Rossby wave packet properties in a changing climate

Dr. Georgios Fragkoulidis

As the concentration of greenhouse gases in the atmosphere increases, climate model simulations agree on the response of certain global thermodynamic aspects. Global mean temperature and water vapor concentration will keep increasing, the sea level will keep rising, and the various components of the cryosphere will keep declining. A complicating factor, however, is that these changes are not distributed uniformly in the atmosphere, which induces large uncertainties in the response of the atmospheric circulation at both a global and a regional scale. These uncertainties prevent us from making robust statements about the future characteristics of weather extremes in specific regions.

Our work involves employing newly-developed diagnostics of Rossby wave packet properties in reanalysis data and output from multi-member climate model ensembles. These diagnostics are local in space and time, so they do not obscure the spatiotemporal evolution of the upper-tropospheric flow and facilitate an investigation of its interplay with weather-related flow features such as cyclones and blocks. Based on this strategy, hypotheses can be formulated regarding the long-term variability in the magnitude, frequency, and duration of temperature and precipitation extremes.

The figures show the average Rossby wave packet amplitude for the Northern Hemisphere winter in a historical simulation of the 1980-2010 period and the projected change for the 2070-2100 period (CESM Large Ensemble; RCP8.5 scenario).