COLA Report 9

Meeting on Problems in Initializing Soil Wetness: Review

P. A. Dirmeyer

January 1995


Preface

It has been well recognized that the memory required for dynamical prediction of seasonal climate anomalies resides primarily in the slowly varying boundary conditions at the earth's surface. The role of tropical sea surface temperature anomalies has been investigated through a large number of observational and modeling experiments. About twenty years ago, atmospheric general circulation models were forced by hypothetical (quite unrealistic) sea surface temperature anomalies. However, during the past ten years only realistic (observed) sea surface temperature anomalies are used to force atmospheric models. Similarly, about ten years ago, hypothetical (quite unrealistic) land surface anomalies were used to force general circulation models. With the advent of more realistic models of the land-surface processes, a few GCM experiments have begun to show that large-scale realistic anomalous soil wetness, which may persist for a season or longer, can influence seasonal mean land surface temperature and rainfall.

Recognizing the need for accurate specification of soil wetness to initialize GCMs for weather and climate prediction, the Center for Ocean-Land-Atmosphere Studies, with the encouragement and support of E. Kalnay, convened an informal meeting on 19 August 1994 to discuss the problems faced by atmospheric modelers in initializing soil wetness for forecasts and climate studies. The participants were principally scientists involved in the numerical simulation or prediction of the atmosphere, and land-atmosphere interactions, although hydrologists and program officials were also in attendance. Current problems include the lack of reliable data over much of the world, spin-up and climate drift of soil moisture in the numerical models, inconsistent representation of soil moisture between different models, and the scientific merit of statistical methods for initializing soil wetness. Several speakers gave presentations, and a subsequent discussion session allowed the attendees to deliberate on the more pressing issues. This meeting served in part as a prelude to the GEWEX workshop on global soil moisture held in Longmont, Colorado during 4-6 October 1994.


Complete copies of this report are available from:
Center for Ocean-Land-Atmosphere Studies
4041 Powder Mill Road, Suite 302
Calverton, MD 20705-3106
(301) 595-7000
(301) 595-9793 Fax


last update: 17 February 1995
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