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

Authors
1 Former Master Student of Watershed Management, Department of Rangeland and Watershed Management, Malayer University, Malayer, Iran
2 Assistant Professor of Climatology, Department of Rangeland and Watershed Management Malayer University, Malayer, Iran
Abstract
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 2009-2012, 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 6 categorized patterns of sea level pressure. The highest values of MFC were observed at 1000, 925 and 850 hPa levels and at 12:00 and 18:00 UTC. MFC value strongly decreased in dusty days at the 700, 600 and 500 hPa and at 06:00 UTC. The relative humidity significantly decreased at 12:00, while the maximum increase was recorded at 18:00 and 00:00 UTC.
Keywords

Azizi, G., Shamsipur, A. A., Miri, M. and Safarrad, T. Statistical and synoptically analysis of dust in the western half of Iran. Environ. Stud., 2012; 38(63): 123-134.
Banacos, P.C. and Schultz D.M. The use of moisture flux convergence in forecasting convective initiation. Historical and operational perspectives. Weather. Forecast., 2005; 20: 351-366.
Csavina, J., Field, J., Félix, O., Corral-Avitia, A.Y., Eduardo S.A. and Betterton-Eric A. Effect of wind speed and relative humidity on atmospheric dust concentrations in semi-arid climates. Sci. Total Environ., 2014; 487: 82-90.
Farajzadeh-Asl, M., Karimi-Ahmadabad, M., Qaemi, h. and Mobasheri, M.R. The transfer of moisture in winter precipitation in the West of Iran. Modares Journal of Human Sciences, 2009; 13(1): 194-217. (In Persian)
Ghavidel-Rahimi, J. Investigation Moisture Flux Convergence in Super heavy rains of Hurricane Faith over Chabahar coasts. Modares Journal of Human Sciences. 2011; 15: 101-118. (In Persian)
Karimi-Ahmadabad, M., Farajzadeh-Asl, M. Moistures Flux and Spatial and Temporal Patterns of Moistures resources of precipitations in Iran. Geographical Science and Applied Research Journal. 2011; 11(22):  109-128. (In Persian)
Lee, J.J. and Kim C.H. Roles of surface wind, NDVI and snow cover in the recent changes in Asian dust storm occurrence frequency, Atmos. Environ., 2012; 59: 366-375.
Mosavi B.M. and Ashraf, B. Study of airs instability and synoptic pattern of dust storms affecting the occurrence of Mashhad. Geography and Regional Development Research Journal. 2012; 18: 27. (In Persian)
Nouri, H., Gayoor, H., Massoodian S.A. and Azadi, M. Investigation of frequency moisture flux convergence and moisture sources precipitation of southern coasts of the Caspian Sea. Geography and Environmental Planning Journal. 2013; 51: 1-14. (In Persian)
Omidvar, K. Synoptic analysis of Sand storms in the desert Yazd-Ardekan. Geographical Research. 2006; 81: 43-87. (In Persian)
Penalba, O., Bettolli, M.L. A classification of the sea level pressure daily fields in southern South America: an application to daily rainfall in the Pampas region. Geophysical Research Abstracts. 2010; Vol. 12, EGU2010-11556.
Saavedra, S., Rodríguez, A., Taboada, J.J., Souto, J.A. and Casares, J.J. Synoptic patterns and air mass transport during ozone episodes in northwestern Liberia. Sci. Total Environ., 2012; 441: 97-110.
United Nations Environment Programme. Establishing a WMO Sand and Dust Storm Warning Advisory and Assessment System Regional Node for West Asia: Current Capabilities and Needs, Technical Report, WMO. 2013; No: 1121.