Correcting Rules for Xian Urban Air Quality Forecasts with Empirical Mode Decomposition
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Abstract:
The daily average concentrations of PM10，SO2，NO2 and meteorological factors (precipitation and wind) of the corresponding time from 2001 to 2007 in Xi’an, Shaanxi Province, are analyzed with Empirical Mode Decomposition (EMD). The periods are tested and the variance contribution rates are calculated of each intrinsic mode function (IMF) by the maximum entropy spectral analysis as well, for improving the accuracy rate of the urban air quality forecast system (CAPPS2) and instituting the correcting rules for the numerical forecast model. The results show: the main period of PM10 concentration fluctuation is about a week, has clear weekendeffect, and matches well with major scavenging process, but the concentration fluctuations of SO2 and NO2 do not synchronize the scavenging processes, suggesting that the pollution of Xi’an is emissionguided, and the correction rules based on the weekendeffect are ideal for the improvement of PM10 and SO2 numerical forecast results, and uncertain for NO2.
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Supported by:Beijing E-Tiller Technology Development Co., Ltd.
Supported by:Beijing E-Tiller Technology Development Co., Ltd.