Shipboard Measurements of Surface Flux and Near Surface Profiles and Surface Flux Parameterization

2012 ◽  
Author(s):  
Qing Wang
Keyword(s):  
Surface Flux ◽  
Near Surface ◽  
Flux Parameterization ◽  
Surface Profiles

Impacts of Air–Sea Flux Parameterizations on the Intensity and Structure of Tropical Cyclones

2013 ◽  
Vol 141 (7) ◽  
pp. 2308-2324 ◽  
Author(s):  
Benjamin W. Green ◽  
Fuqing Zhang
Keyword(s):  
Wind Speed ◽  
Tropical Cyclone ◽  
Tropical Cyclones ◽  
Latent Heat ◽  
Weather Prediction ◽  
Surface Flux ◽  
Surface Fluxes ◽  
Sensible Heat ◽  
Near Surface ◽  
Flux Parameterization

Abstract Fluxes of momentum and moist enthalpy across the air–sea interface are believed to be one of the most important factors in determining tropical cyclone intensity. Because these surface fluxes cannot be directly resolved by numerical weather prediction models, their impacts on tropical cyclones must be accounted for through subgrid-scale parameterizations. There are several air–sea surface flux parameterization schemes available in the Weather Research and Forecasting (WRF) Model; these schemes differ from one another in their formulations of the wind speed–dependent exchange coefficients of momentum, sensible heat, and moisture (latent heat). The effects of surface fluxes on the intensity and structure of tropical cyclones are examined through convection-permitting WRF simulations of Hurricane Katrina (2005). It is found that the intensity (and, to a lesser extent, structure) of the simulated storms is sensitive to the choice of surface flux parameterization scheme. In agreement with recent studies, the drag coefficient CD is found to affect the pressure–wind relationship (between minimum sea level pressure and maximum 10-m wind speed) and to change the radius of maximum near-surface winds of the tropical cyclone. Fluxes of sensible and latent heat (i.e., moist enthalpy) affect intensity but do not significantly change the pressure–wind relationship. Additionally, when low-level winds are strong, the contribution of dissipative heating to calculations of sensible heat flux is not negligible. Expanding the sensitivity tests to several dozen cases from the 2008 to 2011 Atlantic hurricane seasons demonstrates the robustness of these findings.

scholarly journals Convective self–aggregation in a mean flow

2021 ◽  
Vol 21 (13) ◽  
pp. 10337-10345
Author(s):  
Hyunju Jung ◽  
Ann Kristin Naumann ◽  
Bjorn Stevens
Keyword(s):  
Momentum Flux ◽  
Surface Flux ◽  
Surface Heat ◽  
Horizontal Wind ◽  
Convective System ◽  
Mean Flow ◽  
Near Surface ◽  
Surface Heat Exchange ◽  
The Mean ◽  
Self Aggregation

Abstract. Convective self-aggregation is an atmospheric phenomenon seen in numerical simulations in a radiative convective equilibrium framework thought to be informative of some aspects of the behavior of real-world convection in the deep tropics. We impose a background mean wind flow on convection-permitting simulations through the surface flux calculation in an effort to understand how the asymmetry imposed by a mean wind influences the propagation of aggregated structures in convection. The simulations show that, with imposing mean flow, the organized convective system propagates in the direction of the flow but slows down compared to what pure advection would suggest, and it eventually becomes stationary relative to the surface after 15 simulation days. The termination of the propagation arises from momentum flux, which acts as a drag on the near-surface horizontal wind. In contrast, the thermodynamic response through the wind-induced surface heat exchange feedback is a relatively small effect, which slightly retards the propagation of the convection relative to the mean wind.

scholarly journals Impacts of Horizontal Resolution and Air–Sea Flux Parameterization on the Intensity and Structure of simulated Typhoon Haiyan (2013)

2019 ◽  
Author(s):  
Mien-Tze Kueh ◽  
Wen-Mei Chen ◽  
Yang-Fan Sheng ◽  
Simon C. Lin ◽  
Tso-Ren Wu ◽  
...  
Keyword(s):  
Surface Flux ◽  
Horizontal Resolution ◽  
Weather Research And Forecasting ◽  
Grid Spacing ◽  
Transfer Coefficients ◽  
Typhoon Intensity ◽  
Flux Parameterization ◽  
Upper Level ◽  
Positive Effect

Abstract. This study investigates the impacts of horizontal resolution and surface flux formulas on typhoon intensity and structure simulations through the case study of the Super Typhoon Haiyan (2013). Three different sets of surface flux formulas in the Weather Research and Forecasting Model were tested using grid spacing of 1, 3, and 6 km. Both increased resolution and more reasonable surface flux formulas can improve typhoon intensity simulation, but their impacts on storm structures are different. A combination of decrease in momentum transfer coefficient and increase in enthalpy transfer coefficients has greater potential to yield stronger storm. This positive effect of more reasonable surface flux formulas can be efficiently enhanced when the grid spacing is appropriately reduced to yield intense and contracted eyewall structure. As resolution increases, the eyewall becomes more upright and contracted inward. The size of updraft cores in the eyewall shrinks and the region of downdraft increases; both updraft and downdraft become more intense. As a result, the enhanced convective cores within the eyewall are driven by more intense updrafts within a rather small fraction of spatial area. This contraction of eyewall is associated with an upper level warming process, which may be partly attributed to air detrained from the intense convective cores. This resolution dependence of spatial scale of updrafts is related to the model effective resolution as determined by grid spacing.

scholarly journals Verification of Land–Atmosphere Coupling in Forecast Models, Reanalyses, and Land Surface Models Using Flux Site Observations

2018 ◽  
Vol 19 (2) ◽  
pp. 375-392 ◽  
Author(s):  
Paul A. Dirmeyer ◽  
Liang Chen ◽  
Jiexia Wu ◽  
Chul-Su Shin ◽  
Bohua Huang ◽  
...  
Keyword(s):  
Surface Energy ◽  
Land Surface ◽  
Model Development ◽  
Surface Flux ◽  
Surface Fluxes ◽  
Model Systems ◽  
Shortwave Radiation ◽  
Spatial And Temporal Variability ◽  
Near Surface ◽  
Flux Tower

Abstract This study compares four model systems in three configurations (LSM, LSM + GCM, and reanalysis) with global flux tower observations to validate states, surface fluxes, and coupling indices between land and atmosphere. Models clearly underrepresent the feedback of surface fluxes on boundary layer properties (the atmospheric leg of land–atmosphere coupling) and may overrepresent the connection between soil moisture and surface fluxes (the terrestrial leg). Models generally underrepresent spatial and temporal variability relative to observations, which is at least partially an artifact of the differences in spatial scale between model grid boxes and flux tower footprints. All models bias high in near-surface humidity and downward shortwave radiation, struggle to represent precipitation accurately, and show serious problems in reproducing surface albedos. These errors create challenges for models to partition surface energy properly, and errors are traceable through the surface energy and water cycles. The spatial distribution of the amplitude and phase of annual cycles (first harmonic) are generally well reproduced, but the biases in means tend to reflect in these amplitudes. Interannual variability is also a challenge for models to reproduce. Although the models validate better against Bowen-ratio-corrected surface flux observations, which allow for closure of surface energy balances at flux tower sites, it is not clear whether the corrected fluxes are more representative of actual fluxes. The analysis illuminates targets for coupled land–atmosphere model development, as well as the value of long-term globally distributed observational monitoring.

Advanced Surface Flux Parameterization

2001 ◽  
Author(s):  
Shouping Wang ◽  
James Doyle ◽  
Qing Wang
Keyword(s):  
Surface Flux ◽  
Flux Parameterization

scholarly journals Impact of New Solar Radiation Parameterization in the Eta Model on the Simulation of Summer Climate over South America

2006 ◽  
Vol 45 (2) ◽  
pp. 318-333 ◽  
Author(s):  
T. A. Tarasova ◽  
J. P. R. Fernandez ◽  
I. A. Pisnichenko ◽  
J. A. Marengo ◽  
J. C. Ceballos ◽  
...  
Keyword(s):  
Solar Radiation ◽  
South America ◽  
Surface Air Temperature ◽  
Surface Flux ◽  
Global Precipitation Climatology Project ◽  
South Atlantic Convergence Zone ◽  
Horizontal Resolution ◽  
The South ◽  
Near Surface ◽  
Incident Solar Radiation

Abstract The regional Eta workstation (WS) model with horizontal resolution of 40 km has been integrated over South America for January 2003. The NCEP–DOE Reanalysis II was used for initial and lateral boundary conditions. The comparison of the model-simulated and satellite-derived values of monthly mean incident solar radiation at the surface demonstrates that the former values are larger by 20%–30% over the entire region. To improve the surface flux representation in the model, a new solar radiation scheme has been implemented in it. An offline comparison of the original and the new radiation schemes with the detailed line-by-line method demonstrates a higher accuracy for the new scheme. With the new scheme, the model-simulated incident solar radiation at the surface is in a better agreement with the satellite-derived data. Nevertheless, a noticeable systematic difference of 10%–20% still remains, probably because of the incorrect description of cloud parameters in the model. The lower incident solar radiation in the new version of the model causes a decrease of near-surface air temperature by 0.1°–1°C and a decrease of precipitation rate by up to 20%–30% over most of the continent. The increase in the simulated incident solar radiation and temperature is found in the region of the South Atlantic convergence zone, which is responsible for the enhanced cloudiness and precipitation in the central and southeastern parts of Brazil during summer. The model results are compared with observational data of meteorological stations, the Global Precipitation Climatology Project (GPCP), and the South American Low-Level Jet Experiment (SALLJEX) and are discussed.

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