Regional center for northern africa, middle east and europe of the wmo sds-was
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Forecast evaluationThe forecasts of dust optical depth (DOD) are compared with the total aerosol optical depth (AOD) provided by the AERONET network for 42 selected dust-prone stations located in Northern Africa, Middle East and Southern Europe that are listed in Appendix A. Evaluation scores are computed in order to assess the performance of the median multi-model on a monthly, seasonal and annual basis. Since AERONET retrievals include the contribution of different types of particles, not only mineral dust, it is intended to restrict the comparison to situations in which dust is the dominant aerosol type. Threshold discrimination is made by discarding observations with an Ångström exponent 440-870 higher than 0.6 (Pérez et al., 2006). Although observations with an Ångström exponent 440-870 higher than 0.6 are discarded in order to restrict the evaluation to situations in which mineral dust is the dominant aerosol type, other particles are always present (anthropogenic aerosol, products from biomass burning, etc.). Therefore, negative bias can be expected. The evaluation system is applied to instantaneous forecast values of DOD ranging from the initial day (D) at 15:00 UTC to the following day (D+1) at 12:00 UTC. Rather than time-interpolated, AERONET observations are assigned to the nearest multiple-of-3 hour. In case more than one observation is assigned to the same hour, only the closest-in-time is considered. ResultsThe scores of the evaluation are presented in Tables 5, 6 and 7.
Table 5. Monthly scores for the median multi-model
Table 6. Seasonal scores for the median multi-model
Table 7. Annual scores for the median multi-model The evolution of the scores with time is shown in figures 2 to 5  
Figure 2. Monthly (left) and seasonal (right) mean bias of the median multi-model  
Figure 3. Monthly (left) and seasonal (right) root mean square error of the median multi-model Download 1.28 Mb. Share with your friends:
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