Stages Of Tropical Cyclones Research Articles

Exploring the Influence of Tropical Cyclones on Regional Air Quality Using Multimodal Deep Learning Techniques.

Tropical cyclones (TC) are dynamic atmospheric phenomena featuring extreme low-pressure systems and powerful winds, known for their devastating impacts on weather and the environment. The main purpose of this paper is to consider the subtle involvement of TCs in the air quality index (AQI), focusing on aspects related to the air quality before, during and after cyclones. This research employs multimodal methods, which include meteorological data and different satellite observations. Deep learning approaches, i.e., ConvLSTM, CNN and Real-ESRGAN models, are combined with a regression model to analyze the temporal variability in the air quality associated with tropical cyclones. Deep learning models are deployed to uncover complex patterns and non-linear interdependencies between cyclones' features and the AQI to give predictive insights into the air quality fluctuations throughout the different stages of tropical cyclones. Furthermore, this study explores the aftermaths of TCs in terms of the air quality with respect to post-cyclone recovery. The findings offer an enhanced view of the role of TCs in the regional or global air quality, which will be useful for policymakers, meteorologists and environmental researchers. Utilizing a CNN for tropical cyclone (TC) classification and the extra trees regressor (ETR) for AQI prediction results in accuracy of 92.02% for the CNN and an R2 of 83.33% for the ETR. Hence, this work adds to our knowledge and enlightens us on the complex interactions between TCs and the air quality, highlighting wider public health concerns regarding climate adaptation and urban renewal.

Recent shortening of the mature tropical cyclone stage over the western North Pacific

AbstractThis study investigates long‐term trends related to the mature stage duration of tropical cyclones (TCs) over the western North Pacific (WNP) during June–November between 1982 and 2021. There is a significant shortening in the mean duration of the WNP mature TC stage, which is defined as the period when a TC is within 5 kt of its lifetime maximum intensity. This shortening is induced by a significant (weak) poleward migration in the starting (ending) location of the WNP mature TC stage, which can be further explained by changes in environmental conditions. From 1982 to 2021, there have been significant increases in maximum potential intensity and 700–500‐hPa relative humidity over most of the WNP, which has broadly expanded the TC‐favorable area poleward. Consequently, WNP TCs can start their mature stages and reach their lifetime maximum intensities at higher latitudes. By contrast, there are only weak changes in 850‐hPa relative vorticity and 850–200‐hPa vertical wind shear (VWS). Given the dominant role of VWS in modulating the TC weakening rate, the TC‐suppressive area over the subtropical WNP has shown lesser changes, thus leading to insignificant changes in the ending location of the mature TC stage.

Historical Variability and Lifecycles of North Atlantic Midlatitude Cyclones Originating in the Tropics

AbstractNorth Atlantic tropical and post‐tropical cyclones impact midlatitude regions, but the inhomogeneous observational record of the latter stages of tropical cyclones precludes many climatological analyses. The frequency of tropical‐origin storms basin‐wide is projected to increase under anthropogenic climate change, so establishing confidence in our knowledge of their historical variability and lifecycles—against which climate model simulations may be evaluated—is important. We used a Lagrangian feature‐tracking algorithm to identify tropical cyclones that impacted Northeast North America and Europe in seven global reanalysis data sets, distinguishing systems that retained warm‐core structures or underwent warm seclusion from those that underwent extratropical transition, acquiring cold‐core, frontal structures. Over the last four decades, ∼25% and ∼10% of tropical‐origin cyclones made landfall across Northeast North America and Europe, respectively, as warm‐core systems, with, on average, higher wind speeds than cold‐core systems. Historical warm‐core and cold‐core landfalls also exhibit distinct tracks, likely responding to differing steering flow and midlatitude conditions.

Estimation of Hurricane Intensity from ATMS-Derived Temperature Anomaly using Machine Learning

The warm-core structure is one of the basic characteristics that vary during the different stages of tropical cyclones (TCs). The warm core structure of the TCs during2016-2019 over the Atlantic Ocean was derived based on the observations of the ATMS onboard S-NPP. From linear regression, the mean prediction error (MPE) is 39.04 mph for Vmax and 14.47 hPa for Pmin. The root-mean-square error(RMSE) is 42.70 mph for the maximum sustained wind (Vmax) and 77.69 hPa for the minimum sea-level pressure (Pmin). Several machine learning (ML) techniques are used to develop the Atlantic TC intensity (Vmax and Pmin) estimation models. The support vector machine (SVM) model has the best performance with the MPE of 14.62 mph for Vmaxan 7.66 hPa for Pmin, and the RMSE of 19.91 mph for Vmax and 10.58 hPa for Pmin. Adding latitude and day of year (DOY) can further improve the estimation of Vmax by decreasing MPE to 13.01mph and RME to 17.33 mph using SVM. Best estimation of Pminoccurs when adding the day of year to the training process, as the MPE is 7.23 hPa and RMS is 9.88 hPa. Other TC information, such as longitude and local time, does not help to improve the performance of the hurricane intensity estimation models significantly.

PRECIPITATION AND LATENT HEATING PROPERTIES OF TROPICAL CYCLONE IN THE NORTHWEST PACIFIC MEASURED BY GPM DPR AND HIMAWARI-8

Abstract. Using observations from the GPM Tropical Cyclone Overpass Dataset and Himawari-8, this study statistically analyses the tropical cyclones (above Typhoon categories) in the Northwest Pacific during the tropical cyclone (TC) frequent period (from May to October) of 2014–2018. Moreover, a case (Super Typhoon “Mangkhut”) was analysed in detail. This study uses a semi-manual method to identify three life cycle stages of tropical cyclones: developing stage, mature stage, and dissipating stage. The statistical results show that the distribution of precipitation and latent heat varies with positions and the tropical cyclone has the maximum precipitation (11.62 mm/h) at the mature stage along with the maximum convection ratio (22.97%) at the developing stage. It is most obvious that the release of latent heat in the upper cloud at developing stage and in the lower cloud at mature stage. The latent heat profile of convective precipitation presents a “bottom-heavy” structural, and the stratiform precipitation has a “top-heavy” latent heat profile. The proportion of stratiform precipitation to total precipitation (74.31%) is the largest, but the average precipitation of the stratiform (4.12 mm/h) is lower than the average precipitation of convective clouds (10.55 mm/h). The average particle radius of the stratiform precipitation is 1.13 mm, while the average precipitation particle radius of the convective cloud precipitation is 1.79 mm. Based on these statistical results, this paper briefly analyses the characteristics of cloud precipitation microphysical mechanisms in three life cycle stages. Besides, the latent heating profile distribution found in this study are related to the vertical variation of precipitation rate, which are different in terms of the type of precipitation cloud.

Mesoscale convective systems in association with tropical cyclones over Bay of Bengal

The early stages of tropical cyclones (TCs) are extremely complex, and their understanding presents a challenge to researchers worldwide. Better understanding of the role of mesoscale convective systems (MCS) in the formative stage of TC will increase the ability to predict their characteristics including intensification and movement. Objective of the study is to analyze the interaction of multiple mesoscale structures during different stages of TC. In this study, Kalpana-1 half-hourly satellite infrared imageries are used to observe the interaction between MCSs and their environment. Average areas of MCS are calculated based on different cloud top temperatures (CTTs) viz −30, −50, −70 °C and also for different stages of TC based on five TCs during 2010–2012. The analysis has been carried out with respect to variations of (1) number of clusters, (2) distance between the clusters, (3) average distance of clusters from the center of the TC, and (4) area of clusters with respect to intensity (T number) of TC. Results indicate that merger of mesoscale convective vortices is a common precursor event during TC genesis. The average distances between clusters almost remain same during genesis and growing phase, and it gradually decreases during mature phase of TC. Further, there is decrease in the average distance of cloud clusters from the center of TC with respect to increase in intensity up to 2.5–3.5 after that the distance decreases with increase in intensity as the cloud pattern changes to central dense overcast or eye pattern. The average areas of the clusters associated the cyclonic disturbances increases from genesis phase till the intensity reaches T3.0; thereafter, it decreases gradually with increase in intensity. The number of clusters, the distances between them and their average distances from the center of the disturbance, and the total area of clusters show diurnal variations which is more significant during initial stage of formation. The study will be helpful in better understanding of physical processes in diurnal variations of convection and relation between convection and intensity of the storm.

The Prediction of Northern Hemisphere Tropical Cyclone Extended Life Cycles by the ECMWF Ensemble and Deterministic Prediction Systems. Part I: Tropical Cyclone Stage*

Abstract This study has explored the prediction errors of tropical cyclones (TCs) in the European Centre for Medium-Range Weather Forecasts (ECMWF) Ensemble Prediction System (EPS) for the Northern Hemisphere summer period for five recent years. Results for the EPS are contrasted with those for the higher-resolution deterministic forecasts. Various metrics of location and intensity errors are considered and contrasted for verification based on IBTrACS and the numerical weather prediction (NWP) analysis (NWPa). Motivated by the aim of exploring extended TC life cycles, location and intensity measures are introduced based on lower-tropospheric vorticity, which is contrasted with traditional verification metrics. Results show that location errors are almost identical when verified against IBTrACS or the NWPa. However, intensity in the form of the mean sea level pressure (MSLP) minima and 10-m wind speed maxima is significantly underpredicted relative to IBTrACS. Using the NWPa for verification results in much better consistency between the different intensity error metrics and indicates that the lower-tropospheric vorticity provides a good indication of vortex strength, with error results showing similar relationships to those based on MSLP and 10-m wind speeds for the different forecast types. The interannual variation in forecast errors are discussed in relation to changes in the forecast and NWPa system and variations in forecast errors between different ocean basins are discussed in terms of the propagation characteristics of the TCs.

Water Vapor Budget in a Developing Tropical Cyclone and Its Implication for Tropical Cyclone Formation

Abstract Evolution of the water vapor budget from the tropical wave stage to the tropical cyclone stage is examined using a high-resolution numerical model simulation. The focus is on a time window from 27 h prior to genesis to 9 h after genesis, and the diagnoses are carried out in the framework of the marsupial paradigm. Analysis shows that the vertically integrated inward moisture flux accounts for a majority of the total condensation and that its fractional contribution increases from the tropical wave stage to the tropical cyclone stage. The fractional contribution of the local evaporation is much smaller and decreases from the tropical wave stage to the tropical cyclone stage. It is also shown that the radial moisture flux above 850 hPa is rather weak prior to genesis but increases significantly after genesis because of the deepening of the inflow layer. The decrease in the fractional contribution of the local evaporation, or the increase in the fractional contribution of the vertically integrated inward moisture flux, is due to the strengthening of the low-level convergence associated with the secondary circulation. The intensification of the secondary circulation can be attributed to the organized convection and concentrated diabatic heating near the circulation center. The results suggest that the local evaporation and its positive interaction with the primary circulation may not be as important as generally appreciated for tropical cyclone development. By contrast, the increase in the fractional contribution by the inward moisture flux with the storm intensification implies the importance of the positive feedback among the primary circulation, the secondary circulation, and convection for tropical cyclone development.

Characteristics of Convective Processes and Vertical Vorticity from the Tropical Wave to Tropical Cyclone Stage in a High-Resolution Numerical Model Simulation of Tropical Cyclone Fay (2008)

Abstract The statistics of convective processes and vertical vorticity from the tropical wave to tropical cyclone stage are examined in a high-resolution simulation of Tropical Cyclone Fay (2008). The intensity of vertical velocity follows approximately the truncated lognormal distribution in the model simulation, which is consistent with previous observational studies. The upward motion at the pregenesis stage is weaker compared to mature hurricanes or midlatitude thunderstorms. The relatively strong upward velocities occupying a small areal fraction make a substantial contribution to the upward mass and moisture fluxes and condensation. It is also found that upward motion and downward motion both intensify with time, but the former is stronger than the latter, and the mean vertical motion and the mean vertical mass flux thus increase with time. By contrast, the maximum anticyclonic vorticity is comparable to the maximum cyclonic vorticity in magnitude. Both cyclonic vorticity and anticyclonic vorticity intensify with time, but the former covers a larger areal fraction in the lower and middle troposphere and becomes dominant throughout the troposphere after genesis. Sensitivity tests with different model resolutions were carried out to test the robustness of the results. When the horizontal grid spacing is reduced, the size of updrafts decreases and the number of updrafts increases, but the areal fraction of updrafts, the mean vertical velocity, and the mean vertical mass flux are rather insensitive to the model resolution, especially in the lower troposphere and when the model resolution is 1 km or higher. This may explain why models with relatively coarse resolution can simulate tropical cyclogenesis reasonably well.

Spatial distributions of tropical cyclones and gravity anomalies

Spatial distributions of the beginnings and most intense stages of tropical cyclones (TCs) in the northwestern part of the Pacific Ocean are compared with gravity anomalies (GAs) in the zone of action of cyclones. The possible influence of GAs on hurricanes that reached land in the Gulf of Mexico region and in the southeastern part of China is considered. The relation of the formal feedback between some characteristics of the intensity of TCs and spatially averaged GAs is shown. It is suggested that GAs can be regarded as a factor affecting the life cycle of a TC to a certain extent.

Prediction of Tropical Cyclogenesis Using Scatterometer Data

In the present work, a new technique based on the data mining approach has been discussed for the prediction of tropical cyclogenesis using the ocean wind vectors derived from the sea-winds scatterometer on QuikScat satellite. The technique is based on similarity of given wind pattern with wind vector signatures of developing systems, available from the past observations. A database has been formed in this work using the QuikScat-observed vector wind patterns associated with the early stages of tropical cyclones that developed in the North Indian basin during the years 2000-2008. The prediction of possibility of cyclogenesis, in a given scene, is determined by matching it with all the archived scenes in a database using vector block matching algorithm. The system is predicted as developing, if its matching index exceeds the predetermined threshold value (0.5). The prediction of cyclo genesis can be made 24-96 h prior to its classification as a tropical storm by the Joint Typhoon Warning Centre. The probability of detection of the technique is determined using the equivalent of the Jackknife approach in the database as 0.93. The algorithm is tested with a continuous wind data of years 2007-2009 for active cyclone months (excluding the scenes archived in a database). All the 14 tropical disturbances that developed into tropical storms during the test period were predicted using the discussed method, and two false alarms were found.

Indications of the influence of the force of gravity on tropical cyclones in the northwestern part of the Pacific Ocean

Peculiarities of the spatial distribution of the begin� nings and the most intense stages of tropical cyclones in the northwestern part of the Pacific Ocean are dem� onstrated in this paper in comparison with the values of the gravity force anomalies in the cyclone zone. Relations are distinguished in which some group char� acteristics of the tropical cyclones and the spatially average values of the gravity force anomalies are for� mally inversely related. On the basis of these results, the supposition that gravity force anomalies can to some extent influence the cyclonic regime in the study region is put forward. The author is not familiar with any special empiri� cal (detailed) investigations on the role of gravity force anomalies (GFAs) in the life of tropical cyclones. It is likely that in monographs [1, 2] the influence of the GFAs on the hydrometeorological processes is investi� gated for the first time. There are also sections dedi� cated to tropical cyclones. Here, the tropical cyclones are only one of the phenomena that illustrate the validity of the ideas and research methods described in the monographs. Therefore, only general words are said about the influence of the GFAs. Publication [3] is also dedicated to research into gravity force anoma� lies. However, here, as well as in the previous publica� tions of this author, the role of the GFA is predomi� nantly studied in the Antarctic region. Quite large ter� ritories are considered, and only general estimates of the GFA level are given for the entire territory. This approach to estimates of the influence of GFAs is cor� rect in the analysis of extratropical cyclones, taking into account their size. The sizes of the tropical cyclones are significantly

Reevaluating the Role of the Saharan Air Layer in Atlantic Tropical Cyclogenesis and Evolution

Abstract The existence of the Saharan air layer (SAL), a layer of warm, dry, dusty air frequently present over the tropical Atlantic Ocean, has long been appreciated. The nature of its impacts on hurricanes remains unclear, with some researchers arguing that the SAL amplifies hurricane development and with others arguing that it inhibits it. The potential negative impacts of the SAL include 1) vertical wind shear associated with the African easterly jet; 2) warm air aloft, which increases thermodynamic stability at the base of the SAL; and 3) dry air, which produces cold downdrafts. Multiple NASA satellite datasets and NCEP global analyses are used to characterize the SAL’s properties and evolution in relation to tropical cyclones and to evaluate these potential negative influences. The SAL is shown to occur in a large-scale environment that is already characteristically dry as a result of large-scale subsidence. Strong surface heating and deep dry convective mixing enhance the dryness at low levels (primarily below ∼700 hPa), but moisten the air at midlevels. Therefore, mid- to-upper-level dryness is not generally a defining characteristic of the SAL, but is instead often a signature of subsidence. The results further show that storms generally form on the southern side of the jet, where the background cyclonic vorticity is high. Based upon its depiction in NCEP Global Forecast System meteorological analyses, the jet often helps to form the northern side of the storms and is present to equal extents for both strengthening and weakening storms, suggesting that jet-induced vertical wind shear may not be a frequent negative influence. Warm SAL air is confined to regions north of the jet and generally does not impact the tropical cyclone precipitation south of the jet. Composite analyses of the early stages of tropical cyclones occurring in association with the SAL support the inferences from the individual cases noted above. Furthermore, separate composites for strongly strengthening and for weakening storms show few substantial differences in the SAL characteristics between these two groups, suggesting that the SAL is not a determinant of whether a storm will intensify or weaken in the days after formation. Key differences between these cases are found mainly at upper levels where the flow over strengthening storms allows for an expansive outflow and produces little vertical shear, while for weakening storms, the shear is stronger and the outflow is significantly constrained.

Raindrop Size Distribution Measurements in Tropical Cyclones

Abstract Characteristics of the raindrop size distribution in seven tropical cyclones have been studied through impact-type disdrometer measurements at three different sites during the 2004–06 Atlantic hurricane seasons. One of the cyclones has been observed at two different sites. High concentrations of small and/or midsize drops were observed in the presence or absence of large drops. Even in the presence of large drops, the maximum drop diameter rarely exceeded 4 mm. These characteristics of raindrop size distribution were observed in all stages of tropical cyclones, unless the storm was in the extratropical stage where the tropical cyclone and a midlatitude frontal system had merged. The presence of relatively high concentrations of large drops in extratropical cyclones resembled the size distribution in continental thunderstorms. The integral rain parameters of drop concentration, liquid water content, and rain rate at fixed reflectivity were therefore lower in extratropical cyclones than in tropical cyclones. In tropical cyclones, at a disdrometer-calculated reflectivity of 40 dBZ, the number concentration was 700 ± 100 drops m−3, while the liquid water content and rain rate were 0.90 ± 0.05 g m−3 and 18.5 ± 0.5 mm h−1, respectively. The mean mass diameter, on the other hand, was 1.67 ± 0.3 mm. The comparison of raindrop size distributions between Atlantic tropical cyclones and storms that occurred in the central tropical Pacific island of Roi-Namur revealed that the number density is slightly shifted toward smaller drops, resulting in higher-integral rain parameters and lower mean mass and maximum drop diameters at the latter site. Considering parameterization of the raindrop size distribution in tropical cyclones, characteristics of the normalized gamma distribution parameters were examined with respect to reflectivity. The mean mass diameter increased rapidly with reflectivity, while the normalized intercept parameter had an increasing trend with reflectivity. The shape parameter, on the other hand, decreased in a reflectivity range from 10 to 20 dBZ and remained steady at higher reflectivities. Considering the repeatability of the characteristics of the raindrop size distribution, a second impact disdrometer that was located 5.3 km away from the primary site in Wallops Island, Virginia, had similar size spectra in selected tropical cyclones.

A View on Tropical Cyclones as CISK

The author's view on tropical cyclones as the conditional instability of the second kind (CISK) is presented. Many theoretical and numerical studies of tropical cyclones have discussed the original CISK of Ooyama (1964, 1969) and Charney and Eliassen (1964) in which frictional convergence plays an important role. In this paper, the author emphasizes that this CISK is applied primarily to the eyewall circulation in intense tropical cyclones, and describes other types of CISK, which are appropriate to explain many of tropical disturbances and tropical depressions, and the formation and early development stages of tropical cyclones. In addition, the importance of resolving mesoscale organized convection in coarse-resolution numerical models is emphasized.

A Simplified System of Equations for Simulation of Tropical Cyclones

Abstract A simplified system of equations which can simulate the development and mature stages of tropical cyclones is presented. The model is similar to that presented by Ooyama, except that the assumption of incompressible fluid layers is relaxed. Instead, the governing equations for a compressible fluid in isentropic coordinates are discretized vertically by considering three fluid layers with constant potential temperature. This makes the inclusion of thermodynamic processes more straightforward. The governing equations in the adiabatic case are mathematically equivalent to the equations used by Ooyama, except with an extra term in the pressure gradient force. The model equations are solved using a spectral method where the basis functions are the normal modes of the linearized equations. Numerical simulations show that the model sensitivity to vertical stability, sea surface temperature and midlevel moisture are similar to results from more general models. The sensitivity to these factors can be expl...

Intensification Criteria for Tropical Depressions of the Western North Atlantic

Abstract A five-year study for the period 1968–72 evaluated several of the factors which have been generally considered favorable for the development of a tropical depression into a tropical storm or hurricane. The study area considered all depressions in the western North Atlantic south of latitude 35°N and west of longitude 55°W. The individual and cumulative importance of these factors as criteria for assessing the potential for development of a tropical depression into a tropical storm within 24 h is discussed. The results of the study have led to modifications of the criteria for operational use at the National Hurricane Center (NHC). The criteria currently used at NHC are presented together with a brief discussion of plans to obtain objectively a quantitative development potential index for all intensity stages of tropical cyclones.