اسم المؤلف:
جول ميخائيل طليا بيداويد
اسم المشرف:
طه رؤوف شير محمد
المستخلص:
This study aims at analyzing and explaining the effect of the frequency and the days of continuation of secondary and modern centers; and the extensions of the single, integrated and the extensions of adjacent pressure systems at lower surface and upper surface which is influencing the climate of Iraq.Analysis and explanation of hourly data of samples composed of three meteorological stations, i.e. Mosul (in the north), Baghdad (in the middle) and Basra (in the south) depending on the two observation measurements of (00, 12) have been done.The data has been converted into monthly rates for a duration of (11) years. Afterwards, the researcher extracted the rates of temperature, atmospheric pressure, and relative humidity throughout this study period.The study has demonstrated that the frequency percentage of the single systems was (53.90%), the integrated (40.81%) and the adjacent (5.27%). Lack of frequency of integrated and adjacent systems is due to the fact that, occurrence of integration and adjacency process requires conditions relating to the characteristics of the system itself : its depth and its power of influence. Furthermore, there is a duty for the surface effect which - if suitable - will contribute in decreasing their speeds and consequently lead to the integration and adjacency process. The study has also declared that Iraq is affecting because of the influences of surface and upper pressure extensions of the single, integrated and adjacent systems more than modern and secondary centers. This is due to the remoteness of Iraq from the territories of the evolution of the main centers of the pressure systems. Moreover, the study has also showed that, the Indian Seasonal depression is one of the most influential atmospheric depressions on Iraq's climate. The percentage of the frequency of itssecondarycenters was (46.39%) and its pressure extensions ratio was (47.01%). The annual rate of temperature, atmospheric pressure and relative humidity for the two observations of (0000, 1200) at the Basra station - which is considering as the first Iraqi station influenced by the arrival of the Indian Seasonal cyclone, and the last station influenced by its withdrawal - during the progress of the cyclone's secondary centers were (27.6, 43.7)Co, (1003.5, 1000.3) millibars, (35%, 14%); and of the cyclones extensions were (26.6, 40)Co (1005.2, 1004.0) millibars, (44%, 18%).In compare with their pressure extensions, the study has showed that the secondary centers of the thermal depressions have recorded an increase in the temperature during their control over Iraq.As for modern centers of single and integrated anticyclones, they recorded lower rates of temperatures in compare with their pressure extensions, and values higher than their extensions. Due to the inverse relationship between temperature and relative humidity, the modern centers recorded humidity rates lower than their pressure extensions.With regard to the anticyclones, the Siberian high - with its modern centers - was the most instrumental anticyclone on the climate of Iraq. Its percentage was (52.56%); while the frequency percentage of their atmospheric extensions was (40.7%). As far as the European anticyclone is concerned, the lowest rate of temperature was recorded during its control of its modern centers and pressure extensions over Iraq. The annual rates of temperature, atmospheric pressure and relative humidity during the control of its modern centers over Mosul meteorological station were (5.9, 13.5)C0, (1022.6, 1023) millibars, (81%, 50%), while during the progress of its extensions, the rates of the previous climatic elements arrived at (9.3, 18.8) C0, (1021.5, 1017.7) millibars, (79%, 47%).To identify the impact of length of duration of the pressure systems on temperature in Iraq, two pressure systems have been selected : the Siberian anticyclone and the Indian seasonal cyclone. Their continuance period has been divided into three categories : (3 - 6) days, (7 - 9) days, and (10) days and over. The ratio of Analysis of Variance (ANOVA) - or as it is known as (F - ratio) - has been utilized to analyze the results. The study has concluded that, when calculating the continuance duration of both systems extensions the first category was the most frequent one. This is due to the fact that, the location of Iraq at the northern semi tropical latitudes give rises to the succession of pressure systems to come through. The results of the equation (the calculated values) - when compared to the critical value (in X2 tables) - have showed that there were no significant differences between the samples of the first days and the samples of the last days for the examined time series; i.e. Ho cannot be rejected. However, the absolute differences have been raised among each sample's data alone, i.e. among the years belonging to each sample alone, due to : 1 - The variance of the strength of the secondary and modern centers that deliver their extensions to Iraq.2 - The variance of the strength and the depth of the system and the arrival of its extensions to the pressure level of (850) millibars.3 - The effects of upper aerial waves which enhance or weaken the effect of surface the systems.
