1.
Čurić, M.
(1987): Dependence of the mesostructure of the cold
front cloud system on the shape of frontal profile. Geofizika, 4, 5-15. (in Serbian)
ABSTRACT:
A waveform and the smooth slantwise sloped types of the frontal profiles
are considered. Cloud systems associated with such profiles are analyzed.
A double wave of frontal profile is followed by two cloud bands oriented
parallel to the approaching cold front. A smooth slantwise sloped profile is
accompanied by one relatively uniform cloud system. Cloud system evolution is
treated by simple theoretical consideration of dynamical and microphysical
factors of clouds. It is shown that the microphysical products can enhance
value of the frontal profile slope up to 30%.
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2.
Rančić, M.
(1987): Some analytical solutions for propagation of gravity waves along a
small-scale frontal surface. Geofizika, 4, 17-26.
ABSTRACT:
Propagation of the gravity waves along a small-scale frontal surface is
considered. The simplified perturbation perturbation
equations, which can be applied to describe this phenomenon, are introduced and
a method to solve them is exposed.
The main difficulty in finding analytical solution to the resulting
initial value problem is in taking into account the frontal inclination towards
ground. It is shown how this problem can be overcome by an approximate solution
in form of a Bessel-Fourier series, provided the inclination is partially
ignored in the governing equations.
In order to demonstrate the role of the frontal inclination in the
propagation of disturbances along the frontal surface, some properties of the
exact solution, which can be obtained after substitution of the wavelike
solution in the complete system, are analysed. It is shown that inclination leads
to the appearance of an instability of downstream propagating waves. This
phenomenon is further described and discussed.
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3.
Penzar,
ABSTRACT:
In order to obtain a more accurate evaluation of efficiency of the solar
system the measurements of global irradiation by Moll-Gorczynski
solarigraph were analysed with respect to levels of
energy instead to arithmetic means of irradiation. The time variation of
irradiation levels in daily and yearly course is considered. The structure of
global irradiation energy presented on the tilted plane and put in the
mathematical model improved the simulation of work of the entire solar
installation.
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4.
Bajić, A.
(1987): Cold air outbreak and the Adriatic bora. Geofizika, 4,
27-34.
ABSTRACT:
The case studies of two cold air outbreaks in Zagreb which cause a local wind bora on the eastern Adriatic area are presented ( 17 December 1978 and 7 January 1982 ).
The cold air outbreak on 17 December 1978 appeared as a shallow zone of large equivalent potential temperature drop ( Q e ) and NE wind with maximum at 800 m above ground. The stable layer which was placed above this zone was more expressed in terms of vertical Q e - rather than temperature-structure which was consequence of very humid and warm air advected from SW above the cold bora layer. This upstream bora layer characteristics and strengthening of cyclonic activity on the Tyrrhenian Sea caused a longlasting and strong bora associated with precipitation on the northern Adriatic . The strongest bora with maximum gusts of 35.2 m s -1 and with the longest duration of bora was 28-40 hours with the maximum gusts varying from 14.9 m s -1 to 34.7 m s -1 .
In the case of 7 January 1982 , a strong bora, associated with anticyclone strengthening over the middle Europe , occurred along the entire Adriatic coast as a consequence of an expressed cold and dry air outbreak. The main characteristic in this situation was a narrow zone of sudden drop of Q e and NE wind with a maximum at 2.5 km altitude. The stability above this zone was smaller than in the first situation and the temperature fall occurred throughout the troposphere. Due to extremely dry air supply, the bora occurred without precipitation lasting from 16 to 31 hours and even 52 hours in Senj. The maximum gusts varied from 17.0 m s -1 to 35.4 m s -1 .
Two case studies are not enough for a general conclusion but it should be emphasized that the bora had quite different characteristics in the considered frontal situations.
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5.
Rakovec, J.
(1987): Preliminary report on spectral characteristics of bora
on the
ABSTRACT:
Some results of measurements of the bora wind
in the
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6.
Petkovšek, Z.
(1987): Main bora gusts – a model explanation. Geofizika, 4,
41-50.
ABSTRACT:
In contrast to the known models of bora wind,
originating from the idea of rather uniform hydraulic flow, the basis of this
physical model explanation are observed gust characteristics of bora. The essence of this model explanation is the fact,
that bora is primary a very gusty wind, and the idea
that main gusts are not a consequence of turbulence in a general flow, but of
cylinders of cold air rolling down the slope on the warm side of the ridge.
Main rolls together with the turbulence and partly sliding of cold air develop
a general flow with observed bora characteristics.
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7.
Jurčec, V.
(1987): Mean monthly wind hodographs in the low troposphere in
ABSTRACT:
The analyses of mean monthly vertical wind profiles in the layer from
the ground to 3 km height are shown, on the basis of radiosounding
data in Zagreb-Maksimir, at 00 and 12 GMT, 1972 –
1981. It is shown that a daily variation of vector mean wind extends throughout
the considered layer, with more southerly wind direction in the daytime term.
However, the local effects, which are very pronounced in the daily variation of
speed and direction of the slope and valley winds, are confined to a shallow
surface layer. The upper level daily wind variation is attached to the
influence of mesoscale mountain circulation in the
Alpine region, which, by the entrainment processes, contributes to the low
steadiness of the boundary layer winds. These processes cannot be followed
directly in the monthly mean vertical wind structure, since the mean wind
vectors represent the frequencies of particular wind speed and direction in the
individual months and seasons. These frequencies,
however reflect the changes in large scale atmospheric circulation and its
anomalies, which are responsible for both mesoscale
mountain circulation and the behaviour of local boundary layer wind structure.
Due to the known variation of the large scale flow pattern and their
influence on anomalous monthly mean wind hodographs, one could expect that the
selected 10-years data sampling in not sufficient representative for the
long-term, climatological, wind structure in the
lower troposphere of
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8.
Stravisi, F.
(1987): Climatic variations at
ABSTRACT:
The time series of the annual values of eight climatic elements (atmospheric pressure, air temperature, relative humidity, precipitations, "bora" and southerly winds frequencies, sunshine duration and sea level) recorded at Trieste , northern Adriatic , in the years 1871 - 1985 are reported and analysed. The characteristic spectra are computed by means of least squares method: the most significant periods are 50, 24, 18.30, 12.70, 10.90, 7.80, 4.96, 4.62, 3.67, 3.42, 2.97, and 2.25 years, the last one corresponding to the quasi-biennial oscillation of 27 months.
The linear trends show an almost stationary pressure, an increase of the air temperature (+ 0.003°C a -1 ), a decreasing relative humidity (- 0.03% a -1 ), decreasing precipitations (- 1.5 mm a -1 .), a reduction of "bora" and an increase of southerly winds (- 0.3 and + 0.3 days per year respectively), a reduction of the sunshine duration (- 1.6 h a -1 ) and an increase of the sea level (+ 0.13 cm a -1 ).
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9.
Smirčić,
A., Z. Vučak, Z. Gržetić,
N. Leder, M. Ferenčak and
M. Gačić (1987): Some preliminary results of an
oceanographic experiment in the region of Velebit
Channel, Senj Gate and Kvarnerić
– March 1986. Geofizika,
4, 95-109. (in Croatian)
ABSTRACT:
In order to study the fetch dependence of wind wave energy, intensive
oceanographic measurements have been undertaken in the coastal area of Senj during the period March/April 1986. This area is
characterized by strongest NE wind (bora) in the
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10. Leder, N., M. Ferenčak and Z. Vučak (1987): Inertial – period oscillations in the
ABSTRACT:
Since 1978, Hydrographic Institute of the
Yugoslav Navy has organised continous meteorological
and oceanographic measurements at the oil-driling
platform “Panon”. The existence of
inertial-period oscillations was observed only in summer season when
sub-tropical high pressure disappears and cyclonic disturbances travel towards
the
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11. Bone, M. (1987): On topographic and wind vorticity effects in bora driven
circulation in the
ABSTRACT:
The effects of the bottom topography and input of the atmospheric vorticity to the sea for the NE (bora)
wind driven circulation in the North Adriatic was studied from the numerical
solutions of the vertically integrated Ekman’s
equations. The numerical results for the vertically integrated current show
that the effects of bottom topography and input of the atmospheric vorticity to the sea are of the same importance in the
formation of the characteristic flow pattern and neither can be neglected.
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12. Kuzmić, M. and M. Orlić (1987):
Predicting the currents in the
ABSTRACT:
The wind-induced currents in the Northern Adriatic have been studied by present authors using a hydrodynamical numerical model and empirical data collected in the area. In the model, based on linearized equations of motion and continuity, the wind momentum transferred at the sea surface is the only forcing mechanism. The usual quadratic law of the form:
is used to parameterize the stress 
The parameters in the equation, the drag coefficient ( C D ), the air density ( r a ), and the wind velocity ( u a , v a ) are often taken as constants. In this paper the constant parameters are used to define the starting, reference case; the influence of variability in the parameters, heterogeneous wind field and variable C D in particular, is then examined. Four output fields, the sea-level displacement, vertically averaged current, surface current, and bottom current have been calculated for each simulated case. The predictions of the four fields differ considerably when the heterogeneous stress field, due to wind curl or drag coefficient, is introduced. Modelling results indicate that inadequate knowledge of the stress field combined with local topographic and coastal influences can produce a factor of two difference in current magnitude and tens of degree difference in current direction.
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13. Rajković, B. and G. L. Mellor (1987): Air-sea interaction in
the vicinity of the land-sea boundary in the presence of upwelling.
Geofizika,
4, 147-165.
In order to examine a possible sea-air interaction in the vicinity of
the western edges of continents, successive integrations of a 2 – D
atmosphere and ocean models were performed. The ocean model had prescribed wind
forcing that was obtained from the atmospheric model which in turn had
prescribed sea surface temperature resembling one for well developed upwelling.
Both models are for a hydrostatic and Boussinesq
fluid with a sigma coordinate system. They have high resolution in the
horizontal and a very high resolution in the vertical, capable of resolving
both top and bottom boundary layers. Turbulent fluxes and mixing coefficients
are parameterized with the so-called 2.5 level, second order closure scheme
proposed by Mellor and Yamada. Seaward boundary conditions for the ocean model
and lateral boundary conditions for the atmosphere model were of the radiation
type. The ocean model had prescribed sea surface elevation and y-component of the pressure (buoyancy)
field from the available data.
The diurnal cycle for the atmosphere model was implemented through the specification
of the land surface temperature while night time cooling was modelled with a
Newtonian forcing. The reference thermodynamic state of the atmosphere model
was very similar to the observed state of the atmosphere in the Coastal Ocean
Dynamics Experiment while environmental winds were specified to give values for
the wind-stress close to the observed climatological
values.
The significant modification of the wind-stress profile relative to the
wind-stress profile for the homogeneous sea surface temperature was obtained
when the sea surface temperature was similar to the one for the well-developed upwelling. In the case of the constant sea surface
temperature wind-stress profile was fairly constant in the offshore-onshore
direction except in the vicinity of the coast line. With sea surface
temperature profile resembling well-developed upwelling
the atmosphere model developed wind-stress profile that had pronounced decrease
in 40 km band next to the coast and a weak increase right at the coast.
The ocean model forced with the wind stress obtained from the atmosphere run that had homogeneous sea surface temperature, developed strong upwelling zone and quite strong equatorward current with embedded jet near the coast. Forced with the wind stress from the run with nonhomoheneous sea surface temperature, the ocean run had a much weaker upwelling and a double structure of the longshore current with the poleward flow in the vicinity of the coast line an equatorward flow in the region, away from the coast, where wind stress was bigger than the prescribed, vertically integrad y-component of the pressure gradient force.
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