Weather or not—Global climate databases: Reliable on tropical mountains?

Results Table 1 shows the calculated errors of the global climate data for all mountains studied. Perfor- mance is quite poor with a mean absolute error of 421 mm for WC and 407 mm for C. How- ever, the mean deviation of modelled and measured maximum MAP is drastic with 926 mm for WC and 825 mm for C. Performance is generally better in the foothills than on the moun- tain slopes. Fig 4 and Table 2 show the results of these comparisons for Kilimanjaro, where most of the data were available. On the southern slope, where most of the data come from (Fig 3), WC and C perform quite well in the lower ranges up to about 1700 m (in the case of WC) and about 1300 m (in the case of C), with a mean absolute error of 125 mm and 202 mm. Table 1. Metrics for a comparison between WorldClim (WC) and CHELSA (C) data and the measured data of mean annual precipitation (MAP) based on 170 ground stations. Meru (n = 4) Kili (n = 123) NP (n = 14) SP (n = 9) WU (n = 4) EU (n = 13) Ngu (n = 3) Foot (n = 15) Mount (n = 32) mae WC (mm) 643 467 159 237 240 358 554 155 372 pbias WC (%) 36 28 17 24 18 21 34 17 25 Deviation of max MAP WC (mm) 1182 1949 475 574 503 942 854 1182 mae C (mm) 318 467 265 265 153 190 421 119 310 pbias C (%) 17 31 24 25 13 11 23 14 22 Deviation of max MAP C (mm) 720 1811 658 680 374 777 757 777 mae = mean absolute error, pbias = percentage bias, Kili = Kilimanjaro, NP = North Pare, SP = South Pare, WU = West Usambara, EU = East Usambara, Ngu = Nguru,

Foot = Foothills without Kilimanjaro, Mount = Mountain areas without Kilimanjaro. As the maximum MAP only occurs in the higher mountain areas, no value is given for the foothills. https://doi.org/10.1371/journal.pone.0299363.t001 Fig 4. Comparison of measured MAP (red dots) and modelled values of WC and C (blue dots) for the southern and northern slope of Kilimanjaro separately. https://doi.org/10.1371/journal.pone.0299363.g004 PLOS ONE Global climate datasets on tropical mountains PLOS ONE | https://doi.org/10.1371/journal.pone.0299363 March 13, 2024 7 / 12