Dynamical characteristics of ice supersaturated regions
- ISSN: 1680-7324
- DOI: 10.5194/acpd-12-19871-2012
The typical distributions of dynamical fields within ice supersaturated\nregions are investigated. The dynamical fields divergence, relative\nvorticity, and vertical velocity are analysed statistically in two\nways, namely using the unconditioned data and data conditioned on\nthe presence of ice supersaturation. Two geographical regions are\nconsidered, namely Europe (250 hPa level) and the tropical belt from\n30° S to 30° N on two pressure levels (200 and 150 hPa). The study\nis based on forecast data from the European Centre for Medium-Range\nWeather Forecasts for four months covering the four seasons, June,\nSeptember, December 2011 and March 2012. We find that histograms\n(frequency distributions) and low order moments of the dynamical\nfields differ substantially and statistically significantly inside\nand outside of ice supersaturated regions. As expected, upward and\ndivergent flow favours ice supersaturation. But we find also that\nice supersaturation is mostly located in anti-cyclonic flow. The\nlatter result is probably due to the structure of warm/moist and\ncold/dry air streams in synoptic disturbances in mid-latitudes, but\nprobably merely coincidental in the tropical belt.