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Geographic Constraints
Published in Steven D. Jaffe, Airspace Closure and Civil Aviation, 2016
Every student pilot training on a summer day learns to beware of the “3 Hs”—high, hot, and humid. All three conditions reduce the density of the air, effectively simulating a higher altitude (an effect known as “density altitude”), and degrade takeoff and climb performance of the aircraft. Higher altitudes pose operational constraints for airlines. Thinner air requires more thrust for takeoff, requiring additional fuel and reducing payload capability. High-altitude airports subject to high temperatures, such as Johannesburg (5,558 ft), Mexico City (7,316 ft), and La Paz (13,325 ft), are regularly subject to these limitations. Several methods are used to mitigate the problem. One involves scheduling departures for early morning or evening when temperatures are relatively cool. Technological developments are sometimes used to overcome these limitations. In the 1960s, South African Airways (SAA), in cooperation with Boeing, developed a water-injection method for producing more takeoff thrust for its 707s departing Johannesburg. And in planning its Indian Ocean routes from Johannesburg, SAA designated Durban, just 297 miles to the east on the Indian Ocean coast, as a technical stop for refueling on those days when temperatures significantly limited payload from Johannesburg.
Atmosphere
Published in Mohammad H. Sadraey, Aircraft Performance, 2017
The second one is density altitude hd, the altitude on a standard day at which the density would be equal to the actual air density experienced by the vehicle. Since the forces acting on a wing or fuselage are a direct function of density, the behavior of an airplane depends only on density altitude (although the engine power or thrust depends also on pressure and temperature). This altitude is often determined indirectly (in fact, calculated).
Overcoming the challenges of flow forecasting in a data poor region
Published in Canadian Water Resources Journal / Revue canadienne des ressources hydriques, 2023
Nicholas Kouwen, Amber Langmuir, Lakshminarayanan Ramanathan, Gordon Gallant
In the past, a Donor Catchments approach has been used to apply information from donor catchments to target, or data poor, catchments. Reig, Boucher, and Tremblay (2020) used 11 catchment attributes to determine if a donor catchment was suitable for use in the target catchment. Of these 11, 7 are measurable parameters in DEM’s and digital land cover maps explicitly incorporated in the hydrological modelling and routing in CHARM, namely, catchment slope, fraction of water, Strahler number, drainage density, altitude, land use, Gravelius component and area. Soil type and land cover are highly correlated which brings the total to 8. Thus, the availability of donor catchments becomes very limited because of the requirement for donor and target watersheds needing to be “too similar”. Reig’s most heavily weighted attributes are catchment slope and fraction of water cover, neither of which are used to identify donor catchments in CHARM. In fact, none of the 11 attributes used by Reig, Boucher, and Tremblay (2020) are used in identifying donor catchments in CHARM other than the broad need that all major land cover classes and drainage patterns in the target domain need only to be represented in the donor domain. As well, the various “hydrographic region” attributes need to be similar (e.g. Hudson Bay Lowlands, Canadian Shield, etc.).
Characterization of the middle and upper atmosphere temperatures by Rayleigh scattering Lidar
Published in Instrumentation Science & Technology, 2023
Zhiyuan Fang, Hao Yang, Cheng Li, Zhiqiang Kuang, Xiang Xu, Ruiyin Song, Heng Jin, Ming Zhao
and are atmospheric density, is the altitude, is reference density altitude which is assumed to be 30 km, and are the atmospheric echo altitude, and is atmospheric the two-way transmittance, which is determined by the extinction coefficient of lidar.[18]
Evidence for a change in wind regime during the Last Glacial Maximum from the Sydney region
Published in Australian Journal of Earth Sciences, 2019
Estimates of environmental dose for each sample was completed using measurements of uranium, thorium and potassium by ICP-MS and ICP-OES analysis by Intertek Genalysis. The environmental dose rate was estimated from these measurements using the conversion values of Guérin, Mercier and Adamiec (2011). An assumed water content of 5 ± 2.5 wt% was used for all samples and cosmic dose rate was considered, based on geographic position, sediment density, altitude and depth of overburden following Prescott and Hutton (1994).