The Relationship between Tropical Cyclone Intensity Change and the Strength of Inner-Core Convection

2012 ◽  
Vol 140 (4) ◽  
pp. 1164-1176 ◽  
Author(s):  
Haiyan Jiang
Keyword(s):  
Tropical Cyclone ◽  
Brightness Temperature ◽  
Inner Core ◽  
Cumulative Distribution ◽  
Intensity Change ◽  
Sample Mean ◽  
Convective Parameter ◽  
Significant Difference ◽  
Radar Echo ◽  
The Relationship

Convective intensity proxies measured by the Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI), Precipitation Radar (PR), and Visible and Infrared Scanner (VIRS) are used to assess the relationship between intense convection in the inner core and tropical cyclone (TC) intensity change. Using the cumulative distribution functions of 24-h intensity changes from the 1998–2008 best-track data for global TCs, five intensity change categories are defined: rapidly intensifying (RI), slowly intensifying, neutral, slowly weakening, and rapidly weakening. TRMM observations of global TCs during 1998–2008 are used to generate the distributions of convective properties in the storm’s inner-core region for different storm intensity change categories. To examine the hypothesis of hot towers near the eye as an indicator of RI, hot towers are defined by precipitation features with 20-dBZ radar echo height reaching 14.5 km. The differences in the convective parameters between rapidly intensifying TCs and slowly intensifying, neutral, slowly weakening, and rapidly weakening TCs are quantified using statistical analysis. It is found that statistically significant differences of three out of four convective intensity parameters in the inner core exist between RI and non-RI storms. Between RI and slowly intensifying TCs, a statistically significant difference exists for the minimum 11-μm IR brightness temperature TB11 in the inner core. This indicates that a relationship does exist between inner-core convective intensity and TC intensity change. The results in this study also suggest that the rate of intensification appears to be influenced by convective activity in the inner core and the ability to predict RI might be further improved by using convective parameters. With regard to different convective proxies, the relationships are different. The minimum TB11, upper-level maximum radar reflectivities, and maximum 20-dBZ radar echo height in the inner core are best associated with the rate of TC intensity change, while the minimum 85-GHz polarization corrected brightness temperature (PCT) shows some ambiguities in relation to intensity change. The minimum 37-GHz PCT shows no significant relationship with TC intensity change, probably because of the contamination of the ice scattering signal by emission from rain and liquid water in this channel. By examining the probability of RI for each convective parameter for which statistically significant differences at the 95% level were found of RI and non-RI cases, it is found that all three parameters provide additional information relative to climatology. The most skillful parameter is minimum TB11, and the second is maximum 20-dBZ height, followed by minimum 85-GHz PCT. However, the increases of RI probability from the larger sample mean by using these predictors are not very large. When using the existence of hot towers as a predictor, it is found that the probabilities of RI and slowly intensifying increase and those of slowly weakening and rapidly weakening decrease for samples with hot towers in the inner core. However, the increases for intensifying and decreases for weakening are not substantial, indicating that hot towers are neither a necessary nor a sufficient condition for RI.

Changes of Lightning Activity and Vertical Structure in the Inner Core Preceding Tropical Cyclone Rapid Intensification

2020 ◽  
Author(s):  
Weixin Xu
Keyword(s):  
Tropical Cyclone ◽  
Inner Core ◽  
Radar Reflectivity ◽  
Lightning Activity ◽  
Intensity Change ◽  
Complete Understanding ◽  
Radar Echo ◽  
Storm Dynamics ◽  
Total Lightning ◽  
Imaging Sensor

<p>Previous studies suggested that lightning activity could be an indicator of Tropical Cyclone (TC) intensity change but their relationships vary greatly and at times appear contradictory. The importance of total lightning for TC intensification study and forecasting applications has also been pinpointed by several studies. Recently, we revisited this problem using 16 years of TRMM Lightning Imaging Sensor (LIS) measurements and found that reduced (elevated) inner-core total lightning marked rapidly intensifying (weakening) TCs, whereas outer rainband total lightning had opposite trends. It is also shown that the reduced lightning frequency in the inner cores of rapidly intensifying storms was coincident with reduced volumes of 30-dBZ radar reflectivity in the mixed-phase cloud region (-5 to -40 oC), suggesting the lack of large ice particles (e.g., graupel) in the inner cores of rapidly intensifying TCs (which is considered to be important for cloud electrification). To better understand the physical process responsible for these results, we have examined the vertical profiles of radar reflectivity, distribution of precipitation/convection, overshooting radar echo tops (CloudSat), and microwave ice scattering signatures provided by GPM and CloudSat overpasses. This data fusion exercise uniquely provides a more complete understanding of storm electrification, convective intensity, ensemble precipitation microphysics, and storm dynamics in relation to TC intensity change. For example, we have distinguished the convective and microphysical structures between rapidly intensifying (RI) TCs with and without enhanced lightning activity, RI and steady-state TCs, and RI and rapidly weakening TCs.</p>

scholarly journals A 10-Year Survey of Tropical Cyclone Inner-Core Lightning Bursts and Their Relationship to Intensity Change

2017 ◽  
Vol 33 (1) ◽  
pp. 23-36 ◽  
Author(s):  
Stephanie N. Stevenson ◽  
Kristen L. Corbosiero ◽  
Mark DeMaria ◽  
Jonathan L. Vigh
Keyword(s):  
Tropical Cyclone ◽  
North Atlantic ◽  
Inner Core ◽  
Promising Result ◽  
Vertical Wind Shear ◽  
Intensity Change ◽  
Grid Spacing ◽  
Tropical Depressions ◽  
Using Data ◽  
The Relationship

Abstract This study seeks to reconcile discrepancies between previous studies analyzing the relationship between lightning and tropical cyclone (TC) intensity change. Inner-core lightning bursts (ICLBs) were identified from 2005 to 2014 in North Atlantic (NA) and eastern North Pacific (ENP) TCs embedded in favorable environments (e.g., vertical wind shear ≤ 10 m s−1; sea surface temperatures ≥ 26.5°C) using data from the World Wide Lightning Location Network (WWLLN) transformed onto a regular grid with 8-km grid spacing to replicate the expected nadir resolution of the Geostationary Lightning Mapper (GLM). Three hypothesized factors that could impact the 24-h intensity change after a burst were tested: 1) prior intensity change, 2) azimuthal burst location, and 3) radial burst location. Most ICLBs occurred in weak TCs (tropical depressions and tropical storms), and most TCs intensified (remained steady) 24 h after burst onset in the NA (ENP). TCs were more likely to intensify 24 h after an ICLB if they were steady or intensifying prior to burst onset. Azimuthally, 75% of the ICLBs initiated downshear, with 92% of downshear bursts occurring in TCs that remained steady or intensified. Of the ICLBs that initiated or rotated upshear, 2–3 times more were associated with TC intensification than weakening, consistent with recent studies finding more symmetric convection in intensifying TCs. The radial burst location relative to the radius of maximum wind (RMW) provided the most promising result: TCs with an ICLB inside (outside) the RMW were associated with intensification (weakening).

scholarly journals Recent Advances in Our Understanding of Tropical Cyclone Intensity Change Processes from Airborne Observations

Atmosphere ◽  
2021 ◽  
Vol 12 (5) ◽  
pp. 650
Author(s):  
Robert F. Rogers
Keyword(s):  
Tropical Cyclone ◽  
Inner Core ◽  
Vertical Shear ◽  
Intensity Change ◽  
Change Processes ◽  
Cyclone Intensity ◽  
Secondary Eyewall Formation ◽  
Warm Core ◽  
Major Hurricane ◽  
Upper Level

Recent (past ~15 years) advances in our understanding of tropical cyclone (TC) intensity change processes using aircraft data are summarized here. The focus covers a variety of spatiotemporal scales, regions of the TC inner core, and stages of the TC lifecycle, from preformation to major hurricane status. Topics covered include (1) characterizing TC structure and its relationship to intensity change; (2) TC intensification in vertical shear; (3) planetary boundary layer (PBL) processes and air–sea interaction; (4) upper-level warm core structure and evolution; (5) genesis and development of weak TCs; and (6) secondary eyewall formation/eyewall replacement cycles (SEF/ERC). Gaps in our airborne observational capabilities are discussed, as are new observing technologies to address these gaps and future directions for airborne TC intensity change research.

scholarly journals A View of Tropical Cyclones from Above: The Tropical Cyclone Intensity Experiment

2017 ◽  
Vol 98 (10) ◽  
pp. 2113-2134 ◽  
Author(s):  
James D. Doyle ◽  
Jonathan R. Moskaitis ◽  
Joel W. Feldmeier ◽  
Ronald J. Ferek ◽  
Mark Beaubien ◽  
...  
Keyword(s):  
Tropical Cyclone ◽  
Lower Stratosphere ◽  
Inner Core ◽  
Horizontal Resolution ◽  
Intensity Change ◽  
Naval Research ◽  
Atmospheric Conditions ◽  
Tropical Cyclone Intensity ◽  
High Definition ◽  
Cyclone Intensity

Abstract Tropical cyclone (TC) outflow and its relationship to TC intensity change and structure were investigated in the Office of Naval Research Tropical Cyclone Intensity (TCI) field program during 2015 using dropsondes deployed from the innovative new High-Definition Sounding System (HDSS) and remotely sensed observations from the Hurricane Imaging Radiometer (HIRAD), both on board the NASA WB-57 that flew in the lower stratosphere. Three noteworthy hurricanes were intensively observed with unprecedented horizontal resolution: Joaquin in the Atlantic and Marty and Patricia in the eastern North Pacific. Nearly 800 dropsondes were deployed from the WB-57 flight level of ∼60,000 ft (∼18 km), recording atmospheric conditions from the lower stratosphere to the surface, while HIRAD measured the surface winds in a 50-km-wide swath with a horizontal resolution of 2 km. Dropsonde transects with 4–10-km spacing through the inner cores of Hurricanes Patricia, Joaquin, and Marty depict the large horizontal and vertical gradients in winds and thermodynamic properties. An innovative technique utilizing GPS positions of the HDSS reveals the vortex tilt in detail not possible before. In four TCI flights over Joaquin, systematic measurements of a major hurricane’s outflow layer were made at high spatial resolution for the first time. Dropsondes deployed at 4-km intervals as the WB-57 flew over the center of Hurricane Patricia reveal in unprecedented detail the inner-core structure and upper-tropospheric outflow associated with this historic hurricane. Analyses and numerical modeling studies are in progress to understand and predict the complex factors that influenced Joaquin’s and Patricia’s unusual intensity changes.

Examination of the Combined Effect of Deep-layer Vertical Shear Direction and Lower-Tropospheric Mean Flow on Tropical Cyclone Intensity and Size Based on the ERA5 Reanalysis

2021 ◽  
Author(s):  
Buo-Fu Chen ◽  
Christopher A. Davis ◽  
Ying-Hwa Kuo
Keyword(s):  
Tropical Cyclone ◽  
Inner Core ◽  
Vertical Wind Shear ◽  
Reanalysis Data ◽  
Vertical Shear ◽  
Shear Direction ◽  
Mean Flow ◽  
Representative Subset ◽  
Favorable Conditions ◽  
The Relationship

AbstractIdealized numerical studies have suggested that in addition to vertical wind shear (VWS) magnitude, the VWS profile also affects tropical cyclone (TC) development. A way to further understand the VWS profile’s effect is to examine the interaction between a TC and various shear-relative low-level mean flow (LMF) orientations. This study mainly uses the ERA5 reanalysis to verify that, consistent with idealized simulations, boundary-layer processes associated with different shear-relative LMF orientations affect real-world TC’s intensity and size. Based on analyses of 720 TCs from multiple basins during 2004–2016, a TC affected by an LMF directed toward downshear-left in the Northern Hemisphere favors intensification, whereas an LMF directed toward upshear-right is favorable for expansion. Furthermore, physical processes associated with shear-relative LMF orientation may also partly explain the relationship between the VWS direction and TC development, as there is a correlation between the two variables.The analysis of reanalysis data provides other new insights. The relationship between shear-relative LMF and intensification is not significantly modified by other factors [inner-core sea surface temperature (SST), VWS magnitude, and relative humidity (RH)]. However, the relationship regarding expansion is partly attributed to environmental SST and RH variations for various LMF orientations. Moreover, SST is critical to the basin-dependent variability of the relationship between the shear-relative LMF and intensification. For Atlantic TCs, the relationship between LMF orientation and intensification is inconsistent with all-basin statistics unless the analysis is restricted to a representative subset of samples associated with generally favorable conditions.

scholarly journals Interaction of an Asymmetric Double Vortex and Trochoidal Motion of a Tropical Cyclone with the Concentric Eyewall Structure

2006 ◽  
Vol 63 (3) ◽  
pp. 1069-1081 ◽  
Author(s):  
Masahito Oda ◽  
Mikio Nakanishi ◽  
Gen’ichi Naito
Keyword(s):  
Tropical Cyclone ◽  
Numerical Experiment ◽  
Tropical Cyclones ◽  
Rotation Period ◽  
Echo Intensity ◽  
Dynamics Model ◽  
The Third ◽  
Radar Echo ◽  
The Relationship ◽  
Typhoon Herb

Abstract Radar echo images demonstrate that mature tropical cyclones frequently have a concentric eyewall structure, which consists of the inner eyewall, echo-free moat, and outer eyewall regions. Near the inner and outer eyewalls, well-defined wind maxima are generally observed. This indicates that two large vertical vorticity regions exist just inside radii of the two wind maxima near the inner and outer eyewalls. Therefore, the concentric eyewall structure can be considered to be a double vortex composed of the inner vortex and the outer vortex ring. In this study, the contour dynamics model is used on the f plane to analyze the characteristics of flows with either a symmetric double vortex or an asymmetric one, and examined the relationship between the movement of the inner vortex in an asymmetric double vortex and a trochoidal motion of a tropical cyclone with an asymmetric concentric eyewall structure. Results show that, depending on the degree of an interaction of a double vortex, the evolution of the inner vortex is classified into three patterns: the first is that the center of the inner vortex is stationary, which is seen only for the symmetric double vortex; the second is that the track of the center of the inner vortex draws a circle; and the third is that it draws a spiral. A numerical experiment based on an observed flow around Typhoon Herb was also performed. The time evolution of the double vortex is very similar to that of radar echo intensity of Typhoon Herb. Also the rotation period and amplitude of the inner vortex in the numerical experiment were comparable with those of the trochoidal motion in the observation. These suggest that, in tropical cyclones with the concentric eyewall structure, the interaction of an asymmetric double vortex can become a cause of trochoidal motion.

scholarly journals Short-Term Tropical Cyclone Intensity Forecasting from Satellite Imagery Based on the Deviation Angle Variance Technique

2020 ◽  
Vol 35 (1) ◽  
pp. 285-298 ◽  
Author(s):  
Liang Hu ◽  
Elizabeth A. Ritchie ◽  
J. Scott Tyo
Keyword(s):  
Tropical Cyclone ◽  
Satellite Imagery ◽  
Forecast Model ◽  
Intensity Change ◽  
Deviation Angle ◽  
Short Term ◽  
Cyclone Intensity ◽  
The North ◽  
Intensity Forecast ◽  
The Relationship

Abstract The deviation angle variance (DAV) is a parameter that characterizes the level of organization of a cloud cluster compared with a perfectly axisymmetric tropical cyclone (TC) using satellite infrared (IR) imagery, and can be used to estimate the intensity of the TC. In this study, the DAV technique is further used to analyze the relationship between satellite imagery and TC future intensity over the North Atlantic basin. The results show that the DAV of the TC changes ahead of the TC intensity change, and this can be used to predict short-term TC intensity. The DAV-IR 24-h forecast is close to the National Hurricane Center (NHC) 24-h forecast, and the bias is lower than NHC and other methods during weakening periods. Furthermore, an improved TC intensity forecast is obtained by incorporating all four satellite bands. Using SST and TC latitude as the other two predictors in a linear regression model, the RMSE and MAE of the DAV 24-h forecast are 13.7 and 10.9 kt (1 kt ≈ 0.51 m s−1), respectively, and the skill space of the DAV is about 5.5% relative to the Statistical Hurricane Intensity Forecast model with inland decay (Decay-SHIFOR) during TC weakening periods. Considering the DAV is an independent intensity technique, it could potentially add value as a member of the suite of operational intensity forecast techniques, especially during TC weakening periods.

scholarly journals Passive Microwave Quantification of Tropical Cyclone Inner-Core Cloud Populations Relative to Subsequent Intensity Change

2016 ◽  
Vol 144 (11) ◽  
pp. 4461-4482 ◽  
Author(s):  
Daniel S. Harnos ◽  
Stephen W. Nesbitt
Keyword(s):  
Tropical Cyclone ◽  
Inner Core ◽  
Statistical Significance ◽  
Deep Convection ◽  
Detection Algorithm ◽  
Passive Microwave ◽  
Intensity Change ◽  
Atmospheric Column ◽  
Full Intensity ◽  
Relative Prevalence

Abstract Characteristics of over 15 000 tropical cyclone (TC) inner cores are evaluated coincidentally using 37- and 85-GHz passive microwave data to quantify the relative prevalence of cold clouds (i.e., deep convection and stratiform clouds) versus predominantly warm clouds (i.e., shallow cumuli and cumulus congestus). Results indicate greater presence of combined liquid and frozen hydrometeors associated with cold clouds within the atmospheric column for TCs undergoing subsequent rapid intensification (RI) or intensification. RI episodes compared to the full intensity change distribution exhibit approximately an order of magnitude increase for inner-core cold cloud frequency relative to warm cloud presence. Incorporation of an objective ring detection algorithm shows the robust presence of rings associated with hydrometeors for 85-GHz polarization corrected temperatures () and 37-GHz vertically polarized brightness temperatures () for differentiating RI with significance levels ≥99.99%, while 37-GHz false color rings of a combined cyan and pink appearance surrounding a region that is not cyan or pink lack statistical significance for discriminating RI against lesser intensification. Rings of depressed and enhanced tied to RI suggest the combined presence of liquid and frozen hydrometeors within the atmospheric column, indicative of cold clouds. The rings also exhibit preferences for those with collocated more widespread ice scattering signatures to be more commonly associated with RI and general intensification.

scholarly journals The Role of Near-Core Convective and Stratiform Heating/Cooling in Tropical Cyclone Structure and Intensity

2018 ◽  
Vol 75 (1) ◽  
pp. 297-326 ◽  
Author(s):  
Guanghua Chen ◽  
Chun-Chieh Wu ◽  
Yi-Hsuan Huang
Keyword(s):  
Tropical Cyclone ◽  
Inner Core ◽  
Core Region ◽  
Intensity Change ◽  
Moderate Intensity ◽  
Convective Heating ◽  
Core Size ◽  
Heating And Cooling ◽  
Diabatic Processes ◽  
Spiral Rainbands

The effects of convective and stratiform diabatic processes in the near-core region on tropical cyclone (TC) structure and intensity change are examined by artificially modifying the convective and stratiform heating/cooling between 40- and 80-km radii. Sensitivity experiments show that the absence of convective heating in the annulus can weaken TC intensity and decrease the inner-core size. The increased convective heating generates a thick and polygonal eyewall, while the storm intensifies more gently than that in the control run. The removal of stratiform heating can slow down TC intensification with a moderate intensity, whereas the doubling of stratiform heating has little effect on the TC evolution compared to the control run. The halved stratiform cooling facilitates TC rapid intensification and a compact inner-core structure with the spiral rainbands largely suppressed. With the stratiform cooling doubled, the storm terminates intensification and eventually develops a double-eyewall-like structure accompanied by the significantly outward expansion of the inner-core size. The removal of both stratiform heating and cooling generates the strongest storm with the structure and intensity similar to those in the experiment with stratiform cooling halved. When both stratiform heating and cooling are doubled, the storm first decays rapidly, followed by the vertical connection of the updrafts at mid- to upper levels in the near-core region and at lower levels in the collapsed eyewall, which reinvigorates the eyewall convection but with a large outward slope.

scholarly journals Reassessing the Use of Inner-Core Hot Towers to Predict Tropical Cyclone Rapid Intensification*

2015 ◽  
Vol 30 (5) ◽  
pp. 1265-1279 ◽  
Author(s):  
Xiao-Yong Zhuge ◽  
Jie Ming ◽  
Yuan Wang
Keyword(s):  
Tropical Cyclone ◽  
Inner Core ◽  
Prediction Method ◽  
Vertical Shear ◽  
Intensity Change ◽  
False Alarms ◽  
Rapid Intensification ◽  
Central Pacific ◽  
Prediction Scheme ◽  
Skill Scores

Abstract The hot tower (HT) in the inner core plays an important role in tropical cyclone (TC) rapid intensification (RI). With the help of Tropical Rainfall Measurement Mission (TRMM) data and the Statistical Hurricane Intensity Prediction Scheme dataset, the potential of HTs in operational RI prediction is reassessed in this study. The stand-alone HT-based RI prediction scheme showed little skill in the northern Atlantic (NA) and eastern and central Pacific (ECP), but yielded skill scores of >0.3 in the southern Indian Ocean (SI) and western North Pacific (WNP) basins. The inaccurate predictions are due to four scenarios: 1) RI events may have already begun prior to the TRMM overpass. 2) RI events are driven by non-HT factors. 3) The HT has already dissipated or has not occurred at the TRMM overpass time. 4) Large false alarms result from the unfavorable environment. When the HT was used in conjunction with the TC’s previous 12-h intensity change, the potential intensity, the percentage area from 50 to 200 km of cloud-top brightness temperatures lower than −10°C, and the 850–200-hPa vertical shear magnitude with the vortex removed, the predictive skill score in the SI was 0.56. This score was comparable to that of the RI index scheme, which is considered the most advanced RI prediction method. When the HT information was combined with the aforementioned four environmental factors in the NA, ECP, South Pacific, and WNP, the skill scores were 0.23, 0.32, 0.42, and 0.42, respectively.

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