Sensors for physical fluxes at the sea surface: energy, heat, water, salt

Abstract

Abstract. The current status of meteorological sensors used aboard ships and buoys to measure the air-sea fluxes of momentum, heat, and freshwater is reviewed. Methods of flux measurement by the bulk aerodynamic, inertial dissipation and eddy-correlation methods are considered; and areas are identified where improvements are needed in measurement of the basic variables. In some cases, what is required is the transition from emergent to operational technology, in others new technologies are needed. Uncertainties in measured winds caused by flow distortion over the ship are discussed; and the possible role of computational fluid mechanics models to obtain corrections is considered. Basic studies are also needed on the influence of waves and rain on the fluxes. The issues involved in the specification of sea surface temperature are described, and the relative merits of the available sensors are discussed. The improved capability of buoy-mounted systems will depend on the emergence of low-power instruments, and/or new means of increasing the available power capacity. Other issues covered include the continuing uncertainty about the performance of rain gauges and short-wave radiometers. Also, the requirements for new instruments to extend the range of observations to extreme wind conditions are outlined, and the latest developments in the measurement of aerosol fluxes by eddy-correlation are presented.

A New Air–Sea Interaction Gridded Dataset from ICOADS With Uncertainty Estimates

“…A full comparison of the fluxes with the WHOI moorings and other sources of high-quality flux and meteorological data is planned. Differences are expected to arise from biases in the meteorological variables, the different spatial scales of the datasets, deficiencies in the bulk formulas or model physics, or problems with the mooring data themselves (Weller et al 2008). …”

Thermodynamic properties of sea air

“…While transport properties themselves cannot directly be computed from the equilibrium properties summarized in this paper, the deviation of measured or modelled conditions from those equilibrium properties represent the system's distance from equilibrium and estimate the thermodynamic Onsager forces (Glansdorff and Prigogine, 1971;De Groot and Mazur, 1984) driving the irreversible fluxes. Consequently, standard formulas which use measurable parameters to estimate the physical fluxes of energy, heat, water, or salt at the sea surface are based on equilibrium properties of seawater and humid air (Stull, 2003;Weller et al, 2008). For example, the corresponding bulk formulas for the ocean-atmosphere latent heat flux (Weare et al, 1981;Baosen, 1989;Wells and King-Hele, 1990) are more correctly expressed in terms of the sea-air specific humidity at the condensation point (Sects.…”

Observations to Quantify Air-Sea Fluxes and their Role in Climate Variability and Predictability

“…More commonly fluxes are computed from meteorological variables using bulk flux algorithms with roughly half the accuracy of directly-measured fluxes. The in situ instruments are described in detail [28]. Costs for highquality bulk meteorological and direct flux packages have declined since the detailed assessment of [1].…”

“…In situ sensors for the fluxes of energy, heat, water and salt were recently reviewed [28]. There is a continuing need to investigate the performance of existing sensors, for example calibration and comparability of radiometers remains a challenge, gas flux sensors are of marginal accuracy and reliability in open ocean conditions, and aerosol flux measurements are in their infancy.…”