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291.
Daehyun Kim Jong-Seong Kug In-Sik Kang Fei-Fei Jin Andrew T. Wittenberg 《Climate Dynamics》2008,31(2-3):213-226
Impacts of convective momentum transport (CMT) on tropical Pacific climate are examined, using an atmospheric (AGCM) and coupled GCM (CGCM) from Seoul National University. The CMT scheme affects the surface mainly via a convection-compensating atmospheric subsidence which conveys momentum downward through most of the troposphere. AGCM simulations—with SSTs prescribed from climatological and El Nino Southern Oscillation (ENSO) conditions—show substantial changes in circulation when CMT is added, such as an eastward shift of the climatological trade winds and west Pacific convection. The CMT also alters the ENSO wind anomalies by shifting them eastward and widening them meridionally, despite only subtle changes in the precipitation anomaly patterns. During ENSO, CMT affects the low-level winds mainly via the anomalous convection acting on the climatological westerly wind shear over the central Pacific—so that an eastward shift of convection transfers more westerly momentum toward the surface than would occur without CMT. By altering the low-level circulation, the CMT further alters the precipitation, which in turn feeds back on the CMT. In the CGCM, CMT affects the simulated climatology by shifting the mean convection and trade winds eastward and warming the equatorial SST; the ENSO period and amplitude also increase. In contrast to the AGCM simulations, CMT substantially alters the El Nino precipitation anomaly patterns in the CGCM. Also discussed are possible impacts of the CMT-induced changes in climatology on the simulated ENSO. 相似文献
292.
Future climate change scenarios over Korea using a multi-nested downscaling system: A pilot study 总被引:1,自引:0,他引:1
Song-You Hong Nan-Kyoung Moon Kyo-Sun Sunny Lim Jong-Won Kim 《Asia-Pacific Journal of Atmospheric Sciences》2010,46(4):425-435
This study examines a scenario of future summer climate change for the Korean peninsula using a multi-nested regional climate system. The global-scale scenario from the ECHAM5, which has a 200 km grid, was downscaled to a 50 km grid over Asia using the National Centers for Environmental Prediction (NCEP) Regional Spectral Model (RSM). This allowed us to obtain large-scale forcing information for a one-way, double-nested Weather and Research Forecasting (WRF) model that consists of a 12 km grid over Korea and a 3 km grid near Seoul. As a pilot study prior to the multi-year simulation work the years 1995 and 2055 were selected for the present and future summers. This RSM-WRF multi-nested downscaling system was evaluated by examining a downscaled climatology in 1995 with the largescale forcing from the NCEP/Department of Energy (DOE) reanalysis. The changes in monsoonal flows over East Asia and the associated precipitation change scenario over Korea are highlighted. It is found that the RSM-WRF system is capable of reproducing large-scale features associated with the East-Asian summer monsoon (EASM) and its associated hydro-climate when it is nested by the NCEP/DOE reanalysis. The ECHAM5-based downscaled climate for the present (1995) summer is found to suffer from a weakening of the low-level jet and sub-tropical high when compared the reanalysis-based climate. Predicted changes in summer monsoon circulations between 1995 and 2055 include a strengthened subtropical high and an intensified mid-level trough. The resulting projected summer precipitation is doubled over much of South Korea, accompanied by a pronounced surface warming with a maximum of about 2 K. It is suggested that downscaling strategy of this study, with its cloud-resolving scale, makes it suitable for providing high-resolution meteorological data with which to derive hydrology or air pollution models. 相似文献
293.
Statistical relationship between two types of El Niño events and climate variation over the Korean Peninsula 总被引:3,自引:0,他引:3
Jong-Seong Kug Min-Seop Ahn Mi-Kyung Sung Sang-Wook Yeh Hong-Sik Min Young-Ho Kim 《Asia-Pacific Journal of Atmospheric Sciences》2010,46(4):467-474
Recently, a new type of El Niño (Warm-Pool El Niño) is more often observed than the conventional El Niño (Cold-Tongue El Niño); each has a distinctive spatial pattern. The two types of El Niño have different teleconnections; therefore their impacts on a specific region can be considerably different. In this study, we focus on statistical relationship between climate variation in Korea and the two types of El Niño. When the two types of El Niño are not separately considered, the statistical relation between climate variables in Korea and the El Niño events is weak in general. When the two types of El Niño are separately considered, however, each type exhibits significant relationship with climate variation in Korea. Therefore, consideration of two types of El Niño separately can potentially improve climate prediction over the Korean Peninsula. 相似文献
294.
Diurnal variation of simulated 2007 summertime precipitation over South Korea in a real-time forecast model system 总被引:1,自引:0,他引:1
Kyungna Kim Dae-Yong Eom Dong-Kyou Lee Ying-Hwa Kuo 《Asia-Pacific Journal of Atmospheric Sciences》2010,46(4):505-512
A real-time forecast (RTF) system using Weather Research and Forecast (WRF) model version 2.2 is used to evaluate the diurnal variation of precipitation over South Korea in the summer (June to August) of 2007. The characteristics of the observed precipitation are also analyzed. The analysis and simulation period is divided into two sub-periods following the end of the changma, or East Asian monsoon, in 2007: Period_1 is from 1 June to 21 July, and Period_2 is from 22 July to 31 August. A 24-h precipitation cycle is observed over the entire period. The diurnal variation of precipitation over the South Korea shows that the nighttime maximum precipitation in Period_1 is affected by a largescale system; in contrast, the daytime maximum precipitation in Period_2 resulted from mesoscale convections is induced by thermal instability and moisture advection. The phases of the diurnal variation of simulated precipitation are consistent with those of the observed precipitation. The daytime rainfall amount of simulated precipitation in Period_2 is overestimated, and the convective rain process significantly affects the simulated total precipitation. The daytime overestimated precipitation is associated with overestimations of low-level temperature and moisture during the daytime in the model simulations as compared with the observations. 相似文献
295.
We have reanalyzed the high-resolution spectrum of Titan between 2.87 and 3.12 μm observed with NIRSPEC/Keck II on 2001 Nov. 21 in southern summer, using updated CH3D and C2H6 line-by-line models. From new synthetic spectra, we identify all but a few of the previously unidentified significant absorption spectral features in this wavelength range as due to these two species, both of which had been previously detected by Voyager and ground-based observations at other wavelengths. We also derive opacities and reflectivities of haze particles as functions of altitude for the 2.87-2.92 μm wavelength range, where Titan's atmosphere is partially transparent down to the surface. The extinction per unit altitude is observed to increase from 100 km (∼8 mbar) toward lower altitude. The derived total optical depth is approximately 1.1 for the 2.87-2.92 μm range. At wavelengths increasing beyond 2.92 μm the haze layers become much more optically thick, and the surface is rapidly hidden from view. These conclusions apply to equatorial and southern-temperate regions on Titan, excluding polar regions. We also find it unlikely that there is a large enhancement of the tropospheric CH4 mole fraction over the value reported from analysis of the Huygens/GCMS observations. 相似文献
296.
Jupiter exhibits bright H+3 auroral arcs at 3-4 microns that cool the hot (>1000 K) ionosphere above the ∼10−7 bar level through the infrared bands of this trace constituent. Below the 10−7 bar level significant cooling proceeds through infrared active bands of CH4, C2H2, and C2H6. We report the discovery of 3-micron line emission from these hydrocarbon species in spectra of the jovian south polar region obtained on April 18 and 20, 2006 (UT) with CGS4 on the United Kingdom Infrared Telescope. Estimated cooling rates through these molecules are 7.5×10−3, 1.4×10−3, and , respectively, for a total nearly half that of H+3. We derive a temperature of 450 ± 50 K in the 10−7-10−5 bar region from the C2H2 lines. 相似文献
297.
A. Baran R. Oreiro A. Pigulski F. Pérez Hernández A. Ulla M. D. Reed C. Rodríguez-López P. Moskalik S.-L. Kim W.-P. Chen R. Crowe M. Siwak L. Armendarez P. M. Binder K.-J. Choo A. Dye J. R. Eggen R. Garrido J. M. González Pérez S. L. Harms F.-Y. Huang D. Kozie H.-T. Lee J. MacDonald L. Fox Machado T. Monserrat J. Stevick S. Stewart D. Terry A.-Y. Zhou S. Zoa 《Monthly notices of the Royal Astronomical Society》2009,392(3):1092-1105
298.
Patrick A. Woudt Brian Warner Julian Osborne Kim Page 《Monthly notices of the Royal Astronomical Society》2009,395(4):2177-2182
High-speed photometry in 2008 shows that the light curve of V842 Cen possesses a coherent modulation at 56.825 s, with sidebands at 56.598 and 57.054 s. These have appeared since this nova remnant was observed in 2000 and 2002. We deduce that the dominant signal is the rotation period of the white dwarf primary and the sidebands are caused by reprocessing from a surface moving with an orbital period of 3.94 h. Thus, V842 Cen is an intermediate polar (IP) of the DQ Herculis subclass, is the fastest rotating white dwarf among the IPs and is the third fastest known in a cataclysmic variable. As in other IPs, we see no dwarf nova oscillations, but there are often quasi-periodic oscillations in the range 350–1500 s. There is a strong brightness modulation with a period of 3.78 h, which we attribute to negative superhumps, and there is an even stronger signal at 2.886 h which is of unknown origin but is probably a further example of that seen in GW Lib and some other systems. We used the Swift satellite to observe V842 Cen in the ultraviolet and in X-rays, although no periodic modulation was detected in the short observations. The X-ray luminosity of this object appears to be much lower than that of other IPs in which the accretion region is directly visible. 相似文献
299.
Biogeochemistry of nitrous oxide in groundwater in a forested ecosystem elucidated by nitrous oxide isotopomer measurements 总被引:3,自引:0,他引:3
K. Koba K. Osaka Y. Tobari S. Toyoda N. Ohte M. Katsuyama N. Suzuki M. Itoh H. Yamagishi M. Kawasaki S.J. Kim N. Yoshida T. Nakajima 《Geochimica et cosmochimica acta》2009,73(11):3115-1037
The biological and physical controls on microbial processes that produce and consume N2O in soils are highly complex. Isotopomer ratios of N2O, with abundance of 14N15N16O, 15N14N16O, and 14N14N18O relative to 14N14N16O, are promising for elucidation of N2O biogeochemistry in an intact ecosystem. Site preference, the nitrogen isotope ratio of the central nitrogen atom minus that of the terminal nitrogen atom, is useful to distinguish between N2O via hydroxylamine oxidation and N2O via nitrite reduction.We applied this isotopomer analysis to a groundwater system in a temperate coniferous-forested ecosystem. Results of a previous study at this location showed that the N2O concentration in groundwater varied greatly according to groundwater chemistry, i.e. NO3−, DOC, and DO, although apportionment of N2O production to nitrification or denitrification was ambiguous. Our isotopic analysis (δ15N and δ18O) of NO3− and N2O implies that denitrification is the dominant production process of N2O, but definitive information is not derived from δ15N and δ18O analysis because of large variations in isotopic fractionations during production and consumption of N2O. However, the N2O site preference and the difference in δ15N between NO3− and N2O indicate that nitrification contributes to total N2O production and that most measured N2O has been subjected to further N2O reduction to N2. The implications of N2O biogeochemistry derived from isotope and isotopomer data differ entirely from those derived from conventional concentration data of DO, NO3−, and N2O. That difference underscores the need to reconsider our understanding of the N cycle in the oxic-anoxic interface. 相似文献
300.
Paul Duuring Stephen M. Rowins Bradley S. M. McKinley Jenni M. Dickinson Larry J. Diakow Young-Seog Kim Robert A. Creaser 《Mineralium Deposita》2009,44(4):463-496
The Toodoggone district comprises Upper Triassic to Lower Jurassic Hazelton Group Toodoggone Formation volcanic and sedimentary
rocks, which unconformably overlie submarine island-arc volcanic and sedimentary rocks of the Lower Permian Asitka Group and
Middle Triassic Takla Group, some of which are intruded by Upper Triassic to Lower Jurassic plutons and dikes of the Black
Lake suite. Although plutonism occurred episodically from ca. 218 to 191 Ma, the largest porphyry Cu–Au ± Mo systems formed
from ca. 202 to 197 Ma, with minor mineralization occurring from ca. 197 to 194 Ma. Porphyry-style mineralization is hosted
by small-volume (<1 km3), single-phase, porphyritic igneous stocks or dikes that have high-K calc-alkaline compositions and are comparable with volcanic-arc
granites. The Fin porphyry Cu–Au–Mo deposit is anomalous in that it is 16 m.y. older than any other porphyry Cu–Au ± Mo occurrence
in the district and has lower REEs. All porphyry systems are spatially restricted to exposed Asitka and Takla Group basement
rocks, and rarely, the lowest member of the Hazelton Group (i.e., the ca. 201 Ma Duncan Member). The basement rocks to intrusions
are best exposed in the southern half of the district, where high rates of erosion and uplift have resulted in their preferential
exposure. In contrast, low- and high-sulfidation epithermal systems are more numerous in the northern half of the district,
where the overlying Hazelton Group rocks dominate exposures. Cogenetic porphyry systems might also exist in the northern areas;
however, if they are present, they are likely to be buried deeply beneath Hazelton Group rocks. High-sulfidation epithermal
systems formed at ca. 201 to 182 Ma, whereas low-sulfidation systems were active at ca. 192 to 162 Ma. Amongst the studied
epithermal systems, the Baker low-sulfidation epithermal deposit displays the strongest demonstrable genetic link with magmatic
fluids; fluid inclusion studies demonstrate that its ore fluids were hot (>468°C), saline, and deposited metals at deep crustal
depths (>2 km). Sulfur, C, O, and Pb isotope data confirm the involvement of a magmatic fluid, but also suggest that the ore
fluid interacted with Asitka and Takla Group country rocks prior to metal deposition. In contrast, in the Shasta, Lawyers,
and Griz-Sickle low-sulfidation epithermal systems, there is no clear association with magmatic fluids. Instead, their fluid
inclusion data indicate the involvement of low-temperature (175 to 335°C), low-salinity (1 to 11 equiv. wt.% NaCl) fluids
that deposited metals at shallow depths (<850 m). Their isotope (i.e., O, H, Pb) data suggest interaction between meteoric
and/or metamorphic ore fluids with basement country rocks. 相似文献