Fluctuations of surface air temperature in the Eastern Mediterranean |
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Authors: | H M Hasanean |
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Institution: | (1) Astronomy and Meteorology Department, Faculty of Science, Cairo University, Egypt, EG |
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Abstract: | Summary Changes in surface air temperature during the last century are widely discussed among researchers in the field of climatic
change. Using various techniques, we investigate trends and periodicity of surface air temperature series from eight meteorological
stations in the Eastern Mediterranean. For the analysis, we use the Mann-Kendall rank test, low-pass filtering, autocorrelation
spectral analysis and maximum entropy spectral analysis. The latter two tests are compared. The study is based on series over
one hundred years in length for four stations, and over fifty years in length for the other four. Increasing and decreasing
surface temperature trends were found. These trends, however, are only significant for Malta, Jerusalem, and Tripoli at the
99% confidence level (positive trend) and for Amman at the 95% confidence level (negative trend). We also found inter-decadal
variations in surface air temperature, including a fairly regular quasi 20-year oscillation, although its amplitude varied
between different cycles. A period of warming began around 1910 at all stations. During the 1970s, the annual mean temperature
series exhibit warming, but this warming was not uniform, continuous or of the same order at all the stations.
The results of the Autocorrelation Spectral Analysis and the Maximum Entropy Spectral Analysis are similar, pointing to the
reliability of the results. The quasi-biennial oscillation (QBO) exists at all stations during both increasing and decreasing
trends. Similarly, a broad maximum from 3–8 years (related to El Ni?o) is found at Malta, Athens, Jerusalem, Beirut, and Latakia.
An inverse relationship between El Ni?o and the North Atlantic Oscillation with surface air temperature over the Eastern Mediterranean
is found at a highly significant confidence level.
Received November 15, 1999 Revised August 29, 2000 |
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