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Validity, reliability and certainty of PERSIANN and TRMM satellite-derived daily precipitation data in arid and semiarid climates

Khojand Keyvan, Shaghaghian Mahmood Reza, Ghadampour Zahra, Sabzevari Touraj

Acta Geophysica

2022

Vol. 70, no 4

1745--1767

Having doubts about the adequacy of reliability level of satellite-derived precipitation products, along with their application in large number of hydrological models, has led to many studies on evaluating the efficiency of such data. In this study, two new procedures were proposed to compute reliability and certainty degrees of PERSIANN and TRMM 3B42RT data sets, and six traditional indicators were used to evaluate their validation. In addition, the cumulative density function (cdf) of the above-mentioned data sets was compared with the ground-based observations in 23 synoptic stations in Fars, Iran. The Kolmogorov–Smirnov test was performed using the data sets at 5% significance level which led to the result of null hypothesis that was not being rejected, suggesting that the satellite-derived daily precipitation data (SDDPD) and ground based observations are drawn from the same distribution. Results indicated that TRMM and PERSIANN follow quite similar probability pattern of ground-based observations in arid and semiarid climate, respectively. However, data probability pattern of TRMM cannot be considered similar to ground-based observations in arid region, neither can PERSIANN in semiarid climate. Among common cross-validating attributes, the values of ME and BIAS, in addition to RMSE and MAE, led to the conclusion that in PERSIANN, the rainfall daily rates are almost underestimated while TRMM overestimates the values mainly in semiarid regions. Moreover, the PERSIANN was found to be significantly correlated with IDM (De Martonne aridity Index), and the values of underestimation increased with growth of the index. The reliability values of SDDPD over the study area, for both TRMM and PERSIANN, show the reverse trend with increasing IDM in almost all acceptable error intervals. Along with effects of climate conditions, the reliability degrees of PERSIANN seem quite more consistent at different acceptable error intervals in comparison with the corresponding values of TRMM. In addition to validity and reliability, the error entropy of SDDPD, as an index for uncertainty degree, increases as the IDM rises, which is theoretically corresponds with reliability concept. However, in comparison with PERSIANN, TRMM data set, overall, has higher degree of uncertainty. In addition, to evaluate effect of daily rainfall intensity on the uncertainty degree of SDDPD, the uncertainty degree slightly increases as daily rainfall intensifies to about 15 mm/day. But for higher daily rainfall intensities, on the other hand, the uncertainty degree seems to gradually decline as the daily rainfall increases.

Modelling rainfall runoff relations using HEC-HMS in a semi-arid region: Case study in Ain Sefra watershed, Ksour Mountains (SW Algeria)

Derdour A., Bouanani A., Babahamed K.

Journal of Water and Land Development

2018

no. 36

45--55

Ain Sefra is one of the Algerian cities that had been experienced several devastating floods during the past 100 years. The purpose of this study is to simulate runoff in the semi-arid region of Ain Sefra watershed through the employing of the Hydrologic Engineering Center – Hydrologic Modelling System (HEC-HMS). In this paper, the frequency storm is used for the meteorological model, the Soil Conservation Service – curve number (SCS-CN) is selected to calculate the loss rate and Soil Conservation Service unit hydrograph method have been applied to simulate the runoff rate. After calibration and validation, the simulated peak discharges were very close with observed values. The Nash–Sutcliffe efficiency coefficient was 0.95, indicates that the hydrological modeling results are satisfactory and accepted for simulation of rainfall-runoff. The peak discharges obtained for the 10, 50, 100 and 1000 year storms are respectively 425.8, 750.5, 904.3 and 1328.3 m3∙s–1.

Ain Sefra jest jednym z algierskich miast, które doświadczyły kilku niszczących powodzi w ciągu minionych 100 lat. Celem badań prezentowanych w pracy było symulowanie odpływu w regionie o klimacie półsuchym w zlewni Ain Sefra z wykorzystaniem systemu modelowania hydrologicznego HEC-HMS. W pracy użyto częstotliwości opadów nawalnych do konstruowania modelu meteorologicznego, liczbę krzywych Służby Ochrony Gleb USA – ang. Soil Consevation Service (SCS-CN) wybrano do obliczenia tempa strat, a metodę jednostkowego hydrogramu Służby Ochrony Gleb USA użyto do symulowania szybkości odpływu. Po przeprowadzeniu kalibracji i walidacji modelu symulowane maksymalne odpływy były bardzo bliskie wartościom obserwowanym. Współczynnik wydajności Nasha–Sutcliffa równy 0,95 wskazuje, że wyniki modelowania hydrologicznego są zadowalające i mogą być przyjęte do symulowania relacji opad–odpływ. Uzyskane maksymalne odpływy dla 10-, 50-, 100- i 1000-letnich opadów nawalnych wynoszą odpowiednio 425,8, 750,5, 904,3 i 1328,3 m3∙s–1.