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Abstract
Short-period cycles in the large-scale atmospheric circulation were investigated with time series of kinetic energy, its generation and outflow, which were computed twice a day for a 5-year period over the North American Continent. The spectra were computed from the autocorrelation curves, and were compared with the red noise spectra to evaluate the statistical significance of the energy cycles.
The maxima of time spectra of different energy parameters show frequent agreement. The commonly reported kinetic energy cycles with periods of one to two weeks are observed; however, they are not statistically significant and also show very high year-to-year irregularity. Significant cycles with periods around 40 days and 2–4 days are also noted.
Abstract
Short-period cycles in the large-scale atmospheric circulation were investigated with time series of kinetic energy, its generation and outflow, which were computed twice a day for a 5-year period over the North American Continent. The spectra were computed from the autocorrelation curves, and were compared with the red noise spectra to evaluate the statistical significance of the energy cycles.
The maxima of time spectra of different energy parameters show frequent agreement. The commonly reported kinetic energy cycles with periods of one to two weeks are observed; however, they are not statistically significant and also show very high year-to-year irregularity. Significant cycles with periods around 40 days and 2–4 days are also noted.
Abstract
Kinetic energy transformations from the view-point of energetics of the large-scale circulation are investigated with a series of subsynoptic scale radiosonde network soundings. Individual terms of the kinetic energy equation are evaluated along with the gradient form of the Richardson number.
A bimodal character of the vertical profile of kinetic energy generation having maxima in the upper and lower troposphere that is similar to what we observe in the genera1 circulation-scale disturbances is observed in the subsynoptic scale disturbances studied. However, the inflow of kinetic energy into the area indicates that, on the average, more kinetic energy could be dissipated than generated even during intense thunderstorm activity. Large pulsations of kinetic energy generation and dissipation with time are observed. Extrema of upper level generation are observed to occur mainly in layers where the Richardson number is relatively low.
Abstract
Kinetic energy transformations from the view-point of energetics of the large-scale circulation are investigated with a series of subsynoptic scale radiosonde network soundings. Individual terms of the kinetic energy equation are evaluated along with the gradient form of the Richardson number.
A bimodal character of the vertical profile of kinetic energy generation having maxima in the upper and lower troposphere that is similar to what we observe in the genera1 circulation-scale disturbances is observed in the subsynoptic scale disturbances studied. However, the inflow of kinetic energy into the area indicates that, on the average, more kinetic energy could be dissipated than generated even during intense thunderstorm activity. Large pulsations of kinetic energy generation and dissipation with time are observed. Extrema of upper level generation are observed to occur mainly in layers where the Richardson number is relatively low.
Abstract
The energetics in numerical weather forecast experiments with the NCAR general circulation model have been analyzed. The 6-layer, 5-degree, second-generation global model was used to make two 10-day forecasts with the same initial conditions. The two experiments differed primarily in the methods of convective parameterization.
Hemispheric integrals of the model energies and energy transformations are presented in the context of their approach to a quasi-equilibrium climatology. Spectral and spatial analyses of the eddy energies and transformations provide further insight into the model response to the initial conditions. After the initial adjustment, the eddy kinetic energy appears to lag the conversion from eddy available potential energy to eddy kinetic energy by at least 48 h in the long waves (wavenumbers 1–4) and by approximately 24 h in the baroclinic waves (wavenumbers 5–7), whereas little or no time lag is apparent in the short waves (wavenumbers 8–12).
The sensitivity of the forecast energetics to two different convective parameterizations is also examined. There is little appreciable difference between the two experiments in the eddy kinetic energy integrals during the first 36 h of the forecast, but temporal patterns of the eddy transformations are distinctly different after 12 h.
Abstract
The energetics in numerical weather forecast experiments with the NCAR general circulation model have been analyzed. The 6-layer, 5-degree, second-generation global model was used to make two 10-day forecasts with the same initial conditions. The two experiments differed primarily in the methods of convective parameterization.
Hemispheric integrals of the model energies and energy transformations are presented in the context of their approach to a quasi-equilibrium climatology. Spectral and spatial analyses of the eddy energies and transformations provide further insight into the model response to the initial conditions. After the initial adjustment, the eddy kinetic energy appears to lag the conversion from eddy available potential energy to eddy kinetic energy by at least 48 h in the long waves (wavenumbers 1–4) and by approximately 24 h in the baroclinic waves (wavenumbers 5–7), whereas little or no time lag is apparent in the short waves (wavenumbers 8–12).
The sensitivity of the forecast energetics to two different convective parameterizations is also examined. There is little appreciable difference between the two experiments in the eddy kinetic energy integrals during the first 36 h of the forecast, but temporal patterns of the eddy transformations are distinctly different after 12 h.
Abstract
A comprehensive energetics analysis has been performed on the NCAR general circulation model. The analysis involves January and July simulation experiments with the 6-layer, 5-degree, second-generation model with two different convective schemes. Spectral analysis of the energy transformations in the wave-number domain was performed separately on a global and hemispheric basis as well as for the tropics and mid-latitudes. Latitudinal distributions of energy variables were also examined.
A qualitative agreement with observational estimates is generally recognized in the transformations of eddy energies. Quantitatively, however, the eddy energies, conversions and energy transfer between wavenumbers are weaker than observational estimates. It is noteworthy that substantial differences exist in the energetics of the two versions of the model with different convective schemes.
Abstract
A comprehensive energetics analysis has been performed on the NCAR general circulation model. The analysis involves January and July simulation experiments with the 6-layer, 5-degree, second-generation model with two different convective schemes. Spectral analysis of the energy transformations in the wave-number domain was performed separately on a global and hemispheric basis as well as for the tropics and mid-latitudes. Latitudinal distributions of energy variables were also examined.
A qualitative agreement with observational estimates is generally recognized in the transformations of eddy energies. Quantitatively, however, the eddy energies, conversions and energy transfer between wavenumbers are weaker than observational estimates. It is noteworthy that substantial differences exist in the energetics of the two versions of the model with different convective schemes.
Abstract
Four numerical simulations of the global atmosphere for January 1979 are analyzed to study the formation of blocking in terms of Northern Hemisphere energetics. The Goddard Laboratory for Atmospheres (GLA) 4° × 5° latitude-longitude grid general circulation model (GCM) and 2° × 2.5° grid GCM are employed with the GLA and Geophysical Fluid Dynamics Laboratory (GFDL) initial datasets.
The difficulty in simulating a realistic blocking due to inadequate wave–wave interaction can be attributed in part to inadequate grid resolution. Among four simulations, the simulations by the high resolution GCM produce realistically strong blockings with compatible spectral energetics as in the observed blocking episodes. The latitude–height cross sections of the energy variables of wavenumber 1 is presented to describe the dipole structure of blockings. Blocking development is also examined in time series of barotropic and baroclinic components of energy and associated conversions.
Abstract
Four numerical simulations of the global atmosphere for January 1979 are analyzed to study the formation of blocking in terms of Northern Hemisphere energetics. The Goddard Laboratory for Atmospheres (GLA) 4° × 5° latitude-longitude grid general circulation model (GCM) and 2° × 2.5° grid GCM are employed with the GLA and Geophysical Fluid Dynamics Laboratory (GFDL) initial datasets.
The difficulty in simulating a realistic blocking due to inadequate wave–wave interaction can be attributed in part to inadequate grid resolution. Among four simulations, the simulations by the high resolution GCM produce realistically strong blockings with compatible spectral energetics as in the observed blocking episodes. The latitude–height cross sections of the energy variables of wavenumber 1 is presented to describe the dipole structure of blockings. Blocking development is also examined in time series of barotropic and baroclinic components of energy and associated conversions.
Abstract
A series of 12 monthly flights along a fixed path in Wisconsin and a series of 4 long-range flights over extensive areas of the United States and Canada were performed during 1963 to measure systematically the surface albedo over various types of the earth's surface, using an instrumented light airplane operating at a low level. An approximate total of 24,000 mi. was flown and roughly 210,000 sets of the measurements were processed for this study. Techniques of measurement and data treatment are discussed.
It is shown, and discussed in detail, that the regional differences and seasonal variations of the surface albedo due to thc structure and state of the earth's surface cover are significant. The snow cover is the most important modification of the earth's surface, giving a significantly higher albedo. A quantitative relationship between the increase of surface albedo and snow cover is examined. The surface albedo measured during the flights over typical surface covers over North America, including cities, is presented. The surface covers and their textures over the North American Continent were studied mainly in terms of land use, vegetation type and phenology, soil type, and ground snow cover. The surface albedo values were estimated for various regions of the continent from the flight measurement data, considering the similarity and differences in surface structure among the regions. The resulting seasonal albedo maps of North America are presented and discussed, along with the seasonal variation of the meridional profile of thc continental surface albedo.
Abstract
A series of 12 monthly flights along a fixed path in Wisconsin and a series of 4 long-range flights over extensive areas of the United States and Canada were performed during 1963 to measure systematically the surface albedo over various types of the earth's surface, using an instrumented light airplane operating at a low level. An approximate total of 24,000 mi. was flown and roughly 210,000 sets of the measurements were processed for this study. Techniques of measurement and data treatment are discussed.
It is shown, and discussed in detail, that the regional differences and seasonal variations of the surface albedo due to thc structure and state of the earth's surface cover are significant. The snow cover is the most important modification of the earth's surface, giving a significantly higher albedo. A quantitative relationship between the increase of surface albedo and snow cover is examined. The surface albedo measured during the flights over typical surface covers over North America, including cities, is presented. The surface covers and their textures over the North American Continent were studied mainly in terms of land use, vegetation type and phenology, soil type, and ground snow cover. The surface albedo values were estimated for various regions of the continent from the flight measurement data, considering the similarity and differences in surface structure among the regions. The resulting seasonal albedo maps of North America are presented and discussed, along with the seasonal variation of the meridional profile of thc continental surface albedo.
