scholarly journals Impact of assimilating airborne Doppler radar velocity data using the ARPS 3DVAR on the analysis and prediction of Hurricane Ike (2008)

2012 ◽  
Vol 117 (D18) ◽  
pp. n/a-n/a ◽  
Author(s):  
Ningzhu Du ◽  
Ming Xue ◽  
Kun Zhao ◽  
Jinzhong Min
Keyword(s):  
Doppler Radar ◽  
Velocity Data ◽  
Hurricane Ike ◽  
Radar Velocity ◽  
Airborne Doppler Radar

scholarly journals An Automated 2D Multipass Doppler Radar Velocity Dealiasing Scheme

2006 ◽  
Vol 23 (9) ◽  
pp. 1239-1248 ◽  
Author(s):  
Jian Zhang ◽  
Shunxin Wang
Keyword(s):  
Doppler Radar ◽  
Radar Data ◽  
Velocity Fields ◽  
Velocity Data ◽  
Computationally Efficient ◽  
High Confidence ◽  
Reference Velocity ◽  
External Reference ◽  
Wind Velocities ◽  
Radar Velocity

Abstract An automated 2D multipass velocity dealiasing scheme has been developed to correct velocity fields when wind velocities are very large compared to the Nyquist velocity of the weather Doppler radars. The new velocity dealiasing algorithm is based on the horizontal continuity of velocity fields. The algorithm first determines a set of reference radials and gates by finding the weakest wind region. Then from these reference radials and gates, the scheme checks continuities among adjacent gates and corrects for the velocity values with large differences that are close to 2 × (Nyquist velocity). Multiple passes of unfolding are performed and velocities identified as “folded” with low confidence in an earlier pass are not unfolded until a discontinuity is detected with high confidence at a subsequent pass. The new velocity dealiasing scheme does not need external reference velocity data as do many existing algorithms, thus making it more easily applicable. Over 1000 radar volume scans that include tornadoes, hurricanes, and typhoons are selected to test and to evaluate the new algorithm. The results show that the new algorithm is very robust and very computationally efficient. In cases with many data voids, the new algorithm shows improvements over the current WSR-88D operational velocity dealiasing scheme. The new dealiasing algorithm is a simple and stand-alone program that can be a very useful tool to various Doppler radar data users.

Mapping of Airborne Doppler Radar Data

1994 ◽  
Vol 11 (2) ◽  
pp. 572-578 ◽  
Author(s):  
Wen-Chau Lee ◽  
Peter Dodge ◽  
Frank D. Marks ◽  
Peter H. Hildebrand
Keyword(s):  
Doppler Radar ◽  
Radar Data ◽  
Doppler Radar Data ◽  
Airborne Doppler Radar

scholarly journals STARE velocity at large flow angles: is it related to the ion acoustic speed?

2006 ◽  
Vol 24 (3) ◽  
pp. 873-885 ◽  
Author(s):  
M. V. Uspensky ◽  
A. V. Koustov ◽  
S. Nozawa
Keyword(s):  
Electron Flow ◽  
Line Of Sight ◽  
Velocity Data ◽  
Ion Acoustic ◽  
E Region ◽  
Linear Fit ◽  
Radar Velocity ◽  
Large Flow ◽  
Eiscat Measurements ◽  
Acoustic Speed

Abstract. The electron drift and ion-acoustic speed in the E region inferred from EISCAT measurements are compared with concurrent STARE radar velocity data to investigate a recent hypothesis by Bahcivan et al. (2005), that the electrojet irregularity velocity at large flow angles is simply the product of the ion-acoustic speed and the cosine of an angle between the electron flow and the irregularity propagation direction. About 3000 measurements for flow angles of 50°–70° and electron drifts of 400–1500 m/s are considered. It is shown that the correlation coefficient and the slope of the best linear fit line between the predicted STARE velocity (based solely on EISCAT data and the hypothesis of Bahcivan et al. (2005)) and the measured one are both of the order of ~0.4. Velocity predictions are somewhat better if one assumes that the irregularity phase velocity is the line-of-sight component of the E×B drift scaled down by a factor ~0.6 due to off-orthogonality of irregularity propagation (nonzero effective aspect angles of STARE observations).

scholarly journals A Velocity Dealiasing Scheme Based on Minimization of Velocity Differences between Regions

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Yue Yuan ◽  
Ping Wang ◽  
Di Wang ◽  
Junzhi Shi
Keyword(s):  
Radial Velocity ◽  
Wind Shear ◽  
Doppler Radar ◽  
Heavy Precipitation ◽  
Probability Of Detection ◽  
Strong Wind ◽  
Velocity Data ◽  
Step Velocity ◽  
Noise Data ◽  
Radial Velocity Data

The velocity dealiasing is an essential work of automatic weather phenomenon identification, nowcasting, and disaster monitoring based on radial velocity data. The noise data, strong wind shear, and isolated echo region in the Doppler radar radial velocity data severely interfere with the velocity dealiasing algorithm. This paper proposes a two-step velocity dealiasing algorithm based on the minimization of velocity differences between regions to solve this problem. The first step is to correct aliased velocities by minimizing the sum of gradients in every region to eliminate abnormal velocity gradients between points. The interference of noise data and strong wind shear can be reduced by minimizing the whole gradients in a region. The second step is to dealiase velocities by the velocity differences between different isolated regions. The velocity of an unknown isolated region is determined by the velocities of all known regions. This step improves the dealiasing results of isolated regions. In this paper, 604 volume scan samples, including typhoons, squall lines, and heavy precipitation, were used to test the algorithm. The statistical results and analysis show that the proposed algorithm can dealiase the velocity field with a high probability of detection and a low false alarm rate.

scholarly journals Procedures to Improve the Accuracy of Airborne Doppler Radar Data

2002 ◽  
Vol 19 (3) ◽  
pp. 322-339 ◽  
Author(s):  
Brian L. Bosart ◽  
Wen-Chau Lee ◽  
Roger M. Wakimoto
Keyword(s):  
Doppler Radar ◽  
Radar Data ◽  
Correction Method ◽  
Fine Tuning ◽  
Earth Surface ◽  
Doppler Radar Data ◽  
Tilt Error ◽  
Corrected Data ◽  
Flight Level ◽  
Airborne Doppler Radar

Abstract The navigation correction method proposed in Testud et al. (referred to as the THL method) systematically identifies uncertainties in the aircraft Inertial Navigation System and errors in the radar-pointing angles by analyzing the radar returns from a flat and stationary earth surface. This paper extends the THL study to address 1) error characteristics on the radar display, 2) sensitivity of the dual-Doppler analyses to navigation errors, 3) fine-tuning the navigation corrections for individual flight legs, and 4) identifying navigation corrections over a flat and nonstationary earth surface (e.g., ocean). The results show that the errors in each of the parameters affect the dual-Doppler wind analyses and the first-order derivatives in different manners. The tilt error is the most difficult parameter to determine and has the greatest impact on the dual-Doppler analysis. The extended THL method can further reduce the drift, ground speed, and tilt errors in all flight legs over land by analyzing the residual velocities of the earth surface using the corrections obtained in the calibration legs. When reliable dual-Doppler winds can be deduced at flight level, the Bosart–Lee–Wakimoto method presented here can identify all eight errors by satisfying three criteria: 1) the flight-level dual-Doppler winds near the aircraft are statistically consistent with the in situ winds, 2) the flight-level dual-Doppler winds are continuous across the flight track, and 3) the surface velocities of the left (right) fore radar have the same magnitude but opposite sign as their counterparts of right (left) aft radar. This procedure is able to correct airborne Doppler radar data over the ocean and has been evaluated using datasets collected during past experiments. Consistent calibration factors are obtained in multiple legs. The dual-Doppler analyses using the corrected data are statistically superior to those using uncorrected data.

A New Airborne Doppler Radar

1962 ◽  
Vol 15 (4) ◽  
pp. 439-442
Author(s):  
Minoru Okada ◽  
Jun Tamiya
Keyword(s):  
Angular Velocity ◽  
Doppler Radar ◽  
Vertical Axis ◽  
Radar System ◽  
Low Speed ◽  
Single Beam ◽  
Depression Angle ◽  
New Type ◽  
Airborne Doppler Radar

Many airborne doppler radars in use at present work with several beams in fixed directions and a pair of beams switched in sequence. In this paper, which was presented at the convention held in Dusseldorf in May 1961 (Journal, 14, 480), a new type of doppler radar is described in which a single beam is rotated around the vertical axis with a uniform angular velocity, keeping the depression angle constant. With this type of radar, combined with certain circuits in the transmitter-receiver, the frequency tracker and the data stabilizer, it is possible to measure the velocity of positive as well as negative values (including zero); it also allows easier functioning of data-stabilization. Further, a small and lightweight radar system may be constructed in this manner. This type of doppler radar is considered to be of particular use for small, low-speed aircraft.

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