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- Author or Editor: Richard J. Reed x
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Abstract
The potential vorticity on isentropic surfaces is used to study a characteristic type of upper-level frontogenesis — the development of a sloping stable layer marked by strong vertical wind shear and rapid upward decrease in humidity. In the case studied it was found that the intense portion of the frontal zone consisted of a thin wedge of stratospheric air which had descended to very low levels (700 to 800 millibars), the frontal boundaries being a folded portion of the original tropopause.
The circulation within the frontal zone was indirect solenoidal, and surface cyclogenesis accompanied or slightly preceded the strengthening of the upper-level front. Although the frontal zone formed entirely within a polar air-mass, the strong adiabatic heating at and near the warm boundary could give the false impression that tropical air was present there at the end stage.
Abstract
The potential vorticity on isentropic surfaces is used to study a characteristic type of upper-level frontogenesis — the development of a sloping stable layer marked by strong vertical wind shear and rapid upward decrease in humidity. In the case studied it was found that the intense portion of the frontal zone consisted of a thin wedge of stratospheric air which had descended to very low levels (700 to 800 millibars), the frontal boundaries being a folded portion of the original tropopause.
The circulation within the frontal zone was indirect solenoidal, and surface cyclogenesis accompanied or slightly preceded the strengthening of the upper-level front. Although the frontal zone formed entirely within a polar air-mass, the strong adiabatic heating at and near the warm boundary could give the false impression that tropical air was present there at the end stage.
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Abstract
A two-level graphical prediction model is extended so as to include the effects of heating of cold air by relatively warm water. Orographic effects are also included in the model.
The model is applied to a case of a major storm development in the Gulf of Alaska attended by a strong outbreak of Arctic air from the Alaskan mainland. In this case the effects of nonadiabatic heating and orography appeared to be significant and in a direction which tended to improve the forecast.
Abstract
A two-level graphical prediction model is extended so as to include the effects of heating of cold air by relatively warm water. Orographic effects are also included in the model.
The model is applied to a case of a major storm development in the Gulf of Alaska attended by a strong outbreak of Arctic air from the Alaskan mainland. In this case the effects of nonadiabatic heating and orography appeared to be significant and in a direction which tended to improve the forecast.
Abstract
A method is presented for preparing 1000-millibar (surface) prognostic charts. The method makes use of the graphical technique developed by Fjörtoft and is based on a baroclinic model which resembles closely that employed by Estoque in the prediction of cyclone development.
Three cases tested to date have yielded correlations of 0.93, 0.89 and 0.88 between predicted and observed 1000-mb height changes.
Abstract
A method is presented for preparing 1000-millibar (surface) prognostic charts. The method makes use of the graphical technique developed by Fjörtoft and is based on a baroclinic model which resembles closely that employed by Estoque in the prediction of cyclone development.
Three cases tested to date have yielded correlations of 0.93, 0.89 and 0.88 between predicted and observed 1000-mb height changes.
Abstract
The relative importance of horizontal advection and vertical motion in producing the day-to-day changes in total ozone amount is calculated, and the manner in which these two factors combine to produce the well-known ozone-weather relationships is explained. The calculations show that at most one third of the range of daily values is attributable to vertical motions, the remainder presumably being the result of horizontal advection.
Abstract
The relative importance of horizontal advection and vertical motion in producing the day-to-day changes in total ozone amount is calculated, and the manner in which these two factors combine to produce the well-known ozone-weather relationships is explained. The calculations show that at most one third of the range of daily values is attributable to vertical motions, the remainder presumably being the result of horizontal advection.
Abstract
Composite fields of the large-scale variables determined from three months of observations at a triangular array of stations are used to determine the vorticity budget of easterly wave disturbances in the tropical western Pacific. The measurements reveal substantial imbalances which are largest in the disturbed or convectively active region of the waves. In this region there exists an apparent vorticity sink for the large-scale motions in the lower half of the troposphere and an apparent source in a relatively thin layer of the upper troposphere.
Cumulus modelling assumptions are employed to estimate vertical cloud mass flux and vertical profiles of cloud vorticity. It is concluded that the low-level sink and upper-level source can be attributed to the removal of vorticity-rich air from the lower layers and its deposition aloft by deep convection.
Abstract
Composite fields of the large-scale variables determined from three months of observations at a triangular array of stations are used to determine the vorticity budget of easterly wave disturbances in the tropical western Pacific. The measurements reveal substantial imbalances which are largest in the disturbed or convectively active region of the waves. In this region there exists an apparent vorticity sink for the large-scale motions in the lower half of the troposphere and an apparent source in a relatively thin layer of the upper troposphere.
Cumulus modelling assumptions are employed to estimate vertical cloud mass flux and vertical profiles of cloud vorticity. It is concluded that the low-level sink and upper-level source can be attributed to the removal of vorticity-rich air from the lower layers and its deposition aloft by deep convection.
