Trend analysis of time series rainfall data using robust statistics

Abstract

A temporal rainfall analysis was carried out for the study area, Rajahmundry city located in lower Godavari basin, India, during the period 1960–2013. Both the parametric and non-parametric approaches were envisaged for identifying the trends at different temporal scales. Linear and robust regression analysis revealed a negative trend at weekly scale during monsoon months, but failed to signify the slope at 95% confidence level. The magnitude of Sen's slope was observed to be negative during the months of April–September. Results of the Mann–Kendall test ascertained the negative rainfall trends during the monsoon months of June and July with a significant trend at 95% confidence interval. Application of robust statistics for long-term rainfall analysis helped to address the outlier's problem in the dataset. The Mann–Kendall test rejected the null hypothesis for all months except February–May and August after exclusion of outliers. Overall, a negative trend during monsoon season and a positive trend during post-monsoon season were observed using a robust non-parametric approach. Further, good correlation was found between the total rainfall and rainy days during the study period. On average, 21.25% days of a year is considered as rainy, while heavy and extreme rainfall in this region together occupies nearly 15% of the rainy days.

Variabilidade espacial e temporal da precipitação pluviométrica na região hidrográfica do Paraguaçu - BA

“…In the upper and middle Paraguaçu, the data showed the presence of outliers, behavior that is usual in historical series of pluviometric data, as verified in the studies by Wu and Qian (2017) and Phuong et al (2019). These outliers are very common in rainfall time series, as the information comes from the measurement of a natural and random phenomenon, with the possibility of sudden large-scale events (PAUL et al, 2017).…”

Assessment of rainfall trend at the airports using non-parametric statistics approach

“…Several studies over India observed no significant trend in mean of rainfall [15]. Despite non-presence of monsoonal rainfall trend in India, there is a significant trend present on a regional scale [16], [17]. In conclusion, intense precipitation rate is reduced in most Asian country, and the same goes to number of rainy days and annual rainfall [18], [19].…”

“…The method is robust to outliers [29] and is appropriate to determine presence of trends [32]. The trend slope gives the rate of increase or decrease in linear trend and direction of change [16], [32] and it involves the calculation of the slope for all ordinal point-time pairs and then using this median slope as an overall slope estimate [30]. The linear model for this method can be describe as [35]: (5) where, Q, D and t represents slope, constant, time respectively.…”

Characterization of Spatio-temporal Trends in Long-term Rainfall of Three Weather Stations in Benin: Implications for Agricultural Decision Making.

“…The latter information can guide suitable adaptation measures such as water conservation techniques, use of shallow ground water for irrigation, shifting planting dates and use of drought-resistant crop varieties (Marie et al 2020). Rainfall trend analysis plays an important role for water resources management (Paul et al 2017) and agricultural activities (Ademe et al 2020). A change in the rainfall pattern may ultimately lead to drought and flood in different regions, which has a direct impact on soil degradation and agricultural productivity (Gummadi et al 2018;Asfaw et al 2018;Onyutha 2018;Arouna et al 2021).…”