scholarly journals A measurement system for vertical seawater profiles close to the air/sea interface

2017 ◽  
Author(s):  
Richard P. Sims ◽  
Ute Schuster ◽  
Andrew J. Watson ◽  
Ming Xi Yang ◽  
Frances E. Hopkins ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
System Response ◽  
Vertical Profiles ◽  
Near Surface ◽  
Wind Speeds ◽  
Small Frame ◽  
System Response Time ◽  
Wave Heights ◽  
Gas Measurements ◽  
Vertical Gradients

Abstract. This paper describes a Near Surface Ocean Profiler, which has been designed to precisely measure vertical gradients in the top 10 m of the ocean. Variations in the depth of seawater collection are minimised when using the profiler compared to conventional CTD/rosette deployments. The profiler consists of a remotely operated winch mounted on a tethered yet free floating buoy, which is used to raise and lower a small frame housing sensors and inlet tubing. Seawater at the inlet depth is pumped back to the ship for analysis. The profiler can be used to make continuous vertical profiles or to target a series of discrete depths. The profiler has been successfully deployed during wind speeds up to 10 m s−1 and significant wave heights up to 2 m. We demonstrate the potential of the profiler by presenting measured vertical profiles of the trace gases carbon dioxide and dimethylsulfide. Trace gas measurements use an efficient microporous membrane equilibrator to minimise the system response time. The example profiles show vertical gradients in the upper 5 m for temperature, carbon dioxide and dimethylsulfide of 0.15 °C, 4 μatm and 0.4 nM respectively.

scholarly journals A measurement system for vertical seawater profiles close to the air–sea interface

Ocean Science ◽  
2017 ◽  
Vol 13 (5) ◽  
pp. 649-660 ◽  
Author(s):  
Richard P. Sims ◽  
Ute Schuster ◽  
Andrew J. Watson ◽  
Ming Xi Yang ◽  
Frances E. Hopkins ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
System Response ◽  
Vertical Profiles ◽  
Near Surface ◽  
Wind Speeds ◽  
Small Frame ◽  
System Response Time ◽  
Wave Heights ◽  
Gas Measurements ◽  
Vertical Gradients

Abstract. This paper describes a near-surface ocean profiler, which has been designed to precisely measure vertical gradients in the top 10 m of the ocean. Variations in the depth of seawater collection are minimized when using the profiler compared to conventional CTD/rosette deployments. The profiler consists of a remotely operated winch mounted on a tethered yet free-floating buoy, which is used to raise and lower a small frame housing sensors and inlet tubing. Seawater at the inlet depth is pumped back to the ship for analysis. The profiler can be used to make continuous vertical profiles or to target a series of discrete depths. The profiler has been successfully deployed during wind speeds up to 10 m s−1 and significant wave heights up to 2 m. We demonstrate the potential of the profiler by presenting measured vertical profiles of the trace gases carbon dioxide and dimethylsulfide. Trace gas measurements use an efficient microporous membrane equilibrator to minimize the system response time. The example profiles show vertical gradients in the upper 5 m for temperature, carbon dioxide and dimethylsulfide of 0.15 °C, 4 µatm and 0.4 nM respectively.

scholarly journals Observations of snowdrift over Antarctic snow and blue-ice surfaces

2001 ◽  
Vol 32 ◽  
pp. 168-174 ◽  
Author(s):  
Richard Bintanja ◽  
H. Lilienthal ◽  
H. Tüg
Keyword(s):  
Meteorological Data ◽  
Austral Summer ◽  
Vertical Profiles ◽  
Near Surface ◽  
Ice Surface ◽  
Antarctic Snow ◽  
Drift Density ◽  
Weak Winds ◽  
Vertical Gradients ◽  
Surface Drift

AbstractVertical profiles of snowdrift density and concurrent meteorological data were measured over Antarctic snow and blue ice during a 1 month field experiment in austral summer 1997/98. It is found that drift densities and transport rates over blue ice are significantly smaller than over snow, which can be attributed mainly to the limited availability of snow particles at the blue-ice surface. Hence, over blue ice, near-surface drift densities and vertical gradients in drift density are relatively small. Over blue ice, snowdrift can occur in very weak winds, presumably because of the smoothness of the surface. Over snow, in contrast, drift occurs only in much stronger winds, such that the shear stress applied by the flow can overcome the cohesive interparticle bonds.

scholarly journals Projected Changes in European and North Atlantic Seasonal Wind Climate Derived from CMIP5 Simulations

2019 ◽  
Vol 32 (19) ◽  
pp. 6467-6490 ◽  
Author(s):  
Kimmo Ruosteenoja ◽  
Timo Vihma ◽  
Ari Venäläinen
Keyword(s):  
North Atlantic ◽  
Climate Models ◽  
Global Climate ◽  
Arctic Sea Ice ◽  
Global Climate Models ◽  
Near Surface ◽  
Wind Speeds ◽  
The North ◽  
Seasonal Wind ◽  
Projected Changes

Abstract Future changes in geostrophic winds over Europe and the North Atlantic region were studied utilizing output data from 21 CMIP5 global climate models (GCMs). Changes in temporal means, extremes, and the joint distribution of speed and direction were considered. In concordance with previous research, the time mean and extreme scalar wind speeds do not change pronouncedly in response to the projected climate change; some degree of weakening occurs in the majority of the domain. Nevertheless, substantial changes in high wind speeds are identified when studying the geostrophic winds from different directions separately. In particular, in northern Europe in autumn and in parts of northwestern Europe in winter, the frequency of strong westerly winds is projected to increase by up to 50%. Concurrently, easterly winds become less common. In addition, we evaluated the potential of the GCMs to simulate changes in the near-surface true wind speeds. In ocean areas, changes in the true and geostrophic winds are mainly consistent and the emerging differences can be explained (e.g., by the retreat of Arctic sea ice). Conversely, in several GCMs the continental wind speed response proved to be predominantly determined by fairly arbitrary changes in the surface properties rather than by changes in the atmospheric circulation. Accordingly, true wind projections derived directly from the model output should be treated with caution since they do not necessarily reflect the actual atmospheric response to global warming.

scholarly journals Humidity Measurement in Carbon Dioxide with Capacitive Humidity Sensors at Low Temperature and Pressure

Sensors ◽  
2018 ◽  
Vol 18 (8) ◽  
pp. 2615 ◽  
Author(s):  
Andreas Lorek ◽  
Jacek Majewski
Keyword(s):  
Carbon Dioxide ◽  
Low Temperature ◽  
Sensor Calibration ◽  
Humidity Sensors ◽  
Near Surface ◽  
Adsorption Sites ◽  
Carbon Dioxide Gas ◽  
Individual Calibration ◽  
German Aerospace ◽  
Available Information

In experimental chambers for simulating the atmospheric near-surface conditions of Mars, or in situ measurements on Mars, the measurement of the humidity in carbon dioxide gas at low temperature and under low pressure is needed. For this purpose, polymer-based capacitive humidity sensors are used; however, these sensors are designed for measuring the humidity in the air on the Earth. The manufacturers provide only the generic calibration equation for standard environmental conditions in air, and temperature corrections of humidity signal. Because of the lack of freely available information regarding the behavior of the sensors in CO2, the range of reliable results is limited. For these reasons, capacitive humidity sensors (Sensirion SHT75) were tested at the German Aerospace Center (DLR) in its Martian Simulation Facility (MSF). The sensors were investigated in cells with a continuously humidified carbon dioxide flow, for temperatures between −70 °C and 10 °C, and pressures between 10 hPa and 1000 hPa. For 28 temperature–pressure combinations, the sensor calibration equations were calculated together with temperature–dependent formulas for the coefficients of the equations. The characteristic curves obtained from the tests in CO2 and in air were compared for selected temperature–pressure combinations. The results document a strong cross-sensitivity of the sensors to CO2 and, compared with air, a strong pressure sensitivity as well. The reason could be an interaction of the molecules of CO2 with the adsorption sites on the thin polymeric sensing layer. In these circumstances, an individual calibration for each pressure with respect to temperature is required. The performed experiments have shown that this kind of sensor can be a suitable, lightweight, and relatively inexpensive choice for applications in harsh environments such as on Mars.

Background component of carbon dioxide concentration in the near-surface air

2014 ◽  
Vol 50 (6) ◽  
pp. 576-582 ◽  
Author(s):  
V. N. Aref’ev ◽  
N. Ye. Kamenogradsky ◽  
F. V. Kashin ◽  
A. V. Shilkin
Keyword(s):  
Carbon Dioxide ◽  
Carbon Dioxide Concentration ◽  
Background Component ◽  
Near Surface

scholarly journals Local Characteristics of the Nocturnal Boundary Layer in Response to External Pressure Forcing

2017 ◽  
Vol 56 (11) ◽  
pp. 3035-3047 ◽  
Author(s):  
Steven J. A. van der Linden ◽  
Peter Baas ◽  
J. Antoon van Hooft ◽  
Ivo G. S. van Hooijdonk ◽  
Fred C. Bosveld ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Wind Speed ◽  
Stable Boundary Layer ◽  
Dynamical Behavior ◽  
Geostrophic Wind ◽  
External Pressure ◽  
Near Surface ◽  
Stable Boundary ◽  
Wind Speeds ◽  
Turbulent Characteristics

AbstractGeostrophic wind speed data, derived from pressure observations, are used in combination with tower measurements to investigate the nocturnal stable boundary layer at Cabauw, the Netherlands. Since the geostrophic wind speed is not directly influenced by local nocturnal stability, it may be regarded as an external forcing parameter of the nocturnal stable boundary layer. This is in contrast to local parameters such as in situ wind speed, the Monin–Obukhov stability parameter (z/L), or the local Richardson number. To characterize the stable boundary layer, ensemble averages of clear-sky nights with similar geostrophic wind speeds are formed. In this manner, the mean dynamical behavior of near-surface turbulent characteristics and composite profiles of wind and temperature are systematically investigated. The classification is found to result in a gradual ordering of the diagnosed variables in terms of the geostrophic wind speed. In an ensemble sense the transition from the weakly stable to very stable boundary layer is more gradual than expected. Interestingly, for very weak geostrophic winds, turbulent activity is found to be negligibly small while the resulting boundary cooling stays finite. Realistic numerical simulations for those cases should therefore have a comprehensive description of other thermodynamic processes such as soil heat conduction and radiative transfer.

scholarly journals Analysis of work load by computer system response time in different type of VDT tasks

1985 ◽  
Vol 21 (4) ◽  
pp. 211-217 ◽  
Author(s):  
Akinori KOMATSUBARA ◽  
Yoshimi YOKOMIZO ◽  
Sakae YAMAMOTO ◽  
Kageyu NORO
Keyword(s):  
Response Time ◽  
Computer System ◽  
Work Load ◽  
System Response ◽  
System Response Time

scholarly journals The role of open lead interactions in atmospheric ozone variability between Arctic coastal and inland sites

Elem Sci Anth ◽  
2016 ◽  
Vol 4 ◽  
Author(s):  
Peter K. Peterson ◽  
Kerri A. Pratt ◽  
William R. Simpson ◽  
Son V. Nghiem ◽  
Lemuel X. Pérez Pérez ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Sea Ice ◽  
Ozone Depletion ◽  
Surface Ozone ◽  
Optical Absorption Spectroscopy ◽  
Atmospheric Ozone ◽  
Vertical Profiles ◽  
Large Spatial Scale ◽  
Near Surface ◽  
Air Masses

Abstract Boundary layer atmospheric ozone depletion events (ODEs) are commonly observed across polar sea ice regions following polar sunrise. During March-April 2005 in Alaska, the coastal site of Barrow and inland site of Atqasuk experienced ODEs (O3< 10 nmol mol-1) concurrently for 31% of the observations, consistent with large spatial scale ozone depletion. However, 7% of the time ODEs were exclusively observed inland at Atqasuk. This phenomenon also occurred during one of nine flights during the BRomine, Ozone, and Mercury EXperiment (BROMEX), when atmospheric vertical profiles at both sites showed near-surface ozone depletion only at Atqasuk on 28 March 2012. Concurrent in-flight BrO measurements made using nadir scanning differential optical absorption spectroscopy (DOAS) showed the differences in ozone vertical profiles at these two sites could not be attributed to differences in locally occurring halogen chemistry. During both studies, backward air mass trajectories showed that the Barrow air masses observed had interacted with open sea ice leads, causing increased vertical mixing and recovery of ozone at Barrow and not Atqasuk, where the air masses only interacted with tundra and consolidated sea ice. These observations suggest that, while it is typical for coastal and inland sites to have similar ozone conditions, open leads may cause heterogeneity in the chemical composition of the springtime Arctic boundary layer over coastal and inland areas adjacent to sea ice regions.

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