Seasonal Highlights
1. Climate in China
During spring 2013, seasonal surface air temperature averaged over China was 11.4℃, with 1.0℃ above normal (10.4℃). Temperatures were 1~2℃ above normal in most Northwest China, eastern Southwest China, central and western Inner Mongolia, western North China, western Huanghuai, western Jiangnan and South China, with 2~4℃ above normal in northern Xinjiang, eastern Inner Mongolia and most Gansu. Meanwhile, temperatures were 1~2℃ below normal in northern Inner Mongolia, most Northeast China et al.
For the season, the whole country-mean precipitation was 155.6mm which was 8.3% above normal (143.7mm). Precipitations were observed 20-100% above normal in northern Inner Mongolia, western Northwest China, northeastern Tibet, southern Qinghai, central Southwestern China, eastern Northwest China, Huanghuai, western Jiangnan, most South China, with precipitations at least 100% more than normal in locations. Meanwhile, precipitations were observed 20-80% below normal in most North China, central and eastern Inner Mongolia, eastern North Xinjiang, most Gansu, southwestern Tibet, southwestern Yunnan, with precipitations at least 80% less than normal in locations.
In Spring 2013，extreme events of high temperatures(HT), consecutive high temperature days (CHTD) and daily precipitation(DP) and consecutive no measurable precipitation Days (CNMPD) were observed in China. Daily maximum temperatures reached threshold of HT extreme events in 13 stations in Yunnan, Sichuan, Qinghai and Guangxi. Extreme events of CHTD were observed in 2 stations of Hainan. Meanwhile, DP extreme events occurred in 19 stations, which were located in Hunan, Hubei, Fujian, Guangdong, Guangxi, Gansu, Guizhou and Xinjiang provinces, with DP setting new record in 3 station as Yongding of Fujian (170 mm), Danzhai of Guizhou (181.8 mm) and Yecheng of Xinjiang(49 mm). However, CNMPD extreme events occurred in 28 stations of Sichuan, Yunan and Inner-Mongolia.
2. World Climate
During Spring 2013, temperatures were 2-3℃ above normal in northern Siberia, southern Europe, Central Asia, northern West Asia, most China, northeastern and partly southwestern North America, parts of North Africa, West Africa and East Africa, mid-southern Australia, with temperatures 3℃ above normal in locations. Meanwhile, temperatures were 2-3℃ below normal in northeastern Europe, northwestern West Siberia, Alaska and northwestern and central North America, with temperatures at least 3℃ below normal in locations.
For the season, precipitations were observed at least 50% more than normal in southern Europe, eastern Siberia, partly eastern Siberia, partly West Asia, northwestern South Asia, central and northern North America and Alaska, parts of central and northern South America, southern West Africa, East Africa, partly western Australia. Precipitations were observed at least 50% less than normal in northern Europe, northern West Siberia, most northern China, western North America, and western South America, parts of North Africa and West Africa, northeastern Australia, with no precipitation in parts of above regions.
3. General Circulation Features
Northern Hemisphere: During the boreal spring, in the field of 500hPa geopotential height anomaly, the negative phase of the Arctic Oscillation was observed, with positive anomalies above 4 dam covering regions from the eastern part of north polar zone to northern North Pacific and above 8 dam over the Bering Sea, while negative anomalies covering most areas between 40°N and 60°N and below -8 dam over northern West Siberian Plain, central North Pacific and the region from eastern North Atlantic Ocean to West Europe.
Southern Hemisphere: During the boreal spring, in the field of 500hPa geopotential height anomaly, negative anomalies covered most areas between 40°S and 60°S, with values below -4 dam over southern South Pacific, some parts of East Antarctic and some parts of southeastern South Atlantic Ocean. Meanwhile, positive anomalies above 4 dam were only observed over southwestern South Atlantic Ocean.