Search Results
You are looking at 1 - 10 of 16 items for
- Author or Editor: Philip F. Clapp x
- Refine by Access: All Content x
Abstract
No Abstract Available.
Abstract
No Abstract Available.
Abstract
Recent work on mean-motion models of the general circulation has led to renewed interest in the parameterization (i.e., expression in terms of model-generated average variables) of the horizontal flux of heat in the atmosphere by transient eddies on the scale of cyclones.
A brief review is made of previous work on this subject and some new computations are presented, leading to confirmation of the usual assumption that the cross-isotherm flux of heat can be expressed using the well-known “Austausch coefficient” method. This empirical finding appears to agree with what is expected from the theory of cyclone development.
When considering heat flow over the globe it is necessary to account for the transient flux component parallel, as well as perpendicular, to the mean isotherms. Apparently, no empirical work has yet been done on this subject.
The geographical fields of the parallel component for different seasons of several years were examined in the light of a theoretical study of Welander, which suggests that, in a rotating fluid, there must be a component of heat flux parallel to the thermal wind and proportional to the mean temperature gradient. Appartently, Welander's conclusion (obtained for the case of small-scale turbulence) does not appear to be applicable to macroscale heat transfer on the scale of traveling wave cyclones. Nevertheless, some variants of this concept may lead to a useful parameterization of the parallel flux.
Abstract
Recent work on mean-motion models of the general circulation has led to renewed interest in the parameterization (i.e., expression in terms of model-generated average variables) of the horizontal flux of heat in the atmosphere by transient eddies on the scale of cyclones.
A brief review is made of previous work on this subject and some new computations are presented, leading to confirmation of the usual assumption that the cross-isotherm flux of heat can be expressed using the well-known “Austausch coefficient” method. This empirical finding appears to agree with what is expected from the theory of cyclone development.
When considering heat flow over the globe it is necessary to account for the transient flux component parallel, as well as perpendicular, to the mean isotherms. Apparently, no empirical work has yet been done on this subject.
The geographical fields of the parallel component for different seasons of several years were examined in the light of a theoretical study of Welander, which suggests that, in a rotating fluid, there must be a component of heat flux parallel to the thermal wind and proportional to the mean temperature gradient. Appartently, Welander's conclusion (obtained for the case of small-scale turbulence) does not appear to be applicable to macroscale heat transfer on the scale of traveling wave cyclones. Nevertheless, some variants of this concept may lead to a useful parameterization of the parallel flux.
Abstract
The most likely number of days with snow on the ground during an individual month is expressed empirically as a function of the mean temperature and total precipitation for that month, as well as the presence or absence of a snow cover at the end of the preceding month. Although this study is of some value in the field of synoptic climatology, it was designed primarily to serve as a useful method for generating snow cover within numerical weather-prediction models which do not contain water- or snow-budget formulas.
Abstract
The most likely number of days with snow on the ground during an individual month is expressed empirically as a function of the mean temperature and total precipitation for that month, as well as the presence or absence of a snow cover at the end of the preceding month. Although this study is of some value in the field of synoptic climatology, it was designed primarily to serve as a useful method for generating snow cover within numerical weather-prediction models which do not contain water- or snow-budget formulas.
Abstract
No Abstract Available.
Abstract
No Abstract Available.
Abstract
A synthesis is made of several published studies of the normal heat budget of the lower troposphere over the Northern Hemisphere in winter. Charts of heat sources and sinks are presented, based on two independent methods, one using the thermodynamic energy equation and the other a heat-balance procedure. Although there are differences in important details, both methods indicate that the horizontal scale of heating is the same as that of the normal lower-tropospheric temperature field, but that the field of heating is almost 90° out of phase with that of temperature.
This result has an important bearing on the energy budget of the circulation. It is concluded that the heat-balance method is correct in indicating that there is a positive correlation between the normal temperature and heating fields. According to the energy transformation equations, this means that there is a positive transformation from heating to potential energy at the scale of the climatological long waves. This energy is directly available for maintaining these waves against friction.
It is hoped that this study will be of some use in the design of numerical general circulation experiments, and as a basis of comparison with data from meteorological satellites.
Abstract
A synthesis is made of several published studies of the normal heat budget of the lower troposphere over the Northern Hemisphere in winter. Charts of heat sources and sinks are presented, based on two independent methods, one using the thermodynamic energy equation and the other a heat-balance procedure. Although there are differences in important details, both methods indicate that the horizontal scale of heating is the same as that of the normal lower-tropospheric temperature field, but that the field of heating is almost 90° out of phase with that of temperature.
This result has an important bearing on the energy budget of the circulation. It is concluded that the heat-balance method is correct in indicating that there is a positive correlation between the normal temperature and heating fields. According to the energy transformation equations, this means that there is a positive transformation from heating to potential energy at the scale of the climatological long waves. This energy is directly available for maintaining these waves against friction.
It is hoped that this study will be of some use in the design of numerical general circulation experiments, and as a basis of comparison with data from meteorological satellites.
Abstract
Basic problems encountered in the preparation of medium- and long-range forecasts by numerical methods are revealed through the use of time-averaged charts.
It is found that forecasts up to five days in advance may be prepared by use of the vorticity-tendency equation, provided certain broad-scale sources and sinks of vorticity are taken into account. Since these appear in the final prognosis as locally time-averaged values, it is probable that they may be sufficiently well represented by crude approximations.
It is not possible to forecast for a month or more in advance by integrating the tendency equation, because of approximate balance between the terms not containing time derivatives. A modified conservation equation is suggested as the solution to this problem.
Finally, it is suggested that the eddy transfer of meteorological properties will not be a major problem in long-range forecasting, since this transfer can probably be expressed in terms of the large-scale circulation.
Abstract
Basic problems encountered in the preparation of medium- and long-range forecasts by numerical methods are revealed through the use of time-averaged charts.
It is found that forecasts up to five days in advance may be prepared by use of the vorticity-tendency equation, provided certain broad-scale sources and sinks of vorticity are taken into account. Since these appear in the final prognosis as locally time-averaged values, it is probable that they may be sufficiently well represented by crude approximations.
It is not possible to forecast for a month or more in advance by integrating the tendency equation, because of approximate balance between the terms not containing time derivatives. A modified conservation equation is suggested as the solution to this problem.
Finally, it is suggested that the eddy transfer of meteorological properties will not be a major problem in long-range forecasting, since this transfer can probably be expressed in terms of the large-scale circulation.
Abstract
TIROS nephanalyses are used to obtain global maps and latitudinal profiles of average cloud amount for the four seasons for the year March 1962 through February 1963. It is found that the gross patterns and season-to-season variations of these cloud distributions bear a striking resemblance to corresponding features of normal cloudiness, although there are some differences which call for further study. In many cases anomalies in cloudiness can be related to corresponding anomalies of the general circulation.
In considering the magnitude as distinct from the pattern of cloudiness, there is some suggestion that during the chosen period the TIROS nephanalyses gave too much cloudiness for large cloud amount, and too little for small cloud amount.
Abstract
TIROS nephanalyses are used to obtain global maps and latitudinal profiles of average cloud amount for the four seasons for the year March 1962 through February 1963. It is found that the gross patterns and season-to-season variations of these cloud distributions bear a striking resemblance to corresponding features of normal cloudiness, although there are some differences which call for further study. In many cases anomalies in cloudiness can be related to corresponding anomalies of the general circulation.
In considering the magnitude as distinct from the pattern of cloudiness, there is some suggestion that during the chosen period the TIROS nephanalyses gave too much cloudiness for large cloud amount, and too little for small cloud amount.
Abstract
In 1947 a suggestion was made by one of the authors that the existence of fast narrow currents in the upper troposphere was due to the bringing together, or confluence, of warm and cold air masses from northerly and southerly regions. In the present paper an attempt is made to extend this theory by a somewhat more detailed examination of the dynamics of confluence. It is suggested that the energy of the jet is derived from a direct transformation of potential into kinetic energy. This source of energy is independent of stability in the usual sense, a fact which may be of some importance in understanding the general circulation. A comparison is made between this theory and the known behavior of the jet stream. Here extensive use is made of recent synoptic studies by Palmén and his co-workers and of charts showing the normal appearance of the hemispheric jet stream (which are shown for the first time). It is concluded that these observational studies tend to confirm the theory of confluence.
Abstract
In 1947 a suggestion was made by one of the authors that the existence of fast narrow currents in the upper troposphere was due to the bringing together, or confluence, of warm and cold air masses from northerly and southerly regions. In the present paper an attempt is made to extend this theory by a somewhat more detailed examination of the dynamics of confluence. It is suggested that the energy of the jet is derived from a direct transformation of potential into kinetic energy. This source of energy is independent of stability in the usual sense, a fact which may be of some importance in understanding the general circulation. A comparison is made between this theory and the known behavior of the jet stream. Here extensive use is made of recent synoptic studies by Palmén and his co-workers and of charts showing the normal appearance of the hemispheric jet stream (which are shown for the first time). It is concluded that these observational studies tend to confirm the theory of confluence.
Abstract
Vertical velocities compatible with climatological heating functions are computed. The physical assumptions in the thermodynamic equation incorporate radiational heating, heat flux from the underlying boundary, and heat of condensation. The computation is performed for the four seasons, and a comparison with other studies indicates that the method gives fairly good results that may be related to climatological cloudiness and rainfall.
Abstract
Vertical velocities compatible with climatological heating functions are computed. The physical assumptions in the thermodynamic equation incorporate radiational heating, heat flux from the underlying boundary, and heat of condensation. The computation is performed for the four seasons, and a comparison with other studies indicates that the method gives fairly good results that may be related to climatological cloudiness and rainfall.
