Impacts of Evaporation from Raindrops on Tropical Cyclones. Part I: Evolution and Axisymmetric Structure

Sawada, Masahiro; Iwasaki, Toshiki

doi:10.1175/2009jas3040.1

Cited by 26 publications

(22 citation statements)

References 39 publications

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“…The Coriolis torque makes a small contribution at large radii, particularly in C3, and the eddy fluxes are near zero beyond a 100-km radius. These results are generally consistent with other studies that have assessed the angular momentum budget for idealized simulations (e.g., Sawada and Iwasaki 2010;Chan and Chan 2014).…”

Section: November 2016 S T O V E R N a N D R I T C H I Esupporting

confidence: 92%

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Simulated Sensitivity of Tropical Cyclone Size and Structure to the Atmospheric Temperature Profile

Stovern

Ritchie

2016

Journal of the Atmospheric Sciences

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This study uses the WRF ARW to investigate how different atmospheric temperature environments impact the size and structure development of a simulated tropical cyclone (TC). In each simulation, the entire vertical virtual temperature profile is either warmed or cooled in 18C increments from an initial specified state while the initial relative humidity profile and sea surface temperature are held constant. This alters the initial amount of convective available potential energy (CAPE), specific humidity, and air-sea temperature difference such that, when the simulated atmosphere is cooled (warmed), the initial specific humidity and CAPE decrease (increase), but the surface energy fluxes from the ocean increase (decrease).It is found that the TCs that form in an initially cooler environment develop larger wind and precipitation fields with more active outer-core rainband formation. Consistent with previous studies, outer-core rainband formation is associated with high surface energy fluxes, which leads to increases in the outer-core wind field. A larger convective field develops despite initializing in a low CAPE environment, and the dynamics are linked to a wider field of surface radial inflow. As the TC matures and radial inflow expands, large imports of relative angular momentum in the boundary layer continue to drive expansion of the TC's overall size.

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Section: November 2016 S T O V E R N a N D R I T C H I Esupporting

confidence: 92%

“…Sawada and Iwasaki (2010) found that slower TC development occurs in experiments with more evaporative cooling. Evaporative cooling induces cool downdrafts and decreases CAPE near the eyewall, which is unfavorable for the development of an axisymmetric TC structure.…”

Section: Discussionmentioning

confidence: 98%

Simulated Sensitivity of Tropical Cyclone Size and Structure to the Atmospheric Temperature Profile

Stovern

Ritchie

2016

Journal of the Atmospheric Sciences

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“…Nevertheless, the resulting frictional loss of AAM is increased (+δMloss), and accordingly, more dissipation of kinetic energy. Note that the increased transport of AAM through the friction-induced secondary flow at the upper PBL also explains the enlarged wind circulation in the MYNN case (Sawada and Iwasaki 2010).…”

Section: Discussion Of the Results A Impacts Of The Primary And Secomentioning

confidence: 87%

“…As discussed in the literature, TCs are energized by the released latent heat because of the condensation of moist convection within the eyewall and rainbands (Nolan et al 2007;Sawada and Iwasaki 2010). Fraction of this latent heat energy is transformed into the available potential energy (APE) and the KE of the system.…”

Section: B Ke Balance During Intensificationmentioning

confidence: 99%

Impacts of Surface Drag Coefficient and Planetary Boundary Layer Schemes on the Structure and Energetics of Typhoon Megi (2010) during Intensification

Coronel

Sawada²,

Iwasaki

2016

Journal of the Meteorological Society of Japan

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The sensitivity of the simulated Typhoon Megi (2010) to frictional perturbations is studied by conducting experiments with the Deardorff planetary boundary layer parameterization. Here, we increase the surface drag by 50 % (Cd1.5) and change the scheme to Mellor-Yamada-Nakanishi-Niino Level 3 (MYNN) using the Meteorological Research Institute/Japan Meteorological Agency nonhydrostatic model. At 2-km horizontal resolution, the control run simulates deeper central pressure, and shallower maximum winds and inflow layer that are comparable to observations. In this study, Cd1.5 and MYNN are found to introduce substantial change on Megi's low-level wind structures by disrupting the gradient-wind balance more than the control run. Increasing the surface drag reduces low-level tangential velocity and induces a stronger inflow near the surface and toward the center of the storm. This results in a narrow radius and lower height of the maximum tangential wind. On the contrary, the MYNN case increases the cyclone's size and elevates the level of the induced inflow at the boundary layer, far from the center. From the energetics point of view, the impact of the imbalance introduced by the experiments during the initial stage of intensification is dual, i.e., while it enhances the generation of kinetic energy, it also amplifies frictional dissipation. In the kinetic energy equation, the induced inflow strengthens the secondary circulation, and subsequently, intensifies the dynamical energy conversion. On the other hand, our results illustrate that the mechanism for energy loss in Cd1.5 is significantly different from that in MYNN due to their different impacts on wind structures and momentum flux. Nevertheless, the increase in energy gain in both experiments is overweighed by the loss due to large dissipation of absolute angular momentum, leaving less kinetic energy for further intensification.

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“…This study also highlights the possible differences in changes in the outer circulation when the initial vortex has a different outer-wind profile. An initial vortex with a rapid decrease in tangential winds with radius (such as that used in Sawada and Iwasaki 2010) will have a different response to heating compared with one that has a slow decrease (such as that used in Hill and Lackmann 2009). Wang et al (2015) used an idealized full-physics numerical model to show that high sea surface temperature (SST) is favorable to TC size growth.…”

Section: Outer Windsmentioning

confidence: 99%

The Outer-Core Wind Structure of Tropical Cyclones

Chan

2018

Journal of the Meteorological Society of Japan

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This paper presents a summary of several seminal observational and numerical studies on climatology and possible change mechanisms of the outer-core wind structure of a tropical cyclone (TC). This has generally been referred to as size, a term also used in this review despite various definitions being given in the literature. In all the ocean basins where TCs exist, TC size has been found to vary with season, year, decade, latitude and longitude. Such variations are related to the synoptic flow patterns in which the TCs are embedded. Several factors have been identified as responsible for changes in TC size, including: environmental humidity, vortex structure, sea surface temperature and planetary vorticity. Each of these factors can modify the transport of lower tropospheric angular momentum into the TC and cause changes in its size. The paper ends with a discussion of outstanding issues in the study of the outer-core wind structure of a TC.

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Impacts of Evaporation from Raindrops on Tropical Cyclones. Part I: Evolution and Axisymmetric Structure

Cited by 26 publications

References 39 publications

Simulated Sensitivity of Tropical Cyclone Size and Structure to the Atmospheric Temperature Profile

Simulated Sensitivity of Tropical Cyclone Size and Structure to the Atmospheric Temperature Profile

Impacts of Surface Drag Coefficient and Planetary Boundary Layer Schemes on the Structure and Energetics of Typhoon Megi (2010) during Intensification

The Outer-Core Wind Structure of Tropical Cyclones

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