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排序方式: 共有221条查询结果,搜索用时 15 毫秒
101.
Seung-Woo Lee Jan Kouba Bob Schutz Do Hyeong Kim Young Jae Lee 《Journal of Geodesy》2013,87(10-12):923-934
This paper addresses real-time monitoring of the precipitable water vapor (PWV) from GNSS measurements and presents some results obtained from 6-month long GNSS PWV experiments using international and domestic GNSS networks. In the real-time GNSS PWV monitoring system a server/client structure is employed to facilitate formation of PWV networks and single-differenced GNSS measurements are utilized to mitigate errors in GNSS satellites’ orbits and clocks. An issue relating to baseline length between the server and clients is discussed in detail and as a result the PWV monitor is configured to perform in two modes depending on the baseline length. The server estimates sequentially the zenith wet delay of the individual stations, which is then converted into the PWV of the stations. We evaluate system performance by comparing the real-time PWV solution with reference solutions including meteorological measurements obtained with radiosondes and deferred-time precision GNSS PWV solutions. Results showed that the standard deviation of difference between the real-time PWV and the reference solutions ranged from 2.1 to 3.4 mm in PWV for a 6-month long comparison, which was improved to 1.4 to 2.9 mm by reducing comparison period to 20 days in winter. 相似文献
102.
Do Young Oh 《Urban geography》2013,34(7):1066-1068
In this study, we use a Geographic Information System-based index to measure spatial accessibility of public high schools. The index is applied to the Baton Rouge Metropolitan Statistical Area in 1990, 2000, and 2010. Overall, urban areas had consistently worse accessibility scores compared with suburban and rural areas. High schools with more African American students tended to have poorer accessibility levels. Schools with lower accessibility tended to be associated with poorer average student performance, and the effect strengthened between 2000 and 2010. In developing a better understanding of the accessibility of public high schools, this paper reaffirms the significance of space, place, and race, and challenges the notion of declining relevance of accessibility in Louisiana public education policymaking. 相似文献
103.
Chang Ki Kim Michael Leuthold William F. Holmgren Alexander D. Cronin Eric A. Betterton 《Pure and Applied Geophysics》2016,173(2):637-655
Accurate forecasts of solar irradiance are required for electric utilities to economically integrate substantial amounts of solar power into their power generation portfolios. A common failing of numerical weather models is the prediction of scattered clouds at the top of deep PBL which are generally difficult to be resolved due to complicated processes in the planetary boundary layer. We improved turbulence parameterization for better predicting solar irradiance during the scattered clouds’ events using the Weather Research and Forecasting model. Sensitivity tests show that increasing the exchange coefficient leads to enhanced vertical mixing and a deeper mixed layer. At the top of mixed layer, an adiabatically ascending air parcel achieved the water vapor saturation and finally scattered cloud is generated. 相似文献
104.
From the late 1990s, many studies on local geoid construction have been made in South Korea. However, the precision of the previous geoid has remained about 15 cm due to distribution and quality problems of gravity and GPS/levelling data. Since 2007, new land gravity data and GPS/levelling data have been obtained through many projects such as the Korean Land Spatilaization, Unified Control Point and Gravity survey on the Benchmark. The newly obtained data are regularly distributed to a certain degree and show much better improvement in their quality. In addition, an airborne gravity survey was conducted in 2008 to cover the Korean peninsula (South Korea only). Therefore, it is expected that the precision of the geoid could be improved. In this study, the new South Korean gravimetric geoid and hybrid geoid are presented based on land, airborne, ship‐borne, altimeter gravity data, geopotential model and topographic data. As for the methodology, the general remove‐restore approach was applied with the best chosen parameters in order to produce a precise local geoid. The global geopotential model EGM08 was used to remove the low‐frequency components using degree and order up to 360 and the short wavelength part of the gravity signal was dealt with by using the Shuttle Radar Topography Mission data. The parameters determined empirically in this study include for Stokes’ integral 0.5° and for Wong‐Gore kernel 110–120°, respectively and 10 km for both the Bjerhammar sphere depth and attenuation factor. The final gravimetric geoid in South Korea ranges from 20–31 m with a precision of 5.45 cm overall compared to 1096 GPS/levelling data. In addition, the South Korean hybrid geoid produces 3.46 cm and 3.92 cm for degrees of fitness and precision, respectively and a better statistic of 2.37 cm for plain and urban areas was achieved. The gravimetric and hybrid geoids are expected to improve further when the refined land gravity data are included in the near future. 相似文献
105.
M. A. Do 《新西兰海洋与淡水研究杂志》2013,47(1):99-108
The basic acoustical methods for estimating the volume backscattering strength and the absolute biomass density are commonly known. However, the detailed techniques for minimising errors in fitting the calibrated parameters of an echo sounding system in these computations are still not adequately examined and discussed. This paper describes and discusses the following computing techniques involved in the absolute biomass estimation: (i) the fitting of the calibrated time varied gain (TVG) curve, the selection of its operating interval, and the correction of its response; (ii) the compensation for the limitation of the signal bandwidth; (iii) the computation of the equivalent beam width of a transducer using its calibrated beam patterns; and (iv) the accuracy in the conversion from the volume backscattering to the absolute fish density using individual fish target strength measurements. 相似文献
106.
107.
108.
A. Erdem E. Budding E. Soydugan F. Soydugan S.S. Doğru D. Doğru M. Tüysüz A. Dönmez H. Bakiş Y. Kaçar C. Çiçek Z. Eker O. Demircan 《New Astronomy》2009,14(2):109-120
We present a photometric study of three chromospherically active stars with long periods (V340 Gem, SAO 62042 and FI Cnc). The observations were made at the ÇOMU Observatory in 2006 and 2007. We have made initial photometric analyses of V340 Gem and SAO 62042, which are newly discovered RS CVn–type SB1 binaries, and established the photometric variations of FI Cnc, which is a single G8III active star. Photometric rotation periods of these stars were obtained by analyzing their light variations. The light variations, observed over three or more consecutive orbital cycles, were investigated by using spot models with the program SPOT. We also discussed the surface differential rotation coefficient for the primary component of the SB1 binary star SAO 62042 in this study, using our own photometric period together with an orbital period taken from the literature. 相似文献
109.
Alexandrine Marteel Vania Gaspari Claude F. Boutron Carlo Barbante Paolo Gabrielli Paolo Cescon Giulio Cozzi Christophe P. Ferrari Aurélien Dommergue Kevin Rosman Sungmin Hong Soon Do Hur 《Climatic change》2009,92(1-2):191-211
Cr, Fe, Rb, Ba and U were determined by inductively coupled plasma sector field mass spectrometry (ICP-SFMS) in various sections of the 3,270 m deep ice core recently drilled at Dome C on the high East Antarctic plateau as part of the EPICA program. The sections were dated from 263 kyr bp (depth of 2,368 m) to 672 kyr bp (depth of 3,062 m). When combined with the data previously obtained by Gabrielli and co-workers for the upper 2,193 m of the core, it gives a detailed record for these elements during a 672-kyr period from the Holocene back to Marine Isotopic Stage (MIS) 16.2. Concentrations and fallout fluxes of all elements are found to be highly variable with low values during the successive interglacial periods and much higher values during the coldest periods of the last eight climatic cycles. Crustal enrichment factors indicates that rock and soil dust is the dominant source for Fe, Rb, Ba and U whatever the period and for Cr during the glacial maxima. The relationship between Cr, Fe, Rb, Ba and U concentrations and the deuterium content of the ice appears to be similar before and after the Mid-Brunhes Event (MBE, around 430 kyr bp). Mean concentration values observed during the successive interglacials from the Holocene to MIS 15.5 appear to vary from one interglacial to another at least for part of the elements. Concentrations observed during the successive glacial maxima suggest a decreasing trend from the most recent glacial maxima (MIS 2.2 and 4.2) to the oldest glacial maxima such as MIS 14.2, 14.4 and 16.2, which could be linked with changes in the size distribution of dust particles transported from mid-latitude areas to the East Antarctic ice cap. 相似文献
110.
Local Meteorological and Synoptic Characteristics of Fogs Formed over Incheon International Airport in the West Coast of Korea 总被引:2,自引:0,他引:2
Fogs observed over Incheon international airport (IIA) in the west
coast of Korea from January 2002 to August 2006 are classified into categories
of coastal fog, cold sea fog, and warm sea fog based on the areal extent of the
fogs and the difference between the air temperature (T) and the SST, i.e.,
cold sea fog if TSST = T-SST>0oC and warm sea fog if TSST
<0oC. The numbers of coastal, cold, and warm sea fog cases
are 64, 26, and 9. Coastal fogs form most frequently in winter, while cold sea
fogs occur mostly in summer and warm sea fogs are observed from January to May
but not in November and December. On average the air gets colder by
1.6oC during the three hours leading up to the coastal fog
formation, and an additional cooling of 1.1oC occurs during the
fog. The change in the dew point temperature (Td) is minimal except
during the fog (0.6oC). Decreases in T for the cold and warm
sea fogs are relatively smaller. The average Td is higher than SST
during the cold sea fog periods but this Td is more than
4oC higher than that for the corresponding non-fog days,
suggesting that cold sea fogs be formed by the cooling of already humid air
(i.e., Td>SST). Increases of Td are significant during the
warm sea fog periods (1.4oC), implying that efficient moisture
supply is essential to warm sea fog formation. Four major synoptic patterns are
identified in association with the observed fogs. The most frequent is a north
Pacific high that accounts for 38% of cases. Surface or upper inversions are
present in 77%, 69%, and 81% of the fog periods for coastal, cold, and
warm sea fogs, respectively. 相似文献