Highlights

General Circulation Features

Northern Hemisphere

During January, the mean 500hPa geopotential height field exhibited a 4-wave pattern at mid-high latitudes. Troughs that located at Europe and east to Northern America were deeper than normal. Correspondingly, negative anomalies covered most of Europe and the regions from western North Atlantic to eastern North America, with center values below -12 dam. Meanwhile, positive departures above 4 dam controlled most Russia and Polar Region, with center values above 12 dam. In this month, both Northern Hemisphere subtropical high and Northwest Pacific subtropical high were stronger than normal.

Southern Hemisphere

In this month, a 3-wave pattern appeared in the mid-high latitudes at the mean 500hPa geopotential height field. Positive departures greater than 4 dam were found in the south-central Pacific, the southwestern Atlantic and the southeastern India Ocean. Meanwhile, negative anomalies covered the regions south to Australia and southwest to South America.

Climate for China

During January, the mean surface air temperatures were near or slightly above average in much of China, with positive departures above 2℃ in central Neimenggu, southwestern Heilongjiang and northwestern Jilin. In the last half of January, cold air activities influenced on the most of China, surface air temperatures were obviously lower than average in the some areas of Guizhou, Guangdong, Guangxi, Fujian and Hainan. In this month, rainfall totals were 50% below normal in eastern Neimenggu, southern Northeast China, eastern and southern North China, northern Ningxia and southern Shanxi. Rainfall totals of 50-100% more than normal were received in the regions such as most of Northwest China, central Neimenggu and most Tibet.

Tropical Features

Sea Surface Temperatures(SSTs)

During January, the positive SST anomalies above 0.5℃ were found in the central and western equatorial Pacific. Sea surface temperatures were near average in the eastern equatorial Pacific. Correspondingly, the SST indices of NINO 4, NINO 3 and NINO 1+2 regions were 0.7℃, 0.3℃ and 0℃, respectively. In addition, positive anomalies above 0.5℃ remained in the eastern equatorial India Ocean.

Circulation

Wind Field

In this month, at the lower troposphere (850hPa), westerly anomalies covered the central and eastern equatorial Pacific, with center values above 4m/s. Easterly anomalies controlled the regions between the equatorial India Ocean and western equatorial Pacific. At the upper troposphere (200hPa), easterly anomalies were found in the central and eastern equatorial Pacific and westerly anomalies above 8m/s were found in the regions from equatorial India Ocean to western equatorial Pacific.

Southern Oscillation

During January, the Southern Oscillation Index was -1.1.

Convection over the Tropics

During January, the anomalous outgoing longwave radiation (OLR) distribution exhibited that enhanced convections were over the central equatorial Pacific and suppressed convections were over the western equatorial Pacific. In the lower troposphere (850hPa) divergent wind field, the convergent center was over 140°E, 10°S, and the divergent center was around 105°W, 0°. Correspondingly, the divergent and the convergent centers at the upper troposphere (200hPa) were over 145°E, 10°S and around 105°W, 0°, respectively.