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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, an isothermal body with homogeneous thermal properties is used to estimate the exchange of heat and water vapour in cocoa pods. But, the model is based on the assumption that the dew point temperature of air in the canopy rises faster than the surface temperature of the pods.
Abstract: Dew forms on cocoa pods after sunrise when the dew-point temperature of air in the canopy rises faster than the surface temperature of the pods. Exchanges of heat and water vapour are estimated by treating a pod as an isothermal body with homogeneous thermal properties. Two treatments of this simple model are discussed. First, the heat balance equation is simplified to a form which allows the environmental limits for condensation to be derived explicitly. Second, the equation is solved numerically to find the duration and mean depth of wetness as a function of environmental variables. Consistent with observation, the thermal lag of the pod is about 1 to 3K; condensation to a depth of 10 to μm occurs when air at sunrise is almost saturated and windspeed is light. Condensation on cocoa pods is likely to be significant in the spread of Black Pod, a serious fungal disease.

38 citations

Journal ArticleDOI
TL;DR: The orientation of the model to the wind had little effect on the bulk resistance of the fleece, but the resistance on the windward side was substantially lower than on the leeward side.
Abstract: Penetration of an animal’s coat by wind reduces its thermal insulation and increases heat loss to the environment. From studies of the sensible heat loss from a life-sized model sheep covered with fleece, the average fleece resistance r¯ f (s cm -1 ) was related to windspeed u (m s -1 ) by 1/ r¯ f ( u ) = l/ r¯ f (0) + cu , where c is a dimensionless constant. As c is expected to be inversely proportional to coat depth I , the more general relation k¯ ( u ) = k¯ (0) + c9u was evaluated, where k¯ = I / r¯ f is the thermal diffusivity (cm 2 s -1 ) of the fleece and c9 = cI is another constant (cm). The orientation of the model to the wind had little effect on the bulk resistance of the fleece, but the resistance on the windward side was substantially lower than on the leeward side.

38 citations

Journal ArticleDOI
TL;DR: Pearl millet was grown on stored water at Niamey, Niger to determine the physiological basis of exploitation and conservation of water by crops during drought and the important role of tillers is discussed in relation to the development and maintenance of a canopy.
Abstract: Pearl millet [Pennisetum americanum] was grown on stored water at Niamey, Niger, at row spacings of 38, 75 or 150 cm to determine the physiological basis of exploitation and conservation of water by crops during drought. Between 18 and 32 days after sowing, roots grew rapidly beneath all crops, reaching 140 cm in the narrow spacing, but there were differences between crops in the pattern of growth. Soil cores and trench profiles indicated that plants in wider rows had fewer deeper roots. Substantial differences in both the amount and pattern of shoot growth were recorded in the different populations. Initially growth was fastest at the narrow spacing but stopped by day 45 and eventually the wide spacing produced most DM due mainly to greater survival of tillers. The partitioning of aboveground DM into vegetative and reproductive fractions was similar at all 3 spacings and was consistent with figures for comparable crops elsewhere. The important role of tillers is discussed in relation to the development and maintenance of a canopy

37 citations

Proceedings ArticleDOI
01 Jan 1988

37 citations

Journal ArticleDOI
TL;DR: In this paper, the authors explored the suggestion by Idso and his colleagues that the response of stomata to saturation vapour pressure deficit may prove to be an artefact of porometry and revealed several potential sources of error leading to anomalously small ratios of aerodynamic to stomatal resistance both for leaves and for canopies.

36 citations


Cited by
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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