Android App for Argo Floats

INCOIS has deployed more than 400 Argo floats till now and soon reaching a special milestone of 500 Indian Argo floats. In this context there is a necessity to have a unique application by which scientists can effectively and efficiently track all the information of these floats and also monitor the active floats among them regularly. The present work describes about an Android application or app which eases the work of researchers to track the information of these Argo floats as well as monitor them regularly. This app is designed and developed to give all the information related to Argo floats like its various types, its deployed positions, its current positions, its functionality, search option, etc., in the form of maps and charts in turn uses real time data to give latest status of Argo floats. In addition to it, this app is also useful in advising the scientists involved in Argo program about the floats in danger of getting grounded or beached that need immediate attention. This app is a very useful tool for the scientists to check the current status of Argo floats from anywhere or anytime using a smart phone

An investigation into the sampling bias of Argo profiling floats in the Southern Ocean

Numerous Argo floats (approximately 3800 floats) have been deployed in the world's oceans to gather hydrographic and biogeochemical data from the upper 2000 m. However, limited research has been done on the spatial and temporal distribution and potential sampling bias of Argo profiling floats brought on by the effects of bathymetric steering of currents, as well as oceanic features, such as meanders and eddies, that affect their distribution over the global ocean. This study investigates the sampling distribution of profiling floats and assesses the mechanisms that impact their trajectories and distribution in the Atlantic sector of the Southern Ocean. The study reveals that Argo floats are influenced and steered towards frontal jets, which in turn are steered by the underlying bathymetry. Argo floats have a 30 % higher probability of sampling regions where depths range from 4000 - 5000 m, rather than shallow regions of the oceans. Using bootstrapping, this result was shown to be statistically significant at the 95 % confidence interval. The sampling bias is associated with floats becoming entrained into deep reaching frontal jets that occur in the Southern Ocean and dominate the deeper waters. This is shown by analyzing the Argo float positions in relation to mean geostrophic currents which shows that there is a 40 % higher probability (statistically significant at the 95 % confidence level) of finding Argo floats in regions where geostrophic currents range from 0.1 - 0.22 m.s-1 even though the majority of surface currents in the Southern Ocean are found below 0.05 m.s-1. This indicates a non-uniform distribution of Argo floats in the Southern Ocean, which leads to a spatial sampling bias in the float data. This has implications for how we characterize the oceanography or understand the distribution and variability of oceanographic processes and its relation to climate

Observing mesoscale eddy effects on mode-water subduction and transport in the North Pacific.

While modelling studies suggest that mesoscale eddies strengthen the subduction of mode waters, this eddy effect has never been observed in the field. Here we report results from a field campaign from March 2014 that captured the eddy effects on mode-water subduction south of the Kuroshio Extension east of Japan. The experiment deployed 17 Argo floats in an anticyclonic eddy (AC) with enhanced daily sampling. Analysis of over 3,000 hydrographic profiles following the AC reveals that potential vorticity and apparent oxygen utilization distributions are asymmetric outside the AC core, with enhanced subduction near the southeastern rim of the AC. There, the southward eddy flow advects newly ventilated mode water from the north into the main thermocline. Our results show that subduction by eddy lateral advection is comparable in magnitude to that by the mean flow--an effect that needs to be better represented in climate models

XBT, ARGO Float and Ship-Based CTD Profiles Intercompared under Strict Space-Time Conditions in the Mediterranean Sea: Assessment of Metrological Comparability

open5noAccurate measurement of temperature and salinity is a fundamental task with heavy implications in all the possible applications of the currently available datasets, for example, in the study of climate changes and modeling of ocean dynamics. In this work, the reliability of measurements obtained by oceanographic devices (eXpendable BathyThermographs, Argo floats and Conductivity-Temperature-Depth sensors) is analyzed by means of an intercomparison exercise. As a first step, temperature profiles from XBT probes, deployed by commercial ships crossing the Ligurian and Tyrrhenian seas during the Ship of Opportunity Program (SOOP), were matched with profiles from Argo floats quasi-collocated in space and time. Attention was then paid to temperature/salinity profiling Argo floats. Since Argo floats usually are not recovered and should last up to five years without any re-calibration, their onboard sensors may suer some drift and/or oset. In the literature, refined methods were developed to post-process Argo data, in order to correct the response of their profiling CTD sensors, in particular adjusting the salinity drift. The core of this delayed-mode quality control is the comparison of Argo data with reference climatology. At the same time, the experimental comparison of Argo profiles with ship-based CTD profiles, matched in space and time, is still of great importance. Therefore, an overall comparison of Argo floats vs. shipboard CTDs was performed, in terms of temperature and salinity profiles in the whole Mediterranean Sea, under space-time matching conditions as strict as possible. Performed analyses provided interesting results. XBT profiles confirmed that below 100mdepth the accordance with Argo data is reasonably good, with a small positive bias (close to 0.05 °C) and a standard deviation equal to about 0.10 °C. Similarly, side-by-side comparisons vs. CTD profiles confirmed the good quality of Argo measurements; the evidence of a drift in time was found, but at a level of about E-05 unit/day, so being reasonably negligible on the Argo time-scale. XBT, Argo and CTD users are therefore encouraged to take into account these results as a good indicator of the uncertainties associated with such devices in the Mediterranean Sea, for the analyzed period, in all the climatological applications.openBordone, Andrea; Pennecchi, Francesca; Raiteri, Giancarlo; Repetti, Luca; Reseghetti, FrancoBordone, Andrea; Pennecchi, Francesca; Raiteri, Giancarlo; Repetti, Luca; Reseghetti, Franc

Indian Argo Trajectories and Surface Currents

An important objective of Argo is measurement of ocean circulation. As Argo floats collect salinity/temperature profiles, they also give information on the surface and subsurface currents. Indian National Centre for Ocean Information Services (INCOIS) being a Regional Data Assembly Centre for Indian Argo has so far launched 160 floats in the Indian Ocean to develop the global ocean observation system as a part of international cooperation project and is responsible for real time generation and dissemination of this data. This work is an attempt to extract information on sea surface in application to the Lagrangian part of the Argo floats. This report constitutes two sections. The first section documents the process of operational generation and dissemination of the Argo trajectory data. The second section describes the data product, Surface Currents and its comparison with Simple Ocean Data Assimilation & Drifting buoy currents

Bio-Optical Sensors on Argo Floats

The general objective of the IOCCG BIO-Argo working group is to elaborate recommendations for establishing a framework for the future development of a cost-effective, bio-optical float network corresponding to the needs and expectations of the scientific community. In this context, our recommendations will necessarily be broad; they range from the identification of key bio-optical measurements to be implemented on floats, to the real-time management of the data flux resulting from the deployment of a "fleet of floats". Each chapter of this report is dedicated to an essential brick leading towards the goal of implementing a bio-optical profiling float network. The following topics are discussed in the Chapters listed below: - Chapter 2 reviews the scientific objectives that could be tackled through the development of such networks, by allowing some of the gaps in the present spatio-temporal resolution of bio-optical variables to be progressively filled. - Chapter 3 identifies the optical and bio-optical properties that are now amenable to remote and autonomous measurement through the use of optical sensors mounted on floats. - Chapter 4 addresses the question of sensor requirements, in particular with respect to measurements performed from floats. - Chapter 5 proposes and argues for the development of dedicated float missions corresponding to specific scientific objectives and relying on specific optical sensor suites, as well as on specific modes of float operation. - Chapter 6 identifies technological issues that need to be addressed for the various bio-optical float missions to become even more cost-effective. - Chapter 7 covers all aspects of data treatment ranging from the development of various quality control procedures (from real-time to delayed mode) to the architecture required for favoring easy access to data. - Chapter 8 reviews the necessary steps and experience required before the operational implementation of different types of float networks can become a reality.JRC.H.5-Land Resources Managemen

Variational assimilation of Lagrangian data in oceanography

We consider the assimilation of Lagrangian data into a primitive equations circulation model of the ocean at basin scale. The Lagrangian data are positions of floats drifting at fixed depth. We aim at reconstructing the four-dimensional space-time circulation of the ocean. This problem is solved using the four-dimensional variational technique and the adjoint method. In this problem the control vector is chosen as being the initial state of the dynamical system. The observed variables, namely the positions of the floats, are expressed as a function of the control vector via a nonlinear observation operator. This method has been implemented and has the ability to reconstruct the main patterns of the oceanic circulation. Moreover it is very robust with respect to increase of time-sampling period of observations. We have run many twin experiments in order to analyze the sensitivity of our method to the number of floats, the time-sampling period and the vertical drift level. We compare also the performances of the Lagrangian method to that of the classical Eulerian one. Finally we study the impact of errors on observations.Comment: 31 page

Matchup Characteristics of Sea Surface Salinity Using a High-Resolution Ocean Model

Sea surface salinity (SSS) satellite measurements are validated using in situ observations usually made by surfacing Argo floats. Validation statistics are computed using matched values of SSS from satellites and floats. This study explores how the matchup process is done using a high-resolution numerical ocean model, the MITgcm. One year of model output is sampled as if the Aquarius and Soil Moisture Active Passive (SMAP) satellites flew over it and Argo floats popped up into it. Statistical measures of mismatch between satellite and float are computed, RMS difference (RMSD) and bias. The bias is small, less than 0.002 in absolute value, but negative with float values being greater than satellites. RMSD is computed using an “all salinity difference” method that averages level 2 satellite observations within a given time and space window for comparison with Argo floats. RMSD values range from 0.08 to 0.18 depending on the space–time window and the satellite. This range gives an estimate of the representation error inherent in comparing single point Argo floats to area-average satellite values. The study has implications for future SSS satellite missions and the need to specify how errors are computed to gauge the total accuracy of retrieved SSS values