Joint Seminar: Theory, Method, and Implementation of Targeted Observation for Improving Forecasts of High-impact Ocean-Atmospheric Events

High-impact ocean-atmospheric events, such as ENSO, typhoons, Kuroshio large meander and blocking, often result in substantial economic and societal losses on regional or even global scales. Accurately forecasting these events is crucial, yet it remains a persistent challenge. Observations play a pivotal role not only in comprehending these events but also in enhancing predictive capabilities. Targeted observation, an optimized strategy dedicated to numerical forecasting, addresses the critical question of “Where the best observations should be deployed?” Its theoretical foundation relies on the faster growth rate of patterned perturbations in contrast to their random counterparts. Essentially, identifying  optimally growing perturbations and locating sensitive areas significantly affecting related prediction results are the key of targeted observation.

Given the complex environments of high-impact ocean-atmospheric events, the conditional non-linear optimal perturbation (CNOP) approach was proposed. This method seeks the optimal perturbation that causes the largest prediction errors at a future time within a fully nonlinear framework. The CNOP-based targeted observations have been widely explored across various fields, including typhoon, ENSO, IOD, Ural blocking, anomalous Kuroshio variations, etc. In Observing System Simulation Experiments (OSSEs), observation arrays built within the CNOP-based sensitive areas have demonstrated noteworthy superiority over conventional observations. Additionally, certain applications, such as targeted observations for predicting typhoons and vertical temperature profiles in the Yellow Sea, have yielded meaningful results in realistic field experiments within Observing System Experiments (OSEs). These findings indicate that the CNOP-based targeted observation is an efficient strategy for enhancing the forecast skills of high-impact ocean-atmospheric events. Its effectiveness and cost-saving properties make it urgently needed. This presentation will introduce the theory of targeted observation, demonstrate related applications using the CNOP approach, and discuss its future prospects and challenges.