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Showing 2 results for Extreme Precipitation
The Influence of Madden-Julian Oscillation on Occurrence of February to April Extreme Precipitation (Flood and Drought) in Fars Province
S.mj Nazemosadat, H Ghaed Amini Asadabadi,
Volume 12, Issue 46 (1-2009)
Abstract
The Madden–Julian Oscillation (MJO) known as the dominant mode of tropical and extratropical intraseasonal variability has an important role in the coupled ocean-atmosphere system. This study investigates the eastward propagation of the MJO and its impact on monthly (February-April) maximum and minimum precipitation in Fars Province. The positive and negative phases of MJO were categorized for the period 1979-2002. The maximum and minimum values of monthly precipitation was then determined for each phase as well as for the entire length of records. The given results have indicated that, in February, both maximum and minimum precipitation during negative phase were significantly greater than the corresponding values during the positive phase. This implies that the enhanced February precipitation and flood events are associated to the negative MJO phase. On the other hand, severe water shotage in February was linked with prevalence of the positive phase. The results for April were mostly found to be similar to February except that minimum precipitation was not significantly associated to the positive phase. In contrast to February, minimum monthly precipitation in March was found to coincide with the negative MJO phase. Maximum precipitation, however, could coincide with neither of extreme phases of MJO.
Application of Circular Statistics in Seasonality Analysis of Extreme Precipitation Occurrence Time in Urmia Lake Basin
R. Samadi, Y. Dinpashoh, A. Fakheri-Fard,
Volume 27, Issue 3 (12-2023)
Abstract
A hydrological parameter affecting the management of water resource systems is changes in the amount and occurrence time of extreme precipitation (OTEP). In this research, the seasonality of precipitation in the Lake Urmia (LU) basin was analyzed using the daily extreme precipitation data of 30 rain gauges in the statistical period of 1991-2018. The uniformity of OTEP was tested by Rayleigh and Kuiper’s tests at 0.1, 0.05, and 0.01 levels. The slope of the trend line for OTEP was estimated using the modified Sen slope estimator. The uniformity of OTEP was rejected at each level. The results revealed two strong seasons: late winter and early spring (S1) and autumn (S2) for OTEP. The results showed a general median seasonality index of 0.3, which changed to 0.82 and 0.9 for S1 and S2, respectively, after dividing the whole year into two seasons. The seasonal strength of S1 was similar in both the western and eastern parts of LU, but the west of the lake was stronger than the eastern part in S2. In S1, negative and positive trends in the OTEP were observed on average in 40% and 60% of the stations, respectively, with corresponding values of 77% and 27% for S2, respectively.

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