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Temperature Variability and Trends in North Libya from 1961 to 1990

Temperature Variability and Trends in North Libya from 1961 to 1990. Younis Al-Fenadi Libyan National Meteorological Centre (LNMC) Fenadi@yahoo.com. Climate Definitions. 1 – AMS (Huschke, 1959)

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Temperature Variability and Trends in North Libya from 1961 to 1990

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  1. Temperature Variability and Trends in North Libya from 1961 to 1990 Younis Al-Fenadi Libyan National Meteorological Centre (LNMC) Fenadi@yahoo.com

  2. ClimateDefinitions 1 – AMS (Huschke, 1959) “ the slowly varying aspects of the atmosphere-hydrosphere-land surface system. It is typically characterized in terms of suitable averages of the climate system of periods of a month or more, taking into consideration the variability in these time averaged quantities” 2 – Met. Office Glossary (1991) : “the climate of a locality is the synthesis of the day-to-day values of the meteorological elements that affect the locality”.

  3. Climate variability The issue of climate variability and change goes back to the 19th century with the Swedish professor Svante Arrhenius. (Moore, 1998) It is a term used to describe deviation of climate statistics and calculated averages over a given specific month, season or year from the long term climate statistic. And measured by variations in the climate statistics, and ranges over many time and space scales (Geer, 1996) An important issue in the study of climate variability is to find out whether the variations of climate variables are natural or anthropogenic.

  4. MediterraneanClimate Closed sea - 21 countries – Complex mountain features and land topography. The Med. basin makes a transitional zone : westerly flow affecting northern and central Europe and the arid zone of the subtropical high over the deserts in North Africa. The Mediterranean climate is quite complex as it involves influences from various phenomena: the Siberian high pressure system, the El Niño Southern Oscillation (ENSO) and, the North Atlantic Oscillation (NAO).

  5. Mediterranean climate studies Many studies with different results, such as: 1 - Metaxas et al. (1991): studied SST and AT for 120 years. In Med. SST and AT have the same main characteristics as those observed over the north hemisphere and the whole globe. 2 - Larrasoanaetal. (2003): studied variations of Saharan dust supply into the eastern Mediterranean Sea. The variation in dust supply was found to be related to changes in the climate variables source areas located north of the central Saharan watershed.

  6. 3 - Raicichet al. (2001) have studied precipitation and the teleconnections between sea level pressure and sea level elevation, and the Indian summer monsoon and Sahel rainfall. They have found significant correlations between Indian monsoon, Sahel rainfall and sea level pressure difference with differences between western and eastern basins of the Mediterranean. 4 - Moron and Ward (1998) have studied ENSO teleconnections with climate variability in the European and African sectors, including the Mediterranean basin. The study has shown that ENSO influence is noticeable in the Sahel region of Africa.

  7. Surface Temperature and Trends Combined annual land-surface and sea surface temperature anomalies in C from 1861 to 2000. (Source: IPCC, 2001).

  8. GeographyandclimateofLibya

  9. Why Temperature in Libya? http://www.wmo.int/pages/mediacentre/news_members/documents/Libya.pdf

  10. Data Description The data consist of: - Monthly mean surface temperature - 8 Libyan stations - The stations are distributed along North Libya - The data from January 1961 to December 1990 - Obtained from the climate directorate LNMC

  11. Selected Stations

  12. Data Distribution

  13. Data Statistics

  14. Data Seasonal Cycle

  15. Trend Analysis for individual stations Climate variability or change is detected by temperature upward growth or a downward decline trend. Chatfield (2001) has described the trend as “ long-term change in the underlying mean level per unit time”. According to this, the global warming or cooling could be referred to as a trend over a period of years. Trend analysis fits a general trend model to time series data, e.g. linear; quadratic; exponential growth curve and S-curve.

  16. The quadratic trend equation

  17. Quadratic trend calculations

  18. Results The quadratic model analysis for the 8 stations in North Libya has shown different weak and strong temperature trends. The trend differs from one station to another. The clearest trend was found in Sirte, Shahat, Zwara, Tripoli, Misurata and Nalut, but it was found weak in Benina and Derna. The annual temperature variability and fluctuation was wide in Benina, Tripoli, and Derna. However, An upward temperature trend was clearly identified starting from the mid-1970s in most of the stations.

  19. North Libya Temperature Index (NLTI) The NLTI time series is a monthly time series of air surface temperature from January 1961 to December 1990. It is obtained by spatially averaging the values of the 8 stations. We consider the averaged index to be more reliable than the eight individual stations separately since the averaging procedure helps to reduce error effects. The index also gives a summary measure of monthly surface temperature over North Libya.

  20. NLTI Trend analysis (Annual means)

  21. NLTI Trend analysis (Annual means)

  22. NLTI standardized annual temperature trend

  23. NLTI Trend analysis (Seasonal means) MAM

  24. NLTI Trend analysis (Seasonal means) DJF

  25. NLTI Trend analysis (Seasonal means) SON

  26. NLTI Trend analysis (Seasonal means) JJA

  27. NLTI large-scale Teleconnections 1 - North Atlantic Oscillation (NAO) 2 - El Nino Southern Oscillation (ENSO) 3 – NCAR/NCEP fields 4 – http://climexp.knmi.nl

  28. NLTI correlation with SLP (DJF and JJA)

  29. NLTI correlation with SLP (SON and MAM)

  30. NAO correlation with NCAR/NCEP sea level pressure SLP

  31. NLTI correlation with 2m temperature (DJF and MAM)

  32. NLTI correlation with 2m temperature (SON and JJA)

  33. NAO correlation with NCAR/NCEP 2m temperature index

  34. Conclusion • Instantaneous (lag is zero) teleconnections in SLP between NLTI and NAO were evident during the winter season (December-February). • Instantaneous (lag is zero) teleconnections in 2m air surface temperature between NLTI and ENSO were evident during wintertime (December-February). • Instantaneous (lag is zero) teleconnections show that NAO has a strong effect during winter season (December-February). • Evidence was found that ENSO influences NLTI at spring season (March – May).

  35. Finally, due to the absence of previous statistical and climatic studies on temperature trend and variability over Libya, it is not possible to compare and contrast the results obtained in this work with those of others

  36. Thanks

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