Analysis of the influence of ENSO phenomena on wave climate on the central coastal zone of Rio de Janeiro (Brazil) (original) (raw)
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Ocean and Coastal Research, 2022
Understanding how wave climate variability and its trends change over time are crucial analyses required to mitigate potential wave-induced impacts and adapt coastal areas to such effects. The long-term trends and breakpoints of the wave energy flux (WEF) and its relationship with teleconnection patterns in southern Brazil were studied using ERA-5 wave reanalysis with validation using a waverider. We determined that the interannual mean WEF (WEFm) and extreme WEF (WEF98) that reaches the southern Brazil have increased over the past four decades, with a increment of 0.063 and 0.17 kW/m/year, respectively 0.63 and 0.29% per year. By the Muggeo method we determined that subperiods with increasing WEFm trends are related to the SSE and SSW quadrants and that these are also the most energetic ones and with the highest annual increment rates of WEFm and WEF98. Our results also suggest that the positive trends observed in interannual WEF values are likely related to the long term transition of cold to warm Atlantic Multidecadal Oscillation (AMO) phase in the western South Atlantic Ocean. From a coastal risk perspective, it is important to understand the relationship between climatic indices and the wave climate to support long-term coastal management policies.
Brazil Wave Climate from a High-Resolution Wave Hindcast
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A detailed climatology of ocean wind waves in the South Atlantic Ocean, based on ERA-5 reanalysis and in a higher-resolution wave hindcast (ERA-5H), both developed by the European Centre for Medium-Range Weather Forecasts, is presented. The higher resolution of the wave fields in the ERA-5H (22 km) allowed for a better description of the wind sea and swell features compared to previous global and regional studies along the Brazilian coast. Overall, it is shown that swell waves are more prevalent and carry more energy in the offshore area of the study area, while wind sea waves dominate the nearshore regions, especially along the northern coast of Brazil. The influence of different climate indices on the significant wave heights patterns is also presented, with two behavioral groups showing opposite correlations to the North Atlantic Oscillation and Southern Annular Mode than to the Southern Oscillation Index. The analysis of the decadal trends of wind sea and swell heights during th...
Brazilian offshore wave climate based on NWW3 reanalysis
Brazilian Journal of Microbiology, 2010
This paper provides a description of the wave climate off the Brazilian coast based on an eleven-year time series (Jan/1997-Dec/2007) obtained from the NWW3 operational model hindcast reanalysis. Information about wave climate in Brazilian waters is very scarce and mainly based on occasional short-term observations, the present analysis being the first covering such temporal and spatial scales. To define the wave climate, six sectors were defined and analyzed along the Brazilian shelf-break: South (W1), Southeast (W2), Central (W3), East (W4), Northeast (W5) and North (W6). W1, W2 and W3 wave regimes are determined by the South Atlantic High (SAH) and the passage of synoptic cold fronts; W4, W5 and W6 are controlled by the Intertropical Convergence Zone (ITCZ) and its meridional oscillation. The most energetic waves are from the S, generated by the strong winds associated to the passage of cold fronts, which mainly affect the southern region. Wave power presents a decrease in energy levels from south to north, with its annual variation showing that the winter months are the most energetic in W1 to W4, while in W5 and W6 the most energetic conditions occur during the austral summer. The information presented here provides boundary conditions for studies related to coastal processes, fundamental for a better understanding of the Brazilian coastal zone.
Analysis of extreme wave events on the southern coast of Brazil
Natural Hazards and Earth System Sciences, 2014
Using the wave model SWAN (simulating waves nearshore), high waves on the southwestern Atlantic generated by extra-tropical cyclones are simulated from 2000 to 2010, and their impact on the Rio Grande do Sul (RS) coast is studied. The modeled waves are compared with buoy data and good agreement is found. The six extreme events in the period that presented significant wave heights above 5 m, on a particular point of interest, are investigated in detail. It is found that the cyclogenetic pattern between the latitudes 31.5 and 34 • S is the most favorable for developing high waves. Hovmöller diagrams for deep water show that the region between the south of Rio Grande do Sul up to a latitude of 31.5 • S is the most energetic during a cyclone's passage, although the event of May 2008 indicates that the location of this region can vary, depending on the cyclone's displacement. On the other hand, the Hovmöller diagrams for shallow water show that the different shoreface morphologies were responsible for focusing or dissipating the waves' energy; the regions found are in agreement with the observations of erosion and progradation regions. It can be concluded that some of the urban areas of the beaches of Hermenegildo, Cidreira, Pinhal, Tramandaí, Imbé and Torres have been more exposed during the extreme wave events on the Rio Grande do Sul coast, and are more vulnerable to this natural hazard.
Revista Brasileira de Geografia Física
Unplanned occupations and extreme metocean events increase risk of material and lives losses due to socioenvironmental disasters in coastal zones. Such processes have harmed goods, industries, tourism, traditional populations and sensitive ecosystems along the coast of Rio Grande do Norte State (RN), Northeast Brazil. Long-term monitoring data of metocean drivers are scarce off RN's littoral, which are critical in decision-takings for mitigation and adaptation actions along densely populated coastal areas. This study aims to assess extreme ocean waves off RN's eastern coast. Time series of wind speed, tide and wave parameters have been obtained from satellite altimetry and ERA5 reanalysis, between 1979 and 2021, in a virtual station at 6.0ºS/34.7ºW. Generalized Pareto Distribution (GPD) was fitted to wave significant high (Hs). Registers of coastal disasters were collected from online media. Waves have reached Hs maximum of 3.30 m, average of 0.76 m, coming from east-southeast and southeast. Winter and spring seasons have presented higher waves, related to action of trade winds. Wind speed occurred mainly between 6 and 8 m/s. GPD estimated Hs increasing up to 2.4 times above its average, each 2 years, overtaking 2.7 times its average per decade. Previous increasing of wind speed is more important than its scalar value, to form an extreme wave. Hs at the virtual station had its upper peak either at the same day or one-two days before of coastal damage, which means that ocean storms offshore propagate coastward quickly.
Evaluation of the Seasonal Pattern of Wind-Driven Waves on the South-Southeastern Brazilian Shelf
Transfer Phenomena in Fluid and Heat Flows, 2017
The focus on renewable energy sources on the last few decades has pushed studies on wave energy availability. In this sense, this study aims to determine annual characteristics of the wave climate on the South-Southeastern Brazilian Shelf (SSBS) to improve the comprehension of the Brazilian wave climate, as well as, to give an insight on the more energetic coastal spots in this area. To accomplish that, the sea state model TOMAWAC was used to simulate 18 years of wave conditions on the SSBS which were later converted to a single year, representative of the Brazilian wave climate. The results showed a strong annual pattern of steadier sea state in summer and spring and a more agitated one in autumn and winter. The results also showed that in the Santa Marta cape, the seasonal wave power oscillates between 8 and 11 kW/m, and at Ilhabela, between 7 and 11 kW/m. At the Farol island, on the other hand, the seasonal wave power varies around 11 and 19 kW/m, yielding much more energy but, at the cost of an extremely higher variation throughout the year.
Continental Shelf Research, 2010
In this paper, a possible increase in wind wave heights in the south-eastern south American continental shelf between 32°S and 40°S is investigated. Both time series of in situ (1996-2006) and topex (1993-2001) annual mean significant wave heights gathered at the continental shelf and adjacent ocean present apparent positive trends. Even though these trends are not statistically different from zero, it must be taken into account that the available in situ and satellite data have a short span and, moreover, in situ data present several gaps. Several papers presented evidence about a possible change on the low atmospheric circulation in this region of the southern hemisphere. Consequently, a weak increase in wave height might be occurring, which would be hard to quantify due to the shortness and the insufficiency of the available observations. In order to study a possible trend in mean annual wind wave heights simulating waves nearshore (swan) model forced with ncep/ncar surface wind was implemented in a regional domain for the period 1971-2005. The annual root-mean-square heights of the simulated wave show significant trends at several locations of the inner continental shelf and the adjacent ocean. The most significant increase is observed between 1991-2000 and 1981-1990 decades. The largest difference (0.20 m, 9%) occurs around 34°S-48°W. The wave height increase is somewhat lower, 7%, in the continental shelf and in the río de la plata estuary. The annual mean energy density (spatially averaged) also presents a significant positive trend (0.036 m 2/yr) and relatively high inter-annual variability. The possible link between this inter-annual variability and el niño-southern oscillation (enso) was investigated but no apparent relationship was found. A possible increase in the annual mean energy density of waves would be able to produce changes in the littoral processes and, consequently, in the erosion of the coast.
The impacts of inter-El Nino event and Atlantic variability on the Northeast Brazil climate
2000
The effects of inter-El Nino event and Atlantic variability on the climate of the Brazilian Northeast (NE) are investigated from observations and a numerical model. The results show that El Niños followed by dry (wet) conditions in NE are strong and long (weak and short) events and have the strongest warming in the eastern (central) Pacific. Moreover, the dry
Brazilian Journal of Oceanography, 2013
Sea level (SL), wind, air temperature (AT) and sea surface temperature (SST) variations in the coastal region of Ubatuba, northern coast of São Paulo, are assessed. A Lanczos-square cosine filter, with a 40-hour window, was applied over the SL time series between 1978 and 2000, except for the period comprising 1984 to 1986. In order to study subtidal effects on mean sea level (MSL), SL numerical filtering indicated that there was a virtually complete removal of semidiurnal and diurnal astronomical tidal components over the period of study. Results indicated an average raw SL rise of 2.3 mm/year, whereas average filtered MSL was of the order of 0.7 mm/year. Despite the overall positive MSL trend, the lunar nodal cycle of 18.6 years seemed to be the explanation for the SL series pattern. Correlations between MSL and parallel wind had a maximum correlation coefficient around 0.6, with 99% statistical confidence, while MSL and perpendicular wind correlations were not statistically significant. These results may be explained by Ekman dynamics. Data records of AT and SST between 1990 and 2003 showed positive trends for both variables. During this period, AT rose about 0.087 °C /year for the raw series and 0.085 °C /year for the monthly time series, and SST showed a rise of 0.047 °C /year and 0.046 °C/year, for the raw and monthly time series, respectively. The monthly climatology for both AT and SST showed higher values in February with 27.79 o C and 28.59 o C for AT and SST, respectively, and the lowest in July with 21.12 o C for AT and 21.91 o C for SST.
Interannual variability of the sea surface temperature in the South Brazil Bight
1999
The Northern Indian Ocean (NIO) sea surface temperature (SST) warming, associated with the El Niño/Southern Oscillations (ENSO) and the Indian Ocean Dipole (IOD) mode, is investigated using the International Comprehensive Ocean-Atmosphere Data Set (ICOADS) monthly data for the period 1979−2010. Statistical analyses are used to identify respective contribution from ENSO and IOD. The results indicate that the first NIO SST warming in September−November is associated with an IOD event, while the second NIO SST warming in spring-summer following the mature phase of ENSO is associated with an ENSO event. In the year that IOD co-occurred with ENSO, NIO SST warms twice, rising in the ENSO developing year and decay year. Both shortwave radiation and latent heat flux contribute to the NIO SST variation. The change in shortwave radiation is due to the change in cloudiness. A cloud-SST feedback plays an important role in NIO SST warming. The latent heat flux is related to the change in monsoonal wind. In the first NIO warming, the SST anomaly is mainly due to the change in the latent heat flux. In the second NIO warming, both factors are important.