Velocity–Azimuth Display Analysis of Doppler Velocity for HIWRAP

2015 ◽  
Vol 54 (8) ◽  
pp. 1792-1808 ◽  
Author(s):  
Lin Tian ◽  
Gerald M. Heymsfield ◽  
Anthony C. Didlake ◽  
Stephen Guimond ◽  
Lihua Li
Keyword(s):  
Deep Convection ◽  
Doppler Velocity ◽  
Rapid Intensification ◽  
Wind Fields ◽  
Operational Forecasts ◽  
Analysis Technique ◽  
The Mean ◽  
Conical Scan ◽  
Along Track ◽  
Doppler Analysis

AbstractThe velocity–azimuth display (VAD) analysis technique established for ground-based scanning radar is applied to the NASA High-Altitude Imaging Wind and Rain Airborne Profiler (HIWRAP). The VAD technique provides a mean vertical profile of the horizontal winds for each complete conical scan of the HIWRAP radar. One advantage of this technique is that it has shown great value for data assimilation and for operational forecasts. Another advantage is that it is computationally inexpensive, which makes it suitable for real-time retrievals. The VAD analysis has been applied to the HIWRAP data collected during NASA’s Genesis and Rapid Intensification Processes (GRIP) mission. The traditional dual-Doppler analysis for deriving wind fields in the nadir plane is also presented and is compared with the VAD analysis. The results show that the along-track winds from the VAD technique and dual-Doppler analysis agree in general. The VAD horizontal winds capture the mean vortex structure of two tropical cyclones, and they are in general agreement with winds from nearby dropsondes. Several assumptions are made for the VAD technique. These assumptions include a stationary platform for each HIWRAP scan and constant vertical velocity of the hydrometeors along each complete scan. As a result, the VAD technique can produce appreciable errors in regions of deep convection such as the eyewall, whereas in stratiform regions the retrieval errors are minimal. Despite these errors, the VAD technique can still adequately capture the larger-scale structure of the hurricane vortex given a sufficient number of flight passes over the storm.

Reducing Errors in Velocity–Azimuth Display (VAD) Wind and Deformation Retrievals from Airborne Doppler Radars in Convective Environments

2020 ◽  
Vol 37 (12) ◽  
pp. 2251-2266
Author(s):  
Charles N. Helms ◽  
Matthew L. Walker McLinden ◽  
Gerald M. Heymsfield ◽  
Stephen R. Guimond
Keyword(s):  
Wind Field ◽  
Doppler Radar ◽  
Weighting Function ◽  
Deep Convection ◽  
Absolute Error ◽  
Doppler Velocity ◽  
Wind Fields ◽  
Time Data ◽  
Single Antenna ◽  
Median Absolute Error

AbstractThe present study describes methods to reduce the uncertainty of velocity–azimuth display (VAD) wind and deformation retrievals from downward-pointing, conically scanning, airborne Doppler radars. These retrievals have important applications in data assimilation and real-time data processing. Several error sources for VAD retrievals are considered here, including violations to the underlying wind field assumptions, Doppler velocity noise, data gaps, temporal variability, and the spatial weighting function of the VAD retrieval. Specific to airborne VAD retrievals, we also consider errors produced due to the radar scans occurring while the instrument platform is in motion. While VAD retrievals are typically performed using data from a single antenna revolution, other strategies for selecting data can be used to reduce retrieval errors. Four such data selection strategies for airborne VAD retrievals are evaluated here with respect to their effects on the errors. These methods are evaluated using the second hurricane nature run numerical simulation, analytic wind fields, and observed Doppler radar radial velocities. The proposed methods are shown to reduce the median absolute error of the VAD wind retrievals, especially in the vicinity of deep convection embedded in stratiform precipitation. The median absolute error due to wind field assumption violations for the along-track and for the across-track wind is reduced from 0.36 to 0.08 m s−1 and from 0.35 to 0.24 m s−1, respectively. Although the study focuses on Doppler radars, the results are equally applicable to conically scanning Doppler lidars as well.

scholarly journals Generalized VTD Retrieval of Atmospheric Vortex Kinematic Structure. Part I: Formulation and Error Analysis

2008 ◽  
Vol 136 (3) ◽  
pp. 995-1012 ◽  
Author(s):  
Ben Jong-Dao Jou ◽  
Wen-Chau Lee ◽  
Su-Ping Liu ◽  
Yu-Cheng Kao
Keyword(s):  
Doppler Radar ◽  
Geometric Distortion ◽  
Doppler Velocity ◽  
New Paradigm ◽  
Wind Fields ◽  
Radar Signature ◽  
Tangential Wind ◽  
The Mean ◽  
Domain 3 ◽  
Atmospheric Vortices

Abstract The primary circulation of atmospheric vortices, such as tropical cyclones and tornadoes, can be estimated from single-Doppler radar observations using the ground-based velocity track display (GBVTD) algorithm. The GBVTD algorithm has limitations in the following four areas: 1) distortion in the retrieved asymmetric wind fields, 2) a limited analysis domain, 3) the inability to resolve the cross-beam component of the mean wind, and 4) the inability to separate the asymmetric tangential and radial winds. This paper presents the generalized velocity track display (GVTD) algorithm, which eliminates the first two limitations inherent in the GBVTD technique and demonstrates the possibility of subjectively estimating the mean wind vector when its signature is visible beyond the influence of the vortex circulation. In this new paradigm, the GVTD algorithm fits the atmospheric vortex circulation to a new variable VdD/RT in a linear azimuth angle (θ′), rather than the Doppler velocity Vd in a nonlinear angle (ψ), which is used in GBVTD. Key vortex kinematic structures (e.g., mean wind, axisymmetric tangential wind, etc.) in the VdD/RT space simplify the interpretation of the radar signature and eliminate the geometric distortion inherent in the Vd display. This is a significant improvement in diagnosing vortex structures in both operations and research. The advantages of using VdD/RT are illustrated using analytical atmospheric vortices, and the properties are compared with GBVTD. The characteristics of the VdD/RT display of Typhoon Gladys (1994) can be approximated by a constant mean wind plus an axisymmetric vortex.

scholarly journals Mesoscale Features Associated with Tropical Cyclone Formations in the Western North Pacific

2008 ◽  
Vol 136 (6) ◽  
pp. 2006-2022 ◽  
Author(s):  
Cheng-Shang Lee ◽  
Kevin K. W. Cheung ◽  
Jenny S. N. Hui ◽  
Russell L. Elsberry
Keyword(s):  
Tropical Cyclone ◽  
North Pacific ◽  
Western North Pacific ◽  
Large Scale ◽  
North Pacific Ocean ◽  
Deep Convection ◽  
Mesoscale Convective System ◽  
Convective System ◽  
Synoptic Patterns ◽  
The Mean

Abstract The mesoscale features of 124 tropical cyclone formations in the western North Pacific Ocean during 1999–2004 are investigated through large-scale analyses, satellite infrared brightness temperature (TB), and Quick Scatterometer (QuikSCAT) oceanic wind data. Based on low-level wind flow and surge direction, the formation cases are classified into six synoptic patterns: easterly wave (EW), northeasterly flow (NE), coexistence of northeasterly and southwesterly flow (NE–SW), southwesterly flow (SW), monsoon confluence (MC), and monsoon shear (MS). Then the general convection characteristics and mesoscale convective system (MCS) activities associated with these formation cases are studied under this classification scheme. Convection processes in the EW cases are distinguished from the monsoon-related formations in that the convection is less deep and closer to the formation center. Five characteristic temporal evolutions of the deep convection are identified: (i) single convection event, (ii) two convection events, (iii) three convection events, (iv) gradual decrease in TB, and (v) fluctuating TB, or a slight increase in TB before formation. Although no dominant temporal evolution differentiates cases in the six synoptic patterns, evolutions ii and iii seem to be the common routes taken by the monsoon-related formations. The overall percentage of cases with MCS activity at multiple times is 63%, and in 35% of cases more than one MCS coexisted. Most of the MC and MS cases develop multiple MCSs that lead to several episodes of deep convection. These two patterns have the highest percentage of coexisting MCSs such that potential interaction between these systems may play a role in the formation process. The MCSs in the monsoon-related formations are distributed around the center, except in the NE–SW cases in which clustering of MCSs is found about 100–200 km east of the center during the 12 h before formation. On average only one MCS occurs during an EW formation, whereas the mean value is around two for the other monsoon-related patterns. Both the mean lifetime and time of first appearance of MCS in EW are much shorter than those developed in other synoptic patterns, which indicates that the overall formation evolution in the EW case is faster. Moreover, this MCS is most likely to be found within 100 km east of the center 12 h before formation. The implications of these results to internal mechanisms of tropical cyclone formation are discussed in light of other recent mesoscale studies.

scholarly journals On interpreting studies of tracer transport by deep cumulus convection and its effects on atmospheric chemistry

2008 ◽  
Vol 8 (20) ◽  
pp. 6037-6050 ◽  
Author(s):  
M. G. Lawrence ◽  
M. Salzmann
Keyword(s):  
Atmospheric Chemistry ◽  
Large Scale ◽  
Deep Convection ◽  
Convective Transport ◽  
Advective Transport ◽  
Tracer Transport ◽  
Transport Models ◽  
Mass Fluxes ◽  
Split Treatment ◽  
The Mean

Abstract. Global chemistry-transport models (CTMs) and chemistry-GCMs (CGCMs) generally simulate vertical tracer transport by deep convection separately from the advective transport by the mean winds, even though a component of the mean transport, for instance in the Hadley and Walker cells, occurs in deep convective updrafts. This split treatment of vertical transport has various implications for CTM simulations. In particular, it has led to a misinterpretation of several sensitivity simulations in previous studies in which the parameterized convective transport of one or more tracers is neglected. We describe this issue in terms of simulated fluxes and fractions of these fluxes representing various physical and non-physical processes. We then show that there is a significant overlap between the convective and large-scale mean advective vertical air mass fluxes in the CTM MATCH, and discuss the implications which this has for interpreting previous and future sensitivity simulations, as well as briefly noting other related implications such as numerical diffusion.

scholarly journals Verifying Operational Forecasts of Land–Sea-Breeze and Boundary Layer Mixing Processes

2020 ◽  
Vol 35 (4) ◽  
pp. 1427-1445
Author(s):  
Ewan Short
Keyword(s):  
Boundary Layer ◽  
Diurnal Cycle ◽  
Spatial Scales ◽  
Sea Breeze ◽  
Absolute Error ◽  
Wind Fields ◽  
Mixing Processes ◽  
Relative Contribution ◽  
The Mean ◽  
Diurnal Wind

AbstractForecasters working for Australia’s Bureau of Meteorology (BoM) produce a 7-day forecast in two key steps: first they choose a model guidance dataset to base the forecast on, and then they use graphical software to manually edit these data. Two types of edits are commonly made to the wind fields that aim to improve how the influences of boundary layer mixing and land–sea-breeze processes are represented in the forecast. In this study the diurnally varying component of the BoM’s official wind forecast is compared with that of station observations and unedited model guidance datasets. Coastal locations across Australia over June, July, and August 2018 are considered, with data aggregated over three spatial scales. The edited forecast produces a lower mean absolute error than model guidance at the coarsest spatial scale (over 50 000 km2), and achieves lower seasonal biases over all spatial scales. However, the edited forecast only reduces errors or biases at particular times and locations, and rarely produces lower errors or biases than all model guidance products simultaneously. To better understand physical reasons for biases in the mean diurnal wind cycles, modified ellipses are fitted to the seasonally averaged diurnal wind temporal hodographs. Biases in the official forecast diurnal cycle vary with location for multiple reasons, including biases in the directions that sea breezes approach coastlines, amplitude biases, and disagreement in the relative contribution of sea-breeze and boundary layer mixing processes to the mean diurnal cycle.

scholarly journals ANALISIS FAKTOR-FAKTOR YANG MEMPENGARUHI IMPLEMENTASI ANGGARAN BERBASIS KINERJA

2019 ◽  
Vol 3 (3) ◽  
Author(s):  
Kaillin Lalli Randa ◽  
Ida Ayu Purba Riani ◽  
Balthazar Kreuta
Keyword(s):  
Data Analysis ◽  
Organizational Commitment ◽  
Positive Influence ◽  
Least Square ◽  
Ordinary Least Square ◽  
Average Value ◽  
Data Analysis Technique ◽  
Analysis Technique ◽  
Partial Analysis ◽  
The Mean

The purpose of the study was to analyze what factors influence the Performance Based Budget by using a sample of 87 respondents working at the Secretariat of the Papuan People's Representative Council. While the data analysis technique used is the Ordinary least square (OLS) technique. The results of the study are indicated by the calculation of the mean (mean) of 32 item questions and 87 respondents and the result is 137.31. If the value is compared to the criteria that the author has set, then the average value is included in the "Very Good" category. While the results of the partial analysis of organizational commitment (X1) have a significant and positive influence on the performance-based budget of 1,261. Keywords: Performance Based Budget

scholarly journals Wind speed variability between 10 and 116 m height from the regional reanalysis COSMO-REA6 compared to wind mast measurements over Northern Germany and the Netherlands

2016 ◽  
Vol 13 ◽  
pp. 151-161 ◽  
Author(s):  
Michael Borsche ◽  
Andrea K. Kaiser-Weiss ◽  
Frank Kaspar
Keyword(s):  
Wind Speed ◽  
The Netherlands ◽  
Diurnal Cycle ◽  
Correlation Coefficients ◽  
Wind Fields ◽  
Northern Germany ◽  
Significance Level ◽  
The North ◽  
The Mean ◽  
Regional Reanalysis

Abstract. Hourly and monthly mean wind speed and wind speed variability from the regional reanalysis COSMO-REA6 is analysed in the range of 10 to 116 m height above ground. Comparisons with independent wind mast measurements performed between 2001 and 2010 over Northern Germany over land (Lindenberg), the North Sea (FINO platforms), and The Netherlands (Cabauw) show that the COSMO-REA6 wind fields are realistic and at least as close to the measurements as the global atmospheric reanalyses (ERA20C and ERA-Interim) on the monthly scale. The median wind profiles of the reanalyses were found to be consistent with the observed ones. The mean annual cycles of variability are generally reproduced from 10 up to 116 m in the investigated reanalyses. The mean diurnal cycle is represented qualitatively near the ground by the reanalyses. At 100 m height, there is little diurnal cycle left in the global and regional reanalyses, though a diurnal cycle is still present in the measurements over land. Correlation coefficients between monthly means of the observations and the reanalyses range between 0.92 at 10 m and 0.99 at 116 m, with a slightly higher correlation of the regional reanalyses at Lindenberg at 10 m height which is significant only at a lower than 95 % significance level. Correlations of daily means tend to be higher for the regional reanalysis COSMO-REA6. Increasing temporal resolution further, reduces this advantage of the regional reanalysis. At around 100 m, ERA-Interim yields a higher correlation at Lindenberg and Cabauw, whereas COSMO-REA6 yields a higher correlation at FINO1 and FINO2.

scholarly journals High-Resolution Ensemble HFV3 Forecasts of Hurricane Michael (2018): Rapid Intensification in Shear

2020 ◽  
Vol 148 (5) ◽  
pp. 2009-2032 ◽  
Author(s):  
Andrew T. Hazelton ◽  
Xuejin Zhang ◽  
Sundararaman Gopalakrishnan ◽  
William Ramstrom ◽  
Frank Marks ◽  
...  
Keyword(s):  
Tropical Cyclones ◽  
Early Stage ◽  
Vertical Wind Shear ◽  
Vertical Shear ◽  
Rapid Intensification ◽  
Forecast System ◽  
The Mean ◽  
Cubed Sphere ◽  
Environmental Prediction ◽  
The Relationship

Abstract The FV3GFS is the current operational Global Forecast System (GFS) at the National Centers for Environmental Prediction (NCEP), which combines a finite-volume cubed sphere dynamical core (FV3) and GFS physics. In this study, FV3GFS is used to gain understanding of rapid intensification (RI) of tropical cyclones (TCs) in shear. The analysis demonstrates the importance of TC structure in a complex system like Hurricane Michael, which intensified to a category 5 hurricane over the Gulf of Mexico despite over 20 kt (10 m s−1) of vertical wind shear. Michael’s RI is examined using a global-nest FV3GFS ensemble with the nest at 3-km resolution. The ensemble shows a range of peak intensities from 77 to 159 kt (40–82 m s−1). Precipitation symmetry, vortex tilt, moisture, and other aspects of Michael’s evolution are compared through composites of stronger and weaker members. The 850–200-hPa vertical shear is 22 kt (11 m s−1) in the mean of both strong and weak members during the early stage. Tilt and moisture are two distinguishing factors between strong and weak members. The relationship between vortex tilt and humidification is complex, and other studies have shown both are important for sheared intensification. Here, it is shown that tilt reduction leads to upshear humidification and is thus a driving factor for intensification. A stronger initial vortex and early evolution of the vortex also appear to be the key to members that are able to resist the sheared environment.

scholarly journals Operational Multiple-Doppler Wind Retrieval Inferred from Long-Range Radial Velocity Measurements

2008 ◽  
Vol 47 (11) ◽  
pp. 2929-2945 ◽  
Author(s):  
Olivier Bousquet ◽  
Pierre Tabary ◽  
Jacques Parent du Châtelet
Keyword(s):  
Radial Velocity ◽  
Doppler Velocity ◽  
Velocity Measurements ◽  
Wind Fields ◽  
Pulse Rise Time ◽  
Wind Retrieval ◽  
Radar Network ◽  
Precipitation Regimes ◽  
Operational Networks ◽  
Scanning Strategies

Abstract The recent deployment of an innovative triple pulse rise time (PRT) scheme within the French operational radar network allows for the simultaneous collection of reflectivity and radial velocity measurements up to a range of 250 km with no ambiguity. This achievement brings new perspectives in terms of operational exploitation of Doppler measurements including the capability to consistently perform multiple-Doppler wind synthesis in a fully operational framework. Using real and simulated Doppler observations, the authors show that the 3D wind fields retrieved in that framework can definitely be relied upon to achieve a consistent and detailed mapping of the airflow structure in various precipitation regimes despite radar baselines averaging ∼180 km and very limited scanning strategies. This achievement could be easily transposed to other operational networks and represents a remarkable opportunity to add further value to operational Doppler velocity measurements.

The mean doppler velocity derived by an advanced ionospheric sounder — dynasonde

2001 ◽  
Vol 27 (6-7) ◽  
pp. 1121-1126 ◽  
Author(s):  
C.C. Lee ◽  
J.Y. Liu ◽  
C.J. Pan
Keyword(s):  
Doppler Velocity ◽  
The Mean
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