Dr Frederiksen is an authority on dynamical theories and parameterizations of atmospheric processes. He has pioneered the first successful theories of localised cyclogenesis and the structures of storm tracks, of blocking and its life-cycles, of the origin, three-dimensional structures and seasonality of the major teleconnection patterns, of the genesis of the Madden-Julian oscillation and the classes of convectively coupled equatorial waves. He has established a statistical mechanics theory of coherent states, developed the first tractable closure theory for inhomogeneous turbulence, developed eddy viscosity, stochastic backscatter and eddy-topographic force parameterizations, and significantly improved climate simulations and weather predictions.