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Margaretta Welly
Universitas Lampung

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Model Stokastik Curah Hujan Harian dari Beberapa Stasiun Curah Hujan di Way Jepara Ahmad Zakaria; Margaretta Welly; Mirnanda Cambodia
Rekayasa : Jurnal Ilmiah Fakultas Teknik Universitas Lampung Vol 19, No 2 (2015): Edisi Agustus 2015
Publisher : UNIVERSITAS LAMPUNG

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Abstract

This research was conducted to study and know the characteristics of periodic and stochastic models of daily rainfall in the Way Jepara. This study used secondary data, namely daily rainfall data with a data length of 13 years (1997-2013) from the station Braja Arjosari, Braja Indah, and Jepara Lama. In this study , daily rainfall data is processed into the form of time series before it was trans- formed into the spectrum of rainfall using the program FFT (Fast Fourier Transform). One year of daily rainfall data periodicity, only used 512 rainfall data are periodic. Spectrum rainfall pro- duce data series stochastic rainfall is assumed as the difference (error) between the actual rainfall data with periodic rainfall models. Based on data from the series of stochastic, the stochastic com- ponent is calculated using the approach of autoregressive models. Stochastic model generated us- ing the least squares method (least square method) or autoregressive model of order three. Vali- dation of stochastic series between the measured data and the model is done by calculating the correlation coefficient. From the research, the correlation coefficient obtained an average of three stations of the daily rainfall. Value of the average correlation coefficient ( R ) between the data with a model pe- riodic rainfall amounted to 0.97305, the data series is stochastic and stochastic models of 0.99150, and between data and periodic stochastic models are at 0.99963. From the results, it can be concluded that the periodic stochastic models of rainfall Way Jepara region gives very accurate results and the approach significantly.
Analisa Karakteristik Hujan di Kota Bandar Lampung Margaretta Welly
Rekayasa : Jurnal Ilmiah Fakultas Teknik Universitas Lampung Vol 19, No 3 (2015): Edisi Desember 2015
Publisher : UNIVERSITAS LAMPUNG

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Abstract

Knowledge of the characteristics of rainfall causes floods and droughts is an important thing. This research intends to investigate the characteristics of rainfall in the city of Bandar Lampung in or- der to predict and anticipate events of drought and flood in Bandar Lampung. The data used in this study is the annual rainfall data obtained from four rainfall stations in Bandar Lampung from 1987 until 2006. The stations that are: Pahoman Station, Sukarame, Sumur Putri, and Kemiling (Sumber Rejo). The results showed that the pattern and trend of the respective data from each of the stations the rain is not too different from each other. Most of the stations showed decreased dy - namically on rainfall. Although this decline did not occur in the rest of the station, but in general decline is clearly visible when the trend was taken fourth. A dry year, the year in which the annual precipitation totals less than 90% of the average annual rainfall, dominated after the year 2000. Most of the rainfall in the year El Nino is below the average annual precipitation. Near Pahoman, there have been five times the annual rainfall is below average at the time of El Nino (1991, 1992, 1993, 2002, 2004). Near Sukarame, there has been four times the annual rainfall is below aver- age at the time of El Nino (1991, 1997, 2002, 2004). At the Sumur Putri station, there has been four times the annual rainfall is below average at the time of El Nino (1991, 1993, 2002, and 2004). Near Kemiling, there has been four times the annual rainfall is below average at the time of El Nino (1991, 1992, 1997, 2002). This suggests the possibility of EL Nino events are associ- ated with a decrease in rainfall in each station.