Freezing behavior of stratospheric sulfate aerosols inferred from trajectory studies
- NASA Ames Research Center, Moffett Field, CA (United States)
- San Jose State Univ., CA (United States)
Temperature histories based on 10-day back trajectories for six ER-2 flights during AASE I and AAOE are presented. These trajectories along with the properties of the observed PSC (polar stratospheric cloud) particles are used here to infer the physical state of the pre-existing sulfuric acid aerosols. Of all the ER-2 flights described here, only the PSCs observed on the flights of January 24 and 25, 1989 are consistent with the thermo-dynamics of liquid ternary solutions of H{sub 2}SO{sub 4}/HNO{sub 3}/H{sub 2}O (Type Ib PSCs). For these two days, back trajectories indicate that the air mass was exposed to SAT (sulfuric acid tetrahydrate) melting temperatures about 24 hours prior to being sampled by the ER-2. For the remaining ER-2 flights (January, 16, 19, and 20 for the AASE I campaign and August 17 for the AAOE campaign), the observed PSCs were probably composed of amorphous solid solutions of HNO{sub 3} and H{sub 2}O (Type Ic PSCs). Formation of such Type Ic PSCs requires the presence of solid H{sub 2}SO{sub 4} aerosols since liquid aerosols yield ternary solutions. The 10-day back trajectories of these flights indicate that the air mass was not exposed to SAT melting temperatures during the past week and had experienced cooling/warming cycles prior to being sampled by the ER-2. These temperature histories, recent laboratory measurements and the properties of glassy solids suggest that stratospheric H{sub 2}SO{sub 4} aerosols may undergo a phase transition to SAT upon warming at {approximately}198 K after going through a cooling cycle to about 194 K or lower. 23 refs., 2 figs., 1 tab.
- OSTI ID:
- 250025
- Journal Information:
- Geophysical Research Letters, Journal Name: Geophysical Research Letters Journal Issue: 13 Vol. 22; ISSN GPRLAJ; ISSN 0094-8276
- Country of Publication:
- United States
- Language:
- English
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