John L. Monteith

Bio: John L. Monteith is an academic researcher from International Crops Research Institute for the Semi-Arid Tropics. The author has contributed to research in topics: Atmosphere & Transpiration. The author has an hindex of 58, co-authored 138 publications receiving 30024 citations. Previous affiliations of John L. Monteith include Goddard Space Flight Center & University of Nottingham.

Analysis of Microclimate

Abstract: Physics of Plant Environment Edited by W. R. Van Wijk. Pp. xvi + 383. (Amsterdam: North-Holland Publishing Company, 1963.) 80s.

Mass Transfer: (ii) Particles

Abstract: Small particles such as pollen grains, spores, pathogens, and pollutant materials may be transported long distances by the wind and deposited at the surface or inhaled by animals. This chapter reviews the physics of particle transfer and deposition. In still air particles sediment under gravity at speeds depending on their mass and shape, and very small particles move with random Brownian motion. In moving air they may be impacted on or intercepted by objects in their path. Equations describing these mechanisms are developed, and measurements of particle depostion are interpreted to show the influence of particle size, windspeed, target size, and surface microstructure on deposition and retention. Particles with diameters in the range 0.1 – 2 μ m deposit much more rapidly on tall canopies than current theory predicts, but above and below this size range there is reasonable understanding of the physical principles governing deposition. Hygroscopic particles grow rapidly in humidity gradients, altering their depostion rates. The chapter concludes with a section on deposition mechanisms when small particles are inhaled, indicating the hazards posed by inhaled sub-micron-sized pollutant aerosols.

Microclimatology of Radiation: (ii) Radiation Interception by Solid Structures

Abstract: In microclimatology and micrometeorology, radiative fluxes are usually expressed per unit area of ground. In environmental physics, we are also concerned with radiation intercepted by leaves at angle in canopies, sloping land surfaces, and animal coats. This chapter describes methods for estimating the radiation intercepted by solid structures in terms that depend on the geometry of the surface (defining a “shape factor”) and the directional properties of incident radiation. Shape factors are derived for simple geometric shapes such as ellipsoids, cones, and cylinders, to which the shapes of animals, trees, and shrubs can often be approximated. Direct and diffuse radiation is treated.

Crop evapotranspiration : guidelines for computing crop water requirements

Abstract: (First edition: 1998, this reprint: 2004). This publication presents an updated procedure for calculating reference and crop evapotranspiration from meteorological data and crop coefficients. The procedure, first presented in FAO Irrigation and Drainage Paper No. 24, Crop water requirements, in 1977, allows estimation of the amount of water used by a crop, taking into account the effect of the climate and the crop characteristics. The publication incorporates advances in research and more accurate procedures for determining crop water use as recommended by a panel of high-level experts organised by FAO in May 1990. The first part of the guidelines includes procedures for determining reference crop evapotranspiration according to the FAO Penman-Monteith method. These are followed by updated procedures for estimating the evapotranspiration of different crops for different growth stages and ecological conditions.

Large Area Hydrologic Modeling and Assessment Part i: Model Development

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, nonpoint 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.

Primary Production of the Biosphere: Integrating Terrestrial and Oceanic Components

Abstract: Integrating conceptually similar models of the growth of marine and terrestrial primary producers yielded an estimated global net primary production (NPP) of 104.9 petagrams of carbon per year, with roughly equal contributions from land and oceans. Approaches based on satellite indices of absorbed solar radiation indicate marked heterogeneity in NPP for both land and oceans, reflecting the influence of physical and ecological processes. The spatial and temporal distributions of ocean NPP are consistent with primary limitation by light, nutrients, and temperature. On land, water limitation imposes additional constraints. On land and ocean, progressive changes in NPP can result in altered carbon storage, although contrasts in mechanisms of carbon storage and rates of organic matter turnover result in a range of relations between carbon storage and changes in NPP.

Correction of flux measurements for density effects due to heat and water vapour transfer

Abstract: When the atmospheric turbulent flux of a minor constituent such as CO2 (or of water vapour as a special case) is measured by either the eddy covariance or the mean gradient technique, account may need to be taken of variations of the constituent's density due to the presence of a flux of heat and/or water vapour. In this paper the basic relationships are discussed in the context of vertical transfer in the lower atmosphere, and the required corrections to the measured flux are derived. If the measurement involves sensing of the fluctuations or mean gradient of the constituent's mixing ratio relative to the dry air component, then no correction is required; while with sensing of the constituent's specific mass content relative to the total moist air, a correction arising from the water vapour flux only is required. Correspondingly, if in mean gradient measurements the constituent's density is measured in air from different heights which has been pre-dried and brought to a common temperature, then again no correction is required; while if the original (moist) air itself is brought to a common temperature, then only a correction arising from the water vapour flux is required. If the constituent's density fluctuations or mean gradients are measured directly in the air in situ, then corrections arising from both heat and water vapour fluxes are required. These corrections will often be very important. That due to the heat flux is about five times as great as that due to an equal latent heat (water vapour) flux. In CO2 flux measurements the magnitude of the correction will commonly exceed that of the flux itself. The correction to measurements of water vapour flux will often be only a few per cent but will sometimes exceed 10 per cent.