Diurnal Warming Observations with ASIP in the subtropical Northern Atlantic

European Geosciences Union General Assembly 2015 (EGU2015), 12-17 April 2015, Vienna, Austria.-- 1 pageQuantification of air-sea exchange fluxes of energy, moisture, momentum and gases require in situ-measurements of the near-surface layer of the ocean. In the framework of the Salinity Processes in the Upper Ocean Regional Study (SPURS) project, we participated in two cruises to the North Atlantic Salinity Maximum (NASM) region. Observations in the upper ocean are obtained with the Air Sea Interaction Profiler (ASIP), which is an upwardly-rising microstructure instrument designed to study processes in the mixing layer of the ocean. ASIP operates autonomously for up to two days, obtaining undisturbed profiles within the water column from depth to the immediate surface. During the SPURS experiment, ASIP was deployed on several occasions, resulting in a total of over 1000 profiles of the ocean surface boundary layer. ASIP is equipped with microstructure sensors for temperature (FP07), conductivity (SBE07), shear, accurate C-T sensors, a PAR and an oxygen sensor. The high resolution temperature profiles obtained, combined with information on local meteorological variables, allow for an accurate study of the temporal and vertical variability of diurnal warming of the upper ocean boundary layer. Characteristics of the measured diurnal warming at the ocean surface and at specific depth levels are compared to physics-based models of near-surface warming. Mixing rates in the upper ocean are determined from the turbulent dissipation rate, calculated from profiles of the turbulent shear. This information is used to quantify variability between the modeled and observed diurnal warming signalPeer Reviewe

Objective analysis of simulated Equatorial Atlantic ocean data on seasonal time scales

In this study we objectively analyze simulated Equatorial Atlantic ocean data on seasonal time scales using a technique based on optimal interpolation. The purpose is twofold : (1) to estimate the accuracy of the FOCAL/SEQUAL (Programme Français Océan-Climat en Atlantique Equatorial/Seasonal Equatorial Atlantic Response Program) array for mapping large-scale seasonal variations in the depth of the 20° isotherm, and (2) to examine the potential of 20 FOCAL drifting buoys drogued with thermistor chains for enhancing that mapping accuracy. This latter point leads to the development of heuristic model for drifter motion in order to identify the most favorable time and location for buoy deployments. Results are discussed for a number of assumptions about oceanic variability required by both the optimal interpolation procedure and the drifting buoy model. (D'après résumé d'auteur

The Near Surface Equatorial Indian Ocean in 1979. Part I: Linear Dynamics

Different wind field analyses are used to force a one layer adiabatic model of the near equatorial surface circulation in the Indian Ocean in 1979. The model simulates the major features of the observations: eastward jets were present in April-May and in October-November in the central Indian Ocean in phase with the local winds; the seasonal changes of thermocline depth in the western part of the basin are related to the near equatorial currents. Significant discrepancies are also found. Some are due to the uncertainty in the wind fields. Correlation between different wind fields are only of the order of 0.75 for the low frequencies and magnitude can vary by a factor of 1.5. Others are attributed to model inadequacies especially the neglect of nonlinearity and the oversimplification of the vertical structure. There is an unrealistic energy focus in the central Indian Ocean though, in general, seasonal changes are underestimated by at least 30%. Simpler dynamics failed to produce a reasonable agreement over the whole basin. A Yoshida jet did well for the currents in the central part of the basin, but did not reproduce the mass changes in the west. Sverdrup equilibrium reproduces the model zonal slope of the thermocline, but not the currents

Pre-registration of CT pulmonary volumetric image data

Bakalárska práca sa zaoberá predregistráciou pľúcnych objemových CT obrazových dát. Predregistrácia je riešená metódou fázovej korelácie pri rozklade 3D obrazu na 2D rezy usporiadané za sebou. Práca ďalej popisuje geometrické transformácie, interpolácie, výpočet podobnostných kritérií, optimalizáciu registrácie obrazu a proces samotnej registrácie obrazu. Predregistračný softvér je navrhnutý v programovom prostredí MATLAB^®, kde prebieha predregistrácia 3D reálnych CT obrazových dát s dôrazom na rýchlosť procesu.This bachelor thesis is dealing with pre-registration of CT pulmonary volumetric image data. Pre-registration is solved by phase correlation method, which decomposes 3D images into 2D slices arranged in a row. It further describes the geometric transformations, interpolation, calculations of similarity criteria, optimization of registration of images and the image registration process itself. The pre-registration software runs in MATLAB^®, which works with 3D images of real CT image data with an emphasis on process speed.

Measuring solid precipitation using heated tipping bucket gauges: an overview of performance and recommendations from WMO‐SPICE

Comunicación presentada en: TECO-2016 (Technical Conference on Meteorological and Environmental Instruments and Methods of Observation) celebrada en Madrid, del 27 al 30 de septiembre de 2016

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

The Role of Phytoplankton Dynamics in the Seasonal and Interannual Variability of Carbon in the Subpolar North Atlantic - a Modeling Study

We developed an ecosystem/biogeochemical model system, which includes multiple phytoplankton functional groups and carbon cycle dynamics, and applied it to investigate physical-biological interactions in Icelandic waters. Satellite and in situ data were used to evaluate the model. Surface seasonal cycle amplitudes and biases of key parameters (DIC, TA, pCO2, air-sea CO2 flux, and nutrients) are significantly improved when compared to surface observations by prescribing deep water values and trends, based on available data. The seasonality of the coccolithophore and "other phytoplankton" (diatoms and dinoflagellates) blooms is in general agreement with satellite ocean color products. Nutrient supply, biomass and calcite concentrations are modulated by light and mixed layer depth seasonal cycles. Diatoms are the most abundant phytoplankton, with a large bloom in early spring and a secondary bloom in fall. The diatom bloom is followed by blooms of dinoflagellates and coccolithophores. The effect of biological changes on the seasonal variability of the surface ocean pCO2 is nearly twice the temperature effect, in agreement with previous studies. The inclusion of multiple phytoplankton functional groups in the model played a major role in the accurate representation of CO2 uptake by biology. For instance, at the peak of the bloom, the exclusion of coccolithophores causes an increase in alkalinity of up to 4 mol kg(sup 1) with a corresponding increase in DIC of up to 16 mol kg(sup 1). During the peak of the bloom in summer, the net effect of the absence of the coccolithophores bloom is an increase in pCO2 of more than 20 atm and a reduction of atmospheric CO2 uptake of more than 6 mmolm(sup 2) d(sup 1). On average, the impact of coccolithophores is an increase of air-sea CO2 flux of about 27 %. Considering the areal extent of the bloom from satellite images within the Irminger and Icelandic Basins, this reduction translates into an annual mean of nearly 1500 tonnes C yr(sup 1)