A Recent Study of Seasonal and Interannual Climate Variability over the Eastern Mediterranean Region

The present work aims to investigate seasonal and interannual climatic variability over the eastern Mediterranean (EM) region through the period (19492016). The monthly data of meteorological elements of temperature, pressure and precipitation for the EM region during the period (1949-2016) has used and analyzed. Moreover, the monthly NCEP/NCAR reanalysis data composites for these meteorological elements over the EM region have used. The seasonal and interannual variability of meteorological elements (surface air temperature, air temperature at 1000 hpa level, 500 hpa level, 500 hpa geopotential height, mean sea level pressure and precipitation) over the EM region during that period is studied. The anomaly, time series and correlation coefficient techniques, methods used for the data analysis. The results revealed that the climate variability of the EM region varied dramatically from season to season and from year to year through the period of study (1949-2016). There is a seasonal positive trend of temperature at 1000 hpa and 500 hpa levels and Geopotential height of 500 hpa level over the EM region. Meanwhile, it found a seasonal negative trend of mean sea level pressure and precipitation rate. For the interannual climatic variable over the EM region, it noticed that there was a positive trend of annual air temperature at the levels of 1000 hpa and 500 hpa. Meanwhile, there exists an annual negative trend anomaly of mean sea level pressure, 500 hpa geopotential height and precipitation rate over the EM region through the study period. It has become clear that the climate regime over the EM region is a complex regime.


Introduction
The eastern Mediterranean (EM) is a region with a strongly seasonal climate due to the variability dominant of high and low pressure systems.This seasonal climatic variability is inclusive of both temperatures as well as precipitation.
Moreover, much of the climate in the region is affected by mountainous terrain [1].In addition, EM region has a specific position to create a climate with strongly seasonal precipitation over it.The EM climate is a unique climate due to the position of EM region.It lies between the subtropical region and extratropical region to the north.Its position includes the Mediterranean Sea [2].In fact, the climate of the EM region is mostly temperate with warm to hot, dry summers, and mild, with relatively wet winters [3] [4] [5].In the southern EM region, the northeastern part of Africa, an arid, hot desert climate prevails, where precipitation has small amounts [6].However, the temperature and precipitation gradients across the region of EM are remarkable [7].It found that precipitation patterns in the EM region do not only depend on the synoptic weather conditions, but also on the pronounced topography [8] and [9].It is noticed that precipitation could increase in mountainous regions in the north east of EM region, and possibly in the Northern part of Africa; southern region of the EM owes to the northward expansion of the tropical rain belt [10] [11].The EM region is likely to be greatly affected by climate change, associated with increases in the frequency and intensity of droughts and hot weather conditions [12].In fact, the EM region suffered from an abnormally warm and dry winter season in 2006.It found that, there was a positive correlation coefficient between the geopotential height anomaly at 500 hpa over Europe and the increase of surface air temperature and mean sea level pressure mainly in the eastern Mediterranean [13] [14].He found that there existed of a teleconnection between the global mean surface air temperature and precipitation over Europe including the eastern Mediterranean region.It is obvious that the climate of the EM region lies in the transition zone between the Mediterranean climate and the semi-arid/arid climate.A study of a 39-year period was to determine whether climate changes had taken place.It found that changes of atmospheric conditions during summer and the transitional seasons (mainly autumn) supported a warmer climate over the EM.This change is already statistically evident in surface air temperatures which had exhibited positive trends of 0.2˚C/decade -1˚C/decade.The EM region is under climate change leading to warmer and drier conditions through the period of study [15].Recently, it found that there was a relationship between geopotential height variability over Europe and existing extreme abnormal weather over the Eastern Mediterranean and Middle East during December 2013 [16].For abrupt climatic variations in the EM, it is necessary to investigate the climatic variability over the EM for a long period.The aim of the present study is to investigate a recent study of the seasonal and interannual variability of the climatological parameters over the EM region through the period .

Data and Methodology
The monthly data of NCEP/NCAR reanalysis composites for the meteorological parameters are used.The meteorological elements used in the present work are (air temperature in the surface, 1000 hpa level, 500 hpa level, 500 hpa geopotential height, mean sea level pressure and precipitation rate).The domain of the present study is the eastern Mediterranean region of (23˚N -50˚N) latitudes and (20˚E -46˚E) longitudes.These data are gridded data with mish (12 × 12) grid points of the eastern Mediterranean region.Whereas, the NCEP/NCAR gridded for these meteorological data are with temporal interpolation of 2.5 degree latitude × 2.5 degree longitude global grid (144 × 73).The period of this scientific work is the period .However, the long-term means for monthly values of the meteorological parameters has taken for the period .This data supported from the site of NOAA/OAR/ESRL PSD, Boulder, Colorado, USA and according to [17].The method of research through this work is unique method.Where there is a combination of several techniques has used.The data sets analyzed using time series, anomaly methodology and linear correlation coefficient techniques.The correlation analysis follows the Pearson correlation method according to [18].

Study of the Teleconnection between the Meteorological Elements over EM Region through the Period (1949-2016)
To study the seasonal and annual teleconnection between the meteorological elements over the EM region the linear correlation coefficient techniques are used.The results observed that: 1) For the winter season, there is a strong direct relationship between the 500 hpa level air temperature and 1000 hpa level air temperature with a correlation coefficient (0.818) over the EM region through the period of study.In addition to that, there is an outstanding direct relation of 500 hpa level geopotential height and 1000 hpa level air temperature with a correlation coefficient (0.760).
Meanwhile, there exists an inverse relationship between the precipitation rate over the EM region and mean surface pressure with a correlation coefficient (−0.784), as it is clear from Table 1.
2) For the spring season, there is a strong direct relationship between the 1000 hpa level air temperature and 500 hpa level geopotential height with a correlation coefficient (0.859) over the EM region.In addition, there is an outstanding direct relation of 1000 hpa level air temperature and 500 hpa level geopotential height with a correlation coefficient (0.749), as shown in Table 2.
3) For the summer season, there is a strong direct relationship between the 1000 hpa level air temperature and 500 hpa level geopotential height with a cor-    3.
4) For autumn season, there is an outstanding direct relationship between the 500 hpa level air temperature and 1000 hpa level air temperature with a correlation coefficient (0.709) over the EM region.In addition, there is an outstanding direct relation of 1000 hpa level air temperature and 500 hpa level geopotential height with a correlation coefficient (0.725), as clear from Table 4.
5) For annual correlations, there is a strong direct annual relationship between the 500 hpa level air temperature and 1000 hpa level air temperature with a correlation coefficient (0.800) over the EM region through the period of study.In addition to that, there is an outstanding direct relation of 1000 hpa level air temperature and 500 hpa level geopotential height with a correlation coefficient (0.759).Meanwhile, there exists an inverse relationship between the annual precipitation rate over the EM region and mean surface pressure with a correlation coefficient (−0.744), as it is clear from Table 5.

Discussion and Conclusion
The seasonal and interannual climatic variability over the EM region through the period (1949-2016) was investigated.To challenge this aim, the monthly data of NCEP/NCAR reanalysis data for the meteorological parameters (air temperature at the surface, 1000 hpa level, 500 hpa level, 500 hpa geopotential height, mean sea level pressure and precipitation rate) have been used.It is  Annual time series analysis shows that there is a positive trend of annual air temperature at the levels of 1000 hpa and 500 hpa.Meanwhile, there exists an annual negative trend anomaly of mean sea level pressure, 500 hpa geopotential height and precipitation rate over the EM region through the study period.A teleconnection study of climatic variability of the meteorological elements over the EM region through the period (1949-2016) is done.For the winter season, there is a strong direct relationship between the 500 hpa level air temperature and 1000 hpa level air temperature.In addition to that, there is an outstanding direct relation of 500 hpa level geopotential height and 1000 hpa level air temperature.
Meanwhile, there exists an inverse relationship between the precipitation rate over the EM region and mean surface pressure with correlation coefficient.For the spring season, there is a strong direct relationship between the 1000 hpa level air temperature and 500 hpa level geopotential height.Moreover, there is an outstanding direct relation of 1000 hpa level air temperature and 500 hpa level geopotential height.For the summer season, there is a strong direct relationship between the 1000 hpa level air temperature and 500 hpa level geopotential height.For autumn season, there is an outstanding direct relationship between the 500 hpa level air temperature and 1000 hpa level air temperature.In addition, there is an outstanding direct relation of 1000 hpa level air temperature and

Figure 3 .
Figure 3. Seasonal distribution of the mean sea level pressure anomaly over the Eastern Mediterranean region through the period (1949-2016).(a) For winter season, (b) For spring season, (c) For summer season, and (d) For autumn season.

Figure 4 .
Figure 4. Seasonal distribution of the geopotential height anomaly at 500-hpa level over the Eastern Mediterranean region through the period (1949-2016).(a) For winter season, (b) For spring season, (c) For summer season, and (d) For autumn season.

Figure 5 . 7 )Figure 6 .
Figure 5. Seasonal distribution of precipitation rate (mm/day) for the Eastern Mediterranean region through the period (1949-2016).(a) For winter season, (b) For spring season, (c) For summer season, and (d) For autumn season.

1 )Figure 7 . 2 )
Figure 7. Anomaly of the annual distribution of the climatic parameters over the Eastern Mediterranean region through the period (1949-2016).(a) Surface air temperature, (b) 500 hpa level air temperature, (c) Mean sea level pressure, (d) 500 hpa level geopotential height, (e) Precipitation rate.

Figure 8 .
Figure 8.Time series of the annual anomaly of the climatic parameters over the Eastern Mediterranean region through the period (1949-2016).(a) Surface air temperature, (b) 500 hpa level air temperature, (c) Mean sea level pressure, (d) 500 hpa level geopotential height, (e) Precipitation rate.
.4236/gep.2018.61009150 Journal of Geoscience and Environment Protection 500 hpa level geopotential height.For annual correlations, there is a strong direct annual relationship between the 500 hpa level air temperature and 1000 hpa level air temperature through the period of study.In addition to that, there is an outstanding annual direct relation of 1000 hpa level air temperature and 500 hpa level geopotential height.Meanwhile, there exists an inverse relationship between the annual precipitation rate over the EM region and mean surface pressure.So the climatic regime over the EM region is a complex regime.The results of this scientific work are the point strength for a future research of the climatic variability and development of climatic features over the EM region.Finally, one can conclude that there exists a seasonal and interannual dramatic climatic variability over the EM region through the period (1949-2016).

Table 1 .
Winter season correlation coefficient matrix between the meteorological elements over the Eastern Mediterranean region through the period (1948-2016).Whereas, B: The mean air temperature over the EM at 1000 hpa level; C: The mean air temperature over the EM at 500 hpa level; D: The mean sea level pressure on the EM; E: The mean geopotential height over the EM at 500 hpa level; F: The precipitation rate of the EM.

Table 2 .
Spring season correlation coefficient matrix between the meteorological elements over the Eastern Mediterranean region through the period (1948-2016).

Table 3 .
Summer season correlation coefficient matrix between the meteorological elements over the Eastern Mediterranean region through the period (1948-2016).

Table 4 .
Autumn season correlation coefficient matrix between the meteorological elements over the Eastern Mediterranean region through the period (1948-2016).

Table 5 .
Annual correlation coefficient matrix between the meteorological elements over the Eastern Mediterranean region through the period.precipitation rate varied from season to season and from region to region through the study period.This sharp variety of climatic parameters from season to season results from the change of the originality of air currents over the EM from season to season.There is a seasonal positive trend of temperature at 1000 hpa and 500 hpa and geopotential height of 500 hpa level over the EM region through the period of study.Meanwhile, it found a seasonal negative trend of mean sea level pressure and precipitation rate over EM region during the study period.From analysis of interannual distribution of climatic variations over EM region, it noticed that almost of meteorological elements had values less than its normal.However, the rainfall amount, distribution have an outstanding positive anomaly over the northern part of EM region.