scholarly journals review of Investigation of observational error sources in multi Doppler radar vertical air motion retrievals: Impacts and possible solutions

2019 ◽  
Author(s):  
Anonymous
Keyword(s):  
Doppler Radar ◽  
Observational Error ◽  
Error Sources ◽  
Air Motion

The Value of Photoelectric Occultation Timings in Lunar Motion Studies

1971 ◽  
Vol 2 ◽  
pp. 587-588 ◽  
Author(s):  
Thomas C. Van Flandern
Keyword(s):  
The Other ◽  
The Moon ◽  
Observational Error ◽  
Additional Time ◽  
Current Application ◽  
Error Sources ◽  
Lunar Motion ◽  
Lunar Ephemeris ◽  
Motion Studies

AbstractThe two most important advantages of photoelectric timings of occultations over visual timings are accuracy and freedom from systematic error. The observational error is so small compared with uncertainties in the lunar ephemeris, star positions, limb corrections, and such, that the value of the observations will continue to increase as time goes on and the other error sources are eliminated.A recent result made possible largely by the availability of photoelectric timings over the last 20 yr is a new value for the secular acceleration of the Moon, with corresponding consequences for the Ephemeris Time scale.An important current application for simultaneous photoelectric and visual observations is the determination of ‘personal equation’ for the visual observers. Experiments so far indicate the visual observers require a minimum of 0.1 sec to detect that an event has occurred, plus additional time to react to it; hence, typical personal equations are around 0.4 sec.

Airflow and Precipitation Properties within the Stratiform Region of Tropical Storm Gabrielle during Landfall

2009 ◽  
Vol 137 (6) ◽  
pp. 1954-1971 ◽  
Author(s):  
Dong-Kyun Kim ◽  
Kevin R. Knupp ◽  
Christopher R. Williams
Keyword(s):  
Doppler Radar ◽  
Tropical Storm ◽  
Parameter Study ◽  
Melting Layer ◽  
Bright Band ◽  
Maximum Reflectivity ◽  
Stratiform Region ◽  
Raindrop Size Distribution ◽  
Air Motion ◽  
Rainfall Estimates

Abstract Kinematic and microphysical characteristics of a stratiform rainband within Tropical Storm Gabrielle during landfall on 14 September 2001 were investigated using data from a collocated 915-MHz wind profiler and scanning Doppler radar. The curved 60-km-wide rainband was relatively intense with mesoscale updrafts and downdrafts exceeding ±1 m s−1. The bright band is classified as strong, as indicated by reflectivity factors in excess of 50 dBZ and rainfall rates below the bright band peaking at 10–20 mm h−1. The melting layer microphysical processes were examined to understand the relation between brightband processes and precipitation intensity and kinematics (mesoscale downdraft in particular) below the melting layer. The profiler and Doppler radar analyses, designed to maximize vertical resolution of flows within the melting layer, disclose a striking convergence–divergence couplet through the melting layer that implies a prominent cooling-induced finescale circulation. Melting-driven cooling initiates midlevel convergence in the upper part of the melting region, while weak convergence to positive divergence is analyzed within the lower melting layer. A melting-layer parameter study indicates the significance of the level of maximum reflectivity that separates convergence above from divergence below and also reveals a mixture of aggregation and breakup of ice particles, with aggregation being dominant. In this vigorous rainband case, the presence of strong mesoscale downdrafts cannot be ignored for accurate retrievals of raindrop size distribution and precipitation parameters from the Sans Air Motion model. When downdrafts are included, retrieved rainfall estimates were much higher than those under the zero vertical air motion assumption and were slightly less than those from a power-law Z–R relation. The rainfall estimates show a positive correlation with reflectivity factor and brightband intensity (i.e., aggregation degree) but less dependence on brightband height.

scholarly journals 95-GHz Doppler radar and lidar synergy for simultaneous ice microphysics and in-cloud vertical air motion retrieval

2009 ◽  
Vol 114 (D3) ◽  
Author(s):  
Kaori Sato ◽  
Hajime Okamoto ◽  
Masayuki K. Yamamoto ◽  
Shoichiro Fukao ◽  
Hiroshi Kumagai ◽  
...  
Keyword(s):  
Doppler Radar ◽  
Motion Retrieval ◽  
Ice Microphysics ◽  
Air Motion

scholarly journals Investigation of observational error sources in multi-Doppler-radar three-dimensional variational vertical air motion retrievals

2019 ◽  
Vol 12 (3) ◽  
pp. 1999-2018 ◽  
Author(s):  
Mariko Oue ◽  
Pavlos Kollias ◽  
Alan Shapiro ◽  
Aleksandra Tatarevic ◽  
Toshihisa Matsui
Keyword(s):  
Doppler Radar ◽  
Model Simulation ◽  
Three Dimensional ◽  
Wrf Model ◽  
Sampling Time ◽  
Added Value ◽  
Limiting Factors ◽  
Convective Systems ◽  
Air Motion ◽  
Wind Retrievals

Abstract. Multi-Doppler-radar network observations have been used in different configurations over the last several decades to conduct three-dimensional wind retrievals in mesoscale convective systems. Here, the impacts of the selected radar volume coverage pattern (VCP), the sampling time for the VCP, the number of radars used, and the added value of advection correction on the retrieval of the vertical air motion in the upper part of convective clouds are examined using the Weather Research and Forecasting (WRF) model simulation, the Cloud Resolving Model Radar SIMulator (CR-SIM), and a three-dimensional variational multi-Doppler-radar retrieval technique. Comparisons between the model truth (i.e., WRF kinematic fields) and updraft properties (updraft fraction, updraft magnitude, and mass flux) retrieved from the CR-SIM-generated multi-Doppler-radar field are used to investigate these impacts. The findings are that (1) the VCP elevation strategy and sampling time have a significant effect on the retrieved updraft properties above 6 km in altitude; (2) 2 min or shorter VCPs have small impacts on the retrievals, and the errors are comparable to retrievals using a snapshot cloud field; (3) increasing the density of elevation angles in the VCP appears to be more effective to reduce the uncertainty than an addition of data from one more radar, if the VCP is performed in 2 min; and (4) the use of dense elevation angles combined with an advection correction applied to the 2 min VCPs can effectively improve the updraft retrievals, but for longer VCP sampling periods (5 min) the value of advection correction is challenging. This study highlights several limiting factors in the retrieval of upper-level vertical velocity from multi-Doppler-radar networks and suggests that the use of rapid-scan radars can substantially improve the quality of wind retrievals if conducted in a limited spatial domain.

Measurements of Air Motion in Regions of Clear Air Turbulence using High-power Doppler Radar

Nature ◽  
1972 ◽  
Vol 239 (5370) ◽  
pp. 267-269 ◽  
Author(s):  
K. A. BROWNING ◽  
J. R. STARR ◽  
A. J. WHYMAN
Keyword(s):  
High Power ◽  
Doppler Radar ◽  
Power Doppler ◽  
Air Turbulence ◽  
Air Motion

scholarly journals Investigation of observational error sources in multi Doppler radar vertical air motion retrievals: Impacts and possible solutions

2018 ◽  
Author(s):  
Mariko Oue ◽  
Pavlos Kollias ◽  
Alan Shapiro ◽  
Aleksandra Tatarevic ◽  
Toshihisa Matsui
Keyword(s):  
Doppler Radar ◽  
Three Dimensional ◽  
Sampling Time ◽  
Added Value ◽  
Limiting Factors ◽  
Convective System ◽  
Mesoscale Convective ◽  
Air Motion ◽  
Wind Retrievals ◽  
The Impact

Abstract. Multi-Doppler radar network observations have been used in different configurations over the last several decades to conduct three-dimensional wind retrievals in mesoscale convective systems. Here, the impact of the selected radar volume coverage pattern (VCP), the sampling time for the VCP, the number of radars used, and the added value of advection correction on the retrieval of the vertical air motion in the upper part of convective clouds is examined using the Weather Research and Forecasting (WRF) model simulation, the Cloud Resolving Model Radar SIMulator (CR-SIM) and a three-dimensional variational multi-Doppler radar retrieval technique. Comparisons between the model truth (i.e., WRF kinematic fields) and updraft properties (updraft fraction, updraft magnitude, and mass flux) retrieved from the CR-SIM-generated multi-Doppler radar field are used to investigate these impacts. In overall, the VCP elevation strategy and sampling time is found to have a significant effect on the retrieved updraft properties above 6 km altitude. Retrievals conducted using a 2-min or shorter VCPs show small impacts on the updraft retrievals, and the errors are comparable to retrievals using a snapshot cloud field. Increasing the density of elevations angles and/or an addition of data from one more radar can reduce this uncertainty. It is found that the VCP with dense elevation angles appears to be more effective than the addition of data from the fourth radar, if the VCP is performed in 2 minutes. The use of dense elevation angles combined with an advection correction applied to the 2-min VCPs can effectively improve the updraft retrievals. For longer VCP sampling periods (5 min) the errors are considerably larger, and the value of advection correction is challenging due to the rapid deformation of the dynamical structures in the simulated mesoscale convective system. This study highlights several limiting factors in the retrieval of upper-level vertical velocity from multi-Doppler radar networks and suggests that the use of rapid-scan radars can substantially improve the quality of wind retrievals if conducted in a limited spatial domain.

scholarly journals Climatology of High Cloud Dynamics Using Profiling ARM Doppler Radar Observations

2013 ◽  
Vol 26 (17) ◽  
pp. 6340-6359 ◽  
Author(s):  
Heike Kalesse ◽  
Pavlos Kollias
Keyword(s):  
Great Plains ◽  
Doppler Radar ◽  
Doppler Velocity ◽  
High Cloud ◽  
Cloud Properties ◽  
Atmospheric Radiation Measurement ◽  
Air Motion ◽  
Standard Deviations ◽  
Macrophysical Properties ◽  
High Clouds

Abstract Ice cloud properties are influenced by cloud-scale vertical air motion. Dynamical properties of ice clouds can be determined via Doppler measurements from ground-based, profiling cloud radars. Here, the decomposition of the Doppler velocities into reflectivity-weighted particle velocity Vt and vertical air motion w is described. The methodology is applied to high clouds observations from 35-GHz profiling millimeter wavelength radars at the Atmospheric Radiation Measurement Program (ARM) Southern Great Plains (SGP) climate research facility in Oklahoma (January 1997–December 2010) and the ARM Tropical Western Pacific (TWP) site in Manus (July 1999–December 2010). The Doppler velocity measurements are used to detect gravity waves (GW), whose correlation with high cloud macrophysical properties is investigated. Cloud turbulence is studied in the absence and presence of GW. High clouds are less turbulent when GW are observed. Probability density functions of Vt, w, and high cloud macrophysical properties for the two cloud subsets (with and without GW) are presented. Air-density-corrected Vt for high clouds for which GW (no GW) were detected amounted to hourly means and standard deviations of 0.89 ± 0.52 m s−1 (0.8 ± 0.48 m s−1) and 1.03 ± 0.41 m s−1 (0.86 ± 0.49 m s−1) at SGP and Manus, respectively. The error of w at one standard deviation was estimated as 0.15 m s−1. Hourly means of w averaged around 0 m s−1 with standard deviations of ±0.27 (SGP) and ±0.29 m s−1 (Manus) for high clouds without GW and ±0.22 m s−1 (both sites) for high clouds with GW. The midlatitude site showed stronger seasonality in detected high cloud properties.

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