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RISS 인기검색어
- 검색키워드
- 저자 : Vissa, V. (검색결과 4 건)
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Response of Upper Ocean and Impact of Barrier Layer on Sidr Cyclone Induced Sea Surface Cooling
Naresh Krishna Vissa,A.N.V. Satyanarayana,B. Prasad Kumar 한국해양과학기술원 2013 Ocean science journal Vol.48 No.3
In the present study an attempt has been made to investigate the impact of salinity stratification on the SST during the tropical cyclone (TC) passage. In this context, a severe post monsoon cyclone, Sidr, (Category 4) that developed over the south-eastern Bay of Bengal (BoB) during 11-16 November, 2007 was chosen as a case study. Pre-existence of a thick barrier layer (BL), temperature inversions and a higher effective oceanic layer for cyclogenesis (EOLC) were noticed along the path of the Sidr cyclone. The analysis of available Argo floats along the Sidr cyclone track also revealed less cooling during as well as after its passage as was reported from satellite derived SST. The role of BL on Sidr induced sea surface cooling was investigated using a diagnostic mixed layer model. Model results also depict the reduced sea surface cooling during the passage of Sidr. This is attributed to the presence of BL which results in the inhibition of the entrainment of cool thermocline water into the shallow mixed layer. Climatological as well as in situ observations of tropical cyclone heat potential (TCHP) and EOLC shows that the Sidr cyclone propagated towards the regions of higher EOLC.
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Gopinadh Konda,Naresh Krishna Vissa 한국기상학회 2021 Asia-Pacific Journal of Atmospheric Sciences Vol.57 No.4
The boreal summer intraseasonal oscillations (BSISO) are the prominent features of South Asian summer monsoon and mainly governed by the internal atmospheric dynamics and air-sea interactions. The present study aims to understand and evaluate the relationship between the convection and the associated air-sea interactions during the BSISO over the Indian monsoon region. To accomplish this, the present study utilizes observations and the 22 general circulation model (GCM) simulations from the Coupled Model Intercomparison Project Phase 5 (CMIP5). Representation of Indian monsoon season rainfall, sea surface temperature (SST) and latent heat fluxes in CMIP5 models such as climatological and intraseasonal are assessed using Global Precipitation Climatology Project rainfall by Taylor diagram metric. Results suggest that the majority of CMIP5 models simulated the northward propagation of precipitation and zonal wind at 850 hPa. However, models bias of BSISO variance shows significant spatial heterogeneity over the regions of the Arabian Sea (AS), Sub-Continent of India (SCI) and Bay of Bengal (BoB). The CMIP5 model which shows large biases in the mean state is degrading the northward propagation of BSISO. The phase relationship of ocean (land) and atmospheric interactions are diagnosed with lead-lag regression analysis. On ISO timescales over north Indian Ocean (NIO) convection leads the turbulent fluxes and westerly winds by a week. However, the majority of the models shows large uncertainty to represent this prominent feature over AS and SCI. Further, improper representation of the lead-lag relationship of SST and precipitation on ISO scales over the AS, BoB, and NIO in the CMIP5 models are attributing for significant bias variances. The present study advocates that BSISO propagation in CMIP5 models is mainly attributing from the internal atmospheric dynamics and air-sea interactions. However, for the realistic amplitude simulation of BSISO, proper representation of air-sea feedback mechanisms is crucial in CMIP5 models. The present study further suggests that the oceanic feedback processes of the CMIP5 models need to be improved for the accurate prediction of the intraseasonal variations.
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Population-Based Molecular Epidemiology of Leprosy in Cebu, Philippines
Sakamuri, R. M.,Kimura, M.,Li, W.,Kim, H.-C.,Lee, H.,Kiran, M. D.,Black, W. C.,Balagon, M.,Gelber, R.,Cho, S.-N.,Brennan, P. J.,Vissa, V. American Society for Microbiology 2009 Journal of clinical microbiology Vol.47 No.9
<P>To address the persisting problem of leprosy in Cebu, Philippines, we compiled a database of more than 200 patients who attend an established referral skin clinic. We described the patient characteristics in conventional demographic parameters and also applied multiple-locus variable-number tandem-repeat (VNTR) analysis (MLVA) and single nucleotide polymorphism (SNP) typing for Mycobacterium leprae in biopsied skin lesion samples. These combined approaches revealed that transmission is ongoing, with the affected including the young Cebuano population under 40 years of age in both crowded cities and rural areas of the island. The emergence of multicase families (MCF) is indicative of infection unconstrained by standard care measures. For the SNPs, we designed a low-cost PCR-restriction fragment length polymorphism typing method. MLVA in M. leprae was highly discriminatory in this population yet could retain broad groups, as defined by the more stable SNPs, implying temporal marker stability suitable for interpreting population structures and evolution. The majority of isolates belong to an Asian lineage (SNP type 1), and the rest belong to a putative postcolonial lineage (SNP type 3). Specific alleles at two VNTR loci, (GGT)5 and 21-3, were highly associated with SNP type 3 in this population. MLVA identified M. leprae genotype associations for patients with known epidemiological links such as in MCFs and in some villages. These methods provide a molecular database and a rational framework for targeted approaches to search and confirm leprosy transmission in various scenarios.</P>
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Rapid Variable-Number Tandem-Repeat Genotyping for Mycobacterium leprae Clinical Specimens
Kimura, M.,Sakamuri, R. M.,Groathouse, N. A.,Rivoire, B. L.,Gingrich, D.,Krueger-Koplin, S.,Cho, S.-N.,Brennan, P. J.,Vissa, V. American Society for Microbiology 2009 Journal of clinical microbiology Vol.47 No.6
<P>Mycobacterium leprae is the noncultivable pathogen of leprosy. Since the genome sequence of an isolate of M. leprae has become available, multiple-locus variable-number tandem-repeat (VNTR) analysis (MLVA) has been explored as a tool for strain typing and identification of chains of transmission of leprosy. In order to discover VNTRs and develop methods transferable to clinical samples, MLVA was applied to a global collection of M. leprae isolates derived from leprosy patients and propagated in armadillo hosts. PCR amplification, agarose gel electrophoresis, and sequencing methods were applied to DNA extracts from these infected armadillo tissues (n = 21). We identified polymorphisms in 15 out of 25 short-tandem-repeat (STR) loci previously selected by in silico analyses of the M. leprae genome. We then developed multiplex PCR for amplification of these 15 loci in four separate PCRs suitable for fluorescent fragment length analysis and demonstrated STR profiles highly concordant with those from the sequencing methods. Subsequently, we extended this method to DNA extracts from human clinical specimens, such as skin biopsy specimens (n = 30). With these techniques, mapping of multiple loci and differentiation of genotypes have been possible using total DNA extracts from limited amounts of clinical samples at a reduced cost and with less time. These practical methods are therefore available and applicable to answer focused epidemiological questions and to allow monitoring of the transmission of M. leprae in different countries where leprosy is endemic.</P>
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