Statistical assessment of sea-surface salinity from SMAP: Arabian sea, Bay of Bengal and a promising Red Sea application

© The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Menezes, V. V. Statistical assessment of sea-surface salinity from SMAP: Arabian sea, Bay of Bengal and a promising Red Sea application. Remote Sensing, 12(3), (2020): 447, doi:10.3390/rs12030447.Sea-surface salinity (SSS) is an essential climate variable connected to Earth’s hydrological cycle and a dynamical component of ocean circulation, but its variability is not well-understood. Thanks to Argo floats, and the first decade of salinity remote sensing, this is changing. While satellites can retrieve salinity with some confidence, accuracy is regionally dependent and challenging within 500–1000 km offshore. The present work assesses the first four years of the National Aeronautics and Space Administration’s Soil Moisture Active Passive (SMAP) satellite in the North Indian Ocean. SMAP’s improved spatial resolution, better mitigation for radio-frequency interference, and land contamination make it particularly attractive to study coastal areas. Here, regions of interest are the Bay of Bengal, the Arabian Sea, and the extremely salty Red Sea (the last of which has not yet received attention). Six SMAP products, which include Levels 2 and 3 data, were statistically evaluated against in situ measurements collected by a variety of instruments. SMAP reproduced SSS well in both the Arabian Sea and the Bay of Bengal, and surprisingly well in the Red Sea. Correlations there were 0.81–0.93, and the root-mean-square difference was 0.38–0.67 for Level 3 data.This research and open-access publication were funded by NASA grant number 80NSSC18K133 (NASA Ocean Salinity Science Team)

Accelerated freshening of Antarctic Bottom Water over the last decade in the Southern Indian Ocean

© The Author(s), 2017. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Science Advances 3 (2017): e1601426, doi:10.1126/sciadv.1601426.Southern Ocean abyssal waters, in contact with the atmosphere at their formation sites around Antarctica, not only bring signals of a changing climate with them as they move around the globe but also contribute to that change through heat uptake and sea level rise. A repeat hydrographic line in the Indian sector of the Southern Ocean, occupied three times in the last two decades (1994, 2007, and, most recently, 2016), reveals that Antarctic Bottom Water (AABW) continues to become fresher (0.004 ± 0.001 kg/g decade−1), warmer (0.06° ± 0.01°C decade−1), and less dense (0.011 ± 0.002 kg/m3 decade−1). The most recent observations in the Australian-Antarctic Basin show a particularly striking acceleration in AABW freshening between 2007 and 2016 (0.008 ± 0.001 kg/g decade−1) compared to the 0.002 ± 0.001 kg/g decade−1 seen between 1994 and 2007. Freshening is, in part, responsible for an overall shift of the mean temperature-salinity curve toward lower densities. The marked freshening may be linked to an abrupt iceberg-glacier collision and calving event that occurred in 2010 on the George V/Adélie Land Coast, the main source region of bottom waters for the Australian-Antarctic Basin. Because AABW is a key component of the global overturning circulation, the persistent decrease in bottom water density and the associated increase in steric height that result from continued warming and freshening have important consequences beyond the Southern Indian Ocean.The 2016 I08S cruise and the analysis and science performed at sea, as well as the individual principal investigators were funded through multiple National Oceanic and Atmospheric Administration (NOAA) and NSF grants including NSF grant OCE-1437015. The research for this article was mainly completed at sea. For land-based work, V.V.M. relied on her postdoctoral funding through NSF grant OCE-1435665, and A.M.M. was supported in part by NSF grant OCE-1356630 and NOAA grant NA11OAR4310063

Surface heat fluxes over the northern Arabian Gulf and the northern Red Sea: Evaluation of ECMWF-ERA5 and NASA-MERRA2 reanalyses

© The Author(s), 2019. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Al Senafi, F., Anis, A., & Menezes, V. Surface heat fluxes over the northern Arabian Gulf and the northern Red Sea: Evaluation of ECMWF-ERA5 and NASA-MERRA2 reanalyses. Atmosphere, 10(9), (2019): 504, doi:10.3390/atmos10090504.The air–sea heat fluxes in marginal seas and under extreme weather conditions constitute an essential source for energy transport and mixing dynamics. To reproduce these effects in numerical models, we need a better understanding of these fluxes. In response to this demand, we undertook a study to examine the surface heat fluxes in the Arabian Gulf (2013 to 2014) and Red Sea (2008 to 2010)—the two salty Indian Ocean marginal seas. We use high-quality buoy observations from offshore meteorological stations and data from two reanalysis products, the Modern-Era Retrospective analysis for Research and Applications version 2 (MERRA2) from the National Aeronautics and Space Administration (NASA) and ERA5, the fifth generation of the European Centre for Medium-Range Weather Forecasts (ECMWF) atmospheric reanalyses of global climate. Comparison of the reanalyses with the in situ-derived fluxes shows that both products underestimate the net heat fluxes in the Gulf and the Red Sea, with biases up to −45 W/m 2 in MERRA2. The reanalyses reproduce relatively well the seasonal variability in the two regions and the effects of wind events on air–sea fluxes. The results suggest that when forcing numerical models, ERA5 might provide a preferable dataset of surface heat fluxes for the Arabian Gulf while for the Red Sea the MERRA2 seems preferable.This study was funded by the Research Sector at Kuwait University (project #ZS03/16) and by NSF (grant #OCE-1435665) supporting V.M

Westward mountain-gap wind jets of the northern Red Sea as seen by QuikSCAT

© The Author(s), 2018. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Remote Sensing of Environment 209 (2018): 677-699, doi:10.1016/j.rse.2018.02.075.We analyse ten years of QuikSCAT satellite surface winds to statistically characterize the spatio-temporal variability of the westward mountain-gap wind jets over the northern Red Sea. These wind jets bring relatively cold and dry air from the Arabian Desert, increasing heat loss and evaporation over the region similar to cold-air outbreaks from mid and subpolar latitudes. QuikSCAT captures the spatial structure of the wind jets and agrees well with in situ observations from a heavily instrumented mooring in the northern Red Sea. The local linear correlations between QuikSCAT and in situ winds are 0.96 (speed) and 0.85 (direction). QuikSCAT also reveals that cross-axis winds such as the mountain-gap wind jets are a major component of the regional wind variability. The cross-axis wind pattern appears as the second (or third) mode in the four vector Empirical Orthogonal Function analyses we performed, explaining between 6% to 11% of the wind variance. Westward wind jets are typical in winter, especially in December and January, but with strong interannual variability. Several jets can occur simultaneously and cover a large latitudinal range of the northern Red Sea, which we call large-scale westward events. QuikSCAT recorded 18 large-scale events over ten years, with duration between 3 to 8 days and strengths varying from 3–4 to 9–10 m/s. These events cause large changes in the wind stress curl pattern, imposing a remarkable sequence of positive and negative curl along the Red Sea main axis, which might be a wind forcing mechanism for the oceanic mesoscale circulation.This work was supported by NSF grant OCE-1435665 and NASA grant NNX14AM71G

Evaporative implications of dry-air outbreaks over the northern Red Sea.

Author Posting. © American Geophysical Union, 2019. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research-Atmospheres, 124(9), (2019): CP3-4861, doi: 10.1029/2018JD028853.We investigate the impacts of westward wind events on the Red Sea evaporation using the 35‐year second Modern‐Era Retrospective analysis for Research and Applications reanalysis and a 2‐year‐long record of in situ observations from a heavily instrumented air‐sea interaction mooring. These events are common during boreal winter, and their effects are similar to cold‐air outbreaks that occur in midpolar and subpolar latitudes. They cause extreme heat loss from the sea, which is dominated by latent heat fluxes. Different from cold‐air outbreaks, the intensified heat loss is due to the low relative humidity as we show through latent heat flux decomposition. Rainfall is negligible during these events, and we refer to them as dry‐air outbreaks. We also investigate the general atmospheric circulation pattern that favors their occurrence, which is associated with an intensified Arabian High at the north‐central portion of the Arabian Peninsula—a feature that seems to be an extension of the Siberian High. The analyses reveal that the westward winds over the northern Red Sea and the winter Shamal winds in the Persian Gulf are very likely to be part of the same subsynoptic‐scale feature. The second Modern‐Era Retrospective analysis for Research and Applications reanalysis indicates that the occurrence of westward wind events over the northern Red Sea has grown from 1980 to 2015, especially the frequency of large‐scale events, the cause of which is to be investigated. We hypothesize that dry‐air outbreaks may induce surface water mass transformation in the surface Red Sea Eastern Boundary Current and could represent a significant process for the oceanic thermohaline‐driven overturning circulation.We thank the three anonymous reviewers and the associated editor who provided valuable comments that contributed to the improvement of the present paper. We wish to acknowledge the use of the Ferret program (NOAA/PMEL) and NCL (doi: 10.5065/D6WD3XH5) for analysis and graphics in this paper. We thanks Julie Hildebrandt for helping with the final manuscript version, Marcio Vianna for fruitful discussion about this work, and Stephen Swift for pointing out the long time series from Yenbo and Wejh at the National Climatic Data Center (NCDC/NOAA). We acknowledge the Global Modeling and Assimilation Office (GMAO) and the Goddard Earth Sciences Data and Information Services Center (GESDISC) for the dissemination of MERRA‐2 reanalysis and the NCDC/NOAA for making the Global Surface Summary of the Day freely and easily available on the internet. MERRA‐2 and QuikSCAT winds at 25 and 12.5 km data are available online (https://disc.gsfc.nasa.gov/datareleases/merra_2_data_release; www.remss.com/missions/qscat/; and https://podaac.jpl.nasa.gov, respectively). The in situ data from the WHOI/KAUST mooring is available at a WHOI repository (http://uop.whoi.edu/projects/kaust/form.php) and provided solely for academic and research purposes. The mooring data collected during the WHOI‐KAUST collaboration was made possible by award USA00001, USA00002, and KSA00011 to the WHOI by the KAUST in the Kingdom of Saudi Arabia. This work was supported by NSF grant OCE‐1435665 and NASA grant NNX14AM71G.2019-10-0

Interannual variability of the South Indian Countercurrent

Author Posting. © American Geophysical Union, 2016. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Oceans 121 (2016): 3465–3487, doi:10.1002/2015JC011417.In the present work, we investigate the interannual variability of the South Indian Countercurrent (SICC), a major and still understudied current of the Indian Ocean circulation. To characterize the interannual variability of the SICC, four different data sets (altimetry, GLORYS, OFAM3, and SODA) are analyzed using multiple tools, which include Singular Spectrum Analysis and wavelet methods. The quasi-biennial band dominates the SICC low-frequency variance, with the main peak in the 1.5–1.8 year interval. A secondary peak (2.1–2.5 year) is only found in the western basin. Interannual and decadal-type modulations of the quasi-biennial signal are also identified. In addition, limitations of SODA before the 1960s in the SICC region are revealed. Within the quasi-biennial band, the SICC system presents two main patterns with a multiple jet structure. One pattern is characterized by a robust northern jet, while in the other the central jet is well developed and northern jet is weaker. In both patterns, the southern jet has always a strong signature. When the northern SICC jet is stronger, the northern cell of the subtropical gyre has a triangular shape, with its southern limb having a strong equatorward slant. The quasi-biennial variability of the SICC is probably related to the Indian Ocean tropical climate modes that are known to have a strong biennial characteristic.ARC Discovery Project Grant Number: DP130102088; NSF Grant Number: OCE-091716; Ocean Science Division of VM Oceanica2016-11-2

Variation in feeding ecology of five cnemidophorine lizard species along Brazilian eastern coast

Feeding ecology of a particular species is associated to population dynamics and contributes for the understanding of natural history and trophic interactions in ecosystems. We investigated changes in the feeding habits of 16 populations belonging to five cnemidophorine lizard species (being four bisexual and one unisexual) along approximately 4000 km extension of the Brazilian eastern coast. Fieldwork was carried out in 15 areas of restinga habitats and for each cnemidophorine population, the composition of the diet was analyzed based on the number, volume (mm3) and frequency of each prey category or plant material.The arthropods were categorized in the taxonomic level of Order or Family (e.g.Formicidae). Cnemidophorine populations/species studied were mainly carnivorous and had, in general, a diet consisting predominantly of larvae and/or termites, with few instances of plant material consumption. The availability of termites locally at each restinga habitat was not a determinant factor in the increase of termite consumption by the local cnemodophorine population. However, differences in diet composition among populations partially resulted from differential consumption of termites, leading to the formation of two distinct groups depending on higher or lesser consumption of termites. Some populations had onthonegetic variation in diet, but males and females of different populations/species tended to have similar diet composition. The head width of lizards affected significantly the volume and the length of the largest prey ingested in 60% (3/5) of the species studied, indicating that adults tended to consume larger food items compared to coespecifics juveniles. The high level of importance of termites and larvae in almost all populations/species probably contributed to the low intra-and interspecific differences in food habit. The diet of cnemidophorine species studied in restinga habitats in general, tended to be similar to that found to other cnemidophorines, regardless its geographic distribution. Invertebrates were the dominant prey on cnemidophorines diet, but predation on vertebrates was also registered.A ecologia alimentar de uma determinada espécie está associada a dinâmica da população e contribui para a compreensão da história natural e das interações tróficas nos ecossistemas. No presente estudo, investigamos mudanças nos hábitos alimentares de 16 populações pertencentes a cinco espécies de lagartos cnemidophorines (quatro bissexuais e uma unissexual) ao longo de aproximadamente 4000 km da costa leste brasileira. O trabalho de campo foi realizado em 15 áreas de restinga. A composição da dieta de cada população foi baseada no número, volume (mm3) e frequência de cada categoria de presa e de material vegetal. Os artrópodes foram categorizados no nível taxonômico de Ordem ou Família (por exemplo, Formicidae). As populações/ espécies de cnemidophorines estudadas foram principalmente carnívoras com uma dieta constituída predominantemente por larvas e/ou cupins, com pouco consumo de material vegetal. A disponibilidade de cupins localmente em cada restinga não foi um fator determinante no aumento do consumo de cupins pela população do lagarto cnemidophorino local. No entanto, as diferenças na composição da dieta entre as populações resultaram do consumo diferencial de cupins, levando a formação de dois grupos distintos, dependendo do consumo maior ou menor de cupins. Algumas populações apresentaram variação ontogenética na dieta, mas machos e fêmeas tenderam a ter uma composição alimentar semelhante em cada população/espécie. A largura da cabeça afetou significativamente o volume e o comprimento da maior presa ingerida em 60% (3/5) das espécies estudadas, indicando que os adultos tendem a consumir itens alimentares maiores que os jovens coespecíficos. O elevado índice importância de cupins e larvas em quase todas as populações/espécies provavelmente contribuiu para as baixas diferenças intra e interespecíficas no hábito alimentar. A dieta das espécies estudadas, em geral, tendeu a ser semelhante a encontrada para outros cnemidophorinos, independentemente de sua distribuição geográfica. Os invertebrados foram as presas predominantes na dieta, mas a predação em vertebrados foi também registrada.Asociación Herpetológica Argentin

Contributions of mean and shape of blood pressure distribution to worldwide trends and variations in raised blood pressure: A pooled analysis of 1018 population-based measurement studies with 88.6 million participants

© The Author(s) 2018. Background: Change in the prevalence of raised blood pressure could be due to both shifts in the entire distribution of blood pressure (representing the combined effects of public health interventions and secular trends) and changes in its high-blood-pressure tail (representing successful clinical interventions to control blood pressure in the hypertensive population). Our aim was to quantify the contributions of these two phenomena to the worldwide trends in the prevalence of raised blood pressure. Methods: We pooled 1018 population-based studies with blood pressure measurements on 88.6 million participants from 1985 to 2016. We first calculated mean systolic blood pressure (SBP), mean diastolic blood pressure (DBP) and prevalence of raised blood pressure by sex and 10-year age group from 20-29 years to 70-79 years in each study, taking into account complex survey design and survey sample weights, where relevant. We used a linear mixed effect model to quantify the association between (probittransformed) prevalence of raised blood pressure and age-group- and sex-specific mean blood pressure. We calculated the contributions of change in mean SBP and DBP, and of change in the prevalence-mean association, to the change in prevalence of raised blood pressure. Results: In 2005-16, at the same level of population mean SBP and DBP, men and women in South Asia and in Central Asia, the Middle East and North Africa would have the highest prevalence of raised blood pressure, and men and women in the highincome Asia Pacific and high-income Western regions would have the lowest. In most region-sex-age groups where the prevalence of raised blood pressure declined, one half or more of the decline was due to the decline in mean blood pressure. Where prevalence of raised blood pressure has increased, the change was entirely driven by increasing mean blood pressure, offset partly by the change in the prevalence-mean association. Conclusions: Change in mean blood pressure is the main driver of the worldwide change in the prevalence of raised blood pressure, but change in the high-blood-pressure tail of the distribution has also contributed to the change in prevalence, especially in older age groups

Repositioning of the global epicentre of non-optimal cholesterol

High blood cholesterol is typically considered a feature of wealthy western countries(1,2). However, dietary and behavioural determinants of blood cholesterol are changing rapidly throughout the world(3) and countries are using lipid-lowering medications at varying rates. These changes can have distinct effects on the levels of high-density lipoprotein (HDL) cholesterol and non-HDL cholesterol, which have different effects on human health(4,5). However, the trends of HDL and non-HDL cholesterol levels over time have not been previously reported in a global analysis. Here we pooled 1,127 population-based studies that measured blood lipids in 102.6 million individuals aged 18 years and older to estimate trends from 1980 to 2018 in mean total, non-HDL and HDL cholesterol levels for 200 countries. Globally, there was little change in total or non-HDL cholesterol from 1980 to 2018. This was a net effect of increases in low- and middle-income countries, especially in east and southeast Asia, and decreases in high-income western countries, especially those in northwestern Europe, and in central and eastern Europe. As a result, countries with the highest level of non-HDL cholesterol-which is a marker of cardiovascular riskchanged from those in western Europe such as Belgium, Finland, Greenland, Iceland, Norway, Sweden, Switzerland and Malta in 1980 to those in Asia and the Pacific, such as Tokelau, Malaysia, The Philippines and Thailand. In 2017, high non-HDL cholesterol was responsible for an estimated 3.9 million (95% credible interval 3.7 million-4.2 million) worldwide deaths, half of which occurred in east, southeast and south Asia. The global repositioning of lipid-related risk, with non-optimal cholesterol shifting from a distinct feature of high-income countries in northwestern Europe, north America and Australasia to one that affects countries in east and southeast Asia and Oceania should motivate the use of population-based policies and personal interventions to improve nutrition and enhance access to treatment throughout the world.Peer reviewe