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The choice of a 50 ms-1 cut off is an arbitrary one, which could miss spurious values that are less than 50 ms-1. It is also possible , that this cut off point could penalise realistic winds, such as in hurricanes. However, given the spatial resolution of ERA5 data, it is thought that in general, 10m wind components higher than 50 ms-1 are not realistic for this resolution, even if the observed magnitude is higher - this has been seen in the case of a hurricane , as is the case for Hurricane Ivan in the Caribbean on 12 September 2004 at 20 UTC, when the . This case is illustrated in Fig. 1, below, where the the analysed winds are compared with the 4v winds. The minimum value of the analysed 10 metre V wind component was components is -53 ms-1, see Table 2, below.
(see Table 2) whilst the minimum value of the 4v 10 metre V wind components is -29 ms-1. Even though the analysed wind speeds are not as large as the observed ones (the estimated peak wind speeds for Ivan were of order 70 ms-1), the 4v winds are thought to give a more realistic representation of the winds, for this resolution.
| Fig. 1a | Fig. 1b |
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| Fig. 1a. The analysed 10m winds for 12 September 2004, 20 UTC, featuring Hurricane Ivan. The regional plot domain is centred on the Caribbean. | Fig. 1b. As Fig 1a, but for the 4v 10m winds. |
For dates before this system check was introduced into ERA5 (i.e. for the period The tables below, for January 1979 to 18 February 2020), the two tables below give details when the 10m wind components (the 10 metre U wind component and 10 metre V wind component) exceed 50 ms-1.
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