Impacts of ocean gateway and basin width on Tertiary tropical climate variability in a prototype model     

Soon-Il An  Jae-Heung Park  Baek-Min Kim  Axel Timmermann  Fei-Fei Jin 《Theoretical and Applied Climatology》2012,107(1-2):155-164

Using a simple tropical climate model, we investigated possible impacts of changes in oceanic seaways (Panama and Tethys) and ocean basin sizes (great Pacific and narrow Atlantic) on tropical climate variability during Tertiary. Our model showed that the opening of seaways had little influence on climate variability in the tropical Pacific because the climate variability in the Pacific Ocean’s large basins were internally generated, regardless of the variation in the tropical Atlantic Ocean. Conversely, the climate variability in the tropical Atlantic Ocean was highly dependent on the tropical Pacific Ocean; thus, an opening seaway, particularly the Panama seaway, was crucial in generating the interannual variability in the tropical Atlantic Ocean. We also found that in the Pacific Ocean, basin size strongly modified the period and amplitude of the interannual variability of both the Pacific and Atlantic Oceans due to ocean wave dynamics.  相似文献   

On the relationship between the Bowen ratio and the near-surface air temperature   总被引：1，自引：0，他引：1  

Jaeil Cho  Taikan Oki  Pat J.-F. Yeh  Wonsik Kim  Shinjiro Kanae  Kyoichi Otsuki 《Theoretical and Applied Climatology》2012,108(1-2):135-145

The sensitivity of land surface energy partitioning to near-surface air temperature (T _a) is a critical issue to understand the interaction between land surface and climatic system. Thus, studies with in situ observed data compiled from various climates and ecosystems are required. The relations derived from such empirical analyses are useful for developing accurate estimation methods of energy partitioning. In this study, the effect of T _a on land surface energy partitioning is evaluated by using flux measurement data compiled from a global network of eddy covariance tower sites (FLUXNET). According to the analysis of 25 FLUXNET sites (60 site-years) data, the Bowen ratio is found to have a linear relation with the bulk surface resistance normalized by aerodynamic and climatological resistance parameters in general, of which the slope and intercept are dependent on T _a. Energy partitioning in warmer atmosphere is less sensitive to changes in land surface conditions. In addition, a negative relation is found between Bowen ratio and T _a, and this relation is stronger above less vegetated surface and under low vapor pressure deficit and low received radiative energy condition. The empirical results obtained in this study are expected to be useful in gaining better understanding of alternating surface energy partitioning under increasing T _a.  相似文献   

Impact of MJO on the diurnal cycle of rainfall over the western Maritime Continent in the austral summer     

Ji-Hyun Oh  Kwang-Yul Kim  Gyu-Ho Lim 《Climate Dynamics》2012,38(5-6):1167-1180

This paper investigates the impact of the Madden-Julian Oscillation (MJO) on the diurnal cycle of rainfall over the western Maritime Continent during the austral summer. For this purpose, cyclostationary empirical orthogonal function analysis is applied to the tropical rainfall measuring mission rain rate and the Japanese Reanalysis-25 data for the period 1998–2008. The real-time multivariate MJO index by Wheeler and Hendon (Mon Wea Rev 132:1917–1932, 2004) is adopted to define the intensity and the phase of MJO. It is demonstrated that the hourly maximum rain rate over the domain tends to increase when convectively active phase of MJO approaches the Maritime Continent. In contrast, the hourly maximum rain rate tends to decrease when convectively suppressed phase of MJO resides over the region. The changes in the rain rate due to MJO differ over the ocean and the land. This difference is the greatest when the MJO is in the mature stage. Throughout the day during this stage, terrestrial rain rates show minimum values while diurnally varying oceanic rain rates record maximum values. Thus, precipitation becomes more intense in the morning over the Java Sea and is weakened in the evening over Borneo and Sumatra during the mature stage of MJO. During the decaying stage of MJO over the Maritime Continent, the diurnal cycle of precipitation weakens significantly over the ocean but only weakly over land. Analyses suggest that the anomalous lower level winds accompanied by MJO interact with the monsoonal flow over the Maritime Continent. Westerlies induced by MJO convection in the mature stage are superimposed on the monsoonal westerlies over the equator and increase wind speed mainly over the Java Sea due to the blocking effect of orography. Mountainous islands induce flow bifurcation, causing near-surface winds to converge mainly over the oceanic channels between two islands. As a result, heat flux release from the ocean to the atmosphere is enhanced by the increased surface wind resulting in instability as described in the wind-induced surface heat exchange mechanism. This may contribute to heavy rainfall over the Java Sea in the morning during the mature stage. On the other hand, convergence and vertical velocity over the islands, which play important roles in inducing nighttime rainfall, tend to be weak in the evening during the mature stage of MJO. Strong westerlies arising from MJO and the seasonal flow during the mature stage tend to interrupt convergence over islands. This interruption of convergence by MJO gives rise to decreased rain rates over the land regions.  相似文献   

Changma onset definition in Korea using the available water resources index and its relation to the Antarctic oscillation     

Ki-Seon Choi  Bin Wang  Do-Woo Kim 《Climate Dynamics》2012,38(3-4):547-562

This study defines the Changma onset using the available water resources index (AWRI) for 25?years (1985–2009) and verifies the validity of this definition. The three conditions for defining the Changma onset are established as follows: (i) The first day exceeding the June AWRI (threshold) averaged over the 25-year period. (ii) The continuation of the value over the threshold for at least 1?week after the onset. (iii) After the continuation of more than 1?week, the non-continuation of the value under the threshold for at least 1?week. The 25-year average Changma onset date is 24 June with a standard deviation of 9?days. The defined Changma onset is verified through the analysis on the relationship with the Antarctic oscillation (AAO). AAO in June shows a high correlation with not only the Changma onset but also the June precipitation (AWRI) in Korea. These three variables are influenced by Mascarene and Australian (positive AAO pattern) highs from in the preceding March. When these two pressure systems develop, the cold cross-equatorial flow in the direction from the region around Australia to the equator is intensified, which in turn, forces a western North Pacific high (WNPH) to develop northward; this eventually drives the rain belt north. As a result, the Changma begins early in the positive AAO phase, and the June precipitation increases in Korea. In addition, a WNPH that develops more northward increases the landfalling frequency of tropical cyclones in Korea, which plays an important role in increasing the June precipitation.  相似文献   

Reduction of the thermocline feedback associated with mean SST bias in ENSO simulation   总被引：1，自引：1，他引：0  

Baoqiang Xiang  Bin Wang  Qinghua Ding  Fei–Fei Jin  Xiouhua Fu  Hyung-Jin Kim 《Climate Dynamics》2012,39(6):1413-1430

Associated with the double Inter-tropical convergence zone problem, a dipole SST bias pattern (cold in the equatorial central Pacific and warm in the southeast tropical Pacific) remains a common problem inherent in many contemporary coupled models. Based on a newly-developed coupled model, we performed a control run and two sensitivity runs, one is a coupled run with annual mean SST correction and the other is an ocean forced run. By comparison of these three runs, we demonstrated that a serious consequence of this SST bias is to severely suppress the thermocline feedback in a realistic simulation of the El Ni?o/Southern Oscillation. Firstly, the excessive cold tongue extension pushes the anomalous convection far westward from the equatorial central Pacific, prominently diminishing the convection-low level wind feedback and thus the air-sea coupling strength. Secondly, the equatorial surface wind anomaly exhibits a relatively uniform meridional structure with weak gradient, contributing to a weakened wind-thermocline feedback. Thirdly, the equatorial cold SST bias induces a weakened upper-ocean stratification and thus yields the underestimation of the thermocline-subsurface temperature feedback. Finally, the dipole SST bias underestimates the mean upwelling through (a) undermining equatorial mean easterly wind stress, and (b) enhancing convective mixing and thus reducing the upper ocean stratification, which weakens vertical shear of meridional currents and near-surface Ekman-divergence.  相似文献   

Cluster analysis of tropical cyclone tracks in the Southern Hemisphere   总被引：1，自引：0，他引：1  

Hamish A. Ramsay  Suzana J. Camargo  Daehyun Kim 《Climate Dynamics》2012,39(3-4):897-917

A probabilistic clustering method is used to describe various aspects of tropical cyclone (TC) tracks in the Southern Hemisphere, for the period 1969–2008. A total of 7 clusters are examined: three in the South Indian Ocean, three in the Australian Region, and one in the South Pacific Ocean. Large-scale environmental variables related to TC genesis in each cluster are explored, including sea surface temperature, low-level relative vorticity, deep-layer vertical wind shear, outgoing longwave radiation, El Niño-Southern Oscillation (ENSO) and the Madden-Julian Oscillation (MJO). Composite maps, constructed 2 days prior to genesis, show some of these to be significant precursors to TC formation—most prominently, westerly wind anomalies equatorward of the main development regions. Clusters are also evaluated with respect to their genesis location, seasonality, mean peak intensity, track duration, landfall location, and intensity at landfall. ENSO is found to play a significant role in modulating annual frequency and mean genesis location in three of the seven clusters (two in the South Indian Ocean and one in the Pacific). The ENSO-modulating effect on genesis frequency is caused primarily by changes in low-level zonal flow between the equator and 10°S, and associated relative vorticity changes in the main development regions. ENSO also has a significant effect on mean genesis location in three clusters, with TCs forming further equatorward (poleward) during El Niño (La Niña) in addition to large shifts in mean longitude. The MJO has a strong influence on TC genesis in all clusters, though the amount modulation is found to be sensitive to the definition of the MJO.  相似文献   

The potential of vegetation feedback to alleviate climate aridity over the United States associated with a 2×CO2 climate condition     

Chang-Eui Park  Chang-Hoi Ho  Su-Jong Jeong  Jinwon Kim  Song Feng 《Climate Dynamics》2012,38(7-8):1489-1500

This study examines the potential impact of vegetation feedback on changes in summer climate aridity over the contiguous United States (US) due to the doubling of atmospheric CO₂ concentration using a set of 100-year-long climate simulations made by a global climate model interactively coupled with a dynamic vegetation model. The Thornthwaite moisture index (I _m ), which quantifies climate aridity on the basis of atmospheric water supply (i.e., precipitation) and atmospheric water demand (i.e., potential evapotranspiration, PET), is used to measure climate aridity. Warmer atmosphere and drier surface resulting from increased CO₂ concentration increase climate aridity over most of the contiguous US. This phenomenon is due to larger increments in PET than in precipitation, regardless of the presence or absence of vegetation feedback. Compared to simulations without active dynamic vegetation feedback, the presence of vegetation feedback significantly alleviates the increase in aridity. This vegetation-feedback effect is most noticeable in the subhumid regions such as southern, midwestern and northwestern US, primarily by the increasing vegetation greenness. In these regions, the greening in response to warmer temperatures enhances moisture transfer from soil to atmosphere by evapotranspiration (ET). The increased ET and subsequent moistening over land areas result in weaker surface warming (1–2?K) and PET (3–10?mm?month^?1), and greater precipitation (4–10?mm?month^?1). Collectively, they result in moderate increases in I _m . Our results suggest that moistening by enhanced vegetation feedback may prevent aridification under climatic warming especially in areas vulnerable to climate change, with consequent implications for mitigation strategies.  相似文献   

朝鲜平南盆地叠加褶皱构造特征     

金炳成  刘永江  卞昌男  朴明华 《吉林大学学报(地球科学版)》2019,49(3):737-745

对于朝鲜平南盆地沉积盖层内发育的倒转褶皱,过去一般认为是直立褶皱的次级从属褶皱。通过对平南盆地内倒转褶皱发育区详细的地质调查,结合煤炭开发过程中获得的地质及钻探资料,提出平南盆地内叠加褶皱的主要识别标志为：地质平面图上呈现不同类型的两组褶皱脊线的交叉;倒转褶皱的轴面被直立褶皱改造弯曲;直立褶皱的两翼发育的倒转褶皱表现为两组牵引褶皱。查明了平南盆地存在3个阶段的褶皱构造：第一阶段为东西向的倒转褶皱,形成于印支期;第二阶段褶皱为东西向的直立褶皱,形成于早燕山期;第三阶段褶皱为北北东向的直立褶皱,形成于晚燕山期。  相似文献   

Comparative analysis of four stem taper models for Quercus glauca in Mount Halla,Jeju Island,South Korea     

LUMBRES Roscinto Ian Canicosa  LEE Young Jin  CHOI Hyung Soon  KIM Sung Yong  JANG Mi Na  ABINO Azyleah Caizares  SEO Yeon Ok  KIM Chan Soo  PARK Jung Hwan 《山地科学学报》2014,11(2):442-448

This study was conducted to fit the diameter-height data of Quercusglaucain Jeju Island, South Korea to the four commonly used stem taper equations andto evaluate the performance of the four stem taper models using four statistical criteria： Fit index （FI）, root mean square error （RMSE）, bias （）,and absolute mean difference （AMD）. Results showed that the Kozak02stem taper equation provided the best FI（0.9847）, RMSE（1.5745）,（-0.0030 cm） and AMD （1.0990 cm） whileMax and Burkhart model had the poorest performance among the four stem taper models based on the four evaluation statistics （FI ： 0.9793,RMSE ： 1.8272, ： 0.3040 cm and AMD ： 1.3060 cm）. These stem taper equations can serve as a useful tool for forest managers in estimating the diameter outside bark at any given height, merchantable stem volumes and total stem volumesof the standing trees of Quercusglaucain theGotjawal forests located in Mount Halla, Jeju Island, South Korea.  相似文献   

Genetic environment of the Geumeum Mo (–Cu) mineralization in Korea     

Yong Hwan AhnSeon-Gyu Choi  Ji Yun LeeTae Hyeong Kim  In Kul Yoo 《Journal of Geochemical Exploration》2009

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