scholarly journals The 13–14 December 2001 IMPROVE-2 Event. Part I: Synoptic and Mesoscale Evolution and Comparison with a Mesoscale Model Simulation

2005 ◽  
Vol 62 (10) ◽  
pp. 3474-3492 ◽  
Author(s):  
Matthew F. Garvert ◽  
Brian A. Colle ◽  
Clifford F. Mass
Keyword(s):  
Large Scale ◽  
Mesoscale Model ◽  
Model Simulation ◽  
Heavy Precipitation ◽  
Middle Level ◽  
Model Verification ◽  
Precipitation Event ◽  
Low Level ◽  
Baroclinic Zone

Abstract This paper describes the large-scale synoptic and mesoscale features of a major precipitation event that affected the second Improvement of Microphysical Parameterization through Observational Verification Experiment (IMPROVE-2) study area on 13–14 December 2001. The fifth-generation Pennsylvania State University–NCAR Mesoscale Model (MM5) was used to simulate both the synoptic and mesoscale features of the storm. Extensive model verification was performed utilizing the wealth of observational assets available during the experiment, including in situ aircraft measurements, radiosondes, radar data, and surface observations. The 13–14 December 2001 storm system was characterized by strong low-level cross-barrier flow, heavy precipitation, and the passage of an intense baroclinic zone. The model realistically simulated the three-dimensional thermodynamic and kinematic fields, the forward-tilted vertical structure of the baroclinic zone, and the associated major precipitation band. Deficiencies in the model simulations included an attenuated low-level jet accompanying the middle-level baroclinic zone and the lack of precipitation associated with the surface front; NOAA P-3 aircraft in situ data indicated that the model required 1.33-km grid spacing to capture realistically the complex mesoscale forcing related to terrain features. Despite the relatively skillful portrayal of mesoscale and synoptic structures, the model overpredicted precipitation in localized areas on the windward slopes and over a broad area to the lee of the Oregon Cascades.

scholarly journals Multiscale Mountain Waves Influencing a Major Orographic Precipitation Event

2007 ◽  
Vol 64 (3) ◽  
pp. 711-737 ◽  
Author(s):  
Matthew F. Garvert ◽  
Bradley Smull ◽  
Cliff Mass
Keyword(s):  
Mesoscale Model ◽  
Precipitation Forecast ◽  
Precipitation Event ◽  
Small Scale ◽  
Second Phase ◽  
Mountain Waves ◽  
Low Level ◽  
Orographic Rainfall ◽  
Vertically Propagating ◽  
Horizontal Wavelength

Abstract This study combines high-resolution mesoscale model simulations and comprehensive airborne Doppler radar observations to identify kinematic structures influencing the production and mesoscale distribution of precipitation and microphysical processes during a period of heavy prefrontal orographic rainfall over the Cascade Mountains of Oregon on 13–14 December 2001 during the second phase of the Improvement of Microphysical Parameterization through Observational Verification Experiment (IMPROVE-2) field program. Airborne-based radar detection of precipitation from well upstream of the Cascades to the lee allows a depiction of terrain-induced wave motions in unprecedented detail. Two distinct scales of mesoscale wave–like air motions are identified: 1) a vertically propagating mountain wave anchored to the Cascade crest associated with strong midlevel zonal (i.e., cross barrier) flow, and 2) smaller-scale (<20-km horizontal wavelength) undulations over the windward foothills triggered by interaction of the low-level along-barrier flow with multiple ridge–valley corrugations oriented perpendicular to the Cascade crest. These undulations modulate cloud liquid water (CLW) and snow mixing ratios in the fifth-generation Pennsylvania State University–National Center for Atmospheric Research (PSU–NCAR) Mesoscale Model (MM5), with modeled structures comparing favorably to radar-documented zones of enhanced reflectivity and CLW measured by the NOAA P3 aircraft. Errors in the model representation of a low-level shear layer and the vertically propagating mountain waves are analyzed through a variety of sensitivity tests, which indicated that the mountain wave’s amplitude and placement are extremely sensitive to the planetary boundary layer (PBL) parameterization being employed. The effects of 1) using unsmoothed versus smoothed terrain and 2) the removal of upstream coastal terrain on the flow and precipitation over the Cascades are evaluated through a series of sensitivity experiments. Inclusion of unsmoothed terrain resulted in net surface precipitation increases of ∼4%–14% over the windward slopes relative to the smoothed-terrain simulation. Small-scale waves (<20-km horizontal wavelength) over the windward slopes significantly impact the horizontal pattern of precipitation and hence quantitative precipitation forecast (QPF) accuracy.

scholarly journals A hydrometeorological model intercomparison as a tool to quantify the forecast uncertainty in a medium size basin

2008 ◽  
Vol 8 (4) ◽  
pp. 819-838 ◽  
Author(s):  
A. Amengual ◽  
T. Diomede ◽  
C. Marsigli ◽  
A. Martín ◽  
A. Morgillo ◽  
...  
Keyword(s):  
Large Scale ◽  
Mesoscale Model ◽  
Northern Italy ◽  
Precipitation Event ◽  
Medium Size ◽  
Hydrological Models ◽  
Model Intercomparison ◽  
Mesoscale Models ◽  
Prediction And Prevention ◽  
The One

Abstract. In the framework of AMPHORE, an INTERREG III B EU project devoted to the hydrometeorological modeling study of heavy precipitation episodes resulting in flood events and the improvement of the operational hydrometeorological forecasts for the prediction and prevention of flood risks in the Western Mediterranean area, a hydrometeorological model intercomparison has been carried out, in order to estimate the uncertainties associated with the discharge predictions. The analysis is performed for an intense precipitation event selected as a case study within the project, which affected northern Italy and caused a flood event in the upper Reno river basin, a medium size catchment in the Emilia-Romagna Region. Two different hydrological models have been implemented over the basin: HEC-HMS and TOPKAPI which are driven in two ways. Firstly, stream-flow simulations obtained by using precipitation observations as input data are evaluated, in order to be aware of the performance of the two hydrological models. Secondly, the rainfall-runoff models have been forced with rainfall forecast fields provided by mesoscale atmospheric model simulations in order to evaluate the reliability of the discharge forecasts resulting by the one-way coupling. The quantitative precipitation forecasts (QPFs) are provided by the numerical mesoscale models COSMO and MM5. Furthermore, different configurations of COSMO and MM5 have been adopted, trying to improve the description of the phenomena determining the precipitation amounts. In particular, the impacts of using different initial and boundary conditions, different mesoscale models and of increasing the horizontal model resolutions are investigated. The accuracy of QPFs is assessed in a threefold procedure. First, these are checked against the observed spatial rainfall accumulations over northern Italy. Second, the spatial and temporal simulated distributions are also examined over the catchment of interest. And finally, the discharge simulations resulting from the one-way coupling with HEC-HMS and TOPKAPI are evaluated against the rain-gauge driven simulated flows, thus employing the hydrological models as a validation tool. The different scenarios of the simulated river flows – provided by an independent implementation of the two hydrological models each one forced with both COSMO and MM5 – enable a quantification of the uncertainties of the precipitation outputs, and therefore, of the discharge simulations. Results permit to highlight some hydrological and meteorological modeling factors which could help to enhance the hydrometeorological modeling of such hazardous events. Main conclusions are: (1) deficiencies in precipitation forecasts have a major impact on flood forecasts; (2) large-scale shift errors in precipitation patterns are not improved by only enhancing the mesoscale model resolution; and (3) weak differences in flood forecasting performance are found by using either a distributed continuous or a semi-distributed event-based hydrological model for this catchment.

scholarly journals Evaluation of Two Cloud-Resolving Models Using Bin or Bulk Microphysics Representation for the HyMeX-IOP7a Heavy Precipitation Event

Atmosphere ◽  
2020 ◽  
Vol 11 (11) ◽  
pp. 1177
Author(s):  
Diana Arteaga ◽  
Céline Planche ◽  
Christina Kagkara ◽  
Wolfram Wobrock ◽  
Sandra Banson ◽  
...  
Keyword(s):  
Hydrological Cycle ◽  
Wrf Model ◽  
Heavy Precipitation ◽  
Sensitivity Study ◽  
Precipitation Event ◽  
Convective System ◽  
Wind Fields ◽  
Massif Central ◽  
Surface Precipitation ◽  
Low Level

The Mediterranean region is frequently affected in autumn by heavy precipitation that causes flash-floods or landslides leading to important material damage and casualties. Within the framework of the international HyMeX program (HYdrological cycle in Mediterranean EXperiment), this study aims to evaluate the capabilities of two models, WRF (Weather Research and Forecasting) and DESCAM (DEtailed SCAvenging Model), which use two different representations of the microphysics to reproduce the observed atmospheric properties (thermodynamics, wind fields, radar reflectivities and precipitation features) of the HyMeX-IOP7a intense precipitating event (26 September 2012). The DESCAM model, which uses a bin resolved representation of the microphysics, shows results comparable to the observations for the precipitation field at the surface. On the contrary, the simulations made with the WRF model using a bulk representation of the microphysics (either the Thompson scheme or the Morrison scheme), commonly employed in NWP models, reproduce neither the intensity nor the distribution of the observed precipitation—the rain amount is overestimated and the most intense cell is shifted to the East. The different simulation results show that the divergence in the surface precipitation features seems to be due to different mechanisms involved in the onset of the precipitating system: the convective system is triggered by the topography of the Cévennes mountains (i.e., south-eastern part of the Massif Central) in DESCAM and by a low-level flux convergence in WRF. A sensitivity study indicates that the microphysics properties have impacted the thermodynamics and dynamics fields inducing the low-level wind convergence simulated with WRF for this HyMeX event.

scholarly journals The 13–14 December 2001 IMPROVE-2 Event. Part II: Comparisons of MM5 Model Simulations of Clouds and Precipitation with Observations

2005 ◽  
Vol 62 (10) ◽  
pp. 3520-3534 ◽  
Author(s):  
Matthew F. Garvert ◽  
Christopher P. Woods ◽  
Brian A. Colle ◽  
Clifford F. Mass ◽  
Peter V. Hobbs ◽  
...  
Keyword(s):  
Liquid Water ◽  
Mesoscale Model ◽  
Heavy Precipitation ◽  
Precipitation Event ◽  
State University ◽  
Cloud Liquid Water ◽  
Aircraft Flight ◽  
Oregon Cascades ◽  
Microphysical Parameterization ◽  
Mass Concentrations

Abstract This paper compares airborne in situ observations of cloud microphysical parameters with the fifth-generation Pennsylvania State University–National Center for Atmospheric Research (PSU–NCAR) Mesoscale Model (MM5) simulations, using the Reisner-2 bulk microphysical parameterization, for a heavy precipitation event over the Oregon Cascades on 13–14 December 2001. The MM5 correctly replicated the extent of the snow field and the growth of snow particles by vapor deposition measured along aircraft flight tracks between altitudes of 4.9 and 6 km, but overpredicted the mass concentrations of snow. The model produced a broader number distribution of snow particles than observed, overpredicting the number of moderate-to-large-sized snow particles and underpredicting the number of small particles observed along the aircraft flight track. Over the mountain crest, the model overpredicted depositional growth of snow and mass concentrations of snow, but underpredicted the amount of cloud liquid water and conversion of snow to graupel. The misclassification of graupel as snow and excessive amounts of snow resulted in the model overpredicting precipitation on the lee slopes and in localized areas along the foothills of the Cascades. The model overpredicted cloud liquid water over the lower windward slopes and foothills, where accretion of cloud liquid water by rain was the primary precipitation-producing mechanism.

scholarly journals Contrasting stable water isotope signals from convective and large-scale precipitation phases of a heavy precipitation event in southern Italy during HyMeX IOP 13: a modelling perspective

2019 ◽  
Vol 19 (11) ◽  
pp. 7487-7506
Author(s):  
Keun-Ok Lee ◽  
Franziska Aemisegger ◽  
Stephan Pfahl ◽  
Cyrille Flamant ◽  
Jean-Lionel Lacour ◽  
...  
Keyword(s):  
Large Scale ◽  
Cold Front ◽  
Heavy Precipitation ◽  
Convective Precipitation ◽  
Water Isotopes ◽  
Precipitation Event ◽  
Stable Water Isotopes ◽  
Heavy Precipitation Event ◽  
The North ◽  
Upper Level

Abstract. The dynamical context and moisture transport pathways embedded in large-scale flow and associated with a heavy precipitation event (HPE) in southern Italy (SI) are investigated with the help of stable water isotopes (SWIs) based on a purely numerical framework. The event occurred during the Intensive Observation Period (IOP) 13 of the field campaign of the Hydrological Cycle in the Mediterranean Experiment (HyMeX) on 15 and 16 October 2012, and SI experienced intense rainfall of 62.4 mm over 27 h with two precipitation phases during this event. The first one (P1) was induced by convective precipitation ahead of a cold front, while the second one (P2) was mainly associated with precipitation induced by large-scale uplift. The moisture transport and processes responsible for the HPE are analysed using a simulation with the isotope-enabled regional numerical model COSMOiso. The simulation at a horizontal grid spacing of about 7 km over a large domain (about 4300 km ×3500 km) allows the isotopes signal to be distinguished due to local processes or large-scale advection. Backward trajectory analyses based on this simulation show that the air parcels arriving in SI during P1 originate from the North Atlantic and descend within an upper-level trough over the north-western Mediterranean. The descending air parcels reach elevations below 1 km over the sea and bring dry and isotopically depleted air (median δ18O ≤-25 ‰, water vapour mixing ratio q≤2 g kg−1) close to the surface, which induces strong surface evaporation. These air parcels are rapidly enriched in SWIs (δ18O ≥-14 ‰) and moistened (q≥8 g kg−1) over the Tyrrhenian Sea by taking up moisture from surface evaporation and potentially from evaporation of frontal precipitation. Thereafter, the SWI-enriched low-level air masses arriving upstream of SI are convectively pumped to higher altitudes, and the SWI-depleted moisture from higher levels is transported towards the surface within the downdrafts ahead of the cold front over SI, producing a large amount of convective precipitation in SI. Most of the moisture processes (i.e. evaporation, convective mixing) related to the HPE take place during the 18 h before P1 over SI. A period of 4 h later, during the second precipitation phase P2, the air parcels arriving over SI mainly originate from north Africa. The strong cyclonic flow around the eastward-moving upper-level trough induces the advection of a SWI-enriched African moisture plume towards SI and leads to large-scale uplift of the warm air mass along the cold front. This lifts moist and SWI-enriched air (median δ18O ≥-16 ‰, median q≥6 g kg−1) and leads to gradual rain out of the air parcels over Italy. Large-scale ascent in the warm sector ahead of the cold front takes place during the 72 h preceding P2 in SI. This work demonstrates how stable water isotopes can yield additional insights into the variety of thermodynamic mechanisms occurring at the mesoscale and synoptic scale during the formation of a HPE.

Integrating Model Evaluation and Observations into a Production-Release Pipeline

2020 ◽  
Author(s):  
Philipp S. Sommer ◽  
Ronny Petrik ◽  
Beate Geyer ◽  
Ulrike Kleeberg ◽  
Dietmar Sauer ◽  
...  
Keyword(s):  
Evaluation System ◽  
Large Scale ◽  
Climate Models ◽  
Model Simulation ◽  
Regional Climate ◽  
Regional Climate Models ◽  
Active Communication ◽  
The Individual ◽  
Scientific Questions

<p>The complexity of Earth System and Regional Climate Models represents a considerable challenge for developers. Tuning but also improving one aspect of a model can unexpectedly decrease the performance of others and introduces hidden errors. Reasons are in particular the multitude of output parameters and the shortage of reliable and complete observational datasets. One possibility to overcome these issues is a rigorous and continuous scientific evaluation of the model. This requires standardized model output and, most notably, standardized observational datasets. Additionally, in order to reduce the extra burden for the single scientist, this evaluation has to be as close as possible to the standard workflow of the researcher, and it needs to be flexible enough to adapt it to new scientific questions.</p><p>We present the Free Evaluation System Framework (Freva) implementation within the Helmholtz Coastal Data Center (HCDC) at the Institute of Coastal Research in the Helmholtz-Zentrum Geesthacht (HZG). Various plugins into the Freva software, namely the HZG-EvaSuite, use observational data to perform a standardized evaluation of the model simulation. We present a comprehensive data management infrastructure that copes with the heterogeneity of observations and simulations. This web framework comprises a FAIR and standardized database of both, large-scale and in-situ observations exported to a format suitable for data-model intercomparisons (particularly netCDF following the CF-conventions). Our pipeline links the raw data of the individual model simulations (i.e. the production of the results) to the finally published results (i.e. the released data). </p><p>Another benefit of the Freva-based evaluation is the enhanced exchange between the different compartments of the institute, particularly between the model developers and the data collectors, as Freva contains built-in functionalities to share and discuss results with colleagues. We will furthermore use the tool to strengthen the active communication with the data and software managers of the institute to generate or adapt the evaluation plugins.</p>

Strong Cross-Barrier Flow under Stable Conditions Producing Intense Winter Orographic Precipitation: A Case Study over the Subtropical Central Andes

2009 ◽  
Vol 24 (4) ◽  
pp. 1009-1031 ◽  
Author(s):  
Maximiliano Viale ◽  
Federico A. Norte
Keyword(s):  
Heavy Precipitation ◽  
Stable Stratification ◽  
Central Andes ◽  
Precipitation Event ◽  
Windward Side ◽  
Orographic Precipitation ◽  
Near Surface ◽  
Low Level ◽  
Precipitation Enhancement ◽  
Subtropical Central Andes

Abstract The most intense orographic precipitation event over the subtropical central Andes (36°–30°S) during winter 2005 was examined using observational data and a regional model simulation. The Eta-Programa Regional de Meteorología (PRM) model forecast was evaluated and used to explore the airflow structure that generated this heavy precipitation event, with a focus on orographic influences. Even though the model did not realistically reproduce any near-surface variables, nor the precipitation shadow in the leeside lowlands, its reliable forecast of heavy precipitation over the windward side and the wind fields suggests that it can be used as a valuable forecasting tool for such events in the region. The synoptic flow of the 26–29 August 2005 storm responded to a well-defined dipole from low to upper levels with anomalous low (high) geopotential heights at midlatitudes (subtropical) latitudes located off the southeast Pacific coast, resulting in a large meridional geopotential height gradient that drove a strong anomalous cross-barrier flow. Precipitation enhancement in the Andes was observed during the entire event; however, the highest rates were in the prefrontal sector under the low-level stable stratification and cross-barrier winds exceeding 2.5 standard deviations (σ) from the climatological monthly mean. The combination of strong cross-mountain winds with the stable stratification in the air mass of a frontal system, impinging on the high Andes range, appears to be the major factor in determining the flow structure that produced the pattern of precipitation enhancement, with uplift maximized near mountaintops and low-level blocking upwindleading to the formation of a low-level along-barrier jet. Additionally, only the upstream wind anomalies for the 15 heaviest events over a 10-yr (1967–76) period were investigated. They exhibited strong anomalous northwesterly winds for 14 of the 15 events, whereas for the remaining event there were no available observations to evaluate. Thus, these anomalies may also be exploited for forecasting capabilities.

scholarly journals The Explicit Wake Parametrisation V1.0: a wind farm parametrisation in the mesoscale model WRF

2015 ◽  
Vol 8 (4) ◽  
pp. 3481-3522 ◽  
Author(s):  
P. J. H. Volker ◽  
J. Badger ◽  
A. N. Hahmann ◽  
S. Ott
Keyword(s):  
Large Scale ◽  
Wind Farm ◽  
Mesoscale Model ◽  
Wind Farms ◽  
Simulation Models ◽  
Offshore Wind ◽  
Offshore Wind Farms ◽  
Eddy Simulation ◽  
Large Eddy

Abstract. We describe the theoretical basis, implementation and validation of a new parametrisation that accounts for the effect of large offshore wind farms on the atmosphere and can be used in mesoscale and large-scale atmospheric models. This new parametrisation, referred to as the Explicit Wake Parametrisation (EWP), uses classical wake theory to describe the unresolved wake expansion. The EWP scheme is validated against filtered in situ measurements from two meteorological masts situated a few kilometres away from the Danish offshore wind farm Horns Rev I. The simulated velocity deficit in the wake of the wind farm compares well to that observed in the measurements and the velocity profile is qualitatively similar to that simulated with large eddy simulation models and from wind tunnel studies. At the same time, the validation process highlights the challenges in verifying such models with real observations.

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