Air Pollution as a Climate Forcing: A Workshop
Day 2 Presentations
A Few Insights on Air Pollution and Climate from ACE-Asia
Department of Oceanography, University of Hawaii, Honolulu, HI, U.S.A.
You may download a MS PowerPoint version (4.0 MB) of this presentation.
In the spring of 2001 scientists from 13 countries studied the natural and anthropogenic aerosols that leave Asia for the Pacific. In view of the paucity of earlier observations, perhaps it is not surprising that some surprises were found.
1. Dust very definitely transports soot on its surface, thereby modifying its optical properties significantly. Yet most of the measured aerosol absorption is still due to submicron particles, so the main mass of the soot is not on mineral particles.
2. Evidently dust reacts with nitric acid very quickly (the size distributions of nitrate and soluble calcium are almost identical), but there is much less sulfate on dust that expected. Does the SO2 reaction require higher RH than we encountered? Yet the f(RH) of dust remained low enough that we could identify dust layers in part by their low f(RH).
3. We saw surprisingly little gradient in elemental carbon (1-3 ug EC/sm3) from the NSF/NCAR C-130 once we left the boundary layer. That's of interest for producing satellite products, since the assumed altitude of absorbers is critical for retrieval algorithms.
4. The layering was often very complex. In one profile near Pyonyang we found 13 distinct aerosol and clean layers in the lowest 5.5 km. The challenge this offers to models is profound. How much of that detail do models need to describe to do good radiative transfer calculations?
Chemical transport models of Eastern Asia have already been improved by comparison with ACE-Asia data. This data set will help us understand the ways in which pollution interacts with (semi)-natural aerosols.