The Numerical Study of Low Level Jets Formation in South Eastern of Iran

Authors: Mehdi Salehi Barough, Saviz Sehat Kashani, A.A. Bidokhti, A.Ranjbar

Abstract:

The presence of cold air with the convergent topography of the Lut valley over the valley-s sloping terrain can generate Low Level Jets (LLJ). Moreover, the valley-parallel pressure gradients and northerly LLJ are produced as a result of the large-scale processes. In the numerical study the regional MM5 model was run leading to achieve an appropriate dynamical analysis of flows in the region for summer and winter. The results of this study show the presence of summer synoptical systems cause the formation of north-south pressure gradients in the valley which could be led to the blowing of winds with the velocity more than 14 ms-1 and vulnerable dust and wind storms lasting more than 120 days. Whereas the presence of cold air masses in the region in winter, cause the average speed of LLJs decrease. In this time downslope flows are noticeable in creating the night LLJs.

Keywords: Cold advection, Low Level Jet, MM5 Model, Pressure gradient

Digital Object Identifier (DOI): doi.org/10.5281/zenodo.1055517

References:

[1] Liu, M., and Westphal, D.L., and Holt, T.R., and XU, Q., "Numerical simulation of a low-level jet over complex terrain in southern Iran", Mon.Weath.Rev, 128, 1309-1327, 2000.
[2] Lockman G. M., J.E. Overland, 1998: "Atmospheric Structure and Momentum Balance during a Gap Wind Shelikof Strait, Alaska", Mon.Weath. Rev., 117, 1817-1833.
[3] Macklin, S.A., N. A. Bond and J.P. Walker, 1990: "Structure of a lowlevel jet over lower Cook Inlet, Alaska", Mon. Weath. Rev., 118, 2568- 2578
[4] Steenburgh, W. J., D. M. Schultz, and B.A. Colle, 1998: "the Structure and Evolution of Gap Outflow over the Gulf of Tehuantepec, Mexico", Mon. Wea. Rev., 126, 2673-2691.
[5] Mehdi Salehi Barough, A. Sedaghatkerdar, Saviz Sehat Kashani, A.A. Bidokhti, A. Ranjbar, "Implementation of MM5 Model for Evaluation of Northerly Surface Flows over Complex Terrain in South Eastern of Iran in the Hot Season of the Year", envocHEALTH2009, India, 16-19 Sep. 2009.
[6] Saviz Sehat Kashani, A. Sedaghatkerdar, A.A. Bidokhti, A. Ranjbar, Mehdi Salehi Barough, "The Numerical Evaluation of Low level Jets Formation in Lut Valley Region in Winter", envocHEALTH2009, India, 16-19 Sep. 2009.