Bandara Internasional Kualanamu, yang beroperasi sejak tahun 2013, merupakan bandara baru yang melayani penerbangan komersial yang menggantikan Bandara Polonia. Sebagai bandara baru, Bandara Internasional Kualanamu memerlukan kajian pengaruh unsur cuaca terhadap kelancaran operasi penerbangan, diantaranya unsur suhu dan tekanan udara permukaan (QFE). Penelitian menggunakan metode regresi linear berganda untuk menentukan korelasi antara suhu dan tekanan udara terhadap daya angkat pesawat (lift). Selain itu, penelitian melakukan perhitungan nilai ketinggian kerapatan udara (density height) menggunakan nilai suhu dan tekanan udara. Hasil penelitian menunjukkan bahwa suhu dan tekanan udara secara bersama-sama berpengaruh sangat kuat terhadap lift di setiap bulan sepanjang tahun. Penurunan nilai suhu dan/atau kenaikan nilai tekanan udara berbanding lurus dengan kenaikan nilai lift. Suhu udara mempunyai pengaruh terkuat pada bulan April (92,93%) dan terlemah pada bulan Maret (84,82%). Tekanan udara mempunyai pengaruh terkuat pada bulan September (24,80%) dan terlemah pada bulan Februari (8,76%). Hasil perhitungan menggunakan rumus density height menunjukkan bahwa pada tahun 2015 nilai density height tertinggi terjadi pada bulan Juni (1756,34ft) dan terendah pada bulan Januari (1469,11ft). Sedangkan pada tahun 2016, nilai density height tertinggi terjadi pada bulan Maret (1806,32ft) dan terendah pada bulan Februari (1513,23ft). Kata-kata kunci: suhu udara, tekanan udara, lift, density height.
Located adjacent to the Indian Ocean and the Malacca Strait as a source of water vapour, and traversed by the Barisan Mountains which raise the air orographically causing high diurnal convective activity over the North Sumatra region. The convective system that was formed can cause heavy rainfall over a large area. Weather Research and Forecasting (WRF) was a numerical weather model used to make objective weather forecasts. To improve the weather forecasts accuracy, especially for predict heavy rain events, needed to improve the output of the WRF model by the assimilation technique to correct the initial data. This research was conducted to compare the output of the WRF model with- and without assimilation on 17 June 2020 and 14 September 2020. Assimilation was carried out using the 3D-Var technique and warm starts mode on three assimilation schemes, i.e. DA-AMSU which used AMSU-A satellite data, DA-MHS which used MHS satellite data, and DA-BOTH which used both AMSU-A and MHS satellite data. Model output verification was carried out using the observational data (AWS, AAWS, and ARG) and GPM-IMERG data. The results showed that the satellite data assimilation corrects the WRF model initial data, so as increasing the accuracy of rainfall predictions. The DA-BOTH scheme provided the best improvement with a final weighted performance score of 0.64.
Nias is the largest island in the Indian Ocean west of Sumatra. The geographical condition of Nias Island which is a small island surrounded by waters causes strong weather dynamics and high intensity of rainfall. This study was conducted to determine changes in weather dynamics conditions during high rainfall on Nias Island, including the parameters of the vertical profile of air humidity, vorticity, divergence, vertical velocity, reflectivity; and cloud top temperatures. The simulation was carried out on 4 days of heavy rain in 2020, each representing each season period, namely 7 February 2020 for December-January-February (DJF), 30 April 2020 for March-April-May (MAM), 3 August 2020 for June-July-August (JJA), and 8 October 2020 for September-October-November (SON). The data used are Final Analysis Data (FNL) with a spatial resolution of 1°x1° as input data for the Weather Research and Forecast (WRF) model, IR1 data (band#13 – 10.4µm) Himawari-8 satellite, and observational rainfall data from the Binaka and Global Meteorological Stations. Precipitation Measurement – The Integrated Multi-Satellite Retrievals for GPM (GPM IMERG) with a spatial resolution of 0.1°x0.1°. The results showed that the presence of Cumulonimbus convective clouds caused heavy rain, with cloud top temperatures reaching -60°C to -80°C. The relatively humid atmosphere, accompanied by the convection mechanism that occurs, causes the convective activity on Nias Island to be quite intense.
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