Scale Effects on Averaging of Cloud Droplet and Aerosol Number Concentrations: Observations and Models

Gultepe, I.; Isaac, G.A.
May 1999
Journal of Climate;5/1/99, Vol. 12 Issue 5, p1268
Academic Journal
The purpose of this study, using in situ observations from five field projects, is to analyze cloud boundaries and averaging scales related to droplet number concentration (Nd ) and total aerosol number concentration (Na ), and to discuss parameterizations of these variables for use in numerical weather prediction and global climate models. Here Nd and Na for stratus and stratocumulus clouds are averaged over various lengths from 1 km up to 35 km. The relationships between these variables for 1-s and 200-s data are compared with current param-eterizations. Comparisons between Nd and Na show that Na plays an important role for activating cloud droplets. The variability in Nd from 1-s data is estimated to have a standard deviation of about 6150 cm 23 . Median values of Nd representing scales from about 0.1 km up to approximately 35 km are found to be dependent on scale and the presence of clear patches in the clouds. The average values of Nd are also dependent on the lower concentration threshold used to define the cloud boundaries. It is concluded that scale effects, including clear air regions, should be considered when developing parameterization schemes used for modeling studies of cloud systems.


Related Articles

  • Spectral actinic flux in the lower troposphere: measurement and 1-D simulations for cloudless, broken cloud and overcast situations. Kylling, A.; Webb, A. R.; Kift, R.; Gobbi, G. P.; Ammannato, L.; Barnaba, F.; Bais, A.; Kazadzis, S.; Wendisch, M.; Jäkel, E.; Schmidt, S.; Kniffka, A.; Thiel, S.; Junkermann, W.; Blumthaler, M.; Silbernagl, R.; Schallhart, B.; Schmitt, R.; Kjeldstad, B.; Thorseth, T. M. // Atmospheric Chemistry & Physics;2005, Vol. 5 Issue 7, p1975 

    In September 2002, the first INSPECTRO campaign to study the influence of clouds on the spectral actinic flux in the lower troposphere was carried out in East Anglia, England. Measurements of the actinic flux, the irradiance and aerosol and cloud properties were made from four ground stations...

  • Effects of aerosol organics on cloud condensation nucleus (CCN) concentration and first indirect aerosol effect. Wang, J.; Lee, Y.-N.; Daum, P. H.; Jayne, J.; Alexander, M. L. // Atmospheric Chemistry & Physics Discussions;2008, Vol. 8 Issue 3, p9783 

    Aerosol microphysics, chemical composition, and CCN properties were measured on the Department of Energy Gulfstream-1 aircraft during the Marine Stratus/Stratocumulus Experiment (MASE) conducted over the coastal waters between Point Reyes National Seashore and Monterey Bay, California, in July...

  • What do we know about phase transition processes relevant to atmospheric aerosols? Wagner, Paul E. // AIP Conference Proceedings;2000, Vol. 534 Issue 1, p561 

    Various dynamical processes observed in the atmosphere are related to phase transitions from the gas phase. In this presentation selected nucleation and condensation processes are considered and their relevance to atmospheric aerosols is discussed. A few recent experimental studies are reviewed....

  • Lasing on a cloudy afternoon. Borrmann, Stephan; Curtius, Joachim // Nature;8/22/2002, Vol. 418 Issue 6900, p826 

    Describes the use of high-intensity laser pulses in analyzing the composition of clouds. Indirect effects of aerosols on climate; Features of water droplets with sodium chloride; Three-photon process in the droplets; Limitation of laser ablation mass spectrometry.

  • Three Different Behaviors of Liquid Water Path of Water Clouds in Aerosol–Cloud Interactions. Han, Qingyuan; Rossow, William B.; Zeng, Jian; Welch, Ronald // Journal of the Atmospheric Sciences;2/1/2002, Vol. 59 Issue 3, p726 

    Estimates of the indirect aerosol effect in GCMs assume that either cloud liquid water path is constant (Twomey effect) or increases with increased droplet number concentration (drizzle-suppression or Albrecht effect). On the other hand, if cloud thermodynamics and dynamics are considered, cloud...

  • Aerosol Influence on Cloud Microphysics Examined by Satellite Measurements and Chemical Transport Modeling. Schwartz, S. E.; Benkovitz, C. M.; Guo, G. // Journal of the Atmospheric Sciences;2/1/2002, Vol. 59 Issue 3, p714 

    Anthropogenic aerosols are hypothesized to decrease cloud drop radius and increase cloud droplet number concentration enhancing cloud optical depth and albedo. Here results have been used from a chemical transport model driven by the output of a numerical weather prediction model to identify an...

  • GCM Simulations of the Aerosol Indirect Effect: Sensitivity to Cloud Parameterization and Aerosol Burden. Menon, Surabi; Genio, Anthony D. Del; Koch, Dorothy; Tselioudis, George // Journal of the Atmospheric Sciences;2/1/2002, Vol. 59 Issue 3, p692 

    In this paper the coupling of the Goddard Institute for Space Studies (GISS) general circulation model (GCM) to an online sulfur chemistry model and source models for organic matter and sea salt that is used to estimate the aerosol indirect effect is described. The cloud droplet number...

  • Overview of the research activities and results at Puijo semi-urban measurement station. Leskinen, Ari; Portin, Harri; Komppula, Mika; Miettinen, Pasi; AroIa, Antti; Lihavainen, Heikki; Hatakka, Juha; Laaksonen, Ari; Lehtinen, Kari E. J. // Boreal Environment Research;2009, Vol. 14 Issue 4, p576 

    We introduce a new measurement station that we established in 2005 in an observation tower at Puijo in Kuopio. At Puijo we measure several meteorological parameters, aerosol and cloud droplet size distribution, aerosol optical properties and trace gas concentrations. We summarize the research...

  • Observations of aerosol-cloud interactions at the Puijo semi-urban measurement station. Portin, Harri J.; Komppula, Mika; Leskinen, Ari P.; Romakkaniemi, Sami; Laaksonen, Ari; Lehtinen, Kari E. J. // Boreal Environment Research;2009, Vol. 14 Issue 4, p641 

    The Puijo measurement station has produced continuous data on aerosol-cloud interactions since June 2006. The station is located on the top floor of an observation lower in a semi-urban environment near the town of Kuopio in central Finland. The top of the tower (306 m a.s.1.) has been detected...


Read the Article


Sorry, but this item is not currently available from your library.

Try another library?
Sign out of this library

Other Topics