The Arctic system is one of the most vulnerable region under climate change conditions and it has suffered important changes on last decades. Several recent studies have suggested the influence of moisture transport in the observed sea ice loss on this region. Changes in moisture transport could affect the arctic region by changing the cloud cover, by affecting river discharge or by direct effect of precipitation over the sea ice, for example. Atmospheric rives (ARs) represent one of the main mechanism of global moisture transport, being especially relevant on the connection between lower and higher latitudes. Despite this importance, the influence of ARs over the Arctic system has not been widely study.

The objective of this is work is to establish a first step on the study of the influence of the occurrence of ARs over the polar region. For this purpose, the lagrangian model FLEXPART was used to analyze moisture sources for those regions of maximum occurrence of ARs for the period 1994-2014 in order to analyze the origin of moisture transported by these meteorological structures. The location of ARs affecting the Arctic was realized using an automated algorithm and the region of maximum occurrence was defined taking into account the number of ARs detected for August and September (when sea ice is minimum over the Arctic ocean) over a band of 10° of latitude centered on 60°N. For these regions and considering those days of ARs occurrence, the anomalous moisture sources was defined in relation with mean situation for the complete period.

From the results, main moisture sources for ARs events extends over the North Atlantic and North Pacific oceans, moreover local input of moisture over the region of maximum ARs occurrence seems to be especially relevant. It is interesting to highlight the moisture uptake from Eastern Asia for the month of August. In general it could be conclude that, for ARs events the moisture uptake around and over the maximum occurrence area highly increase becoming relevant sources of moisture feeding up the event.

The location of the origin of the moisture that feed up Arctic ARs is an important step forward on the study of the influence of these structures over the region. Further analysis regarding the contribution of moisture from ARs over the region should be realized in order to complete the relation ARs-sea ice; being this study suitable for a future work.

The optimal exploitation of water from a dam reservoir requires a comprehensive knowledge of future availability of water resources. In this case the amount of water that will be available in the future is important. Also, we need to examine the flows at the dam from a short-term perspective. This is necessary to avoid overflowing and to minimize damage. In order to facilitate forecasting of the water resources, many different techniques have been developed through the years. In this paper, using annual mean flow data (since 1958-2005) obtained from jelogir majin Hydrometric station at Karkheh River (upstream of Karkheh Dam), the Auto Regressive Integrated Moving average (ARIMA) model, for prediction of annual mean inflow to Karkheh Dam reservoir was accomplished. On the basic of comparison the results of the model with measured data, the performance of ARIMA (4, 1, 1) model by conditional least square (CLS) estimation parameter method is acceptable.The SAS and SPSS softwares were used to implement of the models.

In the last decades many studies have pointed out an increasing number of natural hazards associated with extremes in precipitation and drought conditions. Generally, dry and hot conditions across the Europe impact on the Mediterranean region. The Mediterranean is located at the border between the tropical climate zone and the mid latitude climate belt. Due to its large extension and diverse topography, it shows large climatic differences that make its climate scientifically interesting.  

The aim of this study is to analyze the moisture transport during the 2003 drought episode observed over the surroundings of the Mediterranean. The region was defined according to the 5th Intergovernmental Panel on Climate Change (IPCC) Assessment Report. The episode was identified using Standardized Precipitation Evapotranspiration Index (SPEI), calculated using monthly CRU (TS3.24.01) precipitation and potential evapotranspiration (PET). One of the crucial advantages of the SPEI over the other widely used drought indexes is its multi-scalar characteristics, which enable identification of different drought types. Therefore, the monthly SPEI-1, SPEI-3, SPEI-6, SPEI-12 and SPEI-24 indexes were used to identify the episodes on different time scales. This episode was the most severe during the period 1980-2015 according to the SPEI-1 analysis. Analyses of precipitation, potential evapotranspiration, omega at 500hPa, and vertically integrated moisture flux have been conducted to characterize the anomalous patterns over the region during the event. A Lagrangian approach was then applied in order to investigate possible changes in the moisture transport from and toward the Mediterranean region during the episode. This approach is based on the FLEXPART model integrated with the ERA-Interim data set.

Here we propose a new methodology for calculating the Standardized Evapotranspiration Deficit Index (SEDI) at the global scale using the difference between the actual evapotranspiration (ET) and the atmospheric evaporative demand (AED). ET was estimated by the Global Land Evaporation Amsterdam Model (GLEAM) v3a. The SEDI has been proposed recently to quantify drought severity based on the difference between actual evapotranspiration (ET) and the atmospheric evaporative demand (AED). Our findings demonstrate that, regardless of the AED dataset used for calculations, a log-logistic distribution is needed in order to fit the ED time series. As such, in many regions worldwide, the SEDI is insensitive to the AED method used for calculation. The SEDI showed significant correlations with the Standardized Precipitation Evapotranspiration Index (SPEI) across a wide range of regions, particularly for short SPEI time-scales. Overall, while this work provides a robust approach for calculating spatially and temporally comparable SEDI estimates, regardless of the climate region and land surface conditions, further studies remain needed to assess the performance and the applicability of the SEDI to quantify drought severity across varying crop and natural vegetation areas.

Western Iberia is frequently struck by intense mid-latitude cyclones coming from the North Atlantic basin and often impinging extreme weather over large swaths of the Iberian Peninsula (IP). The spatial distribution and characterization of past floods and landslides with important social consequences in Portugal for the period 1865-2015 was performed within the context of the DISASTER project (Zezere et al., 2014). From this database, a major hydro-geomorphologic event was selected, the February 1979, in order to study its atmospheric forcings and to analyze its societal impacts.

The February 1979 event is a top ranked event in the DISASTER database regarding the total number of affected (18578), displaced (14322) and evacuated (4244) people in Portugal and in the Tagus basin (7677, 4816 and 2834, respectively).

Most of the days considered in this event produced daily precipitation values over or within the 90^th-95^th percentile of the corresponding long term daily precipitation series (available at high resolution between 1950 and 2008). Most of the event precipitation occurred in days characterized by wet Circulation Weather Types, i.e. cyclonic (C), west (W) or southwest (SW) types, which agrees with the assessment of wet days obtained by Trigo and DaCamara (2000) and Ramos et al. (2014) for the IP domain.

Also, throughout this period, the North Atlantic Ocean is crossed several times by narrow and prolonged bands of high moisture concentration, with cores above 9 g/kg, that originate near the Caribbean islands and move towards extratropical latitudes by the influence of southwestern low-level jets of medium or high intensity. These are mostly persistent Atmospheric Rivers (ARs) reaching the western IP coast and affecting most of the month of February until the 16^th.

Overall, regarding the large-scale circulation, a deep low-pressure system located over the North Atlantic and reaching western IP, allowed for the frequent passage of frontal systems over the territory which was responsible for this precipitation event. In addition, local convective instabilities and strong moisture transport from the Tropical Atlantic produced an extremely intense 15-day precipitation event over western IP, that establishes as the meteorological trigger of the February 1979 Disaster event.

Acknowledgements: This work was financed by national funds through FCT - Portuguese Foundation for Science and Technology, I.P., under the framework of the project FORLAND Hydro-geomorphologic risk in Portugal: driving forces and application for land use planning (PTDC/ATPGEO/1660/2014). A. M. Ramos was also supported by a FCT postdoctoral grant (FCT/DFRH/ SFRH/BPD/84328/2012).