Does the Flooding of a Depression East of the Caspian Sea have an Impact on Local Weather and Climate?

In the central-eastern part of the Caspian Sea, several depressions are present. Currently, their flooding is under consideration for achieving a positive impact on regional weather and climate as well as for combining this effort with energy production and several economical and agricultural projects. In this connection, the Technological Holding Institute (THI) is studying the impact of previous, natural depression (Ashisor and Karagie) floodings on the regional climate. Historical data (maps, travelogue, etc.) confirms that depressions were a part of a Caspian Sea in a recent memory (not more than 150-200 years ago).

We present a study of the impact of the flooding of two depressions, which are not flooded yet, on the regional environment and weather. For this purpose, we used the WRF-NOAHMP model in combination with a dynamic lake model (WRF-NOAHMP-LAKE). The model was forced by ERA5 data during June 2017 and operated either without (Control) and with (Impact) of the flooding effect.

Over and in the region of the artificial lakes, we found substantial effects on the surface water and land surface temperature fields as well as the atmospheric 2-m surface temperature and moisture fields. Also the depth of the planetary boundary layer was reduced. In the impact runs, the diurnal cycle of the 2-m temperature was damped by up to 4 degrees in comparison to the control and the surface moisture was enhanced by 3 g/kg. Particularly interesting was a change of the sea breeze and related convergence zones in the region of the artificial lake, which - in combination with a modification of the PBL structure - resulted in an enhancement of cloudiness and even of precipitation southwesterly of the lake and over the southern part of the lake.

Overall, a substantial positive impact on the regional environment and the weather pattern was found. Therefore, it is worthwhile to consider a realization of this flooding project to support economic and agricultural projects in a continental desert region.