Particle backscatter and relative humidity measured across cirrus clouds and comparison with microphysical cirrus modelling

doi:10.5194/acp-12-9135-2012

GSTDTAP > 地球科学

DOI	10.5194/acp-12-9135-2012
	Particle backscatter and relative humidity measured across cirrus clouds and comparison with microphysical cirrus modelling
	M. Brabec, F. G. Wienhold, B. P. Luo, H. Vömel, F. Immler, P. Steiner, E. Hausammann, U. Weers, and T. Peter
	2012-10-05
发表期刊	Atmospheric Chemistry and Physics
出版年	2012
英文摘要	Advanced measurement and modelling techniques are employed to estimate the partitioning of atmospheric water between the gas phase and the condensed phase in and around cirrus clouds, and thus to identify in-cloud and out-of-cloud supersaturations with respect to ice. In November 2008 the newly developed balloon-borne backscatter sonde COBALD (Compact Optical Backscatter and AerosoL Detector) was flown 14 times together with a CFH (Cryogenic Frost point Hygrometer) from Lindenberg, Germany (52° N, 14° E). The case discussed here in detail shows two cirrus layers with in-cloud relative humidities with respect to ice between 50% and 130%. Global operational analysis data of ECMWF (roughly 1° × 1° horizontal and 1 km vertical resolution, 6-hourly stored fields) fail to represent ice water contents and relative humidities. Conversely, regional COSMO-7 forecasts (6.6 km × 6.6 km, 5-min stored fields) capture the measured humidities and cloud positions remarkably well. The main difference between ECMWF and COSMO data is the resolution of small-scale vertical features responsible for cirrus formation. Nevertheless, ice water contents in COSMO-7 are still off by factors 2–10, likely reflecting limitations in COSMO's ice phase bulk scheme. Significant improvements can be achieved by comprehensive size-resolved microphysical and optical modelling along backward trajectories based on COSMO-7 wind and temperature fields, which allow accurate computation of humidities, homogeneous ice nucleation, resulting ice particle size distributions and backscatter ratios at the COBALD wavelengths. However, only by superimposing small-scale temperature fluctuations, which remain unresolved by the numerical weather prediction models, can we obtain a satisfying agreement with the observations and reconcile the measured in-cloud non-equilibrium humidities with conventional ice cloud microphysics. Conversely, the model-data comparison provides no evidence that additional changes to ice-cloud microphysics – such as heterogeneous nucleation or changing the water vapour accommodation coefficient on ice – are required.
领域	地球科学
URL	查看原文
引用统计
文献类型	期刊论文
条目标识符	http://119.78.100.173/C666/handle/2XK7JSWQ/288074
专题	地球科学
推荐引用方式 GB/T 7714	M. Brabec, F. G. Wienhold, B. P. Luo, H. Vömel, F. Immler, P. Steiner, E. Hausammann, U. Weers, and T. Peter. Particle backscatter and relative humidity measured across cirrus clouds and comparison with microphysical cirrus modelling[J]. Atmospheric Chemistry and Physics,2012.
APA	M. Brabec, F. G. Wienhold, B. P. Luo, H. Vömel, F. Immler, P. Steiner, E. Hausammann, U. Weers, and T. Peter.(2012).Particle backscatter and relative humidity measured across cirrus clouds and comparison with microphysical cirrus modelling.Atmospheric Chemistry and Physics.
MLA	M. Brabec, F. G. Wienhold, B. P. Luo, H. Vömel, F. Immler, P. Steiner, E. Hausammann, U. Weers, and T. Peter."Particle backscatter and relative humidity measured across cirrus clouds and comparison with microphysical cirrus modelling".Atmospheric Chemistry and Physics (2012).