摘要:

The concentration of nitrous oxide has been measured in air samples collected between 1976 and 1980 at several monitoring stations and aboard Oceanographic vessels in the major world oceans. These measurements demonstrate that the tropospheric nitrous oxide concentration is increasing at ∼0.2% per year, thus confirming earlier observations of the increase based on stored samples. The measurements also show that the concentration of nitrous oxide in the northern hemisphere is higher than in the southern hemisphere, the average difference during the sampling interval having been about 0.8 parts per billion (ppb), compared to a January 1, 1978 northern hemisphere dry air mole fraction of 300.2 ppb. The data are well represented by a simple box model which relates the tropospheric rate of increase to an exponentially increasing source function. The observed increase may be explained by combustion of fossil fuels and agricultural activity, with a total source strength of ∼11 × 1010mol/yr as of January 1, 1978. A substantial fraction of this production is explained by combustion, and agricultural production is therefore considerably less than has been previously estimated. The concentration of nitrous oxide in the preindustrial unperturbed troposphere is estimated to have been between 281 and 291 ppb, depending upon the rate of increase of the mean anthropogenic source function, and the preindustrial latitudinal distribution is estimated to have been nearly uniform. According to the model projections, the concentration of tropospheric nitrous oxide in the year 2000 will be 5 to 7% above present values. The observed rate of tropospheric increase directly affects the production of stratospheric nitric oxide, and plays a significant role in the earth's radiation balance, conservatively estimated as 10–15% of the effect due to increasing carbon d

ISSN:0148-0227    

DOI:10.1029/JC086iC08p07185

年代:1981

数据来源: WILEY

摘要:

A two‐step technique, in which the N2O/CO2ratio is measured by ultrasonic phase‐shift gas chromatography and the dry air CO2concentration is measured by nondispersive infrared analysis, has been developed for the determination of the mole fraction of nitrous oxide in dry air. The N2O concentration is given by the product of these two independent measurements and has a precision (±1 standard deviation) ranging between 0.3 and 0.5%. The absence of systematic errors has been verified by extensive standard intercomparisons and by independent cross checks of the sample extraction procedures. The results of extensive measurements by this technique, reported in a companion paper, fix the mean tropospheric dry air mole fraction of nitrous oxide in the northern hemisphere as of January 1, 1978 at 300.2±0.6 parts per billion, including systematic uncertai

ISSN:0148-0227    

DOI:10.1029/JC086iC08p07197

年代:1981

数据来源: WILEY

摘要:

We have made field measurements of methane fluxes from rice paddies, fresh water lakes, and saltwater marshes to infer estimates of the size of these sources of atmospheric methane. The rice‐paddy measurements, the first of their kind, show that the principal means of methane escape is through the plants themselves as opposed to transport across the water‐air interface via bubbles or molecular diffusion. Nitrogen‐fertilized plants release much more methane than unfertilized plants but even these measured rates are only one fourth as large as those inferred earlier by Koyama and on which all global extrapolations have been based to date. We also compare our measured methane fluxes from lakes and marshes to similar earlier data and find that extant data and flux‐measurement methods are insufficient for reliable global extrapo

ISSN:0148-0227    

DOI:10.1029/JC086iC08p07203

年代:1981

数据来源: WILEY

摘要:

A model for the photochemistry of the global troposphere constrained by observed concentrations of H2O, O3, CO, CH4, NO, NO2, and HNO3is presented. Data for NO and NO2are insufficient to define the global distribution of these gases but are nonetheless useful in limiting several of the more uncertain parameters of the model. Concentrations of OH, HO2, H2O2, NO, NO2, NO3, N2O5, HNO2, HO2NO2, CH3O2, CH3OOH, CH2O, and CH3CCl3are calculated as functions of altitude, latitude, and season. Results imply that the source for nitrogen oxides in the remote troposphere is geographically dispersed and surprisingly small, less than 107tons N yr−1. Global sources for CO and CH4are 1.5 × 109tons C yr−1and 4.5 × 108tons C yr−1, respectively. Carbon monoxide is derived from combustion of fossil fuel (15%) and oxidation of atmospheric CH4(25%), with the balance from burning of vegetation and oxidation of biospheric hydrocarbons. Production of CO in the northern hemisphere exceeds that in the southern hemisphere by about a factor of 2. Industrial and agricultural activities provide approximately half the global source of CO. Oxidation of CO and CH4provides sources of tropospheric O3similar in magnitude to loss by in situ photochemistry. Observations of CH3CCl3could offer an important check of the tropospheric model and results shown here suggest that computed concentrations of OH should be reliable within a factor of 2. A more definitive test requires better definition of release rates for CH3CCl3and improved measurements for its distribution in the atm

ISSN:0148-0227    

DOI:10.1029/JC086iC08p07210

年代:1981

数据来源: WILEY

摘要:

The two‐dimensional distributions of CO and O3in the free troposphere during July and August, 1974, are discussed. The data confirm the previous findings that both of these gases are considerably more abundant in the northern hemisphere, but the degree of the asymmetry is somewhat different from what had been reported previously, especially for CO. When examined with respect to other available data sets, the conclusion is drawn that a pronounced seasonal cycle exists for CO in both hemispheres which may be driven by the likely seasonal cycle of the OH radical. The data also indicate that CO concentrations exhibit significant variability with height in the northern hemisphere, whereas southern hemispheric concentrations are quite constant with altitude except in cases where interhemispheric exchange of air may be occurring. A discussion on the vertical and horizontal transport processes inferred from the CO and O3measurements is presented. The possible interdependence of the photochemical cycles of these two trace gases is also discusse

ISSN:0148-0227    

DOI:10.1029/JC086iC08p07255

年代:1981

数据来源: WILEY

摘要:

Stratospheric measurements of the C2H6mixing ratio up to 30 km and of the C3H8mixing ratio up to 18 km altitude are reported. The observed vertical gradient of C2H6is much weaker than that calculated from a one‐dimensional steady state model, indicating lower concentrations of atomic chlorine in the lower stratosphere than those predicted by models. From the measured C2H6profile a tentative estimate for the Cl concentration is derive

ISSN:0148-0227    

DOI:10.1029/JC086iC08p07267

年代:1981

数据来源: WILEY

摘要:

A summary of the results of 10 balloon‐borne in situ measurements of C1O in the stratosphere is presented. All observations were carried out close to local noon at 32°N latitude with solar zenith angles between 24° and 55°. The mean of nine of the observations, which for the most part fall within a well‐defined envelope, is compared with a recently calculated [C1O] distribution between 25 and 42 km at the appropriate latitude and time of day. It is found that while reasonable agreement exists in the 35‐ to 40‐km region, the ratio of calculated to observed [C1O]increases monotonically with decreasing altitude below 35 km, reaching approximately three at 25 km. The tenth observation exhibits a mixing ratio nearly an order of magnitude greater than the mean. An analysis of the relevant chemistry below 30 km is presented which indicates that the discrepancy between the observed mean and the calculated [C1O] distribution can be linked to uncertainties in the [OH]/[NO] ratio in the lower stratosphere. A comparison is made between the in situ resonance fluorescence observation reported here and the remote laser heterodyne radiometer measurements of Menzies. Finally, the fractional destruction of Ox= O3+ O(3P) by C1Ox= Cl + C1O, based on the observed mean of the in situ [C1O] and [O(3P)] midday observations, is presented for the altitude interva

ISSN:0148-0227    

DOI:10.1029/JC086iC08p07273

年代:1981

数据来源: WILEY

摘要:

The temperature and pressure dependence of line widths for theandtransitions of ClO have been determined by microwave spectroscopy. The widths for both transitions are found to be the same within experimental error. The width parameter for nitrogen broadening is 3.35±0.17 MHz/torr at 317 K and 4.44±0.23 MHz/torr at 218

ISSN:0148-0227    

DOI:10.1029/JC086iC08p07279

年代:1981

数据来源: WILEY

摘要:

A chemiluminescence analyzer was used to measure NOxmixing ratios at the west coast of Ireland. Two measurement modes allowed the determination of NO and NOx= NO + NO2. In a third mode using a molybdenum converter, higher signals were observed than was in the second mode indicating that nitrogen compounds other than NO + NO2are registered. They are denoted ‘excess NOx.’ The average NO2mixing ratio for a 3 week period was 101±87 pptv. In pure marine air masses identified by means of trajectory calculations, the NO2mixing ratios were lower and exhibited in addition a diurnal variation with nighttime values of 37±6 pptv and average values of 87±47 pptv. Possible origins of the diurnal variation are discussed. For such conditions, the NO mixing ratio generally was immeasurably small, certainly less than 10 pptv. The excess NOxis also higher during the day compared with nighttime values of about 70 pptv. Further studies are required to identify the compounds in

ISSN:0148-0227    

DOI:10.1029/JC086iC08p07283

年代:1981

数据来源: WILEY

摘要:

A fast response chemiluminescent ozone sensor was mounted in a National Center for Atmospheric Research Queen Air aircraft instrumented for air motion, temperature, and humidity measurements. The vertical flux of ozone was then obtained by the eddy correlation technique for several flights in the day‐time atmospheric boundary layer over eastern Colorado. Because of the range and mobility of the aircraft, this technique can be utilized for a wide variety of situations. For example, a flight leg over an interstate highway shows large negative fluctuations in O3due to vehicular emission of NO that are well correlated with positive temperature and vertical velocity fluctuations. On one flight the significant terms in the mean ozone concentration budget (and also, for comparison, the sensible heat and humidity budgets) were evaluated from the airplane measurements. For this flight, which occurred under clear skies over range and cropland about 100 km northeast of Denver, the time rate of change of ozone density in the lower half of the boundary layer was about 2.4 ng m−3s−1. This was several times larger than the contributions by horizontal advection and the divergence of the vertical eddy flux of ozone. Thus, most of the observed increase in ozone concentration must have been the result of internal photochemical production of ozone. This may be the first well‐documented example where the rate of O3increase with time is shown to be balanced by photochemical production of O3. The deposition velocity of ozone for this case was about 0.47

ISSN:0148-0227    

DOI:10.1029/JC086iC08p07291

年代:1981

数据来源: WILEY