Relative Humidity and Moisture Flux Convergence during the Dusty Days in Alvand Mountain

The moisture flux convergence (MFC) and relative humidity in dusty days at different times and levels over the Alvand Mountain was investigated. The required basic data for the years ۲۰۰۹-۲۰۱۲, including relative humidity, visibility and synoptic codes, were gathered from Hamadan synoptic station, while sea level pressure, uwind, vwind and specific humidity data were gathered from NCER/NCAR site. The dusty days were categorized into four groups, according to WMO protocol. Sea level pressure (SLP) patterns were classified using cluster analysis (CA). MFC function, jet stream and omega maps were computed using special moisture and horizontal and vertical components of wind, SLP and omega data in various levels and times for each sea level pressure pattern. The results showed ۶ categorized patterns of sea level pressure. The highest values of MFC were observed at ۱۰۰۰, ۹۲۵ and ۸۵۰ hPa levels and at ۱۲:۰۰ and ۱۸:۰۰ UTC. MFC value strongly decreased in dusty days at the ۷۰۰, ۶۰۰ and ۵۰۰ hPa and at ۰۶:۰۰ UTC. The relative humidity significantly decreased at ۱۲:۰۰, while the maximum increase was recorded at ۱۸:۰۰ and ۰۰:۰۰ UTC.

کلیدواژه ها:

Sea level pressure (SLP) ، Omega ، Temporal variations ، Dust storms ، Hamadan