Diurnal Variation of the Convective Area and Eye Size Associated with the Rapid Intensification of Tropical Cyclones

Lee, Jaedeok; Wu, Chia-Chien; Ito, Kosuke

doi:10.1175/mwr-d-19-0345.1

Cited by 14 publications

(29 citation statements)

References 69 publications

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“…Ocean feedback would be one of the essential components for TC intensity forecasts. Previous studies demonstrated that when the storm passes over a cold‐core eddy region or low ocean heat content area, TC intensity could be weakened depending on the TC translation speed (Lee et al., 2020; Lin et al., 2009; Ma, 2020). Figure 6 shows the number of convective cells and 36‐h integrated 10‐m atmospheric wind and 2‐m ocean current.…”

Section: Resultsmentioning

confidence: 99%

“…For example, the lower OLR is typically coincident with deep convective areas. Figure 8 depicts the IRWVln (Lee et al., 2020) and simulated OLR at 1200 UTC 21 October. As shown in the IRWVln field, Typhoon Lan had a distinct eye and concentric eyewall structure (Figure 8a).…”

Section: Resultsmentioning

confidence: 99%

“…Thus, deep atmosphere profiles, such as temperature, humidity, pressure, and wind, were retrieved. To distinguish convective clouds from active convective clouds, mixed‐phase state, and inactive convective clouds, the infrared window minus water‐vapor channel taking a natural logarithm (IRWVln) shown in Equation is used (Lee et al., 2020).

IRWVln = \overset{true¯}{T_{11.2 μ m}} \times \ln (\frac{true}{T_{6.9 μ m}}) .

…”

Section: Methodsmentioning

confidence: 99%

“…The first flight path of the T‐PARCII mission on Typhoon Lan recorded on October 21, 2017, shows a successful observation of the eyewall of Typhoon Lan (Figure 1a), with a distinct eye and eyewall structure. Alternatively, the eyewalls are surrounded by deep convective clouds (IRWVln ≤ 0 K), at least penetrating the layer between 400 and 300 hPa (Lee et al., 2020). During the first observation, 21 dropsondes, mainly for the eyewall, were dropped.…”

Section: Methodsmentioning

confidence: 99%

“…This transition area may reveal changes from the convective area or mixed-phase into the non-convective area. Lee et al (2020) theoretically defined these areas as follows: convective area ≤−1 K, −1 K < mixed-phase <1 K, and non-convective area ≥1 K. Concretely, deep convection penetrating layers between 300 and 400 hPa should be smaller than 0 K of IRWVln. Based on in situ observation data, this study suggests that the mixed-phase and non-convective area definitions should be revised as 0 K < mixed-phase ≤5 and non-convective area >5 K. However, these results should be thoroughly reevaluated using sufficient dropsonde data because these box plots were only calculated using 26 dropsondes.…”

Section: Relationship Between Irwvln and In Situ Rhmentioning

confidence: 99%

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Effects of the Assimilation of Relative Humidity Reproduced From T‐PARCII and Himawari‐8 Satellite Imagery Using Dynamical Initialization and Ocean‐Coupled Model: A Case Study of Typhoon Lan (2017)

et al. 2021

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Effects of the assimilation of relative humidity (RH) reproduced from dropsonde data from the Tropical cyclones‐Pacific Asian Research Campaign for Improvement of Intensity estimations/forecasts (T‐PARCII) campaign and Himawari‐8 satellite data on the simulation of Typhoon Lan (2017) were investigated herein using a weather research and forecasting model. The lateral boundary and initial conditions were obtained from Global Forecast System (GFS) forecast data. Four experiments varying from the initial vortex, assimilation of the reproduced RH (ARH), and ocean model (OCEAN, three‐dimensional Price‐Weller‐Pinkel upper‐ocean circulation model) activation were conducted for 42 h to evaluate tropical cyclone (TC) forecast performance: the GFS experiment and dynamical initialization (DI) experiments such as DI, DI‐OCEAN, and DI‐ARH‐OCEAN, respectively. All track forecast errors were less than 100 km until landfall, that is, up to 36 h. TC intensity forecasts such as the minimum sea‐level pressure and maximum surface wind speed were slightly improved in DI‐related experiments compared to the GFS experiment. The DI‐ARH‐OCEAN experiment, in particular, demonstrated improvements in both TC forecasts and convective areas. The ocean‐coupled experiments yielded significant sea surface temperature cooling in the rear‐right quadrant of TC, forming a stable boundary layer that could suppress the convective activity, particularly in the lower troposphere. These findings support that compared to the original DI method, ARH could improve initial conditions, resulting in more accurate TC forecasts. Furthermore, it may argue the necessity and urgency of regular aircraft surveillance of TCs in the western North Pacific area.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

IRWVln = \overset{true¯}{T_{11.2 μ m}} \times \ln (\frac{true}{T_{6.9 μ m}}) .

…”

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Relationship Between Irwvln and In Situ Rhmentioning

confidence: 99%

See 3 more Smart Citations

Effects of the Assimilation of Relative Humidity Reproduced From T‐PARCII and Himawari‐8 Satellite Imagery Using Dynamical Initialization and Ocean‐Coupled Model: A Case Study of Typhoon Lan (2017)

et al. 2021

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Diurnal variations of tropical cyclone outer region size growth

Hong

2023

Atmospheric Science Letters

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Various aspects of tropical cyclones (TCs) fluctuate with the diurnal cycle. TC size is critical to the extent of its damage, but diurnal variations in the growth of the outer region size have largely remained unexplored. This paper examines the diurnal variations in the growth of the radius of gale‐force winds (34 kt; R34) by analyzing best‐track data from 2001 to 2019 for both North Atlantic TCs and global TCs outside of the North Atlantic region. Statistically significant diurnal variations was found for R34 growth, with the maximum 6‐h growth rate occurring at 2100–0300 local solar time (LST) for North Atlantic TCs, and at 0300–0900 LST for global TCs excluding the North Atlantic which experienced rapid intensification (≥30 knots within 24 h). The higher R34 6‐h growth rates during the night were linked to a larger extent of very deep convective clouds with infrared brightness temperatures <208 K during this time.

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Importance of self‐induced vertical wind shear and diabatic heating on the Fujiwhara effect

Lee

Ito

Chan

2023

Quart J Royal Meteoro Soc

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This study hypothesises that the motion of binary tropical cyclones (TCs) can be modified by diabatic heating (DH) asymmetry associated with self-induced vertical wind shear. To demonstrate this hypothesis in the quiescent environment, a set of the idealised f -plane numerical experiments such as identical (varied in the initial separation distance) and non-identical (varied in TC intensity and size) experiments are conducted. Results show that the binary TC tracks are affected by the initial separation distance, and TC intensity and size, that is, TC influence radius. Identical experiments show that the critical distance for separating, merging or repelling motion is 8 • (where 1 • ≃ 111 km). The binary TC interaction shows that single large-scale cyclonic and anticyclonic circulations can develop as a result of the superposition of the circulation of the binary TCs in the lower and upper troposphere. These two different large-scale circulations result in a vertically sheared environment in each TC. Potential vorticity (PV) tendency diagnosis shows that the TC motion is consistent with a positive region of the local tendency of PV. To quantify the contribution of each PV diagnostic term to the TC motion, we calculate each vector of the PV tendency diagnostic equation. In the merger case, the horizontal advection vector (HADV) appears to be greater than the DH vector (DHV) due to attraction. In the repulsion case, the DHV is largely compensated by the HADV. Specifically, the strong shear-induced DH generated in the lower troposphere and downshear or downshear-left quadrant can modify the TC motion in collaboration with the transport of PV to the middle and upper troposphere by offsetting the PV imbalance via the HADV. Overall, these results validate our hypothesis, which we refer to as the three-dimensional Fujiwhara effect.

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Diurnal Variation of the Convective Area and Eye Size Associated with the Rapid Intensification of Tropical Cyclones

Cited by 14 publications

References 69 publications

Effects of the Assimilation of Relative Humidity Reproduced From T‐PARCII and Himawari‐8 Satellite Imagery Using Dynamical Initialization and Ocean‐Coupled Model: A Case Study of Typhoon Lan (2017)

Effects of the Assimilation of Relative Humidity Reproduced From T‐PARCII and Himawari‐8 Satellite Imagery Using Dynamical Initialization and Ocean‐Coupled Model: A Case Study of Typhoon Lan (2017)

Diurnal variations of tropical cyclone outer region size growth

Importance of self‐induced vertical wind shear and diabatic heating on the Fujiwhara effect

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