Observations of the Boundary Layer near Tornadoes and in Supercells Using a Mobile, Collocated, Pulsed Doppler Lidar and Radar

2014 ◽  
Vol 31 (2) ◽  
pp. 302-325 ◽  
Author(s):  
Howard B. Bluestein ◽  
Jana B. Houser ◽  
Michael M. French ◽  
Jeffrey C. Snyder ◽  
George D. Emmitt ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Spatial Resolution ◽  
Phased Array ◽  
High Spatial Resolution ◽  
Vertical Shear ◽  
Doppler Velocity ◽  
Doppler Lidar ◽  
Pulsed Doppler ◽  
Ground Clutter ◽  
X Band

Abstract During the Second Verification of the Origins of Rotation in Tornadoes Experiment (VORTEX2), in the spring of 2010, a mobile and pulsed Doppler lidar system [the Truck-Mounted Wind Observing Lidar Facility (TWOLF)] mounted on a truck along with a mobile, phased-array, X-band Doppler radar system [Mobile Weather Radar–2005 X-band, phased array (MWR-05XP)] was used to complement Doppler velocity coverage in clear air near the radar–lidar facility and to provide high-spatial-resolution vertical cross sections of the Doppler wind field in the clear-air boundary layer near and in supercells. It is thought that the magnitude and direction of vertical shear and possibly the orientation and spacing of rolls in the boundary layer have significant effects on both supercell and tornado behavior; MWR-05XP and TWOLF can provide data that can be used to measure vertical shear and detect rolls. However, there are very few detailed, time-dependent and spatially varying observations throughout the depth of the boundary layer of supercells and tornadoes. This paper discusses lidar and radar data collected in or near six supercells. Features seen by the lidar included gust fronts, horizontal convective rolls, and small-scale vortices. The lidar proved useful at detecting high-spatial-resolution, clear-air returns at close range, where the radar was incapable of doing so, thus providing a more complete picture of the boundary layer environment ahead of supercells. The lidar was especially useful in areas where there was ground-clutter contamination. When there was precipitation and probably insects, and beyond the range of the lidar, where there was no ground-clutter contamination, the radar was the more useful instrument. Suggestions are made for improving the system and its use in studying the tornado boundary layer.

scholarly journals The next generation airborne polarimetric Doppler weather radar

2014 ◽  
Vol 3 (2) ◽  
pp. 111-126 ◽  
Author(s):  
J. Vivekanandan ◽  
W.-C. Lee ◽  
E. Loew ◽  
J. L. Salazar ◽  
V. Grubišić ◽  
...  
Keyword(s):  
Spatial Resolution ◽  
Phased Array ◽  
Doppler Velocity ◽  
Airborne Radar ◽  
Dual Polarization ◽  
Polarization Measurements ◽  
Phased Array Radar ◽  
X Band ◽  
Temporal And Spatial ◽  
Airborne Phased Array Radar

Abstract. Results from airborne field deployments emphasized the need to obtain concurrently high temporal and spatial resolution measurements of 3-D winds and microphysics. A phased array radar on an airborne platform using dual-polarization antenna has the potential for retrieving high-resolution, collocated 3-D winds and microphysical measurements. Recently, ground-based phased array radar (PAR) has demonstrated the high time-resolution estimation of accurate Doppler velocity and reflectivity of precipitation and clouds when compared to mechanically scanning radar. PAR uses the electronic scanning (e-scan) to rapidly collect radar measurements. Since an airborne radar has a limited amount of time to collect measurements over a specified sample volume, the e-scan will significantly enhance temporal and spatial resolution of airborne radar observations. At present, airborne weather radars use mechanical scans, and they are not designed for collecting dual-polarization measurements to remotely estimate microphysics. This paper presents a possible configuration of a novel airborne phased array radar (APAR) to be installed on an aircraft for retrieving improved dynamical and microphysical scientific products. The proposed APAR would replace the aging, X-band Electra Doppler radar (ELDORA). The ELDORA X-band radar's penetration into precipitation is limited by attenuation. Since attenuation at C-band is lower than at X-band, the design specification of a C-band airborne phased array radar (APAR) and its measurement accuracies are presented. Preliminary design specifications suggest the proposed APAR will meet or exceed ELDORA's current sensitivity, spatial resolution and Doppler measurement accuracies of ELDORA and it will also acquire dual-polarization measurements.

scholarly journals The next generation airborne polarimetric Doppler weather radar

2014 ◽  
Vol 4 (1) ◽  
pp. 1-42 ◽  
Author(s):  
J. Vivekanandan ◽  
W.-C. Lee ◽  
E. Loew ◽  
J. L. Salazar ◽  
V. Grubišić ◽  
...  
Keyword(s):  
Spatial Resolution ◽  
Phased Array ◽  
Doppler Velocity ◽  
Airborne Radar ◽  
High Time Resolution ◽  
Dual Polarization ◽  
Phased Array Radar ◽  
X Band ◽  
Temporal And Spatial ◽  
Airborne Phased Array Radar

Abstract. Results from airborne field deployments emphasized the need to obtain concurrently high temporal and spatial resolution measurements of 3-D winds and microphysics. A phased array radar on an airborne platform using dual-polarization antenna has the potential for retrieving high resolution, collocated 3-D winds and microphysical measurements. Recently, ground-based phased array radar (PAR) demonstrated the high time resolution estimation of accurate Doppler velocity and reflectivity of precipitation and clouds when compared to mechanically scanning radar. PAR uses the electronic scanning (e-scan) to rapidly collect radar measurements. Since an airborne radar has a limited amount of time to collect measurements over a specified sample volume, the e-scan will significantly enhance temporal and spatial resolution of airborne radar observations. At present, airborne weather radars use mechanical scan, and they are not designed for collecting dual-polarization measurements to remotely estimate microphysics. This paper presents a possible configuration of a novel Airborne Phased Array Radar (APAR) to be installed on an aircraft for retrieving improved dynamical and microphysical scientific products. The proposed APAR would replace the aging, X-band Electra Doppler radar (ELDORA). The ELDORA X-band radar's penetration into precipitation is limited by attenuation. Since attenuation at C-band is lower than at X-band, the design specification of a C-band airborne phased array radar (APAR) and its measurement accuracies are presented.

scholarly journals 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

2010 ◽  
Vol 27 (10) ◽  
pp. 1652-1664 ◽  
Author(s):  
Ewan J. O’Connor ◽  
Anthony J. Illingworth ◽  
Ian M. Brooks ◽  
Christopher D. Westbrook ◽  
Robin J. Hogan ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Convective Boundary Layer ◽  
Sonic Anemometer ◽  
Horizontal Wind ◽  
Inertial Subrange ◽  
Doppler Velocity ◽  
Doppler Lidar ◽  
Convective Boundary ◽  
Dissipation Rates

Abstract 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.

scholarly journals Rapid Variations in Intergranular Space

1993 ◽  
Vol 141 ◽  
pp. 222-224 ◽  
Author(s):  
A. Nesis ◽  
A. Hanslmeier ◽  
R. Hammer ◽  
R. Komm ◽  
W. Mattig ◽  
...  
Keyword(s):  
Line Width ◽  
Spatial Resolution ◽  
High Spatial Resolution ◽  
Doppler Velocity ◽  
Continuum Intensity ◽  
Velocity Gradients ◽  
The Continuum ◽  
Intergranular Space

AbstractSpectrograms of high spatial resolution taken every 15s reveal rapid variations of the continuum intensity and line width. Variations of the latter seem to be related to Doppler velocity gradients.

Stress Mapping Below Flip-Chip Bumps With High Spatial Resolution Using Piezoresistive CMOS Sensors

2011 ◽  
Author(s):  
Benjamin Lemke ◽  
Oliver Paul ◽  
Shankar Ganapathysubramanian ◽  
Patrick Nardi ◽  
Rajashree Baskaran
Keyword(s):  
Spatial Resolution ◽  
Plane Stress ◽  
Flip Chip ◽  
High Spatial Resolution ◽  
Electroless Nickel ◽  
Vertical Shear ◽  
Shear Stresses ◽  
Stress Distributions ◽  
Stress Sensors ◽  
Applied Forces

This paper presents a CMOS stress sensor chip including arrays of piezoresistive sensor elements with high spatial resolution sensitive to the in-plane stress components σxx – σyy and σxy, to the out-of-plane stress σxz and σyz, and to the normal stress sum σΣ = (σxx + σyy)/2 − σzz. For the first time, an application of novel vertical stress sensors is presented, measuring the mechanical stress distributions below electroless nickel (eNi) bumps subject to lateral shear forces and vertical compression. All measured stress values are linearly proportional to the applied forces. The vertical shear stress sensors resolve residual vertical shear stresses of up to 51 MPa in the shear experiments. An adjustable numerical model is established assuming two different Young’s moduli of silicon nitride (SiN) emulating the adhesion between the SiN and eNi. Qualitative agreement of the in-plane stress distributions between experiment and numerical simulation is found in the shear and compression experiments, while good correlation for σΣ is found only for temperature uncompensated stress values in the compression test. The modeling of the absolute values shows differences to the experimental data of about ±30%.

scholarly journals Improving GNSS-R Sea Surface Altimetry Precision Based on the Novel Dual Circularly Polarized Phased Array Antenna Model

2021 ◽  
Vol 13 (15) ◽  
pp. 2974
Author(s):  
Zhen Cui ◽  
Wei Zheng ◽  
Fan Wu ◽  
Xiaoping Li ◽  
Cheng Zhu ◽  
...  
Keyword(s):  
High Precision ◽  
Spatial Resolution ◽  
Measurement Accuracy ◽  
Phased Array ◽  
High Spatial Resolution ◽  
Beam Width ◽  
Sea Surface ◽  
Antenna Gain ◽  
Phased Array Antenna ◽  
Circularly Polarized

Antenna is one of the key payloads of the GNSS-R system, and the gain is an important performance parameter. The signal-to-noise ratio (SNR) of the received signal can be improved by increasing the gain of the GNSS-R antenna, therefore the measurement accuracy is improved. However, the antenna gain and its beam width, these two performance parameters, are contradictory. If the gain of the antenna is increased, its beam width will inevitably become narrower. This narrowed beam width will affect the width of the survey strip for the GNSS-R system, which cannot meet the requirement of the high-precision and high-spatial resolution spaceborne GNSS-R sea surface altimetry in the future. In this paper, a novel dual circularly polarized phased array antenna (NDCPPA) is proposed and investigated. First, the GNSS-R satellites currently operating in orbit are all cGNSS-R systems, which use the traditional element antenna (TEA) method for measurement. The antenna used in this method is with low gain, which limits the improvement of sea surface measurement accuracy. In response to this problem, this paper establishes an NDCPPA model of iGNSS-R measurement system based on the theory of coherent signal processing on the sea surface. This model uses the high-gain scanning beam to increase the gain of the iGNSS-R antenna without affecting its coverage area, thereby improving the sea surface altimetry precision. Second, in order to verify the gain improvement effect brought by adopting the NDCPPA model, an NDCPPA model verification prototype for iGNSS-R sea surface altimetry was designed and fabricated, and then measured in a microwave anechoic chamber. The measurement results show that, compared with the TEA method, the antenna gain of our proposed verification prototype is enhanced by 9.5 dB. And the measured and designed value of the gain of the verification prototype matches well. Third, based on the GPS L1 signal, the NDCPPA model is used to analyze the effect of improving the precision of sea surface altimetry. Compared with the TEA method, the proposed model can increase the altimetric precision of the nadir point from 7.27 m to 0.21 m, which effectively improves the performance of the iGNSS-R altimetry. The NDCPPA model proposed in this article can provide the theoretical method basis and the crucial technical support for the future high-precision and high-spatial-resolution GNSS-R sea surface altimetry verification satellite.

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