Monthly Highlights

Climate in China

During January, the monthly mean surface air temperatures were observed 1-2℃below normal in most of the regions south to the Yangtze River, northern Xinjiang and western Inner Mongolia. Temperatures were observed near or above normal in the other regions. In northern Northeast China and the mid-eastern Qing-Zang Plateau, temperatures were found 2-4℃ above normal. For the month, precipitations were found more than average in the regions from eastern Southwest China eastward to Jiangnan, mid-eastern and southwestern Tibet, central Northeast China, and local regions of Xinjiang, with 100% more than average in local regions. Meanwhile, precipitations were observed less than average in the other regions, with 50-100% below average in southern South China, mid-eastern Northwest China, southern North China and most of Inner Mongolia.

Climate in the World

During January, the monthly mean surface air temperatures were observed 1-3℃ below normal in northern West Africa, the coasts of the Mediterranean Sea, western South Asia, central Asia and most of the regions south to the Yangtze River in China. Meanwhile temperatures were observed near or above normal in the other regions, with 2~6℃ above normal in most of the south half of USA, northern Europe-Asia continent, eastern Qing-Zang Plateau and Alaska, and even more than 8℃ above normal in local regions.

For the month, precipitations were observed more than 50% above average in the regions from southwestern USA eastward to northeast, northern Venezuela, central Argentina, North Europe, northern Central Asia，northern Mongolia, northern Pakistan, central India and the regions from southern Qing-Zang Plateau southward to Bay of Bengal, and even two times more than average in local regions. Precipitations were found 50-100% less than average in western Europe, most of Turkey, the regions from southern Pakistan to northwestern India, most of northern China and southern South China, southern East Siberia, the coasts of northern West Africa and local regions of south, mid-western and southeastern Australia, southeastern and northwestern USA and northern Argentina.

General Circulation Features

Northern Hemisphere: During January，the mean 500hPa geopotential height field exhibited a 3-wave pattern at the mid-high latitudes. An abnormal ridge developed over the northeastern North Pacific. In the height anomaly field, the areas from northeastern Canada to western Europe were covered by negative anomalies. Meanwhile, most of the other regions in the mid-high latitudes were dominated by positive anomalies, with the central values above 16 dam over the northern North Pacific. The Northwest Pacific subtropical high was larger than normal and extended remarkably westward.

Southern Hemisphere: For the month, the mean 500hPa geopotential height field showed a 4-wave pattern at the mid-high latitudes. Positive anomalies above 4 dam covered the southeastern South Atlantic and the region from the southwestern South Pacific to Antarctic. Meanwhile, heights in the other regions were observed near or below normal, with central values below -12 dam over the southern South Pacific.

Tropical Features

Sea Surface Temperatures (SSTs): During January, above 0.5℃ SST anomalies dominated the central and western equatorial Pacific, with central values above 1.5℃ around the dateline. SSTs were observed near-normal in the eastern equatorial Pacific. SST anomalies in the eastern equatorial Pacific decreased remarkably compared with last month. Weak negative SST anomalies controlled the offshore of South America. Near-normal SSTs were observed in the equatorial Indian Ocean. Correspondingly, the SST indices of NINO 4, NINO 3, NINO 1+2 and NINO Z were 1.1℃, 0.3℃, -0.1℃and 0.6℃, respectively. The SST indices of NINO 3 decreased from 0.7℃ to 0.3℃.

Subsurface Temperatures: During January, the abnormally warm water weakened in the central equatorial Pacific.

Warm Pools: During January, the areas of the western equatorial Pacific warm pool and the equatorial Indian Ocean warm pool were found larger than normal, and the intensities were stronger than normal.

Wind Field: During January, at the lower troposphere (850hPa), westerly anomalies controlled most of the equatorial Indian Ocean and the equatorial Pacific with central values above 4m/s except that weak easterly anomalies maintained near the dateline. At the upper troposphere (200hPa), easterly anomalies above 4m/s covered most of the eastern equatorial Pacific while the near-normal zonal winds controlled the central and western equatorial Pacific. Westerly anomalies above 4m/s controlled the equatorial Indian Ocean.

Southern Oscillation: During January, the Southern Oscillation Index (SOI) was 0.3 which increased 0.8 compared with last month.

Convection over the Tropics: For the month, the anomalous outgoing longwave radiation (OLR) distribution exhibited that active convections were observed between 130ºE and 170ºE over the western equatorial Pacific and convections were suppressed from western Indonesia to most of Australia. In the lower troposphere (850hPa) divergent wind field, the convergent center was found near 145°E, 9°S and no obvious divergent center was observed over the tropical Pacific. Correspondingly, at the upper troposphere (200hPa), the divergent center was found near 145°E, 5°S and no obvious convergent center was observed over the tropical Pacific.

ENSO Monitoring and Forecasting

a) During January, above 0.5℃ SST anomalies dominated the central and western equatorial Pacific. SSTs were observed near-normal in the eastern equatorial Pacific. SST anomalies in the eastern equatorial Pacific decreased remarkably compared with last month. the SST indices of NINO 4, NINO 3, NINO 1+2 and NINO Z were 1.1℃, 0.3℃, -0.1℃and 0.6℃, respectively. The SST indices of NINO 3 decreased from 0.7℃ to 0.3℃.

b) During January, the abnormally warm water weakened in the central equatorial Pacific.

c) The Southern Oscillation Index (SOI) was 0.3 which increased 0.8 compared with last month.

d) At the lower troposphere (850hPa), westerly anomalies kept controlling most of the equatorial Pacific.

Recent oceanic and atmospheric status of the tropical Pacific showed that El Nino conditions sustained but weakened. The evolution of this activity will continue to be monitored.