Local Advection Research Articles

A Validation of FruitLook Data Using Eddy Covariance in a Fully Mature and High-Density Japanese Plum Orchard in the Western Cape, South Africa

The cultivation of Japanese plums (Prunus salicina Lindl.) in South Africa has increased over the years, yet their water use is unknown. Their cultivation in the Western Cape Province of South Africa is highly dependent on supplementary irrigation, indicating their high water use demand. This study used remote sensing techniques to estimate the actual evapotranspiration (ETc act) of the Japanese plums to assess their water use on a large scale. The accuracy of the procedure had to be validated before getting to tangible conclusions. The eddy covariance was used to measure ETc act in an African Delight plum orchard to validate the FruitLook remote sensing data for the 2023–2024 hydrological year and irrigation season. The seasonal and annual plum crop water requirements measured using the eddy covariance system were 751 and 996 mm, while those estimated by FruitLook were 744 and 948 mm, respectively. Although FruitLook slightly underestimated plum ETc act by a Pbias of −6.15%, it performed well with a Nash–Sutcliffe efficiency (NSE) of 0.91. FruitLook underestimated evapotranspiration mainly during the peak summer season with full vegetation cover when the model may inaccurately represent irrigation impacts, soil moisture availability, and localized advection effects, better captured by the eddy covariance system. Based on the results, FruitLook proved to be sufficiently accurate for large-scale applications to estimate evapotranspiration in Japanese plum orchards in the Western Cape.

Surface Transport of Technical Waters from Fukushima NPP to the South Kuril Fishing Zone

This study explores the potential for the penetration of technical waters from the Fukushima nuclear power plant (Fukushima NPP) into the fishing areas of Russia. Using a Lagrangian approach, which examines the advection of a large number of passive markers simulating waters released from the Fukushima NPP, the typical transport pathways to the South Kuril Islands are investigated, and an estimate of the time of such transport is provided. Calculations are conducted using satellite-derived and modelled velocity fields for the test year from August 24, 2022, to August 24, 2023. This study focuses on the advection of Lagrangian markers and highlights the potential for the rapid arrival of them from the Fukushima NPP into the southern Kuril region. This article emphasizes the importance of considering the seasonal variability in Kuroshio meandering and the impact of local mesoscale vortex advection related to the propagation of Lagrangian markers from the Fukushima NPP.

Steady state regimes in lid driven cavity flows of magnetic fluids in the presence of an external magnetic field

In this work, we study the flow of magnetic fluids in a square top lid driven cavity in the presence of an applied magnetic field. The magnetic field is generated by a steady electric current flowing through a wire placed underneath the cavity. The magnetization of the magnetic fluid is described by an evolution equation that combines magnetization relaxation, advection and interaction with the flow via the vorticity. The governing equations are solved via a vorticity-streamfunction formulation implemented in a finite difference scheme. The main governing physical parameters of the examined cavity flow are the Reynolds number, ranging from 50 to 500, the magnetic pressure coefficient, which measures the relative importance between magnetic and inertial forces, ranging from 0 to 1000, and Péclet number which is O(1) and measures the ratio between the magnetization relaxation time and the flow time scale. We have examined the different mechanisms which cause changes in the local fluid magnetization, i.e., flow vorticity and advection. In particular, we examine how vorticity of the flow intensifies deviations of the magnetization of the fluid with respect to the local equilibrium of magnetization. In addition, we identify a complex topological structure of the flow inside the cavity characterized by the magnetic effects that dominate the generation of secondary structures of vorticity induced by the effect of field gradient, orientation and a non-uniformity in the fluid magnetization inside the cavity.

Evaporation Driven by Atmospheric Boundary Layer Processes over a Shallow Saltwater Lagoon in the Altiplano

Abstract Observations over a saltwater lagoon in the Altiplano show that evaporation E is triggered at noon, concurrent to the transition of a shallow, stable atmospheric boundary layer (ABL) into a deep mixed layer. We investigate the coupling between the ABL and E drivers using a land–atmosphere conceptual model, observations, and a regional model. Additionally, we analyze the ABL interaction with the aerodynamic and radiative components of evaporation using the Penman equation adapted to saltwater. Our results demonstrate that nonlocal processes are dominant in driving E. In the morning, the ABL is controlled by the local advection of warm air (∼5 K h−1), which results in a shallow (<350 m), stable ABL, with virtually no mixing and no E (<50 W m−2). The warm-air advection ultimately connects the ABL with the residual layer above, increasing the ABL height h by ∼1 km. At midday, a thermally driven regional flow arrives to the lagoon, which first advects a deeper ABL from the surrounding desert (∼1500 m h−1) that leads to an extra ∼700-m h increase. The regional flow also causes an increase in wind (∼12 m s−1) and an ABL collapse due to the entrance of cold air (∼−2 K h−1) with a shallower ABL (∼−350 m h−1). The turbulence produced by the wind decreases the aerodynamic resistance and mixes the water body releasing the energy previously stored in the lake. The ABL feedback on E through vapor pressure enables high evaporation values (∼450 W m−2 at 1430 LT). These results contribute to the understanding of E of water bodies in semiarid conditions and emphasize the importance of understanding ABL processes when describing evaporation drivers.

Cross-media transfer of polycyclic aromatic hydrocarbons in the Naples metropolitan area, southern Italy

At present, an in-depth knowledge of polycyclic aromatic hydrocarbons (PAHs) in the multimedia system of the urban environment remains limited. Taking the Naples metropolitan area (NMA) for instance, we simulated the cross-media transfer of PAHs using a multimedia urban model, involving air, water, soil, sediment, vegetation, and impervious film. The results indicated that the predicted PAH values in 2015 match well with their corresponding in-situ monitoring data. The PAH emission inventory and the simulated mass in various media all showed a downward trend from 2015 to 2020 due to national energy conservation policies and Corona Virus Disease 2019. The simulated mass of PAHs in the soil and sediment phases was 896.8 and 232.7 kg in 2020, respectively, contributing together to 96.7% of PAHs in the NMA. And they were identified as the greatest sinks for PAHs, and exhibited the longest retention duration, with values of PAH persistence reaching approximately 548.8 – 2,0642.3 hours. The results of transfer fluxes indicated that local emissions and atmospheric advection were the primary routes affecting the distribution of PAHs. The sensitivity analysis indicated that atmospheric advection rate was the most critical parameter for air, soil, vegetation, and film, whereas water concentration and sediment degradation rate were vital for water and sediment, respectively. This study offered valuable insights into how human activity contributes to the status and fate of PAHs in the urban environment.

Numerical study on the mechanism of drag modulation by dispersed drops in two-phase Taylor–Couette turbulence

The presence of a dispersed phase can significantly modulate the drag in turbulent systems. We derived a conserved quantity that characterizes the radial transport of azimuthal momentum in the fluid–fluid two-phase Taylor–Couette turbulence. This quantity consists of contributions from advection, diffusion and two-phase interface, which are closely related to density, viscosity and interfacial tension, respectively. We found from interface-resolved direct numerical simulations that the presence of the two-phase interface consistently produces a positive contribution to the momentum transport and leads to drag enhancement, while decreasing the density and viscosity ratios of the dispersed phase to the continuous phase reduces the contribution of local advection and diffusion terms to the momentum transport, respectively, resulting in drag reduction. Therefore, we concluded that the decreased density ratio and the decreased viscosity ratio work together to compete with the presence of a two-phase interface for achieving drag modulation in fluid–fluid two-phase turbulence.

Revisiting reference evapotranspiration calculation under regional advection and its effect on single and dual crop coefficients: An empirical approach for quinoa crop

AbstractAdvection is a prevailing meteorological phenomenon in the arid and semi‐arid environments that directly affects the crop and soil hydrology. It could have a great impact on the rate of standard crop evapotranspiration (ETc) in the irrigated areas. Therefore, it is required to take it into consideration while computing crop water requirement through the physically based meteorological procedures. The objectives of this study are (1) simple modification of the Penman–Monteith (PM) equation in calculation of the grass reference evapotranspiration (ETo) to implement the local advection, (2) comparing the single (Kc) and dual crop coefficient (Kcb) of two quinoa cultivars (Titicaca, and Q5) with and without advection correction and (3) presenting a simple model to calculate the advection factor using the maximum air temperature and mean relative humidity for the future crop growth modelling studies. Both Q5 and Titicaca showed unexpectedly very high ETc and potential transpiration (Tp) as 1568 mm and 1003 mm, and 1156 mm and 829 mm, respectively, due to occurrence of regional advection, whereas very high unrealistic Kc and Kcb values for Q5 revealed the impact of strong local advection and external energy. Therefore, we modified ETo to implement the advection effect through introducing the advection factor, ETc/Rn (Rn is the net radiation), as a function of maximum air temperature and mean relative air humidity during the growing season [ETc/Rn = exp (0.025Tmax – 0.015RHavg)] which resulted in higher ETo values, and consequently lower and more realistic Kc and Kcb. As a result, modified maximum Kc values of 1.14 and 1.55 and the modified maximum Kcb of 0.94 and 1.0 were obtained for Titicaca and Q5 cultivars, respectively. This procedure leads to a more accurate site‐specific Kc estimation and indirectly reliable ETc estimation as a function of advection factor and its multiplication by the non‐modified ETo. Furthermore, for direct estimation of ETc through the PM equation, the coefficients of aerodynamic and canopy resistance components of PM equation were modified for estimation of ETc by the non‐modified Rn, which resulted in accurate estimation of ETc.

Scale‐Dependent Drivers of Marine Heatwaves Globally

AbstractMarine heatwaves (MHWs) are prolonged extreme warm water events, threatening marine ecosystems. Understanding drivers of MHWs over the global ocean is essential for their forecast. Here, we use an eddy‐resolving coupled global climate model with improved realism of MHWs to evaluate the drivers of MHWs at different spatial scales, that is, MHWs defined based on temperature anomalies at different spatial scales. The properties of MHWs are scale‐dependent, being generally weaker, less frequent, and longer with increasing spatial scales. The primary driver of MHWs shifts from local oceanic intrinsic advection to atmospheric forcing as their spatial scale becomes larger. The transition spatial scale between the ocean and atmosphere‐driven regimes varies geographically, being larger in eddy‐rich regions but smaller in gyre interior. This study suggests the complicated dynamics of MHWs at different spatial scales and provides guidance on improving their forecast capacity.

The Lower Thermospheric Winter‐To‐Summer Meridional Circulation: 2. Impact on Atomic Oxygen

AbstractAs a companion study of the Part 1 (J. C. Wang et al., 2022, https://doi.org/10.1029/2022JA030948), the impact of the lower‐thermospheric circulation on atomic oxygen (O) in the mesosphere and lower thermosphere (MLT) region is investigated in this Part 2 using Specified Dynamics Configuration Runs of the Whole Atmosphere Community Climate Model eXtended (SD‐WACCMX) output. The asymmetry of the O profile in the summer and winter MLT region is mainly driven by local vertical advection, which is associated with the lower‐thermospheric winter‐to‐summer circulation and middle‐to‐upper thermospheric summer‐to‐winter circulation. It is found that meridional transport and eddy diffusion only weakly modulate the O budget within this altitude range. The globally and annually averaged transport effect due to the vertical advection is quantitatively estimated. It is shown that the vertical advection is the dominant mechanism in redistributing O at altitudes between 84 and 103 km, suggesting the vertical wind can efficiently transport O between its source and sink region within the vertical column. This study demonstrates that whole atmosphere coupling on seasonal time scales is a complex interaction involving multiple underlying mechanisms within the space‐atmosphere interaction region.

Transients of Marangoni and Stefan advection dynamics during generic sessile droplet evaporation

We probe the transient evolution of Marangoni thermo-hydrodynamics in the liquid domain and the Stefan advection in the gaseous domain during evaporation of sessile droplets with generic contact line dynamics [both constant contact radius (CCR) and constant contact angle (CCA) modes]. A transient arbitrary Lagrangian–Eulerian framework was considered to computationally model the evaporation phenomenon over the droplet lifetime. The governing equations corresponding to the transport processes in both liquid and gaseous domains are simulated in a fully coupled manner, while precisely tracing the liquid–vapor interface and three phase contact line. The effects of the wetting state and contact line dynamics during CCR and CCA modes were explored, and good agreement with experimental observations is noted. The results show that the non-uniformity in an internal temperature field due to evaporation leads to formation of multi-vortex Marangoni patterns in the flow field at initial periods. At the quasi-stable state, the temperature variation becomes monotonic, thereby resulting in a single recirculation vortex in both liquid and gaseous domains. For the CCR mode, the strength of these advection fields is solely governed by a critical contact angle of ∼32°, which is determined to correspond to the critical Marangoni number. Beyond this critical point, viscous action becomes significant, and the fluid motion mitigates progressively with the formation of twin vortices at final stages due to localized heat advection near the contact line. For the CCA mode, the strength of initial vortices augments with progressing time due to amplified evaporative fluxes at smaller contact radius. The internal thermofluidic patterns and evaporative modes in turn modulate the external Stefan flow fields and neighborhood temperature fields. These findings may hold strong implications for efficient functioning of practical droplet based processes involving transport, mixing, and deposition of dissolved particles.

Linkage of the Circumglobal Teleconnection and the Interannual Variability of Early Spring Diabatic Heating over Low-Latitude Highlands in Southeast Asia

Abstract This study explores the linkage of the circumglobal teleconnection (CGT) on the variability of early spring diabatic heating over the Southeast Asian low-latitude highlands (SEALLH) using ERA5 data. The early spring diabatic heating over the SEALLH shows significant interannual variability with a quasi-3-yr period. Anomalies in the advection of the early spring diabatic heating in the troposphere over the SEALLH associated with CGT are mainly responsible for the interannual variability of early spring diabatic heating over the SEALLH. When CGT is in phase with an anomalous cyclone over the eastern midlatitude North Atlantic, an anomalous cyclone usually dominates the west SEALLH throughout the troposphere. Stronger-than-normal southerly winds located on the east flank of the anomalous cyclone in the lower–upper troposphere transport more high-enthalpy air mass from lower latitudes to the SEALLH and then result in stronger-than-normal early spring diabatic heating over the SEALLH. When CGT is in phase with an anomalous anticyclone over the eastern North Atlantic, the opposite conditions occur, and weaker-than-normal early spring diabatic heating is observed over the SEALLH. Such significant correlation between CGT and early spring diabatic heating over the SEALLH can persist from winter to early summer. The key physical processes revealed in the observational analysis are mostly confirmed by the historical simulation performed with the EC-EARTH3 model. Significance Statement The low-latitude highlands in Southeast Asia are one of the earliest diabatic heating sources in the Asian summer monsoon region. Variability of diabatic heating over the low-latitude highlands in Southeast Asia significantly regulates the weather and climate over the Asian summer monsoon region. However, the interannual variability of early spring diabatic heating over the low-latitude highlands in Southeast Asia remains unclear. This study determines that the circumglobal teleconnection links with the interannual variability of early spring diabatic heating over the low-latitude highlands in Southeast Asia via modulating the local advection process from the previous winter. These results build a bridge connecting the anomalous signals occurring in the upper reaches of the low-latitude highlands in Southeast Asia with the weather and climate in the local and lower reaches of the low-latitude highlands in Southeast Asia.

Correlation between heat transfer and flow in an internal combustion engine evaluated with a MEMS sensor

Understanding heat transfer is important for developing high-performance internal combustion engines, but heat transfer mechanisms have not yet been elucidated. The objective of this study is to clarify the correlation between flow and heat transfer in an engine. Local instantaneous heat flux and advection speed adjacent to a wall were measured using a resistance-type three-point heat flux sensor to achieve this purpose. Furthermore, local instantaneous Nusselt and Reynolds numbers were calculated based on the measured heat flux and the advection speed using two characteristic lengths: (1) bore diameter and (2) penetration depth. Consequently, it was found that the ensemble-averaged Nusselt numbers varied exponentially as a function of the ensemble-averaged Reynolds numbers in both models, and good correlation equations could be derived. The penetration-depth model reproduced the experimental values more precisely. On the other hand, the Reynolds number index of the bore-diameter model corresponds with the heat transfer on the rear wall of a cylinder installed in a flow. This suggests an analogy between the engine and rear wall of a cylinder. Additionally, the impacts of each heat transfer factor were evaluated. As a result, it was found that a dominant factor until the heat flux peak is the temperature difference between the gas and wall. However, its effect becomes small after the heat flux peak, and it was found that the density and advection speed mainly affect the heat flux decrease.

Broadband attenuation-based measurements of bubble size distributions

Oceanic bubbles generated by breaking waves are a key mechanism for air-sea gas exchange. Dense bubble plumes can also interfere with acoustic propagation in shallow water due to their high scattering and attenuation. Most studies of oceanic bubbles have used narrow-band acoustical and optical techniques to quantify bubble size distributions under breaking waves in open water. To study bubble distributions at estuarine tidal fronts, where localized downwelling and advection can generate large bubbles plumes, we developed a measurement system for estimating bubble size distributions via broadband excess attenuation. The system consists of two transducers (3–30 kHz and 30–110 kHz) and two hydrophones mounted on a towable frame. Testing was performed in a laboratory wave tank to measure bubble distributions below a field-scale (1 + meter) breaking wave. This presentation will discuss the bubble size distributions observed at different locations along the breaking wave crest in the direction of propagation and their associated time scales and sound speed anomalies. We also compare these distributions with those previously observed in open water and will present preliminary results from a field deployment of the system in the Connecticut River estuary.

Simulation of cytoskeleton protein filament network behavior facilitated by motor proteins and crosslinking agents.

The cytoskeleton of a cell serves several important purposes and is composed of protein filaments including microtubules and actin filaments, which form an interconnected network. The nature of this network is influenced by forces exerted by motor proteins, including kinesin and myosin. The dynamic organization of filaments that occurs within these networks can be controlled by varying the degree of motor driven activity and filament crosslinking. Various degrees of filament aggregation, segregation, and intermixing have been observed in multi-filament, multi-motor composite systems. To better understand the underlying principles driving these rearrangements and recognizing key parameters for directing the dynamics of these systems, we have developed a minimal diffusion-advection based model. The model explicitly describes the diffusion and advection driven transport of individual filaments, impeded by steric interactions and crosslinking. We find that this simple model sufficiently captures key features of the experimentally observed filament reorganization and distribution in these composite systems. Specifically, we find that advection of microtubule filaments driven by processive kinesin motors yields aggregation of both microtubule and actin filaments in the network. It also co-localizes the different filament structures. This aggregation and colocalization is further enhanced by adding crosslinker proteins to either of the filaments. However, an additional increase in advection driven by the motion of actin filaments propelled via non-processive myosin motors disrupts the self-organization of these filaments and yields diffuse, well mixed networks. Based on these results, we hypothesize that diffusivity and localized advection present two key parameters that can be tuned to alter the structure and dynamics of multi-filament active networks.

Life cycle of stratocumulus clouds over 1 year at the coast of the Atacama Desert

Abstract. Marine stratocumulus clouds of the eastern Pacific play an essential role in the earth's energy and radiation budget. Parts of these clouds off the western coast of South America form the major source of water to the hyperarid Atacama Desert coastal region at the northern coast of Chile. For the first time, a full year of vertical structure observations of the coastal stratocumulus and their environment is presented and analyzed. Installed at Iquique Airport in northern Chile in 2018/2019, three state-of-the-art remote sensing instruments provide vertical profiles of cloud macro- and micro-physical properties, wind, turbulence, and temperature as well as integrated values of water vapor and liquid water. Distinct diurnal and seasonal patterns of the stratocumulus life cycle are observed. Embedded in a land–sea circulation with a superimposed southerly wind component, maximum cloud occurrence and vertical extent occur at night but minima at local noon. Nighttime clouds are maintained by cloud-top cooling, whereas afternoon clouds reappear within a convective boundary layer driven through local moisture advection from the Pacific. During the night, these clouds finally re-connect to the maritime clouds in the upper branch of the land–sea circulation. The diurnal cycle is much more pronounced in austral winter, with lower, thicker, and more abundant (5×) clouds than in summer. This can be associated with different sea surface temperature (SST) gradients in summer and winter, leading to a stable or neutral stratification of the maritime boundary layer at the coast of the Atacama Desert in Iquique.

Two types of helical-core equilibrium states in tokamak plasmas

Helical distortion in the core region and its formation mechanism in weakly reversed magnetic shear tokamak plasmas are investigated using three-dimensional magnetohydrodynamic (MHD) equilibrium calculations and MHD stability analysis. It is found that there are two different types of helical equilibrium states: one is a rigid-body shift in the core region on a poloidal cross-section, while the other is a local advection only around the magnetic axis. Linear stability analysis of the corresponding axisymmetric equilibrium is carried to understand the origin of these two types of helical equilibrium states. The analysis shows that the former is related to the current-driven internal-kink instability, while the latter is linked to the pressure-driven quasi-interchange instability. The kink-mode-driven helical equilibrium state appears when the minimum value of the safety factor is close to unity, while the quasi-interchange-driven helical equilibrium state appears when is below unity. The appearance of the quasi-interchange state is attributed to the weak magnetic shear at the inner rational surface and finite β.

The Value of a Hole in Coal: Assessment of Seasonal Thermal Energy Storage and Recovery in Flooded Coal Mines

Seasonal storage and extraction of heat in legacy coal mines could help decarbonize the space heating sector of many localities. The modelled evolution of a conceptual mine-water thermal scheme is analysed in this study, involving cyclical storage of heat in an enclosed underground coal mine. Conductive heat transport simulations are performed in a 3D model of a flooded room-and-pillar panel, based on typical mine layouts, to quantify the maximum thermal recovery from the host rock in different scenarios. We show that, by optimizing the seasonal management, from 25% to 45% of the energy transferred to the subsurface could be potentially recovered at the end of the first operational year. The modelled heat retrieval, achieved by subsurface cold-water circulation, does not consider the potentially enhancing effect of local advection around mine voids and applies to cases of relatively low dispersal of heat by the regional groundwater flow. The cumulative heat recovered from the modelled host rock could equal the thermal energy provided by the “mined” coal in less than 70 years. A comparison of the value of the original coal “mined,” at today’s prices, to a representative value for the heat recycled in the space created by its extraction, suggests that within less than 3 decades of thermal cycling similar monetary values are reached for the specific conditions modelled.

Three‐Dimensional Permeability Inversion Using Convolutional Neural Networks and Positron Emission Tomography

AbstractQuantification of heterogeneous multiscale permeability in geologic porous media is key for understanding and predicting flow and transport processes in the subsurface. Recent utilization of in situ imaging, specifically positron emission tomography (PET), enables the measurement of three‐dimensional (3‐D) time‐lapse radiotracer solute transport in geologic media. However, accurate and computationally efficient characterization of the permeability distribution that controls the solute transport process remains challenging. Leveraging the relationship between local permeability variation and solute advection behavior, an encoder‐decoder based convolutional neural network (CNN) is implemented as a permeability inversion scheme using a single PET scan of a radiotracer pulse injection experiment as input. The CNN can accurately capture the 3‐D spatial correlation between the permeability and the radiotracer solute arrival time difference maps in geologic cores. We first test the inversion accuracy using synthetic test datasets and then test the accuracy on a suite of experimental PET imaging datasets acquired on four different geologic cores. The network‐predicted permeability maps from the geologic cores are used to parameterize forward numerical models that are directly compared with the experimental PET imaging data. The results indicate that a single trained network can generate robust 3‐D permeability inversion maps in seconds. Numerical models parameterized with these permeability maps closely capture the experimentally observed solute arrival time behavior. This work provides an unprecedented approach for efficiently characterizing multiscale permeability heterogeneity in complex geologic samples.

Nonlocal multiscale modelling of tumour-oncolytic viruses interactions within a heterogeneous fibrous/non-fibrous extracellular matrix.

In this study we investigate computationally tumour-oncolytic virus (OV) interactions that take place within a heterogeneous extracellular matrix (ECM). The ECM is viewed as a mixture of two constitutive phases, namely a fibre phase and a non-fibre phase. The multiscale mathematical model presented here focuses on the nonlocal cell-cell and cell-ECM interactions, and how these interactions might be impacted by the infection of cancer cells with the OV. At macroscale we track the kinetics of cancer cells, virus particles and the ECM. At microscale we track (i) the degradation of ECM by matrix degrading enzymes (MDEs) produced by cancer cells, which further influences the movement of tumour boundary; (ii) the re-arrangement of the microfibres that influences the re-arrangement of macrofibres (i.e., fibres at macroscale). With the help of this new multiscale model, we investigate two questions: (i) whether the infected cancer cell fluxes are the result of local or non-local advection in response to ECM density; and (ii) what is the effect of ECM fibres on the the spatial spread of oncolytic viruses and the outcome of oncolytic virotherapy.

Decreasing Dust Over the Middle East Partly Caused by Irrigation Expansion

AbstractThe importance of the effects of anthropogenic activities on modulating the global dust cycle has been increasingly recognized. Over the Middle East, we find in observations that there has been a significant decrease in dust optical depth from 2007 to 2019 during which global irrigated areas especially in the Middle East and South Asia have rapidly expanded. Whether irrigation expansion contributes to the decrease of dust in the Middle East is investigated based on observations/reanalyses and global climate model simulations with and without irrigation. Results show that irrigation over the northeast Middle East and Pakistan supplements water to the soil. By increasing local evaporation and moisture advection, irrigation enhances precipitation over the whole Middle East and the northwest Indian subcontinent. As a result, dust wet deposition by precipitation is elevated. Owing to irrigation‐induced land surface cooling, surface wind speed decreases as the planetary boundary layer becomes stable. Along with increased soil moisture, reduced surface wind speed suppresses local dust emissions. Enhanced dust wet deposition and suppressed dust emissions cause atmospheric dust reduction over the Middle East. Vegetation greening in the Middle East as the climate warms has no contribution because there is no obvious trend found in observations.