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- Author or Editor: VITO PAGNOTTI x
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Abstract
Two cases of east coast cyclogenesis are compared. They occur under weak and strong synoptic scale forcing, respectively. A set of objective analyses with one degree latitude-longitude horizontal resolution and 100 mb vertical resolution is used to support the diagnostic analysis. A more limited subjectively prepared data set is used as a check against the objective analyses.
Vertical motions are computed from a diagnostic ten-level nonlinear balance model. The vertical motions are partitioned into contributions from latent heat release, thermal advection and differential vorticity advection. Energetics, after Lorenz, are computed from the balanced vertical motions.
One of the principal results is that thermal advection and latent heat release are both of nearly equal importance to low level convergence and vorticity production for the weak cyclone event, while differential cyclonic vorticity advection in addition is crucial to the deeper, more intense development. The kinematic analysis discloses that ascent peaks in the lower troposphere near 800 mb and again in the middle troposphere, between the mountains and the coast, for both storm developments. Convergence of in situ water vapor is the primary precipitation source. Some evidence is presented that there is a lower and upper tropospheric coupling during the passage of the weak cyclone south of New England. The stronger cyclone case is dominated by prominent synoptic-scale forcing in the upper troposphere.
An energetics analysis reveals that the barotclinic and barotropic conversions are contributing to the development of eddy kinetic energy during both storm periods. However, baroclinic conversions and the generation term show peaks when the strong storm's secondary circulation is peaking, while for the weak secondary counterpart no such correspondence is observed-in fact, minima in contributions occur.
Abstract
Two cases of east coast cyclogenesis are compared. They occur under weak and strong synoptic scale forcing, respectively. A set of objective analyses with one degree latitude-longitude horizontal resolution and 100 mb vertical resolution is used to support the diagnostic analysis. A more limited subjectively prepared data set is used as a check against the objective analyses.
Vertical motions are computed from a diagnostic ten-level nonlinear balance model. The vertical motions are partitioned into contributions from latent heat release, thermal advection and differential vorticity advection. Energetics, after Lorenz, are computed from the balanced vertical motions.
One of the principal results is that thermal advection and latent heat release are both of nearly equal importance to low level convergence and vorticity production for the weak cyclone event, while differential cyclonic vorticity advection in addition is crucial to the deeper, more intense development. The kinematic analysis discloses that ascent peaks in the lower troposphere near 800 mb and again in the middle troposphere, between the mountains and the coast, for both storm developments. Convergence of in situ water vapor is the primary precipitation source. Some evidence is presented that there is a lower and upper tropospheric coupling during the passage of the weak cyclone south of New England. The stronger cyclone case is dominated by prominent synoptic-scale forcing in the upper troposphere.
An energetics analysis reveals that the barotclinic and barotropic conversions are contributing to the development of eddy kinetic energy during both storm periods. However, baroclinic conversions and the generation term show peaks when the strong storm's secondary circulation is peaking, while for the weak secondary counterpart no such correspondence is observed-in fact, minima in contributions occur.
Abstract
The relationship between midtropospheric synoptic features and midstratospheric temperature in winter is investigated by examining averages of 5–10 yr of observations, monthly mean observations, and daily records. It is found that midstratospheric warm regions lie above midtropospheric troughs and subtropical ridges, while stratospheric cold regions occur above high-latitude tropospheric ridges. Thus, at high latitudes, an inverse correlation exists between 500-mb height and 10-mb temperatures; this correlation seems to be simultaneous in nature. The implications of these results are discussed with relation to the general circulation of the stratosphere, and in particular to the relative importance of hydrostatic adjustment, planetary wave propagation, and tidal energy.
Abstract
The relationship between midtropospheric synoptic features and midstratospheric temperature in winter is investigated by examining averages of 5–10 yr of observations, monthly mean observations, and daily records. It is found that midstratospheric warm regions lie above midtropospheric troughs and subtropical ridges, while stratospheric cold regions occur above high-latitude tropospheric ridges. Thus, at high latitudes, an inverse correlation exists between 500-mb height and 10-mb temperatures; this correlation seems to be simultaneous in nature. The implications of these results are discussed with relation to the general circulation of the stratosphere, and in particular to the relative importance of hydrostatic adjustment, planetary wave propagation, and tidal energy.
Abstract
Results of a study on back-door cold fronts for the months April through October of 1964–71 are presented. Results include information on frequency, associated air-mass duration, precipitation, temperature and dew-point temperature changes, sky cover, and rate of frontal movement. Composite 850- and 500-mb height contours are also constructed.
Our findings include: (1) for the sample period, southward penetration of back-door cold fronts is a maximum in June as is frontal frequency, (2) orography plays a prominent role in funneling shallow cold air pools southward east of the Appalachians, (3) more than half of all frontal passages are associated with trace amounts or less of precipitation, (4) heaviest precipitation tends to occur in conjunction with the advancing cold fronts at the more southern and western locations and with the returning warm fronts at northern and eastern locations, (5) temperature changes following frontal passage decrease from north to south and from the coast inland (dew-point temperature changes follow a similar pattern but not so clearly), and (6) cloudiness increases following frontal passage, especially at southern and inland locations.
The composite study reveals a short-wave trough at both the 850- and 500-mb level just east of Hudson Bay preceding the initial movement of back-door cold fronts southward. This short wave intensifies east-southeastward toward the Canadian Maritime Provinces while anticyclogenesis takes place upstream.
Abstract
Results of a study on back-door cold fronts for the months April through October of 1964–71 are presented. Results include information on frequency, associated air-mass duration, precipitation, temperature and dew-point temperature changes, sky cover, and rate of frontal movement. Composite 850- and 500-mb height contours are also constructed.
Our findings include: (1) for the sample period, southward penetration of back-door cold fronts is a maximum in June as is frontal frequency, (2) orography plays a prominent role in funneling shallow cold air pools southward east of the Appalachians, (3) more than half of all frontal passages are associated with trace amounts or less of precipitation, (4) heaviest precipitation tends to occur in conjunction with the advancing cold fronts at the more southern and western locations and with the returning warm fronts at northern and eastern locations, (5) temperature changes following frontal passage decrease from north to south and from the coast inland (dew-point temperature changes follow a similar pattern but not so clearly), and (6) cloudiness increases following frontal passage, especially at southern and inland locations.
The composite study reveals a short-wave trough at both the 850- and 500-mb level just east of Hudson Bay preceding the initial movement of back-door cold fronts southward. This short wave intensifies east-southeastward toward the Canadian Maritime Provinces while anticyclogenesis takes place upstream.
