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- Author or Editor: STEPHEN CLODMAN x
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Abstract
This technique finds the horizontal movement of the pattern of a meteorological variable by comparing the fields of the variable at successive times. A test vector is applied to the older field, and this vector is iteratively adjusted to maximize the correlation with the new field. Thus the translation velocity of the field is estimated. This translation vector can, with appropriate adjustments, be applied to a present analysis field to obtain a short-range forecast.
This study will demonstrate the forecasting of sea level pressure with a variety of procedures based on correlation matching. One of thew procedures is extrapolative. Another applies the translation predicted by a guidance model to translate an observed field. A third procedure applies the same guidance translation to the observed-guidance field difference so as to update the guidance model result. Development as well as translation of the field is allowed for.
Case study testing, doing 6- and 12-h forecasts, is done for eastern North America in winter and early spring. The different approaches are evaluated and compared to the guidance model directly used. The results show good skill for the pattern correlation methods with the updated guidance model generally best. The advantages and uses of this approach as a forecast or analysis tool are discussed.
Abstract
This technique finds the horizontal movement of the pattern of a meteorological variable by comparing the fields of the variable at successive times. A test vector is applied to the older field, and this vector is iteratively adjusted to maximize the correlation with the new field. Thus the translation velocity of the field is estimated. This translation vector can, with appropriate adjustments, be applied to a present analysis field to obtain a short-range forecast.
This study will demonstrate the forecasting of sea level pressure with a variety of procedures based on correlation matching. One of thew procedures is extrapolative. Another applies the translation predicted by a guidance model to translate an observed field. A third procedure applies the same guidance translation to the observed-guidance field difference so as to update the guidance model result. Development as well as translation of the field is allowed for.
Case study testing, doing 6- and 12-h forecasts, is done for eastern North America in winter and early spring. The different approaches are evaluated and compared to the guidance model directly used. The results show good skill for the pattern correlation methods with the updated guidance model generally best. The advantages and uses of this approach as a forecast or analysis tool are discussed.
Abstract
Shape fitting is a method of fitting mathematical equations representing a definite shape to a meteorological field. Here, a nine-parameter vortex representation is fitted to the sea-level pressure field of a strong midlatitude low. A severe winter storm case (26–27 January 1978 in eastern North America) is documented to illustrate the method and to show that it produces an accurate fit and meaningfully describes the storm. The residual difference between the fit equations and the pressure field of the low can be interpreted as finer scale detail of the field. Applications to analysis and verification am briefly demonstrated. Test forecasts using the shape fit itself are also shown, using different possible forecast assumptions.
Abstract
Shape fitting is a method of fitting mathematical equations representing a definite shape to a meteorological field. Here, a nine-parameter vortex representation is fitted to the sea-level pressure field of a strong midlatitude low. A severe winter storm case (26–27 January 1978 in eastern North America) is documented to illustrate the method and to show that it produces an accurate fit and meaningfully describes the storm. The residual difference between the fit equations and the pressure field of the low can be interpreted as finer scale detail of the field. Applications to analysis and verification am briefly demonstrated. Test forecasts using the shape fit itself are also shown, using different possible forecast assumptions.
Abstract
The surface stress is computed by the method of geostrophic departures using 23 days of double theodolite wind observations at Shilo, Manitoba. The main results are as follows. Relations between the stress and the geostrophic wind fit these data better than do similar expressions using the surface wind. The stress varies linearly, rather than quadratically, with wind speed. For a given surface or geostrophic wind speed, the stress increases with increasing Richardson number and warm air advection.
Abstract
The surface stress is computed by the method of geostrophic departures using 23 days of double theodolite wind observations at Shilo, Manitoba. The main results are as follows. Relations between the stress and the geostrophic wind fit these data better than do similar expressions using the surface wind. The stress varies linearly, rather than quadratically, with wind speed. For a given surface or geostrophic wind speed, the stress increases with increasing Richardson number and warm air advection.
