High Resolution Dynamical Downscaling of Air Temperature and Precipitation using WRF-ARW Model Over Iraq

Abstract

The ability of the Weather Research and Forecasting (WRF-ARW) model to simulate precipitation variability throughout the Middle East, especially Iraq, is evaluated in this study. The Weather Research and Forecasting model (WRF v 4.2.1) was used. Using a two-way nesting technique and Mercator projection, the WRF model was set up with two nested grids with high regional resolution at 30 km (WRF30km) and 10 km (WRF10km) horizontal grid spacing. From the surface to 50 hPa, both domains have 41 vertical levels. The outer domain covers the Middle East region and the smaller one covers the Iraq region. The ARW supports horizontal nesting, allowing higher resolution over a region of interest, by introducing additional grids, which is available only for horizontal refinement. The nested grids are rectangular and are aligned with the parent (coarser) grid within which they are nested. To predict many atmospheric parameters WRF-ARW model was used based on the initial conditions taken from National Centre for Atmospheric Research (NCAR) records for the period from 23 to 25 of march 2019. The study area is essentially an area bounded by longitudes 35°-55° and latitudes 29°-38° typically including the area of Iraq. The WRF-ARW model was set up on a Linux platform with a 10 km grid size in the zonal and meridional directions. The aim of this study is to evaluate the two WRF tools dynamical downscaling and nesting) at high resolution (30 and 10 km), for simulating rainfall and temperature over Iraq.