arXiv subjects

Christine Ziehmann

Publications and source records attributed to Christine Ziehmann.

4 recordsLinked to original sources

arXiv2004

Singular vector ensemble forecasting systems and the prediction of flow dependent uncertainty

The ECMWF ensemble weather forecasts are generated by perturbing the initial conditions of the forecast using a subset of the singular vectors of the linearised propagator. Previous results show that when creating probabilistic forecasts from this ensemble better forecasts are obtained if the mean of the spread and the variability of the spread are calibrated separately. We show results from a simple linear model that suggest that this may be a generic property for all singular vector based ensemble forecasting systems based on only a subset of the full set of singular vectors.

physics.ao-ph↗

arXiv2003

A note on the use of the word 'likelihood' in statistics and meteorology

We highlight the different uses of the word 'likelihood' that have arisen in statistics and meteorology, and make the recommendation that one of these uses should be dropped to prevent confusion and misunderstanding.

physics.ao-ph↗

arXiv2003

Five guidelines for the evaluation of site-specific medium range probabilistic temperature forecasts

Probabilistic temperature forecasts are potentially useful to the energy and weather derivatives industries. However, at present, they are little used. There are a number of reasons for this, but we believe this is in part due to inadequacies in the methodologies that have been used to evaluate such forecasts, leading to uncertainty as to whether the forecasts are really useful or not and making it hard to work out which forecasts are best. To remedy this situation we describe a set of guidelines that we recommend should be followed when evaluating the skill of site-specific probabilistic medium range temperature forecasts. If these guidelines are followed then the results of validation can be used directly by forecast users to make decisions about which forecasts to use. If they are not followed then the results of validation may be interesting, but will not be practically useful for users. We find that none of the published studies that evaluate such forecasts fall within our guidelines, and that, as a result, none convey the information that the users need to make appropriate decisions about which forecasts are best.

physics.ao-ph↗

arXiv2003

A New Framework for the Assessment and Calibration of Medium Range Ensemble Temperature Forecasts

We present a new framework for the assessment and calibration of medium range ensemble temperature forecasts. The method is based on maximising the likelihood of a simple parametric model for the temperature distribution, and leads to some new insights into the predictability of uncertainty.

physics.ao-ph↗