TRENDS OF WAVE HEIGHTS IN INDONESIA’S FISHERIES MANAGEMENT AREAS (IFMAS) DURING 1977–2021 (45 YEARS)

• Main Author: Azhari, Ainun
• Format: Theses
• Language: Indonesia
• Subjects: Ilmu kebumian
• Online Access: https://digilib.itb.ac.id/gdl/view/76985
• Institution: Institut Teknologi Bandung

Wind speed and wave height are important in supporting maritime activities, fishing activities, adaptation, and climate change mitigation, especially in a maritime country like Indonesia. This study aims to determine trends in wind speed and wave height in the Indonesia’s Fisheries Management Areas (IFMAs) and Tropical Cyclone (TC) events that occur around Indonesian waters (Bay of Bengal, western Pacific Ocean, northeastern Indian Ocean, and western Australian waters) for 45 years (1977–2021). Wind and wave data (Significant Wave Height/SWH, wind sea, and swell) comes from the fifth-generation European Center for Medium-Range Weather Forecast (ECMWF) Reanalysis (ERA5). TC data derived from the International Best Track Archive for Climate Stewardship (IBTrACS). Trends in wind speed, wave height, and TC occurrence were calculated using linear regression. This study investigates the effect of the Pacific Decadal Oscillation (PDO) phenomenon on wind speed and wave height values in the Indonesian WPP as well as the occurrence of TCs around Indonesian waters, which are divided into two periods, namely the PDO warm phase (1977–2007; 31 years) and cold (1977–2007; 31 years) and cold ( 2008–2021; 14 years). Discussion of wind speed and wave height trends covers 1977–2021 (45 years), seasonal differences (December–February/DJF; March–May/MAM; June–August/JJA; and September–November/SON), as well as warm phase PDO and cold. Changes in the trend of occurrence and strength of TCs are analyzed in the long term (1977–2021; 45 years), as well as during the warm and cold phases of the PDO. The long-term trend distribution (1977–2021; 45 years) of wind speed and wind sea in Indonesian waters has almost the same pattern, namely an increasing trend of wind speed (2.00 cm/s/year) and wind sea (<0.40 cm/year) significantly in WPP 572 (West Sumatran waters). The increasing trend of wind speed and wind sea in Indonesian WPP occurred during the SON period, with maximum values reaching 2.80 cm/s/year and 0.40 cm/year. SWH and swell trends for 45 years (1977–2021) have been significant in almost all Indonesian waters (<0.40 cm/year). During the DJF period, the increase in SWH and swell trends in Indonesian waters reached 0.80 cm/year, especially in WPP 717 (north Papua waters). The values of wind speed, SWH, wind sea, and swell in all regions of Indonesia have increased by 1–4 cm/s/year (wind speed) and 0.40–1.20 cm/year (SWH, wind sea, and swell). iv However, there was an increase in wind speed (6 cm/s/year) and wave height (0.60–1.60 cm/year), greater than the PDO period's warm phase in northern and eastern Indonesian waters. The number of TCs for 45 years (1977–2021) around Indonesian waters has generally decreased insignificantly, namely around 1–3 events every 100 years. However, the of TCs generally increases by 0.140 to 1.035 x 104 kts2 every ten years. During the cold phase of the PDO (2008–2021; 14 years), the number and Accumulated Cyclone Energy (ACE) of TCc occurred in the western Pacific Ocean experienced the largest increase with values of around 27 events/100 years and 230.84 x 104 kts2/decade, respectively.