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
During the Asian Winter season, which spans from November to February, the phenomenon of cold surge often occurs, leading to increased convective activity over the western Indonesian Maritime ...Continent. The location of Natuna Island, situated in the southern part of the South China Sea, is of particular importance for studying cold surges due to their propagation over this area. In this study, the vertical structure of the atmosphere was analyzed using radiosonde observation data collected at the Meteorological Station of Ranai Natuna. The analysis focused on physical parameters such as air temperature and relative humidity, atmospheric kinematics including wind direction and speed, as well as atmospheric thermodynamic parameters such as Lifting Condensation Level (LCL), Level of Free Convection (LFC), Equilibrium Level (EL), Convective Available Potential Energy (CAPE), and Convective Inhibition (CIN). The results indicate that during the passage of a cold surge, air temperature (T) tends to be higher in the lower troposphere, including at the surface, but lower in the middle and upper troposphere. Relative humidity (RH) also tends to be higher during cold surges, with a significant increase in the middle and upper troposphere. In the lower troposphere, the wind direction shifts from east to northeast at a higher speed compared to when a cold surge is absent. Furthermore, the LCL and LFC heights are elevated during the presence of a cold surge, while the EL height shows an insignificant decrease. It is worth noting that intense rainfall occurs, particularly when the cold surge is more pronounced, even though the values of CAPE and CIN do not change significantly.
El Niño is a phenomenon that can affect changes in weather and climate elements in Indonesia, especially rainfall. During the El Niño events, the rainfall in Maluku region tended to decrease. This ...condition can indeed cause prolonged drought. However, El Niño events also have a positive impact, especially in water areas. During the El Niño events, the chlorophyll-a concentration in the water will increase. This is due to the upwelling process that removes nutrients from the sea. High chlorophyll-a concentrations will bring pelagic fish species in the waters. The correlation test between sea surface temperature (SST) during El Niño and chlorophyll-a has a value of -0.91. This correlation value indicates that when SST increases, the chlorophyll-a concentration in the waters will decrease, on the other hand, if SST has decreased, the chlorophyll-a concentration in the water will increase. The value of chlorophyll-a concentration in the water during the El Niño event (July - February) showed a significant increase compared to during normal conditions. Of all the El Niño events, 2015 to 2016 was the year with the strongest El Niño events. The chlorophyll-a concentration during El Niño 2015 to 2016 was very high, ranging from 0.2 to 1.0 mg / m3. The results obtained indicate that the El Niño event has a positive correlation with the increase in chlorophyll-a concentration in the water. El Niño merupakan fenomena yang tidak bisa dihindari, kejadian El Niño dapat mengurangi curah hujan seperti di wilayah Maluku. Namun, kejadian El Niño juga mempunyai dampak postif khususnya di wilayah perairan. Pada saat terjadi El Niño maka konsentrasi klorofil-a di perairan akan meningkat. Hal ini disebabkan karena adanya proses upwelling yang mengangkat nutrisi dari dalam laut. Konsentrasi klorofil-a yang tinggi akan mendatangkan jenis ikan pelagis di perairan. Uji korelasi antara suhu permukaan laut (SST) pada saat El Niño dengan klorofil-a memiliki nilai - 0.91. Nilai korelasi ini menunjukkan bahwa pada saat SST mengalami kenaikan maka konsentrasi klorofil di perairan akan menurun, sebaliknya jika SST mengalami penurunan maka konsentrasi klorofil diperairan akan meningkat. Nilai konsentrasi klorofil-a diperairan pada saat kejadian El Niño (Juli - Februari) menunjukkan peningkatan yang cukup signifikan dibandingkan pada saat tidak terjadi El Niño . Dari semua kejadian El Niño , tahun 2015 - 2016 merupakan kejadian dengan El Niño yang sangat kuat. Konsentrasi klorofil-a pada saat El Niño 2015 - 2016 sangat tinggi berkisar 0.2 - 1.0 mg/m3. Dari hasil yang didapatkan menunjukkan bahwa kejadian El Niño dapat mempengaruhi konsentrasi klorofil-a diperairan.
Suhu udara permukaan (SUP) merupakan salah satu indikator penting dalam konteks terjadinya perubahan iklim. Penelitian ini bertujuan untuk mengkaji variasi temporal dan spasial beserta trend SUP di ...Pulau Jawa pada tahun 1990-2019. Data yang digunakan diperoleh dari observasi Badan Meteorologi Klimatologi dan Geofisika (BMKG) dan data pemodelan reanalisis (GHCN_CAMS, ERA-5, JRA-55, dan GISTEMP-v4). Data observasi BMKG diperoleh berdasarkan data bulanan dari stasiun BMKG yang tersebar di seluruh Pulau Jawa (16 stasiun). Hasilnya menunjukkan bahwa terjadi peningkatan SUP dalam 30 tahun sebesar 0,11-1,24℃. Variasi spasial menunjukkan bahwa daerah dengan SUP tertinggi terdapat di Pulau Jawa sebelah utara bagian timur dan terendah di dataran tinggi Pulau Jawa bagian barat. SUP di Pulau Jawa tertinggi terjadi pada periode bulan September-Oktober-November (SON) dan terendah pada periode bulan Juni-Juli-Agustus (JJA). Hasil uji statistik menggunakan metode Mann Kendall test dengan significance level 1% menunjukkan bahwa semua data observasi BMKG mengalami trend peningkatan kecuali untuk Banyuwangi. Trend peningkatan SUP per tahun berkisar antara 0,017-0,048℃. Hal ini menunjukkan bahwa perubahan iklim secara regional telah terjadi di Pulau Jawa selama 30 tahun terakhir berdasarkan trend perubahan SUP.
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.
Mesoscale Convective Complex (MCC) was first introduced in 1980 through research on infrared (IR) satellite images by Maddox. The MCC phenomenon can caused rain with a long period of time. This study ...aims to determine the atmospheric conditions when MCC occurred in East Kalimantan and surroundings area on December 26, 2021. The research data used in this study is Himawari-8 satellite data to display cloud top temperatures and convective cloud distribution using the CCO method and image interpretation using RGB method. Analysis of atmospheric conditions was also carried out on air humidity, vertical velocity, and reflectivity in the atmosphere obtained from weather radar data from the Stasiun Meteorologi Sultan Aji Muhammad Sulaiman - Sepinggan. Based on the results of the analysis, MCC was identified as a mature phase on December 26, 2021 at 12.00 UTC. Airmass RGB analysis shows the presence of clouds which are known as Cb clouds through CCO analysis as well as warm air masses with high humidity in East Kalimantan. Negative value of vertical velocity also indicates an updraft of moist air masses and the maximum reflectivity value of the CMAX product, which is 53 dBz, indicates strong convection activity.
Madden-Julian oscillation (MJO) is an atmospheric oscillation due to atmospheric phenomenon that occurs due to the uniformity of solar energy received at the surface of the earth, MJO is a natural ...occurrence in the sea-atmosphere system. When the MJO is active, in general there will be a disturbance in the upper air which is then followed by an anomaly at sea surface pressure causing the changes in the wind on the surface. The changes in the surface wind affectthe sea surface currents which then cause the occurrence of coastal upwelling downwelling. The upwelling process itself is a process whereby a sea mass is pushed upward along the continent, when the beach is to the left of the wind direction, the ecological transport leads to the mass of water away from the coast. As a result, there is a mass vacuum (divergence) in the coastal area. This mass void will be filledby the mass of water from the inner layer that moves to the surface. Indonesian territory itself is passed by MJO in phases 3, 4 and 5, while for Sumatra region is passed by MJO phase 3 and 4. This research aims to identify the propagation of coastal upwelling during MJO on the west coast of Sumatera, therefore the data of geopotential height, surface pressure sea (MSLP), zonal and meridional components and sea surface temperature are used to analyze how the MJO effecton the coastal upwelling occurs in the research area. The analysis was conducted in June, July and August by comparing the atmospheric conditions at the time of strong MJO in phases 3 and 4 with normal viewing of anomaly geopotential height and MSLP and then seeing the anomaly surface wind changes from zonal wind (u) and meridional wind (v) and changes in SST in Sumatra region. The result shows that there is a change of GH and MSLP when MJO passes the west coast of Sumatra and then follows the change in the value of u and v and SST to identify the upwelling, while the anomaly change negative SST does not occur when MJO is active but has time lag (lag). In this analysis it was found that SST anomaly occurs when the anomaly changes in both the upper and surface water occurring after 5 days in phases 3, 4 and 5.
On August 22 2020, hail was reported in Sekadau, West Kalimantan at 21:23 WIB. The phenomenon of hail does not usually occur at night. So, further research is needed to find out how the cloud growth ...phase and Cumulonimbus (Cb) cloud structure are in this phenomenon. This research utilizes remote sensing instruments in the form of a C-Band type weather radar for the Supadio Meteorological Station and the Himawari 8 Satellite, as well as a radiosonde instrument that is closest to the time and location of the hail events. The results of satellite imagery show that nocturnal hail occurs before the clouds reach the mature phase, with the cloud top temperature at the time of hail less than -60 ºC. The maximum reflectivity detected by the radar using CMAX products shows a less significant value with an intensity of up to 52 dBZ. The VCUT product shows the maximum intensity altitude is at an altitude of 5 – 8 km. This shows that there is a process of ice condensation on the freezing level layer. The ZHAIL product image shows that there is a potential for hail in the Sekadau area with a probability of more than 80%. The occurrence of ice rain at Sekadau at night is caused by the presence of Cumulonimbus clouds with very cold peak temperatures and the mixing process above the freezing level which supports the formation of ice condensation in Cb clouds.
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