نعمت احمدی

Weather conditions have always affected the man’s life; so he is used to adopt his life with Weather conditions, one of which is the condition of Cold waves. Cold days and cold waves are examples of extreme-temperature that include unusual notable amount of minimum temperature. Reduction of minimum temperature depends on heating degree and wind speed. Cold waves can be considered as a natural disaster or a provider of ideal weather in summer. Thus, present paper tries to analyze cold wave that mitigates weather in the warm period of year, besides cold waves of cold period in ten years.

To pattern the cold waves of Iran in a ten-year period of time (2004-2013) three-hour minimum data of European Centre for Medium-Range Weather Forecasts (ECMWF) with distance of 1 * 1 degree latitude and Longitude has been used. In present study, a cold day due to relative notion of Coldness in different time and places, is defined as a day in which standard score of minimum temperature is below -1. For this reason, minimum data of all days was separated by MATLAB software; then by using the standard score those day with Anomalies below -1 known as cold days were diagnosed. In the next step all the days (569 days) that had this characteristic by MATLAB and based on sea level pressure patterns correlation were divided into five different classes includes Spring, Summer, Autumn, late Autumn, early winter and winter And interpreted them synoptic patterns. In the next step wind speed and also minimum and maximum temperature difference thresholds was used to distinction between the Radiative cool waves from the advective cool waves, so that minimum and maximum temperature difference below 8 ° C and wind speed more than Breeze threshold was used as advective cool waves criteria.

By extracting 569 days of negative anomalies between 2004 and 2013 it became clear that 2013 with 124 days and 2006 with 20 days (with negative anomalies below -1) have the most and the least negative anomalies respectively, in the mentioned research period. August, which have 83 days of negative anomalies, also contained the highest anomaly in selected 10 years. Analyzing level pressure patterns correlation between five presented patterns showed that interclass correlation of late autumn and early winter was 0.94 and more than all other groups. The highest correlation between groups was also between fourth (late autumn and early winter pattern) and fifth classes (winter pattern). In the days which cold waves entered the country, wind speed never reached to high-speed level and never exceed of the average wind speed. This speed never reached the average wind speed in summer but the frequency of light wind was higher than other seasons. While the frequency of breeze flow in the second and cold half of year is more than the first or warm half of the year; low speed of waves produce more intensive and continues cold wave when it’s accompanied by cold weather. Cold waves of Iran are usually advection and enter country from north and through west flows. In spring pattern (first pattern) west systems cause reduction of temperature and mitigation of Iran weather especially in western and northern regions of country. Minimum and maximum temperature difference in northwest of Iran was lower than 5 ° C in this pattern, while it was observed in water areas only in the other patterns. The highest difference between daily minimum and maximum temperature has been recorded in the second class (summer pattern).

Flows from the high altitude subtropical East lead to cold advection air of higher altitudes toward east and north east of Iran. But withdrawal of subtropical high pressure was the main factor of cool waves in this pattern. Siberian high pressure has caused low difference of daily minimum and maximum temperature in northeast of Iran and Alborz mountains in the autumn pattern (third pattern). Wind speed in North of Iran was more than the other region. And also stability conditions was the most in this pattern. There was low differences between minimum and maximum in south of Zagros mountains that was due to advection of cold air by African high pressure. In late autumn and early winter pattern (forth pattern) a complete advective Pattern is ruling over country. The fifth class (winter pattern) is advective- Radiative

The notion of climate change indicates a significant change in climate and environmental conditions over a long period of time (from a few decades to centuries). These changes can occur in mean radiation, temperature, precipitation, atmospheric patterns, wind, and other climate parameters. Increased global average temperature and occurrence of climate extremes such as floods, storms, hails, tropical storms, heat waves, sea level rise and melting of polar ice caps are the most important effect of climate change. The present study sought to analyze the effect of climate change and global warming on temperature trends in Iran atmospheric levels. One advantage of the present study is that it investigates temperature changes at sea surface and other atmospheric levels, whereas many recent researches just emphasize on sea level. The present study used data received from the European Center for Medium-range Weather Forecast (ECMWF) for a period of 60 years, from 1951 to 2010, with a network resolution of 1 × 1° Latitude and Longitude for sea level data (Slp) and 850, 700 and 500 hPa levels. After converting extracted data using statistical extension of Net-cdf for excel 2007, the temperature trend for sea levels of 850, 700 and 500 hPa were calculated. The correlation between temperature and its anomalies was measured using elevation levels of 850, 700 and 500 hPa and the temperature anomaly maps and synoptic pattern were developed on a regional scale, and finally their relationship with temperature trends were analyzed and interpreted. Iran had an average temperature of 18.06 °C during the 60 year period (1951 to 2010). 1999, with an average temperature of 20 C°, was the hottest year during this time. From 1993 onwards (except for 1997 and 2007), the average temperature was more than the 60-year average (18.06 C°). By comparing 30-year periods (from 1951 to 1980 and from 1981 to 2010) with each other, we observed that sea level temperature increase in the second 30-year period was more than the first period temperature increase at other atmospheric levels. This increase is most possibly due to the effects of global warming. Temperature increase in the first and second periods were 0.24 and 0.63 °C, respectively. Because of closeness to sea level and under the influence of surface conditions, 850 hPa level shows maximum temperature increase compared to other atmospheric levels (after sea level). Also due to the impact of sea level during the first and second periods, this factor is highly correlated with the sea level atmospheric condition. Despite the fact that correlation values of 850, 700 and 500 hPa levels were significant in both first and second periods at 1% level, they have increased in second period at all atmospheric levels.  In other words, there is a clear increasing trend in the second period and few decreasing changes are observed.
Regarding the patterns observed at sea level in the second period, two low-pressure closed cell trough which had been observed in the first period in India and Pakistan, merged in the second period. At 850 hPa, the subtropical high pressure located over Atlantic in the first period moved to East Africa in the second period and created a closed high pressure subtropical cell over Libya with an elevation of 1500 hPa. Compared to the first period, this high pressure cell has a higher altitude. At 700 hPa level, STHP ridge extended significantly in the second period, and in this period, central regions of Iran exhibit wide ranges of air sinking with a deep layer of warm air. Over the 60 year-period, temperature of atmospheric levels in Iran have exhibited an increasing trend, which from 1993 onwards had a much steeper slope of increase. Compared to the first period (with almost normal periods of increasing and decreasing, and a slightly fluctuating rhythm), the second thirty-year period is expected to exhibit a constant and continuous increase. Additionally, warmer SLP at sea level and 850 hPa level, the northward expansion of the Hadley cell, and finally more intense subsidence of STHP toward lower atmospheric levels (above sea level and 850 hPa) exacerbate the effects of global warming on Iran atmosphere.

"Race" has been a question in the minds of some Iranians specially the inhabitants of Azerbaijan; concerning the racial category, what is the racial category of Azerbaijan people? Turk or Azery? The importance of this matter comes to attention when discussion of Panturkism and Panturanism (noniranianism) emerges and highly discussed in Iran. This subject can be understood easily by the researchers and authors of contemporary history and political science researchers. The result of this reseach that has been done with analysis and correspoading method and using first hand sourcos, reveal this truth that the people of Azerbaijan are called Turk since they have a Turkic language/dialect on one hand; on the other hand, nowadays some authors, mostly foreigners and pro-Panturkism political and Panturanism groups try to fabricate a fake history and also try to inspire Turkic race and identity to the people of Azerbaijan. Meanwhile the works of many researchers from credible world scientific centers and even in Iran’s neighboring countries believe to the fundamental racial differences between Azerbaijan inhabitants and Turkic tribes and also the fundamental similarities between Azerbaijan inhabitants and the inhabitants of the Iranian plateau.

World war II, which was started in 1939 as a result of some political disputes, had various political, economic and social consequences in Iran. Historians have long been concerned with the Allied military presence in Iran during1941-1945. The Governments of Foroughi, Ahmad Qavam, Ali Soheili, Bayat, Sadrolashraf and Ebrahim Hakimi assumed power in this juncture. Foroughi, the first prime minister after Reza Shah, played a critical role in hushing the status. The period of Ghavam’s premiership was spent with economic crisis due to the presence of the confederates in Iran and results due to the WW2. The age of Soheili accompanied with the conference of the confederate heads in Iran which is known as Tehran conference. Generally the principal trait of years 1941to 1945 and the most important concern of Iranian governments during that period were involvement with results due to the presence of the confederates in Iran and the issues related to post war in national and international areas. In the present Article, the presupposition is that government’s approach to Iran's occupation in many cases was passive and as a result of accepting the demands of the Allies. Therefore, the passive position of the Government in foreign policy and political instability in domestic affairs caused social crises and economic pressure on the people.