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- Author or Editor: R. E. Leonard x
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Abstract
A topographic map of the upper surface of the canopy of a red pine (Pinus resinosa) plantation was drawn from 275 canopy heights measured on a grid of 0.9 × 1.5 m. The distribution of heights was approximately normal, with a mean of 11.6 m; and a standard deviation of 1.6 m; this is an improved method of designating stand height. The roughness parameter s 0 and zero-plane displacement of the stand were estimated from the canopy map data, using both Kung's logarithmic formula and Lettau's equation for obstacle size and shape. These values were compared with measured s 0 and d from wind and temperature profiles in near-neutral conditions. Lettau's formula, assuming the obstacles were uniform square-packed paraboloids, gave s 0=138cm and d10.6 m. Kung's formula gave s 0=75 cm and d=9.7 m. Measured profiles gave a median s 0=100 cm after d was fixed at its median value of 9.6 m.
Abstract
A topographic map of the upper surface of the canopy of a red pine (Pinus resinosa) plantation was drawn from 275 canopy heights measured on a grid of 0.9 × 1.5 m. The distribution of heights was approximately normal, with a mean of 11.6 m; and a standard deviation of 1.6 m; this is an improved method of designating stand height. The roughness parameter s 0 and zero-plane displacement of the stand were estimated from the canopy map data, using both Kung's logarithmic formula and Lettau's equation for obstacle size and shape. These values were compared with measured s 0 and d from wind and temperature profiles in near-neutral conditions. Lettau's formula, assuming the obstacles were uniform square-packed paraboloids, gave s 0=138cm and d10.6 m. Kung's formula gave s 0=75 cm and d=9.7 m. Measured profiles gave a median s 0=100 cm after d was fixed at its median value of 9.6 m.
Abstract
The problem of a small-amplitude wave propagating over a flat porous bed is reanalyzed subject to the bottom boundary conditionwhere u represents the horizontal velocity in the fluid,ũ s represents the horizontal velocity within the bed as predicted by Darcey's law, K is the permeability and the subscript 0 denotes evaluation at the bottom (z=0). The term α is a constant whose value depends on the porosity of the bed at the interface and must be determined experimentally. The boundary condition is of the form of a “radiation-type” condition commonly encountered in heat conduction problems.
The important physical quantities (velocity, velocity potential, streamfunction, shear stress and energy dissipation) have been derived and are presented, subject to natural conditions. The bottom boundary layer is represented by the linearized Navier-Stokes equations under the usual boundary layer approximation. It is found that the boundary layer velocity distribution and shear stress can be greatly altered from impermeable bed predictions. Theoretical results for energy dissipation and shear stress are compared to existing data and are found to agree very well. The predictions of classical small-amplitude wave theory are not appreciably modified away from the boundary.
Abstract
The problem of a small-amplitude wave propagating over a flat porous bed is reanalyzed subject to the bottom boundary conditionwhere u represents the horizontal velocity in the fluid,ũ s represents the horizontal velocity within the bed as predicted by Darcey's law, K is the permeability and the subscript 0 denotes evaluation at the bottom (z=0). The term α is a constant whose value depends on the porosity of the bed at the interface and must be determined experimentally. The boundary condition is of the form of a “radiation-type” condition commonly encountered in heat conduction problems.
The important physical quantities (velocity, velocity potential, streamfunction, shear stress and energy dissipation) have been derived and are presented, subject to natural conditions. The bottom boundary layer is represented by the linearized Navier-Stokes equations under the usual boundary layer approximation. It is found that the boundary layer velocity distribution and shear stress can be greatly altered from impermeable bed predictions. Theoretical results for energy dissipation and shear stress are compared to existing data and are found to agree very well. The predictions of classical small-amplitude wave theory are not appreciably modified away from the boundary.
Abstract
The Clouds and the Earth's Radiant Energy System (CERES) spacecraft sensors are designed to measure broadband earth-reflected solar shortwave (0.3–5 µm) and earth-emitted longwave (5– > 100 µm) radiances at the top of the atmosphere as part of the Mission to Planet Earth program. The scanning thermistor bolometer sensors respond to radiances in the broadband shortwave (0.3–5 µm) and total-wave (0.3– > 100 µm) spectral regions, as well as to radiances in the narrowband water vapor window (8–12 µm) region. The sensors are designed to operate for a minimum of 5 years aboard the NASA Tropical Rainfall Measuring Mission and Earth Observing System AM-I spacecraft platforms that are scheduled for launches in 1997 and 1998, respectively. The flight sensors and the in-flight calibration systems will he calibrated in a vacuum ground facility using reference radiance sources, tied to the international temperature scale of 1990. The calibrations will be used to derive sensor gains, offsets, spectral responses, and point spread functions within and outside of the field of view. The shortwave, total-wave, and window ground calibration accuracy requirements (1 sigma) are ±0.8, ±0.6, and ±0.3 W m−2 sr−1, respectively, while the corresponding measurement precisions are ±0.5% and ±1.0% for the broadband longwave and shortwave radiances, respectively. The CERES sensors, in-flight calibration systems, and ground calibration instrumentation are described along with outlines of the preflight and in-flight calibration approaches.
Abstract
The Clouds and the Earth's Radiant Energy System (CERES) spacecraft sensors are designed to measure broadband earth-reflected solar shortwave (0.3–5 µm) and earth-emitted longwave (5– > 100 µm) radiances at the top of the atmosphere as part of the Mission to Planet Earth program. The scanning thermistor bolometer sensors respond to radiances in the broadband shortwave (0.3–5 µm) and total-wave (0.3– > 100 µm) spectral regions, as well as to radiances in the narrowband water vapor window (8–12 µm) region. The sensors are designed to operate for a minimum of 5 years aboard the NASA Tropical Rainfall Measuring Mission and Earth Observing System AM-I spacecraft platforms that are scheduled for launches in 1997 and 1998, respectively. The flight sensors and the in-flight calibration systems will he calibrated in a vacuum ground facility using reference radiance sources, tied to the international temperature scale of 1990. The calibrations will be used to derive sensor gains, offsets, spectral responses, and point spread functions within and outside of the field of view. The shortwave, total-wave, and window ground calibration accuracy requirements (1 sigma) are ±0.8, ±0.6, and ±0.3 W m−2 sr−1, respectively, while the corresponding measurement precisions are ±0.5% and ±1.0% for the broadband longwave and shortwave radiances, respectively. The CERES sensors, in-flight calibration systems, and ground calibration instrumentation are described along with outlines of the preflight and in-flight calibration approaches.
