Monthly Highlights

1. Climate in China

During March 2012, the surface air temperature averaged over China was 3.5℃, which was 0.3℃ lower than normal (3.8℃), but 1.0℃ higher than last year (2.5℃). While monthly mean surface air temperatures were 1~3℃ above normal in northern Xinjiang, temperatures were near or below normal in most China, with 1-2℃ less than normal in central and eastern Inner Mongolia, most Northeast China, eastern North China, eastern Huanghuai, western Xinjiang, central and southern Hubei, central and northern Hunan, northeastern Guizhou, with temperature at least 2℃ below normal in locations.

In March, average precipitation over China was 31.4 mm, which was 9.0% more than normal (28.9 mm), and 54.4% more than last year (20.4mm). Precipitations were observed 50%-100% more than normal in southwestern Xinjiang, southern and eastern Qinghai, parts of eastern Tibet, central and eastern Inner Mongolia, most Northeast China, central and eastern Jiangnan, Jiangsu, northern Anhui, western and northern Sichuan, with precipitations at least 100% more than normal in locations. Meanwhile precipitations were observed 30%-50% less than normal in central and eastern Xinjiang, western Tibet, northern Qinghai, Gansu，western Inner Mongolia, northern Inner Mongolia and the northern part of Northeast China, southern Guizhou, southern Yunnan, central and eastern South China, with precipitations at least 80% less than normal in locations.

During March, extremes of Daily Temperature Drop (DTD)， Consecutive No Measurable Precipitation Days (CNMPD) , Consecutive Measurable Precipitation Days (CMPD) were observed in China. DTD extremes occurred in 78 stations, which were located in Heilongjiang, Inner-Mongolia, Jilin, Gansu, Yunnan, Sichuan, Guizhou, etc., with widespread DTDs of 10-19℃ and new records in 23 stations, such as Zhalaiteqi (17.0℃),etc.. Meanwhile, CNMPDs occurred in 78 stations in Hebei, Inner-Mongolia, Southeast China,etc., reached or broke the extreme thresholds, with CNMPDs of 46-209 days and new records in 11 stations, i.e. Wuhouqi (129 days), guying (87 days), Bazhou (108 days), Fucheng (102 days), Batang (146 days) and Yajiang (131 days), etc. CMPD occurred in 15 stations in Zhejiang, Anhui, Hunan and Jiangxi, etc., with CMPD breaking records in Dongtou ( 18 days ).

2. World Climate

During March 2012, temperature in most places of the world was colder than normal. Temperatures were 1-4℃ below normal in most mid-eastern Europe, most Siberia, Northeast China, Central Asia, northwestern North America, most South America, northern Africa, most Australia, with temperatures at least 4℃ below normal in central Siberia. Meanwhile, temperatures were 1-8℃ above normal in North Europe, West Europe, and most America, with temperatures at least 8℃ above normal in central America.

For the month, precipitations were at least 50-100% more than normal in eastern Europe, west Siberia, partly east Siberia, Central Asia, northeast China, partly eastern China, southern Southeast Asia, most Australia, mid-western Canada, central and eastern America, locations of South America and Africa, with precipitations at least 200% less normal in parts of above regions. Meanwhile, precipitations were observed 50-100% less than normal in western and southern Europe, central and eastern Siberia, Mongolia, central and western China, central and northern Southeast Asia, most South Asia, western America and its eastern parts, southern South America and its northwestern parts, central Australia and West Africa, with no precipitations in parts of above regions.

3. General Circulation Features

Northern Hemisphere: During March 2012, the field of mean 500hPa geopotential height exhibited a four-wave pattern over mid-high latitudes. In the field of height anomaly, positive anomalies above 4 dam covered regions over western Europe, central Russia, central North Pacific and eastern North America, with central values above 20 dam over western Europe. Meanwhile, negative anomalies below -4 dam covered regions to the west of Ural and regions from eastern Russia to western North America, with central values below -16 dam over the locations to the west of Ural. During the month, the northwestern Pacific subtropical high was not observed.

Southern Hemisphere: For the month, zonal circulation dominated over mid-high latitudes at the mean 500hPa geopotential height. In the field of height anomaly, negative anomalies below -4 dam covered most of the polar region and the Weddell Sea, with central values below -8 dam over the Weddell Sea. Meanwhile, positive anomalies mainly covered most areas between 40^°S and 60^°S, with central values above 4 dam over the southwestern South Atlantic Ocean and part of southern South Pacific Ocean.

4. Tropical Features

Sea Surface Temperatures (SSTs): In March 2012, negative SST anomalies were between -0.5℃ and -1.0℃ in most areas between 160°E and 130°W of the equatorial Pacific, and SSTs were near or above normal in the rest equatorial Pacific. NINO1+2 and NINO 3 indices were 0.2℃ and -0.2℃, the same as last month. Nino4, NINO 3.4 and NINO Z indices were -0.6℃, -0.5℃ and -0.3℃, with rises of 0.3℃, 0.2℃ and 0.2℃ from last month, respectively. Meanwhile, SSTs were close to or below normal in the equatorial Indian Ocean.

Subsurface Temperatures: During March, anomalously cold subsurface water in the equatorial central Pacific weakened while the anomalously warm subsurface water in equatorial western Pacific maintained.

Warm Pools: During March, areas of the Indian Ocean warm pool and the western Pacific warm pool were both near normal. The warm pool intensity was below normal in the Indian Ocean and above normal in the western Pacific.

Wind Field: During March, at lower troposphere (850hPa), easterly anomalies dominated over the central equatorial Pacific while westerly anomalies enhanced in the western equatorial Pacific. At upper troposphere (200hPa), westerly anomalies enhanced over most of the equatorial Pacific.

Southern Oscillation: For the month, the Southern Oscillation Index (SOI) was 0.3, same as last month.

Convections over the Tropics: During March, the anomalous outgoing long-wave radiation (OLR) showed that enhanced convection was over sea regions from the South China Sea to northern Australia. Meanwhile, suppressed convection was near the date line.

In the divergent wind field at lower troposphere (850hPa), a convergent center was around 140°E, 5ºS and a divergent center was around 0º，12.5ºS. At upper troposphere (200hPa), the corresponding divergent and convergent centers were near 140ºE，5ºS and 0º，10ºS, respectively.

5. ENSO monitoring and outlook

Recent monitoring showed that the very weak La Niña event ended in March 2012 with the duration of 6 months.

Based on models’ prediction and diagnoses of the oceanic and atmospheric variations, the ENSO-neutral conditions are expected to persist through the coming summer, and the occurrence or not of El Nino conditions depends on development of the westerly anomaly in the equatorial western Pacific in following several months.