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.

Key Improvements in the APCC climate forecasts include: APCC climate outlook renewal, development of higher resolution MME seasonal forecast verification system, changes to BSISO (Boreal Summer Intraseasonal Oscillation) forecasts, regional expansion of FHEWS (Fire and Haze Early Warning System), and development of seasonal climate digital data production system for dynamic web sevices.

• Starting from November 2023, APCC is disseminating its redesigned seasonal climate outlook which was developed based on the results from APCC climate outlook subscribers’survey. The new version has much higher readability and visibility compared to the previous one.

• APCC has developed higher resolution observation pre-processing and climate verification system to evaluate the forecast skills of high-resolution MME seasonal forecasts provided since September 2022.

• The region of APCC FHEWS (Fire and Haze Early Warning System) was expanded to Malaysia and its extended forecasts are available from 2023.

• APCC provided BSISO impact anomaly up to four weeks and expand its area to 50 degrees of north, including the Korean Peninsula and expect that this information will help users who need medium-range forecast in the Asian monsoon region.

• APCC is planning to provide the dynamic web services for climate forecasts, climate monitoring, and climate indices through the renewed APCC website from early 2024.

The globe is getting warmer and the real-time seasonal forecast of 2-m temperature in the long-term is influenced by the global warming since 2013. In the global scale, temperature warming in the seasonal forecast model forecasts are not much different from those of real world; but the regional scale, the differences make it difficult to use the temperature forecast without post processing. Especially, East Asia area often undergoes cold waves in the real world, while the climate model produces above normal temperature forecasts in the most time. Thus suitable post processing is necessary to use the climate model forecasts positively in various sectors. The long-term trend of models and real observation temperature are analyzed and proper correction of long-term trend of temperature can lead some improvement of forecast skill in this study. Also this study will pave the way to use the temperature climate forecast in the real-time operation of APCC MME.

Although demand for and international interest in sub-seasonal to seasonal (S2S) forecast are rapidly increasing worldwide, the development and predictability of S2S prediction is still insufficient compared to other time scales (e.g., weather and season). APCC is one of worldwide organizations that has produced and provided seasonal forecast and is seeking to expand its scope to S2S forecasts. As a preparatory step for this, a system was established and basic research was conducted to develop the APCC S2S MME predicton system. First, usability was identified though a comprehensive review based on a survey of the current status of international S2S MME prediction systems and research. Through various sensitivity experiments to prepare daily data processing methods for individual models, standards suitable for APCC S2S MME operation were developed. In addition, the possibility of MME usability (MME efficiency) was diagnosed at a S2S time scale, and the possibility of securing S2S data was explored through the 5th APCC MME Model Providers’ Meeting. Based on these results, we plan to utilize them in the future operation of the APCC S2S prediction system and development of technologies.

APCC has been operating the WMO (World Meteorological Organization) Lead Center for Long Range Forecast MME (WMO LC-LRFMME) with KMA (Korea Meteorological Administration) since 2011 to provide climate forecast services. The WMO LC-LRFMME collects forecast data from 14 Global Producing Center (GPC) and standardizes forecast and hindcast data and displaying the MME results including deterministic and probabilistic method through the website on a monthly basis. Also the WMO LC-LRFMME provided the seasonal forecast information to Regional Climate Outlook Forums (RCOF), Global Seasonal Climate Updates (GSCU) and KMA to a consensus on the state of the global and regional climate outlook. In 2023, the WMO LC-LRFMME’s seasonal forecast system improvements have been performed to provide customized seasonal prediction information and improve system management.

APCC is also operating the WMO S2S (Subseasonal-to-Seasonal Predcition Project) ICO (International Coordination Office) to establish an international collaboration in the field of climate prediction and continuously communicating with a group of experts in the climate filed by attending international conferences such as IPCC (Intergovernmental Panel on Climate Change) and regional climate forums.