1. Department of Physics; Addis Ababa University; Addis Ababa Ethiopia
2. Karlsruhe Institute of Technology (KIT); Institute for Meteorology and Climate Research (IMK-ASF); Karlsruhe Germany
3. Department of Earth and Environmental Sciences; Botswana International University of Science and Technology (BIUST); Palapye Botswana
4. University of Texas at Dallas; Dallas/Fort Worth Texas USA
5. Department of Physics; Mekele University; Mekele Ethiopia