1. Institute of Applied Physics, Russian Academy of Sciences, 46 Ulyanov Str., Nizhny Novgorod 603950, Russia
2. Research and Education Mathematical Center “Mathematics for Future Technologies,” Nizhny Novgorod State University, Nizhny Novgorod 603950, Russia
3. Department of Mathematical Sciences, Atmospheric Sciences Group, University of Wisconsin, P.O. Box 413, Milwaukee, Wisconsin 53217, USA
4. Shirshov Institute of Oceanology, Russian Academy of Sciences, 36 Nahimovskiy Pr., Moscow 117997, Russia