摘要:

A study is presented of the general response of an ice age ice sheet model recently developed by Weertman (1976). The model is subjected to fluctuating insolation on time scales of the order of the variations in the earth's orbital parameters, which happen also to be the characteristic internal time scales of the ice sheets themselves. Because of this equivalence in time scales the model displays a wide range of behavior for reasonable parameter values, ranging from periodic growth and decay of ice sheets alternating with interglacial intervals to growth of large permanent ice sheets of periodically fluctuating size. The model displays nonlinear behavior analogous to a rectifier; as a consequence, a possible explanation of the 100,000‐year cycle observed in geological climate time series is suggeste

ISSN:0148-0227    

DOI:10.1029/JC082i031p04909

年代:1977

数据来源: WILEY

摘要:

Variations in the net heat flux into the North Pacific Ocean from 1956 to 1964 are computed by a new method, proposed in this study, which allows computation of the net heat flux by using hydrographie data from the Kuroshio area only. This is a first attempt at such calculations since Montgomery (1954, 1974) showed that computing the heat flux for a single ocean current is meaningless if the mass flux of the current is not constant in time. The results of these calculations were then investigated, and the net heat flux variations were related to both changes in the flux of mass and changes in the mean temperature of flow of the Kuroshio. A more quantitative analysis indicated that 60–70% of the variance of the net heat flux was due to changes in the mass flux and 30–40% was due to changes in the flow temperature. The interannual variations in the net heat flux were largely a result of changes in mass flux, while the mean annual variations were closely related to changes in flow temperature. The net heat flux values were also compared with sea surface temperature anomalies in the North Pacific, but no relation was fo

ISSN:0148-0227    

DOI:10.1029/JC082i031p04915

年代:1977

数据来源: WILEY

摘要:

Stratospheric aerosols were collected on special surfaces to determine both the physical state of the particles and the nature of included undissolved granules. Physically, each aerosol particle is composed of a somewhat volatile slurry mixture of crystalline‐like material in a liquid matrix. Variations in the relative amounts of liquid at different times cause changes in particle fluidity. Although all particles contain a significant portion of the crystalline material, they are fluid in the atmosphere in the altitude range from 12 to 32 km and are physically similar at all geographic locations from 5°N to 89°N latitude and from 55°W to 175°W longitude. No evidence of frozen particles has been found even at stratospheric temperatures of −65°C. Undissolved granules are found in only one third of the aerosol particles, and sometimes the granules are found alone outside the slurry matrix. Thus we conclude that in general, these undissolved granules are not active nucleating agents for stratospheric aerosols. Furthermore, these granules now contain mostly sulfur, sodium, and possibly lighter elements, whereas before they contained silicon and other heavy elements attributed to volcanic eruptions. We conclude that other important sources besides volcanos dominate the granular component after long quiet periods without significant volcanic

ISSN:0148-0227    

DOI:10.1029/JC082i031p04921

年代:1977

数据来源: WILEY

摘要:

Zonal cross sections of the monthly means of zonal wind and of the phase and amplitude of the planetary waves in the southern hemisphere for the region from the surface to 0.2 mbar are presented for the months of July and August 1973. The data used include satellite‐based observations of temperature, and the results compare well with operational height analyses in the troposphere. Large amplitudes are found for zonal wave numbers 1, 2, and 3. Simultaneous zonal wind and wave structure changes appear to be qualitatively consistent with theoretical prediction

ISSN:0148-0227    

DOI:10.1029/JC082i031p04930

年代:1977

数据来源: WILEY

摘要:

Perturbing the stratospheric composition affects the stratospheric temperature profile via the radiation balance. Changes in temperature affect chemical reaction rates, which in turn feed back on stratospheric composition. The effect of temperature feedback on ozone concentration has been investigated for three types of perturbations: (1) stratospheric injection of NOx, (2) release of fluorocarbons, and (3) doubling CO2. Temperature feedback had approximately a 10% restoring effect on ozone for small ozone reductions because of either stratospheric NOxinjection or release of fluorocarbons. Doubling CO2concentrations increased total ozone by 2.9%. Calculations of ozone reduction including temperature feedback were as much as 20% less than fixed temperature calculations using the U.S. Standard Atmosphere temperature profile.

ISSN:0148-0227    

DOI:10.1029/JC082i031p04935

年代:1977

数据来源: WILEY

摘要:

Recent observations at shoreline sites downwind and over water from urban areas have shown enhanced ozone concentrations when the predominant wind direction is from the urban area to the site. Kinetic photochemical computations simulating this situation have been performed and are compared with similar calculations in which overwater transport is replaced by overland transport. The ‘overwater effect’ is reproduced by the calculations, giving an increase in the ozone maximum of ∼7% for the conditions chosen. The effect is shown to result principally from an enhancement of the NO2/NO ratio during overwater transport, with a concomitant increase in ozone concentrations as a result. Another consequence of the overwater transport is increased conversion ratios in the chemical production chains of peroxyacetyl nitrate, nitric acid, and gaseous su

ISSN:0148-0227    

DOI:10.1029/JC082i031p04943

年代:1977

数据来源: WILEY

摘要:

Nine stations were occupied in the vicinity of Walvis Bay, Namibia, during a detailed study of the distribution of methane in this highly productive coastal environment. The principal features of the observed coastal methane distribution included (1) excess methane in the mixed layer of from 2 times to greater than 300 times solubility equilibrium with the atmosphere, (2) a subsurface maximum, located in the top of the pycnocline, at which concentrations ranged from 2.6 to 440 times solubility equilibrium, (3) an intermediate depth minimum, where concentrations were comparable to those offshore at similar depths and which we attribute to the influence of onshore movement of subsurface offshore water, and (4) a bottom maximum, which we attribute to input of methane to the water column from the anoxic sediments in the Walvis Bay area. An attempt was made to identify the relative importance for methane supply to the coastal mixed layer of in situ biological production and of eddy diffusive and advective transport of methane‐rich water which has been in contact with the bottom at the coast. Calculations suggest that both in situ production and physical processes are major sources of excess methane for the highly productive coastal surface waters. However, the complicated circulation patterns make quantification extremely difficul

ISSN:0148-0227    

DOI:10.1029/JC082i031p04947

年代:1977

数据来源: WILEY

摘要:

All methods of measuring the integrated properties of cloud, rain, or hail populations such as the water content, precipitation rate, kinetic energy, or radar reflectivity are subject to statistical sampling errors due to the Poisson distributed fluctuations of the number of particles sampled in each particle size interval and the weighted sum of the associated variances in proportion to their contribution to the integral parameter to be measured. This work generalizes and extends that of Joss and Waldvogel (1969) by providing a general derivation of the fractional standard deviation (FSD) of any integrated propertyXsuch thatX(D) =cDnfor any particle size distribution whereDis the particle diameter: In addition, for the case of exponential size spectra we derive general expressions for the FSD of all integral parameters for sampling devices of constant volume or for (area × time) devices in which sampling volume is a function of particle fall speed. We present a set of universal curves applicable to the exponential size distribution which permits the estimation of the FSD of any such parameters fromn= 0, which corresponds to the measurement of total number concentration, ton= 6, Which corresponds to the radar reflectivity factor. Equations and curves are also provided to permit corrections for finite upper limits to the size spectrum and, in the case of rain, for a realistic fall speed law. Examples are included to illustrate the magnitude of the expected FSD for a variety of rain and hailfall parameters with sampling instruments now in use. A comparison is made with observed rainfall data to illustrate the methods presented in this paper and some of the difficulties in distinguishing fluctuations of physical and statistical origin

ISSN:0148-0227    

DOI:10.1029/JC082i031p04955

年代:1977

数据来源: WILEY

摘要:

From an analysis of factors that could contribute to the existing differences between experimental and theoretical values of the energy dissipated per unit length in a return stroke channel of lightning a revised value of approximately 1×104J/m is deduced

ISSN:0148-0227    

DOI:10.1029/JC082i031p04967

年代:1977

数据来源: WILEY

摘要:

A portable 50‐MHz coherent radar was operated at Poker Flat, Alaska, in October 1976 to observe backscatter from refractive index fluctuations in the lower atmosphere. This report presents several comparisons of wind profiles determined by the radar and by sounding balloons launched nearby. In addition, a profile of relative refractivity turbulence structure constant determined by the portable radar is compared with a profile of structure constant calculated from balloon data by using a recent mode

ISSN:0148-0227    

DOI:10.1029/JC082i031p04969

年代:1977

数据来源: WILEY