摘要:

Two techniques designed for measurements of NOx(NO + NO2) were intercompared during aircraft flights made in the spring of 1984 in the middle free troposphere over the eastern Pacific Ocean and southwestern United States. One NO chemiluminescence instrument was equipped with a ferrous sulphate converter, another with a photolytic converter. The ferrous sulphate‐equipped instrument was apparently much less specific for NO2. It registered levels about 3 times larger than the photolytic converter and gave NO2/NO ratios that were much larger than photochemical calculations would indicate as reasonable. Additionally, the results imply that active NOxwas only 10–20% of total odd nitrogen in the middle free troposph

ISSN:0148-0227    

DOI:10.1029/JD093iD12p15803

年代:1988

数据来源: WILEY

摘要:

During the 1984 spring program of the NASA Global Tropospheric Experiment, measurements of NO, NO2, O3, and CO were made during two aircraft flights that encountered tropopause fold events. The technique used to measure NOx(NO + NO2) is described. In the neighborhood of both tropopause fold events, CO and O3were strongly anticorrelated [Danielsen et al., 1987;Hipskind et al., 1987]. In one fold, encountered over the eastern Pacific Ocean at night, NOxwas positively correlated with O3, negatively correlated with the dew point, and negatively correlated with CO, consistent with the stratospheric origin of the air mass. In this fold at altitudes between 5.5 and 6.0 km, NOxreached mixing ratios near 150 parts per trillion by volume (pptv), considerably larger than the levels of 10–50 pptv in the air external to the fold. In contrast, in a daytime encounter with a fold over the southwestern United States at altitudes of 6.7–8.8 km, NOxdid not correlate well with CO, O3, or dew point, but remained roughly constant at levels of 100–200 pptv. Outside of the fold, in a region of strong convective activity, NOxpeaked to just over 500 pptv. It appears that mixing of tropospheric air containing elevated NOxweakened the expected trends for the fold over the continent compared to the fold over the ocean, and therefore NOxmay not always be a good tracer of air of recent stratospheric origin. However, the observations emphasize that the stratospheric source of NOxacts to introduce NOxover a short period and through a large vertical region of the troposphere, not just near the tropopause, as is assumed in many tropospheric m

ISSN:0148-0227    

DOI:10.1029/JD093iD12p15813

年代:1988

数据来源: WILEY

摘要:

Using a chemiluminescent detector, vertical profiles of NO were measured during the STRATOZ III mission from June 4–26, 1984. The mission's flight track started close to Paris, went west across the North Atlantic, south along the east coast of North America and the west coast of South America. It returned north along the east coast of South America, crossed the Atlantic around the equator and continued north along the west coast of North Africa and continental Europe. It covered the latitudes between 67°N and 60°S and the altitudes between 0 and 12 km. The coastal profiles in the northern hemisphere and in the tropics exhibited a C shape, with higher NO concentration values in the planetary boundary layer and the upper troposphere, whereas the measurements over the ocean showed low values in the upper troposphere. The NO mixing ratios in the southern hemisphere, south of 20°S latitude, were lower than in the northern latitudes and showed little increase in the upper troposphere. The two‐dimensional NO distribution along the flight track is derived, and the possible sources of the NO in the high troposphere are briefly dis

ISSN:0148-0227    

DOI:10.1029/JD093iD12p15831

年代:1988

数据来源: WILEY

摘要:

Ozone concentration profiles from the ground to above the stratospheric peak have been obtained, for the first time, in an equatorial rain forest environment near Manaus (3°S 60°W). We have described in detail the average ozone profile in the troposphere, the observed variations, and a major biomass‐burning event that occurred near the end of the experiment. The average ozone mixing ratio at 1000 mbar was 13 parts per billion by volume (ppbv), increasing to 45 ppbv at 500 mbar. From 500 mbar upward, in the free troposphere, the mixing ratio stays roughly constant. The peak O3concentration occurs at 20 mbar (26.6 km) reaching 4.4×1012molecules cm−3. The values in the troposphere are much lower than results from the low‐latitude Atlantic coast. The average gradient below 1000 m in Manaus is twice as large. The diurnal variation is strongest near the surface, decreasing upward. Close to the surface the ozone gradient is largest in the early morning, decreasing toward noon. A significant pollution (burning) event, near the end of the experiment, was responsible for large changes in ozone concentrations, which increased first in the lower troposphere but eventually reached the free troposphere

ISSN:0148-0227    

DOI:10.1029/JD093iD12p15850

年代:1988

数据来源: WILEY

摘要:

Results are presented on the tropospheric distribution of C2–C5hydrocarbons based on (1) shipboard measurements over the eastern Pacific Ocean from latitude 47°N to 47°S, (2) ground‐based measurements at a remote coastal site in northern California (39°N), and (3) airborne studies of the troposphere over Colorado and over the eastern Pacific Ocean (38°N) during the summer and winter seasons. A total of 1077 hydrocarbon samples were processed during these comprehensive field programs. In agreement with previous studies, the shipboard measurements show large north‐to‐south gradients for virtually all nonmethane hydrocarbons (NMHCs) and clearly indicate their northern hemispheric sources. Ethane, the most abundant NMHC, is present at a concentration of 2 ppb in the northern hemisphere (NH) mid‐latitudes, with southern hemisphere (SH) concentrations of about 0.3 ppb. All other NMHC concentrations are in the sub‐ppb range. The measurements at the remote coastal site of Point Arena, California, show that NMHC concentrations can decrease by a factor of 2 or more during the passage of cold fronts in winter and spring. During these events the behavior of NMHCs is strongly correlated with primary anthropogenic species (e.g., CH2Cl2, CH2ClCH2Cl, and CH3CCl3) as well as secondary oxygenates (e.g., peroxyacetyl nitrate (PAN) and ozone). Aircraft measurements of NMHC concentrations made over Colorado and near the coastal zone of northern California were higher over land than over the ocean in the lower troposphere (<5 km). Upper tropospheric concentrations were found to be lower and, in general, much less spatially variable than those present in the lower troposphere. Because of the differences in NMHC concentrations between ocean and land and between lower and upper troposphere evident in the measurements, it is possible that weather systems associated with significant horizontal and vertical transport can cause large temporal and spatial variations in NMHC concentrations on local and

ISSN:0148-0227    

DOI:10.1029/JD093iD12p15861

年代:1988

数据来源: WILEY

摘要:

The relationship of photochemical ozone production versus photochemical loss of an ozone precursor, that is, either NOxor nonmethane hydrocarbons (NMHCs), is studied by using a box model with particular emphasis on the nonlinearity problem of the relationship with respect to the concentration of the precursor. Model calculations indicate that the composition of NMHCs, the ratio of NMHCs to NOx, and the background concentrations of natural hydrocarbons, CO, and CH4all play important roles in determining the nonlinearity of O3production with respect to the loss of NOx. In addition, influences on the nonlinearity due to radical loss via reactions of HO2with RO2, exchanges between PAN and NO2, and inclusion of nighttime NOxloss processes are also investigated. Mechanisms that contribute to the nonlinearity are discussed. The nonlinear property of O3production versus loss of hydrocarbons and CO is different from that of NOx. When the sum of CO and all hydrocarbons, including CH4, natural NMHCs, and anthropogenic NMHCs, is used as the reference O3precursor, the nonlinearity is much less pronounced for ambient conditions usually found in rural air.

ISSN:0148-0227    

DOI:10.1029/JD093iD12p15879

年代:1988

数据来源: WILEY

摘要:

The reaction probability, γ, of N2O5(to form HNO3) with monodisperse NH3/H2SO4/H2O aerosols has been measured in a flow tube reactor at atmospheric pressure. Experiments were performed at temperatures of 274 and 293 K and at relative humidities of 1–76%. It appears that the presence of a liquid phase is necessary for reaction. With NH4HSO4aerosol, γ values are nonzero, even below the deliquescence point of the pure salt, and show a gradual increase with increasing relative humidity up to constant values of 0.05 and 0.09 for 293 and 274 K, respectively. Experiments with aerosols of varied NH3/H2SO4ratios suggest that evaporation of NH3from the NH4HSO4aerosols creates excess H2SO4on the surface. This can take up water vapor to provide the reactant for N2O5below the deliquescence point of NH4HSO4. The present observations are consistent with the reaction of N2O5with moist aerosols being a major removal mechanism for odd nitrogen and a major source of HNO3in the nighttime troposphere. The same reaction on H2SO4aerosols may be of significance in the stratosph

ISSN:0148-0227    

DOI:10.1029/JD093iD12p15889

年代:1988

数据来源: WILEY

摘要:

We consider the general problem of the meridional distribution and seasonal variability of long‐lived atmospheric constituents. Here “long‐lived” means that the time scale of the constituent exceeds the atmospheric exchange time across the region of interest. The relevant time scale is the “dynamic lifetime,” defined here as the ratio of the total atmospheric loading of the constituent to the total global source. Provided that this quantity is large (greater than about 5 years for the troposphere), the constituent attains a “gradient equilibrium” in which spatial gradients of mixing ratio are weak and the meridional and seasonal structure take on a form which, for a given source, is independent of the dynamic lifetime. Analysis of this structure involves clarification of the nature of atmospheric exchange processes and leads us to highlight thé nonuniqueness of such concepts as “interhemispheric exchange times.” These results are illustrated using a two‐dimensional transport model to conduct simulations of idealized long‐lived constituents with, in most cases, a simple mid‐latitude northern hemisphere source and a sink with uniform decay rate. It is suggested that these results will aid the synthesis of observations of long‐lived tropospheric constituents and will simplify the validation of transport models. More generally, this kind of approach might help to identify the effects of transport on trace constituent structures and thereby contribute to the understanding of the distributions of constituents which are not “long

ISSN:0148-0227    

DOI:10.1029/JD093iD12p15897

年代:1988

数据来源: WILEY

摘要:

Variability in atmospheric CO2concentration over periods of 1–5 days at Cape Matatula, American Samoa, was studied. The variability was found to be the result of the alternating influences of three air mass source regions. Partitioning of Samoa CO2data according to these air mass source regions revealed annual cycles in the partitioned data sets corresponding to those of the tropical South Pacific, the mid‐latitude southern hemisphere, and the tropical North Pacific regi

ISSN:0148-0227    

DOI:10.1029/JD093iD12p15914

年代:1988

数据来源: WILEY

摘要:

A coupled climate‐sea ice model that includes land‐sea resolution in the atmosphere, a mixed layer ocean, and a ground layer is used to investigate the impact of sea ice and leads within the ice pack on climate. Results show that a feedback process between the ocean and atmosphere exists, called the lead‐temperature feedback, such that changes in the winter minimum lead fraction can cause large changes in the simulated annual zonally averaged surface air temperature in the north polar regions. Compared to a control case where the minimum lead fraction is 1.1%, these changes in temperature range from a decrease of about 1.0°K, when leads are eliminated, to an increase of 1.0°K, when the winter minimum lead fraction is increased to 4.3%. Seasonally, this temperature change ranges up to 2.0°K. An examination of the surface energy fluxes shows that the changes in the sensible heat flux, in response to changes in the lead fraction, contribute the most to these temperature changes. The absorbed solar radiation is also affected by the changes in the winter minimum lead fraction; however, the small changes in lead area during the winter and the period of open ocean during the summer reduce its impact. The increase in the sensible heat flux to the atmosphere, along with the changes in the other fluxes, in response to increases in winter minimum lead fraction, forms the positive lead‐temperature feedback between larger lead area and warming. This feedback process has major implications for both polar and glob

ISSN:0148-0227    

DOI:10.1029/JD093iD12p15919

年代:1988

数据来源: WILEY