Seasonal variations, trend in the tropopause height/temperature over Indian stations and its modulations by SST anomalies of east Pacific Ocean

Global warming due to increase in the Green House Gases is now well known. There are several studies, also, suggesting discernible changes over the years in respect of meteorological parameters like, rainfall events, frequency and intensity of tropical cyclones/hurricanes, maximum/minimum temperature, SST of oceans etc, on regional as well as global scale. The present study besides finding out seasonal variations in tropopause height and temperature across each 5° latitude over India based on a longer data set, has demarcated the locations where significant trend in respect of temperature and height was observed over Indian region on annual scale besides investigating the possible causes of this trend. The study has also confirmed significant linear associationship between tropopause temperature/height over Indian stations and SST anomalies of east Pacific Ocean with SST leading by one year.

Rapid dynamical evolution of ITCZ events over the east Pacific

The latitudinal location of the east Pacific Ocean intertropical convergence zone (ITCZ) changes on time scales of days to weeks during boreal spring. This study focuses on tropical near-surface dynamics in the days leading up to the two most frequent types of ITCZ events, nITCZ (Northern Hemisphere) and dITCZ (double). There is a rapid, daily evolution of dynamical features on top of a slower, weekly evolution that occurs leading up to and after nITCZ and dITCZ events. Zonally-elongated bands of anomalous cross-equatorial flow and off-equatorial convergence rapidly intensify and peak one day before or the day of these ITCZ events, followed one or two days later by a peak in near-equatorial zonal wind anomalies. In addition, there is a wide region north of the southeast Pacific subtropical high where anomalous northwesterlies strengthen prior to nITCZ events and southeasterlies strengthen before dITCZ events. Anomalous zonal and meridional near-surface momentum budgets reveal that the terms associated with Ekman balance are of first-order importance preceding nITCZ events, but that the meridional momentum advective terms are just as important before dITCZ events. Variations in cross-equatorial flow are promoted by the meridional pressure gradient force (PGF) prior to nITCZ events and the meridional advection of meridional momentum in addition to the meridional PGF before dITCZ events. Meanwhile, variations in near-equatorial easterlies are driven by the zonal PGF and the Coriolis force preceding nITCZ events and the zonal PGF, the Coriolis force, and the meridional advection of zonal momentum before dITCZ events.

Ecological considerations for species distribution modelling of euphausiids in the north east Pacific Ocean

Euphausiids are a keystone species in marine food webs of the north-east Pacific Ocean, important for forage fish, commercial fish species and marine predators such as seabirds and whales. Ecosystem-based fisheries management relies on realistic lower-trophic level information for forecasting under future changing climate scenarios. We synthesised information from quantitative modelling studies analysing the relationship between euphausiids and their environment for two species of euphausiids which dominate assemblages in this region – Euphausia pacifica and Thysanoessa spinifera. Studies analysed suggest that variables reflecting the physical and biological environment in situ, features reflecting the geomorphic marine landscape, and large-scale climate indices all significantly affect euphausiid biomass and distribution. Temperature was the most tested predictor variable in the euphausiid models reviewed, however it was significant in fewer models than other variables tested. We review and compare model structures, predictor variable selection and temporal lag phases, to develop recommendations for species distribution modelling of euphausiids in the north-east Pacific Ocean. We believe the results from this review will be applicable globally across regions with similar climates where euphausiids are numerous, and can be adapted for different species and environments.

Muricauda oceani sp. nov., isolated from the East Pacific Ocean

A Gram-stain-negative bacterium, designated strain 501str8T, was isolated from a sediment sample collected from the East Pacific Ocean. 16S rRNA gene sequence analysis revealed that strain 501str8T belonged to the genus Muricauda , with closely related type strains Muricauda aquimarina SW-63T (98.5 %), Muricauda lutimaris SMK-108T (98.3 %) and Muricauda ruestringensis B1T (97.9 %). Up-to-date bacterial core gene set analysis revealed that strain 501str8T represented one independent lineage with M. aquimarina SW-63T. The average nucleotide identity values of strain 501str8T with M. aquimarina SW-63T and M. lutimaris SMK-108T were 80.2 and 81.3 %, respectively. In silico DNA–DNA hybridization values between strain 501str8T and M. aquimarina SW-63T and M. lutimaris SMK-108T were 22.8 and 32.9 %, respectively. The predominant isoprenoid quinone was menaquinone-6, and iso-C15 : 0, iso-C17 : 0 3-OH and iso-C15 : 1 G were the dominant cellular fatty acids. The G+C content of the genomic DNA was 42.8 mol%. Differential phylogenetic distinctiveness and chemotaxonomic differences, together with the phenotypic properties observed in this study, revealed that strain 501str8T could be differentiated from closely related species. Therefore, we propose that strain 501str8T represents a novel species of the genus Muricauda , for which the name Muricauda oceani sp. nov. is suggested. The type strain is 501str8T (=JCM 33902T=MCCC 1K04567T).

Intra-seasonal Oscillation of Abyssal Currents in the Middle East Pacific Ocean

<p>In this work, the intra-seasonal oscillation of the abyssal currents in the Middle East Pacific Ocean is investigated using direct observations from ADCP instruments, which are mounted on a subsurface mooring deployed at 154oW，10oN. The observation shows that the intra-seasonal (20-100 days) oscillation part of the kinetic energy accounts for more than 40% of the low-frequency flow kinetic energy between 200~2000m, while accounts for more than 50% under 2000m; the intra-seasonal oscillation of meridional flow is more obvious than that of zonal flow. The meridional velocity in the upper layer (100-1000m) shows an oscillation at periods of 50~90 days, which is most obvious at the depth of 500m; from 200m to the bottom layer currents shows an synchronous oscillation at a period of 30 days lasting for several months, and the oscillation signal is the strongest in the deep layer (4600m); The correlation is good between the 20~40 day band passed meridional current at the bottom layer and that of the geostrophic current. The observed temperature of 4000m and 5000m also shows similar characteristics of 30 days period oscillation, which has good correlation to the sea level height. The reanalysis data shows the 30 days oscillation of the abyssal currents is propagated from west to east at a speed of about 0.29m/s while the 40~100 day oscillation is propagated at a speed of about 0.1m/s; the intensity of the intra-seasonal oscillation has obvious interannual variations, which may be related to the change of the eddy energy of the sea surface.</p>