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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

Total-ozone variations have been updated through 1981 for four regions in north temperate latitudes, the five climatic zones, both hemispheres, and the world. Also updated through 1981 are ozone values in height layers 32–48 km, 24–32 km, 16–24 km, 8–16 km and 2–8 km, based on Umkehr and ozonesonde observations mainly in north temperate latitudes. The data are presented in terms of year-average values and smoothed seasonal values.

On the basis of linear regression applied to year-average values, between 1970 and 1981 the change in total ozone was −0.5% in north temperate latitudes, −1.2% in the Northern Hemisphere, and −0.4% for the world, none significant at the 5% level. Between 1958 and 1981 the respective values were 1.3%, 1.0% and 0.6%, none significant. We find little evidence of a decrease in total ozone following the large nuclear explosions in 1961 and 1962.

In the 32–48 km layer sensitive to anthropogenic effects, Umkehr observations suggest an ozone decrease in north temperate latitudes of about 2% between 1970 and 1981, though the influence of volcanic aerosols on Umkehr measurements for this layer are apparent and must be considered when evaluating ozone trends. For this same time interval both Umkehr and ozonesonde observations provide evidence of a 1–3% decrease in ozone in 16–24 and 24–32 km layers of these latitudes. In the tropospheric 2–8 km layer of north temperate latitudes the ozonesonde data suggest a significant 12% increase in ozone between 1970 and 1981, but little ozone change in the 8–16 km layer. Taking into account the indicated ozone variations in north polar latitudes and south temperate latitudes, there is very good evidence for an ozone decrease through most of the stratosphere, and an ozone increase through most of the troposphere, during the interval 1970–1981.

Above the ozone maximum at about 24 km there has been a negative correlation between time variations in seasonal temperature and ozone during 1970–81, whereas below this height the correlations have been positive with the maximum correlation 0.47 in the 8–16 km layer of north polar latitudes. Ozone variations in the 8–16 km layer of north temperate latitudes appear as closely attuned to sea-surface temperature variations in the equatorial eastern Pacific (Southern Oscillation) as to the quasi-biennial oscillation. The long-term variations in ozone and water vapor in the 16–24 km layer of north temperate latitudes have been similar to the estimated long-term variations in equatorial tropopause temperature.

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J. K. Angell
and
J. Korshover

Abstract

The relation between sea-surface temperature (SST) in the eastern equatorial Pacific (0°–10°S, 180°–;80°W), and surface pressure, latitude and longitude of the four centers of action (Icelandic and Aleutian Lows, Atlantic and Pacific Highs), has been examined based on seasonal data from 1899 through 1978. The relation between this SST and indexes of the 700 mb zonal flow has been examined based on seasonal data from 1949 through 1983. Warm equatorial SST has been associated, in a significant fashion, with stronger than average westerly winds at 700 mb in the 20–35°N latitude band, weaker than average westerly winds at 700 mb in the 35–55°N band, below-average central pressure of the Pacific High, Atlantic High and Aleutian Low, southward displacement of the Icelandic Low, and eastward displacement of the Atlantic High. The only evidence of a precursor to warm equatorial SST (El Niño) is the relatively small distance between the centers of the Aleutian Low and Pacific High two seasons before warmest SST, but this relation, though indicated to be significant, is too weak to be of use in prediction.

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J. K. Angell
and
J. Korshover

Abstract

Examined is the effect on surface temperature of the volcanic eruptions of Asama and Laki in 1783, Tambora in 1815, Coseguina in 1835, Krakatoa in 1883, Santa Maria, Soufrière and Pelée in 1902, and Agung in 1963, using temperature records extending back to 1781. These records include New Haven, Connecticut, in North America; Edinburgh, De Bilt, Copenhagen, Berlin and Vilnius in Northern Europe; Geneva, Basel, Hohen-peissenberg, Vienna and Budapest in Central Europe; the “Central England” data of Manley; and the merged Northern Hemisphere data of Groveman and Landsberg and Jones et al. At New Haven and in Europe there is more evidence of a cooling following eruptions in subtropical and temperate latitudes than in equatorial latitudes (despite the similarity in mean dust-veil index), with a cooling most evident following the Asama and Laki eruptions in Japan and Iceland, and next most evident following the Coseguina eruption in Nicaragua. Following the tremendous Tambora eruption, the eruption with the largest dust-veil index, there is obvious cooling at New Haven, but not in Europe and perhaps not for the hemisphere as a whole. Hemispheric cooling is indicated to have been most pronounced following the Agung eruption—of the six eruption episodes the one with the smallest dust veil index but the best temperature data. Based on an application of Student's t-test to station, regional and hemispheric data, on 27 occasions (out of a possible 96) the average temperature for the 5-year period after the eruption is significantly (at the 5% level) lower than the average temperature for the 5- year period before the eruption, but in no case is the average temperature after the eruption significantly higher. It is proposed that cooling is not more apparent following some eruptions because of the tropospheric warming associated with strong and persistent El Niño episodes occurring shortly after the eruptions.

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J. K. Angell
and
J. Korshover

Abstract

Based on linear regression, during 1950–85 the year-average, United States cloudiness (defined here as an average of cloud amount and sunshine duration) increased by a significant 0.8% per decade, with the increase greatest in the South Central region (1.3% per decade). During 1970–85, however, the United States cloudiness increased by only 0.4% per decade, a nonsignificant amount. Over the 36-year interval, most of the cloudiness increase was in autumn (2.1% per decade for the contiguous United States), but during 1970–85 the cloudiness increase was similar (about 0.4% per decade) in all four seasons.

For the United States as a whole, cloudiness has been above average at the time of strong El Niños. such as those in 1972–73 and 1982–83, but often below average at the time of weaker El Niños As a consequence, over the 36-year interval the maximum correlation between seasonal SST (in the region 0°–10°S, 180°–80°W) and United States cloudiness is only 0.26 (cloudiness leading this SST by about one season), just significant at the 5% level taking account of serial correlations. The correlation (r) has been largest in southwestern (r = 0.26) and north central (r = 0.30) regions of the United States and least in the northeastern region (r = 0.09).

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J. K. Angell
and
J. Korshover

Abstract

Examined are annual, quasi-biennial and long-term variations in percentage of possible sunshine (S) within six regions of the contiguous United States, based on observations at 103 stations for the years 1950–1972. S averages 20% greater in summer than in winter, and 20–25% greater in the Southwest than in the Northeast. There is a tendency for S to be maximum near the time of quasi-biennial east wind maximum at 50 mb in the tropics, with the average difference in S at times of east and west wind maxima varying from 1.5% to 0.7% within the regions, and equal to 1.0% for the United States as a whole. The authors believe this difference is related to a quasi-biennial variation in eccentricity of the polar vortex. Within the United States during the 23-year period there has been a highly significant 8% decrease in S during autumn, and a somewhat compensatory 3% increase during spring. The pronounced long-term downward trend in S during autumn, with its implication of an upward trend in albedo, represents an interesting climatological phenomenon with impact on a local and perhaps hemispheric scale. In all six regions there has been a year-average decrease in S since 1964, with values varying from 2.9% in the Northeast to 0.2% in the Southwest, and amounting to a significant 1.3% for the United States as a whole. The possibility is considered that this decrease is related either to an overall increase in cloudiness, an increase in aircraft-induced cirrus cloudiness, or an increase in turbidity due to pollution.

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J. K. Angell
and
J. Korshover

Abstract

The tendency for a long-term decrease in annual sunshine duration within the contiguous United States reversed abruptly in 1972, and in 1976 the sunshine duration was 2% above average. The reversal was particularly pronounced in autumn, with the 11% decrease between 1953 and 1972 replaced by a 7% increase thereafter. In the light of this recent increase, it is unlikely that the earlier decrease in sunshine duration was chiefly due to aircraft-induced cirrus cloudiness, and the close relation between the percentage change in sunshine duration and amount of solar radiation received at the earth's surface within the United States also makes it unlikely that an increase in atmospheric turbidity was mainly responsible. Rather, long-term (climatological) changes in area cloudiness are undoubtedly the basic cause of the observed changes in sunshine duration. It is emphasized that these long-term changes in sunshine duration or cloudiness, of as much as 10% and extending over 10 years or more, may be of significance when considering certain applications of solar energy.

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J. K. Angell
and
J. Korshover

Abstract

Based on smoothed year-average data for the period 1964–76, there has been considerable similarity among the time trends in equatorial tropopause temperature, water vapor amount in the low stratosphere at Washington, DC, and total ozone in north temperate latitudes, the latter two trends in particularly close agreement with a six-month lag (ozone variation following water vapor variation). The trends in these three parameters have been generally out of phase with the temperature trend in the low stratosphere of north temperate latitudes. The phase lag between radiosonde-derived and rocketsonde-derived temperature variations over the United States suggests that an out-of-phase relation may exist between temperature trends and ozone trends (the latter obtained from Umkehr measurements) in the upper midlatitude stratosphere.

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J. K. Angell
and
J. Korshover

Abstract

The average sea surface temperature in the equatorial eastern Pacific (0–10°S, 180–90°W, and hereafter known as SST *) has been compared with United States surface temperatures for winter and summer (and to a lesser extent spring and autumn) and the year as a whole. Based on year-average temperatures during the period 1931-77, Pacific Coast temperatures have been in phase with SST *, but at other longitudes within the contiguous United States the temperature has tended to lag SST * by about one year, and in southeast and south-central United States the temperature has been nearly out-of-phase with SST *. However, none of these relations is significant at the 95% level taking into account the serial correlation in the data. Based on seasonal data (annual variation eliminated) between 1893 and 1979, the average United States temperature has lagged SST * by three seasons, with the correlation of 0.14 at this lag significant at the 95% level. At Washington, DC, for the period 1868-1979 the correlation at 0.21 at a lag of three seasons is significant at the 99% level. During the period 1895-1979 the relation between SST * and winter temperatures at major cities in the United States has varied from nearly out-of-phase in southeast and south-central regions to nearly in-phase in northwest and north-central regions, and with a 3-season lag in northeast and central regions. Absolute values of the maximum or minimum correlations at each site generally have ranged from 0.36 (significant at the 99% level) to 0.24 (significant at the 95% level). There is little evidence of a meaningful relation between SST * and spring and summer temperatures in the United States. However, the correlation of 0.36 between autumn temperature at Washington, DC, and SST * three seasons earlier is significant at the 99% level (based on years 1868–1979) and the correlation of 0.20 between average autumn temperature in the United States and SST * three seasons earlier is significant at the 95% level (based on years 1893–1979). In summary, while there undoubtedly is a relation between sea surface temperature in the region 0–10°S, 180–90°W, and United States surface temperatures for some seasons and locations, the lag correlation is usually too small to make the relation, in itself, very useful as a predictive tool.

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James K. Angell
and
J. Korshover

Abstract

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