A database for the outer sizes of tropical cyclones over the Middle Americas

Published: 9 July 2024| Version 1 | DOI: 10.17632/5bpzbwhynd.1
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Description

Tropical cyclones (TCs) are catastrophic phenomena and represent a constant threat to populations settled in the tropics. We analyzed 191 and 336 TCs over the North Atlantic (NA) and the Eastern North Pacific (EP) basins, respectively, during the 2000-2020 period. This database also provides the TC location, TC outer sizes defined by the two algorithms, and TC spatial metrics every 6 hours. This dataset is in a tabulate-delimited text format with six-hourly information on the location, maximum winds, central pressure, and size of TCs over the NA and EP. This dataset format is based on the format provided by HURDAT2 and by the TC outer size data. Our dataset considers: 1) inclusion of non-synoptic best track times (other than 00, 06, 12, and 18Z) (mainly to indicate landfall and intensity maximum); 2) inclusion of non-developing tropical depressions; and 3) inclusion of precipitation radii. The TC tracks are obtained from HURDAT2. Sizes are presented both by quadrant oriented for the cardinal points (NNE, NNW, SSW, and SSE) in kilometers (km). The shape metrics: asymmetry (A), solidity (S), and dispersion (D). The information comes in this format: EP132006, LANE, 17, EP132006: TC code LANE: TC name 17: Number of entries of this TC in our dataset In lines like this: 20120704 0600 12.1 -105.3 55 1006 354.91 552.39 645.30 817.04 592.41 0.57 0.24 0.13 144.14 44.53 141.00 899.99 307.42 20120704 : date (YYMMDD). 0600 : hour (hhmm). 12.1 : TC center latitude (Positive: North Hemisphere, Negative: South Hemisphere). -105.3 : TC center longitude (Negative: Western Hemisphere, Positive: Eastern Hemisphere). 55 : Maximum wind speed on surface average in one minute (knots). 1006 : Minimum sea level pressure (hPa). 354.91 : Maximum extent (in km) of the northeastern quadrant defined by ROCLOUD. 552.39 : Maximum extent (in km) of the northwestern quadrant defined by ROCLOUD. 645.30 : Maximum extent (in km) of the southwestern quadrant defined by ROCLOUD 817.04 : Maximum extent (in km) of the southeastern quadrant defined by ROCLOUD. 592.41 : Mean extent (in km) of the four quadrants defined by ROCLOUD. 0.57 : Asymmetry value that varies from 0 to 1. 0.24 : Dispersion value that varies from 0 to 1. 0.13 : Solidity value that varies from 0 to 1. 144.14 : Maximum extent (in km) of the northeastern quadrant defined by RBP. 44.53 : Maximum extent (in km) of the northwestern quadrant defined by RBP. 141.00 : Maximum extent (in km) of the southwestern quadrant defined by RBP. 899.99 : Maximum extent (in km) of the southeastern quadrant defined by RBP. 307.42 : Mean extent (in km) of the four quadrants defined by RBP. Missing data is denoted by -9999, as the satellite imagery is not constantly available.

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We developed the Radius of the Outermost CLOUD (ROCLOUD) algorithm. This technique is based on Phyton programming language and determines the outer TC size by combining wind field profile data and convective cluster locations. The ROCLOUD technique measures the distance between the TC center reported by HURDAT2 and the farthest convective cluster located inside the outer TC size obtained by PA21. The algorithm automatically carries out the following steps for each TC position: 1. IR images are segmented based on BTs < 233 K. The technique segments pixels or groups of pixels with similar characteristics inside the outer TC size obtained by PA21. 2. Cumulus polygons, which represent areas with intense TC precipitation, are determined when the IR images are greater than 50 pixels (~ 800 km2). 3. The cumulus polygons that intersect the outer TC size are selected to define the maximum extension from the TC center per quadrant. The quadrants are defined according to the TC displacement. 4. TCs that interact with the Intertropical Convergence Zone (ITCZ) are analyzed following these two steps: If the TC position is located in the latitudinal band 0°N-10°N, the cumulus clouds exceeding the outer TC size will not be considered for obtaining the maximum extent per quadrant. Therefore, we assume these cumulus clouds belong to the ITCZ. 5. If the TC position is located northwards 10°N and the outer TC size interacts with the ITCZ cloud band, the cumulus clouds that exceed the outer TC size limits will be discarded for calculating the maximum extent per quadrant. 6. The distance of the edged cumulus polygons from the TC center is determined for the four TC quadrants, which are expressed in kilometers (km) and degrees (°). 7. The mean radius is calculated as an average of the four quadrant radii. If a quadrant radius has no value, it is not considered for the average. The technique of Radius of Precipitation Bands (RPB) was developed as a modification of ROCLOUD. The RPB algorithm follows steps 1-5 of ROCLOUD, but it considers the IMERG rainfall data to define the maximum extension per quadrant of 2.5 mm/h. For more details, see the full paper on the database.

Institutions

Universidad Nacional Autonoma de Mexico

Categories

Climatology, Tropical Meteorology, Tropical Cyclone

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