Broad Objectives

Better understand sub-seasonal tropical-extratropical interaction pathways

Identify periods and regions of increased predictability (“forecasts of opportunity”)

Improve subseasonal-to-seasonal forecasts of weather and climate for applications

Research Priorities

Understand physical mechanisms of tropical-extratropical interaction

Assess the physical mechanisms and robustness of mid-latitude circulation and weather responses to the spectrum of three-dimensional tropical diabatic heating on all subseasonal time scales, from tropical cyclones to the boreal winter and summer ISO. Identify mechanisms of extra-tropical forcing of tropical convection and circulation on all subseasonal time scales.

Develop new comprehensive estimates of tropical heating

Synthesize available satellite radiance and radar measurements with modern reanalysis products to produce four-dimensional estimates of tropical heating. 

Mechanistic numerical experiments to assess mechanisms and potential predictability

Carry out a broad array of numerical experiments with tropical diabatic heating estimates to further refine understanding of mechanisms. Use state-of-the art models with the (observed) tropical heating embedded to assess potential predictability of mid-latitude weather and circulation.

Development of down-scaling and error correction methods for applications.

Identify the main errors associated with teleconnections, especially those associated with extratropical response to tropical forcing. Develop postprocessing techniques to correct systematic teleconnection related model errors.

For more information please access the full version of the sub-project Science Plan. 

Implementation

The objectives of the science plan will be implemented on two time scales. On a shorter time scale they will benefit from being executed within the framework of a coordinated program, and on longer time-scale they will evolve independently and interweave as progress in research reaches the stage of transfer to applications.

An intense international program of one year, the Year of Tropics-Midlatitude Interactions and Teleconnections (YTMIT), should be implemented. This program is designed to foster relationships between research, forecasting, and stakeholder communities, and will facilitate the sharing of common interests to explore the links between the tropics and midlatitudes. The international program will include an integrated observations component (using existing products of Global Observing System, reanalyses), an operational forecast and reforecast component (using the S2S and NMME databases), an applications component, and a research component aligned with the research priorities of this science plan and WCRP mission. The research component will consist of a combination of theoretical, diagnostic, and modeling studies and will be focused on understanding the physical nature of the tropics-midlatitude interactions and teleconnections and their potential as sources of predictability.

Collaboration with other WMO projects, and S2S subprojects such as WCRP Working Group on Seasonal to Interannual Prediction (WGSIP), MJOTF-S2S Joint Project on MJO and Maritime Continent Interactions, S2S sub-project on extreme weather, and the S2S sub-project on verification.

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