Turbulence In Stratosphere Research Articles

Characteristic Analysis of Relationship Between Precipitation and Turbulence in the Troposphere and Lower Stratosphere Over Tropical Western Pacific

AbstractThis study aims to analyze the distribution characteristics of turbulence in the western Pacific tropical region and determine the correlation between turbulence and precipitation. The obtained results show that due to the combined action of large wind shear and thermal convection, the near‐surface layer is conducive to the generation of large‐scale turbulence, and the maximum Thorpe scale can reach more than 600 m. A strong mixing zone of turbulence is generated in 10–16 km, with the monthly average occurrence rate of turbulence being about 40% and the maximum value reaching 50%. There is less turbulence in lower stratosphere due to the rapidly increased atmosphere static stability. All Thorpe scales in stratosphere are less than 100 m. The response of turbulence to precipitation in the upper troposphere is strongly affected by clouds. At the altitude in the clouds, the enhancement of precipitation has a negative relationship with turbulence. The average value of and turbulence layer thickness on rainy days are both smaller than those when the precipitation weakened. At the altitude above the clouds, the enhancement of precipitation has a slight promotion effect on the turbulence, especially for the emergence of large‐scale turbulence. When the precipitation intensifies, the amount of turbulence with greater than 150 m accounts for 6.7% of the total, while the proportion is only 2.6% on less rainy days.

Climatology of Clear‐Air Turbulence in Upper Troposphere and Lower Stratosphere in the Northern Hemisphere Using ERA5 Reanalysis Data

AbstractSpatial and temporal distributions of Clear‐Air Turbulence (CAT) in the Northern Hemisphere were investigated using 41 years (1979–2019) of the European Centre for Medium‐range Weather Forecast Reanalysis version 5 (ERA5) data. We used two groups of CAT diagnostics to determine occurrence frequencies: (a) commonly used empirical turbulence indices (TI1, TI2, and TI3) and their components [vertical wind shear (VWS), deformation, ‐divergence, and divergence tendency], and (b) theoretical instability indicators [Richardson number (Ri), potential vorticity (PV), and Brunt‐Vӓisӓlӓ frequency]. The empirical indices showed high frequencies of moderate‐or‐greater (MOG)‐level CAT potential over the East Asian, Eastern Pacific, and Northwestern Atlantic regions in winter. Over East Asia, the entrance region of strong upper‐level jets showed the highest frequencies in TI1, TI2, and TI3 due mainly to strong VWS. The Eastern Pacific and Northwestern Atlantic areas near the exit region of jets had relatively high frequencies of these indices and also Ri. PV frequency was high on the southern side of jet primarily due to negative relative vorticity. Long‐term increasing trends of MOG‐level CAT potential also appeared in those three regions mainly due to warming in lower latitudes. The most significant increasing trend was found over East Asia, due to the strengthening of the East Asian jet and increased VWS due to the strong meridional temperature gradients in the mid‐troposphere induced by warming in the tropics and cooling in eastern Eurasia. These trends over East Asia, if continued, are expected to be of importance to efficient aviation operations across the northwestern Pacific Ocean.

Observations of Dynamic Turbulence in the Lower Stratosphere over Inner Mongolia Using a High-resolution Balloon Sensor Constant Temperature Anemometer

Observations of Dynamic Turbulence in the Lower Stratosphere over Inner Mongolia Using a High-resolution Balloon Sensor Constant Temperature Anemometer

The Interaction Between the Turbulence and Gravity Wave Observed in the Middle Stratosphere Based on the Round‐Trip Intelligent Sounding System

AbstractBased on the round‐trip intelligent sounding system, the structure function and spectrum analysis method were carried out to analyze the scale interactions between the small‐scale gravity wave and turbulence in the middle stratosphere. The result showed that the generation of turbulence was closely related to the Kelvin‐Helmholtz (KH) billows. An upscale energy cascade occurred on the spatial scale of KH billows, while a downscale energy cascade occurred on a larger spatial scale (gravity wave scale), which resulted in the breaking of the gravity wave and generation of turbulence. From the multilevel signal measurement, the obvious interactions between turbulence and gravity can be found. The two‐dimensional turbulence that the inverse energy cascade in 2‐D exists simultaneously with a direct enstrophy cascade to the small scales was found, which is considered to be the first‐hand observation result of relevant height.

The Case for Combining a Large Low‐Band Very High Frequency Transmitter With Multiple Receiving Arrays for Geospace Research: A Geospace Radar

AbstractWe argue that combining a high‐power, large‐aperture radar transmitter with several large‐aperture receiving arrays to make a geospace radar—a radar capable of probing near‐Earth space from the upper troposphere through to the solar corona—would transform geospace research. We review the emergence of incoherent scatter radar in the 1960s as an agent that unified early, pioneering research in geospace in a common theoretical, experimental, and instrumental framework, and we suggest that a geospace radar would have a similar effect on future developments in space weather research. We then discuss recent developments in radio‐array technology that could be exploited in the development of a geospace radar with new or substantially improved capabilities compared to the radars in use presently. A number of applications for a geospace radar with the new and improved capabilities are reviewed including studies of meteor echoes, mesospheric and stratospheric turbulence, ionospheric flows, plasmaspheric and ionospheric irregularities, and reflection from the solar corona and coronal mass ejections. We conclude with a summary of technical requirements.

Scintillation index analysis of an optical wave propagating through the moderate-to-strong turbulence in satellite communication links

In laser satellite communications, studies of the scintillation index that are based on the three-layer altitude-dependent turbulence model have paid little attention to the different character of stratospheric turbulence from turbulence in the other two layers. This difference is a consequence of the special power spectrum with a power law exponent of 5. By adopting different wave structure functions at different altitudes in the extended Rytov theory, we analyze the scintillation index along the slant path in the regime of moderate-to-strong turbulence. Our results show that the weak fluctuation theory is limited to a smaller zenith angle, and the scintillation index has a larger maximum value in the focusing regime, when compared to the Kolmogorov model. We also find that the change of the scintillation index with the outer scale of the stratospheric turbulence only appears with moderate-to-strong turbulence, and it weakens with the increase of the turbulence outer scale. Moreover, the impact of the Gaussian beam radius on the scintillation index is different in the downlink and the uplink paths. We can approximate the downlink beam as a plane wave in most cases, but we must optimize the uplink beam to minimize the irradiance fluctuation.

Retrieving atmospheric turbulence information from regular commercial aircraft using Mode-S and ADS-B

Abstract. Navigational information broadcast by commercial aircraft in the form of Mode-S EHS (Mode-S Enhanced Surveillance) and ADS-B (Automatic Dependent Surveillance–Broadcast) messages can be considered a new source of upper tropospheric and lower stratospheric turbulence estimates. A set of three processing methods is proposed and analysed using a quality record of turbulence encounters made by a research aircraft.The proposed methods are based on processing the vertical acceleration or the background wind into the eddy dissipation rate. Turbulence intensity can be estimated using the standard content of the Mode-S EHS/ADS-B.The results are based on a Mode-S EHS/ADS-B data set generated synthetically based on the transmissions from the research aircraft. This data set was validated using the overlapping record of the Mode-S EHS/ADS-B received from the same research aircraft. The turbulence intensity, meaning the eddy dissipation rate, obtained from the proposed methods based on the Mode-S EHS/ADS-B is compared with the value obtained using on-board accelerometer. The results of the comparison indicate the potential of the methods. The advantages and limitation of the presented approaches are discussed.

Comparing turbulent parameters obtained from LITOS and radiosonde measurements

Abstract. Stratospheric turbulence is important for the mixing of trace species and the energy balance, but direct measurements are sparse due to the required resolution and accuracy. Recently, turbulence parameters such as the energy dissipation rate ε were inferred from standard radiosonde data by means of a Thorpe analysis. To this end, layers with vertically decreasing potential temperature are analysed, which is expected to indicate turbulence. Such an application assumes a proportionality between the Thorpe length LT and the Ozmidov scale LO. While this relation is accepted for the ocean, experimental evidence for such proportionality in the stratosphere is sparse. We have developed a high-resolution (8 kHz) turbulence measurement system called LITOS (Leibniz Institute Turbulence Observations in the Stratosphere), which for the first time resolves the inner scale of turbulence in the stratosphere. Therewith the energy dissipation rate ε can be determined by spectral analysis. This independent value for ε enables us to check the relation LO ∝ LT. In our measurements no such proportionality can be seen, although the mean of the ratio LO/LT is close to what is assumed in radiosonde analyses. Dissipation rates for individual layers obtained from radiosondes deviate up to a factor of ~3000 from those obtained by spectral analysis. Some turbulent layers measured by LITOS are not observed by the radiosonde at all, and vice versa. However, statements about the statistical mean seem to be possible by Thorpe analysis.

Characteristics of stratospheric turbulent layers measured by LITOS and their relation to the Richardson number

Based on high-resolution turbulence measurements performed with the newly established balloon-borne instrument Leibniz Institute Turbulence Observations in the Stratosphere (LITOS) during the Balloon Experiments for University Students (BEXUS) 6 and BEXUS 8 campaigns from Kiruna, we derived characteristics of stratospheric turbulence layers, like their thickness and distance in between. Typically, the layers are ∼15–130 m thick and have a distance of ∼60–270 m, and their number increases with altitude. Due to the very high measurement resolution of LITOS in the range of millimeters, we obtain energy dissipation rate profiles with unprecedented precision. Within the turbulent layers we get a mean dissipation rate of 3.4×10−2W/kg (BEXUS 6) and 1.1 × 10−2 W/kg (BEXUS 8) corresponding to a heating rate of 1 to ∼3 K/d. The profiles show an increase of the energy dissipation with altitude. Comparisons with the Richardson number Ri preclude a clear correlation between the occurrence of turbulence and Ri 1/4 and far beyond, independent of the scale over which Ri has been determined.

Gravity wave breaking in easterly flow over Greenland and associated low level barrier- and reverse tip-jets

A first evidence of severe turbulence in the lower stratosphere during easterly tropospheric flow over Greenland is presented. A numerical simulation shows the turbulence to be associated with gravity wave breaking and that simulating with a horizontal resolution of 3 km gives substantially greater and more realistic turbulence than at a 9 km horizontal resolution. It is concluded that real-time simulations at high resolutions would improve aviation forecasts. As the atmospheric flow impinges on South-Greenland a barrier jet, a reverse tip jet and amplified mountain waves with secondary wave breaking are generated at the same time.

Energetics of small scale turbulence in the lower stratosphere from high resolution radar measurements

Abstract. Very high resolution radar measurements were performed in the troposphere and lower stratosphere by means of the PROUST radar. The PROUST radar operates in the UHF band (961 MHz) and is located in St. Santin, France (44°39’ N, 2°12’ E). A field campaign involving high resolution balloon measurements and the PROUST radar was conducted during April 1998. Under the classical hypothesis that refractive index inhomogeneities at half radar wavelength lie within the inertial subrange, assumed to be isotropic, kinetic energy and temperature variance dissipation rates were estimated independently in the lower stratosphere. The dissipation rate of temperature variance is proportional to the dissipation rate of available potential energy. We therefore estimate the ratio of dissipation rates of potential to kinetic energy. This ratio is a key parameter of atmospheric turbulence which, in locally homogeneous and stationary conditions, is simply related to the flux Richardson number, Rf .Key words. Meteorology and atmospheric dynamics (turbulence) – Radio science (remote sensing)

Influence of stratospheric turbulence on infrared imaging

We introduce a model for the power spectrum of stratospheric turbulence that is based on data from in situ measurements and on results of the theory of saturated internal gravity waves. We then study the effect of that stratospheric turbulence on the scintillation and the coherence of starlight and on the degradation of star image. It is shown that, because the stratospheric phase structure function is approximately quadratic over a distance comparable with the aperture of a large telescope, stratospheric turbulence does not significantly degrade short-exposure images of star but does degrade long-exposure ones. The influence of stratosphere on star image degradation is more important in the IR than in the visible range because of the specific dependence of the stratospheric coherence radius on the light wavelength. Star image motion and blurring are determined by different characteristics of the atmosphere and cannot be explained solely on the basis of the Kolmogorov model. The modified astronomical imaging theory predicts greater improvement in resolution as the result of tilt removal than does a conventional theory.

High resolution turbulence observations in the middle and lower atmosphere by the MU radar with fast beam steerability: preliminary results

Refractive index fluctuations or turbulence in the mesosphere, stratosphere and troposphere are observed with the aid of the fast beam steerability of the MU (middle and upper atmosphere) radar which operates at 46.5 MHz with 1 MW peak radiation power and 8330 m 2 antenna aperture. Morphology of the mesospheric and stratospheric turbulence is studied by making use of the high altitude and time resolutions. Sixteen beam observations based on the fast beam steerability reveal advection properties and spatial variability of echoing regions in the troposphere. These results demonstrate new possibilities for this system in the investigation of three dimensional structures of turbulence.

‘‘Glow-discharge’’ ionic anemometer

We have developed an ionic anemometer utilizing a glow discharge for the purpose of observing stratospheric turbulence. The anemometer has a three-electrode structure; two electrodes made of Ni mesh hold a glow discharge between them and act as the source of ion tracers. The third electrode collects the ions interacting with wind. The minimum detectable wind speed is less than 1 cm/s over a pressure range of 15–35 Torr. The lifetime of this device is more than 50 h. The anemometer has been successfully operated on balloon-borne experiments carried out in 1983 and 1984.

大気球塔載グロー放電型電離式風速計による成層圏乱流の観測

1. Introduction In situ measurements of stratospheric tur-bulence are important in order to verify the theorem of gravity-wave stress in the middle atmospheric dynamics [see Yamanaka and Tanaka (1984a) and references therein]. We have already performed an observation at 24-26km levels using sensitive propellor anemo-meters reeled down and up from balloon, and have reported on multiple gust layers probably associated with gravity waves just before breakdown (see Yamanaka and Tanaka, 1984c; Yamanaka et al., 1985b). However, we could not detect such quick and weak fluctuations as measured so far by Barat's (1975, 1982b) anemometres ionique. Many investigators have tried to apply ion-ized air generated by a corona discharge for tracers in various air flows [see Yamanaka et al. (1985a) and references therein]. For balloon-borne use, however, none of them could observe stratospheric turbulence longer than few hours, possibly because the corona dis-charge is transient and unstable. Long dura-tion observations are necessary to reveal the life cycles of layered turbulence, in particular those generated by long gravity waves which must be different from that of short waves (Yamanaka and Tanaka, 1984b). The longest period of internal gravity waves is approxi-

On the Contamination of Stratospheric Turbulence Measurements by Wind Shear

Analysis of the velocity filed measured by ballon-borne anemometers through a clear air turbulent patch is presented. It is shown that, except in the case where the ballon altitude is constant, the vertical wind shear related to nonturbulent motions may create a contamination above the outer scale of the turbulent field. The results is typical of all turbulence measurements obtained along non-constant altitude trajectories: it may explain some intriguing characteristics of the gust velocity spectra measured by instrumented aircraft.

Fine Altitude Resolution Observations of Stratospheric Turbulent Layers by the Arecibo 430 MHz Radar

Abstract Stratospheric turbulence is now observed by the Arecibo 430 MHz radar with an improved altitude resolution of 150 m. Turbulence is observed to occur in thin layers with a thickness usually less than the altitude resolution, and estimated to be about 50 m. A clear correlation is found between the power, wind shear and spectral width of the echoes. A simple method of estimating the energy dissipation rate and the eddy diffusivity is examined. Values of the order of 0.2 m2 s−1 are found for the eddy diffusivity coefficient in the lower stratosphere, showing the importance of turbulence on vertical transport.

Some Characteristics of Clear-Air Turbulence in the Middle Stratosphere

Abstract Analysis of clear-air turbulence measurements obtained from highly sensitive balloon-borne instrumentation is presented. Emphasis is placed on the structure of the turbulent velocity field in the inertial range. Regions of weak turbulence are found to be associated with low Richardson numbers and negative temperature gradients. Measurements of the turbulent energy intensity are presented. The extension of the inertial range is found to be consistent with theoretical values in the case of stably stratified flow. The turbulence intensity varies significantly over a two-hour time interval. An important result is the observational evidence for a 2/3 law behavior in the structure function at scales where the turbulent velocity field cannot be isotropic: this behavior cannot be explained by a two-dimensional turbulence field.

Atmospheric Turbulence Measurements from a Subsonic Aircraft

THE operation of constant-temp erature and constantcurrent fine wire and thin film anemometers on an aircraft is discussed. Instrumentation has allowed data with a 10-kHz bandwidth to be gathered. Atmospheric turbulence data^ gathered at flight Mach numbers of 0.28 and 0.83 and operating altitudes of 3.6-12.5 km, are presented. Samples of results from studies of stratospheric turbulence, and the turbulence structure of the tropopause boundary, are described.

First low-power VHF radar observations of tropospheric, stratospheric and mesospheric winds and turbulence at the Arecibo Observatory

First VHF radar measurements with height resolution of 300 m and angular resolution of 1.7° were carried out in low latitudes at the Arecibo Observatory, Puerto Rico. A short outline is given of the experimental set-up which consisted of a 160W average power radar-transceiver and a self-contained digital radar control and data acquisition unit. The new VHF feed system of the Arecibo dish is described shortly. Reliable radar echoes were detected from the troposphere, lower stratosphere and from some heights in the mesosphere, indicating that the described VHF radar is capable of proper investigations of dynamical processes in the low latitude middle atmosphere. The angular dependence of aspect sensitive tropospheric and stratospheric turbulence structures was measured to be 1.5–2.5 dB degree −1. Echoes from the mesosphere indicate a patchy structure of turbulence. The analysis of the signal-to-noise ratio shows considerably high reflectivity in the upper troposphere, which can be caused by high-reaching tropical cumulus convection. Wind profiles measured with the VHF radar between 7.5 and 19.5 km with a height resolution of 300m are very similar to radiosonde wind profiles. Mesospheric VHF radar winds are roughly consistent in amplitude with tidal winds.