Regional climate models (RCMs) are used to add the effects of nonresolved scales to coarser resolved model simulations by using a finer grid within a limited domain. We identify large‐scale secondary circulations (SCs) relative to the driving global climate model (GCM) in an RCM simulation over Europe. By applying a clustering technique, we find that the SC depends on the large‐scale flow prescribed by the driving GCM data. Evidence is presented that the SC is caused by the different representations of orographic effects in the RCM and the GCM. Flow modifications in the RCM caused by the Alps lead to large‐scale vortices in the SC fields. These vortices are limited by the RCM boundaries, causing artificial boundary‐parallel flows. The SC is associated with geopotential height and temperature anomalies between RCM and GCM and has the potential to produce systematic large‐scale biases in RCMs.
This paper develops a notion of capacity-delayerror-boundaries as a performance model of networked sources and systems. The goal is to provision effective capacities that sustain certain statistical delay guarantees with a small probability of error. We use a stochastic non-equilibrium approach that models the variability of traffic and service to formalize the influence of delay constraints on the effective capacity. Permitting unbounded delays, known ergodic capacity results from information theory are recovered in the limit. We prove that the model has the property of additivity, that enables composing capacity-delayerror-boundaries obtained for sources and systems as if in isolation. A method for construction of capacity-delay-errorboundaries is devised based on moment generating functions, which includes the large body of results from the theory of effective bandwidths. Solutions for essential sources, channels, and respective coders are derived, including Huffman coding, MPEG video, Rayleigh fading, and hybrid ARQ. Results for tandem channels and for the composition of sources and channels are shown.
Abstract. The sensitivity of the October 1996 Medicane in the western
Mediterranean basin to sea surface temperatures (SSTs) is investigated with a
regional climate model via ensemble sensitivity simulations. For 11 SST
states, ranging from −4 K below to +6 K above the observed SST field
(in 1 K steps), 24-member ensembles of the medicane are simulated. By using
a modified phase space diagram and a simple compositing method, it is shown
that the SST state has a minor influence on the tracks of the cyclones but a
strong influence on their intensities. Increased SSTs lead to greater
probabilities of tropical transitions, to stronger lower- and upper-level warm
cores and to lower pressure minima. The tropical transition occurs sooner
and lasts longer, which enables a greater number of transitioning cyclones to
survive landfall over Sardinia and re-intensify in the Tyrrhenian Sea. The
results demonstrate that SSTs influence the intensity of fluxes from the sea,
which leads to greater convective activity before the storms reach their
maturity. These results suggest that the processes at steady state for
medicanes are very similar to tropical cyclones.
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