Highlights

General Circulation Features

Northern Hemisphere

During March, the mean 500hPa geopotential height field exhibited a 3-wave pattern at mid-high latitudes. Negative anomalies controlled northern North America and northern Asia, with center values below -12 dam over the islands of northern Canada. Meanwhile, positive anomalies above 4 dam controlled the regions from the mid-north Pacific to the east shore of North America, northern Africa to the Qing-zang Plateau and the west shore of Europe to the region east to Greenland, with the most 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 dominated the mid-high latitudes at the mean 500hPa geopotential height field. Positive anomalies greater than 4 dam were over the southern Atlantic and the polar region. Meanwhile, negative anomalies controlled the regions over the ocean south to southern Africa, South America and New Zealand.

Climate for China

During March, the mean surface air temperatures were above normal in much of China, with positive anomalies above 2℃ in southern Xinjiang, the Qing-zang Plateau, western Yunnan, most of North China, Shanxi and Hubei. In this month, most China received less than normal rainfall totals. Rainfall totals of 50-90% less than normal were observed in most North China, mid-south Northeast China, much of the Qing-zang Plateau, the mid-lower region of the Yangze River, most Yunnan, Hainan and part of Gongdong. Above 50% more than normal rainfall totals were received in eastern and northern Northeast China, most Xinjiang, southeastern Tibet and Sichuan Basin.

Tropical Features

Sea Surface Temperatures(SSTs)

During March, positive SST anomalies above 0.5℃ controlled the western equatorial Pacific. Sea surface temperatures were near normal in the central and eastern equatorial Pacific except negative SST anomalies below –1.0℃ were observed in offshore of Peru. Correspondingly, the SST indices of NINO 4, NINO 3 and NINO 1+2 regions were 0.3℃, 0.1℃ and –0.7℃, respectively. In addition, normal conditions were observed in the equatorial Indian Ocean.

Circulation

Wind Field

In this month, at the lower troposphere (850hPa), weak westerly anomalies controlled most of the equatorial Pacific and the Indian Ocean. Easterly anomalies controlled the regions round the date line. At the upper troposphere (200hPa), westerly anomalies above 4m/s were over the central and eastern equatorial Pacific. Over the western equatorial Pacific, the zonal winds were normal. Weak westerly anomalies were observed over much of the equatorial Indian Ocean.

Southern Oscillation

During March, the Southern Oscillation Index was -0.3.

Convection over the Tropics

During March, the anomalous outgoing longwave radiation (OLR) distribution exhibited that enhanced convections were over the western equatorial Pacific while convections were suppressed over the region east to the date line. In the lower troposphere (850hPa) divergent wind field, the convergent center was over 150°E, 7°S, and the divergent center was around 100°W, 12°S. Correspondingly, the divergent and the convergent centers at the upper troposphere (200hPa) were over 160°E, 7°S and around 98°W, 4°S, respectively.