Monthly Highlights

1. Climate in China

In January 2012, China monthly mean surface air temperature was -7.2℃, 1.7℃ lower than normal (-5.5℃) and the 2nd lowest during recent 28 years, but 1.2℃ higher than last year. Monthly mean surface air temperatures were observed 1-2℃ above normal in central-northern Yunnan but near or below normal over the rest parts of China, with temperatures 2-3℃ lower than normal in most Xinjiang, eastern Inner Mongolia, central and northwestern Gansu, most Heilongjiang, central and northwestern Jilin, northwestern Liaoning, most Guizhou, Guangxi and central and western Guangdong and at least 3℃ below normal in parts of northern China.

For the month, the mean precipitation was 16.8 mm over China, and it was 30.1% more than normal (12.9 mm). Precipitations were 30%-100% more than normal in southern and the eastern Jiangnan area, South China, northern and southeastern Southwest China, most Xinjiang, eastern and southern Qinghai, central and southern Gansu and Ningxia and at least 100% above normal in central and eastern Xinjiang, eastern and southern Qinghai, parts of southern Gansu, northern Sichuan, eastern Tibet, most Fujian, northwestern Guangxi, northern Hainan. meanwhile, precipitations was 30%-80% less than normal in Northeast China, most North China, the Huanghuai area, the Jianghuai area, the Jianghan area, northern Xinjiang, most Inner Mongolia, northwestern Qinghai, western Gansu, central Tibet, northern Yunnan and at least 80% below normal in parts of above regions.

In January, extremes of Low Temperature (LT), Daily Temperature Drop (DTD), Consecutive Temperature Drop (CTD), Consecutive Rainy Day (CRD) and Consecutive No Measurable Precipitation Day (CNMPD) were observed in China. Daily minimum temperatures of 42 stations in Xinjiang, Xizang, Gansu, Shaanxi, Shanxi and Inner Mongolia reached the threshold of LT extremes, and new records were reported in Manzhouli (-44.9℃), Luntai (-25.6℃) and Gongga(-17.0℃). DTD extremes occurred in 17 stations, which were located in Xinjiang, Yunnan, Sichuan, etc., with widespread DTDs of 6-14℃ and new records in Luliang (11.0℃) and Shilin (11.0℃). CTDs ranged from 11℃ to 20℃in Xinjiang, Yunnan, Sichuan and Hebei. CTD extremes were observed in 14 stations and the record was broken in Yongren (14.5℃). Additionally, CRD extremes occurred in 14 stations of Xinjiang, Yunnan, Guizhou, Sichuan and Hunan, with CRD of 4-30 days and new records in Bijie (30 days), Qianxi (25 days), Huishui (20 days) and Gongxian (23 days). Meanwhile, CNMPDs in 80 stations of Heilongjiang, Jilin, Hebei, Jiangsu, Anhui, Hubei, Sichuan, etc., reached the extreme thresholds, with CNMPDs of 30-70 days and new records in Wuhouqi (97 days), Litang (79 days), Linkou (68 days), Ningan (65 days), Dongning (65 days) and Wangqing (65 days).

2. World Climate

During January 2012, temperatures were 1-4℃ above normal in west Europe, most northern Russia, the western Indo-China Peninsula, northeastern West Asia, most North America, southern South America, southern Africa, parts of Australia coastal areas, with temperatures at least 4℃ above normal in central-south Canada and parts of northern Russia. Meanwhile, temperatures were 1-4℃ below normal in southeastern Europe, southern Russia and the eastern Far East, most Asia, Alaska and parts of northwestern Canada, parts of northern South America, central West Africa and central Australia, with temperatures 4-8℃ below normal in Alaska and parts of Kazakhstan.

For the month, precipitations were observed 50-100% more than average in central-eastern Europe, part of eastern Siberia, most southern China, northern Southeast Asia, most South Asia, northern West Asia, western Canada, central and partly northern South America, parts of northwestern and northeastern Australia, with precipitations at least 200% above normal in parts of above regions. Meanwhile, precipitations were at least 50% less than average in most Siberia, southern West Asia, northern Central Asia, the western Indian Peninsula, most northern China, most America, parts of northwestern and southern South America, most Africa and central Australia, with no precipitations in parts of above regions.

3. General Circulation Features

Northern Hemisphere: During January 2012, the field of mean 500hPa geopotential height exhibited a four-wave pattern over -mid-high latitudes. In the field of height anomaly, positive anomalies above 4 dam covered regions from the northern North Atlantic Ocean to western Europe, regions from the Arctic polar area to northwestern Russia and Northeast Asia, as well as regions from the eastern North Pacific to western United States, with central values above 20 dam over the Arctic polar area. Meanwhile, negative anomalies below -4 dam covered eastern Europe, regions from central Mongolia to Central Asia, the western North Pacific, and regions from the northeastern North Pacific to northwestern North America, with central values below -8 dam over regions from the northeastern North Pacific to the northwestern North America. During the month, the area of the northwestern Pacific subtropical high was smaller than normal. Its intensity was weaker, and the west end of its ridge shifted further east.

Southern Hemisphere: For the month, zonal circulation dominated over mid-high latitudes of the mean 500hPa geopotential height. In the field of height anomaly, positive anomalies above 4 dam covered the regions from the southeastern South Pacific to the southwestern South Atlantic Ocean, and also the southeastern South Indian Ocean, with central values above 8 dam over the southeastern South Pacific Ocean. Meanwhile, negative anomalies below -4 dam covered the regions from the South Pole to the high latitude of the South Atlantic Ocean and the southwestern South Pacific, with central values below -12 dam over parts of the South Pole and parts of high latitudes of the South Atlantic Ocean.

4. Tropical Features

Sea Surface Temperatures (SSTs): During January 2012, SSTs were 0.5-1.0℃ below normal  across most the central and eastern equatorial Pacific, and the minimum SSTs was 1.5℃ below normal. NINO 4 index was -1.2℃, with a drop of 0.1℃ from last month. At the same time, NINO 3 index was -0.8℃, increased by 0.1℃ from last month. NINO 3.4 and NINO Z indices were -1.1℃and -1.0℃, virtually unchanged from the previous month.

Subsurface Temperatures: During January 2012, anomalously cold subsurface water weakened in the equatorial eastern Pacific, and strengthened in the equatorial central Pacific.

Warm Pools: During January 2012, the area of the Indian Ocean warm pool was larger than normal, while its intensity was slightly above normal. The area and intensity of the western Pacific warm pool was near normal.

Wind Field: For the month, at lower troposphere (850hPa), easterly anomalies dominated the central and western equatorial Pacific, and weak westerly anomalies appeared in the eastern region. At upper troposphere (200hPa), westerly anomalies were observed over the most equatorial Pacific.

Southern Oscillation: For the month, the Southern Oscillation Index (SOI) was 1.0, with a drop of 1.1 from last month.

Convections over the Tropics: During January, the anomalous outgoing long-wave radiation (OLR) showed that enhanced convection was observed over equatorial Indonesia. Meanwhile, suppressed convection was observed over the central equatorial Pacific.

At lower troposphere (850hPa) divergent wind field, the convergent center was around 135°E, 10°S. At upper troposphere (200hPa), the corresponding divergent center was near 135°E, 5°S.

5. ENSO monitoring and outlook

Recent monitoring results showed that the La Nina conditions had peaked during the period from December 2011 to January 2012. Based on model predictions and current monitoring of the ocean and atmosphere features, the La Nina conditions will start its decaying phase in February 2012 and is expected to transit to ENSO-neutral conditions in the late period of next spring.