Abstract
The main objective of this study is to examine trend and homogeneity through the analysis of rainfall variability patterns in Iran. The study presents a review on the application of homogeneity and seasonal time series analysis methods for forecasting rainfall variations. Trend and homogeneity methods are applied in the time series analysis from collecting rainfall data to evaluating results in climate studies. For the homogeneity analysis of monthly, seasonal and annual rainfall, homogeneity tests were used in 140 stations in the 1975–2014 period. The homogeneity of the monthly and annual rainfall at each station was studied using the autocorrelation (ACF), and the von Neumann (VN) tests at a significance level of 0.05. In addition, the nature of the monthly and seasonal rainfall series in Iran was studied using the Kruskal-Wallis (KW) test, the Thumb test (TT), and the least squares regression (LSR) test at a significance level of 0.05. The present results indicate that the seasonal patterns of rainfall exhibit considerable diversity across Iran. Rainfall seasonality is generally less spatially coherent than temporal patterns in Iran. The seasonal variations of rainfall decreased significantly throughout eastern and central Iran, but they increased in the west and north of Iran during the studied interval. The present study comparisons among variations of patterns with the seasonal rainfall series reveal that the variability of rainfall can be predicted by the non-trended and trended patterns.
Highlights
Rainfall is an essential climatic element because it is the most important factor in the regionalization of climate and environmental conditions
Non-homogeneity created due to of changes in the method test of data collection short periods are recorded for some created due to changes in the method of data collection over short periods are recorded for stations
We found that positive rainfall trends were 0.006 mm per decade in spring
Summary
Rainfall is an essential climatic element because it is the most important factor in the regionalization of climate and environmental conditions. Researchers reported temporal and spatial variability in rainfall across Asia including Iran. Rainfall affects both the temporal and spatial patterns of climate variability. In the rainfall seasonality analysis in Iran, Talaee et al (2014) noted that rainfall showed a decreasing trend in Iran in the previous years [1,2]. Some researchers [3,4,5,6,7] recognized indirect indications of trend and long-term variability of rainfall. Analysis of rainfall seasonality is important in investigating the influence of climate variability on the regional climate and environmental conditions [5]. The trend and homogeneity of the rainfall series in
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