Freezing thresholds and cirrus cloud formation mechanisms inferred from in situ measurements of relative humidity
By W. Haag, Bernd Kärcher, J. Ström, A. Minikin, Ulrike Lohmann, J. Ovarlez, Andreas Stohl. 2003
173 citations recorded by the source corpus.
Factors controlling the microphysical link between distributions of relative humidity above ice saturation in the upper troposphere and lowermost stratosphere and cirrus clouds are examined with the help of microphysical trajectory simulations. Our findings are related to results from aircraft measurements and global model studies. We suggest that the relative humidities at which ice crystals form in the atmosphere can be inferred from in situ measurements of water vapor and temperature close to, but outside of, cirrus clouds. The comparison with concomitant measurements performed inside cirrus clouds provides a clue to freezing mechanisms active in cirrus. The analysis of field data taken at northern and southern midlatitudes in fall 2000 reveals distinct differences in cirrus cloud freezing thresholds. Homogeneous freezing is found to be the most likely mechanism by which cirrus form at southern hemisphere midlatitudes. The results provide evidence for the existence of heterogeneous freezing in cirrus in parts of the polluted northern hemisphere, but do not suggest that cirrus clouds in this region form exclusively on heterogeneous ice nuclei, thereby emphasizing the crucial importance of homogeneous freezing. The key features of distributions of upper tropospheric relative humidity simulated by a global climate model are shown to be in general agreement with both, microphysical simulations and field observations, delineating a feasible method to include and validate ice supersaturation in other large-scale atmospheric models, in particular chemistry-transport and weather forecast models.
Subfields: Atmospheric Science, Global and Planetary Change
View Paper: https://www.semanticscholar.org/paper/e7e4b389de6353902c61ba78aa9648b73f9671fb
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Citations in the corpus
- Overview of Ice Nucleating Particles (2017, methodology): “…also reported that homogeneous and heterogeneous IN can occur from the ambient aerosol population as is expected based on numerous theoretical and modeling studies (Haag et al. 2003; K ä rcher and Lohmann 2003; K ä rcher and Spichtinger 2009; Spichtinger and Cziczo 2010, and references therein).”
- Review of the vapour pressures of ice and supercooled water for atmospheric applications (2005, background): “For example, the calorimeter data of Handa et al. (1986) showed that a bulk sample was largely transformed to hexagonal ice in 10 minutes at 200 to 210 K, but complete conversion was not observed until 215 K. Mauersberger and Krankowsky annealed their samples for at least 15 minutes, and usually…”
- Transport impacts on atmosphere and climate: Aviation (2009, unknown): “130% (Haag et al., 2003), then it is possible that they may alter ambient cloud properties either by forming additional cirrus in”
- Effect of sulfuric acid coating on heterogeneous ice nucleation by soot aerosol particles (2005, background): “A similar temporal behavior of nice and Sice was also observed in previous homogeneous freezing experiments with pure sulfuric acid aerosols [Möhler et al., 2003] and was consistently explained with detailed process modeling [Haag et al., 2003a].”
- Review of Aerosol–Cloud Interactions: Mechanisms, Significance, and Challenges (2016, background): “…cirrus in parts of the polluted Northern Hemisphere as revealed from the distinct differences in RHi freezing thresholds from in situ measurements of cirrus clouds during the Interhemispheric Differences in Cirrus Properties From Anthropogenic Emissions (INCA) field experiment (Haag et al. 2003).”
- Modification of cirrus clouds to reduce global warming (2009, background): “An important process for ice crystal production in cirrus clouds is homogeneous freezing nucleation, which seems fairly well understood (Sassen and Dodd 1988, Heymsfield and Sabin 1989, Koop et al 2000, DeMott 2002, Lin et al 2002, Möhler et al 2003, Haag et al 2003a, Koop 2004).”
- Ice supersaturations and cirrus cloud crystal numbers (2008, background): “…al., 1993; Heymsfield and Milosevitch, 1995; Heymsfield et al., 1998; Gierens et al., 1999, 2000; Jensen et al., 2001, 2005a,b; Ovarlez et al., 2002; Haag et al., 2003; Spichtinger et al., 2003, 2004; Gayet et al., 2004, 2006; Comstock and Ackerman, 2004; Lee et al., 2004; Gao et al., 2004;…”