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Abstract
Sea level pressure, surface air temperature, and 700-mb temperature and geopotential height show a probable association with the 11-year solar cycle which can be observed only if the data are divided according to the phase of the Quasi-Biennial Oscillation. The range of the response is as large as the interannual variability of the given element, and the correlations prove statistically meaningful when tested by Monte Carlo techniques. The sign of the correlations changes over the hemisphere on the spatial scale of extensive teleconnections. The correlations at 700 mb tend to be of opposite sign in the east and west years of the QBO, a result which Labitzke and van Loon also found in an analysis of the stratosphere. The pattern of correlation between the 700-mb heights on the Northern Hemisphere and the solar flux is the same as that of point-to-point correlations (teleconnections) between the 700-mb height at selected points and the heights at all other points. We interpret this similarity as a property of the atmosphere's internal dynamics, a favored resonance evoked within the atmosphere itself or by extraneous effects.
Abstract
Sea level pressure, surface air temperature, and 700-mb temperature and geopotential height show a probable association with the 11-year solar cycle which can be observed only if the data are divided according to the phase of the Quasi-Biennial Oscillation. The range of the response is as large as the interannual variability of the given element, and the correlations prove statistically meaningful when tested by Monte Carlo techniques. The sign of the correlations changes over the hemisphere on the spatial scale of extensive teleconnections. The correlations at 700 mb tend to be of opposite sign in the east and west years of the QBO, a result which Labitzke and van Loon also found in an analysis of the stratosphere. The pattern of correlation between the 700-mb heights on the Northern Hemisphere and the solar flux is the same as that of point-to-point correlations (teleconnections) between the 700-mb height at selected points and the heights at all other points. We interpret this similarity as a property of the atmosphere's internal dynamics, a favored resonance evoked within the atmosphere itself or by extraneous effects.
Abstract
Composite surface pressure, temperature, and precipitation anomalies are mapped over the Indian and Pacific sectors during the various stages of Warm and Cold Events in the Southern Oscillation. In the year before the development of positive sea surface temperature anomalies in the central and eastern equatorial Pacific (Year–1 of a Warm Event), a strong South Pacific High is associated with below normal surface pressure over Australia and the Indian Ocean. This occurs concurrently with a poleward displacement of the Pacific convergence zones, with above normal air temperature and precipitation over the subtropical Pacific, and opposite conditions along the equator. By the next year (Year 0) of the Warm Event, thew anomalies have the opposite sign. The sequence of anomalies during a Cold Event is inverse to that during a Warm Event but otherwise the anomaly patterns are remarkably similar.
It appears that enhanced convection and low surface pressure within the Pacific convergence zones contribute to the observed westerly wind anomalies in the western equatorial Pacific at the end of Year–1, which are in turn tied to the onset of above normal equatorial SST in the following year. The observed reversal in atmospheric anomalies over the Indian and Pacific oceans daring Warm Events is an extreme manifestation of a general biennial tendency in these anomalies, with Cold Events occupying the opposite extreme.
Abstract
Composite surface pressure, temperature, and precipitation anomalies are mapped over the Indian and Pacific sectors during the various stages of Warm and Cold Events in the Southern Oscillation. In the year before the development of positive sea surface temperature anomalies in the central and eastern equatorial Pacific (Year–1 of a Warm Event), a strong South Pacific High is associated with below normal surface pressure over Australia and the Indian Ocean. This occurs concurrently with a poleward displacement of the Pacific convergence zones, with above normal air temperature and precipitation over the subtropical Pacific, and opposite conditions along the equator. By the next year (Year 0) of the Warm Event, thew anomalies have the opposite sign. The sequence of anomalies during a Cold Event is inverse to that during a Warm Event but otherwise the anomaly patterns are remarkably similar.
It appears that enhanced convection and low surface pressure within the Pacific convergence zones contribute to the observed westerly wind anomalies in the western equatorial Pacific at the end of Year–1, which are in turn tied to the onset of above normal equatorial SST in the following year. The observed reversal in atmospheric anomalies over the Indian and Pacific oceans daring Warm Events is an extreme manifestation of a general biennial tendency in these anomalies, with Cold Events occupying the opposite extreme.
Abstract
The 200-mb tropical wind fields analyzed at Florida State University for 1965–74 and the 200 and 700 mb tropical wind fields from the National Meteorological Center for 1979–82 were used to explore the mechanism for the interannual variation of the tropical easterly jet. This jet is generally weaker during the summers of Warm Events (dry summers) in the Southern Oscillation when anomalously warm surface water appears over the eastern and central equatorial Pacific and drought occurs over the Indian subcontinent. It is observed that divergence (convergence) exists on the upstream (downstream) side of the jet. The tropical divergent circulations, i.e., the east-west Walker and the local Hadley circulations, during such summers are weakened and shifted eastward. Therefore, divergence anomalies appear in the upper troposphere over equatorial Africa or the cast coast of Africa, whole convergence anomalies exist over the Indian subcontinent or the Arabian Sea. These changes of the tropical divergent circulations may cause the change in the energetics maintenance of the tropical easterly jet. Our analysis shows that the divergence anomalies of the divergent kinetic energy flux appear over the east coast of Africa, and the convergence anomalies of divergent kinetic energy flux appear over the Indian subcontinent. It is inferred from these anomalies of kinetic energy flux that the kinetic energy generation and destruction associated with the tropical easterly jet are less in dry summers.
Based upon these changes in the upper-level tropical circulations during dry summers, a suggestion is altered that relates the anomalously warm surface water over the eastern and central equatorial Pacific to the weakening of the low-level monsoon circulation and the tropical easterly jet.
Abstract
The 200-mb tropical wind fields analyzed at Florida State University for 1965–74 and the 200 and 700 mb tropical wind fields from the National Meteorological Center for 1979–82 were used to explore the mechanism for the interannual variation of the tropical easterly jet. This jet is generally weaker during the summers of Warm Events (dry summers) in the Southern Oscillation when anomalously warm surface water appears over the eastern and central equatorial Pacific and drought occurs over the Indian subcontinent. It is observed that divergence (convergence) exists on the upstream (downstream) side of the jet. The tropical divergent circulations, i.e., the east-west Walker and the local Hadley circulations, during such summers are weakened and shifted eastward. Therefore, divergence anomalies appear in the upper troposphere over equatorial Africa or the cast coast of Africa, whole convergence anomalies exist over the Indian subcontinent or the Arabian Sea. These changes of the tropical divergent circulations may cause the change in the energetics maintenance of the tropical easterly jet. Our analysis shows that the divergence anomalies of the divergent kinetic energy flux appear over the east coast of Africa, and the convergence anomalies of divergent kinetic energy flux appear over the Indian subcontinent. It is inferred from these anomalies of kinetic energy flux that the kinetic energy generation and destruction associated with the tropical easterly jet are less in dry summers.
Based upon these changes in the upper-level tropical circulations during dry summers, a suggestion is altered that relates the anomalously warm surface water over the eastern and central equatorial Pacific to the weakening of the low-level monsoon circulation and the tropical easterly jet.
Abstract
We describe the global correlations between a measure of the Southern Oscillation and sea level pressure and surface air temperature in the northern winter. The stability of these correlations were tested on the Northern Hemisphere for an 80-year period, and it turned out that most stable correlation coefficients were found over India, the North Pacific Ocean, the Rocky Mountains, and the central and western North Atlantic Ocean. On the Southern Hemisphere most records are too short for a similar test, but the following may tentatively be said about the Southern Oscillation in middle and high southern latitudes: when pressure is low in lower latitudes over the South Pacific Ocean it tends to be high at higher latitudes of that ocean, high over East Antarctica and low in the belt of westerlies in the Indian and South Atlantic oceans. In the zonal average on both hemispheres the pressure gradients in this extreme of the oscillation tend to be steeper at lower latitudes and flatter at higher latitudes than in the other extreme. The apparent large-scale sympathetic variations between the SO and temperature are shown to occur over the relatively wide range of periods dust have been attributed to the SO itself.
Abstract
We describe the global correlations between a measure of the Southern Oscillation and sea level pressure and surface air temperature in the northern winter. The stability of these correlations were tested on the Northern Hemisphere for an 80-year period, and it turned out that most stable correlation coefficients were found over India, the North Pacific Ocean, the Rocky Mountains, and the central and western North Atlantic Ocean. On the Southern Hemisphere most records are too short for a similar test, but the following may tentatively be said about the Southern Oscillation in middle and high southern latitudes: when pressure is low in lower latitudes over the South Pacific Ocean it tends to be high at higher latitudes of that ocean, high over East Antarctica and low in the belt of westerlies in the Indian and South Atlantic oceans. In the zonal average on both hemispheres the pressure gradients in this extreme of the oscillation tend to be steeper at lower latitudes and flatter at higher latitudes than in the other extreme. The apparent large-scale sympathetic variations between the SO and temperature are shown to occur over the relatively wide range of periods dust have been attributed to the SO itself.
Abstract
We have investigated the relationship between the extremes of the Southern Oscillation and the following quantities at 700 mb in winter, 1948/1949 to 1978/1979: eddy transfer of sensible heat, temperature, geopotential height and geostrophic wind. In the phase of the Southern Oscillation when pressures are high over the tropical South Indian Ocean and low over the tropical South Pacific Ocean, in contrast with the opposite pressure distribution, the zonal mean poleward flux of sensible heat in the quasistationary waves tends to be higher in middle latitudes; the temperatures and heights tend to be lower between 30 and 60°N with the maximum difference at 45°N; the geostrophic wind tends to be stronger south of 45°N and weaker to the north; and the transfer of sensible heat by the transient waves tends to be stronger south of 45°S, and weaker to the north.
In this extreme of the Southern Oscillation the zonal mean geostrophic wind on both hemispheres is stronger in the subtropics and weaker at higher latitudes than in the other extreme when pressures are high over the tropical South Pacific and low in the tropical South Indian Ocean.
Abstract
We have investigated the relationship between the extremes of the Southern Oscillation and the following quantities at 700 mb in winter, 1948/1949 to 1978/1979: eddy transfer of sensible heat, temperature, geopotential height and geostrophic wind. In the phase of the Southern Oscillation when pressures are high over the tropical South Indian Ocean and low over the tropical South Pacific Ocean, in contrast with the opposite pressure distribution, the zonal mean poleward flux of sensible heat in the quasistationary waves tends to be higher in middle latitudes; the temperatures and heights tend to be lower between 30 and 60°N with the maximum difference at 45°N; the geostrophic wind tends to be stronger south of 45°N and weaker to the north; and the transfer of sensible heat by the transient waves tends to be stronger south of 45°S, and weaker to the north.
In this extreme of the Southern Oscillation the zonal mean geostrophic wind on both hemispheres is stronger in the subtropics and weaker at higher latitudes than in the other extreme when pressures are high over the tropical South Pacific and low in the tropical South Indian Ocean.
Abstract
Tropical teleconnections to the seesaw in winter mean temperatures between Greenland and northern Europe are described in terms of the trade winds, African precipitation, sea surface temperatures and Gulf Stream intensity as indicated by changes in relative sea levels. There is a statistically significant correlation between the strength of the northeast and southeast trades in the Atlantic during seesaw winters, but not in other winters. Latitudinal differences in the position of the ITCZ over Africa, as defined by the belt of heaviest precipitation, are seen between the two modes of the seesaw but not in other circulation types.
Relative sea levels on either side of the Gulf Stream show that geostrophic velocity of the surface current is out of phase with the strength of the trades in the North Atlantic Ocean during seesaw winters, which presumably indicates that in this region steric effects on the current prevail over the influence of the wind. Small-magnitude pressure anomaly patterns of the type seen during seesaw winters are present in autumns preceding those winters, and sea surface temperature anomalies associated with the seesaw occur at all latitudes in summers and autumns preceding, and springs following seesaw winters.
Abstract
Tropical teleconnections to the seesaw in winter mean temperatures between Greenland and northern Europe are described in terms of the trade winds, African precipitation, sea surface temperatures and Gulf Stream intensity as indicated by changes in relative sea levels. There is a statistically significant correlation between the strength of the northeast and southeast trades in the Atlantic during seesaw winters, but not in other winters. Latitudinal differences in the position of the ITCZ over Africa, as defined by the belt of heaviest precipitation, are seen between the two modes of the seesaw but not in other circulation types.
Relative sea levels on either side of the Gulf Stream show that geostrophic velocity of the surface current is out of phase with the strength of the trades in the North Atlantic Ocean during seesaw winters, which presumably indicates that in this region steric effects on the current prevail over the influence of the wind. Small-magnitude pressure anomaly patterns of the type seen during seesaw winters are present in autumns preceding those winters, and sea surface temperature anomalies associated with the seesaw occur at all latitudes in summers and autumns preceding, and springs following seesaw winters.
Abstract
We have investigated the well-known tendency for winter temperatures to be low over northern Europe when they are high over Greenland and the Canadian Arctic, and conversely. Well-defined pressure anomalies over most of the Northern Hemisphere are associated with this regional seesaw in temperature, and these pressure anomalies are so distributed that the pressure in the region of the Icelandic low is negatively correlated with the pressure over the North Pacific Ocean and over the area south of 50°N in the North Atlantic Ocean, Mediterranean and Middle East, but positively correlated with the pressure over the Rocky Mountains. The composite patterns of pressure anomalies in the seesaw are almost identical to the fist eigenvector in the monthly mean pressure, but the standard deviations of pressure anomalies in seesaw mouths are as large as the standard deviations of monthly means in general. Since 1840 the seesaw, as defined by temperatures in Scandinavia and Greenland, occurred in more than 40% of the winter months and the occurrences are seemingly not randomly distributed in time as one anomaly pattern would be more frequent than the other for several decades. For this reason the circulation anomalies in the seesaw come to play an important part in deciding the level of regional mean temperatures in winter and thus in deciding the long-term temperature trends. These regional temperature trends are then closely associated with change in frequency of atmospheric circulation types, and it is therefore unlikely that the trends are caused directly by changes in insolation or in atmospheric constituents and aerosols.
Abstract
We have investigated the well-known tendency for winter temperatures to be low over northern Europe when they are high over Greenland and the Canadian Arctic, and conversely. Well-defined pressure anomalies over most of the Northern Hemisphere are associated with this regional seesaw in temperature, and these pressure anomalies are so distributed that the pressure in the region of the Icelandic low is negatively correlated with the pressure over the North Pacific Ocean and over the area south of 50°N in the North Atlantic Ocean, Mediterranean and Middle East, but positively correlated with the pressure over the Rocky Mountains. The composite patterns of pressure anomalies in the seesaw are almost identical to the fist eigenvector in the monthly mean pressure, but the standard deviations of pressure anomalies in seesaw mouths are as large as the standard deviations of monthly means in general. Since 1840 the seesaw, as defined by temperatures in Scandinavia and Greenland, occurred in more than 40% of the winter months and the occurrences are seemingly not randomly distributed in time as one anomaly pattern would be more frequent than the other for several decades. For this reason the circulation anomalies in the seesaw come to play an important part in deciding the level of regional mean temperatures in winter and thus in deciding the long-term temperature trends. These regional temperature trends are then closely associated with change in frequency of atmospheric circulation types, and it is therefore unlikely that the trends are caused directly by changes in insolation or in atmospheric constituents and aerosols.
Abstract
No abstract available.
Abstract
No abstract available.
Abstract
Description of the seesaw in wintertime climate between Greenland and northern Europe is continued in terms of variations in long waves, frequencies of highs and lows, zonal geostrophic winds, precipitation, sea ice and sea surface temperatures. The monthly variations in four circulation modes are described. Significant spatial correlations exist between the zonal. component of the geostrophic wind in the area of the strongest westerlies in the North Atlantic Ocean and the zonal geostrophic wind elsewhere north of 20°N in winter. Long waves 1 and 2 change substantially from one phase of the seesaw to the other at 63°N. At 45°N only wave 2 changes appreciably between phases.
Large, statisticaly significant anomalies occur during and after seesaw winters in the atmosphere-ocean-ice system of the North Atlantic Ocean and its periphery, as well as in the North Pacific Ocean. Anomalies of sea surface temperature which develop during seesaw winters tend to persist through the subsequent spring and summer. In addition, the seesaw modes are characterized by significantly different ice conditions in Davis Strait, near Newfoundland, and in the Baltic Sea in winter and during the following spring.
Abstract
Description of the seesaw in wintertime climate between Greenland and northern Europe is continued in terms of variations in long waves, frequencies of highs and lows, zonal geostrophic winds, precipitation, sea ice and sea surface temperatures. The monthly variations in four circulation modes are described. Significant spatial correlations exist between the zonal. component of the geostrophic wind in the area of the strongest westerlies in the North Atlantic Ocean and the zonal geostrophic wind elsewhere north of 20°N in winter. Long waves 1 and 2 change substantially from one phase of the seesaw to the other at 63°N. At 45°N only wave 2 changes appreciably between phases.
Large, statisticaly significant anomalies occur during and after seesaw winters in the atmosphere-ocean-ice system of the North Atlantic Ocean and its periphery, as well as in the North Pacific Ocean. Anomalies of sea surface temperature which develop during seesaw winters tend to persist through the subsequent spring and summer. In addition, the seesaw modes are characterized by significantly different ice conditions in Davis Strait, near Newfoundland, and in the Baltic Sea in winter and during the following spring.
Abstract
The circulation anomalies over the whole Southern Hemisphere in the First GARP Global Experiment (FGGE) were not those that one would expect in either extreme of the Southern Oscillation; examples of the anomalies in such extremes are given. The zonally averaged pressure gradients between 50 and 65°S in FGGE when compared with those of several other years turned out to be abnormally strong in winter (2.5σ above the mean), and moderately strong in summer (1.4σ. above the mean). The 500 mb heights were above normal in middle latitudes and below normal at high latitudes when compared with station data from series 16–29 years long. As the computations are based on operational analyses they are not final, although the conclusions are unlikely to be changed by the use of the complete FGGE data set.
Abstract
The circulation anomalies over the whole Southern Hemisphere in the First GARP Global Experiment (FGGE) were not those that one would expect in either extreme of the Southern Oscillation; examples of the anomalies in such extremes are given. The zonally averaged pressure gradients between 50 and 65°S in FGGE when compared with those of several other years turned out to be abnormally strong in winter (2.5σ above the mean), and moderately strong in summer (1.4σ. above the mean). The 500 mb heights were above normal in middle latitudes and below normal at high latitudes when compared with station data from series 16–29 years long. As the computations are based on operational analyses they are not final, although the conclusions are unlikely to be changed by the use of the complete FGGE data set.
