摘要:

Between March 1979 and June 1980, air was collected on the Hawaii‐Tahiti shuttle expedition of the Global Atmospheric Research Program. A north‐south track was repeatedly sampled and the air analyzed to provide eight sets of data on the concentration,13C/12C, and18O/16O ratios of atmospheric carbon dioxide between 20°N and 17°S latitude near 155°W. In the northern hemisphere the13C/12C ratio of the CO2seasonally added to and withdrawn from the atmosphere was found to be nearly constant at circa 30‰ less than standard PDB. This ratio is consistent with photosynthesis and respiration of terrestrial vegetation as the cause of the seasonal cycle. The ratio was progressively less negative southward, reaching about −13‰ at 17°S. This shift in ratio suggests that air‐sea exchange is important in producing the seasonal variation in the southern hemisphere, since this exchange probably occurs with little kinetic isotopic fractionation. The seasonally adjusted13C/12C ratio of atmospheric CO2increased steadily southward from −7.55‰ near 16°N to −7.47‰ near 17°S, as expected from a predominantly northern hemisphere source of a CO2from fossil fuel combustion and a barrier to atmospheric mixing in the tropics. A peak in CO2concentration near the equator was not found in the north‐south trend in13C/12C ratio. This lack of an isotopic peak suggests that the high concentrations of CO2near the equator is produced by the release of CO2from sea water and is not related to biological

ISSN:0148-0227    

DOI:10.1029/JD089iD03p04615

年代:1984

数据来源: WILEY

摘要:

Approximately half of the nitrogen and phosphorus entering deep waters of the contemporary ocean are transported from the surface in inorganic form as preformed nutrients. A simple model for ocean chemistry is presented and shown to account for the present level of atmospheric CO2. Fluctuations in preformed nutrients, modulated by changes in insolation and circulation at high latitudes, can result in significant variations in CO2. It is suggested that these changes may account for the apparent control on climate exercised by secular variations in the orbital parameters of the earth.

ISSN:0148-0227    

DOI:10.1029/JD089iD03p04629

年代:1984

数据来源: WILEY

摘要:

The objective of this work is to evaluate the potential of tropical glaciers and ice caps for the reconstruction of past climatic conditions by the analysis of firn and ice cores. Samples were collected in pits and from cores retrieved on three snow fields in the South American Andes: Quelccaya Ice Cap and Huascarán in Peru and Chimborazo in Ecuador. These are compared with results from west Africa and Indonesia. Measurements include the microparticle concentration, oxygen isotopic abundance ratios, and total beta radioactivity, which in polar regions often exhibit seasonal depositional cycles. Annual variations in these three parameters are fairly well defined on Quelccaya and Huascarán and are apparently absent on Chimborazo. The Quelccaya Ice Cap contains the best preserved annual signal for all three parameters and, although in some instances the annual cycle is difficult to distinguish, the measurement of more than one stratigraphic parameter aids in the interpretation of the firn core records. The relatively flat bottom topography under Quelccaya suggests a simple ice flow regime, and depth‐age calculations indicate that an ice core to bedrock should contain a record of 600 to 1300 years. This inference was confirmed by drilling to bedrock in 1983. This investigation of tropical glaciers indicates that the Quelccaya Ice Cap on the eastern edge of the Peruvian Andes has excellent potential to contain a lengthy and interpretable record of climatic conditions within the tropics of South Amer

ISSN:0148-0227    

DOI:10.1029/JD089iD03p04638

年代:1984

数据来源: WILEY

摘要:

The ratio of oxygen isotopes in glacial ice is often used as an indicator of climatic conditions during the period of time in which the ice was deposited. We have developed a model which predicts the isotopic composition of snow, given the composition of the source water and the meteorological path between the formation of an air‐water parcel in the boundary layer and the final deposition of precipitation onto the ice sheets. After comparing the model results with isotope data from the present, we draw inferences about the past isotopic composition of continental ice sheets. Our results depend strongly on the details of the meteorological path. They are consistent with standard interpretations of isotope data, but in some cases they allow alternate interpretation

ISSN:0148-0227    

DOI:10.1029/JD089iD03p04647

年代:1984

数据来源: WILEY

摘要:

The carbon chemistry of rivers and lakes has been severely affected by man's activities. This is evident from the data base of the SCOPE/UNEP project, Carbon Transport in Major World Rivers. Increase of erosion following deforestation and agriculture removes carbon from the biosphere into inland deposition centers, lakes, and reservoirs and causes the organic carbon load of rivers to increase. Organic sewage and eroded soil carbon fuel respiration in rivers thus increases the CO2pressure and diminishes the O2and NO3loads in relation to the total organic content. Nutrient release causes eutrophication of lakes and coastal seas, resulting in enhanced primary productivity and CO2sequestering. Loss of CaCO3in upstream lakes and boosting PCO2cause increasing undersaturation of streams with respect to carbonate minerals. In estuaries this undersaturation leads to the corrosion of marine carbonate, as is experimentally shown for the River Elbe, fixing riverine free CO2as bicarbonate permanently. All sinks combined, up to 1015g C per year can additionally be sequestered from the anthropogenically enhanced carbon cycle.

ISSN:0148-0227    

DOI:10.1029/JD089iD03p04657

年代:1984

数据来源: WILEY

摘要:

At the Goddard Laboratory for Atmospheric Sciences (GLAS) we have developed a physically based satellite temperature sounding retrieval system, involving the simultaneous analysis of HIRS2 and MSU sounding data, for determining atmospheric and surface conditions which are consistent with the observed radiances. In addition to determining accurate atmospheric temperature profiles even in the presence of cloud contamination, the system provides global estimates of day and night sea or land surface temperatures, snow and ice cover, and parameters related to cloud cover. The inverse radiative transfer equation approach to the multi‐spectral analysis of the data, and details of its implementation, are described. Ice, snow, and cloud fields derived for January 1979 are consistent with other measures of similar parameters obtained from AVHRR and SMMR. Monthly mean sea‐surface temperature fields agree with those derived from ship and buoy measurements to 0.

ISSN:0148-0227    

DOI:10.1029/JD089iD03p04677

年代:1984

数据来源: WILEY

摘要:

The effect of the meridional and vertical dynamical heat fluxes on climate sensitivity is investigated using an annual mean coupled high and low latitude radiative‐dynamical model of the northern hemisphere. The model was constructed by incorporating a meridional (atmosphere and ocean) dynamical heat flux parameterization into a two‐zone (low latitude 0°–30°N and high latitude 30°–90°N) version of the vertical radiative‐convective model. The atmospheric vertical dynamical heat flux is parameterized through the convective adjustment with two critical lapse rates: the moist adiabatic lapse rate and the critical value for baroclinic adjustment. The meridional dynamical heat flux is related to the meridional temperature gradient empirically. Cloud covers and altitudes and relative humidity are fixed. Ice albedo‐temperature feedback is included. The feedback in the dynamical heat fluxes is found to produce a strong stabilizing effect on climate. The warming of the hemispheric mean surface temperature induced by a 2% increase in solar constant and a doubling of carbon dioxide concentration could be increased by as much as a factor of 4 if the feedbacks from the meridional and vertical dynamical heat fluxes were both eliminated. The coupling effect of the vertical and meridional heat fluxes is also calculated to be very strong (i.e., the vertical flux feedback is strongly stabilizing in the presence of meridional flux feedback but destabilizing in its absence. In fact, the model's current climate is unstable in the latter case.) The interactions of the dynamical heat flux with other temperature‐dependent feedbacks such as radiation, ice albedo, and humidity and their subsequent effects on climate

ISSN:0148-0227    

DOI:10.1029/JD089iD03p04699

年代:1984

数据来源: WILEY

摘要:

Two different monthly mean analyses of low, middle, and high cloud amounts for January 1977 and July 1979 are compared: 3DNEPH is a condensed version (northern hemisphere only) of the Air Force 3D‐Neph analysis, which incorporates satellite data plus surface observations of clouds and auxiliary meteorological data. SFCOBS is objectively analyzed from surface observations of clouds. The SFCOBS and 3DNEPH analyses of low cloud amounts agree qualitatively in the winter extratropics. The 3DNEPH ITCZ is much more sharply defined than the SFCOBS. The sensitivity of radiative fluxes to 3DNEPH, SFCOBS, and zonal mean 3DNEPH clouds is then evaluated. The fluxes are diagnosed by a cloud‐radiation model utilizing “observed” monthly mean temperature and water vapor fields and are verified against satellite data. The outgoing longwave radiative flux clearly verifies best for 3DNEPH clouds and worst for zonal mean 3DNEPH clouds in the tropics. It is predominantly controlled by surface temperature in the winter extratropics. Generally speaking, the shortwave fluxes do not verify as well as the longwave fluxes. Also, outside of the winter extratropics, the net radiative fluxes correlate poorly with observation. Biases in the zonal mean long and shortwave fluxes can be reduced by adjusting other cloud‐related parameters. Based upon the above results, it may be worthwhile to construct a monthly mean cloud climatology from a condensed version of the 3D‐Neph. However, alternative strategies should also be explored, such as the development of cloud analysis schemes that constrain the model‐diagnosed net radiative flux to be consistent wit

ISSN:0148-0227    

DOI:10.1029/JD089iD03p04713

年代:1984

数据来源: WILEY

摘要:

The coupled gas‐ and aqueous‐phase photochemistry of a stratiform cloud in a remote region of the marine atmosphere is investigated with a time‐dependent box model. Both scavenging of ambient acidic aerosols and gases as well as aqueous‐phase chemical reactions within droplets are found to be important sources of acidity to cloud water and can lead topH levels in cloud water in the remote marine atmosphere well below 5.6. The major sources of acidity via aqueous‐phase chemical reactions are the generation of sulfuric acid from dissolved SO2and the generation of formic acid from dissolved formaldehyde. In both cases, aqueous‐phase free radicals can play a significant role either directly by oxidizing dissolved SO2and HCHO or indirectly by producing the aqueous‐phase oxidant H2O2. The rate of SO2conversion to sulfuric acid is sensitive to a variety of parameters including the accommodation or sticking coefficient for SO2, H2O2, HO2, and OH, the liquid water content, and the ambient levels of SO2, HNO3, and other acidic or basic gases. Because high levels of SO2tend to deplete cloud water of H2O2, the possibility exists that thepH of precipitation in polluted regions will respond nonlinearly to reduced

ISSN:0148-0227    

DOI:10.1029/JD089iD03p04739

年代:1984

数据来源: WILEY

摘要:

The turbulent fluxes of ozone and latent and sensible heat are computed from fast‐response measurements made aboard a National Oceanic and Atmospheric Administration aircraft over downtown Philadelphia and the surrounding suburbs during the afternoon and evening of August 22, 1979. In the afternoon the ozone flux at a height of 200 m is downward throughout the region with the largest magnitude (−2 (ppb) m s−1) occurring over the urban center. During the afternoon at both 200 m and a few hundred meters below cloud base, the horizontal profile of mean ozone concentration peaks at 130 ppb over the urban core with values of the order of 90 ppb to the southeast and northwest. The urban ozone concentration at 200 m decreases to 35 ppb by early evening. The normalized variances and spectra of vertical velocity, temperature, and ozone show little change with height or location in the urban center and northwest suburbs during the afternoon in good agreement with normalized statistics obtained over rural terrain (Kaimal et al., 1976; Lenschow et al., 1980). Data from a cloud penetration by the aircraft is used to estimate a mean updraft velocity of 4 m s−1and an updraft area of approximately 1 km2. The flux of ozone due to the mean motion in the updraft is 2 orders of magnitude larger than the turbulent eddy fluxes within th

ISSN:0148-0227    

DOI:10.1029/JD089iD03p04757

年代:1984

数据来源: WILEY