A Comparison of Moderate and Extreme ERA‐5 Daily Precipitation With Two Observational Data Sets

A comparison of moderate to extreme daily precipitation from the ERA-5 reanalysis by the European Centre for Medium-Range Weather Forecasts against two observational gridded data sets, EOBS and CMORPH, is presented. We assess the co-occurrence of precipitation days and compare the full precipitation distributions. The co-occurrence is quantified by the hit rate. An extended generalized Pareto distribution (EGPD) is fitted to the positive precipitation distribution at every grid point and confidence intervals of quantiles compared. The Kullback–Leibler divergence is used to quantify the distance between the entire EGPDs obtained from ERA-5 and the observations. For days exceeding the local 90th percentile, the mean hit rate is 65% between ERA-5 and EOBS (over Europe) and 60% between ERA-5 and CMORPH (globally). Generally, we find a decrease of the co-occurrence with increasing precipitation intensity. The agreement between ERA-5 and EOBS is weaker over the southern Mediterranean region and Iceland compared to the rest of Europe. Differences between ERA-5 and CMORPH are smallest over the oceans. Differences are largest over NW America, Central Asia, and land areas between 15°S and 15°N. The confidence intervals on quantiles are overlapping between ERA-5 and the observational data sets for more than 80% of the grid points on average. The intensity comparisons indicate an excellent agreement between ERA-5 and EOBS over Germany, Ireland, Sweden, and Finland, and a disagreement over areas where EOBS uses sparse input stations. ERA-5 and CMORPH precipitation intensity agree well over the midlatitudes and disagree over the tropics

Extreme tropical cyclone activities in the southern Pacific Ocean

International audienceABSTRACT This research concerning the South Pacific Ocean shows the 10‐year and interannual variability of extreme cyclones (categories 4 and 5). The intensity of these cyclones has been reanalysed on the basis of GMS, GOES and NOAA satellite images with the Dvorak technique. In the period 1980–2016, 63 cyclones reached categories 4 and 5. During the decade 1980–1989, the intensity of cyclones of at least 115 knots over 1 min (100 knots over 10 min used by the meteorological centres in the South Pacific) was underestimated: we found 19 such cyclones, as opposed to 11 in IBTrACS, and 6 in the SPEArTC and in the Joint Typhoon Warning Center (JTWC) databases. Between 1980 and 2016, the number of extreme cyclones did not show any tendency to increase. The 1983 season was the most active, with six cyclones of categories 4 and 5 that do not figure in the JTWC database for the South Pacific. Only one intense cyclone has been reported in the SPEArTC and five cyclones in IBTrACS in 1983. El Niño episodes concurred with a much higher number of cyclones of at least 115 knots than La Niña episodes. More than half of the category 5 (at least 140 knots) cyclones were observed during El Niño years. The South Pacific Ocean is the theatre of very intense cyclones, comparable to those in the western or eastern North Pacific. Thus, by reanalysing satellite images, an intensity of 170 knots was attributed to cyclone Hina (March 1985), which was probably one of the strongest in the southern hemisphere since 1980