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Description of empirical scaling factors applied as part of the model e.g. scaling factors to derive short-term exceedance statistics from long-term means.
The AQSR adopts data quality objectives (DQOs) for modelling uncertainty set by the AQD, within supplementary assessment under the AQD. The AQSR adopts DQOs in terms of uncertainty set by the AQDD4, which acts as a guide for quality assurance programmes when identifying an acceptable level of uncertainty for assessment methods appropriate for supplementary assessment under the AQDD4. Uncertainty is defined in the AQD as the maximum deviation of the measured and calculated concentration levels for 90% of individual monitoring points over the period considered by the limit value (or target value), without taking into account the timing of events. The uncertainty of modelling should be interpreted as applicable in the region of the appropriate LV or TV. The fixed measurements that have been selected for comparison with the modelling results should be representative of the scale covered by the model. Final guidance clarifying the recommended methods for assessing model performance with respect to the DQOs has yet to be agreed. The comparisons with monitoring data presented in https://uk-air.defra.gov.uk/library/reports?report_id=1086 have therefore included data from all sites including those with measured values not in the vicinity of the LVs or TVs and a highly detailed assessment of the spatial representativity of the sites has not been carried out.