Systematic analysis of interannual and seasonal variations of model-simulated tropospheric NO2 in Asia and comparison with GOME-satellite data

[摘要] Systematic analyses of interannual and seasonal variations of troposphericNO₂ vertical column densities (VCDs) based on GOME satellite data andthe regional scale chemical transport model (CTM), Community Multi-scale AirQuality (CMAQ), are presented for the atmosphere over eastern Asia between1996 and June 2003. A newly developed year-by-year emission inventory (REAS)was used in CMAQ. The horizontal distribution of annual averaged GOMENO₂ VCDs generally agrees well with the CMAQ results. However,CMAQ/REAS results underestimate the GOME retrievals with factors of 2–4over polluted industrial regions such as Central East China (CEC), a majorpart of Korea, Hong Kong, and central and western Japan. The most probablereasons for the underestimation typically over the CEC are accuracy of thebasic energy statistic data, emission factors, and socio-economic data usedfor construction of emission inventory. For the Japan region, GOME and CMAQNO₂ data show reasonable agreement with respect to interannualvariation and show no clear increasing trend. For CEC, GOME and CMAQNO₂ data indicate a very rapid increasing trend from 2000. Analyses ofthe seasonal cycle of NO₂ VCDs show that GOME data have larger dipsthan CMAQ NO₂ during February–April and September–November.Sensitivity experiments with fixed emission intensity reveal that thedetection of emission trends from satellite in fall or winter has a largererror caused by the variability of meteorology. Examination during summertime and annual averaged NO₂ VCDs are robust with respect tovariability of meteorology and are therefore more suitable for analyses ofemission trends. Analysis of recent trends of annual emissions in Chinashows that the increasing trends of 1996–1998 and 2000–2002 for GOME andCMAQ/REAS show good agreement, but the rate of increase by GOME isapproximately 10–11% yr⁻¹ after 2000; it is slightly steeperthan CMAQ/REAS (8–9% yr⁻¹). The greatest difference wasapparent between the years 1998 and 2000: CMAQ/REAS only shows a fewpercentage points of increase, whereas GOME gives a greater than 8% yr⁻¹ increase. The exact reason remains unclear, but the most likelyexplanation is that the emission trend based on the Chinese emission relatedstatistics underestimates the rapid growth of emissions.

[学科分类] 大气科学