scholarly journals Observed and Modeled Mountain Waves from the Surface to the Mesosphere Near the Drake Passage

2022 ◽  
Keyword(s):  
Middle Atmosphere ◽  
Weather Prediction ◽  
Wrf Model ◽  
Drake Passage ◽  
Horizontal Resolution ◽  
Observation Time ◽  
Small Scale ◽  
Atmospheric Infrared Sounder ◽  
Mountain Waves ◽  
State Of The Science

Abstract Four state-of-the-science numerical weather prediction (NWP) models were used to perform mountain wave- (MW) resolving hind-casts over the Drake Passage of a 10-day period in 2010 with numerous observed MW cases. The Integrated Forecast System (IFS) and the Icosahedral Nonhydrostatic (ICON) model were run at Δx ≈ 9 and 13 km globally. TheWeather Research and Forecasting (WRF) model and the Met Office Unified Model (UM) were both configured with a Δx = 3 km regional domain. All domains had tops near 1 Pa (z ≈ 80 km). These deep domains allowed quantitative validation against Atmospheric InfraRed Sounder (AIRS) observations, accounting for observation time, viewing geometry, and radiative transfer. All models reproduced observed middle-atmosphere MWs with remarkable skill. Increased horizontal resolution improved validations. Still, all models underrepresented observed MW amplitudes, even after accounting for model effective resolution and instrument noise, suggesting even at Δx ≈ 3 km resolution, small-scale MWs are under-resolved and/or over-diffused. MWdrag parameterizations are still necessary in NWP models at current operational resolutions of Δx ≈ 10 km. Upper GW sponge layers in the operationally configured models significantly, artificially reduced MW amplitudes in the upper stratosphere and mesosphere. In the IFS, parameterized GW drags partly compensated this deficiency, but still, total drags were ≈ 6 time smaller than that resolved at Δx ≈ 3 km. Meridionally propagating MWs significantly enhance zonal drag over the Drake Passage. Interestingly, drag associated with meridional fluxes of zonal momentum (i.e. ) were important; not accounting for these terms results in a drag in the wrong direction at and below the polar night jet.

scholarly journals Verification of Forecast Weather Surface Variables over Vietnam Using the National Numerical Weather Prediction System

2016 ◽  
Vol 2016 ◽  
pp. 1-11 ◽  
Author(s):  
Tien Du Duc ◽  
Lars Robert Hole ◽  
Duc Tran Anh ◽  
Cuong Hoang Duc ◽  
Thuy Nguyen Ba
Keyword(s):  
Numerical Weather Prediction ◽  
Weather Prediction ◽  
Model Performance ◽  
Wrf Model ◽  
Horizontal Resolution ◽  
Prediction System ◽  
Regional Models ◽  
Global Spectral Model ◽  
Numerical Weather ◽  
The Us

The national numerical weather prediction system of Vietnam is presented and evaluated. The system is based on three main models, namely, the Japanese Global Spectral Model, the US Global Forecast System, and the US Weather Research and Forecasting (WRF) model. The global forecast products have been received at 0.25- and 0.5-degree horizontal resolution, respectively, and the WRF model has been run locally with 16 km horizontal resolution at the National Center for Hydro-Meteorological Forecasting using lateral conditions from GSM and GFS. The model performance is evaluated by comparing model output against observations of precipitation, wind speed, and temperature at 168 weather stations, with daily data from 2010 to 2014. In general, the global models provide more accurate forecasts than the regional models, probably due to the low horizontal resolution in the regional model. Also, the model performance is poorer for stations with altitudes greater than 500 meters above sea level (masl). For tropical cyclone performance validations, the maximum wind surface forecast from global and regional models is also verified against the best track of Joint Typhoon Warning Center. Finally, the model forecast skill during a recent extreme rain event in northeast Vietnam is evaluated.

scholarly journals Observed versus simulated mountain waves over Scandinavia – improvement of vertical winds, energy and momentum fluxes by enhanced model resolution?

2017 ◽  
Vol 17 (6) ◽  
pp. 4031-4052 ◽  
Author(s):  
Johannes Wagner ◽  
Andreas Dörnbrack ◽  
Markus Rapp ◽  
Sonja Gisinger ◽  
Benedikt Ehard ◽  
...  
Keyword(s):  
High Energy ◽  
Horizontal Resolution ◽  
Small Scale ◽  
Mountain Waves ◽  
Stratospheric Intrusion ◽  
Momentum Fluxes ◽  
Wave Effects ◽  
Energy And Momentum ◽  
Vertical Winds ◽  
Mesoscale Simulations

Abstract. Two mountain wave events, which occurred over northern Scandinavia in December 2013 are analysed by means of airborne observations and global and mesoscale numerical simulations with horizontal mesh sizes of 16, 7.2, 2.4 and 0.8 km. During both events westerly cross-mountain flow induced upward-propagating mountain waves with different wave characteristics due to differing atmospheric background conditions. While wave breaking occurred at altitudes between 25 and 30 km during the first event due to weak stratospheric winds, waves propagated to altitudes above 30 km and interfacial waves formed in the troposphere at a stratospheric intrusion layer during the second event. Global and mesoscale simulations with 16 and 7.2 km grid sizes were not able to simulate the amplitudes and wavelengths of the mountain waves correctly due to unresolved mountain peaks. In simulations with 2.4 and 0.8 km horizontal resolution, mountain waves with horizontal wavelengths larger than 15 km were resolved, but exhibited too small amplitudes and too high energy and momentum fluxes. Simulated fluxes could be reduced by either increasing the vertical model grid resolution or by enhancing turbulent diffusion in the model, which is comparable to an improved representation of small-scale nonlinear wave effects.

The impact of SST on the weather forecast quality in the Bulgarian Antarctic Base area on Livingstone Island

2020 ◽  
Author(s):  
Boriana Chtirkova ◽  
Elisaveta Peneva
Keyword(s):  
Prediction Models ◽  
Weather Prediction ◽  
Wrf Model ◽  
Weather Forecast ◽  
Horizontal Resolution ◽  
Initial Time ◽  
Test Cases ◽  
Validation Data ◽  
The Impact ◽  
Forecast Quality

<p>The weather forecast of good quality is essential for the humans living and operating in the Bulgarian Antarctic Base. The numerical weather prediction models in southern high latitude regions still need improvement as the user community is limited, little test cases are documented and validation data are scarce. Not lastly, the challenge of distributing the output results under poor internet conditions has to be addressed.</p><p>The Bulgarian Antarctic Base (BAB) is located on the Livingstone Island coast at 62⁰S and 60⁰W. The influence of the Southern ocean is significant, thus important to be correctly taken into account in the numerical forecast. The modeling system is based on the WRF model, configured in three nested domains down to 1 km horizontal resolution, centered in BAB. The main objective of the study is to quantify the Sea Surface Temperature (SST) impact and to recommend the frequency and way to perform measurements of the SST near the base. The focus is on prediction of right initial time and period of “bad” weather events like storms, frontal zones, and severe winds. Several test cases are considered with available measurements of temperature, pressure and wind speed in BAB during the summer season in 2017. The numerical 3 days forecast is performed and the model skill to capture the basic meteorological events in this period is discussed. Sensitivity experiments to SST values in the nearby marine area are concluded and the SST influence on the model forecast quality is analyzed.</p>

scholarly journals Bulk Convergence of Cloud-Resolving Simulations of Moist Convection over Complex Terrain

2012 ◽  
Vol 69 (7) ◽  
pp. 2207-2228 ◽  
Author(s):  
Wolfgang Langhans ◽  
Juerg Schmidli ◽  
Christoph Schär
Keyword(s):  
Control Volume ◽  
Weather Prediction ◽  
Horizontal Resolution ◽  
Small Scale ◽  
Computational Domain ◽  
Moist Convection ◽  
Bulk Properties ◽  
Convective Systems ◽  
Convective Structures ◽  
Vertical Fluxes

Abstract The explicit treatment of moist convection in cloud-resolving models with kilometer-scale horizontal resolution is increasingly used for atmospheric research and numerical weather prediction purposes. However, several previous studies have implicitly questioned the physical validity of this approach, as the accurate representation of the structure and evolution of moist convective phenomena requires considerably higher resolution. Unlike these studies, which focused on single convective systems, here the convergence of bulk properties of an ensemble of moist convective cells in kilometer-scale simulations is considered. To address the convergence, the authors focus on the bulk net heating and moistening in a large control volume, the associated vertical fluxes, and the diurnal evolution of regionally averaged precipitation. Besides numerical convergence, “physical” convergence (Reynolds number increases with resolution) is addressed for two conceptually different subgrid-mixing approaches (1D mesoscale and 3D LES). Simulations are conducted for a 9-day period of diurnal summer convection over the Alps, using a large computational domain with grid spacings of 4.4, 2.2, 1.1, and 0.55 km and grid-independent topography. Results show that for the model and episode considered, the simulated bulk properties and vertical fluxes converge numerically toward the 0.55-km solution. In terms of bulk effects, differences between the simulations are surprisingly small, even within the physical convergence framework that exhibits a sensitivity of the small-scale dynamics and ensuing convective structures to the horizontal resolution. Despite some sensitivities related to the applied turbulence closure, the results support the feasibility of kilometer-scale models to appropriately represent the bulk feedbacks between moist convection and the larger-scale flow.

scholarly journals The MaCWAVE program to study gravity wave influences on the polar mesosphere

2006 ◽  
Vol 24 (4) ◽  
pp. 1159-1173 ◽  
Author(s):  
R. A. Goldberg ◽  
D. C. Fritts ◽  
F. J. Schmidlin ◽  
B. P. Williams ◽  
C. L. Croskey ◽  
...  
Keyword(s):  
Gravity Wave ◽  
Large Scale ◽  
Planetary Wave ◽  
Middle Atmosphere ◽  
Lower Thermosphere ◽  
Wave Structure ◽  
Wave Activity ◽  
Small Scale ◽  
Mountain Waves ◽  
The Mean

Abstract. MaCWAVE (Mountain and Convective Waves Ascending VErtically) was a highly coordinated rocket, ground-based, and satellite program designed to address gravity wave forcing of the mesosphere and lower thermosphere (MLT). The MaCWAVE program was conducted at the Norwegian Andøya Rocket Range (ARR, 69.3° N) in July 2002, and continued at the Swedish Rocket Range (Esrange, 67.9° N) during January 2003. Correlative instrumentation included the ALOMAR MF and MST radars and RMR and Na lidars, Esrange MST and meteor radars and RMR lidar, radiosondes, and TIMED (Thermosphere Ionosphere Mesosphere Energetics and Dynamics) satellite measurements of thermal structures. The data have been used to define both the mean fields and the wave field structures and turbulence generation leading to forcing of the large-scale flow. In summer, launch sequences coupled with ground-based measurements at ARR addressed the forcing of the summer mesopause environment by anticipated convective and shear generated gravity waves. These motions were measured with two 12-h rocket sequences, each involving one Terrier-Orion payload accompanied by a mix of MET rockets, all at ARR in Norway. The MET rockets were used to define the temperature and wind structure of the stratosphere and mesosphere. The Terrier-Orions were designed to measure small-scale plasma fluctuations and turbulence that might be induced by wave breaking in the mesosphere. For the summer series, three European MIDAS (Middle Atmosphere Dynamics and Structure) rockets were also launched from ARR in coordination with the MaCWAVE payloads. These were designed to measure plasma and neutral turbulence within the MLT. The summer program exhibited a number of indications of significant departures of the mean wind and temperature structures from ``normal" polar summer conditions, including an unusually warm mesopause and a slowing of the formation of polar mesospheric summer echoes (PMSE) and noctilucent clouds (NLC). This was suggested to be due to enhanced planetary wave activity in the Southern Hemisphere and a surprising degree of inter-hemispheric coupling. The winter program was designed to study the upward propagation and penetration of mountain waves from northern Scandinavia into the MLT at a site favored for such penetration. As the major response was expected to be downstream (east) of Norway, these motions were measured with similar rocket sequences to those used in the summer campaign, but this time at Esrange. However, a major polar stratospheric warming just prior to the rocket launch window induced small or reversed stratospheric zonal winds, which prevented mountain wave penetration into the mesosphere. Instead, mountain waves encountered critical levels at lower altitudes and the observed wave structure in the mesosphere originated from other sources. For example, a large-amplitude semidiurnal tide was observed in the mesosphere on 28 and 29 January, and appears to have contributed to significant instability and small-scale structures at higher altitudes. The resulting energy deposition was found to be competitive with summertime values. Hence, our MaCWAVE measurements as a whole are the first to characterize influences in the MLT region of planetary wave activity and related stratospheric warmings during both winter and summer.

scholarly journals Impact of microphysics parameterization schemes in simulation of vardah cyclone using the advanced mesoscale weather research and forecasting model

2018 ◽  
Vol 7 (3.29) ◽  
pp. 272 ◽  
Author(s):  
P Janardhan Saikumar ◽  
T Ramashri
Keyword(s):  
Tropical Cyclone ◽  
Weather Prediction ◽  
Wrf Model ◽  
Numerical Weather Prediction Model ◽  
Horizontal Resolution ◽  
Cyclone Track ◽  
Microphysics Scheme ◽  
Parameterization Schemes ◽  
Single Moment ◽  
Indian Meteorological Department

The very severe Tropical Cyclone Vardah caused huge damage to property and life in south India during December 2016. The sensitivity of numerical simulations of the very severe tropical cyclone Vardah to different physics parameterization schemes is carried out to determine the best microphysics and cumulus physics parameterization schemes. The WRF Numerical weather prediction model configured with two nested domains. The horizontal resolution of domain-1is 27 km and domain-2 is 9 km. The tropical cyclone Vardah simulated track results were compared with the best track data given by the Indian Meteorological Department (IMD). WRF model Simulations were carried out using different microphysics (mp) parameterization schemes by fixing convective cumulus physics (cu) option to Grell-3D ensemble scheme and boundary layer option to updated Yonsei University scheme. The Vardah Cyclone track well simulated using WRF Single Moment-3 (WSM3) microphysics scheme in combination with G3D cumulus physics scheme. The cumulus physics and microphysics parameterization schemes influence the cyclone track prediction skill.  

Evaluation of a WRF model in forecasting extreme rainfall in the urban data-scarce coastal city of Alexandria, Egypt

2021 ◽  
Author(s):  
Adele Young ◽  
Biswa Bhattacharya ◽  
Emma Daniels ◽  
Chris Zevenbergen
Keyword(s):  
High Resolution ◽  
Boundary Conditions ◽  
Temporal Variability ◽  
Weather Prediction ◽  
Wrf Model ◽  
Extreme Rainfall ◽  
Small Scale ◽  
Lead Times ◽  
Spatial And Temporal Variability ◽  
Urban Drainage

<p>High-resolution precipitation models are essential to forecast urban pluvial floods. Global Numerical Weather Prediction Models (NWPs) are considered too coarse to accurately forecast flooding at the city scale. High-resolution radar nowcasting can be either unavailable or insufficient to forecast at the required lead-times.  Downscaling models are used to increase the resolution and extend forecast by several days when initialised with global NWPs. However, resolving weather processes at smaller spatial scales and sub-daily temporal resolutions has its challenges and does not necessarily result in more accurate forecast but instead only increase the computational requirements. Additionally, in ungauged regions, forecast verification is a challenge as in-situ measurements and radar estimates remain scarce or non-existent. This research evaluates the ability of a dynamically downscaled WRF model to capture the spatial and temporal variability of rainfall suitable for an urban drainage flood forecast model and evaluated against IMERG Global Precipitation Model (GPM) Satellite Precipitation Products (SPPs).<br> A WRF model was set-up with one-way nesting, three nested domains at horizontal grid resolutions 10km, 3.33km and 1km, a 1hourly temporal output, a spin-up time of 12 hours and evaluated at different lead times up to 48 hrs. The analysis was performed for three (3)  winter frontal systems during the period 2015-2019 in the highly urbanised coastal Mediterranean city of Alexandria in Egypt which experiences floods from extreme precipitation. The Global Forecast System (GFS), and European Centre for Medium Range (ECMWF) forecast were used as initial and lateral boundary conditions. <br>Initial results indicate the WRF models could capture extreme rainfall for all events. There is some agreement with the IMERG data and the model correctly forecasted a decrease in rainfall as the systems transition from coastal to inland areas. In general, GFS and ECMWF initialised WRF models overestimated rainfall estimates compared to IMERG data. Differences in GFS and ECMWF initialised models (multi-model approach) highlight the sensitivity of models to initial and boundary conditions and emphasises the need for post-processing and data assimilation when possible to generate accurate small-scale features. A study such as this provides knowledge for understanding, future applications and limitations of using Quantitative Precipitation Forecasts (QPFs) in urban drainage models. Additionally, the potential use of IMERG GPM to verify spatial and temporal variability of forecast in ungauged and data-scarce regions. Future analysis will evaluate the skill of ensembles precipitation systems in characterising forecast uncertainty in such applications. </p>

scholarly journals Objective Calibration of Numerical Weather Prediction Model: Application on Fine Resolution COSMO Model over Switzerland

Atmosphere ◽  
2021 ◽  
Vol 12 (10) ◽  
pp. 1358
Author(s):  
Antigoni Voudouri ◽  
Euripides Avgoustoglou ◽  
Izthak Carmona ◽  
Yoav Levi ◽  
Edoardo Bucchignani ◽  
...  
Keyword(s):  
Numerical Weather Prediction ◽  
Climate Models ◽  
Optimal Parameter ◽  
Weather Prediction ◽  
Model Performance ◽  
Horizontal Resolution ◽  
Small Scale ◽  
Surface Exchange ◽  
Numerical Weather ◽  
The Impact

The objective calibration method originally performed on regional climate models is applied to a fine horizontal resolution Numerical Weather Prediction (NWP) model over a mainly continental domain covering the Alpine Arc. The method was implemented on the MeteoSwiss COSMO (consortium for a small-scale modeling) model with a resolution of 0.01° (approximately 1 km). For the model calibration, five tuning parameters of the parameterization schemes affecting turbulence, soil-surface exchange and radiation were chosen. A full year was simulated, with the history of the soil included (hindcast) to find the optimal parameter value. A different year has been used to give an independent assessment of the impact of the optimization process. Although the operational MeteoSwiss model is already a well-tuned configuration, the results showed that a slight model performance gain is obtained by using the Calibration of COSMO (CALMO) methodology.

scholarly journals Fog climatology and stability index for Plovdiv 1991-2018

2021 ◽  
Author(s):  
Nikolay Penov ◽  
Anastasiya Stoycheva ◽  
Guergana Guerova
Keyword(s):  
Numerical Weather Prediction ◽  
Weather Prediction ◽  
Wrf Model ◽  
Stability Index ◽  
Threshold Value ◽  
Economic Losses ◽  
Small Scale ◽  
Seasonal Behavior ◽  
Numerical Weather ◽  
Fog Forecasting

<p>Despite the continuous improvement of weather prediction fog diagnosis and forecasting remains a challenge with large economic losses for public services and in particular aviation where the cost of flight delays and rescheduling is estimated to hundreds of million euros per year. Today the operational fog forecasting is mainly done with "in-house" developed tools, which is understandable due to the fog life cycle peculiarity. The aim of this work is to investigate the fog climatology for Plovdiv, Bulgaria for the period 1991 - 2018 and to use it for calculation a threshold value of stability index, which can be implemented as an operational forecast tool. The climatology shows well-defined seasonal behavior of the fog and that the majority of the fog registrations are with horizontal visibility below 200 m. A 10-year moving average of the fog registrations time series shows a decrease after 2012. Stability index values for various visibility ranges are calculated and compared. In the last decade, there are major improvements in horizontal and spatial resolution, microphysics, and initial conditions of the Numerical Weather Prediction models.  However, fog forecasting remains a challenge due to the small scale of the phenomena and local effects, which can remain unresolved by the models. One fog case in January 2013 is selected for numerical weather prediction simulations with the WRF model for the city of Plovdiv. The reliability of the index is evaluated both with observations and model data. It was found that while the index with its site-specific threshold value well describes the fog evolution, the WRF model has large deviations in temperature compared to the observations during daytime.</p>

Middle-Atmosphere Mountain Waves and Drag Near the Drake Passage: Observations, mini-MIP, and an OSSE

2020 ◽  
Author(s):  
Christopher Kruse ◽  
Joan Alexander ◽  
Lars Hoffmann ◽  
Inna Polichtchouk ◽  
Annelize van Niekerk ◽  
...  
Keyword(s):  
General Circulation ◽  
Middle Atmosphere ◽  
Drake Passage ◽  
Fundamental Physics ◽  
Mountain Waves ◽  
Vertical Fluxes ◽  
Team Project ◽  
Horizontal Momentum ◽  
Observing System Simulation Experiment ◽  
International Space Science Institute

<p>Orographic gravity wave (OGW) drag is one of the fundamental physics parametrizations employed in every global numerical model across timescales from weather to climate. These parameterizations have significant influences, both direct and indirect, on the atmosphere’s general circulation from the troposphere at least through the mesosphere. Despite their significant influence, observational constraints on these parameterizations are still largely lacking.</p><p>Presented here is a team project jointly supported by SPARC and the International Space Science Institute with the overall objective of providing new quantitative constraints for OGW drag parameterizations. Specific objectives are to evaluate methods that quantify vertical fluxes of horizontal momentum (MF) from satellite observations via an observing system simulation experiment (OSSE), a validation of WRF, UKMO, ECMWF, and ICON models against satellite and balloon observations, and an inter-comparison of OGW properties (e.g. MF and drag) within these models. Evaluation of satellite-based estimates of MF and model validation/inter-comparison will help to better quantify actual MF in the stratosphere, providing the best stratospheric MF and drag estimates for parameterizations to reproduce to date.</p><p>Two unique aspects of the project are that all models involved are deep, extending up to 1 Pa. The motivations for doing so was to include entire instrument weighting functions for AIRS observations, allowing direct, quantitative comparison between AIRS (and other satellite-borne) observations and the models. The second is the effort to perform an OSSE within the simulations, allowing comparison between MF from satellite-based methods within the models to the true MF in the models.</p><p>Preliminary results show that higher-res models (dx = 3 km) compare well and produce significantly more MF than lower-res global models, but the higher-res models still underrepresent OGW amplitudes. Mesospheric tides in analyses used to force the models significantly modulate resolved GWs and their drags.</p>

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