Argo Buoys Research Articles

Evaluating the Absolute Calibration Accuracy and Stability of AIRS Using the CMC SST

We compare the daily mean and standard deviation of the difference between the sea surface skin temperature (SST) derived from clear sky Atmospheric InfraRed Sounder (AIRS) data from seven atmospheric window channels between 2002 and 2020 and collocated Canadian Meteorological Centre (CMC) SST data from the tropical oceans. After correcting the mean difference for cloud contamination and diurnal effects, the remaining bias relative to the CMC SST, is reasonably consistent with estimates of the AIRS absolute accuracy based on the uncertainty of the pre-launch calibration. The time series of the bias produces trends well below the 10 mK/yr level required for climate change evaluations. The trends are in the 2 mK/yr range for the five window channels between 790 and 1231 cm−1, and +5 mK/yr for the shortwave channels. Between 2002 and 2020, the time series of the standard deviation of the difference between the AIRS SST and the CMC SST dropped fairly steadily to below 0.4 K in several AIRS window channels, a level previously only seen in gridded SST products relative to the Argo buoys.

The Potential Vertical Distribution of Bigeye Tuna (Thunnus obesus) and Its Influence on the Spatial Distribution of CPUEs in the Tropical Atlantic Ocean

Understanding the potential vertical distribution of bigeye tuna (Thunnus obesus) is necessary to understand the catch rate fluctuations and the stock assessment of bigeye tuna. To characterize the potential vertical distribution of this fish while foraging and determine the influences of the distribution on longline efficiency in the tropical Atlantic Ocean, the catch per unit effort (CPUE) data were compiled from the International Commission for the Conservation of Atlantic Tunas and the Argo buoy data were downloaded from the Argo data center. The raw Argo buoy data were processed by data mining methods. The CPUE was standardized by support vector machine before analysis. We assumed the depths with the upper and lower limits of the optimum water temperatures of 15°C and 9°C as the preferred swimming depth, while the lower limit of the temperature (12°C) associated with the highest hooking rate as the preferred foraging depth (D12) of bigeye tuna during the daytime in the Atlantic Ocean. The preferred swimming depth and foraging depth range in the daytime were assessed by plotting the isobath based on Argo buoy data. The preferred swimming depth and vertical structure of the water column were identified to investigate the spatial effects on the CPUE by using a generalized additive model (GAM). The empirical cumulative distribution function was used to assess the relationship between the spatial distribution of CPUE and the depth of 12°C isolines and thermocline. The results indicate that 1) the preferred swimming depth of bigeye tuna in the tropical Atlantic is from 100 m to 400 m and displays spatial variation; 2) the preferred foraging depth of bigeye tuna is between 190 and 300 m and below the thermocline; 3) the number of CPUEs peaks at a relative depth of 30-50 m (difference between the 12°C isolines and the lower boundary of the thermocline); and 4) most CPUEs are within the lower depth boundary of the thermocline levels (LDBT) which is from 160 m to 230 m. GAM analysis indicates that the general relationship between the nominal CPUE and LDBT is characterized by a dome shape and peaks at approximately 190 m. The oceanographic features influence the habitat of tropical pelagic fish and fisheries. Argo buoy data can be an important tool to describe the habitat of oceanic fish. Our results provide new insights into how oceanographic features influence the habitat of tropical pelagic fish and fisheries and how fisheries exploit these fish using a new tool (Argo profile data).

Water dynamics in the western Bering Sea and its impact on chlorophyll a concentration

To study the water dynamics in the western Bering Sea, the time series of geostrophic velocities derived from satellite altimetry, Global total current (Copernicus Globcurrent) velocities, Argo buoys, and ship, borne data are analyzed. We demonstrate that the surface currents in the study area are characterized by a significant seasonal and interannual variability. In January, the southwestern currents are prevailing in the western Bering Sea, the geostrophic currents are connected to the continental slope, and mesoscale anticyclonic movement of waters is observed on the shelf. In July, the surface flow is oriented to the northeast along the continental slope, and cyclonic water movement prevails on the shelf. The formation of mesoscale anticyclones in late winter – early spring – is related to the supply of low-temperature and low-salinity Bering Sea shelf water. The temporal variability of the direction and current velocity in the western part of the Bering Sea during the summer period is associated with the wind and coastal upwelling. The presence of coastal upwelling and eddies should be considered as one of the factors leading to the high concentration of chlorophyll a on a shelf and continental slope in the summer.

Inversion of Evaporation and Water Vapor Transport Using HY-2 Multi-Sensor Data

HY-2 satellite is the first marine dynamic environment satellite of China. In this study, global evaporation and water vapor transport of the global sea surface are calculated on the basis of HY-2 multi-sensor data from April 1 to 30, 2014. The algorithm of evaporation and water vapor transport is discussed in detail, and results are compared with other reanalysis data. The sea surface temperature of HY-2 is in good agreement with the ARGO buoy data. Two clusters are shown in the scatter plot of HY-2 and OAFlux evaporation due to the uneven global distribution of evaporation. To improve the calculation accuracy, we compared the different parameterization schemes and adopted the method of calibrating HY-2 precipitation data by SSM/I and Global Precipitation Climatology Project (GPCP) data. In calculating the water vapor transport, the adjustment scheme is proposed to match the balance of the water cycle for data in the low latitudes.

The mesocyclone over the northern part of the Japan/East sea in February 2013

The case of the influence of the mesoscale cyclone (MC) on the northern part of the Japan/East Sea in 1011 February 2013 was investigated. The passage of the MC was accompanied by a sharp increase in the wind to storm values, a reduction in the total heat transfer by almost two times, an increase of the momentum flux by four times. The perturbations of the hydrological characteristics in the MC trace, estimated from the data of two Argo buoys, were traced to a depth of 300 meters off the west coast of Hokkaido island and up to ~100 m in the deep-water area, which is due to the difference in the background stability of vertical structures. Some estimates of the contribution of various factors to the observed variability of the upper sea layer are given.

СТРУКТУРА ВНУТРИГОДОВОЙ ИЗМЕНЧИВОСТИ ГИДРОФИЗИЧЕСКИХ ПОЛЕЙ ОКЕАНА В ГЛОБАЛЬНОЙ ВЕРСИИ МОДЕЛИ NEMO С СИСТЕМОЙ УСВОЕНИЯ ДАННЫХ

To analyze the intra-annual variability of the thermal and dynamic characteristics of the ocean, we used the calculations based on the NEMO model, including the assimilation of observational temperature and salinity data by Argo buoys, as well as satellite data on ice cover and sea surface temperature. The features of the geographical and vertical distributions of annual and semi-annual variations in water temperature and globaly averaged spectrum of current velocity are considered. The areas with a prevailing contribution of semi-annual fluctuations are identified. They are in the equatorial zone and in the northwestern Indian Ocean, which is under the influence of the monsoon processes.

Izmenchivost' tolshchiny peremeshannogo sloya v Chernom more i ee svyaz' s dinamikoy vod i atmosfernym vozdeystviem

Purpose . Spatio-temporal variability of the mixed layer depth (MLD) in different regions of the Black Sea in 1985–2017, its relationship with large- and meso-scale dynamics and wind velocity are investigated. Metods and Results . The study is based on the hydrological data archive for 1985–2017 including the measurements of the ship expeditions, the Argo buoys and the moored buoy “Aqalog”. Seasonal and interannual variability of the mixed layer depth was determined using the density criterion ( dr = = 0,07kg/m 3 ) between the surface layers and the base of the upper mixed layer. Conclusions . In January – March, the large-scale and mesoscale dynamics significantly affects the mixed layer depth variability. Minimum monthly average values of the mixed layer depth in winter are observed in the mesoscale cyclonic eddies and in the center of the sea (20–30 m), the moderate values – on the periphery of the basin (40–45 m) and the maximum ones – in the mesoscale anticyclones (60–70 m). Several times the mixed layer depth values exceeding 150 m were detected in the downwelling areas of the basin. Analysis of the whole period (1985–2017) shows that the mixed layer density was never more than 1015 kg/m 3 . This isopycnal limits the maximum possible depth of the upper mixed layer. The impact of wind velocity on the spatial and temporal variability of the mixed layer thickness is the largest in spring and autumn when the seasonal thermocline is weak. It is less important in summer when solar heating stabilizes the upper layer, and in winter when the mixed layer depth is large. Rise of the mixed layer depth in summer is observed in recent years that is associated with rise of the wind speed in a warm period of a year.

Characteristics of the Kamchatka Current Eddies

The characteristics of eddies in the Kamchatka Current from its source in the Bering Sea to Paramushir Island south of Kamchatka are considered for the first time. The Kamchatka Current in the Olyutorsky Bay contains anticyclonic eddies having a cold core of low salinity with the diameter to 90 km and to 120 km located south of the Avacha Bay. The characteristics of the Kamchatka Current eddies are determined using Terra and Aqua satellite data and the data of Argo buoys and surface drifters. The maximum velocity of a surface current in an eddy south of Kamchatka reaches 1 m/s. Satellite observations demonstrate that such eddies propagate in the Bering Sea from east to west to the latitude of Karaginsky Island and further to southwest to the Kamchatka Strait. The thermohaline characteristics of the eddies located in the northwestern Bering Sea and south of Kamchatka are close to each other. At the same time, during 1990–2017, in the eddy core temperature rose by 1°C and salinity decreased by 0.5 psu. Salinity anomalies at minimum temperature were significant in 1990 and 2004–2006 and were small in 1996–1998 and 2015–2016. The most probable reason for the salinity variations at minimum temperature is that the intensity of tidal mixing varies in the lunar nodal cycle.

Vosproizvedenie glubokovodnoy tsirkulyatsii Chernogo morya s pomoshch'yu modeli INMOM i sopostavlenie rezul'tatov s dannymi buev ARGO

Purpose. The present paper is focused on theoretical analysis of hydrophysical characteristics of the Black Sea in 2011. Methods and Results. The Black Sea hydrophysical characteristics are calculated using a version of the marine circulation σ -model (Institute of Numerical Mathematics Ocean Model – INMOM) for the Black, Azov and Marmara seas (BAMS) with high spatial 1 km resolution and 20 σ -levels distributed non-uniformly over the depth. Quality of the simulated salinity and temperature fields is assessed by their comparison with the data of the ARGO deep-profiling floats available for the period under consideration. Degree of correspondence of the modeled current fields to the observed ones is estimated based on the average deep-sea current velocities calculated from the data on the Argo profiling floats’ movements. Conclusion. The comparative analysis results show that the INMOM adequately reproduced vertical distribution of the Black Sea hydrophysical characteristics. Comparison of the simulated temperature and salinity fields with those derived from the ARGO buoys data demonstrates the fact that the strong-est deviations of the characteristics under study are observed in the sea upper layers (0–100 m); whereas in the deep-water layers (300–1500 m), the degree of consistency between the simulated results and the field data is much more higher. On the depths below 800 meters, the deep-sea anticyclonic flows with the velocities attaining 1.5 cm/s are present. The revealed feature is not typical of the generally accepted scheme of the Black Sea cyclonic circulation.

Reconstruction of the Black Sea Deep-Water Circulation Using INMOM and Comparison of the Results with the ARGO Buoys Data

Reconstruction of the Black Sea Deep-Water Circulation Using INMOM and Comparison of the Results with the ARGO Buoys Data

Aquarius Sea Surface Salinity Gridding Method Based on Dual Quality–Distance Weighting

A new method for improving the accuracy of gridded sea surface salinity (SSS) fields is proposed in this paper. The method mainly focuses on dual quality–distance weighting of the Aquarius level 2 along-track SSS data according to quality flags, which represent nonnominal data conditions for measurements. In the weighting progress, 14 data conditions were considered, and their geospatial distributions and influences on the SSS were also visualized and evaluated. Three interpolation methods were employed, and weekly gridded SSS maps were produced for the period from September 2011 to May 2015. These maps were evaluated via comparisons with concurrent Argo buoy measurements. The results show that the proposed method improved the accuracy of the SSS fields by approximately 36% compared to the officially released weekly level 3 products and yielded root mean squared difference (RMSD), correlation and bias values of 0.19 psu, 0.98 and 0.01 psu, respectively. These findings indicate a significant improvement in the accuracy of the SSS fields and provide a better understanding of the influences of different conditions on salinity.

Winter convection in the Lofoten Basin according to ARGO buoys and hydrodynamic modeling

In the center of the Lofoten basin in the Norwegian Sea, a unique natural phenomenon which is located which is a quasi-permanent anticyclonic Lofoten vortex (LV). Winter deep convection is a necessary condition for its stability and one of the main mechanisms of its existence, as it creates favorable conditions for its annual regeneration. Another mechanism to maintain a high anticyclonic vorticity in the center of the basin is the capture of mesoscale eddies that break away from the Norwegian Current. Despite the fact that the important role of deep convection in the mechanisms of annual regeneration of the LV is generally recognized, today in the scientific community there is no consensus on the intensity of winter convection in the region. We estimate a depth of mixed layer (MLD) in the Lofoten basin. We use the method formulated by Dukhovskoy for estimation. Unlike other known methods, this method does not have any predetermined criterion of density difference, and a necessary rule is determined by the features of the profile itself. We compared estimation of MLD in the Lofoten basin according to MITgcm data and ARGO buoys data. Estimates of the MLD and the spatial distribution of their maximum values are obtained for the Lofoten basin. The spatial distribution of Argo profiles is considered. It is shown that T-S diagrams constructed on these profiles are characterized by a pronounced homogeneity and a slight change in density inside the Lofoten vortex (LV) in contrast to the profiles located outside the vortex. The LV area coincides completely with the region of the highest values of the MLD, and this proves the key role of deep convection in the existence of an anticyclonic vortex in the center of the basin, as well as the need for its study. Graphs of the spatial distribution of MLD in excess of 300 and 500 m are analyzed.

Mesoscale dynamics and walleye pollock catches in the Navarin Canyon area of the Bering Sea

Large canyons incise the shelf break of the eastern Bering Sea to be preferred sites of the cross-shelf exchange. The mesoscale eddy activity is particularly strong near the shelf-break canyons. To study the mesoscale dynamics in the Navarin Canyon area of the Bering Sea, the time series of velocities derived from AVISO satellite altimetry between 1993 and 2015, drifters, Argo buoys, and ship-borne data are analyzed. We demonstrate that the strength of anticyclonic eddies along the shelf edge in spring and summer is determined by the wind stress in March–April. The increased southward wind stress in the central Bering Sea forced a supply of low-temperature and low-salinity outer shelf water to the deep basin and formation of the anticyclonic mesoscale circulation seaward of the Navarin Canyon. Enhanced northwestward advection of the Bering Slope Current water leads to increase in an ice-free area in March and April and increased bottom-layer temperature at the outer shelf. The strong (weak) northwestward advection of the eastern Bering Sea waters, determined by eastern winds in spring, creates favorable (unfavorable) conditions for the pollock abundance in the western Navarin Canyon area in summer.

MODELING OF DEEP CURRENTS IN THE JAPAN SEA: RELATIONSHIP WITH THE CURRENTS IN THE THERMOCLINE LAYER

Geostrophic deep circulation in the Japan Sea is modeled using the primitive equation multilayer model developed by N.B. Shapiro and E.M. Mikhaylova (Marine Hydrophysical Istitute, RAS). The main simulated patterns are the cyclonic gyres along the sea margins and in the deep basins and the anticyclonic circulation above underwater rises, that generally corresponds with the schemes based on deep floats tracking. The deep circulation is more intense in the subarctic sector than in the subtropical sector and the most intense cyclonic gyre is simulated in the Japan Basin, with the current speed up to 7–8 cm/s at its eastern margin. Speed of the simulated currents compares well with that derived from Argo data. Weakening anticyclonic circulation in the southwestern part of the sea under forcing of cyclonic wind stress curl or decrease of volume transport in the Korea Strait causes increasing of the simulated deep currents in the entire sea and the cyclonic gyres in the whole water column in its subarctic sector. Therefore, the wind and thermal forcing indirectly affect the deep circulation through the water mass redistribution by the surface currents. The deep cyclonic gyre in the Japan Basin has strong seasonal variation, strengthening in winter and weakening in summer, in line with the buoys data. The gyre intensification is accompanied with its shrinkage and the current speed decreasing at its periphery, that explains the seasonal variation of the deep currents at the northern slope of the Japan Basin observed by deep mooring. This winter strengthening of the gyre, both in the deep and intermediate layers, increases the currents barotropy, whereas the gyre strengthening in the surface layer in summer, when it weakens below 100–150 m, increases the baroclinicity. Despite of relatively low spatial resolution, the model captures deep dynamic structures related to local bottom topographic features, such as anticyclonic eddies around underwater rises and seamounts and cyclonic eddies above topographic depressions in the subarctic sector. The reverse currents were simulated above Yamato Rise, Korea Plateau, and in the Ulleung Basin in condition of the weakened deep circulation adjusting in one or two months. The reverse currents are tracked by Argo buoys, too, they follow the changes of surface currents.

Upper ocean response to typhoon Megi (2010)

In this paper, the response of the upper ocean to typhoon Megi is analyzed and studied by using the sea surface temperature (SST), 500hPa height field and wind field of NCEP reanalysis data and Argo buoy data. The results show that sea surface temperature (SST) will decrease significantly after typhoon, and on the right side of typhoon path cooling is more obvious than the left; the temperature changes dramatically on the right side of Megi path, and correspondingly the depth variation in mixed layer is also intense, and the distance between buoy and the center of the typhoon will al so affect the severity of the temperature variavtion, the salinity may increase or decrease after typhoon, it depends on the evaporation and precipitation or other relevant factors in this area.

Skills of different hydrographic networks in capturing changes in the Mediterranean Sea at climate scales

CR Climate Research Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials CR 63:1-18 (2015) - DOI: https://doi.org/10.3354/cr01270 Skills of different hydrographic networks in capturing changes in the Mediterranean Sea at climate scales J. Llasses1,*, G. Jordà1, D. Gomis1,2 1Mediterranean Institute for Advanced Studies (IMEDEA, UIB-CSIC), c/Miquel Marquès 21, 07190 Esporles, Spain 2University of the Balearic Islands, Physics Department, Cra.Valldemossa km 7.5, 07122 Palma, Spain *Corresponding author: josep.llasses@uib.es ABSTRACT: The skills of 5 observational networks are explored in the context of the monitoring of climate signals in the Mediterranean Sea. Namely we explore the capabilities of hydrographic surveys and ships of opportunity, of Argo buoys, of a (virtual) regularly distributed mooring network, of the present-day observational system (which makes use of the 3 kinds of observations) and of a targeted future system. The skills of each observational network are quantified as follows: first, the output of a realistic regional circulation model (considered here as the virtual truth) is sampled at the same time and location of the actual observations gathered by each observational network. An objective analysis scheme based on Optimal Statistical Interpolation is then applied to the pseudo-observations to obtain gridded products, which are compared to the model output in order to infer the capability of each sampling to capture the true fields. We do it for different periods (for 1962-2000 and for the whole 21st century) and for different parameters (temperature, salinity and the rate of deep water formation in the Western Mediterranean). Results indicate that the skills to reproduce large scale climatic signals depend on the depth and variable, ranging from >90% of explained monthly variance and <5% relative trend errors for the upper (0-100 m) and intermediate layer (100-400 m) temperature fields, to <60% of variance and 30% relative trend errors for the upper layer salinity field. When averaging temperature and salinity over the whole basin volume, both annual values and long term trends are properly captured by all the networks, though the deep water formation rate in the Western Mediterranean is largely overestimated. Conversely, regional features are missed by all the sampling networks, since none of them has an adequate spatial distribution to capture small scale processes. KEY WORDS: Climate variability · Mediterranean · Monitoring · Observing systems · Climate change Full text in pdf format Supplementary material NextCite this article as: Llasses J, Jordà G, Gomis D (2015) Skills of different hydrographic networks in capturing changes in the Mediterranean Sea at climate scales. Clim Res 63:1-18. https://doi.org/10.3354/cr01270 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in CR Vol. 63, No. 1. Online publication date: March 18, 2015 Print ISSN: 0936-577X; Online ISSN: 1616-1572 Copyright © 2015 Inter-Research.

An Improved Model for L-Band Brightness Temperature Estimation Over Foam-Covered Seas Under Low and Moderate Winds

In this study, an improved T B model is proposed on the basis of the SSA model and Monahan foam coverage model. A 22-month matched dataset from the Aquarius observation and Argo buoys was collected to build the improved model. However, it was determined that the wind-induced emissivity calculated from the SSA model at low wind speed (WS) displays obvious deviation compared with the satellite observations, which can be corrected using the systematical error correct coefficient (SECC). To evaluate the effects of sea wave spectra on T B , different sea wave spectra are used and compared in the SSA model and the foam coverage model. A new set of parameters for the foam coverage model for different spectra is obtained by fitting the wind-induced emissivity calculated from a 16-month matching dataset of the Aquarius and Argo buoys. The SSA model with a Kudryavtsev spectrum, as well as the improved foam coverage model, is selected for simulating the satellite T B under low and moderate winds. Finally, a 6-month match dataset obtained in 2013 is used for model validation. The root mean square error (RMSE) of the estimated brightness temperature is approximately 0.5 K in V polarization and less than 0.7 K in H polarization. The correlation coefficient is approximately 0.9, except for the case with 45.6° in H polarization. The bias between simulation and observation in V polarization is lower than that in H polarization, and the biases in both polarizations are acceptable when the WS is less than 20 m/s.

Assessment of the initial sea surface temperature product of the scanning microwave radiometer aboard on HY-2 satellite

HY-2 satellite is the first satellite for dynamic environmental parameters measurement of China, which was launched on 16th August 2011. A scanning microwave radiometer (RM) is carried for sea surface temperature (SST), sea surface wind speed, columnar water vapor and columnar cloud liquid water detection. In this paper, the initial SST product of RM was validated with in-situ data of National Data of Buoy Center (NDBC) mooring and Argo buoy. The validation results indicate the accuracy of RMSST is better than 1.7°C. The comparison of RM SST and WindSat SST shows the former is warmer than the latter at high sea surface wind speed and the difference between these SSTs is depend on the sea surface wind speed. Then, the relationship between the errors of RM SST and sea surface wind speed was analyzed using NDBC mooring measurements. Based on the results of assessment and errors analysis, the suggestions of taking account of the affection of sea surface wind speed and using sea surface wind speed and direction derived from the microwave scatteromter aboard on HY-2 for SST product calibration were given for retrieval algorithm improvement.

Estimate of Ocean Mixed Layer Deepening after a Typhoon Passage over the South China Sea by Using Satellite Data

Abstract The ocean responses to Typhoon Cimaron, which influenced the South China Sea (SCS) from 1 to 8 November 2006, are analyzed. Based on satellite-observed sea surface temperature (SST) and climatological temperature profiles in the SCS, mixed layer deepening, an important parameter characterizing turbulent mixing and upwelling driven by strong typhoon winds, is derived. Corresponding to the SST drop of 4.4°C on 3 November 2006, the mixed layer deepened by 104.5 m relative to the undisturbed depth of 43.2 m, which is consistent with a simulation result from a mixed layer model. Furthermore, baroclinic geostrophic velocity and vorticity are calculated from the surface temperature gradient caused by the typhoon. The negative vorticity, associated with the typhoon cooling, indicated an anticyclonic baroclinic circulation strongest at the base of the mixed layer and at the depth of 50 m, the geostrophic speed reached as high as 0.2 m s−1. Typhoon Cimaron proceeded slowly (1.7 m s−1) when it was making a southwestward turn on 3 November 2006, resulting in a subcritical condition with a Froude number (the ratio of typhoon translation speed to first baroclinic mode speed) of 0.6 around the maximum SST drop location and facilitating high SST cooling and mixed layer deepening because of the absence of inertial-gravity waves in the wake of the typhoon. Comparison of Argo buoy data with the climatological temperature suggests that the average uncertainty in the mixed layer deepening estimation caused by the difference between Argo and climatological temperature profiles is less than 10 m.

A new interpolation method for observation data obtained from ARGO buoys system

Experimental and observation data obtained from various sources are used in studying and solving many problems of geophysical hydrodynamics. A method for interpolation of observation data on regular grids is presented in the paper. The method takes into account the transport of data by currents and allows one to improve the accuracy of interpolation of these observation data fields by introducing ‘pseudo observations’.