Plant Water Relations and Carbon Dynamics

A biochemical model of photosynthetic CO2 assimilation in leaves of C3 species

LARGE AREA HYDROLOGIC MODELING AND ASSESSMENT PART I: MODEL DEVELOPMENT¹

ABSTRACT: A conceptual, continuous time model called SWAT (Soil and Water Assessment Tool) was developed to assist water resource managers in assessing the impact of management on water supplies and nonpoint source pollution in watersheds and large river basins. The model is currently being utilized in several large area projects by EPA, NOAA, NRCS and others to estimate the off‐site impacts of climate and management on water use, non‐point source loadings, and pesticide contamination. Model development, operation, limitations, and assumptions are discussed and components of the model are described. In Part II, a GIS input/output interface is presented along with model validation on three basins within the Upper Trinity basin in Texas.

Coupling an Advanced Land Surface–Hydrology Model with the Penn State–NCAR MM5 Modeling System. Part I: Model Implementation and Sensitivity

This paper addresses and documents a number of issues related to the implementation of an advanced land surface–hydrology model in the Penn State–NCAR fifth-generation Mesoscale Model (MM5). The concept adopted here is that the land surface model should be able to provide not only reasonable diurnal variations of surface heat fluxes as surface boundary conditions for coupled models, but also correct seasonal evolutions of soil moisture in the context of a long-term data assimilation system. In a similar way to that in which the modified Oregon State University land surface model (LSM) has been used in the NCEP global and regional forecast models, it is implemented in MM5 to facilitate the initialization of soil moisture. Also, 1-km resolution vegetation and soil texture maps are introduced in the coupled MM5–LSM system to help identify vegetation/water/soil characteristics at fine scales and capture the feedback of these land surface forcings. A monthly varying climatological 0.15° × 0.15° green vegetation fraction is utilized to represent the annual control of vegetation on the surface evaporation. Specification of various vegetation and soil parameters is discussed, and the available water capacity in the LSM is extended to account for subgrid-scale heterogeneity. The coupling of the LSM to MM5 is also sensitive to the treatment of the surface layer, especially the calculation of the roughness length for heat/moisture. Including the effect of the molecular sublayer can improve the simulation of surface heat flux. It is shown that the soil thermal and hydraulic conductivities and the surface energy balance are very sensitive to soil moisture changes. Hence, it is necessary to establish an appropriate soil moisture data assimilation system to improve the soil moisture initialization at fine scales.

A General Model for the Origin of Allometric Scaling Laws in Biology

Allometric scaling relations, including the 3/4 power law for metabolic rates, are characteristic of all organisms and are here derived from a general model that describes how essential materials are transported through space-filling fractal networks of branching tubes. The model assumes that the energy dissipated is minimized and that the terminal tubes do not vary with body size. It provides a complete analysis of scaling relations for mammalian circulatory systems that are in agreement with data. More generally, the model predicts structural and functional properties of vertebrate cardiovascular and respiratory systems, plant vascular systems, insect tracheal tubes, and other distribution networks.

A simple hydrologically based model of land surface water and energy fluxes for general circulation models

A generalization of the single soil layer variable infiltration capacity (VIC) land surface hydrological model previously implemented in the Geophysical Fluid Dynamics Laboratory general circulation model (GCM) is described. The new model is comprised of a two‐layer characterization of the soil column, and uses an aerodynamic representation of the latent and sensible heat fluxes at the land surface. The infiltration algorithm for the upper layer is essentially the same as for the single layer VIC model, while the lower layer drainage formulation is of the form previously implemented in the Max‐Planck‐Institut GCM. The model partitions the area of interest (e.g., grid cell) into multiple land surface cover types; for each land cover type the fraction of roots in the upper and lower zone is specified. Evapotranspiration consists of three components: canopy evaporation, evaporation from bare soils, and transpiration, which is represented using a canopy and architectural resistance formulation. Once the latent heat flux has been computed, the surface energy balance is iterated to solve for the land surface temperature at each time step. The model was tested using long‐term hydrologic and climatological data for Kings Creek, Kansas to estimate and validate the hydrological parameters, and surface flux data from three First International Satellite Land Surface Climatology Project Field Experiment intensive field campaigns in the summer‐fall of 1987 to validate the surface energy fluxes.

<i>Principles of Environmental Physics</i>

PREFACE TO THE SECOND EDITION LIST OF SYMBOLS 1. SCOPE OF ENVIRONMENTAL PHYSICS 2. GAS LAWS Pressure, volume and temperature Specific heats Lapse rate Water and water vapour Other gases 3. TRANSPORT LAWS General transfer equation Molecular transfer processes Diffusion coefficients Radiation laws 4. RADIATION ENVIRONMENT Solar radiation Terrestrial radiation Net radiation 5. MICROCLIMATOLOGY OF RADIATION (i) Interception Direct solar radiation Diffuse radiation Radiation in crop canopies 6. MICROCLIMATOLOGY OF RADIATION (ii) Absorption and reflection Radiative properties of natural materials Net radiation 7. MOMENTUM TRANSFER Boundary layers Wind profiles and drag on uniform surfaces Lodging and windthrow 8. HEAT TRANSFER Convection Non-dimensional groups Measurements of convection Conduction Insulation of animals 9. MASS TRANSFER (i) Gases and water vapour Non-dimensional groups Measurement of mass transfer Ventilation Mass transfer through pores Coats and clothing 10.MASS TRANSFER (ii) Particles Steady motion 11.STEADY STATE HEAT BALANCE (i) Water surfaces and vegetation Heat balance equation Heat balance of thermometers Heat balance of surfaces Developments from the Penman Equation 12.STEADY STATE HEAT BALANCE (ii) Animals Heat balance components The thermo-neutral diagram Specification of the environment Case studies 13.TRANSIENT HEAT BALANCE Time constant General cases Heat flow in soil 14.CROP MICROMETEOROLOGY (i) Profiles and fluxes Profiles Profile equations and stability Measurement of flux above the canopy 15.CROP MICROMETEOROLOGY (ii) Interpretation of measurements Resistance analogues Case studies: Water vapour and transpiration Carbon dioxide and growth Sulphur dioxide and pollutant fluxes to crops Transport within canopies APPENDIX BIBLIOGRAPHY REFERENCES INDEX

Multi‐model <scp>CMIP5</scp> and <scp>CORDEX</scp> simulations of historical summer temperature and precipitation variabilities over West Africa

ABSTRACT The mean climatology, inter‐model variability and spatio‐temporal patterns of temperature and precipitation over West Africa from Coupled Model Intercomparison Project 5 ( CMIP5 ), CMIP5_SUBSET [ensemble of global climate models driving COordinated Regional climate Downscaling EXperiment ( CORDEX )] and CORDEX multi‐model ensembles are evaluated and intercompared for the monsoon season (June–September). We find that, while CORDEX fails to outperform the simulated mean climatology of temperature by the CMIP5 ensembles, it substantially improves precipitation and provides more realistic fine‐scale features tied to local topography and landuse. This improved performance over the region is found to depend more on the internal models physics than the driving boundary conditions and results from a more consistent and realistic simulation of monsoon precipitation across the various regional climate models ( RCMs ). Rotated empirical orthogonal function ( REOF ) analysis indicates that the CORDEX ensemble captures better the spatio‐temporal variability of both temperature and precipitation (first REOF mode), in particular depicting the warming and Sahel precipitation recovery in recent decades over West Africa. On the other hand, the spatial patterns and associated time series of the last two REOF modes in CORDEX mostly follow the CMIP5_SUBSET pointing towards a strong role of the boundary forcing in the RCM simulation of precipitation variability.