HIAPER mission: The missions would be a combination of remote and direct sensing flight legs. After flying out to a region of interest, the airplane would fly above the area, possibly in a closed (e.g. circular) flight pattern using a downward-looking water vapor differential absorption lidar (DIAL), Doppler radar, and thermal mapper. Dropwindsondes would provide details of the intervening mean thermodynamic and dynamic structure. The airplane would then descend and continue to carry out the same flight pattern within and beneath the cloud layer(s), directly measuring thermodynamic and dynamic variables, as well as microphysical, chemical, and short- and long-wave radiation, and eddy fluxes of heat, momentum and trace chemical species. The flight pattern will be advected with the mean wind in the cloud layer so that the direct measurements would occur in the same air mass which had been probed remotely. Closed flight pattern may permit measurments of divergence, which can be integrated with height and combined with measurements of the depth of the MBL (measured remotely via lidar and directly via soundings) to obtain independent estimates of entrainment at the top of the MBL, as well as across other layers. The entire pattern would be repeated for as long as time permits.
Extensions to this basic strategy would be: 1) Use constant-level balloons (equipped with GPS navigation) to label the airmass so that the airplane could return to the same airmass on subsequent flights and thus measure temporal evolution over several days. The balloons might be dispensed by HIAPER on its first flight to the area, by another aircraft, or by a ship which would provide complimentary measurements. 2) Use the same flight strategy with a suite of chemical measurements to estimate their budgets (in both clear and cloudy atmospheres), since this flight plan allows evaluation of all the terms in the budget of a species whose mean and fluctuation values can be measured.