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11.
The value of recreational fishing in the Great Barrier Reef, Australia: A pooled revealed preference and contingent behaviour model 总被引:2,自引:0,他引:2
Given the focus on protecting natural assets in the Great Barrier Reef Marine Park in Australia, it is important for managers and policy makers to understand the value of recreational fishing in the area, and how changes in management may affect those recreational values. Travel cost methods were used to estimate the value of recreational fishing in the Capricorn Coast in Central Queensland using data from on-site surveys conducted at boat ramps. The study also uses contingent behaviour models to estimate the change in the value of recreational fishing as conditions vary. Results indicate that there are high values associated with recreational fishing activity along the Capricorn Coast, and that the demand for recreational fishing is inelastic and that values are relatively insensitive to changes in catch rates. 相似文献
12.
Thermal internal boundary layer characteristics at a tropical coastal site as observed by a mini-SODAR under varying synoptic conditions 总被引:1,自引:0,他引:1
Thara V. Prabha R. Venkatesan Erich Mursch-Radlgruber G. Rengarajan N. Jayanthi 《Journal of Earth System Science》2002,111(1):63-77
Atmospheric boundary layer observations are conducted at a coastal site during a transition phase from winter to summer season
over the Indian peninsula. Thermal Internal Boundary Layer (TIBL) characteristics in presence of an off-shore and a weakly
influenced on-shore synoptic wind are examined with the help of measurements carried out with a mini-SODAR (SOund Detection
And Ranging), tethered balloon, and tower-based micrometeorological measurements. Influence of the changing synoptic scale
conditions on turbulent characteristics of TIBL is discussed.
Mini-SODAR data showed the development and decay of sea and land breeze. It is seen that the characteristics of TIBL over
the coastal land after sea breeze onset are similar to that of a shallow convective boundary layer (CBL) commonly found over
plain land. Inside the TIBL, a maximum wind speed was noted close to the surface due to the penetration of sea breeze. In
the off-shore case, a distinct sea breeze circulation was observed unlike in the case of on-shore flow. In the presence of
weak on-shore case, a ‘minor sea’ breeze is noted before the establishment of sea breeze and a reduction in the momentum fluxes
gives rise to decrease in the turbulence intensity. Updraft in the sea breeze front was stronger during weak synoptic conditions.
Influence of synoptic changes on the sea breeze-land breeze circulation such as onset, strength and duration of the sea-land
breeze are also examined.
This work was done while the first author was a visiting scientist at IGCAR, Kalpakkam, India. 相似文献
13.
Thara V. Prabha Monique Y. Leclerc Anandakumar Karipot David Y. Hollinger Erich Mursch-Radlgruber 《Boundary-Layer Meteorology》2008,126(2):219-236
Observations of low-level jets (LLJs) at the Howland AmeriFlux site in the USA and the jet’s impact on nocturnal turbulent
exchange and scalar fluxes over a tall forest canopy are discussed. Low-frequency motions and turbulent bursts characterize
moderately strong LLJs, whereas low-frequency motions are suppressed during periods with strong LLJs and enhanced shear. An
analysis based on the shear-sheltering hypothesis seeks to elucidate the effect of LLJs on flux measurements. In the absence
of shear sheltering, large eddies penetrate the roughness sublayer causing enhanced mixing while during periods with shear
sheltering, mixing is reduced. In the absence of the latter, ‘upside-down’ eddies are primarily responsible for the enhanced
velocity variances, scalar and momentum fluxes. The integral length scales over the canopy are greater than the canopy height.
The variance spectra and cospectra from the wavelet analysis indicate that large eddies (spatial scale greater than the low-level
jet height) interact with active canopy-scale turbulence, contributing to counter-gradient scalar fluxes. 相似文献
14.
Prabha R. Nair K. Susan George K. Parameswaran Marina Aloysius Denny P. Alappattu Mannil Mohan P.K. Kunhikrishnan 《Journal of Atmospheric and Solar》2009,71(17-18):1771-1783
In-situ measurements of number density, size distribution, and mass loading of near-surface aerosols were carried out at Kharagpur, a site on the eastern part of Indo-Gangetic Plains during the winter month of December 2004. The data have been used to investigate wintertime characteristics of aerosols and their effects on the occurrence of haze. The aerosol number density is found to be of the order of 109 m?3 and mass loading is ~265±70 μg m?3 (5–8 times that reported from south Indian sites). The diurnal patterns and day-to-day variations in aerosol number density and mass loading are closely associated with atmospheric boundary layer height. During haze events, the number density of submicron particles is found to be 2–5 times higher than that during non-hazy period. This could be attributed to the enhanced concentration of anthropogenic aerosols, low atmospheric boundary layer height/ventilation coefficient and airflow convergence. 相似文献
15.
A numerical two-dimensional-mesoscale model with a level 1.5 closure scheme for turbulence is described. The model is used to simulate the boundary layer over coastal complex terrain. Meteorological data available from the Øresund land-sea-land terrain experiment are used to study the performance of the model. The model could simulate generally observed complexities in the mean wind and temperature fields. Internal boundary layers over the water and land surfaces were identified by the height of lowest value in the turbulence kinetic energy profile and this showed good agreement with radiosonde (RS) observations.Some disagreements with the data were also noticed, especially near the surface. The wind speed was over-predicted. Attempts were made to improve the model performance by adopting different schemes for model initialisation. Results showed that initialisation with an early model start time and observed wind profile near the inflow boundary improved the performance. The wind speed over-prediction could be further minimised by using a more realistic objective initialisation scheme. The problem centred around the proper estimation of the turbulent diffusion coefficient K through the closure scheme. Despite using the most popular empirical relationships in the level 1.5 closure scheme, these differences persisted. While this needs further investigation, the present model can be used to supply wind fields for practical purposes such as air pollution calculations. 相似文献
16.
17.
Summary A K-type diffusion model coupled with a massconsistent wind model is applied for one of the rural biological waste disposal
sites in Austrian Alps. The site is situated in the P?ls valley in the eastern Alps, 250 km south-west of Vienna in Austria
Aim of the study is to demonstrate dispersion of H2S from the site to near by village. Model simulations are carried out each for an evening and a morning transition case characterized
by flow reversals. The role of locally generated wind in changing the pollutant distribution over nearby residential area
is investigated. Surface observations at two stations toward the open boundaries of the main valley are used to derive the
turbulence parameters and then to obtain initial inputs of wind profiles. The turbulence parameters behave analogous to that
over a plane terrain after the establishment of the valley wind. The model simulations are done for eight hours during the
evening transition and eighteen hours for the morning transition by incorporating the wind field from a mass consistent wind
model. The results are compared with SF6 tracer experiments conducted during those periods. The model outputs and the observations at various points inside the valley
are in good correlation except for NW part of the valley after the reversal of valley wind. The results also reveal the potential
of a simple approach with minimized inputs.
Received August 15, 1997 Revised August 15, 1998 相似文献
18.
Accurate information about the solar irradiance at the soil surface is essential for many agricultural, hydrological and environmental models that take into account the surface energy balance. The main goal of present study was to evaluate the solar irradiance predictions from the Advanced Research Weather Research and Forecasting (ARW) model for both clear sky and cloudy conditions. An extended observational dataset from the Georgia Automated Environmental Monitoring Network (AEMN) provided hourly solar irradiance at the surface and other collocated surface level measurements. The radiation bias (determined from the difference between the ARW predictions and AEMN observations) showed a linear relationship with the cloud optical depth and the cirrus cloud amount from the moderate resolution imaging spectroradiometer (MODIS). For cloud-free days, the ARW model had a positive radiation bias that exceeded 120 W m?2 over coastal and urban areas of Georgia. The model radiation and air temperature bias increased with increasing aerosol optical depth derived from the MODIS observations during the cloud-free days, attributed to fire events that lasted intermittently throughout the study period. The model biases of temperature, mixing ratio, wind speed, and soil moisture were linearly dependent on the radiation bias. 相似文献
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20.
Pramit Kumar Deb Burman Thara V. Prabha Ross Morrison Anandakumar Karipot 《Boundary-Layer Meteorology》2018,169(1):115-138
Observations from the Cloud-Aerosol Interaction and Precipitation Enhancement Experiment-Integrated Ground Observation Campaign (CAIPEEX-IGOC) provide a rare opportunity to investigate nocturnal atmospheric surface-layer processes and surface-layer turbulent characteristics associated with the low-level jet (LLJ). Here, an observational case study of the nocturnal boundary layer is presented during the peak monsoon season over Peninsular India using data collected over a single night representative of the synoptic conditions of the Indian summer monsoon. Datasets based on Doppler lidar and eddy-covariance are used for this purpose. The LLJ is found to generate nocturnal turbulence by introducing mechanical shear at higher levels within the boundary layer. Sporadic and intermittent turbulent events observed during this period are closely associated with large eddies at the scale of the height of the jet nose. Flux densities in the stable boundary layer are observed to become non-local under the influence of the LLJ. Different turbulence regimes are identified, along with transitions between turbulent periods and intermittency. Wavelet analysis is used to elucidate the presence of large-scale eddies and associated intermittency during nocturnal periods in the surface layer. Although the LLJ is a regional-scale phenomenon it has far reaching consequences with regard to surface-atmosphere exchange processes. 相似文献