1. Climate in China
In March 2015, the surface air temperature averaged over China was 5.8ºC, with 1.7ºC above normal (4.1ºC), ranking the 4th highest since 1961. The mean precipitation was 21.8 mm over China, which was 26.1% less than normal （29.5mm). For the month, extremes of Daily Temperature Drop (DTD) and Consecutive Temperature Drop (CTD) were observed in China.
2. General Circulation Features
Northern Hemisphere: During March 2015, in the field of mean 500hPa geopotential height anomaly, negative anomalies below -4 dam covered the region from northern Russia to its nearby Arctic Ocean, the central northern North Pacific and the region from northeastern North America to the northwestern North Atlantic, with central values below -16 dam over the northwestern North Atlantic. Meanwhile, positive anomalies above 4 dam covered the region from southeastern Russia to the northwestern North Pacific, northern North America and the region from the northeastern North Atlantic to Eastern Europe, with central values above 12 dam over parts of Europe. During the month, the northwestern Pacific subtropical high was weaker than normal, with the area smaller than normal. The position of the northwestern Pacific subtropical high extended further westward and shifted northward than normal.
Southern Hemisphere: For the month, in the field of mean 500hPa geopotential height anomaly, negative anomalies below -4 dam were observed over parts of the South Atlantic, the ocean south of Australia and parts of the southeastern and central South Pacific, with central values below -8 dam over parts of the ocean south of Australia. Meanwhile, positive anomalies over 4 dam covered the central southern South Pacific, parts of the South Indian Ocean and locations of the Southwest Atlantic, with central values over 12 dam over parts of the South Pacific.
3. Tropical Features
Sea Surface Temperatures (SSTs): In March 2015, SSTs were over 0.5℃ above normal in most of the central equatorial Pacific, with SSTs 1.5℃ above normal near the Dateline. Indices of Niño1+2，Niño3，Niño4，Niño3.4 and Niño Z were 0.0℃，0.1℃，1.1℃，0.6℃ and 0.5℃, respectively. The Indian Ocean Basin-Wide SSTA variation index (IOBW) was 0.3. The North Atlantic Triple (NAT) index was 2.0, indicating the development of positive phase of North Atlantic tripole mode.
Subsurface Temperatures: In March, the center of the anomalously warm subsurface water was located in the equatorial central Pacific around 160°W with the central values above 5℃, and the anomalously warm subsurface water extended eastward.. Meanwhile, the anomalously cool subsurface water weaken in the far equatorial eastern Pacific, with the center around 90ºW in the equatorial eastern Pacific and central values below -1℃.
Warm Pools: For the month, the area of the Indian Ocean warm pool was near normal, but the intensity was below normal. The area of the western Pacific warm pool was larger than normal and the intensity was prominently above normal.
Wind Field: For the month, at lower troposphere (850hPa), the westerly anomalies dominated the most equatorial Pacific with the center around 160ºE. At upper troposphere (200hPa), the westerly anomalies prevailed over the equatorial Indian Ocean and the equatorial eastern Pacific, while the easterly anomalies controlled the equatorial central-western Pacific.
Southern Oscillation: For the month, the Southern Oscillation Index (SOI) was -0.7.
Convections over the Tropics: During March 2015, the anomalous outgoing longwave radiation (OLR) showed that convections were active around the region of the tropical central Pacific near the dateline, with central values below -30 W/m2. Meanwhile, convections were suppressed from the tropical eastern Indian Ocean to the Maritime Continent, and the region of tropical central Pacific east of the dateline around 160ºW, with central values above 15W/m2.
4. ENSO Monitoring and Outlook
Based on the diagnoses of predictors and predictions of dynamical and statistical models, the current El Nino event is expected to go through summer 2015.
Therefore, we will closely monitor the development of ENSO conditions and update our ENSO wrap-up in time.