IS THERE A GRIČ ATTRACTOR?

In this study the time series of monthly averages of temperature, cloudiness and solar radiation are analyzed to investigate the chaotic properties of the local climate, and the possibility of the estimation of an minimum number of independent variables necessary to model the time evolution of the underlying climate system. The analysis of observations is based on a statistical procedure, called "correlation algorithm", leading to the measures of dimensionality or degrees of freedom which control the underlying dynamics. The results show that there is no indication of the existence of a lowdimensional attractor of the Zagreb-Grič time series. Within a climate system, it is possible to isolate a three-variable subsystem, controlling the large amplitudes of the local climate. These are: temperature, cloudiness and solar radiation. The existence of autocorrelation in the time series, due to solar radiation, has enabled the detection of a low-dimensional attractor. When the seasonal cycle has been theoretically filtered out of the series, the correlation disapped, as well as the low-dimensional climate subsystem

The Adriatic bora: special case studies

Two cases of the most severe bora episodes along the Adriatic coast of Croatia are investigated. In the first case of 29 January 1994 the absolute maximum gust of 48.5 m s-1 was recorded in Split. The second case is related to the longer-lasting bora of 13-17 March 1962, when it was possible to investigate the vertical atmospheric by means of downstream sounding in Split and two upstream sounding in Zagreb and Beograd. Although in both cases the bora onset is caused by a frontal passage, the maximal local speeds occur afterwards and coincide with a pronounced short period pressure perturbation. Both cases were characterized by the temporal occurrence of the well marked superadiabatic layers in the low troposphere. The vertical structure in the March case shows the temperature inversion in Split data that is strongest during the maximum bora speed, and an unstable layer below inversion, in agreement with the turbulent “dead” region defined in the internal hydraulic theory

OLUJNA BURA NA JADRANU 1987-1993

Sažetak - U prvom je dijelu rada analizirana čestina pojave olujne bure u periodu 1987-1993. na osnovu postojećih podataka s pet postaja duž jadranske obale. U razmatranom periodu najviše je olujnih bura zabilježeno u Splitu, dok su u Senju olujne bure, za razliku od prethodnoga 30-godišnjega perioda, bile rijetke. Iako se olujna bura obično javlja zimi, u proteklom se razdoblju u Splitu u 30% slučajeva pojavila u proljetnom, a dva puta u ljetnom periodu. Najveće vrijednosti srednjih satnih brzina izmjerene su u Splitu i apsolutni maksimum bio je 24.7 ms-1 , a najveći maksimalni satni udari bili su u Senju, s apsolutnim maksimumom od 47.6 ms-1. Olujna je bura u Senju puhala najdulje 21 sat, u Splitu 17, a u Dubrovniku 20 sati. U drugom je dijelu rada detaljno analizirana situacija s olujnom burom 30.1-1.2.1987. Pritom su korišteni vertikalni profili i vremenski vertikalni presjeci, dobiveni izentropskim dijagnostičkim modelom visoke rezolucije. Analizom sinoptičkih karata i vertikalnih presjeka zaključeno je da je olujna bura u Dubrovniku, kao posljedica prolaska hladne fronte, kratkotrajna, dok se olujna bura u Senju razvila uspostavljanjem postfrontalne situacije s inverzijom, karakteristične za nastanak i održanje dugotrajne bure na toj lokaciji

OLUJNA BURA NA JADRANU 1987-1993

Sažetak - U prvom je dijelu rada analizirana čestina pojave olujne bure u periodu 1987-1993. na osnovu postojećih podataka s pet postaja duž jadranske obale. U razmatranom periodu najviše je olujnih bura zabilježeno u Splitu, dok su u Senju olujne bure, za razliku od prethodnoga 30-godišnjega perioda, bile rijetke. Iako se olujna bura obično javlja zimi, u proteklom se razdoblju u Splitu u 30% slučajeva pojavila u proljetnom, a dva puta u ljetnom periodu. Najveće vrijednosti srednjih satnih brzina izmjerene su u Splitu i apsolutni maksimum bio je 24.7 ms-1 , a najveći maksimalni satni udari bili su u Senju, s apsolutnim maksimumom od 47.6 ms-1. Olujna je bura u Senju puhala najdulje 21 sat, u Splitu 17, a u Dubrovniku 20 sati. U drugom je dijelu rada detaljno analizirana situacija s olujnom burom 30.1-1.2.1987. Pritom su korišteni vertikalni profili i vremenski vertikalni presjeci, dobiveni izentropskim dijagnostičkim modelom visoke rezolucije. Analizom sinoptičkih karata i vertikalnih presjeka zaključeno je da je olujna bura u Dubrovniku, kao posljedica prolaska hladne fronte, kratkotrajna, dok se olujna bura u Senju razvila uspostavljanjem postfrontalne situacije s inverzijom, karakteristične za nastanak i održanje dugotrajne bure na toj lokaciji

A CASE STUDY OF A COLD AIR OUTBREAK ON 20 APRIL 1997 OVER CROATIA

This paper presents the weather situation on 20-23 April 1997, which was one of the strongest cold outbreaks ever recorded in April in Croatia. The processes leading to extremely low temperatures and heavy snowdrifts in the Dalmatian inland occurred on the front line between a polar air outbreak over central Europe and a deepening Mediterranean cyclone approaching the Adriatic. The genesis of a mesoscale vortex in the Adriatic has been diagnosed with the aid of satellite imagery and a high-resolution numerical model. The analysis of surface data has shown how the frontal system from the north slowed down over the Dinaric Alps and at mid-Adriatic, where the cyclogenetic process took place. The analysis of the vertical cross-sections produced using the rawinsonde data and the numerical model outputs have shown that the model successfully reproduced the intensity and time changes of the various meteorological frelds. In particular, the model successfully reproduced a mesoscale cyclone developed in the lower troposphere over the southern Adriatic on 23 April

IS THERE A GRIČ ATTRACTOR?

In this study the time series of monthly averages of temperature, cloudiness and solar radiation are analyzed to investigate the chaotic properties of the local climate, and the possibility of the estimation of an minimum number of independent variables necessary to model the time evolution of the underlying climate system. The analysis of observations is based on a statistical procedure, called "correlation algorithm", leading to the measures of dimensionality or degrees of freedom which control the underlying dynamics. The results show that there is no indication of the existence of a lowdimensional attractor of the Zagreb-Grič time series. Within a climate system, it is possible to isolate a three-variable subsystem, controlling the large amplitudes of the local climate. These are: temperature, cloudiness and solar radiation. The existence of autocorrelation in the time series, due to solar radiation, has enabled the detection of a low-dimensional attractor. When the seasonal cycle has been theoretically filtered out of the series, the correlation disapped, as well as the low-dimensional climate subsystem

The Adriatic bora: special case studies

Two cases of the most severe bora episodes along the Adriatic coast of Croatia are investigated. In the first case of 29 January 1994 the absolute maximum gust of 48.5 m s-1 was recorded in Split. The second case is related to the longer-lasting bora of 13-17 March 1962, when it was possible to investigate the vertical atmospheric by means of downstream sounding in Split and two upstream sounding in Zagreb and Beograd. Although in both cases the bora onset is caused by a frontal passage, the maximal local speeds occur afterwards and coincide with a pronounced short period pressure perturbation. Both cases were characterized by the temporal occurrence of the well marked superadiabatic layers in the low troposphere. The vertical structure in the March case shows the temperature inversion in Split data that is strongest during the maximum bora speed, and an unstable layer below inversion, in agreement with the turbulent “dead” region defined in the internal hydraulic theory