Analysis of dynamic and thermodynamic of the atmosphere simultaneously with the occurrence of a destructive floodwater in the northwest of Iran (April 14, 2017)

Heavy precipitations and severe floods are one of the most important hazards affecting many parts of the country, including the northwest of the country, and it causes extensive damage to farms, gardens, houses, urban facilities, etc. In this research, the atmospheric conditions accompanying the occurrence of flood events in the northwest of the country on April 14, 2017 are studied. For this purpose, the data of sea level pressure, geopotential height, vertical velocity, zonal and meridional components at pressure levels of 850, 700, 500 and 300 hpa, as well as specific humidity in pressure levels of 1000 and 850 hpa(12 hours before the flood event) were obtained from European Centre for Medium-Range Weather Forecasts with a .075 -degree spatial resolution and the desired maps were drawn and the following results were obtained. The presence of severe gradient of pressure in the sea level in the northwestern region of the country and the high humidity in the lower atmosphere as well as the presence of western troughs at all levels of the troposphere exacerbate the meridian flows, and cause the subsequent formation of jets at a pressure of 700 to 300 hpa on the northwest region of Iran. On the other hand, extreme ascent, due to the severe vertical shear of the horizontal wind and the presence of a great deal of moisture, especially in the lower layers of the atmosphere, have created cumulonimbus clouds from a pressure level of 850 to 370 hpa, with lightning strikes at a pressure of 850 to 600 hpa. All of the above conditions have caused the instability and flooding and extreme precipitations in this region of the country.