摘要:

A series of sampling flights was made to determine the vertical distribution of HT and HTO in the upper troposphere and lower stratosphere up to 18‐km altitude. The HT appears to be well mixed, but striking vertical gradients of HTO were found in the region from 10 to 18 km. These gradients, essentially constant to 18 km, were used to estimate a characteristic time of 2 years for turnover of water vapor in the lower stratospher

ISSN:0148-0227    

DOI:10.1029/JC081i030p05349

年代:1976

数据来源: WILEY

摘要:

Radar observations made with a polarization diversity radar show the existence of a high degree of common orientation of the particles in the upper levels of thunderstorms. Abrupt changes in orientation associated with lightning discharges have frequently been observed, the particles becoming disoriented, or in some cases reoriented, in less than 1 s. Recovery times of the order of 10–15 s were observed. A consequence of the oriented states is the existence of differential propagation characteristics for radio waves propagating through the medium. A differential phase shift of 2.5°/km at 1.8‐cm wavelength is reported for a thunders

ISSN:0148-0227    

DOI:10.1029/JC081i030p05353

年代:1976

数据来源: WILEY

摘要:

Surface ozone measurements made in Antarctica during the 1960's show a pronounced annual variation with a summer minimum and winter to late winter maximum. Furthermore, the maximum in surface ozone precedes that in total ozone by from 3 to 5 months, the indication being a loose coupling between the Antarctic stratosphere and troposphere. The annual cycle in surface ozone, instead of reflecting changes in the Antarctic stratosphere, may be a consequence of the variation in low‐level meridional transport of ozone from higher latitudes into the Antarctic continent by synoptic scale disturbances. As might be expected from a consideration of Antarctic geography and meteorology, no significant diurnal variations occur in surface ozone. The nonperiodic surface ozone fluctuations observed during the late spring and summer months at South Pole station are most likely caused by sporadic breakdowns of the low‐level inversion layer. At the lower latitude stations the day‐to‐day variations in surface ozone are in all likelihood associated with changes in weather

ISSN:0148-0227    

DOI:10.1029/JC081i030p05359

年代:1976

数据来源: WILEY

摘要:

An account is given of the comparison between ozone observations by the Nimbus 4 backscatter ultraviolet instrument and stratospheric radiances measured by satellite infrared spectrometer (Sirs) for the period April 1970 to April 1971. Zonal means of total ozone and stratospheric radiances (temperatures) in the middle and high latitudes display annual cycles. A strong increase of ozone and temperatures is, however, observed at the northern high latitudes during the stratospheric warming of January 1971, ozone increases being very rapid after mid‐October 1970. 2‐mbar temperatures are derived by using Sirs radiances, and their analysis includes the comparison with 2‐mbar mixing ratio of ozone for the months of October 1970 and January 1971. Results of comparison reveal remarkable asymmetries between northern and southern hemispheres. Distribution of satellite‐measured global and hemispheric ozone is compared with the distribution derived by ground‐based observation of total ozone and depicts differences in the southern hemisphere. There is a good correlation between global ozone and global Sirs radiances, both showing a steep fall in February 1971. Satellite observations demonstrate a decrease in global ozone in April 1971 as compared to April 1970. The eddy variations of Sirs radiances show a close correspondence with meridional structure of total ozone. Evidence is presented of strong coupling between planetary wave and zonal flow osc

ISSN:0148-0227    

DOI:10.1029/JC081i030p05365

年代:1976

数据来源: WILEY

摘要:

An inversion technique for recovering the scattering coefficient as a function of height in the earth's atmosphere is investigated. The most sensitive method of aerosol detection requires that spacecraft measurements of the horizon radiance be made during periods of spacecraft twilight in order to utilize the forward scattering properties of aerosols. A solar occultation technique, which allows the twilight measurements to be made when the sun is still above (but close to) the horizon, greatly reduces the complexity of the inversion problem. If the extinction of the setting (rising) sun is also measured, the total scattering coefficient can be recovered with an uncertainty which is approximately twice that of the noise in the radiance signal. Although only single scattering is employed in the analysis, an iterative method of including multiple scattering is suggested.

ISSN:0148-0227    

DOI:10.1029/JC081i030p05375

年代:1976

数据来源: WILEY

摘要:

A simple coronagraph was modified for use aboard Skylab to photograph the earth's horizon just before spacecraft twilight as a device to monitor the aerosol component of the earth's atmosphere above the tropopause. This coronagraph technique allows one to investigate these high‐altitude aerosols from a uniquely favorable position in the particles' forward scattering cone. The method is thus 10–100 times more sensitive than daylight horizon scans made when the sun is well above the horizon. An 8‐month observing program using seven narrow band filters was planned. Owing to a multitude of spacecraft and equipment mishaps, including the loss of access to the solar airlock, only one reducible photograph was obtained on a late November (1973) extravehicular activity. This particular picture was taken through a 250‐Å bandwidth filter centered on 3600 Å. Since aerosol layering is detected as an enhancement of radiation above the Rayleigh background, this wavelength region, although it is free from the spectral influence of ozone, has a relatively high background level compared to longer wavelengths. Even at this high background level the coronagraph picture provides evidence which is consistent with an aerosol layer peaking at 48±1 km. The region photographed was centered on 26.5°E longitude, 63.0°S latitude. This first observation at high southern latitudes suggests the global nature

ISSN:0148-0227    

DOI:10.1029/JC081i030p05383

年代:1976

数据来源: WILEY

摘要:

The mean circulation of shallow seas arises as the residue of chaotic first‐order flow episodes created by winds, tides, and river inflow. The average effect of many such episodes is to generate an internal pressure and shear stress distribution which may differ significantly from a steady solution of the equations of motion. Within the coastal boundary layer (of about 10‐km width), complex average effects of variable flow probably dominate. However, in mid‐shelf regions of the Mid‐Atlantic Bight, for example, classical steady state models adequately describe the main features of the mean circulation. The statistical effects of variable first‐order flow even bring about some simplifications of the theory, i.e., linear internal and bottom friction laws and a decoupling of salt transport from the mean circulation. The mid‐shelf circulation of the Mid‐Atlantic Bight is thus found to consist of four additive components, each driven by offshore wind, longshore wind, longshore pressure gradient, and density contrasts caused by freshwater influx. The longshore pressure gradient enters the theory as a parameter necessary for describing the interaction of a portion of the continental shelf with the rest of the ocean. The pressure gradient driven flow component is responsible for some notable circulation features such as the line of divergence in bottom drift at about the 60‐m isobath. The wind‐driven and thermohaline flow components are familiar in character. Quantitatively, the four components together account satisfactorily for the observed mean

ISSN:0148-0227    

DOI:10.1029/JC081i030p05389

年代:1976

数据来源: WILEY

摘要:

Currents were observed for a 25‐day period in September 1975 at 11 km south of Long Island, where the water is 32 m deep, at three levels by using electromagnetic current meters. Tidal currents were found to be moderately strong, of the order of 20 cm s−1. Nontidal flow is caused by wind stress, horizontal density contrasts due to fresh water influx, and a longshore surface level gradient sloping down south‐westward. The time‐averaged flow has simple characteristics, adequately described by classical Ekman models in frictional equilibrium. By suitable changes in the averaging period, quantitative estimates of a bottom friction coefficient and a longshore pressure gradient are deduced from the data. The bottom friction coefficient agrees with what one would estimate from boundary layer theory for roughness elements of about 70‐cm height. The longshore pressure gradient deduced from the behavior of currents agrees with the evidence of geodetic

ISSN:0148-0227    

DOI:10.1029/JC081i030p05401

年代:1976

数据来源: WILEY