The Mechanisms that Drive Summer Teleconnections: Patterns Associated with High Surface Temperatures

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The large-scale atmospheric circulation is characterized by circumpolar flows that navigate around high- and low-pressure centers distributed across the globe. This circulation varies in time, ranging from a few days to well over decades. When averaged over a season, the climatological circulation features appear fixed geographically as stationary waves of constant amplitudes. Within a season, the large-scale atmospheric circulation can be thought of as comprising of these stationary waves and evolving patterns that deviate from them (i.e., anomalies). The recurring and persistent anomalous patterns are referred to as teleconnection patterns. They can appear naturally as a part of our chaotic atmospheric system and can be excited by events like sustained regional heating over the unusually warm ocean surface. The interference between teleconnection patterns and the attendant stationary waves can intensify high- and low-pressure centers leading to extreme weather and climate events such as droughts and floods as well as unseasonably cold and warm spells. In recent decades, the occurrence of summertime extreme events has increased and its attribution to global warming is unclear. To date, the mechanisms behind the excitation and maintenance of the summertime teleconnection patterns are not well understood. This proposal aims to understand the physical mechanisms that excite summer teleconnection patterns associated with extreme surface temperature signatures. The investigators hypothesize that the inter-decadal increase in the heat wave frequency has coincided with an increased occurrence of particular teleconnection patterns (initiated by diabatic heating) during the boreal summer. The investigators plan to examine the possible impact of interference between these teleconnections and stationary waves on surface temperature. They will assess if there has been any long term (greater than a decade) changes in the frequency and intensity of the summer teleconnection patterns and, if so, explore possible causes of these long-term changes. The research methods include cluster analysis of the combined upper tropospheric geopotential height and surface air temperature fields, various diagnostic analyses of the resulting cluster patterns, surface energy budget analysis, and numerical modeling.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.