High-Resolution Experiments with the ECMWF Model: A Case Study

Dell'osso, Lorenzo

doi:10.1175/1520-0493(1984)112<1853:hrewte>2.0.co;2

Cited by 32 publications

(12 citation statements)

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“…The extent that the Alps modulate GoG cyclogenesis has been studied by terrain modifications in numerical models (Dell'Osso and Tibaldi 1982;Dell'Osso 1984;McGinley and Goerss 1986;Tafferner and Egger 1990;Aebischer and Schär 1998). McGinley and Goerss (1986) find that 12-h forecasts without the Alps for an April 1982 GoG cyclone generate a subsynoptic feature that compares well with the observed low; however, cyclogenesis did not occur in a similar experiment run for a case that occurred a month earlier.…”

Section: Introductionmentioning

confidence: 99%

Development and Tropical Transition of an Alpine Lee Cyclone. Part II: Orographic Influence on the Development Pathway

McTaggart‐Cowan

Galarneau

Bosart

et al. 2010

Monthly Weather Review

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The development and subsequent tropical transition of a subsynoptic-scale cyclone over the Gulf of Genoa (GoG) on 15 November 2007 led to the rapid onset of tropical storm-force winds near the islands of Corsica and Sardinia. This study evaluates the influence of two key ingredients on the cyclogenesis event: a near-surface warm potential temperature perturbation in the lee of the Alps and a mountain-scale potential vorticity (PV) banner.A high-resolution modeling system is used to perform a set of attribution tests in which modifications to the Alpine orography control the presence of the cyclogenetic ingredients. When either feature exists in the initial state, a GoG cyclone develops even when the Alpine barrier is removed; however, when neither the warm perturbation nor the PV banner is present, there is insufficient lower-level PV to couple with the upper-level trough to promote cyclogenesis. A conceptual model involving the complimentary interaction of the two PV features is presented that accurately describes the development location of the cyclone beneath a midlevel vorticity maximum.Despite development in most of the attribution tests, the energy sources for the cyclones vary widely and represent a spectrum of cyclogenetic pathways from baroclinically to convectively dominant. Removal of the Alpine barrier allows for a stronger thermal wave and a baroclinic mode of development, rather than the diabatically generated hurricane-like vortex seen in the control and available observations. Similarly, insufficient flow interaction with the low-resolution representation of the Alps in the global-driving model is shown to favor a baroclinic mode of cyclogenesis in that integration. Adequate resolution of both the Alpine terrain and the incipient cyclone itself are shown to be important to correctly predict the evolution of the system from both structural and energetic perspectives.

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Section: Introductionmentioning

confidence: 99%

Development and Tropical Transition of an Alpine Lee Cyclone. Part II: Orographic Influence on the Development Pathway

McTaggart‐Cowan

Galarneau

Bosart

et al. 2010

Monthly Weather Review

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“…Although the model results indicate as in observations the existence of highly localized diurnal variations of precipitation due to the combined effects of orographic forcing and surface fluxes, there is much to be desired in temporal evolution of simulated precipitation. In these respects an improvement in performance can be expected with the use of a finer spatial grid spacing in the model and also through the use of an 'envelope'-type orography (Dell'Osso, 1983) to appropriately represent the effects of subgrid-scale mountain forcing. It is noted that the formation and evolution of the orographic cloud is unrelated to the band cloud upwind of the island of Hawaii (Smolarkiewicz et al, 1988).…”

Section: Discussionmentioning

confidence: 99%

“…However, accurate predictions of mesoscale atmospheric processes, particularly in the presence of steep mountains, still remain a great challenge. Under such conditions, improvement in the simulations may be obtained through the use of fine-mesh models (Dell'Osso, 1983). Further improvement can also be expected with incorporation of a differencing scheme whose dynamics better represent those of the continuous system, particularly over steep topography.…”

Section: Introductionmentioning

confidence: 99%

A Three-Dimensional Simulation of Airflow and Orographic Rain over the Island of Hawaii

Ueyoshi

Han

1991

Journal of the Meteorological Society of Japan

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A three-dimensional mesoscale numerical model is presented, designed with the capability of simulating the airflow and orographically-induced rain in the presence of steep irregular terrain. The model utilizes a fourth-order accurate version of Arakawa's potential enstrophy and total energy conserving scheme to improve the simulation of nonlinear aspects of the airflow over steep topography, along with an adiabatic reference atmosphere to reduce the effects of orographic truncation errors. The precipitation processes are represented by large-scale condensation.The model is applied to the island of Hawaii. The results of a 24-h simulation indicate the model is generally successful in reproducing leeward eddies depicted in the composite surface airflow patterns.A nondimensional analysis of vortex parameters suggests that the simulated vortex pattern is an atmospheric analog of the Karman vortex street and compares favorably with an observed case of Hawaii vortices. Spatial distribution of simulated rainfall is also generally in good agreement with observations. However, the lack of precipitation in the lowland along the windward as well as leeward coast is apparent.The excess rainfall over the southern peninsula suggests the need for an finer grid mesh to improve representation of the effects of subgrid-scale mountain forcing. An application of the model to regional climate modeling through the use of large-scale objective analyses is also discussed.

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“…This difference of our own and their results may be due to that the mountain forcing in JMA model may be weaker than that of ECMWF model probably because the horizontal resolution of the former is coarser. In fact, Dell'Osso (1984) suggested in his case study with a limited area model that the scale factor for enhancement of orography should be increased with decreasing resolution. Fig.…”

Section: Brief Description Of Envelope Orographymentioning

confidence: 99%

Impact of Envelope Orography on JMA's Hemispheric NWP Forecasts for Winter Circulation

Iwasaki

Sumi

1986

Journal of the Meteorological Society of Japan

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We have investigated some effects of an envelope orography on the forecast fields by a hemispheric spectral model. For that, a series of 29 experiments is conducted for February 1984. The use of envelope orography improves the daily forecasts. In particular, it remarkably reduces the systematic forecast errors of zonal mean and planetary wave fields. This suggests that the envelopetype enhancement of mountain forcing is very effective in the maintenance of planetary scale stationary fields. In the zonal mean field, the forecast error of latitudinal mass distribution that the surface pressure increases (decreases) in lower (higher) latitudes with increasing forecast period, is reduced. That is, the excessive zonal mean equatorward flow in the lower troposphere at middle latitudes is effectively reduced. This flow change also modifies the predicted zonal mean temperature in the lower troposphere.With regard to the stationary waves, the response of the model atmosphere to the envelope orography varies largely with the latitude. In higher latitudes (60N), the improvement of the wave number 3 pattern is most remarkable.Their temporal variation suggests a remote control of the mountain forcings originating from middle latitudes. In middle latitudes (40N), a significant difference between the two forecasts with standard and envelope orographies appears around 80E. Its temporal behavior suggests that the difference is directly caused by the difference of mountain forcings around the Himalayas.Temperature differences between two forecasts occur mainly through the horizontal advection of sensible heat. The forecasts of cold surge events are also modified by the envelope orography.

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High-Resolution Experiments with the ECMWF Model: A Case Study

Cited by 32 publications

References 0 publications

Development and Tropical Transition of an Alpine Lee Cyclone. Part II: Orographic Influence on the Development Pathway

Development and Tropical Transition of an Alpine Lee Cyclone. Part II: Orographic Influence on the Development Pathway

A Three-Dimensional Simulation of Airflow and Orographic Rain over the Island of Hawaii

Impact of Envelope Orography on JMA's Hemispheric NWP Forecasts for Winter Circulation

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