1. Climate in China
During October 2013, the surface air temperature averaged over China was 11.1℃, which was 0.8℃ above normal (10.3℃) and the 9th consecutively warming year since 1961. The spatial pattern of monthly mean surface air temperatures were generally above normal in most of Northwestern China, while below normal in Southwestern China. Positive anomalies with1~2℃ were observed in most of Northwestern China, the middle of Central China, the western Inner Mongolia , the southwestern Shanxi and northeastern Sichuan. Negative anomalies with-1~-2℃were observed in some parts of central-eastern Yunnan and the southwestern Guizhou.
For the month, the precipitation averaged over China was30.8 mm, which was 14.0% less than normal (35.8mm). Precipitations were observed 50~200% above normal in the central and southern part of Northeast China,the northeastern Inner Mongolia, most of Xizang, the central-western part of Sichuan, the central Yunnan and the Yangtze River Delta. Meanwhile, precipitations were near or below normal in the rest regions, being over 80% less than normal in the western part of Northwestern China, the southeastern Shandong, the middle of Central China and most of South China.
In October 2013, the daily precipitation extremes and daily temperature dropextremes were observed in China.
Daily precipitation extremes were observed in 41 stations of 5 provinces as the Fujian, Jiangsu, Zhejiang, Shanghai et al., with the daily precipitation in Shangyu (373.0 mm) and Yuyao (344.7mm) of Zhejiang breaking historical records.
The daily temperature drop extremes occurred in 16 stations of 5 provinces as Hebei, Beijing, Tianjin and Inner-Mongolia et al., with the amplitude of daily temperature drop being around 11~14℃ and breaking the historical records in Baodi (12.7℃) of Tianjin and Miyun (14.0℃) of Beijing.
During September 2013, monthly mean air temperatures were 1~2℃ above normal in the northwestern, eastern and southern North American, southern South America, western Europe, northwestern and middle-eastern Africa, central and eastern Asia, central Russia, most Australia, with temperatures 2~4℃above normal in locations of northwestern, eastern and southern North American, central Russia and western East Asia. Meanwhile, monthly mean air temperatures were 1~2℃ below normal in mid-western North America, central and northern South America, mid-western and southern Africa, southeastern Europe, northwestern and eastern Russia, western and southern Asia.
For the month, precipitations were at least 50% more than normal in central and eastern North America, most South America, central Europe, western and eastern Russia, northern and southern East Asia, with precipitations at least 200% above normal in locations. Meanwhile, precipitations were 50%～80% less than normal in locations of Alaska, northeastern South Africa, central Europe, northwestern Russia and southwest East Asia.
3. General Circulation Features
Northern Hemisphere: During October 2013, in the field of mean 500hPageopotential height anomaly, negative anomalies below-4 dam covered the Polar Regions, the northern North Atlantic Ocean, the northwestern North Pacific Ocean, and some parts of northern North America, with central values below-8 dam over parts of the Polar Regions and the northern North Atlantic Ocean. Meanwhile, positive anomalies above4 dam covered the WesternEurope, northern Africa, North East Asia, andsome parts of the northeastern North Pacific Ocean, with central values above8 dam. During the month, the northwestern Pacific subtropical high was weaker than normal, with the area smaller than 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, the southeastern South Pacific and southern South Atlantic Ocean. Meanwhile, negative anomalies below -4 dam covered the southwestern South Pacific and the southern South Indian Ocean, with the central value blow -8 dam.
4. Tropical Features
Sea Surface Temperatures (SSTs): During October 2013, weak negative SST anomalies (SSTA) dominated the most equatorial central and eastern Pacific, with central values below -1.0℃. Niño 1+2, Niño 3, Niño 4, Niño 3.4 and Niño Z indices were -0.6℃,-0.2℃,0.0℃,-0.3℃ and -0.2℃, with indices of Niño 1+2,Niño3,Niño3.4 and Niño Z drops of 0.1℃, 0.1℃, 0.2℃and 0.1℃respectively and with Niño 4 no change from last month.
Subsurface Temperatures: During October 2013, anomalously warm subsurface water enhanced near the dateline. Meanwhile, anomalously cold subsurface water enhanced in middle of the equatorial mid-eastern Pacific.
Warm Pools: During October 2013, the area of the Indian Ocean warm pool was slightly larger than normal and its intensity was bigger than normal. Both of the area and intensity of the western Pacific warm pool were above normal.
Wind Field: During October 2013, both at lower troposphere (850hPa) and upper troposphere (200hPa), westerly anomalies covered the most equatorial Pacific.
Southern Oscillation: For the month, the Southern Oscillation Index (SOI) was -0.1, with a drop of 0.5 from last month.
Convections over the Tropics: During October 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 central and eastern Pacific. At lower troposphere (850hPa) divergent wind field, a convergent center was around 140ºE, 10ºN, and a divergent center was over 110ºW, 15ºS. At upper troposphere (200hPa), a divergent center was near 145ºE, 10ºN, and a convergent center was around 90ºW, 5ºS.
5. ENSO Monitoring and Outlook
Considering the status of the central and eastern equatorial Pacific, Subsurface seas temperatures have increased obviously and been above average since June 2013, although sea surface temperatures are still weak negative anomaly at present. Based on the predictions of dynamical and statistical models, ENSO-neutral is expected into the Northern Hemisphere winter and will turn into above-average neutral conditions in the following spring.
Therefore, we will closely monitor the development of ENSO conditions and update our ENSO wrap-up in time.