Monthly Highlights

1. Climate in China

In January 2011, monthly mean surface air temperature of China was -8.3℃, being 2.4℃ below normal (-5.9℃) and ranked the second low. The monthly mean surface air temperatures were more than 2℃ below normal in most of China, and were more than 6℃ below normal in the northern Xinjiang. Meanwhile, the monthly mean surface air temperatures were slightly higher than normal in the northwestern Heilongjiang, most of the Qinghai-Tibetan Plateau, the western Yunnan, and etc. The average monthly total precipitation over China was 8.2 mm, being 3.9 mm less than normal (12.1 mm). For the month, precipitations were more than 30% below normal over most of China, with more than 80% below normal in the southern Northeast China, the eastern North China, most of Huang-Huai areas, the southern Xinjiang, the western Qinghai, the central-southern Tibet, and etc. Meanwhile, precipitations were 50-200% above normal in part of the northeastern Heilongjiang, part of the eastern Inner Mongolia and the northern Xinjiang, the eastern Northwest and Southwest China, the southwestern Tibet, and etc., with more than 200% above normal in locations.

In January, daily minimum temperatures of 57 stations in Heilongjiang, Jilin, Shanxi, Henan, Shandong, Jiangsu, Zhejiang, Sichuan, Yunnan, Gansu, and Xinjiang reached the threshold of extreme low temperature, and new records were reported in Wudalianchi (-45.0℃), Nongan (-39.3℃), Hengqu (-14.5℃), Mulei (-32.1℃), Bayinbuluke (-49.6℃). The days of consecutive no measurable precipitation in 89 stations reached their extreme thresholds, which mainly located in North China and Huang-Huai areas. And new records of consecutive no measurable precipitation days were reported in 8 stations, which were Haiyang (104 days), Qufu (108 days), Xintai (107 days), Fengqiu (110 days), and etc. Till the end of January, the days of consecutive no measurable precipitation were 99 in Beijing, which ranked the second on record.

2. World Climate

During January 2011, the monthly mean surface air temperatures were observed higher than normal in most of Europe, the northern and part of the southern Asia, most of Africa, the southern Australia, the northwestern and part of northeastern North America, most of South America, and etc., with 4℃ above normal in the northern Asia and part of the northeastern North America. Meanwhile, the air temperatures were lower than normal in part of Eastern Europe, most of Asia, the northern Australia, the central-eastern North America, part of the eastern and northwestern South America, and etc., with more than 8℃ below normal in the northern Central Asia.

For the month, precipitation amounts were more than 50% below normal in the western and eastern Asia, the western and part of the northern Africa, part of the eastern and northwestern Australia, the southwestern and part of the northern North America, part of the central South America, and etc. Meanwhile, precipitation amounts were observed 50-200% above normal in the northeastern Europe, the northern Asia, part of the central Asia, part of the northwestern Indochina Peninsula, part of the southwestern Africa, part of the western and central-southern Australia, part of regions from the northwestern to central North America, the central-eastern and part of the northern South America, and etc., with more than 200% above normal in locations.

3. General Circulation Features

Northern Hemisphere: During January 2011, the Arctic Oscillation lied on the negative phase during most of the month. The field of mean 500hPa geopotential height exhibited a 3-wave pattern over the mid-high latitudes. The area and intensity of polar vortex over Asian area were both greater than normal. Meanwhile, the position of East Asia trough located more eastward than normal, and its intensity was greater than normal. There was no Northwest Pacific subtropical high system in the month. In the anomaly field of 500hPa geopotential height, positive anomalies dominated north of 50°N in the northern hemisphere. Positive anomalies above 4 dam covered the regions from the Siberia to the northern North Pacific, the Northeast Pacific, and the northern North Atlantic Ocean, with central values above 16 dam over the southern Greenland and West Siberia. Meanwhile, negative anomalies below -4 dam covered the regions over Northwest Pacific and central North Atlantic, with central values below -8 dam over Northwest Pacific.

Southern Hemisphere: In the anomaly field of 500hPa geopotential height, the negative anomalies below -4 dam mainly covered the Southeast Pacific Ocean Basin and the Antarctic-Pacific Ridge, with central values below -12 dam. Meanwhile, positive anomalies above 4 dam covered the Southeast Pacific Ocean Basin, South Indian Ocean, and South Atlantic Ocean, with central values above 16 dam over South Indian Ocean.

4. Tropical Features

Sea Surface Temperatures (SSTs): During January 2011, SSTs were at least 1.0℃ below normal in the central and eastern equatorial Pacific with minimum below -2.0℃. NINO 1+2, NINO 3, and NINO Z indices were -0.4℃, -1.3℃ and, -1.3℃, with increases of 1.0℃, 0.3℃, and 0.2℃ from last month, respectively. NINO 3.4 and NINO 4 indices were -1.6℃ and -1.5℃, both dropping 0.1℃. Meanwhile, SSTs were around 0.5℃ above normal in the equatorial western Pacific.

Subsurface Temperatures: During January 2011, anomalous cold subsurface water area and intensity almost kept unchanged, with central values below -6℃. Anomalous warm subsurface water enhanced slightly and extended eastward.

Warm Pools: During January 2011, the area and intensity of the Indian Ocean warm pool were above normal. The area of the western Pacific warm pool was slightly below normal, but its intensity was still above normal.

Wind Field：For the month, at lower troposphere (850hPa), easterly anomalies prevailed over most of the equatorial central and western Pacific. At upper troposphere (200hPa), westerly anomalies covered the equatorial Pacific east of the Dateline.

Southern Oscillation: For the month, the Southern Oscillation Index (SOI) was 1.9, dropping 0.7 from last month.

Convections over the Tropics: During January 2011, the anomalous Outgoing Longwave Radiation (OLR) showed that enhanced convection was observed in the South China Sea, while suppressed convection was observed from east part of the equatorial western Pacific to the area near the dateline. In the lower troposphere (850hPa) divergent wind field, a convergent center was around 140ºE, 15ºS, and a divergent center was near 90ºW, 10ºS. At the upper troposphere (200hPa), the corresponding divergent center was near 130ºE, 15ºS, and a convergent center was around 80ºW, 30ºS.

5. ENSO Monitoring and Outlook

Monitoring showed that during January 2011, negative SSTA weakened in the equatorial eastern Pacific and enhanced in the central Pacific. NINO Z index was -1.3℃, with up of 0.2℃. Since July 2010, SSTA continuously kept above -0.5℃ for seven months, while the sum of seven months SSTA was -9.1℃, which could be up to threshold of moderate La Niña event in the future.

SOI was 1.9 with high positive value. Anomalous cold subsurface water controlled most of the central and eastern equatorial Pacific. Anomalous warm subsurface water enhanced and extended eastward. The low-level enhanced easterly anomalies prevailed over most of the equatorial central and western Pacific. These observations suggested La Nina would still continue in the next few months. Furthermore, most statistical and dynamic climate models surveyed by NCC predicted that La Niña conditions lasted till the spring 2011.

La Nina conditions persisted for seven months. It is expected to last until spring 2011 and be ENSO-neutral condition during summer 2011. Therefore, we will closely monitor the development of ENSO conditions and update our ENSO wrap-up in time.