Djelovanje atmosfere na Jadran: danas te u uvjetima očekivanih klimatskih promjena

Meteorological forcing of the Adriatic is examined under the present and predicted climate conditions. Fields from the time slice-experiment performed with ECHAM4 model (W. May and E. Roeckner: A time-slice experiment with the ECHAM4 AGCM at high resolution – the impact of horizontal resolution on annual mean climate change, Climate Dynamics, 17, 2001, 407–420) are closely analysed for the Adriatic region. Results obtained for the control period, when compared to a number of data, are found to reproduce the main features of the present-day surface heat flux, water flux and wind field above the Adriatic. In the future, the Adriatic should experience a reduction of heat loss to the atmosphere as well as an enhanced evaporation accompanied with a reduced precipitation leading to an overall increase of fresh-water loss to the atmosphere. The changes in synoptic activity should lead to an abatement of bora winds and to a reduced frequency of sirocco events which, however, are expected to be much more persistent. Finally, changes in the dynamics of the Adriatic, induced by altered meteorological forcing, are briefly discussed.Istražuje se djelovanje atmosfere na Jadran, u sadašnjim te u izmijenjenim uvjetima očekivanih klimatskih promjena. Detaljno se analiziraju meteorološka polja nad Jadranom, dobivena modelom ECHAM4 u eksperimentu »vremenskih odrezaka« (W. May and E. Roeckner: A time-slice experiment with the ECHAM4 AGCM at high resolution – the impact of horizontal resolution on annual mean climate change, Climate Dynamics, 17, 2001, 407–420). Usporedba razultata dobivenih za kontrolno razdoblje s nizom postojećih mjerenja pokazuje da model dobro reproducira glavne značajke opaženih površinskih protoka topline, vlage te polja vjetra nad Jadranom. Možemo očekivati da će Jadran u budućnosti manje topline predavati atmosferi te da će se povećati isparavanje s njegove površine i smanjiti oborina na njegovom području – što bi u konačnici trebalo dovesti do povećanog prijenosa vlage iz mora u atmosferu. Promjene u sinoptičkoj aktivnosti dovest će do slabljenja bure te do manje čestine epizoda juga – ali povećanog trajanja. Na kraju se ukratko diskutiraju posljedice ovih promjena na dinamiku Jadrana

Long-term measurements at Bakar tide-gauge station (east Adriatic)

U radu su detaljno prikazana mjerenja satnih visina razine mora na mareografskoj postaji Bakar, smještenoj na istočnoj obali Jadrana. Mareografska je postaja utemeljena 1929. godine, a prikupljeni podaci predstavljaju najdulji vremenski niz nekog oceanografskog parametra izmjerenog u Republici Hrvatskoj. Podaci su do sada korišteni u mnogobrojnim znanstvenim studijama a imali su i praktičnu primjenu. Vodostaji su izmjereni analognim plovčanim mareografom uz koji su nedavno postavljena i dva digitalna instrumenta. U radu je opisana lokacija bakarske postaje, njena operativna povijest, održavanje, princip mjerenja, provjera lokalne mareografske nule te povijest geodetskih niveliranja. Uključeni su i detalji o uzorkovanju, provjeri kvalitete i obradi podataka. Također, dan je kratak pregled najvažnijih znanstvenih rezultata proizašlih iz ovih mjerenja, a spomenute su i neke praktične primjene. Podaci su dostupni u bazi SEANOE (Međugorac i sur., 2021; https://doi.org/10.17882/85171).We present hourly sea levels at Bakar tide-gauge station, located on the east coast of the Adriatic Sea. The station was established in 1929. The recorded data represent the longest time series of an oceanographic parameter measured in Croatia. They have been used in various scientific studies and practical applications. Sea levels were collected using float-type chart-recording tide gauge to which two digital instruments have been added recently. We describe station\u27s location, its operational history, maintenance, principle of measurements, recorder zero checks and practice, and leveling history. Details on data sampling, quality checks and processing are included. Also, a brief summary of the most important results derived from these data is given and some practical applications are mentioned. The data are available through SEANOE (Međugorac et al., 2021; https://doi.org/10.17882/85171)

Novi pristup motrenju promjena razine mora u Hrvatskoj

The paper comprises an overview of recent international and national efforts and activities directed towards the improvement of tide gauge network on the eastern coast of the Adriatic Sea. A brief overview of the available measuring techniques is given first. Then the characteristics of Adriatic sea level are outlined, followed by a note on the history of sea level measurements and research in the Adriatic. The present sea level related activities are introduced by the institutional structure in Croatia, followed by a summary of recent projects and programmes (European Sea Level Service – Research Infrastructure (ESEAS-RI), Mediterranean Global Observing Sea Level System (MedGLOSS), Project Adriatic and Adriatic Tides and Sea Level On-line). Concrete activities on the upgrade of Croatian tide gauges, data acquisition and maintenance, and on-line data presentation are presented in detail. In addition, the initiation of measurements of vertical land movements is documented, as a Continuous GPS antenna and receiver (CGPS) has been installed in 2004 at the roof of the Split Harbour tide gauge. A lot of effort has been put into the rescue of historical sea level records, both by digitising and scanning of the charts, which will prevent data loss in case of their ruination or disappearance. Finally, the impact of the recent activities on the scientific exploration of high-frequency resonant coupling of air pressure disturbances with the eastern Adriatic waters is highlighted in the paper, as such research is not possible to carry out properly with the measuring systems based on the analog records.Rad sadrži pregled novijih međunarodnih i domaćih aktivnosti usmjerenih prema poboljšanju mareografske mreže na istočnoj obali Jadranskog mora. Najprije su prikazani dostupni mjerni sustavi. Zatim su ukratko prikazana svojstva razine Jadranskog mora, te povijesni razvoj mareografije i istraživanja kolebanja razine mora. Sadašnje aktivnosti u tim istraživanjima prikazane u ovom radu obuhvaćaju institucinalnu strukturu u Republici Hrvatskoj, te pregled novijih projekata i programa (Europska mareografska mreža – istraživačka infrastruktura (ESEAS-RI), Mediteranska implementacija Globalnog sustava za pra}enje razine mora (MedGLOSS), Morske mijene i razina Jadrana on-line, Projekt Jadran). Detaljno su prikazane aktivnosti koje su dovele do nadogradnje hrvatskih mareografa, prijenosa i obrade podataka, te internetskog prikaza podataka u realnom vremenu. Osim toga, u radu se dokumentira uspostava mjerenja vertikalnih pomaka tla, koja je inicirana postavljanjem CGPS sustava na krovu splitskog mareografa tijekom 2004. godine. Prilično truda je uloženo u spašavanje povijesnih mareografskih zapisa, koristeći digitalizaciju i skeniranje zapisa, što će spriječiti trajan gubitak podataka u slučaju uništenja originalnih zapisa. Naposljetku, prikazana su najnovija istraživanja visokofrekventnih oscilacija razine mora i rezonantnog prijenosa energije iz atmosfere u more, omogućena uspostavom 1-minutnih mjerenja na mareografskim postajama, a koja nisu bila moguća s prethodnim analognim sustavima mjerenja

Seši u Plitvičkim jezerima

A campaign of high-frequency measurements of water level was carried in the two largest of the Plitvice Lakes, Prošće and Kozjak, to study seiches in the lakes. Measurements were performed at 1-min sampling rate during a 46-day interval, at two opposite ends in each lake, which also provided information on the phase relations. Power spectra were calculated to determine the periods of the normal modes. The observed peaks in the spectra were interpreted with the help of theoretical results obtained by the simple numerical method of Defant, where two different historical bathymetries were used. The lake Prošće oscillates at the periods of 8.5 min, 5.0 min, 3.3 min and 2.2 min, the oscillations being related respectively to uni-, bi-, three- and five-nodal seiche modes, whereas the four-nodal mode (2.5–2.7 min) was not significant during the experiment. The lake Kozjak oscillates at 9.0 min, 4.9 min and 2.6 min, which corresponds respectively to the uni-, bi- and four-nodal mode, the five-nodal mode is likely at the period of 1.9 min, while the three-nodal mode (~ 3.4 min) was not generated; the deeper sub-basin displays its own principal mode at the period of 2.3 min. The discrepancy between the observed and the calculated periods is attributed to poor representation of the basin by the historical bathymetries, especially at Prošće, but also to changes in basin depth, due to continuous process of tufa growth.Poduzeta su visokofrekventna mjerenja razine vode u dva najveća plitvička jezera, u Prošću i u Kozjaku, kako bi se istražili seši. Mjerenja su rađena s intervalom uzorkovanja od 1 minute tijekom perioda od 46 dana i to na dva suprotna kraja u svakom jezeru, što je dalo informaciju i o međusobnom odnosu faza. Izračunati su spektri snage kako bi se odredili periodi vlastitih modova. Opaženi maksimimi su interpretirani uz pomoć teorijskih rezultata, dobivenih jednostavnom numeričkom metodom Defanta, pri čemu su se koristile dvije različite povijesne batimetrije. Jezero Prošće oscilira s periodima od 8,5 min, 5,0 min, 3,3 min i 2,2 min, što odgovara redom modu seša s jednom, dvije, tri i pet čvornih linija, dok se mod s četiri čvorne linije (oko 2,5–2,7 min) nije znatnije pobudio tijekom eksperimenta. Jezero Kozjak oscilira s periodima 9,0 min, 4,9 min te 2,6 min, što odgovara redom prvom, drugom i četvrtom modu, peti mod se vjerojatno odvija na periodu od 1,9 min dok se treći mod (~ 3,4 min) nije pobudio; dublji podbazen Kozjaka oscilira svojim vlastitim osnovnim modom na periodu 2.3 min. Neslaganje između opaženih i izračunatih perioda može se pripisati manjkavostima batimetrije kojom je opisan bazen, naročito u slučaju Prošća, ali i promjeni dubine jezera uslijed trajnog procesa rasta sedre