scholarly journals Performance Evaluation of High-Resolution Simulations with COSMO over South Italy

Atmosphere ◽  
2020 ◽  
Vol 12 (1) ◽  
pp. 45
Author(s):  
Edoardo Bucchignani ◽  
Paola Mercogliano
Keyword(s):  
Weather Forecasting ◽  
Dew Point ◽  
Small Scale ◽  
Boundary Layer Height ◽  
South Italy ◽  
Scale Modeling ◽  
Radio Sounding ◽  
Model Configuration ◽  
Forecasting System ◽  
Good Agreement

This study aims to assess the capabilities of a weather forecasting system based on simulations performed with the COSMO (COnsortium for Small-scale Modeling) model over a domain located in southern Italy, employing a spatial resolution of about 1 km, driven by ECMWF-IFS global data. The model is run daily at the Italian Aerospace Research Center (CIRA), and the evaluation was performed from January to May 2018 using a combination of observational data, specifically data provided by the CIRA meteorological station, wind profiler and ceilometer. Moreover, data provided by radio sounding located at Pratica di Mare and ground stations at two other locations were also used. A model configuration optimized through a tuning procedure over the domain considered was employed, while the evaluation was performed by comparing daily values of several variables and using standard monitoring indices. The results highlight that the model has good capability in reproducing daily values of temperature, while precipitation intensity is generally underestimated, even if rain patterns are well captured (alternating rainy and dry days). Good agreement is also reported for wind speed, especially at 100 and 500 m altitude. Regarding radio sounding data, the COSMO model configuration selected can reproduce the vertical profile of temperature and dew point, with the exception of inversion points. Evaluation against ceilometer data is achieved in terms of cloud height and planetary boundary layer height.

scholarly journals A Sensitivity Analysis with COSMO-LM at 1 km Resolution over South Italy

Atmosphere ◽  
2020 ◽  
Vol 11 (4) ◽  
pp. 430
Author(s):  
Edoardo Bucchignani ◽  
Antigoni Voudouri ◽  
Paola Mercogliano
Keyword(s):  
Sensitivity Analysis ◽  
Small Scale ◽  
Heat Temperature ◽  
Weather Forecasts ◽  
South Italy ◽  
Temperature And Precipitation ◽  
Scale Modeling ◽  
Model Configuration ◽  
Forecasting System ◽  
Global Data

The results of a sensitivity analysis based on COSMO-LM (COnsortium for Small-Scale MOdeling—Lokal Model) simulations driven by ECMWF-IFS (European Centre for Medium-Range Weather Forecasts—Integrated Forecasting System). global data over a domain located in southern Italy are presented. Simulations have been performed at very high resolution (about 1 km). The main aim of this study is to individuate the most sensitive physical and numerical parameters of the model configuration, comparing a set of 18 simulations in terms of temperature and precipitation against ground observations. The parameters that result in having more influence for a proper representation of temperature and precipitation fields are the heat resistance length of laminar layer (which accounts for the high complexity of the interaction of the atmosphere with the underlying surface) and the minimal diffusion coefficient for heat. Temperature values are strongly influenced also by the vertical variation of critical relative humidity. An optimized tuning of these parameters allows COSMO-LM to improve the representation of simulated main features of this area, with significant bias reductions.

scholarly journals Ceilometers as planetary boundary layer height detectors and a corrective tool for COSMO and IFS models

2020 ◽  
Vol 20 (20) ◽  
pp. 12177-12192
Author(s):  
Leenes Uzan ◽  
Smadar Egert ◽  
Pavel Khain ◽  
Yoav Levi ◽  
Elyakom Vadislavsky ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Planetary Boundary Layer ◽  
Small Scale ◽  
Transform Method ◽  
Pollution Dispersion ◽  
Boundary Layer Height ◽  
Scale Modeling ◽  
Richardson Method ◽  
Parcel Method

Abstract. The significance of planetary boundary layer (PBL) height detection is apparent in various fields, especially in air pollution dispersion assessments. Numerical weather models produce a high spatial and temporal resolution of PBL heights; however, their performance requires validation. This necessity is addressed here by an array of eight ceilometers; a radiosonde; and two models – the Integrated Forecast System (IFS) global model and COnsortium for Small-scale MOdeling (COSMO) regional model. The ceilometers were analyzed with the wavelet covariance transform method, and the radiosonde and models with the parcel method and the bulk Richardson method. Good agreement for PBL height was found between the ceilometer and the adjacent Bet Dagan radiosonde (33 m a.s.l.) at 11:00 UTC launching time (N=91 d, ME =4 m, RMSE =143 m, R=0.83). The models' estimations were then compared to the ceilometers' results in an additional five diverse regions where only ceilometers operate. A correction tool was established based on the altitude (h) and distance from shoreline (d) of eight ceilometer sites in various climate regions, from the shoreline of Tel Aviv (h=5 m a.s.l., d=0.05 km) to eastern elevated Jerusalem (h=830 m a.s.l., d=53 km) and southern arid Hazerim (h=200 m a.s.l., d=44 km). The tool examined the COSMO PBL height approximations based on the parcel method. Results from a 14 August 2015 case study, between 09:00 and 14:00 UTC, showed the tool decreased the PBL height at the shoreline and in the inner strip of Israel by ∼100 m and increased the elevated sites of Jerusalem and Hazerim up to ∼400 m, and ∼600 m, respectively. Cross-validation revealed good results without Bet Dagan. However, without measurements from Jerusalem, the tool underestimated Jerusalem's PBL height by up to ∼600 m.

Catastrophic Effects of Floods on Environment and Health: Evidence from Pakistan

2016 ◽  
Vol 5 (2) ◽  
Author(s):  
Falak Shad Memon ◽  
M. Yousuf Sharjeel
Keyword(s):  
Paradigm Shift ◽  
Weather Forecasting ◽  
Human Life ◽  
National Level ◽  
Operational Cost ◽  
Site Assessment ◽  
Environment And Health ◽  
Forecasting System ◽  
Frame Work ◽  
Multiple Levels

<span>Torrential rains and floods have been causing irreplaceable losses to both human lives and environment in <span>Pakistan. This loss has reached to an extent of assively aggrieved situation to reinstate life at <span>operationally viable position. This paper unfolds the notion that only constructive paradigm shift to <span>overcome this phenomenon is vital as a strategy. Multiple levels of observations and on-site assessment <span>of various calamity-prone venues were considered to probe into this scenario. Some of the grave site in <span>Sindh and Punjab were observed and necessarily practicable measures were recommended to avoid loss to <span>human health and environment. The paper finds that a consistent drastic management authority on <span>national level with appropriate caliber and forecasting expertise can reduce the damage to human life and <span>environment to great extent. Weather forecasting system need to be installed at many appropriately <span>observed cities and towns in the country with adequate man power, funds and technical recourses. By <span>implementing the proper frame work of prevention and mitigation of floods country can save the major <span>costs cleanup and recovery. These measures are expected to reduce operational cost of state in terms of <span>GDP and GNP to restore life and environment.</span></span></span></span></span></span></span></span></span></span></span></span><br /><br class="Apple-interchange-newline" /></span>

scholarly journals Coupling between the JULES land-surface scheme and the CCATT-BRAMS atmospheric chemistry model (JULES-CCATT-BRAMS1.0): applications to numerical weather forecasting and the CO<sub>2</sub> budget in South America

2013 ◽  
Vol 6 (1) ◽  
pp. 453-494 ◽  
Author(s):  
D. S. Moreira ◽  
S. R. Freitas ◽  
J. P. Bonatti ◽  
L. M. Mercado ◽  
N. M. É. Rosário ◽  
...  
Keyword(s):  
South America ◽  
Atmospheric Chemistry ◽  
Land Surface ◽  
Amazon Basin ◽  
Mean Squared Error ◽  
Weather Forecasting ◽  
Dew Point ◽  
Surface Model ◽  
Co2 Concentrations ◽  
Wide Range

Abstract. This article presents the development of a new numerical system denominated JULES-CCATT-BRAMS, which resulted from the coupling of the JULES surface model to the CCATT-BRAMS atmospheric chemistry model. The performance of this system in relation to several meteorological variables (wind speed at 10 m, air temperature at 2 m, dew point temperature at 2 m, pressure reduced to mean sea level and 6 h accumulated precipitation) and the CO2 concentration above an extensive area of South America is also presented, focusing on the Amazon basin. The evaluations were conducted for two periods, the wet (March) and dry (September) seasons of 2010. The statistics used to perform the evaluation included bias (BIAS) and root mean squared error (RMSE). The errors were calculated in relation to observations at conventional stations in airports and automatic stations. In addition, CO2 concentrations in the first model level were compared with meteorological tower measurements and vertical CO2 profiles were compared with aircraft data. The results of this study show that the JULES model coupled to CCATT-BRAMS provided a significant gain in performance in the evaluated atmospheric fields relative to those simulated by the LEAF (version 3) surface model originally utilized by CCATT-BRAMS. Simulations of CO2 concentrations in Amazonia and a comparison with observations are also discussed and show that the system presents a gain in performance relative to previous studies. Finally, we discuss a wide range of numerical studies integrating coupled atmospheric, land surface and chemistry processes that could be produced with the system described here. Therefore, this work presents to the scientific community a free tool, with good performance in relation to the observed data and re-analyses, able to produce atmospheric simulations/forecasts at different resolutions, for any period of time and in any region of the globe.

scholarly journals Experimental and Numerical Investigation about Small Clearance Journal Bearings under Static Load Conditions

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Carlo Alberto Niccolini Marmont Du Haut Champ ◽  
Fabrizio Stefani ◽  
Paolo Silvestri
Keyword(s):  
Three Dimensional ◽  
Journal Bearings ◽  
Radial Clearance ◽  
Small Scale ◽  
Test Rig ◽  
Small Clearance ◽  
Dimensional Simulation ◽  
Dynamic Loading Conditions ◽  
Static And Dynamic Loading ◽  
Good Agreement

The aim of the present research is to characterize both experimentally and numerically journal bearings with low radial clearances for rotors in small-scale applications (e.g., microgas turbines); their diameter is in the order of ten millimetres, leading to very small dimensional clearances when the typical relative ones (order of 1/1000) are employed; investigating this particular class of journal bearings under static and dynamic loading conditions represents something unexplored. To this goal, a suitable test rig was designed and the performance of its bearings was investigated under steady load. For the sake of comparison, numerical simulations of the lubrication were also performed by means of a simplified model. The original test rig adopted is a commercial rotor kit (RK), but substantial modifications were carried out in order to allow significant measurements. Indeed, the relative radial clearance of RK4 RK bearings is about 2/100, while it is around 1/1000 in industrial bearings. Therefore, the same original RK bearings are employed in this new test rig, but a new shaft was designed to reduce their original clearance. The new custom shaft allows to study bearing behaviour for different clearances, since it is equipped with interchangeable journals. Experimental data obtained by this test rig are then compared with further results of more sophisticated simulations. They were carried out by means of an in-house developed finite element (FEM) code, suitable for thermoelasto-hydrodynamic (TEHD) analysis of journal bearings both in static and dynamic conditions. In this paper, bearing static performances are studied to assess the reliability of the experimental journal location predictions by comparing them with the ones coming from already validated numerical codes. Such comparisons are presented both for large and small clearance bearings of original and modified RKs, respectively. Good agreement is found only for the modified RK equipped with small clearance bearings (relative radial clearance 8/1000), as expected. In comparison with two-dimensional lubrication analysis, three-dimensional simulation improves prediction of journal location and correlation with experimental results.

scholarly journals A pan-African medium-range ensemble flood forecast system

2015 ◽  
Vol 19 (8) ◽  
pp. 3365-3385 ◽  
Author(s):  
V. Thiemig ◽  
B. Bisselink ◽  
F. Pappenberger ◽  
J. Thielen
Keyword(s):  
Large Scale ◽  
Practical Implication ◽  
River Basins ◽  
Flood Forecasting ◽  
Small Scale ◽  
Flood Forecast ◽  
Flood Events ◽  
Forecast System ◽  
Pan African ◽  
Forecasting System

Abstract. The African Flood Forecasting System (AFFS) is a probabilistic flood forecast system for medium- to large-scale African river basins, with lead times of up to 15 days. The key components are the hydrological model LISFLOOD, the African GIS database, the meteorological ensemble predictions by the ECMWF (European Centre for Medium-Ranged Weather Forecasts) and critical hydrological thresholds. In this paper, the predictive capability is investigated in a hindcast mode, by reproducing hydrological predictions for the year 2003 when important floods were observed. Results were verified by ground measurements of 36 sub-catchments as well as by reports of various flood archives. Results showed that AFFS detected around 70 % of the reported flood events correctly. In particular, the system showed good performance in predicting riverine flood events of long duration (> 1 week) and large affected areas (> 10 000 km2) well in advance, whereas AFFS showed limitations for small-scale and short duration flood events. The case study for the flood event in March 2003 in the Sabi Basin (Zimbabwe) illustrated the good performance of AFFS in forecasting timing and severity of the floods, gave an example of the clear and concise output products, and showed that the system is capable of producing flood warnings even in ungauged river basins. Hence, from a technical perspective, AFFS shows a large potential as an operational pan-African flood forecasting system, although issues related to the practical implication will still need to be investigated.

Heat-flow experiments in liquid 4He with a variable cylindrical geometry

1987 ◽  
Vol 174 ◽  
pp. 209-231 ◽  
Author(s):  
H. Gao ◽  
G. Metcalfe ◽  
T. Jung ◽  
R. P. Behringer
Keyword(s):  
Cylindrical Geometry ◽  
Small Scale ◽  
Onset Of Convection ◽  
Aspect Ratios ◽  
A Value ◽  
Prandtl Numbers ◽  
Convection Rolls ◽  
Flow Experiments ◽  
Increasing Function ◽  
Good Agreement

This paper first describes an apparatus for measuring the Nusselt number N versus the Rayleigh number R of convecting normal liquid 4He layers. The most important feature of the apparatus is its ability to provide layers of different heights d, and hence different aspect ratios [Gcy ]. The horizontal cross-section of each layer is circular, and [Gcy ] is defined by [Gcy ] = D/2d where D is the diameter of the layer. We report results for 2.4 [les ] [Gcy ] [les ] 16 and for Prandtl numbers Pr spanning 0.5 [lsim ] Pr [lsim ] 0.9 These results are presented in terms of the slope N1 = RcdN/dR evaluated just above the onset of convection at Rc. We find that N1 is only a slowly increasing function of [Gcy ] in the range 6 [lsim ] [Gcy ] [lsim ] 16, and that it has a value there which is quite close to 0.72. This value of N1 is in good agreement with variational calcuations by Ahlers et al. (1981) pertinent to parallel convection rolls in cylindrical geometry. Particularly for [Gcy ] [lsim ] 6, we find additional small-scale structure in N1 associated with changes in the number of convection rolls with changing [Gcy ]. An additional test of the linearzied hydrodynamics is given by measurements of Rc. We find good agreement between theory and our data for Rc.

scholarly journals Improvements in medium range weather forecasting system of India

2014 ◽  
Vol 123 (2) ◽  
pp. 247-258 ◽  
Author(s):  
V S PRASAD ◽  
SAJI MOHANDAS ◽  
SURYA KANTI DUTTA ◽  
M DAS GUPTA ◽  
G R IYENGAR ◽  
...  
Keyword(s):  
Weather Forecasting ◽  
Medium Range ◽  
Forecasting System

scholarly journals Gravity-wave effects on tracer gases and stratospheric aerosol concentrations during the 2013 ChArMEx campaign

2016 ◽  
Author(s):  
Fabrice Chane Ming ◽  
Damien Vignelles ◽  
Fabrice Jegou ◽  
Gwenael Berthet ◽  
Jean-Batiste Renard ◽  
...  
Keyword(s):  
Gravity Wave ◽  
Lower Stratosphere ◽  
Weather Forecasting ◽  
Stratospheric Aerosol ◽  
Thin Layers ◽  
Vertical Wind ◽  
Specific Humidity ◽  
Small Scale ◽  
Strong Activity ◽  
Dynamical Parameters

Abstract. Coupled balloon-borne observations of Light Optical Aerosol Counter (LOAC), M10 meteorological global positioning system (GPS) sondes, ozonesondes and GPS radio occultation data, are examined to identify gravity-wave (GW) induced fluctuations on tracer gases and on the vertical distribution of stratospheric aerosol concentrations during the 2013 ChArMEx (Chemistry-Aerosol Mediterranean Experiment) campaign. Observations reveal signatures of GWs with short vertical wavelengths less than 4 km in dynamical parameters and tracer constituents which are also correlated with the presence of thin layers of strong local enhancements of aerosol concentrations in the upper troposphere and the lower stratosphere. In particular, this is evident from a case study above Ile du Levant (43.02 °N, 6.46 °E) on 26–29 July 2013. Observations show a strong activity of dominant mesoscale inertia GWs with horizontal and vertical wavelengths of 370–510 km and 2–3 km respectively, and periods of 10–13 h propagating southward at altitudes of 13–20 km and eastward above 20 km during 27–28 July which is also captured by the European Center for Medium range Weather Forecasting (ECMWF) analyses. Ray-tracing experiments indicate the jet-front system to be the source of observed GWs. Simulated vertical profiles of dynamical parameters with large stratospheric vertical wind maximum oscillations ± 40 mms−1 are produced for the dominant mesoscale GW using the simplified linear GW theory. Parcel advection method reveals signatures of GWs in the ozone mixing ratio and the specific humidity. Simulated vertical wind perturbations of the dominant GW and small-scale perturbations of aerosol concentration (aerosol size of 0.2–0.7 μm) are in phase in the lower stratosphere. Present results support the importance of vertical wind perturbations in the GW-aerosol relation. The observed mesoscale GW induces a strong modulation of the amplitude of tracer gases and the stratospheric aerosol background.

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