1. Climate in China
In January 2014, the surface air temperature averaged over China was -3.4ºC, which was 1.6ºC above normal (-5.0ºC) and ranked the 2nd highest since 1961. And the mean temperature over North China also ranked the 2nd highest since 1961. The mean precipitation over China was 6.2 mm, which was 53.0% less than normal (13.2mm), being the minimum since 1987. And it was only 3.7 mm over South China, being 91.6% less than normal (44.3 mm) and ranking the minimum since 1951.In the month, extremes of Daily Minimum Temperature (DMT), Daily Temperature Drop (DTD), and Consecutive Non-Precipitation Days (CNPD) were observed in China.
2. General Circulation Features
Northern Hemisphere: During January 2014, in the field of mean 500hPageopotential height anomaly, negative anomalies below -4 dam covered northern Eurasia, eastern North America, and eastern North Atlantic Ocean. Meanwhile, positive anomalies above 4 dam covered polar region, western North America, and central North Atlantic Ocean. 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 shifted further eastward and northward than normal.
Southern Hemisphere: For the month, in the field of mean 500hPageopotential height anomaly, positive anomalies over 4 dam were observed over eastern South Pacific, Southwest Indian Ocean. Meanwhile, negative anomalies below -4 dam were observed over western South Pacific, Southeast Indian Ocean, and the mid-high latitudes of South Atlantic Ocean.
3. Tropical Features
Sea Surface Temperatures (SSTs): During January 2014, SSTs were about 0.5℃ above normal over the western equatorial Pacific, about 0.5℃ below normal over most central-eastern equatorial Pacific, and slightly above normal over the southeastern part of the eastern equatorial Pacific off the west coast of South America. Niño1+2, Niño3, Niño4, Niño3.4 and NiñoZ indices were 0.3℃, -0.4℃, -0.2℃, -0.5℃ and -0.2℃, respectively. SSTs were slightly below normal over the northern tropical Indian Ocean, and over 0.5℃ above normal over most southern subtropical Indian Ocean. The Indian Ocean basin-wide index (IOBW) was 0℃. SSTs were near normal over the tropical Atlantic Ocean.
Subsurface Temperatures: During January 2014, anomalously warm subsurface water dominated in the western equatorial Pacific, with the central value above 4℃ near 165ºE. Meanwhile, anomalously cold subsurface water controlled most central-eastern equatorial Pacific, with the central value below -3℃ in the central Pacific near 145ºW. A shallow layer of anomalously warm subsurface water covered the eastern part of the eastern equatorial Pacific about 50 m, with the central value above 1℃.
Warm Pools: For the month, the area of both Indian Ocean and western Pacific warm pools was slightly larger than normal, with the intensity of the Indian Ocean warm pool slightly above normal and that of the western Pacific warm pool significantly above normal.
Wind Field: For the month, at lower troposphere (850hPa), anomalous westerly winds covered the equatorial Indian Ocean, most western equatorial Pacific, and the eastern equatorial Pacific, with the central value over 6 m/s in the western equatorial Pacific. The central equatorial Pacific to the east of dateline was controlled by weak anomalous easterly winds. At upper troposphere (200hPa), westerly wind anomaliesdominated over the equatorial Indian Ocean and eastern equatorial Pacific, with the central value over 12 m/s in the eastern equatorial Pacific. Weak easterly anomalies controlled the central and western equatorial Pacific.
Southern Oscillation: For the month, the Southern Oscillation Index (SOI) was 1.2.
Convections over the Tropics:During January 2014, the anomalous outgoing longwave radiation (OLR) showed that convection was active over the western equatorial Pacific, with the central value below -30W/m2. However, inactive convection controlled the eastern tropical Indian Ocean and the central equatorial Pacific around 150ºW-180º. Convection was near normal over most tropical Atlantic Ocean, except for enhanced convection over the northern tropical Atlantic Ocean.
4. ENSO Monitoring and Outlook
At present, ENSO-neutral with slightly cold condition continues. However, the negative anomaly of the subsurface Pacific heat content has weakened substantially since late January 2014. Furthermore, westerly wind anomalies at 850 hPa level have dominated in the central-eastern equatorial Pacific since early February 2014, which will likely warm the SST of the Niño regions in the coming month.
According to the multiple timescale variations of the recent air-sea conditions in the tropical Pacific, and the consensus forecast from dynamical and statistical models, ENSO-neutral is expected to continue through the next 3 months, with slightly cold and warm conditions in the earlier and later periods, respectively.
Therefore, we will closely monitor the development of ENSO conditions and update our ENSO wrap-up in time.