LAND SURFACE - ATMOSPHERE INTERACTIONS FOR CLIMATE MODELING

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1 LAND SURFACE - ATMOSPHERE INTERACTIONS FOR CLIMATE MODELING

2 LAND SURFACE-ATMOSPHERE INTERACTIONS FOR CLIMATE MODELING Observations, Models and Analysis Edited by ERICF. WOOD Water Resources Program, Princeton University, New Jersey, U.S.A. Reprinted from Surveys in Geophysics, Volume 12, Nos. 1-3 (1991) KLUWER ACADEMIC PUBLISHERS DORDRECHT / BOSTON / LONDON

3 Library of Congress Cataloging-in-Publication Data Land surface, atmosphere interactions for climate model ing observations, models, and analysis I edited by Eric F. Wood. p. cm. Inc 1 udes index. ISBN (alk. paper) 1. Climatology--Mathematical models. 2. Landforms--Mathematical models. I. Wood, Eric F. QC981.L dc ISBN-13: e-isbn-13: : / Published by Kluwer Academic Publishers, P.O. Box 17, 3300 AA Dordrecht, The Netherlands. Kluwer Academic Publishers incorporates the publishing programmes of D. Reidel, Martinus Nijhoff, Dr W. Junk and MTP Press. Sold and distributed in the U.S.A. and Canada by Kluwer Academic Publishers, 101 Philip Drive, Norwell, MA 02061, U.S.A. In all other countries, sold and distributed by Kluwer Academic Publishers Group, P.O. Box 322, 3300 AH Dordrecht, The Netherlands. Printed on acid-free paper All Rights Reserved 1991 Kluwer Academic Publishers Softcover reprint of the hardcover 1 st edition 1991 No part of the material protected by this copyright notice may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording or by any information storage and retrieval system, without written permission from the copyright owner.

4 TABLE OF CONTENTS Preface vii PART I OBSERVATIONS AND OBSERVATIONAL NEEDS 1. Insight from Large-Scale Observational Studies of Land/Atmosphere Interactions W. James Shuttleworth 3 2. Some Aspects of the HAPEX-MOBILHY Programme: The Data Base and the Modelling Strategy 1. Noilhan, 1.e. Andre, P. Bougeault, J.P. Goutorbe, and P. Lacarrere Passive Microwave Remote Sensing Contribution to Hydrological Variables Bhaskar J. Choudhury Modeling and Observing Land-Surface-Atmosphere Interactions on Large Scales Piers Sellers Land Surface Hydrology in a General Circulation Model- Global and Regional Fields Needed for Validation Robert E. Dickinson and Patrick J. Kennedy Simulation of Daily Precipitation in the Pacific Northwest Using a Weather Classification Scheme Larry L. Wilson, Dennis P. Lettenmaier, and Eric F. Wood 127 PART II MODELING AND ANALYSIS 7. A Refinement of the Combination Equations for Evaporation P.C.D. Milly A Statistical-Dynamical Approach to Parameterize Subgrid-Scale Land Surface Heterogeneity in Climate Models Roni Avissar Evapotranspiration and Runoff from Large Land Areas: Land Surface Hydrology for Atmospheric General Circulation Models J.S. Famiglietti and E.F. Wood Climate and the Equilibrium State of Land Surface Hydrology Parameterizations Dara Entekhabi and Peter S. Eagleson Partial Analysis Applied to Scale Problems in Surface Moisture Fluxes V. Kuhnel, J.e.1. Dooge, J.P.I. O'Kane, and R.I. Romanowicz 221

5 vi TABLE OF CONTENTS 12. Distributed Parameterization of Complex Terrain Lawrence E. Band Modeling Basin-Scale Hydrology in Support of Physical Climate and Global Biogeochemical Studies: An Example Using the Zambezi River Charles J. Vorosmarty and Berrien Moore III 271 List of Authors 313

6 PREFACE It is well known that the interactions between land surfaces and the atmosphere, and the resulting exchanges in water and energy have a tremendous affect on climate. The inadequate representation of land-atmosphere interactions is a major weakness in current climate models, and is providing the motivation for the HAPEX and ISLSCP experiments as well as the proposed Global Energy and Water Experiment (GEWEX) and the Earth Observing System (EOS) mission. The inadequate representation reflects the recognition that the well-known physical relationships, which are well described at small scales, result in different relationships when represented at the scales used in climate models. Understanding this transition in the mathematical relationships with increased space-time scales appears to be very difficult, and has led to different approaches; at one extreme, the famous "bucket" model where the land-surface is a simple one layer storage without vegetation; the other extreme may be Seller's Simple Biosphere Model (Sib) where one big leaf covers the climate model grid. Given the heterogeneous nature of landforms, soils and vegetation within a climate model grid, the development of new land surface parameterizations, and their verification through large scale experiments is perceived to be a challenging area of research for the hydrology and meteorology communities. This book evolved from a workshop held at Princeton University to explore the status of land surface parameterizations within climate models, and how observational data can be used to assess these parameterizations and improve models. Two major questions are address: what can we learn from field experiments (both past and present) concerning which processes and in what detail are important; and given the computational scale of climate models relative to the heterogeneity of land surfaces and its atmospheric forcings, what is the appropriate scale for representing land processes within climate models and for evaluating climate change impacts on hydrologic systems? Concerning the first question, there have been a number of field experiments whose aims are to gather information on the interactions between the land and atmosphere. The first part of the book is devoted to observations and observational needs, with the first paper by J. Shuttleworth providing an overview of many recent experiments and currently planned experiments in Europe, Africa (Niger), Brazil and Canada, as well as new experiments under GEWEX. The HAPEX and ISLSCP (Fife) scale experiments described in this paper are expanded upon in papers 2 and 4. How passive microwave remote sensing can contribute to observations, and data sets needed for validation of both regional and global climate models round out Part I of the volume. The second issue, concerning the appropriate scale for modeling land processes, is in essence the debate on the sensitivity of climate to these processes - greater Surveys in Geophysics 12: vii-viii, 1991.

7 viii PREFACE sensitivity, requires greater detail. What modeling results have been, or can be, generated to investigate this question? What modeling experiments need to be performed to resolve the "scale" question and what is the tradeoff' among model complexity, the physical basis for land parameterizations and observational data for estimating model parameters? Many of these issues are addressed in the second part of the book on models and analyses. Five papers in this section address the handling of subgrid variability arising from variability in soils, topography and vegetation. Incorporating, testing and validating these new land-atmospheric parameterizations within global climate models is the next challenge facing hydrologists as is tying the climate model predictions back to the river catchment scale. An initial approach is to take climate disturbances predicted from climate models and incorporate them within the land hydrology models. Paper 13 presents a study for the Zambezi River, a catchment sufficiently large that it covers a number of climate model grids. Support for the workshop and preparation of this volume was made possible through a grant from the Andrew W. Mellon Foundation. This support is gratefully acknowledged. Department of Civil Engineering and Operations Research Princeton University Princeton, NJ U.S.A. ERIC F. WOOD