Regional climate modeling for Georgia with RegCM4.7

In this study, the latest version of the Abdus Salam International Center for Theoretical Physics (ICTP) Regional Climate Model RegCM4.7.0 is used to simulate climate of Georgia for the period 1986-2005.

Georgia is the mountainous country located in the south-western part of the Greater Caucasus. Its area is 69.875 km². Mountains cover significant part of the territory 54% of them is located at 1,000 m elevation. From the west Georgia is washed by the Black Sea, from the south it borders with Turkey and Armenia, from the south-east – with Azerbaijan and from the north – with the Russian Federation.

Georgia displays diverse climate and vegetation types: there are almost all climate types from high mountains eternal snow and glaciers to steppe continental climate of eastern Georgia and the Black Sea coastal subtropical humid climate.

To simulate climate with high horizontal resolution and represent more special details for the complex terrain of Georgia the double-nested dynamic downscaling method has been used. First, RegCM was driven by ERA-Interim data at a grid spacing of 50 km. For 50 km resolution simulation, we defined central latitude and central longitude of model domain clat=42.27, clon=42.70 degrees as well as 30 number of points in the N/S direction and 60 number of points in the E/W direction. The 12-km resolution RegCM simulation was nested in the simulation at 50 km resolution. For 12 km resolution simulation, we chose central latitude and central longitude of model domain clat=42, clon =43 degrees as well as 48 N/S 100 E/W points. We selected domain size to be large enough to account for the relevant large-scale processes (such as the large-scale flow modulations due to orographic features and water bodies) but at the same time small enough in size to minimize the use of computational resources.  

We have used the default BATS (Biosphere-atmosphere transfer scheme) land surface parameterization scheme, Emanuel cumulus convective parameterization scheme, SUBEX (Sub-grid Explicit Moisture Scheme) moisture scheme and Holstlag planetary boundary layer scheme for the simulations.

The simulated surface annual and seasonal air temperature and precipitation as well as extreme climate events are compared with Climatic Research Unit (CRU), ERA5 reanalysis, GPCP data sets. For extreme events analyzes, we chose and used some indices, defined by the Expert Team on Climate Change Detection and Indices, recommended by the World Meteorological Organization.

This work was supported by Shota Rustaveli National Science Foundation of Georgia (SRNSFG) № FR-19-8110.