Publication Date:
2016-12-23
Description:
We explore uncertainties in observed daily precipitation extremes over the terrestrial tropics and subtropics (50°S – 50°N) based on five commonly used products; CHIRPS, GPCC-FDD, T3B42, PERSIANN-CDR and GPCP-1DD. We use the precipitation indices R10mm and Rx1day, developed by the Expert Team on Climate Change Detection and Indices, to explore the behavior of ‘moderate’ and ‘extreme’ extremes, respectively. In order to assess the sensitivity of extreme precipitation to different grid sizes we perform our calculations on four common spatial resolutions (0.25°x0.25°, 1°x1°, 2.5°x2.5° and 3.75°x2.5°). The impact of the chosen ‘order of operation’ in calculating these indices is also determined. Our results show that moderate extremes are relatively insensitive to product and resolution choice while extreme extremes can be very sensitive. For example, at 0.25°x0.25° quasi-global mean Rx1day values vary from 37 mm in PERSIANN-CDR to 62 mm in T3B42. We find that the inter-product spread becomes prominent at resolutions of 1°x1° and finer, thus establishing a minimum effective resolution at which observational products agree. Without improvements in inter-product spread, these exceedingly large observational uncertainties at high spatial resolution may limit the usefulness of model evaluations. As has been found previously, resolution sensitivity can be largely eliminated by applying an order of operation where indices are calculated prior to regridding. However, this approach is not appropriate when true area averages are desired (e.g. for model evaluations).
Print ISSN:
0148-0227
Topics:
Geosciences
,
Physics
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