Rainfall trend detection using statistical tests in North Coast of Egypt

Abstract

The Mediterranean Coast in Egypt has witnessed a significant change in climate over the past two decades. However, relying solely on prognoses without applying rigorous statistical tests may lead to unreliable results. This research aimed to investigate the historical performance of the rainfall data trend and its change through the time and identify the change points along the Mediterranean coast area of Egypt in order to gain comprehensive insights into future changes. Thus, four tests were applied on the Global Precipitation Climatology Centre (GPCC) data with spatiotemporal resolution (0.25o, Month) to identify abrupt and continuous trends. The applied tests classified into two: parametric and non-parametric tests. Non-parametric tests, such as Mann–Kendall and Sen’s slope tests, were employed to assess trends in the data, while the Pettit test was used as a change point test. On the other hand, the parametric test employed the Buishand test to detect change points. The GPCC rainfall time series last version is available from 1900 until 2019, where those 119 years of time span are divided into three periods; (1900–1940), (1941–1980) and (1981–2019). The research offers a rigorous approach to understanding past trends and identifying change points, revealing decreasing trends in rainfall during 1900–1940 and 1981–2019. January and March had the highest decreases in these periods. 69% of stations showed a significant decrease in annual rainfall, mainly along the Mediterranean coast. Change points were identified in 1931 (delta region) and 1999 (Sinai), with no significant change in the West delta.