured on an Atlantic cruise (ANT VII/1) of the German research vessel Polarstern from 15 September to 9 October 1988, in rain and ambient air by a chemiluminescence technique. For gas phase H2O2 cryogenic sampling was employed. The presented results show an increase of gas-phase mixing ratios of about 45 pptv per degree latitude between 50° N and 0°, and a maximum of 3.5 ppbv around the equator. Generally higher mixing ratios were observed in the Southern Hemisphere, with a clear diurnal variation. The H2O2 mixing ratio is correlated to the UV radiation intensity and to the temperature difference between air and ocean surface water.  相似文献   

5.
Measurements of the concentrations of carbonyl sulfide (COS) in the marine atmosphere were made over a period of two years in the southern Indian Ocean (Amsterdam Island, 37°50 S–77°31 E; March 1987–February 1988 and April 1989–February 1990). The mean atmospheric COS concentration for the whole period was 475±48 pptv (n=544). Atmospheric COS concentrations show no significant seasonal variation with a summer to winter ratio of 1.05. Taking into account the observed variability of the atmospheric COS concentration (10%), a value of 1.4 yr is estimated as a lower limit for the atmospheric COS lifetime. A comparison of the COS data at Amsterdam Island with those obtained in the Southern Hemisphere in the past 12 yr does not reveal any significant trend in the tropospheric background COS mixing ratio.  相似文献   

6.
Measurements of NOx (NO +NO2) and the sum of reactive nitrogenconstituents, NOy, were made near the surface atAlert (82.5°N), Canada during March and April1998. In early March when solar insolation was absentor very low, NOx mixing ratios were frequentlynear zero. After polar sunrise when the sun was abovethe horizon for much or all of the day a diurnalvariation in NOx and NOy was observed withamplitudes as large as 30–40 pptv. The source ofactive nitrogen is attributed to release from the snowsurface by a process that is apparently sensitized bysunlight. If the source from the snowpack is a largescale feature of the Arctic then the diurnal trendsalso require a competing process for removal to thesurface. From the diurnal change in the NO/NO2ratio, mid-April mixing ratios for the sum of peroxyand halogen oxide radicals of 10 pptv werederived for periods when ozone mixing ratios were inthe normal range of 30–50 ppbv. Mid-day ozoneproduction and loss rates with the active nitrogensource were estimated to be 1–2 ppbv/day and in nearbalance. NOy mixing ratios which averaged only295±66 pptv do not support a large accumulation inthe high Arctic surface layer in the winter and springof 1998. The small abundance of NOy relative tothe elevated mixing ratios of other long-livedanthropogenic constituents requires that reactivenitrogen be removed to the surface during transport toor during residence within the high Arctic.  相似文献   

7.
Simultaneousindependent measurements of NOy and NOx(NOx= NO + NO2) by high-sensitivitychemiluminescence systems and of PAN (peroxyacetylnitrate) and PPN (peroxypropionyl nitrate) by GC-ECDwere made at Spitsbergen in the Norwegian Arcticduring the first half year of 1994. The average mixingratio of the sum of PAN and PPN (denoted PANs)increased from around 150 pptv in early winter to amaximum of around 500 pptv in late March, whereasepisodic peak values reached 800 pptv. This occurredsimultaneously with a maximum in ozone which increasedto 45–50 ppbv in March–April. The average NOxmixing ratio was 27 pptv and did not show any cyclethrough the period. The NOy mixing ratio showeda maximum in late March, while the difference betweenNOy and PAN decreased during spring. This is anindication of the dominance of PAN in the NOybudget in the Arctic, but possible changes in theefficiency of the NOy converter could alsocontribute to this. Although most PAN in theArctic is believed to be due to long range transport,the observations indicate local loss and formationrates of up to 1–2 pptv h-1 in April–May.Measurements of carbonyl compounds suggest thatacetaldehyde was the dominant, local precursor ofPAN.Now at 1.  相似文献   

8.
Shipboard measurements of atmospheric dimethyl sulfide were made during two transects along the east coast of the United States and at several stations in the Gulf of Maine. Limited measurements of carbon disulfide and hydrogen sulfide are also reported. The mean DMS mixing ratio was 29 pptv (=25, n=84, median 19 pptv) during the Atlantic transects, and 101 pptv (=67, n=77, median 79 pptv) in the Gulf of Maine. Distinct diurnal variations were found in the DMS data from the transects. The meteorology of the study area appears to control day-to-day differences in the magnitude of these diurnal variations, although rapid daytime oxidation is suggested in some cases. Diurnal variations were also evident in near-shore stations in the Gulf of Maine due to nocturnal boundary-layer inversion. Diurnal variation was not evident at other sites in the Gulf due to large scale changes in the atmospheric circulation pattern, which effectively masked any effects due to oxidation processes. Model simulations confirm that the DMS levels and diurnal variation found during the transects are not consistent with atmospheric oxidation processes alone. Atmospheric CS2 and H2S mixing ratios were less than 3 pptv during the transects, except for a single period of higher CS2 mixing ratios (reaching 11 pptv) during advection of continental air. Calculations of the flux of oceanic sulfur to the eastern United States show that the contribution of natural sulfur to the North American sulfur budget is small compared to anthropogenic sources.  相似文献   

9.
Springtime measurements of NOx, ozone, PAN,J(NO2), and other compounds were made near Ny-Ålesund,Svalbard (78°54N, 11°53E), in 1994 and Poker Flat,Alaska (65°08N, 147°29W), in 1995. At Svalbard medianmixing ratios for PAN and NOx of 237 and 23.7 pptv,respectively, were observed. The median mixing ratios at Poker Flat for PANand NOx were 79.5 and 85.9 pptv, respectively. These data areused to estimate thermal PAN decomposition using several differentapproaches. At Svalbard PAN decomposition was very small, while at PokerFlat up to 30 pptv/h PAN decomposed. At both sites the NOx/PANratio increased with temperature between –10 and 20°C implyingthat PAN decomposition is an important NOx source. In-situozone production was calculated from the measured NO, NO2,O3, J(NO2), and temperature data, using thesteady state assumption Median ozone production was 605 pptv/h at PokerFlat, and one order of magnitude smaller at Svalbard during the daytime.Only at Poker Flat could a direct influence on the diurnal ozone cycle beobserved from in-situ production. These results imply that PAN decompositionis a major source of NOx in the high latitude troposphere, andthat this contributes to the observed spring maximum in surface ozone.  相似文献   

10.
Aircraft observations of oxides of nitrogen (NO y ), measured with a ferrous sulfate converter, over the sea surrounding the Japanese islands (30–43° N, 131–141° E) were carried out in the winter of 1983 and 1984 at altitudes mostly between 3 and 8 km. NO y defined here is the sum of NO, NO2, and other unstable oxides of nitrogen that are converted to NO by ferrous sulfate. The main observations were:
  1. Over the Pacific Ocean between the latitudes of 30–35° N, the observed NO y mixing ratio between 3 and 8 km was a fairly constant 200 pptv. The NO mixing ratio increased with altitude from 15 pptv at 3 km to 35 pptv at 7 km.
  2. Over the Sea of Japan, tropospheric NO y mesured between 1 and 6 km started increasing with latitude North of 35° N and reached about 1000 pptv at 40° N.
  3. NO y was measured in an air mass transported from the stratosphere near a tropopause fold region. When the ozone mixing ratio was between 80 and 140 ppbv, the NO y mixing ratio was about 200 pptv.
  相似文献   

11.
In 1978–1980 nine aircraft flights to an altitude of up to 15 km were made over western Europe. Sulfur dioxide was measured with a sensitive chemiluminescence method consisting of separate sampling and analysis stages and application of a wet chemical filter procedure (detection limit: 8 pptv SO2).The measurements performed in the upper troposphere and lower stratosphere lead to some unexpected results: (a) the meteorological conditions at the tropopause level have an important influence on the observed SO2 mixing ratio; (b) between the 500 mb and the actual tropopause level the SO2 mixing ratio is found to be <100 pptv, and weak vertical gradients of SO2 suggest only a small flux of tropospheric SO2 into the stratosphere; (c) increasing SO2 mixing ratios within the first kilometers of the stratosphere give strong support to a stratospheric source of SO2.In the light of improved one-dimensional models considering the vertical distribution of stratospheric sulfur compounds (Crutzen, 1981; Turco et al. 1981) it can be shown that the oxidation of organic sulfur compounds (e.g., OCS, CS2) seems to be a stratospheric source of SO2. Furthermore, the flux calculations based on the SO2 mixing ratios measured at the tropopause level indicate that the contribution of tropospheric (man-made) SO2 to the stratospheric aerosol layer is of only minor importance.  相似文献   

12.
Local ozone production and loss rates for the arctic free troposphere (58–85° N, 1–6 km, February–May) during the TroposphericOzone Production about the Spring Equinox (TOPSE) campaign were calculated using a constrained photochemical box model. Estimates were made to assess the importance of local photochemical ozone production relative to transport in accounting for the springtime maximum in arctic free tropospheric ozone. Ozone production and loss rates from our diel steady-state box model constrained by median observations were first compared to two point box models, one run to instantaneous steady-state and the other run to diel steady-state. A consistent picture of local ozone photochemistry was derived by all three box models suggesting that differences between the approaches were not critical. Our model-derived ozone production rates increased by a factor of 28 in the 1–3 km layer and a factor of 7 in the 3–6 kmlayer between February and May. The arctic ozone budget required net import of ozone into the arctic free troposphere throughout the campaign; however, the transport term exceeded the photochemical production only in the lower free troposphere (1–3 km) between February and March. Gross ozone production rates were calculated to increase linearly with NOx mixing ratiosup to 300 pptv in February and for NOx mixing ratios up to 500 pptv in May. These NOx limits are an order of magnitude higher thanmedian NOx levels observed, illustrating the strong dependence ofgross ozone production rates on NOx mixing ratios for the majority of theobservations. The threshold NOx mixing ratio needed for netpositive ozone production was also calculated to increase from NOx 10pptv in February to 25 pptv in May, suggesting that the NOx levels needed to sustain net ozone production are lower in winter than spring. This lower NOx threshold explains how wintertime photochemical ozone production can impact the build-up of ozone over winter and early spring. There is also an altitude dependence as the threshold NOx neededto produce net ozone shifts to higher values at lower altitudes. This partly explains the calculation of net ozone destruction for the 1–3 km layerand net ozone production for the 3–6 km layer throughout the campaign.  相似文献   

13.
Simultaneous shipboard measurements of atmospheric dimethylsulfide and hydrogen sulfide were made on three cruises in the Gulf of Mexico and the Caribbean. The cruise tracks include both oligotrophic and coastal waters and the air masses sampled include both remote marine air and air masses heavily influenced by terrestrial or coastal inputs. Using samples from two north-south Caribbean transects which are thought to represent remote subtropical Atlantic air, mean concentrations of DMS and H2S were found to be 57 pptv (74 ng S m-3, =29 pptv, n=48) and 8.5 pptv (11 ng S m-3, =5.3 pptv, n=36), respectively. The ranges of measured concentrations for all samples were 0–800 pptv DMS and 0–260 pptv H2S. Elevated concentrations were found in coastal regions and over some shallow waters. Statistical analysis reveals slight nighttime maxima in the concentrations of both DMS and H2S in the remote marine atmosphere. The diurnal nature of the H2S data is only apparent after correcting the measurements for interference due to carbonyl sulfide. Calculations using the measured ratio of H2S to DMS in remote marine air suggest that the oxidation of H2S contributes only about 11% to the excess (non-seasalt) sulfate in the marine boundary layer.  相似文献   

14.
A series of 149 measurements of the HCHO mixing ratio were made between 0 and 10 km altitude and 70° N to 60° S latitude during TROPOZ II. The data show a vertical decrease of the HCHO mixing ratio with altitude at all latitudes and a broad latitudinal maximum in the HCHO mixing ratio between 30° N and 30° S at all altitudes. The measured mixing ratios of HCHO are considerably higher than those expected from CH4 oxidation alone, but agree broadly with the average latitude by altitude distribution of HCHO derived by a 2D model including emissions of C1–C7 hydrocarbons. A number of the regional scale deviations of the measured HCHO distribution from the average modelled one can be explained in terms of the local wind field.  相似文献   

15.
The set of high-resolution infrared solar observations made with the Atmospheric Trace Molecule Spectroscopy (ATMOS)-Fourier transform spectrometer from onboard Spacelab 3 (30 April-1 May 1985) has been used to evaluate the total budgets of the odd chlorine and fluorine chemical families in the stratosphere. These budgets are based on volume mixing ratio profiles measured for HCl, HF, CH3Cl, ClONO2, CCl4, CCl2F2, CCl3F, CHClF2, CF4, COF2, and SF6 near 30° north latitude. When including realistic concentrations for species not measured by ATMOS, i.e., the source gases CH3CCl3 and C2F3Cl3 below 25 km, and the reservoirs ClO, HOCl and COFCl between 15 and 40 km (five gases actually measured by other techniques), the 30° N zonal 1985 mean total mixing ratio of chlorine, Cl, was found to be equal to (2.58±0.10) ppbv (parts per billion by volume) throughout the stratosphere, with no significant decrease near the stratopause. The results for total fluorine indicate a slight, but steady, decrease of its volume mixing ratio with increasing altitude, around a mean stratospheric value of (1.15±0.12) ppbv. Both uncertainties correspond to one standard deviation. These mean springtime 1985 stratospheric budgets are commensurate with values reported for the tropospheric Cl and F concentrations in the early 1980s, when allowance is made for the growth rates of their source gases at the ground and the time required for tropospheric air to be transported into the stratosphere. The results are discussed with emphasis on conservation of fluorine and chlorine and the partitioning among source, sink, and reservoir gases throughout the stratosphere.  相似文献   

16.
The atmospheric concentration of peroxyacetylnitrate (PAN) was measured during a cruise of the R.S. Polarstern from Bremerhaven (Germany) to Rio Grande do Sul (Brazil) in September/ October 1988. The measurements were made in-situ by a combination of electron capture gaschromatography with a cryogenic preconcentration step. The theoretical lower limit of detection (3) was 0.4 ppt. The mixing ratios of PAN varied by more than three orders of magnitude from 2000 ppt in the English Channel to less than 0.4 ppt south of the Azores (38° N). South of 35° N, PAN levels were below the detection limit, except at 30–31° S off the eastern coast of South America. Here, PAN mixing ratios of 10 to 100 ppt were detected in continentally influenced air masses. Detectable levels of PAN were mostly observed in air masses of continental or high northern origin. Changes in the wind directions were usually associated with substantial changes in the PAN mixing ratios.  相似文献   

17.
Atmospheric hydroxyl (OH), hydroperoxy (HO2), total peroxy (HO2 and organic peroxy radicals, RO2) mixing ratios and OH reactivity (first order OH loss rate) were measured at a rural site in central Pennsylvania during May and June 2002. OH and HO2 mixing ratios were measured with laser induced fluorescence (LIF); HO2 + RO2 mixing ratios were measured with chemical ionization mass spectrometry (CIMS). The daytime maximum mixing ratios were up to 0.6 parts per trillion by volume (pptv) for OH, 30 pptv for HO2, and 45 pptv for HO2 + RO2. A parameterized RACM (Regional Atmospheric Chemistry Mechanism) box model was used to predict steady state OH, HO2 and HO2 + RO2 concentrations by constraining the model to the measured OH reactivity and previously measured volatile organic compound (VOC) distributions. The averaged model calculations are generally in good agreement with the observations. For OH, the model matched the observations for day and night, with an average observed-to-modeled ratio of 0.80. In previous studies such as PROPHET98, nighttime NO was near 0 pptv and observed nighttime OH was significantly larger than modeled OH. In this study, nighttime observed and modeled OH agree to within measurement and model uncertainties because the main source of the nighttime OH was the reaction HO2 + NO → OH + NO2, with the NO being continually emitted from the surrounding fertilized corn field. The observed-to-modeled ratio for HO2 is 1.0 on average, although daytime HO2 is underpredicted by a factor of 1.2 and nighttime HO2 is over-predicted by a factor of ∼2. The average measured and modeled HO2 + RO2 agree well during daytime, but the modeled value is about twice the measured value during nighttime. While measured HO2 + RO2 values agree with modeled values for NO mixing ratios less than a few parts per billion by volume (ppbv), it increases substantially above the expected value for NO greater than a few ppbv. This observation of the higher-than-expected HO2 + RO2 with the CIMS technique confirms the observed increase of HO2 above expected values at higher NO mixing ratios in HO2 measurements with the LIF technique. The maximum instantaneous O3 production rate calculated from HO2 and RO2 reactions with NO was as high as 10–15 ppb h−1 at midday; the total daily O3 production varied from 13 to 113 ppbv d−1 and was 48 ppbv d−1 on average during this campaign.  相似文献   

18.
Measurements of formaldehyde (HCHO) were made at the Cape Verde Atmospheric Observatory between November 2006 and June 2007 using the Long-Path Differential Optical Absorption Spectroscopy (LP-DOAS) technique. Observations show that typical HCHO mixing ratios ranged between 350 and 550 pptv (with typical 2-σ uncertainties of ~110 pptv), with several events of high HCHO, the maximum being 1,885?±?149 pptv. The observations indicate a lack of strong seasonal or diurnal variations, within the uncertainty of the measurements. A box model is employed to test whether the observations can be explained using known hydrocarbon photochemistry; the model replicates well the typical diurnal profile and monthly mean values. The model results indicate that on average 20% of HO2 production and 10% of OH destruction can be attributed to the mean HCHO levels, suggesting that even at these low average mixing ratios HCHO plays an important role in determining the HOx (HO2+OH) balance of the remote marine boundary layer.  相似文献   

19.
Simultaneous observations of several chlorine source gases, as well asHCl and ClO, have been performed in the Arctic stratosphere on 1 and 9February 1994, using balloon-borne instrumentation as a contribution toSESAME (Second European Stratospheric Arctic and Mid latitude Experiment).The observed mixing ratios of HCl and N2O show a clearanticorrelation. No severe loss of HCl was observed inside the vortex duringour measurement. These measurements showed that during this period at 20 kmand above, HCl was either in excess, or at least as abundant, asClONO2 and comprised between 50 and 70% of theavailable chlorine, Cly. On 1 February, measurements were madeinside the polar vortex. The air mass sampled on this day showed a clearsignature of diabatic descent, and also enhanced levels of ClO with amaximum of 230 pptv at 22.5 km. A 10 day backward trajectory analysis showedthat these air masses had passed a large region of low temperatures a fewhours prior to the measurement. Temperatures along the back trajectory atthe 475 K and 550 K levels (20.1 and 23.7 km respectively) were cold enoughfor heterogeneous chlorine activation to occur, in agreement with theobserved elevated ClO mixing ratios.  相似文献   

20.
Aerological observations carried out on board ORV Sagarkanya at a stationary location (20° N, 89° E) over the Head Bay of Bengal during August 18–21, 1990 were analysed to study the thermodynamic structure of the marine boundary layer in relation to a monsoon depression which formedin situ with its centre at 20° N, 88° E. The q(mixing ratio) reversal observed at 850 hPa prior to formation of the low pressure area shifted to a higher level (h<700 hPa) with the formtion of the low. Positive buoyancy below 850 hPa prior to the formation of the low indicated conditions favourable for deep convection. When the low pressure area intensified into a depression, negative buoyancy was observed at lower levels.  相似文献   

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