طبقه بندي همديدي فضايي توده هاي هوا در حوضه هاي جنوب غربي ايران

Spatial Synoptic Classification Air Masses in Basins of South-Western of Iran

In this study, Spatial Synoptic Classification (SSC) was used to identify and classify air masses in basins of south-western part of Iran. The method of SSC classifies the air masses into six groups based on origin and their moderation in its direction. Include Dry Polar (DP), Moist Polar (MP), Dry Tropical (DT), Moist Tropical (MT), Dry Moderate (DM) and Moist Moderate (MM) air masses. This denomination to identify properties of air masses. Typical days (as evidence) are needed to determine the properties of air masses and their classification. Arrangement line of the surface of the surface level maps and 850 hpa level represent the transference of special air mass to under study area. Primary criteria of typical days selection for each air mass at each station were used through the exact evaluation of datum and surface level climatological maps and 850 hpa levels. An each selected typical days was tracked from the origin to the domain under study and their features were evaluated. The selected typical days determine the particularity of an air mass. Hour time of 3, 9, 15, and 21 UTC for 10 synoptic stations during the statistical period of 1961-1999 was used to classify air mass in term of variable such as temperature, dew point temperature, pressure QFF, cloudiness, the direction and speed of wind. Related variable was merged using PCA and dimensions of matrix were reduced. In this study mode P was used to identify air masses and discriminantal analysis was used to classify air masses. So that the features representative of typical days were used as input for discriminant analysis function for the purpose of air masses classification. Accordingly we effect of air masses on basins of south - western of country (Iran) in winter, December to February, was identify using SSC. Climatologic conditions and accumulative effects determine by air masses that from this region pass.