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Southern Latitudes (southern + latitude)

Distribution by Scientific Domains

Life Sciences	50%

Selected Abstracts

The Ultraviolet Radiation Environment of High Southern Latitudes: Springtime Behavior over a Decadal Timescale,

PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 2 2005
Yixiang Liao
ABSTRACT Four spectroradiometers located at latitudes from 55° to 90°S conducted near-continuous measurements of ground-level solar ultraviolet irradiance from 1990 through 2001. The behavior during months from October through December is of special interest because this period includes the springtime loss in column ozone and the naturally large irradiances of early summer. Monthly integrated irradiances using biological weightings for erythema and damage to DNA show a distortion of the normal annual cycle in irradiance, with enhanced values occurring in October and November. In some cases, these irradiances exceed those near summer solstice in December. Changes in local cloudiness and column ozone both contribute significantly to interannual variability in erythemal irradiance. This is particularly the case at Palmer Station, near 65°S, where the monthly integrated erythemal irradiance in November 1997 was more than double that observed 5 years earlier. In general, at sites on the Antarctic continent, interannual variability in monthly integrated erythemal irradiance is greatest in November, when the observation for any given year can fall 40% above or below the multiyear mean. Near the tip of South America, interannual variability is approximately half that seen in Antarctica. [source]

Thermal performance in three different low-cost dwellings for the tropical climate of Brazil

BAUPHYSIK, Issue 1 2008
Marlon Leão Msc.
The aim of this project was to analyze the thermal performance of passive low-cost housing in half-humid tropical climate. The houses are located in Cuiabá-MT (15.5° southern latitude), one of the hottest cities in Brazil. The data about the typology of the houses were obtained from three representative construction systems; wood, masonry, and prefabricated. The measurements had been carried out through a year, during 20 consecutive days of each season and were evaluated by three distinct methodologies: (1) analyses of previous recommendations of the construction where the envelope materials were compared with the Brazilian standard NBR 15220-3/ 2005, (2) frequency, through dry bulb temperature with values of 18 °C and 29 °C, and (3) performance, by analysis of comfort levels and bioclimatic strategies processed by Analysis Bio 2.1.2 program in accordance to the adapted Bioclimatic Chart of Givoni for developing countries. Thermisches Verhalten dreier kostengünstiger Wohnhaustypen im tropischen Klima Brasiliens. Ziel des Projektes war, das thermische Verhalten kostengünstiger Passivwohnhäuser im halbfeuchten tropischen Klima zu untersuchen. Die Häuser befinden sich in Cuiabá-MT (15.5° südlicher Breite), eine der heißesten Städte Brasiliens. Die Daten über die Typologie der Häuser wurden von drei repräsentativen Bauweisen gewonnen: Holz, Mauerwerk und Massivbauweise. Die Messungen wurden innerhalb eines Jahres während jeweils 20 aufeinanderfolgenden Tagen in den vier Jahreszeiten durchgeführt und nach drei Kriterien ausgewertet: (1) Untersuchung der Konstruktionsempfehlungen und Vergleich der Außenwandkonstruktion mit der brasilianischen Norm NBR 15220-3/2005, (2) Häufigkeitsverteilung der Temperaturwerte 18 °C und 29 °C, sowie (3) thermisches Verhalten mit Untersuchung der Behaglichkeit und eines bioklimatischen Konzepts mit Hilfe der Software Analysis Bio 2.1.2 in Übereinstimmung mit dem darin verwendeten Bioklimatischen Diagramm für Entwicklungsländer nach Givoni. [source]

CHRONOLOGY OF THE LAST GLACIATION IN CENTRAL STRAIT OF MAGELLAN AND BAHÍA INÚTIL, SOUTHERNMOST SOUTH AMERICA

GEOGRAFISKA ANNALER SERIES A: PHYSICAL GEOGRAPHY, Issue 2 2005
R.D. McCULLOCH
ABSTRACT. Glacier fluctuations in the Strait of Magellan tell of the climatic changes that affected southern latitudes at c. 53,55°S during the Last Glacial Maximum (LGM) and Late-glacial/Holocene transition. Here we present a revised chronology based on cosmogenic isotope analysis, 14C assays, amino acid racemisation and tephrochronology. We unpick the effect of bedrock-derived lignite which has affected many 14C dates in the past and synthesise new and revised dates that constrain five glacier advances (A to E). Advance A is prior to the LGM. LGM is represented by Advance B that reached and largely formed the arcuate peninsula Juan Mazia. Carbon-14and 10Be dating show it occurred after 31 250 cal yrs BP and culminated at 25 200,23 100 cal yrs BP and was then followed by the slightly less extensive advance C sometime before 22 400,20 300 cal yrs BP. This pattern of an early maximum is found elsewhere in South America and more widely. Stage D, considerably less extensive, culminated sometime before 17 700,17 600 cal yrs BP and was followed by rapid and widespread glacier retreat. Advance E, which dammed a lake, spanned 15 500,11770 cal yrs BP. This latter advance overlaps the Bølling-Allerød interstadials and the glacier retreat occurs during the peak of the Younger Dryas stadial in the northern hemisphere. However, the stage E advance coincides with the Antarctic Cold Reversal (c. 14800,12700 cal yrs BP) and may indicate that some millennial-scale climatic fluctuations in the Late-glacial period are out of phase between the northern and southern hemispheres. [source]

Long-term changes in the chromosomal inversion polymorphism of Drosophila subobscura.

JOURNAL OF ZOOLOGICAL SYSTEMATICS AND EVOLUTIONARY RESEARCH, Issue 3 2004

Abstract The chromosomal polymorphism of 13 European populations of Drosophila subobscura has been compared with that of the same populations collected 15,35 years ago. The chromosomal polymorphism of the old populations differs significantly from that of the new populations, mainly for chromosomes U and O. There is a very good agreement between the geographical space and the genetic space as shown by a graphical representation of the 26 statistical populations (13 old and 13 new) obtained by a principal coordinate analysis. This reflects both the existence of significant latitudinal clines for the frequencies of some chromosomal arrangements in the old and new samples and systematic changes that have taken place in these populations during the period that elapsed between the two surveys. An increase in the frequency of those arrangements typical of southern latitudes and a decrease for those common in northern latitudes is observed in all populations , Mediterranean, Atlantic and Central European. Furthermore, the genetic distances of the new populations to a southern population of reference have decreased in comparison with those of the old populations. These changes could be the result of climatic factors that are correlated with latitude. In particular, the assumption that global warming is responsible for all the changes observed appears rather likely. Whether these systematic changes of the chromosomal polymorphism are a consequence of local adaptations or have been produced by migration from the south remains an open question. Zusamennfassung Der gegenwärtige chromosomale Inversionspolymorphismus in 13 europäischen Populationen von Drosophila subobscura wurde mit dem Zustand in denselben Populationen verglichen, die vor 15 bis 35 Jahren untersucht worden waren. Der Chromosomenpolymorphismus der ,,alten'' Populationen unterscheidet sich signifikant von dem der ,,neuen'' Populationen, besonders für die Chromosomen U und O. Eine sehr gute Übereinstimmung zeigt sich zwischen der geographischen Komponente und der genetischen Komponente bei einer graphischen Darstellung der 26 Populationen (13 alte und 13 neue Populationen) durch eine Koordinatenanalyse. Das spiegelt beides wider, die Existenz von signifikanten breitenabhängigen Klinen in der Häufigkeit einiger chromosomaler Strukturtypen in den alten und den neuen Populationen, aber auch die systematischen Änderungen, die sich bei diesen Populationen im Laufe der Zeit zwischen den beiden Untersuchungen ereignet haben. Eine Zunahme in den Häufigkeiten jener Chromosomenstrukturen, die typisch für südliche Breiten sind, und eine Abnahme solcher Strukturen, die häufig in nördliche Breiten sind, konnte beobachtet werden - in den mediterranen, den atlantischen und den mitteleuropäischen Populationen in der gleichen Weise. Außerdem haben die genetischen Distanzen der neuen Populationen zu einer südlichen Referenzpopulation im Vergleich zu denen der alten Populationen abgenommen. Diese Veränderungen wurden vermutlich von klimatischen Faktoren bestimmt, die mit der geographischen Breite korreliert sind. Insbesonders erscheint die Annahme, daß die globale Erwärmung für die Veränderungen des Chromosomenpolymorphismus dafür verantwortlich ist, ziemlich wahrscheinlich. Ob diese systematischen Transformationen des Chromosomenpolymorphismus ein Konsequenz lokaler Anpassungen oder auf Migration aus dem Süden zurückzuführen sind, bleibt eine offene Frage. [source]