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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.


Papers
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Journal ArticleDOI
TL;DR: In this article, a simple, mechanistic model was developed to interpret measurements of the growth and yield of sorghum at different levels of nitrogen fertilization and water supply in semiarid conditions.
Abstract: Nitrogen fertilization is important in achieving high sorghum [Sorghum bicolor (L) Moench] yields Under semiarid conditions, however, the response to N is confounded by seasonal differences in water availability A simple, mechanistic model was developed to interpret measurements of the growth and yield of sorghum at different levels of N and water supply The structure of the sorghum-N model was equivalent to a previously developed maize-N (Zea mays L) model, including the N uptake function, which depends on thermal units The sorghum-N model was developed considering experimental results obtained in the tropical climate of Katherine, Australia After adjusting coefficients to describe leaf and grain development for sorghum instead of maize, the model simulated crop N uptake, growth, and grain yield Without any further changes in the model, sorghum grown in the subtropical climate of Lawes, Australia, with grain yields ranging from 121 to 886 g m -2 , was well simulated by the model A third set of data obtained in an irrigation-N application experiment at Hyderabad, India, was compared against model results After adjusting the coefficients that describe the development of the cultivar and the soil organic content at this location, the model produced results comparable to experimental results Analysis of the model results led to two interesting hypotheses concerning the experiment at Hyderabad: (i) the irrigation level of the well-watered treatment appeared to be inadequate to avoid drought stress at the end of the cropping season, and (ii) there was seemingly about 4 g N m -2 of soil N unavailable to the crop in each of the irrigation treatments Overall, the sorghum-N model proved useful in interpreting and analyzing field measurements of development, growth, and yield of sorghum grown under diverse conditions

22 citations

Journal ArticleDOI
TL;DR: In this paper, the authors derived an equation to show how the net effect of aerosol on the lower atmosphere depends on the reflection coefficient of the surface and on the aerodynamic and surface resistances to vapour transfer.
Abstract: SUMMARY The convergence of heat below subsidence inversions was estimated from radiosonde ascents on fine summer days. Sensible heat input from the ground was estimated from measurements of heat fluxes and net radiation over a wheat field. Absorption and back scattering of solar radiation by aerosol throughout the atmosphere were calculated from measurements of solar radiation at the ground. Radiation absorbed by aerosol in the thermal boundary layer heated the lower atmosphere at an average rate of 3.3degC day-’ (60Wrn-’), about twice as fast as estimated for gaseous constituents. An equation is derived to show how the net effect of aerosol on the lower atmosphere depends on the reflection coefficient of the surface and on the aerodynamic and surface resistances to vapour transfer. Over the wheat, the net effect was almost zero when the crop was transpiring fast, but when the crop was mature, aerosol caused net cooling. I. INTRODUCTION As part of a wider attempt to identify possible causes of climatic change, attention has recently been directed to the absorption and scattering of solar radiation by aerosol, processes which modify the heat balance of the atmosphere and the radiation budget at the earth’s surface. Calculations by Mitchell (1971), and by others, demonstrate that aerosol may be responsible either for cooling or for heating the lower atmosphere depending on factors such as the height, thickness and optical properties of the layer and the relative inputs of sensible and latent heat from the ground. The main sources of uncertainty in predicting thermal effects of aerosol in the atmosphere are an incomplete knowledge of (i) optical properties and distribution of aerosol, and (ii) the relationship between net radiation and sensible heat flux at the earth’s surface. We have made direct measurements, during summer anticyclonic conditions in Britain, of heat storage in the lower atmosphere, coupled with measurements of surface radiation and heat fluxes. In the first instance, the measurements were analysed to show the importance of radiant energy absorbed by aerosol in determining the energy budget of the lower atmosphere. The analysis was then extended to estimate the influence of atmospheric aerosol on the input of sensible heat to the atmosphere from the ground. It appears that aerosol may be responsible for a net heating or cooling of the lower atmosphere at a rate which depends on surface reflectivity and on the ratio of aerodynamic and surface resistances to vapour transfer. 2. THEORY During anticyclonic weather in Britain, inversions formed by subsidence are common at heights between 1 and 2km. Below the main inversion, the atmosphere is heated by radiation and by an input of sensible heat from the ground. Heat may also be entrained from the warmer air above the inversion as discussed by Cattle and Weston (1975). For simplicity, we shall consider the heat budget of a ‘thermal boundary layer’ defined as that layer of the atmosphere above which there was no measurable change of temperature due 95

21 citations


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Book
01 Jan 1998
TL;DR: In this paper, an updated procedure for calculating reference and crop evapotranspiration from meteorological data and crop coefficients is presented, based on the FAO Penman-Monteith method.
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.

21,958 citations

Journal ArticleDOI
TL;DR: 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 as discussed by the authors.
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.

6,674 citations

Journal ArticleDOI
10 Jul 1998-Science
TL;DR: Integrating conceptually similar models of the growth of marine and terrestrial primary producers yielded an estimated global net primary production of 104.9 petagrams of carbon per year, with roughly equal contributions from land and oceans.
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.

4,873 citations

Journal ArticleDOI
TL;DR: In this article, 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, where the correction to measurements of water vapour flux will often be only a few per cent but will sometimes exceed 10 percent.
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.

4,174 citations