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J. K. Angell and Korshover

Abstract

The global variation in temperature, during the period 1958–75 is investigated using a sample of 63 radiosonde stations. The surface temperature as well as the mean temperature in 850–300 mb and 300–100 mb layers is examined, the latter based on thickness analysis. Between 1958 and 1965 there was a significant cooling averaging about 0.3°C over much of the globe, but since 1965 the temperature variations have been small. During the past few years there has been a slight warming in most latitudes. The meridional temperature gradient between the tropics and temperate latitudes has continuously increased, but since 1965 the temperature gradient between temperate and polar latitudes has decreased, with an especially large surface warming indicated for Antarctica. In the tropical troposphere, a temperature oscillation of about 3-year period and 0.3°C amplitude has been dominant since 1965. The eruption of Mt. Agung in 1963 may have decreased the surface temperature by as much as 0.2°C in the tropics, 0.4°C in the south extratropics and 0.6°C in the north extratropics. In the south extmtropics there was also a 0.7°C warming and cooling in the 300–100 mb and 850–300 mb layers, respectively, in the year of the eruption. Also shown is the variation with longitude of the temperature changes and the tendency for increased spatial variability of temperature.

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J. K. Angell and J. Korshover

Abstract

Rocketsonde-derived temperature variations within north polar, north subtropical and equatorial zones of the western hemisphere are examined for height layers of 26–35, 36–45 and 46–55 km for the years 1965–76, inclusive. As a comparison, radiosonde-derived temperature variations are examined for the surface to 16 km and 16–24 km layers for the same hemisphere and zones. The rocketsonde data suggest, in general, a warming in middle and upper stratosphere prior to 1970, and a somewhat larger (up to 5°C) cooling thereafter, yielding a temperature variation basically in phase with sunspot number, but the radiosonde data for the low stratosphere do not indicate such a variation. While this discrepancy raises questions concerning the representativeness of either or both sets of data, model findings do suggest that any warming resulting from enhanced ultraviolet radiation at sunspot maximum would be an order of magnitude greater in the middle and high stratosphere than in the low stratosphere. A quasi-biennial oscillation in temperature clearly extends at least up to the stratopause (50 km) in equatorial and subtropical zones, with a maximum amplitude (with the given smoothing) of about 1°C near 30 or 40 km, and a phase shift with height twice as large in the equatorial zone as in the subtropics.

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J. K. Angell and J. Korshover

Abstract

Planimetering of the area poleward of contours in the main belt of westerlies on 300 mb mean-monthly polar stereographic maps indicates that the size of the 300 mb north circumpolar vortex was larger in 1976 than in any year since initiation of the record in 1963, and that the size of the winter vortex of 1976–77 was also the largest of record. Other “firsts” for the winter of 1976–77 include the displacement of the vortex furthest in the direction of the Greenwich meridian and the closest approach of the vortex center to the North Pole (smallest eccentricity). It is shown that the large vortex size and small eccentricity in the winter of 1976–77 are qualitatively, but not quantitatively, in agreement with the previously noted relations of these parameters with the quasi-biennial wind oscillation of the low tropical stratosphere.

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J. K. Angell and J. Korshover

Abstract

During the pronounced 1982–83 El Niño, the 300 mb north circumpolar vortex was displaced further toward Japan (from its mean seasonal locations) than observed since the beginning of the vortex record in 1963. However, during the strong 1972–73 El Niño, the vortex was displaced toward the 180th meridian, and during the weaker 1965–66 El Niño toward the eastern Pacific, so that vortex displacements are not indicated to have been the same for different El Niño episodes. Based on the full 21-year record, the vortex has tended to be displaced toward 90°W when sea surface temperature (SST) in the region 0°–10°S, 180–80°W was above average, but toward the 180th meridian when the magnitude of SST deviation from average is considered.

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J. K. ANGELL and J. KORSHOVER

Abstract

During the past decade in extratropical latitudes, springtime stratospheric temperatures tended to be relatively high during the even years and relatively low during the odd years, with some evidence for a phase reversal in the troposphere. In the Southern Hemisphere this even-year stratospheric temperature excess appears to have progressed poleward with time, with the maximum excess occurring near the Tropic of Capricorn in 1955 and near the Antarctic Circle in 1965, where the excess averaged 8°C. even at 100 mb.

Total ozone measurements in both hemispheres tend to confirm such a poleward trend. Furthermore, in agreement with a period of order 20 yr. implied by the stratospheric temperature differences, the difference between (spring-time) even-year and odd-year total ozone amounts at Arosa, Switzerland, exhibits about a 20-yr. periodicity from 1928 to 1966, with the ozone amounts averaging 10 percent higher during the spring of the even years around 1960.

Springtime surface temperatures in Scandinavia have undergone a similar (15- to 20-yr.) periodicity since 1850, with odd-year temperature excesses averaging 2°C. around 1959. After 1920, European stations exhibit like variations, but there is little evidence for such surface-temperature fluctuations in North America or in the tropical and temperate latitudes of the Southern Hemisphere.

It is suggested that there is an association between the cycling interval of the quasi-biennial tropical oscillation and the above fluctuations of period of order of 20 yr.

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J. Korshover and J. K. Angell

Abstract

The number and location of stagnation days within the eastern United States, as estimated mainly from a surface geostrophic-wind criterion, me presented by month and for the year 1983 as a whole. The distribution of stagnation days in 1983 was quite typical of the 40-year mean, with the number of such days failing halfway between the relatively high number observed in 1981 and the relatively low number observed in 1982. A diagram shows the variation of “grid-point days” of stagnation with latitude and longitude for 1981–1983.

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J. Korshover and J. K. Angell

Abstract

The number and location of stagnation days within the eastern United States, as estimated mainly from a surface geostrophic-wind criterion, is presented by month and for the year 1985. The number of “grid-point days” of stagnation was exactly the same in 1985 as in 1984, a year with relatively little stagnation. However, the stagnation in 1985 occurred mainly over the mid-Atlantic states whereas in 1984 it occurred mainly over the Southeast.

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J. K. Angell and J. Korshover

Abstract

Based on a network of 63 well-spaced radiosonde stations around the world, the global temperature within the surface to 100 mb layer was lower in 1976 than in any year since commencement of the record in 1958, and the 1976 surface temperature equated the global record for the lowest temperature set in 1964; but even so the trend in global temperature since 1965 has been small compared to the 0.5°C decrease during 1960–65. Between 1958 and 1976 the surface to 100 mb temperature in north extratropics decreased by about 1°C, with the decrease twice as great in winter as in summer, and in 1976 this region was 0.2°C lower than in any previous year of record. During the northern winter of 1976–77, both temperate zones were very cold but the polar and tropical zones were quite warm, so that in the hemispheric or global average the season was not anomalous. In the Eastern Hemisphere of the northern extratropics there has been considerable surface warming during the past decade (although a cooling aloft), and this may explain the Soviet concern with warming related to carbon dioxide emissions. There has been a slight overall increase in temperature in the tropics since 1965, mostly in the Western Hemisphere, on which have been superimposed large and significant temperature variations of about a three-year period. These variations, probably related to the Southern Oscillation (and recently not so pronounced), extend in obvious fashion also into north extratropics, and should be taken into account for diagnoses and prognoses in northern latitudes. The rate of increase of carbon dioxide at Mauna Loa and the South Pole is augmented in the warm phase of the tropical oscillation, presumably because of a relation between atmospheric and oceanic temperature. There is evidence for a consistent quasi-biennial variation in temperature at all latitudes, with the temperature approximately 0.1°C higher than average about six months prior to the quasi-biennial west wind maximum at 50 mb in the tropics. The spatial and temporal variability in temperature have tended to increase over the period of record, in accord with the increase in meridional temperature gradient in both hemispheres and the indicated increase in lapse rate in the Northern Hemisphere.

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J. K. Angell and J. Korshover

Abstract

Tropospheric temperatures tended to cool after the Agung (8°S) eruption in 1963, but warm after the El Chichón (17°N) eruption in 1982. Thus, over the one-year period following the eruptions, Northern Hemisphere surface temperature is indicated as cooling 0.34°C after Agung, but warming 0.37°C after El Chichón, a difference significant at the 0.5% level according to Student';s t-test. This difference in Northern Hemisphere temperature change is mainly due to differences in north temperate latitudes where, over the one-year period, the surface temperature is indicated as cooling 0.36°C after Agung but warming 1.27°C after El Chichón. It is proposed that the warming after El Chichón is mostly due to the anomalously warm sea surface temperature (SST) in the eastern equatorial Pacific (El Niño) in 1982–83, the relation between SST and tropospheric temperature being an obvious one in the tropics but of a more indirect nature in midlatitudes. The best evidence so far for a tropospheric cooling due to El Chichón is in the north subtropics (10–30°N) where the zonally-averaged air temperature continued to cool after the eruption in the spring of 1982, whereas SST in the region 0–10°S, 180–80°W warmed abruptly, the opposite of the relation usually observed. Since this SST returned nearly to normal at the end of 1983, the cooling effect of El Chichón should be more evident in 1984.

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J. K. Angell and J. Korshover

Abstract

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