1. Climate in China

During September 2013, the mean precipitation of China was 69.3 mm, which was 6.2% more than normal (65.3mm). Percentages of precipitation anomalies were 30-100% more than normal in most eastern and middle Inner Mongolia, northwestern Heilongjiang, mid-northern North China and northern Shannxi, southern Huanghuai, northern Jianghuai, southern Jianghan, western Jiangnan, middle South China, northeastern Southwest China, southeastern TibetPlateau and western Xinjiang, with 100% more than normal in western Jiangnan, parts of Xinjiang and Anhui. Meanwhile, Precipitation anomalies were 30-80% less than normal in western and southeastern Inner Mongolia, southern Heilongjiang, southern North China, southern shannxi to ShandongPeninsula, mid-eastern Jiangnan, parts of southern Southwest China, western Xizang, mid-southern Xinjiang, and with 80% less than normal in parts of the above regions. Precipitation anomalies for the rest of the regions in China were close to normal.

For the month, the surface air temperature averaged over China was 16.8°C, which was 0.2℃ above normal (16.6℃). Monthly mean surface air temperatures were near or above normal in most northern China. Air temperature anomalies were 1-2℃ above normal in southern Shanxi and Shannxi, northern Henan, parts of Shandong, Zhejiang, southwestern Xinjiang, western Inner Mongolia. Meanwhile, temperature of the rest of the regions in China was lower than normal, negative anomalies were 1-2℃ in locations of eastern Chongqing, southwestern Hubei and northwestern Hunan. In September 2013, extreme events of Daily Precipitation (DP), Consecutive Precipitation Day (CPD) and Daily Temperature Drop (DTD) were observed in China. Extreme Daily Precipitation events were observed in 23 stations in 13 provinces as the Hubei Hunan, Sichuan, Yunnan, et al., with Hanzhong(123.0 mm) of Shanxi breaking historical records. At the same time, the extreme of Consecutive Precipitation Day (CPD) events of 36 stations occurred in Sichuan, Chongqing, Shanxi, Gansu, Qinghai and Hainan, with Wushan of Chongqing(15days) breaking historical records. The extreme of Daily Temperature Drop events for 17 stations also occurred over Northeast China, with amplitude of temperature dropping around 12-18℃, such as Fuxin(17.1℃) of Liaoning and Nongan(16.4℃) of Jilin broke the historical records.

2. Climate in the World

In September 2013, monthly mean air temperatures were 1-2℃ above normal in the northern part of North American, western Europe, part of central and Far East of Russia, Western Asia, Central Asia, most Australia and the eastern Africa, with temperatures 2-4℃ above normal in locations of the northern part of North America, Western Asia and the eastern Australia. Meanwhile, monthly mean air temperatures were 1-2℃ below normal in most of South America, the northern and southern Africa, the eastern Europe and the central-northern Asia.

For the month, precipitations were at least 50% more than normal in the western and Far East of Russia, the northeastern part of East Asia, the parts of western and eastern Africa, the southern North America, the eastern South America, with precipitations at least 200% above normal in locations of the eastern Europe, the western and Far East of Russia. Meanwhile, the precipitations were 50% less than normal in the northern Europe, Western Asia, Central Asia, the most Australia, the eastern and southern Africa, and the western South America.

3. General Circulation Features

Northern Hemisphere: During September 2013, the field of mean 500hPageopotential height exhibited a four-wave pattern over the mid-high latitudes. In the field of height anomaly, positive anomalies above 4 dam covered the Polar Regions, the northwestern North Atlantic Ocean, the northern North Pacific Ocean, and northern North America, with central values above 12 dam over parts of the Polar Regions. Meanwhile, negative anomalies below -4 dam covered eastern and central Europe, northeastern Asia, regions from Alaska to the northeast North Pacific Ocean, parts of the northern Atlantic Ocean, with central values below -8 dam over eastern and central Europe. During the month, the northwestern Pacific subtropical high was weaker than normal, with area below normal. The position of its ridge shifted more northward and eastward than normal.

Southern Hemisphere: For the month, in the field of height anomaly, positive anomalies above 4 dam covered the regions from most of the Antarctic to the southern South Pacific, with central values above 24 dam. Meanwhile, negative anomalies below -4 dam covered the southern and central South Pacific, the southeastern South Indian Ocean, and the sea south to Africa, the southern South Atlantic Ocean and southern South America, with central value blow -16 dam over the southern South Pacific.

4. Tropical Features

Sea Surface Temperatures (SSTs): During September 2013, weak negative SST anomalies (SSTA) dominated over the most equatorial eastern Pacific, with the central value below -1.0℃. Niño 1+2, Niño 3, Niño 4, Niño 3.4 and Niño Z indices were -0.5℃、-0.1℃、0.0℃、-0.1℃ and -0.1℃,with rises of 0.4℃, 0.4℃, 0.2℃and 0.2℃for Niño 1+2、Niño3、Niño3.4 and Niño Z index, no change for Niño 4 from last month.

Subsurface Temperatures: During September 2013, anomalously warm subsurface water dominated most of the equatorial Pacific Ocean. Meanwhile, anomalously cold subsurface water persisted in the equatorial eastern Pacific.

Warm Pools: During September 2013, the area of the Indian Ocean warm pool was slightly smaller than normal and its intensity was below normal. The area and intensity of the western Pacific warm pool were both above normal.

Wind Field: During September 2013, at lower troposphere (850hPa), the westerly anomalies covered the most equatorial central-eastern Pacific, and easterly anomalies dominated in the western region. At upper troposphere (200hPa), westerly anomalies covered the most equatorial Pacific.

Southern Oscillation: For the month, the Southern Oscillation Index (SOI) was 0.4, with a rise of 0.4 from last month.

Convections over the Tropics: During September 2013, the anomalous outgoing long wave radiation (OLR) showed that convection enhanced in the equatorial western Pacific, while convections were suppressed in parts of the equatorial eastern-central Pacific. At lower troposphere (850hPa) divergent wind field, a convergent center was around 120ºE, 20ºN, and a divergent center was over 120ºW, 10ºS. At upper troposphere (200hPa), a divergent center was near 130ºE, 15ºN, and a convergent center was around 115ºW, 10ºS.

5. ENSO Monitoring and Outlook

At present, the east part of tropic Pacific sea surface temperature is weak negative anomaly. The weak east wind is prevailing and the convection is weak in the east and middle part of the equatorial Pacificrecently. The heat content of upper layer ocean in the tropic remained weak positive anomaly.The ENSO-neutral conditions are expected to persist throughthe autumn and winter according to model forecasts and the diagnostic analysis.

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