Indonesia is influenced by two types of monsoons, namely, the Asian and Australian monsoons. The differences in conditions occurring during these monsoon phenomena can affect sea surface temperatures (SSTs). This study aims to determine the effect of these monsoons on the SSTs in the southeast Indian Ocean and the Indonesian throughflow (ITF) region. SST and geostrophic current data obtained from Copernicus Marine Service and surface wind speed and direction data from the European Center for Medium-Range Weather Forecasts (ECMWF) from March 2019 to February 2020 were statistically and descriptively analyzed. Observational conductivity–temperature–depth (CTD) data obtained in December 2019 were used to identify statistical errors in the Copernicus Marine Service SST data. The results of the SST data verification show a 0.85°C RMSE and 0.6°C MAE; they are significantly correlated at 0.82 with a 95% confidence level. The results of this study generally show that geostrophic currents move to the east, and SST tends to be warmer during the Asian monsoon period than during the Australian monsoon period, which has a cooler SST (with geostrophic currents moving to the northwest). Specifically, the SST conditions in the ITF region and southeast Indian Ocean cool from the MAM period. This cooling period intensifies during the JJA period and subsides in the SON period. The Australian monsoon, which is dominant during the DJF period, causes warmer-than-average SST conditions in the northern part of Indonesia, particularly the northern part of the ITF.

This study aims to analyze the effect of the differences in intensity and track of tropical cyclones upon significant wave heights and direction of ocean waves in the southeast Indian Ocean. We used the tropical cyclone data from Japan Aerospace Exploration Agency (JAXA) starting from December 1997 to November 2017. The significant wave height and wave direction data are reanalysis data from Copernicus Marine Environment Monitoring Service (CMEMS), and the mean sea level pressure, surface wind speed, and wind direction data are reanalysis data from European Center for Medium-Range Weather Forecasts (ECMWF) from December 1997 to November 2017. The results show that the significant wave height increases with the increasing intensity of tropical cyclones. Meanwhile, the direction of the waves is influenced by the presence of tropical cyclones when tropical cyclones enter the categories of 3, 4, and 5. Tropical cyclones that move far from land tend to have higher significant wave height and wider affected areas compared to tropical cyclones that move near the mainland following the coastline

Cyclone is one of the most destructive hidrometeorological disaster on the Earth. Cyclone can happen in the area that is influenced by El Nino (La Nina) activity. Both cyclone and El Nino (La Nina) can cause extreme weather condition or extreme climate condition in the tropical area. This research is aimed to find the impact of El Nino (La Nina) phenomenon to intensity of the cyclone around Indonesia. The intensity of cyclone is classified by the Saffir-Simpson Hurricane Scale. Besides, relationship of El Nino (La Nina) with lifetime and frequency of cyclone around Indonesia is also studied. This research will compare between the cyclone data on the year with El Nino (La Nina) and the cyclone data on the normal year. This research is using the cyclone data in 10 years between 2007 until 2017 from the JAXA (Japan Aerospace Exploration Agency) website. Besides, the El Nino index on Nino 3.4 as the data of ENSO activity is also used. The method that is used by the research is the statistical method. From the analysis, generally found that El Nino (La Nina) has significant positive impact to the intensity and the lifetime of cyclones around Indonesia. Specifically, El Nino (La Nina) has significant positive impact to the intensity and the lifetime of cyclones in the northern part of equator. Meanwhile, it doesn’t show the significant correlation in the southern part of the equator. The impact of El Nino (La Nina) to the cyclone frequency can’t be conducted on this research so that it needs further research.

Fenomena cuaca seperti cold surge, southerly surge, dan Borneo vortex dapat menjadi penyebab anomali musim hujan di Indonesia. Penelitian ini mengkaji dinamika atmosfer saat terjadinya cold surge, southerly surge, dan Borneo vortex di benua maritim Indonesia (BMI) bagian barat pada tanggal 9 – 15 Desember 2012 dengan memanfaatkan model weather research and forecasting (WRF). Penelitian ini menggunakan final global data. Untuk verifikasi digunakan data angin, kelembapan relatif, curah hujan hasil observasi, serta data curah hujan global satellite mapping of precipitation (GSMaP). Metode yang digunakan adalah metode statistik dan deskriptif. Hasilnya didapatkan bahwa model WRF mampu merespon kehadiran cold surge, southerly surge dan Borneo vortex dengan baik. Hal ini dibuktikan dengan nilai mean absolute error (MAE) pada kelembapan relatif, kecepatan angin, dan curah hujan yang secara umum masih di bawah nilai toleransi kesalahan. Nilai korelasi yang sangat kuat juga didapatkan pada unsur curah hujan. Namun, model WRF belum mampu mengikuti pola spasial curah hujan GSMaP. Hasil kajian menggunakan keluaran model WRF didapatkan bahwa kehadiran southerly surge mengurangi intensitas cold surge dan Borneo vortex serta menyebabkan penurunan curah hujan di BMI bagian barat. Sementara itu, meningkatnya intensitas cold surge dan Borneo vortex menyebabkan peningkatan curah hujan di BMI bagian barat.