This study examines the 1950–2017 temporal changes in climate extremes in Israel, which is located in the East Mediterranean (EM), a region which suffers from a scarcity of long and reliable datasets. It is well known that most long‐term records are affected by artificial shifts most commonly caused by station relocation, instrumental modification and local environmental changes. Therefore, for the first time, a thorough homogenization (detection and correction) routine was developed and implemented in the long‐term records. Consequently, a new daily adjusted dataset has been generated, including 34 temperature stations and 60 precipitation stations. Based on this comprehensive dataset, 38 extreme indices recommended by the Expert Team on Climate Change Detection and the Expert Team on Sector‐specific Climate Indices have been calculated. These indices will help various sectors to plan properly mitigation actions and adaptation for climate change, in addition to facilitating future studies for the EM. The results showed highly significant changes in temperature extremes associated with warming, especially for those indices derived from the daily minimum temperature (TN, 1950–2017), whereas the maximum temperature (TX) exhibited a similar increasing magnitude of the TN (~0.55°C/decade) in the last 30 years. The warming trends, which are non‐monotonic, seem to have been particularly strong since the early 1990s. The coastal area is characterized by higher heat stress during the nighttime, while mountains exhibit a strong tendency towards increasing temperatures during the noon hours. A reduction in the total precipitation amount and in the number of wet days with a tendency towards more intense wet days was found. Although all the regional trends of the precipitation indices were not statistically significant (p ≤ .05), they showed a fine spatial coherence.
An evaluation of 23 models, participating in the Coupled Model Inter‐comparison Project phase 5 (CMIP5), in representing extreme precipitation indices (EPI), over the Eastern Mediterranean (EM) and the Fertile Crescent (FC), was performed. The models ensemble was then used to predict the EPIs evolution in the 21st century under (Representative Concentration Pathway, RCP) RCP4.5 and RCP8.5 scenarios. Models' performance was determined with respect to gridded precipitation observations from the APHRODITE project. The ensemble mean was found to perform relatively well in capturing the EM steep precipitation gradient, the FC structure and the EPI trends in the observations period (1970–2000). Over the EM, CMIP5 models agree on a future decrease in the following three EPIs; total precipitation (TP), consecutive wet days, and number of wet days by the values of 20–35%, 10–20%, and 20–35%, respectively. In the FC, extremely wet days (P95) are expected to increase by approximately 25%, except for the south eastern coasts of the Mediterranean Sea, which show significant decreases in P95, particularly for RCP8.5 and at the end of the 21st century. Hence, while TP is expected to decrease, extreme precipitation is expected to increase, at least for the north‐eastern part of the FC. This will significantly influence agriculture and floods' potential in a region already suffering from political unrest. The changes in EPIs are related to changes in the synoptic patterns over the EM, especially the predicted changes in cyclones frequency and intensity in the 21st century, due to changes in storm tracks governed by the phase of the North Atlantic Oscillation and the expected expansion of the Hadley Cell towards the poles in a warmer climate.
Climate trends analyses are studied through the analysis of long‐term records which usually are compromised by artificial non‐climatic factors (e.g., station relocation, instrumental replacements, etc). The impact of these factors on the analysis must be assessed and corrected in a procedure called “Homogenization,” before computing any trends. An unbiased analysis is essential for the East Mediterranean climate change, which suffers from scarcity of long and reliable datasets. Here, for the first time, we address these problems by jointly applying some of the state‐of‐the‐art homogenization methods, to long‐term Israeli temperature records (TX and TN) at five different meteorological stations throughout the period of 1950–2011. All of the studied time series were found to be inhomogeneous, where instrumentational issues were responsible for almost 50% of the breaks. The most frequent adjustments range between [−0.6, +0.6] oC while some larger adjustments do not fall within the range of the [−1, +1] °C interval. The adjustment of these breaks is crucial because they introduce large errors that may lead to wrong conclusions about the estimated trends. The difference in the seasonal and annual trends between raw and homogenized series was analysed applying the Mann–Kendall test. The general annual trend differences before and after homogenization, fell within the range of [−0.12, 0.16] oC/decade. Based on the homogenized dataset, a highly significant positive trend was found for the annual trueTN¯ with 0.15 °C/decade (p = .002) whereas the trueTX¯ trend was 0.10 °C/decade (p = .051). In general, the maximum temperature trends are lower and less statistically significant than those for minimum temperature. The most pronounced seasonal trends were recorded for the summer, which was characterized by significant positive trends for trueTX¯ (0.15 °C/decade) and trueTN¯ (0.23 °C/decade), while the winter had mainly no significant positive trends.
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