GIST-PM-Asia v1: development of a numerical system to improve particulatematter forecasts in South Korea using geostationary satellite-retrievedaerosol optical data over Northeast Asia

摘要

To improve short-term particulate matter (PM) forecasts in South Korea, theinitial distribution of PM composition, particularly over the upwind regions,is primarily important. To prepare the initial PM composition, the aerosoloptical depth (AOD) data retrieved from a geostationary equatorial orbit(GEO) satellite sensor, GOCI (Geostationary Ocean Color Imager) which coversa part of Northeast Asia (113–146°?E; 25–47°?N), were used.Although GOCI can provide a higher number of AOD data in a semicontinuousmanner than low Earth orbit (LEO) satellite sensors, it still has a seriouslimitation in that the AOD data are not available at cloud pixels and overhigh-reflectance areas, such as desert and snow-covered regions. To overcomethis limitation, a spatiotemporal-kriging (STK) method was used to betterprepare the initial AOD distributions that were converted into the PMcomposition over Northeast Asia. One of the largest advantages in using theSTK method in this study is that more observed AOD data can be used toprepare the best initial AOD fields compared with other methods that usesingle frame of observation data around the time of initialization. It isdemonstrated in this study that the short-term PM forecast system developedwith the application of the STK method can greatly improve PM₁₀predictions in the Seoul metropolitan area (SMA) when evaluated withground-based observations. For example, errors and biases of PM₁₀predictions decreased by ?～??60 and ?～??70 %, respectively, duringthe first 6?h of short-term PM forecasting, compared with those without theinitial PM composition. In addition, the influences of several factors on theperformances of the short-term PM forecast were explored in this study. Theinfluences of the choices of the control variables on the PM chemicalcomposition were also investigated with the composition data measured viaPILS-IC (particle-into-liquid sampler coupled with ion chromatography) and low air-volume sample instruments at a site near Seoul. Toimprove the overall performances of the short-term PM forecast system,several future research directions were also discussed and suggested.