Spatial and temporal changes of daily temperature extremes are investigated over Egypt using a standard set of 23 indices. Our analysis uses a database consisting of complete, high quality and homogenous daily maximum and minimum air temperature records at 40 stations, spanning the period from 1983 to 2015. The trends were assessed using a least squares regression model, and its significance was determined by means of the modified Mann-Kendall test (p < .05). Results demonstrate that the frequency, intensity, and persistence of warm extremes increased significantly over the study period, with a clear spatial gradient from southeast to northwest. The strongest warming was more evident in coastal areas along the Red Sea and the Sinai Peninsula. In contrast, changes in cold extremes were mostly non-significant, with a divergence in the trends (i.e. positive and negative). Changes in variability indices such as the diurnal temperature range (DTR) were more consistent with those of warm extremes than with cold extremes. Our results also demonstrate that maximum air temperature witnessed stronger warming than minimum air temperature, leading to a dramatic increase in DTR, especially in the last decade. This study also points at the possible physical mechanisms responsible for the detectable changes in temperature extremes using sea level pressure and geopotential field data. Results indicate that anomalous warm events over Egypt are directly related to easterly winds that bring warm and dry air from the Arabian Peninsula and the Iranian Plateau, accompanied by strong ridges over the eastern Mediterranean and an intensification of the Asian monsoon lows. On the other hand, the occurrence of anomalous cold events can be linked to the east-west pressure gradient between the North Atlantic Highs and the Siberian and Persian Troughs, which enhances a northerly and northwesterly cold advection from Northern Europe to Egypt. This situation is also combined with a subsidence of cooler air from the mid to low troposphere. Overall, the observed changes in warm extremes could have profound ecological, hydrological and socioeconomic impacts, especially for crop production, water resources management and energy consumption. As such, improving the insight and understanding of such changes is of considerable importance to provide guidance to policymakers and stakeholders to develop more appropriate adaptation strategies.
KAUST Repository Item: Exported on 2020-10-01
Acknowledgements: The authors are grateful to the Egyptian Meteorological Authority for providing daily rainfall data used in this study. This work was supported by the research project PCIN-2015-220 and CGL2014-52135-C03-01 financed by the Spanish Commission of Science and Technology and the European Regional Development Fund (FEDER), IMDROFLOOD financed by the Water Works 2014 co-funded call of the European Commission and INDECIS, which is part of the European Research Area for Climate Services (ERA4CS), an ERA-NET initiated by JPI Climate, and funded by the Swedish Research Council for Environment, Agricultural Sciences and Spatial Planning (FORMAS), the German Aerospace Centre (DLR), the Austrian Federal Ministry of Science, Research and Economy (BMWFW), the Innovation Fund Denmark (IFD), the Spanish Ministerio de Economía (MINECO), the French National Research Agency (ANR) with co-funding by the European Union (Grant 690462). AK is supported by Juan de la Cierva Fellowship. MFM was funded by the King Abdullah University of Science and Technology (KAUST). This work was also supported by the Sultan Qaboos University, Muscat, the Sultanate of Oman, as a part of the HM Trust Fund (Strategic Project # SR/ART/GEOG/17/01). Finally, we would like to thanks you for your great time and effort.