[SLS] Itamar Karbi (Weizmann Institute of Science)

“Reassessing the future changes in mid-latitude atmospheric waves”

Transient mid-latitude atmospheric waves shape the extra-tropical weather and climate by setting the storm tracks, and regulating the distribution of heat, moisture, and momentum from daily to multi-decadal timescales. The intensity and position of these waves are projected to change considerably by the end of this century, leading to significant societal impacts across the extra-tropics. However, to date, most previous studies have investigated the future changes in atmospheric waves by pooling together waves with different length scales, thus not accounting for potential different responses across wavelengths to anthropogenic emissions. Here, we reexamine the response of mid-latitude atmospheric waves to anthropogenic emissions by separately analyzing the response of the waves across spatial scales. First, we aim to understand the seasonal asymmetry in the future changes in austral atmospheric waves, which are projected to intensify in winter, but to shift poleward in summer. We find that strengthening of large-scale waves drives the winter intensification, while a reduced intensity of small-scale waves contributes to the summer poleward shift. Our analysis further shows that seasonal differences in upper-level warming patterns account for the contrasting responses across scales and seasons. Second, we find that the scale-dependent response of the waves manifests in temperature variability: in the Southern Hemisphere, we find a shift, in coming decades, towards spatially larger and less persistent temperature anomalies and extreme heat events. Third, we reveal that changes in atmospheric waves in boreal winter do not emerge from the internal variability due to opposite responses of large and small wavelengths. By separately analyzing large- and small-scale waves, we find that large-scale waves are projected to intensify and emerge from the internal variability during the 21st century. These results highlight the importance of investigating scale-dependent changes in the mid-latitude climate, to avoid masking the distinct impacts of different length scales, and to provide more accurate climate projections.

Sack Lunch Seminar Series —
Informal seminar series within PAOC (Program in Atmospheres, Oceans, and Climate) that focuses on more specialized topics than the PAOC Colloquium. The presentations are either given by an invited speaker or by a member of PAOC and can focus on new research or discussion of a paper of particular interest.

Contact: sacklunch-committee@mit.edu