First, the chemical, radiative and microphysical measurements required for accomplishing the three objectives are very similar. Lastly, to understand the role of aerosols in direct and indirect radiative forcing, we need solar radiation flux observations for clear and cloudy skies under pristine and polluted conditions. Second, the regional emissions which lead to sulfates can also lead to increased tropospheric ozone. Third, the possible importance of anthropogenic emissions from the Indian sub-continent is a critical issue for all of the three objectives listed above. Schematic of air flow into the upper tropical troposphere.
Horizontal lines are contours of constant potential temperature.
Lastly, the ITCZ provides an unexplored but potentially significant mechanism for linking aerosols, clouds and chemistry. A is upward transport of air converging in the lower troposphere at the ITCZ followed by deep convection. If either of the routes B or C contribute to the chemical composition of the upper tropical troposphere, it follows that there will be an import of stratospheric air. Such air is ozone-rich, dry, and slightly lower in CO 2 and it contains particles from the Junge aerosol layer. The question as to whether stratospheric particles can affect cirrus formation in the upper tropical troposphere creates a strong link between the 3 objectives of this proposal, and throws new light on the possible role of the stratosphere in climate.