1. Climate in China

In July 2015, the surface air temperature averaged over China was 22.1ºC, with 0.2ºC above normal (21.9ºC). The mean precipitation was 88.7 mm over China, which was 26.5% less than normal (120.6mm). For the month, extremes of Daily Precipitation (DP)，High Temperature (HT), extremes of Consecutive High Temperature Days (CHTD) were observed in China.

2. General Circulation Features

Northern Hemisphere: During July 2015, in the field of mean 500hPa geopotential height anomaly, positive anomalies above 4 dam covered the regions from the polar region to northeastern North America, southern Europe, Central Asia, locations of southern Central Siberia and locations of northeastern Pacific. Meanwhile, negative anomalies below -4 dam covered the regions from northeastern Atlantic Ocean to West Siberia, central North Pacific and locations of western North America. For the month, the northwestern Pacific subtropical high was weaker than normal, with the area smaller than normal. The position of its western ridge point was eastward than normal and its ridge line shifted northward than normal.

Southern Hemisphere: For the month, in the field of mean 500hPa geopotential height anomaly, positive anomalies over 4 dam were observed over southern Atlantic Ocean, southeastern Indian Ocean and locations of central South Pacific. Meanwhile, negative anomalies below -4 dam covered the Antarctica and Drake Strait.

3. Tropical Features

Sea Surface Temperatures (SSTs): In July 2015, SSTs were over 0.5℃ above normal in most of the central and eastern equatorial Pacific, especially above 2℃ in some locations. Indices of Niño1+2，Niño3，Niño4，Niño3.4 and Niño Z were 3.0℃、2.2℃、1.0℃、1.6℃ and 1.8℃, respectively. The Indian Ocean Basin-Wide SSTA variation index (IOBW) was 0.5. The North Atlantic Triple (NAT) index was 1.6 and kept in the persistent positive phase.

Subsurface Temperatures: In July, the anomalously warm subsurface water shifted eastward to the region around 100°W, with the central values above 6℃. Meanwhile, the anomalously cool subsurface water controlled the equatorial western Pacific, with the central value below -2℃.

Warm Pools: For the month, the areas of both the Indian Ocean and the western Pacific warm pools were larger than normal and their intensities were both above normal.

Wind Field: For the month, at lower troposphere (850hPa), the westerly anomalies dominated over most equatorial Pacific and central equatorial Indian Ocean, while the easterly anomalies dominated over eastern equatorial Indian Ocean. At upper troposphere (200hPa), the westerly anomalies prevailed over most equatorial Indian Ocean, while the easterly anomalies were observed over most of the central-eastern equatorial Pacific.

Southern Oscillation: For the month, the Southern Oscillation Index (SOI) was -1.3.

Convections over the Tropics: During July 2015, the anomalous outgoing longwave radiation (OLR) showed that convections were active around the central-eastern equatorial Pacific, with central values below -30 W/m². However, convections were suppressed around the region from the western equatorial Pacific to the eastern equatorial Indian Ocean.

4. ENSO Monitoring and Outlook

The equatorial SST in the east-central Pacific is expected increased in the next month. There is a great chance that a strong El nino will continue through Northern Hemisphere winter of 2015/2016.

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