Evaluation of near-surface groundwater aquifers through integrated geophysical and geodetic measurements

Abstract Extensive geophysical and geodetic measurements were carried out to evaluate the groundwater aquifer, trace the basement relief, as well as detect the igneous intrusions and structural elements (mainly faults) that affect the occurrence of groundwater in the study area. The fieldwork included resistivity sounding, a geomagnetic survey, and Global Positioning System measurements. The magnetic results showed the presence of a group of main faults in East-west trend at the western part of the area and major fault at the northern part of the area of NW-SW trend. The findings also showed the presence of two igneous rock intrusions located in the middle of the eastern part of the valley. Pronounced differences in the depths of basement rocks have been identified, ranging between 0 and 900 m from the surface. Both high horizontal movements and high shear strain rates have been found to be concentrated at the southeast of the study area and it was noted that high stress was accumulated along the main observed faults and at the main groundwater aquifers. The geoelectrical results confirmed the presence of two aquifers; a shallow aquifer (Quaternary aquifer) that narrows northwards and a Nubian sandstone aquifer, which considered the main aquifer. The Nubian sandstone aquifer carries groundwater in the region, which overlies the last geoelectric unit represented by the basement complex layer and geological structures affecting the potential availability of groundwater in the study area, as proved by the geomagnetic survey and stress accumulation

Impact of mineral dust on cloud formation in a Saharan outflow region

We present a numerical modelling study investigating the impact of mineral dust on cloud formation over the Eastern Mediterranean for two case studies: (i) 25 September 2008 and (ii) 28/29 January 2003. In both cases dust plumes crossed the Mediterranean and interacted with clouds forming along frontal systems. For our investigation we used the fully online coupled model WRF-chem. <br><br> The results show that increased aerosol concentrations due to the presence of mineral dust can enhance the formation of ice crystals. This leads to slight shifts of the spatial and temporal precipitation patterns compared to scenarios where dust was not considered to act as ice nuclei. However, the total amount of precipitation did not change significantly. The only exception occurred when dust entered into an area of orographic ascent, causing glaciation of the clouds, leading to a local enhancement of rainfall. The impact of dust particles acting as giant cloud condensation nuclei on precipitation formation was found to be small. Based on our simulations the contribution of dust to the CCN population is potentially significant only for warm phase clouds. Nevertheless, the dust-induced differences in the microphysical structure of the clouds can contribute to a significant radiative forcing, which is important from a climate perspective

Climate Change and Weather Extremes in the Eastern Mediterranean and Middle East

Observation‐based and modeling studies have identified the Eastern Mediterranean and Middle East (EMME) region as a prominent climate change hotspot. While several initiatives have addressed the impacts of climate change in parts of the EMME, here we present an updated assessment, covering a wide range of timescales, phenomena and future pathways. Our assessment is based on a revised analysis of recent observations and projections and an extensive overview of the recent scientific literature on the causes and effects of regional climate change. Greenhouse gas emissions in the EMME are growing rapidly, surpassing those of the European Union, hence contributing significantly to climate change. Over the past half‐century and especially during recent decades, the EMME has warmed significantly faster than other inhabited regions. At the same time, changes in the hydrological cycle have become evident. The observed recent temperature increase of about 0.45°C per decade is projected to continue, although strong global greenhouse gas emission reductions could moderate this trend. In addition to projected changes in mean climate conditions, we call attention to extreme weather events with potentially disruptive societal impacts. These include the strongly increasing severity and duration of heatwaves, droughts and dust storms, as well as torrential rain events that can trigger flash floods. Our review is complemented by a discussion of atmospheric pollution and land‐use change in the region, including urbanization, desertification and forest fires. Finally, we identify sectors that may be critically affected and formulate adaptation and research recommendations toward greater resilience of the EMME region to climate change. The Eastern Mediterranean and Middle East is warming almost two times faster than the global average and other inhabited parts of the world Climate projections indicate a future warming, strongest in summers. Precipitation will likely decrease, particularly in the Mediterranean Virtually all socio‐economic sectors will be critically affected by the projected changes The Eastern Mediterranean and Middle East is warming almost two times faster than the global average and other inhabited parts of the world Climate projections indicate a future warming, strongest in summers. Precipitation will likely decrease, particularly in the Mediterranean Virtually all socio‐economic sectors will be critically affected by the projected change

Climate Change and Weather Extremes in the Eastern Mediterranean and Middle East

Observation-based and modeling studies have identified the Eastern Mediterranean and Middle East (EMME) region as a prominent climate change hotspot. While several initiatives have addressed the impacts of climate change in parts of the EMME, here we present an updated assessment, covering a wide range of timescales, phenomena and future pathways. Our assessment is based on a revised analysis of recent observations and projections and an extensive overview of the recent scientific literature on the causes and effects of regional climate change. Greenhouse gas emissions in the EMME are growing rapidly, surpassing those of the European Union, hence contributing significantly to climate change. Over the past half-century and especially during recent decades, the EMME has warmed significantly faster than other inhabited regions. At the same time, changes in the hydrological cycle have become evident. The observed recent temperature increase of about 0.45 degrees C per decade is projected to continue, although strong global greenhouse gas emission reductions could moderate this trend. In addition to projected changes in mean climate conditions, we call attention to extreme weather events with potentially disruptive societal impacts. These include the strongly increasing severity and duration of heatwaves, droughts and dust storms, as well as torrential rain events that can trigger flash floods. Our review is complemented by a discussion of atmospheric pollution and land-use change in the region, including urbanization, desertification and forest fires. Finally, we identify sectors that may be critically affected and formulate adaptation and research recommendations toward greater resilience of the EMME region to climate change.Peer reviewe

Projected changes in heat wave characteristics in the eastern Mediterranean and the Middle East

According to observed twentieth century temperature trends and twenty-first century climate model projections, the region that encompasses the eastern Mediterranean and the Middle East (EMME) is identified as a climate change hot spot. We extend previous studies by a comprehensive climatology of heat waves in the EMME based on regional climate model simulations for the recent past and the end of the twenty-first century. A percentile-based definition of heat waves is used to account for local climatic conditions. Spatial patterns of several heat wave properties are assessed and associated with atmospheric circulation regimes over specific locations. To cover a range of possible future climates, we use three SRES emission scenarios. According to our results, all indices that characterize heat wave severity will strongly increase compared with the control period of 1961–1990. The northern part of the EMME could be exposed to increased heat wave amplitudes by 6–10 °C, and the southern part may experience 2–3 months more combined hot days and tropical nights. Heat wave peak temperatures will be higher due to the overall mean warming as well as stronger summer anticyclonic conditions. The projected changes will affect human health and the environment in multiple ways and call for impact studies to support the development of adaptation strategies. Keyword

Site response assessment at the city of Al Khobar, eastern Saudi Arabia, from microtremor and borehole data

Al Khobar City is affected by distant earthquakes from the Zagros fold-fault belt, which is part of the subduction zone between the Arabian and Eurasian plates. These earthquakes have generated substantial site effects on the sedimentary layers, which in turn significantly influence earthquake ground motions in the area. Mapping of site response using microtremor measurements compared with geological and borehole data from Al Khobar City is the main objective of this work. The resonance frequency and the corresponding horizontal-to-vertical (H/V) ratio values have been calculated using the Nakamura technique on data from seismograph instruments deployed at 113 sites in Al Khobar City for different time periods. The recording length was about 1 h with a sampling frequency of 100 Hz. Most of the measured sites present three peaks of resonance frequency; the first peak ranges from 0.33 to 1.03 Hz, the second peak ranges from 1.03 to 1.23 Hz, while the third one ranges from 1.23 to 1.73 Hz. Tests have been conducted to ensure that these peaks are of natural origin The northern zones of Al Khobar City have lower resonance frequency values, indicating great sediment thickness. In contrast, the southern parts of the city have higher resonance frequency values, suggesting shallow bedrock depths. Furthermore, 29 geotechnical boreholes have been drilled to different depths in Al Khobar City. Standard penetration test (SPT) data has been corrected and used to calculate the resonance frequency at their locations. The borehole results showed that the resonance frequency values range from 0.27 to 1.95 Hz. These results are well correlated with those from the microtremor measurements. Accordingly, the first peak has been interpreted as being due to the impedance contrast between the limestone bedrock and the overlying sediments, while the third peak originates from a boundary between the uppermost surface layer and the underlying sediments