Monthly Highlights
1. Climate in China
During March 2013, the surface air temperature averaged over China was 6.3℃, which was warmer than normal (4.1℃) by 2.2℃. Monthly mean surface air temperatures were 2-4℃ above normal in most of China, with 4-6℃ above normal in northern and eastern Xinjiang, most of Gansu, western Inner Mongolia, western Shaanxi, eastern Sichuan and western Guizhou. Meanwhile, negative anomalies were around 1-2℃ in northeastern Inner Mongolia, most of Northeast China and northwestern Tibet, with 4℃ below normal in locations .
For the month, the mean precipitation of China was 26.1 mm, which was 11.5% less than normal (29.5mm). Percentages of precipitation anomalies were observed 20-80% below normal in most of China, with 80-100% below normal in central and southern Xinjiang, northwestern Tibet, central and western Inner Mongolia, southeastern Northwest China, most of North China and northern Huanghuai. Meanwhile, precipitations were 20-50% above normal in eastern Inner Mongolia, most of Northeast China, the western Jiangnan area, central South China and parts of Southwest China, with precipitations 50% more than normal in locations.
In March, the extremes of Consecutive No Measurable Precipitation Day (CNMPD) were observed in China. Until the March 31, CNMPD extremes occurred in 13 stations, which were located in Yunnan, Sichuan, Inner Mongolia and Xinjiang provinces (District), with widespread of CNMPD from 19 to 120 days and new records observed in 5 stations.
2. Climate in the World
During March 2013, mean temperatures were 1-4℃ above normal in most Eurasia and parts of eastern Siberia south of 50ºN，most of West Africa, North Africa and South Africa, parts of southwestern and eastern North America, central northern and southeastern Australia, with temperatures 4-6℃ above normal in regions from northern Central Asia to northwestern East Asia, parts of eastern North America and at least 6℃ above normal in locations. Meanwhile, mean temperatures were 1-4℃ below normal in most Eurasia north of 50ºN, most South Asia, locations of southern West Asia, parts of northwestern and central southern North America, southern South America, with temperatures 4-8℃ below normal in regions from northeastern Europe to northwestern Siberia, locations of western South Asia, locations of central North America and at least 8℃ below normal in locations.
For the month, precipitations were 50%-200% above normal in eastern and southern Europe, parts of western, southern and eastern Siberia, most Central Asia, northern South Asia, locations of Southeast Asia, locations of western, eastern and southern Africa, locations of northwestern North America, parts of central northern and southeastern South America, locations of western and southern Australia, with precipitations at least 200% above normal in parts. Meanwhile, precipitations were at least 50% below normal in parts of northwestern Europe, parts of central northern Siberia, northern East Asia, most northern Africa and locations of southern Africa, parts of northeastern and southwestern North America, locations of western South America, parts of northern Australia, with no precipitation in parts.
3. General Circulation Features
Northern Hemisphere: During March 2013, 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 the Arctic, northern Africa, the mid-latitude regions in Asia and the northern North Pacific, with central values above 8 dam over parts of the northern North Pacific. Meanwhile, negative anomalies below -4 dam covered the regions from eastern North America to the Okhotsk Sea via the northern North Atlantic Ocean and northern Eurasia, with central values below -16 dam in the northeastern North Atlantic Ocean. During the month, the northwestern Pacific subtropical high was near normal.
Southern Hemisphere: For the month, the field of mean 500hPa geopotential height exhibited a three-wave pattern over mid-high latitudes. In the field of height anomaly, negative anomalies below -4 dam covered the Antarctic, the southern South Pacific near the Antarctic, higher latitudes of the southern South Indian Ocean, and the southwestern South Atlantic Ocean, with central values below -12 dam in parts of the southern South Pacific. Meanwhile, positive anomalies above 4 dam covered the southern South Indian Ocean, South Pacific between 40-50ºS, and the regions from the Drake Passage to the Antarctic Peninsula, with central values above 8 dam in the southern South Indian Ocean and the regions near the Antarctic Peninsula.
4. Tropical Features
Sea Surface Temperatures (SSTs): During March 2013, sea surface temperatures (SST) were near average across the most equatorial eastern and central Pacific. ENSO-neutral conditions continued but with slight negative SSTA ,which was obvious weakened, with the central values below -1.0℃. Niño 1+2, Niño 3, Niño 4, Niño 3.4 and Niño Z indices were -0.1℃, 0.1℃, -0.2℃, -0.2℃ and -0.1℃,with a drop of 0.1℃ for Niño 4 index from last month, but distinctly increasing for other Niño indices during March.
Subsurface Temperatures: During March 2013, anomalously warm subsurface water moved eastward and weakened slightly in the equatorial western Pacific, with central values above 2℃. Meanwhile, anomalously cold subsurface water distinctly weakened in the equatorial eastern and central Pacific, and positive temperature anomalies occurred in the subsurface of the partly eastern Pacific.
Warm Pools: During March 2013, areas of the Indian Ocean warm pool and the western Pacific warm pool were near normal, and their intensities were both above normal.
Wind Field: During March 2013, at lower troposphere (850hPa), the weak easterly wind anomalies covered the equatorial western Pacific, while weak westerly wind anomalies covered the equatorial eastern Pacific. At upper troposphere (200hPa), westerly wind anomalies controlled the equatorial central and eastern Pacific, and the winds were near normal in the equatorial western Pacific.
Southern Oscillation: For the month, the Southern Oscillation Index (SOI) was 1.2, with a rise of 1.4 from last month.
Convections over the Tropics: During March 2013, the anomalous outgoing long wave radiation (OLR) showed that convection was slightly active in the equatorial western Pacific and the tropical eastern Indian Ocean, and near normal over other regions of the equatorial Pacific.
At lower troposphere (850hPa) divergent wind field, a convergent center was around 150ºE, 10ºS, and no obvious divergent center. At upper troposphere (200hPa), a divergent center was near 170ºE, 10ºS, and no obvious convergent center.
5. ENSO Monitoring and Outlook
By combining the diagnoses of the short-term variation trend in the anomalously atmospheric and oceanic behaviors with the results of ENSO model forecasts, ENSO is most likely to turn gradually into warm and neutral conditions by the following summer.
Therefore, we will closely monitor the development of ENSO conditions and update our ENSO wrap-up in time.