Geosciences Dept. Seminar: Climate change and extreme indices analysis across Israel based on an innovative homogenized daily dataset
Yizhak Yosef, TAU (PhD defense)
In recent decades more and more research has focused on climate change in general, and extreme weather in particular, mainly due to the expected broad effects on society and various economic sectors (e.g., agriculture, health, water, and energy). Climate trends are studied through the analysis of long-term records which most of them are affected by a number of non-climatic factors (e.g. station relocation, instrumental modification, environmental changes, etc). These factors usually have a major impact on time series, in the form of abrupt and/or gradual changes ('break-point') which compromise their validity to represent climate variability and change. Therefore, the impact of these factors must be assessed and corrected in a procedure called 'Homogenization', before computing any trends. An unbiased analysis is essential for the East Mediterranean region, 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 and precipitation records.
A thorough homogenization routine was developed in order to detect and adjust artificial shifts. As a consequence, a new daily adjusted dataset that contains 34 temperature and 60 precipitation stations was generated. Based on this new daily homogenized dataset, extreme indices recommended by the Expert Team on Climate Change Detection and the Expert Team on Sector-specific Climate Indices were calculated. Results showed highly significant changes in temperature extremes associated with warming, especially for those indices derived from daily minimum temperature along a reduction in the total precipitation amount and a tendency toward more intense wet days. The homogenization process, followed by some of the changes observed in the extreme indices in Israel will be presented.
Seminar Organizer: Prof. Eyal Haifetz