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Balagizi, Charles M., et Marcello Liotta. « Key Factors of Precipitation Stable Isotope Fractionation in Central-Eastern Africa and Central Mediterranean ». Geosciences 9, no 8 (31 juillet 2019) : 337. http://dx.doi.org/10.3390/geosciences9080337.
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The processes of isotope fractionation in the hydrological cycle naturally occur during vapor formation, vapor condensation, and moisture transportation. These processes are therefore dependent on local and regional surface and atmospheric physical features such as temperature, pressure, wind speed, and land morphology, and hence on the climate. Because of the strong influence of climate on the isotope fractionation, latitudinal and altitudinal effects on the δ18O and δ2H values of precipitation at a global scale are observed. In this study, we present and compare the processes governing precipitation isotope fractionation from two contrasting climatic regions: Virunga in Central-Eastern Africa and the Central Mediterranean (Stromboli and Sicily, Italy). While Virunga is a forested rainy tropical region located between Central and Eastern Africa, the Mediterranean region is characterized by a rainy mild winter and a dry hot summer. The reported δ18O and δ2H dataset are from precipitation collected on rain gauges sampled either on a monthly or an approximately bimonthly basis and published in previous papers. Both regions show clearly defined temporal and altitudinal variations of δ18O and δ2H, depending on precipitation amounts. The Central Mediterranean shows a clear contribution of local vapor forming at the sea–air interface, and Virunga shows a contribution from both local and regional vapor. The vapor of Virunga is from two competing sources: the first is the continental recycled moisture from soil/plant evaporation that dominates during the rainy season, and the second is from the East African Great Lakes evaporation that dominates during the dry season.
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Langmann, B., K. Sellegri et E. Freney. « Secondary organic aerosol formation during June 2010 in Central Europe : measurements and modelling studies with a mixed thermodynamic-kinetic approach ». Atmospheric Chemistry and Physics Discussions 13, no 10 (15 octobre 2013) : 26761–93. http://dx.doi.org/10.5194/acpd-13-26761-2013.
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Abstract. Until recently secondary organic carbon (SOC) aerosol mass concentrations have been systematically underestimated by three-dimensional atmospheric-chemistry-aerosol models. With a newly proposed concept of aging of organic vapours more realistic model results for organic carbon aerosol mass concentrations could be achieved. Applying a mixed thermodynamic-kinetic approach for SOC aerosol formation shifted the aerosol size distribution towards particles in the cloud condensation nuclei size range, thereby emphasising the importance of SOC aerosol formation schemes for modelling realistic cloud and precipitation formation. The additional importance of hetero-molecular nucleation between H2SO4 and organic vapours remains to be evaluated in three-dimensional atmospheric-chemistry-aerosol models. Here a case study is presented focusing on Puy-de-Dôme, France in June 2010. Even though nucleation events at Puy-de-Dôme were rare during the chosen period of investigation a weak event in the boundary layer could be reproduced by the model when nucleation of low-volatile secondary organic vapour is included. Differences in the model results with and without nucleation of organic vapour are visible in the lower free troposphere over several days of the period. Taking into account nucleation of organic vapour leads to an increase in accumulation mode particles due to coagulation of nucleation and aitken mode particles. Moreover, the measurements indicate a considerable increase in SOC aerosol mass concentration during the measurement campaign, which could be reproduced by modelling using a simplified thermodynamic-kinetic approach for SOC aerosol formation and increased biogenic VOC precursor emissions. Comparison with a thermodynamic SOC aerosol formation approach shows a huge improvement in modelled SOC aerosol mass concentration with the thermodynamic-kinetic approach for SOC aerosol formation and a slight improvement of modelled particle size distribution.
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Langmann, B., K. Sellegri et E. Freney. « Secondary organic aerosol formation during June 2010 in Central Europe : measurements and modelling studies with a mixed thermodynamic-kinetic approach ». Atmospheric Chemistry and Physics 14, no 8 (16 avril 2014) : 3831–42. http://dx.doi.org/10.5194/acp-14-3831-2014.
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Abstract. Until recently secondary organic carbon aerosol (SOA) mass concentrations have been systematically underestimated by three-dimensional atmospheric-chemistry-aerosol models. With a newly proposed concept of aging of organic vapours, more realistic model results for organic carbon aerosol mass concentrations can be achieved. Applying a mixed thermodynamic-kinetic approach for SOA formation shifted the aerosol size distribution towards particles in the cloud condensation nuclei size range, thereby emphasising the importance of SOA formation schemes for modelling realistic cloud and precipitation formation. The additional importance of hetero-molecular nucleation between H2SO4 and organic vapours remains to be evaluated in three-dimensional atmospheric-chemistry-aerosol models. Here a case study is presented focusing on Puy-de-Dôme, France in June 2010. The measurements indicate a considerable increase in SOA mass concentration during the measurement campaign, which could be reproduced by modelling using a simplified thermodynamic-kinetic approach for SOA formation and increased biogenic volatile organic compound (VOC) precursor emissions. Comparison with a thermodynamic SOA formation approach shows a huge improvement in modelled SOA mass concentration with the thermodynamic-kinetic approach for SOA formation. SOA mass concentration increases by a factor of up to 6 accompanied by a slight improvement of modelled particle size distribution. Even though nucleation events at Puy-de-Dôme were rare during the chosen period of investigation, a weak event in the boundary layer could be reproduced by the model in a sensitivity study when nucleation of low-volatile secondary organic vapour is included. Differences in the model results with and without nucleation of organic vapour are visible in the lower free troposphere over several days. Taking into account the nucleation of organic vapour leads to an increase in accumulation mode particles due to coagulation and condensational growth of nucleation and Aitken mode particles.
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Ayadi, Houda, Jan Machac, Milan Svanda, Noureddine Boulejfen et Lassaad Latrach. « Proof of Concept of Reconfigurable Solvent Vapor Sensor Tag with Wireless Power Transfer for IoT Applications ». Applied Sciences 12, no 20 (12 octobre 2022) : 10266. http://dx.doi.org/10.3390/app122010266.
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In this paper, a concept of a reconfigurable chipless radio frequency identification (RFID) sensor tag for detecting solvent vapors/gas in IoT applications was presented. The concept was based on the authors’ previously published rectangular loop structure equipped with a U-folded dipole loaded with a glide-symmetrical interdigital capacitor coated with a thin layer of tetrasulfonated copper phthalocyanine deposited as a sensing layer to improve the sensing capability in the presence of acetone vapor. In order to further maximize the sensitivity of the designed structure to the desired solvent, a circuit for a central frequency adjustment using a radio frequency varactor diode biased with a wireless power transfer (WPT) was designed. By varying the DC bias of the diode, a continuous tunable range of approximately 200 MHz was achieved. The proposed reconfigurable wireless sensor tag was manufactured and the frequency shift was verified by measurement. The proposed external frequency control can be applied to a wide class of electrical resonators.
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Wang, Weiguo, Hongyi Li, Jian Wang et Xiaohua Hao. « Water Vapor from Western Eurasia Promotes Precipitation during the Snow Season in Northern Xinjiang, a Typical Arid Region in Central Asia ». Water 12, no 1 (2 janvier 2020) : 141. http://dx.doi.org/10.3390/w12010141.
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Atmospheric water vapor plays an important role in the water cycle, especially in arid Central Asia, where precipitation is invaluable to water resources. Understanding and quantifying the relationship between water vapor source regions and precipitation is a key problem in water resource research in typical arid Central Asia, Northern Xinjiang. However, the relationship between precipitation and water vapor sources is still unclear of snow season. This paper aimed at studying the role of water vapor source supply in the Northern Xinjiang precipitation trend, which was investigated using the Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model. The results showed that the total water vapor contributed from Western Eurasia and the North Polar area presented upward trends similar to the precipitation change trend, which indicated that the water vapor contribution from the two previous water vapor source regions supplied abundant water vapor and maintained the upward precipitation trend from 1980 to 2017 in Northern Xinjiang. From the climatology of water vapor transport, the region was controlled by midlatitude westerlies and major water vapor input from the western boundary, and the net water vapor flux of this region also showed an annual increasing trend. Western Eurasia had the largest moisture percentage contribution to Northern Xinjiang (48.11%) over the past 38 years. Northern Xinjiang precipitation was correlated with water vapor from Western Eurasia, the North Polar area, and Siberia, and the correlation coefficients were 0.66, 0.45, and 0.57, respectively. These results could aid in better understanding the water cycle process and climate change in this typical arid region of Central Asia.
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Brouwers, M. G., et C. W. Ormel. « How planets grow by pebble accretion ». Astronomy & ; Astrophysics 634 (30 janvier 2020) : A15. http://dx.doi.org/10.1051/0004-6361/201936480.
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Context. Proto-planets embedded in their natal disks acquire hot envelopes as they grow and accrete solids. This ensures that the material they accrete – pebbles, as well as (small) planetesimals – will vaporize to enrich their atmospheres. Enrichment modifies an envelope’s structure and significantly alters its further evolution. Aims. Our aim is to describe the formation of planets with polluted envelopes from the moment that impactors begin to sublimate to beyond the disk’s eventual dissipation. Methods. We constructed an analytical interior structure model, characterized by a hot and uniformly mixed high-Z vapor layer surrounding the core, located below the usual unpolluted radiative-convective regions. Our model assumes an ideal equation of state and focuses on identifying trends rather than precise calculations. The expressions we derived are applicable to all single-species pollutants, but we used SiO2 to visualize our results. Results. The evolution of planets with uniformly mixed polluted envelopes follows four potential phases. Initially, the central core grows directly through impacts and rainout until the envelope becomes hot enough to vaporize and absorb all incoming solids. We find that a planet reaches runaway accretion when the sum of its core and vapor mass exceeds a value that we refer to as the critical metal mass – a criterion that supersedes the traditional critical core mass. The critical metal mass scales positively with both the pollutant’s evaporation temperature and with the planet’s core mass. Hence, planets at shorter orbital separations require the accretion of more solids to reach runaway as they accrete less volatile materials. If the solids accretion rate dries up, we identify the decline of the mean molecular weight – dilution – as a mechanism to limit gas accretion during a polluted planet’s embedded cooling phase. When the disk ultimately dissipates, the envelope’s inner temperature declines and its vapor eventually rains out, augmenting the mass of the core. The energy release that accompanies this does not result in significant mass-loss, as it only occurs after the planet has substantially contracted.
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Michalsky, Joseph J., et Peter W. Kiedron. « Moderate spectral resolution solar irradiance measurements, aerosol optical depth, and solar transmission, from 360 to 1070 nm, using the refurbished rotating shadow band spectroradiometer (RSS) ». Atmospheric Measurement Techniques 15, no 2 (24 janvier 2022) : 353–64. http://dx.doi.org/10.5194/amt-15-353-2022.
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Abstract. This paper reports on a third-generation rotating shadow band spectroradiometer (RSS) used to measure global and diffuse horizontal plus direct normal irradiances and transmissions at 1002 wavelengths between 360 and 1070 nm. The prism-dispersed spectral data are from the Atmospheric Radiation Measurement (ARM) Southern Great Plains site in north-central Oklahoma (36.605∘ N, 97.486∘ W) and cover dates between August 2009 and February 2014. The refurbished RSS isolates the detector in a vacuum chamber with pressures near 10−7 torr. This prevents the deposition of outgassed vapors from the interior of the spectrometer shell on the cooled detector that affected the operation of the first commercial RSS. Methods for (1) ensuring the correct wavelength registration of the data and (2) deriving extraterrestrial responses over the entire spectrum, including throughout strong water vapor and oxygen bands, are described. The resulting data produced are archived as ARM data records and include cloud-screened aerosol optical depths, spectral irradiances and direct normal solar transmission, as well as normalized diffuse and global irradiances.
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Lamb, Dennis, et Raymond A. Shaw. « Visualizing Vapor Pressure : A Mechanical Demonstration of Liquid–Vapor Phase Equilibrium ». Bulletin of the American Meteorological Society 97, no 8 (1 août 2016) : 1355–62. http://dx.doi.org/10.1175/bams-d-15-00173.1.
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Abstract Water phase transitions are central to climate and weather. Yet it is a common experience that the principles of phase equilibrium are challenging to understand and teach. A simple mechanical analogy has been developed to demonstrate key principles of liquid evaporation and the temperature dependence of equilibrium vapor pressure. The system is composed of a circular plate with a central depression and several hundred metal balls. Mechanical agitation of the plate causes the balls to bounce and interact in much the same statistical way that molecules do in real liquid–vapor systems. The data, consisting of the number of balls escaping the central well at different forcing energies, exhibit a logarithmic dependence on the reciprocal of the applied energy (analogous to thermal energy kBT) that is similar to that given by Boltzmann statistics and the Clausius–Clapeyron equation. These results demonstrate that the enthalpy (i.e., latent heat) of evaporation is well interpreted as the potential energy difference between molecules in the vapor and liquid phases, and it is the fundamental driver of vapor pressure increase with temperature. Consideration of the uncertainties in the measurements shows that the mechanical system is described well by Poisson statistics. The system is simple enough that it can be duplicated for qualitative use in atmospheric science teaching, and an interactive animation based on the mechanical system is available online for instructional use (http://phy.mtu.edu/vpt/).
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Zhou, Yu-shu, Ze-ming Xie et Xin Liu. « An Analysis of Moisture Sources of Torrential Rainfall Events over Xinjiang, China ». Journal of Hydrometeorology 20, no 10 (1 octobre 2019) : 2109–22. http://dx.doi.org/10.1175/jhm-d-19-0010.1.
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Abstract Water vapor is a primary rainfall source for the development of torrential rainfall events. By using a Lagrangian flexible particle dispersion model (FLEXPART), the water vapor transports associated with torrential rainfall over Xinjiang, China, during April–September of 2008–15 are examined in this study. The results show that water vapor related to torrential rainfall events is mostly transported by westerly winds. The moisture sources for the development of torrential rainfall over four areas (Altay, Ili Valley, Hami, and Aksu-Kashgar) are mainly from Xinjiang and central Asia. The north Asia area and the Mediterranean/Black/Caspian Sea region are also important contributors to moisture source over the Altay area. Over Ili Valley, both the central Asia area and Xinjiang contribute 40% of water vapor to rainfall sources. Over the Hami area, 70% of the moisture source is from the Xinjiang. Over the Aksu-Kashgar area, the central Asia region is the most important moisture source area.
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Huang, Wei, Song Feng, Jianhui Chen et Fahu Chen. « Physical Mechanisms of Summer Precipitation Variations in the Tarim Basin in Northwestern China ». Journal of Climate 28, no 9 (1 mai 2015) : 3579–91. http://dx.doi.org/10.1175/jcli-d-14-00395.1.
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Abstract The Tarim basin (TB) in northwestern China is one of the most arid regions in the middle latitudes, where water is scarce year-round. This study investigates the variations of summer precipitation in the TB and their association with water vapor fluxes and atmospheric circulation. The results suggest that the variations of summer precipitation in the TB are dominated by the water vapor fluxes from the south and east, although the long-term mean water vapor mostly comes from the west. The anomalous water vapor fluxes are closely associated with the meridional teleconnection pattern around 50°–80°E and the zonal teleconnection pattern along the Asian westerly jet in summer. The meridional teleconnection connects central Asia and the tropical Indian Ocean; the zonal teleconnection resembles the “Silk Road pattern.” The two teleconnections lead to negative height anomalies in central Asia and positive height anomalies in the Arabian Sea and India and in northern central China. The anomalous pressure gradient force, caused by these height anomalies, leads to anomalous ascending motion in the TB and brings low-level moisture along the eastern periphery of the Tibetan Plateau and water vapor from the Arabian Sea passing over the Tibetan Plateau to influence precipitation development in the study region.
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Kostin, Aleksey. « Mineralization in the andesitic lava from Kildyam volcanic complex, central Yakutia, Russia ». IOP Conference Series : Earth and Environmental Science 906, no 1 (1 novembre 2021) : 012006. http://dx.doi.org/10.1088/1755-1315/906/1/012006.
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Abstract This contribution presents the first detailed analysis of a new volcanic succession of olivine-pyroxenites, andesite, and dacite discovered in the Kildyam Late Jurassic complex in Central Yakutia. Petrographic and microprobe studies confirmed the liquid immiscibility in silicate melts during crystallization. Immiscible liquids are preserved as globules of one glass in another in andesites and as melted inclusions of native iron in matrix, clinopyroxene and plagioclase phenocrysts. Our analyses reveal the complex textural relationships between silicates and Fe-oxides, native iron and (Cu, Pb, Ag and Au)-rich phases, and provide unequivocal textural evidences, not observed previously. Purpose of this research is to preserve a very important data on IO (Iron Oxide) or IOCG (Iron Oxide Copper Gold) mineralization. Obtained results support occurrence and diverse of gold, silver, copper and lead minerals in magnetite lavas. During the early stage of fine-grained subvolcanic olivine-clinopyroxenite end pyrrhotite, globular igneous sulfides is a first proposed style of economic deposit formation. The second proposed style of economic mineralization in Kildyam is to be a magnetite-bearing lava; iron enrichment of the melilitic melt phase, followed by iron depletion and silica enrichment. The vesicle-hosted alloys and sulfides provide significant new data on metal transport and precipitation from high-temperature magmatic vapors. During syneruptive vapor phase exsolution, volatile metals (Cu-Zn, Fe-Al-Cu, Ni-Fe-Cu-Sn) and Ag-Cu-sulfides contribute to the formation of economic concentrations. Major conclusions contribute to 3-step genetic model. (1) Early-formed magmatic minerals led to partial dissolution of olivine-clinopyroxenite and their enrichment in Cu, Co and Ni relative to other metals, while troilite globules droplets grew.(2) First stage of division into two immiscible silicate and sulfide melt liquids (a) K-rich dacitic and rhyolithic glass, and (b) vesicles of heavy sulfide minerals with a large segregations and drops of native iron. (3) Lava of fused magnetite crystals and voids enriched in silver and gold, and (b) globular disseminated chalcopyrite in mineralized melilitic rocks.
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Hadad, Dani, Jean-Luc Baray, Nadège Montoux, Joël Van Baelen, Patrick Fréville, Jean-Marc Pichon, Pierre Bosser et al. « Surface and Tropospheric Water Vapor Variability and Decadal Trends at Two Supersites of CO-PDD (Cézeaux and Puy de Dôme) in Central France ». Atmosphere 9, no 8 (1 août 2018) : 302. http://dx.doi.org/10.3390/atmos9080302.
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We present an analysis of decadal in situ and remote sensing observations of water vapor over the Cézeaux and puy de Dôme, located in central France (45° N, 3° E), in order to document the variability, cycles and trends of surface and tropospheric water vapor at different time scales and the geophysical processes responsible for the water vapor distributions. We use meteorological stations, GPS (Global Positioning System), and lidar datasets, supplemented with three remote sources of water vapor (COSMIC-radio-occultation, ERA-interim-ECMWF numerical model, and AIRS-satellite). The annual cycle of water vapor is clearly established for the two sites of different altitudes and for all types of measurement. Cezeaux and puy de Dôme present almost no diurnal cycle, suggesting that the variability of surface water vapor at this site is more influenced by a sporadic meteorological system than by regular diurnal variations. The lidar dataset shows a greater monthly variability of the vertical distribution than the COSMIC and AIRS satellite products. The Cézeaux site presents a positive trend for the GPS water vapor total column (0.42 ± 0.45 g·kg−1/decade during 2006–2017) and a significant negative trend for the surface water vapor mixing ratio (−0.16 ± 0.09 mm/decade during 2002–2017). The multi-linear regression analysis shows that continental forcings (East Atlantic Pattern and East Atlantic-West Russia Pattern) have a greater influence than oceanic forcing (North Atlantic Oscillation) on the water vapor variations.
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Schröder, Marc, Maarit Lockhoff, Frank Fell, John Forsythe, Tim Trent, Ralf Bennartz, Eva Borbas et al. « The GEWEX Water Vapor Assessment archive of water vapour products from satellite observations and reanalyses ». Earth System Science Data 10, no 2 (15 juin 2018) : 1093–117. http://dx.doi.org/10.5194/essd-10-1093-2018.
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Abstract. The Global Energy and Water cycle Exchanges (GEWEX) Data and Assessments Panel (GDAP) initiated the GEWEX Water Vapor Assessment (G-VAP), which has the main objectives to quantify the current state of the art in water vapour products being constructed for climate applications and to support the selection process of suitable water vapour products by GDAP for its production of globally consistent water and energy cycle products. During the construction of the G-VAP data archive, freely available and mature satellite and reanalysis data records with a minimum temporal coverage of 10 years were considered. The archive contains total column water vapour (TCWV) as well as specific humidity and temperature at four pressure levels (1000, 700, 500, 300 hPa) from 22 different data records. All data records were remapped to a regular longitude–latitude grid of 2∘ × 2∘. The archive consists of four different folders: 22 TCWV data records covering the period 2003–2008, 11 TCWV data records covering the period 1988–2008, as well as 7 specific humidity and 7 temperature data records covering the period 1988–2009. The G-VAP data archive is referenced under the following digital object identifier (doi): https://doi.org/10.5676/EUM_SAF_CM/GVAP/V001. Within G-VAP, the characterization of water vapour products is, among other ways, achieved through intercomparisons of the considered data records, as a whole and grouped into three classes of predominant retrieval condition: clear-sky, cloudy-sky and all-sky. Associated results are shown using the 22 TCWV data records. The standard deviations among the 22 TCWV data records have been analysed and exhibit distinct maxima over central Africa and the tropical warm pool (in absolute terms) as well as over the poles and mountain regions (in relative terms). The variability in TCWV within each class can be large and prohibits conclusions about systematic differences in TCWV between the classes.
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Fiedler, V., M. Dal Maso, M. Boy, H. Aufmhoff, J. Hoffmann, T. Schuck, W. Birmili et al. « The contribution of sulphuric acid to atmospheric particle formation and growth : a comparison between boundary layers in Northern and Central Europe ». Atmospheric Chemistry and Physics 5, no 7 (20 juillet 2005) : 1773–85. http://dx.doi.org/10.5194/acp-5-1773-2005.
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Abstract. Atmospheric gaseous sulphuric acid was measured and its influence on particle formation and growth was investigated building on aerosol data. The measurements were part of the EU-project QUEST and took place at two different measurement sites in Northern and Central Europe (Hyytiälä, Finland, March-April 2003 and Heidelberg, Germany, March-April 2004). From a comprehensive data set including sulphuric acid, particle number size distributions and meteorological data, particle growth rates, particle formation rates and source rates of condensable vapors were inferred. Growth rates were determined in two different ways, from particle size distributions as well as from a so-called timeshift analysis. Moreover, correlations between sulphuric acid and particle number concentration between 3 and 6 nm were examined and the influence of air masses of different origin was investigated. Measured maximum concentrations of sulphuric acid were in the range from 1x106 to 16x106cm-3. The gaseous sulphuric acid lifetime with respect to condensation on aerosol particles ranged from 2 to 33min in Hyytiälä and from 0.5 to 8 min in Heidelberg. Most calculated values (growth rates, formation rates, vapor source rates) were considerably higher in Central Europe (Heidelberg), due to the more polluted air and higher preexistent aerosol concentrations. Close correlations between H2SO4 and nucleation mode particles (size range: 3-6 nm) were found on most days at both sites. The percentage contribution of sulphuric acid to particle growth was below 10% at both places and to initial growth below 20%. An air mass analysis indicated that at Heidelberg new particles were formed predominantly in air advected from southwesterly directions.
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Leydecker, Al, et John M. Melack. « Evaporation from Snow in the Central Sierra Nevada of California ». Hydrology Research 30, no 2 (1 avril 1999) : 81–108. http://dx.doi.org/10.2166/nh.1999.0005.
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Evaporation from snow was calculated with the mean-profile method using single-level meteorological data at eight locations representing a variety of alpine and sub-alpine terrain in the central Sierra Nevada, California. Four to six years of data were analyzed at most of the sites. Evaporation from snow was highest in mid-winter, when the vapor pressure gradient between the snow surface and the air was at its maximum, and declined throughout the snowmelt season. Near the end of snowmelt, condensation of water vapor on the snow surface often matched or exceeded evaporative loss. Annual evaporation from the snowpack varied from 12 to 156 mm. We estimate mean annual regional evaporation in the sub-alpine and alpine zones (excluding evaporation from tree-captured snow and during wind re-deposition) as 80 to 100 mm, approximately 7 per cent of the maximum accumulation during an average snow year. Evaporation during snowmelt contributed only minor amounts to the total seasonal loss, typically around 25 mm, or about 2% of the maximum average accumulation.
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Demoz, B. B., D. O’C Starr, K. D. Evans, A. R. Lare, D. N. Whiteman, G. Schwemmer, R. A. Ferrare, J. E. M. Goldsmith et S. E. Bisson. « The Cold Front of 15 April 1994 over the Central United States. Part I : Observations ». Monthly Weather Review 133, no 6 (1 juin 2005) : 1525–43. http://dx.doi.org/10.1175/mwr2932.1.
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Abstract Detailed observations of the interactions of a cold front and a dryline over the central United States that led to dramatic undulations in the boundary layer, including an undular bore, are investigated using high-resolution water vapor mixing ratio profiles measured by Raman lidars. The lidar-derived water vapor mixing ratio profiles revealed the complex interaction between a dryline and a cold-frontal system. An elevated, well-mixed, and deep midtropospheric layer, as well as a sharp transition (between 5- and 6-km altitude) to a drier region aloft, was observed. The moisture oscillations due to the undular bore and the mixing of the prefrontal air mass with the cold air at the frontal surface are all well depicted. The enhanced precipitable water vapor and roll clouds, the undulations associated with the bore, the strong vertical circulation and mixing that led to the increase in the depth of the low-level moist layer, and the subsequent lifting of this moist layer by the cold-frontal surface, as well as the feeder flow behind the cold front, are clearly indicated. A synthesis of the Raman lidar–measured water vapor mixing ratio profiles, satellite, radiometer, tower, and Oklahoma Mesonet data indicated that the undular bore was triggered by the approaching cold front and propagated south-southeastward. The observed and calculated bore speeds were in reasonable agreement. Wave-ducting analysis showed that favorable wave-trapping mechanisms existed; a low-level stable layer capped by an inversion, a well-mixed midtropospheric layer, and wind curvature from a low-level jet were found.
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Zhang, Guang, et Yingying Ma. « Clear-Sky Surface Solar Radiation and the Radiative Effect of Aerosol and Water Vapor Based on Simulations and Satellite Observations over Northern China ». Remote Sensing 12, no 12 (15 juin 2020) : 1931. http://dx.doi.org/10.3390/rs12121931.
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The distribution and trend of clear-sky surface solar radiation (SSR) and the quantitative effects of aerosol and water vapor are investigated in northern China during 2001–2015 using radiation simulations and satellite observations. Clear-sky SSR in northern China is high in summer and low in winter, which is dominated by astronomical factors and strongly modulated by the seasonal variations of radiative effects of aerosol (ARE) and water vapor (WVRE). The larger variation of WVRE than ARE indicates that water vapor plays a more important role in moderating the seasonal variation of clear-sky SSR. Clear-sky SSR shows an overall decreasing trend of –0.12 W/m2 per year, with decrease more strongly than –0.60 W/m2 per year in west-central Shandong and increase (about 0.40 W/m2) in south-central Inner Mongolia. The consistency of spatial distribution and high correlation between clear-sky SSR and ARE trend indicate that the clear-sky SSR trend is mainly determined by aerosol variation. Dust mass concentration decreases about 16% in south-central Inner Mongolia from 2001 to 2015, resulting in the increase in clear-sky SSR. In contrast, sulfate aerosol increases about 92% in west-central Shandong, leading to the decreasing trend of clear-sky SSR.
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Zueva, Svetlana, Francesco Ferella, Valentina Corradini, Elena V. Baturina, Nicolò M. Ippolito et Francesco Vegliò. « An Effective New Treatment of Fluoride-Containing Sludge Resulting from the Manufacture of Photovoltaic Cells ». Processes 9, no 10 (29 septembre 2021) : 1745. http://dx.doi.org/10.3390/pr9101745.
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The circular economy and maximization of environmental sustainability are increasingly becoming the vision and mission of companies competing in present-day global markets. In particular, in the energy sector, the transition from fossil fuels to renewable sources of energy has become the widespread mantra. One typical example is the deployment of devices which produce clean energy, such as solar photovoltaic panels and solar thermal panels, wind generators, tidal stream generators, wave power generators, etc. These are undoubtedly generating clean energy, but their manufacture creates hazardous by-products, the disposal of which results in increased environmental pollution. Chemical Vapor Deposition (CVD) is widely used in manufacturing of solar photovoltaic cells. In these processes, typically, crystalline silicon is precipitated from chlorosilanes, iodides, bromides and fluorides. Polluting by-products include deposition of a silicon film, formation of SiO2 powder and formation of toxic vapors of HF, SiH4 and PH3. Usually, these gaseous products are eliminated in a central scrubber, whose unwanted by-product consists in large quantities of hazardous fluorine-containing sludge. This article concerns an effective and inexpensive detoxification of fluorinated sludge, developed by the authors during research into the sludge collected from the scrubber of a PV cell manufacturing plant located in southern Italy.
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Fiedler, V., M. Dal Maso, M. Boy, H. Aufmhoff, J. Hoffmann, T. Schuck, W. Birmili, F. Arnold et M. Kulmala. « The contribution of sulphuric acid to atmospheric particle formation and growth : a comparison between boundary layers in Northern and Central Europe ». Atmospheric Chemistry and Physics Discussions 5, no 1 (3 février 2005) : 573–605. http://dx.doi.org/10.5194/acpd-5-573-2005.
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Abstract. Atmospheric gaseous sulphuric acid was measured and its influence on particle formation and growth was investigated building on aerosol data. The measurements were part of the EU-project QUEST and took place at two different measurement sites in Northern and Central Europe (Hyytiälä, Finland, March–April 2003 and Heidelberg, Germany, March–April 2004). From a comprehensive data set including particle number size distributions, sulphuric acid, and meteorological data, particle growth rates, particle formation rates and source rates of condensable vapors were calculated. Growth rates were determined in two different ways, from particle size distributions as well as from a so-called timeshift analysis. Moreover, correlations between sulphuric acid and particle number concentration between 3 and 6 nm were examined and the influence of different air masses was analyzed. Measured concentrations of sulphuric acid were in the range from 2·106 to 16·106 cm-3. The gaseous sulphuric acid lifetime with respect to condensation on aerosol particles ranged from 2 to 33 min in Hyytiälä and from 28 s to 8 min in Heidelberg. Most calculated values (growth rates, formation rates, vapor source rates) were considerably higher in Central Europe (Heidelberg), due to the more polluted air and higher preexistent aerosol concentrations. Close correlations between H2SO4 and nucleation mode particles (size range: 3–6 nm) were found on many days at both sites but several observation days also lacked such correlations. The percentage contribution of sulphuric acid to particle growth was below 10% at both places, to initial growth below 20%. An air mass analysis indicated that at Heidelberg new particles were formed predominantly in air advected from southwesterly directions.
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Zhao, Siwen, Jie Zhang, Yibo Du, Ruipeng Ji et Miaomiao Niu. « Modulation of Coupled Modes of Tibetan Plateau Heating and Indian Summer Monsoon on Summer Rainfall over Central Asia ». Journal of Climate 35, no 5 (1 mars 2022) : 1441–58. http://dx.doi.org/10.1175/jcli-d-20-0813.1.
Texte intégralRésumé :
Abstract It has been suggested that summer rainfall over central Asia (CA) is significantly correlated with the summer thermal distribution of the Tibetan Plateau (TP) and the Indian summer monsoon (ISM). However, relatively few studies have investigated their synergistic effects of different distribution. This study documents the significant correlations between precipitation in CA and the diabatic heating of TP and the ISM in summer based on the results of statistical analysis and numerical simulation. Summer precipitation in CA is dominated by two water vapor transport branches from the south that are related to the two primary modes of anomalous diabatic heating distribution contributed by the TP and ISM precipitation, that is, the “+−” dipole mode in the southeastern TP and the Indian subcontinent (IS), and the “+−+” tripole mode in the southeastern TP, the IS, and southern India. Both modes exhibit obvious midlatitude Silk Road pattern (SRP) wave trains with cyclone anomalies over CA, but with different transient and stationary eddies over South Asia. The different locations of anomalous anticyclones over India govern two water vapor transport branches to CA, which are from the Arabian Sea and the Bay of Bengal. The water vapor flux climbs while being transported northward and can be transported to CA with the cooperation of cyclonic circulation. The convergent water vapor and ascending motion caused by cyclonic anomalies favor the precipitation in CA. Further analysis corroborates the negative south Indian Ocean dipole in February could affect the tripole mode distribution of TP heating and ISM via the atmospheric circulation, water vapor transport, and anomalous Hadley cell circulation. The results indicate a reliable prediction reference for summer precipitation in CA.
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Li, Yafei, Franziska Aemisegger, Andreas Riedl, Nina Buchmann et Werner Eugster. « The role of dew and radiation fog inputs in the local water cycling of a temperate grassland during dry spells in central Europe ». Hydrology and Earth System Sciences 25, no 5 (19 mai 2021) : 2617–48. http://dx.doi.org/10.5194/hess-25-2617-2021.
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Abstract. During dry spells, non-rainfall water (hereafter NRW) mostly formed from dew and fog potentially plays an increasingly important role in temperate grassland ecosystems with ongoing global warming. Dew and radiation fog occur in combination during clear and calm nights, and both use ambient water vapor as a source. Research on the combined mechanisms involved in NRW inputs to ecosystems is rare, and distillation of water vapor from the soil as a NRW input pathway for dew formation has hardly been studied. Furthermore, eddy covariance (EC) measurements are associated with large uncertainties on clear, calm nights when dew and radiation fog occur. The aim of this paper is thus to use stable isotopes as tracers to investigate the different NRW input pathways into a temperate Swiss grassland at Chamau during dry spells in summer 2018. Stable isotopes provide additional information on the pathways from water vapor to liquid water (dew and fog) that cannot be measured otherwise. We measured the isotopic composition (δ18O, δ2H, and d=δ2H-8⋅δ18O) of ambient water vapor, NRW droplets on leaf surfaces, and soil moisture and combined them with EC and meteorological observations during one dew-only and two combined dew and radiation fog events. The ambient water vapor d was found to be strongly linked with local surface relative humidity (r=-0.94), highlighting the dominant role of local moisture as a source for ambient water vapor in the synoptic context of the studied dry spells. Detailed observations of the temporal evolution of the ambient water vapor and foliage NRW isotopic signals suggest two different NRW input pathways: (1) the downward pathway through the condensation of ambient water vapor and (2) the upward pathway through the distillation of water vapor from soil onto foliage. We employed a simple two-end-member mixing model using δ18O and δ2H to quantify the NRW inputs from these two different sources. With this approach, we found that distillation contributed 9 %–42 % to the total foliage NRW, which compares well with estimates derived from a near-surface vertical temperature gradient method proposed by Monteith in 1957. The dew and radiation fog potentially produced 0.17–0.54 mm d−1 NRW gain on foliage, thereby constituting a non-negligible water flux to the canopy, as compared to the evapotranspiration of 2.7 mm d−1. Our results thus underline the importance of NRW inputs to temperate grasslands during dry spells and reveal the complexity of the local water cycle in such conditions, including different pathways of dew and radiation fog water inputs.
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Li, Xiaofei, Ninglian Wang et Zhanhao Wu. « Terrain Effects on Regional Precipitation in a Warm Season over Qinling-Daba Mountains in Central China ». Atmosphere 12, no 12 (16 décembre 2021) : 1685. http://dx.doi.org/10.3390/atmos12121685.
Texte intégralRésumé :
The terrain effects of Qinling–Daba Mountains on reginal precipitation during a warm season were investigated in a two-month day-to-day experiment using the Weather Research and Forecasting (WRF) model. According to the results from the terrain sensitivity experiment with lowered mountains, Qinling–Daba Mountains have been found to have an obvious effect on both the spatial-temporal distribution and diurnal cycle of reginal precipitation from July to August in 2019, where the Qinling Mountains mainly enhanced the precipitation around 34° N, and the Daba Mountains mainly enhanced it around 32° N at the time period of early morning and midnight. Horizontal distribution of water vapor and convective available potential energy (CAPE), as well as cross section of vertical velocity of wind and potential temperature has been studied to examine the key mechanisms for these two mountains’ effect. The existence of Qinling Mountains intercepted transportation of water vapor from South to North in the lower troposphere to across 34° N and caused an obvious enhancement of CAPE in the neighborhood, while the Daba Mountains intercepted the northward water vapor transportation to across 32° N and caused an enhanced CAPE nearby. The time period of the influence is in a good accordance with the diurnal cycle. In the cross-section, the existence of Qinling Mountains and Daba Mountains are found to stimulate the upward motion and unstable environment effectively at around 34° N and 32° N, separately. As a result, the existence of the two mountains lead to a favorable environment in water vapor, thermodynamic, and dynamic conditions for this warm season precipitation.
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Wang, Tao, Ting-Yong Li, Jian Zhang, Yao Wu, Chao-Jun Chen, Ran Huang, Jun-Yun Li, Si-Ya Xiao et Tatiana Artemevna Blyakharchuk. « A Climatological Interpretation of Precipitation δ18O across Siberia and Central Asia ». Water 12, no 8 (28 juillet 2020) : 2132. http://dx.doi.org/10.3390/w12082132.
Texte intégralRésumé :
Siberia and Central Asia are located at middle to high latitudes, encompassing a large landlocked area of the Eurasian continent and vast tracts of permafrost, which are sensitive to global climate change. Here, we investigated the data from 15 Global Network of Isotopes in Precipitation (GNIP) stations to clarify the relationship between precipitation δ18O (δ18OP) and the local temperature and precipitation amount on the monthly, seasonal, and annual timescales. Three main conclusions as following: (1) On the monthly time scale, the variation in δ18OP is mainly controlled by the “temperature effect”. (2) The weighted average value of precipitation δ18O (δ18Ow) exhibited “temperature effect” over 60° N–70° N. However, δ18Ow was dominated by multiple factors from 40° N to 60° N (e.g., the North Atlantic Oscillation (NAO) and water vapor source changes). (3) The variations of δ18OW can be attributed to the changes in pathway of the westerly dominated by the NAO at annual timescale. Therefore, it is possible to reconstruct the histories of past atmospheric circulations and water vapor sources in this region via δ18O in geologic archives, e.g., speleothem and ice core records.
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Cleverly, James, Chao Chen, Nicolas Boulain, Randol Villalobos-Vega, Ralph Faux, Nicole Grant, Qiang Yu et Derek Eamus. « Aerodynamic Resistance and Penman–Monteith Evapotranspiration over a Seasonally Two-Layered Canopy in Semiarid Central Australia ». Journal of Hydrometeorology 14, no 5 (1 octobre 2013) : 1562–70. http://dx.doi.org/10.1175/jhm-d-13-080.1.
Texte intégralRésumé :
Abstract Accurate prediction of evapotranspiration E depends upon representative characterization of meteorological conditions in the boundary layer. Drag and bulk transfer coefficient schemes for estimating aerodynamic resistance to vapor transfer were compared over a semiarid natural woodland ecosystem in central Australia. Aerodynamic resistance was overestimated from the drag coefficient, resulting in limited E at intermediate values of vapor pressure deficit. Large vertical humidity gradients were present during the summer, causing divergence between momentum and vapor transport within and above the canopy surface. Because of intermittency in growth of the summer-active, rain-dependent understory and physiological responses of the canopy, leaf resistance varied from less than 50 s m−1 to greater than 106 s m−1, in which the particularly large values were obtained from inversion of drag coefficient resistance. Soil moisture limitations further contributed to divergence between actual and reference E. Unsurprisingly, inclusion of site-specific meteorological (e.g., vertical humidity gradients) and hydrological (e.g., soil moisture content) information improved the accuracy of predicting E when applying Penman–Monteith analysis. These results apply regardless of canopy layering (i.e., even when the understory was not present) wherever atmospheric humidity gradients develop and are thus not restricted to two-layer canopies in semiarid regions.
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Campos-Arias, Polleth, Germain Esquivel-Hernández, José Francisco Valverde-Calderón, Stephanie Rodríguez-Rosales, Jorge Moya-Zamora, Ricardo Sánchez-Murillo et Jan Boll. « GPS Precipitable Water Vapor Estimations over Costa Rica : A Comparison against Atmospheric Sounding and Moderate Resolution Imaging Spectrometer (MODIS) ». Climate 7, no 5 (3 mai 2019) : 63. http://dx.doi.org/10.3390/cli7050063.
Texte intégralRésumé :
The quantification of water vapor in tropical regions like Central America is necessary to estimate the influence of climate change on its distribution and the formation of precipitation. This work reports daily estimations of precipitable water vapor (PWV) using Global Positioning System (GPS) delay data over the Pacific region of Costa Rica during 2017. The GPS PWV measurements were compared against atmospheric sounding and Moderate Resolution Imaging Spectrometer (MODIS) data. When GPS PWV was calculated, relatively small biases between the mean atmospheric temperatures (Tm) from atmospheric sounding and the Bevis equation were found. The seasonal PWV fluctuations were controlled by two of the main circulation processes in Central America: the northeast trade winds and the latitudinal migration of the Intertropical Convergence Zone (ITCZ). No significant statistical differences were found for MODIS Terra during the dry season with respect GPS-based calculations (p > 0.05). A multiple linear regression model constructed based on surface meteorological variables can predict the GPS-based measurements with an average relative bias of −0.02 ± 0.19 mm/day (R2 = 0.597). These first results are promising for incorporating GPS-based meteorological applications in Central America where the prevailing climatic conditions offer a unique scenario to study the influence of maritime moisture inputs on the seasonal water vapor distribution.
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Meza, Amalia, Luciano Mendoza, María Paula Natali, Clara Bianchi et Laura Fernández. « Diurnal variation of precipitable water vapor over Central and South America ». Geodesy and Geodynamics 11, no 6 (novembre 2020) : 426–41. http://dx.doi.org/10.1016/j.geog.2020.04.005.
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Cai, Zhongyin, et Lide Tian. « Processes Governing Water Vapor Isotope Composition in the Indo-Pacific Region : Convection and Water Vapor Transport ». Journal of Climate 29, no 23 (15 novembre 2016) : 8535–46. http://dx.doi.org/10.1175/jcli-d-16-0297.1.
Texte intégralRésumé :
Abstract In an effort to understand the mechanisms controlling water vapor isotope composition in the Indo-Pacific region, encompassing southeastern Asia, this study investigates the spatial and interannual patterns in summer [June–September (JJAS)] water vapor isotopologues retrieved from the Tropospheric Emission Spectrometer (TES), especially those patterns associated with convection and water vapor transport. Both precipitation and water vapor isotope values exhibit a V-shaped longitudinal pattern in their spatial variations, reflecting the gradual rainout and increase in convective intensity along water vapor transport routes. On the temporal scale, compared with the 2006–10 JJAS mean conditions, TES water vapor δD over the eastern Indian Ocean and southeastern Asia (R_W120; 10°S–30°N, 80°–120°E) is higher in the 2009 JJAS El Niño event when convective activity is reduced and lower in the 2010 JJAS La Niña event when convective activity is enhanced. This is consistent with the direct response of water vapor δD to deep convection. In contrast, TES water vapor δD over the western Pacific (R_WP; 10°S–30°N, 120°–140°E) is higher in the La Niña year than in the El Niño year, although convective activity in R_WP varies in the same manner as in R_W120. A comparison of water vapor δD values with convection and water vapor transport suggests that the westward transport of water vapor–isotopic anomalies and changes in the flux of water vapor transported from the central to the western Pacific lead to such an opposite response in the R_WP. These findings help interpret what causes the interannual variations recorded by Indo-Pacific water isotopologues.
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Shi, Lei, Carl Schreck et Marc Schröder. « Assessing the Pattern Differences between Satellite-Observed Upper Tropospheric Humidity and Total Column Water Vapor during Major El Niño Events ». Remote Sensing 10, no 8 (28 juillet 2018) : 1188. http://dx.doi.org/10.3390/rs10081188.
Texte intégralRésumé :
As part of the activities for the Global Energy and Water Exchanges (GEWEX) water vapor assessment project, the consistency of satellite-observed upper tropospheric humidity (UTH) and total column water vapor (TCWV) is examined. The examination is focused on their respective patterns during major El Niño events. The analysis shows that the two datasets, consisting of one measurement of vertically averaged relative humidity in the upper troposphere and one of absolute water vapor integrated over the atmospheric vertical column with dominant contribution from the lower troposphere, are consistent over the equatorial central–eastern Pacific, both showing increases of water vapor during major El Niño events as expected. However, the magnitude of drying in the TCWV field over the western Pacific is much weaker than that of moistening over the central–eastern Pacific, while the UTH field exhibits equivalent magnitude of drying and moistening. Furthermore, the drying in the UTH field covers larger areas in the tropics. The difference in their patterns results in an opposite phase in the time series during a major El Niño event when a tropical average is taken. Both UTH and TCWV are closely correlated with major climate indices. However, they have significantly different lag correlations with the Niño 3.4 index in both the sign (positive or negative) and lag time over tropical oceans.
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Zhu, Shuiping, Zhilin Zhang, Haisheng Chen et Yong Li. « Numerical Investigation of a Bionic Vapor Chamber Based on Leaf Veins for Cooling Electronic Devices ». Sustainability 15, no 2 (6 janvier 2023) : 1125. http://dx.doi.org/10.3390/su15021125.
Texte intégralRésumé :
In order to solve the problem of integrated heat dissipation in electronic chips under continuous high-intensity operation and thus ensure their stable and normal operation, a novel bionic vapor chamber with a composite structure of leaf vein grooves is proposed. Leaf veins produce effective nutrient transport; however, how the wick core of the leaf vein groove porous composite structure affects heat transfer and flow in the vapor chamber remains elusive. In this study, the effects of the groove parameters, including the central groove diameter (D), the ratio of the inner and outer circle diameter (γ), and the number of grooves (N), on the temperature, velocity, and pressure distribution of the bionic vapor chamber were investigated based on a simplified numerical model. The results show that the maximum temperature difference at the condensing surface was reduced by approximately 50% as compared to the conventional vapor chamber, implying better temperature homogeneity. In addition, the heat and mass transfer performance of the vapor chamber improved as parameter γ increased. Moreover, the effects of variations in parameters N and D on the performance of the vapor chamber were competitive, with larger values of parameters N and D enhancing the heat transfer performance of the vapor chamber, and smaller parameter values reducing the flow pressure drop of the liquid. This provides a reference for research on the optimization of bionic vapor chambers.
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Zhao, Shuai, Jipeng Sun, Shuli Wang et Zhihui Sun. « Modeling and Numerical Simulation of the Inlet Velocity on Oil–Water Two-Phase Vapor Separation Efficiency by the Hydrocyclone ». Energies 15, no 13 (4 juillet 2022) : 4900. http://dx.doi.org/10.3390/en15134900.
Texte intégralRésumé :
The density of tar vapor and water vapor produced by coal pyrolysis is different. Different centrifugal forces will be generated when they flow through the hydrocyclone. The water vapor and tar vapor are divided into inner and outer layers. According to this phenomenon, the moisture in the tar can be removed. In this paper, a Eulerian gas–liquid two-phase flow model is established by numerical simulation to study the effect of inlet velocity on the separation effect of a designed hydrocyclone (split ratio 0.2). The results show that the inlet velocity and moisture content have an influence on the volume distribution characteristics, tangential velocity, axial velocity, pressure drop distribution, and separation efficiency of tar vapor and water vapor in the hydrocyclone. When the inlet velocity increases from 2.0 to 12.0 m/s, the central swirl intensity increases, and the negative pressure sweep range at the overflow outlet increases. The axial velocity increased from 2.8 to 14.9 m/s, tar vapor content at the overflow outlet decreased from 74% to 37%, and at the underflow outlet increased from 89% to 92%. When the moisture content is lower than 10%, the hydrocyclone with the split ratio of 0.20 is no longer suitable for the separation of oil–water two-phase vapor. However, when the water content is higher than 20%, the purity of tar vapor at the underflow outlet can reach 92%, and the overflow outlet needs multistage separation to realize tar purification.
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Putra, Nandy, Wayan Nata Septiadi, Ranggi Sahmura et Cahya Tri Anggara. « Application of Al2O3 Nanofluid on Sintered Copper-Powder Vapor Chamber for Electronic Cooling ». Advanced Materials Research 789 (septembre 2013) : 423–28. http://dx.doi.org/10.4028/www.scientific.net/amr.789.423.
Texte intégralRésumé :
The development of electronic devices pushes manufacturers to create smaller microchips with higher performance than ever before. Microchip with higher working load produces more heat. This leads to the need of cooling system that able to dissipate high heat flux. Vapor chamber is one of highly effective heat spreading device. Its ability to dissipate high heat flux density in limited space made it potential for electronic cooling application, like Central Processing Unit (CPU) cooling system. The purpose of this paper is to study the application of Al2O3Nanofluid as working fluid for vapor chamber. Vapor chamber performance was measured in real CPU working condition. Al2O3Nanofluid with concentration of 0.1%, 0.3%, 0.5%, 1%, 2% and 3% as working fluid of the vapor chamber were tested and compared with its base fluid, water. Al2O3nanofluid shows better thermal performance than its base fluid due to the interaction of particle enhancing the thermal conductivity. The result showed that the effect of working fluid is significant to the performance of vapor chamber at high heat load, and the application of Al2O3nanofluid as working fluid would enhance thermal performance of vapor chamber, compared to other conventional working fluid being used before.
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Yang, Zhao, Francina Dominguez, Xubin Zeng, Huancui Hu, Hoshin Gupta et Ben Yang. « Impact of Irrigation over the California Central Valley on Regional Climate ». Journal of Hydrometeorology 18, no 5 (12 avril 2017) : 1341–57. http://dx.doi.org/10.1175/jhm-d-16-0158.1.
Texte intégralRésumé :
Abstract Irrigation, while being an important anthropogenic factor affecting the local to regional water cycle, is not typically represented in regional climate models. An irrigation scheme is incorporated into the Noah land surface scheme of the Weather Research and Forecasting (WRF) Model that has a calibrated convective parameterization and a tracer package is used to tag and track water vapor. To assess the impact of irrigation over the California Central Valley (CCV) on the regional climate of the U.S. Southwest, simulations are run (for three dry and three wet years) both with and without the irrigation scheme. Incorporation of the irrigation scheme resulted in simulated surface air temperature and humidity that were closer to observations, decreased depth of the planetary boundary layer over the CCV, and increased convective available potential energy. The result was an overall increase in precipitation over the Sierra Nevada range and the Colorado River basin during the summer. Water vapor rising from the irrigated region mainly moved northeastward and contributed to precipitation in Nevada and Idaho. Specifically, the results indicate increased precipitation on the windward side of the Sierra Nevada and over the Colorado River basin. The former is possibly linked to a sea-breeze-type circulation near the CCV, while the latter is likely associated with a wave pattern related to latent heat release over the moisture transport belt.
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Klein, H., S. Nickovic, W. Haunold, U. Bundke, B. Nillius, M. Ebert, S. Weinbruch et al. « Saharan dust and ice nuclei over Central Europe ». Atmospheric Chemistry and Physics 10, no 21 (1 novembre 2010) : 10211–21. http://dx.doi.org/10.5194/acp-10-10211-2010.
Texte intégralRésumé :
Abstract. Surface measurements of aerosol and ice nuclei (IN) at a Central European mountain site during an episode of dust transport from the Sahara are presented. Ice nuclei were sampled by electrostatic precipitation on silicon wafers and were analyzed in an isothermal static vapor diffusion chamber. The transport of mineral dust is simulated by the Eulerian regional dust model DREAM. Ice nuclei and mineral dust are significantly correlated, in particular IN number concentration and aerosol surface area. The ice nucleating characteristics of the aerosol as analyzed with respect to temperature and supersaturation are similar during the dust episode than during the course of the year. This suggests that dust may be a main constituent of ice nucleating aerosols in Central Europe.
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Yu, Wandi, Andrew E. Dessler, Mijeong Park et Eric J. Jensen. « Influence of convection on stratospheric water vapor in the North American monsoon region ». Atmospheric Chemistry and Physics 20, no 20 (27 octobre 2020) : 12153–61. http://dx.doi.org/10.5194/acp-20-12153-2020.
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Abstract. We quantify the connection between deep convective occurrence and summertime 100 hPa water vapor anomaly over the North American (NA) region and find substantial consistency between their interannual variations and also that the water vapor mixing ratio over the NA region is up to ∼1 ppmv higher when deep convection occurs. We use a Lagrangian trajectory model to demonstrate that the structure and the location of the NA anticyclone, as well as the tropical upper tropospheric temperature, mediate the moistening impact of convection. The deep convection mainly occurs over the Central Plains region. Most of the convectively moistened air is then transported to the center of the NA anticyclone, and the anticyclonic structure helps maintain high water vapor content there. This explains both the summer seasonal cycle and interannual variability of the convective moistening efficiency in the NA region and can provide valuable insight into modeling stratospheric water vapor.
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Albert, P., R. Bennartz, R. Preusker, R. Leinweber et J. Fischer. « Remote Sensing of Atmospheric Water Vapor Using the Moderate Resolution Imaging Spectroradiometer ». Journal of Atmospheric and Oceanic Technology 22, no 3 (1 mars 2005) : 309–14. http://dx.doi.org/10.1175/jtech1708.1.
Texte intégralRésumé :
Abstract This paper presents first validation results for an algorithm developed for the retrieval of integrated columnar water vapor from measurements of the Moderate Resolution Imaging Spectroradiometer (MODIS) instrument on board the polar-orbiting Terra and Aqua platforms. The algorithm is based on the absorption of reflected solar radiation by atmospheric water vapor and allows the retrieval of integrated water vapor above cloud-free land surfaces. A comparison of the retrieved water vapor with measurements of the Microwave Water Radiometer at the Atmospheric Radiation Measurement (ARM) Southern Great Plains (SGP) site for a 10-month period in 2002 showed an rms deviation of 1.7 kg m−2 and a bias of 0.6 kg m−2. A comparison with radio soundings in central Europe from July 2002 to April 2003 showed an rms deviation of 2 kg m−2 and a bias of −0.8 kg m−2.
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Prueger, J. H., J. L. Hatfield, T. B. Parkin, W. P. Kustas, L. E. Hipps, C. M. U. Neale, J. I. MacPherson, W. E. Eichinger et D. I. Cooper. « Tower and Aircraft Eddy Covariance Measurements of Water Vapor, Energy, and Carbon Dioxide Fluxes during SMACEX ». Journal of Hydrometeorology 6, no 6 (1 décembre 2005) : 954–60. http://dx.doi.org/10.1175/jhm457.1.
Texte intégralRésumé :
Abstract A network of eddy covariance (EC) and micrometeorological flux (METFLUX) stations over corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] canopies was established as part of the Soil Moisture–Atmosphere Coupling Experiment (SMACEX) in central Iowa during the summer of 2002 to measure fluxes of heat, water vapor, and carbon dioxide (CO2) during the growing season. Additionally, EC measurements of water vapor and CO2 fluxes from an aircraft platform complemented the tower-based measurements. Sensible heat, water vapor, and CO2 fluxes showed the greatest spatial and temporal variability during the early crop growth stage. Differences in all of the energy balance components were detectable between corn and soybean as well as within similar crops throughout the study period. Tower network–averaged fluxes of sensible heat, water vapor, and CO2 were observed to be in good agreement with area-averaged aircraft flux measurements.
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Garman, RH, DE Dodd et B. Ballantyne. « Central neurotoxicity induced by subchronic exposure to 2,4-pentanedione vapour ». Human & ; Experimental Toxicology 14, no 8 (août 1995) : 662–71. http://dx.doi.org/10.1177/096032719501400807.
Texte intégralRésumé :
1 Male and female Fischer 344 rats were exposed to 2,4- pentanedione (2,4-PD) vapour acutely (4 h) at 1265 or 1811 ppm, or for 6 h day-1 , 5 days a week for 14 weeks to 0, 101, 307 or 650 ppm. 2 Mortality occurred during or within a few hours of the acute exposures (10% at 1265 ppm; 70% at 1811 ppm). No animal had gross or microscopic brain lesions. 3 All female rats (20) and 10 of 30 male rats exposed to 650 ppm 2,4-PD vapour died by the 38th study day (29 exposures); there were no subsequent male deaths. Twenty-five of the 30 animals that died, and seven of the 15 males that survived, had light microscopical evidence of degenerative lesions, principally within the caudate/putamen nuclei, nuclei of the cerebellar medulla, and vestibular nuclei. Less frequently involved, in animals that died, were various regions of the cerebral cortex. The early histopathological lesions, seen from the 16th study day (12 exposures) to the 38th study day (28 exposures) were characterised by malacia. When present, lesions in male rats surviving the 14-weeks of 650 ppm 2, 4-PD expo sure were characterised by malacia and gliosis. No peripheral nerve lesions were seen by light or transmis sion electron microscopy. 4 Neither mortality nor neuropathology were seen in rats subchronically exposed to 101 or 307 ppm, 2,4-PD vapour.
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Lackmann, Gary M. « The South-Central U.S. Flood of May 2010 : Present and Future* ». Journal of Climate 26, no 13 (1 juillet 2013) : 4688–709. http://dx.doi.org/10.1175/jcli-d-12-00392.1.
Texte intégralRésumé :
Abstract Previous studies have documented a feedback mechanism involving the cyclonic low-level jet (LLJ), poleward moisture flux and flux convergence, and condensational heating. Increased water vapor content and potentially heavier precipitation accompanying climate warming suggest the hypothesis that this feedback could strengthen with warming, contributing to amplification of precipitation extremes beyond what the thermodynamically controlled vapor increase would provide. Here, this hypothesis is tested with numerical simulations of a severe flooding event that took place in early May 2010 in the south-central United States. Control simulations with a mesoscale model capture the main features of the May 2010 flooding event. A pseudo–global warming approach is used to modify the current initial, surface, and boundary conditions by applying thermodynamic changes projected by an ensemble of GCMs for the A2 emission scenario. The observed synoptic pattern of the flooding event is replicated but with modified future thermodynamics, allowing isolation of thermodynamic changes on the moisture feedback. This comparison does not indicate a strengthening of the LLJ in the future simulation. Analysis of the lower-tropospheric potential vorticity evolution reveals that the southern portion of the LLJ over the Gulf of Mexico in this event was strengthened through processes involving the terrain of the Mexican Plateau; this aspect is largely insensitive to climate change. Despite the lack of LLJ strengthening, precipitation in the future simulation increased at a super Clausius–Clapeyron rate because of strengthened convective updrafts.
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Yu, W., L. Tian, Y. Ma, B. Xu et D. Qu. « Simultaneous monitoring of stable oxygen isotope composition in water vapour and precipitation over the central Tibetan Plateau ». Atmospheric Chemistry and Physics 15, no 18 (16 septembre 2015) : 10251–62. http://dx.doi.org/10.5194/acp-15-10251-2015.
Texte intégralRésumé :
Abstract. This study investigated daily δ18O variations of water vapour (δ18Ov) and precipitation (δ18Op) simultaneously at Nagqu on the central Tibetan Plateau for the first time. Data show that the δ18O tendencies of water vapour coincide strongly with those of associated precipitation. The δ18O values of precipitation affect those of water vapour not only on the same day, but also for the following several days. In comparison, the δ18O values of local water vapour may only partly contribute to those of precipitation. During the entire sampling period, the variations of δ18Ov and δ18Op at Nagqu did not appear dependent on temperature, but did seem significantly dependent on the joint contributions of relative humidity, pressure, and precipitation amount. In addition, the δ18O changes in water vapour and precipitation can be used to diagnose different moisture sources, especially the influences of the Indian monsoon and convection. Moreover, intense activities of the Indian monsoon and convection may cause the relative enrichment of δ18Op relative to δ18Ov at Nagqu (on the central Tibetan Plateau) to differ from that at other stations on the northern Tibetan Plateau. These results indicate that the effects of different moisture sources, including the Indian monsoon and convection currents, need be considered when attempting to interpret paleoclimatic records on the central Tibetan Plateau.
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Terekhov, Alexey, Nurlan Abayev et Irina Vitkovskaya. « The effect of changing stratification in the atmosphere in central zone of Eurasia according to vegetation data of Tien Shan mountains during 2002-2019 ». E3S Web of Conferences 149 (2020) : 03004. http://dx.doi.org/10.1051/e3sconf/202014903004.
Texte intégralRésumé :
On the basis of long-term dynamics of the July’s vegetation data (NDVI and VCI indices) for 31 ranges of the Tien Shan and Jungarian Alatau arid mountains located in the Eurasia center are found the atmosphere stratification change. The variability of Atlantic Ocean water vapor transport ability over Northern Tien Shan ranges to the Inner Tien Shan was detected. This phenomenon not related to the overall seasonal humidity but is obviously associated with atmosphere stratification regimes. The analyzed period consists of two eras from 2002–2008 and 2008–2019 years, which differ in the regime of accessibility of the Inner Tien Shan ranges for water vapor from Atlantic Ocean. The overall tendency of the changes in 2002–2019 is the increase in the availability ocean water vapor to the Inner Tien Shan ranges. Recorded changes may be due to global air temperature increases and atmospheric processes intensification.
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Salman, Aseel D., et Osama T. Al-Taai. « Spatiotemporal Distribution for Precipitable Water Vapor and Precipitation Over Iraq during the Period (1979-2019) ». NeuroQuantology 20, no 1 (31 janvier 2022) : 256–71. http://dx.doi.org/10.14704/nq.2022.20.1.nq22265.
Texte intégralRésumé :
Water vapor plays an important role in transporting sensible heat and latent heat and is important in cloud fashioning, and precipitation fashioning, it’s one of the more important greenhouse gases so it plays an essential role in climate change. To strengthen understanding of climate change, it is necessary to analyze the spatial and temporal PWV and P distribution and variations and association between them. This research aims to calculate Precipitable Water Vapor and Precipitation Conversion Efficiency and spatial and temporal PWV and P distribution and association between them for Iraq for the period (1979-2019). In this research temperature and dew point temperature and precipitation has been downloaded from ECMWF to calculate saturation vapor pressure and actual vapor pressure and mixing ratio and that’s necessary to calculate Precipi table Water Vapor and Precipitation Conversion Efficiency. spatial distribution and temporal variation of monthly and total annual and a seasonal average of PWV and P have been studied for twelve stations covering north, east, west, central and southern (Sulaymaniah, Zakho, Kirkuk, Mosul, Erbil, Khanaqine Baghdad, Rutba, Karbala, Smawa, Nasiryia, Amarah). The results showed that larger Precipitable water vapor does not necessarily correspond to larger PCE, as well as the Precipitable water vapor increases in the station that characterizes high temperature and location near a water source so its increase in south station and decrease in the northeast stations . While precipitation increase in stations that located in mountains region and characterize by low temperature so its increase in Sulaymaniyah, Erbil and Zakho stations. And there is a negative relation between P and PWV.
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Federico, S., C. Bellecci et R. L. Walko. « A LEPS approach to the predictability of intense rain storms in the Central Mediterranean basin ». Advances in Geosciences 16 (9 avril 2008) : 89–95. http://dx.doi.org/10.5194/adgeo-16-89-2008.
Texte intégralRésumé :
Abstract. This study investigates a method for best member selection of a Limited area model Ensemble Prediction System (LEPS) with the goal to increase quantitative precipitation forecast. A case study that occurred between 22-24 May 2002 over Calabria, southern Italy, is discussed. Mediterranean storms often develop under upper level disturbances which are usually associated with high values of potential vorticity. Anomalously high values of potential vorticity can be identified by the METEOSAT water vapor channel centered around 6.3 μm because they are associated with dark band on the METEOSAT image. This signature offers a chance to identify the upper level disturbance that can be exploited in data void countries as Calabria. The working hypothesis is that the uncertainty in the representation of the upper-level disturbance has a major impact on the precipitation forecast. This issue is utilized in an ensemble forecast where member forecasts are compatible with the analysis and forecast errors. These members are grouped in five clusters by a hierarchical clustering technique which utilizes the height of the dynamical tropopause to compute distances between members. Therefore the members of a cluster have a similar representation of the upper level disturbance. For each cluster a representative member is selected and its pseudo water vapor image is compared with the corresponding METEOSAT 7 water vapor image at a specific time, antecedent to the rain occurrence over Calabria. The subjective evaluation of the comparison allows to gain physical insight in the storm evolution and to select representative members which are more in agreement with the METEOSAT image. Results, even if for a case study, show the feasibility of the methodology that, if confirmed by further investigations, could be valuable in data void countries as the central Mediterranean basin.
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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 (1 mars 2022) : 1399–421. http://dx.doi.org/10.1175/jcli-d-21-0329.1.
Texte intégralRésumé :
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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Yang, Long, Maofeng Liu, James A. Smith et Fuqiang Tian. « Typhoon Nina and the August 1975 Flood over Central China ». Journal of Hydrometeorology 18, no 2 (31 janvier 2017) : 451–72. http://dx.doi.org/10.1175/jhm-d-16-0152.1.
Texte intégralRésumé :
Abstract The August 1975 flood in central China was one of the most destructive floods in history. Catastrophic flooding was the product of extreme rainfall from Typhoon Nina over a 3-day period from 5 to 7 August 1975. Despite the prominence of the August 1975 flood, relatively little is known about the evolution of rainfall responsible for the flood. Details of extreme rainfall and flooding for the August 1975 event in central China are examined based on empirical analyses of rainfall and streamflow measurements and based on downscaling simulations using the Weather Research and Forecasting (WRF) Model, driven by Twentieth Century Reanalysis (20CR) fields. Key hydrometeorological features of the flood event are placed in a climatological context through hydroclimatological analyses of 20CR fields. Results point to the complex evolution of rainfall over the 3-day period with distinctive periods of storm structure controlling rainfall distribution in the flood region. Blocking plays a central role in controlling anomalous storm motion of Typhoon Nina and extreme duration of heavy rainfall. Interaction of Typhoon Nina with a second tropical depression played a central role in creating a zone of anomalously large water vapor transport, a central feature of heavy rainfall during the critical storm period on 7 August. Analyses based on the quasigeostrophic omega equation identified the predominant role of warm air advection for synoptic-scale vertical motion. Back-trajectory analyses using a Lagrangian parcel tracking algorithm are used to assess and quantify water vapor transport for the flood. The analytical framework developed in this study is designed to improve hydrometeorological approaches for flood-control design.
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Wanderley, Henderson Silva. « Tenência do vapor de água na baixa Troposfera da América do Sul ». Caderno de Geografia 30, no 61 (4 avril 2020) : 323. http://dx.doi.org/10.5752/p.2318-2962.2020v30n61p323.
Texte intégralRésumé :
O vapor de água é um constituinte importante da atmosfera por interferir na distribuição da temperatura, participar ativamente dos processos de absorção e emissão de calor sensível e latente pela atmosfera e por ser um dos principais agentes do efeito estufa. No entanto, o entendimento de como o vapor de água variou nas ultimas décadas é escasso principalmente para regiões como a América do Sul. Deste modo, este estudo teve como objetivo identificar a existência de tendências na concentração de vapor de água na baixa troposfera da América do Sul. Para o desenvolvimento deste estudo foram utilizadas informações médias mensais e anuais da concentração de vapor de água troposférico, compreendidos entre os anos 1980 a 2014, analisadas para o nível bárico de 700 hPa, provenientes de radiossondagens. As tendências foram calculadas pelo teste estatístico não paramétrico de Mann-Kendall juntamente com a análise de regressão linear mediante a utilização do teste de significância para o coeficiente angular da regressão. Os resultados mostraram dois padrões distintos de tendência para o vapor de água atmosférico. Um de aumento para as regiões Norte, Central e Leste do continente Sul Americano e um de redução para o Sul do continente.
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Zhao, Kailiang, Guofeng Zhu, Jiawei Liu, Liyuan Sang, Yinying Jiao, Xinrui Lin, Lei Wang et al. « Temporal and Spatial Distribution of Cloud Water Content in Arid Region of Central Asia ». Sustainability 14, no 23 (29 novembre 2022) : 15936. http://dx.doi.org/10.3390/su142315936.
Texte intégralRésumé :
To evaluate the distribution characteristics of water vapor content (WVC), cloud liquid water content (CLWC) and cloud ice water content (CIWC) in arid areas of central Asia from 1980 to 2019 were analyzed by using average data of ERA5 in the European Centre for Medium-Range Weather Forecasts. The results show that: On the spatial scale, the WVC in the arid area of central Asia is mainly between 2 and 26 kg·m−2. The area of maximum water vapor content is distributed in southwestern Kazakhstan and southwestern Tajikistan, with a maximum value of 26 kg·m−2. The minimum areas are distributed in eastern Tajikistan, central Kyrgyzstan, central Tajikistan, and western Xinjiang, China, with the lowest WVC of 2 kg·m−2. The maximum of CLWC areas were mainly distributed in northwest Kazakhstan, with a maximum value of 0.08 kg·m−2, while the minimum areas were distributed in Tajikistan, eastern Kyrgyzstan, and northwest China, with a minimum value of 0.02 kg·m−2. The maximum areas of CIWC were distributed in the north of Tajikistan and the west of Kyrgyzstan, possessing a maximum value of 0.06 kg·m−2. The minimum area is distributed in the western part of Central Asia with a minimum value of 0.01 kg·m−2. From 1980 to 2019, the WVC generally increased, while the annual average CIWC and CLWC appeared a downward trend.
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Hanesiak, John, Mark Melsness et Richard Raddatz. « Observed and Modeled Growing-Season Diurnal Precipitable Water Vapor in South-Central Canada ». Journal of Applied Meteorology and Climatology 49, no 11 (1 novembre 2010) : 2301–14. http://dx.doi.org/10.1175/2010jamc2443.1.
Texte intégralRésumé :
Abstract High-temporal-resolution total-column precipitable water vapor (PWV) was measured using a Radiometrics Corporation WVR-1100 Atmospheric Microwave Radiometer (AMR). The AMR was deployed at the University of Manitoba in Winnipeg, Canada, during the 2003 and 2006 growing seasons (mid-May–end of August). PWV data were examined 1) to document the diurnal cycle of PWV and to provide insight into the various processes controlling this cycle and 2) to assess the accuracy of the Canadian regional Global Environmental Multiscale (GEM) model analysis and forecasts (out to 36 h) of PWV. The mean daily PWV was 22.6 mm in 2003 and 23.8 mm in 2006, with distinct diurnal amplitudes of 1.5 and 1.8 mm, respectively. It was determined that the diurnal cycle of PWV about the daily mean value was controlled by evapotranspiration (ET) and the occurrence/timing of deep convection. The PWV in both years reached its hourly maximum later in the afternoon as opposed to at solar noon. This suggested that the surface and atmosphere were well coupled, with ET primarily being controlled by the vapor pressure deficit between the vegetation/surface and atmosphere. The decrease in PWV during the evening and overnight periods of both years was likely the result of deep convection, with or without precipitation, which drew water vapor out of the atmosphere, as well as the nocturnal decline in ET. The results did not change for days on which low-level winds were light (i.e., maximum winds from the surface to 850 hPa were below 20 km h−1), which supports the notion that the diurnal PWV pattern was associated with the daily cycles of local ET and convection/precipitation and was not due to advection. Comparison of AMR PWV with the Canadian GEM model for the growing seasons of 2003 and 2006 indicated that the model error was 3 mm (13%) or more even in the first 12 h, with mean absolute errors ranging from 2 to 3.5 mm and root-mean-square errors from 3 to 4.5 mm over the full 36-h forecast period. It was also found that the 3–9-h forecast period of GEM had better error scores in 2006 than in 2003.
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Kuwagata, Tsuneo, Atusi Numaguti et Nobuhiko Endo. « Diurnal Variation of Water Vapor over the Central Tibetan Plateau during Summer. » Journal of the Meteorological Society of Japan 79, no 1B (2001) : 401–18. http://dx.doi.org/10.2151/jmsj.79.401.
Texte intégral
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Markham, B. L., J. S. Schafer, B. N. Holben et R. N. Halthore. « Atmospheric aerosol and water vapor characteristics over north central Canada during BOREAS ». Journal of Geophysical Research : Atmospheres 102, no D24 (1 décembre 1997) : 29737–45. http://dx.doi.org/10.1029/97jd00241.
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Yu, W., L. Tian, Y. Ma, B. Xu et D. Qu. « Simultaneous monitoring of stable oxygen isotope composition in water vapour and precipitation over the central Tibetan Plateau ». Atmospheric Chemistry and Physics Discussions 15, no 10 (22 mai 2015) : 14445–72. http://dx.doi.org/10.5194/acpd-15-14445-2015.
Texte intégralRésumé :
Abstract. This study investigated the daily δ18O variations of water vapour (δ18Ov) and precipitation (δ18Op) simultaneously at Nagqu on the central Tibetan Plateau for the first time. The data show that the δ18O tendencies of water vapour coincide strongly with those of associated precipitation. The δ18O values of water vapour affect those of precipitation not only on the same day, but also for the following several days. In turn, the δ18O values of precipitation also affect those of water vapour. Hence, there exists an interaction between δ18Ov and δ18Op, and the interaction decreases gradually with time. During the entire sampling period, the variations of δ18Ov and δ18Op at Nagqu did not appear dependent on temperature, but did seem significantly dependent on the joint contributions of relative humidity, surface pressure, and precipitation amount. In addition, the δ18O changes in water vapour and precipitation can be used to diagnose different atmospheric trajectories, especially the influences of the Indian monsoon and convection. Moreover, intense activities of the Indian monsoon and convection may cause the enrichment of δ18Op relative to δ18Ov at Nagqu (on the central Tibetan Plateau) to differ from that at other stations on the northern Tibetan Plateau. These results indicate that the effects of different moisture sources, including the Indian monsoon and convection currents, need be considered when attempting to interpret paleoclimatic records on the central Tibetan Plateau.