A method for estimating the turbulent kinetic energy dissipation rate from a vertically pointing Doppler lidar, and independent evaluation from balloon-borne in situ measurements

A method of estimating dissipation rates from a vertically pointing Doppler lidar with high temporal and spatial resolution has been evaluated by comparison with independent measurements derived from a balloon-borne sonic anemometer. This method utilizes the variance of the mean Doppler velocity from a number of sequential samples and requires an estimate of the horizontal wind speed. The noise contribution to the variance can be estimated from the observed signal-to-noise ratio and removed where appropriate. The relative size of the noise variance to the observed variance provides a measure of the confidence in the retrieval. Comparison with in situ dissipation rates derived from the balloon-borne sonic anemometer reveal that this particular Doppler lidar is capable of retrieving dissipation rates over a range of at least three orders of magnitude. This method is most suitable for retrieval of dissipation rates within the convective well-mixed boundary layer where the scales of motion that the Doppler lidar probes remain well within the inertial subrange. Caution must be applied when estimating dissipation rates in more quiescent conditions. For the particular Doppler lidar described here, the selection of suitably short integration times will permit this method to be applicable in such situations but at the expense of accuracy in the Doppler velocity estimates. The two case studies presented here suggest that, with profiles every 4 s, reliable estimates of ϵ can be derived to within at least an order of magnitude throughout almost all of the lowest 2 km and, in the convective boundary layer, to within 50%. Increasing the integration time for individual profiles to 30 s can improve the accuracy substantially but potentially confines retrievals to within the convective boundary layer. Therefore, optimization of certain instrument parameters may be required for specific implementations.

Charge measurements in stratiform cloud from a balloon based sensor

Abstract. The electrification of stratiform clouds has is little investigated in comparison with thunderstorms and fair weather atmospheric electricity. Theory indicates that, at the upper and lower horizontal boundaries of layer clouds, charging will arise from vertical flow of cosmogenic ions in the global atmospheric electric circuit. Charge is transferred to droplets and particles, affecting cloud microphysical processes such as collision and droplet activation. Due to the lack of in-situ measurements, the magnitude and distribution of charge in stratiform clouds is not well known. A sensitive, inexpensive, balloon borne charge sensor has been developed to make in-situ measurements of edge charging in stratiform cloud using a standard meteorological radiosonde system. The charge sensor has now been flown through over 20 stratiform clouds and frequently detected charge up to 200 pC m-3 near cloud edges. These results are compared with measurements from the same sensor used to investigate charge in particle layers, such as volcanic ash from the Eyjafjallajökull eruption, and Saharan dust in the Cape Verde Isles. 1.

Balloon-borne disposable radiometer for cloud detection

A low cost, disposable instrument for measuring solar radiation during meteorological balloon flights through cloud layers is described. Using a photodiode detector and low thermal drift signal conditioning circuitry, the device showed less than 1% drift for temperatures varied from +20 °C to −35 °C. The angular response to radiation, which declined less rapidly than the cosine of the angle between the incident radiation and normal incidence, is used for cloud detection exploiting the motion of the platform. Oriented upwards, the natural motion imposed by the balloon allows cloud and clear air to be distinguished by the absence of radiation variability within cloud, where the diffuse radiation present is isotropic. The optical method employed by the solar radiation instrument has also been demonstrated to provide higher resolution measurements of cloud boundaries than relative humidity measurements alone.

Summertime stratospheric processes at northern mid-latitudes: comparisons between MANTRA balloon measurements and the Canadian Middle Atmosphere Model

In this paper we report on a study conducted using the Middle Atmospheric Nitrogen TRend Assessment (MANTRA) balloon measurements of stratospheric constituents and temperature and the Canadian Middle Atmosphere Model (CMAM). Three different kinds of data are used to assess the inter-consistency of the combined dataset: single profiles of long-lived species from MANTRA 1998, sparse climatologies from the ozonesonde measurements during the four MANTRA campaigns and from HALOE satellite measurements, and the CMAM climatology. In doing so, we evaluate the ability of the model to reproduce the measured fields and to thereby test our ability to describe mid-latitude summertime stratospheric processes. The MANTRA campaigns were conducted at Vanscoy, Saskatchewan, Canada (52◦ N, 107◦ W)in late August and early September of 1998, 2000, 2002 and 2004. During late summer at mid-latitudes, the stratosphere is close to photochemical control, providing an ideal scenario for the study reported here. From this analysis we find that: (1) reducing the value for the vertical diffusion coefficient in CMAM to a more physically reasonable value results in the model better reproducing the measured profiles of long-lived species; (2) the existence of compact correlations among the constituents, as expected from independent measurements in the literature and from models, confirms the self-consistency of the MANTRA measurements; and (3) the 1998 measurements show structures in the chemical species profiles that can be associated with transport, adding to the growing evidence that the summertime stratosphere can be much more disturbed than anticipated. The mechanisms responsible for such disturbances need to be understood in order to assess the representativeness of the measurements and to isolate longterm trends.

A self-calibrating electrometer for atmospheric charge measurements from a balloon platform

Charged aerosol particles and water droplets are abundant throughout the lower atmosphere, and may influence interactions between small cloud droplets. This note describes a small, disposable sensor for the measurement of charge in non-thunderstorm cloud, which is an improvement of an earlier sensor [K. A. Nicoll and R. G. Harrison, Rev. Sci. Instrum. 80, 014501 (2009)]. The sensor utilizes a self-calibrating current measurement method. It is designed for use on a free balloon platform alongside a standard meteorological radiosonde, measuring currents from 2 fA to 15 pA and is stable to within 5 fA over a temperature range of 5 °C to −60 °C. During a balloon flight with the charge sensor through a stratocumulus cloud, charge layers up to 40 pC m−3 were detected on the cloud edges.

Note: Active optical detection of cloud from a balloon platform

A disposable backscatter instrument is described for optical detection of cloud in the atmosphere from a balloon-carried platform. It uses an ultra-bright light emitting diode (LED) illumination source with a photodiode detector. Scattering of the LED light by cloud droplets generates a small optical signal which is separated from background light fluctuations using a lock-in technique. The signal to noise obtained permits cloud detection using the scattered LED light, even in daytime. The response is interpreted in terms of the equivalent visual range within the cloud. The device is lightweight (150 g) and low power (∼30 mA), for use alongside a conventional meteorological radiosonde.

Note: A balloon-borne accelerometer technique for measuring atmospheric turbulence

A weather balloon and its suspended instrument package behave like a pendulum with a moving pivot. This dynamical system is exploited here for the detection of atmospheric turbulence. By adding an accelerometer to the instrument package, the size of the swings induced by atmospheric turbulence can be measured. In test flights, strong turbulence has induced accelerations greater than 5g, where g = 9.81 m s−2. Calibration of the accelerometer data with a vertically orientated lidar has allowed eddy dissipation rate values of between 10−3 and 10−2 m2 s−3 to be derived from the accelerometer data. The novel use of a whole weather balloon and its adapted instrument package can be used as a new instrument to make standardized in situ measurements of turbulence.

Coordinated weather balloon solar radiation measurements during a solar eclipse

Solar eclipses provide a rapidly changing solar radiation environment. These changes can be studied using simple photodiode sensors, if the radiation reaching the sensors is unaffected by cloud.Transporting the sensors aloft using standard meteorological instrument packages modified to carry extra sensors, provides one promising but hitherto unexploited possibility for making solar eclipse radiation measurements. For the 20th March 2015 solar eclipse, a coordinated campaign of balloon-carried solar radiation measurements was undertaken from Reading (51.44N, 0.94W), Lerwick (60.15N, 1.13W) and Reykjavik (64.13N, 21.90W), straddling the path of the eclipse.The balloons reached sufficient altitude at the eclipse time for eclipse-induced variations in solar radiation and solar limb darkening to be measured above cloud. Because the sensor platforms were free to swing, techniques have been evaluated to correct the measurements for their changing orientation. In the swing-averaged technique, the mean value across a set of swings was used to approximate the radiation falling on a horizontal surface; in the swing-maximum technique, the direct beam was estimated by assuming the sensing surface becomes normal to the solar beam direction at a maximum swing. Both approaches, essentially independent,give values that agree with theoretical expectations for the eclipse-induced radiation changes.

An investigation of yarn snarling and balloon flutter instabilities in ring spinning

This article reports theoretical and experimental investigation on yarn snarling and balloon fluttering in ring spinning. Yarn snarling and balloon fluttering affect yarn breakage in ring spinning. The theoretical model has incorporated the tangential component of air drag on a ballooning yarn, which was ignored in previous models. The results show that yarn snarling happens in the balloon when the ratio of yarn length in the balloon to balloon height is greater than a specific value that depends on the yarn type and count. Yarn tension experiences an obvious change before and after yarn snarling. The balloon flutter appears between normal balloons while the balloon loops are changing. Fluttering balloon shapes that oscillate periodically between two and three loop configurations as yarn tension varies periodically have also been observed experimentally.

Modelling yarn balloon motion in ring spinning

Air-drag on a ballooning yarn and balloon shape affect the yarn tension and ends-down (yarn breakage), which in turn affects energy consumption and yarn productivity in ring spinning. In this article, a mathematical model of yarn ballooning motion in ring spinning is established. The model can be used to generate balloon shape and predict tension in the ballooning yarn under given spinning conditions. Yarn tension was measured using a computer data acquisition system and the balloon shapes were captured using a digital camera with video capability during the experiments using cotton and wool yarns at various balloon-heights and with varying yarn-length in the balloon. The air-drag coefficients on ballooning cotton and wool yarns in ring spinning were estimated by making a “best fit” between the theoretical and experimental turning points. The theoretical results were verified with experimental data. The effects of air-drag and balloon shape on yarn tension are discussed.

Examining the effects of balloon control ring on ring spinning

The ring spinning process has been used to produce fine and high quality staple fibre yarns. The stability of the rotating yarn loop (i.e. balloon) between the yarn-guide and the traveller-ring is crucial to the success and economics of this process. Balloon control rings are used to contain the yarn-loop, by reducing the yarn tension and decreasing the balloon flutter instability. Flutter instability here refers to the uncontrolled changes in a ballooning yarn under dynamic forces, including the air drag. Due to the significant variation in the length and radius of the balloon during the bobbin filling process, the optimal location for the balloon control ring is not easily determined. In order to address this difficulty, this study investigates the variation in the radius of a free balloon and examines the effect of balloon control rings of various diameters at different locations on yarn tension and balloon flutter stability. The results indicate that the maximum radius of a free balloon and its corresponding position depend not only on the yarn-length to balloon-height ratio, but also on yarn type and count. A control ring of suitable radius and position can significantly reduce yarn tension and decrease flutter instability of free single-loop balloons. While the balloon control rings are usually fixed to, and move in sinc with, the ring frame, results reported in this study suggest that theoretically, a balloon control ring that always remains approximately half way between the yarn-guide and the ring rail during spinning can lead to significant reduction in yarn tension.

Improving wool/polyester yarn quality by transposal spinning with movable balloon control ring

To improve yarn quality in ring spinning frame, this paper examines transposal spinning with the movable balloon control ring. The left-transposal spinning and the right-transposal spinning were experimented to spin two yarns; after installing the movable balloon control ring, the two methods were respectively used to spin two other yarns again. All the experiments were on the same ring frame and the raw material was wool/polyester blend roving with a ration of 30/70. The main quality indexes of the four yarns were tested and analyzed, including hairiness, tensile property, evenness and usual faults. The results show that the yarn spun by the left-transposal spinning has a better quality than the right-transposal spinning, and after adding the movable balloon control ring, the improvement of yarn hairiness strength and evenness, as well usual faults, is very obvious. So, in the advantage of transposal spinning, the method of installing the movable balloon control ring can improve some deteriorative problems and make yarn quality better. In addition, the method gives new insight into energy efficiency. The research in this field in on the way and the result is in accord with the Low-carbon Economy.

Balloon cell melanoma: a case report with polarized and non-polarized dermatoscopy and dermatopathology

Balloon cell melanoma is a rare melanoma subtype, with only one previous case with dermatoscopy published. It is often non-pigmented, leading to diagnostic difficulty, and there is a tendency for lesions to be thick at diagnosis. We report a case of balloon cell melanoma on the forearm of a 61-year-old man with both polarized and non-polarized dermatoscopy and dermatopathology. It presented as a firm pale nodule with focal eccentric pigmentation. The clinical images evoke a differential diagnosis of dermatofibroma, dermal nevus, Spitz nevus and basal cell carcinoma as well as melanoma. This melanoma was partially pigmented due to a small, pigmented superficial spreading component on the edge of the non-pigmented balloon cell nodule, prompting further evaluation. In retrospect there was the clue to malignancy of polarizing-specific white lines (chrysalis structures) and polymorphous vessels, including a pattern of dot vessels. The reticular lines exclude basal cell carcinoma, polarizing-specific white lines are inconsistent with the diagnosis of dermal nevus and their eccentric location is inconsistent with both Spitz nevus and dermatofibroma. Excision biopsy was performed, revealing a superficial spreading melanoma with two distinct invasive components, one of atypical non-mature epithelioid cells and the other an amelanotic nodular component, comprising more than 50% of the lesion, characterized by markedly distended epithelioid melanocytes showing pseudo-xanthomatous cytoplasmic balloon cell morphology. A diagnosis of balloon cell melanoma, Breslow thickness 1.9 mm, mitotic rate 3 per square millimeter was rendered. Wide local excision was performed, as was sentinel lymph node biopsy, which was negative.

Use of gastric balloon manometry for estimation of intra-abdominal pressure in horses

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