Upper Atmospheric Winds Research Articles

Developments regarding Type II secondary sonic booms and topography

Type II secondary sonic booms are those that reflect from the primary boom carpet, enter the stratosphere, and turn back toward the ground if the upper atmospheric winds are favorable. A study initially described by the authors at the Forum Acusticum meeting in September 2023 predicted that the Type II secondary sonic boom rays could be profoundly affected by small angle changes in the topography of the ground. The current work provides an update on those ray tracing predictions, namely, that the amplitudes of Type II secondary sonic booms are substantially reduced by the topography. Such results may explain why secondary sonic booms historically have been reported for supersonic operations over water but not for over land. A grid refinement study will also be summarized. [Work supported by the FAA through ASCENT Project 57 under the supervision of Sandy Liu. Any opinions, findings, conclusions, or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the FAA.]

Air show primary sonic booms across a seismic network

Cates and Sturtevant (2002) and others have shown that sonic booms can be recorded using existing seismic networks. To revive this capability for current research, data from permanent seismic stations were utilized to extract primary sonic boom signals from known supersonic flights. The sonic booms were produced on October 14, 2022 near Edward Air Force Base, CA, associated with an Air Show corresponding to the 75th anniversary of the first supersonic flight. The sonic booms were created by F-22, F-18, and F-15 aircraft. The experimental results show that primary sonic booms were measured at different times by seismic networks in Southern California over an area of not less than 10 000 km2 (∼3900 mi2). Secondary booms did not occur during this event due to inadequate upper atmospheric winds. [Work supported by the FAA through ASCENT Project 57 under the supervision of Sandy Liu. Any opinions, findings, conclusions, or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the FAA.]

Changes to Sea Surface Temperatures and Vertical Wind Shear and Their Influence on Tropical Cyclone Activity in the Caribbean and the Main Developing Region

Sea surface temperatures and vertical wind shear are essential to tropical cyclone formation. TCs need warm SSTs and low shear for genesis. Increasing SSTs and decreasing VWS influences storm development. This work analyzes SST and VWS trends for the Caribbean, surrounding region, and the Atlantic hurricane main developing region from 1982–2020. Storm intensity increases significantly during this period. Annual and seasonal trends show that regional SSTs in the MDR are warming annually at 0.0219 °C yr−1 and, per season, 0.0280 °C yr−1. Simultaneously, VWS decreases during the late rainfall season, at 0.056 m/s yr−1 in the MDR and 0.0167 m/s yr−1 in the Caribbean and surrounding area. The Atlantic Warm Pool is expanding at 0.51 km2 per decade, increasing upper atmospheric winds and driving VWS changes. Correlations of large-area averages do not show significant relationships between TC intensity, frequency, and SSTs/VWS during the LRS. The observed changes appear to be associated with regional warming SSTs impacting TC changes. Plain Language Abstract: Tropical cyclone (TC) formation requires warm ocean waters and low wind shear. Changes to sea surface anomalies and wind shear influences are essential to understanding storm development and intensification. The ability to forecast storm changes is vital to human lives and livelihoods. This work analyzes sea surface temperatures (SSTs) and vertical wind shear (VWS) trends in the Caribbean, surrounding areas, and the Atlantic main developing region (MDR). We found increasing SSTs, decreasing wind shears, an expanding Atlantic Warm Pool (AWP), and increased storm intensity during the Atlantic hurricane season.

A compact static birefringent interferometer for the measurement of upper atmospheric winds: concept, design and lab performance

Abstract. A new compact static wind imaging interferometer, called the Birefringent Doppler Wind Imaging Interferometer (BIDWIN), has been developed for the purpose of observing upper atmospheric winds using suitably isolated airglow emissions. The instrument combines a field-widened birefringent delay plate placed between two crossed Wollaston prisms with an imaging system, waveplates and polarizers to produce four fixed 90∘ phase-stepped images of the interference fringes conjugate to the scene of interest. A four-point algorithm is used to extract line-of-sight Doppler wind measurements across the image of the scene. The arrangement provides a similar throughput to that of a field-widened Michelson interferometer; however, the interferometric component of BIDWIN is smaller, simpler to assemble and less complicated to operate. Consequently, the instrument provides a compact, lightweight and robust alternative that can be constructed and operated with lower cost. In this paper, the instrument concept is presented, and the design and optimization of a prototype version of the instrument are discussed. Characterization of the lab prototype is presented, and the performance of the instrument is examined by applying the instrument to measure a low-velocity two-dimensional Doppler wind field with a high precision (5 m s−1) in the lab.

Thermospheric Neutral Winds as the Cause of Drift Shell Distortion in Earth’s Inner Radiation Belt

Recent analysis of energetic electron measurements from the Magnetic Electron Ion Spectrometer instruments onboard the Van Allen Probes showed a local time variation of the equatorial electron intensity in the Earth’s inner radiation belt. The local time asymmetry was interpreted as evidence of drift shell distortion by a large-scale electric field. It was also demonstrated that the inclusion of a simple dawn-to-dusk electric field model improved the agreement between observations and theoretical expectations. Yet, exactly what drives this electric field was left unexplained. We combine in-situ field and particle observations, together with a physics-based coupled model, the Rice Convection Model (RCM) Coupled Thermosphere-Ionosphere-Plasmasphere-electrodynamics (CTIPe), to revisit the local time asymmetry of the equatorial electron intensity observed in the innermost radiation belt. The study is based on the dawn-dusk difference in equatorial electron intensity measured at L = 1.30 during the first 60 days of the year 2014. Analysis of measured equatorial electron intensity in the 150–400 keV energy range, in-situ DC electric field measurements and wind dynamo modeling outputs provide consistent estimates of the order of 6–8 kV for the average dawn-to-dusk electric potential variation. This suggests that the dynamo electric fields produced by tidal motion of upper atmospheric winds flowing across Earth’s magnetic field lines - the quiet time ionospheric wind dynamo - are the main drivers of the drift shell distortion in the Earth’s inner radiation belt.

Direct observations of a Mt Everest snowstorm from the world's highest surface‐based radar observations

Direct observations of a Mt Everest snowstorm from the world's highest surface‐based radar observations

Efficient framework for the examination of the field of view sensitivity of a field-widened birefringent interferometer.

An efficient approach is presented that allows the field of view sensitivities of a field-widened birefringent interferometer constructed from several stacked birefringent slabs to be examined. The approach utilizes a Jones matrix framework that is valid for birefringent slabs that have their optic axis parallel to the surface of the slab. It neglects Fresnel effects and multiple reflections, but accounts for birefringent splitting and does not neglect higher-order angular effects. The simplified approach allows the angular sensitivity of the optical path difference near the field-widened configuration to be examined in the presence of misalignment and mismatches between the components. Understanding these effects is critical to developing wide-field interferometers that can be utilized for imaging purposes. Here, we present the developed framework and apply it to examine the field of view effects of a three-element field-widened static birefringent interferometer that is being developed for the measurement of upper atmospheric winds. We examine the sensitivity of the device to rotational misalignment, mismatches, and wavelength shifts. Comparisons among the modeled interference fringes, output from Zemax optical design software, and lab observations are used to validate the approach. It is also shown that the approach accurately simulates parasitic fringes associated with unwanted coupling between extraordinary and ordinary waves at the interfaces.

Going to Extremes: Installing the World’s Highest Weather Stations on Mount Everest

Abstract As the highest mountain on Earth, Mount Everest is an iconic peak that offers an unrivalled natural platform for measuring ongoing climate change across the full elevation range of Asia’s water towers. However, Everest’s extreme environment challenges data collection, particularly on the mountain’s upper slopes, where glaciers accumulate mass and mountaineers are most exposed. Weather stations have operated on Everest before, including the world’s previous highest, but coverage has been sparse in space and time. Here we describe the installation of a network of five automatic weather stations (AWSs), including the two highest stations on Earth (8,430 and 7,945 m MSL) which greatly improves monitoring of this iconic mountain. We highlight sample applications of the new data, including an initial assessment of surface energy fluxes at Camp II (6,464 m MSL) and the South Col (7,945 m MSL), which suggest melt occurs at both sites, despite persistently below-freezing air temperatures. This analysis indicates that melt may even be possible at the 8,850 m MSL summit, and prompts a reevaluation of empirical temperature index models used to simulate glacier melt in the Himalayas that focus only on air temperature. We also provide the first evaluation of numerical weather forecasts at almost 8,000 m MSL and use of model output statistics to reduce forecast error, showcasing an important opportunity to improve climber safety on Everest. Looking forward, we emphasize the considerable potential of these freely available data for understanding weather and climate in the Himalayas and beyond, including tracking the behavior of upper-atmosphere winds, which the AWS network is uniquely positioned to monitor.

Discovery of a lunar air temperature tide over the ocean: a diagnostic of air-sea coupling

The lunar semidiurnal (L2) tide in the Earth’s atmosphere is unique as a purely mechanically forced periodic signal and it has been detected in upper atmosphere winds and temperature and in surface barometric pressure. L2 signals in surface air temperature, L2(T), have only been detected at a single land station (results published almost a century ago). We report observational determinations of L2(T) over the ocean by using data from 38 moored buoys across the tropical Pacific and Atlantic. In contrast to published speculation that L2(T) should be negligible over ocean, we find that the observed L2(T) is fairly close to that consistent with an adiabatic L2 pressure variation. Any deviations from purely adiabatic behavior are a measure of diabatic effects on the surface air—expected to be dominated by damping processes, notably heat exchange with the ocean surface. With the aid of climate model simulations that include L2-tide-like variations, we demonstrate that our observations of L2(T) provide a unique diagnosis for the strength of air-sea coupling and a useful constraint on climate model formulations of this coupling.

Global‐scale external magnetic fields at Mars measured at satellite altitude

AbstractThe Martian magnetic field is unique among those of the terrestrial planets. It is the net result of the interaction of the solar wind and the interplanetary magnetic field (IMF) with crustal remnant magnetization and a planetary ionosphere. Internal fields of crustal origin have been the subject of extensive studies; the focus of our work is identification and characterization of contributions from external magnetic fields using the Mars Global Surveyor (MGS) vector magnetic field data. We investigate the magnitude, average spatial structure, and temporal variability of the external magnetic field at MGS mapping altitude of 400 km by first subtracting the expected contributions from crustal fields using existing global crustal field models. We identify periodicities and spatial structure in the field related to the day‐night cycle and Carrington rotations, as well as variations corresponding to an annual cycle and short aperiodic signals. We suggest that ionospheric currents driven by upper atmosphere winds contribute to the observed zonal structure in the daily variation in the external magnetic field. Finally, we discuss the potential for magnetic sounding studies using time‐varying external fields and surface magnetometry measurements from the InSight mission to be launched in 2018.

Airborne Internet Providing Tethered Balloon System

In this paper we shall introduce a new system for providing wireless network communication over a specified area using 'lighter than air' balloons. This technology will replace the existing fiber optic network system. This will be done by using a tethered balloon along with the payload (containing a receiver, a transmitter and a radio communication device).This payload will be suspended from the ground at an altitude (depending on the area of coverage required). Users under this area will be able to access this system directly for internet connectivity. This system can be used over large areas like universities, companies and societies to provide internet facility to their users through Wi-Fi or over an area where the user is specified (commercial purposes). Currently Google is working on similar idea called the 'Google Loon' in which they use high altitude balloons which float at an altitude twice as high as air planes and the weather. They recently tested this system over New-Zealand by providing internet to their pilot testers on ground. Their balloons not being stationary, move with directional winds and have to be replaced one after the other to maintain consistency. This can be a huge problem over the areas where upper atmospheric winds are not in favorable direction. We can resolve this problem by using our stationary tethered balloon system which can communicate with the loon balloons to provide internet facility over a desired area. Moreover when our balloon will communicate with the loon balloon it will increase the coverage area as the loon balloon has to communicate to a point which is above the ground. Our system will not only replace the existing fiber optic system but it will also be self- sustaining i.e. It will generate its own power using solar panels.

The Arctic is unravelling

Though many seem to view climate change-related deviations in the Arctic as nothing more than as a distant early warning for the ‘rest of us’, new research indicates that loss of Arctic sea ice could be affecting the jet stream in such a way as to be impacting weather in the northern hemisphere. Uncharacteristically long blocking patterns being linked to the weakening circulation of upper atmospheric winds in the northern hemisphere are being connected not only to the bitter North American winter of 2013/2014 and to the uncommonly cool summer of 2014, but also to extreme weather events, many of them involving copious amounts of precipitation. Hence, changes in the cryosphere a world away, once regarded as largely isolated and innocuous, now appear to be affecting the lives—and livelihoods—of those living in the urban northern hemisphere.

Nonlinear regression method for estimating neutral wind and temperature from Fabry–Perot interferometer data

The Earth's thermosphere plays a critical role in driving electrodynamic processes in the ionosphere and in transferring solar energy to the atmosphere, yet measurements of thermospheric state parameters, such as wind and temperature, are sparse. One of the most popular techniques for measuring these parameters is to use a Fabry-Perot interferometer to monitor the Doppler width and breadth of naturally occurring airglow emissions in the thermosphere. In this work, we present a technique for estimating upper-atmospheric winds and temperatures from images of Fabry-Perot fringes captured by a CCD detector. We estimate instrument parameters from fringe patterns of a frequency-stabilized laser, and we use these parameters to estimate winds and temperatures from airglow fringe patterns. A unique feature of this technique is the model used for the laser and airglow fringe patterns, which fits all fringes simultaneously and attempts to model the effects of optical defects. This technique yields accurate estimates for winds, temperatures, and the associated uncertainties in these parameters, as we show with a Monte Carlo simulation.

Infrasound as a remote sensing technique for the upper atmosphere

Understanding and specification of the higher altitudes of the atmosphere with global overage over all local times is hampered by the challenges of obtaining direct measurements in the upper atmosphere. Methods to measure the properties of the atmosphere above the stratopause is an active area of scientific research. In this presentation, we revisit the use of infrasound as a passive remote sensing technique for the upper atmosphere. In the past, various studies focused on the sensitivity of infrasound to various upper atmospheric processes. It has been shown that the current state-of-the-art climatologies for the middle and upper atmosphere are not always in agreement with the acoustic data, suggesting a use of infrasound as a complementary remote sensing technique. Previously, we reported on the error in thermospheric celerities which was found to be in accord with the typical uncertainty in upper atmospheric winds and temperature. In this presentation, we report on the expected variation of the various infrasound observables from a forward modeling perspective. This information, in combination with the experimental measurement error provides constraints on the expected resolution from the inverse problem. With this information, we minimize misfits in travel time and source location using a Levenberg-Marquardt search algorithm in combination with ray theory.

Solar initiative at Oukaimeden Observatory

AbstractThe solar research program at Oukaimeden Observatory started in 1988 with the helioseimological IRIS network. The Moroccan researchers involved in this research have analyzed solar observations in order to detect and characterize the solar sphere modes of oscillations. In the coming year, the researchers at the Oukaimeden Observatory will add new research capabilities by joining the International Space Weather Initiative (ISWI), installing a suite of optical instruments, comprising a Remote Equatorial Nighttime Observatory of Ionospheric Regions (RENOIR). The scope and objectives to be achieved in this proposed project are to: •deploy a Fabry-Perot interferometer and wide-angle imaging system to the Observatoire Astronomique Universitaire de LOukaimeden;•train students and researchers from Cadi Ayyad University on the operation of the equipment and related analysis techniques;•collect and analyze data from the equipment to study properties of upper-atmospheric winds and temperatures and how they relate to the occurrence of space weather; and•develop an international collaboration network with other researchers using similar instrumentation in Brazil and Peru. We will present here the plan we intend to develop for the Moroccan solar program in connection with ISWI.

A novel polarization interferometer for measuring upper atmospheric winds

A static polarization interferometer for measuring upper atmospheric winds is presented, based on two Savart plates with their optical axes perpendicular to each other. The principle and characteristics of the interferometer are described. The interferometer with a wide field of view can offer a stable benchmark optical path difference over a specified spectral region of 0.55–0.63 μm because there are no quarter wave plates. Since the instrument employs a straight line common-path configuration but without moving parts and slits, it is very compact, simple, inherently robust and has high throughput. The paper is limited to a theoretical analysis.

Satellite detection of hazardous volcanic clouds and the risk to global air traffic

Remote sensing instruments have been used to identify, track and in some cases quantify atmospheric constituents from space-borne platforms for nearly 30 years. These data have proven to be extremely useful for detecting hazardous ash and gas (principally SO2) clouds emitted by volcanoes and which have the potential to intersect global air routes. The remoteness of volcanoes, the sporadic timings of eruptions and the ability of the upper atmosphere winds to quickly spread ash and gas, make satellite remote sensing a key tool for developing hazard warning systems. It is easily recognized how powerful these tools are for hazard detection and yet there has not been a single instrument designed specifically for this use. Instead, researchers have had to make use of instruments and data designed for other purposes. In this article the satellite instruments, algorithms and techniques used for ash and gas detection are described from a historical perspective with a view to elucidating their value and shortcomings. Volcanic clouds residing in the mid- to upper-troposphere (heights above 5 km) have the greatest potential of intersecting air routes and can be dispersed over many 1,000s of kilometres by the prevailing winds. Global air traffic vulnerability to the threat posed by volcanic clouds is then considered from the perspectives of satellite remote sensing, the upper troposphere mean wind circulation, and current and forecast air traffic density based on an up-to-date aircraft emissions inventory. It is concluded that aviation in the Asia Pacific region will be increasingly vulnerable to volcanic cloud encounters because of the large number of active volcanoes in the region and the increasing growth rate of air traffic in that region. It is also noted that should high-speed civil transport (HSCT) aircraft become operational, there will be an increased risk to volcanic debris that is far from its source location. This vulnerability is highlighted using air traffic density maps based on NOx emissions and satellite SO2 observations of the spread of volcanic clouds.

Inversion of infrasound signals for atmospheric remote sensing

This paper investigates the utilization of observed long-range infrasound signals to improve our knowledge of upper atmospheric winds and temperatures. A series of numerical experiments designed to provide a mathematical framework for implementation of this idea is presented. The statistical performance of a realistic infrasonic upper atmospheric remote sensing network over a range of different environmental and propagation modeling assumptions, source types, and geophysical variables (season, local-time, latitude, etc) is quantified. For a series of fictitious events, infrasonic observables are calculated with 3D Cartesian ray tracer and a series of atmospheric profiles spanning the range of geophysical parameters. These synthetic measurements are then inverted to estimate the original atmospheric background fields.

Conceptual Study of Gondola Stabilization in a Balloon System

Pointing stabilization of a gondola carried by a stratospheric balloon is a challenging problem due to upper atmospheric winds and due to the multibody nature of the balloon system. The gondola provides a platform for a scientific experiment that requires point stabilization. The experiment apparatus is inside a capsule attached to the gondola base. The proposed actuator is a displacement mechanism that moves the capsule along the gondola base. The current paper presents a feasibility study of this concept. The flight dynamic model of the balloon system is formulated and analyzed, and a preliminary investigation of feasible control logic is presented and tested. Nomenclature A = system matrix B = control matrix b = length Cba = rotation matrix (a !b) CD = drag coefficient D = drag d = length F = force g = gravity acceleration I = moment of inertia I� = controller input K = kinetic energy K = stiffness matrix L� = length M = mass matrix m� = mass n = surface normal direction p = roll rate q = pitch rate R = control weight matrix R� = vectrix r = yaw rate S = state weight matrix T = torque t = time U = potential energy u = control vector V = velocity W = wind velocity X = state vector XI = balloon inertial coordinate YI = balloon inertial coordinate ZI = balloon inertial coordinate � = control displacement � = pitch angle � a = air density � � = length � = roll angle = yaw angle ! = angular velocity ! � = angular velocity matrix Subscripts B = balloon C = capsule G = gondola P = payload T = tether � = wild card Superscripts A=B = subscriptA relative to subscriptB � = time derivative in the inertial frame � = time derivative in the local frame

Three‐dimensional modeling of the trajectories of visible noctilucent cloud particles: An indication of particle nucleation well below the mesopause

Noctilucent clouds (NLC) form in summer at high latitudes at altitudes close to 83 km. Visually they can be observed best in the latitude band 50° to 65°. The cloud particles are most likely transported by the upper atmosphere winds over substantial distances from their birth place (site of nucleation) to the site of their observation and subsequently to warmer regions where they sublimate again. Here we use a 3‐D Lagrangian ice transport model to identify the nucleation sites of NLC particles which are observed vertically above a latitude of 69°N (e.g., by ground‐based lidars at the ALOMAR observatory). We limit the study to particles which have radii larger than either 50 nm or 20 nm when being observed. We find that these particles were nucleated on average only 3 km higher than observed at 69°N. The latter statement implies that nucleation of NLC particles occurs on average more than a scale height below the local mesopause. Furthermore, NLC particles observed overhead at 69°N were nucleated on average about 9° in latitude north of the observation site. Their transport time between nucleation and reaching the observation site is clearly and positively correlated with the latitude difference between the nucleation and observation sites (a similar strong correlation does not exist between the radius and the transport time of the observed particle). The median value of transport times of NLC particles observed above 69°N is 36 hours.