This study develops a physical-empirical seasonal forecast model for the northeastern Asian summer monsoon. Thorough this model, summer (June, July and August) precipitation in mid-latitude East Asia is predicted. Mutivariate Empirical Orthogonal Function analysis (MEOF) is adapted to define the summer monsoon. The three leading MEOF modes from 850-hPa geopotential height and recipitation

represent the summer monsoon. The first mode represents the variation through the western North Pacific subtropical high (WNPSH) in the mid-latitude East Asia. The WNPSH is a prominent component in East Asia that could also affect the mid-latitude area. The second mode represents the zonal wave transport of geopotential height and surface temperature through the Eurasian Continent. The

northeastern Asian summer monsoon in the downstream region is influenced by the zonal wave transport. The last mode represents the variation by dipole pattern over the Okhotsk Sea and south side of Japan. Collectively, these three modes account for a large portion of the variability of the northeastern Asian summer monsoon.

The lead-lag correlations between principle component (PC) time series from MEOF and surface variables (2-m temperature, sea level pressure) from observation during winter and spring are analyzed to select predictors. In addition to this, simultaneous correlations between PCs and summer prediction fields of 500-hPa geopotential height, 850-hPa temperature, precipitation by APEC Climate Center (APCC)-Multi model ensemble (MME) system are also examined. Through stepwise regression function, two predictors are selected for each PC. These predictors reveal the physical evolving processes of the northeastern Asian summer monsoon

separately.

Independent prediction is conducted from 1983 to 2005 through 1-leave-out cross-validated strategy. During this period, the forecast skills for PCs are 0.76, 0.69, and 0.73, respectively. The predicted PCs and spatial patterns of MEOF are reconstructed to make the spatial prediction fields of precipitation. The area averaged prediction skill of the precipitation over mid-latitude East Asia in terms of temporal correlation coefficient is 0.41, which shows moderate improvement of forecast skill from that by only dynamical models (0.21).

Independent prediction is conducted from 2008 to 2016. Using the predicted PCs, real-time forecast for Korea precipitation can be improved. The second and third modes are closely related to August Korea precipitation: strong cyclonic flow over the northeastern China brings a moisture flux convergence over Korea, and a strong anticyclonic flow over the south of Japan draws a humid southerly wind over Korea. Thus, the prediction of the northeastern Asian summer monsoon can be adapted to the national-scale real-time forecast.

1. 서론

2. 연구 자료 및 방법

2.1 연구 자료

2.1.1 관측 자료

2.1.2 역학 모델 자료

2.2 동아시아 여름 몬순의 정의

2.3 예측 방법

2.3.1 잠재 예측 인자 선정

2.3.2 예측 인자 선정

2.3.3 예측과 후측 모의 검증

3. 중위도 동아시아 여름 몬순

3.1 첫 번째 모드 : 북서태평양 고기압

3.2 두 번째 모드: 중위도 파동 전파

3.3 세 번째 모드: 오호츠크해 저기압 모드

3.4 역학 모델에서의 동아시아 여름 몬순

4. 예측

4.1 예측 인자 선정

4.2 예측과 검증

5. 결론

REFERENCE