Measurements of ice water content in tropopause region Arctic cirrus during the SAGE III Ozone Loss and Validation Experiment (SOLVE)

Abstract

A new instrument, the closed‐path laser hygrometer (CLH), was flown on the NASA DC‐8 aircraft during the Stratospheric Aerosol and Gas Experiment (SAGE) III Ozone Loss and Validation Experiment (SOLVE) campaign in 1999–2000 to measure condensed‐phase water. The ice water content (IWC) of Arctic cirrus was determined from in situ measurements of condensed‐ and gas‐phase water. The IWC values obtained from the CLH observations are compared to those determined by integrating particle size distributions measured by a Forward Scattering Spectrometer Probe (FSSP) also flown on the DC‐8. The considerably greater IWC seen by the CLH implies the presence of particles with diameters greater than the FSSP's upper limit of 20 μm. The evidence for and implications of the presence of large ice crystals in Arctic cirrus is discussed.