The Mann-Kendall test is a commonly-used nonparametric test for time trend. However, the standard P-values obtained from it are based on an assumption of independence between observations (since the theory is that of the Kendall correlation). However, observations in time series are often autocorrelated: knowing that one observation is larger than the mean may tell you that the next observation...

Kendall Rank Correlation Let (X1, Y1), · · · , (Xn, Yn) be a bivariate random sample of size n. The Pearson correlation coefficient provides an optimal measure of the degree of association between the X’s and the Y ’s when the sample is drawn from a bivariate normal distribution. The Pearson correlation coefficient is reasonably robust for many other distributions as well. The Kendall correlati...

Global warming is a result of the greenhouse effect caused by gases released into atmosphere; It usually expressed as an increase in measured average temperatures. In addition to this, extreme weather events such droughts, floods, and severe hurricanes become more frequent, specified severe. The effects global climate change on hydrological meteorological variables are increasing day day. There...

temperature is one of the most important climate variables that many economic and social plans related to its changes. because of the importance of this issue, this study investigated the changes of it in the province khuzestan. meteorological data that used in this study is mean temperature in annual and seasonal timescale. the study area is abadan, ahwaz, dezful and omidiye stations. for anal...

in the management of river basins, prediction of river water quality is essential to maintain water quality within standard limits. this study performed a time-series analysis of the prediction of chlorine concentration and electrical conductivity time series data for the period of 1991-2005 from sefidrood river in northern iran. the seasonal prediction of chlorine and electrical conductivity t...

In this paper two nonparametric tests for monotonic trend detection are compared with respect to their power and accuracy. The importance of comparing powers at equal empirical signiicance levels rather than nominal levels, is stressed. Therefore, an appropriate graphical method is presented. The eeect of the sampling frequency is also assessed using a trajectory representation that visualizes ...

drought is one of the natural phenomena which occurs in all climates in different parts of the world. iran is located in the dry belt of the world. the increase of desertification, drought reoccurrence, and destruction by human in this geographical region needs more studies on spatial and temporal trend of rainfall. in this study, trends of climatic drought during 1975-76/ 2004-05 in seasonal a...

Piecewise Linear Representation has been widely used to compress online data which are collected by sensors. However, the current existing methods, including Piecewise Aggregate Approximation and Perceptually Important Points cannot own both advantages of calculation speed and recovery accuracy at the same time. In order to improve the Piecewise Linear Representation performance, this work prop...

in this paper trends of precipitation and stream flow are analyzed in the atrak river basin in the north khorasan province. normal score linear regression, mann-kendall, and seasonal kendall trend tests were adopted. three precipitation variables and two stream flow variables including total precipitation, maximum daily precipitation, and number of rainy days, mean discharge and peak discharge ...