scholarly journals Sensitivity experiments of a severe rainfall event in north-western Italy: 17 August 2006

2008 ◽  
Vol 2 (1) ◽  
pp. 133-138 ◽  
Author(s):  
M. Milelli ◽  
E. Oberto ◽  
A. Parodi
Keyword(s):  
Weather Prediction ◽  
Numerical Weather Prediction Model ◽  
Precipitation Forecast ◽  
Small Scale ◽  
Moist Convection ◽  
Cosmo Model ◽  
Quantitative Precipitation Forecast ◽  
Scale Modelling ◽  
North Western ◽  
Priority Project

Abstract. This study is embedded into a wider project named "Tackle deficiencies in Quantitative Precipitation Forecast (QPF)'' in the framework of the COSMO (COnsortium for Small-scale MOdelling) community. In fact QPF is an important purpose of a numerical weather prediction model, for forecasters and customers. Unfortunately, precipitation is also a very difficult parameter to forecast quantitatively. This priority project aims at looking into the COSMO Model deficiencies concerning QPF by running different numerical simulations of various events not correctly predicted by the model. In particular, this work refers to a severe event (moist convection) happened in Piemonte region during summer 2006. On one side the results suggest that details in orography representation have a strong influence on accuracy of QPF. On the other side COSMO Model exhibits a poor sensitivity on changes in numerical and physical settings when measured in terms of QPF improvements. The conclusions, although not too general, give some hint towards the behaviour of the COSMO Model in a typical convective situation.

scholarly journals A meteo-hydrological prediction system based on a multi-model approach for precipitation forecasting

2008 ◽  
Vol 8 (1) ◽  
pp. 143-159 ◽  
Author(s):  
S. Davolio ◽  
M. M. Miglietta ◽  
T. Diomede ◽  
C. Marsigli ◽  
A. Morgillo ◽  
...  
Keyword(s):  
Hydrological Model ◽  
Weather Prediction ◽  
Coupled System ◽  
Numerical Weather Prediction Model ◽  
Precipitation Forecast ◽  
Precipitation Forecasting ◽  
Quantitative Precipitation Forecast ◽  
Forecasting System ◽  
Hydrological Prediction ◽  
Model Approach

Abstract. The precipitation forecasted by a numerical weather prediction model, even at high resolution, suffers from errors which can be considerable at the scales of interest for hydrological purposes. In the present study, a fraction of the uncertainty related to meteorological prediction is taken into account by implementing a multi-model forecasting approach, aimed at providing multiple precipitation scenarios driving the same hydrological model. Therefore, the estimation of that uncertainty associated with the quantitative precipitation forecast (QPF), conveyed by the multi-model ensemble, can be exploited by the hydrological model, propagating the error into the hydrological forecast. The proposed meteo-hydrological forecasting system is implemented and tested in a real-time configuration for several episodes of intense precipitation affecting the Reno river basin, a medium-sized basin located in northern Italy (Apennines). These episodes are associated with flood events of different intensity and are representative of different meteorological configurations responsible for severe weather affecting northern Apennines. The simulation results show that the coupled system is promising in the prediction of discharge peaks (both in terms of amount and timing) for warning purposes. The ensemble hydrological forecasts provide a range of possible flood scenarios that proved to be useful for the support of civil protection authorities in their decision.

scholarly journals Can Lagrangian Extrapolation of Radar Fields Be Used for Precipitation Nowcasting over Complex Alpine Orography?

2012 ◽  
Vol 27 (1) ◽  
pp. 28-49 ◽  
Author(s):  
Pradeep V. Mandapaka ◽  
Urs Germann ◽  
Luca Panziera ◽  
Alessandro Hering
Keyword(s):  
High Resolution ◽  
Comprehensive Evaluation ◽  
Weather Prediction ◽  
Summer Rainfall ◽  
Numerical Weather Prediction Model ◽  
Precipitation Forecast ◽  
Small Scale ◽  
Lead Times ◽  
Radar Echo ◽  
Short Term Forecasting

Abstract In this study, a Lagrangian radar echo extrapolation scheme (MAPLE) was tested for use in very short-term forecasting of precipitation over a complex orographic region. The high-resolution forecasts from MAPLE for lead times of 5 min–5 h are evaluated against the radar observations for 20 summer rainfall events by employing a series of categorical, continuous, and neighborhood evaluation techniques. The verification results are then compared with those from Eulerian persistence and high-resolution numerical weather prediction model [the Consortium for Small-scale Modeling model (COSMO2)] forecasts. The forecasts from the MAPLE model clearly outperformed Eulerian persistence forecasts for all the lead times, and had better skill compared to COSMO2 up to lead time of 3 h on average. The results also showed that the predictability achieved from the MAPLE model depends on the spatial structure of the precipitation patterns. This study is a first implementation of the MAPLE model over a complex Alpine region. In addition to comprehensive evaluation of precipitation forecast products, some open questions related to the nowcasting of rainfall over a complex terrain are discussed.

scholarly journals EMPOL 1.0: a new parameterization of pollen emission in numerical weather prediction models

2013 ◽  
Vol 6 (6) ◽  
pp. 1961-1975 ◽  
Author(s):  
K. Zink ◽  
A. Pauling ◽  
M. W. Rotach ◽  
H. Vogel ◽  
P. Kaufmann ◽  
...  
Keyword(s):  
Numerical Weather Prediction ◽  
Prediction Models ◽  
Weather Prediction ◽  
Birch Pollen ◽  
Small Scale ◽  
Pollen Emission ◽  
Numerical Weather ◽  
Pollen Concentrations ◽  
Scale Modelling ◽  
Reactive Trace Gases

Abstract. Simulating pollen concentrations with numerical weather prediction (NWP) systems requires a parameterization for pollen emission. We have developed a parameterization that is adaptable for different plant species. Both biological and physical processes of pollen emission are taken into account by parameterizing emission as a two-step process: (1) the release of the pollen from the flowers, and (2) their entrainment into the atmosphere. Key factors influencing emission are temperature, relative humidity, the turbulent kinetic energy and precipitation. We have simulated the birch pollen season of 2012 using the NWP system COSMO-ART (Consortium for Small-scale Modelling – Aerosols and Reactive Trace Gases), both with a parameterization already present in the model and with our new parameterization EMPOL. The statistical results show that the performance of the model can be enhanced by using EMPOL.

scholarly journals Numerical simulations of June 7, 2020 convective precipitation over Slovakia using deterministic, probabilistic, and convection-permitting approaches

Időjárás ◽  
2021 ◽  
Vol 125 (4) ◽  
pp. 571-607
Author(s):  
André Simon ◽  
Martin Belluš ◽  
Katarína Čatlošová ◽  
Mária Derková ◽  
Martin Dian ◽  
...  
Keyword(s):  
Satellite Imagery ◽  
Weather Prediction ◽  
Severe Weather ◽  
Precipitation Forecast ◽  
Convective Precipitation ◽  
Small Scale ◽  
Limited Area ◽  
Systematic Effect ◽  
The Impact

The paper presented is dedicated to the evaluation of the influence of various improvements to the numerical weather prediction (NWP) systems exploited at the Slovak Hydrometeorological Institute (SHMÚ). The impact was illustrated in a case study with multicell thunderstorms and the results were confronted with the reference analyses from the INCA nowcasting system, regional radar reflectivity data, and METEOSAT satellite imagery. The convective cells evolution was diagnosed in non-hydrostatic dynamics experiments to study weak mesoscale vortices and updrafts. The growth of simulated clouds and evolution of the temperature at their top were compared with the brightness temperature analyzed from satellite imagery. The results obtained indicated the potential for modeling and diagnostics of small-scale structures within the convective cloudiness, which could be related to severe weather. Furthermore, the non-hydrostatic dynamics experiments related to the stability and performance improvement of the time scheme led to the formulation of a new approach to linear operator definition for semi-implicit scheme (in text referred as NHHY). We demonstrate that the execution efficiency has improved by more than 20%. The exploitation of several high resolution measurement types in data assimilation contributed to more precise position of predicted patterns and precipitation representation in the case study. The non-hydrostatic dynamics provided more detailed structures. On the other hand, the potential of a single deterministic forecast of prefrontal heavy precipitation was not as high as provided by the ensemble system. The prediction of a regional ensemble system A-LAEF (ALARO Limited Area Ensemble Forecast) enhanced the localization of precipitation patterns. Though, this was rather due to the simulation of uncertainty in the initial conditions and also because of the stochastic perturbation of physics tendencies. The various physical parameterization setups of A-LAEF members did not exhibit a systematic effect on precipitation forecast in the evaluated case. Moreover, the ensemble system allowed an estimation of uncertainty in a rapidly developing severe weather case, which was high even at very short range.

scholarly journals Sensitivity of forecast skill to the parameterisation of moist convection in a limited-area ensemble forecast system

2018 ◽  
Author(s):  
Matteo Vasconi ◽  
Andrea Montani ◽  
Tiziana Paccagnella
Keyword(s):  
Forecast Skill ◽  
Precipitation Forecast ◽  
Limited Area ◽  
Forecast Errors ◽  
Total Precipitation ◽  
Moist Convection ◽  
Cosmo Model ◽  
Spatio Temporal ◽  
Convection Schemes ◽  
Ensemble Systems

Abstract. The parameterisation of convection in limited-area models is an important source of uncertainty as regards the spatio-temporal forecast of precipitation. As for the limited-area model COSMO, hitherto, only the Tiedtke convection scheme was available for the operational runs of the model in convection-parameterised mode. In addition to this the Bechtold scheme, implemented in ECMWF global model, has recently been adapted for COSMO applications. The development and implementation of ensemble systems in which different convection schemes are used, provides an opportunity to upgrade state-of-the-art probabilistic systems at the convection-parameterised scale. The sensitivity of the COSMO model forecast skill to the use of either the Tietdke or the Bechtold schemes is assessed by performing different sets of experiments. The performance of COSMO model run with the different schemes is investigated in ensemble mode with particular attention to the types of forecast errors (e.g. location, timing, intensity) provided by the different convection schemes in terms of total precipitation. A 10-member ensemble has been run for approximately 2 months with the Bechtold scheme, using the same initial and boundary conditions as members 1–10 of the operational COSMO-LEPS ensemble system (which has 20 members, all run with the Tiedtke scheme). The performance of these members is assessed and compared to that of the system made of members 1–10 of COSMO-LEPS in terms of total precipitation prediction. Finally, the performance of an experimental 20-member ensemble system (which has 10 members run with the Bechtold plus 10 members run with the Tiedtke scheme) is compared to that of operational COSMO-LEPS over the 2-month period. The new system turned out to have higher skill in terms of precipitation forecast with respect to COSMO-LEPS over the period. In this approach the use of the Bechtold scheme is proposed as a perturbation for the COSMO-LEPS ensemble, relatively to how uncertainties in the model representation of the cumulus convection can be described and quantified.

scholarly journals The hydro-meteorological chain in Piemonte region, North Western Italy - analysis of the HYDROPTIMET test cases

2005 ◽  
Vol 5 (6) ◽  
pp. 845-852 ◽  
Author(s):  
D. Rabuffetti ◽  
M. Milelli
Keyword(s):  
Numerical Models ◽  
Precipitation Forecast ◽  
Test Cases ◽  
Warning Systems ◽  
Alert System ◽  
Run Off ◽  
Quantitative Precipitation Forecast ◽  
Prediction And Prevention ◽  
Meteorological Models ◽  
North Western

Abstract. The HYDROPTIMET Project, Interreg IIIB EU program, is developed in the framework of the prediction and prevention of natural hazards related to severe hydro-meteorological events and aims to the optimisation of Hydro-Meteorological warning systems by the experimentation of new tools (such as numerical models) to be used operationally for risk assessment. The objects of the research are the mesoscale weather phenomena and the response of watersheds with size ranging from 102 to 103 km2. Non-hydrostatic meteorological models are used to catch such phenomena at a regional level focusing on the Quantitative Precipitation Forecast (QPF). Furthermore hydrological Quantitative Discharge Forecast (QDF) are performed by the simulation of run-off generation and flood propagation in the main rivers of the territory. In this way observed data and QPF are used, in a real-time configuration, for one-way forcing of the hydrological model that works operationally connected to the Piemonte Region Alert System. The main hydro-meteorological events that affected Piemonte Region in the last years are analysed, these are the HYDROPTIMET selected test cases of 14–18 November 2002 and 23–26 November 2002. The results obtained in terms of QPF and QDF offer a basis to evaluate the sensitivity of the whole hydro-meteorological chain to the uncertainties in the numerical simulations. Different configurations of non-hydrostatic meteorological models are also evaluated.

scholarly journals Does the Representation of Flow Structure and Turbulence at a Cold Front Converge on Multiscale Observations with Model Resolution?

2017 ◽  
Vol 145 (11) ◽  
pp. 4345-4363 ◽  
Author(s):  
Ben Harvey ◽  
John Methven ◽  
Chloe Eagle ◽  
Humphrey Lean
Keyword(s):  
Flow Structure ◽  
Cold Front ◽  
Spatial Scales ◽  
Weather Prediction ◽  
Turbulent Fluxes ◽  
Numerical Weather Prediction Model ◽  
Shear Instability ◽  
Small Scale ◽  
Convective Boundary ◽  
Direct Evaluation

In situ aircraft observations are used to interrogate the ability of a numerical weather prediction model to represent flow structure and turbulence at a narrow cold front. Simulations are performed at a range of nested resolutions with grid spacings of 12 km down to 100 m, and the convergence with resolution is investigated. The observations include the novel feature of a low-altitude circuit around the front that is closed in the frame of reference of the front, thus allowing the direct evaluation of area-average vorticity and divergence values from circuit integrals. As such, the observational strategy enables a comparison of flow structures over a broad range of spatial scales, from the size of the circuit itself ([Formula: see text]100 km) to small-scale turbulent fluctuations ([Formula: see text]10 m). It is found that many aspects of the resolved flow converge successfully toward the observations with resolution if sampling uncertainty is accounted for, including the area-average vorticity and divergence measures and the narrowest observed cross-frontal width. In addition, there is a gradual handover from parameterized to resolved turbulent fluxes of moisture and momentum as motions in the convective boundary layer behind the front become partially resolved in the highest-resolution simulations. In contrast, the parameterized turbulent fluxes associated with subgrid-scale shear-driven turbulence ahead of the front do not converge on the observations. The structure of frontal rainbands associated with a shear instability along the front also does not converge with resolution, indicating that the mechanism of the frontal instability may not be well represented in the simulations.

Validity of the hydrostatic approximation at convection-resolving scales: Diagnostic analysis and model intercomparison

2020 ◽  
Author(s):  
Christian Zeman ◽  
Nikolina Ban ◽  
Nils Wedi ◽  
Christoph Schär
Keyword(s):  
Climate Models ◽  
Horizontal Resolution ◽  
Vertical Wind ◽  
Small Scale ◽  
Reconstruction Technique ◽  
Cosmo Model ◽  
Operational Forecasts ◽  
Scale Modelling ◽  
Hydrostatic Approximation ◽  
Vertical Accelerations

<div>The increasing availability of computing power allows the use of kilometer-scale convection-resolving weather and climate models for operational forecasts. One of the open questions at these scales concerns the validity of the hydrostatic approximation, which assumes that vertical accelerations are small compared to the balancing forces of gravity and the vertical pressure gradient. This assumption is valid as long as the ratio of vertical to horizontal length scales of motion is small. Results from previous studies suggest that the horizontal resolution at which the hydrostatic approximation becomes invalid is highly dependent on the particular model, model configuration, and case setup.</div><div> </div><div>While most of the previous studies have been conducted with an idealized setup, this work will concentrate on a real-world case. To this end, a few summer days with strong convection over complex terrain in Europe are simulated with the nonhydrostatic regional Consortium for Small-scale Modelling (COSMO) model with horizontal resolutions ranging from 12 km to 275 m. To assess the validity of the hydrostatic approximation, we developed a hydrostatic reconstruction technique and diagnose the vertical wind using the hydrostatic set of equations. The diagnosed values are then compared to the actual nonhydrostatic up- and downdrafts with a statistical analysis of vertical wind speed frequencies for the different resolutions.</div><div> </div><div>Results suggest that the diagnosed hydrostatic vertical velocities are very similar to the nonhydrostatic vertical velocities up to horizontal resolutions of 1 km and thus the use of the hydrostatic approximations at these scales still seems to be a valid option.</div><div> </div><div> <div>Furthermore, the study contains an intercomparison of precipitation and vertical winds produced by the nonhydrostatic COSMO model and the hydrostatic Integrated Forecast System (IFS) from ECMWF for the same case. The intercomparison supports the previous findings that at resolutions of ∼2 km and ∼4 km the effect of the hydrostatic approximation is negligible. The results also show that a small enough timestep size is essential in order to properly resolve the high vertical velocities associated with convection.</div> </div>

Gridded Operational Consensus Forecasts of 2-m Temperature over Australia

2012 ◽  
Vol 27 (2) ◽  
pp. 301-322 ◽  
Author(s):  
Chermelle Engel ◽  
Elizabeth E. Ebert
Keyword(s):  
Bias Correction ◽  
Statistical Approach ◽  
Weather Prediction ◽  
Weighted Average ◽  
Numerical Weather Prediction Model ◽  
Small Scale ◽  
Coarse Scale ◽  
Consensus Forecasts ◽  
Average Consensus ◽  
Almost All

Abstract This paper describes an extension of an operational consensus forecasting (OCF) scheme from site forecasts to gridded forecasts. OCF is a multimodel consensus scheme including bias correction and weighting. Bias correction and weighting are done on a scale common to almost all multimodel inputs (1.25°), which are then downscaled using a statistical approach to an approximately 5-km-resolution grid. Local and international numerical weather prediction model inputs are found to have coarse scale biases that respond to simple bias correction, with the weighted average consensus at 1.25° outperforming all models at that scale. Statistical downscaling is found to remove the systematic representativeness error when downscaling from 1.25° to 5 km, though it cannot resolve scale differences associated with transient small-scale weather.

scholarly journals Performance of IMD multi-model ensemble and WRF (ARW) model for sub-basin wise rainfall forecast during monsoon 2012

MAUSAM ◽  
2021 ◽  
Vol 67 (2) ◽  
pp. 323-332
Author(s):  
ASHOK KUMAR DAS ◽  
SURINDER KAUR
Keyword(s):  
Prediction Models ◽  
Weather Prediction ◽  
India Meteorological Department ◽  
Precipitation Forecast ◽  
False Alarms ◽  
Model Ensemble ◽  
Rainfall Forecast ◽  
Quantitative Precipitation Forecast ◽  
Arw Model ◽  
Nwp Model

The Numerical Weather Prediction models, Multi-model Ensemble (MME) (27 km × 27 km) and WRF (ARW) (9 km × 9 km) operationally run by India Meteorological Department (IMD) have been utilized to estimate sub-basin wise rainfall forecast. The sub-basin wise operational Quantitative Precipitation Forecast (QPF) have been issued by 10 field offices named Flood Meteorological Offices (FMOs) of IMD located at different flood prone areas of the country. The daily sub-basin wise NWP model rainfall forecast for 122 sub basins under these 10 FMOs for the flood season 2012 have been estimated on operational basis which are used by forecasters at FMOs as a guidance for the issue of operational sub-basin QPF for flood forecasting purposes. The performance of the MME and WRF (ARW) models rainfall at the sub-basin level have been studied in detail. The performance of WRF (ARW) and MME models is compared in the heavy rainfall case over the river basins (Mahanadi etc.) falls under FMO, Bhubaneswar and it is found that WRF (ARW) model gives better result than MME. It is also found that performance of WRF (ARW) is little better than MME when compared over all the flood prone river sub basins of India. For high rainfall categories (51-100,  >100 mm), generally these leads to floods, the success rate of model rainfall forecasts are less and false alarms are more. The NWP models are able to capture the rainfall events but there is difference in magnitudes of sub basin wise rainfall estimates.

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