Establishment of High-resolution Multi-Model Ensemble (MME) Subseasonal to Seasonal (S2S) Prediction Framework and Diversification of Web Contents to Strengthen the Usability of APCC Climate Information

Dr. Yoojin Kim, Dr. Hyungjin Kim, Dr. Bong-Geun Song, Dr. Hyungju Lee, Ms. A-Young Lim, Mr. Changmook Lim, Ms. Daeun Jung, Mr. Im-Gook Jung, Mr. Jaew
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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.

Starting from April 2022, APCC has changed the official seasonal climate outlook release date from the 20th to the 15th of every month by courtesy of the contribution of the APCC MME Producing Centres (PCs). The release date was already moved up 5 days (25th to 20th) in 2019. Going one step further to meet the user needs and promote our competitiveness, APCC started issuing its climate outlook on the 15th which is 10 days earlier in total than before. Along with the earlier outlook release, seasonal climate forecast information in higher spatial resolution is one of the top priorities of user needs according to the results of the APCC's user survey conducted in 2020. The spatial resolution of APCC's forecast data has been 2.5° in latitude × 2.5° in longitude until recently, which was not highly resolved enough to meet user needs. Accordingly, APCC officially launched higher resolution (1° in latitude × 1° in longitude) MME forecast system in September 2022.

The new MME probabilistic forecast from selected models for East Asian region based on the relationship between ENSO-western Pacific precipitation and East Asian climate has been also provided from June 2022. The region of APCC FHEWS (Fire and Haze Early Warning System) was expanded to Malaysia in 2022, and its extended forecast is planned to be available in 2023.

In 2022, 4 out of 15 individual models were upgraded and applied to the APCC MME forecast system: ECCC CanSIPSv2.1, HMC SL-AV-072L96, JMA MRI-CPS3, and KMA GloSea6GC3.2. Improvements of these new models include upgraded atmospheric and ocean models, bigger ensemble size, and hindcast period shifted to more recent years. Also, CWB's model data were produced by their new HPC.

APCC improved BSISO information by reflecting recent climate characteristics and their influence. To do this, the climatological reference period has been updated from 1981-2010 to 1991-2020 for all BSISO information, following the World Meteorological Organization's recommendation to use the most-recent 30-year period as the climatological standard. Graphical representations on the BSISO website were also improved to increase readability and visibility. We expect that this improvement will help enhance user experience.

Under the global warming, seasonal forecast of temperature at 2-m during the APCC MME's hindcast period (1991-2010) are analyzed to understand the dynamical forecast models' ability to resolve the global warming trend. Most dynamical models have similar warming linear trend with the real world's one in the view of globally averaged temperature. However, in the regional scale, dynamical models could not simulate the specific warming or neutral trend and tend to forecast a bit warmer temperature roughly in the globe, regardless the variation of regions. Futher, it is introduced two methods to correct the temperature forecast; one is applying the research results about linear trend and tendency of the APCC MME and the other is bias correction using quantile mapping of temperature distribution, that can improve temperataure predictability in the future.

APCC has been opearting the WMO (World Meteorological Organization) Lead Center for Long Range Forecast (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 2022, 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 ICO (International Coordination Office) to establish an international collaboration in the fileld of climate prediction and continuously communicating with a group of experts in the climate filed by attending international conferences susch as IPCC and regional climate forums.