REMOTE-SENSING OF CARBON-MONOXIDE OVER THE CONTINENTAL UNITED-STATES ON SEPTEMBER 12-13, 1993

Tropospheric carbon monoxide (CO) column densities were retrieved from 491 nadir infrared spectra obtained by the University of Wisconsin's High-Resolution Interferometer Sounder (HIS) during a cross-country fl ight of a NASA ER-2 on September 12-13, 1993 (UT). A classical, Fourie r-based signal-processing technique was utilized to retrieve the CO co lumn density from the 2135-2200 cm(-1) portion of the CO 1-0 vibration -rotation band. Error analysis indicates column CO retrieval uncertain ties of approximately +/-10%. Retrieved CO column densities over the w estern United States from this flight, similar to 1.2 x 10(18) cm(-2), agree well with previous ground-based CO column measurements over the western United States at the same season. Derived CO sensitivity func tions for these measurements possess a broad peak centered in the 500- 600 mbar region, thus implying the retrieved tropospheric CO mixing ra tios are indicative of the mean free troposphere (mft). Across the Uni ted States, three spatial groupings of CO were observed: west, mft CO similar to 76 parts per billion by volume (ppbv); midwest, mft CO simi lar to 56 ppbv; and east, mft CO similar to 71 ppbv. Weather map and b ack trajectory analyses indicate different source regions for the air parcels in each of these regions. The low CO amounts over the midwest most likely result from the mixing of rapidly subsiding air naturally low in CO with a low-altitude inflow of similarly clean subtropical ai r off the Gulf of Mexico. These results demonstrate the utility of sat ellite infrared spectrometer observations to globally map tropospheric CO abundances and further reveal the impact of synoptic scale atmosph eric circulations on CO abundances.