PERBANDINGAN KARAKTERISTIK DISTRIBUSI UKURAN BUTIRAN HUJAN DI PADANG DAN DI KOTOTABANG
DOI:
https://doi.org/10.25077/jfu.4.3.%25p.2015Abstract
ABSTRAK
Distribusi ukuran butiran hujan atau raindrop size distribution (RDSD) di Padangdan di Kototabang, Sumatera Barat,  telah dibandingkan. Perbandingan dilakukan melalui pengamatan particle size velocity (Parsivel) selama Maret 2014 – Mei 2015 untuk Padang dan Januari 2014 – Januari 2015 untuk Kototabang. RDSD dimodelkan dengan distribusi gamma dan parameternya didapatkan menggunakan metode momen. Terlihat bahwa intensitas curah hujan yang tinggi lebih banyak di Padang daripada di Kototabang. Selain itu, butiran hujan yang berukuran besar di Padang lebih banyak daripada di Kototabang. Banyaknya butiran hujan yang berukuran besar ini berdampak pada nilai radar reflectivity (Z) di Padang yang sedikit lebih besar dari Kototabang untuk intensitas curah hujan yang sama. Karena itu nilai koefisien A yang ada dalam persamaan Z-R di Padang juga sedikit lebih besar dari Kototabang. Sedikitnya perbedaan karakteristik RDSD antara Padang dan Kototabang, disebabkan oleh hujan yang terjadi  di Padang dan di Kototabang kemungkinan berasal dari awan konvektif yang sama, yaitu awan dari Samudra Hindia.  Awan tersebut mengalami proses yang berbeda di Kototabangdisebabkan oleh adanya pegunungan di sekitar daerah ini sehingga menimbulkan hujan dengan RDSD yang agak berbeda dengan di Padang.
Kata kunci: raindrop size distribution, metode momen, Parsivel, Padang, Kototabang
Abstract
Characteristics of raindrop size distribution (RDSD) in Padang and Kototabang have been compared through particle size distribution (Parsivel) observation during March 2014 – May 2015 for Padang and January 2014 – January 2015 for Kototabang. The RDSD was parameterized by the modified gamma distribution and its parameter was calculated by the moment method. It was found that the occurrence frequency of heavy rain in Padang is higher than Kototabang. Moreover, rains in Padang have more large-sized drop than Kototabang. As consequence, the radar reflectivity factor (Z) in Padang was slightly larger than Kotabang for the same rainfall rate. A small difference in the RDSD between Padang and Kototabang may indicate that the precipitating cloud of the two regions is the same, i.e., same origin (Indian Ocean). However, the cloud will undergo different process when it reaches Sumatera. At Kototabang, it will be influenced by the mountain around this region which can cause orographic precipitation. The orographic precipitation is characterized by the large concentration of small size drops as found at Kototabang in this study.
Keywords: raindrop size distribution, moment method, Parsivel, Padang, Kototabang
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Copyright (c) 2024 Rio Chandra, Marzuki -, Hiroyuki Hashiguchi
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