Water Vapor Temperature Research Articles

On the Climate Impacts of Upper Tropospheric and Lower Stratospheric Ozone

AbstractThe global warming simulations of the general circulation models (GCMs) are generally performed with different ozone prescriptions. We find that the differences in ozone distribution, especially in the upper tropospheric and lower stratospheric (UTLS) region, account for important model discrepancies shown in the ozone‐only historical experiment of the Coupled Model Intercomparison Project Phase 5 (CMIP5). These discrepancies include global high cloud fraction, stratospheric temperature, and stratospheric water vapor. Through a set of experiments conducted by an atmospheric GCM with contrasting UTLS ozone prescriptions, we verify that UTLS ozone not only directly radiatively heats the UTLS region and cools the upper parts of the stratosphere but also strongly influences the high clouds due to its impact on relative humidity and static stability in the UTLS region and the stratospheric water vapor due to its impact on the tropical tropopause temperature. These consequences strongly affect the global mean effective radiative forcing of ozone, as noted in previous studies. Our findings suggest that special attention should be paid to the UTLS ozone when evaluating the climate effects of ozone depletion in the 20th century and recovery in the 21st century. UTLS ozone difference may also be important for understanding the intermodel discrepancy in the climate projections of the CMIP6 GCMs in which either prescribed or interactive ozone is used.

Comparison of global observations and trends of total precipitable water derived from microwave radiometers and COSMIC radio occultation from 2006 to 2013

Abstract. We compare atmospheric total precipitable water (TPW) derived from the SSM/I (Special Sensor Microwave Imager) and SSMIS (Special Sensor Microwave Imager/Sounder) radiometers and WindSat to collocated TPW estimates derived from COSMIC (Constellation System for Meteorology, Ionosphere, and Climate) radio occultation (RO) under clear and cloudy conditions over the oceans from June 2006 to December 2013. Results show that the mean microwave (MW) radiometer – COSMIC TPW differences range from 0.06 to 0.18 mm for clear skies, from 0.79 to 0.96 mm for cloudy skies, from 0.46 to 0.49 mm for cloudy but non-precipitating conditions, and from 1.64 to 1.88 mm for precipitating conditions. Because RO measurements are not significantly affected by clouds and precipitation, the biases mainly result from MW retrieval uncertainties under cloudy and precipitating conditions. All COSMIC and MW radiometers detect a positive TPW trend over these 8 years. The trend using all COSMIC observations collocated with MW pixels for this data set is 1.79 mm decade−1, with a 95 % confidence interval of (0.96, 2.63), which is in close agreement with the trend estimated by the collocated MW observations (1.78 mm decade−1 with a 95 % confidence interval of 0.94, 2.62). The sample of MW and RO pairs used in this study is highly biased toward middle latitudes (40–60∘ N and 40–65∘ S), and thus these trends are not representative of global average trends. However, they are representative of the latitudes of extratropical storm tracks and the trend values are approximately 4 to 6 times the global average trends, which are approximately 0.3 mm decade−1. In addition, the close agreement of these two trends from independent observations, which represent an increase in TPW in our data set of about 6.9 %, are a strong indication of the positive water vapor–temperature feedback on a warming planet in regions where precipitation from extratropical storms is already large.

Relationship between drought and air temperature and actual water vapor pressure in the Heihe River Basin, Northwest China

Relationship between drought and air temperature and actual water vapor pressure in the Heihe River Basin, Northwest China

Characterization of atmospheric thermodynamic variables by Raman lidar in the frame of the International Network for the Detection of Atmospheric Composition Change - NDACC

In November 2012 the Raman Lidar system BASIL, located at the Univ. of Basilicata (Potenza), was approved to enter in NDACC, with the goal of providing accurate routine measurements of the vertical profiles of atmospheric temperature and water vapour mixing ratio. In this presentation we illustrate and discuss water vapour mixing ratio and temperature measurements carried out during these four years and their comparisons with the radiosondes launched from nearby Institute IMAA-CNR (7 km away).

Corrosion kinetics and mechanisms of ZrC1-x ceramics in high temperature water vapor.

The corrosion kinetics and mechanisms of ZrC1−x ceramics in water vapor between 800 and 1200 °C were investigated. The results showed that there was only cubic ZrO2 phase in the corrosion layer when corroded at 800 °C, while a scale layer consisted of a mixture of cubic and monoclinic ZrO2 phases when corroded at 1000 °C and 1200 °C. A series of crystallographic relationships at the ZrC/c-ZrO2 interface were detected. The c-ZrO2 formed near the interface retained some crystallographic orientations of the initial ZrC before corrosion, presenting an “inheritance in microstructure” between c-ZrO2 and ZrC. The corrosion behavior mainly followed a parabolic relationship. The incremental rate of weight gain increased with increased corrosion temperature and decreased C/Zr ratio and the carbon vacancy was passive to the decrease of corrosion rate. The main corrosion controlling mechanism changed from phase boundary reactions to surface diffusion and then to grain boundary diffusion with increased temperature.

Insights into the hydrothermal stability of zeolite 13X

Zeolite 13X, a hydrophilic adsorbent, can be used for storing thermal energy. However, its crystallinity can degrade under hydrothermal stress in the aqueous atmosphere of an adsorption storage device. This would result in a loss of energy storage capacity. There is still no known method for predicting the long-term hydrothermal stability of zeolites under relevant adsorption storage conditions. A solution for this could be a kinetic model designed with experimental data to predict hydrothermal degradation. The objective of the present study was to examine the hydrothermal stability of zeolite 13X under relevant adsorption storage conditions and to analyze its degradation in respect to the influencing factors of water vapor pressure, temperature and period of treatment. The investigated zeolite 13X powder and zeolite 13X beads have been treated at temperatures between 200 and 350 °C and water vapor pressures up to 31 kPa for treatment periods of up to 312 h. We have analyzed the changes in the zeolite structure, composition and adsorption properties by X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, 27Al/29Si MAS NMR spectroscopy, molybdate method and water sorption. The results show a degradation of the crystalline zeolite 13X phase into an amorphous phase under all hydrothermal conditions, although to different degrees. Under specific hydrothermal conditions a portion of the primary crystalline phase withstands further treatment. Based on chemical decomposition mechanisms, we discuss this phenomenon. The complex stability behavior of the zeolite 13X demonstrates that a prediction beyond experimental data cannot be recommended.

Retrieving K-Band Instantaneous Microwave Land Surface Emissivity Based on Passive Microwave Brightness Temperature and Atmospheric Precipitable Water Vapor Data

An algorithm has been developed for retrieving instantaneous K-band microwave land surface emissivity using only brightness temperature and atmospheric precipitable water vapor content (PWV) data. The radiative transfer model is simplified to a new microwave emissivity retrieval model using two assumptions: 1) emissivities at 18.7 and 23.8 GHz with horizontal polarization are approximately equal, and 2) simple parameterizations exist between atmospheric transmittance and PWV and between atmospheric effective radiating temperature and PWV. The new technique does not need infrared land surface temperature as the input data, and it overcomes the limitation of previous algorithms under cloudy conditions. The estimated instantaneous emissivities are validated at single points and in the regional area. The results demonstrate that this simplified algorithm has the best root mean square error of 0.017, a bias of 0.004 in the single-point validation, and an $R^{2}$ of 0.66 and a RMSE of 0.021 in the regional validation. This simplified algorithm has the potential to obtain instantaneous microwave land surface emissivity under both cloud-free and cloudy conditions.

Understanding the surface temperature cold bias in CMIP5 AGCMs over the Tibetan Plateau

The temperature biases of 28 CMIP5 AGCMs are evaluated over the Tibetan Plateau (TP) for the period 1979–2005. The results demonstrate that the majority of CMIP5 models underestimate annual and seasonal mean surface 2-m air temperatures (Tas) over the TP. In addition, the ensemble of the 28 AGCMs and half of the individual models underestimate annual mean skin temperatures (Ts) over the TP. The cold biases are larger in Tas than in Ts, and are larger over the western TP. By decomposing the Ts bias using the surface energy budget equation, we investigate the contributions to the cold surface temperature bias on the TP from various factors, including the surface albedo-induced bias, surface cloud radiative forcing, clear-sky shortwave radiation, clear-sky downward longwave radiation, surface sensible heat flux, latent heat flux, and heat storage. The results show a suite of physically interlinked processes contributing to the cold surface temperature bias. Strong negative surface albedo-induced bias associated with excessive snow cover and the surface heat fluxes are highly anticorrelated, and the cancelling out of these two terms leads to a relatively weak contribution to the cold bias. Smaller surface turbulent fluxes lead to colder lower-tropospheric temperature and lower water vapor content, which in turn cause negative clear-sky downward longwave radiation and cold bias. The results suggest that improvements in the parameterization of the area of snow cover, as well as the boundary layer, and hence surface turbulent fluxes, may help to reduce the cold bias over the TP in the models.

A global satellite environmental data record derived from AMSR-E and AMSR2 microwave Earth observations

Abstract. Spaceborne microwave remote sensing is widely used to monitor global environmental changes for understanding hydrological, ecological, and climate processes. A new global land parameter data record (LPDR) was generated using similar calibrated, multifrequency brightness temperature (Tb) retrievals from the Advanced Microwave Scanning Radiometer for EOS (AMSR-E) and the Advanced Microwave Scanning Radiometer 2 (AMSR2). The resulting LPDR provides a long-term (June 2002–December 2015) global record of key environmental observations at a 25 km grid cell resolution, including surface fractional open water (FW) cover, atmosphere precipitable water vapor (PWV), daily maximum and minimum surface air temperatures (Tmx and Tmn), vegetation optical depth (VOD), and surface volumetric soil moisture (VSM). Global mapping of the land parameter climatology means and seasonal variability over the full-year records from AMSR-E (2003–2010) and AMSR2 (2013–2015) observation periods is consistent with characteristic global climate and vegetation patterns. Quantitative comparisons with independent observations indicated favorable LPDR performance for FW (R ≥ 0.75; RMSE ≤ 0.06), PWV (R ≥ 0.91; RMSE ≤ 4.94 mm), Tmx and Tmn (R ≥ 0.90; RMSE ≤ 3.48 °C), and VSM (0.63 ≤ R ≤ 0.84; bias-corrected RMSE ≤ 0.06 cm3 cm−3). The LPDR-derived global VOD record is also proportional to satellite-observed NDVI (GIMMS3g) seasonality (R ≥ 0.88) due to the synergy between canopy biomass structure and photosynthetic greenness. Statistical analysis shows overall LPDR consistency but with small biases between AMSR-E and AMSR2 retrievals that should be considered when evaluating long-term environmental trends. The resulting LPDR and potential updates from continuing AMSR2 operations provide for effective global monitoring of environmental parameters related to vegetation activity, terrestrial water storage, and mobility and are suitable for climate and ecosystem studies. The LPDR dataset is publicly available at http://files.ntsg.umt.edu/data/LPDR_v2/.

MAX-DOAS measurements of HONO slant column densities during the MAD-CAT campaign: inter-comparison, sensitivity studies on spectral analysis settings, and error budget

Abstract. In order to promote the development of the passive DOAS technique the Multi Axis DOAS – Comparison campaign for Aerosols and Trace gases (MAD-CAT) was held at the Max Planck Institute for Chemistry in Mainz, Germany, from June to October 2013. Here, we systematically compare the differential slant column densities (dSCDs) of nitrous acid (HONO) derived from measurements of seven different instruments. We also compare the tropospheric difference of SCDs (delta SCD) of HONO, namely the difference of the SCDs for the non-zenith observations and the zenith observation of the same elevation sequence. Different research groups analysed the spectra from their own instruments using their individual fit software. All the fit errors of HONO dSCDs from the instruments with cooled large-size detectors are mostly in the range of 0.1 to 0.3 × 1015 molecules cm−2 for an integration time of 1 min. The fit error for the mini MAX-DOAS is around 0.7 × 1015 molecules cm−2. Although the HONO delta SCDs are normally smaller than 6 × 1015 molecules cm−2, consistent time series of HONO delta SCDs are retrieved from the measurements of different instruments. Both fits with a sequential Fraunhofer reference spectrum (FRS) and a daily noon FRS lead to similar consistency. Apart from the mini-MAX-DOAS, the systematic absolute differences of HONO delta SCDs between the instruments are smaller than 0.63 × 1015 molecules cm−2. The correlation coefficients are higher than 0.7 and the slopes of linear regressions deviate from unity by less than 16 % for the elevation angle of 1°. The correlations decrease with an increase in elevation angle. All the participants also analysed synthetic spectra using the same baseline DOAS settings to evaluate the systematic errors of HONO results from their respective fit programs. In general the errors are smaller than 0.3 × 1015 molecules cm−2, which is about half of the systematic difference between the real measurements.The differences of HONO delta SCDs retrieved in the selected three spectral ranges 335–361, 335–373 and 335–390 nm are considerable (up to 0.57 × 1015 molecules cm−2) for both real measurements and synthetic spectra. We performed sensitivity studies to quantify the dominant systematic error sources and to find a recommended DOAS setting in the three spectral ranges. The results show that water vapour absorption, temperature and wavelength dependence of O4 absorption, temperature dependence of Ring spectrum, and polynomial and intensity offset correction all together dominate the systematic errors. We recommend a fit range of 335–373 nm for HONO retrievals. In such fit range the overall systematic uncertainty is about 0.87 × 1015 molecules cm−2, much smaller than those in the other two ranges. The typical random uncertainty is estimated to be about 0.16 × 1015 molecules cm−2, which is only 25 % of the total systematic uncertainty for most of the instruments in the MAD-CAT campaign. In summary for most of the MAX-DOAS instruments for elevation angle below 5°, half daytime measurements (usually in the morning) of HONO delta SCD can be over the detection limit of 0.2 × 1015 molecules cm−2 with an uncertainty of ∼ 0.9 × 1015 molecules cm−2.

Thermodynamic study of MgSO4 – H2O system dehydration at low pressure in view of heat storage

Study about magnesium sulfate – water vapor equilibrium proved to be very interesting especially on the use of dehydration-hydration reactions for the heat storage application in recent research. Heat is realized by hydration of lower hydrates as this reaction is exothermic. Therefore, reversible reaction, endothermic thermal dehydration of higher hydrates, is used for charging of system and in this state the energy can be stored over long time. Even if magnesium sulfate appears as promising candidate with high theoretical energy density of 2.8GJ/m−3, technological process is rather complicated. The main problem that thermodynamic and kinetic data are poorly understood to present. In these study salt hydrates equilibrium of magnesium sulfate was investigated by new approach. It makes possible to understand the dehydration reaction of MgSO4·6H2O for heat storage application. Dehydration reaction under various water vapor pressures and temperatures were investigated by thermogravimetric analysis. The result showed that water content in the solid phase is a function of temperature for given water vapor pressure. So, we can conclude that this magnesium sulfate – water vapor system is bivariant and some hydrates appear as the non-stoichiometric hydrates.

Detection of haze and its intensity based on visibility and relative humidity estimated from MODIS data

ABSTRACTOver recent years, air pollution has become a serious environmental problem with frequent occurrence of hazy days in many Chinese cities. In this study, a satellite-based method was developed to detect haze and its intensity for the Chinese city of Nanjing. This detection was based on the joint consideration of two indices, visibility, and relative humidity. They were determined from the Moderate Resolution Imaging Spectroradiometer-derived aerosol optical thickness, surface temperature, and precipitable water vapour data. Evaluated against the in situ measured results, haze and its intensity were found to be detected at a maximum accuracy of 81.7% and 60%, respectively. Of the two indices, visibility plays a more important role than relative humidity in affecting the detection accuracy. It is concluded that it is feasible to detect haze and its intensity from satellite data.

A numerical study of the convection triggering and propagation associated with sea breeze circulation over Hainan Island

AbstractBased on high‐resolution numerical simulations, the effects of sea breeze circulation (SBC) on associated convective initiation and propagation over Hainan Island are investigated. The results show that the blocking of synoptic wind on the windward side of the mountains inhibits the occurrence of windward‐side valley breeze and sea breeze. In the context of low mountains, weak synoptic wind not only favors the combination of the SBC with the valley breeze circulation on the leeward side of the mountains but also makes the convergence zone between the synoptic wind and the leeward‐side combined circulation stay near the tops of the mountains, leading to the accumulation of large quantities of water vapor taking place over the mountaintops. The combined effect of enhanced water vapor and high temperatures over the mountaintops can result in the generation of much larger convective available potential energy (CAPE) than the surrounding areas. The coupling of the large CAPE with the considerable converging ascending motion and abundant water vapor near the tops of the mountains promotes the occurrence of a strong convection band (CB) over the mountaintops. During the CB propagation under the steering of synoptic wind, the flow across the CB continuously and strongly opposes the SBC front and the fronts of the Kelvin‐Helmholtz billows behind, resulting in successive and strong lifting motion as well as large quantities of water vapor and high CAPE near these fronts. These lead to an apparent downstream wave‐like propagation of the CB.

Water vapor variation and the effect of aerosols in China

This study analyzes the annual and seasonal trends in precipitable water vapor (PWV) and surface temperature (Ts) over China from 1979 to 2015, and the relationships between PWV and Ts and between PWV and aerosol absorption optical depth (AAOD), using data from radiosonde stations, weather stations and multiple satellite observations. The results revealed a positive PWV trend between 1979 and 1999, and a negative PWV trend between 2000 and 2015. Analysis of the differences in the PWV trend among different stations types showed that the magnitude of the trends were in the order main urban stations > provincial capital stations > suburb stations, suggesting that anthropogenic activities have a strong influence on the PWV trend. The AAOD exhibited a significant positive trend in most regions of China from 2005 to 2015 (confidence level 95%). Using spatial correlation analysis, we showed that PWV trend derived from Moderate Resolution Imaging Spectroradiometer (MODIS) satellite observations is correlated with Ts, with an annual correlation coefficient of 0.596. In addition, the spatial correlation between PWV and AAOD showed a negative relationship, with the highest correlation coefficients of −0.76 and −0.71 observed in mid-eastern China and central northwest China, respectively, suggesting that the increase in AAOD in recent years may be one of the reasons for the decrease in PWV since the 2000s in China.

Detection of Tropical Overshooting Cloud Tops Using Himawari-8 Imagery

Abstract: Overshooting convective cloud Top (OT)-accompanied clouds can cause severe weather conditions, such as lightning, strong winds, and heavy rainfall. The distribution and behavior of OTs can affect regional and global climate systems. In this paper, we propose a new approach for OT detection by using machine learning methods with multiple infrared images and their derived features. Himawari-8 satellite images were used as the main input data, and binary detection (OT or nonOT) with class probability was the output of the machine learning models. Three machine learning techniques—random forest (RF), extremely randomized trees (ERT), and logistic regression (LR)—were used to develop OT classification models to distinguish OT from non-OT. The hindcast validation over the Southeast Asia and West Pacific regions showed that RF performed best, resulting in a mean probabilities of detection (POD) of 77.06% and a mean false alarm ratio (FAR) of 36.13%. Brightness temperature at 11.2 μm (Tb11) and its standard deviation (STD) in a 3 × 3 window size were identified as the most contributing variables for discriminating OT and nonOT classes. The proposed machine learning-based OT detection algorithms produced promising results comparable to or even better than the existing approaches, which are the infrared window (IRW)-texture and water vapor (WV) minus IRW brightness temperature difference (BTD) methods.

Degradation of SOFCs by Various Impurities: Impedance Spectroscopy and Microstructural Analysis

Introduction SOFC is considered as a promising power generation system due to high electric efficiency and fuel flexibility. However, coal gas, for example, contains various impurities. In this study, siloxane, poisoning effect of siloxane to Ni-ScSZ cermet anodes is analyzed by applying Electrochemical Impedance Spectroscopy (EIS). Spectroscopy data are analyzed by the distribution of relaxation times (DRT) method[1] to investigate details of electrode resistance. Furthermore, microstructural analysis was made by electron microscopy. Experimental Electrolyte-supported cells with ScSZ (10 mol% Sc2O3 - 1 mol% CeO2-89 mol% ZrO2) plate (20 mmφ×0.2 mmt) were used in this study. Mixture of 56 wt.% NiO and 44 wt.% ScSZ was used for the anode and was sintered at 1300 oC for 3 h. Mixture of (La0.8Sr0.2)0.98MnO3 (LSM) and ScSZ with a weight ratio of 1:1 was used for the cathode. Electrode area was 8×8 mm2 and Pt mesh was used as the current collector. Figures 1 and 2 describe the experimental setup. Siloxane (decamethylcyclopentasiloxane) was supplied to the fuel cell using the bubbler setup. The fuel consisted of 97% H2 and 3% H2O. Cell temperature was 800oC. Table 1 shows the EIS conditions. EIS data analyzed by DRT enable the identification of electrode processes. FESEM-EDX was applied to investigate changes in the anode microstructure and composition after the cell performance tests. Results and discussion Figure 3 shows EIS spectra measured after 0h and 100h. Figure 4 shows the DRT result of the Fig. 3 data. Impedance semicircles, especially at the lower frequency, DRT peaks became larger with time. The DRT peak with relaxation time around 102~103 sec at 0h became wider, but the DRT peak around the 10-1~100 sec did not change. DRT peak around 10-1~100 sec may originate from the diffusion of H2 gas, that around 102~103 sec for charge transfer reaction and ionic transport[2][3]. Figure 5 shows EDX mapping of zirconium, silicon and oxygen. Ni particle on the anode surface is covered by silica. This reaction is considered as [4]: [(CH3)2SiO]5+25H2O→5Si(OH)4(g)+10CO+30H2 (1)Si(OH)4(g)→SiO2(s)+2H2O(2) Silica was formed under SOFC operating conditions at high temperature and high water vapour partial pressure. Therefore, cell performance degraded by inhibiting gas diffusion and covering by Ni particles with silica in the siloxane poisoning of Ni-based anodes.

Enhancing Anodic Catalytic Activity at High Fuel Utilization By Infiltration of Ni Nanoparticles

The performance of SOFCs degrades with increasing fuel utilization, since the fuel oxidation reaction faces increased competition for the three-phase-boundary (TPB) sites in the anode from adsorbed water vapor species. Introduction of addition TPB sites by infiltration of Ni nanoparticles into the anode is an effective way to alleviate this problem. Both liquid and vapor phase infiltration of Ni nanoparticles into commercially available Ni/YSZ cermet anodes have been explored. The microstructure of the anode has been examined by µ-CT and FIB/SEM 3-D reconstructions. The cells have been electrochemically characterized by I-V and EIS techniques in a temperature range of 600°C-800°C. The infiltrated Ni nanoparticles have been characterized by image analysis of SEM micrographs from fracture cross-sections, before and after electrochemical testing. The effect of the nanoparticles on cell electrochemical performance as a function of temperature and anode input water vapor content, the stability of the nanoparticles, as well as the thermodynamics of vapor phase infiltration of Ni will be presented.

Long‐term trends in precipitation and precipitation extremes and underlying mechanisms in the U.S. Great Basin during 1951–2013

AbstractUsing daily precipitation records from 151 stations, the Mann‐Kendall nonparametric test, and the rotated empirical orthogonal function, this study examined trends in precipitation and precipitation extremes and underlying mechanisms in the U.S. Great Basin during 1951–2013. The results indicate that annual total precipitation, 1 day and 5 day maximum precipitation, extreme precipitation days over the 95th and 99th percentiles trended upward during 1951–2013. Spatially, stations experienced significant positive trends in six indices are mostly distributed in the eastern basin, while those experienced significant negative trends are a few and situated in the western basin. Four distinct modes characterized by different patterns of annual precipitation variations were identified. They are the northeastern, southern, midwestern, and midnorthern modes. In addition, we found that the effects of El Niño–Southern Oscillation and Pacific Decadal Oscillation on precipitation was low in the basin. The intensifying high‐pressure system over the western North Pacific in winter and the increasing water vapor and air temperature of the atmosphere over the basin in winter and spring were mainly responsible for the upward trends in six indices during 1951–2013. Nevertheless, the topography regulates the effects of synoptic conditions on precipitation, contributing to the “east‐west” contrast in station distribution between those experienced negative and positive trends. Overall, precipitation and precipitation extremes increased significantly in the eastern and northern basin while increases were not significant in the western and southern basin. This information has important implications for not only predicting future precipitation changes but also mitigating precipitation‐change‐associated risks on ecosystems and human society in the Great Basin.

Water vapor electron scattering cross-section measurements using a hydrophobic ionic liquid

The interface of ionic liquid (IL) 1-ethyl-3-methylimidazolium-bis-(trifluoromethylsulfonyl)-imide, [EMIM][Tf2N], was examined in the presence of water vapor using lab-based ambient pressure X-ray photoelectron spectroscopy (APXPS) with a monochromatic Al Kα X-ray source. Room temperature water vapor exposures to [EMIM][Tf2N] ranged from 10−6 to 2.0Torr with no evidence of water uptake at the IL-vapor interface. The hydrophobic nature of [EMIM][Tf2N] allowed for measuring the attenuation of F 1s, O 1s, N 1s, C 1s and S 2p APXPS peaks as a function of pressure, allowing for the determination of the electron scattering cross-section (σe) of gas phase water. The elemental diversity of [EMIM][Tf2N] allowed for the extraction of σe over a 520eV kinetic energy range in the absence of a variable energy X-ray source. Herein we show that lab-based APXPS in combination with an elementally diverse, unreactive substrate is an effective tool for the determination of electron scattering cross sections for gas phase species.

Measuring Water Vapor and Ash in Volcanic Eruptions With a Millimeter-Wave Radar/Imager

Millimeter-wave remote sensing technology can significantly improve measurements of volcanic eruptions, yielding new insights into eruption processes and improving forecasts of drifting volcanic ash for aviation safety. Radiometers can measure water vapor density and temperature inside eruption clouds, improving on existing measurements with infrared cameras that are limited to measuring the outer cloud surface. Millimeter-wave radar can measure the 3D mass distribution of volcanic ash inside eruption plumes and their nearby drifting ash clouds. Millimeter wavelengths are better matched to typical ash particle sizes, offering better sensitivity than longer wavelength existing weather radar measurements, as well as the unique ability to directly measure ash particle size in-situ. Here we present sensitivity calculations in the context of developing the WAMS (Water and Ash Millimeter-wave Spectrometer) instrument. WAMS, a radar/radiometer system designed to use off-the-shelf components, would be able to measure water vapor and ash throughout an entire eruption cloud, a unique capability.