Thresholds in atmosphere–soil moisture interactions: Results from climate model studies

[1] The potential predictability of the effects of warm season soil moisture anomalies over the central United States has been investigated in a series of general circulation model (GCM) experiments with the National Center for Atmospheric Research (NCAR) Community Climate Model version 3 Land Surface Model (CCM3/LSM). Three different types of experiments have been developed, all starting in either March (representing precursor conditions) or June (conditions at the onset of the warm season): (1) “anomaly” runs with large, exaggerated initial soil moisture reductions, aimed at evaluating the physical mechanisms by which soil moisture can affect the atmosphere; (2) “predictability” runs aimed at evaluating whether typical soil moisture initial anomalies (indicative of year-to-year variability) can have a significant effect, and if so, for how long; and (3) “threshold” runs aimed at evaluating if a soil moisture anomaly must be of a specific size (i.e., a threshold crossed) before a significant impact on the atmosphere is seen. The anomaly runs show a large, long-lasting response in soil moisture as well as surface temperature, sea level pressure, and precipitation; effects persist for at least a year. The predictability runs, on the other hand, show very little impact of the initial soil moisture anomalies on the subsequent evolution of soil moisture and other atmospheric parameters; internal variability is most important, with the initial state of the atmosphere (representing remote effects such as SST anomalies) playing a more secondary role on seasonal and shorter timescales. The threshold runs, devised to help resolve the dichotomy in anomaly and predictability results, suggest that, at least in CCM3/LSM, the vertical profile of soil moisture is the most important factor and that deep soil zone anomalies exert a more powerful, long-lasting effect than do anomalies in the near-surface soil zone. We therefore suggest that soil moisture feedbacks may be more important in explaining interannual to decadal droughts evident in the historic and recent prehistoric records, but less important on monthly to seasonal timescales.

[1]  Robert S. Webb,et al.  Temporal and spatial patterns of Holocene dune activity on the Great Plains of North America: megadroughts and climate links , 2001 .

[2]  F. Robertson,et al.  Diagnosing warm season precipitation over the GCIP region from a GCM and reanalysis , 2001 .

[3]  A. Robock,et al.  The Global Soil Moisture Data Bank , 2000 .

[4]  J. Shukla,et al.  Impact of Initial Soil Wetness on Seasonal Atmospheric Prediction , 1999 .

[5]  R. Pielke,et al.  Seasonal weather prediction as an initial value problem , 1999 .

[6]  Randal D. Koster,et al.  A Simple Framework for Examining the Interannual Variability of Land Surface Moisture Fluxes , 1999 .

[7]  J. Overpeck,et al.  2000 Years of Drought Variability in the Central United States , 1998 .

[8]  James J. Hack,et al.  Response of Climate Simulation to a New Convective Parameterization in the National Center for Atmospheric Research Community Climate Model (CCM3) , 1998 .

[9]  G. Bonan.  The Land Surface Climatology of the NCAR Land Surface Model Coupled to the NCAR Community Climate Model , 1998 .

[10]  James J. Hack,et al.  The Hydrologic and Thermodynamic Characteristics of the NCAR CCM3 , 1998 .

[11]  James J. Hack,et al.  The Energy Budget of the NCAR Community Climate Model: CCM3* , 1998 .

[12]  D. Gutzler,et al.  Evidence for a relationship between spring snow cover in North America and summer rainfall in New Mexico , 1997 .

[13]  Dara Entekhabi,et al.  Timescales of Land Surface Evapotranspiration Response. , 1997 .

[14]  R. Koster,et al.  The Influence of Land Surface Moisture Retention on Precipitation Statistics. , 1996 .

[15]  Daniel R. Cayan,et al.  Interannual Climate Variability and Snowpack in the Western United States , 1996 .

[16]  A. Robock,et al.  Scales of temporal and spatial variability of midlatitude soil moisture , 1996 .

[17]  R. Oglesby,et al.  A 100-Yr CCM1 Simulation of North China's Hydrologic Cycle , 1996 .

[18]  P. Dirmeyer.  Vegetation stress as a feedback mechanism in midlatitude drought , 1994 .

[19]  J. Hack.  Parameterization of moist convection in the National Center for Atmospheric Research community climate model (CCM2) , 1994 .

[20]  Thomas R. Karl,et al.  Observed Impact of Snow Cover on the Heat Balance and the Rise of Continental Spring Temperatures , 1994, Science.

[21]  Robert Atlas,et al.  The Effect of SST and Soil Moisture Anomalies on GLA Model Simulations of the 1988 U.S. Summer Drought. , 1993 .

[22]  Albert A. M. Holtslag,et al.  Local Versus Nonlocal Boundary-Layer Diffusion in a Global Climate Model , 1993 .

[23]  Alan K. Betts,et al.  Comparison between the land surface response of the ECMWF model and the FIFE‐1987 data , 1993 .

[24]  Barry Saltzman,et al.  Equilibrium Climate Statistics of a General Circulation Model as a Function of Atmospheric Carbon Dioxide. Part I: Geographic Distributions of Primary Variables , 1992 .

[25]  Robert J. Oglesby,et al.  Springtime Soil Moisture, Natural Climatic Variability, and North American Drought as Simulated by the NCAR Community Climate Model 1 , 1991 .

[26]  Jerome Namias,et al.  Spring and Summer 1988 Drought over the Contiguous United States—Causes and Prediction , 1991 .

[27]  Syukuro Manabe,et al.  The Influence of Soil Wetness on Near-Surface Atmospheric Variability , 1989 .

[28]  D. Erickson,et al.  Soil Moisture and the Persistence of North American Drought , 1989 .

[29]  Mojib Latif,et al.  The Effect of Eurasian Snow Cover on Regional and Global Climate Variations , 1989 .

[30]  Syukuro Manabe,et al.  The influence of potential evaporation on the variabilities of simulated soil wetness and climate , 1988 .

[31]  D. F. Grigal,et al.  Vertical root distributions of northern tree species in relation to successional status , 1987 .

[32]  S. Manabe.  CLIMATE AND THE OCEAN CIRCULATION: II. THE ATMOSPHERIC CIRCULATION AND THE EFFECT OF HEAT TRANSFER BY OCEAN CURRENTS , 1969 .

[33]  S. Manabe.  CLIMATE AND THE OCEAN CIRCULATION1 , 1969 .

[34]  M. Stern,et al.  THE FLOW OF A STABLE ATMOSPHERE OVER A HEATED ISLAND, PART 1 , 1953 .