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- Author or Editor: D. G. Dartt x
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Abstract
A program for automated streamline analysis is described based an “optimum interpolation” techniques. Streamlines may be directly interpolated from irregularly timed and spaced wind observations. Smoothing of the wind analysis because of random observational errors can be included, and an estimate of the quality of the analysis as a function of the density and accuracy of the observations way also be derived. The interpolation method is demonstrated with sample streamline maps, and some are compared with those prepared operationally, at 250 mb, for the tropical Pacific. Occasional differences between the two analyses occur in regions of poor data coverage; otherwise, there is general agreement. This technique can also be applied easily to describe other wind field parameters such as streamfunctions, vorticity, divergence, etc.
Abstract
A program for automated streamline analysis is described based an “optimum interpolation” techniques. Streamlines may be directly interpolated from irregularly timed and spaced wind observations. Smoothing of the wind analysis because of random observational errors can be included, and an estimate of the quality of the analysis as a function of the density and accuracy of the observations way also be derived. The interpolation method is demonstrated with sample streamline maps, and some are compared with those prepared operationally, at 250 mb, for the tropical Pacific. Occasional differences between the two analyses occur in regions of poor data coverage; otherwise, there is general agreement. This technique can also be applied easily to describe other wind field parameters such as streamfunctions, vorticity, divergence, etc.
Abstract
Height-time sections of mean monthly observed upper-air zonal winds at stations within 20 degrees of the equator show not only an almost biennial oscillation of the wind in the middle or upper stratosphere but that there is a relative wave, 180 degrees out of phase to the first, which occurs in the lower stratosphere. The two waves are merged near the equator; they are best distinguished from each other about 9N to 15N and, although still noticeable as separate occurrences of westerlies from 15N to 20N, the intensity of the westerlies is much reduced. Both waves occur at progressively higher levels from one biennium to the next. This observed double cycle is caused by the combination of the fundamental annual and biennial waves, and the upward progression appears due to the difference in phase lags with height of these two component waves.
Abstract
Height-time sections of mean monthly observed upper-air zonal winds at stations within 20 degrees of the equator show not only an almost biennial oscillation of the wind in the middle or upper stratosphere but that there is a relative wave, 180 degrees out of phase to the first, which occurs in the lower stratosphere. The two waves are merged near the equator; they are best distinguished from each other about 9N to 15N and, although still noticeable as separate occurrences of westerlies from 15N to 20N, the intensity of the westerlies is much reduced. Both waves occur at progressively higher levels from one biennium to the next. This observed double cycle is caused by the combination of the fundamental annual and biennial waves, and the upward progression appears due to the difference in phase lags with height of these two component waves.
Abstract
Daily data at 16 stations along five latitudes from 13°N. to 33°S. were carefully examined at the 50-, 100-, and 500-mb. levels for evidence of longitudinal phase progression of the quasi-biennial oscillation (QBO). At 50 mb. there is evidence of west to east progression although there are many irregularities and much uncertainty. The phase dates differ by days at low latitudes. At 100 and 500 mb., it appears that the QBO originates in tropical America and progresses both eastward and westward, occurring last in the Indian Ocean. The progression time ranges from 1 to 2 yr. At 500 and 100 mb., however, a cellular phase progression in possible due to the difficulty of identifying corresponding waves with a very meager network.
It appears now that the QBO may not be simultaneous in longitude and that its speed and even direction of propagation, like its other properties, may very from cycle to cycle. The analysis is being expanded to other levels and latitudes to obtain better continuity in following each wave.
Abstract
Daily data at 16 stations along five latitudes from 13°N. to 33°S. were carefully examined at the 50-, 100-, and 500-mb. levels for evidence of longitudinal phase progression of the quasi-biennial oscillation (QBO). At 50 mb. there is evidence of west to east progression although there are many irregularities and much uncertainty. The phase dates differ by days at low latitudes. At 100 and 500 mb., it appears that the QBO originates in tropical America and progresses both eastward and westward, occurring last in the Indian Ocean. The progression time ranges from 1 to 2 yr. At 500 and 100 mb., however, a cellular phase progression in possible due to the difficulty of identifying corresponding waves with a very meager network.
It appears now that the QBO may not be simultaneous in longitude and that its speed and even direction of propagation, like its other properties, may very from cycle to cycle. The analysis is being expanded to other levels and latitudes to obtain better continuity in following each wave.
Abstract
The observed variability patterns of monthly mean zonal winds over an 11-year period, from 80°N–70°S and from 20–65 km, are explained in terms of component patterns of a long-term mean, quasi-biennial, annual and semi-annual periodic variations. Interannual variations are displayed by monthly mean height-time sections for each of eleven years, and Northern Hemisphere–-Southern Hemisphere differences are seen from 11-year mean, latitude-month sections for each 10 km. An 11-year mean, height-month section at the equator shows the transition of the easterly regime at low levels to a westerly one at highest levels. Summer easterlies extend from equator to pole, from 30 to 50 km, but winter westerlies extend from equator to about 70° only at 60 km. Also, only at 60 km are there westerlies from pole to pole during the equinoxes. The stronger Southern Hemisphere westerly circulation of the troposphere is found to extend to at least 40 km, and possibly to 60 km. Southern summer easterlies are the same as, or stronger than, those in the Northern Hemisphere. Improved latitudinal rocket network coverage is needed in the Southern Hemisphere. Finer time resolution is essential everywhere to obtain diurnal variations.
Abstract
The observed variability patterns of monthly mean zonal winds over an 11-year period, from 80°N–70°S and from 20–65 km, are explained in terms of component patterns of a long-term mean, quasi-biennial, annual and semi-annual periodic variations. Interannual variations are displayed by monthly mean height-time sections for each of eleven years, and Northern Hemisphere–-Southern Hemisphere differences are seen from 11-year mean, latitude-month sections for each 10 km. An 11-year mean, height-month section at the equator shows the transition of the easterly regime at low levels to a westerly one at highest levels. Summer easterlies extend from equator to pole, from 30 to 50 km, but winter westerlies extend from equator to about 70° only at 60 km. Also, only at 60 km are there westerlies from pole to pole during the equinoxes. The stronger Southern Hemisphere westerly circulation of the troposphere is found to extend to at least 40 km, and possibly to 60 km. Southern summer easterlies are the same as, or stronger than, those in the Northern Hemisphere. Improved latitudinal rocket network coverage is needed in the Southern Hemisphere. Finer time resolution is essential everywhere to obtain diurnal variations.
Abstract
The mean and individual seasonal reversal progressions are described for each of the 11 years of available rocket observations from 80°N to 80°S, and from 20 to 65 km. Isochrone sections were based on the time sections of the preceding paper and on frequencies of east-west wind data.
In the Northern Hemisphere the mean spring reversal starts in early April at highest altitudes and progresses downward and southward. The mean fall reversal proceeds simultaneously both upward from 20 km and downward from 60 km at high latitudes and then southward and downward. Both the onset and direction of the spring reversal are highly irregular from year to year, but the fall process is very uniform and rapid, starting in August and reaching 20 km in the subtropics in two months.
The Southern Hemisphere spring reversal appears to move from low to high latitudes oppositely to that in the Northern Hemisphere, and downward, taking about three months to reach 60°S at 20 km. The Southern Hemisphere fall proceeds to low latitudes and altitudes from both highest subtropical altitudes and lowest polar altitudes. The local nature of spring reversals for individual years is stressed.
Abstract
The mean and individual seasonal reversal progressions are described for each of the 11 years of available rocket observations from 80°N to 80°S, and from 20 to 65 km. Isochrone sections were based on the time sections of the preceding paper and on frequencies of east-west wind data.
In the Northern Hemisphere the mean spring reversal starts in early April at highest altitudes and progresses downward and southward. The mean fall reversal proceeds simultaneously both upward from 20 km and downward from 60 km at high latitudes and then southward and downward. Both the onset and direction of the spring reversal are highly irregular from year to year, but the fall process is very uniform and rapid, starting in August and reaching 20 km in the subtropics in two months.
The Southern Hemisphere spring reversal appears to move from low to high latitudes oppositely to that in the Northern Hemisphere, and downward, taking about three months to reach 60°S at 20 km. The Southern Hemisphere fall proceeds to low latitudes and altitudes from both highest subtropical altitudes and lowest polar altitudes. The local nature of spring reversals for individual years is stressed.
Abstract
The 10.7-cm solar radio flux is considered to be highly correlated with solar extreme ultraviolet radiation, thermospheric temperatures, sunspots, and the 27-day and 11-year solar cycles. To investigate the possibility of ultraviolet radiation being a cause of the quasi-biennial oscillation in tropical stratospheric winds and temperatures, the daily values of 10.7-cm flux were subjected to a non-linear, curve-fitting analysis to determine the major component sinusoidal frequencies of the time series. No evidence was found for a period near 26 months; hence, to the extent that extended ultraviolet 10-cm flux relationship is valid, ultraviolet insolation does not appear to vary with a quasi-biennial oscillation.
Abstract
The 10.7-cm solar radio flux is considered to be highly correlated with solar extreme ultraviolet radiation, thermospheric temperatures, sunspots, and the 27-day and 11-year solar cycles. To investigate the possibility of ultraviolet radiation being a cause of the quasi-biennial oscillation in tropical stratospheric winds and temperatures, the daily values of 10.7-cm flux were subjected to a non-linear, curve-fitting analysis to determine the major component sinusoidal frequencies of the time series. No evidence was found for a period near 26 months; hence, to the extent that extended ultraviolet 10-cm flux relationship is valid, ultraviolet insolation does not appear to vary with a quasi-biennial oscillation.
