One case study for the aerosol layer originated from siberian forest fire during the latter days of May Kohei HONDA Atmospheric Environment Division Global Environment and Marine Department Japan Meteorological Agency

Appearances s From 22 to 24 in May 2003, the condition, that the sun was obscured in daytime and its color was likely red, was continued especially in the north part of JAPAN. SAPPORO RYORI Taken from Sapporo District Meteorological Observatory. The daylight was week even if there was almost no clouds in the sky. The color of the sun seems to be red rather than yellow.

This figure shows the time series of direct solar radiation during 22 from 24 May 2003, and the most clear condition in the whole observing periods. How much the sun light was reduced ? s At SAPPORO, the direct solar radiation of the sun was very lower than that of the common year, even if the sky was clear. s It is clear, that the direct solar radiation was reduced to about 30% at the minimum case.

Aerosol Optical depth and wavelength dependency s At RYORI, aerosol optical depth at 500nm derived from sun photometer was up to 10 times than usual. s The Ångstrome exponent was about 1.3. The particle size is not so big. Yellow sand Forest fire

In what height did the aerosol layer suspended? s RYORI Lidar system detected the strong and continuous aerosol layer at around 3km height on 23 May s The depolarization ratio of the aerosol layer was smaller in comparison with that of dust aerosols. This fact shows that the particles had spherical shapes or smaller radius than laser wavelength, 532nm.

Where were the aerosols done from? s We calculated the back trajectories with the global reanalyzed meteorological data from Ryori at 3km height to 7 days before. s The result shows that the aerosols were around lake Bikal on 19 May.

What happened on 19 May? Red circles are the stations reported SMOKE on 19 May These are picked up from SYNOP reports. s There were many meteorological stations observed and reported smokes on 19 May s They were almost on the trajectory line.

How often the SMOKE report made around south-east siberia. s The figure below shows the daily time series of the number of meteorological stations which reported smoke. s The figure below shows that the forest fires were occurred more frequently in 2003 than 2002.

Conclusions s The dens turbid conditions, occurred in north Japan on May 2003, was supposed to be the influence of suspended smoke aerosol layers originated from the large-scale forest fires in east side of Lake Bikal. s In Siberia, forest fire occurs frequently every year. But in 2003, its effects appeared strongly in north Japan, because … s The frequencies and scales of forest fires were bigger in 2003 then usual s The synoptic meteorological conditions on May 2003 were more influenceable to North Japan.