Gradient Wind Research Articles

Distributions for two-point statistics of scattered signals with variable scattering strength

This article describes the distribution of complex products of the amplitudes of randomly scattered signals observed at two points. The signals at the two points are assumed to be fully saturated (zero-mean real and imaginary parts) and partially correlated, and to have a variance that is randomly modulated by the environment (e.g. turbulence, vegetation, or terrain variations). These assumptions are shown to lead to a new distribution for the real and imaginary parts of the complex product, called the compound variance gamma (), which involves a Gauss hypergeometric function. The distribution generalizes the compound gamma (), which applies to one-point statistics with randomly modulated scattering, and the variance gamma (), which applies to two-point statistics without random modulation. The is shown to provide an excellent fit to two-point statistics derived from realistic simulations of sound propagation in the atmosphere including turbulent scattering, refraction by wind and temperature gradients, and ground reflections.

Dynamic soaring in wind turbine wakes

Dynamic soaring for UAVs is a flight technique that enables continuous, powerless periodic flight patterns in the presence of a wind gradient. However, sufficiently large wind gradients are uncommon over land, while at offshore locations the largest wind gradients are located close to the ocean surface, thereby limiting the scope of practical application. An intrinsic feature of wind turbines is that they inherently produce very sharp wind gradients in the near wake. Therefore, in this paper, we propose and investigate periodic stationary dynamic soaring trajectories in the near wake of wind turbines. We additionally consider the potential of dynamic soaring for revitalizing the wind turbine wake. To this end, we apply periodic optimal control based on a simplified model for the glider dynamics and the wind profile in the wake. The cost function maximizes the revitalization of the wake. We compute optimal orbits for a range of different wing spans and different mass-scaling assumptions. The largest glider configuration, with a wingspan of 10 m and a mass of 222.6 kg, achieves a wake revitalization of about 0.94% of the total turbine thrust.

Modelling and simulation of wind flow: A gradient method of identifying windy region

This paper presents biharmonic modelling and simulations of surface wind flow, which identify windy locales through wind speed gradients. The bulk measured and meteosat wind speed data encapsulate the wind isotachs and wind flow gradients, which are very useful in identifying windy locales. Thus, this paper presents a biharmonic wind flow model, BWFM for the development of wind isotachs and gradients to identify locales suitable for installing solar photovoltaic power plants within the study areas. The techniques include the acquisition of wind speed data (1980–2020) from the National Aeronautic and Space Administration (NASA), development of multiple BWFM solutions (free and forced) depending on the presence and absence of forcing function, respectively. The forcing function represents the topographic and orographic features of the study areas. The spatial development of isopleth of the study areas, unveiled the isotachs. The wind speed gradients were obtained by scalar computation of 2-D wind speed gradients. Comparison of forced solution with the threshold or maximum free solution engendered the identification of windy locales. The results of the model were validated against NASA data. The average wind speed threshold isotach (2.83 m/s) and wind gradient ([Formula: see text]) for the study areas (All Regions) were established by scalar computation of free solution gradients. The study areas include Northern, Eastern, Central and Western Regions recorded the following maximum forced average wind speeds (2.725, 2.755, 2.875 and 1.794 m/s, respectively) and maximum wind flow gradients (insignificant, 0.03767, 0.08469 and infinitesimal [Formula: see text], respectively). These results are useful for identifying windy locales for installation of solar and wind facilities.

Variations in global zonal wind from 18 to 100 km due to solar activity and the quasi-biennial oscillation and El Niño–Southern Oscillation during 2002–2019

Abstract. Variations of global wind are important in changing the atmospheric structure and circulation, in coupling of atmospheric layers, and in influencing the wave propagations. Due to the difficulty of directly measuring zonal wind from the stratosphere to the lower thermosphere, we derived a global balance wind (BU) dataset from 50∘ S to 50∘ N and during 2002–2019 using the gradient wind theory and SABER temperatures and modified by meteor radar observations at the Equator. The dataset captures the main feature of global monthly mean zonal wind and can be used to study the variations (i.e., annual, semi-annual, ter-annual, and linear) of zonal wind and the responses of zonal wind to quasi-biennial oscillation (QBO), El Niño–Southern Oscillation (ENSO), and solar activity (F10.7). The same procedure is performed on the MERRA-2 zonal wind (MerU) to validate BU and its responses below 70 km. The annual, semi-annual, and ter-annual oscillations of BU and MerU have similar amplitudes and phases. The semi-annual oscillation of BU has peaks around 80 km, which are stronger in the southern tropical region and coincide with previous satellite observations. As the increasing of the values representing QBO wind, both values of representing BU and MerU (short for BU and MerU) change from increasing to decreasing with the increasing height and extend from the Equator to higher latitudes. Both BU and MerU increase with the increasing of the values of multivariate ENSO index (MEI) and decrease with increasing F10.7​​​​​​​ in the southern stratospheric polar jet region below 70 km. The responses of winds to ENSO and F10.7 exhibit hemispheric asymmetry and are more significant in the southern polar jet region. While above 70 km, BU increases with the increasing of MEI and F10.7. The negative linear changes of BU at 50∘ N are absent in MerU during October–January. The discussions on the possible influences of the temporal intervals and sudden stratospheric warmings (SSWs) on the variations and responses of BU illustrate the following: (1) the seasonal variations and the responses to QBO are almost independent on the temporal intervals selected; (2) the responses to ENSO and F10.7 are robust but slightly depend on the temporal intervals; (3) the linear changes of both BU and MerU depend strongly on the temporal intervals; (4) SSWs affect the magnitudes but do not affect the hemispheric asymmetry of the variations and responses of BU at least in the monthly mean sense. The variations and responses of global zonal wind to various factors are based on BU, which is derived from observations, and thus provide a good complement to model studies and ground-based observations.

Ballooning of Surface‐Advected Freshwater Bulge in a Rotating Frame

AbstractThis research delves into the intrinsic dynamics of an anticyclonic circulation that involves a ballooning bulge generated by a generalized river plume over an idealized shelf topography. The circulation features a strong jet‐stream overshooting the estuary mouth, curving toward the coast, and a returning flow along the shoreside edge. Our study focuses on the ballooning process, which involves the jet‐stream’s expansion and the freshwaters’ downstream movement. We demonstrate that the negative curvature vorticity, generated by flow inertia, sustains this process by amplifying the jet‐stream through anticyclonic gradient wind balance. Our research presents new insights into the origin of the negative curvature vorticity associated with the anticyclonic bending of the jet‐stream. The negative curvature vorticity regulates the ration between streamline’s and trajectory's radius, promoting the freshwaters’ escape from the jet‐stream and facilitating the bulge’s ballooning. The negative shear vorticity over the downshelf coast near the estuary mouth is the source of the curvature vorticity. The banking and curvature‐acceleration processes, which stand for the cross‐stream variation of the downstream component of the pressure force and the turning of the jet‐stream, respectively, trade‐off this shear vorticity to form the negative curvature vorticity.

Optimal trajectory planning of a small UAV using solar energy and wind energy

Due to size limitations and the working environment near the ground, small low-altitude unmanned aerial vehicles (UAVs) cannot carry large-area solar cells and energy storage devices. Solar energy alone has only a limited effect on the improvement of their endurance. To solve this problem, this study proposes the combination of solar energy technology and dynamic soaring technology to improve the endurance of small UAVs. Then, the optimal energy acquisition strategy based on the combination of solar energy and dynamic soaring technology is analyzed in terms of energy. The motion equations and energy acquisition and consumption models of a small solar UAV based on horizontal wind shear are established. Moreover, an optimal trajectory planning problem with the maximum charging power of rechargeable batteries as the optimization objective is proposed. The optimal trajectory is solved based on the hp adaptive pseudo-spectral method, and the optimal trajectory combining the two technologies is simulated and compared with the constant-altitude constant-velocity (CACV) trajectory of the UAV using only solar technology. The simulation results show that under the flight background of tmission = 6:00 (summer sunrise) and β = 0.125 s−1 (wind gradient of the wind shear), the optimized O-type trajectory decreased the energy consumption power by 39.86% and increased the solar energy acquisition power by 86.34% compared to the CACV trajectory. Consequently, the small UAV stores more energy in the rechargeable batteries to improve the endurance performance. Compared to the environment where the sun is located on the leeward side of the wind shear, the environment where the sun is located on the windward side of the wind shear can enable the UAV to acquire more energy through the optimized O-type trajectory.

Winter cold extremes over the eastern North America: Pacific origins of interannual-to-decadal variability

Winter cold extreme events have been observed to frequently take place over North America mainly over its east side, which show significant interannual and decadal variability and cause huge economic losses in the United States. However, it is unclear what leads to the interannual-decadal variability of winter cold extremes over the eastern North America. In this study, we indicate that the decadal variability of winter cold extremes over the eastern North America, whose period is shortened in the recent decades, is mainly tied to Pacific decadal oscillation (PDO), whereas their interannual variability is mainly regulated by Victoria mode (VM). A positive PDO promotes cold extremes in the lower latitudes of the eastern North America mainly owing to the presence of positive Pacific North American (PNA+) patterns, whereas a positive VM is favorable for intense cold extremes in the higher latitudes of the eastern North America mainly due to the occurrence of negative North Pacific oscillation (NPO−) patterns. Thus, the positive VM and PDO combine to significantly contribute to the interannual-to-decadal variability of winter cold extremes over the eastern North America through changes in the winter NPO− and PNA+ patterns due to the variations of meridional background potential vorticity gradient and basic zonal winds. These new findings can help us understand what are the origins of the interannual-decadal variability of winter cold extremes over the eastern North America.

Strong High‐Latitude Zonal Wind Gradient Observed by CHAMP and Simulated by TIEGCM

AbstractUsing 6 days cross‐track wind data from CHAMP, we investigate the high‐latitude westward wind gradient and reversal that occurs at fixed longitudes (−120° ∼ −30° GLon in the Northern Hemisphere, 150° ∼ 210° GLon in the Southern Hemisphere). The driver of the wind gradient at 60° ∼ 70° GLat and in the noon sector is investigated via TIEGCM. The wind gradient is driven by the combined effects of the Earth's geomagnetic field configuration and the energy deposition from the solar wind. The temporal variations of the neutral wind cell in afternoon sector are critical to the formation of wind gradient. The development of wind gradient is due to the equatorward expansion of the afternoon westward wind cell from the geographic high‐latitudes to 60° ∼ 70° GLat. Whereas the disappearance is associated with the poleward contraction from 60° to ∼70° GLat to higher latitudes. A further diagnostic analysis of model results shows that the primary internal driver of the wind gradient is a balance between ion drag and pressure gradient. In the acceleration phase, ion drag causes the formation of the strong gradient of westward wind, whereas pressure gradient decelerates it. A similar result is found in the deceleration phase. The ion drag is controlled predominantly by both the electron density and the relative motion between the ions and neutrals.

A Study of Wind Shear Influences on the Aerodynamic Performances of a UAV Airfoil

In order to study the flight strategies of birds in shear wind and realize the long-range flight of an unmanned aerial vehicle (UAV), the aerodynamic performances of a UAV’s airfoil under different shear wind are studied using numerical methods. The results are calculated using the RANS method in shear wind with a linear and logarithmic distribution of velocity. The results show that the slope of the lift curve, the maximum lift coefficient and the stall angle decrease when the velocity gradient is positive or increasing, conversely, they increase at a negative gradient compared to gradient-free wind fields. A positive gradient of wind significantly increased the maximum lift-drag ratio and the effective angle of attack. Compared with linear distributed shear wind with the same velocity at both the lowest and highest points of the flow field, logarithmic distribution decreases the slope of the lift curve, the maximum lift coefficient and the maximum lift-drag ratio and the effective angle of attack. Therefore, a shear wind with a positive gradient is beneficial to the increase of lift-drag ratio and more conducive to cruise flight, and a negative gradient is beneficial for increased lift and more conducive to take-off and landing of UAVs. The velocity distributions influence the aerodynamic performances of the airfoil which is related to the speed and gradient distribution of shear wind.

Does Extended Sawyer–Eliassen Equation Effectively Capture the Secondary Circulation of a Simulated Tropical Cyclone?

Abstract The validity of the gradient wind balance in a tropical cyclone (TC) remains controversial, especially for the boundary layer and the upper outflow layer, even though this balance is assumed in the derivation of the Sawyer–Eliassen (SE) equation. This study derives an extended SE equation with the relaxation of the gradient wind and hydrostatic balance in cylindrical r–z coordinates, and then we diagnose the secondary circulation using this unbalanced SE equation and the azimuthally averaged tangential wind and thermodynamical fields from a three-dimensional numerical simulation of an intensifying TC. The gradient wind and hydrostatic imbalance produce two additional time-dependent forcing terms on the right-hand side (rhs) of SE equation, which are proved to be negligible for diagnosing the secondary circulation, even as the storm evolves rapidly. The use of the unbalanced basic state deforms the fields of coefficients that appear in the SE equation, and thus the forced secondary flows. The results indicate that the unbalanced solution captures the boundary layer inflow better than the balanced solution described by Bui et al. and the pseudobalanced solution described by Heng et al. The unbalanced solution is closer to the simulation because more unbalanced components are included. Many previous studies always employ the thermal wind balance relation to simplify the SE equation, which is invalid in an unbalanced vortex and result in an overestimation of the boundary layer inflow. These unbalanced dynamics could provide a reliable diagnosis of the secondary flow near the boundary layer.

How Does Horizontal Diffusion Influence the Intensification and Maximum Intensity of Numerically Simulated Tropical Cyclones?

Abstract Recent studies have demonstrated the sensitivity of simulated tropical cyclone (TC) intensity to horizontal diffusion in numerical models. It is unclear whether such sensitivity comes from the horizontal diffusion in or above the boundary layer. To address this issue, both an Ooyama-type model and a full-physics model are used to conduct sensitivity experiments with reduced or enlarged horizontal mixing length (lh) in the boundary layer and/or in the free atmosphere. Results from both models show that enlarging (reducing) lh throughout the model domain considerably reduces (increases) the TC intensification rate and quasi-steady intensity. A new finding is that changing lh above the boundary layer imposes a much greater influence than that in the boundary layer. Large lh above the boundary layer is found to effectively reduce the radial gradient of tangential wind inside the radius of maximum tangential wind and thus the inward flux of absolute vorticity, reducing the positive tangential wind tendency and the TC intensification rate and the steady-state intensity. In contrast, although larger lh in the boundary layer reduces the boundary layer tangential wind tendency, it also leads to the more inward-penetrated inflow and thus enhances the inward flux of absolute vorticity, which offsets part of the direct negative contribution by horizontal diffusion, making the net change in tangential wind tendency not obvious. Results from three-dimensional simulations also show that the resolved eddies contribute negatively to TC spinup when lh is small, while its effect weakens when lh is enhanced either in or above the boundary layer.

UNPRECEDENTED DURATION OF THE 2020 ANTARCTIC OZONE DEPLETION

In this work, we show a trend of lengthening the period of high intensity of the Antarctic polar vortex in late spring and early summer (November–December), which has been traced over the past 30 years. This trend is observed both in the dynamics of the main characteristics of the polar vortex (vortex area and wind speed along the vortex edge) and in the Antarctic ozone hole area. A clear manifestation of this is the polar vortex dynamics in 2020, when there were unusually high wind speeds along the vortex edge throughout the entire period of its existence and record values of vortex area and ozone hole area from mid-November to December. In addition, the polar vortex existed until the last week of December, which is an unprecedented case. To analyze the Antarctic polar vortex dynamics, we used the vortex delineation method by geopotential values determined from the maximum temperature gradient and maximum wind speed characterizing the vortex edge.

Monsoon Depression Amplification by Horizontal Shear and Humidity Gradients: A Shallow Water Perspective

Abstract Transient, synoptic-scale vortices produce a large fraction of total rainfall in most monsoon regions and are often associated with extreme precipitation. However, the mechanism of their amplification remains a topic of active research. For monsoon depressions, which are the most prominent synoptic-scale vortex in the Asian–Australian monsoon, recent work has suggested that meridional gradients in zonal wind in the vortex environment may produce growth through barotropic instability, while meridional gradients in environmental humidity have also been proposed to cause amplification through coupling with precipitating convection. Here, a two-dimensional shallow water model on a sphere with parameterized precipitation is used to examine the relative role played by these two environmental gradients. By systematically varying the meridional moisture gradient and meridional wind shear for both weak, quasi-linear waves and finite-amplitude isolated vortices, we show that rotational winds in the initial vortex are amplified most strongly by meridional shear of the environmental zonal wind, while vortex precipitation rates are most sensitive to environmental moisture gradients. The growth rate in the presence of both gradients is less than the sum of growth rates in the presence of isolated gradients, as the phase relation between moisture and vorticity anomalies becomes distorted with increasing shear. These results suggest that background meridional gradients in both zonal wind and environmental humidity can contribute to the amplification of vortices to monsoon depression strength, but with some degree of decoupling of the dry rotational flow and the moist convection.

Observation of Scintillation Enhancements and Large‐Scale Structures Within the Equatorial Ionization Anomaly During a Sudden Stratospheric Warming Event

AbstractTotal electron content (TEC) and L‐band scintillations measured by several networks of GPS and GNSS receivers that operate in South and Central America and the Caribbean region are used to observe the morphology of the equatorial ionization anomaly (EIA), examine the evolution of plasma bubbles, and investigate the enhancement of L‐band scintillations that occurred on February 12 and 13, 2016. A few weak and short magnetic storms developed these days, and a minor sudden stratospheric warming (SSW) event was initiated a few days before. During these unusual conditions, TEC maps reported a split of the otherwise continuous crests of the EIA and the formation of a large‐scale (thousands of kilometers) almost‐circular structure. The western part of the southern crest faded, and a north‐south aligned segment developed near the center of the South American continent, joining the north and south crests of the EIA, forming an anomaly that resembled a closed loop on the eastern side of the continent. Concurrently with the anomaly events, several GPS stations reported increases in the L‐band scintillation index from 0.4 to values greater than 1. We analyzed TEC values from receivers between ±6° from the magnetic equator to identify and follow TEC depletions associated with plasma bubbles when they reach different stations. Although the magnetic activity was moderate (Kp = 3°), we believe that the anomaly redistribution and the scintillation enhancements are not related to a prompt penetration electric field but to enhancing the semidiurnal lunar tide propitiated by the onset of the minor SSW event. We found that depending on the lunar tide phase cycle, the neutral wind's meridional component can augment sub‐km scale irregularities and enhance L‐band scintillations through the wind gradient instability when U·n < 0 or the action of wind gradients (U) within the bubbles. Our observations imply that the SSW event enables prominent changes in the thermosphere wind system at F‐region altitudes.

A Review of Offshore Renewable Energy in South America: Current Status and Future Perspectives

This paper addresses the current status and future research and development perspectives associated with technologies to harness offshore renewable energy, including offshore wind, waves, tides, ocean currents, and thermal and salinity gradient, in South America (SA). It focuses on five countries: Argentina, Brazil, Chile, Colombia and Uruguay. At first, a comprehensive survey presents the number of scientific papers classified based on the resource to show the tendency and importance of such subjects in the academic community. Each country’s electricity matrix and grid connection are shown to understand the region’s renewable source participation situation. The potential of offshore renewable resources is addressed by considering the published technical papers in scientific journals. The main conflicts and synergies associated with ocean space utilization are presented by considering the exclusive economic zone of each country. The status of the regulatory frameworks to promote and development of offshore renewable energies is presented. Two sections are dedicated to presenting the active, decommissioned and planned projects, research groups and laboratory infrastructures to develop the technologies. The last section discusses the future perspectives on the development of this sector in SA. It is observed that SA, with more than 25,000 km of coastline, has a great potential for offshore renewable energy; however, so far, these resources have not been explored commercially. Larger investment in the sector, establishing an adequate legal framework and deploying full-scale demonstration projects at sea are necessary for the commercialization of such technologies in SA.

Tribological characterization of functionally gradient wind turbine brake pads reinforced with rare earth metal oxide

Copper-based brake pad materials with various fractions of praseodymium oxide and yttrium oxide are fabricated through the powder metallurgy processing technique. The influence of praseodymium oxide and yttrium oxide on the microstructure, microhardness, and tribological characteristics of the fabricated specimens are analyzed. The specimen with desired density, high hardness, wear resistance, and optimal friction coefficient is fabricated with gradient layers (pure copper at the brake pad – brake caliper interface and composite at the brake pad – brake disc interface). The result suggested that as the load gradually increases, the wear rate also increases. The surface morphology, elemental composition, and phase composition of the fabricated specimen and worn surface were characterized using advanced instrumental characterization.

Study on the Influence of Gradient Wind on the Aerodynamic Characteristics of a Two-Element Wingsail for Ship-Assisted Propulsion

It is well known that sail-assisted propulsion works under gradient wind conditions in the atmospheric boundary layer, and is an energy-saving device for fuel consumption. In order to study the aerodynamic characteristics of a wingsail in the atmospheric boundary layer above sea level, a transition SST turbulence model was used for numerical simulation of the wingsail with uniform and gradient wind conditions. We concluded that gradient wind conditions can delay the stall caused by an increased angle of attack. This is because the airflow on the suction surface of the wingsail in the spanwise direction exerts an acceleration towards the top of the wingsail. At the same time, supplementary airflow compresses the separated vortex, thus delaying the stall of the two-element wingsail. Under gradient wind conditions, the flow separation of the wingsail develops rapidly in the stall angles. Once a flat separation vortex is formed at the trailing edge of the wingsail, with the slow increase of flap deflection angle, flow separation rapidly expands and a deep stall occurs. Therefore, a small change of the flap deflection angle in the near-stall angles may lead to a deep stall of the wingsail, which should be avoided in engineering applications. Finally, the influence of the average speed of the gradient wind on the aerodynamic performance of the two-element wingsail was analyzed.

Dry air valley in the upper troposphere over the eastern Mediterranean-western Tibetan Plateau

Based on AIRS satellite observations and ERA-Interim reanalysis data, we investigated the seasonal evolution of the dry air valley (DAV) in the upper troposphere over regions from the eastern Mediterranean to the western Tibetan Plateau (EM-WTP). We find that monsoon-related descending motion is the main driver for the DAV, and its contribution to the DAV is 61%. The intensity of DAV increases rapidly in June, reaches its maximum in late July and early August, then weakens gradually until it disappears in early October. From May to July, zonal temperature gradient over the Mediterranean Sea increases and the southerly wind in the western South Asia High enhances, resulting in an enhancement of descending motion over the Mediterranean. Meanwhile, the northerly wind and zonal vorticity gradient over south of the Aral Sea strengthen due to the thermal-dynamical effect of the Tibetan-Iranian Plateau, consequently, descending motion over south of the Aral Sea intensifies. From August to September, the descending motion weakens quickly over the Mediterranean but remains nearly steady over south of the Aral Sea. As a result, the east-west water vapor gradient increases over the DAV, and water vapor in the DAV converges horizontally due to the transport of westerlies. Accordingly, the DAV intensity decreases. Apart from the descending motion, the dry air intrusion from the lower stratosphere associated with tropopause fold events also has an impact on the DAV intensity. However, the contribution of the tropopause fold events to the DAV is rather small, no >10%.

Accessibility Study of a Compact Wind Tunnel with an Unequal Spacing Grid for the Outdoor Wind Environment

One of the key issues in architectural design and regional planning is to create a safe and comfortable outdoor building environment, which calls for more studies. Wind tunnel experiments and computational fluid dynamic (CFD) simulations are the primary methods for the current studies. The airflow and boundary conditions are controllable for the wind tunnel experiment, and the data is reliable. In most wind tunnel platforms, spires and roughness elements are applied to create the gradient wind of the atmospheric boundary layer, leading to the oversized, high construction cost, and complex operation. In this paper, in order to explore a simple method for measuring and studying the outdoor building wind environment using wind tunnels, a compact wind tunnel platform adopting grids with unequal spacing was designed and tested, based on the theoretical model of the atmospheric boundary layer. A comparison between the test results and the theoretical values indicated that this new wind tunnel platform could achieve a gradient wind field and is accessible in applying low-speed wind tunnels to the measurement and research of the building wind environment. The application case in a high-rise building of the central business district (CBD) region in Beijing, was presented in this paper. Compared with another analytical method, the CFD simulation, the compact wind tunnel revealed its applicability that could be used for predicting and evaluating the outdoor wind environment around the building. This compact wind tunnel is more flexible and convenient than the traditional ones, with a smaller size, easier construction and operation, and lower costs. Therefore, we suggest more applications of this compact wind tunnel platform in future experimental studies of outdoor wind environments.

Effect of SST in the Northwest Indian Ocean on Synoptic Eddies over the South China Sea-Philippine Sea in June

Synoptic eddies (with a period of two to eight days) are active in the South China Sea-Philippine Sea (SCS-PS) and control weather variations. In addition, the intensity and frequency of synoptic eddies may change along with variations in sea surface temperatures (SST). This paper presented the influence of SST in the northwest Indian Ocean on synoptic eddies in the lower troposphere over the SCS-PS in June. Our statistical analysis showed a significant negative correlation between the SST in the northwest Indian Ocean and the synoptic scale eddy kinetic energy (EKE) in the SCS-PS. By analyzing the EKE budget of synoptic eddies, we found that the variation in the synoptic scale EKE over the SCS-PS is mainly due to the change in the monthly zonal wind gradient, which affects the barotropic energy conversion between the monthly mean flow and the synoptic eddies. Additionally, the northwest Indian Ocean SST modulates the monthly flow over the SCS-PS by alternating the strength of the Walker circulation in the west Pacific and Indian Ocean. Finally, the influence of SST in the northwest Indian Ocean on EKE in the SCS-PS was reproduced using the simplified atmospheric general circulation model, SPEEDY.