SST Products Research Articles

Annual and semiannual variations of phytoplankton biomass and production in the central Gulf of California estimated from satellite data

Surface waters of the Midriff Islands region of the Gulf of California persistently have the lowest temperatures (SST) and the highest nutrient concentrations of all surface waters of the gulf. The purpose of this work was to characterize the annual and semiannual variations of satellite-derived SST, chlorophyll a (Chlsat), and phytoplankton production (PP) along transects in Ballenas Channel (transect A), between Ángel de la Guarda and Tiburón islands (transect B), and San Pedro Mártir Basin (SPMB) (transect C). This was done with monthly composites of SST, Chlsat, and PP for 2005 and 2006. Chlsat and PP have annual and semiannual components of variation at the three transects, but the temporal setup is different for each transect. In Ballenas Channel the two maxima occurred in March–June and October, while along transect B in March–May and in late autumn and early winter, and at SPMB in February–May and October–December. The explanation for the differences is in the physical dynamics of these areas. Strong turbulence and stratification caused low Chlsat and PP, and intermediate stratification caused high values for transects A and B. On the eastern side of transect C, upwelling caused the highest Chlsat and PP of our data set (up to 9.7 mg m–3 and 7.8 g C m–2 d–1). Photosynthesis in our study area is not limited by iron. Low summer Chlsat and PP values are caused by strong stratification inhibiting nutrient eddy diffusion from below the thermocline to the euphotic zone. Nevertheless, the summer Chlsat and PP values for the Midriff Islands region (often >1 mg m–3 and >1 g C m–2 d–1) are relatively high.

Subarctic and Arctic sea surface temperature and its relation to ocean heat content 1982–2010

This is an examination of SST variability in the Subarctic and Arctic during the 29 year period 1982–2010, based primarily on data from the Pathfinder AVHRR data set as well as operational SST products from NOAA and the UK Meteorological Office. A goal is to explore the connection between SST variations in the subpolar gyres and SST variations further north, with emphasis on the Nordic Seas because of their atmospheric exposure and connection to the overturning circulation. After identifying and correcting for biases in Pathfinder AVHRR (also present in the operational products) the seasonal cycle and 29‐year warming trend is described. The analysis shows that much of the warming of the North Atlantic subpolar gyre during the period occurred in 1990s and compensated for cooling during the decades of the early 1960s to mid‐1990s in this same region. Superimposed on this warming trend the analysis reveals a succession of residual SST anomalies with 0.5°C amplitudes that seem to move out of the North Atlantic subpolar gyre into the Nordic Seas following the North Atlantic and Norwegian Currents. Within the Nordic Seas these SST anomalies slowly advect in a counterclockwise direction. After approximately six years part of the anomalies exits the Nordic Seas through the East Greenland Current. The connection between these SST anomalies and underlying anomalies of 0/300 m heat content is discussed. The existence of these SST anomaliesand their origin at lower latitudes highlights the importance of ocean exchanges in influencing Arctic climate.

Widening the application of AATSR SST data to operational tasks through the Medspiration Service

For over a decade the ATSR series of sensors produced high quality SST data products, but the narrow swath did not encourage their use for operational tasks. This changed in 2005 when the European Space Agency's Medspiration Service introduced AATSR data in the GHRSST L2P format. This paper describes the opportunities provided by the Medspiration system for facilitating the complementary use of SST products from AATSR and from other satellite sensors. It explains how, following the implementation by Medspiration of GHRSST procedures, data products and tools, AATSR data are now being used around the world to complement the use of other sources of SST and to facilitate bias adjustments between them. Despite the limited daily coverage of AATSR its broadly reliable accuracy and stability seem to be beneficial to SST analyses that merge all available observations. The new analyses are already contributing to improved ocean and weather forecasting. This represents an unforeseen but significant role for the ATSR series, through which it continues to make an important contribution to the operational uses of SST.

MODIS standard SST product application in Sardinian coastal and marine waters

MODIS standard SST product application in Sardinian coastal and marine waters

Advanced sea surface temperature retrieval using the Japanese geostationary satellite, Himawari-6

Producing high-quality match-ups coupling the Japanese geostationary satellite, Himawari-6 (H6), and buoy SST observations, we have developed the new SST retrieval method. Kawamura et al. (2010) developed the previous version of SST product called MTSAT SST, which left several scientific/technical questions. For solving them, 6,711 algorithm tuning match-ups with precise navigation and 240,476 validation match-ups are generated for covering all seasons and wide ocean coverage. For discriminating the previous MTSAT SST, we call the new version of SST H6 SST. It is found that the SZA dependences of MTSAT SST algorithm are different from area to area of SZA > 40–50° N/S. The regionally different SZA dependences are treated by dividing the H6 disk coverage into five areas by the latitude lines of 40° N/S first and the longitude lines of 100° K and 180° K. Using the algorithm tuning match-ups, Nonlinear SST (NLSST) equations are derived for all of the five areas. Though the sun zenith angle dependency correction term is also examined, there is no significant regional difference. Therefore, this term is used in the H6 SST algorithm again. The new H6 SST equation is formed by the areal NLSST and the sun zenith angle dependency term for each area. The statistical evaluation of H6 SST using the validation match-ups show the small negative biases and the RMS errors of about 0.74° K for each area. For the full H6 disk, the bias is −0.1° K and the RMS error 0.74° K. The histogram of H6 SST minus the in situ SST for each area has a similar Gaussian shape with small negative skewness, and the monthly validation of H6 SST for each area is consistent with those for the whole period and the histograms

The β3-Adrenoceptor Agonist GW427353 (Solabegron) Decreases Excitability of Human Enteric Neurons via Release of Somatostatin

beta3 Adrenoceptor (beta3-AR) is expressed on adipocytes and enteric neurons. GW427353 is a human selective beta3-AR agonist with visceral analgesic effects. Some of its effects may involve release of somatostatin (SST) and actions on enteric neurons. The aim of this study was to investigate the mode of action of GW427353 in human submucous neurons. Voltage sensitive dye imaging was used to record from human submucous neurons. SST release from human primary adipocytes was measured with enzyme-linked immunoabsorbent assay. Immunohistochemistry was used to detect adiponectin, beta3-AR, SST, SST2 receptors, tyrosine hydroxylase (TH), and protein gene product 9.5. Confocal imaging showed cytoplasmic beta3-AR labeling in somata of submucous neurons and nerve varicosities. GW427353 had no direct postsynaptic actions but decreased fast synaptic input to submucous neurons. Tissue perfusion with GW427353 reduced nicotine-evoked neuronal spike frequency, an effect prevented by the beta3-AR antagonist SR-59230 and the SST2-receptor antagonist CYN154806 and mimicked by the SST2 receptor agonist octreotide. Adipocytes expressed adiponectin, beta3-AR, and SST. TH-positive fibers were in close proximity to adipocytes. Submucous neurons expressed SST2 receptors. Human primary adipocytes released SST in response to GW427353 in a concentration-dependent manner, an effect abolished by SR-59230. Inhibitory action of GW427353 involves release of SST which stimulates inhibitory SST2 receptors on human submucous neurons. Adipocytes are a potential source for SST. beta3-AR activation may be a promising approach to reduce enteric neuron hyperexcitability. The action of GW427353 may be the neurophysiologic correlate of its beneficial effect in patients with irritable bowel syndrome.

Ocean tidal cooling effect on summer sea fog over the Okhotsk Sea

Ocean tide is a periodic phenomenon of the rise and fall of the sea level that depends on the bathymetry and positions of the moon and sun relative to the earth. In the Okhotsk Sea, the ocean tide causes strong vertical mixing in the upper ocean, generating rich structures in summer SST with extraordinarily cold patches on Kashevarov Bank, along the Kuril Islands, northeast of the Terpeniya Peninsula, and inside Shelikhov Bay. The present study analyzes and synthesizes a suite of ship‐board and satellite observations, and numerical simulations to investigate the ocean tidal cooling effect on summer sea fog over the Okhotsk Sea. Over the tide‐induced cold patches, atmospheric stability increases, and surface wind weakens markedly possibly through suppressed atmospheric vertical mixing. Our analysis of ship‐board observations reveals frequent sea‐fog occurrence over the cold patches with a maximum exceeding 70% along the Kuril Islands in July–August. Numerical simulations with the Weather Research and Forecasting (WRF) model support that the cold patches cool air temperature, decelerate surface wind, and form a strong surface inversion layer up to 0.5 km high, creating favorable conditions for sea‐fog occurrence. The WRF simulation without the tidal cooling effect reduces sea‐fog occurrence by more than 20% over cold patches, illustrating the importance of SST products for climate models.

Regional Atmospheric Simulation of Monthly Precipitation Using High-Resolution SST Obtained from an Ocean Assimilation Model: Application to the Wintertime Japan Sea

The present study examines the influence of an assimilation SST product on simulated monthly precipitation. The high-resolution SST structures located close to the oceanic front and coastal areas are important in regional atmospheric simulations over semienclosed marginal seas such as the Japan Sea. Two simulations are conducted using assimilation and interpolation SST products (experiments R and N, respectively), for January 2005. The surface heat fluxes and PBL height in experiment R are lower than those in experiment N in coastal areas and the cold tongue. A decrease of 4 K in SST leads to decreases of 120 W m−2 in surface sensible and latent fluxes and 300 m in PBL height. The precipitation in experiment R is less than that in experiment N for the sea area except at 38°N, 137°E. The cold tongue in the central Japan Sea acts to reduce moisture supply via the latent heat flux, resulting in low precipitation in coastal areas. The fact that the difference between observed and modeled precipitation in experiment R is 21% less than that in experiment N demonstrates that the assimilation of SST data leads to improved regional atmospheric simulations of monthly precipitation.

Decreased somatostatin is related to the hypersensitivity of intestinal epithelia to LPS via upregulated TLR4–TBK1 pathway in rats chronically exposed to ethanol

Chronic alcoholics are predisposed to the development of a systemic inflammatory response syndrome, which is usually triggered in the gut. This study aimed to investigate in rats the role of intestinal epithelial inflammatory responsiveness in the susceptibility of alcoholics to excessive inflammation. Thirty Wistar rats were randomly divided into three groups: 10 rats killed immediately after acclimation (baseline control), 10 rats treated with 25% (vol/vol) ethanol for 6 months (ethanol group), and 10 rats given double-distilled water until killed simultaneously with the ethanol group (9-month control). The intestinal microflora, the epithelial histology and ultrastructure, the level of Toll-like receptor 4 (TLR4), TANK-binding kinase-1 (TBK1), and activated nuclear factor-κB (NF-κB) in the intestinal mucosa, and somatostatin (SST) levels in plasma and small intestine were evaluated in each group. Isolated intestinal epithelia from each rat were used to examine lipopolysaccharide (LPS) responsiveness with or without SST pretreatment by quantification of TLR4, TBK1, activated NF-κB, interferon-γ (IFN-γ), and tumor necrosis factor-α (TNF-α). Compared with both the control groups, the amount of mucosal Escherichia coli in the ethanol group was not changed, whereas the number of intestinal lactobacilli in the ethanol group was significantly reduced ( P < .05). Mild inflammatory injury and upregulation of TLR4 and TBK1 were observed in the intestinal mucosa of the ethanol group. The LPS-enhanced in vitro expression of TLR4, TBK1, and production of IFN-γ and TNF-α in isolated intestinal epithelia of the ethanol group were significantly higher than those in either control group ( P < .05) and were dramatically inhibited by SST ( P < .05), whereas NF-κB was activated by LPS only in the control groups. The plasma and intestinal levels of SST in the ethanol group were significantly lower than those in either control group ( P < .05). These findings suggest that impairment of intestinal SST production by chronic ethanol administration leading to upregulation of the TLR4–TBK1 pathway may be one of the mechanisms underlying the LPS hypersensitivity of intestinal epithelia.

The 2004–2008 mean and annual cycle of temperature, salinity, and steric height in the global ocean from the Argo Program

The Argo Program has achieved 5 years of global coverage, growing from a very sparse global array of 1000 profiling floats in early 2004 to more than 3000 instruments from late 2007 to the present. Using nearly 350,000 temperature and salinity profiles, we constructed an upper-ocean climatology and monthly anomaly fields for the 5-year era, 2004–2008. A basic description of the modern upper ocean based entirely on Argo data is presented here, to provide a baseline for comparison with past datasets and with ongoing Argo data, to test the adequacy of Argo sampling of large-scale variability, and to examine the consistency of the Argo dataset with related ocean observations from other programs. The Argo 5-year mean is compared to the World Ocean Atlas, highlighting the middle and high latitudes of the southern hemisphere as a region of strong multi-decadal warming and freshening. Moreover the region is one where Argo data have contributed an enormous increment to historical sampling, and where more Argo floats are needed for documenting large-scale variability. Globally, the Argo-era ocean is warmer than the historical climatology at nearly all depths, by an increasing amount toward the sea surface; it is saltier in the surface layer and fresher at intermediate levels. Annual cycles in temperature and salinity are compared, again to WOA01, and to the National Oceanography Center air–sea flux climatology, the Reynolds SST product, and AVISO satellite altimetric height. These products are consistent with Argo data on hemispheric and global scales, but show regional differences that may either point to systematic errors in the datasets or their syntheses, to physical processes, or to temporal variability. The present work is viewed as an initial step toward integrating Argo and other climate-relevant global ocean datasets.

Mapping surface temperature in large lakes with MODIS data

Satellite sensor MODIS on two platforms can produce Sea Surface Temperature over certain regions about three to four times per day. Our objective was to test if the MODIS SST product can be applied for lakes whose surface areas are large enough to be observed at the MODIS spatial resolution and to compare the satellite-derived lake surface temperatures with in situ measurements. Surface temperatures for Lakes Vänern and Vättern in Sweden, two of the largest European lakes, are extracted from the MODIS/Terra images for period 2001–2003. The results are analyzed on different quality levels, as all MODIS L2 products are equipped with an additional quality flag. We present temperature development over 2001–2003, and show the capability of the MODIS SST product to couple the known thermodynamical features in the lakes under study, where temperature varies greatly with space and time. These results can complement lake monitoring programs anywhere.

Evaluating the Decomposition of Tropical Atlantic Drifter Observations

Abstract Because the tropical Atlantic is characterized by regions of strong seasonal variability that have been sampled inhomogeneously by surface drifters, Eulerian averages of these Lagrangian observations in spatially fixed bins may be aliased. In the Pacific, this problem has been circumvented by first calculating seasonal or monthly means. In the Atlantic, such an approach is of limited value because of the relatively sparse database of drifter observations. As an alternative, a methodology is developed in which drifter-observed currents and sea surface temperatures are grouped into bins and, within each bin, simultaneously decomposed into a time-mean, annual and semiannual harmonics, and an eddy residual with a nonzero integral time scale. The methodology is evaluated using a temporally homogeneous SST product and in situ SST observations, and also using simulated drifter observations in an eddy-resolving model of the Atlantic Ocean. These analyses show that, compared to simple bin averaging, the decomposition developed herein yields significantly improved estimates of time-mean values in regions of strong seasonal variability. The methodology can also successfully estimate the distribution of the seasonal harmonics’ amplitude and phase throughout much of the tropical Atlantic.

Somatostatin receptors and autoimmune‐mediated diabetes

Somatostatin (SST) peptide is produced by various SST-secreting cells throughout the body and acts as a neurotransmitter or paracrine/autocrine regulator in response to ions, nutrients, peptides hormones and neurotransmitters. SST is also widely distributed in the periphery to regulate the inflammatory and immune cells in response to hormones, growth factors, cytokines and other secretive molecules. SST peptides are considered the most important physiologic regulator of the islet cell, gastrointestinal cell and immune cell functions, and the importance of SST production levels has been implicated in several diseases including diabetes. The expression of SST receptors has also been found in T lymphocytes and primary immunologic organs. Interaction of SST and its receptors is also involved in T-cell proliferation and thymocyte selection. SSTR gene-ablated mice developed diabetes with morphologic, physiologic and immunologic alterations in the endocrine pancreas. Increased levels of mononuclear cell infiltration of the islets are associated with the increased levels of antigen-presenting cells located in the islets and peripancreatic lymph nodes. Increased levels of SST were also found in antigen-presenting cells and are associated with a significant increase of CD8 expression levels on CD4(+)/CD8(+) immature thymocytes. These findings highlight the crucial role of this neuroendocrine peptide and its receptors in regulating autoimmune functions.

Merging satellite infrared and microwave SSTs: Methodology and evaluation of the new SST

The Global Ocean Data Assimilation Experiment (GODAE) requires the availability of a global analyzed SST field with high-resolution in space (at least 10 km) and time (at least 24 hours). The new generation SST products would be based on the merging of SSTs from various satellites data and in situ measurements. The merging of satellite infrared and microwave SST data is investigated in this paper. After pre-processing of the individual satellite data, objective analysis was applied to merge the SST data from NOAA AVHRR (National Oceanic and Atmospheric Administration, Advanced Very High Resolution Radiometer), GMS S-VISSR (Geostationary Meteorological Satellite, Stretched-Visible Infrared Spin Scan Radiometer), TRMM MI (Tropical Rainfall Measuring Mission, Microwave Imager: TMI) and VIRS (Visible and Infrared Scanner). The 0.05° daily cloud-free SST products were generated in three regions, viz., the Kuroshio region, the Asia-Pacific Region and the Pacific, during one-year period of October 1999 to September 2000. Comparisons of the merged SSTs with Japan Meteorological Agency (JMA) buoy SSTs show that, with considerable error sources from individual satellite data and merging procedure, an accuracy of 0.95 K is achieved. The results demonstrate the practicality and advantages of merging SST measurements from various satellite sensors.

Near Real Time SLA and SST products during 2-years of MFS pilot project: processing, analysis of the variability and of the coupled patterns

Abstract. The Near Real Time (NRT) operational products developed from satellite data (AVHRR, Topex/Poseidon, Ers-2) in the framework of the Mediterranean Forecasting System Pilot Project (MFSPP, autumn 1998–autumn 2000) are described and compared to delayed time products over the Mediterranean sea. MFSPP SLA and SST data are then discussed in the general context of the Mediterranean circulation, showing the interannual variability of the fields and identifying recurrent or anomalous features at mesoscale/sub-basin scales. Finally, MFSPP data are used to test, on a regional (Mediterranean) context, a multivariate method to identify coupled modes of variability, consisting in the SVD of the covariance between SST and SLA. Key words. Oceanography: general (marginal and semi-closed seas) – Oceanography: physical (sea level variations; upper ocean processes)

Calibration of the AATSR instrument

The Advanced Along Track Scanning Radiometer (AATSR) on ESA's ENVISAT mission is the latest in a series of instruments designed to measure global sea-surface-temperatures to an accuracy of 0.3K and to monitor global vegetation coverage and cloud properties. The accuracy of the SST and other scientific products depends on the accuracy of the top-of-atmosphere radiometric measurements. To ensure that AATSR meets its scientific goals, the instrument is equipped with precision on-board calibration targets. To verify the accuracy of the on-board calibration, a thorough pre-launch calibration exercise was performed, covering field-of-view measurements, visible and infrared radiometric calibrations. The radiometric responses of the visible/near infrared channels were measured, and the in-flight VISible Calibration unit (VISCAL) was calibrated. The calibrations of the thermal infrared channels were verified over a range of target temperatures between 210K to 315K and corrections derived for detector non-linearity. Tests were also performed to verify freedom from any significant scan dependent variations or effects due to changes in the thermal environment.

Improved sea surface temperature measurements from space

We investigate ATSR's skin SST precision by comparing all the available high resolution (1km) ATSR data coincident with global drifting buoy records for the months of February and March 1992. Comparisons are made at two spatial levels: using spatially averaged ATSR data, and at the full (1km) resolution. SSTs in each case are derived using both the standard algorithm and one using the 3.7µm and 11µm nadir channels. The mean bulk‐skin temperature bias is 0.45K (night) and 0.13K (day). The precision is greater: (i) at night than during the day, (ii) when 12µm noise contamination in the standard SST product is removed, (iii) when using a ½° subset for which a corresponding 1km match‐up exists. Our highest precision subset has an r.m.s. scatter of just 0.25K and must approach the geophysical limit set by the inherent variability of the skin effect.