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1.
The knowledge of connectivity among breeding and overwintering populations of migratory bird species is critical for the conservation of their habitats. Conventional field work for the tracking of migratory birds involving bird banding often yields poor results due to low recovery rates, or is expensive when satellite tracking methods are used. Intrinsic tools such as genetic markers, stable isotopes, strontium isotopes and trace elements have been successfully used for tracing origins and/or migratory pathways of bird populations. We studied elemental signatures in the tail feathers to group breeding populations and an overwintering population of Mallards (Anas platyrhynchos). Tail feathers from five locations in Canada and the U.S. were analyzed using Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS). We used 18 elements to discriminate between Mallard populations. Linear discriminant analysis on a selected set of elements demonstrated that 93% of the Mallards could be accurately located back to their predicted locations. Mallard feathers from Arkansas (an important overwintering area), grouped together with any combination of elements as predictors. We predicted the breeding locations of overwintering Mallards from Arkansas. Our results confirm that the LA-ICP-MS technique shows high potential to estimate the origin of migratory animals. 相似文献
2.
Effect of finite sampling on atmospheric spectra 总被引：2，自引：0，他引：2
The effect of a finite averaging time on variances is well known, but its effect on power spectra is less clearly understood. We present numerical solutions for the spectral distortion arising from sampling over a finite time interval T and show that the commonly used filter function (1 – sinc2f
T), valid for variances, is a reasonable approximation for power spectra only when T 10
m
, where f is the cyclic frequency, and
m
is the dominant time scale of the process. Our results exhibit an increasingly steeper low-frequency roll-off as T decreases relative to
m
, indicating that the measured spectrum is subject to a greater suppression of the lower frequencies (f > 1/T) than predicted by (1 – sinc2f
T). This suppression is, in a sense, compensated by an overestimation of spectral estimates in the frequency range f 1/T. 相似文献
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Another look at sonic thermometry 总被引：5，自引：3，他引：5
In this note we reassess the role of sonic thermometry in boundary-layer studies. The sonic temperature signal, when corrected for crosswind velocity contamination, very closely approximates the virtual temperature of air. This variable is needed for many boundary-layer calculations. We describe preliminary tests with a new sonic anemometer-thermometer that performs the velocity correction in real time. Our test results offer new insights into the nature of the velocity error on temperature standard deviations and fluxes. They also draw attention to the high noise threshold that appears as an f
+1 rise in the fS(f) spectrum when spectral levels drop below 10-4 °C2. 相似文献
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6.
J. C. Kaimal 《Boundary-Layer Meteorology》1973,4(1-4):289-309
The paper describes the basic similarity in the spectral forms for velocity and temperature, and the cospectral forms for stress and heat flux in a stably stratified surface layer. A practical scheme is developed for estimating these spectra and cospectra using only height and Richardson number. From this development emerges certain simple relationships between Richardson number, turbulent dissipation rates, characteristic length scales and structure parameters. The paper also presents evidence for isotropy in the surface layer, and the dependence of the limiting wavelength for the 4/3 ratio between transverse and longitudinal velocity components on height and stability. 相似文献
7.
Variability of Summer Monsoon Rainfall in India on Inter-Annual and Decadal Time Scales 总被引：1，自引：0，他引：1 
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下载免费PDF全文 Porathur Vareed JOSEPH Bindu GOKULAPALAN Archana NAIR Shinu Sheela WILSON 《大气和海洋科学快报》2013,6(5):398-403
Indian Summer Monsoon Rainfall(ISMR)exhibits a prominent inter-annual variability known as troposphere biennial oscillation.A season of deficient June to September monsoon rainfall in India is followed by warm sea surface temperature(SST)anomalies over the tropical Indian Ocean and cold SST anomalies over the western Pacific Ocean.These anomalies persist until the following monsoon,which yields normal or excessive rainfall.Monsoon rainfall in India has shown decadal variability in the form of 30 year epochs of alternately occurring frequent and infrequent drought monsoons since1841,when rainfall measurements began in India.Decadal oscillations of monsoon rainfall and the well known decadal oscillations in SSTs of the Atlantic and Pacific oceans have the same period of approximately 60 years and nearly the same temporal phase.In both of these variabilities,anomalies in monsoon heat source,such as deep convection,and middle latitude westerlies of the upper troposphere over south Asia have prominent roles. 相似文献
8.
Josia Jacob Prosenjit Ghosh A. P. Dineshbabu P. Sabu K. Srinivas Bindu Sulochanan 《Journal of Oceanography》2014,70(3):251-266
Coastal marine environments are important links between the continents and the open ocean. The coast off Mangalore forms part of the upwelling zone along the southeastern Arabian Sea. The temperature, salinity, density, dissolved oxygen and stable oxygen isotope ratio (δ18O) of surface waters as well as those of bottom waters off coastal Mangalore were studied every month from October 2010 to May 2011. The coastal waters were stratified in October and November due to precipitation and runoff. The region was characterised by upwelled bottom waters in October, whereas the region exhibited a temperature inversion in November. The surface and bottom waters presented almost uniform properties from December until April. The coastal waters were observed to be most dense in January and May. Comparatively cold and poorly oxygenated bottom waters during the May sampling indicated the onset of upwelling along the region. δ18O of the coastal waters successfully documented the observed variations in the hydrographical characteristics of the Mangalore coast during the monthly sampling period. We also noted that the monthly variability in the properties of the coastal waters of Mangalore was related to the hydrographical characteristics of the adjacent open ocean inferred from satellite-derived surface winds, sea surface height anomaly data and sea surface temperatures. 相似文献
9.
Acoustic sounder and tower data obtained at the Boulder Atmospheric Observatory (BAO) are used to examine several features of the wave and turbulence structure associated with a disturbed nocturnal inversion. General features, including mean fields and Richardson number, for the case selected for this study are presented. Spectral analysis of the tower data reveals a separation of energy into wavelike and turbulent fluctuations. Analysis of the heat flux, however, shows upward counter-gradient fluxes in the vicinity of a low-level jet and near the top of the inversion. Cospectral analysis shows that the major contribution to the upward heat flux occurs at frequencies that would normally be considered characteristic of waves. In some cases, the upward flux is associated with a phase shift between vertical velocity w and fluctuating temperature θ different from the quadrature relation that would be expected of internal waves. Time series analysis reveals that these unexpected positive fluxes occur in relatively short bursts. Analysis of time series of θ and w in other cases, as well as inspection of acoustic sounder records, shows that sometimes such upward fluxes can result from a combination of wave motion and horizontal temperature advection. In this case the advection is associated with a shallow cold front. 相似文献
10.
The Kansas and Minnesota experiments 总被引：6，自引：0，他引：6
Two experiments conducted almost 20 years ago have come to be regarded as important milestones in boundary-layer research. This paper recounts the motivation for those experiments, describes how they were conducted, and summarizes their results.The National Center for Atmospheric Research is sponsored by the National Science Foundation. 相似文献