Echo Structures Research Articles

Anomalous Sporadic‐E Enhancements and Field‐Aligned Irregularities at Low‐Latitudes During the Intense Geomagnetic Activities on 17–18 March 2015

AbstractDuring the intense geomagnetic activities on 17–18 March 2015, the anomalous enhancements of critical frequency of sporadic‐E (foEs) and field‐aligned irregularities (FAIs) were recorded in the mid‐ and low‐latitude E‐region. The foEs peaks present good consistency with the occurrence of the FAIs. The AE and PC indices show the similar variation of five continuous peaks of 5‐hr period on 17 March, indicating it is the successive substorms responsible for the sequential Joule heating events. The equatorward wind surges due to the Joule heating in polar region transferred the 5‐hr period oscillations to the mid‐latitude Mesosphere and Low‐Thermosphere (MLT) atmosphere and even to the low‐latitude sporadic‐E (Es) layer. The 5‐hr oscillations emerged in the AE and PC indices, mid‐latitude MLT region winds, and low‐latitude foEs in sequence, indicating the disturbances were traveling equatorward and reached low‐latitude E‐region. The anomalous FAIs observed by the HCOPAR presented the descending and intermittent echo structures. The substorm‐related oscillations are considered to modulate the MLT region tidal winds and induce the anomalous sporadic‐E enhancements and FAIs through the wind‐shear instability.

Effects of echo phase on bottlenose dolphin jittered-echo detection.

The ability of bottlenose dolphins to detect changes in echo phase was investigated using a jittered-echo paradigm. The dolphins' task was to produce a conditioned vocalization when phantom echoes with fixed echo delay and phase changed to those with delay and/or phase alternated ("jittered") on successive presentations. Conditions included: jittered delay plus constant phase shifts, ±45° and 0°-180° jittered phase shifts, alternating delay and phase shifts, and random echo-to-echo phase shifts. Results showed clear sensitivity to echo fine structure, revealed as discrimination performance reductions when jittering echo fine structures were similar, but envelopes were different, high performance with identical envelopes but different fine structure, and combinations of echo delay and phase jitter where their effects cancelled. Disruption of consistent echo fine structure via random phase shifts dramatically increased jitter detection thresholds. Sensitivity to echo fine structure in the present study was similar to the cross correlation function between jittering echoes and is consistent with the performance of a hypothetical coherent receiver; however, a coherent receiver is not necessary to obtain the present results, only that the auditory system is sensitive to echo fine structure.

Mid‐Latitude Mesospheric Responses of the Solar Eclipse on 21 June 2020 Observed by the Wuhan MST Radar

AbstractAn annular solar eclipse shifted across the earth from the middle of Africa to the Pacific on 21 June 2020. The Wuhan Mesosphere‐Stratosphere‐Troposphere (MST) radar was located on the eclipse path to provide us a rare opportunity to investigate the atmospheric responses to the rapid variation of solar radiations. The east, north, and vertical beams of the Wuhan MST radar were applied to record the echoes from mesosphere with 10 min sampling period. A Digisonde located near the MST radar was also used to investigate the variations of ionospheric Es layer during the solar eclipse. The mesosphere region between 70 and 80 km heights presented obvious responses to the eclipse. The echoes disappeared at around the eclipse maximum, indicating the dominant role of the solar radiation. The descending and ascending echo structures were recorded in the first and recovery phases of the eclipse, respectively. The Digisonde also found the evidence of the eclipse induced gravity waves in the Es layer that just above the mesosphere. The lunar shadow produced southward winds on the northside of the eclipse path is considered to induce the descending echo structure. The upward propagating gravity waves generated during the eclipse may be responsible for the ascending echo structure.

Correlations between clinical severity of pulmonary tuberculosis, thyroid function and some cytokines

To estimate the interrelations between thyroid profile, some cytokines and clinical severity of new case of cavitary pulmonary tuberculosis 43 patients with cavitary pulmonary tuberculosis and 10 healthy volunteers were studied. Thyroid glands of all patients before chemotherapy and volunteers from control group were examined by ultrasound. The levels of free thyroxine, thyroid stimulating hormone and antibodies to thyroglobulin and thyroid peroxidase in the serum were defined. At the same time the levels of tumor necrosis tumor necrosis factor, interferon-gamma and interleukin-2, -6, and -4 were measured. Correlations between clinical severity of new case of pulmonary tuberculosis, thyroid functions, and these cytokines were studied. The pathological changes of thyroid echo structures were recovered in more than half of patients. The level of thyroxine in tuberculous patients was decreased down to lower-normal significance. In tuberculous patients with pathological echo structure of the thyroid the thyroxine level decreasing was more significant. The thyroxine stimulating hormone level was increased in these patients. The increasing of tumor necrosis tumor factor and the interleukin-6 levels and the decreasing of interleukin-4 level were demonstrated in tuberculous patients comparing with healthy persons. Positive correlation between clinical severity of new case of pulmonary tuberculosis, thyroid functions, and these cytokines were determined. The high percentage defined cases of thyroid pathology in tuberculous patients is caused the necessity the screening of thyroid function in tuberculous patients for in time diagnosis of its subclinical disorders and their correction to restore cytokines balance and improving of antituberculosis chemotherapy efficacy.

Mammatus‐Like Echo Structures Along the Base of Upper‐Tropospheric Outflow‐Layer Clouds of Typhoons Observed by Cloud Radar

AbstractUpper‐tropospheric clouds in the outflow layer of typhoons can affect the track of typhoons (tropical cyclones) through radiation effects. In this study, the microstructure of the outflow‐layer clouds of several typhoons was examined. Cloud radar observations of three typhoons around Japan revealed numerous protuberances in echoes along the base of the upper‐level clouds, which are referred to as mammatus‐like echoes. The horizontal and vertical scales of these mammatus‐like echoes were 0.5–3.0 and 0.3–1.5 km, respectively. Vertical observations revealed downward (upward) Doppler velocities in (between) the hanging echo regions. Upward and downward velocity maxima were estimated at 3 m s−1 around the mammatus‐like echoes. Neutral stratification developed in the dry layer beneath the cloud base in which the mammatus‐like echoes formed. These mammatus‐like structures may promote mixing along the cloud base that contributes to dissipation of the outflow‐layer clouds.

Key Technologies of Hydrometeor Classification and Mosaic Algorithm for X-band Polarimetric Radar

The advantages of X-band polarimetric weather radar focus on its high spatio-temporal resolution and capability of multi-radar networking. However, the previously designed hydrometeor classification algorithm (HCA) for S-band weather radar is unsuitable for X-band weather radar due to the difference of backscattering characteristics and heavy precipitation attenuation. Therefore, the key technologies of hydrometeor classification algorithm and multi-radar mosaic algorithm for X-band polarimetric weather radar are proposed. First, it is found that the melting layer detection algorithm designed for S-band polarimetric weather radar is not suitable for X-band weather radar through analysis on the data collected by Beijing X-band radar network. A melting layer detection method based on quasi-vertical profile is proposed, which greatly improves the accuracy of obtaining the melting information. Second, a confidence threshold adjustment method is proposed to accurately estimate the data quality in the case of precipitation and clutter superposition. Third, an optimization method of membership functions based on data statistics is proposed to reconstruct the classification parameters suitable for Beijing X-band radar network. Finally, a multi-radar mosaic method based on rainfall attenuation is proposed, in which the reflectivity factors of networking radars are weighted and averaged by the data quality factor. Compared with the traditional method, it is found that the structural inhomogeneity of X-band radar mosaic result is effectively reduced. Those modifications effectively enhance the reliability of classification mosaic results of X-band weather radar network and provide technical support for the rapid deployment of X-band radar in China. Three typical precipitation cases in Beijing during the flood season in 2016 are used to compare the observational efficiency between X-band weather radar network and S-band operational radar. For the cases of convective rainfall, fine echo structures and reasonable hydrometeor distributions are found in X-band radar mosaic results. Especially for convective rainfall with short duration and small spatial scale, the advantage of X-band radar is more obvious, which alleviates the limited detection ability of S-band operational radar in urban areas. In addition, the hail falling area identified by X-band radar can be verified by manual observation in national weather stations. The performance of X-band weather radar network in large-scale stratiform precipitation, however, is not as good as S-band weather radar.

A Quality Control Method of Ground-Based Weather Radar Data Based on Statistics

The detection of meteorological targets using ground-based weather radars usually suffers from ground clutter and beam blockage. These nonmeteorological or weakened signals should be identified so quality control should be implemented before weather radar data can be used. Conventional quality control methods aim at differentiating between echo structures of ground clutter and meteorological targets, and use terrain information to calculate beam blockage regions based upon standard atmospheric refraction. However, it is difficult to achieve the goal for long-term large data sets by conventional methods due to the complexity and diversity of weather radar echoes. In this paper, regions of ground clutter and beam blockage are first identified through the statistics on spatial distribution of reflectivity and fuzzy logic classification, and then they are used as masks to remove data from the scan. The new method is applied to data of the Nanjing weather radar in China. By the aid of a proposed evaluation scheme and the visual recognition, quality control results of the new method are compared with those of the conventional methods. It is found that the new method can provide better identification of ground clutter or beam blockage and thus better quality control results. The new scheme has a good prospect in operational service for its principle advantages, easy applicable conditions, and better performance compared with conventional methods.

On Contrasting Ensemble Simulations of Two Great Plains Bow Echoes

AbstractBow echo structures, a subset of mesoscale convective systems (MCSs), are often poorly forecast within deterministic numerical weather prediction model simulations. Among other things, this may be due to the inherent low predictability associated with bow echoes, deficient initial conditions (ICs), and inadequate parameterization schemes. Four different ensemble configurations assessed the sensitivity of the MCSs’ simulated reflectivity and radius of curvature to the following: perturbations in initial and lateral boundary conditions using a global dataset, different microphysical schemes, a stochastic kinetic energy backscatter (SKEB) scheme, and a mix of the previous two. One case is poorly simulated no matter which IC dataset or microphysical parameterization is used. In the other case, almost all simulations reproduce a bow echo. When the IC dataset and microphysical parameterization is fixed within a SKEB ensemble, ensemble uncertainty is smaller. However, while differences in the location and timing of the MCS are reduced, variations in convective mode remain substantial. Results suggest the MCS’s positioning is influenced primarily by ICs, but its mode is most sensitive to the model error uncertainty. Hence, correct estimation of model error uncertainty on the storm scale is crucial for adequate spread and the probabilistic forecast of convective events.

Coordinated observations of F region 3 m field‐aligned plasma irregularities associated with medium‐scale traveling ionospheric disturbances

AbstractThree meter field‐aligned irregularities (3 m FAIs) associated with medium‐scale traveling ionospheric disturbances (MSTIDs) that occurred on 5 February 2008 were observed by using the Chung‐Li 52 MHz coherent scatter radar. Interferometry measurements show that the plasma structures responsible for the 3 m FAI echoes are in a clumpy shape with a horizontal dimension of about 10–78 km in a height range of 220–300 km. In order to investigate the dynamic behaviors of the plasma irregularities at different scales in the bottomside of F region, the VHF radar echo structures from the 3 m FAIs combined with the 630 nm airglow images provided by the Yonaguni all‐sky imager are compared and analyzed. The results show that the radar echoes were located at the west edge of the depletion zones of the 630 nm airglow image of the MSTIDs. The bulk echo structures of the 3 m FAIs drifted eastward at a mean trace velocity of about 30 m/s that is in general agreement with the zonal trace velocity of the MSTIDs shown in the 630 nm airglow images. These results suggest that the observed F region 3 m FAIs for the present case can be regarded as the targets that are frozen in the local region of the MSTIDs. In addition, the radar‐observed 3 m FAI echo intensity and spectral width bear high correlations to the percentage variations of the 630 nm emission intensity. These results seem to suggest that through the nonlinear turbulence cascade process, the MSTID‐associated 3 m FAIs are very likely generated from the kilometer‐scale plasma irregularities with large amplitude excited by the gradient drift instability.

Blind source extraction based on time-frequency characteristics for underwater object acoustic scattering

The physical mechanism and signal characteristics of acoustic scattering are the vital basis for target recognition. But underwater target acoustic scattering components are aliasing in time-frequency (TF) domain, for which the target elastic acoustic scattering characteristics are difficult to detect. Additionally, the existing blind source separation methods are effective only on condition that the number of array elements is equal to or greater than the number of the source signals. To address these problems, a novel TF domain blind source extraction method of separating target acoustic scattering components is proposed in this paper. The method only uses the TF energy characteristic differences among the target acoustic scattering components, and special limitations on target echo structures are unnecessary. Image morphology filter is used to remove the cross-term interference from time-frequency distribution (TFD) of the received array signals. Then, the single source which shows maximum energy concentration at the corresponding auto-term TF points is extracted through three operations: i) selecting the single source auto-term TF points from the auto-term ones; ii) constructing the spatial TFD matrix according to the selected single source auto-term TF points; iii) obtaining the single source by decomposing the eigenvalue of their spatial TFD matrix. Finally, the extracted single signal is excluded by the tightening process from the received array signals, and each single signal is separated successively by repeating the above steps. In addition, a signal processing model which can describe the physical characteristics of the target echoes is established based on the separated signal components. Simulations illustrate that the image morphological filter can remove the cross-term interference and improve the TF resolution of the Wigner-Ville distribution. Anechoic pool experimental results show that the TF domain blind source extraction algorithm can well separate each target acoustic scattering component, it can also achieve a higher output signal-to-noise ratio. Furthermore, the separated elastic acoustic scattering components are in good agreement with the results computed by the surface wave generating theory, so the method can provide the robust and reliable feature for underwater target recognition.

LIGHT ECHOES FROM SUPERNOVA 2014J IN M82

Type Ia SN 2014J exploded in the nearby starburst galaxy M82 = NGC 3032, and was discovered at Earth about seven days later on 2014 January 21, reaching V maximum light around 2014 February 5. SN 2014J is the closest SN Ia in at least four decades and probably many more. Recent HST/WFC3 imaging (2014 September 5 and 2015 February 2) of M82 around SN 2014J reveals a light echo at radii of about 0.6 arcsec from the SN (corresponding to about 12 pc at the distance of M82). Likely additional light echoes reside at a smaller radii of about 0.4 arcsec. The major echo signal corresponds to echoing material about 330 pc in the foreground of SN 2014J, and tends to be bright where pre-existing nebular structure in M82 is also bright. The second, likely echo corresponds to foreground distances of 80 pc in front of the SN. Even one year after maximum light, there are indications of further echo structures appearing at smalle radii, and future observations may show how extinction in these affect detected echo farther from the SN, which will affect interpretion of details of the three-dimensional structure of this gas and dust. Given enough data we might even use these considerations to constrain the near-SN material's shadowing on distant echoing clouds, even without directly observing the foreground structure. This is in addition to echoes in the near future might also reveal circumstellar structure around SN 2014J's progenitor star from direct imaging observations and other techniques.

E region radar echoes from low‐latitude field‐aligned irregularities due to gravity waves and tides: A case study using radar, lidar, and radiosonde observations and simulations

AbstractOn the night of 5 February 2011, the height‐time plot of echo from E region field‐aligned irregularities (FAI) received by the Indian mesosphere‐stratosphere‐troposphere radar at Gadanki (13.5°N, 79.2°E) shows a slow‐descending layered structures separated by nearly 8 km in the height region 80–100 km and vertically elongated structures with quasiperiodic variations at higher heights. The stratospheric thermal structure also shows similar slowly descending structures with nearly 8 km separation. Hodograph of 7–9 km band‐pass filtered radiosonde zonal and meridional winds over Gadanki form clearly an ellipse, and the dominant period obtained from the ratio of major to minor axes of the ellipse is nearly 24 h indicating the presence of a nonmigrating diurnal tide with vertical wavelength of 8 km. The two‐dimensional spectrum of temperature perturbations, which are assumed to be due to gravity waves, shows dominant periods near 1 h and 1.5 h. The spectrum of FAI echo also shows similar dominant periods. Altitude‐time cross section of vertical ion velocity is computed using winds composed of observed gravity wave and tidal parameters. As the diurnal tide over Tirunelveli (8.7°N, 77.8°E) shows weaker amplitudes above 90 km, the removal of tidal contribution clearly reveals the observed FAI echo structure of vertically slanting plasma blob structures at higher heights and slowly descending continuous structures separated by 8 km at lower heights. The present study clearly demonstrates the role of tides and gravity waves in the formation of descending echo structures and quasiperiodic echoes respectively.

Evolution of the Population of Precipitating Convective Systems over the Equatorial Indian Ocean in Active Phases of the Madden–Julian Oscillation

AbstractThree-dimensional radar reflectivity fields from a dual-wavelength Doppler polarimetric radar (S-PolKa) deployed in the equatorial Indian Ocean are used to evaluate the composition of the population of convective cloud elements during active phases of the MJO. Rainfall in active periods was intermittent, occurring in 11 episodes of about 2–4 days, separated by several nonrainy days. Data for these 2-day periods were composited relative to the time of maximum rainfall. Analysis of the S-PolKa data shows the makeup of the convective population during the rainfall episodes. Four types of echo structures were analyzed statistically for the 11 rainfall episodes: shallow convective echoes (SCE), deep convective cores (DCC), wide convective echo cores (WCC), and broad stratiform (BSR) echo regions. SCE and DCC events were most frequent before the maximum rainfall, with the peak frequency of SCE leading that of DCCs. WCCs were most frequent during the rainfall maximum, and BSR regions were most frequent in the later part of the rainfall episode. Composited ECMWF Interim Re-Analysis (ERA-Interim) data and 3-hourly atmospheric soundings indicate that the 2–4-day episodes were related to the passage of equatorial waves. In the early part of a rainfall episode, the wave-passage conditions were unstable, favoring deep penetrating convective elements, while in the later period the wave divergence profile was commensurate with convective systems in late anvil-producing stages. These results support the stretched building-block notion of the life cycle of tropical convection and confirm satellite-based interpretations of SCE, DCC, WCC, and BSR statistics in the composition of the convective population.

Studies on Meteorological Parameters and Mixing Height in Gold Mining Area

Gold mining at Kolar Gold Fields is closed but some industries in this area are in operation and some may like to be established. Data on atmospheric and meteorological parameters were generated using SODAR (Sound Detection and Ranging) and automatic weather station in different seasons. Over 2000 sodar echograms were recorded and classified into six categories like rising layer, thermal plume (free), ground based layer (spiky top), ground based layer (flat top), ground based multiple layers and dot echo structures. Using echograms, unstable period was determined to know the diluting capability of atmosphere for pollutants in the seasons. The highest duration of mixing heights revealed the period of highest dispersion. Based on the sodar echograms and mixing height, stability classes for the different times of the day were evaluated, which can be used for the estimation of dispersion coefficients. Influence of wind speed, wind direction, temperature, humidity, solar radiation and rainfall on mixing heights was studied. Statistical model was developed for the prediction of mixing height. Model adequacy was checked using F-statistics, normal distribution curve and correlation between predicted and measured values of mixing heights.

Sjögren syndrome: A case report

Sjögren syndrome is a systemic autoimmune disorder that affects the exocrine glands. The authors present the case of a 50-year-old woman diagnosed with this syndrome on the basis of clinical and serological findings. Sonography of the major salivary glands revealed normal-sized glands with echo structures that were diffusely inhomogeneous due to the presence of multiple hypoechoic areas. Parenchymal vascularization was significantly increased on color Doppler imaging. These findings confirmed the diagnosis and revealed active disease manifested by glandular hypervascularization. This represents a typical case of Sjögren syndrome and illustrates the diagnostic value in these cases of salivary gland sonography, which is effective, noninvasive, and repeatable and provides accurate information on the vascularization status of the glands.

Coordinated sporadic E layer observations made with Chung-Li 30 MHz radar, ionosonde and FORMOSAT-3/COSMIC satellites

A nighttime sporadic E (Es) layer responsible for range spread Es trace in ionogram and quasi-periodic echoes scattered from 5-m field-aligned electron density irregularities (FAIs) is investigated by using a ground-based 30 MHz coherent scatter radar, ionosonde and FORMOSAT-3/COSMIC satellite. A comparison shows a positive correlation between the 30 MHz radar backscatter and critical frequency foEs of the Es trace, which are consistent with earlier observational results. Interferometry measurement indicates that the spatial patterns of the radar echoes from the FAIs were in patchy form with vertical extent of about a few kilometers and horizontal dimensions of about 10–20 km. The echo structures experienced quasi-periodic oscillations not only in vertical but also in horizontal directions with periods of approximately 5–6 min. Observed Doppler velocities of the FAIs also exhibited quasi-periodic oscillations with the same periods. From their downward phase movement, these oscillations were very likely attributed to the modulations of upward propagating gravity waves with vertical wavelengths of about 10–20 km. In addition, vertical shears of the FAI Doppler velocity were observed, which are believed to result from the change in the phase of gravity wave with height. A physical process is proposed in this article to account for the relation between gravity wave-perturbed neutral wind and height variation of the FAI Doppler velocity. It is believed that the oscillations in the Doppler velocity profiles are associated with the wave-induced polarization electric fields in a finite plasma structure in the azimuth direction.

Regional, Seasonal, and Diurnal Variations of Extreme Convection in the South Asian Region

AbstractTemporal and spatial variations of convection in South Asia are analyzed using eight years of Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar (PR) data and NCEP reanalysis fields. To identify the most extreme convective features, three types of radar echo structures are defined: deep convective cores (contiguous 3D convective echo ≥40 dBZ extending ≥10 km in height) represent the most vertically penetrative convection, wide convective cores (contiguous convective ≥40 dBZ echo over a horizontal area ≥1000 km2) indicate wide regions of intense multicellular convection, and broad stratiform regions (stratiform echo contiguous over an area ≥50 000 km2) mark the mesoscale convective systems that have developed the most robust stratiform regions.The preferred locations of deep convective cores change markedly from India’s east coast in the premonsoon to the western Himalayan foothills in the monsoon. They form preferentially in the evening and over land as near-surface moist flow is capped by dry air aloft. Continental wide convective cores show a similar behavior with an additional nocturnal peak during the monsoon along the Himalayan foothills that is associated with convergence of downslope flow from the Himalayas with moist monsoonal winds at the foothills. The oceanic wide convective cores have a relatively weak diurnal cycle with a midday maximum. Convective systems exhibiting broad stratiform regions occur primarily in the rainiest season and regions—during the monsoon, over the ocean upstream of coastal mountains. Their diurnal patterns are similar to those of the wide convective cores.

Effect of Rebamipide on Quality of Peptic Ulcer Healing in Rat

The aim of this study is to elucidate the effects and the mechanism of rebamipide, omeprazole, and their combination treatment on quality of peptic ulcer healing (QOUH). Peptic ulcer models were induced by acetic acid exposure of the serosa of rat stomach. Forty Sprague-Dawley (SD) rats were divided randomly into four groups of ten rats each. Saline 2 ml/d (group 1), rebamipide 60 mg/kg/d (group 2), omeprazole 10 mg/kg/d (group 3) as well as its combination regimen (group 4) were administrated for 7 days. After sacrifice, size of the ulcer and focal layer structures were measured in vitro by miniature ultrasonic probe, and the mucosal sections were stained with hematoxylin and eosin (HE) for histological examination; the levels of interleukin (IL)-8/prostaglandin E(2) (PGE(2)) were evaluated by enzyme-linked immunosorbent assay (ELISA) and malondialdehyde (MDA) level was evaluated by thiobarbituric acid (TBA) method. Macroscopically, compared with the control group, the maximal diameters of the ulcers in the medication groups were significantly reduced (P < 0.05), and the layer echo structures of gastric wall were partially rebuilt. Histologically, ulcer range and inflammatory infiltration were less severe compared with the control group. In addition, mucosal MDA and IL-8 levels were significantly decreased, while PGE(2) level was significantly increased in the medication groups. Between the two monotherapy groups, there was no statistical difference in terms of PGE(2) and MDA levels. However, PGE(2) level was significantly increased, while MDA and IL-8 levels were significantly decreased in the combination group. Rebamipide as well as omeprazole and the combination regimen may improve QOUH through increasing the level of PGE(2), decreasing the levels of IL-8 and MDA in gastric mucosa, and this may potentially result in reduced recurrence of ulcer; moreover, the combination regimen was identified as having more antiulcer effects than monotherapy.

Motion of echo structures observed with volume imaging atmospheric radar

Volume imaging radar often shows echo patterns on horizontal scale ∼ 100 – 1000 m , moving across the radar. The echoes could be from convection, and moving at near the background wind velocity; other explanations are clouds or regions of turbulence. This paper studies the motion of echoes, with a two-dimensional correlation method widely used for cloud motion winds and tracking weather radar echoes, but not applied before to wind profiling radar. Data are from the MU (middle and upper atmosphere) radar, Japan. Several factors causing an underreading of echo speed are removed; however, remaining data still show echoes moving a few m s - 1 slower than the background wind, with similar direction. This could be explained by convection, consistent also with some increased vertical-beam spectral width showing turbulence. Motion of convective echoes slower than the background wind could bias other radar wind measurements.

Pilomatricoma: Sonographic features

Pilomatricomas (also known as calcifying epitheliomas of Malherbe) are benign subcutaneous tumors that arise from the cutaneous adnexa and usually affect young subjects. They typically present as solitary asymptomatic nodules located in most cases on the face or neck. On ultrasonography, pilomatricomas appear as hypoechoic lesions with inhomogeneous echo structures, well-defined margins, and posterior shadowing. Color Doppler generally reveals a single artery that penetrates the lesion and gives rise to multiple intralesional branches. Diagnosis is based on clinical and histological findings. The authors present a typical case of pilomatricoma diagnosed on the basis of clinical and sonographic findings that were subsequently confirmed by histology.