scholarly journals On the Evaporation Duct for Inhomogeneous Conditions in Coastal Regions

2007 ◽  
Vol 46 (4) ◽  
pp. 538-543 ◽  
Author(s):  
G. L. Geernaert
Keyword(s):  
Relative Humidity ◽  
Spatial Variability ◽  
Meteorological Parameters ◽  
Meteorological Conditions ◽  
Coastal Regions ◽  
Evaporation Duct ◽  
Model Predictions ◽  
Simplifying Assumptions ◽  
Spatially Homogeneous ◽  
Spatially Varying

Abstract Evaporation ducts are ubiquitous phenomena over the oceans, and they are responsible for much of the over-the-horizon propagation occurring with millimeter and microwave radars. The height of the evaporation duct depends on meteorological parameters, most notably air and water temperature and relative humidity. In most cases, models that predict the height of the evaporation duct are based on Monin–Obukhov similarity (MOS) theory, and uncertainties in model predictions are often attributed to the simplifying assumptions behind MOS theory. In this paper, an extension to MOS theory is introduced that accommodates spatial variability of meteorological parameters in coastal regions. It is found that for even weakly varying meteorological conditions there are substantial differences in duct heights predicted when spatially varying conditions are invoked versus spatially homogeneous conditions.

scholarly journals Impacts of meteorological conditions on PM2.5 and PM10 pollution in Zhengzhou, China

2021 ◽  
Vol 257 ◽  
pp. 03025
Author(s):  
Rui Gao ◽  
Bairong Wang ◽  
Shunxiang Huang
Keyword(s):  
Air Quality ◽  
Relative Humidity ◽  
Meteorological Parameters ◽  
Meteorological Conditions ◽  
Backward Trajectory ◽  
Aerosol Pollution ◽  
Reduce Emissions ◽  
Pm2.5 And Pm10 ◽  
The Relationship ◽  
Local Emissions

Meteorological conditions play an important role in aerosol pollution. In this study, the relationships between wind, temperature, relative humidity, and aerosol concentrations (PM2.5 and PM10) in Zhengzhou from January 2016 to December 2017 were analysed. Backward trajectory model was also used to investigate the relationship between meteorological parameters and regional transport of pollutants. Significant seasonal variations can be observed in the time series of pollutants and wind, temperature and relative humidity. The simulation of backward trajectories indicated that pollutants from southeast is critical to the air quality in Zhengzhou, in addition to local emissions of pollutants. To improve the air quality in Zhengzhou, joint efforts to reduce emissions in both Zhengzhou and its southeast adjacent regions should be considered.

scholarly journals The effect of meteorological conditions on hazel (Corylus spp.) and alder (Alnus spp.) pollen concentration in the air of Szczecin

2012 ◽  
Vol 60 (2) ◽  
pp. 65-70 ◽  
Author(s):  
Małgorzata Puc
Keyword(s):  
Wind Speed ◽  
Relative Humidity ◽  
Air Temperature ◽  
Pollen Season ◽  
Meteorological Parameters ◽  
Meteorological Conditions ◽  
Maximum Temperature ◽  
Pollen Count ◽  
Pollen Concentration ◽  
In The Beginning

The aim of the study was to determine seasonal variations in concentrations of hazel and alder pollen count due to meteorological parameters. Measurements were performed using the volumetric method. The analysed meteorological parameters were the maximum temperature, relative humidity, rainfall and wind speed. The beginning and end of a season were established by the 95 % method. During seven years of study, the highest concentration of hazel pollen in the air was noted in 2003 (the total number was two - three times higher than in the other years), with the pollen season starting in most years in the beginning of January and lasting till the end of March or beginning of April. The highest concentration of alder pollen in the air was noted in 2003, similarly as hazel pollen. The pollen season started in the beginning of January (in 2003 and 2006 in the beginning of March) and lasted till the turn of the March and April. The highest pollen count of 674 grains×m<sup>-3</sup> was observed in the end of March. A positive and statistically signifi cant correlation (Pearson's coeffi cient and multiple regression) was found between the hazel and alder pollen concentration and air temperature and wind speed. A negative correlation was found in case of the relative humidity. A lot of analysed correlations were signifi cant (significance level of p=0.05), although the percentage of explained variation (R<sup>2</sup>) was very low. Besides the individual rhythm of pollination, the meteorological conditions are the most important factors (mainly air temperature and wind speed) influencing the analysed pollen concentration in the air.

scholarly journals Mechanism of Spatiotemporal Air Quality Response to Meteorological Parameters: A National-Scale Analysis in China

2019 ◽  
Vol 11 (14) ◽  
pp. 3957 ◽  
Author(s):  
Zhi Qiao ◽  
Feng Wu ◽  
Xinliang Xu ◽  
Jin Yang ◽  
Luo Liu
Keyword(s):  
Air Pollution ◽  
Air Quality ◽  
Wind Speed ◽  
Relative Humidity ◽  
Meteorological Parameters ◽  
Pollution Index ◽  
Hierarchical Cluster ◽  
Meteorological Conditions ◽  
Air Pollution Control ◽  
National Scale

The air quality over China exhibits seasonal and regional variation, resulting from heterogeneity in industrialization, and is highly affected by variability in meteorological conditions. We performed the first national-scale exploration of the relationship between the Air Pollution Index (API) and multiple meteorological parameters in China, using partial correlation and hierarchical cluster analyses. Relative humidity, wind speed, and temperature were the dominant factors influencing air quality year-round, due to their significant effects on pollutant dispersion and/or transformation of pollutants. The response of the API to single or multiple meteorological factors varied among cities and seasons, and a regional clustering of response mechanisms was observed, particularly in winter. Clear north–south differentiation was detected in the mechanisms of API response to relative humidity and wind speed. These findings provide insight into the spatiotemporal variation in air quality sensitivity to meteorological conditions, which will be useful for implementing regional air pollution control strategies.

Theoretical Principles of Streaming Current Detection

1989 ◽  
Vol 21 (6-7) ◽  
pp. 443-453 ◽  
Author(s):  
S. K. Dentel ◽  
K. M. Kingery
Keyword(s):  
Velocity Profile ◽  
Electrophoretic Mobility ◽  
Double Layer ◽  
Initial Attempt ◽  
Streaming Current ◽  
Coagulant Dosage ◽  
Model Predictions ◽  
Double Layer Model ◽  
Simplifying Assumptions ◽  
Current Detection

In spite of the increased use of streaming current detectors (SCDs) as a means of monitoring and/or controlling coagulant dosage, knowledge regarding fundamental workings is incomplete. This paper provides an initial attempt at predicting and verifying functioning compared to electrophoretic mobility. The instrument's components -- the sensor and the signal processor -- are first described. Equations modelling electro-double layer behavior in its sensor are then developed. Simplifying assumptions include the use of a capacitance model of the double layer and a triangular velocity profile for fluid within the sensor's annulus. More complex modelling approaches are also suggested which incorporate the Gouy-Chapman electro-double layer model and an exact solution for the velocity profile. Experimental results confirm predictions of the simplified model under conditions of low potential. A monotonic relationship exists between streaming current electrophoretic mobility, which is required for its use as a control parameter. Deviations from model predictions are suggested to be due to charge characteristics of the sensor surfaces themselves.

Dune-scale cross-strata across the fluvial-deltaic backwater regime: Preservation potential of an autogenic stratigraphic signature

Geology ◽  
2020 ◽  
Vol 48 (12) ◽  
pp. 1144-1148
Author(s):  
Chenliang Wu ◽  
Jeffrey A. Nittrouer ◽  
Travis Swanson ◽  
Hongbo Ma ◽  
Eric Barefoot ◽  
...  
Keyword(s):  
Spatial Variability ◽  
Mississippi River ◽  
Nonuniform Flow ◽  
Hydrodynamic Conditions ◽  
Flow Conditions ◽  
Bed Topography ◽  
Fundamental Building Block ◽  
Bed Form ◽  
Spatially Varying ◽  
Topography Data

Abstract Dune-scale cross-beds are a fundamental building block of fluvial-deltaic stratigraphy and have been recognized on Earth and other terrestrial planets. The architecture of these stratal elements reflects bed-form dynamics that are dependent on river hydrodynamic conditions, and previous work has documented a multitude of scaling relationships to describe the morphodynamic interactions between dunes and fluid flow. However, these relationships are predicated on normal flow conditions for river systems and thus may be unsuitable for application in fluvial-deltaic settings that are impacted by nonuniform flow. The ways in which dune dimensions vary systematically due to the influence of reach-averaged, nonuniform flow, and how such changes may be encoded in dune cross-strata, have not been investigated. Herein, we explored the influence of backwater flow on dune geometry in a large modern fluvial channel and its implications for interpretation of systematic variability in dune cross-strata in outcrop-scale stratigraphy. This was accomplished by analyzing high-resolution channel-bed topography data for the lowermost 410 km of the Mississippi River, which revealed that dune size increases to a maximum before decreasing toward the river outlet. This spatial variability coincides with enhanced channel-bed aggradation and decreasing dune celerity, which arise due to backwater hydrodynamics. An analytical model of bed-form stratification, identifying spatial variability of cross-set thickness, indicates a prominent downstream decrease over the backwater region. These findings can be used to inform studies of ancient fluvial-deltaic settings, by bolstering assessments of proximity to the marine terminus and associated spatially varying paleohydraulics.

scholarly journals Effects of atmospheric dynamics and aerosols on the fraction of supercooled water clouds

2017 ◽  
Vol 17 (3) ◽  
pp. 1847-1863 ◽  
Author(s):  
Jiming Li ◽  
Qiaoyi Lv ◽  
Min Zhang ◽  
Tianhe Wang ◽  
Kazuaki Kawamoto ◽  
...  
Keyword(s):  
Relative Humidity ◽  
Vertical Velocity ◽  
Meteorological Parameters ◽  
Temporal Correlation ◽  
Supercooled Liquid ◽  
Satellite Observation ◽  
Static Stability ◽  
Global Scale ◽  
Atmospheric Dynamics ◽  
Horizontal Wind

Abstract. Based on 8 years of (January 2008–December 2015) cloud phase information from the GCM-Oriented Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) Cloud Product (GOCCP), aerosol products from CALIPSO and meteorological parameters from the ERA-Interim products, the present study investigates the effects of atmospheric dynamics on the supercooled liquid cloud fraction (SCF) during nighttime under different aerosol loadings at global scale to better understand the conditions of supercooled liquid water gradually transforming to ice phase. Statistical results indicate that aerosols' effect on nucleation cannot fully explain all SCF changes, especially in those regions where aerosols' effect on nucleation is not a first-order influence (e.g., due to low ice nuclei aerosol frequency). By performing the temporal and spatial correlations between SCFs and different meteorological factors, this study presents specifically the relationship between SCF and different meteorological parameters under different aerosol loadings on a global scale. We find that the SCFs almost decrease with increasing of aerosol loading, and the SCF variation is closely related to the meteorological parameters but their temporal relationship is not stable and varies with the different regions, seasons and isotherm levels. Obviously negative temporal correlations between SCFs versus vertical velocity and relative humidity indicate that the higher vertical velocity and relative humidity the smaller SCFs. However, the patterns of temporal correlation for lower-tropospheric static stability, skin temperature and horizontal wind are relatively more complex than those of vertical velocity and humidity. For example, their close correlations are predominantly located in middle and high latitudes and vary with latitude or surface type. Although these statistical correlations have not been used to establish a certain causal relationship, our results may provide a unique point of view on the phase change of mixed-phase cloud and have potential implications for further improving the parameterization of the cloud phase and determining the climate feedbacks.

scholarly journals Inter-community variability in total particle number concentrations in the eastern Los Angeles air basin

2010 ◽  
Vol 10 (23) ◽  
pp. 11385-11399 ◽  
Author(s):  
N. Hudda ◽  
K. Cheung ◽  
K. F. Moore ◽  
C. Sioutas
Keyword(s):  
Los Angeles ◽  
Spatial Variability ◽  
Spatial Variation ◽  
Urban Areas ◽  
Particle Number ◽  
Meteorological Conditions ◽  
Monitoring Station ◽  
Size Distributions ◽  
Central Monitoring ◽  
Seasonal And Diurnal Variations

Abstract. Ultrafine Particles (UFP) can display sharp gradients in their number concentrations in urban environment due to their transient nature and rapid atmospheric processing. The ability of using air pollution data generated at a central monitoring station to assess exposure relies on our understanding of the spatial variability of a specific pollutant associated with a region. High spatial variation in the concentrations of air pollutants has been reported at scales of 10s of km for areas affected by primary emissions. Spatial variability in particle number concentrations (PNC) and size distributions needs to be investigated, as the representativeness of a monitoring station in a region is premised on the assumption of homogeneity in both of these metrics. This study was conducted at six sites, one in downtown Los Angeles and five located about 40–115 km downwind in the receptor areas of Los Angeles air basin. PNC and size distribution were measured using Condensation Particle Counters (CPC) and Scanning Mobility Particle Sizer (SMPS). The seasonal and diurnal variations of PNC implied that PNC might vary significantly with meteorological conditions, even though the general patterns at the sites may remain generally similar across the year due to consistency of sources around them. Regionally transported particulate matter (PM) from upwind urban areas of Los Angeles lowered spatial variation by acting as a "homogenizing" factor during favorable meteorological conditions. Spatial variability also increased during hours of the day during which the effects of local sources predominate. The spatial variability associated with PNC (quantified using Coefficients of Divergence, CODs), averaged about 0.3, which was generally lower than that based on specific size ranges. Results showed an inverse relationship of COD with particles size, with fairly uniform values in the particle range which is associated with regional transport. Our results suggest that spatial variability, even in the receptor regions of Los Angeles Basin, should be assessed for both PNC and size distributions, and should be interpreted in context of seasonal and diurnal influences, and suitably factored if values for exposure are ascertained using a central monitoring station.

scholarly journals DUNE EROSION AND SEDIMENT PROFILE DUE TO WAVE UPRUSH

1988 ◽  
Vol 1 (21) ◽  
pp. 106
Author(s):  
T.A. Fenaish ◽  
M.F. Overton ◽  
J.S. Fisher
Keyword(s):  
Steady State ◽  
Shoreline Change ◽  
Meteorological Conditions ◽  
Beach Profile ◽  
Coastal Regions ◽  
Steady State Condition ◽  
Severe Storms ◽  
Dune Erosion ◽  
Major Threat ◽  
Equilibrium Profile

Shorelines are continuously adjusting in response to the changing hydraulic and meteorological conditions. Storms that generate large waves and surge conditions can alter the nearshore topography and relocate the beach shorelines, often with substantial amounts of beach and dune erosion. Such storms pose a major threat to coastal developments for which the economic impact can be significant. The ability to predict the rate of erosion and, consequently the shoreline change, is important in making decisions regarding the planning and managing of the coastal regions. In general, the available methods for the prediction of beach and dune erosion are based on the assumption of post-storm equilibrium profile. In this approach it is assumed that, for a given set of wave and surge conditions, the entire beach reaches a steadystate, and that the volume of sand released from the dune is equal to the volume of sand required to establish this profile. Existing methods that are based on this concept include those developed by Edelman (1968, 1972), Vellinga (1982, 1983, 1986), Kriebel and Dean (1984), Sargent and Birkemeier (1985), and Kobayashi (1987).. The reliance of these methods on the assumption of steady-state condition limits their application to extreme events generated by severe storms. Generally, storms do not have sufficient duration or intensity, such that the beach profile attains equilibrium during the storm.

scholarly journals Effects of the solar eclipse on 15 January 2010 on the surface O<sub>3</sub>, NO, NO<sub>2</sub>, NH<sub>3</sub>, CO mixing ratio and the meteorological parameters at Thiruvanathapuram, India

2010 ◽  
Vol 28 (6) ◽  
pp. 1199-1205 ◽  
Author(s):  
S. K. Sharma ◽  
T. K. Mandal ◽  
B. C. Arya ◽  
M. Saxena ◽  
D. K. Shukla ◽  
...  
Keyword(s):  
Wind Speed ◽  
Relative Humidity ◽  
Solar Eclipse ◽  
Meteorological Parameters ◽  
Total Solar Eclipse ◽  
Ozone Formation ◽  
Mixing Ratio ◽  
Night Time ◽  
Photochemical Ozone ◽  
Surface O3

Abstract. In this paper, we present the effect of total solar eclipse on surface O3, NO, NO2, NH3, CO mixing ratio and the meteorological parameters on 15 January 2010 at Thiruvanathapuram, India. On the day of total solar eclipse (i.e., 15 January 2010), the decrease in mixing ratio of surface O3 and NO2 is observed after the beginning of the solar eclipse events (11:15 to 15:30). Decrease in surface O3 may be due to decreased efficiency of the photochemical ozone formation, whereas, mixing ratio of NO and NH3 have been changed following the night time chemistry. Surface O3 reduced to 20.3 ppb after 22 min of full phase of the eclipse. During the solar eclipse period, the ambient temperature and wind speed have decreased, whereas, relative humidity has increased as expected.

Effects of Various Parameters on Nanofluid Thermal Conductivity

2006 ◽  
Vol 129 (5) ◽  
pp. 617-623 ◽  
Author(s):  
Seok Pil Jang ◽  
Stephen U. S. Choi
Keyword(s):  
Thermal Conductivity ◽  
Thermal Behavior ◽  
Volume Fraction ◽  
Heat Transfer Fluids ◽  
New Concepts ◽  
Model Predictions ◽  
Simplifying Assumptions ◽  
Thermal Phenomena ◽  
First Time ◽  
Good Agreement

The addition of a small amount of nanoparticles in heat transfer fluids results in the new thermal phenomena of nanofluids (nanoparticle-fluid suspensions) reported in many investigations. However, traditional conductivity theories such as the Maxwell or other macroscale approaches cannot explain the thermal behavior of nanofluids. Recently, Jang and Choi proposed and modeled for the first time the Brownian-motion-induced nanoconvection as a key nanoscale mechanism governing the thermal behavior of nanofluids, but did not clearly explain this and other new concepts used in the model. This paper explains in detail the new concepts and simplifying assumptions and reports the effects of various parameters such as the ratio of the thermal conductivity of nanoparticles to that of a base fluid, volume fraction, nanoparticle size, and temperature on the effective thermal conductivity of nanofluids. Comparison of model predictions with published experimental data shows good agreement for nanofluids containing oxide, metallic, and carbon nanotubes.

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