Monthly Highlights

1.Climate in China

The month of June registered a slightly higher mean temperature of China, ranking the fifth for the same period in history since 1961（fig.1）. Except the eastern part of Heilongjiang Province where temperatures were 1-2℃ lower than normal, the rest of China recorded temperatures that were close to or higher than normal. In most areas along the middle and lower reaches of the Yangtze River, most part of North China and Northwest China, the monthly mean temperatures were 1-2℃ higher, while in some localities they were more than 2℃ higher. During the month, northeastern parts of North China, most parts of Northeast China, northeastern Inner Mongolia, the Yellow River-Huai River basin, the southern Jiangnan, southern Guizhou, and parts of Xinjiang Uighur Autonomous Region measured a precipitation that was 30-100% over average for the same periods. The remaining parts of China were close to or less than normal, in which the middle and lower reaches of Yangtze River, western Inner Mongolia to western Gansu Province, and parts of Xinjiang measured a 50% decline or above in precipitation and some localities witnessed no precipitation for the whole month.

2.Climate in the World

The month of June registered average temperatures, which were 1-2℃ lower than normal for most parts of the world except Australia, while for other areas it was close to or higher than normal, out of which the western part of West Asia, Central Asia and mid-western Russia and western United States registered higher temperatures by 2-4℃（fig.2）

During the month, global precipitations were generally on the less side. Precipitations in southeastern Europe, areas from Kazakhstan to the Sayan Mountains, north coast of Russia, most parts of eastern China, the Indian Peninsula and most parts of Southeast Asia, eastern Australia, southern West Africa, eastern United States, eastern Brazil and northeastern Argentina met an increase by 50% compared with the mean precipitations for the same periods, in some localities by 100%. The rest of the world recorded less or close to normal precipitations, out of which the most parts of Eurasia, northwestern Africa, South Africa, mid-western Australia, central USA and most parts of South America witnessed a decline by 50-90%, while a few localities measured nil for the whole month.

3. General Circulation Features

Northern Hemisphere: The month of June saw a 4-wave pattern in circulation fields over the middle/higher latitudes at 500hPa geo-potential height, with a smaller polar vortex coverage than normal. At the corresponding geo-potential height anomaly field, the polar region had a negative anomaly zone (-4~-8 dam). Above 40~60 ºN was a positive anomaly zone (＞4 dam), in which the four positive anomaly centres (＞8 dam) were located in vicinity of the Newfoundland Island, North Europe, the northern part of western Siberia, and the coastal waters just off the Kamchatka peninsula, while the rest regions heights were close to normal for the same period. During the month, the Northwest Pacific subtropical high was obviously larger in size and stronger in intensity than normal for the same period, the ridge point extended slightly westward, and the ridge line was in normal location.

Southern Hemisphere: The month of June featured a 3-wave pattern in the circulation fields over the middle/higher latitudes at 500hPa. In the associated anomaly field, a positive anomaly zone (4-8 dam) was located over the southern part of the Weddell Sea in the polar region. Above the middle/high latitudes, two negative anomaly (<-4 dam) zones existed over the central South Pacific and the region from western part of the South Indian Ocean to the western part of the South Atlantic respectively, while rest areas were close to or higher than normal.

4. Tropical Features

Sea surface temperatures (SSTs)：The month of June registered positive SST anomalies by more than 0.5℃ covering the equatorial Indian Ocean, central and west Pacific around the Equator, with their scopes showing a marked expansion from the previous month, and SSTs of the eastern equatorial Pacific were close to normal（fig.6）. SST indices in different sea zones were 0.2℃ in Nino Z, 0.5℃ in Nino 4, and -0.3℃ in Nino 1+2 respectively. In comparison with the previous month, SST indices were 0.2℃ higher. The SST indices were 0.1℃ in Nino 3, and 0.4℃ in Nino 3.4 , which were 0.1℃ and 0.3℃ higher than the previous month respectively.

Subsurface Temperatures: The month of June measured such a pattern that with the exception of the equatorial coastal South America where a small scope of abnormally cold water were recorded, the equatorial Pacific were dominated with abnormally warm water, particularly the subsurface layer down to about 150 meters, where the zone of abnormally warm water at 3.0℃ witnessed a noticeable expansion from that in the previous month, extending eastward up to an area in vicinity of 140ºW.

Warm Pool: The month of June reported a larger expanse of the West Pacific warm pool compared with normal. However, the overall expanse of the Indian Ocean warm pool was close to normal. Moreover, the intensities of warm pools in both West Pacific and the Indian Ocean remained slightly stronger.

Wind Field: The month of June noticed such a pattern that the lower troposphere (850hPa) within 100-150 ºE above the equator was dominated by a weak westerly wind anomaly, and the wind fields over other equatorial waters were close to normal. At the upper troposphere (200hPa) a 4-8m/s easterly wind anomaly prevailed over most parts of the equatorial Pacific, but the wind field over the equatorial Indian Ocean was close to normal.

Southern Oscillation: The month of June registered a Southern Oscillation Index of -0.5, an increase by 0.2 from the previous month.

Convection over the Tropics: In June, the OLR anomaly field showed that the tropical South Indian Ocean and the most of tropical Southwest Pacific met stronger convective activities than normal, but the convective activities in the central and eastern tropical Pacific were close to normal. In the divergent wind fields of the lower troposphere (850hPa), the convergent zone with large values was located at 120ºE,15 ºN, and the divergent center was located near 105ºW,20ºS. In the upper troposphere (200hPa), the corresponding divergent center was located near 120ºE, 15ºN, with the convergent center located around 110ºW,20ºS.

5. ENSO Monitoring and Forecasting

(1) The month of June registered positive SST anomalies of 0.5℃ for the central and western equatorial Pacific and SSTs of the eastern equatorial Pacific were close to normal. SST indices of the key sea zones were slightly higher than those in May.

(2) Southern Oscillation Index was -0.5, an increase by 0.2 from the previous month.

(3) The abnormally warm water in the central equatorial Pacific extended further eastward compared with the previous month.

(4) Zonal wind at 850hPa above the equatorial Pacific was close to normal; and most parts of the equatorial Pacific at 200hPa was dominated by a 4-8m/s easterly wind anomaly.

(5) ENSO prediction model showed that in the forthcoming 1-2 months, the eastern equatorial Pacific will remain normal or slightly warmer.

The monitoring showed that the current central/eastern tropical Pacific SSTs were close to normal. They are expected to remain normal/slightly warmer in the next 1-2 months. The future developments of both tropical oceans and atmosphere are going to be closely watched.