On the Non-Gaussianity of the Height of Sea Waves

The objective of this paper is to prove that the sea wave height is not a Gaussian process. This is contrary to the common belief, as the height of a sea wave is generally considered a Gaussian process. With this aim in mind, an empirical study of the buoys along the US coast at a random day is pursued. The analysis differs from those in the literature in that we study the Gaussianity of the process as a whole and not just of its one-dimensional marginal. This is done by making use of random projections and a variety of tests that are powerful against different types of alternatives. The study has resulted in a rejection of the Gaussianity in over 96% of the studied cases.

Impacts of the Wave-Dependent Sea Spray Parameterizations on Air–Sea–Wave Coupled Modeling under an Idealized Tropical Cyclone

While sea spray can significantly impact air–sea heat fluxes, the effect of spray produced by the interaction of wind and waves is not explicitly addressed in current operational numerical models. In the present work, the thermal effects of the sea spray were investigated for an idealized tropical cyclone (TC) through the implementation of different sea spray models into a coupled air–sea–wave numerical system. Wave-Reynolds-dependent and wave-steepness-dependent sea spray models were applied to test the sensitivity of local wind, wave, and ocean fields of this TC system. Results show that while the sensible heat fluxes decreased by up to 231 W m−2 (364%) and 159 W m−2 (251%), the latent heat fluxes increased by up to 359 W m−2 (89%) and 263 W m−2 (76%) in the simulation period, respectively. This results in an increase of the total heat fluxes by up to 135 W m−2 (32%) and 123 W m−2 (30%), respectively. Based on different sea spray models, sea spray decreases the minimum sea level pressure by up to 7 hPa (0.7%) and 8 hPa (0.8%), the maximum wind speed increases by up to 6.1 m s−1 (20%) and 5.7 m s−1 (19%), the maximum significant wave height increases by up to 1.1 m (17%) and 1.6 m (25%), and the minimum sea surface temperature decreases by up to 0.2 °C (0.8%) and 0.15 °C (0.6%), respectively. As the spray has such significant impacts on atmospheric and oceanic environments, it needs to be included in TC forecasting models.

Penilaian Potensi Bencana Gempabumi dan Tsunami untuk Pelindungan Infrastruktur Migas dan PLTU di Cilacap, Jawa Tengah

Kilang minyak Pertamina dan PLTU Indonesia Power milik pemerintah di Kota Cilacap berada di wilayah dengan percepatan tanah puncak (PGA) = 0,4-0,5 g, percepatan pseudo spectral (PSA Ss) = 0,9-1 g dan (PSA S1) = 0,4-0,5g pada situs batuan SB, 2% probabilitas dalam 50 tahun (SNI 1726:2019). Penilaian potensi bencana gempabumi di kota ini pada kelas situs SC memiliki nilai SDS= 0,67g dan SD1= 0,43 g, sedangkan SDS = 0,73g dan SD1= 0,50 g pada kelas situs SD. Sesuai dengan ketentuan SNI 1726:2019, struktur gedung dan non gedung katagori risiko I, II, III dan IV pada kelas situs SC dan SD tersebut di atas berkatagori desain seismik D. Gaya geser desain seismik pada dasar silos tangki minyak adalah Qd = (0,24~ 0,34)*10496,4 x 103 =(2.309,21~2.519,14) x 103 (N). Potensi landaan tsunami dengan runup high berkisar antara 2,5-6 m. Bangunan gedung dan non gedung yang tidak sesuai dengan katagori desain seismik, dapat dilakukan penguatan atau retrofitting sesuai ketentuan. Untuk memperkecil gaya geser desain seismik pada dasar silos, dapat dilakukan dengan rekayasa keteknikan pada fondasi. Untuk meminimalisir bahaya tsunami dapat dibuat tembok penahan atau ditanam pemecah gelombang tsunami (sea wave tsunami breaker) di sekitar kilang minyak dan PLTU yang berhadapan langsung dengan laut. Jalur evakuasi tsunami berupa jalan lebar dengan arah selatan-utara dan bangunan bertingkat penyelamatan tsunami di sepanjang jalan di kota ini sebaiknya dibuat, khususnya di wilayah sekitar kilang minyak dan PLTU.Katakunci: Katagori risiko, katagori desain seismik, runup high, tsunami.

The Impact of Tropical Cyclone Seroja to The Rainfall and Sea Wave Height in East Nusa Tenggara

Natural events following the activity of the Tropical Cyclone Seroja in April 2021 are investigated. During its active phase, Tropical Cyclone Seroja generated extreme rainfall events in some sub-provinces of East Nusa Tenggara (NTT): Ngada, Alor, Belu, Rote Ndao on 4 April, 2021, Kupang on 4 to 5 April, 2021, East Sumba on 4 to 6 April, 2021. Moreover, these extreme rainfall events triggered flood in Alor, East Flores, Lembata, The City of Kupang, Kupang, East Sumba, Malaka, Belu, and North Central Timor. The maximum sea wave height of the Indian Ocean at the Southern part of NTT was also increasing, from 4 meters on 1 to 2 April, 2021 up to 6 meters on 3 April, 2021, and rose to higher than 7 meters on 4 to 6 April, 2021. On 7 to 9 April, 2021, the sea wave height declined as the Tropical Cyclone Seroja moved to the Southwest of NTT.

Wave height and period on 16 March, 21 April, and 22 September 2019, in the Ujung Batee coastal waters and Lampanah coastal waters, Aceh Besar District, Indonesia

Waves are one of the sea parameters that affect the rate of retreat of the coastline. This research investigation was carried out in the coastal waters of Ujong Batee and Lampanah, Aceh Besar District on 16 March, 21 April, and 22 September 2019, with the aim of examining wave parameters, namely wave height and period. Then the wave measurement data sampled at the research station location was carried out by purposive random sampling method. Sea wave data were taken using a scale board that has been labeled with numbers and a stopwatch. Wave measurements were carried out approximately 1000 times. Then the sea wave data is processed to obtain the wave height and period and then analyzed. The results obtained that the wave heights on 16 March, 21 April, and 22 September 2019 were 67 cm, 83 cm, and 80 cm in Ujong Batee and 55 cm, 67 cm, and 66 cm in Lampanah. While the wave period is 12 seconds on March 16, April 21, and September 22 in Ujong Batee and Lampanah. Thus, the wave height and period at both locations ranged from 50 cm to 80 cm and 12 s.

Kajian Energi Gelombang Laut Di Daerah Abrasi Serangai, Bengkulu Utara Melalui Pengamatan Tinggi Gelombang Laut

<p class="AbstractText"><span lang="EN-AU">The Serangai area, Batik Nau District, North Bengkulu has the highest average abrasion speed of 20 m/year. The abrasion could cause the coastal area to erode the coastline till several tens of meters. The purpose of this study was to determine the height of the ocean waves and to determine the energy of the ocean waves that has the potential to accelerate the abrasion process in the Serangai area. The research was carried out on November 5-7, 2018 in the Serangai beach area at a depth of 5 m using SBE 26 Plus Seagauge Wave equipment. The results showed that the observed wave height was between 0.8-1.6 m with a significant wave height (Hs) of 1.38 m. In addition, the wave period ranges from 5-11 s with a significant wave period (Ts) of 8.2 s. The result also shows that the maximum wave height of 1.6 m occurred on November 7, 2018 with maximum wave energy of 1800 J/m². This result can perhaps accelerate the abrasion process in the Serangai area. It can also be seen that the wave height in the Serangai region is higher than in several other areas in Indonesia. However, it is necessary to continue observing the wave height to see the seasonal variations in sea wave height in Serangai area.</span></p>