Observed changes in relative humidity and dew point temperature in coastal regions of Iran

The analysis of trends in hydroclimatic parameters and assessment of their statistical significance have recently received a great concern to clarify whether or not there is an obvious climate change. In the current study, parametric linear regression and nonparametric Mann?CKendall tests were applied for detecting annual and seasonal trends in the relative humidity (RH) and dew point temperature (T _dew) time series at ten coastal weather stations in Iran during 1966?C2005. The serial structure of the data was considered, and the significant serial correlations were eliminated using the trend-free pre-whitening method. The results showed that annual RH increased by 1.03 and 0.28?%/decade at the northern and southern coastal regions of the country, respectively, while annual T _dew increased by 0.29 and 0.15°C per decade at the northern and southern regions, respectively. The significant trends were frequent in the T _dew series, but they were observed only at 2 out of the 50 RH series. The results showed that the difference between the results of the parametric and nonparametric tests was small, although the parametric test detected larger significant trends in the RH and T _dew time series. Furthermore, the differences between the results of the trend tests were not related to the normality of the statistical distribution.     

Phase equilibria and P-T-t path of metapelitic rocks in SE-Hamedan,Sanandaj-Sirjan Zone,Iran

Mineralogy and Petrology - In the southeast of Hamedan, in the Sanandaj-Sirjan Zone of Iran, metamorphic rocks display different metamorphic assemblages formed during dynamothermal and contact...     

Comparison of artificial neural network and multivariate linear regression methods for estimation of daily soil temperature in an arid region

Soil temperature (T _S) strongly influences a wide range of biotic and abiotic processes. As an alternative to direct measurement, indirect determination of T _S from meteorological parameters has been the focus of attention of environmental researchers. The main purpose of this study was to estimate daily T _S at six depths (5, 10, 20, 30, 50 and 100?cm) by using a multilayer perceptron (MLP) artificial neural network (ANN) model and a multivariate linear regression (MLR) method in an arid region of Iran. Mean daily meteorological parameters including air temperature (T _a), solar radiation (R _S), relative humidity (RH) and precipitation (P) were used as input data to the ANN and MLR models. The model results of the MLR model were compared to those of ANN. The accuracy of the predictions was evaluated by the correlation coefficient (r), the root mean-square error (RMSE) and the mean absolute error (MAE) between the measured and predicted T _S values. The results showed that the ANN method forecasts were superior to the corresponding values obtained by the MLR model. The regression analysis indicated that T _a, RH, R _S and P were reasonably correlated with T _S at various depths, but the most effective parameters influencing T _S at different depths were T _a and RH.     

Investigation of meteorological extreme events over coastal regions of Iran

In this study, in order to detect probable trends and effects of climatic extreme events of precipitation and temperature as well as maximum relative humidity, dew point temperature, sunshine hours, and wind speed, 12 stations on the northern and southern coastlines of Iran were investigated from 1977 to 2007. For this purpose, 27 indices of precipitation and temperature, which are specified by the Expert Team of the World Meteorological Organization and Climate Variability and Predictability, were calculated by using RClimDex software. The Mann?CKendall method was also used to detect possible trends in the data time series. The results indicate that temperature indices are absolutely consistent with warming. Warm nights, hot days, and hot day and night frequencies increased, while cold spell and cool day and night frequencies declined. The minimum temperature experienced a considerable rise both in its maximum and minimum values. The minimum temperature had a higher increase than the maximum temperature. Therefore, diurnal temperature ranges have experienced dramatic declines. In the northern coastal sites, hot day frequency and hottest day temperature showed higher magnitudes than those of the southern sites as a result of the significant increase in the maximum sunshine hours in northern stations. This enhancement led to a considerable increase in the maximum wind speed. Consequently, relative humidity declined in the northern sites. Precipitation indices indicate few significant trends over the studied period. Temporal precipitation distribution was different from station to station. Three precipitation patterns were detected at individual stations, although an overall regional rainfall pattern was not detectable. On the whole, the results of this study emphasize that the water resources in the studied area are going to become problematic.