Journal articles on the topic 'Water Vapor Enhancement Factor'
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Sairanen, H. A., and M. O. Heinonen. "Enhancement Factor for Water Vapor–Pressure Correction in Humid Methane." International Journal of Thermophysics 35, no. 6-7 (July 2014): 1280–89. http://dx.doi.org/10.1007/s10765-014-1720-3.
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Vejmelková, Eva, Monika Čáchová, Dana Koňáková, Pavel Reiterman, and Robert Černý. "Lime Plasters Containing Waste Ceramic Powder as Partial Replacement of Siliceous Aggregates." Advanced Materials Research 1035 (October 2014): 77–82. http://dx.doi.org/10.4028/www.scientific.net/amr.1035.77.
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Waste materials are utilized with an increasing frequency in the building industry, during the last decades. The motivation is both environmental and economical. In this paper, waste ceramic powder produced at the grinding of hollow brick blocks used in precise-walling technologies, is applied as a partial replacement of siliceous aggregates of lime plasters. The designed plaster mixes are analyzed from the point of view of their basic physical, mechanical, hygric and thermal properties. The bulk density, matrix density, open porosity, compressive strength, bending strength, water vapor diffusion permeability, water vapor diffusion coefficient, water vapor diffusion resistance factor, thermal conductivity and specific heat capacity are the investigated parameters. A reference lime plaster is analyzed as well, for the sake of comparison. Experimental results show a remarkable enhancement of mechanical properties of the plasters with the increasing dosage of ceramic powder. Moreover, the thermal insulation properties are improved and the water vapor diffusion capability of the plasters with ceramic powder increases.
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Davis, Sean M., A. Gannet Hallar, Linnea M. Avallone, and William Engblom. "Measurement of Total Water with a Tunable Diode Laser Hygrometer: Inlet Analysis, Calibration Procedure, and Ice Water Content Determination." Journal of Atmospheric and Oceanic Technology 24, no. 3 (March 1, 2007): 463–75. http://dx.doi.org/10.1175/jtech1975.1.
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Abstract The University of Colorado closed-path tunable diode laser hygrometer (CLH), a new instrument for the in situ measurement of enhanced total water (eTW, the sum of water vapor and condensed water enhanced by a subisokinetic inlet), has recently been flown aboard the NASA DC-8 and WB-57F aircrafts. The CLH has the sensitivity necessary to quantify the ice water content (IWC) of extremely thin subvisual cirrus clouds (∼0.1 mg m−3), while still providing measurements over a large range of conditions typical of upper-tropospheric cirrus (up to 1 g m−3). A key feature of the CLH is its subisokinetic inlet system, which is described in detail in this paper. The enhancement and evaporation of ice particles that results from the heated subisokinetic inlet is described both analytically and based on computational fluid dynamical simulations of the flow around the aircraft. Laboratory mixtures of water vapor with an accuracy of 2%–10% (2σ) were used to calibrate the CLH over a wide range of water vapor mixing ratios (∼50–50 000 ppm) and pressures (∼100–1000 mb). The water vapor retrieval algorithm, which is based on the CLH instrument properties as well as on the spectroscopic properties of the water absorption line, accurately fits the calibration data to within the uncertainty of the calibration mixtures and instrument signal-to-noise ratio. A method for calculating cirrus IWC from the CLH enhanced total water measurement is presented. In this method, the particle enhancement factor is determined from an independent particle size distribution measurement and the size-dependent CLH inlet efficiency. It is shown that despite the potentially large uncertainty in particle size measurements, the error introduced by this method adds ∼5% error to the IWC calculation. IWC accuracy ranges from 20% at the largest IWC to 50% at small IWC (<5 mg m−3).
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Lu, S., T. Ren, Z. Yu, and R. Horton. "A method to estimate the water vapour enhancement factor in soil." European Journal of Soil Science 62, no. 4 (April 4, 2011): 498–504. http://dx.doi.org/10.1111/j.1365-2389.2011.01359.x.
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Mishra, Abhishek Kumar, and Vikas Mishra. "The Variation of Factor of Enhancement in Nucleation Rate with Electric Field for Water Vapour and Ice." International Journal of Engineering and Advanced Technology 10, no. 2 (December 30, 2020): 221–23. http://dx.doi.org/10.35940/ijeat.b2096.1210220.
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the nucleation rate is the parameter to judge the effect of electric field on nucleation of water vapour and ice glaciation. In the presence of electric field the total nucleation is the sum of nucleation due to electric field and nucleation due to diffusion of water molecules. Thus we can say the nucleation rate is enhanced by the factor of RE. This is known as factor of enhancement in nucleation rate. In the present work we will calculate the factor of enhancement in nucleation rate for water vapour and ice on temperature 268 K at different electric fields as a function of super saturation ratio.
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Gran, M., J. Carrera, S. Olivella, and M. W. Saaltink. "Modeling evaporation processes in a saline soil from saturation to oven dry conditions." Hydrology and Earth System Sciences 15, no. 7 (July 4, 2011): 2077–89. http://dx.doi.org/10.5194/hess-15-2077-2011.
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Abstract. Thermal, suction and osmotic gradients interact during evaporation from a salty soil. Vapor fluxes become the main water flow mechanism under very dry conditions. A coupled nonisothermal multiphase flow and reactive transport model was developed to study mass and energy transfer mechanisms during an evaporation experiment from a sand column. Very dry and hot conditions, including the formation of a salt crust, necessitate the modification of the retention curve to represent oven dry conditions. Experimental observations (volumetric water content, temperature and concentration profiles) were satisfactorily reproduced using mostly independently measured parameters, which suggests that the model can be used to assess the underlying processes. Results show that evaporation concentrates at a very narrow front and is controlled by heat flow, and limited by salinity and liquid and vapor fluxes. The front divides the soil into a dry and saline portion above and a moist and diluted portion below. Vapor diffusses not only upwards but also downwards from the evaporation front, as dictated by temperature gradients. Condensation of this downward flux causes dilution, so that salt concentration is minimum and lower than the initial one, just beneath the evaporation front. While this result is consistent with observations, it required adopting a vapor diffusion enhancement factor of 8.
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Wang, Zhangxin, Thomas Horseman, Anthony P. Straub, Ngai Yin Yip, Deyu Li, Menachem Elimelech, and Shihong Lin. "Pathways and challenges for efficient solar-thermal desalination." Science Advances 5, no. 7 (July 2019): eaax0763. http://dx.doi.org/10.1126/sciadv.aax0763.
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Solar-thermal desalination (STD) is a potentially low-cost, sustainable approach for providing high-quality fresh water in the absence of water and energy infrastructures. Despite recent efforts to advance STD by improving heat-absorbing materials and system designs, the best strategies for maximizing STD performance remain uncertain. To address this problem, we identify three major steps in distillation-based STD: (i) light-to-heat energy conversion, (ii) thermal vapor generation, and (iii) conversion of vapor to water via condensation. Using specific water productivity as a quantitative metric for energy efficiency, we show that efficient recovery of the latent heat of condensation is critical for STD performance enhancement, because solar vapor generation has already been pushed toward its performance limit. We also demonstrate that STD cannot compete with photovoltaic reverse osmosis desalination in energy efficiency. We conclude by emphasizing the importance of factors other than energy efficiency, including cost, ease of maintenance, and applicability to hypersaline waters.
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Khalifa, Atia E. "Performances of air gap and water gap MD desalination modules." Water Practice and Technology 13, no. 1 (March 1, 2018): 200–209. http://dx.doi.org/10.2166/wpt.2018.034.
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Abstract Membrane distillation (MD) is a promising thermally-driven membrane separation technology for water desalination. In MD, water vapor is being separated from the hot feed water solution using a micro-porous hydrophobic membrane, due to the difference in vapor pressures across the membrane. In the present work, experiments are conducted to compare the performance of water gap membrane distillation (WGMD) and air gap membrane distillation (AGMD) modules under the main operating and design conditions including the feed and coolant temperatures, membrane material and pore sizes, and the gap width. Results showed that the WGMD module produced higher fluxes as compared to the AGMD module, for all test conditions. The feed temperature is the dominant factor affecting the system flux. The permeate flux increases with reducing the gap width for both water and air gap modules. However, WGMD module was found to be less sensitive to the change in the gap width compared to the AGMD module. The PTFE membrane produced higher permeate flux as compared to the PVDF membrane. Bigger mean pore diameter enhanced the permeate flux, however, this enhancement is marginal at high feed temperatures. With increasing the feed temperature, the GOR values increase and the specific energy consumption decreases.
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Hao, Jiawei, and Er Lu. "Variation of Relative Humidity as Seen through Linking Water Vapor to Air Temperature: An Assessment of Interannual Variations in the Near-Surface Atmosphere." Atmosphere 13, no. 8 (July 24, 2022): 1171. http://dx.doi.org/10.3390/atmos13081171.
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It has generally been regarded that, in the warming climate, atmospheric water vapor may increase due to the enhancement in surface evaporation, which is expected from the Clausius–Clapeyron (C–C) equation, along with the assumption that relative humidity experiences small changes. If the variation in relative humidity is small, the response of water vapor to temperature will be closely in line with the C–C equation. However, whether relative humidity experiences large or small changes needs be assessed, and the change of relative humidity should be compared with the change in surface–air temperature. In this study, we link surface vapor pressure, which characterizes atmospheric water vapor, to surface-air temperature, and treat both the temperature and relative humidity as influencing factors. A method based on linear regression is applied to compare the interannual variabilities of relative humidity and temperature in the interannual variation in surface vapor pressure. Whether the year-to-year perturbation of relative humidity is important, compared with the perturbation in surface-air temperature, is explored Results show that, at high latitudes of both hemispheres, the variation in vapor pressure is dominated by air temperature, and relative humidity has small positive contributions. Thus, the variation in relative humidity over these regions is comparably small, and the response of water vapor to temperature can well follow the C–C equation. Differently, at mid-low latitudes, especially on land, air temperature plays a negative role in the variation in vapor pressure. Relative humidity offsets the negative contribution and dominates the variation in vapor pressure, suggesting that the variation in the relative humidity over these regions is comparably large. Hence, the response of water vapor to temperature deviate from the C–C equation. Analysis indicates that the different results of the dominance from the two influencing factors are affected by the dual effects of precipitation or wet-air transport over land. Both precipitation and the transport of cold wet air could break the C–C relation between water vapor pressure and temperature.
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Goh, Eng Giap, and Kosuke Noborio. "An Improved Heat Flux Theory and Mathematical Equation to Estimate Water Vapor Advection as an Alternative to Mechanistic Enhancement Factor." Transport in Porous Media 111, no. 2 (November 6, 2015): 331–46. http://dx.doi.org/10.1007/s11242-015-0596-4.
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Rousseau, Roman, Diba Ayache, Nicolas Maurin, Wioletta Trzpil, Michael Bahriz, and Aurore Vicet. "Monolithic Double Resonator for Quartz Enhanced Photoacoustic Spectroscopy." Applied Sciences 11, no. 5 (February 26, 2021): 2094. http://dx.doi.org/10.3390/app11052094.
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A new approach for Quartz Enhanced Photoacoustic Spectroscopy is presented, based on an acoustic excitation from the outside of the prongs of a quartz tuning fork, to increase the sensitivity of the sensor. For this purpose, we introduce a monolithic acoustic double-resonator (double-mR) in a T-shape configuration, using 3D printing. It was modelized and experimentally characterized using a 1392 nm distributed feedback laser diode, targeting a water vapor absorption line. The setup showed a two-factor enhancement of the signal, compared to a classical off-beam QEPAS approach and confirmed the strong interest of photolithographic printing techniques for acoustic developments.
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Čáchová, Monika, Dana Koňáková, Eva Vejmelková, Martin Keppert, Kirill Polozhiy, and Robert Černý. "Heat and Water Vapor Transport Properties of Selected Commercially Produced Plasters." Advanced Materials Research 982 (July 2014): 90–93. http://dx.doi.org/10.4028/www.scientific.net/amr.982.90.
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Although plaster belonged to the first structural materials, they are still getting further enhancements. Nowadays different companies are producing and selling plasters that differ either in their composition or purpose. This article is comparing plasters presented on the market in the Czech Republic. Those are lightweight, renovation and even most common lime-cement plasters. Among the studied characteristics were: basic physical properties (for comparison were measurement of two methods: vacuum water saturation and helium pycnometry); they water vapor transport parameters and heat transport parameters. Lightweight and renovation plasters had shown the biggest porosity, lowest thermal conductivity and the highest diffusion resistance factor.
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Vane, Leland M., Franklin R. Alvarez, Anurag P. Mairal, and Richard W. Baker. "Separation of Vapor-Phase Alcohol/Water Mixtures via Fractional Condensation Using a Pilot-Scale Dephlegmator: Enhancement of the Pervaporation Process Separation Factor." Industrial & Engineering Chemistry Research 43, no. 1 (January 2004): 173–83. http://dx.doi.org/10.1021/ie0305667.
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Goh, Eng Giap, and Kosuke Noborio. "Erratum to: An Improved Heat Flux Theory and Mathematical Equation to Estimate Water Vapor Advection as an Alternative to Mechanistic Enhancement Factor." Transport in Porous Media 112, no. 2 (February 27, 2016): 545–47. http://dx.doi.org/10.1007/s11242-016-0655-5.
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Lovell-Smith, Jeremy. "An expression for the uncertainty in the water vapour pressure enhancement factor for moist air." Metrologia 44, no. 6 (October 11, 2007): L49—L52. http://dx.doi.org/10.1088/0026-1394/44/6/n01.
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Ren, Yu, Haipeng Yu, Chenxi Liu, Yongli He, Jianping Huang, Lixia Zhang, Huancui Hu, et al. "Attribution of Dry and Wet Climatic Changes over Central Asia." Journal of Climate 35, no. 5 (March 1, 2022): 1399–421. http://dx.doi.org/10.1175/jcli-d-21-0329.1.
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Abstract Central Asia (CA; 35°–55°N, 55°–90°E) has been experiencing a significant warming trend during the past five decades, which has been accompanied by intensified local hydrological changes. Accurate identification of variations in hydroclimatic conditions and understanding the driving mechanisms are of great importance for water resource management. Here, we attempted to quantify dry/wet variations by using precipitation minus evapotranspiration (P − E) and attributed the variations based on the atmosphere and surface water balances. Our results indicated that the dry season became drier while the wet season became wetter in CA for 1982–2019. The land surface water budget revealed precipitation (96.84%) and vapor pressure deficit (2.26%) as the primary contributing factors for the wet season. For the dry season, precipitation (95.43%), net radiation (3.51%), and vapor pressure deficit (−2.64%) were dominant factors. From the perspective of the atmospheric water budget, net inflow moisture flux was enhanced by a rate of 72.85 kg m−1 s−1 in the wet season, which was mainly transported from midwestern Eurasia. The increase in precipitation induced by the external cycle was 11.93 mm (6 months)−1. In contrast, the drying trend during the dry season was measured by a decrease in the net inflow moisture flux (74.41 kg m−1 s−1) and reduced external moisture from midwestern Eurasia. An increase in precipitation during the dry season can be attributed to an enhancement in local evapotranspiration, accompanied by a 4.69% increase in the recycling ratio. The compounding enhancements between wet and dry seasons ultimately contribute to an increasing frequency of both droughts and floods.
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Chae, Sanghee, Ki-Ho Chang, Seongkyu Seo, Jin-Yim Jeong, Baek-Jo Kim, Chang Ki Kim, Seong Soo Yum, and Jinwon Kim. "Numerical Simulations of Airborne Glaciogenic Cloud Seeding Using the WRF Model with the Modified Morrison Scheme over the Pyeongchang Region in the Winter of 2016." Advances in Meteorology 2018 (2018): 1–15. http://dx.doi.org/10.1155/2018/8453460.
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A model was developed for simulating the effects of airborne silver iodide (AgI) glaciogenic cloud seeding using the weather research and forecasting (WRF) model with a modified Morrison cloud microphysics scheme. This model was used to hindcast the weather conditions and effects of seeding for three airborne seeding experiments conducted in 2016. The spatial patterns of the simulated precipitation and liquid water path (LWP) qualitatively agreed with the observations. Considering the observed wind fields during the seeding, the simulated spatiotemporal distributions of the seeding materials, AgI, and snowfall enhancements were found to be reasonable. In the enhanced snowfall cases, the process by which cloud water and vapor were converted into ice particles after seeding was also reasonable. It was also noted that the AgI residence time (>1 hr) above the optimum AgI concentration (105 m−3) and high LWP (>100 g m−2) were important factors for snowfall enhancements. In the first experiment, timing of the simulated snowfall enhancement agreed with the observations, which supports the notion that the seeding of AgI resulted in enhanced snowfall in the experiment. The model developed in this study will be useful for verifying the effects of cloud seeding on precipitation.
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Chen, Jun, Zhanqing Li, Min Lv, Yuying Wang, Wei Wang, Yingjie Zhang, Haofei Wang, Xing Yan, Yele Sun, and Maureen Cribb. "Aerosol hygroscopic growth, contributing factors, and impact on haze events in a severely polluted region in northern China." Atmospheric Chemistry and Physics 19, no. 2 (January 31, 2019): 1327–42. http://dx.doi.org/10.5194/acp-19-1327-2019.
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Abstract. This study investigates the impact of the aerosol hygroscopic growth effect on haze events in Xingtai, a heavily polluted city in the central part of the North China Plain (NCP), using a large array of instruments measuring aerosol optical, physical, and chemical properties. Key instruments used and measurements made include the Raman lidar for atmospheric water vapor content and aerosol optical profiles, the PC-3016A GrayWolf six-channel handheld particle and mass meter for atmospheric total particulate matter (PM) that has diameters less than 1 and 2.5 µm (PM1 and PM2.5, respectively), the aerosol chemical speciation monitor (ACSM) for chemical components in PM1, and the hygroscopic tandem differential mobility analyzer (H-TDMA) for aerosol hygroscopicity. The changes in PM1 and PM2.5 agreed well with that of the water vapor content due to the aerosol hygroscopic growth effect. Two cases were selected to further analyze the effects of aerosol hygroscopic growth on haze events. The lidar-estimated hygroscopic enhancement factor for the aerosol backscattering coefficient during a relatively clean period (Case I) was lower than that during a pollution event (Case II) with similar relative humidity (RH) levels of 80 %–91 %. The Kasten model was used to fit the aerosol optical hygroscopic growth factor (GF) whose parameter b differed considerably between the two cases, i.e., 0.1000 (Case I) versus 0.9346 (Case II). The aerosol acidity value calculated from ACSM data for Case I (1.35) was less than that for Case II (1.50) due to different amounts of inorganics such as NH4NO3, NH4HSO4, and (NH4)2SO4. Model results based on H-TDMA data showed that aerosol hygroscopic growth factors in each size category (40, 80, 110, 150, and 200 nm) at different RH levels (80 %–91 %) for Case I were lower than those for Case II. For similar ambient RH levels, the high content of nitrate facilitates the hygroscopic growth of aerosols, which may be a major factor contributing to heavy haze episodes in Xingtai.
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Wu, Jiarui, Naifang Bei, Bo Hu, Suixin Liu, Meng Zhou, Qiyuan Wang, Xia Li, et al. "Is water vapor a key player of the wintertime haze in North China Plain?" Atmospheric Chemistry and Physics 19, no. 13 (July 10, 2019): 8721–39. http://dx.doi.org/10.5194/acp-19-8721-2019.
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Abstract. Water vapor has been proposed to amplify the severe haze pollution in China by enhancing the aerosol–radiation feedback (ARF). Observations have revealed that the near-surface PM2.5 concentrations ([PM2.5]) generally exhibit an increasing trend with relative humidity (RH) in the North China Plain (NCP) during 2015 wintertime, indicating that the aerosol liquid water (ALW) caused by hygroscopic growth could play an important role in the PM2.5 formation and accumulation. Simulations during a persistent and heavy haze pollution episode from 5 December 2015 to 4 January 2016 in the NCP were conducted using the WRF-Chem Model to comprehensively quantify contributions of the ALW effect to near-surface [PM2.5]. The WRF-Chem Model generally performs reasonably well in simulating the temporal variations in RH against measurements in the NCP. The factor separation approach (FSA) was used to evaluate the contribution of the ALW effect on the ARF, photochemistry, and heterogeneous reactions to [PM2.5]. The ALW not only augments particle sizes to enhance aerosol backward scattering but also increases the effective radius to favor aerosol forward scattering. The contribution of the ALW effect on the ARF and photochemistry to near-surface [PM2.5] is not significant, being generally within 1.0 µg m−3 on average in the NCP during the episode. Serving as an excellent substrate for heterogeneous reactions, the ALW substantially enhances the secondary aerosol (SA) formation, with an average contribution of 71 %, 10 %, 26 %, and 48 % to near-surface sulfate, nitrate, ammonium, and secondary organic aerosol concentrations. Nevertheless, the SA enhancement due to the ALW decreases the aerosol optical depth and increases the effective radius to weaken the ARF, reducing near-surface primary aerosols. The contribution of the ALW total effect to near-surface [PM2.5] is 17.5 % on average, which is overwhelmingly dominated by enhanced SA. Model sensitivities also show that when the RH is less than 80 %, the ALW progressively increases near-surface [PM2.5] but commences to decrease when the RH exceeds 80 % due to the high occurrence frequencies of precipitation.
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Kim, Jaeyun, Jae Gyu Jang, Jeonghun Kwak, Jong-In Hong, and Sung Hyun Kim. "Enhanced Humid Reliability of Organic Thermoelectrics via Crosslinking with Glycerol." Nanomaterials 9, no. 11 (November 9, 2019): 1591. http://dx.doi.org/10.3390/nano9111591.
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Poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS) has shown significant achievements in organic thermoelectrics (TEs) as an alternative for inorganic counterparts. However, PEDOT:PSS films have limited practical applications because their performance is sensitive to humidity. Crosslinking additives are utilized to improve the reliability of PEDOT:PSS film through enhancing hydrophobicity; among these, polyethylene glycol (PEG) is a widely-used additive. However, ether groups in PEG induce water molecules in the film through the hydrogen bond, which deteriorates the TE reliability. Here, we enhance the TE reliability of the PEDOT:PSS film using glycerol as an additive through the crosslinking reaction between the hydroxyl group in glycerol and the sulfonic acid in PEDOT:PSS. The TE reliability (1/Power factor (PF)) of PEG solution-treated PEDOT:PSS film (PEG solution-treated film) was 57% of its initial absolute value (0 h), after 288 h (two weeks) in a humid environment (95% relative humidity, 27 °C temperature). On the other hand, the glycerol solution-treated PEDOT:PSS film (glycerol solution-treated film) exhibited superior TE reliability and preserved 75% of its initial 1/PF. Furthermore, glycerol vapor treatment enabled the film to have stronger TE humid reliability, maintaining 82% of its initial 1/PF, with the same condition. This enhancement is attributed to the increased hydrophobicity and lower oxygen content of the glycerol vapor-treated PEDOT:PSS film (glycerol vapor-treated film), which provides little change in the chemical composition of PEDOT:PSS.
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Wang, Kaimin, Chunxiang Cao, Bo Xie, Min Xu, Xinwei Yang, Heyi Guo, and Robert Shea Duerler. "Analysis of the Spatial and Temporal Evolution Patterns of Grassland Health and Its Driving Factors in Xilingol." Remote Sensing 14, no. 20 (October 17, 2022): 5179. http://dx.doi.org/10.3390/rs14205179.
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The combination of natural environment changes and human activities affects the growth of grasslands. In order to quantitatively assess the causes of spatial and temporal variation of grasslands in Xilingol, this study assessed the spatial and temporal evolution patterns of grassland health based on MOD13A1 long time series Normalized Difference Vegetation Index (NDVI) data from 2000–2019 using trend analysis. The geodetector model was used to explore the dominant drivers of spatial variation in grassland NDVI, combined with 34 factors covering natural environmental changes and human disturbances over the same period. The results show that the grasslands of Xilingol showed an overall recovery trend from 2000 to 2019, with an average annual NDVI growth rate of 0.0028/a, a monthly increasing rate of 0.0005/month, and 68.06% of the grassland at an average recovery level. Moisture-dominated natural climate change factors, such as Growing Season Precipitation (Prep2), Annual Mean Water Vapor Pressure (WVP), and Annual Mean Relative Humidity (RH), were the underlying cause of grassland health changes during the study period, with the highest explanatory factor being growing season precipitation (q value of 0.59 on a multi-year average). The influence of primary production value among human activities was greater, and the explanatory factor of tertiary production value showed an increasing trend. The interactions among natural and anthropogenic factors significantly enhances their explanatory credibility for NDVI, with the type of interaction dominated by the two-factor enhancement. Risk detection of the top 10 dominant drivers in terms of q statistic were carried out to obtain the threshold range of each driver in the high zone of grassland NDVI, which can provide a scientific reference for the sustainable restoration of grassland.
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Huning, Laurie S., and Steven A. Margulis. "Investigating the Variability of High-Elevation Seasonal Orographic Snowfall Enhancement and Its Drivers across Sierra Nevada, California." Journal of Hydrometeorology 19, no. 1 (January 1, 2018): 47–67. http://dx.doi.org/10.1175/jhm-d-16-0254.1.
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Abstract While orographically driven snowfall is known to be important in mountainous regions, a complete understanding of orographic enhancement from the basin to the mountain range scale is often inhibited by limited distributed data and spatial and/or temporal resolutions. A novel, 90-m spatially distributed snow water equivalent (SWE) reanalysis was used to overcome these limitations. Leveraging this SWE information, the interannual variability of orographic gradients in cumulative snowfall (CS) was investigated over 14 windward (western) basins in the Sierra Nevada in California from water years 1985 to 2015. Previous studies have not provided a detailed multidecadal climatology of orographic CS gradients or compared wet-year and dry-year orographic CS patterns, distributions, and gradients across an entire mountain range. The magnitude of seasonal CS gradients range from over 15 cm SWE per 100-m elevation to under 1 cm per 100 m with a 31-yr average of 6.1 cm per 100 m below ~2500 m in the western basins. The 31-yr average CS gradients generally decrease in higher elevation zones across the western basins and become negative at the highest elevations. On average, integrated vapor transport and zonal winds at 700 hPa are larger during wet years, leading to higher orographically driven CS gradients across the Sierra Nevada than in dry years. Below ~2500 m, wet years yield greater enhancement (relative to dry years) by factors of approximately 2 and 3 in the northwestern and southwestern basins, respectively. Overall, the western Sierra Nevada experiences about twice as much orographic enhancement during wet years as in dry years below the elevation corresponding to the 31-yr average maximum CS.
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Hayashida, S., X. Liu, A. Ono, K. Yang, and K. Chance. "Observation of ozone enhancement in the lower troposphere over East Asia from a space-borne ultraviolet spectrometer." Atmospheric Chemistry and Physics Discussions 15, no. 2 (January 22, 2015): 2013–54. http://dx.doi.org/10.5194/acpd-15-2013-2015.
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Abstract. We report observations from space using ultraviolet (UV) radiance for significant enhancement of ozone in the lower troposphere over Central and Eastern China (CEC). The recent retrieval products of the Ozone Monitoring Instrument (OMI) onboard the Earth Observing System (EOS)/Aura satellite revealed the spatial and temporal variation of ozone distributions in multiple layers in the troposphere. We compared the OMI-derived ozone over Beijing with airborne measurements by the Measurement of Ozone and Water Vapor by Airbus In-Service Aircraft (MOZAIC) program. The correlation between OMI and MOZAIC ozone in the lower troposphere was reasonable, which assured the reliability of OMI ozone retrievals in the lower troposphere under enhanced ozone conditions. The ozone enhancement was clearly observed over CEC, with Shandong Province as its center, and most notable in June in any given year. Similar seasonal variations were observed throughout the nine-year OMI measurement period of 2005 to 2013. The ozone enhancement in June was associated with the enhancement of carbon monoxide (CO) and hotspots, which is consistent with previous studies of in-situ measurements such those made by the MTX2006 campaign. A considerable part of this ozone enhancement could be attributed to the emissions of ozone precursors from open crop residue burning (OCRB) after the winter wheat harvest, in addition to emissions from industrial activities and automobiles. The ozone distribution presented in this study is also consistent with some model studies that apply emissions from OCRB. The lower tropospheric ozone distribution is first shown from OMI retrieval in this study, and the results will be useful in clarifying any unknown factors that influence ozone distribution by comparison with model simulations.
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Hayashida, S., X. Liu, A. Ono, K. Yang, and K. Chance. "Observation of ozone enhancement in the lower troposphere over East Asia from a space-borne ultraviolet spectrometer." Atmospheric Chemistry and Physics 15, no. 17 (September 2, 2015): 9865–81. http://dx.doi.org/10.5194/acp-15-9865-2015.
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Abstract. We report observations from space using ultraviolet (UV) radiance for significant enhancement of ozone in the lower troposphere over central and eastern China (CEC). The recent retrieval products of the Ozone Monitoring Instrument (OMI) onboard the Earth Observing System (EOS) Aura satellite revealed the spatial and temporal variation of ozone distributions in multiple layers in the troposphere. We compared the OMI-derived ozone over Beijing with airborne measurements by the Measurement of Ozone and Water Vapor by Airbus In-Service Aircraft (MOZAIC) program. The correlation between OMI and MOZAIC ozone in the lower troposphere was reasonable, which assured the reliability of OMI ozone retrievals in the lower troposphere under enhanced ozone conditions. The ozone enhancement was clearly observed over CEC, with Shandong Province as its center, and was most notable in June in any given year. Similar seasonal variations were observed throughout the 9-year OMI measurement period of 2005 to 2013. A considerable part of this ozone enhancement could be attributed to the emissions of ozone precursors from industrial activities and automobiles, and possibly from open crop residue burning (OCRB) after the winter wheat harvest. The ozone distribution presented in this study is also consistent with some model studies. The lower tropospheric ozone distribution is first shown from OMI retrieval in this study, and the results will be useful in clarifying any unknown factors that influence ozone distribution by comparison with model simulations.
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Delval, C., B. Fluckiger, and M. J. Rossi. "The rate of water vapor evaporation from ice substrates in the presence of HCl and HBr: Implications for the lifetime of atmospheric ice particles." Atmospheric Chemistry and Physics Discussions 3, no. 3 (May 8, 2003): 2179–218. http://dx.doi.org/10.5194/acpd-3-2179-2003.
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Abstract. Using a multidiagnostic approach the rate Rev or flux Jevof evaporation of H2O and its condensation, kcond, on a 1mm thick ice film have been studied in the temperature range 190 to 240 K as well as in the presence of small amounts of HCl and HBr that left the vapor pressure of H2O on ice unchanged. The resulting Arrhenius expressions with RT in kcal mol-1 for pure ice are Jev=1.6×1028+/−1·exp({−10.3+\\−1.2}/{RT}) [molec cm−2 s−1], kcond=1.7×10−2+\\-1×exp({+1.6+\\−1.5}/{RT}) [s−1], in the presence of an HCl mole fraction in the range 3.2×10−5-6.4×10−3: Jev=6.4×1026+/−1×exp({−9.7+/−1.2}/{RT}) [molec cm−2 s−1], kcond=2.8×10−2+/-1×exp({+1.5+/−1.6}/{RT}) [s−1], and an HBr mole fraction smaller than 6.4×10−3:Jev=7.4×1025+/−1×exp({−9.1+/−1.2}/{RT}) [molec cm−2 s−1], kcond=7.1×10−5+\\−1×exp({+2.6+/−1.5}/{RT}) [s−1]}. The small negative activation energy for H2O condensation on ice points to a precursor mechanism. The corresponding enthalpy of sublimation is DHsubl=Eev-Econd=11.9+/−2.7 kcal mol−1, DHsubl=11.2+/−2.8 kcal mol−1, and DHsubl=11.7+/−2.8 kcal mol−1 whose values are identical within experimental uncertainty to the accepted literature value of 12.3 kcal mol−1. Interferometric data at 633 nm and FTIR absorption spectra in transmission support the kinetic results. The data are consistent with a significant lifetime enhancement for HCl- and HBr-contaminated ice particles by a factor of 3–6 and 10–20, respectively, for submonolayer coverages of HX.
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Chen, Tsing-Chang, Jenq-Dar Tsay, Ming-Cheng Yen, and Jun Matsumoto. "Interannual Variation of the Late Fall Rainfall in Central Vietnam." Journal of Climate 25, no. 1 (January 1, 2012): 392–413. http://dx.doi.org/10.1175/jcli-d-11-00068.1.
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Abstract The heavy rainfall/flood (HRF) event in central Vietnam usually occurs in October–November, the maximum rainfall season. This rainfall maximum undergoes a distinct interannual variation, opposite the interannual variation of sea surface temperature (SST) anomalies averaged over the NOAA Niño-3.4 area—ΔSST(Niño-3.4)—but coincident with the intensification (weakening) of the low-level easterlies at 15°N and westerlies at 5°N. The changes of low-level zonal winds reflect the strengthening (weakening) of the tropical cyclonic shear flow in tropical South/Southeast Asia in response to the tropical Pacific SST anomalies. Because the rainfall maximum in central Vietnam is primarily produced by the HRF cyclone, the interannual rainfall variation in this region should be attributed to the HRF cyclone activity—a new perspective of the climate change in precipitation. On average, one HRF cyclone occurs in each cold late fall. The population of the HRF cyclone may not be an important factor causing the interannual rainfall variation in central Vietnam. During the cold late fall, the rain-producing efficiency of the individual HRF cyclone is statistically almost twice those during warm and normal late falls and the most crucial factor leading to the interannual rainfall variation in central Vietnam. It is shown by further hydrological analysis that the increase (decrease) of the HRF cyclone’s rain-producing efficiency is determined by the large-scale environmental flow through the enhancement (weakening) of the regional convergence of water vapor flux.
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Wang, Xuechuan, Xiaoqin Wang, Taotao Qiang, Xiaoli Hao, and Longfang Ren. "Improvement of the Dyeing Properties of Microfiber Synthetic Leather Base by Hydrolyzed Collagen." Journal of Engineered Fibers and Fabrics 10, no. 4 (December 2015): 155892501501000. http://dx.doi.org/10.1177/155892501501000404.
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The microfiber synthetic leather base was pretreated by sulfuric acid, and then hydrolyzed collagen was grafted onto the pretreated base, in which tanning F-90 was used as cross-linking agent. By the method of single-factor experimental design, F-90 and hydrolyzed collagen dosages were optimized. The change in dye uptake, surface chroma, and dry-rubbing and wet-rubbing fastness properties were discussed. The results showed that when F-90 dosage was 8% and hydrolyzed collagen dosage was 15%, the dyeing properties of modified base improved greatly. Compared with the pretreated base, it was found that the carboxyl content in modified base increased by 186.26% and the amino content increased by 126.21%. The dye uptake improved by 37.74%, the surface chroma deepened, and the dry-rubbing and wet-rubbing fastness improved. The water vapor permeability improved by 64.53% and the hygroscopicity improved by 50.89%. The mechanical properties also had different degrees of enhancement. Furthermore, the base before and after being modified were characterized by SEM-EDS, AFM, TGA and contact angle respectively. The results showed that the loose degree of fiber increased obviously, the relative average roughness decreased, the thermal property also decreased slightly and the hydrophilicity was enhanced.
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Delval, C., B. Fluckiger, and M. J. Rossi. "The rate of water vapor evaporation from ice substrates in the presence of HCl and HBr: implications for the lifetime of atmospheric ice particles." Atmospheric Chemistry and Physics 3, no. 4 (August 1, 2003): 1131–45. http://dx.doi.org/10.5194/acp-3-1131-2003.
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Abstract. Using a multidiagnostic approach the rate Rev [ molec cm-3 s-1] or flux Jev [ molec cm-2 s-1] of evaporation of H2O and its corresponding rate constant for condensation, kcond [s-1 ], on a 1 µm thick ice film have been studied in the temperature range 190 to 240 K as well as in the presence of small amounts of HCl and HBr that left the vapor pressure of H2O on ice unchanged. The resulting Arrhenius expressions for pure ice are Jev = 1.6 · 10 28 ± 1 · exp (- 10.3 ± 1.2/ RT) [ molec cm-2 s-1] , kcond = 1.7 · 10 - 2 ± 1 · exp (+ 1.6 ± 1.5/ RT ) [s -1], in the presence of a HCl mole fraction in the range 3.2 · 10 - 5 - 6.4 · 10 - 3 : Jev = 6.4 · 10 26 ± 1 · exp (- 9.7 ± 1.2/ RT) [ molec cm-2 s-1] , kcond = 2.8 · 10 - 2 ± 1 · exp ( + 1.5 ± 1.6 /RT) [s -1], and a HBr mole fraction smaller than 6.4 · 10 - 3 : Jev = 7.4 · 10 25 ± 1 · exp ( - 9.1 ± 1.2 /RT) [ molec cm-2 s-1] , kcond = 7.1 · 10 - 5 ± 1 · exp (+ 2.6 ± 1.5/ RT) [s -1]. The small negative activation energy for H2O condensation on ice points to a precursor mechanism. The corresponding enthalpy of sublimation is DHsubl = Eev - Econd = 11.9 ± 2.7 kcal mol-1 , DHsubl = 11.2 ± 2.8 kcal mol-1, and DHsubl = 11.7 ± 2.8 kcal mol-1 whose values are identical within experimental uncertainty to the accepted literature value of 12.3 kcal mol-1 . Interferometric data at 633 nm and FTIR absorption spectra in transmission support the kinetic results. The data are consistent with a significant lifetime enhancement for HCl- and HBr-contaminated ice particles by a factor of 3–6 and 10–20, respectively, for submonolayer coverages of HX once the fraction of the ice not contaminated by HX has evaporated.
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Neiman, Paul J., F. Martin Ralph, Benjamin J. Moore, and Robert J. Zamora. "The Regional Influence of an Intense Sierra Barrier Jet and Landfalling Atmospheric River on Orographic Precipitation in Northern California: A Case Study." Journal of Hydrometeorology 15, no. 4 (July 30, 2014): 1419–39. http://dx.doi.org/10.1175/jhm-d-13-0183.1.
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Abstract A 915-MHz wind profiler, a GPS receiver, and surface meteorological sites in and near California’s northern Central Valley (CV) provide the observational anchor for a case study on 23–25 October 2010. The study highlights key orographic influences on precipitation distributions and intensities across northern California during a landfalling atmospheric river (AR) and an associated Sierra barrier jet (SBJ). A detailed wind profiler/GPS analysis documents an intense AR overriding a shallow SBJ at ~750 m MSL, resulting in record early season precipitation. The SBJ diverts shallow, pre-cold-frontal, incoming water vapor within the AR poleward from the San Francisco Bay gap to the northern CV. The SBJ ultimately decays following the passage of the AR and trailing polar cold front aloft. A statistical analysis of orographic forcing reveals that both the AR and SBJ are crucial factors in determining the amount and spatial distribution of precipitation in the northern Sierra Nevada and in the Shasta–Trinity region at the northern terminus of the CV. As the AR and SBJ flow ascends the steep and tall terrain of the northern Sierra and Shasta–Trinity region, respectively, the precipitation becomes enhanced. Vertical profiles of the linear correlation coefficient quantify the orographic linkage between hourly upslope water vapor flux profiles and hourly rain rate. The altitude of maximum correlation (i.e., orographic controlling layer) is lower for the shallow SBJ than for the deeper AR (i.e., 0.90 versus 1.15 km MSL, respectively). This case study expands the understanding of orographic precipitation enhancement from coastal California to its interior. It also quantifies the connection between dry antecedent soils and reduced flood potential.
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Haarig, Moritz, Albert Ansmann, Josef Gasteiger, Konrad Kandler, Dietrich Althausen, Holger Baars, Martin Radenz, and David A. Farrell. "Dry versus wet marine particle optical properties: RH dependence of depolarization ratio, backscatter, and extinction from multiwavelength lidar measurements during SALTRACE." Atmospheric Chemistry and Physics 17, no. 23 (November 30, 2017): 14199–217. http://dx.doi.org/10.5194/acp-17-14199-2017.
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Abstract. Triple-wavelength lidar observations of the depolarization ratio and the backscatter coefficient of marine aerosol as a function of relative humidity (RH) are presented with a 5 min time resolution. The measurements were performed at Barbados (13° N, 59° W) during the Saharan Aerosol Long-range Transport and Aerosol-Cloud interaction Experiment (SALTRACE) winter campaign in February 2014. The phase transition from spherical sea salt particles to cubic-like sea salt crystals was observed with a polarization lidar. The radiosonde and water-vapor Raman lidar observations show a drop in RH below 50 % in the marine aerosol layer simultaneously with a strong increase in particle linear depolarization ratio, which reaches values up to 0.12 ± 0.08 (at 355 nm), 0.15 ± 0.03 (at 532 nm), and 0.10 ± 0.01 (at 1064 nm). The lidar ratio (extinction-to-backscatter ratio) increased from 19 and 23 sr for spherical sea salt particles to 27 and 25 sr (at 355 and 532 nm, respectively) for cubic-like particle ensembles. Furthermore the scattering enhancement due to hygroscopic growth of the marine aerosol particles under atmospheric conditions was measured. Extinction enhancement factors from 40 to 80 % RH of 1.94 ± 0.94 at 355 nm, 3.70 ± 1.14 at 532 nm, and 5.37 ± 1.66 at 1064 nm were found. The enhanced depolarization ratios and lidar ratios were compared to modeling studies of cubic sea salt particles.
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Musina, Diana T., Vadim R. Karibov, and Ngo Q. Khanh. "Electrophilic and Nucleophilic Modifiers as a Factor of Formation of Lipophilic Properties of Surface-Modified Materials." Materials Science Forum 1040 (July 27, 2021): 94–100. http://dx.doi.org/10.4028/www.scientific.net/msf.1040.94.
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Stabilization of the functional properties of dispersed and compact solid metals, as well as regulation of their reactivity, improvement of water-repellent, antifriction and anti-corrosion properties by creating the protective films on the surface is an urgent problem of obtaining resource-saving materials. Previously, the research conducted at REC "Nanotechnology" of Mining University proved that chemisorption of ethylhydridesiloxane vapors together with cationic surfactants based on quaternary ammonium compounds has a beneficial effect on the water-repellent properties of metals. In order to obtain the physicochemical substantiation of the effect of hydrophobization of the surface of modified dispersed metals for the first time, the study of the electrophilic-nucleophilic properties of the active substances of the surface modifiers of dispersed and compact metals was carried out using the methods of quantum-chemical modeling in HyperChem software package. The dipole moment, energy of the highest occupied and the lowest unoccupied molecular orbitals, electrophilic-nucleophilic properties were determined. The series of enhancement of nucleophilic/electrophilic properties and dipole moment for modifiers were obtained. The donor-acceptor properties, the differences in the characteristics of the molecules of alkamone (A), triamone (T) and hydrophobic silicone organic liquid were quantitatively and qualitatively established. The patterns of the formation of hydrophobic properties of the surface during the layering of molecules of ammonium and organosilicon compounds with different electrophilic-nucleophilic properties on dispersed metals have been established. Recommendations for the use of modifiers for the production of high - and superhydrophobic materials are proposed.
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Ghoshdastidar, P. S., and Indrajit Chakraborty. "A Coupled Map Lattice Model of Flow Boiling in a Horizontal Tube." Journal of Heat Transfer 129, no. 12 (March 27, 2007): 1737–41. http://dx.doi.org/10.1115/1.2768102.
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In this work laminar, stratified flow boiling of water is simulated qualitatively by the coupled map lattice (CML) method. The liquid is entering a constant wall temperature horizontal tube (Tw>Tsat at pentrance) in a subcooled condition. A CML is a dynamical system with discrete-time, discrete-space, and continuous states. The procedure basically consists of the following steps: (i) Choose a set of macroscopic variables on a lattice; (ii) decompose the problem into independent components, such as convection, diffusion, phase change, and so on; (iii) replace each component by a simple parallel dynamics on a lattice; and (iv) carry out each unit dynamics successively in each time step until some termination criterion is satisfied. In the present problem, the termination criterion is the laminar-turbulent transition, and hence, the results do not correspond to the steady state. The present modeling by CML is based on the assumption that the flow boiling is governed by (i) nucleation from cavities on the heated surface and migration of vapor into the core, (ii) forced convection, and (iii) phase change in the fluid bulk and mixing. The stirring action of the bubbles is modeled by increasing the fluid momentum and thermal diffusivities by an enhancement factor. The results show that the CML has been able to model flow boiling in a realistic manner.
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Luderer, G., J. Trentmann, T. Winterrath, C. Textor, M. Herzog, H. F. Graf, and M. O. Andreae. "Modeling of biomass smoke injection into the lower stratosphere by a large forest fire (Part II): Sensitivity studies." Atmospheric Chemistry and Physics Discussions 6, no. 4 (July 10, 2006): 6081–124. http://dx.doi.org/10.5194/acpd-6-6081-2006.
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Abstract. The Chisholm forest fire that burned in Alberta, Canada, in May 2001 resulted in injection of substantial amounts of smoke into the lower stratosphere. We used the cloud-resolving plume model ATHAM (Active Tracer High resolution Atmospheric Model) to investigate the importance of different contributing factors to the severe intensification of the convection induced by the Chisholm fire and the subsequent injection of biomass smoke into the lower stratosphere. The simulations show strong sensitivity of the pyro-convection to background meteorology. This explains the observed coincidence of the convective blow-up of the fire plume and the passage of a synoptic cold front. Furthermore, we performed model sensitivity studies to the rate of release of sensible heat and water vapor from the fire. The release of sensible heat by the fire plays a dominant role for the dynamic development of the pyro-cumulonimbus cloud (pyroCb) and the height to which smoke is transported. While the convection is very sensitive to the heat flux from the fire, the emissions of water vapor play a less significant role. The aerosol burden in the plume has a strong impact on the microphysical structure of the resulting convective cloud. The dynamic evolution of the pyroCb, however, is only weakly sensitive to the abundance of cloud condensation nuclei (CCN) from the fire. In contrast to previous findings by other studies of convective clouds, we found that fire CCN have a negative effect on the convection dynamics because they give rise to a delay in the freezing of cloud droplets. Even in a simulation without fire CCN, there is no precipitation formation within the updraft region of the pyroCb. Enhancement of convection by aerosols as reported from studies of other cases of convection is therefore not found in our study.
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Luderer, G., J. Trentmann, T. Winterrath, C. Textor, M. Herzog, H. F. Graf, and M. O. Andreae. "Modeling of biomass smoke injection into the lower stratosphere by a large forest fire (Part II): sensitivity studies." Atmospheric Chemistry and Physics 6, no. 12 (November 17, 2006): 5261–77. http://dx.doi.org/10.5194/acp-6-5261-2006.
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Abstract. The Chisholm forest fire that burned in Alberta, Canada, in May 2001 resulted in injection of substantial amounts of smoke into the lower stratosphere. We used the cloud-resolving plume model ATHAM (Active Tracer High resolution Atmospheric Model) to investigate the importance of different contributing factors to the severe intensification of the convection induced by the Chisholm fire and the subsequent injection of biomass smoke into the lower stratosphere. The simulations show strong sensitivity of the pyro-convection to background meteorology. This explains the observed coincidence of the convective blow-up of the fire plume and the passage of a synoptic cold front. Furthermore, we performed model sensitivity studies to the rate of release of sensible heat and water vapor from the fire. The release of sensible heat by the fire plays a dominant role for the dynamic development of the pyro-cumulonimbus cloud (pyroCb) and the height to which smoke is transported. The convection is very sensitive to the heat flux from the fire. The emissions of water vapor play a less significant role for the injection height but enhance the amount of smoke transported beyond the tropopause level. The aerosol burden in the plume has a strong impact on the microphysical structure of the resulting convective cloud. The dynamic evolution of the pyroCb, however, is only weakly sensitive to the abundance of cloud condensation nuclei (CCN) from the fire. In contrast to previous findings by other studies of convective clouds, we found that fire CCN have a negative effect on the convection dynamics because they give rise to a delay in the freezing of cloud droplets. Even in a simulation without fire CCN, there is no precipitation formation within the updraft region of the pyroCb. Enhancement of convection by aerosols as reported from studies of other cases of convection is therefore not found in our study.
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Liu, Xiaoli, Endian Ma, Zhibin Cao, and Shuanglong Jin. "Numerical Study of a Southwest Vortex Rainstorm Process Influenced by the Eastward Movement of Tibetan Plateau Vortex." Advances in Meteorology 2018 (2018): 1–10. http://dx.doi.org/10.1155/2018/9081910.
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A number of studies revealed the possible eastward movement of the Tibetan Plateau low-pressure system in summer and indicated the enhancement effect of this process on the southwest vortex in the Sichuan Basin, which can induce strong convective precipitation and flood events in China. In this study, a numerical simulation of a southwest vortex rainstorm process was performed. The results show that the low-pressure system originated from the Tibetan Plateau affects the southwest vortex mainly at the middle level, causing the strength increase of southwest vortex (SWV), and acts as a connection between the positive vorticity centers at the upper and lower layers. For the microscopic cloud structure, the vertical updraft of the cloud cluster embedded in the SWV increases as the low-pressure system from the plateau arrives at the Sichuan Basin. Vapor and liquid cloud water at the lower level are transported upward, based on which the ice cloud at the upper level and the warm cloud at the lower level are joined to create favorable conditions for the growth of ice crystals. As the ice crystals grow up, snow and graupel particles form, which substantially elevates the precipitation. This effect leads to the rapid development of SWV rainstorm clouds and the occurrence of precipitation. In addition to the effect of the plateau vortex, the subsequent merging of the convective clouds is another important factor for heavy rainfall because it also leads to development of convective clouds, causing heavy rainfall.
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Glantz, P., D. E. Nilsson, and W. von Hoyningen-Huene. "Estimating a relationship between aerosol optical thickness and surface wind speed over the ocean." Atmospheric Chemistry and Physics Discussions 6, no. 6 (November 21, 2006): 11621–51. http://dx.doi.org/10.5194/acpd-6-11621-2006.
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Abstract. Retrieved aerosol optical thickness (AOT) based on data obtained by the Sea viewing Wide Field Sensor (SeaWiFS) is combined with surface wind speed, obtained at the European Centre for Medium-Range Weather Forecasts (ECMWFs), over the North Pacific for September 2001. In this study a cloud screening approach is introduced in an attempt to exclude pixels partly or fully covered by clouds. The relatively broad swath width for which the nadir looking SeaWiFS instrument scanned over the North Pacific means that the AOT can be estimated according to relatively large range of wind speeds for each of the scenes analyzed. The sensitivity in AOT due to sea salt and hygroscopic growth of the marine aerosols has also been investigated. The validation of the results is based on previous parameterization in combination with the environmental quantities wind speed, RH and boundary layer height (BLH), estimated at the ECMWF. In this study a factor of 2 higher mean AOT is obtained for a wind speed up to about 13 m s−1 for September 2001 over remote ocean areas. Furthermore, a factor of 2 higher AOT is more or less supported by the validation of the results. Approximately, 50% of the enhancement seems to be due to hygroscopic growth of the marine aerosols and the remaining part due to increase in the sea salt particle mass concentrations, caused by a wind driven water vapor and sea salt flux, respectively. Reasonable agreement occurs also between satellites retrieved aerosol optical thickness and AOT observed at several AERONET (Aerosol Robotic NETwork) ground-based remote sensing stations. Finally, possible reasons why relatively large standard deviations occur around the mean values of AOT estimated for a single scene are discussed.
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Georgiev, Christo G., Stephen A. Tjemkes, Athanasios Karagiannidis, Jose Prieto, and Konstantinos Lagouvardos. "Observational Analyses of Dry Intrusions and Increased Ozone Concentrations in the Environment of Wildfires." Atmosphere 13, no. 4 (April 8, 2022): 597. http://dx.doi.org/10.3390/atmos13040597.
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In this study, atmospheric dynamical processes, which govern the intensification of wildfire activity and the associated increase in low-level ozone concentrations, were studied using images, advanced products and vertical profiles derived from satellite observations. The analyses confirm that the influence of deep stratospheric intrusions, identified in the satellite water vapor imagery, on a fire-risk area contributes to the increase in fire activity. The depth of dry stratospheric intrusions, the associated synoptic evolution and the enhanced low-level ozone concentrations caused by vertical transport of stratospheric air and/or related to biomass burning emissions were analyzed using satellite measurements from SEVIRI, IASI and CrIS instruments, complemented with surface observations near the wildfires’ locations. It is shown that the spatial and vertical resolutions of these soundings provide a way of identifying areas of enhanced ozone downwind of wildfires. Influences of the upper-troposphere dynamics and the wind field evolution as factors of uncertainty and complexity in studying the ozone production from wildfire emissions are considered. The combination of satellite soundings and satellite estimations of fire radiative energy and WV imagery may contribute to better understand the ozone enhancement associated with stratospheric intrusion and wildfire emissions.
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Laîné, Alexandre, Masakazu Yoshimori, and Ayako Abe-Ouchi. "Surface Arctic Amplification Factors in CMIP5 Models: Land and Oceanic Surfaces and Seasonality." Journal of Climate 29, no. 9 (April 21, 2016): 3297–316. http://dx.doi.org/10.1175/jcli-d-15-0497.1.
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Abstract Arctic amplification (AA) is a major characteristic of observed global warming, yet the different mechanisms responsible for it and their quantification are still under investigation. In this study, the roles of different factors contributing to local surface warming are quantified using the radiative kernel method applied at the surface after 100 years of global warming under a representative concentration pathway 4.5 (RCP4.5) scenario simulated by 32 climate models from phase 5 of the Coupled Model Intercomparison Project. The warming factors and their seasonality for land and oceanic surfaces were investigated separately and for different domains within each surface type where mechanisms differ. Common factors contribute to both land and oceanic surface warming: tropospheric-mean atmospheric warming and greenhouse gas increases (mostly through water vapor feedback) for both tropical and Arctic regions, nonbarotropic warming and surface warming sensitivity effects (negative in the tropics, positive in the Arctic), and warming cloud feedback in the Arctic in winter. Some mechanisms differ between land and oceanic surfaces: sensible and latent heat flux in the tropics, albedo feedback peaking at different times of the year in the Arctic due to different mean latitudes, a very large summer energy uptake and winter release by the Arctic Ocean, and a large evaporation enhancement in winter over the Arctic Ocean, whereas the peak occurs in summer over the ice-free Arctic land. The oceanic anomalous energy uptake and release is further studied, suggesting the primary role of seasonal variation of oceanic mixed layer temperature changes.
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Park, Seon Ki, and Sojung Park. "On a Flood-Producing Coastal Mesoscale Convective Storm Associated with the Kor’easterlies: Multi-Data Analyses Using Remotely-Sensed and In-Situ Observations and Storm-Scale Model Simulations." Remote Sensing 12, no. 9 (May 11, 2020): 1532. http://dx.doi.org/10.3390/rs12091532.
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A flood-producing heavy rainfall event occurred at the mountainous coastal region in the northeast of South Korea on 5–6 August 2018, subsequent to extreme heat waves, through a quasi-stationary mesoscale convective system (MCS). We analyzed the storm environment via a multi-data approach using high-resolution (1-km) simulations from the Weather Research and Forecasting (WRF) and in situ/satellite/radar observations. The brightness temperature, from the Advanced Himawari Imager water vapor band, and the composite radar reflectivity were used to identify characteristics of the MCS and associated precipitations. The following factors affected this back-building MCS: low-level convergence by the Korea easterlies (Kor’easterlies), carrying moist air into the coast; strong vertical wind shear, making the updraft tilted and sustained; coastal fronts and back-building convection bands, formed through interactions among the Kor’easterlies, cold pool outflows, and orography; mid-level advection of cold air and positive relative vorticity, enhancing vertical convection and potential instability; and vigorous updraft releasing potential instability. The pre-storm synoptic environment provided favorable conditions for storm development such as high moisture and temperature over the coastal area and adjacent sea, and enhancement of the Kor’easterlies by expansion of a surface high pressure system. Upper-level north-northwesterly winds prompted the MCS to propagate south-southeastward along the coastline.
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Danylevsky, V. "Cosmic rays and aerosols in the terrestrial atmosphere." Bulletin of Taras Shevchenko National University of Kyiv. Astronomy, no. 57 (2018): 15–27. http://dx.doi.org/10.17721/btsnua.2018.57.15-27.
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Galactic cosmic rays are considered as one of the external force influencing the Earth’s climate change. The cosmic rays are the main cause of the troposphere ionization. Ions are considered as one of the factors that participates in producing of the aerosol particles and cloud condensation nuclei, when the super saturation level of the water vapor or/and other atmosphere constituents vapor is sufficient. Aerosols are present throughout the atmosphere and affect Earth’s climate directly through backscattering of sunlight and indirectly by altering cloud properties. Both effects are known with considerable uncertainty only, and translate into even bigger uncertainties in future climate predictions. Whereas disputable, the idea is discussed by the scientists that variations in galactic cosmic rays closely correlate with variations in atmospheric cloud cover and therefore constitute a driving force behind aerosol-cloud-climate interactions. A lot of studies were performed to validate or disprove the connection between cosmic ray’s variation (e.g. the Forbush events) and changes of the aerosol content and properties in the atmosphere, cloud cover and properties and other climate parameters, but results are controversial. The enhancement of atmospheric aerosol particle formation by ions generated from cosmic rays was proposed as a physical mechanism explaining this correlation. But the main problem is to find the appropriate physical model which allows to calculate correctly the ion concentrations, nucleation and aerosol particles rate and cosmic rays intensity. Aerosol particle formation occurs in two stages: nucleation to form a critical nucleus and subsequent growth of the critical nucleus to a larger size (>2 – 3 nm) that competes with removal of the freshly nucleated nanoparticles by coagulation with pre-existing aerosols. The most used nucleation and particle growth theories are reviewed and analyzed in the article. The base of the theories is follow. Nucleation is generally defined as creation of molecular embryos or clusters prior to formation of a new phase during the transformation of vapor liquid solid. This process is characterized by a decrease in both enthalpy and entropy of the nucleating system. A free energy barrier is often involved and needs to be surmounted before transformation to the new phase becomes spontaneous. Another limitation in the nucleation and growth of atmospheric nanoparticles lies in significantly elevated equilibrium vapor pressures above small clusters and nanoparticles, also known as the Kelvin (curvature) effect, which considerably restricts growth of freshly nucleated nanoparticles. Ions are capable, under certain conditions, of suppressing or even removing the barrier to nucleation in embryonic molecular clusters of water. But results of the theories are very uncertain so far. Results of the observations of the nucleation and particles formation as well as the special CLOUD experiment results are reviewed and analyzed in the article. The molecular clusters and nuclei can not be observed by remote sensing techniques like sun-photometers, lidars or satellite instruments. The in-situ measurements of the nucleation concentration and particles growth rate are performed in the certain sites only. The observations and experiments revealed the important influence of the trace gases and organic molecules on the nucleation and particle growth rate. Sulphuric acid, ammonia, amines, and oxidised organics play a crucial role in nanoparticle formation in the atmosphere competing with ionmediated mechanism. Saturation pressure of the sulphuric acid and organics vapors at the typical atmospheric conditions is much lower than for water vapor and at typical atmospheric concentration they are capable of suppressing the nucleation barrier. Nucleation with ions started earlier and run faster but the nucleus with sizes ≥ 3 nm more than 90 % of clusters are neutral. Ion-mediated mechanism can dominate when sulphuric asid and organic molecules concentration is low. But more observations in the different atmosphere layers and locations and experiments at different conditions is required to better understanding the ion-mediated nucleation in the atmosphere. Nucleation contribution to the aerosol content and properties in the terrestrial atmosphere is also simulated by the special modules included to the regional and global models of the atmosphere and climate, e.g. GEOS-Chem and CAM5. Comparison of the simulation and observations has showed that in general the averaged model results are in good agreement with observational data at some sites but same biases were revealed at some sites too. It requires the further analysis and models developments. Also ion-mediated mechanism contribution was also estimated by the simulation not more than 10%. Analysis of the observations and models results in the article showed that cosmic rays influencing the aerosol formation also influence the microphysical and optical properties of the particles. First of all particles size distribution is influenced by nucleation mechanism and relative content of the Aitken nuclei increases. Also sulphuric acid can influence the particle refractive index increasing the single-scattering albedo of the aerosols. Modern remote sense technique such as the AERONET sun-photometers can measure the spectral AOD and sky radiance with high accuracy and the reliable size distribution, refractive index and single-scattering albedo averaged over atmosphere column can be determined from that observations, but the AERONET inversion algorithm has to be developed to obtain the particles size finer than 50 nm.
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Guo, Jinyun, Rui Hou, Maosheng Zhou, Xin Jin, and Guowei Li. "Detection of Particulate Matter Changes Caused by 2020 California Wildfires Based on GNSS and Radiosonde Station." Remote Sensing 13, no. 22 (November 12, 2021): 4557. http://dx.doi.org/10.3390/rs13224557.
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From August to October 2020, a serious wildfire occurred in California, USA, which produced a large number of particulate matter and harmful gases, resulting in huge economic losses and environmental pollution. Particulate matter delays the GNSS signal, which affects the like precipitable water vapor (LPWV) derived by the GNSS non-hydrostatic delay. Most of the information of GNSS-derived LPWV is caused by water vapor, and a small part of the information is caused by particulate matter. A new method based on the difference (ΔPWV) between the PWV of virtual radiosonde stations network and GNSS-derived LPWV is proposed to detect the changes of particulate matter in the atmosphere during the 2020 California wildfires. There are few radiosonde stations in the experimental area and they are far away from the GNSS station. In order to solve this problem, we propose to use the multilayer perceptron (MLP) neural network method to establish the virtual radiosonde network in the experimental area. The PWV derived by the fifth-generation European center for medium-range weather forecasts reanalysis model (PWVERA5) is used as the input data of machine learning. The PWV derived by radiosonde data (PWVRAD) is used as the training target data of machine learning. The ΔPWV is obtained based on PWV derived by the virtual radiosonde station network and GNSS in the experimental area. In order to further reduce the influence of noise and other factors on ΔPWV, this paper attempts to decompose ΔPWV time series by using the singular spectrum analysis method, and obtain its principal components, subsequently, analyzing the relationship between the principal components of ΔPWV with particulate matter. The results indicate that the accuracy of PWV predicted by the virtual radiosonde network is significantly better than the fifth-generation European center for the medium-range weather forecast reanalysis model, and the change trend of ΔPWV is basically consistent with the change law of particulate matter in which the value of ΔPWV in the case of fire is significantly higher than that before and after the fire. The mean of correlation coefficients between ΔPWV and PM10 at each GNSS station before, during and after wildfires are 0.068, 0.397 and 0.065, respectively, which show the evident enhancement of the correlation between ΔPWV and particulate matter during wildfires. It is concluded that because of the high sensitiveness of ΔPWV to the change of particulate matter, the GNSS technique can be used as an effective new approach to detect the change of particulate matter and, then, to detect wildfires effectively.
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Hu, Xiaoming, Yana Li, Song Yang, Yi Deng, and Ming Cai. "Process-Based Decomposition of the Decadal Climate Difference between 2002–13 and 1984–95." Journal of Climate 30, no. 12 (June 2017): 4373–93. http://dx.doi.org/10.1175/jcli-d-15-0742.1.
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This study examines at the process level the climate difference between 2002–13 and 1984–95 in ERA-Interim. A linearized radiative transfer model is used to calculate the temperature change such that its thermal radiative cooling would balance the energy flux perturbation associated with the change of an individual process, without regard to what causes the change of the process in the first place. The global mean error of the offline radiative transfer model calculations is 0.09 K, which corresponds to the upper limit of the uncertainties from a single term in the decomposition analysis. The process-based decomposition indicates that the direct effect of the increase of CO2 (0.15 K) is the largest contributor to the global warming between the two periods (about 0.27 K). The second and third largest contributors are the cloud feedback (0.14 K) and the combined effect of the oceanic heat storage and evaporation terms (0.11 K), respectively. The largest warming associated with the oceanic heat storage term is found in the tropical Pacific and Indian Oceans, with relatively weaker warming over the tropical Atlantic Ocean. The increase in atmospheric moisture adds another 0.1 K to the global surface warming, but the enhancement in tropical convections acts to reduce the surface warming by 0.17 K. The ice-albedo and atmospheric dynamical feedbacks are the two leading factors responsible for the Arctic polar warming amplification (PWA). The increase of atmospheric water vapor over the Arctic region also contributes substantially to the Arctic PWA pattern.
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Masunaga, Hirohiko, and Tristan S. L’Ecuyer. "The Southeast Pacific Warm Band and Double ITCZ." Journal of Climate 23, no. 5 (March 1, 2010): 1189–208. http://dx.doi.org/10.1175/2009jcli3124.1.
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Abstract The east Pacific double intertropical convergence zone (ITCZ) in austral fall is investigated with particular focus on the growing processes of its Southern Hemisphere branch. Satellite measurements from the Tropical Rainfall Measuring Mission (TRMM) and Quick Scatterometer (QuikSCAT) are analyzed to derive 8-yr climatology from 2000 to 2007. The earliest sign of the south ITCZ emerges in sea surface temperature (SST) by January, followed by the gradual development of surface convergence and water vapor. The shallow cumulus population starts growing to form the south ITCZ in February, a month earlier than vigorous deep convection is organized into the south ITCZ. The key factors that give rise to the initial SST enhancement or the southeast Pacific warm band are diagnosed by simple experiments. The experiments are designed to calculate SST, making use of an ocean mixed layer “model” forced by surface heat fluxes, all of which are derived from satellite observations. It is found that the shortwave flux absorbed into the ocean mixed layer is the primary driver of the southeast Pacific warm band. The warm band does not develop in boreal fall because the shortwave flux is seasonally so small that it is overwhelmed by other negative fluxes, including the latent heat and longwave fluxes. Clouds offset the net radiative flux by 10–15 W m−2, which is large enough for the warm band to develop in boreal fall if it were not for clouds reflecting shortwave radiation. Interannual variability of the double ITCZ is also discussed in brief.
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Harrison, Stephen J., John R. Mecikalski, and Kevin R. Knupp. "Analysis of Outflow Boundary Collisions in North-Central Alabama." Weather and Forecasting 24, no. 6 (December 1, 2009): 1680–90. http://dx.doi.org/10.1175/2009waf2222268.1.
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Abstract Ninety-four outflow boundary (OB) collisions were documented in north-central Alabama over the summers of 2005–07 using the Advanced Radar for Meteorological and Operational Research (ARMOR) dual-polarimetric radar located at the Huntsville, Alabama, airport. These data were used to extend and verify previous research and to look for new correlations among the various factors that lead to convective initiation (CI) from OB collisions more frequently. For this study, CI is defined as the first occurrence of a ≥35-dBZ radar echo at an elevation angle of 0.8° and within 10 km of the point of collision, from a convective cloud. The radar reflectivity and angle of collision between both OBs along with time of day at which CI occurs most often were analyzed. Also, the presence of cumulus clouds along either/both OBs, or within the area of collision, was examined using Geostationary Operational Environmental Satellite-12 (GOES-12) visible imagery. A more detailed analysis of 23 of the 94 OBs that passed over the Mobile Integrated Profiling System instruments examines the relation among radar reflectivity, updraft magnitude, and water vapor enhancements. This analysis indicates that OB updraft magnitude is positively correlated with OB reflectivity factor. The main findings are that when OBs collide in a more head-on manner, when both colliding OBs have radar reflectivity values of 15 dBZ or greater, or when cumulus clouds preexist along at least one OB, CI is produced at a greater rate. These results, using a much larger dataset than had previously been used for colliding OBs, are subsequently compared with two existing studies.
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Navas-Guzmán, Francisco, Giovanni Martucci, Martine Collaud Coen, María José Granados-Muñoz, Maxime Hervo, Michael Sicard, and Alexander Haefele. "Characterization of aerosol hygroscopicity using Raman lidar measurements at the EARLINET station of Payerne." Atmospheric Chemistry and Physics 19, no. 18 (September 17, 2019): 11651–68. http://dx.doi.org/10.5194/acp-19-11651-2019.
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Abstract. This study focuses on the analysis of aerosol hygroscopicity using remote sensing techniques. Continuous observations of aerosol backscatter coefficient (βaer), temperature (T) and water vapor mixing ratio (r) have been performed by means of a Raman lidar system at the aerological station of MeteoSwiss at Payerne (Switzerland) since 2008. These measurements allow us to monitor in a continuous way any change in aerosol properties as a function of the relative humidity (RH). These changes can be observed either in time at a constant altitude or in altitude at a constant time. The accuracy and precision of RH measurements from the lidar have been evaluated using the radiosonde (RS) technique as a reference. A total of 172 RS profiles were used in this intercomparison, which revealed a bias smaller than 4 % RH and a standard deviation smaller than 10 % RH between both techniques in the whole (in lower) troposphere at nighttime (at daytime), indicating the good performance of the lidar for characterizing RH. A methodology to identify situations favorable to studying aerosol hygroscopicity has been established, and the aerosol hygroscopicity has been characterized by means of the backscatter enhancement factor (fβ). Two case studies, corresponding to different types of aerosol, are used to illustrate the potential of this methodology. The first case corresponds to a mixture of rural aerosol and smoke particles (smoke mixture), which showed a higher hygroscopicity (fβ355=2.8 and fβ1064=1.8 in the RH range 73 %–97 %) than the second case, in which mineral dust was present (fβ355=1.2 and fβ1064=1.1 in the RH range 68 %–84 %). The higher sensitivity of the shortest wavelength to hygroscopic growth was qualitatively reproduced using Mie simulations. In addition, a good agreement was found between the hygroscopic analysis done in the vertical and in time for Case I, where the latter also allowed us to observe the hydration and dehydration of the smoke mixture. Finally, the impact of aerosol hygroscopicity on the Earth's radiative balance has been evaluated using the GAME (Global Atmospheric Model) radiative transfer model. The model showed an impact with an increase in absolute value of 2.4 W m−2 at the surface with respect to the dry conditions for the hygroscopic layer of Case I (smoke mixture).
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Riccobono, F., L. Rondo, M. Sipilä, P. Barmet, J. Curtius, J. Dommen, M. Ehn, et al. "Contribution of sulfuric acid and oxidized organic compounds to particle formation and growth." Atmospheric Chemistry and Physics Discussions 12, no. 5 (May 3, 2012): 11351–89. http://dx.doi.org/10.5194/acpd-12-11351-2012.
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Abstract. Lack of knowledge about the mechanisms underlying new particle formation and their subsequent growth is one of the main causes for the large uncertainty in estimating the radiative forcing of atmospheric aerosols in global models. We performed chamber experiments designed to study the contributions of sulfuric acid and organic vapors to formation and to the early growth of nucleated particles, respectively. Distinct experiments in the presence of two different organic precursors (1,3,5-trimethylbenzene and α-pinene) showed the ability of these compounds to reproduce the formation rates observed in the low troposphere. These results were obtained measuring the sulfuric acid concentrations with two Chemical Ionization Mass Spectrometers confirming the results of a previous study which modeled the sulfuric acid concentrations in presence of 1,3,5-trimethylbenzene. New analysis methods were applied to the data collected with a Condensation Particle Counter battery and a Scanning Mobility Particle Sizer, allowing the assessment of the size resolved growth rates of freshly nucleated particles. The effect of organic vapors on particle growth was investigated by means of the growth rate enhancement factor (Γ), defined as the ratio between the measured growth rate in the presence of α-pinene and the kinetically limited growth rate of the sulfuric acid and water system. The observed Γ values indicate that the growth is dominated by organic compounds already at particle diameters of 2 nm. Both the absolute growth rates and Γ showed a strong dependence on particle size supporting the nano-Köhler theory. Moreover, the separation of the contributions from sulfuric acid and organic compounds to particles growth reveals that the organic contribution seems to be enhanced by the sulfuric acid concentration. The size resolved growth analysis finally indicates that both condensation of oxidized organic compounds and reactive uptake contribute to particle growth.
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Riccobono, F., L. Rondo, M. Sipilä, P. Barmet, J. Curtius, J. Dommen, M. Ehn, et al. "Contribution of sulfuric acid and oxidized organic compounds to particle formation and growth." Atmospheric Chemistry and Physics 12, no. 20 (October 19, 2012): 9427–39. http://dx.doi.org/10.5194/acp-12-9427-2012.
Full textAbstract:
Abstract. Lack of knowledge about the mechanisms underlying new particle formation and their subsequent growth is one of the main causes for the large uncertainty in estimating the radiative forcing of atmospheric aerosols in global models. We performed chamber experiments designed to study the contributions of sulfuric acid and organic vapors to the formation and early growth of nucleated particles. Distinct experiments in the presence of two different organic precursors (1,3,5-trimethylbenzene and α-pinene) showed the ability of these compounds to reproduce the formation rates observed in the low troposphere. These results were obtained measuring the sulfuric acid concentrations with two chemical ionization mass spectrometers confirming the results of a previous study which modeled the sulfuric acid concentrations in presence of 1,3,5-trimethylbenzene. New analysis methods were applied to the data collected with a condensation particle counter battery and a scanning mobility particle sizer, allowing the assessment of the size resolved growth rates of freshly nucleated particles. The effect of organic vapors on particle growth was investigated by means of the growth rate enhancement factor (Γ), defined as the ratio between the measured growth rate in the presence of α-pinene and the kinetically limited growth rate of the sulfuric acid and water system. The observed Γ values indicate that the growth is already dominated by organic compounds at particle diameters of 2 nm. Both the absolute growth rates and Γ showed a strong dependence on particle size, supporting the nano-Köhler theory. Moreover, the separation of the contributions from sulfuric acid and organic compounds to particle growth reveals that the organic contribution seems to be enhanced by the sulfuric acid concentration. Finally, the size resolved growth analysis indicates that both condensation of oxidized organic compounds and reactive uptake contribute to particle growth.
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Rangharajan, Kaushik K., Prashanth Mohana Sundaram, A. T. Conlisk, and Shaurya Prakash. "Surface dependent enhancement in water vapor permeation through nanochannels." Analyst 143, no. 18 (2018): 4256–66. http://dx.doi.org/10.1039/c8an00650d.
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Kumbhani, Sambhav R., Taylor S. Cline, Marie C. Killian, Jared M. Clark, William J. Keeton, Lee D. Hansen, Randall B. Shirts, David J. Robichaud, and Jaron C. Hansen. "Water Vapor Enhancement of Rates of Peroxy Radical Reactions." International Journal of Chemical Kinetics 47, no. 6 (April 24, 2015): 395–409. http://dx.doi.org/10.1002/kin.20917.
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Genard-Zielinski, Anne-Cyrielle, Christophe Boissard, Elena Ormeño, Juliette Lathière, Ilja M. Reiter, Henri Wortham, Jean-Philippe Orts, et al. "Seasonal variations of <i>Quercus pubescens</i> isoprene emissions from an <i>in natura</i> forest under drought stress and sensitivity to future climate change in the Mediterranean area." Biogeosciences 15, no. 15 (August 3, 2018): 4711–30. http://dx.doi.org/10.5194/bg-15-4711-2018.
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Abstract. At a local level, biogenic isoprene emissions can greatly affect the air quality of urban areas surrounded by large vegetation sources, such as in the Mediterranean region. The impacts of future warmer and drier conditions on isoprene emissions from Mediterranean emitters are still under debate. Seasonal variations of Quercus pubescens gas exchange and isoprene emission rates (ER) were studied from June 2012 to June 2013 at the O3HP site (French Mediterranean) under natural (ND) and amplified (AD, 32 %) drought. While AD significantly reduced stomatal conductance to water vapour throughout the research period excluding August, it did not significantly preclude CO2 net assimilation, which was lowest in summer (≈-1 µmolCO2 m−2 s−1). ER followed a significant seasonal pattern regardless of drought intensity, with mean ER maxima of 78.5 and 104.8 µgC gDM-1 h−1 in July (ND) and August (AD) respectively and minima of 6 and < 2 µgC gDM-1 h−1 in October and April respectively. The isoprene emission factor increased significantly by a factor of 2 in August and September under AD (137.8 and 74.3 µgC gDM-1 h−1) compared with ND (75.3 and 40.21 µgC gDM-1 h−1), but no significant changes occurred on ER. Aside from the June 2012 and 2013 measurements, the MEGAN2.1 (Model of Emissions of Gases and Aerosols from Nature version 2.1) model was able to assess the observed ER variability only when its soil moisture activity factor γSM was not operating and regardless of the drought intensity; in this case more than 80 % and 50 % of ER seasonal variability was assessed in the ND and AD respectively. We suggest that a specific formulation of γSM be developed for the drought-adapted isoprene emitter, according to that obtained for Q. pubescens in this study (γSM= 0.192e51.93 SW with SW the soil water content). An isoprene algorithm (G14) was developed using an optimised artificial neural network (ANN) trained on our experimental dataset (ER + O3HP climatic and edaphic parameters cumulated over 0 to 21 days prior to the measurements). G14 assessed more than 80 % of the observed ER seasonal variations, regardless of the drought intensity. ERG14 was more sensitive to higher (0 to −7 days) frequency environmental changes under AD in comparison to ND. Using IPCC RCP2.6 and RCP8.5 climate scenarios, and SW and temperature as calculated by the ORCHIDEE land surface model, ERG14 was found to be mostly sensitive to future temperature and nearly insensitive to precipitation decrease (an annual increase of up to 240 % and at the most 10 % respectively in the most severe scenario). The main impact of future drier conditions in the Mediterranean was found to be an enhancement (+40 %) of isoprene emissions sensitivity to thermal stress.