Impact of SST and Surface Waves on Hurricane Florence (2018): A Coupled Modeling Investigation

AbstractHurricane Florence (2018) devastated the coastal communities of the Carolinas through heavy rainfall that resulted in massive flooding. Florence was characterized by an abrupt reduction in intensity (Saffir-Simpson Category 4 to Category 1) just prior to landfall and synoptic-scale interactions that stalled the storm over the Carolinas for several days. We conducted a series of numerical modeling experiments in coupled and uncoupled configurations to examine the impact of sea surface temperature (SST) and ocean waves on storm characteristics. In addition to experiments using a fully coupled atmosphere-ocean-wave model, we introduced the capability of the atmospheric model to modulate wind stress and surface fluxes by oceanwaves through data from an uncoupled wave model. We examined these experiments by comparing track, intensity, strength, SST, storm structure, wave height, surface roughness, heat fluxes, and precipitation in order to determine the impacts of resolving ocean conditions with varying degrees of coupling. We found differences in the storm’s intensity and strength, with the best correlation coefficient of intensity (r=0.89) and strength (r=0.95) coming from the fully-coupled simulations. Further analysis into surface roughness parameterizations added to the atmospheric model revealed differences in the spatial distribution and magnitude of the largest roughness lengths. Adding ocean andwave features to the model further modified the fluxes due to more realistic cooling beneath the stormwhich in turn modified the precipitation field. Our experiments highlight significant differences in how air-sea processes impact hurricane modeling. The storm characteristics of track, intensity, strength, and precipitation at landfall are crucial to predictability and forecasting of future landfalling hurricanes.

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The impact of wave source terms and coupling strategies on the accuracy of the UKC4 regional coupled atmosphere–ocean–wave forecasting system during extreme events

10.5194/egusphere-egu21-2996 ◽

2021 ◽

Author(s):

Nieves G. Valiente ◽

Andrew Saulter ◽

John Edwards ◽

Huw Lewis ◽

Juan M. Castillo ◽

...

Keyword(s):

Surface Roughness ◽

Momentum Transfer ◽

Wave Model ◽

Atmospheric Model ◽

Source Terms ◽

Wave Source ◽

Wave Growth ◽

Wind Speeds ◽

Coupling Strategy ◽

The Impact

Prediction of severe natural hazards requires accurate forecasting systems. Recently, there is a tendency to move towards more integrated solutions, where different components of the Earth system are coupled to better reproduce the physical feedbacks between them. Atmosphere&#8211;wave coupling should, in principle, improve the momentum flux because there is more detail in the two-way feedback due to the atmosphere receiving a more realistic picture of the surface roughness. However, the coupling between the ocean surface and the wind might become less efficient at transferring momentum during large storms.This study focuses on rapidly developing waves under extratropical storms to understand the sensitivity in atmosphere&#8211;wave present generation source terms and coupling strategies. Here, we analyse the effect of momentum transfer to fast growth waves during both long and fetch limited conditions using the Met Office regional atmosphere&#8211;ocean&#8211;wave coupled research system for the northwestern (NW) European shelf (UKC4).Two different sets of numerical experiments are conducted focusing on the atmosphere&#8211;wave components. The first one explores the sensitivity to two different wave source parameterizations, ST4 and ST6, and uses a two-way feedback coupling strategy (A2W) where a sea-state dependent surface roughness modifies the atmospheric momentum budget. In the second set of simulations, the impact of the coupling strategy is assessed. The A2W approach using ST6 physics is compared against a simpler one-way strategy (A1W) where no wave feedback on the atmospheric model exists and the wind stress is directly passed to the wave model (WAVEWATCHIII) ensuring conservation of momentum.Results demonstrate that ST6 physics allows for a faster wave growth than the currently used ST4 parameterization but might degrade low to mid energy wave states for the NW shelf. ST6 versus ST4 difference in wave growth is larger for higher wind speeds and short fetches. The experiment with ST4 and A2W consistently under-predicts the wave growth in those locations across the NW shelf where fetch dependence is an important factor (i.e., seas at the E of Ireland and the UK for storms coming from the NW-WNW). The implementation in the wave model of physics that depend solely in the wind input (ST6) with the A1W coupling strategy appears to improve growth of young wind-seas, reducing bias in those locations where the storms are underestimated. The analysis of the transfer of momentum across the air-sea boundary layer shows that forecasts of large wave events may require a different coupling approach. The slower wave growth seems to be related to an underestimation of the momentum transfer computed by the wave model when coupling the wind speeds (A2W). This suggests that coupling the wind speeds to the wave model and allowing this to calculate the momentum transfer from the atmosphere to waves and ocean underestimates the transfer by a few percent. For very young to young wind seas, this can be overcome when the surface stress is computed by the atmospheric model and directly passed to the ocean (A1W).

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Simulating carbon exchange using a regional atmospheric model coupled to an advanced land-surface model

Biogeosciences Discussions ◽

10.5194/bgd-5-4161-2008 ◽

2008 ◽

Vol 5 (5) ◽

pp. 4161-4207 ◽

Cited By ~ 5

Author(s):

H. W. Ter Maat ◽

R. W. A. Hutjes

Keyword(s):

Carbon Dioxide ◽

Land Surface ◽

Large Scale ◽

Regional Scale ◽

Atmospheric Model ◽

Surface Fluxes ◽

Heat Fluxes ◽

Surface Model ◽

Carbon Exchange ◽

Regional Atmospheric Modelling System

Abstract. A large scale mismatch exists between our understanding and quantification of ecosystem atmosphere exchange of carbon dioxide at local scale and continental scales. This paper will focus on the carbon exchange on the regional scale to address the following question: What are the main controlling factors determining atmospheric carbon dioxide content at a regional scale? We use the Regional Atmospheric Modelling System (RAMS), coupled with a land surface scheme simulating carbon, heat and momentum fluxes (SWAPS-C), and including also sub models for urban and marine fluxes, which in principle include the main controlling mechanisms and capture the relevant dynamics of the system. To validate the model, observations are used which were taken during an intensive observational campaign in the central Netherlands in summer 2002. These included flux-site observations, vertical profiles at tall towers and spatial fluxes of various variables taken by aircraft. The coupled regional model (RAMS-SWAPS-C) generally does a good job in simulating results close to reality. The validation of the model demonstrates that surface fluxes of heat, water and CO2 are reasonably well simulated. The comparison against aircraft data shows that the regional meteorology is captured by the model. Comparing spatially explicit simulated and observed fluxes we conclude that in general simulated latent heat fluxes are underestimated by the model to the observations which exhibit large standard deviation for all flights. Sensitivity experiments demonstrated the relevance of the urban emissions of carbon dioxide for the carbon balance in this particular region. The same test also show the relation between uncertainties in surface fluxes and those in atmospheric concentrations.

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Spatially Tracking Wave Events in Partitioned Numerical Wave Model Outputs

Journal of Atmospheric and Oceanic Technology ◽

10.1175/jtech-d-18-0228.1 ◽

2019 ◽

Vol 36 (10) ◽

pp. 1933-1944 ◽

Cited By ~ 1

Author(s):

Haoyu Jiang

Keyword(s):

Grid Point ◽

Wave Model ◽

Ocean Waves ◽

Model Verification ◽

Analysis Model ◽

Wave Parameters ◽

Numerical Wave ◽

Wave Models ◽

Spectral Partitioning ◽

The Impact

AbstractNumerical wave models can output partitioned wave parameters at each grid point using a spectral partitioning technique. Because these wave partitions are usually organized according to the magnitude of their wave energy without considering the coherence of wave parameters in space, it can be difficult to observe the spatial distributions of wave field features from these outputs. In this study, an approach for spatially tracking coherent wave events (which means a cluster of partitions originating from the same meteorological event) from partitioned numerical wave model outputs is presented to solve this problem. First, an efficient traverse algorithm applicable for different types of grids, termed breadth-first search, is employed to track wave events using the continuity of wave parameters. Second, to reduce the impact of the garden sprinkler effect on tracking, tracked wave events are merged if their boundary outlines and wave parameters on these boundaries are both in good agreement. Partitioned wave information from the Integrated Ocean Waves for Geophysical and other Applications dataset is used to test the performance of this spatial tracking approach. The test results indicate that this approach is able to capture the primary features of partitioned wave fields, demonstrating its potential for wave data analysis, model verification, and data assimilation.

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Intraseasonal Land–Atmosphere Coupling in the West African Monsoon

Journal of Climate ◽

10.1175/2008jcli2475.1 ◽

2008 ◽

Vol 21 (24) ◽

pp. 6636-6648 ◽

Cited By ~ 47

Author(s):

Christopher M. Taylor

Keyword(s):

Soil Moisture ◽

Sensible Heat Flux ◽

West African Monsoon ◽

West African ◽

Surface Fluxes ◽

Heat Fluxes ◽

The West ◽

African Monsoon ◽

Low Level ◽

The Impact

Abstract Via its impact on surface fluxes, subseasonal variability in soil moisture has the potential to feed back on regional atmospheric circulations, and thereby rainfall. An understanding of this feedback mechanism in the climate system has been hindered by the lack of observations at an appropriate scale. In this study, passive microwave data at 10.65 GHz from the Tropical Rainfall Measuring Mission satellite are used to identify soil moisture variability during the West African monsoon. A simple model of surface sensible heat flux is developed from these data and is used, alongside atmospheric analyses from the European Centre for Medium-Range Weather Forecasting (ECMWF), to provide a new interpretation of monsoon variability on time scales of the order of 15 days. During active monsoon periods, the data indicate extensive areas of wet soil in the Sahel. The impact of the resulting weak surface heat fluxes is consistent in space and time with low-level variations in atmospheric heating and vorticity, as depicted in the ECMWF analyses. The surface-induced vorticity structure is similar to previously documented intraseasonal variations in the monsoon flow, notably a westward-propagating vortex at low levels. In those earlier studies, the variability in low-level flow was considered to be the critical factor in producing intraseasonal fluctuations in rainfall. The current analysis shows that this vortex can be regarded as an effect of the rainfall (via surface hydrology) as well as a cause.

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Towards a unified framework for maximum wave computation from numerical models: outcomes from the LATEMAR project.

10.5194/egusphere-egu2020-13683 ◽

2020 ◽

Author(s):

Alvise Benetazzo ◽

Francesco Barbariol ◽

Paolo Pezzutto ◽

Luciana Bertotti ◽

Luigi Cavaleri ◽

...

Keyword(s):

Numerical Models ◽

Wave Spectrum ◽

Wave Model ◽

Ocean Waves ◽

Unified Framework ◽

Sea State ◽

Large Wave ◽

Wavewatch Iii ◽

Wave Models ◽

The Impact

Reliable prediction of oceanic waves during severe marine storms has always been foremost for offshore platform design, coastal activities, and navigation safety. Indeed, many damaging accidents and casualties during storms were ascribed to the impact with abnormal and unexpected waves. However, predicting extreme wave occurrence is a challenging task, at first, because of their inherent randomness, and because the observation of large ocean waves, of primary importance to assess theoretical and numerical models, is limited by the costs and risks of deployment during severe open-ocean sea-state conditions.In the context of the EU-based Copernicus Marine Environment Monitoring Service (CMEMS) evolution, the LATEMAR project (https://www.mercator-ocean.fr/en/portfolio/latemar/) aimed at improving the modelling of large wave events during marine storms. Indeed, at present, operational systems only provide average and peak wave parameters, with no information on individual waves whatsoever. However, developments of the state-of-the-art third-generation wave models demonstrated that using the directional wave spectrum moments into theoretical statistical models for wave extremes, forecasters are able to accurately infer the expected shape and likelihood of the maximum waves during storms.The main purpose of the activity is therefore to provide the wave models WAM and WAVEWATCH III with common procedures to explicitly estimate the maximum wave heights for each sea state. LATEMAR achieved this goal by: performing an extensive assessment of the model maximum waves using field observations collected from an oceanographic tower; comparing WAM and WAVEWATCH III maximum wave estimates in the Mediterranean Sea; investigating the sensitivity of the maximum waves on the main sea state parameters. All model developments and evaluations resulting from this research project will be directly applicable to the wave model forecasting systems to expand their catalogue.

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Impacts of Atmospheric Reanalysis Uncertainty on Atlantic Overturning Estimates at 25°N

Journal of Climate ◽

10.1175/jcli-d-18-0241.1 ◽

2018 ◽

Vol 31 (21) ◽

pp. 8719-8744 ◽

Cited By ~ 3

Author(s):

Helen R. Pillar ◽

Helen L. Johnson ◽

David P. Marshall ◽

Patrick Heimbach ◽

So Takao

Keyword(s):

Climate Model ◽

Surface Heat ◽

Surface Fluxes ◽

Heat Fluxes ◽

Labrador Sea ◽

Surface Heat Fluxes ◽

Ensemble Mean ◽

Meridional Overturning ◽

The Impact ◽

Average Uncertainty

Atmospheric reanalyses are commonly used to force numerical ocean models, but despite large discrepancies reported between different products, the impact of reanalysis uncertainty on the simulated ocean state is rarely assessed. In this study, the impact of uncertainty in surface fluxes of buoyancy and momentum on the modeled Atlantic meridional overturning at 25°N is quantified for the period January 1994–December 2011. By using an ocean-only climate model and its adjoint, the space and time origins of overturning uncertainty resulting from air–sea flux uncertainty are fully explored. Uncertainty in overturning induced by prior air–sea flux uncertainty can exceed 4 Sv (where 1 Sv ≡ 106 m3 s−1) within 15 yr, at times exceeding the amplitude of the ensemble-mean overturning anomaly. A key result is that, on average, uncertainty in the overturning at 25°N is dominated by uncertainty in the zonal wind at lags of up to 6.5 yr and by uncertainty in surface heat fluxes thereafter, with winter heat flux uncertainty over the Labrador Sea appearing to play a critically important role.

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The impact of wave physics in the CMEMS-IBI ocean system Part A: Wave forcing validation

10.5194/os-2018-165 ◽

2019 ◽

Cited By ~ 1

Author(s):

Romain Rainaud ◽

Lotfi Aouf ◽

Alice Dalphinet ◽

Marcos Garcia Sotillo ◽

Enrique Alvarez-Fanjul ◽

...

Keyword(s):

Ocean Circulation ◽

Wave Spectrum ◽

Circulation Model ◽

Wave Model ◽

Heat Fluxes ◽

Wave System ◽

Peak Period ◽

Wave Forecast ◽

High Frequency Waves ◽

The Impact

Abstract. The Iberian Biscay Ireland (IBI) wave system has the challenge to improve wave forecast and the coupling with ocean circulation model dedicated to western european coast. The momentum and heat fluxes at the sea surface are strongly controlled by the waves and there is a need of using accurate sea state from wave model. This work describes the more recent version of the IBI wave system and highlight the performance of system in comparison with satellite altimeters and buoys wave data. The validation process has been performed for 1-year run of the wave model MFWAM with boundary conditions provided by the global wave system. The results show on the one hand a slightly improvement on significant wave height and peak period, and on the other hand a better surface stress for high wind conditions. This latter is a consequence of using a tail wave spectrum shaped as the Philipps wave spectrum for high frequency waves.

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Sensible Heat Fluxes in the Nearly Neutral Boundary Layer: The Impact of Frictional Heating within the Surface Layer

Journal of the Atmospheric Sciences ◽

10.1175/jas-d-18-0158.1 ◽

2019 ◽

Vol 76 (4) ◽

pp. 1039-1053

Author(s):

J. M. Edwards

Keyword(s):

Boundary Layer ◽

Surface Layer ◽

Frictional Heating ◽

Sensible Heat Flux ◽

Surface Fluxes ◽

Heat Fluxes ◽

Sensible Heat ◽

Simple Modification ◽

Neutral Boundary Layer ◽

The Impact

Abstract The effect of frictional dissipative heating on the calculation of surface fluxes in the atmospheric boundary layer using bulk flux formulas is considered. Although the importance of frictional dissipation in intense storms has been widely recognized, it is suggested here that its impact is also to be seen at more moderate wind speeds in apparently enhanced heat transfer coefficients and countergradient fluxes in nearly neutral conditions. A simple modification to the bulk flux formula can be made to account for its impact within the surface layer. This modification is consistent with an interpretation of the surface layer as one across which the flux of total energy is constant. The effect of this modification on tropical cyclones is assessed in an idealized model, where it is shown to reduce the predicted maximum wind speed by about 4%. In numerical simulations of three individual storms, the impacts are more subtle but indicate a reduction of the sensible heat flux into the storm and a cooling of the surface layer.

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The evaluation of land surface parameters for model to derive land surface fluxes in the Tibetan Plateau

10.5194/egusphere-egu21-1568 ◽

2021 ◽

Author(s):

Weiqiang Ma ◽

Yaoming Ma ◽

Yizhe Han ◽

Wei Hu ◽

Lei Zhong ◽

...

Keyword(s):

Tibetan Plateau ◽

Land Surface ◽

Atmospheric Model ◽

Surface Fluxes ◽

Heat Fluxes ◽

The Tibetan Plateau ◽

Default Model ◽

Model Configuration

Firstly, based on the difference of model and in-situ observations, a serious of sensitive experiments were done by using WRF. In order to use remote sensing products, a land-atmosphere model was initialized by ingesting land surface parameters, such as AMSR-E RS products, and the results were compared with the default model configuration and with in-situ long-term CAMP/Tibet observations.Secondly, a land-atmosphere model was initialized by ingesting AMSR-E products, and the results were compared with the default model configuration and with in-situ long-term CAMP/Tibet observations. The differences between the AMSR-E initialized model runs with the default model configuration and in situ data showed an apparent inconsistency in the model-simulated land surface heat fluxes. The results showed that the soil moisture was sensitive to the specific model configuration. To evaluate and verify the model stability, a long-term modeling study with AMSR-E soil moisture data ingestion was performed. Based on test simulations, AMSR-E data were assimilated into an atmospheric model for July and August 2007. The results showed that the land surface fluxes agreed well with both the in-situ data and the results of the default model configuration. Therefore, the simulation can be used to retrieve land surface heat fluxes from an atmospheric model over the Tibetan Plateau.All of the different methods will clarify the land surface heating field in complex plateau, it also can affect atmospheric cycle over the Tibetan Plateau even all of the global atmospheric cycle pattern.

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Influence of Wave State and Sea Spray on the Roughness Length: Feedback on Medicanes

Atmosphere ◽

10.3390/atmos9080301 ◽

2018 ◽

Vol 9 (8) ◽

pp. 301 ◽

Cited By ~ 13

Author(s):

Umberto Rizza ◽

Elisa Canepa ◽

Antonio Ricchi ◽

Davide Bonaldo ◽

Sandro Carniel ◽

...

Keyword(s):

Surface Roughness ◽

Single Case ◽

Wind Waves ◽

Wave Model ◽

Atmospheric Model ◽

Sea Surface ◽

Sea Spray ◽

High Wind ◽

Wave State ◽

Sea Surface Roughness

Occasionally, storms that share many features with tropical cyclones, including the presence of a quasi-circular “eye” a warm core and strong winds, are observed in the Mediterranean. Generally, they are known as Medicanes, or tropical-like cyclones (TLC). Due to the intense wind forcings and the consequent development of high wind waves, a large number of sea spray droplets—both from bubble bursting and spume tearing processes—are likely to be produced at the sea surface. In order to take into account this process, we implemented an additional Sea Spray Source Function (SSSF) in WRF-Chem, model version 3.6.1, using the GOCART (Goddard Chemistry Aerosol Radiation and Transport) aerosol sectional module. Traditionally, air-sea momentum fluxes are computed through the classical Charnock relation that does not consider the wave-state and sea spray effects on the sea surface roughness explicitly. In order to take into account these forcing, we implemented a more recent parameterization of the sea surface aerodynamic roughness within the WRF surface layer model, which may be applicable to both moderate and high wind conditions. The implemented SSSF and sea surface roughness parameterization have been tested using an operative model sequence based on COAWST (Coupled Ocean Atmosphere Wave Sediment Transport) and WRF-Chem. The third-generation wave model SWAN (Simulating Waves Nearshore), two-way coupled with the WRF atmospheric model in the COAWST framework, provided wave field parameters. Numerical simulations have been integrated with the WRF-Chem chemistry package, with the aim of calculating the sea spray generated by the waves and to include its effect in the Charnock roughness parametrization together with the sea state effect. A single case study is performed, considering the Medicane that affected south-eastern Italy on 26 September 2006. Since this Medicane is one of the most deeply analysed in literature, its investigation can easily shed some light on the feedbacks between sea spray and drag coefficients.

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