scholarly journals Response of a tropical cyclone to a subsurface ocean eddy and the role of boundary layer dynamics

2021 ◽  
Author(s):  
Arjun U. Kumar ◽  
Nils Brüggemann ◽  
Roger K. Smith ◽  
Jochem Marotzke
Keyword(s):  
Boundary Layer ◽  
Tropical Cyclone ◽  
Subsurface Ocean ◽  
Boundary Layer Dynamics

Tropical Cyclone Intensification Simulated in the Ooyama-type Three-layer Model with a Multilevel Boundary Layer

2021 ◽  
Author(s):  
Rong Fei ◽  
Yuqing Wang
Keyword(s):  
Boundary Layer ◽  
Tropical Cyclone ◽  
Vertical Mixing ◽  
Type Model ◽  
Layer Model ◽  
Coriolis Parameter ◽  
Wind Structure ◽  
Model Configuration ◽  
Nonlinear Advection ◽  
Boundary Layer Dynamics

AbstractThe first successful simulation of tropical cyclone (TC) intensification was achieved with a three-layer model, often named the Ooyama-type three-layer model, which consists of a slab boundary layer and two shallow water layers above. Later studies showed that the use of a slab boundary layer would produce unrealistic boundary layer wind structure and too strong eyewall updraft at the top of TC boundary layer and thus simulate unrealistically rapid intensification compared to the use of a height-parameterized boundary layer. To fully consider the highly height-dependent boundary layer dynamics in the Ooyama-type three-layer model, this study replaced the slab boundary layer with a multilevel boundary layer in the Ooyama-type model and used it to conduct simulations of TC intensification and also compared the simulation with that from the model version with a slab boundary layer. Results show that compared with the simulation with a slab boundary layer, the use of a multilevel boundary layer can greatly improve simulations of the boundary-layer wind structure and the strength and radial location of eyewall updraft, and thus more realistic intensification rate due to better treatments of the surface layer processes and the nonlinear advection terms in the boundary layer. Sensitivity of the simulated TCs to the model configuration and to both horizontal and vertical mixing lengths, sea surface temperature, the Coriolis parameter, and the initial TC vortex structure are also examined. The results demonstrate that this new model can reproduce various sensitivities comparable to those found in previous studies using fully physics models.

scholarly journals Surface heterogeneity impacts on boundary layer dynamics via energy balance partitioning

2010 ◽  
Vol 10 (7) ◽  
pp. 17815-17851 ◽  
Author(s):  
N. A. Brunsell ◽  
D. B. Mechem ◽  
M. C. Anderson
Keyword(s):  
Boundary Layer ◽  
Heat Flux ◽  
Latent Heat ◽  
Latent Heat Flux ◽  
Land Surface ◽  
Surface Heterogeneity ◽  
Length Scales ◽  
Surface Conditions ◽  
Boundary Layer Dynamics

Abstract. The role of land-atmosphere interactions under heterogeneous surface conditions is investigated in order to identify mechanisms responsible for altering surface heat and moisture fluxes. Twelve coupled land surface – large eddy simulation scenarios with four different length scales of surface variability under three different horizontal wind speeds are used in the analysis. The base case uses Landsat ETM imagery over the Cloud Land Surface Interaction Campaign (CLASIC) field site for 3 June 2007. Using wavelets, the surface fields are band-pass filtered in order to maintain the spatial mean and variances to length scales of 200 m, 1600 m, and 12.8 km as lower boundary conditions to the model. The simulations exhibit little variation in net radiation. Rather, a change in the partitioning of the surface energy between sensible and latent heat flux is responsible for differences in boundary layer dynamics. The sensible heat flux is dominant for intermediate surface length scales. For smaller and larger scales of surface heterogeneity, which can be viewed as being more homogeneous, the latent heat flux becomes increasingly important. The results reflect a general decrease of the Bowen ratio as the surface conditions transition from heterogeneous to homogeneous. Air temperature is less sensitive to surface heterogeneity than water vapor, which implies that the role of surface heterogeneity in modifying the local temperature gradients in order to maximize convective heat fluxes. More homogeneous surface conditions, on the other hand, tend to maximize latent heat flux. Scalar vertical profiles respond predictably to the partitioning of surface energy. Fourier spectra of the vertical wind speed, air temperature and specific humidity (w, T and q) and associated cospectra (w'T', w'q' and T'q'), however, are insensitive to the length scale of surface heterogeneity, but the near surface spectra are sensitive to the mean wind speed.

scholarly journals The role of boundary layer dynamics on the diurnal evolution of isoprene and the hydroxyl radical over tropical forests

2011 ◽  
Vol 116 (D7) ◽  
Author(s):  
Jordi Vilà-Guerau de Arellano ◽  
Edward G. Patton ◽  
Thomas Karl ◽  
Kees van den Dries ◽  
Mary C. Barth ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Hydroxyl Radical ◽  
Tropical Forests ◽  
Boundary Layer Dynamics

scholarly journals On the role of infiltration and exfiltration in swash zone boundary layer dynamics

2015 ◽  
Vol 120 (9) ◽  
pp. 6329-6350 ◽  
Author(s):  
José Carlos Pintado‐Patiño ◽  
Alec Torres‐Freyermuth ◽  
Jack A. Puleo ◽  
Dubravka Pokrajac
Keyword(s):  
Boundary Layer ◽  
Swash Zone ◽  
Zone Boundary ◽  
Boundary Layer Dynamics

scholarly journals The Impact of Gradient Wind Imbalance on Tropical Cyclone Intensification within Ooyama’s Three-Layer Model

2016 ◽  
Vol 73 (9) ◽  
pp. 3659-3679 ◽  
Author(s):  
Thomas Frisius ◽  
Marguerite Lee
Keyword(s):  
Boundary Layer ◽  
Tropical Cyclone ◽  
Layer Model ◽  
Free Atmosphere ◽  
Gradient Wind ◽  
Maximum Gradient ◽  
Boundary Layer Model ◽  
Advection Term ◽  
Boundary Layer Dynamics ◽  
The Impact

Abstract This paper addresses the validity of the gradient wind balance approximation during the intensification phase of a tropical cyclone in Ooyama’s three-layer model. For this purpose, the sensitivity to various model modifications is examined, given by the inclusion of (i) unbalanced dynamics in the free atmosphere, (ii) unbalanced dynamics in the slab boundary layer, (iii) a height-parameterized boundary layer model, and (iv) a rigid lid. The most rapid intensification occurs when the model employs the unbalanced slab boundary layer, while the simulation with the balanced boundary layer reveals the slowest intensification. The simulation with the realistic height-parameterized boundary layer model exhibits an intensification rate that lies in between. Intensification is induced by a convective ring in all experiments, but a distinct contraction of the radius of maximum gradient wind only takes place with unbalanced boundary layer dynamics. In all experiments the rigid lid and the balance approximation for the free atmosphere have no crucial impact on intensification, and a linear stability analysis cannot explain the found sensitivity to intensification. Most likely the nonlinear momentum advection term plays an important role in the boundary layer. It is found on the basis of a diagnostic radial mass flux equation that the source term for latent heat provides the largest contribution to intensification and contraction. Furthermore, it turns out that the position of the convective ring inside or outside of the radius of maximum gradient wind (RMGW) is of vital importance for intensification and most likely explains the large impact of boundary layer imbalance.

scholarly journals Turbulent transport of energy across a forest and a semiarid shrubland

2018 ◽  
Vol 18 (13) ◽  
pp. 10025-10038 ◽  
Author(s):  
Tirtha Banerjee ◽  
Peter Brugger ◽  
Frederik De Roo ◽  
Konstantin Kröniger ◽  
Dan Yakir ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Turbulent Transport ◽  
Surface Heterogeneity ◽  
Flux Divergence ◽  
Diurnal Cycles ◽  
Turbulent Statistics ◽  
Secondary Circulations ◽  
The Difference ◽  
Boundary Layer Dynamics

Abstract. The role of secondary circulations has recently been studied in the context of well-defined surface heterogeneity in a semiarid ecosystem where it was found that energy balance closure over a desert–forest system and the structure of the boundary layer was impacted by advection and flux divergence. As a part of the CliFF (“Climate feedbacks and benefits of semi-arid forests”, a collaboration between KIT, Germany, and the Weizmann Institute, Israel) campaign, we studied the boundary layer dynamics and turbulent transport of energy corresponding to this effect in Yatir Forest situated in the Negev Desert in Israel. The forest surrounded by small shrubs presents a distinct feature of surface heterogeneity, allowing us to study the differences between their interactions with the atmosphere above by conducting measurements with two eddy covariance (EC) stations and two Doppler lidars. As expected, the turbulence intensity and vertical fluxes of momentum and sensible heat are found to be higher above the forest compared to the shrubland. Turbulent statistics indicative of nonlocal motions are also found to differ over the forest and shrubland and also display a strong diurnal cycle. The production of turbulent kinetic energy (TKE) over the forest is strongly mechanical, while buoyancy effects generate most of the TKE over the shrubland. Overall TKE production is much higher above the forest compared to the shrubland. The forest is also found to be more efficient in dissipating TKE. The TKE budget appears to be balanced on average both for the forest and shrubland, although the imbalance of the TKE budget, which includes the role of TKE transport, is found to be quite different in terms of diurnal cycles for the forest and shrubland. The difference in turbulent quantities and the relationships between the components of TKE budget are used to infer the characteristics of the turbulent transport of energy between the desert and the forest.

scholarly journals Scattering and absorption properties of near-surface aerosol over Gangetic–Himalayan region: the role of boundary layer dynamics and long-range transport

2014 ◽  
Vol 14 (15) ◽  
pp. 21101-21148 ◽  
Author(s):  
U. C. Dumka ◽  
D. G. Kaskaoutis ◽  
M. K. Srivastava ◽  
P. C. S. Devara
Keyword(s):  
Boundary Layer ◽  
Long Range ◽  
Long Range Transport ◽  
Monsoon Circulation ◽  
Anthropogenic Aerosols ◽  
Absorption Properties ◽  
Near Surface ◽  
Range Transport ◽  
Boundary Layer Dynamics

Abstract. Knowledge of light scattering and absorption properties of atmospheric aerosols is of vital importance in evaluating their types, sources and radiative forcing. This is of particular interest over the Gangetic–Himalayan (GH) region due to large aerosol loading over the plains and the uplift over the Himalayan range causing serious effects on atmospheric heating, glaciology and monsoon circulation. In this respect, Ganges Valley Aerosol Experiment (GVAX) was initiated over the region aiming to examine the aerosol properties, source regions, uplift mechanisms and aerosol-cloud interactions. The present study examines the temporal (monthly, seasonal) evolution of scattering (σsp) and absorption (σap) coefficients, their wavelength dependence, and the role of the Indo-Gangetic plains (IGP), boundary-layer dynamics (BLD) and long-range transport (LRT) in the aerosol uplift over the Himalayas. The measurements are performed at the elevated site Nainital via the Atmospheric Radiation Measurement Mobile Facility including several instruments (Nephelometer, Particle Soot Absorption Photometer, etc.) during June 2011 to March 2012. The σsp and σap exhibit a pronounced seasonal variation with monsoon low and post-monsoon (November) high, while the scattering wavelength exponent exhibits higher values during monsoon, in contrast to the absorption Ångström exponent which maximizes in December–March. The analysis is performed separately for particles bellow 10 and 1μm in diameter in order to examine the influence of the particle size on optical properties. The elevated-background measuring site provides the advantage of examining the LRT of natural and anthropogenic aerosols from the IGP and southwest Asia and the role of BLD in the aerosol lifting processes, while the aerosols are found to be well-mixed and aged-type dominant.

scholarly journals Role of the boundary layer dynamics effects on an extreme air pollution event in Paris

2016 ◽  
Vol 141 ◽  
pp. 571-579 ◽  
Author(s):  
J.-C. Dupont ◽  
M. Haeffelin ◽  
J. Badosa ◽  
T. Elias ◽  
O. Favez ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Air Pollution ◽  
Pollution Event ◽  
Boundary Layer Dynamics
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