Ice supersaturations and cirrus cloud crystal numbers

By M. Krämer, C. Schiller, A. Afchine, R. Bauer, I. Gensch, A. Mangold, S. Schlicht, N. Spelten, N. Sitnikov, S. Borrmann and 2 more. 2008

338 citations recorded by the source corpus.

Abstract. Upper tropospheric observations outside and inside of cirrus clouds indicate water vapour mixing ratios sometimes exceeding water saturation. Relative humidities over ice (RH ice ) of up to and more than 200% have been reported from aircraft and balloon measurements in recent years. From these observations a lively discussion continues on whether there is a lack of understanding of ice cloud microphysics or whether the water measurements are tainted with large uncertainties or flaws. Here, RH ice in clear air and in ice clouds is investigated. Strict quality-checked aircraft in situ observations of RH ice were performed during 28 flights in tropical, mid-latitude and Arctic field experiments in the temperature range 183–240 K. In our field measurements, no supersaturations above water saturation are found. Nevertheless, super- or subsaturations inside of cirrus are frequently observed at low temperatures ( ice deviating from saturation, we analysed the number densities of ice crystals recorded during 20 flights. From the combined analysis – using conventional microphysics – of supersaturations and ice crystal numbers, we show that the high, persistent supersaturations observed inside of cirrus can possibly be explained by unexpected, frequent very low ice crystal numbers that could scarcely be caused by homogeneous ice nucleation. Heterogeneous ice formation or the suppression of freezing might better explain the observed ice crystal numbers. Thus, our lack of understanding of the high supersaturations, with implications for the microphysical and radiative properties of cirrus, the vertical redistribution of water and climate, is traced back to the understanding of the freezing process at low temperatures.

Subfields: Atmospheric Science, Global and Planetary Change

View Paper: https://www.semanticscholar.org/paper/1d8116605c93a1ddbfef4f6250a54da5597921c9

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Atmospheric Science

In Global and Planetary Change

Citations in the corpus

Ice structures, patterns, and processes: A view across the icefields (2012, background): “Further laboratory studies and in situ atmospheric observations, combined with better molecularlevel modeling of water interactions with surfaces (Krämer et al., 2009), will be key factors for resolving these questions.”
A microphysics guide to cirrus clouds – Part 1: Cirrus types (2015, methodology): “Nevertheless, from the data set of Krämer et al. (2009) it seems that low Nice are the favored state in TTL cirrus.”
Climate impacts of ice nucleation (2012, methodology): “Also shown are observations of thin tropopause level cirrus from Lawson et al. [2008] (black square) and tropical convective outflow cirrus from Jensen”
Modelling of cirrus clouds – Part 1a: Model description and validation (2008, background): “…range of midlatitude and arctic cirrus clouds ice supersaturation inside the clouds can be found frequently, see for instance the results ofOvarlez et al.(2002); Comstock et al.(2004); Krämer et al.(2008) and also the recent SPARC newsletter about the supersaturation issue (Peter et al., 2008).”