Atmospheric Chemistry and Physics Discussions
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2007
10.5194/acpd-7-4889-2007
http://www.atmos-chem-phys-discuss.net/7/4889/2007/
http://www.atmos-chem-phys-discuss.net/7/4889/2007/acpd-7-4889-2007.html
http://www.atmos-chem-phys-discuss.net/7/4889/2007/acpd-7-4889-2007.pdf
4889
4923
2007-04-10
Physical controls on orographic cirrus inhomogeneity
J. E. Kay
jenkay@ucar.edu
M. Baker
D. Hegg
National Center for Atmospheric Research, Boulder, Colorado, USA
Department of Atmospheric Sciences, University of Washington, Seattle, Washington, USA
Optical depth distributions (P(σ)) are a useful measure of radiatively
important cirrus (Ci) inhomogeneity. Using a parcel model with binned ice
microphysics and kinematic trajectories from a mesoscale weather model (MM5),
we assess physical controls on Ci P(σ) during an orographic Ci case
study. On 19 April 2001, satellite imagery revealed Ci formation in the lee
of the Southern Rocky Mountains and Ci advection along a broad upper level
ridge. Above Lamont, Oklahoma (USA), lidar observations indicated a broad Ci
P(σ). Along MM5 trajectories associated with the observed Ci,
homogeneous freezing and mesoscale variability in vertical velocities led to
broad modeled P(σ) and variability in modeled Ci cloud lifetimes. The
addition of background ice nuclei concentrations (<i>N</i><i><sub>IN</sub></i>=0.03 cm<sup>−3</sup>) to air parcels had little impact on modeled Ci σ
variability. The presence of background <i>N<sub>IN</sub></i> did increase cloud cover by
increasing the frequency of small σ Ci. These results highlight the
importance of homogeneous freezing and mesoscale vertical velocity
variability in controlling Ci P(σ) shapes along realistic upper
tropospheric trajectories.
Albrecht, B.: Aerosols, cloud microphysics and fractional cloudiness, Science, 245, 1227–1330, 1989.
Carlin, B., Fu, Q. Lohmann, U., Mace, G., Sassen, K., and Comstock, J.: High-cloud horizontal inhomogeneity and solar albedo bias, J. Clim., 15(17), 2321–2339, 2002.
Dean, S. M., Lawrence, B N., Grainger, R G. and Heuff, D N.: Orographic cloud in GCM: the missing cirrus, Clim. Dyn., 24, 771–780, 2005.
DeMott, P. J., Cziczo, D. J., Prenni, A. J., Murphy, D. M., Kreidenweis, S. M., Thomson, D. S., Borys, R., and Rogers, D. C.: Measurements of the concentration and composition of nuclei for cirrus formation, Proc. Natl. Acad. Sci., 100(25), 14 655–14 660, 2003.
Durran, D R.: Lee Waves and Mountain Waves in Encyclopedia of Atmospheric Science, Ed. J. Holton, J. Pyle, and J. Curry, Academic Press, 2003.
Field, P. R., Cotton, R. J., Noone, K., Glantz, P., Kaye, P. H., Hirst, E., Greenaway, R. S., Jost, C., Gabriel, R., Reiner, T., Andreae, M., Saunders, C. P. R., Archer, A., Choularton, T., Smith, M., Brooks, B., Hoell, C., Bandy, B., Johnson, D., and Heymsfield, A.: Ice nucleation in orographic wave clouds: Measurements made during INTACC, Q. J. Roy. Meteorol. Soc., 127(575), 1493–1512, 2001.
Fu, Q., Carlin, B., and Mace, G.: Cirrus horizontal inhomogeneity and OLR bias, Geophys. Res. Lett., 27(20), 3341–3344, 2000.
Grell, G. A., Dudhia, H., and Stauffer, D. R.: A description of the fifth generation Penn State NCAR Mesoscale Model (MM5), NCAR Tech Note NCAR/TN-398+STR, National Center for Atmospheric Research (NCAR), Boulder, CO, 121 pp., 1994.
Haag, W. and Kärcher, B.: The impact of aerosols and gravity waves on cirrus clouds at mid-latitudes, J. Geophys. Res., 109(D12), doi:10.1029/2004JD004579, 2004.
Heymsfield, A. J. and Miloshevich, L.: Relative Humidity and Temperature Influences on Cirrus Formation and Evolution: Observations from Wave Clouds and FIRE II, J. Atmos. Sci., 52, 4302–4326, 1995.
Hoyle, C. R., Luo, B. P., and Peter, T.: The origin of high ice crystal number densities in cirrus clouds, J. Atmos. Sci., 62, 2568–2579, 2005.
Kärcher, B. and Lohmann, U.: A parameterization of cirrus cloud formation: heterogeneous freezing, J. Geophys. Res., 108, D14, doi:10.1029/2002JD003220, 2003.
Kärcher, B. and Ström, J.: The roles of dynamical variability and aerosols in cirrus cloud formation, Atmos. Chem. Phys., 3, 823–838, 2003.
Kay, J. E., Physical controls on cirrus cloud inhomogeneity, Ph.D. Thesis, University of Washington, 2006.
Kay, J. E., Baker, M., and Hegg, D.: Microphysical and dynamical controls on cirrus cloud optical depth distributions, J. Geophys. Res., 111, D24205, doi:10.1029/2005JD006916, 2006.
Koop, T., Luo, B., Tslas, A., and Peter, T.: Water activity as the determinant for homogeneous ice nucleation in aqueous solutions, Nature, 406, 611–614, 2000.
Mace, G. G., Clothiaux, E. E., and Ackerman, T. P.: The composite characteristics of cirrus clouds: bulk properties revealed by one year of continuous cloud radar data, J. Clim., 14, 2185–2203, 2001.
Meyers, M P., DeMott, P J., and Cotton, W R.: New primary ice-nucleation parameterization in an explicit cloud model, J. Appl. Meteorol., 55, 2039–2052, 1992.
Reisner, J., Rasmussne, R. M., and Bruintjes, R. T.: Explicit forecasting of supercooled liquid water in winter storms using the MM5 mesoscale model, Q. J. R. Meteorol. Soc., 124,1071–1107, 1998.
Rogers, D. C., DeMott, P. J., Kredenweis, S. M., and Chen, Y.: Measurements of ice nucleating aerosols during SUCCESS, Geophys. Res. Lett., 25(9), 1383–1386, 1998.
Turner, D. D.: Arctic mixed-phase cloud properties from AERI lidar observations: Algorithm and results from SHEBA, J. Appl. Meteorol., 44(4), 427–444, 2005.
Twomey, S. A.: Pollution and the planetary albedo, Atmos. Environ., 8, 1251–1256, 1974.