Monthly Highlights

1. Climate in China

During February 2010, the surface air temperature averaged over China was -2.1℃, with 0.7℃ higher than normal. The monthly mean surface air temperatures were 1~4℃ above normal in most of Northwest China, western North China, most of Southwest China, South China, Jiangnan, Jianghuai and middle Huanghuai, with at least 4℃ above normal in local areas. Meanwhile, the temperatures were 1~4℃ below normal in most of Northeast China, eastern Inner Mongolia, northern Xinjiang, with over 4℃ below normal in locations.

In February, the monthly precipitation averaged over China was 17.0mm, near normal value (16.4mm). The precipitations were observed 30~100% above normal in most of Northeast and Northwest China, southeastern Huanghuai, Jianghuai, eastern Jiangnan, with at least 100% above normal in most of Northeast China, parts of Inner Mongolia, northwestern Gansu, most of Xinjiang, central Zhejiang. Meanwhile precipitations were observed 30~80% less than average in most of Southwest China, western South China, western Jiangnan, most of Qinghai, southern Gansu, middle Inner Mongolia, with at least 80% below normal in parts of above regions.

In early February 2010, Wudalianchi station (-43.6℃), Fujin station (-34.1℃) and Tailai station (-34.3℃) of Heilongjiang experienced severe low temperature, with daily minimum temperatures in Wudalianchi station setting new record. During the middle February, extreme daily temperature drop was observed in 23 stations of Heilongjiang, Jiangxi, Hunan, Guangdong, Sichuan, Guizhou and so on, with the temperature drop being 14-23℃ in general and broking the historical records in Jinxi station of Jiangxi (23.4℃), Tailai station of Heilongjiang (22.9℃), Zhaojue station of Sichuan (18.2℃). Extreme persistent rainy-day occurred in 42 stations of southern Jianghuai, central and northern Jiangnan and Xinjiang during the middle to late February, with the persistent rainy days setting new records in 13 stations.

2. Climate in the World

In February，the monthly mean surface air temperatures were observed 1~4℃ above normal in northwestern North America, eastern United States, eastern Canada, most of South America, most of Africa, southern and western Asia, with 4-6℃ above normal in parts of West Africa and eastern Canada. Meanwhile, temperatures were observed 1~4℃ below normal in central and southeastern United States, southern South America, most of Europe, northern Asia, with 8~10℃ below normal in central Russia.

For the month, precipitations were observed at least 50% above normal in Bolivia, northern Brazil, Guyana and Venezuela, Mexico, southwestern United States, southern West Africa, western Central Africa, central and southern Europe, northwestern China, northeastern China, north shore of the Okhotsk sea, with at least 200% above normal in locations. Meanwhile, precipitations were observed at least 50% below normal in eastern South America, western North America, northern Africa, most of South Asia, southwestern China, eastern and northern Russia, with no precipitation in parts of above regions.

3. General Circulation Features

Northern Hemisphere: In February, the mean 500hPa geopotential height field exhibited a 4-wave pattern at the mid-high latitudes, and two low-value centers were located in near Sakhalin and Newfoundland, respectively. In the geopotential height anomaly field, positive anomalies covered the high-latitude regions north of 60°N , with maximum above 28 dam in the vicinity of Baffin Island. Meanwhile, negative departures covered the regions between 40° N -60°N except for the Ural mountains. Three significant negative anomaly centers were located in the central-western North Atlantic, central-eastern North Pacific, Novosibirsk, with minimums were -16 dam, -8 dam and -8 dam respectively. For the month, the area indices of the northern hemisphere polar vortex and the Northwest Pacific subtropical high (NPSH) were larger than normal. Meantime, the Northwest Pacific subtropical high further extended westward.

Southern Hemisphere: For the month, in the 500hPa geopotential height field, mid-high latitudes atmospheric circulation patterns showed 4-wave structure. In the anomaly field, positive anomalies covered the regions south of 60°S. Meanwhile, two significant negative anomaly centers were located in the South Pacific (140°W -180°, 40° S -60°S) and the South Atlantic Ocean (20°E-80°W，40° -60°S), with the negative center value of -12 dam and -8 dam, respectively.

4. Tropical Features

Sea Surface Temperatures (SSTs): During February 2010, SSTs were more than 0.5℃ above normal in most the central and eastern equatorial Pacific. The positive anomaly center was located in the central equatorial Pacific, with maximum above 1.5℃. Indices of NINO 1+2, NINO 3, NINO 4, NINO 3.4 and NINO Z were 0.1℃, 0.8℃, 1.1℃, 1.3℃ and 0.8℃, with drops of 0.2℃, 0.2℃, 0.3℃, 0.3℃ and 0.3℃ from last month, respectively.

Subsurface Temperatures: During February 2010, anomalously warm subsurface water dominated the central and eastern equatorial Pacific, with the positive centre near 145^oW. Meanwhile, anomalously cold subsurface water controlled the equatorial Pacific west of the date line, with minimum below -2℃.

Warm Pools: During Feb 2010, 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), westerly anomalies covered the equatorial Pacific east of 140ºE, and easterly anomalies prevailed to the west of 140^oE. At upper troposphere (200hPa), westerly anomalies covered the equatorial Pacific west of 180^o, and easterly anomalies in the east of 180^o.

Southern Oscillation: For the month, the Southern Oscillation Index (SOI) was -1.2, with a decrease of 0.4 from last month.

Convections over the Tropics: During February 2010, the anomalous Outgoing Longwave Radiation (OLR) showed that enhanced convection was present over the equatorial Pacific near the Date Line and the eastern equatorial Pacific, whereas suppressed convection covered the western equatorial Pacific and Maritime continent. Convection was near normal over the rest equatorial ocean. In the lower troposphere (850hPa) divergent wind field, a convergent center over the tropical Pacific was at 170ºW, 10ºS, and a divergent center was near 90ºW, 20^oS. At the upper troposphere (200hPa), the corresponding divergent and convergent centers were near 170ºW, 5ºS and 95ºW, 20ºS, respectively.

5. ENSO Monitoring and Outlook

Monitoring showed that during February 2010, SST anomalies were more than 0.5℃ in most of the central and eastern equatorial Pacific. But compared with last month, all NINO indices decreased evidently. Most statistical and dynamic climate models predicted that SSTA over the central and eastern equatorial Pacific would weaken continuously in the future 2-3 months.

Aforementioned analysis indicates that warm condition over the central equatorial Pacific would continue in the future 1-2 months, but positive SSTA over the central and eastern Pacific would decrease persistently. Therefore, we will still closely monitor the developments of ENSO conditions and update our ENSO wrap-up in time.