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J. K. Angell

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J. K. Angell

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Total-ozone variations in five climatic zones and the world as a whole, as well as ozone variations in tropospheric and stratospheric layers of the north temperate zone, have been updated through 1985 by means of Dobson, ozonesonde and Umkehr observations. In the north temperate zone the total-ozone minimum in early 1985 was as pronounced as the total-ozone minimum in early 1983 (both a record 3% below the long-term average), but without the potential explanation afforded by the El Chichón eruption and/or strong El Niño of 1982. Based on linear regression, between 1980 and 1985 the year-average total ozone decreased by 2–3% in north polar, north and south temperate, and tropical zones, but by almost 6% in the south polar zone (Antarctic “ozone hole” phenomenon). For the world as a whole, the decrease in year-average total ozone between 1980 and 1985 is estimated to be 2.7 ± 0.9% (95% confidence interval), with the decrease greatest in the northern autumn (3.3%) and winter (3.1%) and least in the northern summer (1.6%). Ozonesonde and Umkehr observations for 16–24 and 24–32 km layers of the north temperate zone also show record low (since 1970) ozone values in both 1983 and 1985. Based on linear regression, between 1980 and 1985 the year-average ozone in the north temperate zone decreased by about 6% in the 16–24 km layer, nearly 2% in the 24–32 km layer, and nearly 6% in the 32–48 km layer, though the latter decrease is presumably exaggerated because of the bias introduced into the Umkehr measurements by the El Chichón eruption in 1982. There is little evidence of appreciable changes in tropospheric ozone during 1980–85.

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J. K. Angell

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J. K. Angell

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Based on data from the Dobson network, between 1960 and 1987 there has been a zero-lag correlation of 0.48 between the 112 unsmoothed seasonal values of sunspot number and global total ozone, significant at the 1% level taking into account the considerable serial correlation in these data. The maximum correlation of 0.54 is found when sunspot number lags total ozone by two seasons, the result mainly of a phase difference early in the record. On the basis of only 2½ solar cycles, the global total ozone has increased by 1.4% for an increase in sunspot number of 100. The correlation between sunspot number and total ozone has been significant at the 5% level in north temperate and tropical zones—the zones with the most representative data. In the north temperate zone, the correlation between sunspot number and total ozone has been much higher in the west-wind phase of the 50 mb equatorial QBO than in the east-wind phase, but in the tropics the correlation has been much higher in the east-wind phase. Umkehr measurements between 1966 and 1987 in the north temperate zone indicate that the correlation between sunspot number and ozone amount has been higher (0.35, almost significant at the 5% level) in the low stratosphere where transport processes dominate than in the high stratosphere where photochemical processes dominate. During 1932–60 there was a significant correlation of 0.35 between sunspot number and Arosa total ozone 14 seasons later, very different from the nearly in-phase relation found after 1960. Considered is the possible impact of long-term change in transport processes in the low stratosphere on the total-ozone record at a single station such as Arosa.

Between 1966 and 1985 there has been very good agreement between observed global total ozone, and global total ozone calculated from three 2-D stratospheric models that take into account the solar cycle, the time variation in trace gases, and nuclear tests; both observed and calculated variations are closely related to the variation in sunspot number. Between 1960 and 1966, however, the agreement between observation and calculation is poor, the models indicating a pronounced minimum in global total ozone in 1963 due to the nuclear tests of the early 1960s—a minimum not found in this analysis. The observed variation in global total ozone has been compared with the variation predicted by one of the models up to the sunspot maximum in 1990, and the agreement is shown to be good through the northern summer of 1988 if the impact of the QBO on global total ozone is taken into account. On the basis of the present analysis, there has been a 1.0 ± 0.9% decrease in global total ozone between solar cycles 20 and 21, a decrease 70% larger than that indicated by the three stratospheric models.

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J. K. Angell

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Examined in this paper are the variations and trends in tropospheric and low-stratospheric temperature for seven climatic zones, hemispheres, and world for intervals 1958–87 and 1973–87, based on 63 well-distributed radiosonde stations. For the 30-yr interval 1958–87, these data indicate an increase in year-average global temperature at the surface and in the tropospheric 850–300 mb layer of 0.08°C (10 yr)−1 and 0.09°C (10 yr)−1, respectively, just significant at the 5% level. Nevertheless during this interval there is evidence for a slight decrease in year-average temperature at the surface and in the troposphere of the north polar and north temperate zones. The global 300–100 mb temperature is indicated as having decreased by 0.18°C (10 yr)−1 during this 30-yr interval (significant at the 1% level), with a temperature decrease in all seven climatic zones, though largest in the south polar zone (associated with the Antarctic “ozone hole” phenomenon). For the 15-yr interval 1973–87, the global temperature in the low-stratospheric 100–50 mb layer is indicated as having decreased by a significant 0.62°C (10 yr)−1, the decrease again largest in the south polar zone 2.04°C (10 yr)−1 but observed in all zones except the north temperate zone. During 1958–87, there is evidence for an increase in the meridional temperature gradient between equatorial zone and north polar zone both at the surface and in the troposphere, but in the Southern Hemisphere then has been a decrease in this gradient at the surface and essentially no change in the troposphere. In the hemispheric and global average, warming has been greater (though not significantly so) in MAM (March–April–May) and JJA than in DJF and SON, both at the surface and in the troposphere, though in both polar zones the surface warming has been greatest in winter. The close relation between sea-surface temperature in the eastern equatorial Pacific and tropospheric temperature in the tropics is discussed in some detail. Finally, temperature variations and trends in the western hemisphere tropics are examined up to heights of 55 km using high-level radiosonde data and rocketsonde data.

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J. K. Angell

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The variations in United States cloudiness (percent of sky covered by clouds, as estimated subjectively by observers at 100 National Weather Service stations) and sunshine duration (percent of possible sunshine, as estimated objectively by sunshine recorders at these same 100 stations) are examined for years 1950–88. During this period, the correlation between annual values of cloudiness and sunshine duration within the contiguous United States was −0.86, significant at the 1% level. The years of maximum cloudiness and minimum sunshine duration were 1972 and 1982, when strong El Ninos began. The year of maximum sunshine duration was 1988, but the years of minimum cloudiness were 1952–56 (mini dust bowl); the discrepancy a result of the greater long-term increase in cloudiness than decrease in sunshine duration. In the spring of 1988 them were anomalous values of cloudiness (below average) and sunshine duration (above average) in north central, south central and southeast regions of the United States, the deviations from average approaching 10%. In the summer of 1988 these deviations were anomalous only in north central and northwest regions.

Despite the low value of cloudiness in 1988, based on this analysis the United States cloudiness increased by 2.0, ± 1.3% between 1950–68 and 1970–88 (corresponding to a percentage increase of 3.5% since the average cloudiness was 58%, or 5.8 tenths, during 1950–88). The increase in cloudiness was close to 2% in all six regions of the country, and significant at the 5% level in all regions except the southeast. Most of the increase in cloudiness was in autumn, with a negligible increase in spring. The decrease in United States sunshine duration between 1950–69 and 1970–88, however, is indicated to be only −0.8 + 1.2% (corresponding to a percentage decrease of −1.2% since the average sunshine duration was 63% during 1950–88). The difference between cloudiness increase, and sunshine duration decrease is most apparent in the west and may be due in part to an increase in cirrus not thick enough to turn of the sunshine recorder.

There has been a correlation of 0.79 (significant at the 1% level) between annual cloudiness and precipitation within the United States during 1950–88, but the correlation of −0.43 between annual cloudiness and surface temperature (above-average cloudiness associated with below-average temperature) is not quite significant at the 5% level. Considered is the possible relation between the 1987 El Nino and United States cloudiness and sunshine duration.

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J. K. Angell

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J. K. Angell

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This paper summarizes the operational 300-mb constant-level balloon or transosonde flights made by the United States Navy from Iwakuni, Japan during 1957–58. On the average, the transosondes reached the west coast of the United States 3 days after release in winter and 4 days after release in spring and fall. The trajectories traversed the United States farther to the north in winter than in spring or fall. For these flights, the zonal standard deviation of position increased approximately linearly with time since transosonde release, whereas the meridional standard deviation of position remained practically constant after the transosondes had been aloft 3 days.

The mean transosonde-derived wind speed, at 300 mb was 71 kn while the mean cross-contour flow was 7.5 kn and the mean deviation between wind and geostrophic wind speed was 12.4 kn. Zonal and meridional ageostrophic winds derived from the transosondes suggest that, at 300 mb, six or seven per cent of the northward transport of momentum at 37 N is brought about by ageostrophic flow.

Power spectrum analysis shows that the meridional wind tends to oscillate with a 54-hr period, corresponding to the average time it takes the transosondes at 300 mb to pass through a typical long wave in the westerlies. The wind speed and zonal wind component tend to oscillate with a period exceeding 5 days, a result of strong winds being found over Japan and off the east coast of the United States. Not as clear-cut is the tendency for the cross-contour flow to oscillate with a period of 30 to 36 hr. Cross-spectrum analysis shows that for oscillations of period exceeding 2 days the maximum zonal wind is to be found near the pre-trough inflection point along the wave-shaped trajectories while the maximum flow toward low pressure occurs near the trough line. However, for oscillations of period 36 to 16 hours the maximum zonal wind is found in the northerlies and the maximum flow toward low pressure occurs on the ridge.

Temperatures interpolated to the 300-mb transosonde positions suggest the presence of ascending air motion across the Pacific Ocean and descending air motion across the United States. Contour heights interpolated to the 300-mb transosonde positions suggest the presence at 300 mb between Japan and the east coast of North America of a northward ageostrophic flow of magnitude 2 kn.

“Abnormal” flow is discussed briefly, and an example thereof is given.

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J. K. Angell

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The dependence upon frequency of the variance and cross variance of zonal-meridional and natural ageostrophic wind components is determined for twelve 300-mb transosonde flights of 60 to 130 hr duration. The main peaks in the variance of these components occur at periods near 50 hr and are assoriated with the transit time of the transosondes through long waves in the westerlies. Two of the longest flights have a secondary peak in the variance of the zonal wind component at a period of 12 hr. For fluctuations of period near 50 hr, the cross variance indicates that the zonal wind component is usually a maximum slightly upstream from the trajectory crest, and that the maximum flow towards low pressure consistently occurs near the inflection point downstream from the trajectory trough line. The evidence for inertial oscillations is inconclusive, partly due to the difficulty in resolving inertial oscillations and fluctuations associated with the but, pending the analysis of more such data, generalization is not attempted.

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J. K. Angell

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No Abstract Available.

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