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- Author or Editor: Uwe Radok x
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Abstract
The skill score S=(R − E)/(T − E) (representing R actual and E expected successful categorical forecasts in a total of T forecasts) remains a valid tool for assessing the overall quality of current probabilistic long-range forecasts, which start from categorical subdivisions of the forecast area. The skill score definition is modified to become a chi variate with one degree of freedom. Two sets of skill scores computed from forecasts of U.S. monthly precipitation and mean temperature are shown to have frequency distributions of similar shape with nonzero means and standard deviations generally corresponding to smaller independent numbers of verification points than those actually used. The largest skill scores of those examined were obtained for recent precipitation forecasts during a period when forecasts using only climatology were similarly skillful. This suggests that co-operation on part of the climate system remains an essential success ingredient in extended forecasting. A sequential procedure for monitoring the changing level of operational forecasting skill is described.
Abstract
The skill score S=(R − E)/(T − E) (representing R actual and E expected successful categorical forecasts in a total of T forecasts) remains a valid tool for assessing the overall quality of current probabilistic long-range forecasts, which start from categorical subdivisions of the forecast area. The skill score definition is modified to become a chi variate with one degree of freedom. Two sets of skill scores computed from forecasts of U.S. monthly precipitation and mean temperature are shown to have frequency distributions of similar shape with nonzero means and standard deviations generally corresponding to smaller independent numbers of verification points than those actually used. The largest skill scores of those examined were obtained for recent precipitation forecasts during a period when forecasts using only climatology were similarly skillful. This suggests that co-operation on part of the climate system remains an essential success ingredient in extended forecasting. A sequential procedure for monitoring the changing level of operational forecasting skill is described.
A representative picture, from the aeronautical point of view, of vertical currents above mountainous country is obtained by letting these currents act on an aircraft set to fly horizontally in still air. Pressure and temperature traces recorded by such an aircraft give the effective vertical velocities and some idea of the temperature lapse rate in the undisturbed stream. Two sets of results are given for illustration. One shows low-level lee waves which were caused presumably by a temperature inversion; the other is a case of strong turbulence side by side with a smooth wave, in which downdrafts reached 1600 ft/min in an 18-knot wind.
A representative picture, from the aeronautical point of view, of vertical currents above mountainous country is obtained by letting these currents act on an aircraft set to fly horizontally in still air. Pressure and temperature traces recorded by such an aircraft give the effective vertical velocities and some idea of the temperature lapse rate in the undisturbed stream. Two sets of results are given for illustration. One shows low-level lee waves which were caused presumably by a temperature inversion; the other is a case of strong turbulence side by side with a smooth wave, in which downdrafts reached 1600 ft/min in an 18-knot wind.
Abstract
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Abstract
As first step in an investigation of changes in the high-level circulation of the southern hemisphere, more than 18,000 radiosonde flights have been used to construct a three-year series of monthly mean cross-sections for the eastern Australian sector and to draw, with their help, monthly mean 200-millibar charts for the entire region of Australia and New Zealand, by methods suited to its sparse upper-air station network. For eleven of the 36 months, the cross sections could be extended as far as the Antarctic coast to show details of a high-latitude jet stream. The 200-mb charts reveal distinct deviations from zonal flow, but only a few of these seem clearly linked to certain seasons or regions. Transitions from summer to winter flow-patterns occurred as a rule abruptly, and on several occasions coincided with the opposite transition in the zonal mean flow of the northern hemisphere.
Abstract
As first step in an investigation of changes in the high-level circulation of the southern hemisphere, more than 18,000 radiosonde flights have been used to construct a three-year series of monthly mean cross-sections for the eastern Australian sector and to draw, with their help, monthly mean 200-millibar charts for the entire region of Australia and New Zealand, by methods suited to its sparse upper-air station network. For eleven of the 36 months, the cross sections could be extended as far as the Antarctic coast to show details of a high-latitude jet stream. The 200-mb charts reveal distinct deviations from zonal flow, but only a few of these seem clearly linked to certain seasons or regions. Transitions from summer to winter flow-patterns occurred as a rule abruptly, and on several occasions coincided with the opposite transition in the zonal mean flow of the northern hemisphere.
Abstract
The “anomaly correlation” between a predicted time series and a verifying series, both of which have had the same climatic history subtracted, combines their “direct” correlation with their two climate correlations and with the variance of the historical series. The direct correlation can be freed of climatic effects to become the “partial” correlation, which therefore seems a better parameter for judging predictive skill.
Abstract
The “anomaly correlation” between a predicted time series and a verifying series, both of which have had the same climatic history subtracted, combines their “direct” correlation with their two climate correlations and with the variance of the historical series. The direct correlation can be freed of climatic effects to become the “partial” correlation, which therefore seems a better parameter for judging predictive skill.
