scholarly journals What caused the frequent and widespread occurrences of noctilucent clouds at middle latitudes in 2020?

2021 ◽  
Author(s):  
Peter Dalin ◽  
Hidehiko Suzuki ◽  
Nikolay Pertsev ◽  
Vladimir Perminov ◽  
Nikita Shevchuk ◽  
...  
Keyword(s):  
Water Vapor ◽  
Volcanic Activity ◽  
Middle Latitude ◽  
Summer Season ◽  
Vapor Concentration ◽  
Water Vapor Concentration ◽  
Noctilucent Clouds ◽  
Middle Latitudes ◽  
Concentration Maximum ◽  
Mesopause Temperature

Abstract. The 2020 summer season has revealed frequent occurrences of noctilucent clouds (NLCs) around the Northern hemisphere at middle latitudes (45–55° N), with the lowest latitude at which NLCs were seen being 34.1° N. In order to investigate a reason for this NLC extraordinary summer season, we have analyzed long-term Aura/MLS satellite data for all available summer periods from 2005 to 2020. Both Aura/MLS summer temperature and water vapor in the upper mesosphere and the mesopause region, between 74 and 89 km altitude, have been considered. We have found that there has been a moderate decrease in the upper mesosphere temperature between 2016 and 2020 and no dramatic changes have been observed in temperature in the summer of 2020 at the middle latitude mesopause. At the same time, water vapor concentration has significantly increased (by about 12–15 %) in the zonal mean H2O value in the 2020 summer compared to 2017, meaning that the summer mesopause at middle latitudes has become more wet. At the same time, no increase in water vapor has been detected at the high latitude high altitude mesopause. A combination of lower mesopause temperature and water vapor concentration maximum at middle latitudes is the main reason for frequent and widespread occurrences of NLCs seen around the globe at middle latitudes in the summer of 2020. The 24th solar cycle minimum cannot explain the H2O maximum in 2020 since the correlation between Lyman-α flux and the amount of water vapor is low. The increase in volcanic activity from 2013 to 2015 (and its recent maximum occurred in 2015) explains the increased amount of water vapor in the upper mesosphere for the past years and its maximum in 2020 due to volcanic water vapor being injected into the atmosphere and transported into the upper mesosphere. The 5-year delay between volcanic activity and water vapor maximum is well explained by a general meridional-vertical atmospheric circulation.

scholarly journals Numerical Simulation of the Water Vapor Separation of a Moisture-Selective Hollow-Fiber Membrane for the Application in Wood Drying Processes

Membranes ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 593
Author(s):  
Nasim Alikhani ◽  
Douglas W. Bousfield ◽  
Jinwu Wang ◽  
Ling Li ◽  
Mehdi Tajvidi
Keyword(s):  
Water Vapor ◽  
Constant Temperature ◽  
Hollow Fiber ◽  
Hollow Fiber Membrane ◽  
Vacuum Pressure ◽  
Vapor Concentration ◽  
Water Vapor Concentration ◽  
Fiber Membrane ◽  
Wood Drying ◽  
Air Velocity

In this study, a simplified two-dimensional axisymmetric finite element analysis (FEA) model was developed, using COMSOL Multiphysics® software, to simulate the water vapor separation in a moisture-selective hollow-fiber membrane for the application of air dehumidification in wood drying processes. The membrane material was dense polydimethylsiloxane (PDMS). A single hollow fiber membrane was modelled. The mass and momentum transfer equations were simultaneously solved to compute the water vapor concentration profile in the single hollow fiber membrane. A water vapor removal experiment was conducted by using a lab-scale PDMS hollow fiber membrane module operated at constant temperature of 35 °C. Three operation parameters of air flow rate, vacuum pressure, and initial relative humidity (RH) were set at different levels. The final RH of dehydrated air was collected and converted to water vapor concentration to validate simulated results. The simulated results were fairly consistent with the experimental data. Both experimental and simulated results revealed that the water vapor removal efficiency of the membrane system was affected by air velocity and vacuum pressure. A high water vapor removal performance was achieved at a slow air velocity and high vacuum pressure. Subsequently, the correlation of Sherwood (Sh)–Reynolds (Re)–Schmidt (Sc) numbers of the PDMS membrane was established using the validated model, which is applicable at a constant temperature of 35 °C and vacuum pressure of 77.9 kPa. This study delivers an insight into the mass transport in the moisture-selective dense PDMS hollow fiber membrane-based air dehumidification process, with the aims of providing a useful reference to the scale-up design, process optimization and module development using hollow fiber membrane materials.

Degradation of Solid Oxide Fuel Cell Cathodes Accelerated at a High Water Vapor Concentration

2010 ◽  
Vol 7 (2) ◽  
Author(s):  
S. H. Kim ◽  
K. B. Shim ◽  
C. S. Kim ◽  
J. T. Chou ◽  
T. Oshima ◽  
...  
Keyword(s):  
Water Vapor ◽  
Voltage Drop ◽  
Cell Voltage ◽  
High Water ◽  
Solid Oxide ◽  
Constant Current ◽  
Vapor Concentration ◽  
Water Vapor Concentration ◽  
Oxide Fuel ◽  
Constant Current Density

The influence of water vapor in air on power generation characteristic of solid oxide fuel cells was analyzed by measuring cell voltage at a constant current density, as a function of water vapor concentration at 800°C and 1000°C. Cell voltage change was negligible at 1000°C, while considerable voltage drop was observed at 800°C accelerated at high water vapor concentrations of 20 wt % and 40 wt %. It is considered that La2O3 formed on the (La0.8Sr0.2)0.98MnO3 surface, which is assumed to be the reason for a large voltage drop.

scholarly journals A Coated Spherical Microresonator for Measurement of Water Vapor Concentration at PPM Levels in Very Low Humidity Environments

2018 ◽  
Vol 36 (13) ◽  
pp. 2667-2674 ◽  
Author(s):  
Arun Kumar Mallik ◽  
Gerald Farrell ◽  
Dejun Liu ◽  
Vishnu Kavungal ◽  
Qiang Wu ◽  
...  
Keyword(s):  
Water Vapor ◽  
Vapor Concentration ◽  
Water Vapor Concentration ◽  
Low Humidity

Simultaneous water vapor concentration and temperature measurements in unsteady hydrogen flames

2009 ◽  
Vol 32 (2) ◽  
pp. 2527-2534 ◽  
Author(s):  
David Blunck ◽  
Sumit Basu ◽  
Yuan Zheng ◽  
Viswanath Katta ◽  
Jay Gore
Keyword(s):  
Water Vapor ◽  
Temperature Measurements ◽  
Vapor Concentration ◽  
Water Vapor Concentration

Trends in noctilucent clouds

2021 ◽  
Author(s):  
Franz-Josef Lübken ◽  
Gerd Baumgarten
Keyword(s):  
Carbon Dioxide ◽  
Water Vapor ◽  
Middle Atmosphere ◽  
Transport Model ◽  
Particle Model ◽  
Noctilucent Clouds ◽  
Middle Latitudes ◽  
Ice Particles ◽  
Highly Correlated ◽  
Ice Water

<p>Noctilucent clouds are often cited as potential indicators of climate change in the middle<br>atmosphere. They owe their existence to the very cold summer mesopause region (~130K) at mid<br>and high latitudes. We analyze trends derived from the Leibniz-Institute Middle Atmosphere<br>Model (LIMA) and the MIMAS ice particle model (Mesospheric Ice Microphysics And tranSport model)<br>for the years 1871-2008 and for middle, high and arctic latitudes, respectively.<br>Model runs with and without an increase of carbon dioxide and water vapor (from methane oxidation)<br>concentration are performed. Trends are most prominent after ~1960 when the increase of both<br>carbon dioxide and water vapor accelerates. Negative trends of (geometric) NLC altitudes are primarily<br>due to cooling below NLC altitudes caused by carbon dioxide increase. Increases of ice particle<br>radii and NLC brightness with time are mainly caused by an enhancement of water vapor.<br>Several ice layer and background parameter trends are similar at high and arctic latitudes but are<br>substantially different at middle latitudes. This concerns, for example, occurrence rates, ice water<br>content (IWC), and number of ice particles in a column. Considering the time period after 1960,<br>geometric altitudes of NLC decrease by approximately 260m per decade, and brightness increases by<br>roughly 50% (1960-2008), independent of latitude. NLC altitudes decrease by approximately 15-20m<br>per increase of carbon dioxide by 1ppmv. The number of ice particles in a column and also at the<br>altitude of maximum backscatter is nearly constant with time. At all latitudes, yearly mean NLC<br>appear at altitudes where temperatures are close to 145+/-1K. Ice particles are present nearly<br>all the time at high and arctic latitudes, but are much less common at middle latitudes. Ice water<br>content and maximum backscatter are highly correlated, where the slope depends on latitude. This<br>allows to combine data sets from satellites and lidars. Furthermore, IWC and the concentration of<br>water vapor at the altitude of maximum backscatter are also strongly correlated. Results from<br>LIMA/MIMAS agree nicely with observations.</p>

Water-vapor Measurements in the Lower Stratosphere

1974 ◽  
Vol 52 (8) ◽  
pp. 1527-1531 ◽  
Author(s):  
H. J. Mastenbrook
Keyword(s):  
Water Vapor ◽  
Lower Stratosphere ◽  
Marked Decrease ◽  
Vapor Concentration ◽  
Water Vapor Concentration ◽  
Mixing Ratio ◽  
Stratospheric Water Vapor ◽  
Mixing Ratios ◽  
Natural Concentration ◽  
General Range

Nearly 10 years of water-vapor measurements to heights of 30 km provide a basis for assessing the natural concentration of stratospheric water vapor and its variability. The measurements which began in 1964 have been made at monthly intervals from the mid-latitude location of Washington, D.C, using a balloon-borne frost-point hygrometer. The observations show the mixing ratio of water-vapor mass to air mass in the stratosphere to be in the general range of 1 to 4 p.p.m. with a modal concentration between 2 and 3 p.p.m. An annual cycle of mixing ratio is evident for the low stratosphere. A trend of water-vapor increase observed during the first 6 years does not persist beyond 1969 or 1970. The 6 year increase was followed by a marked decrease in 1971, with mixing ratios remaining generally below 3 p.p.m. thereafter. The measurements of recent years suggest that the series of observations may have begun during a period of low water-vapor concentration in the stratosphere.

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