5 research outputs found
Generation of scenarios from calibrated ensemble forecasts with a dual ensemble copula coupling approach
Probabilistic forecasts in the form of ensemble of scenarios are required for
complex decision making processes. Ensemble forecasting systems provide such
products but the spatio-temporal structures of the forecast uncertainty is lost
when statistical calibration of the ensemble forecasts is applied for each lead
time and location independently. Non-parametric approaches allow the
reconstruction of spatio-temporal joint probability distributions at a low
computational cost. For example, the ensemble copula coupling (ECC) method
rebuilds the multivariate aspect of the forecast from the original ensemble
forecasts. Based on the assumption of error stationarity, parametric methods
aim to fully describe the forecast dependence structures. In this study, the
concept of ECC is combined with past data statistics in order to account for
the autocorrelation of the forecast error. The new approach, called d-ECC, is
applied to wind forecasts from the high resolution ensemble system COSMO-DE-EPS
run operationally at the German weather service. Scenarios generated by ECC and
d-ECC are compared and assessed in the form of time series by means of
multivariate verification tools and in a product oriented framework.
Verification results over a 3 month period show that the innovative method
d-ECC outperforms or performs as well as ECC in all investigated aspects
Finite-volume models with implicit subgrid-scale parameterization for the differentially heated rotating annulus
The differentially heated rotating annulus is a classical experiment for the investigation of baroclinic flows and can be regarded as a strongly simplified laboratory model of the atmosphere in mid-latitudes. Data of this experiment, measured at the BTU Cottbus-Senftenberg, are used to validate two numerical finite-volume models (INCA and cylFloit) which differ basically in their grid structure. Both models employ an implicit parameterization of the subgrid-scale turbulence by the Adaptive Local Deconvolution Method (ALDM). One part of the laboratory procedure, which is commonly neglected in simulations, is the annulus spin-up. During this phase the annulus is accelerated from a state of rest to a desired angular velocity. We use a simple modelling approach of the spin-up to investigate whether it increases the agreement between experiment and simulation. The model validation compares the azimuthal mode numbers of the baroclinic waves and does a principal component analysis of time series of the temperature field. The Eady model of baroclinic instability provides a guideline for the qualitative understanding of the observations