Trends and multi-annual variability of water temperatures in the river Danube, Serbia

This is the peer reviewed version of the following article: BASARIN, B. ... et al, 2016. Trends and multi-annual variability of water temperatures in the river Danube, Serbia. Hydrological Processes, 30 (18), pp. 3315-3329, which has been published in final form at http://dx.doi.org/10.1002/hyp.10863. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.The relationship between air (Ta) and water temperature (Tw) is very important because it shows how the temperature of a water body might respond to future changes in surface Ta. Mean monthly Tw records of three gauging stations (Bezdan, Bogojevo i Veliko Gradište) were analysed alongside mean monthly discharge (Q) for the same stations. Additionally, Ta series from two meteorological stations (Sombor and Veliko Gradište) were correlated with Tw variations over the period 1950–2012. Locally weighted scatter point smoothing (LOWESS) was used to investigate long-term trends in the raw data, alongside the Mann–Kendall (MK) trend test. Trend significance was established using Yue–Pilon's pre-whitening approaches to determine trends in climate data. Also, the rescaled adjusted partial sums (RAPS) method was used to detect dates of possible changes in the time series. Statistically significant warming trends were observed for annual and seasonal minimum and maximum Tw at all investigated sites. The strongest warming was observed at Bogojevo gauging station for seasonal maximum Tw, with +0.05 °C per year on average. RAPS established that the trend began in the 1980s. This behaviour is linked to climate patterns in the North and East Atlantic which determine the amount of heat advected onto mainland Europe. Statistically significant correlations were found for all Tw on an annual basis. Overall, the strongest correlations (p < 0.01) between Tw residuals and the North Atlantic Oscillation (NAO) were recorded for the winter period. These findings suggest possible predictability of Tw over seasonal time-scales

Sensitivity of evapotranspiration to climatic change in different climates

This paper presents a study of the sensibility of evapotranspiration (ET) to climatic change in four types of climates (i.e., humid, cold semi-arid, warm semi-arid and arid). The use of a reference crop ET (ETo) permits the standardization of ET estimates across varying conditions. So, ETo was estimated with the FAO-56 Penman–Monteith equation using data from eight Iranian sites over a 41-year period (1965–2005). The sensitivity analyses were carried out for air temperature, wind speed and sunshine hours within a possible range of ± 20% (i.e., − 5%, − 10%, − 20%, + 5%, + 10%, + 20%) from the normal long-term climatic variables. The sensitivity of ETo to the same climatic variables revealed significant differences among climates. From the comparison of the sensitivity of ETo to climatic change in different climates, it can be inferred that the sensitivity of ETo to wind speed and air temperature decreased from arid to humid climate, whereas its sensitivity to sunshine hours increased from arid to humid environment. Furthermore, the greatest change in ETo (about ± 9%) was found in arid climate in response to ± 20 change in wind speed.publisher: Elsevier articletitle: Sensitivity of evapotranspiration to climatic change in different climates journaltitle: Global and Planetary Change articlelink: http://dx.doi.org/10.1016/j.gloplacha.2014.01.006 content_type: article copyright: Copyright © 2014 Elsevier B.V. All rights reserved.status: publishe

Short-term forecasting of soil temperature using artificial neural network

Soil temperature is one of the most important meteorological parameters which plays a critical role in land surface hydrological processes. In the current study, artificial neural network (ANN) models were developed and tested for 1-day ahead soil temperature forecasting at 5-, 10-, 20-, 30-, 50- and 100-cm depths. Antecedent soil temperatures plus concurrent and antecedent air temperatures were used as inputs of the ANN models. Soil and air temperatures data were collected from two Iranian weather stations located in humid and arid regions for the period 2004-2005. The models’ accuracies were evaluated using the Nash-Sutcliffe coefficient of efficiency, the correlation coefficient, the root mean square error and the mean bias error between the observed and forecasted soil temperature values. The Nash-Sutcliffe coefficient of efficiency values higher than 0.94 and correlation coefficient higher than 0.96 for all the ANN models show that the models can be successfully applied to provide accurate and reliable short-term soil temperature forecasts.status: publishe

A survey of temperature and precipitation based aridity indices in Iran

In arid and semi-arid lands with warm climates, aridity and associated water scarcity is more severe because of greater populations and associated water use. The goal of this study was to explore the spatial and temporal variations of the de Martonne and Pinna aridity indices over Iran based on temperature and precipitation data from 41 stations for 40 years (1966e2005). The spatially interpolated maps of the aridity indices were prepared using the Ordinary Kriging technique in a GIS environment. The arid and semi-arid regions cover about 88% of Iran according to the de Martonne index, while about 96% of the country’s areas are classified as dry and semi-dry based on the Pinna index. A strong relationship was found between the values of the de Martonne and Pinna indices, confirming their similar spatial distribution. Around 63% of the two indices series had a decreasing tendency. The significant decreasing trends of the aridity indices were observed mainly in the western and northwestern regions of the country. The relative changes of the aridity indices at the stations with significant decreasing trends were in the range of 18% - 54%.publisher: Elsevier articletitle: A survey of temperature and precipitation based aridity indices in Iran journaltitle: Quaternary International articlelink: http://dx.doi.org/10.1016/j.quaint.2014.03.061 content_type: article copyright: Copyright © 2014 Elsevier Ltd and INQUA. All rights reserved.status: publishe

Possible influences of North Atlantic Oscillation on winter reference evapotranspiration in Iran

The North Atlantic Oscillation (NAO) is known to be responsible for most of inter-annual atmospheric variability over the Northern Hemisphere, particularly in Europe and the Mediterranean basin. Owing to the importance of reference evapotranspiration (ETo) in irrigation planning, water resource monitoring and management, we assessed the impact of the NAO on the ETo variability during the winter months from December to March in Iran. The Penman–Monteith FAO 56 method was applied to estimate ETo based on meteorological data from 41 synoptic stations during a period of 40 years (1966–2005). The correlation between the monthly NAO index and the ETo time series was computed using the Spearman's rho test for time lags from 0 to 6 months. The simultaneous and lag correlation analyses demonstrated that the winter ETo series over Iran had negative correlationswith the NAO index at almost all the stations. The highest negative correlation of 0.53 was observed between the January ETo series and the August NAO at Tabriz station located in the northwest of Iran, whereas the highest positive correlation of 0.55 was found between the January ETo series and the simultaneous NAO at Bandar-Lengeh stationwhich is situated on the northern coast of the Persian Gulf. Averaged over the 41 stations, the winter ETo values during the negative phase of the NAO were about 3% higher than those during the positive phase.publisher: Elsevier articletitle: Possible influences of North Atlantic Oscillation on winter reference evapotranspiration in Iran journaltitle: Global and Planetary Change articlelink: http://dx.doi.org/10.1016/j.gloplacha.2014.03.006 content_type: article copyright: Copyright © 2014 Elsevier B.V. All rights reserved.status: publishe