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- Author or Editor: James K. Angell x
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Abstract
Circulations in the vertical-lateral and vertical-longitudinal planes in an unstable planetary boundary layer are compared through the use of tetroon trajectories. On the average, the circulation in the transverse plane is 40% greater than in the longitudinal, but in the afternoon the transverse circulation is twice as great, providing evidence for the existence of longitudinal roll vortices at this time. The absolute magnitude of the transverse circulation increases uniformly with increase in wind speed and increase in the depth of the well-mixed layer, but the longitudinal circulation does not. The tetroon-derived stress increases with increase in wind speed and increase in absolute transverse circulation, suggesting that longitudinal roll vortices represent an efficient mechanism for the earthward transport of momentum. Comparisons are made between these tetroon results and results obtained by Deardorff from a three-dimensional numerical model of the unstable planetary boundary layer.
Abstract
Circulations in the vertical-lateral and vertical-longitudinal planes in an unstable planetary boundary layer are compared through the use of tetroon trajectories. On the average, the circulation in the transverse plane is 40% greater than in the longitudinal, but in the afternoon the transverse circulation is twice as great, providing evidence for the existence of longitudinal roll vortices at this time. The absolute magnitude of the transverse circulation increases uniformly with increase in wind speed and increase in the depth of the well-mixed layer, but the longitudinal circulation does not. The tetroon-derived stress increases with increase in wind speed and increase in absolute transverse circulation, suggesting that longitudinal roll vortices represent an efficient mechanism for the earthward transport of momentum. Comparisons are made between these tetroon results and results obtained by Deardorff from a three-dimensional numerical model of the unstable planetary boundary layer.
Abstract
Between June and November of 1970, 26 GHOST-type constant-level balloons were released from Ascension Island (8S) for flight at 30 and 50 mb. The balloons were positioned by the Interrogation, Recording and Location System (IRLS) aboard the Nimbus D satellite. Eight of the flights at 50 mb and three of the flights at 30 mb were tracked for more than one month, and one 50-mb flight was tracked continuously for more than five months while making seven circumnavigations of the earth. During the period June 1970 to March 1971, the 50-mb flights drifted northward at a mean speed of ∼0.1 m sec−1. The northward drift was a maximum in the Northern Hemisphere winter, suggesting a weak upward extension of the Hadley cell to at least 50 mb (the 30-mb data were insufficient for such an analysis). Superimposed an this drift were oscillations in meridional velocity having an approximate two-month period, with these oscillations also being most pronounced in the Northern Hemisphere winter. Small (1–3 m set−1) short-period fluctuations in meridional velocity were evident directly above the equator at 50 rob. Thew waves appear to move wesiwaid at speeds of 30–40 m sec−1 and to have a wavelength of about 90’ longitude. They were responsible for transporting small amounts of westerly momentum into the winter hemisphere. Kelvin waves were also delineated by flights near the equator. These waves appear to move eastward at speeds of 30–40 m sec−1 and to have a wavelength of 360° longitude. Some comparisons are made between these IRLS data and those obtained from GHOST balloon flights at the same heights in early 1969.
Abstract
Between June and November of 1970, 26 GHOST-type constant-level balloons were released from Ascension Island (8S) for flight at 30 and 50 mb. The balloons were positioned by the Interrogation, Recording and Location System (IRLS) aboard the Nimbus D satellite. Eight of the flights at 50 mb and three of the flights at 30 mb were tracked for more than one month, and one 50-mb flight was tracked continuously for more than five months while making seven circumnavigations of the earth. During the period June 1970 to March 1971, the 50-mb flights drifted northward at a mean speed of ∼0.1 m sec−1. The northward drift was a maximum in the Northern Hemisphere winter, suggesting a weak upward extension of the Hadley cell to at least 50 mb (the 30-mb data were insufficient for such an analysis). Superimposed an this drift were oscillations in meridional velocity having an approximate two-month period, with these oscillations also being most pronounced in the Northern Hemisphere winter. Small (1–3 m set−1) short-period fluctuations in meridional velocity were evident directly above the equator at 50 rob. Thew waves appear to move wesiwaid at speeds of 30–40 m sec−1 and to have a wavelength of about 90’ longitude. They were responsible for transporting small amounts of westerly momentum into the winter hemisphere. Kelvin waves were also delineated by flights near the equator. These waves appear to move eastward at speeds of 30–40 m sec−1 and to have a wavelength of 360° longitude. Some comparisons are made between these IRLS data and those obtained from GHOST balloon flights at the same heights in early 1969.
Abstract
The areal coverage to be expected from 300-millibar constant-pressure balloons (CPB) is examined for various numbers of releases per day from various stations. The meteorological variables which can be measured are discussed. The accuracy of balloon fixes required for useful determinations of velocity and acceleration is determined. It is shown, both theoretically and by computations from nine flights conducted by the Naval Research Laboratory in 1953, that the CPB data are adequate for the representation of the wind and pressure fields over the area covered by the trajectories. Together with radiosonde and rawin data they enable determination of the vertical velocity, but measurement of all the necessary parameters by CPB alone has not been achieved yet.
There is presented an analysis of the geostrophic deviations computed from the trajectory data, including their variation with latitude, wind speed, and pressure-gradient force.
Abstract
The areal coverage to be expected from 300-millibar constant-pressure balloons (CPB) is examined for various numbers of releases per day from various stations. The meteorological variables which can be measured are discussed. The accuracy of balloon fixes required for useful determinations of velocity and acceleration is determined. It is shown, both theoretically and by computations from nine flights conducted by the Naval Research Laboratory in 1953, that the CPB data are adequate for the representation of the wind and pressure fields over the area covered by the trajectories. Together with radiosonde and rawin data they enable determination of the vertical velocity, but measurement of all the necessary parameters by CPB alone has not been achieved yet.
There is presented an analysis of the geostrophic deviations computed from the trajectory data, including their variation with latitude, wind speed, and pressure-gradient force.
