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11.
Sodar performance and preliminary results after one year of measurements at Adelie land coast, east Antarctica 总被引：1，自引：0，他引：1
S. Argentini G. Mastrantonio A. Viola P. Pettre G. Dargaud 《Boundary-Layer Meteorology》1996,81(1):75-103
Dumont d'Urville, on the Antarctic coast, is an area well known for the presence of strong katabatic winds blowing from the Antarctic plateau toward the sea almost all year. Since January 1993, a three-axis Doppler sodar has been operating in this area to investigate the variability of the boundary layer structure and dynamics. In this paper, the capabilities, behavior and advantages of using this ground-based remote-sensing system in Antarctica are evaluated after one year of measurements. This instrument may play an important role in boundary layer studies in remote regions where other profiling techniques (e.g., kitoons, slow ascent balloons) are difficult and expensive. All year long, except in summer when the signal-to-noise ratio was dramatically reduced by the noise of a large group of Adelie penguins, reliable measurements were available up to 900 m. The reliability of the vertical wind velocity has been checked and the influence of the local topography on the flow pattern has been evaluated. Some preliminary results regarding the statistical analysis of the horizontal and vertical velocities and an overview of the main physical processes are also shown. The statistical analysis of the wind speed shows that the wind blows from the 30 ° angular sectors centered at 90 °, 150 °, 180 °, and 0 °. The winds from 90 ° and 150 ° constitute the main local circulation and have, most of the time, the characteristics of a katabatic flow, whereas the winds blowing from 180 °, arising from the surface temperature difference between the sea and the land, are land breezes. Strong winds coming from the ocean (0 °), attributable to the inland penetration of depressions, have been observed in May, October, and November. Finally, some examples of the observed thermal structures, as depicted in the facsimile recording, are shown. 相似文献
12.
H. J. Beine S. Argentini A. Maurizi G. Mastrantonio A. Viola 《Meteorology and Atmospheric Physics》2001,78(1-2):107-113
Summary
Using a triaxial Doppler sodar the planetary boundary-layer structure and the wind flow dynamics at the Arctic site Ny-?lesund
have been studied. The relationship between winds measured at Ny-?lesund and at the nearby atmospheric research station on
Zeppelin mountain was investigated for the first time. While Ny-?lesund receives predominantly katabatic flow (from 120°)
from the Kongsvegen glacier, the field is rotated within the lowest 500 m and arrives at Zeppelin from southerly directions.
Received January 12, 2000/Revised November 21, 2000 相似文献
13.
A. P. Viola I. Petenko G. Mastrantonio S. Argentini V. Bezverhnii 《Meteorology and Atmospheric Physics》1999,70(3-4):133-140
Summary The behaviour of the wind field at the confluence zone of Terra Nova Bay during a transition period from winter to summer
is considered. To explain some observed features the influence of diurnal variations are considered to integrate and complete
the analysis based on annual and seasonal variations. Diurnal variations in the buoyancy difference between two main air masses
coming from the Revees and Priestley glaciers are assumed to contribute to diurnal alteration of the wind direction at the
Nansen ice sheet. The data recorded at three automatic weather stations (AWS) available that period are analysed. Using the
wavelet analysis procedure, it is shown that the contribution of one-day variations of some basic meteorological parameters
and their gradients (in particular of temperature and pressure) is important and comparable with synoptic ones. On the base
of the diurnal variations some aspects of the local circulation have been explained. The basis for the further studies related
to the evolution of katabatic winds in this area are also presented.
Received August 3, 1998 Revised March 12, 1999 相似文献
14.
Natural dams are caused by the blockage of streams as a result of the sudden arrival of detritus material during a glacial surge advance or fast slope collapse threatening downstream populations. Nevertheless, origin, morphological characteristics and stability of dammed lakes are frequently ignored. Six impounded palaeo-lakes were geomorphologically studied in the Benjamin Matienzo gully (32°14′ S–70°02′ W), denominated, from north to south: Goyete, Negro, Casa de Piedra, Lagunita, Susanita and Matienzo. We determined the origin, morphometric parameters, stability index and rate of streamflow rupture for these dammed ancient lakes in order to shed light on the potential outburst flood hazard in this Andean mountain region. According to our findings, we concluded that palaeo-lakes would have had a short life as they turned out to be unstable, except for the Goyete Lake, matching with the lack of fine lacustrine sediments in all river blockages. We also estimated the maximum peak discharge of a probable outburst flow generated during a drastic collapse of these dams. Obtained values range between 22 and 151 m3/s being notably higher than the average annual streamflow of Las Cuevas River (6.6 m3/s), but similar to the instantaneous streamflow of this river (157 m3/s, 2-year recurrence time). 相似文献
15.
We present a numerical investigation of the Kelvin-Helmholtz instability problem, in MHD approximation, for transitions involving continuous variations of both magnetic field and plasma parameters. The variations have been chosen in such a way as to reproduce general features of possible magnetopause transitions. The study, which leads to prediction of a wavelength of maximum instability, has been confronted with recent observational results of surface fluctuations of the magnetopause. 相似文献
16.
Case Studies of the Wintertime Convective Boundary-Layer Structure in the Urban Area of Milan, Italy
The paper describes some aspects of the convective boundary-layer structure based on simultaneous sodar and tethersonde measurements during a field experiment in the urban area of Milan in the period 8 to 20 February, 1993. During this period, fog episodes and strong low-level elevated inversions (with lower boundaries < 400 m) were observed most of the time. A close agreement in the mixing height values, derived from the sodar and tethersonde profiles, has been achieved under these conditions. The validity of the similarity relationships, which have been originally derived to describe the vertical velocity variance and heat flux profiles over horizontally homogeneous terrain under quasi-stationary conditions, was evaluated when applied to the urban boundary layer. 相似文献
17.
Stefania Argentini Giangiuseppe Mastrantonio Igor Petenko Ilaria Pietroni Angelo Viola 《Boundary-Layer Meteorology》2012,143(1):177-188
Measurements in the atmospheric surface layer are generally made with point sensors located in the first few tens of metres.
In most cases, however, these measurements are not representative of the whole surface layer. Standard Doppler sodars allow
a continuous display of the turbulent thermal structure and wind profiles in the boundary layer up to 1000 m, with a few points,
if any, in the surface layer. To overcome these limitations a new sodar configuration is proposed that allows for a higher
resolution in the surface layer. Because of its capabilities (echo recording starting at 2 m, echo intensity vertical resolution
of approximately 2 m, temporal resolution of 1 s) this sodar is called the surface-layer mini-sodar (SLM-sodar). Features
and capabilities of the SLM-sodar are described and compared with the sodar. The comparison of the thermal vertical structure
given by the SLM-sodar and the sodar provides evidence that, in most cases, the surface layer presents a level of complexity
comparable to that of the entire boundary layer. Considering its high vertical resolution, the SLM-sodar is a promising system
for the study of the nocturnal surface layer. The nocturnal SLM-sodar measurements have shown that, depending on wind speed,
the structure of the surface layer may change substantially within a short time period. At night, when the wind speed is greater
than 3 m s−1, mechanical mixing destroys the wavy structure present in the nocturnal layer. Sonic anemometer measurements have shown that,
in such cases, also the sensible heat flux varies with height, reaching a peak in correspondence with the wind speed peak.
Under these conditions the assumption of horizontal homogeneity of the surface layer and the choice of the averaging time
need to be carefully treated. 相似文献