Tese
Variabilidade em escala associada com jatos de baixo nível e ondas de gravidade na camada limite noturna do Pantanal
Fecha
2011-08-22Registro en:
MARTINS, Hardiney dos Santos. Scale variability associated with low-level jets and gravity waves in the nocturnal boundary layer in Pantanal. 2011. 166 f. Tese (Doutorado em Física) - Universidade Federal de Santa Maria, Santa Maria, 2011.
Autor
Martins, Hardiney dos Santos
Institución
Resumen
The Nocturnal Boundary Layer (NBL) turbulent structure above Pantanal Mato-Grossense, under
the influence of low-level jets (LLJ) and gravity waves (GW), is investigated. Experimental data
obtained during the Interdisciplinary Pantanal Experiment (IPE) dry season (IPE-2), and wet
season (IPE-3), carried out between 07th and 22th September, 1999, and 16th and 28th February,
2002, respectively, according to database from Universidade Federal do Mato Grosso, city of
Corumbá. Radiosonde data have been used to identify LLJ presence and classify them as: type 1
LLJ (jet associated to the sheltering surface) and type-2 LLJ (jet which causes upside-down
mixture). In addition to the radiosonde data, fast response data (wind velocity components,
temperature and humidity), measured from a 25m high micrometeorological tower, at 16Hz (IPE-
2) and 8Hz (IPE-3) samples were used. These fast response data were then decomposed in time
and scale via Wavelet Transform (WT), with complex Morlet mother wavelet. From the phase
difference between the wind velocity s vertical component (w) and temperature (T), obtained
through wavelet s cross spectrum, the presence of GW (phase difference near to 90º criterion)
were detected. The next step was to establish categories to analyse Pantanal NBL characteristic
state phenomena, which were based on LLJ, GW and length groups of occurrence. Such groups
are: type 1 LLJ, type 2 LLJ, no LLJ, with GW and no GW. From the amount of data of each
group, statistic parameters (variance, skewness, adimensional kurtosis, correlation coefficients
and covariances) were estimated by scale, in order to investigate the Pantanal NBL turbulence
structure and its variability in scale under the action of each of these groups. It was noticed that,
above all groups, type 1 LLJ is the most global intermittence provocative forcing in all micrometeorological series of data in Pantanal. On the other hand, type 2 LLJ is the less global
intermittence provocative forcing. With GW group shows an intermediate behavior between
groups type 1 LLJ and type 2 LLJ when considering global intermittence promotion. The length
scales 0.4m to 5000m were resolved in this study. It was also noticed that Pantanal NBL shows
two scale bands with remarkable different characteristics due to predominant distinct forcings in
it. For the first length scale band it prevails a mechanical force in the statistical parameters
behavior, to all groups and in both seasons. For the second length scale band it prevents the
action of buoyancy forces and mesoscale effects in the statistical parameters behavior in
Pantanal. As a result, it predominate stable conditions in the dry season; in the wet season,
however, NBL may present as a slightly unstable layer, due to a bigger water heat capacity and
its ability to behave as a energy sink during the day and heat source during the night. The early
evening transition period clearly shows a stable behavior to the dry season and unstable to the
wet season.