Highlights
General Circulation Features
Northern Hemisphere
During March, the mean 500hPa geopotential height field exhibited a 4-wave pattern in the mid-high latitudes. The trough over northern Europe and the trough over North America were stronger than normal. In the height anomaly field, 4~12 dam positive anomalies were over the Barents Sea, the Baikal Lake and the Bering Sea. The other regions were mostly covered by negative anomalies, with minimum center value below –16 dam over the northern Kara Sea. The Northwest Pacific subtropical high was obviously stronger than normal and its area was obviously larger than normal and its position slightly shifted southward.
Southern Hemisphere
During March, in the mean 500hPa geopotential height fields，zonal circulation prevailed over the mid-high latitudes. In the height anomaly field, negative anomalies were over the southern South Atlantic and the southern South Pacific. Meanwhile, positive anomalies of 4~8 dam or near normal heights covered the other regions.
In March, monthly mean surface air temperatures were generally above normal in China. In northern Northeast China, temperatures were 2~6℃ above normal. During March, precipitation totals of 50~100% more than normal were observed in most of northwestern China and North China and the regions between the Yellow River and the Yangtze River. Monthly precipitation totals were 50~90% less than normal in most of Southwest China and northern Northeast China.
Sea Surface Temperatures (SSTs)
During March, positive SST anomalies across the central equatorial Pacific decreased obviously. The maximum center value reduced to 1.0~1.5℃, which was 1.5~2.0℃ in Feb. Meanwhile, the area with negative SST anomalies expanded over the eastern equatorial Pacific. The SST indices of NINO 4, NINO 3 and NINO 1+2 were 0.9℃, 0.2℃ and –0.6℃, respectively. In addition, positive SST anomalies above 0.5℃ were observed in most of the equatorial Indian Ocean.
Circulation
Wind Field
In this month, at the lower troposphere (850hPa), the region of weak easterly anomalies expanded westward over the western equatorial Pacific while westerly anomalies remained over the eastern equatorial Pacific. At the upper troposphere (200hPa), weak westerly anomalies of 2 m/s observed over the eastern equatorial Pacific to the dateline. Meanwhile, zonal wind was near normal over the region from the western equatorial Pacific to the equatorial Indian Ocean.
Southern Oscillation
The Southern Oscillation Index (SOI) was –0.3.
Convection over the Tropics
During March, the anomalous outgoing longwave radiation (OLR) distribution displayed that enhanced convection center was nearby the dateline over the equatorial Pacific but it was weaker than that in last month. Suppressed convection was over the western equatorial Pacific. In the lower troposphere (850hPa) divergent wind field over the tropical Pacific, the convergent center was around 140°E，5°S, while the divergent center was around 95°W，10°S. Correspondingly, at 200hPa, the divergent center was over 145°E，5°N, while the convergent center was around 100°W，5°S.