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161.
Ocean Dynamics - In this study, the relation between rogue wave occurrence statistics and properties of the directional wind-wave spectrum is investigated. The study is conducted by means of the... 相似文献
162.
We have analyzed our long-term (1995–2008) JHKLM photometry for three variable RV Tau supergiants. It follows from this analysis that: the amplitude of the JHK brightness variations is approximately the same, 0
m
. 9–1
m
, for the three stars; a negative linear trend is noticeable in the variations of the mean J brightness for AC Her; and the mean J brightness of R Sct and V Vul remained constant. The observed J brightness fluctuations in the supergiants are shown to be consistent either only with the temperature pulsations (AC Her
and V Vul) or with the temperature and radial pulsations (R Sct). We have detected long-term pulsations in the J brightness and J-H color variations of the supergiants with the following characteristic time scales: ∼1500 days (AC Her), ∼3500 days (R Sct),
and ∼800 and ∼1500 days (V Vul). Our search for a periodic component in the infrared brightness variations of the three stars
has revealed periods that differ from those obtained from optical observations. We show that relatively hot dust shells (T
d ∼ 700–800 K) exist around the supergiants under study; the densest and most massive shell was observed for V Vul. The ranges
of optical-depth variations for the dust shells were τ(1.25 μm) ≈ 0.04–0.10 (AC Her), ≈0.02–0.12 (R Sct), and ≈0.18–0.32 (V Vul). The spectral types in the infrared varied over
narrower ranges than those that followed from optical observations of these stars. 相似文献
163.
164.
Hindcast of oil-spill pollution during the Lebanon crisis in the Eastern Mediterranean, July-August 2006 总被引:2,自引:0,他引:2
Coppini G De Dominicis M Zodiatis G Lardner R Pinardi N Santoleri R Colella S Bignami F Hayes DR Soloviev D Georgiou G Kallos G 《Marine pollution bulletin》2011,62(1):140-153
MOON (Mediterranean Operational Oceanography Network http://www.moon-oceanforecasting.eu) provides near-real-time information on oil-spill detection (ocean color and SAR) and predictions [ocean forecasts (MFS and CYCOFOS) and oil-spill predictions (MEDSLIK)]. We employ this system to study the Lebanese oil-pollution crisis in summer 2006 and thus to assist regional and local decision makers in Europe, regionally and locally. The MEDSLIK oil-spill predictions obtained using CYCOFOS high-resolution ocean fields are compared with those obtained using lower-resolution MFS hydrodynamics, and both are validated against satellite observations. The predicted beached oil distributions along the Lebanese and Syrian coasts are compared with in situ observations.The oil-spill predictions are able to simulate the northward movement of the oil spill, with the CYCOFOS predictions being in better agreement with satellite observations. Among the free MEDSLIK parameters tested in the sensitivity experiments, the drift factor appears to be the most relevant to improve the quality of the results. 相似文献
165.
A high-resolution storm surge model of Apalachee Bay in the northeastern Gulf of Mexico is developed using an unstructured
grid finite-volume coastal ocean model (FVCOM). The model is applied to the case of Hurricane Dennis (July 2005). This storm
caused underpredicted severe flooding of the Apalachee Bay coastal area and upriver inland communities. Accurate resolution
of complicated geometry of the coastal region and waterways in the model reveals processes responsible for the unanticipated
high storm tide in the area. Model results are validated with available observations of the storm tide. Model experiments
suggest that during Dennis, excessive flooding in the coastal zone and the town of St. Marks, located up the St. Marks River,
was caused by additive effects of coincident high tides (~10–15% of the total sea-level rise) and a propagating shelf wave
(~30%) that added to the locally wind-generated surge. Wave setup, the biggest uncertainty, is estimated on the basis of empirical
and analytical relations. The Dennis case is then used to test the sensitivity of the model solution to vertical discretization.
A suite of model experiments is performed with varying numbers of vertical sigma (σ) levels, with different distribution of
σ-levels within the water column and a varying bottom drag coefficient. The major finding is that the storm surge solution
is more sensitive to resolution within the velocity shear zone at mid-depths compared to resolution of the upper and bottom
layer or values of the bottom drag coefficient. 相似文献
166.
Common choke ring ground planes are known to contribute to undesirable antenna pattern narrowing in the elevation plane which
is associated with difficulties of tracking low elevation satellites. Also known is the comparatively narrow frequency bandwidth
of the choke grooves structure. As an alternative, using a convex impedance ground plane has been suggested for full-spectrum
GNSS applications. With such ground planes a pin structure is utilized instead of choke grooves to allow a frequency bandwidth
increase. A semi-spherical shape of the ground plane is shown to provide increased antenna gain for low elevation angles.
Theoretical performance estimates along with experimental test data have been provided. 相似文献
167.
de la Vara Alba Cabos William Sein Dmitry V. Sidorenko Dmitry Koldunov Nikolay V. Koseki Shunya Soares Pedro M. M. Danilov Sergey 《Climate Dynamics》2020,54(11-12):4733-4757
Climate Dynamics - Despite the efforts of the modelling community to improve the representation of the sea surface temperature (SST) over the South Eastern Tropical Atlantic, warm biases still... 相似文献
168.
The evolution and current state of landscapes around Lake Teletskoye have not previously been studied in detail. In the valley of the Malye Chily River, which flows into Lake Teletskoye, the timing of dam failure and draining of two moraine-dammed lakes has been identified. Botanical analysis, ash content determination, and radiocarbon dating of two peat profiles provide insight into postglacial evolution of wetlands related to this landscape. We found clear evidence of the disappearance from the peat of higher vascular species that, today, grows mostly in the plains of Siberia. Correlation of the data obtained with the accepted chronology of the Holocene events in the Russian Altai suggests the following stages of postglacial environmental change in the Malye Chily River valley: (1) the continuation of the Late Würm glaciation degradation (before 7000?cal. yr BP); (2) Holocene Climate Optimum (7000–5000?cal. yr BP); (3) Akkem cooling (5000–4200?cal. yr BP); (4) warm period (4200–3700?cal. yr BP); and (5) Historical cooling (3700–1600?cal. yr BP). 相似文献
169.
O. G. Taranova A. M. Tatarnikov V. I. Shenavrin A. A. Tatarnikova 《Astronomy Letters》2014,40(2-3):120-124
The results of JHKLM photometry for Nova Delphini 2013 obtained in the first sixty days after its outburst are analyzed. Analysis of the energy distribution in a wide spectral range (0.36–5 µm) has shown that the source mimics the emission of normal supergiants of spectral types B5 and A0 for two dates near its optical brightness maximum, August 15.94 UT and August 16.86 UT, respectively. The distance to the nova has been estimated to be D ≈ 3 kpc. For these dates, the following parameters have been estimated: the source’s bolometric fluxes ~9 × 10?7 and ~7.2 × 10?7 erg s?1 cm?2, luminosities L ≈ 2.5 × 105 L ⊙ and ≈2 × 105 L ⊙, and radii R ≈ 6.3 × 1012 and ≈1.2 × 1013 cm. The nova’s expansion velocity near its optical brightness maximum was ~700 km s?1. An infrared (IR) excess associated with the formation of a dust shell is shown to have appeared in the energy distribution one month after the optical brightness maximum. The parameters of the dust component have been estimated for two dates of observations, JD2456557.28 (September 21, 2013) and JD2456577.18 (October 11, 2013). For these dates, the dust shell parameters have been estimated: the color temperatures ≈1500 and ≈1200 K, radii ≈6.5 × 1013 and 1.7 × 1014 cm, luminosities ~4 × 103 L ⊙ and ~1.1 × 104 L ⊙, and the dust mass ~1.6 × 1024 and ~1025 g. The total mass of the material ejected in twenty days (gas + dust) could reach ~1.1 × 10?6 M ⊙. The rate of dust supply to the nova shell was ~8 × 10?8 M ⊙ yr?1. The expansion velocity of the dust shell was about 600 km s?1. 相似文献
170.
Dmitry Khangulyan Slavomir Hnatic Felix Aharonian 《Astrophysics and Space Science》2007,309(1-4):261-265
The inverse Compton (IC) scattering of ultrarelativistic electrons accelerated at the pulsar wind termination shock is generally
believed to be responsible for TeV gamma-ray signal recently reported from the binary system PSR B1259-63/SS2883. In such
a system the acceleration takes place in the presence of a dense radiation field provided by a companion Be2-type star. Thus
it is natural to expect an orbital phase dependence of the acceleration efficiency in the system. The HESS collaboration reported
the tendency of reduction of TeV γ-rays around the periastron. In this paper we study a possible explanation of this effect by the “early” (sub-TeV) cutoffs
in the energy spectrum of accelerated electrons due to the enhanced rate of Compton losses close to the periastron. 相似文献