Toward Improving High-Resolution Numerical Hurricane Forecasting: Influence of Model Horizontal Grid Resolution, Initialization, and Physics

Abstract This paper provides an account of the performance of an experimental version of the Hurricane Weather Research and Forecasting system (HWRFX) for 87 cases of Atlantic tropical cyclones during the 2005, 2007, and 2009 hurricane seasons. The HWRFX system was used to study the influence of model grid resolution, initial conditions, and physics. For each case, the model was run to produce 126 h of forecast with two versions of horizontal resolution, namely, (i) a parent domain at a resolution of about 27 km with a 9-km moving nest (27:9) and (ii) a parent domain at a resolution of 9 km with a 3-km moving nest (9:3). The former was selected to be consistent with the current operational resolution, while the latter is the first step in testing the impact of finer resolutions for future versions of the operational model. The two configurations were run with initial conditions for tropical cyclones obtained from the operational Geophysical Fluid Dynamics Laboratory (GFDL) and HWRF models. Sensitivity experiments were also conducted with the physical parameterization scheme. The study shows that the 9:3 HWRFX system using the GFDL initial conditions and a system of physics similar to the operational version (HWRF) provides the best results in terms of both track and intensity prediction. Use of the HWRF initial conditions in the HWRFX model provides reasonable skill, particularly when used in cases with initially strong storms (hurricane strength). However, initially weak storms (below hurricane strength) posed special challenges for the models. For the weaker storm cases, none of the predictions from the HWRFX runs or the operational GFDL forecasts provided any consistent improvement when compared to the operational Statistical Hurricane Intensity Prediction Scheme with an inland decay component (DSHIPS).

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Ensemble forecasting with a stochastic convective parametrization based on equilibrium statistics

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-11-30457-2011 ◽

2011 ◽

Vol 11 (11) ◽

pp. 30457-30485 ◽

Cited By ~ 3

Author(s):

P. Groenemeijer ◽

G. C. Craig

Keyword(s):

Large Scale ◽

Mesoscale Model ◽

Initial Conditions ◽

Deep Convection ◽

Horizontal Resolution ◽

Ensemble Forecasting ◽

Total Variance ◽

Ensemble Prediction ◽

Ensemble Prediction System ◽

The Impact

Abstract. The stochastic Plant-Craig scheme for deep convection was implemented in the COSMO mesoscale model and used for ensemble forecasting. Ensembles consisting of 100 48 h forecasts at 7 km horizontal resolution were generated for a 2000 × 2000 km domain covering central Europe. Forecasts were made for seven case studies and characterized by different large-scale meteorological environments. Each 100 member ensemble consisted of 10 groups of 10 members, with each group driven by boundary and initial conditions from a selected member from the global ECMWF Ensemble Prediction System. The precipitation variability within and among these groups of members was computed, and it was found that the relative contribution to the ensemble variance introduced by the stochastic convection scheme was substantial, amounting to as much as 76% of the total variance in the ensemble in one of the studied cases. The impact of the scheme was not confined to the grid scale, and typically contributed 25–50% of the total variance even after the precipitation fields had been smoothed to a resolution of 35 km. The variability of precipitation introduced by the scheme was approximately proportional to the total amount of convection that occurred, while the variability due to large-scale conditions changed from case to case, being highest in cases exhibiting strong mid-tropospheric flow and pronounced meso- to synoptic scale vorticity extrema. The stochastic scheme was thus found to be an important source of variability in precipitation cases of weak large-scale flow lacking strong vorticity extrema, but high convective activity.

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The Experimental HWRF System: A Study on the Influence of Horizontal Resolution on the Structure and Intensity Changes in Tropical Cyclones Using an Idealized Framework

Monthly Weather Review ◽

10.1175/2010mwr3535.1 ◽

2011 ◽

Vol 139 (6) ◽

pp. 1762-1784 ◽

Cited By ~ 102

Author(s):

Sundararaman G. Gopalakrishnan ◽

Frank Marks ◽

Xuejin Zhang ◽

Jian-Wen Bao ◽

Kao-San Yeh ◽

...

Keyword(s):

Boundary Layer ◽

Tropical Cyclones ◽

Horizontal Resolution ◽

Grid Resolution ◽

Weather Research And Forecasting ◽

Maximum Wind ◽

Tangential Wind ◽

Intensity Changes ◽

Horizontal Grid ◽

Weather Research

Abstract Forecasting intensity changes in tropical cyclones (TCs) is a complex and challenging multiscale problem. While cloud-resolving numerical models using a horizontal grid resolution of 1–3 km are starting to show some skill in predicting the intensity changes in individual cases, it is not clear at this time what may be a reasonable horizontal resolution for forecasting TC intensity changes on a day-to-day-basis. The Experimental Hurricane Weather Research and Forecasting System (HWRFX) was used within an idealized framework to gain a fundamental understanding of the influence of horizontal grid resolution on the dynamics of TC vortex intensification in three dimensions. HWFRX is a version of the National Centers for Environmental Prediction (NCEP) Hurricane Weather Research and Forecasting (HWRF) model specifically adopted and developed jointly at NOAA’s Atlantic Oceanographic and Meteorological Laboratory (AOML) and Earth System Research Laboratory (ESRL) for studying the intensity change problem at a model grid resolution of about 3 km. Based on a series of numerical experiments at the current operating resolution of about 9 km and at a finer resolution of about 3 km, it was found that improved resolution had very little impact on the initial spinup of the vortex. An initial axisymmetric vortex with a maximum wind speed of 20 m s−1 rapidly intensified to 50 m s−1 within about 24 h in either case. During the spinup process, buoyancy appears to have had a pivotal influence on the formation of the warm core and the subsequent rapid intensification of the modeled vortex. The high-resolution simulation at 3 km produced updrafts as large as 48 m s−1. However, these extreme events were rare, and this study indicated that these events may not contribute significantly to rapid deepening. Additionally, although the structure of the buoyant plumes may differ at 9- and 3-km resolution, interestingly, the axisymmetric structure of the simulated TCs exhibited major similarities. Specifically, the similarities included a deep inflow layer extending up to about 2 km in height with a tangentially averaged maximum inflow velocity of about 12–15 m s−1, vertical updrafts with an average velocity of about 2 m s−1, and a very strong outflow produced at both resolutions for a mature storm. It was also found in either case that the spinup of the primary circulation occurred not only due to the weak inflow above the boundary layer but also due to the convergence of vorticity within the boundary layer. Nevertheless, the mature phase of the storm’s evolution exhibited significantly different patterns of behavior at 9 and 3 km. While the minimum pressure at the end of 96 h was 934 hPa for the 9-km simulation, it was about 910 hPa for the 3-km run. The maximum tangential wind at that time showed a difference of about 10 m s−1. Several sensitivity experiments related to the initial vortex intensity, initial radius of the maximum wind, and physics were performed. Based on ensembles of simulations, it appears that radial advection of the tangential wind and, consequently, radial flux of vorticity become important forcing terms in the momentum budget of the mature storm. Stronger convergence in the boundary layer leads to a larger transport of moisture fluxes and, subsequently, a stronger storm at higher resolution.

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Impacts of Oceanic Preexisting Conditions on Predictions of Typhoon Hai-Tang in 2005

Advances in Meteorology ◽

10.1155/2010/756071 ◽

2010 ◽

Vol 2010 ◽

pp. 1-15 ◽

Cited By ~ 7

Author(s):

Akiyoshi Wada ◽

Norihisa Usui

Keyword(s):

Mixed Layer ◽

Initial Conditions ◽

Horizontal Resolution ◽

Ocean Model ◽

Central Pressure ◽

Surface Cooling ◽

Heat Potential ◽

Spiral Rainbands ◽

The Impact ◽

Preexisting Conditions

We investigated the impact of variations in oceanic preexisting conditions on predictions of Typhoon Hai-Tang (2005) by using a coupled atmosphere-ocean model with 6-km horizontal resolution and providing the oceanic initial conditions on 12 July from 1997 to 2005 to the model. Variations in oceanic preexisting conditions caused variation in predicted central pressure of nearly 18 hPa at 72 h, whereas sea-surface cooling (SSC) induced by Hai-Tang caused a predicted central pressure difference of about 40 hPa. Warm-core oceanic eddies up to a few hundred kilometers across and a deep mixed layer climatologically distributed in the western North Pacific led to high mixed-layer heat potential, which increased latent heat flux, water vapor, and liquid water contents around Hai-Tang's center. These increases were closely associated with Hai-Tang's intensification. SSC negatively affected the eyewall, whereas variations in oceanic preexisting conditions remarkably affected spiral rainbands and the magnitude of SSC.

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The moisture budget of tropical cyclones: large scale environmental constraints and sensitivity to model horizontal resolution

10.5194/egusphere-egu2020-19270 ◽

2020 ◽

Author(s):

Benoit Vanniere ◽

Malcolm Roberts ◽

Pier Luigi Vidale ◽

Kevin Hodges ◽

Marie-Estelle Demory

Keyword(s):

Tropical Cyclones ◽

Large Scale ◽

Climate Models ◽

Potential Temperature ◽

Large Change ◽

Moisture Flux ◽

Horizontal Resolution ◽

Moisture Budget ◽

High Resolution Models ◽

The Impact

Previous studies have shown that, the number, intensity and structure of simulated tropical cyclones (TC) in climate models get closer to the observations as the horizontal resolution is increased. However, the sensitivity of tropical cyclone precipitation and moisture budget to changes in resolution has received less attention. In this study, we use the five-model ensemble from project PRIMAVERA/HighResMIP to investigate the systematic changes associated with the water budget of tropical cyclones in a range of horizontal resolutions from 1&#186; to 0.25&#186;. Our results show that despite a large change in the distribution of TC intensity with resolution, the distribution of precipitation per TC does not change significantly. This result is explained by the large scale balance which characterises the moisture budget of TCs, i.e. radii of ~15&#186; a scale that low and high resolution models represent equally well. The wind profile is found to converge between low and high resolutions for radii > 5&#186;, resulting in a moisture flux convergence into the TC with similar magnitude at low and high resolutions. In contrast to precipitation per TC, the larger TC intensity at higher resolution is explained by the larger surface latent heat flux near the center of the storm, which leads to an increase in equivalent potential temperature and warmer core anomalies, despite representing a negligible contribution to the moisture budget. We discuss the complication arising from the choice of the tracking algorithm when assessing the impact of model resolution and the implications of such a constraint on the TC moisture budget in the context of climate change.

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Experimental Tropical Cyclone Forecasts Using a Variable-Resolution Global Model

Monthly Weather Review ◽

10.1175/mwr-d-15-0159.1 ◽

2015 ◽

Vol 143 (10) ◽

pp. 4012-4037 ◽

Cited By ~ 21

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.

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The Impact of Dropwindsonde Data from the THORPEX Pacific Area Regional Campaign and the NOAA Hurricane Field Program on Tropical Cyclone Forecasts in the Global Forecast System

Monthly Weather Review ◽

10.1175/2011mwr3634.1 ◽

2011 ◽

Vol 139 (9) ◽

pp. 2689-2703 ◽

Cited By ~ 23

Author(s):

Sim D. Aberson

Keyword(s):

Tropical Cyclone ◽

Tropical Cyclones ◽

Initial Conditions ◽

Unexpected Result ◽

Cyclone Track ◽

East Pacific ◽

Global Impacts ◽

The Impact ◽

Pacific Area ◽

Taiwan Region

Four aircraft released dropwindsondes in and around tropical cyclones in the west Pacific during The Observing System Research and Predictability Experiment (THORPEX) Pacific Area Regional Campaign (T-PARC) in 2008 and the Dropwindsonde Observations for Typhoon Surveillance near the Taiwan Region (DOTSTAR); multiple aircraft concurrently participated in similar missions in the Atlantic. Previous studies have treated each region separately and have focused on the tropical cyclones whose environments were sampled. The large number of missions and tropical cyclones in both regions, and additional tropical cyclones in the east Pacific and Indian Oceans, allows for the global impact of these observations on tropical cyclone track forecasts to be studied. The study shows that there are unintended global consequences to local changes in initial conditions, in this case due to the assimilation of dropwindsonde data in tropical cyclone environments. These global impacts are mainly due to the spectral nature of the model system. These differences should be small and slightly positive, since improved local initial conditions should lead to small global forecast improvements. However, the impacts on tropical cyclones far removed from the data are shown to be as large and positive as those on the tropical cyclones specifically targeted for improved track forecasts. Causes of this unexpected result are hypothesized, potentially providing operational forecasters tools to identify when large remote impacts from surveillance missions might occur.

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An assessment of the impact of oceanic initial conditions on the interaction of upper ocean with the tropical cyclones in the Arabian Sea

Journal of Operational Oceanography ◽

10.1080/1755876x.2019.1658567 ◽

2019 ◽

Vol 13 (2) ◽

pp. 121-137

Author(s):

Tanuja Nigam ◽

Kumar Ravi Prakash ◽

Vimlesh Pant

Keyword(s):

Tropical Cyclones ◽

Arabian Sea ◽

Initial Conditions ◽

Upper Ocean ◽

The Impact

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Testing robustness of co-existing climate states

10.5194/egusphere-egu21-9902 ◽

2021 ◽

Author(s):

Charline Ragon ◽

Valerio Lembo ◽

Valerio Lucarini ◽

Christian Vérard ◽

Jérôme Kasparian ◽

...

Keyword(s):

Climate Models ◽

Climate Model ◽

Water Mass ◽

Hydrological Cycle ◽

Initial Conditions ◽

Frictional Heating ◽

Horizontal Resolution ◽

Climate Dynamics ◽

Mechanical Work ◽

The Impact

The climate can be regarded as a stationary non-equilibrium statistical system (Gallavotti 2006): a continuous and spatially inhomogeneous input of solar energy enters at the top-of-atmosphere and compensates the action of non-conservative forces, mainly occurring at small scales, to give rise to a statistically steady state (or attractor) for the whole climate. Depending on the initial conditions and the range of forcing, all other parameters being the same, some climate models have the property to settle down on different attractors. Multi-stability reflects how energy, water mass and entropy can be re-distributed in multiple ways among the climate components, such as the atmosphere, the ocean or the ice, through a different balance between nonlinear mechanisms. Starting from a configuration where competing climate attractors occur under the same forcing, we have explored their robustness performing two kinds of numerical experiment. First, we have investigated the impact of frictional heating on the overall energy balance and we have shown that such contribution, generally neglected in the atmospheric component of climate models, has crucial consequences on conservation properties: it improves the energy imbalance at top-of-atmosphere, typically non negligible in coarse simulations (Wild et al. 2020), strengthens the hydrological cycle, mitigates the mechanical work associated to atmospheric circulation intensity and reduces the heat transport peaks in the ocean. Second, we have compared two bulk formulas for the cloud albedo, one where it is constant everywhere and the other where it increases with latitude, as implemented in the new version of the atmospheric module SPEEDY in order to improve comparisons with observational data (Kucharski 2013). We have checked that this new parameterization does not affect energy and water-mass imbalances, while reduces global temperature and water-mass transport on the attractor, giving rise to a larger conversion of heat into mechanical work in the atmosphere.In order to perform such studies, we have run the climate model MITgcm on coupled aquaplanets at 2.8 horizontal resolution until steady states are reached (Brunetti el al. 2019) and we have applied the Thermodynamic Diagnostic Tool (TheDiaTo, Lembo et al. 2019). &#160;References: Brunetti, Kasparian, V&#233;rard, Climate Dynamics 53, 6293 (2019)Gallavotti, Math. Phys. 3, 530 (2006)Kucharski et al., Bulletin of the American Meteorological Society 94, 25 (2013)Lembo, Lunkeit, Lucarini, Geoscientific Model Development 12, 3805 (2019)Wild, Climate Dynamics 55, 553 (2020)

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Land–Atmosphere Interactions during a Northwestern Argentina Low Event

Monthly Weather Review ◽

10.1175/2010mwr3227.1 ◽

2010 ◽

Vol 138 (7) ◽

pp. 2481-2498 ◽

Cited By ~ 16

Author(s):

Celeste Saulo ◽

Lorena Ferreira ◽

Julia Nogués-Paegle ◽

Marcelo Seluchi ◽

Juan Ruiz

Keyword(s):

Soil Moisture ◽

South America ◽

Land Surface ◽

Initial Conditions ◽

Convective Available Potential Energy ◽

Moisture Flux ◽

Horizontal Resolution ◽

Northwestern Argentina ◽

Low Level ◽

The Impact

Abstract The impact of changes in soil moisture in subtropical Argentina in rainfall distribution and low-level circulation is studied with a state-of-the-art regional model in a downscaling mode, with different scenarios of soil moisture for a 10-day period. The selected case (starting 29 January 2003) was characterized by a northwestern Argentina low event associated with well-defined low-level northerly flow that extended east of the Andes over subtropical latitudes. Four tests were conducted at 40-km horizontal resolution with 31 sigma levels, decreasing and increasing the soil moisture initial condition by 50% over the entire domain, and imposing a 50% reduction over northwest Argentina and 50% increase over southeast South America. A control run with NCEP/Global Data Assimilation System (GDAS) initial conditions was used to assess the impact of the different soil moisture configurations. It was found that land surface interactions are stronger when soil moisture is decreased, with a coherent reduction of precipitation over southern South America. Enhanced northerly winds result from an increase in the zonal gradient of pressure at low levels. In contrast, when soil moisture is increased, smaller circulation changes are found, although there appears to be a local feedback effect between the land and precipitation. The combined effects of changes in the circulation and in local stratification induced by soil wetness modifications, through variations in evaporation and Convective Available Potential Energy (CAPE), are in agreement with what has been found by other studies, resulting in coherent modifications of precipitation when variations of CAPE and moisture flux convergence mutually reinforce.

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The Impact of Horizontal Resolution on North American Monsoon Gulf of California Moisture Surges in a Suite of Coupled Global Climate Models

Journal of Climate ◽

10.1175/jcli-d-16-0199.1 ◽

2016 ◽

Vol 29 (21) ◽

pp. 7911-7936 ◽

Cited By ~ 20

Author(s):

Salvatore Pascale ◽

Simona Bordoni ◽

Sarah B. Kapnick ◽

Gabriel A. Vecchi ◽

Liwei Jia ◽

...

Keyword(s):

United States ◽

North American ◽

Gulf Of California ◽

Large Scale ◽

Horizontal Resolution ◽

North American Monsoon ◽

Geophysical Fluid Dynamics Laboratory ◽

Southwestern United States ◽

Near Surface ◽

The Impact

Abstract The impact of atmosphere and ocean horizontal resolution on the climatology of North American monsoon Gulf of California (GoC) moisture surges is examined in a suite of global circulation models (CM2.1, FLOR, CM2.5, CM2.6, and HiFLOR) developed at the Geophysical Fluid Dynamics Laboratory (GFDL). These models feature essentially the same physical parameterizations but differ in horizontal resolution in either the atmosphere (≃200, 50, and 25 km) or the ocean (≃1°, 0.25°, and 0.1°). Increasing horizontal atmospheric resolution from 200 to 50 km results in a drastic improvement in the model’s capability of accurately simulating surge events. The climatological near-surface flow and moisture and precipitation anomalies associated with GoC surges are overall satisfactorily simulated in all higher-resolution models. The number of surge events agrees well with reanalyses, but models tend to underestimate July–August surge-related precipitation and overestimate September surge-related rainfall in the southwestern United States. Large-scale controls supporting the development of GoC surges, such as tropical easterly waves (TEWs), tropical cyclones (TCs), and trans-Pacific Rossby wave trains (RWTs), are also well captured, although models tend to underestimate the TEW and TC magnitude and number. Near-surface GoC surge features and their large-scale forcings (TEWs, TCs, and RWTs) do not appear to be substantially affected by a finer representation of the GoC at higher ocean resolution. However, the substantial reduction of the eastern Pacific warm sea surface temperature bias through flux adjustment in the Forecast-Oriented Low Ocean Resolution (FLOR) model leads to an overall improvement of tropical–extratropical controls on GoC moisture surges and the seasonal cycle of precipitation in the southwestern United States.

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