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Marzuki,
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Statistical Properties of Cloud Propagation over Sumatra during CPEA-I Rahayu, Aulya; Marzuki,; Vonnisa, Mutya
Makara Journal of Science Vol. 20, No. 4
Publisher : UI Scholars Hub

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Cloud propagation over Sumatra and the surrounding area (10°S-10°N, 70°-120°E) during the Coupling Processes in the Equatorial Atmosphere-I (CPEA-I) campaign (10 April to 9 May 2004) was tracked using brightness temperature (Tb) data from the GOES-9 satellite. The cloud tracking was based on three-dimensional data with a threshold of Tb < 210 K. During the campaign, westward-moving clouds were more dominant than eastward-moving systems, with a ratio of approximately 4:1. This characteristic coincided with the dominant easterly wind aloft. Most clouds propagated with a speed varying between 4 and 35 m/s, with a mean value of 13.7 m/s. If the westward and eastward propagations were separated, the average duration, speed, and span of the westward (eastward) moving clouds are 7.7 (5.8 h), -14.5 (9.8 m/s), and 435.5 (187.1 km), respectively. The characteristics of cloud propagation during the CPEA-I were influenced by environmental factors such as relative humidity, temperature, the vertical movement of air, and wind shear. Such factors interacted with the inactive and active phases of the Madden-Julian Oscillation.
Estimation of Raindrop Size Distribution Parameters Using Rain Attenuation Data from a Ku-Band Communications Satellite Indrayani, Wira; Marzuki,; Vonnisa, Mutya
Makara Journal of Science Vol. 20, No. 3
Publisher : UI Scholars Hub

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The rain attenuation of down-link radio wave signals from the Superbird-C satellite and surface rainfall data have been used to estimate the parameters of exponential raindrop size distribution (DSD) at Koto Tabang (100.32 °E, 0.20 °S), West Sumatra, Indonesia. Prior to analyzing the measured data, the ability of the method to recover the parameters of known DSDs from which the samples were taken was examined. It was found that the method can accurately retrieve the input parameter of the sample. Only six case studies are presented here, so the results are representative rather than definitive. The method successfully estimated the DSD parameters of a stratiform case with steady intensity and deep convective rains of a short duration. This can be inferred from the small difference between the parameters derived from rain attenuation data and those derived from a 2D video disdrometer. The poor performance of the method was observed for a stratiform case with strong rain intensity fluctuation and shallow convective rains with very low rain top height. This phenomenon is probably due to the bias that may be inherent in the estimation of specific rain attenuation, such as the assumption of a constant path length throughout the rain.
Co-Authors Aulya Rahayu, Aulya Indrayani, Wira Mutya Vonnisa