MAO/AETH/S1 - Negative black carbon mass
The MAOS Aethalometer (model AE-31) is an older design that is known to exhibit sensitivity to sudden changes in cabin relative humidity. The origin of this oscillation is attributed to differences in the sample air stream relative humidity (which the sample filter channel is exposed to) compared to the cabin relative humidity (which the reference channel is exposed to). Since the Aethalometer is a difference [sample - reference] of a difference [current calculated black carbon mass from the previous calculated black carbon mass] this effect is exacerbated in high relative humidity areas, such as Manacapuru, Brazil, where an air conditioner is necessary to control the cabin temperature of this mobile lab (small cabin volume). In the present case, the Aethalometer is housed in the MAOS SeaTainer [20-ft x 8-ft x 8-ft] and the effects of changing relative humidity brought about by a cycling air conditioner will magnify this issue.
Employ a 15-minute running average