Monthly Highlights

1. Climate in China

In June 2011, the monthly mean surface air temperature was 20.5℃, with 1.0℃ above normal (19.5℃) being the 2^nd highest since 1951. The temperatures were near and above normal in most China, with temperatures 1~2℃ above normal in most western Northwest and parts of mid-eastern Northwest, most North China, Inner Mongolia, parts of western Northeast, parts of eastern Southwest, locations of southern Jiangnan, and 2～4℃ above normal in most Inner Mongolia and locations of Xinjiang.  

For the month, average precipitation over China was 102.8 mm, with 5.9% more than normal (97.1 mm). Precipitations were at least 50% more than normal in parts of mid-western Northwest, mid-western Tibet and the middle and lower reaches of the Yangtze River, with precipitations at least 100% more than normal in parts. Meanwhile, precipitations were observed at least 20% less than normal in northeastern Northwest, southwestern North China, most Huanghuai, regions from parts of mid-eastern Inner Mongolia to parts of western Northeast, southwestern and parts of eastern Xinjiang, southern Jiangnan, parts of middle and southern Southwest, with precipitations 50~80% less than normal in parts and 80% less than normal in locations.

In June, daily maximum temperature extremes, daily rainfall amounts extremes, persistent rainfall amounts extremes and persistent rainy days extremes were mainly observed in China. Daily maximum temperature extremes occurred in 157 stations, which were mainly located in western Huanghe-Huaihe River valley, northeastern Inner Mongolia, Shannxi, Sichuan, Yunnan and Jiangsu. And daily maximum temperatures, being 37～45℃, broke historical records in 15 stations, being mainly in Sichuan and Henan. During the month, daily rainfall amounts extremes occurred in 53 stations of middle and lower reaches of the Yangtze River valley, Xinjiang and Qinghai, with 8 stations hitting new records. Additionally, persistent rainfall amounts extremes were observed in 47 stations of middle and lower reaches of the Yangtze River valley, Xinjiang and Qinghai, with 5 stations hitting new records. Persistent rainy days extremes occurred in 26 stations of Northeast China, Xinjiang, Shanghai, Zhejiang, Hainan and Guangdong, with 4 stations hitting new records.

2. World Climate

During June 2011, monthly mean temperatures were 1-4℃ above normal in most Europe, parts of mid-eastern Africa, southern and locations of northeastern North America, parts of mid-northern South America, with temperatures 4-6℃ above normal in most mid-northern Russia. Monthly mean surface air temperatures were observed 1-4℃ below normal in regions from southeastern Europe to northern Central Asia, middle South Asia, locations of northern and southern Africa, mid-western North America and northern Australia.

For the month, precipitations were at least 50% less than normal in regions from southeastern West Asia to northwestern South Asia, mid-northern and parts of eastern Africa, southern North America, mid-western and parts of southern South America, northwestern and southeastern Australia, with no precipitation in locations. Meanwhile, precipitations were at least 50% more than normal in locations of northwestern Europe, southwestern West Siberia, western Russian Far East, regions from northwestern East Asia to northern South Asia, most Central Asia, northeastern West Asia, northwestern, middle and parts of southern Africa, most northwestern and locations of western North America, locations of northern South America, mid-northern Australia, with precipitations at least 200% above normal in locations.

3. General Circulation Features

Northern Hemisphere: During June 2011, in the field of 500hPa geopotential height anomaly, positive anomalies above 4 dam covered northeastern North Pacific Ocean, northeastern North America and most of the polar region. Meanwhile, negative anomalies below -4 dam covered northwestern North Pacific Ocean, the North Atlantic Ocean and Central Asia. For the month, the area and intensity of Northwest Pacific Subtropical High were larger and stronger than normal, with its western ridge point and ridge line a bit easterly and northerly, respectively.

Southern Hemisphere: During June 2011, in the field of 500hPa geopotential height anomaly, positive anomalies above 4 dam covered most of the polar region, the southern South Pacific Ocean and the southeastern South Atlantic Ocean, with central values above 12 dam over the southeastern South Atlantic Ocean. Meanwhile, negative anomalies below -4 dam mainly covered southern parts of Australia and adjacent areas of the South Pacific Ocean, southern Africa and its adjacent waters, with central values below -8 dam over the Bellingshausen Sea.

4. Tropical Features

Sea Surface Temperatures (SSTs): During June 2011, the positive SST anomalies (SSTA) were further enlarged in the equatorial central and eastern Pacific, with values within 0~0.5℃. Meanwhile, the offshore positive SSTA in South America of the equatorial eastern Pacific developed, with values within 2.0℃. The SSTA in NINO 1+2, NINO 3, NINO 4, NINO 3.4, and NINO Z regions were 0.7℃, 0.2℃, -0.2℃, 0℃, and 0.1℃, respectively, and the indices increased 0.1℃, 0.3℃, 0.2℃, 0.4℃, and 0.3℃ compared with those in the last month.

Subsurface Temperatures: During June 2011, positive temperature anomalies dominated subsurface equatorial Pacific except for the negative anomalies around 140°W in the equatorial central Pacific at a depth of -100~150 m and in the equatorial western Pacific at a depth of -200~-300 m. The central value of positive anomalies in the equatorial western Pacific at a depth of -100~-200 m reached 4℃, but was slightly lower than that in May.

Warm Pools: During June 2011, the area of the Indian Ocean warm pool was slightly larger than normal and its intensity was above normal. The intensity of the western Pacific warm pool was obviously greater than normal. Meanwhile, its area was larger than normal in the northeastern and southern parts of warm pool, and was less than normal in the southeastern part.

Wind Field: In June 2011, at lower troposphere (850hPa), easterly anomalies dominated over the equatorial central and western Pacific west to 160°W, and westerly anomalies were observed over the equatorial eastern Pacific east to 140°W. At upper troposphere (200hPa), westerly anomalies above 4 m/s covered most of the equatorial central Pacific except for weak easterly anomalies over the equatorial eastern Pacific around 110°W.

Southern Oscillation: For the month, the Southern Oscillation Index (SOI) was 0.3, with a slightly increase compared with that in May (0.2).

Convections over the Tropics: During June, the anomalous outgoing long-wave radiation (OLR) showed that the active region of convection was still over the equatorial western Pacific, but the intensity was slightly weaker than that in May. Meanwhile, the inactive region of convection over the equatorial central Pacific around the date line was slightly smaller.

In the divergent wind field at lower troposphere (850hPa), the convergent and divergent centers were around 120°E, 20°N and 80°W, 25°S, respectively. At upper troposphere (200hPa), the corresponding divergent and convergent centers were near 130°E, 10°N and 120°W, 20°S, respectively.

5. ENSO Monitoring and Outlook

Monitoring on atmospheric and oceanic conditions showed that during June 2011 the regions with positive SSTA in the equatorial central and eastern Pacific were enlarged, and the indices for NINO 3 and NINO Z regions turned to positive; the subsurface SST was generally above normal in most of the equatorial Pacific; SOI increased slightly from 0.2 to 0.3; the zonal wind anomalies filed at lower level maintained the pattern in the equatorial Pacific in May, but the westerly anomalies at higher level in the equatorial middle-eastern Pacific shrank to the equatorial central Pacific; the convection over the equatorial western Pacific was a little weaker than that in May. Above features indicate that SST in the equatorial Pacific was in the neutral condition. Most statistical and dynamic models predicted that the SSTA over the equatorial central-eastern Pacific would keep positive or near normal condition in mid-summer 2011.

Based on the predictions of most statistical and dynamic models and diagnostic analyses, it is expected that SSTA in the equatorial central-eastern Pacific will slightly increase in mid-summer 2011, and SST there will be generally near normal or slightly warmer in summer 2011. Therefore, we will closely monitor the development of ENSO conditions and update our ENSO wrap-up in time.