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1.
Prog Oceanogr ; 209: None, 2022 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-36518908

RESUMO

The strongest episodes of extremely high sea levels in the Mediterranean are regularly observed in the Adriatic Sea, where they can cause substantial damage and loss of human lives. In this study, episodes of positive and negative sea level extremes were extracted from hourly series measured at six tide gauge stations located along the Adriatic coast (Venice, Trieste, Rovinj, Bakar, Split, Dubrovnik) between 1956 and 2019/2020. The time series were first checked for spurious data and then decomposed using tidal analysis, least-squares fitting and filtering procedures into (1) trend; (2) seasonal; (3) tide, (4) longer than 100 d (> 100 d), (5) 10-100 d, (6) 6 h-10 d, and (7) < 6 h components. These components correspond to sea level oscillations dominantly (but not exclusively) forced by (1) climate and isostatic change; (2) seasonal changes in thermohaline properties and circulation patterns, (3) tidal forcing, (4) quasi-stationary atmospheric and ocean circulation and climate variability patterns, (5) planetary atmospheric waves, (6) synoptic, and (7) mesoscale atmospheric processes. Significant differences exist between (1) the northern and middle/southern Adriatic extremes and (2) positive and negative extremes. The heights and return levels of positive (negative) extremes are 50-100% higher (lower) in the northern than in the middle/southern Adriatic. The northern Adriatic positive sea level extremes dominantly occur due to the superposition of the 6 h-10 d component and tide (contributing jointly to âˆ¼70% of the total extreme height), whereas the middle/southern Adriatic positive extremes mostly occur due to the superposition of the 10-100 d component, 6 h-10 d component, and tide (each contributing âˆ¼25% on average). The negative sea level extremes are explained as a combination of the 10-100 d component and tide: in the northern Adriatic tide provides the largest contribution (∼60%), while in the middle/southern Adriatic, the impacts of the two processes are similar (each contributing an average of âˆ¼30%). Over the entire Adriatic, the < 6 h and seasonal components contribute the least to both positive and negative extremes. Sea level trends at all stations are positive; however, the observed sea level rise did not contribute significantly to the total height of extremes. Extreme episodes tend to occur simultaneously over larger parts of the coast and are often clustered within a few days. Both positive and negative extremes have a strong decadal variability, whereas trends of their number, duration and intensity point to shortening of negative extremes and prolonging and strengthening of positive extremes.

2.
Sci Rep ; 12(1): 8463, 2022 05 19.
Artigo em Inglês | MEDLINE | ID: mdl-35589786

RESUMO

Typhoon Maysak (Julian in the Philippines) was a powerful tropical cyclone that strongly impacted coastal regions of the Sea of Japan on 2-4 September 2020. Destructive winds, violent storm waves, and intense rainfall occurred in Japan, on the Korean Peninsula, and in Far-Eastern Russia. Devastating coastal floods caused severe damage to coastal infrastructure and to ships and boats anchored in harbours and were responsible for numerous deaths. Our study indicates that the main reason for the destructive floods was the superposition of storm surge, extreme seiches (meteorological tsunamis), and surf beats. At various sites, different types of sea level oscillations prevailed depending on the atmospheric forcing, local topographic properties, and resonant shelf/coastal zone features. The principal forcing factors of these oscillations were atmospheric pressure and wind stress, but the exact generation mechanism of each specific type of oscillation was strongly site dependent. The uniqueness of the sea level response at each site is the main challenge in our understanding of the generation process and to the mitigation of the hazardous consequences of possible future events.


Assuntos
Tempestades Ciclônicas , Inundações , Japão , Filipinas , Vento
3.
Sci Rep ; 7: 40818, 2017 01 18.
Artigo em Inglês | MEDLINE | ID: mdl-28098195

RESUMO

Present investigations of sea level extremes are based on hourly data measured at coastal tide gauges. The use of hourly data restricts existing global and regional analyses to periods larger than 2 h. However, a number of processes occur at minute timescales, of which the most ruinous are tsunamis. Meteotsunamis, hazardous nonseismic waves that occur at tsunami timescales over limited regions, may also locally dominate sea level extremes. Here, we show that nonseismic sea level oscillations at tsunami timescales (<2 h) may substantially contribute to global sea level extremes, up to 50% in low-tidal basins. The intensity of these oscillations is zonally correlated with mid-tropospheric winds at the 99% significance level, with the variance doubling from the tropics and subtropics to the mid-latitudes. Specific atmospheric patterns are found during strong events at selected locations in the World Ocean, indicating a globally predominant generation mechanism. Our analysis suggests that these oscillations should be considered in sea level hazard assessment studies. Establishing a strong correlation between nonseismic sea level oscillations at tsunami timescales and atmospheric synoptic patterns would allow for forecasting of nonseismic sea level oscillations for operational use, as well as hindcasting and projection of their effects under past, present and future climates.

4.
Sci Rep ; 6: 22924, 2016 Mar 16.
Artigo em Inglês | MEDLINE | ID: mdl-26979129

RESUMO

An ocean surface currents forecasting system, based on a Self-Organizing Maps (SOM) neural network algorithm, high-frequency (HF) ocean radar measurements and numerical weather prediction (NWP) products, has been developed for a coastal area of the northern Adriatic and compared with operational ROMS-derived surface currents. The two systems differ significantly in architecture and algorithms, being based on either unsupervised learning techniques or ocean physics. To compare performance of the two methods, their forecasting skills were tested on independent datasets. The SOM-based forecasting system has a slightly better forecasting skill, especially during strong wind conditions, with potential for further improvement when data sets of higher quality and longer duration are used for training.

5.
Sci Rep ; 5: 11682, 2015 Jun 29.
Artigo em Inglês | MEDLINE | ID: mdl-26119833

RESUMO

A series of tsunami-like waves of non-seismic origin struck several southern European countries during the period of 23 to 27 June 2014. The event caused considerable damage from Spain to Ukraine. Here, we show that these waves were long-period ocean oscillations known as meteorological tsunamis which are generated by intense small-scale air pressure disturbances. An unique atmospheric synoptic pattern was tracked propagating eastward over the Mediterranean and the Black seas in synchrony with onset times of observed tsunami waves. This pattern favoured generation and propagation of atmospheric gravity waves that induced pronounced tsunami-like waves through the Proudman resonance mechanism. This is the first documented case of a chain of destructive meteorological tsunamis occurring over a distance of thousands of kilometres. Our findings further demonstrate that these events represent potentially dangerous regional phenomena and should be included in tsunami warning systems.

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