摘要:

Energy dissipation method and an Iterative Bulk Aerodynamic Method (IBAM) are used to estimate friction velocity (u*) for a wide wind speed range (5.66 to 21.6 ms−1) with convective atmospheric conditions over the ocean during the Genesis of Atlantic Lows Experiment (GALE). Values of u* obtained by the IBAM are in reasonably good agreement with those from the dissipation method. The iterative bulk method appears to do well for wind speeds up to about 21 ms

ISSN:0094-8276    

DOI:10.1029/GL015i005p00401

年代:1988

数据来源: WILEY

摘要:

The “Slope Sea” is a narrow band of ocean that lies between the Gulf Stream and the continental shelf edge in the Mid‐Atlantic Bight. It is composed primarily of slopewater, and a closed cyclonic gyre circulates within the upper few hundred meters of its western end. A two‐year time series of current measurements in this region has shown that the southwestward flowing shelfbreak currents along the shoreward flank of the gyre are directly related to the position of the Gulf Stream, which is typically some 150 to 300 km seaward of the shelfbreak. The mean monthly shelfbreak currents are strongest, towards the southwest at about 30–40 cm s−1, when the Stream is within 150 km of the shelf edge, whereas those currents are close to zero when the Stream is about

ISSN:0094-8276    

DOI:10.1029/GL015i005p00405

年代:1988

数据来源: WILEY

摘要:

It is shown that if data on the latitude variation of winter storm tracks in the North Atlantic are sorted according to the phase of the quasi‐biennial oscillation (QBO) of stratospheric winds in the tropics, then a clear solar cycle variation emerges without any need to smooth the data. For the west phase of the QBO the peak to peak amplitude of the solar cycle variation is about 6° of latitude, with storm tracks occurring equatorward at solar maximum and poleward at solar minimum. This is consistent with the recent work of Labitzke and van Loon, and extends to dynamical effects at the surface the pattern of atmospheric responses that they found. Problems with the acceptance of the concept of solar variability effects on weather are discussed. To relate the solar variable energy inputs to the weather effects which are energetically several orders of magnitude larger, scenarios for a class of mechanisms with two or three stages of amplification are outlined, involving middle atmospheric energy inputs, in contrast to the tropospheric inputs of solar luminosity chang

ISSN:0094-8276    

DOI:10.1029/GL015i005p00409

年代:1988

数据来源: WILEY

摘要:

The three‐dimensional morphology of the spring Antarctic ozone distribution as determined by the Nimbus 7 SBUV instrument is presented for the period October 1–11, 1986. The data show that a clearly defined minimum in ozone relative to the local ozone field extends throughout the stratosphere from the tropopause to above 50 km, though decreasing in intensity with altitude. Near 18 km, ozone in the ozone hole is 50% less than the average surrounding ozone. But even at 50 km the ozone is 20% less than the surrounding ozone field. The ozone minimum in the upper stratosphere is displaced about 6 degrees toward the equator so that observations at a fixed station may provide the illusion that the ozone minimum is restricted only to low altitudes. While the ozone minimum is spatially coherent throughout the stratosphere, there are differences in the behavior of ozone at different altitudes that suggest the existence of at least three distinct altitude domains. Below 30 km, ozone is characterized by classic “ozone hole” behavior. Between 33 and 43 km ozone is more stable, actually increasing during September and October. Above 43 km, ozone has always decreased during September to a minimum in October, but it has also suffered a long‐term decrease of 7–12%

ISSN:0094-8276    

DOI:10.1029/GL015i005p00413

年代:1988

数据来源: WILEY

摘要:

The theory of electrostatic, collisional plasma modes that are driven unstable by a sheared field‐aligned ion flow velocity (i.e.,Vio=Vo(x)eˆz,Bo=Boêz) is presented. The threshold condition for the instability is V′o/νin>2 (1+Ti/Te) and the unstable modes are characterized by k∥«k⟂such that λ∥(=2π/k∥)»λmand 2πρi<λ⟂(=2π/k⟂)≲Lv, where V′o=dVo/dx, νinis the ion‐neutral collision frequency, λmis the electron mean‐free‐path, ρiis the ion gyroradius and Lvis the velocity shear scale length. It is shown that the linear instability provides a direct means of exciting the observed [Basu et al., 1986, 1988] sub‐km scale irregularities in the auroral F‐region. The spectral characteristics of the density and the electric field fluctuations that can be inferred from the theory are

ISSN:0094-8276    

DOI:10.1029/GL015i005p00417

年代:1988

数据来源: WILEY

摘要:

On July 24, 1986 narrow band magnetic field fluctuations were observed by VIKING near the apogee altitude of 13,500 km in the polar cusp region during a period of strong southward interplanetary magnetic field (IMF). The VIKING magnetic field experiment obtained vector magnetic field measurements up to nearly the proton cyclotron frequency (fH=28 Hz). Simultaneously, magnetosheath‐like electrons and ions as well as an upward‐flowing field‐aligned current were observed. The most intense flux of electrons and ions were colocated with a 35 nT depression in the total magnetic field strength of 1860 nT, interpreted as a diamagnetic effect. The density of magnetosheath‐like plasma, estimated from the diamagnetic depression, reached ∼500 cm−3. This extremely high density was also consistent with total plasma density estimates using high frequency waves. Magnetic field fluctuations were observed from 18 to 27 Hz and occurred when the magnetic field strength depression was maximum. These waves were left‐hand elliptically polarized with ellipticity between 0.2 and 0.3 and may propagate in the Alfvén‐ion cyclotron branch of the cold electromagnetic dispersion relation. Possible free energy sources included anisotropies in the electron and i

ISSN:0094-8276    

DOI:10.1029/GL015i005p00421

年代:1988

数据来源: WILEY

摘要:

Long‐term variations in high‐energy (greater than 2 MeV) electron flux at synchronous orbit are examined to reveal their close relationship to geomagnetic activity. The electron flux diminishes rapidly in association with an enhancement of geomagnetic activity (storm) and then increases. The flux becomes higher than the pre‐storm level and its peak occurs approximately 4–5 days after the enhancement of geomagnetic activity. A linear prediction filter is designed for daily sums of Kp as input data and corresponding daily averages of the electron flux (Log value) as output data. The data are those taken in 1984–1985. This filter can successfully reproduce the electron flux behavior observed not only in 1984–1985 but also i

ISSN:0094-8276    

DOI:10.1029/GL015i005p00425

年代:1988

数据来源: WILEY

摘要:

The two Phobos spacecraft, which will start to orbit Mars early in 1989, will be capable of investigating in detail the microphysics of the Mars‐solar wind interaction. Simple scaling arguments and analogies with other planetary bow shocks indicate that the sub‐solar shock standoff distance should be small compared with plasma scalelengths, giving the shocked solar wind insufficient space in which to thermalize downstream before encountering the magnetospheric obstacle. Both the magnetosphere and ionosphere can be affected by particles and waves from the solar wind interact

ISSN:0094-8276    

DOI:10.1029/GL015i005p00429

年代:1988

数据来源: WILEY

摘要:

The altitude distribution of the hot oxygen density was calculated for the upper atmospheres of Venus and Mars for solar cycle maximum and minimum conditions, respectively. The calculated values for Venus are in good agreement with the observed values and are about a factor of twenty larger than the calculated values for Mars at the exobase.

ISSN:0094-8276    

DOI:10.1029/GL015i005p00433

年代:1988

数据来源: WILEY

摘要:

Paleomagnetic measurements on asphaltic samples from two formations in southern Oklahoma have been performed. A bioclastic unit from the Boggy Formation, known as the Buckhorn asphalt, exhibited a stable, characteristic remanent moment (RM) after A.F. demagnetization between 5–20 mT. We infer from our data that very fine, possibly authigenic magnetite, like that shown to have a genetic relationship with the migration through rocks of hydrocarbons [Elmore et al., 1987], is the primary RM carrier in these samples. The tilt corrected paleopole for the Buckhorn asphalt (121.9 E; 43.5N; δp=1.3; δm=2.3) falls on the Early Permian Apparent Polar Wander Path for North America of Irving and Irving [1982], using a 30 Ma window (270–280 Ma). Because the Boggy Form‐ation, containing the Buckhorn asphalt, was depos‐ited during the Late Pennsylvanian (Desmoinesian), we interpret the data to indicate magnetization during minor uplift in the Early Permian of the Arbuckle Mountain region. The RM appears to have been acquired at this time, probably as the result of magnetite production facilitated by the introduction time of sulfate reducing

ISSN:0094-8276    

DOI:10.1029/GL015i005p00436

年代:1988

数据来源: WILEY