Читать книгу Congo Basin Hydrology, Climate, and Biogeochemistry - Группа авторов - Страница 57

Evaluation of the performance of regional climate models is based on the unidirectional nesting technique, which requires prior reduction of errors that can be inherited from lateral forcing conditions (Giorgi & Mearns, 1999), i.e., GCMs (global circulation models). For this reason, conditions with so‐called quasi‐perfect limits and approximately similar observations are used. The following data were used to run the model: ERA‐Interim 1.5 gridded data set (Uppala et al., 2005), with a temporal resolution of 6 h (0000, 0600, 1200, and 1200 UTC). Here, the variables used are air temperature, geopotential height, relative humidity, and a horizontal wind component. The SST is taken from the weekly optimal interpolation SST from the National Administration of the model grid (Reynolds et al., 2002). For the global terrain and land use, we have used the 2‐min resolution global land cover characteristics (GLCC; Loveland et al., 2000) and GTOPO topography data. These data were initialized on 1 January 2000, with parameters such as air temperature, geopotential height, relative humidity, and wind components.

One of the main problems in assessing the performance of RCMs in Central Africa is the lack of high‐quality observation databases at appropriate spatial and temporal resolution. The use of different sources of observational data (in‐situ and satellite), and reanalyses of rainfall, temperature, and wind make it possible to take into account the uncertainties associated with them in Africa (Nikulin et al., 2012). To facilitate the intercomparison between observations and models, we interpolated the data on the model grid. Simulations of precipitation, temperature, and wind are compared with the monthly climatology of the data from: (i) Africa Rainfall Climatology version 2.0 (ARC2; resolution 0.1° × 0.1°; Novella & Thiaw, 2013); (ii) Global Precipitation Climatology Project (GPCP; resolution 0.5° × 0.5°; Huffman et al., 1997); (iii) Climatic Research Unit (CRU; resolution 0.5° × 0.5°; Harris et al., 2013); and (iv) the fifth‐generation European Centre for Medium‐Range Weather Forecasts (ECMWF), reanalysis 0.75° × 0.75° (ERA5). Compared to its predecessor ERA‐Interim, ERA5 offers a higher spatiotemporal resolution and an improvement of the atmospheric model and data assimilation processes (Hersbach et al., 2020).