The influence of Siberian forest fires on carbon monoxide concentrations at Happo, Japan

Surface CO and ozone data were obtained in 1998 at Happo (36.7degreesN. 137.8degreesE, altitude 1840 in) in Japan. Backward trajectory analysis was applied to get the origin of the air mass to the measuring site. The air mass is basically coming from the west over the Asian continent except during summer. A maritime air mass prevails in the summertime, due to a dominant high-pressure system in the Pacific. In most cases, the air mass from the west (from China and Korea) shows a higher CO concentration than the air mass from the north, and the air mass from the Pacific shows the lowest CO concentration, Forest fires in Siberia were highly enhanced in 1998. To assess the influence of these forest fires, air masses from Siberia (from the North/Northwest direction) are divided into two categories: those that passed over the forest-fire region in Siberia and those that did not. This is done using AVHRR/NOAA satellite data and isentropic backward trajectories. The average CO concentration difference between these two categories is about 30ppbv in May. Similar analysis for ozone data also shows concentrations about 7 ppbv higher for the air masses that passed over the forest-fire region in Siberia. These results suggest that air pollutants emitted by forest fires in Siberia in 1998 could be transported and influence the air at Happo in springtime. (C) 2002 Elsevier Science Ltd. All rights reserved.