Measurements of HNO3 and NOy on Cirrus Ice Particles and in Solution Aerosols During CRYSTAL-FACE

NO_x (NO + NO₂) is central to tropospheric O₃ production. The larger family of gases with which NO_x interconverts, NO_y, or total reactive nitrogen, includes HNO₃. One potential mechanism for the removal and/or vertical transport of NO_y is via uptake on ice particles and aerosols. NO_x is unlikely to be subject to such uptake, and HNO₃ is likely the most significant NO_y species subject to uptake. Thus the uptake of HNO₃ has the potential to affect indirectly the O₃ budget of the atmospehre [Lawrence and Crutzen, Tellus, 1998; Meier and Hendricks, JGR, 2002]. To assess the degree of uptake, condensed-phase HNO₃ and NO_y were measured during CRYSTAL-FACE by instruments in adjacent pallets on the WB57. The instruments employed nearly identical inlets for the enhanced (anisokinetic) sampling of condensed-phase species. Each instrument employed a second inlet for the measurement of the gas-phase plus small-particle fraction. Differences in the small-particle sampling by these latter inlets has proven beneficial for the inference of condensed-phase HNO₃ on particles with diameters of order 1 micron. This talk will emphasize the southern survey flight of 9 July 2002, for which we infer the presence of condensed-phase HNO₃ in ternary solutions of H₂O, H₂SO₄, and HNO₃. Ice was found in greater and lesser amounts in the presence of the aerosols, but ice appears to have played little role in the uptake of HNO₃ here, as the aerosols compete very effectively for the HNO₃ in this particular case, due to the relatively large particle volume and the low temperatures. In addition, the condensed-phase NO_y measurements are compared to the condensed-phase HNO₃ measurements described in another presentation at this meeting (Popp et al.) Overall the condensed-phase HNO₃ and NO_y amounts are similar to one another and give no indication that other NO_y species are taken up by cirrus ice particles.