A New Blocking Index and Its Application: Blocking Action in the Northern Hemisphere

Publisher Website
Google Scholar
Abstract
In this paper, a new two-dimensional blocking index is proposed by defining a difference between the daily 500-hPa geopotenial heights at the reference latitude and its north side. The reference latitude is determined by a composite latitude-dependent 500-hPa geopotenial height of blocking events in different seasons and sectors. The new index can take account of the duration, intensity, propagation, and spatial structure of a blocking event. Using this index, the characteristics (frequency, duration, intensity, and preferred occurrence region) of the blocking action in the North Hemisphere (NH) are investigated using a 42-yr sample of blocking events from the NCEP–NCAR reanalyses. It is found that blocking events in the NH are more frequent in the Atlantic–Europe sector than in the Pacific sector in winter and spring and autumn, but more persistent in the Atlantic–Europe sector than in the Pacific sector for all seasons. Blocking events in the Pacific sector tend to have larger amplitudes than t... Abstract In this paper, a new two-dimensional blocking index is proposed by defining a difference between the daily 500-hPa geopotenial heights at the reference latitude and its north side. The reference latitude is determined by a composite latitude-dependent 500-hPa geopotenial height of blocking events in different seasons and sectors. The new index can take account of the duration, intensity, propagation, and spatial structure of a blocking event. Using this index, the characteristics (frequency, duration, intensity, and preferred occurrence region) of the blocking action in the North Hemisphere (NH) are investigated using a 42-yr sample of blocking events from the NCEP–NCAR reanalyses. It is found that blocking events in the NH are more frequent in the Atlantic–Europe sector than in the Pacific sector in winter and spring and autumn, but more persistent in the Atlantic–Europe sector than in the Pacific sector for all seasons. Blocking events in the Pacific sector tend to have larger amplitudes than t...