Bora Wind Research Articles

A case study of bora-driven flow and density changes on the Adriatic Shelf (January 1987)

A numerical modelling study of the response of the Adriatic shelf waters and the Po River plume to a bora wind event has been undertaken using the Princeton Ocean Model (POM). After a bora episode from 16 to 20 January 1987, Advanced Very High Resolution Radiometer (AVHRR) satellite image revealed a cold filament protruding from the Italian coastal area toward the open sea. To understand and numerically simulate the offshore spreading of cold water from the western coastal area, the effects of three external forcings have been examined: wind stress, heat flux and river discharge. Wind stress and surface heat flux, calculated by bulk method from the winds, air temperatures and humidities obtained by Mesoscale Model 5 (MM5) with space and time resolution of 9 km and 1 h, respectively, were used to force the oceanographic model. River discharge was introduced in the oceanographic model as a source term in the continuity equation. Moreover, it was assumed that river water had zero salinity and a 5°C lower temperature than the surrounding sea water, following some climatological estimations. The results of numerous numerical experiments revealed that the filament observed in the AVHRR satellite image was formed by the joint action of three external forcings mentioned, and that none of them could be neglected while considering the observed pattern. Although the bora is, due to its NE direction, downwelling favourable wind for the western Adriatic coast, its alongshore variability induces offshore spreading of cold and less saline Po-influenced water. The effects of air stability and wind wave field are important for the wind stress estimation. The role of the Po River is to reduce sea surface salinity and to prevent cold water from sinking; it is introduced in the oceanographic model mainly through the initial salinity field. The combined effects of the basin topography and surface heat flux create an extra amount of cold water in the western coastal strip, which is then advected by bora wind action toward the open sea. High horizontal resolution of the numerical experiments is important in resolving the alongshore variability of the bora wind field and to correctly simulate the narrow filament observed in the AVHRR image.

Northern Adriatic Sea surface circulation and temperature/pigment fields in September and October 1997

Satellite images of surface chlorophyll- a concentration measured by the sea-viewing wide field-of-view sensor (SeaWiFS) and of sea surface temperature derived from advanced very high resolution radiometer (AVHRR) measurements, combined with in-situ drifter measurements of surface currents, and ancillary wind, Po River discharge and surface salinity data, are used to describe the surface dynamics in the northern Adriatic during the period September–October 1997. The satellite observations revealed very complex mesoscale dynamics, with time scales of a day or two and length scales of about 10 km, including the meandering and instability of basin-scale currents (e.g., the western coastal layer), jets/filaments and eddies. In addition, the two typical patterns of the Po River plume are observed and qualitatively explained in terms of wind forcing. A basin-wide double gyre pattern spreads the rich runoff water across most of the northern Adriatic from mid-September to early October, following Bora wind events and under stratified sea conditions. In contrast, in late October the Po plume is confined to the coast due to weaker winds and de-stratified conditions. This variability in the Po River plume extension is also confirmed by in-situ salinity measurements.

Modeling dense water mass formation and winter circulation in the northern and central Adriatic Sea

In this paper, using an eddy resolving primitive equation model, we attempt to provide quantitative answers to some of the still unresolved or poorly understood dynamical issues related to the general circulation of the northern and central Adriatic Sea. The first question we addressed relates to understanding the effects of the major driving mechanisms on the basin circulation. A series of numerical experiments are carried out to examine the circulation produced by various combinations of different forcing mechanisms. Cold air outbreaks (CAO) associated with the northeasterly bora winds, together with uniform surface cooling and freshwater discharge prescribed near the northwestern corner, give a fairly realistic circulation consistent with the observations. This pattern is comprised of an overall cyclonic gyre in the northern basin, with a strong southward flowing jet along the Italian coastline and a broader northward flow along the Croatian coast. The second question addressed is under what conditions convective mixing extends to the bottom of the Jabuka Pit. While the northern shelf is always uniformly mixed to the bottom, the extent of convection within the Pit depends on the overall stratification prior to onset of the CAO event. Strong subsurface stratification between the intermediate and near-bottom layers prevents deep convection. The third question concerns with the role of the rim current along the Italian coast vs the other circulation components in distributing the North Adriatic Dense Water (NADW) within the basin. In general, the strong density front developed across the shelf break north of the Jabuka Pit restricts the replenishment of the Pit deep layers by the NADW. Rather, the NADW is transported southward along the Italian continental slope in the form of a vein of underflow. The final question addressed is how the thermohaline structure of the water column evolves after the ending of the CAO event, and of the related convection process.

A real data simulation of the Adriatic bora and the impact of mountain height on bora trajectories

This study addresses simulation of the local bora wind and its properties as reflected on typical trajectories. Trajectory calculations are implemented in the Eta Model. The Eta Model has a vertical coordinate which permits a step-like representation of mountains and quasi-horizontal coordinate surfaces, the so-called eta coordinate. A realistic real data simulation of a bora wind case in achieved using the model with a 28 km horizontal resolution and 16 layers in the vertical. Numerical experiments with different mountain heights and shapes in the bora wind region are performed. These are motivated by observational indications and theoretically based expectations that a certain intermediate mountain elevation is required for generation of downslope windstorms with bora wind properties. Three-dimensional trajectories over various mountains mimicing real mountains but differing primarily in elevation are calculated and analysed. The maximum bora wind speed is predicted as expected through three-dimensional channels in the step mountain representations. The results illustrate and are in agreement with the observational evidence that mountain barriers of the elevation of about 1000 m are a necessary requirement for the occurrence of the bora-type downslope windstorms.

Improved bora wind simulation using a nested Eta Model

This paper reports on improvements obtained in simulations of bora wind using a nesting technique in a primitive equations model. A version of the so-called Eta Model is used for both the lower resolution as well as for the higher resolution nested run. For nesting, a technique has been developed whereby for the boundary conditions “underground” model values are used. They are obtained by horizontal interpolation of model variables inside the model's eta layers. Simulations are initialized using real data. This is done in order to assess the model's performance in simulating the bora wind, an important mesoscale phenomenon caused by orography. Improvements achieved by nesting are illustrated by examples of precipitation as well as a trajectories forecast.

Strong Bora Wind -Risk Factor in Traffic

This paper presents a survey of strong bora wind. Bora windof extreme severity, which may blow along the entire Adriaticcoast, usually causes a lot of damage to the electrical power networkand a complete road and sea traffic disruption. Therefore,there is a growing need for introducing the bora risk factor intraffic planning.

Baroclinic Response of the Adriatic Sea to an Episode of Bora Wind

Abstract The response of the Adriatic Sea to bora wind forcing in stratified conditions is analyzed using a baroclinic multilayer model. The model is linearized in the momentum equations and fully nonlinear in the thermodynamic equations. The model was forced with an idealized wind field having horizontal shear and also convergence. The alongshore shear is approximated by a harmonic function of the alongshore distance with an 80-km space scale, and a maximum corresponding to a moderate wind of 3 dyn cm−2. Idealized initial temperature and salinity vertical profiles similar to an autumn situation are assumed. The model was integrated for five days, presumably a duration of a more persistent bora event. Due to strong shear in the bora wind field the sea level is characterized by a series of highs and lows distributed along the longitudinal axis of the Adriatic. The highest positive sea level departures are observed at the northernmost corner of the Adriatic near Venice associated with the wind setup. The st...

Circulation and heat exchanges of the Northern Adriatic in the winter season 1992/93

The sea currents, temperature and conductivity were measured continuously at two stations and two depths of the eastern part of the Northern Adriatic during the winter season 1992/93. Meteorological elements were measured simultaneously at the two nearest meteorological stations on the Croatian coast (Rovinj, Pula). The sea level was also measured in that period at Rovinj. One severe bora storm was observed in the period of measurements. Qualitative good agreement between observed currents and velocities of the earlier developed models for the response of the Northern Adriatic to the bora and sirocco wind forcing has been shown. The sea currents on the Rovinj-Po transect are of the opposite direction to the bora wind because of tis spatial heterogeneity. The sea level observed at Rovinj station rose during the bora blows and it was much higher than what expected in the developed models. The response time of the currents to the bora forcing is computed by using correlation function between currents and wind. The heat exchanges on the sea-atmosphere surface are calculated. The correlation between same wind components and between total heat exchanges for two different stations was made. The sea temperature evolution calculated from meteorological data agrees well with what observed, especially for the Pula station. At the end of the measurement period the new dense water (σt=29.3 kg m−) was observed.

Numerical analysis of vegetation complexes and community diversity of major coastal dinaric mountains

Abstract. This study includes 24 transects on slopes of the Velebit, Biokovo and Orjen mountains, the tallest coastal mountains along the Adriatic Sea, with a very high species richness according to European standards and having the largest regional concentrations of endemics. Within each transect the presence or absence of phytosociological alliances, according to the Zürich‐Montpellier School, was interpreted from local studies. The alliance composition of the transects was compared with methods used in numerical syntaxonomy. Three types of vegetation complexes (N. Dinaric inland, transitional and S. Dinaric coastal) were derived from a numerical classification of the transects; they were defined on the basis of their characteristic alliances. The maritime impact affecting the mountains through the river canyons reduces the contrast in vegetation between inland and coastal slopes. The existence of a climatic macrogradient is indicated by seriation of the basic alliance/transect data matrix leading to a diagonal structure, by a gradual shift of the alliance composition within the same vegetational type, and by the distribution of the transects and alliances along the first axis of a Correspondence Analysis ordination. Transect scores on the second ordination axis are negatively correlated with transect vegetational diversity (number of alliances per transect); this axis may reflect a decrease in humidity and temperature range. This interpretation is supported by the result of a comparison of the total mountain vegetational diversity (Mann‐Whitney test), which showed that Orjen is the most diverse mountain ridge. The expected correlation between plant community diversity and altitude of the transects is blurred, probably due to the impact of the cold Bora wind and subsequent compression of vegetational zones.

Evaporation and heat exchanges between the sea and the atmosphere in the Gulf of Trieste during 1988

Daily mean values of meteo-oceanographic parameters are used to compute evaporation and heat fluxes between the sea and the atmosphere in the Gulf of Trieste during 1988. Incoming solar radiation, long-wave radiation, latent and sensible heat fluxes are considered in the total heat budget. The contribution of the single parameters entering each formula is examined and a comparison between the results from different evaporative formulae is performed. The total heat budget for the year considered gives a net loss of energy of 21 W/m2 which must be supplied by the heat transported by marine currents. The balance is positive for the sea surface from April to July, negative for the remaining period. Long-wave radiation accounts for the 45% of the total heat loss, latent heat for 53% and sensible heat for 2%. Computed annual mean evaporation is 1058 mm, with high peaks of more than 15 mm/day during strong Bora wind events. Evaporation slightly prevails on precipitation giving a net water loss of 30 cm. A comparison with what is found in the literature shows these results representative of the entire North Adriatic Sea. They confirm that this basin represents a sink of heat whose role in the general Mediterranean circulation consists in trasforming surface warmer waters coming from South in denser ones.

Observations on a bottom vein of dense water in the southern Adriatic and Ionian seas

We discuss the motion and spreading of a bottom vein of very dense marine water, which originates (σ ≥ 29.4) in winter through cooling and evaporation processes resulting from the violet Bora wind blowing over the shallow North Adriatic Sea into the deepest layers of the southern Adriatic and Ionian seas (eastern Mediterranean basin). Our analysis is focused on the peculiar physical processes that control this bottom flow. We first describe the vein motion in the southern Adriatic Sea in which this current follows approximately the isobaths (in partial accordance with the conservation of potential vorticity) and the main mixing process of dense water with Levantine Intermediate Water occurring in an offshore‐oriented canyon near Bari. This canyon causes a deepening and flattening of the original vein of dense water, such that downstream the water can be observed only on the Otranto Sill (at depths of ≈ 800 m with σ ≈ 29.25). The subsequent flow in the Ionian Sea follows approximately the 900‐m isobath in the Gulf of Taranto and along the Calabrian and east Sicilian coasts, in agreement with the results of Smith's and Killworth's theoretical models of steady motion of density driven currents over a regular slope, in a rotating system, for stratified fluids.

Numerical modelling of Bora winds

The Bora winds are produced by cold stable air which pours over the Dinaric Alps, often producing intense winds along the Adriatic Coast. Although the flow appears qualitatively similar to the hydraulic flow described by the shallow-water equations, there are certain significant differences: the cold low-level air is continuously stratified and a critical layer in the winds typically occurs near the inversion which caps the cold pool of air. Through two-dimensional numerical mountain wave simulations, we investigate the extent to which hydraulic theory can be used to describe the Bora winds. We analyze the structure of the Bora flow derived from aircraft observations collected during the ALPEX field phase on 15 April 1982 and compare it with a numerical simulation initialized from upstream sounding data. By varying the environmental sounding in our simulations, we find that for this case, neither the critical layer nor the inversion layer play a fundamental dynamical role in generating the strong winds along the lee slope. Instead, the wave overturning which occurs beneath the inversion appears to be the most important factor in producing the strong response. This overturning produces shooting flow over the lee slope and strongly resembles the hydraulic flow which occurs both in shallow water theory and in simulations in which over-turning is suppressed. We believe the hydraulic jump-like mechanism producing the strong Bora slope winds is fundamentally similar to the underlying mechanism which produces the intense winds along the lee slope of the Rocky Mountains. This occurs despite significant differences in the character of the larger scale flow in these two situations.

NATIVE PEOPLE'S OBSERVATION ON LOCAL WINDS ON THE CROATIAN COAST

Local names of the winds from various directions such as sjeverac, oštro, levante and burg (widely known as bora) and their characteristics are mentioned here. The description of this article is based on neither the meteorological nor the climatological measurement, but on the summarization and induction of the local people's experiences, which have a close connection to their occupations—agriculture and fishery. The followings are the major results obtained :(1) The main signs of bores wind are : i) Mountain clouds called “brv”, which look like a form of foehn wall, are formed at the cols at first, then gradually covers all over the ridges of Dinar Alps forming kapa clouds. ii) In the case that the whole sky is covered by low clouds, the relatively high and bright clouds are to be seen in the northwest direction and the dark clouds in the south. (2) The bora wind blows with striking gustiness (na mahove) with a cycle of 3-4 minutes. The bora wind falls down on the coast as if “hard things were thrown on the ground”. The tops of the sea waves turn to sprays by the strong wind, causing a thick, hazy visibility over the sea. This phenomenon is called fumaria at Trieste. (3) Calm after the bora wind, called bonaca in this region, generally continues 2 or 3 days. Then the southerly wind, jugo, begins to blow. (4) There are two types of bora wind recognized widely by native fishermen because of their distinct characteristics. One is jasna bura (literally, bright bora) which means an anticyclonic bora, and the other is mra_??_na bura (dark bora), a cyclonic bora, respectively. The former prevails in the whole region of Adriatic Coast in the Croatian territory, but the latter limits itself to the northern part of the region. The border line may be located between Šibenik and Split.Some shelters from the bora wind are used among the fishermen, who have a good knowledge of the local peculiarities of land and sea, and also of the sequential phenomena by their long experiences.

LOCAL CLIMATOLOGICAL OBSERVATION IN THE SENJ REGION, CROATIA, AND THE AJDOVŠ_??_INA REGION, SLOVENIA, FROM NOVEMBER 1972 TO JANUARY 1973

In order to make clear the local climatological characteristics of bora winds, the observations were carried out in two famous bora regions in Yugoslavia. The main re-sults obtained in the Senj region are as follows: (i) In the case of relatively weak bora, the bora wind begins gradually from the Vratnik Pass to the coast. on the other hand, in the case of strong bora, the bora begins abruptly on the whole lee side slope. (ii) The temperature decreases lesser on the foot of the slope than at the pass in the clear begin-ning of bora. (iii) When the wind velocity at the pass reaches 11-14 m/s, the wind velocity on the foot of the slope increases sharply. The wind on the foot becomes not so strong in the cases that the wind at the pass blows stronger than these wind ranges. (iv) If the vertical structure of the atmosphere is unstable, the wind is relatively weak. (v) The strongest bora region is located on the slope north of Senj. Along the coast, the bora is strong between Senj and Klenovica. The results obtained in the Ajdovscina region are: (i) The axis with strong wind runs parallel to the ridge in the case of relatively weak bora. The horizontal distance between the axis and the mountain ridge is 3-4 km. (ii) If the bora wind becomes more and more strong, a closed region with strong wind west of the Ajdovscina city experiences higher wind velocity than the axis region. (iii) In the case of the strongest bora, the axis moves leewards and accordingly, the strongest wind appears in the center of the basin. (iv) It is considered that the distribution pattern revealed by the wind-shaped trees, reported by Yoshino et al. (1973) in Climatological Notes No. 14, corresponds to the condition of the long year average, which contains the whole cases with wide ranges of wind velocity.

VERTICAL DISTRIBUTION OF THE CLIMATIC ELEMENTS ON THE BORA DAY

The vertical distribution of the climatic elements on the bora day over both sides, windward and leeward, of the Dinar Alps were investigated relating to synoptic patterns. At first, weather maps of the bora day provided by the actual observation in Aj dovscina and Trieste were examined and distinguished into new 6 types. Among these types the cyclonic E (LE) type was taken out of Yoshino's (1971) results because of its higher frequency of occurrences and distinctive value in diurnal variation of climatic elements. The vertical distribution of the wind speed, wind direction, temperature and relative humidity were compared with each other with respect to the occurrence frequency of these or mean value. The results are as follows ; 1) Over Zagreb, a windward station, on the bora days, the winds of 0_??_90 deg. are dominated in the lower layer of the atmosphere. The upper limit of the bora wind tends to appear in different height in accordance with synoptic patterns except LE type. The limits are 1, 500 gpm in HA (anticyclonic A), 2, 000 gpm in HB (anticyclonic B), 2, 500 gpm in LA (cyclonic A), 1, 500 gpm in LB (cyclonic B). Over Split, a leeward station, the bora winds concentrate in lower level than over Zagreb. 2) The height of the upper limits of the bora winds nearly coincides with the heights of mean wind maximum, small lapse rate, and gentle horizontal gradient of temperature. 3) A height of maximum frequency of N to E winds appears at 5000 _??_ 2, 0000 gpm over the windward station and 0_??_500 gpm over the leeward station. 4) On bora days, the inversion often appears between 1, 500 and 2, 000 gpm over the windward station but at the same or lower level over the leeward station. 5) Taking account of the height of inversion layer, wind profile and so on, a model of bora is constructed as in Fig. 4.

VEGETATION ON THE ADRIATIC COAST OF YUGOSLAVIA

The vegetation distribution on the Adrratic coast from Rijeka to Dubrovnik and on the five islands, Krk, Cres, Losinj, Rab and Pag, was studied in relation to the climatic conditions, especially to the local wind, bora. The climax vegetation in this region is the Mediterranean evergreen hard wood forests and deciduous broad leaved forests. The vegetation shows the Mediterranean type on the Adriatic slopes of the Velebit Mts., but, in contrast, the continental type on the inland-facing slopes. The deterioration of vegetation is the most serious on the slopes up to 500 m above the sea level on the coastal region. It looks like a land almost without vegetation. The evergreen oak forests re-main in restricted areas on the Rab island and their degradation types, maquis and garrigue, were found along the coast and on the islands south of Zadar. The poor-vegetation landscape prevails on the windward slopes, but, on the contrary, the forests or the ever-green vegetations on the lee side slopes on the islands.The degree of density of the vegetation was studied for determining quantitatively the effect of the winds in this region. The rough density is found in the coastal and island regions from the north of Senj to the north of Zadar. This region coincides perfectly with the strong bora regions, which was revealed through an intensive investi-gation on the wind-shaped trees. The effect of wind, however, might be in a following way : (i) the original vegetation was destroyed first by human activity, (ii) the strong bora winds hindered the vegetation from restoration, and (iii) overgrazing of goat and sheep and felling of trees for fire-wood intensified the effect of hinderance by the winds.

The Reka-Timavo River System of the Yugoslavian and Italian Karst

The Reka-Timavo River System of the Yugoslavian and Italian Karst PAUL B. ALEXANDER* In the late nineteenth and early twentieth centuries Jovan Cvijic published a series of papers which made the Karst regions of Yugoslavia internationally famous. An area which Cvijic chose for his early descriptive works was the high limestone plateau that overlooks the Gulf of Trieste (Figure 1). This region is known to the Yugoslavs as Kras, to the Italians as Carso, and to the Austrians as Karst. The descriptive work done in this area led to its name being adopted as an international type locality. The Cretaceous limestone formations of the plateau have remained conspicuously above the erosional levels of the less resistant Tertiary limes and flysch. This barren region of solution erosion had long been considered a barrier between Mediterranean and Danubian trade. It was an area well known for its lack of water, lack of vegetation, difficult footing, and its wild bora winds. The scarcity of surface water posed a particularly difficult problem along early transportation routes. Adequate vegetation for forage was limited to the widely spaced pockets of terra rosa which accumulated in the karst surface depressions. After man destroyed the forests of the karsts, the soil was rapidly eroded from the limestone ridges. Much of this soil was washed into the underground channel system. A * Dr. Alexander is an Associate Professor of Geography at the University of Montana, Missoula, Montana 59801. This manuscript was presented at the Annual Meeting of the Association at Bellingham in 1968. Research is based primarily on personal investigation of cave records and Slovene public documents on file at the Slovene Karst Institute at Postojna. The cooperation and assistance of the staff of the institute is hereby acknowledged. 157 158ASSOCIATION of pacific coast geographers large portion of the karst became a bare and rugged lapies surface. In late winter the bora, a cold pulsating northeast wind, blows from the higher plateaus across the karst into low pressure systems of the Mediterranean Sea.1 Rora velocities of 38 meters a second ( 137 kilometers an hour) have been recorded in the interior of Slovenia.2 With the advent of rail communications across the karst, large bora walls had to be constructed to protect the rails from drifting snow. The occupance of the karst has been characterized by small nucleated villages based on meager soil resources that have been developed in the isolated karstdepressions. In striking contrast to the dry, barren karst lands are the green slopes and gentle hills of Brkini. This area adjoins the karst on the east and is underlain by Eocine flysch. Figure 2 indicates the extreme changes which occur in the drainage pattern of the Reka-Timavo River as it flows from the flysch to the limestone area. The headwaters of the Reka-Timavo River lie beneath impressive snowcovered Mount Sneznik. For 50 kilometers the river flows across the clay soils of Brkini. Here the drainage network is well developed and surface water abundant. The large flysch region of Brkini sits like a green oasis among the surrounding barren dry karst plateaus. To the south lies the Plateau of Cicarija, to the northeast lies Zgornja Pivka3 and the high limestones of Javorniki and Sneznik, to the west and northwest lies the Plateau of Karst. The soils of Brkini are fertile and sustain productive fields, lush meadows, and intensive horticultural development. At the village of Brenski Britof the flysch thins and the river flows through barren limestone. Here the river has eroded a precipitous and narrow gorge some 2 kilometers in length. At the end of this gorge the Reka-Timavo River sinks beneath the Upper Cretaceous limestones of the Karst Plateau. The river follows its sub1 During the winter months the snow-covered plateaus and mountains of Javorniki, Sneznik, and Velica Gora become exceedingly cold through the influx of Arctic air and radiation. As the pressure gradient between these high areas and the warm Adriatic Sea increases, a katabatic flow of cold air occurs. 2 Bojan Paradiz, "Burje ? Sloveniji," 10 let hidrometeoroloske sluzbe. Ljubljana, Hidrome Teoroloski zavod L. R. S., 1957, p. 160. 3 For a detailed analysis of a typical Slovene karst region refer to...

The Climate of the Mediterranean Region

Synopsis I. In the first part the characteristic observational facts are given. Average comfortable winter temperatures, hot summers, and a dry period in summer are the significant features. Cloudiness is little, even in winter, in the rainy period. II. The physical explanation is based on the pressure distribution and the main streamlines of the air. In winter, a “lake of low pressure” above the Mediterranean Sea caused by the warm surface water is embedded in the huge region of high pressure from the center of action at the Azores reaching to the continental high pressure. The warm sea intensifies cyclones invading from the Atlantic and gives rise to cyclones in the three parts of the Mediterranean Sea: the Gulf of Lyon, the Adriatic Sea, and the Cyprus region. The first and the last and Northwest Africa as well, are regions of convergence, as is seen from the streamlines of January. In summer the well developed west-to-east pressure gradient causes three main currents directed toward the Persian Gulf. The northern and southern currents, over the high pressure areas of the cool Black Sea and the Mediterranean, respectively, are lines of divergence; the middle current over the heated south European lands is one of convergence. The important wind systems are indicated by this representation. The rainlessness during summer in the southern and eastern portions of the basin finds its explanation in the wind systems, on the one hand, and in the stability of the atmosphere caused by thermal conditions, on the other hand. III. In the last part important local climatic features are presented: excessive rains in the desert; the bora and other cold winds; winter easterlies of Palestine; peaks of temperature; great daily ranges of temperature in the deserts; and the airmass analysis of the sirocco.