This is the PhD dissertation of Yassine Tissaoui successfully defended on July 9, 2024 at NJIT in mechanical engineering. The co-main advisors for the dissertation are Simone Marras (NJIT) and Stephen Guimond (Hampton University).
The increasing frequency and intensity of tropical cyclones (TCs) due to climate
change pose significant challenges for forecasting and mitigating their impacts.
Despite advancements, accurately predicting TC rapid intensification (RI) remains
a challenge. Large eddy simulation (LES) allows for explicitly resolving the large
eddies involved in TC turbulence, thus providing an avenue for studying the
mechanisms behind their intensification and RI. LES of a full tropical cyclone is
very computationally expensive and its accuracy will depend on both explicit and
implicit dissipation within an atmospheric model. This dissertation presents two
novel numerical methodologies with the potential to improve the efficiency of tropical
cyclone LES in the future. The first is a pioneering non-column based implementation
of the Kessler warm rain microphysics parametrization, a method which would
allow for the use of three-dimensional (3D) adaptive mesh refinement (AMR) in
the simulation of moist tropical cyclones. The second is an implementation of
Laguerre-Legendre semi-infinite elements for use in the damping layers of atmospheric
models, a method which was shown to be capable of improving the efficiency of
benchmark atmospheric simulations. Finally, the dissertation presents a study of
two-dimensional (2D) AMR applied to simulations of a rapidly intensifying dry
tropical cyclone and shows that AMR is able to accurately reproduce the results
of simulations using static grids while demonstrating considerable cost savings.
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Discovering Precursors to Tropical Cyclone Rapid Intensification in the Atlantic Basin Using Spatiotemporal Data Mining
Regarded as one of the most dangerous types of natural disaster, tropical cyclones threaten the life and health of human beings and often cause enormous economic loss. However, intensity forecasting of tropical cyclones, especially rapid intensification forecasting, remains a scientific challenge due to limited understanding regarding the intensity change process. We propose an automatic knowledge discovery framework to identify potential spatiotemporal precursors to tropical cyclone rapid intensification from a set of tropical cyclone environmental fields. Specifically, this framework includes (1) formulating RI and non-RI composite environmental fields from historical tropical cyclones using NASA MERRA2 data; (2) utilizing the shared nearest neighbor-based clustering algorithm to detect regions representing relatively homogeneous behavior around tropical cyclone centers; (3) determining candidate precursors from significantly different regions in RI and non-RI groups using a spatiotemporal statistical method; and (4) comparing candidates to existing predictors to select potential precursors. The proposed knowledge discovery framework is applied separately to different factors, including 200 hPa zonal wind, 850–700 hPa relative humidity, and 850–200 hPa vertical shear, to detect potential precursors. Compared to the existing predictors manually labeled, i.e., U200 and U20C, RHLO, and SHRD in the Statistical Hurricane Intensity Prediction Scheme, our automatically discovered precursors have a comparable or better capability for estimating the probability of rapid intensification.
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- Award ID(s):
- 1841520
- PAR ID:
- 10396197
- Date Published:
- Journal Name:
- Atmosphere
- Volume:
- 13
- Issue:
- 6
- ISSN:
- 2073-4433
- Page Range / eLocation ID:
- 882
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract This paper investigates the relationship between long‐term trends (1980–2017) in intensity and wind evolution for tropical cyclones (TCs) within the western tropical Atlantic (WTA) and central/eastern tropical Atlantic (CETA) subbasins. Long‐term TC trends in intensity, intensification time, and wind variability for the CETA were generally more significant than, and in some cases opposite to, those for the WTA. Both the TC intensity levels, as measured by the power dissipation index normalized by storm hours and proportion of rapid intensification intervals (defined as a 12‐hr wind speed increase of 20 kt or more), exhibit no long‐term trends in either subbasin. A TC wind variability index (WVI) calculated over 72‐hr intervals of the TC lifecycle decreases for the WTA over the decades, while the CETA has the 72‐hr intervals with the greatest wind speed fluctuations. The average period of intensification before the peak in TC intensity increases ~0.97 hr/year for the CETA. TC maximum intensity exhibits no trend, suggesting that TCs in the tropical North Atlantic have a trend favoring a longer intensification period to reach their lifetime maximum intensity. A correlation analysis suggests that warmer sea surface temperatures and greater moisture favor longer intensification and greater WVI. In contrast, greater 850‐ to 200‐hPa vertical wind shear is associated with shorter intensification periods and less WVI.
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Abstract The phenomenon that rapid contraction (RC) of the radius of maximum wind (RMW) could precede rapid intensification (RI) in tropical cyclones (TCs) has been found in several previous studies, but it is still unclear how frequently and to what extent RC precedes RI in rapidly intensifying and contracting TCs in observations. In this study, the statistical relationship between RMW RC and TC RI is examined based on the extended best track dataset for the North Atlantic and eastern North Pacific during 1999–2019. Results show that for more than ∼65% of available TCs, the time of the peak contraction rate precedes the time of the peak intensification rate, on average, by ∼10–15 h. With the quantitatively defined RC and RI, results show that ∼50% TCs with RC experience RI, and TCs with larger intensity and smaller RMW and embedded in more favorable environmental conditions tend to experience RI more readily following an RC. Among those TCs with RC and RI, more than ∼65% involve the onset of RC preceding the onset of RI, on average, by ∼15–25 h. The preceding time tends to be longer with lower TC intensity and larger RMW and shows weak correlations with environmental conditions. The qualitative results are insensitive to the time interval for the calculation of intensification/contraction rates and the definition of RI. The results from this study can improve our understanding of TC structure and intensity changes.more » « less
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The FV3GFS is the current operational Global Forecast System (GFS) at the National Centers for Environmental Prediction (NCEP), which combines a finite-volume cubed sphere dynamical core (FV3) and GFS physics. In this study, FV3GFS is used to gain understanding of rapid intensification (RI) of tropical cyclones (TCs) in shear. The analysis demonstrates the importance of TC structure in a complex system like Hurricane Michael, which intensified to a category 5 hurricane over the Gulf of Mexico despite over 20 kt (10 m s−1) of vertical wind shear. Michael’s RI is examined using a global-nest FV3GFS ensemble with the nest at 3-km resolution. The ensemble shows a range of peak intensities from 77 to 159 kt (40–82 m s−1). Precipitation symmetry, vortex tilt, moisture, and other aspects of Michael’s evolution are compared through composites of stronger and weaker members. The 850–200-hPa vertical shear is 22 kt (11 m s−1) in the mean of both strong and weak members during the early stage. Tilt and moisture are two distinguishing factors between strong and weak members. The relationship between vortex tilt and humidification is complex, and other studies have shown both are important for sheared intensification. Here, it is shown that tilt reduction leads to upshear humidification and is thus a driving factor for intensification. A stronger initial vortex and early evolution of the vortex also appear to be the key to members that are able to resist the sheared environment.
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Abstract Understanding physical processes leading to rapid intensification (RI) of tropical cyclones (TCs) under environmental vertical wind shear is key to improving TC intensity forecasts. This study analyzes the thermodynamic processes that help saturate the TC inner core before RI onset using a column‐integrated moist static energy (MSE) framework. Results indicate that the nearly saturated inner core in the lower‐middle troposphere is achieved by an increase in the column‐integrated MSE, as column water vapor accumulates while the mean column temperature cools. The sign of the column‐integrated MSE tendency depends on the competition between surface enthalpy fluxes, radiation, and vertical wind shear‐induced ventilation effect. The reduction of ventilation above the boundary layer due to vertical alignment is crucial to accumulate the energy within the inner core region. A comparison of the RI simulation with a null simulation further highlights the impact of vortex structure on the thermodynamic state adjustment and TC intensification.
- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.3390/atmos13060882
