Investigation of potential vorticity on isentropic surfaces and its relationship to Precipitation over Iran

The main objective of this study was to evaluate potential vorticity on isentropic surfaces, and its relationship with precipitation over Iran by using of a numerical mesoscale model (MM5). The model runs were initiated at 00:00 UTC, 24 and 26 December 2004 to provide 48-h simulations of the cases and 6-hour precipitation data from the synoptic stations of Iran meteorological organization were used.
Potential vorticity (PV) is an important dynamical variable due to its conservative property in the absence of diabatic heating and friction and to its invertibility principle. Therefore PV analysis has been used in a wide range (from mesoscale to of planetary scales) of atmospheric circulations. On the synoptic-scale, isentropic potential vorticity anomalies evolve through a combination of translation (motion/advection), rotation, and deformation by the synoptic-scale wind field (Horinouchi, 2014). For these processes, isentropic potential vorticity is conserved following the motion. This study provides an overall understanding of relationship between isentropic PV and surface precipitation over Iran. The upper tropospheric disturbances are characterized by the folding of PV on the 330 K isentropic surfaces.
The findings have the following major implications. (1) Application of the dynamic tropopause patterns appears to be useful for prediction of precipitation over Iran. (2) In many areas where mean daily PV values were predicted between 1.5PVU and 3PVU, surface precipitations, also have been occurred. (3) Additional research efforts are required for a deeper investigation of the role of PV on precipitation over Iran.