Monthly Highlights

1． Climate in China

During November 2009, the surface air temperature averaged over China was 1.2℃, with 0.9℃ below normal and being the coldest November since 1982. The monthly mean surface air temperatures were below normal in most China, with temperatures at least 2-4℃ below normal in North China, Huanghuai, most Jianghuai, Jianghan, western Jiangnan, most Northeast China and central Inner Mongolia. Only Xizang, Qinghai, western Sichuan and western Yunnan had 1-2℃ above normal temperatures.

The precipitation averaged over China was 24.2mm, with 6.2mm above normal. The precipitations were observed 50-200% more than normal in part of Northwest China, most North China, most Huanghuai, Jianghuai, eastern Jiangnan, and central-eastern South China, with precipitations at least 200% more than normal in locations. Meanwhile precipitations were observed 50-80% less than normal in most southeastern China, western South China.

During early and middle November 2009, central-eastern China experienced severe temperature drop. The ranges of temperature drop surpassed the 95th percentile thresholds for more than 300 stations, with record drops at 37 stations in Heilongjiang, Jilin, Inner Mongolia, Shandong and Henan.

2． Climate in the World

During November 2009, temperatures were observed 1-4℃ below normal in most of eastern and northern Asia, southern South America, Alaska, with temperatures at least 4-6℃ below normal in locations. Meanwhile, the air temperatures were near or above normal in the rest areas. The temperatures were seen 1-4℃ above normal in most Europe, middle West Asia, most Central Asia, the regions from southern Tibet Plateau to northeastern India, most North America, most South America, most Australia, with at least 4-6℃ above normal in locations.

For the month, precipitations were observed 50-100% less than normal in parts of Russia, southern West Asia, most Africa, middle Australia, most North America, eastern South America, southwestern China, the Indo-China Peninsula, with no precipitation in locations. Meanwhile, precipitations were at least 50% more than normal in South Asia, northern West Asia, North China, Northwest China and southeastern China, with precipitations at least 200% more than normal in locations.

3． General Circulation Features

Northern Hemisphere: During November 2009, the mean 500hPa geopotential height field exhibited a 3-wave pattern at the mid-high latitudes. In the 500hPa geopotential height anomaly field, positive anomalies above 4 dam covered the regions from Barents Sea to the Uralskiy Khrebet, northeastern North America and northwestern Pacific, with maximum above 16 dam over Barents Sea. Meanwhile, negative anomalies below -4 dam covered the regions from Alaska to the Chukchi Peninsula, Central Siberia and northeastern North Atlantic Ocean, with minimum below -16 dam. Furthermore, the area of the Northwest Pacific subtropical high was slightly larger than average and its location was more westward than normal.

Southern Hemisphere: For the month, in the 500hPa geopotential height anomaly field, positive anomalies above 4 dam covered the most Antarctic and its vicinity. Meanwhile, the negative anomalies below -4 dam were observed in the oceans west to New Zealand, southern South America and part of southern Atlantic Ocean.

4. Tropical Features

Sea Surface Temperatures (SSTs): During November, the SSTs were more than 0.5℃ above normal in the central-eastern equatorial Pacific, with central value above 2.0℃. The indices of NINO 1+2, NINO 3, NINO 4, NINO 3.4 and NINO Z were 0.5℃, 1.3℃, 1.5℃, 1.7℃and 1.3℃, with a rise of 0.5℃, 0.5℃, 0.2℃, 0.7℃ and 0.4℃ from last month, respectively.

Subsurface Temperatures: During November, the anomalously warm subsurface water in the central-eastern equatorial Pacific further strengthened and shifted eastward in comparison to last month.

Warm Pools: During November, both the area and intensity of the western Pacific and Indian Ocean warm pool were above normal.

Wind Field：For the month, at lower troposphere (850hPa), the equatorial Pacific region west of 160ºW was covered by easterly anomalies, while the region east of it was dominated by the westerly ones (Fig.9). At upper troposphere (200hPa), westerly anomalies covered the equatorial Pacific region west of 160ºE, while easterly ones prevailed over the region east of it.

Southern Oscillation: For the month, the Southern Oscillation Index (SOI) was -0.6, with a rise of 0.7 from last month.

Convections over the Tropics: During November, the anomalous outgoing longwave radiation (OLR) showed that the convections were near normal in the equatorial Pacific. In the lower troposphere (850hPa) divergent wind field, a convergent center in the tropical Pacific was near 170ºE, 5ºN, and a divergent center was near 105ºW, 5ºN. At the upper troposphere (200hPa), the corresponding divergent and convergent centers were near 165ºE, 5ºS; 105ºW, 10ºS, respectively.

5. ENSO Monitoring and outlook

Monitoring showed that during November, the SSTs were more than 0.5℃ above normal in the central-eastern equatorial Pacific, meanwhile the anomalously warm subsurface water in the central-eastern equatorial Pacific further strengthened and shifted eastward in comparison to last month, indicating El Nino was under way to its peak phase. Further, predictions of most statistical and dynamic models indicated the SST anomalies in the central and eastern equatorial Pacific will continue to be above 0.5℃ in the coming 3 months.

Based on aforementioned analysis, El Nino event will persist within the subsequent 2-3 months. Therefore, we need to closely monitor the developments of ENSO conditions and update our ENSO wrap-up in time.