scholarly journals Impact of parameterized convection on a numerically simulated tropical Cyclone structure

MAUSAM ◽  
2021 ◽  
Vol 48 (2) ◽  
pp. 135-156
Author(s):  
MUKUT B. MATHUR
Keyword(s):  
Numerical Models ◽  
Vertical Motion ◽  
Horizontal Resolution ◽  
Tropical Storm ◽  
Numerical Results ◽  
Lagrangian Model ◽  
Convective Heating ◽  
Time Step ◽  
Fine Mesh ◽  
The Impact

ABSTRACT. Condensational heating is a primary source of energy for disturbances like a tropical storm. The resolvable scale condensation and the parameterized convection, in many fine mesh numerical models, are evaluated at intervals greater than the time step, order of a minute, used for computing dynamical processes. The latent heating may depend on the model resolution and the interval at which the precipitation physics is evaluated. Numerical results from a series of short range forecasts are compared to study the impact of varying the horizontal resolution and the interval for evaluating condensation physics, and of excluding the parameterized convective heating. A horizontal grid spacing of 40 km (coarse mesh) or 20 km (fine mesh) in National Centers for Environmental Prediction's Quasi-Lagrangian Model (QLM), and the initial data for a tropical storm case, are utilized. Resolvable scale condensation is invoked only at supersaturated grid points, and a Kuo-type convective parameterization procedure is employed.   Significant structural differences are produced when the interval for computing both parameterized convection and resolvable scale heating is changed, and these differences broaden when the horizontal resolution is increased. The central warm cote structure and storm intensity are simulated better when both condensational processes are evaluated at an interval of twelve time steps than at each time step. Vertical columns in central storm area rapidly become convectively stable, and the maximum in vertical motion and strongest horizontal winds shift in the outer storm area, when both condensational processes are invoked at each time step. The central storm area remains conditionally unstable, and strongest winds develop close to the center, when both condensational processes are evaluated at intervals of twelve time steps.   The central storm area remains conditionally unstable also in the fine mesh experiment in which the parameterized convective heating is excluded and the resolvable scale heating is evaluated at each time step. Intense vertical motion and vigorous heating develop in deep vertical columns, indicating that the heating on the convective scale is simulated as the resolvable scale heating. The vertical distribution of heating and the storm structure, during the first six hours in this case, are similar to those in the fine mesh run in which both condensational processes are evaluated at intervals of twelve time steps. However, the storm intensifies more rapidly after 6 h in the former than in the later case. Numerical results from additional experiments are presented to show that predicted storm structure is modified with a change in interval for invoking either or both condensational processes, and these circulation differences are not due to the initial spin up.   Transfer of moisture and heat from low levels into the higher troposphere in cumulonimbus clouds takes place in several minutes. Above cited and other predictions from the QLM suggest that storm structure. intensity and motion in a mesoscale model are likely to, be improved when parameterized convective heating is included; however, a parameterization scheme that concurrently produces alterations in the entire model cloud depth should be invoked at intervals of several minutes.      

Fog forecasting for Schiphol airport at sub-kilometre scale.  

2021 ◽  
Author(s):  
Gert-Jan Steeneveld ◽  
Roosmarijn Knol
Keyword(s):  
Spatial Resolution ◽  
Numerical Models ◽  
Wrf Model ◽  
Horizontal Resolution ◽  
Physical Processes ◽  
Radiation Fog ◽  
Fog Forecasting ◽  
Elevation Data ◽  
The Individual ◽  
The Impact

<p>Fog is a critical weather phenomenon for safety and operations in aviation. Unfortunately, the forecasting of radiation fog remains challenging due to the numerous physical processes that play a role and their complex interactions, in addition to the vertical and horizontal resolution of the numerical models. In this study we evaluate the performance of the Weather Research and Forecasting (WRF) model for a radiation fog event at Schiphol Amsterdam Airport (The Netherlands) and further develop the model towards a 100 m grid spacing. Hence we introduce high resolution land use and land elevation data. In addition we study the role of gravitational droplet settling, advection of TKE, top-down diffusion caused by strong radiative cooling at the fog top. Finally the impact of heat released by the terminal areas on the fog formation is studied. The model outcomes are evaluated against 1-min weather observations near multiple runways at the airport.</p><p>Overall we find the WRF model shows an reasonable timing of the fog onset and is well able to reproduce the visibility and meteorological conditions as observed during the case study. The model appears to be relatively insensitive to the activation of the individual physical processes. An increased spatial resolution to 100 m generally results in a better timing of the fog onset differences up to three hours, though not for all runways. The effect of the refined landuse dominates over the effect of refined elevation data. The modelled fog dissipation systematically occurs 3-4 h hours too early, regardless of physical processes or spatial resolution. Finally, the introduction of heat from terminal buildings delays the fog onset with a maximum of two hours, an overestimated visibility of 100-200 m and a decrease of the LWC with 0.10-0.15 g/kg compared to the reference.</p>

scholarly journals Experimental Tropical Cyclone Forecasts Using a Variable-Resolution Global Model

2015 ◽  
Vol 143 (10) ◽  
pp. 4012-4037 ◽  
Author(s):  
Colin M. Zarzycki ◽  
Christiane Jablonowski
Keyword(s):  
High Resolution ◽  
Tropical Cyclone ◽  
Initial Conditions ◽  
Weather Prediction ◽  
Horizontal Resolution ◽  
Hurricane Sandy ◽  
Track Forecast ◽  
Time Step ◽  
Variable Resolution ◽  
The Impact

Abstract Tropical cyclone (TC) forecasts at 14-km horizontal resolution (0.125°) are completed using variable-resolution (V-R) grids within the Community Atmosphere Model (CAM). Forecasts are integrated twice daily from 1 August to 31 October for both 2012 and 2013, with a high-resolution nest centered over the North Atlantic and eastern Pacific Ocean basins. Using the CAM version 5 (CAM5) physical parameterization package, regional refinement is shown to significantly increase TC track forecast skill relative to unrefined grids (55 km, 0.5°). For typical TC forecast integration periods (approximately 1 week), V-R forecasts are able to nearly identically reproduce the flow field of a globally uniform high-resolution forecast. Simulated intensity is generally too strong for forecasts beyond 72 h. This intensity bias is robust regardless of whether the forecast is forced with observed or climatological sea surface temperatures and is not significantly mitigated in a suite of sensitivity simulations aimed at investigating the impact of model time step and CAM’s deep convection parameterization. Replacing components of the default physics with Cloud Layers Unified by Binormals (CLUBB) produces a statistically significant improvement in forecast intensity at longer lead times, although significant structural differences in forecasted TCs exist. CAM forecasts the recurvature of Hurricane Sandy into the northeastern United States 60 h earlier than the Global Forecast System (GFS) model using identical initial conditions, demonstrating the sensitivity of TC forecasts to model configuration. Computational costs associated with V-R simulations are dramatically decreased relative to globally uniform high-resolution simulations, demonstrating that variable-resolution techniques are a promising tool for future numerical weather prediction applications.

scholarly journals Differing responses of the quasi-biennial oscillation to artificial SO<sub>2</sub> injections in two global models

2020 ◽  
Vol 20 (14) ◽  
pp. 8975-8987
Author(s):  
Ulrike Niemeier ◽  
Jadwiga H. Richter ◽  
Simone Tilmes
Keyword(s):  
General Circulation ◽  
Climate Model ◽  
Numerical Models ◽  
General Circulation Models ◽  
Horizontal Resolution ◽  
Injection Rate ◽  
Quasi Biennial Oscillation ◽  
Vertical Advection ◽  
The Impact ◽  
Biennial Oscillation

Abstract. Artificial injections of sulfur dioxide (SO2) into the stratosphere show in several model studies an impact on stratospheric dynamics. The quasi-biennial oscillation (QBO) has been shown to slow down or even vanish under higher SO2 injections in the equatorial region. But the impact is only qualitatively but not quantitatively consistent across the different studies using different numerical models. The aim of this study is to understand the reasons behind the differences in the QBO response to SO2 injections between two general circulation models, the Whole Atmosphere Community Climate Model (WACCM-110L) and MAECHAM5-HAM. We show that the response of the QBO to injections with the same SO2 injection rate is very different in the two models, but similar when a similar stratospheric heating rate is induced by SO2 injections of different amounts. The reason for the different response of the QBO corresponding to the same injection rate is very different vertical advection in the two models, even in the control simulation. The stronger vertical advection in WACCM results in a higher aerosol burden and stronger heating of the aerosols and, consequently, in a vanishing QBO at lower injection rate than in simulations with MAECHAM5-HAM. The vertical velocity increases slightly in MAECHAM5-HAM when increasing the horizontal resolution. This study highlights the crucial role of dynamical processes and helps to understand the large uncertainties in the response of different models to artificial SO2 injections in climate engineering studies.

Impact of increasing horizontal and vertical resolution during the HWRF hybrid EnVar data assimilation on the analysis and prediction of Hurricane Patricia (2015)

2020 ◽  
Author(s):  
Jie Feng ◽  
Xuguang Wang
Keyword(s):  
Data Assimilation ◽  
Horizontal Resolution ◽  
Tropical Storm ◽  
Weather Research And Forecasting ◽  
Vertical Resolution ◽  
Model Resolution ◽  
Warm Core ◽  
The Individual ◽  
The Impact ◽  
Hwrf Model

AbstractAlthough numerous studies have demonstrated that increasing model spatial resolution in free forecasts can potentially improve tropical cyclone (TC) intensity forecasts, studies on the impact of model resolution during data assimilation (DA) on TC prediction are lacking. In this study, using the ensemble-variational DA system for Hurricane Weather Research and Forecasting (HWRF) model, we investigated the individual impact of increasing the model resolution of first guess (FG) and background ensemble (BE) forecasts during DA on initial analyses and subsequent forecasts of Hurricane Patricia (2015). The impacts were compared between horizontal and vertical resolutions and also between the tropical storm (TS) and hurricane assimilation during Patricia.The results show that increasing the horizontal or vertical resolution in FG has a larger impact than increasing the resolution in BE on improving the analyzed TC intensity and structure for the hurricane stage. The result is reversed for the TS stage. These results are attributed to the effectiveness of increasing the FG resolution in intensifying the background vortex for the hurricane stage relative to the TS stage. Increasing the BE resolution contributes to improving the analyzed intensity through the better-resolved background correlation structure for both the hurricane and TS stages. Increasing horizontal resolution has an overall larger effect than increasing vertical resolution in improving the analysis at the hurricane stage and their effects are close for the analysis at the TS stage. Additionally, the more accurately analyzed primary, secondary circulation, and warm core structures via the increased resolution in DA lead to improved TC intensity forecasts.

scholarly journals Higher Resolution in an Operational Ensemble Kalman Filter

2014 ◽  
Vol 142 (3) ◽  
pp. 1143-1162 ◽  
Author(s):  
P. L. Houtekamer ◽  
Xingxiu Deng ◽  
Herschel L. Mitchell ◽  
Seung-Jong Baek ◽  
Normand Gagnon
Keyword(s):  
Kalman Filter ◽  
Temporal Resolution ◽  
Ensemble Kalman Filter ◽  
Forecast Model ◽  
Horizontal Resolution ◽  
Ensemble Prediction ◽  
Time Step ◽  
Ensemble Prediction System ◽  
Medium Range ◽  
The Impact

Abstract Recently, the computing facilities available to the Meteorological Service of Canada were significantly upgraded. This provided an opportunity to improve the resolution of the global ensemble Kalman filter (EnKF) and the medium-range Global Ensemble Prediction System (GEPS). In the EnKF, the main upgrades include improved horizontal, vertical, and temporal resolution. With the introduction of the higher horizontal resolution, it was decided to use a filtered topography in order to address an occasional instability problem. At the same time, the number of assimilated radiance observations was increased via a relaxation of the data-thinning procedures. In the medium-range GEPS, which already used the higher horizontal resolution, the filtered topography was also adopted. Likewise, the temporal resolution was increased to be the same as in the short-range integrations of the EnKF. With these changes, the grid used by the Canadian EnKF has 600 × 300 points in the horizontal and 74 vertical levels. The forecast model uses a 20-min time step and, for time interpolation of the model trajectories, model states are stored every hour. The EnKF uses an ensemble having 192 members. This paper sequentially examines the impact of these implemented changes. The upgraded EnKF became operational at the Canadian Meteorological Centre in mid-February 2013.

Assessing Tracer Transport Algorithms and the Impact of Vertical Resolution in a Finite-Volume Dynamical Core

2012 ◽  
Vol 140 (5) ◽  
pp. 1620-1638 ◽  
Author(s):  
James Kent ◽  
Christiane Jablonowski ◽  
Jared P. Whitehead ◽  
Richard B. Rood
Keyword(s):  
Finite Volume ◽  
Vertical Component ◽  
Vertical Motion ◽  
Atmospheric Model ◽  
Horizontal Resolution ◽  
Vertical Resolution ◽  
Tracer Transport ◽  
Dynamical Core ◽  
Lagrangian Coordinate ◽  
The Impact

Abstract Modeling the transport of trace gases is an essential part of any atmospheric model. The tracer transport scheme in the Community Atmosphere Model finite-volume dynamical core (CAM-FV), which is part of the National Center for Atmospheric Research’s (NCAR’s) Community Earth System Model (CESM1), is investigated using multidimensional idealized advection tests. CAM-FV’s tracer transport algorithm makes use of one-dimensional monotonic limiters. The Colella–Sekora limiter, which is applied to increase accuracy where the data are smooth, is implemented into the CAM-FV framework, and compared with the more traditional monotonic limiter of the piecewise parabolic method (the default limiter). For 2D flow, CAM-FV splits dimensions, allowing overshoots and undershoots, with the Colella–Sekora limiter producing larger overshoots than the default limiter. The impact of vertical resolution is also explored. A vertical Lagrangian coordinate is used in CAM-FV, and is periodically remapped back to a fixed Eulerian grid. For purely vertical motion, it is found that less-frequent remapping of the Lagrangian coordinate in CAM-FV improves results. For full 3D tests, the vertical component of the tracer transport dominates the error and limits the overall accuracy. If the vertical resolution is inadequate, increasing the horizontal resolution has almost no effect on accuracy. This is because the vertical resolution currently used in CAM version 5 may not be sufficiently fine enough to resolve some atmospheric tracers and provide accurate vertical advection. Idealized tests using tracers in a gravity wave agree with these results.

Impact of Increasing Horizontal and Vertical Resolution during the HWRF Hybrid EnVar Data Assimilation on the Analysis and Prediction of Hurricane Patricia (2015)

2021 ◽  
Author(s):  
Jie Feng
Keyword(s):  
Data Assimilation ◽  
Horizontal Resolution ◽  
Tropical Storm ◽  
Weather Research And Forecasting ◽  
Vertical Resolution ◽  
Model Resolution ◽  
Warm Core ◽  
The Individual ◽  
The Impact ◽  
Hwrf Model

&lt;p&gt;Although numerous studies have demonstrated that increasing model spatial resolution in free forecasts can potentially improve tropical cyclone (TC) intensity forecasts, studies on the impact of model resolution during data assimilation (DA) on TC prediction are lacking. &amp;#160;In this study, using the ensemble-variational DA system for Hurricane Weather Research and Forecasting (HWRF) model, we investigated the individual impact of increasing the model resolution of first guess (FG) and background ensemble (BE) forecasts during DA on initial analyses and subsequent forecasts of Hurricane Patricia (2015). &amp;#160;The impacts were compared between horizontal and vertical resolutions and also between the tropical storm (TS) and hurricane assimilation during Patricia.&lt;/p&gt;&lt;p&gt;The results show that increasing the horizontal or vertical resolution in FG has a larger impact than increasing the resolution in BE on improving the analyzed TC intensity and structure for the hurricane stage. The result is reversed for the TS stage. &amp;#160;These results are attributed to the effectiveness of increasing the FG resolution in intensifying the background vortex for the hurricane stage relative to the TS stage. &amp;#160;Increasing the BE resolution contributes to improving the analyzed intensity through the better-resolved background correlation structure for both the hurricane and TS stages. &amp;#160;Increasing horizontal resolution has an overall larger effect than increasing vertical resolution in improving the analysis at the hurricane stage and their effects are close for the analysis at the TS stage. Additionally, the more accurately analyzed primary, secondary circulation, and warm core structures via the increased resolution in DA lead to improved TC intensity forecasts.&lt;/p&gt;

scholarly journals A New Experimental Study and SPH Comparison for the Sequential Dam-Break Problem

2020 ◽  
Vol 8 (11) ◽  
pp. 905
Author(s):  
Selahattin Kocaman ◽  
Kaan Dal
Keyword(s):  
Image Processing ◽  
Numerical Models ◽  
Flow Behavior ◽  
Rectangular Channel ◽  
Numerical Results ◽  
Dam Break ◽  
Frame Rate ◽  
Image Processing Technique ◽  
Complex Flow ◽  
The Impact

The floods following the event of a dam collapse can have a significant impact on the downstream environment and ecology. Due to the limited number of real-case data for dam-break floods, laboratory experiments and numerical models are used to understand the complex flow behavior and to analyze the impact of the dam-break wave for different scenarios. In this study, a newly designed experimental campaign was conducted for the sequential dam-break problem in a rectangular channel with a steep slope, and the obtained results were compared against those of a particle-based numerical model. The laboratory tests permitted a better understanding of the physical process, highlighting five successive stages observed in the downstream reservoirs: dam-break wave propagation, overtopping, reflection wave, run-up, and oscillations. Experimental data were acquired using a virtual wave probe based on an image processing technique. A professional camera and a smartphone camera were used to obtain the footage of the experiment to examine the effect of the resolution and frame rate on image processing. The numerical results were obtained through the Smoothed Particle Hydrodynamics (SPH) method using free DualSPHysics software. The experimental and numerical results were in good agreement generally. Hence, the presented data can be used as a benchmark in future studies to validate the SPH and other Computational Fluid Dynamics (CFD) methods.

scholarly journals Tropical cyclones prediction by numerical models in India Meteorological Department

MAUSAM ◽  
2021 ◽  
Vol 57 (1) ◽  
pp. 47-60
Author(s):  
Y. V. RAMA RAO ◽  
H. R. HATWAR ◽  
GEETA AGNIHOTRI
Keyword(s):  
Initial Conditions ◽  
Numerical Models ◽  
Forecast Error ◽  
India Meteorological Department ◽  
Lagrangian Model ◽  
Limited Area ◽  
Track Forecast ◽  
Forecast Errors ◽  
Error Statistics ◽  
The Impact

lkj & bl 'kks/k&Ik= esa Hkkjr ekSle foKku foHkkx ¼Hkk- ekS- fo- fo-½ esa viukbZ xbZ pØokr izfr:fir djus dh dfYir rduhdksa ij ppkZ dh xbZ gSA vDrwcj 1999 esa mM+hlk esa vk, egkpØokr ds izkjfEHkd {ks=ksa esa dkYifud Hkzfeyrk dk mi;ksx djds] pØokr ds fof’k"V ekWMy] Doklh ySaxjfx;u ekWMy ¼D;w- ,y- ,e-½ ls 72 ?kaVs ds iwokZuqeku vkSj Hkkjr ekSle foKku foHkkx ds lhfer {ks= fun’kZ ¼,y- ,- ,e-½ ls 36 ?kaVs ds iwokZuqeku izfr:fir fd, x,A bl 'kks/k esa] 26 ls 28 vDrwcj rd dh izkjafHkd fLFkfr;ksa ds vk/kkj ij D;w- ,y- ,e- ls pØokr ds ekxZ ds iwokZuqeku dh vkSlr =qfV;k¡ 24 ?kaVs ds fy, 21 fd-eh-] 48 ?kaVs ds fy,  91 fd-eh- vkSj 72 ?kaVs ds fy, 179 fd-eh- jghA 1998&2004 rd ds fiNys lkr o"kksZa ds nkSjku D;w- ,y- ,e- ls pØokr ds ekxZ ds iwokZuqeku dh =qfV;ksa ds vk¡dM+ksa ij Hkh blesa ppkZ dh xbZ gSA blds vykok] ,y- ,- ,e- ls fd, x, iwokZuqeku ij izkjafHkd fLFkfr;ksa ds izHkko dh Hkh tk¡p dh xbZA fofHkUu izkjafHkd fLFkfr;ksa ls rS;kj fd, x, vkSlr ¼lesfdr½ iwokZuqeku ls 24 ?kaVs ds iwokZuqeku esa 123 fd-eh- vkSj 36 ?kaVs ds iwokZuqeku esa 81 fd-eh- dh =qfV;k¡ ikbZ xbZ] tks ,dek= iwokZuqeku dh rqyuk esa de jghA bu iz;ksxksa ls ;g irk pyk fd dkYifud Hkzfeyrk okys D;w- ,y- ,e- ekWMy ls pØokr ds ekxZ  dk lVhd iwokZuqeku izkIr fd;k tk ldrk gS tks vHkh rd la[;kRed ekWMyksa ls miyC/k gks ikrk FkkA  In the present paper, the cyclone bogusing techniques followed in India Meteorological Department (IMD) were discussed. Using the idealized vortex in the initial fields for Orissa super cyclone October 1999, the specialized cyclone model, Quasi-Lagrangian Model (QLM) 72 hours track forecast and also 36 hours forecast with IMD limited area model (LAM) were simulated. In this case, the QLM average track forecast errors based on 26-28 October initial conditions were 21 km for 24 hours, 91 km for 48 hours and 179 km for 72 hours. Also the QLM track forecast error statistics during the last 7 years 1998-2004 are discussed. In addition, the impact of initial conditions on the LAM forecast was examined. It was observed that the mean (ensemble) forecast generated from different initial conditions was shown track error of 123 km in 24 hours and 81 km in 36 hours forecast which is less than individual forecast. These experiments have established that the QLM model, with idealized vortex, provides track forecast within an accuracy level that was currently available from numerical models.  

scholarly journals A Rational Numerical Method for Simulation of Drop-Impact Dynamics of Oleo-Pneumatic Landing Gear

2021 ◽  
Vol 11 (9) ◽  
pp. 4136
Author(s):  
Rosario Pecora
Keyword(s):  
Numerical Method ◽  
Initial Conditions ◽  
Impact Load ◽  
Numerical Models ◽  
Landing Gear ◽  
Design Stage ◽  
Impact Dynamics ◽  
State Variables ◽  
Adopted Model ◽  
The Impact

Oleo-pneumatic landing gear is a complex mechanical system conceived to efficiently absorb and dissipate an aircraft’s kinetic energy at touchdown, thus reducing the impact load and acceleration transmitted to the airframe. Due to its significant influence on ground loads, this system is generally designed in parallel with the main structural components of the aircraft, such as the fuselage and wings. Robust numerical models for simulating landing gear impact dynamics are essential from the preliminary design stage in order to properly assess aircraft configuration and structural arrangements. Finite element (FE) analysis is a viable solution for supporting the design. However, regarding the oleo-pneumatic struts, FE-based simulation may become unpractical, since detailed models are required to obtain reliable results. Moreover, FE models could not be very versatile for accommodating the many design updates that usually occur at the beginning of the landing gear project or during the layout optimization process. In this work, a numerical method for simulating oleo-pneumatic landing gear drop dynamics is presented. To effectively support both the preliminary and advanced design of landing gear units, the proposed simulation approach rationally balances the level of sophistication of the adopted model with the need for accurate results. Although based on a formulation assuming only four state variables for the description of landing gear dynamics, the approach successfully accounts for all the relevant forces that arise during the drop and their influence on landing gear motion. A set of intercommunicating routines was implemented in MATLAB® environment to integrate the dynamic impact equations, starting from user-defined initial conditions and general parameters related to the geometric and structural configuration of the landing gear. The tool was then used to simulate a drop test of a reference landing gear, and the obtained results were successfully validated against available experimental data.

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