Sixteenth Session of the Forum on Regional Climate Monitoring Assessment and Prediction for Asia (FOCRAII) Seasonal Outlook over China in Summer 2020 Liu, u, Yunyun yun Wang, g, Yongg gguang uang Contact act: : liuyuny@c yuny@cma.gov.cn ma.gov.cn Bei eijing jing Climate mate Cen enter, er, CMA 07May, ay, 2020 20
Outline 1. Observed anomalous signals and possible impacts 2. Predictions by BCC_CSM1.1(m) 3. Summary
Observed anomalous signals SSTA in DJF 2019/2020 • Positive SSTAs were present in the central- eastern tropical Pacific, tropical Indian, and Atlantic Oceans in DJF. • A weak CP type El Niño event was formed from Oct 2019 to Apr 2020. IOBM Niño 3.4 ATL Niño
Pacific Niño3.4 SST Model Outlook For the future evolution of Niño3.4 index, a majority of models favored decaying trend of Niño3.4 from DJF to JJA, and ENSO-neutral conditions through summer 2020.
Possible impacts of El Niño decaying years In El Niño decaying years, North and Northwest China favor wet conditions, while South China and the lower reach of Yangtze River valley favor dry conditions.
Tropical Indian Ocean warming A In the tropical Indian Ocean, basin-wide warming is expected to persist through summer 2020. Statistically, the basin-wide warming in the tropical Indian Ocean occurs as a lagged response to the Pacific El Niño event, which is favorable to the stronger Philippine sea anticyclone and WPSH.
Atlantic Ocean warming in DJF A • The ATL Niño index was significantly positive in DJF, forming an Atlantic Niño event. • Usually, the Atlantic Niño leads Pacific La Niña event by 6~12 months (Kucharski et al., 2016). • The equatorial Atlantic ocean warming in winter is beneficial to further northward WPSH, and above normal rainfall over North China in summer.
2. Predictions by BCC_CSM1.1(m)
BCC_CSM1.1(m) predicted Z500 anomaly Z500_JJA JA IC: Apr 2020 2020 Jun un. Jul. Aug • Positive height anomalies are favored over Northeast Asia and the western North Pacific, and a near-normal height anomalies are favored over South China and east of Japan in JJA. • WPSH favors stronger and southward in June, and further northward in July-August.
BCC_CSM1.1(m) predicted uv850 anomalies uv850 IC: Apr2020 Anomalous C Philippine anticyclone A Southerly anomalies over the southeastern coast of China
Forecasts for monsoon circulation factors WPSH Intensity Philippine Sea Anticyclone East Asian Summer Monsoon East Asia-Pacific teleconnection
BCC_CSM1.1(m) predicted Precipitation anomaly Predict diction skill Prec ecipitati itation IC: Apr2020 20 • Wet regions are expected over the northern South China, North China, Mongolia, South Japan, South Korea, North India, and Southeast Asia. • Dry regions are expected over the Indo-China Peninsula, South India, and Central Asia.
BCC_CSM1.1(m) predicted T2m anomaly Predict diction skill T2m IC: Apr2020 - - - • The predicted temperature is above normal over most of Asia, and near normal over South China, North India, and part of northeastern Asia. • Besides, the prediction skills of temperature over Asia is higher than that of rainfall in summer.
Long-term trend of T2m over China Probabil bability ty of abov ove-nor ormal al T2m in 2011-2018 2018 Averaged-tempe mperat ature ure in China na • Under the background of global warming, the T2m over China is increasingly warming over the last 30 years.
A: above normal B: below normal Seasonal outlook in JJA 2020 N: near normal The seasonal outlooks combine the model forecasts, the long-term trends, and effects of tropical oceans warming. • Wet regions are expected over South China, North and Northwest China, while dry regions are favored over the eastern Inner Mongolia, northern Xinjiang, and along the Yangtze River valley. • The above normal temperature is favored over most China, except for the Tibetan Plateau and part of South China.
Summary • The WPSH is favored stronger than normal in JJA, with southward in June, and further northward in July-August. • The intensity of EASM is expected near-normal, which is favorable to abundant rainfall north of Yangtze River valley in China. • The above normal rainfall is favored over South China, North and Northwest China, where it is necessary to prevent the flood and rainstorm disasters. • The above-normal temperature is expected over most of China, except for the Tibetan Plateau and part of South China. • Average to above average tropical cyclone activity is favored in the western North Pacific over 2020, with 26-28 TCs genesis and 7-9 TCs landfall onto the southeastern coast of China. The intensity of landing TCs are expected stronger than normal and the moving tracks may be further northwestward.
More Information BCC Webpage: http://forecast.bcccsm.ncc-cma.net/htm/ Dr. Yunyun Liu Beijing Climate Center China Meteorological Administration 46# Zhongguancun South Avenue, Beijing Email: liuyuny@cma.gov.cn 17
Re-forecast configurations for seasonal prediction Model: The fully coupled climate model BCC_CSM1.1m (T106L26) Forecast ： initialized on 1 st of each month , 13-month integration Ensemble forecast ： 24 samples (15 lagged-average-forecast (LAF) and 9 singular-vector (SV) method) Initial data: Atmosphere: NCEP reanalyses for hindcast, and NMC/CMA T639 assimilation for real-time Ocean: NCEP-GODAS oceanic data Hindcast period ： 1991-2013 Data preprocess ： 0-month lead (LM0) ； 1-month lead ( LM1); …; 6-month lead (LM6) Real-forecast for 2019 : initialized on 1 st April
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