NUMERICAL SIMULATIONS OF THE ELBE FLOOD CASE: SENSITIVITY TO INITIAL AND BOUNDARY DATA

Numerical experiments with the model chain of the German Weather Service are conducted to find the reasons for the bad performance of the operational precipitation forecast in the case of the Elbe flood in August 2002. The sensitivity to initial and to boundary data as well as to a new precipitation scheme and the horizontal model resolution is inspected. The greatest improvement concerning the amount and location of the predicted precipitation field is achieved by using ECMWF analysis data as initial fields. Also, the implementation of a precipitation scheme that allows the rain to be advected with the wind exhibits a positive effect. Last, the better resolution of the global model improves the rainfall forecast, whereas the better resolution of the regional model produces worse results

Enumerating Hertzsprung equivalence classes defined by partitions of the symmetric group of degree three

Hertzsprung-mynstur eru umröðunarmynstur þar sem stöður og gildi mynstrana eru skilyrt til að vera aðliggjandi. Fjölskylda mengja slíkra Hertzsprung-mynstra skapa jafngildisflokka undir mynstraskiptajafngildi. Þessa flokka köllum við Hertzsprung-jafngildisflokka. Í þessari ritgerð kynnum við aðferð sem leyfir okkur að telja þessa jafngildisflokka sem Hertzsprung-mynstrin skapa. Til þess að prófa þessa aðferð skoðum við allar skiptingar á samhverfu grúpunni af þriðju gráðu. Hver þeirra getur skapað Hertzsprung-jafngildisflokk. Við náum að finna meirihluta framleiðandi falla sem telja Hertzsprung-jafngildisflokka sem skilgreindir eru af þessum skiptingum.Hertzsprung patterns are permutation patterns in which both positions and values are required to be adjacent. A family of sets of Hertzsprung patterns induces equivalence classes by a pattern-replacement equivalence. In this paper, we introduce a method that allows us to automatically enumerate these equivalence classes for some families. We manage to find the generating functions which enumerate the Hertzsprung-equivalence classes defined by a majority of the set partitions of the symmetric group of degree three

Mechanisms of midlatitude cross-tropopause transport using a potential vorticity budget approach

[ 1] A potential vorticity (PV) budget method has been used to attribute vertical transport across the near-tropopause ( 1 PVU surface) in extratropical weather systems to radiative, latent heating and cooling, and mixing processes. Sources and sinks of PV due to nonconservative processes are calculated online and advected as passive tracers. There is reasonable agreement between the spatial distribution of transport determined from the PV budget method and the transport across the 1 - 2 PVU zone from a passive tracer and trajectories, but different aspects of exchange can be diagnosed with each method. Stratosphere-to-troposphere transport occurred in the broad upper level PV anomalies and was attributed mainly to latent heating and cooling processes; troposphere-to-stratosphere transport occurred toward the tail of a PV filament and in a ridge region and was attributed mainly to radiative processes. The contribution of mixing processes to transport was comparatively small. Using the PV budget method, the domain integrated exchange across the 1 PVU surface was from stratosphere to troposphere, and the magnitude of 1 x 10(15) kg over a 2 day winter integration in a large North Atlantic domain is consistent with stratosphere-troposphere exchange calculations from other studies. This exchange arises from an approximate balance between the dominant stratosphere-to-troposphere transport due to latent heating and cooling processes and troposphere-to-stratosphere transport due to radiative processes. The direction of transport across the tropopause in a fold was found to be critically dependent on the PV surface considered to represent the tropopause