INFRARED-ABSORPTION MEASUREMENT OF CARBON-MONOXIDE COLUMN ABUNDANCE OVER TOKYO

We report column densities of carbon monoxide over Tokyo in November 1 989-August 1991 derived from infrared absorption measurement of the R( 3) line of the 1-0 band at 2158 cm(-1) by using the Sun as a light sou rce. After removing the pollution component near the surface, we obtai n CO column abundances ranging between 1.5 and 5 x 10(18) molecules cm (-2) which correspond to the burden of CO in the free troposphere. The lower envelope of the plot of the CO column density appears to indica te the background with a maximum of 2.5 x 10(18) molecules cm(-2) in s pring and a minimum of 1.5 x 10(18) molecules cm(-2) in fall. The exce ss CO column above this level varies considerably and the variation ex ceeds the error due to uncertainty in the pollution layer thickness. T he only likely explanation for the large day-to-day variability is ant hropogenic emission; hence the free troposphere above Tokyo is also po lluted by CO. Copyright (C) 1996 Elsevier Science Ltd