1. Climate in China

In August 2014, the mean precipitation over China was 104.4 mm, which was close to normal (105.3mm). The surface air temperature averaged over China was 20.6ºC, which was 0.2ºC below normal (20.8ºC). For the month, extremes of Daily Precipitation (DP), extremes of High Temperature (HT) and extremes of Consecutive High Temperature Days (CHTD) were observed in China.

2. General Circulation Features

Northern Hemisphere: During August 2014, in the 500hPa geopotential height anomaly field, positive anomalies above 4 dam covered the regions from northern Central Asia to southwestern Russia, eastern Russia to the Arctic, the southern Greenland to northeastern North America, with central values above 80 dam in the Arctic and the region from southwestern Greenland to northeastern North America. Meanwhile, negative anomalies below -4 dam covered western Europe, region from the northern Central Siberia to the Kara Sea, part of the Northeast Pacific, with central values below -120 dam over the region from the northern Central Siberia to the Kara Sea. The area, strength and high ridge of the northwestern Pacific subtropical high were all near normal.

Southern Hemisphere: For the month, in the 500hPa geopotential height anomaly field, positive anomalies over 4 dam were observed over the sea areas south to Australia, from the sea areas south to Africa to that south to South American via the polar region, with central values above 12 dam. Meanwhile, negative anomalies below -4 dam mainly covered the southwestern South Atlantic Ocean, the southeastern and locations of southwestern South Pacific Ocean, the Antarctic region between 90ºE to 150ºW, the central and southern South Indian Ocean, with central values below -12 dam over the central and southern South Indian Ocean.

3. Tropical Features

Sea Surface Temperatures (SSTs): During August 2014, SSTs were over 0.5℃ above normal in most equatorial Pacific, especially above 1℃ over the equatorial eastern Pacific to the east of 120ºW. Indices of Niño1+2、Niño3、Niño4、Niño3.4 and Niño Z were 1.2℃，0.5℃，0.5℃，0.2℃ and 0.6℃, respectively. The negative Indian Ocean Dipole (IOD) developed in the month, with SSTs near or below normal in the tropical western Indian Ocean and over 0.5℃ above normal in the southeastern Indian Ocean. The IOD index was -0.6℃. SSTs were slightly below normal in the tropical eastern Atlantic Ocean.

Subsurface Temperatures: In August, anomalously warm subsurface water controlled the equatorial central-western Pacific, with the warm center located to the east of the Dateline around 170ºW and central values above 3℃. Under the equatorial eastern Pacific, the anomalously cold subsurface water was very weak, with the cold center around 110ºW and central values below -2℃.

Warm Pools: For the month, the area of Indian Ocean warm pool was near normal, and the area of western Pacific warm pool was larger than normal. Both of their intensities were significantly stronger than normal.

Wind Field: For the month, at lower troposphere (850hPa), westerly anomalies dominated over most equatorial central-eastern Pacific, with central values above 4 m/s. And the equatorial western Pacific was controlled by weak easterly anomalies. At upper troposphere (200hPa), westerly anomalies prevailed over the equatorial eastern Pacific and the regions from the Maritime Continent to the equatorial western Pacific, with central values above 4 m/s. Meanwhile, the equatorial central Pacific was controlled by weak easterly anomalies.

Southern Oscillation: For the month, the Southern Oscillation Index (SOI) was -0.9.

Convections over the Tropics: During August 2014, the anomalous outgoing longwave radiation (OLR) showed that convection was active over the tropical eastern Pacific north of the equator, with central values below -15W/m². However, convection was suppressed over the tropical western Pacific north of the equator, with central values above 15 W/m². Convection was also active over the northwestern Indian Ocean around the Arabian Sea, with central values below -30W/m². Convection over the tropical Atlantic Ocean was near normal.

4. ENSO Monitoring and Outlook

Dynamical models outlook and diagnostic analysis on ENSO cycle suggest a high chance that a weak El Niño event will occur in the coming autumn and winter.

Therefore, we will closely monitor the development of ENSO conditions and update our ENSO wrap-up in time.