Inter-station correlation and estimation errors of areal average rain rate

Abstract

In this study an equation for estimating the error involved in the areal average rain rate considering the inter-station correlation was derived and applied for two cases: the first compared two storm events with different inter-station correlations, and the second evaluated the seasonal variation of estimation error of monthly rainfall. Similar cases, but without considering the rainfall seasonality, were also investigated for the comparison. This study was applied to the Geum River Basin with 28 rain gauge measurements, each having more than 30 years of rainfall data. A summary of the application results follows: (1) When considering the inter-station correlation, the estimation error involved in the areal average rain rate became significantly decreased proportional to the inter-station correlation.(2) The estimation error of monthly areal average rainfall showed strong seasonality with high ones during the wet season and lower ones during the dry season. (3) The estimation error was well proportional to the areal average rain rate as well as to its standard deviation. The ratio of estimation error to the areal average rain rate itself was estimated to be about 0.1 for the case of assuming no inter-station correlations, but decreased to 0.06 for the case of considering the inter-station correlations between measurements. (4) The relation between the standard deviation of areal average rain rate and the estimation error became much stronger than that between the areal average rain rate itself and the estimation error. The ratio of estimation error to the standard deviations of rain rate amount was estimated to be about 0.2 for the case of assuming no inter-station correlations, but decreased to 0.1 for the case of considering the inter-station correlations. This relation was found to be valid for any case of accumulation time such as in daily, monthly, or annual rainfall data.

Pengaruh Sebaran Spasial Hujan terhadap Pemilihan Metode Hujan Wilayah Berbasis Analisis Geospasial

“…Salah satu cara untuk merepresentasikan kondisi hidrologi DAS secara spasial adalah melakukan analisis hujan rerata wilayah. Metode yang sering dimanfaatkan dalam analisis hujan wilayah adalah Metode Rerata Aritmatik, Isohyet dan Thiessen (Yoo , et al, 2008). Metode rerata aritmatik, Thiessen dan Isohyet merupakan metode analisis hujan wilayah yang menitepretasikan faktor kuantitas fisik alat ukur hujan dalam skala geometris (Ribeiro, et al, 2021).…”

“…Kondisi kerapatan stasiun hujan dan sebaran distribusi hujan di DKI Jakarta maupun di kawasan penyangga Jakarta menyebabkan hujan wilayah dengan metode rerata aritmatik tidak dapat digunakan, karena deviasi antar stasion hujan lebih dari 10% sementara kriteria pemanfaatan hujan rerata aritmatik adalah deviasi antar stasion hujan kurang dari 10% (Yoo , et al, 2008). Terjadinya serangkaian banjir yang semakin sering terjadi dan terulang tiap tahun, menuntut upaya lebih besar mengantisipasinya, sehingga kerugian dapat diminimalkan.…”

Estimation of Areal Mean Rainfall in Remote Areas Using B-SHADE Model

“…The arithmetic average method assumes that the rainfall field is homogeneous and that the rain gauge observations are independent; thus, it gives equal weight to all rain gauges [1,6]. The Thiessen polygon technique sets a fixed weighting factor for the areal coverage of a station.…”

“…Kriging methods (e.g., ordinary kriging, universal kriging, and cokriging) are known as geostatistical approaches or multivariate geostatistical techniques with spatial correlation patterns [6,[8][9][10][11]. Previous case studies have confirmed their effectiveness in the spatial interpolation of rainfall within mountainous terrain [11][12][13][14].…”