• Ocean and Polar Research
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• 제26권1호
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• pp.33-42
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• 2004

Effect of freshwater discharge on the long-term salt balance in the Northern and Central Indian River Lagoon (IRL) is successfully simulated by a new analytical solution to a water balance-based one-dimensional salt conservation equation. Sensitivity tests show that the salinity levels drop abruptly even during the dry season (November to May) due to the high surface runoff discharge caused by tropical storms, depressions, and passage of cold fronts. Increasing surface runoff and direct precipitation has risen by ten times, lowering the salinity level down to 12psu in the Northern Central zone, and to 17 psu in the Northern zone. However, the salinity level in the Southern Central zone has decreased to 25 psu. High sensitivity of the Northern Central zone to freshwater discharge can be partially explained by a rapid urbanization in this zone. During the dry season, less sensitivity of the Southern Central zone to the increased surface runoff is attributed to the proximity of the zone to the Sebastian Inlet and a strong diffusion condition possibly resulting from the seawater intrusion to the surficial aquifer at the Vero Beach. During the wet season, however, the whole study area is highly sensitive to freshwater discharge due to the weak diffusion conditions. High sensitivity of the IRL to the given diffusion conditions guarantees that the fresh-water release occurs during strong wind conditions, achieving both flood control in the drainage basin and a proper salinity regime in the IRL.

• Ocean Science Journal
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• 제42권4호
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• pp.241-246
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• 2007

Northern Arabian Sea (NAS) between $17^{\circ}N-20.5^{\circ}N$ and $59^{\circ}E-69^{\circ}E$ was observed by using Argo float daily data fur about 9 months, from April 2002 through December 2002. Results showed that during April - May mixed layer shoaled due to light winds, clear sky and intense solar insolation. Sea surface temperature (SST) rose by $2.3^{\circ}C$ and ocean gained an average of 99.8 $Wm^{-2}$. Mixed layer reached maximum depth of about 71 m during June - September owing to strong winds and cloudy skies. Ocean gained abnormally low $\sim18Wm^{-2}$ and SST dropped by $3.4^{\circ}C$. During the inter monsoon period, October, mixed layer shoaled and maintained a depth of 20 to 30 m. November - December was accompanied by moderate winds, dropping of SST by $1.5^{\circ}C$ and ocean lost an average of 52.5 $Wm^{-2}$. Mixed layer deepened gradually reaching a maximum of 62 m in December. Analysis of surface fluxes and winds suggested that winds and fluxes are the dominating factors causing deepening of mixed layer during summer and winter monsoon periods respectively. Relatively big]h correlation between MLD, net heat flux and wind speed revealed that short term variability of MLD coincided well with short term variability of surface forcing.

• ALGAE
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• 제26권4호
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• pp.317-325
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• 2011

Five benthic species of the genus Gambierdiscus (Dinophyceae) were observed for the first time in the coastal waters of Pakistan, Northern Indian Ocean. The morphology of the epiphytic, ciguatera-related toxic species G. toxicus, G. belizeanus, G. polynesiensis, G. australes and G. cf. yasumotoi are presented here, described by the Kofoid system of thecal plates Po, 3', 7", 6c, 8s, 5"', 1p, 2"" with differences in cell shape, cell size, plates, pores around the apical pore plate by using light and scanning electron microscopy. The occurrence of these potentially toxic dinoflagellate species in Pakistani coastal areas of Manora Channel and Balochistan during high temperatures of 28-$32^{\circ}C$ is cause of concern for human health impacts from ciguatera fish poisoning.

• 대한원격탐사학회지
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• 제26권2호
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• pp.175-188
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• 2010

세계 최초로 정지 상태로 해색을 관측하는 정지궤도해색탑재체(GOCI, Geostationary Ocean Color Imager) 값의 보정을 위해서는 기존의 방법이 아닌 새로운 방법이 요구된다. 본 연구에서는 GOCI의 특별한 특성에 맞는 새로운 대기보정 방법과 양방향성 광반사 분포함수(BRDF, Bidirectional Reflectance Distribution Function) 보정 방법을 소개하고자 한다. GOCI의 대기보정을 위해서 스펙트럼 형태 조화기법(SSMM, Spectral Shape Matching Method)과 Sun Glint Correction Algorithm(SGCA)을 개발하였고, BRDF 보정을 위하여 해수의 고유광특성(IOP, Inherent Optical Property) 값을 이용하는 새로운 방법을 개발하였다. 각 방법은 한반도 주변 해역을 관측한 Sea Viewing Wide Field-of-view Sensor(SeaWiFS) 위성영상을 이용하여 적용하였다. 클로로필 농도 분포 영상을 만들어 본 결과 기존의 방법으로 얻기 어려웠던 탁도높은 해역과 에어로졸의 영향을 많이 받는 지역에서 보다 정확한 자료를 얻을 수 있었다.

• 한국지구과학회지
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• 제28권1호
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• pp.35-44
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• 2007

본 연구에서는 엘니뇨현상과 인도양 쌍극자 모드(Indian Ocean Dipole, IOD) 현상의 상호 관련성과, 우리나라 기온, 강수량에 대한 두 현상의 영향을 분석하였다. 1954년부터 2004년까지 51년간 NINO 3 지수, IOD지수, 그리고 전국 11개 지점 지역평균한 월별 평균기온과 강수량 자료를 사용하였다. 엘니뇨현상과 IOD현상은 봄과 가을에는 동시 상관관계가 존재한다. 인도양에서 해수면온도 분포는 엘니뇨 해에는 남북진동이, IOD 해에는 동서진동 형태가 뚜렷하였다. 엘니뇨 해 우리나라에서는, 여름철에 냉하다우, 겨울철에 온난다우 경향이 뚜렷한 반면에, IOD 해에는 유의한 상관성을 찾을 수 없었다. 대기대순환에서도 엘니뇨 해에는 우리나라를 포함한 중위도에 통계적으로 신뢰할 만한 편차패턴이 나타나지만, IOD 해에는 그렇지 않았다.

• Ocean Systems Engineering
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• 제10권2호
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• pp.181-199
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• 2020

Cyclone Heat Potential (CHP) is an essential parameter for accurate prediction of the intensity of tropical cyclones. The variability of the heat storage in the near-surface layers and the vertical stratification near the surface due to large fresh water inputs create challenges in predicting the intraseasonal and interannual evolution of monsoons and tropical cyclones in the Bay of Bengal. This paper for the first time presents the D26- referenced cyclone heat potential observed in the Bay of Bengal during the period 2012-17 based on the in-situ data collected from 5.5 million demanding offshore instrument-hours of operation in the Ocean Moored Buoy Network for Northern Indian Ocean (OMNI) buoy network by the National Institute of Ocean Technology. It is observed that the CHP in the Bay of Bengal varied from 0-220 kJ/㎠ during various seasons. From the moored buoy observations, a CHP of ~ 90 kJ/㎠ with the D26 isotherm of minimum 100m is favorable for the intensification of the post-monsoon tropical cyclones. The responses of the D26 thermal structure during major tropical cyclone events in the Bay of Bengal are also presented.

• 대한원격탐사학회지
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• 제33권6_1호
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• pp.917-930
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• 2017

본 연구는 2017년부터 "이사부호"를 활용하여 인도양에서 본격적으로 수행되는 관측에 앞서 위성을 활용하여 인도양 쌍극진동(Indian Ocean Dipole, IOD) 변동에 따른 위성에서 추정된 클로로필-a 농도의 시/공간적 변화를 이해하는데 목적이 있다. 특히 단기적인 변화보다는 장기 변화에 초점을 두고 1998년부터 2016년까지 해색위성에서 계산된 월평균 클로로필-a 농도 자료를 이용하여 인도양 전 해역($30^{\circ}E{\sim}120^{\circ}E$, $30^{\circ}S{\sim}30^{\circ}N$)을 대상으로 분석했다. 클로로필-a 농도는 중앙 인도양에서 낮고, 용승해역 및 대륙 주변 해역에서 증가되었다. 계절풍과 해류 시스템의 영향으로 클로로필-a 농도는 봄에 가장 감소하고 여름에 최대를 나타냈다. Empirical Orthogonal Function(EOF) 분석 결과, 첫 번째 모드의 클로로필-a 농도 변화는 엔소(El $Ni{\tilde{n}}o$/Southern Oscillation, ENSO)의 변화와 높은 관계를 보이고, 두 번째 모드의 클로로필-a 농도 변화는 엔소에 의한 영향보다는 인도양 쌍극진동의 변화와 상대적으로 높은 관계를 나타냈다. 클로로필-a 농도는 두 개의 모드에서 공통적으로 동 인도양과 서 인도양에서 서로 상반된 변화를 나타냈다. 클로로필-a 농도 변화는 동 인도양, 서 인도양 및 인도 주변 해역에서는 인도양 쌍극진동과 밀접한 관계를 보이고, 열대 중앙 인도양 중에서는 상대적으로 엔소의 변화와 높은 관계를 나타냈다. 그러나 클로로필-a 농도의 시/공간적 변화는 인도양 쌍극진동의 발생 기작에 따라 다른 반응을 나타냈다. 클로로필-a 농도 변화는 첫 번째 타입 인도양 쌍극진동(엔소 발생시기와 동일)은 여름철에 동 인도양과 서 인도양에서 클로로필-a 농도 차이가 생기고, 최대는 가을에 발생했다. 두 번째 타입 인도양 쌍극진동(엔소 발생 후 그 다음 해 또는 소멸되는 시기)은 봄에 동 인도양과 서 인도양 클로로필-a 농도 차이가 생기고, 여름과 가을에 증가되어, 겨울에 감소되었다. 인도양 쌍극진동의 변동에 따른 클로로필-a 농도 변화는 동 인도양과 서 인도양의 클로로필-a 농도 차이를 발생시키는 과정은 유사하지만, 북부 인도양은 쌍극진동 발생 기작에 따라 상반된 클로로필-a 농도 변화를 나타냈다.

• Ocean and Polar Research
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• 제25권1호
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• pp.75-87
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• 2003

The water balance calculation in the IRL shows that fresh groundwater discharge is the primary factor, with surface runoff from gaged and ungaged areas as the second freshwater contributor. Precipitation and evaporation are almost in balance fer the entire IRL. Due to high freshwater discharge from ground-water, the annual net flow is outward from the IRL to the continental shelf of the Atlantic Ocean resulting in a relatively short flushing time, denoted as $T_{0.5}$ (50% flushing time) and $T_{0.99}$ (99% flushing time). $T_{0.5}$, and. $T_{0.99}$ without a tidal effect in the Northern IRL are 17 and 114 days, respectively, during the dry season. During the wet season, they are 10 and 65 days, respectively. Tidal flushing effects are considered in central IRL due to the proximity to Sebastian Inlet. In the Northern Central zone during dry season, $T_{0.5}$, and. $T_{0.99}$ are 6 and 43 days, respectively and during the wet season 5 and 33 days. In the Southern Central zone they are 2 and 16 days for the dry season,2 and 15 days for the wet season. High groundwater seepage into the IRL is considered to be a positive effect in maintaining relatively good water quality condition even with few narrow inlets.

• Ocean and Polar Research
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• 제24권1호
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• pp.1-18
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• 2002

Seasonal variation in global transport calculated from an ocean general circulation model (OGCM) has been assessed through the comparison with observational estimates. The OGCM based on the GFDL MOM1.1 has honzontal grid interval of 10 and 21 verticle levels, and was integrated for 31 years forced by climatological wind stress, freshwater flux, and heat flux with restoring. General features of the world ocean circulation are well reproduced, which include the western boundary currents such as the Kuroshio and the Agulhas Current, the Equatorial Current system, the Antarctic Circumpolar Current, and the Weddell Sea gyres. Also well resolved is the remarkable seasonal variation in the depth-integrated flows in the northern Indian Ocean due to the monsoonal wind. Monthly variation is found to be dominant in the transport of the Antarctic Circumpolar Current through the Drake Passage in accordance with observational estimates. It has been shown that the mid-latitude depth-integrated flows obey the Sverdrup relation, except for some regions such as continental shelf regions where the interaction between stratification and bottom topography is critical.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2008년도 International Symposium on Remote Sensing
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• pp.285-288
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• 2008

We analyzed evaporation data in the Japanese Ocean Flux Data Sets with Use of Remote Sensing Observations (J-OFURO) Ver.2. There exists huge evaporation in Gulf Stream, Kuroshio Extension, the ocean dessert and the southern part of the Indian Ocean. The temporal variation of evaporation is overwhelmingly large, of which the standard deviation is more than 120(mm), in the Kuroshio Extension region. Also, the result of harmonic analysis gives that this large variation is closely related to annual variation. In addition, the first EOF mode shows long-term variation showing the maximum amplitude between 1992 and 1994 and remarkable decrease after 1994, and large amplitude in the equatorial region and northeast of Australia. The second and third modes were strongly influenced by El Nino. Moreover, we compared J-OFURO2 evaporation product with other products. We used six kinds of data sets (HOAPS3 and GSSTF2 of satellite data, NRA1, NRA2, ERA40 and JRA25 of reanalysis data) for comparison. Most products show underestimation in the most regions, in particular, in the northern North Pacific, mid-latitudes of the eastern South Pacific, and high-latitudes of the South Pacific compared with J-OFUR02. On the other hand, JRA25 and NRA2 show large overestimation in the equatorial regions. RMS difference between NRA2 and J-OFURO2 in the Kuroshio Extension was significantly large, more than 120(mm).