Monthly Highlights

Climate in China

During October 2008, monthly mean surface air temperatures were at least 1℃ above normal in most Northwest China, Inner Mongolia, Northeast China, North China, Huanghuai, Jianghan, Jianghuai and most regions south to the Yangtze River, with 2～4℃above normal in most Northeast China, locations in Inner Mongolia, locations in central-northern and southwestern Xinjiang, parts of Jiangnan, western South China and locations in Southwest China. Temperatures were observed about 1℃ below normal in the central and southern Qinghai-Tibet Plateau. Temperatures were near normal in other regions of China.

For the month, precipitations were observed 50-200% more than normal in central and western Xinjiang, western Inner Mongolia, parts of central and eastern Inner Mongolia, parts of northern Northeast China, central-northern North China, central-eastern Tibet, regions in the upper and middle reaches of the Yangtze River Valley, most eastern South China and locations in western South China, Hainan province, with over 200% more than normal in locations. Meanwhile, precipitations were observed 30-80% less than normal in parts of northern, eastern and southwestern Xinjiang, parts of eastern and central-western Inner Mongolia, parts of central -eastern Northwest China, southwestern North China, central Huanghuai, central Jianghuai, central-western Jiangnan, western South China, western Tibet, with over 80% less than normal in western Tibet, parts of eastern and southwestern Xinjiang.

Climate in the World

During October 2008, temperatures were at least 1℃ above normal in most Eurasia, parts of northern and eastern Africa, northeastern North America and parts of southwestern North America, eastern South America and most Australia, with temperatures at least 4~6℃ above normal in central-northern Russia, eastern Europe and locations in eastern West Asia. Meanwhile, temperatures were about 1℃ below normal in southwestern Europe, northern West Asia, the central-southern Qinghai-Tibet Plateau, locations in northern Africa, northwestern and southeastern North America, northwestern South America and locations in eastern South America, with temperatures at least 2~5℃below normal in Alaska and locations in northern Africa.

For the month, precipitations were at least 50% more than normal in northern and western Europe, central-northern Russia and parts of southeastern Russia, north of northeastern China, most Northwest an Southwest China, parts of Central Asia, southern West Asia, western Africa and parts of eastern Africa, central North America and locations in eastern North America, parts of central South America and locations in southwestern Australia, with precipitations at least 200% more than normal in locations. Meanwhile, precipitations were observed at least 50% less than normal in northeastern Russia, central-northern South Asia, central North Africa, parts of western North America, southwestern South America and parts of eastern South America, most Australia, with no precipitations in locations.

General Circulation Features

Northern Hemisphere: During October 2008, 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 regions from Central Asia to western Russia, parts of southeastern Russia, the central North Pacific Ocean, regions from the Northeastern Pacific Ocean to western North America, regions from northeastern North America to the northern Atlantic Ocean and locations in northern North Africa, with central values above 8 dam over locations. Meanwhile, negative anomalies below -4 dam covered regions from northern Europe to Alaska in United States across Greenland and the Arctic Ocean, with central values below -12 dam. For the month, the subtropical high over the Northwest Pacific was larger and stronger than normal, and its position was located in northward and westward of normal position.

Southern Hemisphere: For the month, in the 500hPa geopotential height anomaly field, positive anomalies above 4 dam covered the polar regions and adjacent sea area, regions from southern Pacific Ocean around 20^oS to most southeastern Australia, with central values above 16 dam over the Polar Regions and adjacent sea area. Meanwhile, negative anomalies below -4 dam covered locations in southwestern South Pacific Ocean and southwestern South Indian Ocean.

Tropical Features

Sea Surface Temperatures (SSTs): During October, positive SST anomalies dominated the western equatorial Pacific and regions between 90ºW-110ºW in the eastern equatorial Pacific, with central values above 0.5℃. Negative SST anomalies appeared in regions from the dateline eastward to 130ºW in the central and eastern equatorial Pacific, with central values below -0.5℃. Furthermore, SST anomalies decreased significantly in the eastern equatorial Pacific. In October, indices of NINO 1+2, NINO 3, NINO 3.4 and NINO Z were -0.2℃, -0.1℃, -0.3℃ and -0.1℃, with drops of 0.9℃, 0.3℃, 0.1℃ and 0.1℃ from last month, respectively. Meanwhile, NINO 4 index was -0.1℃ with a rise of 0.3℃ from last month.

Subsurface Temperatures: During October，anomalously cold subsurface water strengthened significantly in the eastern equatorial Pacific, which was originally extended eastward from the central equatorial Pacific. Meanwhile, the anomalously warm subsurface water strengthened in the western equatorial Pacific.

Warm Pools: During October, area of the western Pacific warm pool was near normal, while area of the Indian Ocean warm pool was above normal. Their intensities were above normal.

Wind Field：For the month, at lower troposphere (850hPa), easterly anomalies prevailed over the most central and western equatorial Pacific, with central values below -4m/s, while weak westerly anomalies covered regions between 120ºW-150ºW in the eastern equatorial Pacific. At upper troposphere (200hPa), westerly anomalies covered the most central and western equatorial Pacific, while easterly anomalies covered the most eastern equatorial Pacific.

Southern Oscillation: For the month, the Southern Oscillation Index (SOI) was 1.6, with a rise of 0.2 from last month.

Convections over the Tropics: During October, the anomalous outgoing longwave radiation (OLR) showed that convection was enhanced over Indonesia and eastern part of the eastern equatorial Pacific, and suppressed over regions between 150ºE-120ºW in the equatorial Pacific. In the lower troposphere (850hPa) divergent wind field, a convergent center was near 120ºE, 10ºN, and a divergent center was near 120ºW, 15ºS. At upper troposphere (200hPa), the corresponding divergent center was near 125ºE, 10ºN, and convergent center was near 130ºW, 15ºS.

ENSO Monitoring and Prediction

(1) During October, positive SST anomalies dominated the western equatorial Pacific and regions between 90ºW-110ºW in the eastern Pacific. Negative SST anomalies appeared in regions from the dateline eastward to 130ºW in the central and eastern equatorial Pacific. Furthermore, SST anomalies decreased significantly in the eastern equatorial Pacific.

(2) During October，anomalously cold subsurface water strengthened significantly in the eastern equatorial Pacific, which was originally extended eastward from the central equatorial Pacific. Meanwhile, the anomalously warm subsurface water strengthened in the western equatorial Pacific.

(3) Southern Oscillation Index (SOI) was 1.6.

(4) For the month, at lower troposphere (850hPa), easterly anomalies prevailed over the most central and western equatorial Pacific, while weak westerly anomalies covered regions between 120ºW-150ºW in the eastern equatorial Pacific.

(5) The convection was enhanced over Indonesia and eastern part of the eastern equatorial Pacific, and suppressed over regions between 150ºE-120ºW in the equatorial Pacific.

(6) Most statistical and dynamic models indicate that ENSO-neutral conditions will continue through the coming winter.

During October, the current status indicates that the tropical Pacific is still in ENSO-neutral conditions. Based on monitoring of recent atmospheric and oceanic conditions in the tropical Pacific and predictions of statistical and dynamic models, ENSO-neutral conditions are expected to continue into the coming winter.