Predictability Mysteries in Cloud-Resolving Models

Hohenegger, Cathy; Lüthi, Daniel; Schär, Christoph
August 2006
Monthly Weather Review;Aug2006, Vol. 134 Issue 8, p2095
Academic Journal
The rapid amplification of small-amplitude perturbations by the chaotic nature of the atmospheric dynamics intrinsically limits the skill of deterministic weather forecasts. In this study, limited-area cloud-resolving numerical weather prediction (NWP) experiments are conducted to investigate the role of mesoscale processes in determining predictability. The focus is set on domain-internal error growth by integrating an ensemble of simulations using slightly modified initial conditions but identical lateral boundary conditions. It is found that the predictability of the three investigated cases taken from the Mesoscale Alpine Programme (MAP) differs tremendously. In terms of normalized precipitation spread, values between 0.05 (highly predictable) and 1 (virtually unpredictable) are obtained. Analysis of the derived ensemble spread demonstrates that the diabatic forcing associated with moist dynamics is the prime source of rapid error growth. However, in agreement with an earlier study it is found that the differentiation between convective and stratiform rain is unable to account for the distinctive precipitation spreads of the three cases. In particular, instability indices are demonstrated to be poor predictors of the predictability level. An alternate hypothesis is proposed and tested. It is inspired by the dynamical instability theory and states that significant loss of predictability only occurs over moist convectively unstable regions that are able to sustain propagation of energy against the mean flow. Using a linear analysis of gravity wave propagation, this hypothesis is shown to provide successful estimates of the predictability level for the three cases under consideration.


Related Articles

  • Moisture level in central US termed `dangerous,' west remains wet.  // American Nurseryman;8/1/95, Vol. 182 Issue 3, p16 

    Focuses on the National Weather Service's Climate Prediction Center's report on the development of long-term moisture surpluses in the central region of the United States. Geographical coverage of the region; Regional weather indications in the long-term Palmer Drought Index; Climate Prediction...

  • Some parts of state see moisture.  // High Plains Journal;8/26/2013, Vol. 131 Issue 34, p2B 

    The article offers weather updates related to Kansas for the week ending August 18, 2013 as of National Agricultural Statistics Service, Kansas field Office, which informs that unseasonably cool temperatures brings moisture to some areas of the state.

  • Reading the skies. Dyson, Cindy // Backpacker;Aug97, Vol. 25 Issue 6, p53 

    Focuses on the observation of clouds fo more specific weather clues. Why wind shifts is good indicator of bad weather; Characteristics of a west wind; Description of a storm called warm fronts. INSET: Cloud reading 101..

  • Explicit Cloud-Scale Models for Operational Forecasts: A Note of Caution. Elmore, Kimberly L.; Stensrud, David J.; Crawford, Kenneth C. // Weather & Forecasting;Aug2002, Vol. 17 Issue 4, p873 

    As computational capacity has increased, cloud-scale numerical models are slowly being modified from pure research tools to forecast tools. Previous studies that used cloud-scale models as explicit forecast tools, in much the same way as a mesoscale model might be used, have met with limited...

  • Toward Improved Prediction of Mesoscale Convective System Dissipation. Gale, Joseph J.; Gallus Jr., William A.; Jungbluth, Karl A. // Weather & Forecasting;Aug2002, Vol. 17 Issue 4, p856 

    The complex issue of mesoscale convective system (MCS) dissipation over the central United States is investigated using both observations and Eta Model output from 47 cases that occurred during May–August 1998–99 in Iowa and surrounding states. The cold pool–shear balance...

  • Modification of the Thermodynamic Structure of the Lower Troposphere by the Evaporation of Precipitation: A GEWEX Cloud System Study. Katzfey, J.J.; Ryan, B.F. // Monthly Weather Review;Jul97, Vol. 125 Issue 7, p1431 

    The importance of subcloud evaporation to the thermodynamics and movement of cold fronts is investigated through inclusion of an explicit cloud scheme within a 30-km resolution limited-area model. Two cases are examined: 18 November 1984 and 26 February 1995. The effect of the subcloud...

  • Weather Log: Raindrops Keep Falling (p. 11).  // Scholastic SuperScience (Teacher's Edition);Apr2002, Vol. 13 Issue 7, pT6 

    Presents a tabulation form for weather forecast. Wind direction; Cloud cover; Temperature.

  • The Surface Downward Longwave Radiation in the ECMWF Forecast System. Morcrette, Jean-Jacques // Journal of Climate;Jul2002, Vol. 15 Issue 14, p1875 

    The surface downward longwave radiation, computed by the European Centre for Medium-Range Weather Forecasts (ECMWF) forecast system used for the ECMWF 40-yr reanalysis, is compared with surface radiation measurements for the April–May 1999 period, available as part of the Baseline Surface...

  • Predict the Weather.  // Backpacker;Jun2010, Vol. 38 Issue 5, p54 

    The article offers information on how to predict the weather by identifying the formation and warning signs of several clouds such as cumulonimbus, nimbostratus, and cirrus clouds.


Read the Article


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

Try another library?
Sign out of this library

Other Topics