Vertical structure variability and equatorial waves during central Pacific and eastern Pacific El Ni?os in a coupled general circulation model     

B. Dewitte  J. Choi  S.-I. An  S. Thual 《Climate Dynamics》2012,38(11-12):2275-2289

Recent studies report that two types of El Ni?o events have been observed. One is the cold tongue El Ni?o or Eastern Pacific El Ni?o (EP El Ni?o), which is characterized by relatively large sea surface temperature (SST) anomalies in the eastern Pacific, and the other is the warm pool El Ni?o (a.k.a. ‘Central Pacific El Ni?o’ (CP El Ni?o) or ‘El Ni?o Modoki’), in which SST anomalies are confined to the central Pacific. Here the vertical structure variability of the periods during EP and CP is investigated based on the GFDL_CM2.1 model in order to explain the difference in equatorial wave dynamics and associated negative feedback mechanisms. It is shown that the mean stratification in the vicinity of the thermocline of the central Pacific is reduced during CP El Ni?o, which favours the contribution of the gravest baroclinic mode relatively to the higher-order slower baroclinic mode. Energetic Kelvin and first-meridional Rossby wave are evidenced during the CP El Ni?o with distinctive amplitude and propagating characteristics according to their vertical structure (mostly first and second baroclinic modes). In particular, the first baroclinic mode during CP El Ni?o is associated to the ocean basin mode and participates to the recharge process during the whole El Ni?o cycle, whereas the second baroclinic mode is mostly driving the discharge process through the delayed oscillator mechanism. This may explain that the phase transition from warm to neutral/cold conditions during the CP El Ni?o is delayed and/or disrupted compared to the EP El Ni?o. Our results have implications for the interpretation of the variability during periods of high CP El Ni?o occurrence like the last decade.  相似文献   

The optimal choice of residue management, crop rotations, and cost of carbon sequestration: empirical results in the Midwest US   总被引：1，自引：0，他引：1  

Suk-Won Choi  Brent Sohngen 《Climatic change》2010,99(1-2):279-294

This study investigates the cost of soil carbon sequestration in the Midwest US. The model addresses several missing components in earlier analyses: the link between the residue level choice and carbon payments, crop rotations, carbon loss when shifting from conservation to conventional tillage and the spatial pattern of carbon sequestration across different soil types. The results suggest that for $100 per metric ton of carbon, 1.5 million metric tons of carbon could be sequestered per year on the 19.9 million hectares of cropland in the study region. These estimates suggest less carbon potential than existing studies because the opportunity costs associated with conservation tillage are fairly high. Annual carbon rental payments are found to be more efficient, as expected, but for smaller programs, per hectare rental payments are not substantially more costly.  相似文献   

Regional Distribution of Perceived Temperatures Estimated by the Human Heat Budget Model （the Klima-Michel Model） in South Korea   总被引：2，自引：0，他引：2  

Jiyoung KIM  Kyu Rang KIM  Byoung-Cheol CHOI  Dae-Geun LEE  Jeong-Sik KIM 《大气科学进展》2009,26(2):275-282

The regional distribution of perceived temperatures (PT) for 28 major weather stations in South Korea during the past 22 years (1983–2004) was investigated by employing a human heat budget model, the Klima-Michel model. The frequencies of a cold stress and a heat load by each region were compared. The sensitivity of PT in terms of the input of synoptic meteorological variables were successfully tested. Seogwipo in Jeju Island appears to be the most comfortable city in Korea. Busan also shows a high frequenc...  相似文献   

Study of accretion disk dynamics in presence of cooling     

Santabrata Das  Chul-Sung Choi 《Astrophysics and Space Science》2009,321(2):109-122

We examine the behaviour of accretion flow around a rotating black hole in presence of cooling. We obtain global flow solutions for various accretion parameters that govern the accreting flow. We show that standing isothermal shock wave may develop in such an advective accretion flow in presence of cooling. This shocked solution has observational consequences as it successfully provides the possible explanations of energy spectra as well as generation of outflows/jets of various galactic and extra-galactic black hole candidates. We study the properties of isothermal shock wave and find that it strongly depends on the cooling efficiency. We identify the region in the parameter space spanned by the specific energy and specific angular momentum of the flow for standing isothermal shock as a function of cooling efficiencies and find that parameter space gradually shrinks with the increase of cooling rates. Our results imply that accretion flow ceases to contain isothermal shocks when cooling is beyond its critical value.  相似文献   

Origin of Halogens and Nitrogen in Enstatite Chondrites     

Alan E. Rubin  Byeon-Gak Choi 《Earth, Moon, and Planets》2009,105(1):41-53

The EH and EL enstatite chondrites are the most reduced chondrite groups, having formed in nebular regions where the gas may have had high C/O and/or pH₂/pH₂O ratios. Enstatite chondrites (particularly EH) have higher CI- and Mg-normalized abundances of halogens (especially F and Cl) and nitrogen than ordinary chondrites and most groups of carbonaceous chondrites. Even relative to CI chondrites, EH and EL chondrites are enriched in F. We have found that literature values for the halogen abundance ratios in EH and EL chondrites are strongly correlated with the electronegativities of the individual halogens. We suggest that the most reactive halogens were the most efficient at forming compounds (e.g., halides) that were incorporated into EH-chondrite precursor materials. It seems plausible that, under the more-oxidizing conditions pertaining to the other chondrite groups, a larger fraction of the halogens remained in the gas. Nitrogen may have been incorporated into the enstatite chondrites as simple nitrides that did not condense under the more-oxidizing conditions in the regions where other chondrite groups formed. Literature data show that unequilibrated enstatite chondrites have light bulk N (δ ¹⁵N ≈ −20‰) compared to most ordinary (−5 to +20‰) and carbonaceous (+20 to +190‰) chondrites; this may reflect the contribution in enstatite chondrites of nitride condensates with δ¹⁵ N values close to the proposed nebular mean (~−400‰). In contrast, N in carbonaceous chondrites is mainly contained within ¹⁵N-rich organic matter. The major carrier of N in ordinary chondrites is unknown.  相似文献   

The thermal conductivity for granite with various water contents     

W.J. Cho  S. Kwon  J.W. Choi 《Engineering Geology》2009,107(3-4):167-171

The thermal conductivities of granite were measured under different conditions of porosity and water content to investigate the effects of the porosity and water content on the thermal conductivity. For the dry samples, the thermal conductivities range from 2.12 W/mK for the rocks with a high porosity to 3.12 W/mK for the ones with a low porosity. Water-sorbed samples have greater thermal conductivities than dry samples of the same granite. The thermal conductivities range from 2.99 W/mK for granites with a high porosity to 3.62 W/mK for ones with a low porosity under saturated condition.  相似文献   

Effects of Concentrated Freshwater Discharge on Hydrography and Mesozooplankton Community in a Dammed Estuary     

An  Na  Kim  Young-Hee  Lee  Sang-Woo  Choi  Keun-Hyung 《Ocean Science Journal》2021,56(1):86-95

Ocean Science Journal - This study examines the different effects of high and low freshwater discharge on the water physical structure of the water column and plankton community in a tide-dominated...  相似文献   

Negative Impacts of Perkinsus olseni Infection in Manila Clam Ruditapes philippinarum Observed from Tidal Flats in Anmyeondo Island on the West Coast of Korea During Post-Spawning Period     

Lee  Hye-Mi  Park  Kyung-Il  Yang  Hyun-Sung  Choi  Kwang-Sik 《Ocean Science Journal》2021,56(3):307-316

Ocean Science Journal - The high load of protozoan parasites in marine bivalves often leads to mass mortalities of the hosts. On the west coast of Korea in the Yellow Sea, the protozoan parasite...  相似文献   

Distribution and Sources of Dissolved and Particulate Heavy Metals (Mn,Co, Ni,Cu, Zn,Cd, Pb) in Masan Bay,Korea     

Park  Sojung  Choi  Mansik  Jang  Dongjun  Joe  Dongjin  Park  Kyunggue 《Ocean Science Journal》2020,55(1):49-67

Ocean Science Journal - In this study, we investigated the spatial and temporal distribution and sources of dissolved and particulate heavy metals in Masan Bay, an area that for a long time has...  相似文献   

A Comparative Evaluation of Stress–Strain and Acoustic Emission Methods for Quantitative Damage Assessments of Brittle Rock     

Jin-Seop Kim  Kyung-Soo Lee  Won-Jin Cho  Heui-Joo Choi  Gye-Chun Cho 《Rock Mechanics and Rock Engineering》2015,48(2):495-508

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