Monthly Highlights
1. Climate in China
During June 2013, the mean precipitation of China was 99.9 mm, which was close to normal (99.3mm). Percentages of precipitation anomalies were above normal in most regions north of the Yellow River and below normal in most regions south of the Yellow River. Precipitation anomalies were 30-200% above normal in most western Northwest China, northern North China, central Northeast China, most Inner Mongolia, Ningxia, the Sichuan Basin, western Xizang, southwestern Anhui, northeastern Jiangxi, eastern Zhejiang, and with 200% above normal in parts of the above regions. Meanwhile, precipitations were 30-80% below normal in southern North China, Huang-Huai area, southwestern Jiangnan, central South China, parts of eastern Southwest China, mid-northern Xizang, part of eastern Xinjiang, most Qinghai, central Shaanxi, Northwestern Liaoning, eastern and northern Heilongjiang, with 80% below normal in locations.
For the month, the surface air temperature averaged over China was 20.7℃, which was warmer than normal (20.0℃) by 0.7℃. Air temperature anomalies were near or above normal in most China. Monthly mean surface air temperatures were 1-2℃ above normal in most Southwest China, western Jiangnan, eastern Northeast China, Qinghai, and southern Shaanxi, with 2℃ above normal in parts of the above regions. Meanwhile, negative anomalies were 1-2℃ in central and northern Xinjiang, northeastern Inner Mongolia and mid-eastern North China.
In June 2013, extreme events of High Temperature (HT), Daily Precipitation (DP), Consecutive Precipitation (CP) and Consecutive Precipitation Day (CPD) were observed in China. Daily maximum temperatures of 20 stations in Yunnan, Guizhou, Chongqing, Hainan, Hubei, and Qinghai provinces (cities) reached the threshold of extreme HT event, with new records in Yunan’s Fugong (40.2℃) and Guizhou’s Leishan (35.9℃).Meanwhile, extreme DP events occurred in 55 stations of 20 provinces (districts) like Xinjiang, Gansu, Anhui, Xizang, Sichuan, Yunnan, and Guangxi, etc., with the daily precipitations of 10 stations breaking historical records, including Xinjiang’s Wensu (67.9mm), Gansu’s Maiji(146mm), Zhangjiachuan (110.5mm), Qingshui (99.5mm), Qinan (84mm), Ningxia’s Xiji (93mm), Shanxi’s Jingle (106.8mm), Hunan’s Ningxiang (222.8mm), Sichuan’s Suijing (327mm) and Xizang’s Rikeze (47.9mm). Extreme CP events occurred in 25 stations of 13 provinces (districts) like Xinjiang, Gansu, and Shanxi, etc., with 9 stations setting new record such as Gansu’s Maiji (163.3mm), Neimenggu’s Dongwuzhumuqin (124.4mm), Shanxi’s Dingxiang (130.5mm), Xizang’s Pulan (118.4mm) and Xinjiang’s Wensu (101.9mm). Extreme CPD events occurred in 36 stations of 13 provinces (districts) like Xinjiang, Qinghai, Gansu, Neimenggu, and Hebei, etc., with new records in Heilongjiang’s Yian (14days), Neimenggu’s Bayannuoergong (6days) and Qinghai’s Xiaozhaohuo (5 days).
2. Climate in the World
During June 2013, precipitations were at least 50% more than normal in the southeastern part of West Europe, the southern and eastern parts of Russia, most South Asia, the western and northern parts of East Asia, the western part of West Africa, the northern part of Central Africa, regions from the northwestern to southeastern parts of Australia, the central and southeastern parts of North America, locations of Alaska, and the central part of Southern America, with precipitations at least 200% above normal in locations. Meanwhile, precipitations were at least 50% less than normal in locations of the northern part of Europe, West Asia, Central Asia, the western part of South Asia, the northeastern part of Australia, most Africa, the southwestern part of the United States, the southern part of South America, with no precipitation in locations.
For the month, monthly mean air temperatures were 1-4℃ above normal in the eastern part of Europe, the mid-northern part of Russia, the central part of East Asia, parts of the western and eastern Africa, the northern part of Australia, the western part of North America, and the southern and mid-eastern parts of South America, with temperatures 4-6℃ above normal in locations of the northern part of Russia. Meanwhile, monthly mean air temperatures were 1-2℃ below normal in Central Asia, the northern part of East Asia, the southern part of West Asia, the northern part of India, the northeastern part of Africa, locations of the western part of Australia, as well as the eastern part of North America and the mid-western part of South America, with temperatures 2-4℃ below normal in locations of the central part of Russia.
3. General Circulation Features
Northern Hemisphere: During June 2013, a four-wave pattern over mid-high latitudes was observed on the field of mean 500 hPa geopotential height. In the field of height anomaly, positive anomalies above 40 gpm covered the northern North Atlantic Ocean, regions from central-northern Europe to northwestern Russia, northeastern East Asia, and regions from Alaska to northwestern North America, with central values above 80 gpm in regions from northern Europe to the southern Barents Sea, Alaska, and northern Canada. Meanwhile, negative anomalies below -40 gpm were observed over the Arctic region, and the regions from the northwestern North Atlantic Ocean to southern Greenland, with central values below -160 gpm over the Arctic region. For the month, the extent of the western North Pacific subtropical high was small than normal, with its intensity below normal, the high ridge extending more northward and retreating further eastward.
Southern Hemisphere: For the month, a four-wave pattern over mid-high latitudes was observed on the field of mean 500 hPa geopotential height. In the field of height anomaly, positive anomalies above 40 gpm covered regions from the central-southern South Atlantic Ocean to the southeastern South Indian Ocean via the Antarctic Pole, and the southeastern and mid-south parts of the South Pacific, with central values above 120 gpm over the southern South Atlantic Ocean. Meanwhile, negative anomalies below -40 gpm covered the southwestern South Indian Ocean and the Drake Passage, with central values below -160 gpm over the Drake Passage.
4. Tropical Features
Sea Surface Temperatures (SSTs): During June 2013, weak negative SST anomalies (SSTA) dominated over most equatorial eastern and central Pacific, with the central value below -2.0℃. Niño 1+2, Niño 3, Niño 4, Niño 3.4 and Niño Z indices were -1.5℃, -0.7℃, -0.1℃, -0.2℃ and -0.5℃,with a rise of 0.1℃ for Niño 3.4 index from last month, and no change in other Niño zones.
Subsurface Temperatures: During June 2013, anomalously warm subsurface water in the equatorial western Pacific intensified slightly, with the central value above 3℃. Meanwhile, anomalously warm subsurface water in the equatorial eastern-central Pacific enhanced from last month, and continually accumulated and upwelled in the equatorial eastern-central Pacific. Anomalously cold subsurface water in the equatorial eastern Pacific shifted eastward with the smaller area, but enhanced evidently in central value.
Warm Pools: During June 2013, the area of the Indian Ocean warm pool was 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 June 2013, at lower troposphere (850hPa), the weak westerly anomalies covered most equatorial Pacific, with westerly wind anomalies about 2-4 m/s covered the western equatorial Pacific. At upper troposphere (200hPa), weak westerly anomalies covered most equatorial eastern and central Pacific, and the zonal winds were near normal in the western equatorial Pacific.
Southern Oscillation: For the month, the Southern Oscillation Index (SOI) was 1.2, with a rise of 0.5 from last month.
Convections over the Tropics: During June 2013, the anomalous outgoing long wave radiation (OLR) showed that convection enhanced in equatorial western Pacific north to Indonesia, while convections were suppressed in equatorial central Indian Ocean. At lower troposphere (850hPa) divergent wind field, a convergent center was around 130ºE, 15ºN, and a divergent center was over 85ºW, 25ºS. At upper troposphere (200hPa), a divergent center was near 120ºE, 10ºN, and a convergent center was around 90ºW, 25ºS.
5. ENSO Monitoring and Outlook
At present, sea surface temperatures are near average across much of the equatorial Pacific, except for below average SSTs in the eastern Pacific Ocean. During the recent period, the above average subsurface temperatures develop in the central-eastern Pacific Ocean. Based on models’ prediction and diagnoses of the oceanic variations, the ENSO-neutral conditions are expected to persist through the coming autumn.
Therefore, we will closely monitor the development of ENSO conditions and update our ENSO wrap-up in time.