Journal of Spatial Analysis

The temperature as an indicator of heat intensity is one of the basic elements of knowing weather. The frost is a condition when the air temperature is less than 0 c Due to the geographical possition of Iran, spring is a season that plants resume a new life after leaving a pause in a periode of the growth. At the beginning of such a periode emerge of sudden cold cause loss bloom (in the case of openinig) or delay in a beginning of plant growth periode (Azizi,2002). Recentley with occuring climate chaos, one of the important climatic disasters which treats human and particularly different  areas of the country are cold waves and sever frosts that in some years covers large area of the country.

    Surface data including minimum daily temperature of the days of 29 to 30 and 25 to 26 of march of 2003 and 2005 in 9 meteorological synoptic stations in the area of north west of Iran in  table (1) was collected  from meteorology organization then the days of cold waves in the above mentioned time periode, were analyzed. In ordet to analyse the synoptic patterns, using ncep/ncar data, maps of sea level pressure ,combined of  geopotential height and vorticity and temperature advection  using Grads were drawn and analysed in the levels of 1000 to 500 hpa.

    As it mentioned, during the time period, 29 to 30 and 25 to 26 of the march in 2003 and 2005, 2 clod system  were located on the area of north west. In oeder to explain and analyze of  synoptic patterns of  mentioned period time, the absolute minimum temperature below 0 degrees celsius of stations in western Azarbayejan province were selected and maps of sea level pressure, combined of  geopotential height and vorticity and temperature advection  using Grads were drawed and analysed in the levels of 1000 to 500 HPA. 

     The results showed that in the time of occuring hazardous cold waves of  29 to 30 of march 2003 and 25 to 26 of march 2005 and analyzing the sea level map in the first day of cold wave with spreading the cold core high pressure  from the eastern Europe and its location on north and east north of the black sea and its pentration from north west corner of the country covered most of the areas of the country. 

    Analyzing the combined maps of geopotential height and vorticity in the levels of 1000 and 850 HPA in the first day of occurrence of  cold, generaly faced with huge anticyclonic development . But in the levels of 700 and 500 HPA , the under studied area was in the south trough of the obtained cold core of the low height locating in the cetral Asia. But on the day of cold peak, high pressure core was exactly located on the under the studied area . Also in the upper levels of atmosphere with locating the back of the trough cumulated  of cold air of upper width on the sea level high pressure centre while strengthening the lower levels anticyclonic flows, led to intensifying cold and frost in the west Azarbayejan province. 

Positive and negative vorticity maximum cells, also conformed the intensity cold circulation flows on the north half of the country in anticyclone and cyclone centers in order. Also analysing the temperature advection in the levels of 1000 to 500 HPA, direction and temperature intensity exactly followed geopotential height maps patterns. 

     Such that in the levels of 1000 hpA of the both cold wave analysed, the anticyclonic cold temperature adcection and northward is located on the north west of the Iran. In temperature advection maps of 29 and 30 march 2003 in 850 HPA in Azarbayejan province, the anticyclonic circulation is matches with sea level high pressure. But in the 2nd cold wave that’s occured on 25 and 26 march 2005, the north west area is between 2 antycyclonic circulation on Mediterranean and cyclon located on south of  Russia that the directions of temperature cold flows is completely north ward in this level. 

    In the temperature advection maps of 700 and 500 HPA, the Azarbayejan province is in the western edge of central Asia trough or south of Russia. 

    The results showed that with studying  atmospheric motions and synoptic systems which create cold flows, we can prevent of spring late  emergence cold wave destructive impact on agricultural products, energy consumption, and road accidentd by  forcasting of these atmospheric conditions.