Monthly Highlights

Climate in China

During January 2010, the monthly mean surface air temperature over China was 1.4℃ above normal. The anomalies of air temperatures were 1~4℃ above normal in western North China, most Northwest China, most Southwest China, Jiangnan, South China and northwestern Heilongjiang, with over 4℃ above normal in locations. Meanwhile, air temperatures were observed 1~2℃ below normal in northern North China, eastern Inner Mongolia and southern Liaoning, with at least 2℃ below in normal in locations.

During January 2010, the precipitations were observed 30~200% more than normal in northern North China, southeastern Inner Mongolia，western Liaoning， central Heilongjiang, northern Xinjiang, most South China, with precipitations at least 200% more than normal in locations. Meanwhile precipitations were observed 30~80% less than normal in southwestern North China, Huanghuai, southern and eastern Northwest China, most Southwest China, Jianghan, Jianghuai, with precipitation at least 80% less than normal in southwestern North China, Huanghuai, eastern Northwest China, southern Xinjiang and southern Southwest China.

During January 2010, most China experienced severe cold wave conditions. Daily minimum temperatures in 85 stations surpassed the 95th percentile thresholds in Inner Mongolia, Heilongjiang, Jilin, Hebei, Xijiang, Beijing and Tianjin, including record minimum temperatures in 26 stations. Totally 35 stations in Heilongjiang, Inner Mongolia, Hebei, Gansu, Ningxia and Xinjiang reported exceptionally temperature drops, with 5 record drops. In January, precipitation persisted in many locations of Northern Xinjiang, central Inner Mongolia and eastern Shandong provinces, the number of consecutive precipitation days in 21 stations exceeded the 95th percentile thresholds and 10 broke records.

Climate in the World

During January 2010, temperatures were 1~4℃ above normal in central and southern East Asia, eastern Russia, southern Central Asia, West Asia, central and northern Africa, northern North America, parts of South America, with temperatures at least 4℃ above normal in Xinjiang China, locations of West Asia, locations of northern North America. Meanwhile, temperatures were 1~4℃ below normal in the large regions from Europe to northern North China via central and western Russia and  Mongolia, southeastern North America and Alaska, northeastern Australia, with temperatures 4~10℃ below normal in regions from northeastern Europe to western Mongolia.

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

General Circulation Features

Northern Hemisphere: During January 2010, the mean 500hPa geopotential height field exhibited a 3-wave pattern at the mid-high latitudes. In the 500hPa geopotential height anomaly field, positive anomalies above 4 dam covered regions from northern North America to West Siberia via the northern North Atlantic Ocean, regions from 20-40ºN in Asia, parts of North Africa, with central values above 16 dam over northwestern North America and Greenland island, Novaya Zemlya. Meanwhile, negative anomalies below -4 dam covered regions from the northeastern North Pacific, the central North Atlantic Ocean, southwestern Europe, with central values below -16 dam in the northeastern North Pacific. For the month, the area of the Northwest Pacific subtropical high (NWPSH) was larger and its intensity was strong. It was located in north of normal position and its west end contracted further west than normal.

Southern Hemisphere: For the month, in the 500hPa geopotential height anomaly field, positive anomalies above 4 dam covered the regions from the southern South Pacific to the southern South Indian Ocean via Antarctica, with central values above 12 dam. Meanwhile, negative anomalies below -4 dam covered the seas south to the Australia and South America.

Tropical Features

Sea Surface Temperatures (SSTs): During January 2010, SSTs were more than 0.5℃ above normal in the central and eastern equatorial Pacific with central value above 2.5℃. Indices of NINO 1+2, NINO 3, NINO 4, NINO 3.4 and NINO Z were 0.3℃, 1.0℃, 1.4℃, 1.6℃ and 1.1℃, with no variation for NINO1+2 and NINO4, and with drops of 0.6℃, 0.2℃ and 0.3℃for NINO 3, NINO 4 and NINOZ from last month, respectively.

Subsurface Temperatures: During January 2010, anomalously warm subsurface water dominated the central and eastern equatorial Pacific, with decreased strength from last month. Meanwhile, anomalously cold subsurface water controlled the equatorial Pacific west of 160ºE with negative central value below -2℃. Anomalously cold subsurface water further shifted eastward from last month.

Warm Pools: During January 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 160ºE, and easterly anomalies prevailed to the west of 160oE. At upper troposphere (200hPa), easterly anomalies covered the equatorial Pacific.

Southern Oscillation: For the month, the Southern Oscillation Index (SOI) was -0.8, with a decrease of 0.3 from last month.

Convections over the Tropics: During January 2010, the anomalous Outgoing Longwave Radiation (OLR) showed that enhanced convection was present over the equatorial Pacific near the Date Line, suppressed convection covered eastern tropical Indian Ocean, and 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 140ºE, 10ºS, and a divergent center was near the equator 80ºW. At the upper troposphere (200hPa), the corresponding divergent and convergent centers were near 170ºE, 5ºS and 80ºW, 30ºS, respectively.

ENSO Monitoring and Outlook

Monitoring showed that during January 2010, SSTs were more than 0.5℃ above normal with central value above 2.5℃ in the central and eastern equatorial Pacific. Compared with last month, both SSTA and subsurface temperature anomaly in the eastern equatorial Pacific decreased evidently. Most statistical and dynamic climate models predicted that SSTA over the central and eastern equatorial Pacific would weaken persistently.

Aforementioned analysis indicates that SSTA over the central and eastern equatorial Pacific would weaken persistently within future two months, with SSTs over the eastern equatorial Pacific going back to the neutral condition, and those over the central equatorial Pacific continuing the warm condition. Therefore, we will still closely monitor the developments of ENSO conditions and update our ENSO wrap-up in time.