Executive Summary

Since its establishment in 2005, APCC (APEC Climate Center) has made great efforts to develop and improve the long-term seasonal forecast technology using the Multi-Model Ensemble (MME) and as a result, it has established a climate prediction system using various global models of the world’s leading climate forecast operating and research institutes to provide climate monitoring information and long-term forecast and verification information on its website and platform every month.

The main Improvements in climate forecasts for the sixth phase (2022–2024) include early provision of forecast information, improved climate outlooks, establishment of a high-resolution MME seasonal forecast verification system, extension of the MME hindcast period, enhancement of the BSISO (Boreal Summer Intraseasonal Oscillation) sub-seasonal forecast system, expansion of the Southeast Asia FHEWS (Fire and Haze Early Warning System) to include Malaysia, establishment of an East Asia MME temperature seasonal forecast correction system, and dynamic web services through a new website.

• Since April 2022, the release date for forecast information has been moved forward by five days, from the 20th of each month to the 15th. 

• To improve the APCC climate outlook that is posted and distributed monthly, a survey of the climate outlooks from other operational climate prediction institutions was conducted. Additionally, feedback on satisfaction and preferences from APCC climate outlook subscribers’s survey was collected. Based on these findings, a newly designed climate outlook with enhanced readability and visibility has been posted and distributed since November 2023.

• A data preprocessing and verification system was established in September 2022 to assess the predictability of high-resolution MME seasonal forecasts.

• The MME hindcast period has been extended from 1991–2010 to 1993–2020 for trial production and analysis of forecast information, with plans to apply this extended period in 2025. In relation to this, the hindcast period for APCC's in-house climate model, SCoPS, has been extended from 1982–2013 to 1982–2016 for the production of hindcast.

• To enhance the usability of BSISO forecast information, the area of BSISO impact anomaly has been expanded to include the Korean Peninsula within 10S–50N, 40E–160E, and the provision period has been extended from three weeks to four weeks. 

• The FHEWS has been expanded to include Malaysia, with information being provided since 2023.

• A linear trend correction system for relatively high MME temperature forecasts in East Asia has been established. 

• Since February 2024, a new website has been providing dynamic web contents for climate forecasts, climate monitoring, and climate indices

The demand and international interest in sub-seasonal forecasting information have surged, yet the development and predictive power of sub-seasonal forecasting technology remain lacking compared to other time scales. As a specialized institution that has produced and provided world-class seasonal forecast information, APCC aims to expand its scope to include sub-seasonal forecasting. As a preparatory step, APCC has established a system and conducted foundational research for operating the MME sub-seasonal forecasting system. Initially, a comprehensive review was conducted based on the current status of domestic and international MME sub-seasonal forecasting systems and internal research. This review helped assess usability and establish criteria suitable for APCC's operational MME sub-seasonal forecast through various sensitivity experiments for processing daily data from individual models. Additionally, the potential for utilizing MME on a sub-seasonal scale was diagnosed. During the 5th APCC MME Model Providers’Meeting, the possibility of securing sub-seasonal forecast data was explored, and real-time forecast information from some models was collected to develop a versatile and efficient pilot system consistent with the APCC MME seasonal forecast system. Furthermore, the potential use and improvement direction of the SCoPS model for sub-seasonal forecast were established through trial production of sub-seasonal forecasts using APCC's in-house model (SCoPS) and comparative evaluation of predictive power with S2S project models. These results are intended to be utilized in future operations of the APCC MME sub-seasonal forecast system and the development of core technologies.

Since 2011, APCC has been operating the WMO (World Meteorological Organization) Lead Center for Long Range Forecast Multi-Model Ensemble (LC-LRFMME) in collaboration with the Korea Meteorological Administration (KMA), providing high-quality climate forecast services that meet the needs of WMO member countries. The Lead Center collects and standardizes long-range forecast data from 15 Global Producing Centers (GPCs) around the world, applying deterministic and probabilistic MME methods to produce seasonal forecast results and verification outcomes. These are consistently and reliably provided to WMO member countries and general users through digital and graphical formats on its website. To strengthen international collaboration, the center offers tailored MME forecast information for various regional climate forums organized by the WMO. In 2024, to ensure more stable services and data management, the center upgraded its computing equipment, enhancing operational data processing capabilities and improving user convenience with an option selection menu.

Additionally, APCC operated the WMO S2S (Subseasonal-to-Seasonal Prediction Project) International Coordination Office (ICO) to establish international collaboration in climate prediction. APCC actively engages with expert groups in the climate field by attending international conferences such as those organized by the IPCC (Intergovernmental Panel on Climate Change) and regional climate forums, continuously maintaining communication with these experts.