Quantitative forecast experiment of a heavy rainfall event over Korea in a global model: horizontal resolution versus lead time issues   总被引：1，自引：0，他引：1  

Jihyeon Jang  Song-You Hong 《Meteorology and Atmospheric Physics》2014,124(3-4):113-127

In this study, we examine the deterministic predictability of heavy rainfall over the Korean peninsula using a global model, the Global/Regional Integrated Model system, by focusing on the effects of horizontal resolution and lead time prior to the onset of the target event. The control run reproduces locally concentrated heavy rainfall over the mid-western part of the Korean peninsula on 27–29 July 2011, with a model setup of about 25 km grid spacing and 24 h in advance of the onset of heavy rainfall. We found that small-scale features are represented well at higher resolution, but without significant change in the distribution of rainfall. Increase of lead time reduces the predictability of large-scale features, accompanying a northward shift of major rainfall. At lower resolution, the accuracy of the heavy rainfall prediction decreases more rapidly as lead time increases. We concluded that the increase in predictability of heavy rainfall achieved by enhancing horizontal resolution is promising, but an additional set of experiments also indicates that efforts should be made to improve the physics packages in models.  相似文献   

Major element variation of the Skaergaard pyroxene and its petrologic implications     

Yun‐Deuk Jang  H. Richard Naslund 《Island Arc》2013,22(2):214-226

Pyroxenes from the Layered Series (LS), Upper Border Series (UBS), and Marginal Border Series (MBS) of the Skaergaard intrusion were analyzed using electron microprobe and mineral separation techniques to examine geochemical variations. In general, pyroxenes from all three series show similar trends in major elements vs % crystallization: SiO₂, MgO, Al₂O₃, and TiO₂ progressively decrease, FeO and MnO progressively increase, and CaO, Fe₂O₃, and P₂O₅ do not change systematically with differentiation. Pyroxenes in the LS and MBS follow a trend similar to that reported by Wager and Brown. The estimated crystallization temperatures closely follow the general trends of published temperature estimates. Major element variation in Skaergaard pyroxenes shows smooth variations with increasing differentiation, indicating that there was no volumetrically significant injection of new magma into the chamber after the initial emplacement. These results strongly support the idea that the Skaergaard intrusion represents in situ crystallization under a closed system magma chamber.  相似文献   

Recent Primary Production and Small Phytoplankton Contribution in the Yellow Sea during the Summer in 2016     

Hyo Keun Jang  Jae Jung Kang  Jae Hyung Lee  Myungjoon Kim  So Hyun Ahn  Jin-Yong Jeong  Mi Sun Yun  In-Seong Han  Sang Heon Lee 《Ocean Science Journal》2018,53(3):509-519

The high nutrient concentration associated with the mixing dynamics of two warm and cold water masses supports high primary production in the Yellow Sea. Although various environmental changes have been reported, no recent information on small phytoplankton contribution to the total primary production as an important indicator for marine ecosystem changes is currently available in the Yellow Sea. The major objective of this study is to determine the small (< 2 μm) phytoplankton contribution to the total primary production in the Yellow Sea during August, 2016. In this study, we found relatively lower chlorophyll a concentrations in the water column than those previously reported in the central waters of the Yellow Sea. Moreover, the overall contribution of small phytoplankton (53.1%) to the total chlorophyll a concentration was considerably higher in this study than that (10.7%) observed previously. Based on the N/P ratio (67.6 ± 36.6) observed in this study, which is significantly higher than the Redfield ratio (16), we believe that phytoplankton experienced P-limiting conditions during the study period. The average daily carbon uptake rate of total phytoplankton in this study was 291.1 mg C m^-2 d^-1 (± 165.0 mg C m^-2 d^-1) and the rate of small phytoplankton was 205.7 mg C m^-2 d^-1 (± 116.0 mg C m^-2 d^-1) which is 71.9% (± 8.8%) of the total daily carbon uptake rate. This contribution of small phytoplankton observed in this study appears to be higher than that reported previously. Our recent measured primary production is approximately 50% lower than the previous values decades ago. The higher contributions of small phytoplankton to the total chlorophyll a concentration and primary production might be caused by P-limited conditions and this resulted in lower chlorophyll a concentration and total primary production in this study compared to previous studies.  相似文献   

Correlations between CPT and FVT Results for Busan Clay     

S. G. Chung  J. G. Chung  W. Y. Jang  J. M. Lee 《Marine Georesources & Geotechnology》2013,31(1):49-63

In this study, CPT and FVT tests are carried out on young, normally consolidated clay (Busan clay, which is an unusually thick deposit) at several locations in the Nakdong River deltaic plane in Busan, Korea. Two correlation techniques are applied for estimating the cone factors for which the uncorrected and corrected field vane strengths are used as the reference strength. First, due to the scattered data over the entire depth, a direct correlation between the tested results (a method generally used in practice), is applied for each depositional environment (facies) that is detected from the CPT profiles and the geological analysis. Secondly, a special attempt is made to determine the cone factors based on the fact that the ratios of the field vane strength and the (q _t  ? σ _v0) and (u ₂ ? u ₀) values to the effective overburden pressure respectively, are approximately constant for each facies (the indirect correlation). It appears that the values obtained from the two techniques are almost identical. However, the direct correlation is sensitively affected by the fabric effects especially in some of the uppermost and lowermost layers of the clay and hence the arithmetic average values of each facies sometimes result in lower correlation coefficients. It is therefore inferred that the indirect correlation is more proficient for estimating the cone factors at each facies and can be used for practical applications. From the results of the indirect correlation, the cone factors of Busan clay are N _kt  = 7.13–13.06, N _kt,corr  = 9.45–17.07, N _Δu  = 6.10–9.88 and N _Δu,corr  = 8.41–12.24, the corrected values of which are considerably smaller or larger than the general ranges recommended by Lunne et al. (1997a). However, good correlations between N _kt and I _P , and between N _Δu (or N _kt ) and B _q , are not found for the clay.  相似文献   

Bi‐Doped TiO2 Electro‐Catalytic System as Fast‐Oxidizing Process for Hydrogen‐Bond Stabilized System          下载免费PDF全文

Wu‐Jang Huang  Sheng‐Jhih Hong  Yaw‐Jian Lin 《洁净——土壤、空气、水》2014,42(8):1154-1156

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A numerical study on severe downslope windstorms occurred on 5 April 2005 at Gangneung and Yangyang, Korea     

Wook Jang  Hye-Yeong Chun 《Asia-Pacific Journal of Atmospheric Sciences》2010,46(2):155-172

Severe downslope windstorms occurred on 5 April 2005 in the Taebaek Mountain Range, located in the eastern coast of Korea, are examined using the Weather Research and Forecasting (WRF) model. Strong winds are observed at Gangneung and Yangyang during two separate periods with a rapidly decreasing period in between. These downslope windstorms are reproduced in the simulation reasonably well, although the rapidly decreasing surface wind speed after the second windstorm could not be captured at Yangyang. It is found that the generation mechanisms of the downslope windstorms in these two periods are somewhat different. The severe wind in the first period is likely due to the reflection of the mountain waves from a critical level that locates near z = 8–9 km. Upward-propagating waves and reflected downward-propagating waves interact constructively in a duct between the critical level and the surface, resulting in strong surface wind. In the second period, the hydraulic-jump theory can be applied in that the wave breaking above the downstream induces a well-mixed region, and severe downslope wind is developed beneath this turbulent region as the streamlines descend along the downstream. Simultaneous lee wave structure is also reproduced during the second windstorm period. The sensitivity of the downslope wind speed to the change in the land-cover map showed that the absorption of trapped lee waves in the boundary layer reduces the downslope wind speed significantly after the second windstorm at Gangneung, improving the model performance, although with no significant impact at Yangyang.  相似文献   

Characterization of chemical properties of atmospheric aerosols over Anmyeon (South Korea), a super site under Global Atmosphere Watch     

Sung-Hwa Park  A. S. Panicker  Dong-In Lee  Woon-Seon Jung  Sang-Min Jang  Min Jang  Dongchul Kim  Yu-Won Kim  Harrison Jeong 《Journal of Atmospheric Chemistry》2010,67(2-3):71-86

This paper reports aerosol chemical properties for the first time over a Korean Global Atmosphere Watch (GAW) supersite, Anmyeon (36°32′N; 126° 19′E), during 2003–2004 period. Total suspended Particulates (TSP) showed significant seasonal variation with consistent higher mass concentrations during spring season (average of up to 230?±?190 μg/m³). PM₁₀ also followed similar trend with higher concentrations during spring (average of up to 170?±?130 μg/m³) and showed reduced concentrations during summer. PM_2.5 showed a significant increase during summer (average of up to 60?±?25 μg/m³), which could be due to the influx of fine mode sea salt aerosols associated with the Changma front (summer monsoon). Chemical composition analysis showed enhanced presence of acidic fractions, majorly contributed by sulphates (SO ₄ ^2- ) and nitrates (NO ₃ ^- ) in TSP, PM₁₀ and PM_2.5 during different seasons. Enhanced presence of Calcium (Ca²⁺) was observed during sand storm days during spring. The high correlation obtained on matrix analysis between crustal ions and acidic ions suggests that the ionic compositions over the site are mainly contributed by terrestrial sources of similar origin. The neutralization factors has been estimated to find the extend of neutralization of acidicity by main basic components, and found to have higher value for Ammonium (up to 1.1) in different seasons, indicating significant neutralization of acidic components over the region by NH ₄ ⁺ . Back trajectory analysis has been performed during different seasons to constrain the possible sources of aerosol origin and the results are discussed in detail.  相似文献   

Pyrosequencing reveals specific associations of bacterial clades Roseobacter and Flavobacterium with the harmful dinoflagellate Cochlodinium polykrikoides growing in culture          下载免费PDF全文

Bum Soo Park  Ruoyu Guo  Weol‐Ae Lim  Jang‐Seu Ki 《Marine Ecology》2017,38(6)

Harmful algal blooms of the dinoflagellate Cochlodinium polykrikoides are of worldwide environmental concern. Previous field studies have demonstrated the association of such algal blooms with free‐living bacteria (FLB) and particle‐associated bacteria (PAB). In the present study, we report evidence for bacterial association with C. polykrikoides in laboratory culture. Sampling was performed at different growth stages (lag, exponential and stationary) and pyrosequencing was used to identify taxa. As a result, the community structures of FLB and PAB were elucidated and significant differences between FLB and PAB were identified by hierarchical cluster analysis and the similarity profiles test (p = .05). The relative abundances of bacterial operational taxonomic units distinctly changed in response to the different phases of C. polykrikoides growth. The Roseobacter genus Marivita and the Flavobacterium genus Winogradskyella were dominant in the FLB and PAB associated with C. polykrikoides, respectively. The Roseobacter clade, which has also exhibited associations with C. polykrikoides blooms in field samples, may influence host cell growth through the provision of vitamins.  相似文献   

Dependency of typhoon intensity and genesis locations on El Ni?o phase and SST shift over the western North Pacific     

Kyung-Ja Ha  Soon-Jo Yoon  Kyung-Sook Yun  Jong-Seong Kug  Yeon-Soo Jang  Johnny C. L. Chan 《Theoretical and Applied Climatology》2012,109(3-4):383-395

The effects of the El Ni?o-Southern Oscillation (ENSO) phase and the shifting of the ENSO sea surface temperature (SST) on the intensity of tropical cyclones (TC) have been extensively investigated in terms of TC genesis locations in the western North Pacific (WNP). To advance the hypothesis for a relation of genesis location–intensity that the TC formation location hints its intensity, two cases have been compared, which include the phase of the decaying El Ni?o turning over to La Ni?a (type I) and the phase that recovers to a neutral condition (type II). In addition, the shift of ENSO SST to the central Pacific warming (CPW) from the East Pacific warming (EPW) has been examined. The genesis potential index (GPI) and the accumulated cyclone energy have been applied to compare the differences between the ENSO phase and the TC formation location. It was apparent that ENSO influences the WNP typhoon formation location depending on the cycle of the ENSO phase. In addition, the typhoon activity was affected by the zonal shift of the El Ni?o SST. The CPW, which has maximum SST over the central Pacific, tends to have a persistently high GPI over the WNP in September–November and June–August, demonstrating that the formation locations of strong TCs significantly shift southeastward compared with the EPW having SST maximum over the eastern Pacific. CPW years revealed a distinguishable relationship between the TC formation location and the TC between the tropical depression (TD) + tropical storm (TS) and the intense typhoon of category 4?+?5.  相似文献   

Stratification and salt-wedge in the Seomjin river estuary under the idealized tidal influence     

Jin Hwan Hwang  Dongmin Jang  Yong Hoon Kim 《Ocean Science Journal》2017,52(4):469-487

Advection, straining, and vertical mixing play primary roles in the process of estuarine stratification. Estuaries can be classified as salt-wedge, partially-mixed or well-mixed depending on the vertical density structure determined by the balancing of advection, mixing and straining. In particular, straining plays a major role in the stratification of the estuarine water body along the estuarine channel. Also, the behavior of a salt wedge with a halocline shape in a stratified channel can be controlled by the competition between straining and mixing induced by buoyancy from the riverine source and tidal forcing. The present study uses Finite Volume Coastal Ocean Model (FVCOM) to show that straining and vertical mixing play major roles in controlling along-channel flow and stratification structures in the Seomjin river estuary (SRE) under idealized conditions. The Potential Energy Anomaly (PEA) dynamic equation quantifies the governing processes thereby enabling the determination of the stratification type. By comparing terms in the equation, we examined how the relative strengths of straining and mixing alter the stratification types in the SRE due to changes in river discharge and the depth resulting from dredging activities. SRE under idealized tidal forcing tends to be partially-mixed based on an analysis of the balance between terms and the vertical structure of salinity, and the morphological and hydrological change in SRE results in the shift of stratification type. While the depth affects the mixing, the freshwater discharge mainly controls the straining, and the balance between mixing and straining determines the final state of the stratification in an estuarine channel. As a result, the development and location of a salt wedge along the channel in a partially mixed and highly stratified condition is also determined by the ratio of straining to mixing. Finally, our findings confirm that the contributions of mixing and straining can be assessed by using the conventional non-dimensional parameters with respect to salt-wedge behavior.  相似文献