Bob Rauber Home Page

Department of Atmospheric Sciences - University of Illinois

Bob Rauber                                                            University of Illinois

Research-RICO
The Rain in Cumulus over the Ocean Campaign (RICO) was organized to study shallow, maritime, cumulus convection, one of the most prevalent cloud types on the planet. Trade wind cumuli typically extend to no greater than 4 km altitude, the height of the tropical trade wind inversion, and are dominated by warm rain processes. They are ubiquitous over much of the tropical oceans, and characterizing their properties is important to understanding the global energy balance and climate. Because of the disparity in the range of scales from the microphysical/cloud scale (microns to a kilometer), to the cloud-interaction scale (kilometers to tens of kilometers), to the ensemble cloud field scale (tens of kilometers or more), past work has tended to focus on processes occurring on only one of these three scales – often neglecting the important interactions that occur across scales. Our objective in RICO in the broadest sense was to characterize and understand the properties of trade wind cumulus at all scales, with particular emphasis on determining the importance of precipitation. At the smallest scale, the most fundamental problem – recognized for over a half century – is explaining the rapid onset of precipitation in shallow tropical clouds. At the intermediate scale, processes controlling the mesoscale structure and coverage of shallow tropical cloud systems are not well understood. At the largest scale, our inability to describe the statistical behavior of trade wind cloud fields confounds our attempts to properly represent the exchange of radiant energy, moist enthalpy, momentum and trace constituents between the atmosphere and ocean over vast expanses of the planet. All these scales are inextricably linked and our goal was to explore the nature of these linkages in RICO.
At the University of Illinois, our goals are to quantify and understand (1) the microphysical and environmental processes influencing the rate of precipitation formation in trade wind cumuli. We are exploring how the warm rain process occurs and the role of sea salt nuclei in enhancing the rate at which rai develops.  We are approaching this using radar and aircraft data; (2) the mechanisms by which precipitation influences the mesoscale organization of trade wind clouds. Our research suggests the importance of precipitation-generated cold pools in reorganizing trade wind clouds. We are using satellite and radar data to quantitatively determine properties of cold-pool generated clouds and compare these with clouds generated by other processes. We are also conducting numerical modeling studies to understand cold pool generation, depth and propagation within the trade wind environment where clouds seldom exceed 4 km in height, the surface layer is humid, and deeper clouds typically produce light rain; (3) the mechanisms by which clouds and precipitation influence the mesoscale substructure of the marine boundary layer. Our research using the clear air Bragg scattering signal from the RICO S-Band radar has led to the discovery of layered substructures with mesoscale variability that are linked to layers of enhanced humidity. We are using this Bragg scattering clear-air signal, together with soundings and LES modeling studies, to understand the origin and properties of these layered substructures, the role of clouds and precipitation in modifying these substructures, and how these substructures feed back onto subsequent cloud and precipitation evolution; (4) the impact of clouds and cloud processing on the distribution of aerosols within the MBL. We are using RICO data, satellite data from CALIPSO, and detailed microphysical modeling to investigate how clouds process aerosols originating in the sub-cloud layer, detrain processed aerosols into halo regions in the immediate cloud vicinity and ultimately redistribute aerosols throughout the marine boundary layer.

RICO Publications (UI authors in bold)

  • Colón-Robles, M., R. M. Rauber, and J. B. Jensen (2006), Influence of low-level wind speed on droplet spectra near cloud base in trade wind cumulus, Geophys. Res. Lett., 33, L20814, doi:10.1029/2006GL027487.
  • Dey, S. L. Di Girolamo, and G. Zhao, 2008: Scale effect on statistics of the macrophysical properties of trade wind cumuli over the tropical western Atlantic during RICO. J. Geophys. Res., 113, D24214, doi 10.1029/2008JD010295.
  • Genkova, I., G. Seiz, P. Zuidema, G. Zhao and L. Di Girolamo, 2007: Cloud-top height comparisons from ASTER, MISR, and MODIS for trade wind cumuli. Remote Sens. Environ., 107, 211-222.
  • Göke, S., H.T. Ochs, and R.M. Rauber, 2007: Radar Analysis of Precipitation Initiation in Maritime versus Continental Clouds near the Florida Coast: Inferences Concerning the Role of CCN and Giant Nuclei. J. Atmos. Sci., 64, 3695–3707
  • Rauber, R.M., B. Stevens, H.T. Ochs, C. Knight, B.A. Albrecht, A.M. Blyth, C.W. Fairall, J.B. Jensen, S.G. Lasher-Trapp, O.L. Mayol-Bracero, G. Vali, J.R. Anderson, B.A. Baker, A.R. Bandy, E. Burnet, J.L. Brenguier, W.A. Brewer, P.R.A. Brown, P. Chuang, W.R. Cotton, L. Di Girolamo, B. Geerts, H. Gerber, S. Göke, L. Gomes, B.G. Heikes, J.G. Hudson, P. Kollias, R.P. Lawson, S.K. Krueger, D.H. Lenschow, L. Nuijens, D.W. O'Sullivan, R.A. Rilling, D.C. Rogers, A.P. Siebesma, E. Snodgrass, J.L. Stith, D.C. Thornton, S. Tucker, C.H. Twohy, and P. Zuidema, 2007a: Rain in shallow cumulus over the ocean. Bull. Amer. Meteor. Soc., 88, 1912–1928.
  • Rauber, R.M., B. Stevens, J. Davison, S. Göke, O.L. Mayol-Bracero, D. Rogers, P. Zuidema, H.T. Ochs, C. Knight, J. Jensen, S. Bereznicki, S. Bordoni, H. Caro-Gautier, M. Colón-Robles, M. Deliz, S. Donaher, V. Ghate, E. Grzeszczak, C. Henry, A. Marie Hertel, I. Jo, M. Kruk, J. Lowenstein, J. Malley, B. Medeiros, Y. Méndez-Lopez, S. Mishra, F. Morales-García, L.A. Nuijens, D. O'Donnell, D.L. Ortiz-Montalvo, K. Rasmussen, E. Riepe, S. Scalia, E. Serpetzoglou, H. Shen, M. Siedsma, J. Small, E. Snodgrass, P. Trivej, and J. Zawislak, 2007b: In the Driver's Seat: Rico and Education. Bull. Amer. Meteor. Soc., 88, 1929–1937
  • Rauber, R.M., B. Stevens, H.T. Ochs, C. Knight, B.A. Albrecht, A.M. Blyth, C.W. Fairall, J.B. Jensen, S.G. Lasher-Trapp, O.L. Mayol-Bracero, G. Vali, J.R. Anderson, B.A. Baker, A.R. Bandy, E. Burnet, J.L. Brenguier, W.A. Brewer, P.R.A. Brown, P. Chuang, W.R. Cotton, L. Di Girolamo, B. Geerts, H. Gerber, S. Göke, L. Gomes, B.G. Heikes, J.G. Hudson, P. Kollias, R.P. Lawson, S.K. Krueger, D.H. Lenschow, L. Nuijens, D.W. O'Sullivan, R.A. Rilling, D.C. Rogers, A.P. Siebesma, E. Snodgrass, J.L. Stith, D.C. Thornton, S. Tucker, C.H. Twohy, and P. Zuidema, 2007c: A Supplement to Rain in Shallow Cumulus Over the Ocean: The RICO Campaign. Bull. Amer. Meteor. Soc., 88, S12–S18.
  • Scalia, S., 2006: A break in the clouds. Weatherwise, 59, 43-47.
  • Snodgrass, E.R., L. Di Girolamo, and R. M. Rauber, 2008: Precipitation characteristics of Trade Winds Clouds during RICO Derived from Radar, Satellite and Aircraft Measurements.  J. Appl. Meteor. and Climatology, 48, 464-483.
  • Tackett, J.L., and L. Di Girolamo, 2009: Enhanced aerosol backscatter adjacent to cloud revealed by satellite-based lidar. Geophys. Res. Lett., 36, L14804,doi:10.1029/2009GL039264
  • Zhao, G., and L. Di Girolamo, 2006: Cloud fraction errors for trade wind cumuli from EOS- Terra instruments.  Geophys. Res. Lett., 33, L.20802, doi: 10.1029/2006GL027088, 2006.
  • Zhao, G., and L. Di Girolamo, 2007: Statistics on the macrophysical properties of trade wind cumuli over the tropical western Atlantic. J. Geophys. Res., 112, D10204, doi:10.1029/2006JD007371, 2007.

    Zhao, G., L. Di Girolamo, S. Dey, A.L. Jones, and M. Bull, 2009: Examination of direct cumulus contamination on MISR-retrieved aerosol optical depth and angstrom coefficient over ocean. Geophys. Res. Lett., 36, L13811, doi:10.1029/2009GL038549.

  • Minor, Hilary A., Robert M. Rauber, Sabine Göke, Larry Di Girolamo, 2011: Trade Wind Cloud Evolution Observed by Polarization Radar: Relationship to Giant Condensation Nuclei Concentrations and Cloud Organization. J. Atmos. Sci., 68, 1075–1096.

Master's Theses and Ph.D. Dissertations from RICO include:

  • Zhao, Guangyu, Ph.D., “Cloud observations from EOS—Terra: from conception to interpretation of cloud climatologies with a focus on small clouds,” May 2006
  • Snodgrass, Eric R., M.S., “Precipitation characteristics from trade wind clouds during RICO derived from radar, satellite and aircraft measurements”, August 2006
  • Colón Robles, Marilé, M.S.,“The influence of low-level wind speed on droplet spectra near cloud base in trade wind cumulus”, October 2006
  • Tackett, Jason L., M.S., Aerosol variability in the vicinity of marine boundary layer clouds observed by satellite-based lidar, September 2009
  • Minor, Hilary, M.S., Trade wind cloud evolution observed by polarization radar: relationship to aerosol characteristics (2010)
  • Davison, Jennifer, Ph.D., “Boundary layer characteristics of the trade wind layer during RICO derived from radar measurements.” (In progress)