Monthly Highlights

1．Climate in China

During June 2009, monthly mean surface air temperatures were 1-2℃ above normal in most Northwest China, most Tibet, parts of Sichuan, central and western Inner Mongolia, most North China, regions between the middle and lower reaches of the Yellow River and the Yangtze River, the most Jiangnan Region, with over 2℃ above normal in parts of above regions. Temperatures were 1-2℃ below normal in most Northeast China, northeastern Inner Mongolia and northern Xinjiang with central values below -2℃. Temperatures were near normal in the rest regions of China.

For the month, precipitations were observed 30-100% more than normal in most Northeast China, northeastern Inner Mongolia and east of North China, with over 200% in western Heilongjiang. Meanwhile, precipitations were observed 30-80% less than normal in the central and eastern Jiangnan Region, west of North China, most Northwest China, most Tibet and central and western Inner Mongolia, with over 80% in western Tibet, southern Xinjiang and western Inner Mongolia. Precipitations were near normal in the rest regions of China.

In June, daily maximum temperature extremes occurred in most North China, northern Huanghuai area and central Sichuan province. Severe heat wave affected western and southern Hebei, central and western Shandong, northern Henan provinces with high temperatures soaring past 40℃ (On June 25th, daily maximum temperature reached 44.4℃ in Shahe station of Hebei province), which prompted new maximum temperature records. Daily precipitation extremes occurred in southern Jiangsu and Anhui, central and western Guangxi, southeastern Guizhou, northeastern Yunnan and western Heilongjiang provinces. New records of daily precipitation were reported in Hefeng station of Hubei, Tongdao station of Hunan, Langxi station of Anhui, Zhanyi station of Yunnan, Beian and Fuyu stations of Heilongjiang provinces. Both daily maximum temperature and precipitation extremes were observed monitored in Ebian station of Sichuan province.

2． Climate in the World

During June 2009, temperatures were 1-2℃ above normal in north-central Russia, central East Asia, most West Asia, southwestern and southeastern Europe, northern North Africa, parts of West Africa, northern South Africa, northwestern and southeastern North America and locations in South America and parts of northwestern Australia, with temperatures at least 4℃ above normal in northeastern Russia. Meanwhile, temperatures were over 1-2℃ below normal in most Central Asia, southcentral and southeastern Russia, northeastern China, central North America and southeastern South America, with temperatures over 4℃ below normal in part of above regions.

For the month, precipitations were at least 50% more than normal in most northeastern China, central Russia and the Far East in Russia, parts of Central Asia, south-central Europe, western Africa and South Africa, southwestern and northeastern North America, central South America, western and southeastern Australia, with precipitations over 200% more than normal in parts of above regions. Meanwhile, precipitations were observed over 50% less than normal in regions from northern South Asia to northwestern China via the Tibetan Plateau, regions from southeastern Europe to western Central Asia, parts of eastern Russia, locations in central Africa, parts of North America, southern South America and northern Australia, with no precipitations in parts of above regions.

3．General Circulation Features

Northern Hemisphere: During June 2009, the mean 500hPa geopotential height field exhibited more short wave troughs than normal at the mid-high latitudes. In the anomaly field, negative anomalies below -4 dam covered the central North Pacific, northeastern China, the northeastern North Atlantic, western coasts of North America and the adjacent area. Meanwhile, positive anomalies above 4 dam covered the Polar Region and the northern North Atlantic, northeastern Asia, southeastern Europe and the eastern North Pacific with central values over 12 dam. For the month, the subtropical high over the Northwest Pacific was slightly larger and stronger, and its location was southward and eastward than normal.

Southern Hemisphere: In June, the mean 500hPa geopotential height field exhibited a 4-wave pattern at the mid-high latitudes. In the anomaly field, most areas were near or above normal except the southeastern Indian Ocean, the southeastern and central-southern South Pacific with negative anomalies below -4 dam. Positive anomalies above 4 dam covered most Antarctic and the middle-high latitude sea area, with central values above 24 dam.

4. Tropical Features

Sea Surface Temperatures (SSTs): During June, the SSTs were above normal in most of the central and eastern equatorial Pacific, with maximum positive departure above 1.0℃. In June, indices of NINO 1+2, NINO 3, NINO 4, NINO 3.4 and NINO Z were 0.6℃, 0.7℃, 0.6℃, 0.6℃ and 0.7℃, with a rise of 0.2℃, 0.4℃, 0.3℃, 0.3℃ and 0.4℃ from last month, respectively.

Subsurface Temperatures: During June, the anomalously warm subsurface water dominated most of the equatorial Pacific.

Warm Pools: During June, both the area and intensity of the western Pacific and Indian Ocean warm pool were above normal.

Wind Field：For the month, at lower troposphere (850hPa), weak westerly anomalies prevailed over the most equatorial Pacific except the regions around the dateline. At upper troposphere (200hPa), easterly anomalies exceeding 4m/s covered the most equatorial Pacific.

Southern Oscillation: For the month, the Southern Oscillation Index (SOI) was 0.0, with a rise of 0.7 from last month.

Convections over the Tropics: During June, the anomalous outgoing longwave radiation (OLR) in the equatorial Pacific showed that the convection was near normal over most of the equatorial Pacific, and enhanced over the vicinity of the Philippines. In the lower troposphere (850hPa) divergent wind field, a divergent center in the tropical Pacific was near 105ºW, 15ºS. Correspondingly, at upper troposphere (200hPa), the convergent center was near 100ºW, 15ºS.

5. ENSO 监测与展望 ENSO Monitoring and outlook

During June 2009, monitoring showed that remarkable El Nino features emerged over the tropical Pacific, with occurring of warmer than normal SSTs over the central and eastern equatorial Pacific, being 0.7℃ of Nino Z index, persisting of anomalously warm subsurface water across the equatorial Pacific, and the westerly anomalies over most of the equatorial Pacific corresponding to weakening Walker circulation. Furthermore, predictions of most statistical and dynamic models indicated the SST anomalies in the central and eastern equatorial Pacific will continue to be above 0.5℃ in coming 3 months.

Based on aforementioned analysis, El Nino conditions emerged in June 2009, an El Nino event is expected to form in the central and eastern equatorial Pacific. In further, we need to closely monitor the developments of ENSO conditions and update ENSO wrap-up in time.