Occurrence Of Liquid Water Research Articles

Study of Detection Limits of Carbonate Phases in Mixtures with Basaltic-like Fine Regolith in the MIR (1–5.5 µm) Spectral Range

The presence of minerals formed under the occurrence of liquid water during the first billion years on Mars was a key discovery, but there is still a large number of open issues that make the study of these mineral deposits a main focus of remote sensing and laboratory studies. Moreover, even though there is extensive research related to the study of the spectral behavior of mixtures, we still lack a full understanding of the problem. The main goal of this work is the analysis of the detection limits of hydrated and carbonate phases within mixtures with basaltic-like fine regolith in the spectral region 1.0–5.5 µm (1818–10,000 cm−1). We selected two different basalt samples and mixed them with two carbonate phases: a dolomite and a calcite. Spectral features have been investigated isolating the main carbonate absorption features and overtones; deriving trends of spectral parameters such as band depth, band area, full-width-half-maximum; percentage and grain size variations. The results obtained in this work show how the presence of a basaltic component can strongly influence the appearance of the hydrated and carbonate features showing different trends and intensities depending on the grain size and percentage of the carbonate components.

Impact of non-uniform wettability in the condensation and condensation-liquid water intrusion regimes in the cathode gas diffusion layer of proton exchange membrane fuel cell

The impact of variations in the wettability properties of the gas diffusion layer substrate on the liquid water distribution and the reactant gas access is studied from pore network simulations considering two main cases: a degradation case where the fraction of hydrophilic pores increases and a case where the spatial distribution of the hydrophobic agent is non-uniform with hydrophobic surfaces and a central region of mixed wettability. Contrary to previous works, this impact is assessed for various regimes of liquid water occurrence. The latter notably include the condensation regime and the mixed regime where the occurrence of liquid water in the gas diffusion layer results from both condensation under the rib and the ingress of liquid water from the catalyst layer or the microporous layer. The study shows that the wettability variation impact is highly dependent on the regime, i.e. on the operating conditions. Whereas this impact is minor when the conditions correspond to the occurrence of the pure condensation regime where the liquid water is confined in the region below the rib, it can be quite significant in the mixed regime when the conditions are such that liquid water is present also in the region below the channel.

Can We Monitor Snow Properties on Sea Ice to Investigate Its Role in Tropospheric Ozone Depletion?

In the lower troposphere over the Arctic Ocean, ozone is often destroyed in spring by chemical chain reactions involving the reactive bromine species Br and BrO. The role of surface snow in generating reactive bromine has been suspected, but many details of the processes not understood. Using unique data such as BrO concentrations from instruments on buoys, Burd et al. (2017, https://doi.org/10.1002/2017JD026906) observed that the snowmelt onset date often coincides with the end of the reactive bromine season. They proposed that the decrease in snow-specific surface area and/or the occurrence of liquid water in snow induced by melting dramatically slows the rate of surface reactions generating bromine, indicating that the physical state of the snow is critical for bromine generation. Their suggestion is discussed, and a method to test it using novel instrumentation recently available is proposed.

Relationship between cloud characteristics and radar reflectivity based on aircraft and cloud radar co-observations

Cloud properties were investigated based on aircraft and cloud radar co-observation conducted at Yitong, Jilin, Northeast China. The aircraft provided in situ measurements of cloud droplet size distribution, while the millimeter-wavelength cloud radar vertically scanned the same cloud that the aircraft penetrated. The reflectivity factor calculated from aircraft measurements was compared in detail with simultaneous radar observations. The results showed that the two reflectivities were comparable in warm clouds, but in ice cloud there were more differences, which were probably associated with the occurrence of liquid water. The acceptable agreement between reflectivities obtained in water cloud confirmed that it is feasible to derive cloud properties by using aircraft data, and hence for cloud radar to remotely sense cloud properties. Based on the dataset collected in warm clouds, the threshold of reflectivity to diagnose drizzle and cloud particles was studied by analyses of the probability distribution function of reflectivity from cloud particles and drizzle drops. The relationship between reflectivity factor (Z) and cloud liquid water content (LWC) was also derived from data on both cloud particles and drizzle. In comparison with cloud droplets, the relationship for drizzle was blurred by many scatter points and thus was less evident. However, these scatters could be partly removed by filtering out the drop size distribution with a large ratio of reflectivity and large extinction coefficient but small effective radius. Empirical relationships of Z-LWC for both cloud particles and drizzle could then be derived.

Investigation on Dynamic Water Transport of PEFCs Combining Neutron Radiography and CFD Simulation

The dynamic water transport of a polymer electrolyte fuel cell was investigated using neutron radiography and CFD simulation. Different operating conditions with dry and humidified gas supply were analyzed at 0.2 and 0.8 A cm-2. The regions with liquid water occurrence were identified using CFD simulations and were verified by neutron radiography. Water accumulation at anode was identified, while at cathode side condensate was sufficiently removed. Thus, the experimentally determined specific pressure drop criterion of 20 mbar m-1 was confirmed for the investigated type of meander-shaped flow field. The observed maximum water thickness was 0.4 mm inside the channel and served as an input for a closer investigation of dynamic water transport using the Volume of Fluid (VOF) model. The water removal capability at anode and cathode were verified with the VOF simulations. The droplet velocity was approximately 44 % / 50 % of gas velocity at anode / cathode for the investigated droplet shapes.

Surface energy balance, melt and sublimation at Neumayer Station, East Antarctica

A surface energy balance model is forced by 13 years of high-quality hourly observations from the Antarctic coastal station Neumayer. The model accurately reproduces observed surface temperatures. Surface sublimation is significant in summer, when absorbed solar radiation heats the surface. Including a first order estimate of snowdrift sublimation in the calculation more than triples the total sublimation, removing 19% of the solid precipitation, indicating that snowdrift sublimation is potentially important for the mass balance of Antarctic ice shelves. Surface melt occurs at Neumayer in all summers, but all the meltwater refreezes. In two-thirds of the cases, the refreezing is quasi-instantaneous (within the model timestep of 6 min), so that no liquid water remains in the snow. For all other events, the occurrence of liquid water in the snowpack at Neumayer agrees well with satellite-based liquid water detection.

Dating gold artifacts applications for noble gas analyses of gold

Native gold contains gases that were incorporated when gold crystallized or that were implanted into the crystal lattice as decay products of uranium, thorium, and potassium. These elements are present in gold as trace elements. The quantity of4He produced by U and Th decay depends on the time when gold crystallized and can, thus, be used for detecting mineral fakes and, perhaps, faked ‘objets d’art’. Gold is also present in meteorites. In particular, meteorites, which represent rocks from the martian crust are of interest because magmatic activity and occurrence of liquid water in the past might have resulted in gold enrichment by hydrothermal fluids and water derived sedimentation. It is anticipated that gold deposits will eventually be detected on Mars.

Mars: Occurrence of liquid water

In the absence of juvenile liquid water, condensation and subsequent melting of ice are the only means of producing liquid water on the Martian surface. However, the evaporation rate is so high that the available heat sources cannot melt ice on Mars. Melting might occur only in concentrated solutions of strongly deliquescent salts.

Mars: Occurrence of Liquid Water

In the absence of juvenile liquid water, condensation of water vapor to ice and subsequent melting of ice are the only means of producing liquid water on the martian surface. However, the evaporation rate is so high that the available heat sources cannot melt pure ice. Liquid water is therefore limited to concentrated solutions of strongly deliquescent salts.