Читать книгу Congo Basin Hydrology, Climate, and Biogeochemistry - Группа авторов - Страница 60

In Figure 4.4, we make an intercomparison of the climatology of seasonal precipitation from the different experiments carried out and the observational data (ARC2 and GPCP) for the period from 2001 to 2006. Observations (Figure 4.4 a–h) show that bands of high rainfall (11–12 mm/day) are visible in all seasons. The alternation of dry and wet seasons is well represented. We observe a spatial difference between the observed data (Figure 4.5 a–d); this difference can be interpreted as the uncertainties (errors) in the production of these data (Nikulin et al., 2012). Although some biases persist, the RegCM experiments (Figure 4.5 i–p) reproduce the rainfall patterns in the study area fairly well according to observations during all seasons. The experiments carried out successfully capture the positions of the observed rainfall maxima, but fail to represent their amplitudes. We note that both experiments tend to underestimate (up to 5 mm/day) the rainfall band observed on the continent, except in mountainous regions and across the oceans where the opposite effect is observed; this difference could be attributed to a thermal breeze, surface parameterization, and the Foehn effect. Despite the large biases obtained in the two RegCM simulation experiments, those of the slab‐ocean experiments seem to be significantly reduced or cancelled in the Indian Ocean compared to the Atlantic Ocean (Figure 4.5 e–p). This implies that contrary to the majority of the RCMs used in Nikulin et al. (2012), which systematically overestimate rainfall over the Indian Ocean, the atmosphere–ocean interactions integrated into this study take into account the dynamics that govern the climate in the Indian Ocean.

Figure 4.4 Seasonal means of rainfall in mm/day for the period 2001–2006: GPCP (a–d), ARC2 (e–h), GFC_CTR (i–l), GFC_SLAB (m–p).

Figure 4.5 Seasonal mean biases of precipitation in mm/day for the period 2001–2006: ARC2 ‐ GPCP (a–d), GFC_SLAB ‐ GPCP (e–h), GFC_CTR ‐ GPCP (i–l), GFC_SLAB ‐ GFC_CTR (m–p).