Thermal low pressures of the Iran plateau

In this study, using reanalysis data  (Era-Interim) of European Center for Medium-Scale Atmospheric (ECMWF) ), the meteorological parameters and  structure of patterns  like sea level pressure, geopotential height and temperature  for  standard pressure levels, relative and Specific humidity in low-troposphere, wind field, relative vorticity, wind,  vertical velocity, convergence and cross section of the relevant quantities were studied by temporal and  spatial intervals  3-hour and 0.125 degree resolution (in terms of latitude and longitude during the period of 1987-2019. The results show the existence of independent thermal low-pressure systems in the form of single cells with local dimensions among the holes and plains of the Iran plateau corresponding to warm cores. Thus the theory that the low pressure conditions in the central regions of Iran, especially in the southeast and east, is the result of the spatial development of the Ganges system (Pakistan), was questioned. In other words, within the vast low-pressure belt of South Asia, different topographic, geographical, and surface cover conditions have led to differences in  radiation absorption  and the formation of local low-pressure centers. These independent low-pressure cells include the low-pressure systems of Dasht-e Kavir, Kavirlot, Rigistan Desert (Afghanistan), Balochistan Plateau (Pakistan) and Jazmourian. Rigestan low pressure and Lut desert low pressure have the highest frequency. The maximum height of these low pressures in Lut and Rigistan is up to about 500 hPa. The warming of the Iran plateau that increased their occurrence frequency in the warm season of the year,  more extension and high intensity, and negative pressure anomalies in the middle of the day, indicates the role of short-wave solar radiation of in amplifying their cyclonic rotation. The cross section of the relative vorticity and the vertical velocity indicate their limited extension to the depth of the troposphere and their thermal mechanism, and the positive and negative changes of these parameters confirm their local characters as separate cells. The formation of these low pressures in the vicinity of thermal mountain high-pressure systems has limited the spatial expansion and integration in the form of a large pressure system on the interior plains.