What can the UK learn from the southern hemisphere winter?

A high resolution spectroscopy survey of symbiotic stars is conducted in the southern hemisphere by the authors, using the Coudé Echelle Spectrograph (CES), equipped with a CCD at the ESO Coudé Auxiliary Telescope (CAT), and concurrently in the northern hemisphere by Bode, Evans, Meaburn and collaborators, using the UK facilities at La Palma. So far, more than 400 spectra of about 70 stars have been obtained, mostly during 1988 and 1989. The southern part of the work will be described below.The discussion of symbiotic stars in the context of novae is not far-fetched. A number of symbiotics are known to have nova-like outbursts, and several novae are not easily distinguished from symbiotic stars. A noteworthy example is the most recently recognized recurrent nova, V745 Sco, first observed by Liller on July 24, 1989. It is described here, both because in late decline it represents a link between novae and symbiotic stars, and because of its current interest.

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Climatology of the “Instant Occlusion” Phenomenon for the Southern Hemisphere Winter

Monthly Weather Review ◽

10.1175/1520-0493(1981)109<0177:cotopf>2.0.co;2 ◽

1981 ◽

Vol 109 (1) ◽

pp. 177-181 ◽

Cited By ~ 9

Author(s):

Andrew M. Carleton

Keyword(s):

Southern Hemisphere ◽

Hemisphere Winter

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Relations between Annular Modes and the Mean State: Southern Hemisphere Winter

Journal of the Atmospheric Sciences ◽

10.1175/jas4012.1 ◽

2007 ◽

Vol 64 (9) ◽

pp. 3328-3339 ◽

Cited By ~ 26

Author(s):

Francis Codron

Keyword(s):

Southern Hemisphere ◽

Low Frequency ◽

Stationary Waves ◽

Annular Modes ◽

The Pacific ◽

Latitudinal Shift ◽

The Indian Ocean ◽

The Mean ◽

Hemisphere Winter ◽

Mean State

Abstract In a zonally symmetric climatology with a single eddy-driven jet, such as prevails in the Southern Hemisphere summer, the midlatitude variability is dominated by fluctuations of the jet around its mean position, as described by the Southern Hemisphere annular mode (SAM). To study whether this result holds for a zonally asymmetric climatology, the observed variability of the Southern Hemisphere winter is analyzed. The mean state in this case is characterized by relatively weak stationary waves; yet there exist significant zonal variations in the mean strength and meridional structure of the subtropical jet stream. As in summer, the winter SAM signature is annular in shape and the corresponding wind anomalies are dipolar; but it is associated with two different behaviors of the eddy-driven jet in different longitudinal ranges. Over the Indian Ocean, the SAM is associated primarily with a latitudinal shift of the jet around its mean position. Over the Pacific sector, it is instead characterized by a seesaw in the wind speed between two distinct latitudes, corresponding to the positions of the midlatitude and subtropical jets. Composites of eddy forcing and baroclinicity over both sectors appear consistent with the two different behaviors. As in the zonal-mean case, high-frequency eddies both force and maintain the low-frequency wind anomalies associated with the SAM. The positive feedback by eddies is, however, not local: changes in the eddy forcing are influenced most strongly by zonal wind anomalies located upstream.

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Effects of Convective Gravity Wave Drag in the Southern Hemisphere Winter Stratosphere

Journal of the Atmospheric Sciences ◽

10.1175/jas-d-12-0238.1 ◽

2013 ◽

Vol 70 (7) ◽

pp. 2120-2136 ◽

Cited By ~ 20

Author(s):

Hyun-Joo Choi ◽

Hye-Yeong Chun

Keyword(s):

Gravity Wave ◽

Southern Hemisphere ◽

Climate Models ◽

Climate Model ◽

Global Climate ◽

Storm Track ◽

Wave Drag ◽

Global Climate Models ◽

Systematic Biases ◽

Hemisphere Winter

Abstract The excessively strong polar jet and cold pole in the Southern Hemisphere winter stratosphere are systematic biases in most global climate models and are related to underestimated wave drag in the winter extratropical stratosphere—namely, missing gravity wave drag (GWD). Cumulus convection is strong in the winter extratropics in association with storm-track regions; thus, convective GWD could be one of the missing GWDs in models that do not adopt source-based nonorographic GWD parameterizations. In this study, the authors use the Whole Atmosphere Community Climate Model (WACCM) and show that the zonal-mean wind and temperature biases in the Southern Hemisphere winter stratosphere of the model are significantly alleviated by including convective GWD (GWDC) parameterizations. The reduction in the wind biases is due to enhanced wave drag in the winter extratropical stratosphere, which is caused directly by the additional GWDC and indirectly by the increased existing nonorographic GWD and resolved wave drag in response to the GWDC. The cold temperature biases are alleviated by increased downwelling in the winter polar stratosphere, which stems from an increased poleward motion due to enhanced wave drag in the winter extratropical stratosphere. A comparison between two simulations separately using the ray-based and columnar GWDC parameterizations shows that the polar night jet with a ray-based GWDC parameterization is much more realistic than that with a columnar GWDC parameterization.

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