Progress Report

Control Theory of Weather-Society Coupling Systems for Supporting Social Decision-Making[A-1] Construction and analysis of new meteorological data leading to “controllability” and design of control methods

A-1A-2A-3B-1B-2»

Progress until FY2024

1. Outline of the project

Background：

Extreme weather events, including tropical cyclones, are complex phenomena that exhibit vast amounts of energy. In this Goal 8, our aim is to develop a theory that would enable us to safely alter extreme weather using minimal external forces.

Objective：

We aim at establishing a systematic method for influencing the future trajectory of extreme weather events, such as tropical cyclones, through small-scale artificial interventions. This will give rise to a new paradigm in meteorological control theory.

Method：

By an integration of state-of-the-art simulations and satellite weather observations, we will construct a novel dataset of the three-dimensional structures of tropical cyclones. Then, this dataset will be analyzed via a blend of process-driven and data-driven approaches (Fig. 1).

Fig.1
Fig. 1. Overview of the R&D Item.

2. Outcome so far

  • ①We have successfully completed to build the research infrastructure and developed the necessary dataset to explore the controllability of tropical cyclones.
  • ② [Process-driven approach] We found that the meso-scale water vapor anomalies solely drive rapid intensification of a tropical cyclone (Fig.2). We are now exploring how to effectively use this novel physical understanding to suggest specific and feasible interventions for controlling severe weather events.
Fig
Fig.2
Fig. 2. (upper left) Simulation of tropical cyclone. (upper right) Same as the upper left figure, but meso-scale water vapor anomalies that induces convections are artificially eliminated in the simulation. (bottom) Timeseries of maximum wind speed of tropical cyclone. Upper figures were depicted at the time of the blue dashed line. The black and brown lines represent the simulation shown in upper left and upper right figures, respectively. It shows that, if water vapor can be continuously dispersed over an area around 100 ㎢, a tropical cyclone could be suppressed to a smaller scale in its early stages by this small-scale perturbation.
  • ③ [Data-driven approach] We improved Ensemble Kalman Control developed in R&D Item A-2 and developed a mathematical method that can input the best possible external force, even for large-scale weather, using simulation results with their uncertainty.
Fig.3
Fig. 3. An example of applying Ensemble Kalman Control to a tropical cyclone simulation. (Left) Timeseries of the central pressure of a tropical cyclone. The black and green lines show the case without and with control, respectively. Since higher central pressure means a weaker tropical cyclone, our control weakens it. (Right) Control input at the time shown by the red dashed line in the left figure. The amount of water vapor in the air closest to the ocean surface in the simulation is changed. Such inputs can be automatically calculated.

3. Future plans

We have discovered that small-scale fluctuations in water vapor can influence the overall strength and development of a tropical cyclone, which could be useful for typhoon control. In cooperation with R&D Item A-2, we also found an efficient method to automatically search for good control inputs through simulation. By combining and deepening these results, we will now focus on designing actual devices to intervene the atmosphere to mitigate tropical cyclones.

A-1A-2A-3B-1B-2»