Climatology of Northern Hemisphere blocking in the ECHAM model

1997 ◽  
Vol 13 (9) ◽  
pp. 649-666 ◽  
Author(s):  
S. Tibaldi ◽  
F. D'Andrea ◽  
E. Tosi ◽  
E. Roeckner
Keyword(s):  
Northern Hemisphere ◽  
Echam Model

Alpha-Effect, Current and Kinetic Helicities for Magnetically Driven Turbulence, and Solar Dynamo

2000 ◽  
Vol 179 ◽  
pp. 387-388
Author(s):  
Gaetano Belvedere ◽  
V. V. Pipin ◽  
G. Rüdiger
Keyword(s):  
Southern Hemisphere ◽  
Northern Hemisphere ◽  
Convection Zone ◽  
Solar Surface ◽  
Momentum Transport ◽  
Angular Momentum Transport ◽  
Magnetic Buoyancy ◽  
Alpha Effect ◽  
Current Helicity

Extended AbstractRecent numerical simulations lead to the result that turbulence is much more magnetically driven than believed. In particular the role ofmagnetic buoyancyappears quite important for the generation ofα-effect and angular momentum transport (Brandenburg & Schmitt 1998). We present results obtained for a turbulence field driven by a (given) Lorentz force in a non-stratified but rotating convection zone. The main result confirms the numerical findings of Brandenburg & Schmitt that in the northern hemisphere theα-effect and the kinetic helicityℋkin= 〈u′ · rotu′〉 are positive (and negative in the northern hemisphere), this being just opposite to what occurs for the current helicityℋcurr= 〈j′ ·B′〉, which is negative in the northern hemisphere (and positive in the southern hemisphere). There has been an increasing number of papers presenting observations of current helicity at the solar surface, all showing that it isnegativein the northern hemisphere and positive in the southern hemisphere (see Rüdigeret al. 2000, also for a review).

The Hemispheric Sign Rule of Current Helicity during the Rising Phase of Cycle 23

2000 ◽  
Vol 179 ◽  
pp. 303-306
Author(s):  
S. D. Bao ◽  
G. X. Ai ◽  
H. Q. Zhang
Keyword(s):  
Solar Cycle ◽  
Southern Hemisphere ◽  
Northern Hemisphere ◽  
Active Regions ◽  
Hemispheric Preference ◽  
Current Helicity

AbstractWe compute the signs of two different current helicity parameters (i.e., αbestandHc) for 87 active regions during the rise of cycle 23. The results indicate that 59% of the active regions in the northern hemisphere have negative αbestand 65% in the southern hemisphere have positive. This is consistent with that of the cycle 22. However, the helicity parameterHcshows a weaker opposite hemispheric preference in the new solar cycle. Possible reasons are discussed.

Status of “AGK4” Project

1978 ◽  
Vol 48 ◽  
pp. 527-533
Author(s):  
Chr. de Vegt
Keyword(s):  
Northern Hemisphere ◽  
Proper Motion ◽  
The Mean ◽  
Spectral Bandpass

The present accuracy limit for the majority of fainter stars on the northern hemisphere is set by the AGK2/3-catalogue, recently completely finished, but it should be noted that its epoch is much earlier (1960). Furtheron the AGK3-catalogue is a direct repetition of the AGK2, the plates have been taken with the same astrograph in a broad blue spectral bandpass and measured visually with the same equipment, therefore virtually an instrumental standard of 1930 is realized again. Figure 1 shows the mean errors of the AGK2/3 catalogue positions as a function of magnitude. The best accuracy for the AGK2/3 data is obtained for the stars of about ninth magnitude: 017 (AGK2) and 020 (AGK3) but decreases for the faint stars with mpg11 to 019 (AGK2) and Pg 027 (AGK3). Here the AGK3 data are even less accurate. With increasing distance to the catalogue epochs, the accuracy of positions decreases due to the proper motion errors. In the upper part of figure 2 the dependence of the AGK2/3 catalogue accuracy on time is shown for the faint stars separately and an averaged value.

Marine and terrestrial investigations in the Norse Eastern Settlement, South Greenland

2001 ◽  
pp. 65-69 ◽  
Author(s):  
Naja Mikkelsen ◽  
Antoon Kuijpers ◽  
Susanne Lassen ◽  
Jesper Vedel
Keyword(s):  
Middle Ages ◽  
Northern Hemisphere ◽  
14Th Century ◽  
Original Series ◽  
Written Sources ◽  
The Middle Ages

NOTE: This article was published in a former series of GEUS Bulletin. Please use the original series name when citing this article, for example: Mikkelsen, N., Kuijpers, A., Lassen, S., & Vedel, J. (2001). Marine and terrestrial investigations in the Norse Eastern Settlement, South Greenland. Geology of Greenland Survey Bulletin, 189, 65-69. https://doi.org/10.34194/ggub.v189.5159 _______________ During the Middle Ages the Norse settlements in Greenland were the most northerly outpost of European Christianity and civilisation in the Northern Hemisphere. The climate was relatively stable and mild around A.D. 985 when Eric the Red founded the Eastern Settlement in the fjords of South Greenland. The Norse lived in Greenland for almost 500 years, but disappeared in the 14th century. Letters in Iceland report on a Norse marriage in A.D. 1408 in Hvalsey church of the Eastern Settlement, but after this account all written sources remain silent. Although there have been numerous studies and much speculation, the fate of the Norse settlements in Greenland remains an essentially unsolved question.

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