DATE2016-05-31 22:51:52
AUTHORSIliana Polychroni (1), Panagiotis T. Nastos (1), John Kapsomenakis (2), Maria Hatzaki (1)
  1. Laboratory Of Climatology And Atmospheric Environment, Department Of Geology And Geoenviroment, National And Kapodistrian University Of Athens, Athens (Greece)
  2. Research Centre For Atmospheric Physics And Climatology, Academy Of Athens, Athens (Greece)
ABSTRACTThe Mediterranean is an area with unique geophysical, historical and cultural history. The climate conditions in the Mediterranean affect significantly the socioeconomic development, specifically over coastal areas. Moreover, climate change may add to existing problems of desertification, water scarcity and food production having impacts in human health and ecosystems. Taking into consideration that the surface temperature is projected to rise over the 21st century and the mean precipitation is likely to decrease in mid-latitude dry regions, according to IPCC 2014, we confronted the challenge to study the joint modes of these two major meteorological variables over the Mediterranean region, because they reflect better the weather conditions than temperature or precipitation statistics taken separately. The objective of this study is to assess and analyze the trends and variability of joint modes of extreme climate indices over the Mediterranean region, during the period 1950-2015. The daily meteorological datasets used in this study concern the high resolution gridded daily mean temperature and precipitation datasets (0.25° x 0.25°), based on the E-OBS dataset from ECA&D. The four combined extreme climate indices, based on joint modes of air temperature and precipitation, concern Cold/Dry days (CD), Cold/Wet days (CW), Warm/Dry days (WD), Warm/Wet days (WW) and are defined by the exceedances of the joint modes of temperature and precipitation using the 25th and 75th percentile levels in order to capture a larger number of events. More specifically, the CD index is defined as the number of days with the daily mean air temperature (T) below the 25th percentile of the daily mean temperature (T25) and simultaneously the daily precipitation (P) below the 25th percentile of the daily precipitation (P25). Accordingly, the other indices are defined; namely, CW index (T<T25 and P>P75), WD index (T>T75 and P<P25) and WW index (T>T75 and P>P75). Furthermore, we considered it necessary to analyze the influence of atmospheric circulation on joint modes of air temperature and precipitation over Mediterranean region. The atmospheric circulation is examined in terms of specific climatic indices, such as the North Atlantic Oscillation index (NAOI), the Mediterranean Oscillation index (MOI), the Eastern Mediterranean Pattern (EMP) and the North Sea Caspian Pattern Index (NCPI).