Metrological challenges for measurements of key climatological observables. Part 4: atmospheric relative humidity

Lovell-Smith, J W; Feistel, Rainer; Harvey, Allan H.; Hellmuth, O.; Bell, S A; Heinonen, Martti; Cooper, Jeff

doi:10.1088/0026-1394/53/1/r40

Cited by 30 publications

(27 citation statements)

References 196 publications

(248 reference statements)

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“…Much less known, however, is the lecture by Heinrich Hertz given in 1885 in which he analysed the thermodynamics of the hydrological cycle in the climate system as a "gigantic steam engine" (Mulligan and Hertz, 1997, p. 41). In fact, rather than CO 2 , water in the troposphere in the form of humidity and clouds contributes the major part to the overall greenhouse effect (Abbot and Fowle Jr., 1908;Emden, 1913;Trenberth et al, 2007;Lacis et al, 2010;Schmidt et al, 2010;Feistel and Ebeling, 2011;Feistel, 2015Feistel, , 2017Lovell-Smith et al, 2016). The global water cycle, along with its observation and modelling, poses a fundamental challenge for climate research (Sherwood et al, 2010;Reid and Valdés, 2011;Tollefsen, 2012;Fasullo and Trenberth, 2012;Josey et al, 2013;Stevens and Bony, 2013;IPCC, 2013).…”

Section: Introductionmentioning

confidence: 99%

Thermodynamic properties of seawater, ice and humid air: TEOS-10, before and beyond

Feistel

2018

Ocean Sci.

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Abstract. In the terrestrial climate system, water is a key player in the form of its different ambient phases of ice, liquid and vapour, admixed with sea salt in the ocean and with dry air in the atmosphere. For proper balances of climatic energy and entropy fluxes in models and observations, a highly accurate, consistent and comprehensive thermodynamic standard framework is requisite in geophysics and climate research. The new Thermodynamic Equation of Seawater -2010 (TEOS-10) constitutes such a standard for properties of water in its various manifestations in the hydrological cycle.

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Section: Introductionmentioning

confidence: 99%

Thermodynamic properties of seawater, ice and humid air: TEOS-10, before and beyond

Feistel

2018

Ocean Sci.

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“…This unofficial use of "psu" does not cause any harm but has been subject to forthright debates (Unesco, 1985(Unesco, , 1986. As an aside, a similar discussion is currently going on regarding the use of "%rh" to denote unitless values of relative humidity (RH) expressed in percent (Lovell-Smith et al, 2016) for an easier distinction between RH and, say, specific humidities or relative uncertainties of RH.…”

Section: Salinity Scalesmentioning

confidence: 99%

“…This estimate is known to be in error by typically 2 % because of the lowered vapour pressure of seawater compared to that of pure water. To get an idea of the relevance of this error, note that a small change in the global latent heat flux by 1 %, or about 1 W m −2 , would exceed by a factor of 200 the flux responsible for the currently observed greenhouse warming of the atmosphere, about 0.005 W m −2 (Lovell-Smith et al, 2016;Feistel, 2015Feistel, , 2017. The estimated energy imbalance of 0.4-0.8 W m −2 of the warming ocean (Cheng et al, 2016) is also within this error range.…”

Section: Helmholtz Function Of Humid Airmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Reply to the short comments of Hannes Schmidt of 04 Apr 2018

Feistel¹

2018

Preprint

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In the terrestrial climate system, water is a key player in the form of its different ambient phases of ice, liquid and vapour, admixed with sea salt in the ocean and with dry air in the atmosphere. For proper balances of climatic energy and entropy fluxes in models and observations, a highly accurate, consistent and comprehensive thermodynamic standard framework is requisite in geophysics and climate research. The new Thermodynamic Equation of Seawater-2010 (TEOS-10) constitutes such a standard for properties of water in its various manifestations in the hydrological cycle. TEOS-10 was recommended internationally in 2009 by the Intergovernmental Oceanographic Commission (IOC) to replace the previous 1980 seawater standard, EOS-80, and in 2011 by the International Union of Geodesy and Geophysics (IUGG) "as the official description for the properties of seawater, of ice and of humid air". This paper briefly reviews the development of TEOS-10, its novel axiomatic properties, the new oceanographic tools it offers and the important tasks that still await solutions by ongoing research. Among the latter are new definitions and measurement standards for seawater salinity and pH in order to establish their metrological traceability to the International System of Units (SI) for the first time after a century of widespread use. Of similar climatological relevance is the development and recommendation of a uniform standard definition of atmospheric relative humidity that is unambiguous and rigorously based on physical principles. "The leading thermodynamic properties of a fluid are determined by the relations which exist between volume, pressure, temperature, energy, and entropy. .. But all the relations existing between these five quantities for any substance. .. may be deduced from the single relation existing for that substance between volume, energy, and entropy."

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“…It has recently been proposed [5,6] to make use of fugacity-based measures for the traditional concept of relative humidity, which would provide more impetus for simple and accurate ways to calculate the fugacity of liquid water and ice.…”

Section: Introductionmentioning

confidence: 99%

Accuracy of Approximations to the Poynting Correction for Ice and Liquid Water

Harvey

2017

J. RES. NATL. INST. STAN.

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Rigorous calculation of the Poynting correction, which describes the effect of pressure on the fugacity of a condensed phase, requires time-consuming evaluation of a thermodynamic potential such as the International Association for the Properties of Water and Steam (IAPWS-95) formulation for water. Simplifying approximations are used in many applications, but the error introduced by the approximations is seldom evaluated. In this work, first-order and second-order approximations were developed for the Poynting correction for both ice and liquid water (including supercooled liquid water), and their errors were evaluated by comparison to the full thermodynamic potentials. The range of conditions covered is from −100 °C to 200 °C at pressures to 20 MPa. Some implications for the calculation of the enhancement factor used in humidity metrology are discussed.

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Metrological challenges for measurements of key climatological observables. Part 4: atmospheric relative humidity

Cited by 30 publications

References 196 publications

Thermodynamic properties of seawater, ice and humid air: TEOS-10, before and beyond

Thermodynamic properties of seawater, ice and humid air: TEOS-10, before and beyond

Reply to the short comments of Hannes Schmidt of 04 Apr 2018

Accuracy of Approximations to the Poynting Correction for Ice and Liquid Water

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