Plume Width Research Articles

NH<sub>3</sub> emissions from large point sources derived from CrIS and IASI satellite observations

Abstract. Ammonia (NH3) is an essential reactive nitrogen species in the biosphere and through its use in agriculture in the form of fertilizer (important for sustaining humankind). The current emission levels, however, are up to 4 times higher than in the previous century and continue to grow with uncertain consequences to human health and the environment. While NH3 at its current levels is a hazard to environmental and human health, the atmospheric budget is still highly uncertain, which is a product of an overall lack of measurements. The capability to measure NH3 with satellites has opened up new ways to study the atmospheric NH3 budget. In this study, we present the first estimates of NH3 emissions, lifetimes and plume widths from large (>∼5 kt yr−1) agricultural and industrial point sources from Cross-track Infrared Sounder (CrIS) satellite observations across the globe with a consistent methodology. The same methodology is also applied to the Infrared Atmospheric Sounding Interferometer (IASI) (A and B) satellite observations, and we show that the satellites typically provide comparable results that are within the uncertainty of the estimates. The computed NH3 lifetime for large point sources is on average 2.35±1.16 h. For the 249 sources with emission levels detectable by the CrIS satellite, there are currently 55 locations missing (or underestimated by more than an order of magnitude) from the current Hemispheric Transport Atmospheric Pollution version 2 (HTAPv2) emission inventory and only 72 locations with emissions within a factor of 2 compared to the inventories. The CrIS emission estimates give a total of 5622 kt yr−1, for the sources analyzed in this study, which is around a factor of ∼2.5 higher than the emissions reported in HTAPv2. Furthermore, the study shows that it is possible to accurately detect short- and long-term changes in emissions, demonstrating the possibility of using satellite-observed NH3 to constrain emission inventories.

More Than Emissions and Chemistry: Fire Size, Dilution, and Background Aerosol Also Greatly Influence Near‐Field Biomass Burning Aerosol Aging

AbstractBiomass burning emits particles (black carbon and primary organic aerosol) and precursor vapors to the atmosphere that chemically and physically age in the atmosphere. This theoretical study explores the relationships between fire size (determining the initial plume width and concentration), dilution rate, and entrainment of background aerosol on particle coagulation, organic aerosol (OA) evaporation, and secondary organic aerosol (SOA) condensation in smoke plumes. We examine the impacts of these processes on aged smoke OA mass, geometric mean diameter (Dg), peak lognormal modal width (σg), particle extinction (E), and cloud condensation nuclei (CCN) concentrations. In our simulations, aging OA mass is controlled by competition between OA evaporation and SOA condensation. Large, slowly diluting plumes evaporate little in our base set of simulations, which may allow for net increases in mass, E, CCN , and Dg from SOA condensation. Smaller, quickly diluting fire plumes lead to faster evaporation, which favors decreases in mass, E, CCN, and Dg. However, the SOA fraction of the smoke OA increases more rapidly in smaller fires due to faster primary organic aerosol evaporation leading to more SOA precursors. Net mass changes for smaller fires depend on background OA concentrations; increasing background aerosol concentrations decrease evaporation rates. Although coagulation does not change mass, it can decrease the number of particles in large/slowly diluting plumes, increasing Dg and E, and decreasing σg. While our conclusions are limited by being a theoretical study, we hope they help motivate future smoke‐plume analyses to consider the effects of fire size, meteorology, and background OA concentrations.

Experimental study of the spray collapse process of multi-hole gasoline fuel injection at flash boiling conditions

In this study, fuel sprays of a 1-hole injector and a 6-hole injector were investigated under a wide range of subcooled and flash-boiling conditions using high-speed imaging in a constant-volume spray chamber. The fuel pressure was held constant at 15 MPa, and the fuel temperature was varied from 25 °C to 85 °C. Ambient pressure in the spray chamber was varied from 20 kPa to 200 kPa and the chamber temperature was held constant at 25 °C. The results show decreasing ambient pressure led to flash boiling for sprays from the 1-hole injector and consequently enhanced fuel atomization; however, the spray processes of the multi-hole injector were not well represented by the single-hole injector when considering spray collapse. For the 6-hole injector, the results showed plume interaction was more important than chamber density in controlling the spray characteristics. Specifically, expanded fuel plumes induced by flash boiling increased interaction between adjacent fuel plumes and consequently affected the spray structure. Slight plume interaction resulted in moderate spray collapse, shorter spray penetration and wider spray angles. Strong plume interaction triggered severe spray collapse, leading to longer spray penetration and smaller spray angles. Plume interaction started in the near nozzle region, and sustained interaction depended on the injector configuration and the superheat degree. At strong flash-boiling conditions (where the ratio of the ambient pressure to the fuel saturation pressure was less than 0.3), plume interaction increased with time and as the spray moved downward away from the nozzle exit due to fast fuel atomization and evaporation. The potential for spray collapse of a multi-hole injector was primarily attributed to the effects of the fuel properties, injector configuration and operating conditions (e.g. ambient pressure, fuel temperature and pressure, etc.) on the development of the plume width relative to changes in the distance between adjacent plumes. Adjusting the parameters to increase the distance between adjacent fuel plumes or decrease plume width, will decrease plume interaction and spray collapse can be suppressed, and vice versa.

The role of tides in the spreading of Mediterranean Outflow waters along the southwestern Iberian margin

The impact of tides on the spreading of the Mediterranean Outflow Waters (MOW) in the Gulf of Cadiz is investigated through a series of targeted numerical experiments using an ocean general circulation model. The full ephimeridic luni-solar tidal potential is included as forcing. The model grid is global with a strong zoom around the Iberian Peninsula. Thus, the interaction of processes of different space and time scales, which are involved in the MOW spreading, is enabled. This is of particular importance in the Strait of Gibraltar and the Gulf of Cádiz, where the width of the MOW plume is a few tens of km. The experiment with enabled tides successfully simulates the main tidal features of the North Atlantic and in the Gulf of Cádiz and the Strait of Gibraltar. The comparison of the fields from simulations with and without tidal forcing shows drastically different MOW pathways in the Gulf of Cádiz: The experiment without tides shows an excessive southwestward spreading of Mediterranean Waters along the North African slope, whereas the run with tides is closer to climatology. A detailed analysis indicates that tidal residual currents in the Gulf of Cádiz are the main cause for these differences.

Velocity measurements of a bench scale buoyant plume applying particle image velocimetry

This paper presents the experimental investigation of the buoyant plume above an electrically heated block of copper. The velocity field in a vertical plane along the plume axis is investigated via particle image velocimetry. Experiments with electrical power from 30 W to 96 W are carried out, which lead to heat source temperatures of 149–307 °C. The resulting flow is laminar for the lowest power setting and undergoes a transition to turbulent flow for higher heat inputs. With increasing heat input the point of transition from laminar to turbulent flow occurs at lower heights.Time-averaged velocity fields are presented together with the according measurement uncertainty that results from the evaluation with particle image velocimetry. Based on these velocity fields a number of characteristic values for the plume is derived in different heights, e.g.maximum velocities, plume widths and flow integrals. In order to further evaluate the transition from laminar to turbulent flow the vertical velocity and the standard deviation of the horizontal velocity along the plume axis and as a function of the Grashof number are investigated. The transition occurs at Grashof numbers in the range 4×108<Gr<2×109, which is in accordance with previous findings. In addition to the velocity measurements, the temperature stratification inside the enclosure is measured to quantify the ambient conditions.

Heavy particle transport in a trellised agricultural canopy during non-row-aligned winds

Agricultural systems are exposed to and influenced by particles of many types (e.g., pathogens, pollen, pests), the concentrations of which are typically highest in the regions immediately surrounding their sources. The intermittent nature of trellised canopies creates an unique canopy architecture that directly affects the shape of particulate plumes and tends to alter their transport patterns in the near-source region. To investigate the behavior of particle plumes near their sources in a trellised canopy, a set of particle release experiments was conducted during a field campaign in an Oregon vineyard in 2013. Specifically, plumes of inert fluorescent microspheres (10–45 μm diameter) were released into the canopy during periods when the mean wind direction was significantly different from the vine-row direction. Plume concentrations were collected at over 100 separate locations in a three-dimensional space <10 canopy heights downwind of the source during each release period. These plumes were more complex than those released during periods of row-aligned winds. A novel analysis approach using the superposition of two orthogonal Gaussian plume equations was developed to quantitatively assess the behavior of the plumes’ shape and its dependence on wind direction and magnitude and on particle release height. Basic plume shape parameters, as determined by integrating the superposed Gaussian equation, varied significantly as a function of the mean wind direction. As the wind direction changed from roughly row-diagonal to directly row-normal, the rate at which the spanwise plume width increased with downwind distance increased by a factor of two. Similarly, the rate at which the plume height increased with downwind distance was higher for row-perpendicular plumes than for row-diagonal plumes. Row-diagonal plumes exhibited a much higher spanwise skewness than did the row-normal plumes, but for all plumes the skewnesses tended towards zero (symmetric) with increasing downwind distance.

Characteristics of near-nozzle spray development from a fouled GDI injector

The near-nozzle spray development of a typical fouled gasoline direct injection (GDI) injector was investigated. The fouled injector had been used in a stratified-charge combustion GDI engine and showed typical characteristics, such as accumulated deposits inside and around the nozzles and a reduced flow rate of 2.9–5.7%. Back-illumination and Mie-scattering methods were employed in spray experiments, in conjunction with a high speed camera and a macro lens, to assess the near-nozzle spray behaviors. The experimental results show that at all injection pressures tested, the interaction between deposits and spray led to several poor spray behaviors during the full injection evolution, including spray distortion, residual fuel storage in the nozzles and deposits layer, liquid splashing, the formation of ligament and large droplets and tip wetting/dripping. These effects all may result in high soot emissions. The after-injection stage of the fouled injector produced more liquid ligaments than that of the new injector. It was also found that high injection pressures did not improve atomization during after-injection, nor reduce the amounts of ligaments and droplet clusters beyond the main spray boundary. The plume width and projected spray area of a single nozzle in the fouled injector were decreased by 5–7% and 17–20%, respectively, due to fuel flow losses. The delays in the start of injection and end of injection were approximately 20 μs and 30–40 μs, respectively.

Modelling subsea gas releases and resulting gas plumes using Computational Fluid Dynamics

A Computational Fluid Dynamics (CFD) model was developed to describe the behavior of a subsea gas release and the subsequent rising gas plume. Four numerical approaches were assessed for their suitability to capture the characteristic behaviors in a rising gas plume by comparing the CFD results with experimental data obtained from an underwater gas release experiment carried out in a towing tank basin with 10 m depth.The k-ε turbulence model was found to be unsatisfactory in capturing random wandering behavior of the subsea gas plume due to the inherent Reynolds-Averaged Navier-Stokes (RANS) nature of the approach. The result is an over-prediction of the plume central line velocity and an under-prediction of the plume width as there was no mechanism to distribute and dissipate the high momentum gained during the initial gas release phase. The results obtained using the Large Eddy Simulation (LES) approach show the inherently random wandering behavior of the plume is successfully captured and both the centerline velocity and the velocity profile are in much better agreement with the experimental data.The study was carried out using air as released gas. This was done to compare with the available experimental data where air was used as the source. However the CFD model developed is applicable for actual subsea gases.

Characterization of the external and internal flow structure of an aerated-liquid injector using X-ray radiography and fluorescence

In the present study, the internal flowfield of aerated-liquid fuel injectors is examined through X-ray radiography and X-ray fluorescence. An inside–out injector, consisting of a perforated aerating tube within an annular liquid stream, sprays into a quiescent environment at a fixed mass flow rate of water and nitrogen gas. The liquid is doped with bromine (in the form of NaBr) to create an X-ray fluorescence signal. This allows for reasonable absorption and fluorescence signals, and one or both diagnostics can be used to track the liquid distribution. The injector housing is fabricated from beryllium (Be), which allows the internal flowfield to be examined (as Be has relatively low X-ray attenuation coefficient). Two injector geometries are compared, illustrating the effects of aerating orifice size and location on the flow evolution. Time-averaged equivalent pathlength and line-of-sight averaged density ρ(y) reveal the formation of the two-phase mixture, showing that the liquid film thickness along the injector walls is a function of the aerating tube geometry, though only upstream of the nozzle. These differences in gas and liquid distribution (between injectors with different aerating tube designs) are suppressed as the mixture traverses the nozzle contraction. The averaged liquid velocity (computed from the density and liquid mass flow rate) reveals a similar trend. This suggests that at least for the current configurations, the plume width, liquid mass distribution, and averaged liquid velocity for the time-averaged external spray are insensitive to the aerating tube geometry.

Taylorian diffusion in mildly inhomogeneous turbulence

Taylor’s theory of dispersion was extended to produce estimates of the far–field growth rate of the plume of a passive scalar in grid turbulence (GT) and in uniformly sheared flow (USF), both of which evolve in the streamwise direction. Expressions for the evolution of the plume width relative to the integral length scale of turbulence were also derived. The predictions of plume growth rate were tested against available data in both of these types of flows and were found to be accurate in an extensive region of USF and compatible with an extrapolated trend in GT, in which the available data did not extend very far from the scalar source. Although in both cases the measured half-width of the plume was comparable in magnitude to the streamwise integral length scale of the turbulence, the far–field approximation seemed to hold.

Low-frequency active acoustic response of underwater bubble plumes

Active, low frequency acoustics may provide a method of locating and identifying methane bubble plumes over a large area by exciting radial and column resonances. In this work, a proof of concept experiment was conducted by measuring the active, low frequency response of an air bubble plume at the Lake Travis Test Station at the University of Texas at Austin. Several flow rates, bubble sizes, and plume widths were investigated. The test consisted of insonifying the plumes at two different standoff distances using a low-frequency chirp from 300-2500 Hz. The plume response was much longer in time than originally expected due to resonant ringing. The long-time response was modeled with a finite element model, which predicted the column resonance. This behavior may be able to be exploited for long-range bubble plume identification. [Work supported by ExxonMobil.]

Evolution and statistics of thermal plumes in tilted turbulent convection

We present a systematic experimental study of thermal plumes within tilted turbulent thermal convection using the shadowgraph technique. The measurements are performed in a rectangular cell (aspect ratio Γx=1 and Γy=0.25) over a wide range of tilt angles (0⩽β⩽π/2rad) at constant Prandtl (Pr≃10) and Rayleigh (Ra≃6.80×1010) numbers. It is found that the plume width, λ, is distributed log-normally in space and the time-averaged most probable plume width, 〈λp〉, has similar scale with the thermal boundary layer thickness, λT. 〈λp〉 and λT slowly increase as tilt angle, β, increases from 0 to 1rad and they broaden rapidly as β>1rad. The average plume area density, 〈Φ〉, deduced from the image intensity, is proposed to represent the heat flux of thermal plumes. Its β dependence is consistent with that of the Nusselt number, Nu, over the tilt angle range. λp and Φ exhibit oscillation of convective flow. The oscillation intensity and period strongly depend on β, but are less affected by Ra and Pr. The plume velocity exhibits a different pattern from that of the two-dimensional convective flow measured at Pr≃6.3 and Ra≃4.42×109. The magnitude of plume velocity peak is weakly affected by the cell tilting. The position of the plume velocity peak increases linearly with increasing β.

Shear dispersion in the turbulent atmospheric boundary layer

The problem of shear dispersion in the atmospheric boundary layer (ABL) is revisited. The aim is to improve understanding of how and why the behaviour of state‐of‐the‐art ‘random flight’ Lagrangian particle dispersion models (RFMs) can differ from that of simpler ‘random displacement’ models (RDMs or eddy diffusivity models). First an asymptotic analysis is used to obtain a formula, valid for quite general profiles of turbulent statistics and the mean wind, for the effective horizontal diffusivity of a tracer in the ABL. Second, with ‘poison gas release’ problems in mind, a large‐deviation approach is used to understand in greater detail the behaviour of the concentration in the tails of the distribution. Results are verified by solving the RFM equations numerically for a large ensemble of particles. Turbulent statistics relevant to stable and neutral boundary‐layer conditions are considered, as is the effect of non‐uniqueness in the RFM equations. The importance of three‐dimensional effects such as the effect of an Ekman spiral in the mean wind are then considered, and criteria determining whether plume widths are controlled by direct horizontal diffusion or by secondary shear dispersion effects are obtained. Finally, a quantitative account of ‘plume bending’ in the stable ABL is presented.

Submarine groundwater discharge and solute transport under a transgressive barrier island

Many recent investigations of groundwater dynamics in beaches employed groundwater models that assumed isotropic, numerically-convenient hydrogeological conditions. Real beaches exhibit local variability with respect to stratigraphy, sediment grain size and associated topographic profile, so that groundwater flow may diverge significantly from idealized models. We used a combination of hydrogeologic field methods and a variable-density, saturated-unsaturated, transient groundwater flow model to investigate SGD and solute transport under Cabretta Beach, a small transgressive barrier island seaward of Sapelo Island, Georgia. We found that the inclusion of real beach heterogeneity drove important deviations from predictions based on theoretical beaches. Cabretta Beach sustained a stronger upper saline plume than predicted due to the presence of a buried silty mud layer beneath the surface. Infiltration of seawater was greater for neap tides than for spring tides due to variations in beach slope. The strength of the upper saline plume was greatest during spring tides, contrary to recent model predictions. The position and width of the upper saline plume was highly dynamic through the lunar cycle. Our results suggest that field measurements of salinity gradients may be useful for estimating rates of tidally and density driven recirculation through the beach. Finally, our results indicate that several important biogeochemical cycles recently studied at Cabretta Beach were heavily influenced by groundwater flow and associated solute transport.

Suppression of Baroclinic Instabilities in Buoyancy-Driven Flow over Sloping Bathymetry

AbstractBaroclinic instabilities are ubiquitous in many types of geostrophic flow; however, they are seldom observed in river plumes despite strong lateral density gradients within the plume front. Supported by results from a realistic numerical simulation of the Mississippi–Atchafalaya River plume, idealized numerical simulations of buoyancy-driven flow are used to investigate baroclinic instabilities in buoyancy-driven flow over a sloping bottom. The parameter space is defined by the slope Burger number S = Nf−1α, where N is the buoyancy frequency, f is the Coriolis parameter, and α is the bottom slope, and the Richardson number Ri = N2f2M−4, where M2 = |∇Hb| is the magnitude of the lateral buoyancy gradients. Instabilities only form in a subset of the simulations, with the criterion that SH ≡ SRi−1/2 = Uf−1W−1 = M2f−2α 0.2, where U is a horizontal velocity scale and SH is a new parameter named the horizontal slope Burger number. Suppression of instability formation for certain flow conditions contrasts linear stability theory, which predicts that all flow configurations will be subject to instabilities. The instability growth rate estimated in the nonlinear 3D model is proportional to ωImaxS−1/2, where ωImax is the dimensional growth rate predicted by linear instability theory, indicating that bottom slope inhibits instability growth beyond that predicted by linear theory. The constraint SH 0.2 implies a relationship between the inertial radius Li = Uf−1 and the plume width W. Instabilities may not form when 5Li &gt; W; that is, the plume is too narrow for the eddies to fit.

Measurements of passive scalar diffusion downstream of regular and fractal grids

The diffusion of heat injected from a line source into turbulence generated by regular and fractal grids with the same solidity and inlet velocity was investigated experimentally with particular interest in the effects of grid geometry and relative location of the source on the width of the thermal plume and the mixing efficiency. These grids included one fractal square grid (FSG) and three regular square grids with mesh sizes that were comparable to the first (RG160), second (RG80) and fourth (RG18) iterations of the fractal grid. The heated line source was inserted on the centre plane of the grids, spanning the entire width of the wind tunnel at either of two downstream locations, an upstream location or a location nearly coincident with a grid. It was found that, in all cases examined, RG160 produced the strongest diffusion of the thermal plume and the highest level of scalar mixing. These observations were consistent with the evolution of the corresponding turbulent diffusivities, which, according to Taylor’s theory of diffusion, are the product of the transverse turbulence intensity and the integral length scale. We argue that to maximise scalar diffusion and mixing of a scalar released from a concentrated source inside a duct, one should prefer a regular grid over a fractal square grid; we also recommend the use of a grid with a mesh size roughly equal to half the height of the duct and placed at approximately one duct height upstream of the source.

Satellite observations of ethylene (C2H4) from the Aura Tropospheric Emission Spectrometer: A scoping study

We present a study focusing on detection and initial quantitative estimates of ethylene (C2H4) in observations from the Tropospheric Emission Spectrometer (TES), a Fourier transform spectrometer aboard the Aura satellite that measures thermal infrared radiances with high spectral resolution (0.1 cm−1). We analyze observations taken in support of the 2008 Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS) mission and demonstrate the feasibility of future development of C2H4 into a TES standard product. In the Northern Hemisphere, C2H4 is commonly associated with boreal fire plumes, motor vehicle exhaust and petrochemical emissions. It has a short lifetime (∼14–32 h) in the troposphere due to its reaction with OH and O3. Chemical destruction of C2H4 in the atmosphere leads to the production of ozone and other species such as carbon monoxide (CO) and formaldehyde. Results indicate a correlation between C2H4 and CO in boreal fire plumes. Quantitative C2H4 estimates are sensitive to assumptions about the plume height and width. We find that C2H4 greater than 2–3 ppbv can be detected in a single TES observation (for a fire plume at 3 km altitude and 1.5 km width). Spatial averaging will be needed for surface-peaking profiles where TES sensitivity is lower.

Two‐dimensional circulation and mixing in the far field of a surface‐advected river plume

AbstractField observations of the Hudson River plume are presented to discuss circulation and mixing in the far field of this coastally trapped buoyant flow. The plume was surface advected and propagated downshelf near the internal wave speed. The plume outflow was characterized by a two‐layer bulge‐like feature but became continuously stratified and vertically sheared in the far field, where Richardson numbers are generally below 0.5. High‐frequency velocity and backscatter data from a moored ADCP revealed strong vertical and horizontal oscillatory motions at the front with a wavelength approximately 7–8 times the plume thickness, consistent with Kelvin‐Helmholtz instabilities. These motions quickly died out after 2–3 cycles. The combination of vertical shear and stratification in the plume leads to a buoyancy flux toward the nose of the plume, which competes with mixing. However, the continued salinity increase of the plume as it propagated downshelf indicates that mixing overcomes this delivery of freshwater to the plume front. A simple 2‐D model is developed, which relates the time rate‐of‐change of the plume salinity to: (1) salt entrainment due to vertical mixing, and (2) freshwater flux and salt removal due to the vertical shear of the stratified plume. Estimates of an entrainment coefficient from this model are consistent with previous estimates from the near field of a river outflow. A scaling of the plume width is obtained by assuming that vertical shears are controlled by both thermal wind and a critical Richardson number. This scaling yields plume widths that are consistent with previous laboratory studies.

Influence of bubble size, diffuser width, and flow rate on the integral behavior of bubble plumes

AbstractA large‐eddy simulation based Eulerian‐Lagrangian model is employed to quantify the impact of bubble size, diffuser diameter, and gas flow rate on integral properties of bubble plumes, such as the plume's width, centerline velocity, and mass flux. Calculated quantities are compared with experimental data and integral model predictions. Furthermore, the LES data were used to assess the behavior of the entrainment coefficient, the momentum amplification factor, and the bubble‐to‐momentum spread ratio. It is found that bubble plumes with constant bubble size and smaller diameter behave in accordance with integral plume models. Plumes comprising larger and non‐uniform bubble sizes appear to deviate from past observations and model predictions. In multi‐diameter bubble plumes, a bubble self‐organisation takes place, i.e., small bubbles cluster in the center of the plume whilst large bubbles are found at the periphery of the plume. Multi‐diameter bubble plumes also feature a greater entrainment rate than single‐size bubble plumes, as well as a higher spread ratio and lower turbulent momentum rate. Once the plume is fully established, the size of the diffuser does not appear to affect integral properties of bubble plumes. However, plume development is affected by the diffuser width, as larger release areas lead to a delayed asymptotic behavior of the plume and consequently to a lower entrainment and higher spread ratio. Finally, the effect of the gas flow rate on the integral plume is studied and is deemed very relevant with regards to most integral plume properties and coefficients. This effect is already fairly well described by integral plume models.

Downwelling wind, tides, and estuarine plume dynamics

AbstractThe estuarine plume dynamics under a downwelling‐favorable wind condition were examined in the windy dry season of the Pearl River Estuary (PRE) using the PRE primitive‐equation Finite‐Volume Community Ocean Model (FVCOM). The wind and tide‐driven estuarine circulation had a significant influence on the plume dynamics on both local and remote scales. Specifically, the local effect of downwelling‐favorable winds on the plume was similar to the theoretical descriptions of coastal plumes, narrowing the plume width, and setting up a vertically uniform downstream current at the plume edge. Tides tended to reduce these plume responses through local turbulent mixing and advection from upstream regions, resulting in an adjustment of the isohalines in the plume and a weakening of the vertically uniform downstream current. The remote effect of downwelling‐favorable winds on the plume was due to the wind‐induced estuarine sea surface height (SSH), which strengthened the estuarine circulation and enhanced the plume transport accordingly. Associated with these processes, tide‐induced mixing tended to weaken the SSH gradient and thus the estuarine circulation over a remote influence scale. Overall, the typical features of downwelling‐favorable wind‐driven estuarine plumes revealed in this study enhanced our understanding of the estuarine plume dynamics under downwelling‐favorable wind conditions.