Arlene Laing

Scientist
TIIMES - MMM
WCAS

Contact Information:
PO Box 3000, Boulder, CO 80307-3000
Office: FL3 - 2014
Telephone: 303-497-8147
Email: laing@ucar.edu
Home Page

Project Summary:

Click on picture to view the entire figure.

Figure 1. Mean Daily Zonal Progression of Organized Convection

Arlene Laing has been studying the characteristics of convective precipitation over Africa — part of a global study of warm-season, continental precipitation endorsed by the World Weather Research Programme (WWRP) of the World Meteorological Organization (WMO).  This work is also part of the NCAR Water Cycle Research Program and is being conducted in collaboration with Dr. Richard Carbone and Dr. Vincenzo Levizzani.

Warm season precipitation cycles were examined for Africa and Europe using Meteosat digital infrared imagery from 1999 to 2003.  A sizeable fraction of the rainfall in Africa results from long-lived “episodes” of deep convection. Episodes are coherent sequences of organized convection that propagate and regenerate on regional and continental scales. Most episodes have phase speeds of 10^-20 m s^-1. A major generating factor for convection is thermal forcing associated with large elevated heat sources. Episodes occur with moderate vertical wind shear.  Daily propagation of organized precipitation in tropical Africa can be interrupted by large-scale changes such as equatorial wave passages.  Convection episodes are less frequent over the subtropics and midlatitudes, where propagation of convection occurs with large-scale westerly wind shear and warm, moist, low-level inflow.  Study results infer the potential for increased predictive skill in sub-seasonal weather prediction, which could enable substantial societal benefits.  The focus for 2007 has been the development of climatologies for organized convection in central and southern Africa.

The next phase of this research is to simulate active and inactive periods, using the Advanced Research WRF model, in order to develop a better understanding of the environments associated with these different regimes.

Presentations:

• A satellite-based study of the propagation of deep convection over Central Africa, Perugia ITA, July 2007
• Diagnosing the precipitation cycles over Africa and Europe from satellite data, Amsterdam NLD, September 2007
• Laing-Moncrieff- Patterns of convection in Africa: Implications for prediction of precipitation, Boulder USA, October 2006
• Patterns of convection in Africa and opportunities for collaboration, Boulder USA, October 2006
• Precipitation in Africa, Boulder USA, July 2007
• Preliminary investigation of deep convection over central and southern Africa, Boulder USA, December 2007
• Propagation and diurnal cycle of deep convection in Sahelian and Soudian Africa, Boulder USA, March 2007
• Propagation of Deep Convection in Africa: Implications for predictability of precipitation, Perugia ITA, July 2007
• The diurnal cycle and propagation of convection in Africa., Pretoria ZAF, November 2006
• Weather Research in Africa: Science for Society, Boulder USA, March 2007

Publications:

Byrne, M. A., A. G. Laing, C. B. Connor, 2007: Predicting tephra dispersion with a mesoscale atmospheric model and a particle fall model: Application of Cerro Negro volcano. J. Appl. Meteor. Climat., 46, 121-135.

Laing, A.G., R. E. Carbone, and V. Levizzani, 2007: The propagation of deep convection in Africa: Implications for predictability of precipitation. Quantification and Reduction of Predictive Uncertainty for Sustainable Water Resources Management (Eds. E. Boegh, H. Kunstmann, T. Wagnerer, A. Hall, L. Bastidas, S. Franks, H. Gupta, D. Rosbjerg, J. Schaake). IAHS Publ. 313, 24-32.

Levizzani, V., R. E. Carbone, R. Ginnetti, A. G. Laing, M. Masotti, S. Melani, M. Pasqui, 2007: Climatology of warm season precipitating clouds: first results for Europe and Mediterranean. Climate and Climate Change: Research Activities of the National Research Council, B. Carli, G. Cavarretta, M. Colacino, S. Fuzzi, National Research Council, Eds., 113-116.