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Observational evidence of the characteristics of the large amplitude, short wavelength stationary waves found in the lee of South America and Australia during the complete first special observing period of the first GARP global experiment is presented. The structure and evolution of the waves are described and their possible origin discussed.
Because of the variety of extraordinary phenomena exhibited by active chromosphere objects, discovery of new, bright surface-active stars is of considerable importance. Ca II emission is a well-known signature of chromospheric activity, serving even as one of the points of definition of the class of RS CVn binary stars. In connection with the present investigation, spectroscopic observations of 27 Ca II emission stars have been conducted. The observations make it possible to identify unambiguously the most chromospherically active stars in the sample. By observing the H-alpha line, rather than H and K, it is possible to distinguish nine of these stars which are likely to be observational targets as interesting as the extremely surface active objects V711 Tau or FK Com. Of the 27 stars surveyed, two (HD 86005, HD 204128) showed H-alpha as an emission feature above continuum, with estimated equivalent width 1-2 A.
Further observational evidence is presented for the existence of large amplitude short stationary waves during the month of January, 1979 in the lee side of South America. These waves are noted not to have been produced by either topography or CISK; their cause was probably related to stronger tropical convective heating over the Amazon and central Pacific during January. This source of stationary forcing was associated with the weaker easterlies and stronger westerlies in the topics, which allowed free propagation of the energy from the stationary forcing into the extratropics.
Large amplitude stationary Rossby waves were discovered with zonal wavenumbers of approx. 7 between 20 S and 40 S over and in the lee of South America. These waves, present during January 1979, disappeared in February, 1979. It was concluded that the waves were not orographically forced because they corresponded to a ridge in the lee of the Andes, and were not forced by observed sea surface temperature anomalies because of their space and time phase relationship. Two 15 day forecast experiments were performed with the GLAS Fourth Order General Circulation Model, and initial conditions corresponding to 5 January and 4 February, 1979. These forecasts reproduce reasonably well the presence of the January wave and their absence in February. Several mechanistic experiments to determine the origin of the waves were also performed. A No Andes forecast shows that the waves do indeed exist independently of orographic forcing. Several experiments modifying the coefficient of latent heat lead to the conclusion that tropical heating is important in the maintenance of the waves.
Results of NCAR thermospheric general circulation model (TGCM) simulations were compared with Dynamics Explorer (DE2) data on the neutral wind, temperature and O and N2 number variations over the south polar cap in the F region in October-November 1981. Attention was focused on variations in the thermospheric characteristics. All variations reached a maximum over the magnetic polar cap, with the largest O and N2 changes being present in the dawn sector of the auroral oval, where Joule heating was maximized. The TGCM simulations for conditions similar to the DE2 passes agreed well with the satellite data, indicating that the variations in the wind, temperature and compositional characteristics are dependent on the magnitude of magnetospheric convection and influenced by the separation between the geomagnetic and geographic poles.
For a number of years, satellites have been employed to measure auroral particles and fields within the high-latitude thermosphere. In the present paper, data from orbit 1174 of the Dynamics Explorer 2 satellite on October 21, 1981, are utilized to calculate the structure of the ionosphere and thermosphere below the satellite altitude down to about 80 km. Attention is given to details regarding the DE 2 measurements, a satellite track model, the calculated ionospheric structure, and the calculated neutral gas heating rates. The investigation demonstrates that the technique of deriving characteristics of the ionosphere and atmosphere below a satellite track promises to be very fruitful for defining the characteristics of the lower thermosphere for use in large numerical models of the thermosphere and ionosphere.
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The dominant component in the mean annual cycle of sea level pressure in the latitudes north of approx. 40 deg S is the yearly wave, whereas to the south of this latitude a half-yearly wave dominantes. In FGGE, however, the usually small yearly wave was large in the Antarctic, owing to the extraordinarily low pressure there in the winter of 1979. The half-yearly wave's amplitude was appreciably above normal in the center of each ocean in middle latitudes, and below normal at high latitudes. The yearly wave in the zonal geostrophic wind was larger than normal over the Antarctic Ocean. Similar results are obtained at 500 mb. The three month mean stationary waves (zonal harmonic waves) were larger than the mean in FGGE. The intra-annual variation of both amplitude and phase of the monthly mean harmonic waves in FGGE was large, which is not surprising as they contain an appreciable transient component, unlike the long term monthly mean waves.
Viking Orbiter images of intracrater dunefields in the Noachis Terra region were examined in order to study the morphology of these landforms and to assess their relationship to local geological settings. The sizes of the dunefields range from 40 to 3600 sq km and vary directly with crater size. Preliminary studies reveal dunefields of two varieties. The most common type is composed of massed straight to slightly wavy crescentic dunes similar to those described by Breed. Dunefields of this type occupy more than 20% of the area of the crater floor, with the dunefield margins often marked by a large dune wall or rampart. Dune spacing ranges between 0.7 and 1.2 km. The second type of dune accumulation consists of clusters of large, widely spaced straight or curved ridges, which often intersect to create rectilinear patterns. Dunes are typically spaced 1.6 to 4 km apart. Earth terrestrial analogs for these dunes are discussed.
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The results of an ozone measurement campaign conducted at Natal, Brazil from March 25 to April 15, 1985 are reported. Complete profiles of ozone, pressure, and temperature were obtained from the ground to 52 km, and all of the profiles correspond with site overpasses by ozone instruments on NASA and NOAA satellites. The profiles from this measurement series show reasonable agreement with established satellite climatologies. Stratospheric ozone variability was 2 percent or less during the 3 weeks of the measurement campaign, with stratospheric temperature and pressure variabilities half that amount. Low variability at a single location for this period implies comparable uniformity for ozone profiles over a large area around the measurement site. The auxiliary pressure and temperature profiles presented here allow the use of this data set as a transfer standard between satellite instruments with different fundamental ozone measurements. Finally, the low ozone variability in the stratosphere at Natal during this measurement series should provide an opportunity for high-quality intercomparisons of measured and modeled ozone concentrations in the equatorial stratosphere and lower mesosphere as well as a consistency check among satellite ozone measurements.
A spectral line survey for interstellar NH3 is being carried out using the 64-m telescopes at Parkes and Tidbinbilla. Both telescopes are equipped with K-band maser receivers yielding system temperatures below 100 K. The preliminary survey is being made with the Parkes antenna (beam = 1.35 arcmin), with follow-up mapping of the more interesting sources at Tidbinbilla (beam = 0.9 arcmin). The selected sources have in general been H II regions from the H2CO surveys made at Parkes. Statistical results from initial observations of the (1,1), (2,2), and (3,3) lines in the preliminary survey are presented.
The possible role that divergent circulations emanating from regions of large scale organized convection may have on the rotational motions of the subsiding branch of the resulting overturnings is considered. Correspondence is found between the cross-equatorial flow emanating from regions of organized convection in the Northern Hemisphere, and the subtropical jet in the vicinity of Australia. The difference field also reveals a good correspondence between changes in the meridional gravity wave component and changes in the intensity of maximum zonal wind. The results are consistent with the picture of a local ageostrophic Hadley overturning in the entrance region of subtropical jets, and they show the importance of adequate resolution of tropical divergent modes.
This study was made in support of the LAWS and GLOBE programs, which aim to design a suitable Doppler lidar system for measuring global winds from a satellite. Observations were taken from 5 deg S to 45 deg S along and off the E and SE Australian coast, thus obtaining representative samples over a large latitude range. Observations were made between 0 and 6 km altitude of aerosol physical and chemical properties in situ from the CSIRO F-27 aircraft; of lidar backscatter coefficients at 10.6 micron wavelength from the F-27 aircraft; of lidar backscatter profiles at 0.694 microns at Sale, SE Australia; and of lidar backscatter profiles at 0.532 microns at Cowley Beach, NE Australia. Both calculations and observations in the free troposphere gave a backscatter coefficient of 1-2 x 10 to the -11/m/sr at 10.6 microns, although the accuracies of the instruments were marginal at this level. Equivalent figures were 2-8 x 10 to the -9/m/sr (aerosol) and 9 x 10 to the -9 to 2 x 10 to the -8/m/sr (lidar) at 0.694 microns wavelength at Sale; and 3.7 x 10 to the -9/m/sr (aerosol) and 10 to the -8 to 10 to the -7/m/sr (lidar) at 0.532 microns wavelength at Cowley Beach. The measured backscatter coefficients at 0.694 and 0.532 microns were consistently higher than the values calculated from aerosol size distributions by factors of typically 2 to 10.
Radiosonde (RS)and satellite-derived (Nimbus-7 LIMS) 100-mb temperatures over New Zealand at 12 GMT are compared for the 1978-79 summer. The colocated LIMS temperature information consists of synoptically mapped values (for 12 GMT), as well as the primary nighttime orbital retrievals valid at about 1030 GMT. The RS time series of temperature is dominated by temporal fluctuations associated mainly with the eastward passage of waves which have characteristic periods of 4-5 and 11-12 days and peak-to-peak amplitudes of 10-15 K. The LIMS temperatures and the corresponding temperature time series are also found to exhibit quite close agreement (in terms of temporal phase for the latter) with the RS data. However, the LIMS-mapped temperature fluctuations suffer from a noticeable attenuation in amplitude (approaching 50 percent for higher-frequency fluctuations), which will affect the accuracy of LIMS-derived estimates of dynamical quantities such as wind velocity and relative vorticity in the lower stratosphere.
Measurements of the altitude, latitude, angle, and energy distributions of 5-80-MeV neutrons at 29 deg S geomagnetic latitude and 8.5-GV cutoff, obtained with the University of California neutron double-scatter telescope on a flight from Alice Springs, Australia, on November 10, 1981, are reported. The data are presented in extensive tables and graphs and characterized in detail. The altitude distribution of upward-moving and downward moving neutrons is found to peak at 100 g/sq cm (as reported for 41 deg N geomagnetic latitude by Preszler et al., 1974), while the angular distributions exhibit dips at 60 and 130 deg and the energy distribution has a flat region at about 20 MeV. The escape current of 0.059 + or - 0.008 neutrons/sq cm sec is consistent with theoretical models for the injection of energetic protons into the earth radiation belt (Merker, 1972 and 1975).
Two case studies of miniholes, rapid ozone decreases, noted in 1987 near the base of the Antarctic peninsula are studied using a digital filter. The results show a strong correlation of the total ozone minihole with a temperature minihole (a negative temperature perturbation), and a westward tilt with altitude of the temperature minihole. The ozone minihole is phase shifted both slightly to the east of a high in the geopotential height field and slightly to the west of a local low in the Ertel potential vorticity field.