Extratropical-Tropical interAction: A unified view on the extratropical impact on the subtropics and tropics at weather timescales

An immediate, critical challenge facing humanity is the impact of weather extremes under a changing climate across the globe.

Accurate weather forecasts and reliable climate projections rely on understanding the complex interactions between the atmospheric circulation and the water cycle.

Largely governed by deep clouds, tropical weather cannot be forecasted more than a day in advance, leaving almost half of humanity living in these regions even more vulnerable.

Although extratropical (outside the tropics) flows can drastically affect tropical clouds and precipitation, this effect has not been systematically quantified or understood.

The novelty of this proposal is in asking a new question: How do extratropical dynamics influence the (sub)tropics?We will build on our recent work and paradigm-challenging preliminary results to study how extratropical dry, cold air intrusions into the tropics dramatically modify its atmosphere and air-sea interaction.

We will use a new global Lagrangian identification approach to study this extratropical-tropical interaction for the first time, and uniquely combine state-of-the-art data from multiple sources, diagnostic tools, and multi-scale modelling.

We will quantify the global spatiotemporal occurrence, variability and trends of these events (WP1); understand their underlying dynamics and precursors in midlatitudes and their impact on the water cycle (WP2); and assess their suitability as predictors of high-impact tropical weather (WP3).

A dedicated international observational flight campaign will allow us to synergistically study the extratropics’ impact on the tropics (WP4).Our findings will advance not only the meteorological community but also the oceanographic, cloud physics and climate dynamics scientific communities, by providing a unified, global view of the interacting large-scale atmospheric dynamics, clouds and precipitation through their common weather timescales, paving the way for timely, accurate weather warnings.