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Abstract
Assuming a simple pyrheliometric station model, an equation is derived relating the amount of insolation Q from a sky whose fraction C is covered by clouds, to the insolation Q 0, arriving at the same surface from a cloudless sky. The equation is of the form
Q/QO=1-(A-a)(1+a)C,
where A is the sum of cloud albedo and absorptivity expressed as fraction of the radiation incident on cloud tops and the symbol a represents the depletion coefficient of insolation in cloudless air in the layer between cloud top and cloud base levels.
The theoretical equation resembles the empirical equation Q/Q 0=1−kC where k is supposed to be a constant. The theoretical equation shows the dependence of k on relevant physical variables.
It is shown that the theoretical equation combined with results of pyrheliometric observations, from which a value of k has been deduced, leads to a value of A which is in close accord with its value obtained by independent methods. On the other hand, if we assume reasonable values for A and a, the resulting value for k is in good agreement with the best value found from pyrheliometric observations.
Abstract
Assuming a simple pyrheliometric station model, an equation is derived relating the amount of insolation Q from a sky whose fraction C is covered by clouds, to the insolation Q 0, arriving at the same surface from a cloudless sky. The equation is of the form
Q/QO=1-(A-a)(1+a)C,
where A is the sum of cloud albedo and absorptivity expressed as fraction of the radiation incident on cloud tops and the symbol a represents the depletion coefficient of insolation in cloudless air in the layer between cloud top and cloud base levels.
The theoretical equation resembles the empirical equation Q/Q 0=1−kC where k is supposed to be a constant. The theoretical equation shows the dependence of k on relevant physical variables.
It is shown that the theoretical equation combined with results of pyrheliometric observations, from which a value of k has been deduced, leads to a value of A which is in close accord with its value obtained by independent methods. On the other hand, if we assume reasonable values for A and a, the resulting value for k is in good agreement with the best value found from pyrheliometric observations.
Abstract
An empirical method described by Klein is applied to calculate insolation for the Lake Hefner, Okla., area for 1 year of the Lake Hefner Studies. For some of the months, the computed values show unsatisfactory agreement with the observed amounts, but the computed annual total is in close accord with the observed annual total.
It is suggested that agreement between the monthly values may be improved by introducing a curvilinear regression in the formula whereby account is taken of the depletion of insolation by sky coverage.
Abstract
An empirical method described by Klein is applied to calculate insolation for the Lake Hefner, Okla., area for 1 year of the Lake Hefner Studies. For some of the months, the computed values show unsatisfactory agreement with the observed amounts, but the computed annual total is in close accord with the observed annual total.
It is suggested that agreement between the monthly values may be improved by introducing a curvilinear regression in the formula whereby account is taken of the depletion of insolation by sky coverage.
Abstract
A method is described for calculating mean values of some meteorological elements for the periods sunrise to sunset, and sunset to sunrise, respectively. The method is simple to apply and requires relatively few data, provided that the diurnal variation of the element concerned may be adequately represented by the first two Fourier waves. The method takes full account of the date of the day and the latitude of the station for which the mean values are desired.
A nomogram is presented to aid computation of the relevant mean values.
Abstract
A method is described for calculating mean values of some meteorological elements for the periods sunrise to sunset, and sunset to sunrise, respectively. The method is simple to apply and requires relatively few data, provided that the diurnal variation of the element concerned may be adequately represented by the first two Fourier waves. The method takes full account of the date of the day and the latitude of the station for which the mean values are desired.
A nomogram is presented to aid computation of the relevant mean values.
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Abstract
Attention is drawn to the observational fact that the rate of turning of the direction of sea and land breezes is far from uniform over the diurnal cycle. A theoretical analysis of the problem is then undertaken for a two-dimensional sea and land breeze model. It is shown that the rate of local turning equals the sum of three principal terms. The first term is −k f (f = Coriolis parameter, k = vertical unit vector), a term known from previous theoretical work; the second is the cross product of the horizontal mesoscale pressure gradient (approximately equivalent to the diurnal heating/cooUng of the land relative to the sea) and the velocity of the breezes; the third involves the cross product of the horizontal large-scale pressure gradient, assumed not be affected by the diurnal beating, and the aforementioned velocity. All three terms represent rotation about the vertical but, while the first term is a constant, the other two are variable both in magnitude and sign. These two variable terms modulate the rate of turning in an important manner. Finally, the theoretical predictions are compared with observations and special situations are studied.
Abstract
Attention is drawn to the observational fact that the rate of turning of the direction of sea and land breezes is far from uniform over the diurnal cycle. A theoretical analysis of the problem is then undertaken for a two-dimensional sea and land breeze model. It is shown that the rate of local turning equals the sum of three principal terms. The first term is −k f (f = Coriolis parameter, k = vertical unit vector), a term known from previous theoretical work; the second is the cross product of the horizontal mesoscale pressure gradient (approximately equivalent to the diurnal heating/cooUng of the land relative to the sea) and the velocity of the breezes; the third involves the cross product of the horizontal large-scale pressure gradient, assumed not be affected by the diurnal beating, and the aforementioned velocity. All three terms represent rotation about the vertical but, while the first term is a constant, the other two are variable both in magnitude and sign. These two variable terms modulate the rate of turning in an important manner. Finally, the theoretical predictions are compared with observations and special situations are studied.
Abstract
The absorption spectra of 49% 73% and 98% sulfuric acid water solutions for wavelengths of 0.3–6.5.μ and those of ammonium sulfate for 0.3–25 μ are either measured for the purposes of this study or quoted from the literature. Sulfuric acid water solutions have an absorption in the range 1.6–6.5μ. Absorption by 49% and 73% solutions is particularly strong. It is much stronger than absorption by liquid water over most of the range. Ammonium sulfate has no absorption of any significance from 0,3 to 2.85μ but has four absorption bands in the range 2.85-25μ, the largest absorption occurring at about 9.25μ in the terrestrial radiation “window.”
The conclusions are as follows: 1) sulfuric acid water solution droplets will absorb solar radiation in the near IR, about 2μ 2) ammonium sulfate particles will not absorb solar radiation; and 3) both will, of course, scatter solar radiation.
The above results are relevant to the absorption of solar radiation by droplets or by solid particles in the lower stratosphere as well as to a similar absorption in the lower atmosphere of industrially polluted areas.
Abstract
The absorption spectra of 49% 73% and 98% sulfuric acid water solutions for wavelengths of 0.3–6.5.μ and those of ammonium sulfate for 0.3–25 μ are either measured for the purposes of this study or quoted from the literature. Sulfuric acid water solutions have an absorption in the range 1.6–6.5μ. Absorption by 49% and 73% solutions is particularly strong. It is much stronger than absorption by liquid water over most of the range. Ammonium sulfate has no absorption of any significance from 0,3 to 2.85μ but has four absorption bands in the range 2.85-25μ, the largest absorption occurring at about 9.25μ in the terrestrial radiation “window.”
The conclusions are as follows: 1) sulfuric acid water solution droplets will absorb solar radiation in the near IR, about 2μ 2) ammonium sulfate particles will not absorb solar radiation; and 3) both will, of course, scatter solar radiation.
The above results are relevant to the absorption of solar radiation by droplets or by solid particles in the lower stratosphere as well as to a similar absorption in the lower atmosphere of industrially polluted areas.
Abstract
After extension of the definition of land breeze and introductory discussion of the problem of nocturnal thunderstorms, tables are presented for Lydda Airport, Israel, showing the diurnal variation of thunderstorms and the associated surface wind-directions. There is a notable excess of nocturnal thunderstorms with wind directions in the quadrant from which the land breeze blows.
The fundamental fact is pointed out that, because of the curvature of the coast of the eastern Mediterranean (concave toward the sea), the fields of the land breezes and the diurnal winds in the friction layer constitute a convergent wind field, particularly pronounced in the winter. The type of low over the eastern Mediterranean in which land-breeze convergences make an important contribution toward the formation of nocturnal thunderstorms is discussed briefly. A diagram shows the divergent nature of the sea breezes in summer, again, first and foremost, because of the concave curvature of the coast.
A number of stations, located on or near notably convex coasts of the eastern Mediterranean, are shown to have daytime maxima of thunderstorm activity.
U. S. Weather Bureau data also show a diurnal variation of thunderstorms which varies fairly consistently with the curvature of the coast of the United States, notably concave sections of the coast showing either a majority of nocturnal thunderstorms or, at least, a sensibly higher percentage than at the nearest convex section of the coast.
Abstract
After extension of the definition of land breeze and introductory discussion of the problem of nocturnal thunderstorms, tables are presented for Lydda Airport, Israel, showing the diurnal variation of thunderstorms and the associated surface wind-directions. There is a notable excess of nocturnal thunderstorms with wind directions in the quadrant from which the land breeze blows.
The fundamental fact is pointed out that, because of the curvature of the coast of the eastern Mediterranean (concave toward the sea), the fields of the land breezes and the diurnal winds in the friction layer constitute a convergent wind field, particularly pronounced in the winter. The type of low over the eastern Mediterranean in which land-breeze convergences make an important contribution toward the formation of nocturnal thunderstorms is discussed briefly. A diagram shows the divergent nature of the sea breezes in summer, again, first and foremost, because of the concave curvature of the coast.
A number of stations, located on or near notably convex coasts of the eastern Mediterranean, are shown to have daytime maxima of thunderstorm activity.
U. S. Weather Bureau data also show a diurnal variation of thunderstorms which varies fairly consistently with the curvature of the coast of the United States, notably concave sections of the coast showing either a majority of nocturnal thunderstorms or, at least, a sensibly higher percentage than at the nearest convex section of the coast.
