Assessing the representation of tropical cyclones in ERA5 with the CNRM tracker

Dulac, William ; Cattiaux, Julien ; Chauvin, Fabrice ; Bourdin, Stella ; Fromang, Sébastien

Année de publication
2023
Résumé
<p align=justify>The ERA5 dataset from the European Center for Medium-Range Weather Foreceasts is the first global reanalysis to reach a horizontal resolution of 31 km and thus provides a unique opportunity to look at tropical cyclones (TC), and in particular at the 3D fields associated with observed TCs. To that end, a specifically calibrated TC tracking scheme is applied on ERA5 along with a track pairing algorithm to match the detected tracks with the IBTrACS catalog in order to investigate how well TCs are represented in the reanalysis. After tuning of the tracking scheme and the application of a dynamic mid-latitude system filtering technique, it is shown that the majority of IBTrACS TCs are detected in ERA5 and that the amount of false alarms is kept reasonably low in most regions. By comparing detected tracks with their IBTrACS counterparts, it is found that TC intensity is still strongly underestimated in ERA5 but that the minimum sea-level pressure distribution is better represented than maximum wind speed. The comparison between the life cycles from both datasets highlights key differences between ERA5 and the best-track catalog, showing in particular that the delay with which TCs from ERA5 reach their peak intensity compared to IBTrACS increases significantly with real TC intensity increase. Finally, the internal structure of TCs in the reanalysis for each intensity class are analyzed and reveal distinct intensification patterns up to Category 3.</p>
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