The impact on temperature and precipitation anomalies over the European continent of the different action centers of blocking events in the Euro-Atlantic sector was investigated. It was found that the position of the ...The impact on temperature and precipitation anomalies over the European continent of the different action centers of blocking events in the Euro-Atlantic sector was investigated. It was found that the position of the blocking action center in the Euro-Atlantic region seems to dominate European climates. When the center of the blocking action is in the Greenland region, there is a strong negative temperature anomaly over Central and Northern Europe, as well as a strong positive precipitation anomaly over southern Europe. However, there tends to be a strong negative temperature anomaly in the west(east) part of Europe when the center of the blocking action is shifted to the Eastern Atlantic and west Europe(east Europe). In particular, when the blocking action center is closer to the European continent, the fall in temperature becomes more evident over Central and south Europe than over other regions. Moreover, it was found that when the region where the blocking action center exists changes from the Eastern Atlantic and west Europe region to the east Europe region, the existing region of dominant positive precipitation anomalies varies from southwest Europe to southeast Europe and the Middle East.展开更多
The North Atlantic Oscillation(NAO) exhibited a marked eastward shift in the mid-1970 s. Observations show that the extreme weather events in Europe have emerged frequently in the past decades. In this paper, based up...The North Atlantic Oscillation(NAO) exhibited a marked eastward shift in the mid-1970 s. Observations show that the extreme weather events in Europe have emerged frequently in the past decades. In this paper, based upon the daily NAO index, we have calculated the frequency of in-situ NAO events in winter during 1950-2011 by defining the Eastern-type NAO(ENAO) and Western-type NAO(WNAO) events according to its position at the east(west) of 10°W. Then, the composites of the blocking frequency, temperature and precipitation anomalies for different types of NAO events are performed. Results show that the frequency of Euro-Atlantic blocking events is distributed along the northwest-southeast(southwest-northeast) direction for the negative(positive) phase. Two blocking action centers in Greenland and European continent are observed during the negative phase while one blocking action center over south Europe is seen for the positive phase. The action center of blocking events tends to shift eastward as the NAO is shifted toward the European continent. Moreover, the eastern-type negative phase(ENAO) events are followed by a sharp decline of surface air temperature over Europe(especially in central, east, and south Europe), which have a wider and stronger impact on the weather over European continent than the western-type negative phase(WNAO) events do. A double- branched structure of positive precipitation anomalies is seen for the negative phase event, besides strong positive precipitation anomalies over south Europe for ENAO event. The eastern-type and western-type positive phase(ENAO+ and WNAO+) can lead to warming over Europe. A single-branched positive precipitation anomaly dominant in central and north Europe is seen for positive phase events.展开更多
基金supported by the National Natural Science Foundation of China (Grant No. 41375067)
文摘The impact on temperature and precipitation anomalies over the European continent of the different action centers of blocking events in the Euro-Atlantic sector was investigated. It was found that the position of the blocking action center in the Euro-Atlantic region seems to dominate European climates. When the center of the blocking action is in the Greenland region, there is a strong negative temperature anomaly over Central and Northern Europe, as well as a strong positive precipitation anomaly over southern Europe. However, there tends to be a strong negative temperature anomaly in the west(east) part of Europe when the center of the blocking action is shifted to the Eastern Atlantic and west Europe(east Europe). In particular, when the blocking action center is closer to the European continent, the fall in temperature becomes more evident over Central and south Europe than over other regions. Moreover, it was found that when the region where the blocking action center exists changes from the Eastern Atlantic and west Europe region to the east Europe region, the existing region of dominant positive precipitation anomalies varies from southwest Europe to southeast Europe and the Middle East.
基金supported by the National Natural Science Foundation of China(Grant No.41375067)
文摘The North Atlantic Oscillation(NAO) exhibited a marked eastward shift in the mid-1970 s. Observations show that the extreme weather events in Europe have emerged frequently in the past decades. In this paper, based upon the daily NAO index, we have calculated the frequency of in-situ NAO events in winter during 1950-2011 by defining the Eastern-type NAO(ENAO) and Western-type NAO(WNAO) events according to its position at the east(west) of 10°W. Then, the composites of the blocking frequency, temperature and precipitation anomalies for different types of NAO events are performed. Results show that the frequency of Euro-Atlantic blocking events is distributed along the northwest-southeast(southwest-northeast) direction for the negative(positive) phase. Two blocking action centers in Greenland and European continent are observed during the negative phase while one blocking action center over south Europe is seen for the positive phase. The action center of blocking events tends to shift eastward as the NAO is shifted toward the European continent. Moreover, the eastern-type negative phase(ENAO) events are followed by a sharp decline of surface air temperature over Europe(especially in central, east, and south Europe), which have a wider and stronger impact on the weather over European continent than the western-type negative phase(WNAO) events do. A double- branched structure of positive precipitation anomalies is seen for the negative phase event, besides strong positive precipitation anomalies over south Europe for ENAO event. The eastern-type and western-type positive phase(ENAO+ and WNAO+) can lead to warming over Europe. A single-branched positive precipitation anomaly dominant in central and north Europe is seen for positive phase events.
