Zonal index and circulation change in the north Atlantic area, 1873–1972

Makrogiannis, T. J.; Bloutsos, A. A.; Giles, Brian D.

doi:10.1002/joc.3370020206

Cited by 24 publications

(18 citation statements)

References 4 publications

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“…Our results for the Atlantic agree with what Makrogiannis et al (1982) found when they studied long term variations of the tonal index over the North Atlantic. They used mean monthly sea-level pressure data and computed mean values along 350N (SLP35) and 550N (SLP55) for an area bounded by the longitudes 600W and 100W, to define a local tonal index: SLP35-SLP55.…”

Section: Discussion and Concluding Remarkssupporting

confidence: 92%

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Long Term Variations of Atmospheric Blocking in the Northern Hemisphere

Lejenäs

1995

Journal of the Meteorological Society of Japan

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Many articles dealing with theoretical and observational aspects of atmospheric blocking have appeared in the literature. So far little attention has been paid to the question of long term variations in blocking frequency. Usually 500-hPa geopotential height data are used in observational studies of atmospheric blocking. We used a 94-year time series of sea-level pressure data in order to extend the analysis back to the first half of the century.Long term variations of frequency of blocked flow as well as individual blocking events have been documented. There are two areas of study, the North Atlantic and Western Europe (400W to 300E) and the Pacific (1600E to 1300W). Low-pass filtered data suggest that there was increased blocking activity during the winter and spring seasons in the Atlantic during 1930-1935 and 1950-1960, whereas there was reduced blocking activity during 1910-1915, in particular during the winters. However, a statistical test did not verify that these peaks are real. Data for the Pacific do not show any outstanding periods with blocked flow.Another result is that there are less blocking episodes in the Pacific than in the Atlantic. Data for the whole time period show that the number of episodes in the Pacific is 60% of the number of episodes in the Atlantic during winter and spring. During summer and autumn there are less blocking episodes in both regions than during the other two seasons. Furthermore, the number of episodes in the Pacific is only 40% of the number of episodes in the Atlantic. We also found that there is a factor of almost 2 between the number of blocking episodes during those decades with the highest number of blocking episodes and those with the lowest. This is true for both the Atlantic and the Pacific.

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Section: Discussion and Concluding Remarkssupporting

confidence: 92%

“…There are a few studies of circulation changes based on observations from the North Atlantic and Europe (Makrogiannis et al, 1982;Bardossy and Caspary, 1990). However, the first one deals with long term variations of a zonal index, and the frequency of low index situations is not the same as frequency of blocked flow.…”

Section: Introductionmentioning

confidence: 99%

Long Term Variations of Atmospheric Blocking in the Northern Hemisphere

Lejenäs

1995

Journal of the Meteorological Society of Japan

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“…The inverse relationship (high index-low precipitation and 6ice 6ersa) is also found in the other PC series, which is less clear due mainly to the influence of easterly patterns for the Mediterranean Coast and the influence of the mountains for the Cantabric area. Another way to compute the zonal index is to take the difference in pressure between 35 and 55°N (Makrogiannis et al, 1982;Makrogiannis, 1983). The inverse relationship is clearer with this index for the 1st annual PC series, except during the 1930s (relatively high index-high precipitation) and the 1950s (relatively low index-low precipitation).…”

Section: Discussionmentioning

confidence: 98%

Spatial and temporal patterns of precipitation in Spain for the period 1880–1992

1998

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“…Previous studies (Parker et al, 1994;Hurrell et al, 2003Hurrell et al, ) described 1901Hurrell et al, -1930 as a period of increased westerly winds and cyclonicity over the mid-latitude North Atlantic. Strong zonal circulation during 1920-1930 was identified by Makrogiannis et al (1982). The 1920s was a period of increased cyclone activity in the North Atlantic with the exception of some increase in blocking activity around 1920 (Slonosky et al, 2000).…”

Section: Discussionmentioning

confidence: 99%

Winter and summer blocking variability in the North Atlantic region – evidence from long-term observational and proxy data from southwestern Greenland

Rîmbu

Lohmann

2011

Clim. Past

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Abstract. We investigate the interannual and decadal variability of the North Atlantic atmospheric blocking frequency and distribution in connection with long-term observational and proxy records from southwestern Greenland. It is shown that warm (cold) conditions in southwestern Greenland during winter are related with high (low) blocking activity in the Greenland-Scandinavian region. The pattern of winter temperature-blocking variability is more complex than the blocking pattern associated to the North Atlantic Oscillation (NAO). We find, furthermore, that a North Atlantic blocking index is significantly correlated with seasonally resolved stable isotope records from Greenland ice cores. Both suggest a possible reconstruction of blocking variability in this region. During summer, high (low) blocking activity in the Euro-Atlantic region is associated with cold (warm) conditions in southwestern Greenland. We conclude that historical temperature records, as well as proxy data from Greenland, can be used to obtain information related to interannual and multidecadal variation of winter and summer blocking during past periods.

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Zonal index and circulation change in the north Atlantic area, 1873–1972

Cited by 24 publications

References 4 publications

Long Term Variations of Atmospheric Blocking in the Northern Hemisphere

Long Term Variations of Atmospheric Blocking in the Northern Hemisphere

Spatial and temporal patterns of precipitation in Spain for the period 1880–1992

Winter and summer blocking variability in the North Atlantic region – evidence from long-term observational and proxy data from southwestern Greenland

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