Improvement to radar reflectivity factor algorithm for spaceborne precipitation radar

2009 ◽  
Author(s):  
Jian Shang ◽  
Ping Zhang ◽  
Ruliang Yang
Keyword(s):  
Radar Reflectivity ◽  
Precipitation Radar ◽  
Reflectivity Factor

scholarly journals Reduction of Nonuniform Beamfilling Effects by Multiple Constraints: A Simulation Study

2015 ◽  
Vol 32 (11) ◽  
pp. 2114-2124 ◽  
Author(s):  
David A. Short ◽  
Robert Meneghini ◽  
Amber E. Emory ◽  
Mathew R. Schwaller
Keyword(s):  
Attenuation Correction ◽  
Vertical Structure ◽  
Radar Data ◽  
Radar Reflectivity ◽  
Radar Signal ◽  
Precipitation Radar ◽  
Sensor Field ◽  
Spaceborne Radar ◽  
Ku Band ◽  
Reflectivity Factor

AbstractA spaceborne precipitation radar samples the vertical structure of precipitating hydrometeors from the top down. The viewing geometry and operating frequency result in certain limitations and opportunities. Among the limitations is attenuation of the radar signal that can cause the measured radar reflectivity factor to be substantially less than the desired quantity, the true radar reflectivity factor. Another error source is the spatial variability in precipitation rates that occurs at scales smaller than the sensor field of view (FOV), giving rise to the nonuniform beamfilling (NUBF) effect. The opportunities arise when the radar return from the surface can be used to obtain constraints on the path-integrated attenuation (PIA) for use in hybrid attenuation correction algorithms. The surface return can also provide some information on the degree of NUBF at off-nadir viewing angles. In this paper ground-based radar data are used to simulate spaceborne radar data at nadir and off-nadir viewing angles at Ku band and Ka band and to test attenuation correction algorithms in the presence of nonuniform beamfilling. The cross-FOV gradient in PIA is found to be an important characteristic for describing the performance of attenuation correction algorithms.

Fuzzy Logic Classification of S-Band Polarimetric Radar Echoes to Identify Three-Body Scattering and Improve Data Quality

2014 ◽  
Vol 53 (8) ◽  
pp. 2017-2033 ◽  
Author(s):  
Vivek N. Mahale ◽  
Guifu Zhang ◽  
Ming Xue
Keyword(s):  
Fuzzy Logic ◽  
Standard Deviation ◽  
Radar Data ◽  
Classification Algorithm ◽  
Radar Reflectivity ◽  
Membership Functions ◽  
Polarimetric Radar ◽  
Radar Echo ◽  
Three Body ◽  
Reflectivity Factor

AbstractThe three-body scatter signature (TBSS) is a radar artifact that appears downrange from a high-radar-reflectivity core in a thunderstorm as a result of the presence of hailstones. It is useful to identify the TBSS artifact for quality control of radar data used in numerical weather prediction and quantitative precipitation estimation. Therefore, it is advantageous to develop a method to automatically identify TBSS in radar data for the above applications and to help identify hailstones within thunderstorms. In this study, a fuzzy logic classification algorithm for TBSS identification is developed. Polarimetric radar data collected by the experimental S-band Weather Surveillance Radar-1988 Doppler (WSR-88D) in Norman, Oklahoma (KOUN), are used to develop trapezoidal membership functions for the TBSS class of radar echo within a hydrometeor classification algorithm (HCA). Nearly 3000 radar gates are removed from 50 TBSSs to develop the membership functions from the data statistics. Five variables are investigated for the discrimination of the radar echo: 1) horizontal radar reflectivity factor ZH, 2) differential reflectivity ZDR, 3) copolar cross-correlation coefficient ρhv, 4) along-beam standard deviation of horizontal radar reflectivity factor SD(ZH), and 5) along-beam standard deviation of differential phase SD(ΦDP). These membership functions are added to an HCA to identify TBSSs. Testing is conducted on radar data collected by dual-polarization-upgraded operational WSR-88Ds from multiple severe-weather events, and results show that automatic identification of the TBSS through the enhanced HCA is feasible for operational use.

scholarly journals Sensitivity of 89–190-GHz Microwave Observations to Ice Particle Scattering

2020 ◽  
Vol 59 (7) ◽  
pp. 1195-1215
Author(s):  
Ruiyao Chen ◽  
Ralf Bennartz
Keyword(s):  
Radar Reflectivity ◽  
Dual Frequency ◽  
Precipitation Radar ◽  
Brightness Temperatures ◽  
Precipitation Measurement ◽  
Microwave Humidity Sounder ◽  
Slant Path ◽  
The One ◽  
Global Precipitation Measurement ◽  
Global Precipitation

AbstractThe sensitivity of microwave brightness temperatures (TBs) to hydrometeors at frequencies between 89 and 190 GHz is investigated by comparing Fengyun-3C (FY-3C) Microwave Humidity Sounder-2 (MWHS-2) measurements with radar reflectivity profiles and retrieved products from the Global Precipitation Measurement mission’s Dual-Frequency Precipitation Radar (DPR). Scattering-induced TB depressions (ΔTBs), calculated by subtracting simulated cloud-free TBs from bias-corrected observed TBs for each channel, are compared with DPR-retrieved hydrometeor water path (HWP) and vertically integrated radar reflectivity ZINT. We also account for the number of hydrometeors actually visible in each MWHS-2 channel by weighting HWP with the channel’s cloud-free gas transmission profile and the observation slant path. We denote these transmission-weighted, slant-path-integrated quantities with a superscript asterisk (e.g., HWP*). The so-derived linear sensitivity of ΔTB with respect to HWP* increases with frequency roughly to the power of 1.78. A retrieved HWP* of 1 kg m−2 at 89 GHz on average corresponds to a decrease in observed TB, relative to a cloud-free background, of 11 K. At 183 GHz, the decrease is about 34–53 K. We perform a similar analysis using the vertically integrated, transmission-weighted slant-path radar reflectivity and find that ΔTB also decreases approximately linearly with . The exponent of 0.58 corresponds to the one we find in the purely DPR-retrieval-based ZINT–HWP relation. The observed sensitivities of ΔTB with respect to and HWP* allow for the validation of hydrometeor scattering models.

scholarly journals Effect of TRMM Orbit Boost on Radar Reflectivity Distributions

2010 ◽  
Vol 27 (7) ◽  
pp. 1247-1254 ◽  
Author(s):  
David A. Short ◽  
Kenji Nakamura
Keyword(s):  
Probability Distributions ◽  
Gaussian Function ◽  
Tropical Rainfall Measuring Mission ◽  
Radar Reflectivity ◽  
Response Functions ◽  
Precipitation Radar ◽  
Mathematical Properties ◽  
Trmm Pr ◽  
Before And After ◽  
Basic Characteristics

Abstract Probability distributions of measured radar reflectivity from the precipitation radar (PR) on board the Tropical Rainfall Measuring Mission (TRMM) satellite show a small, counterintuitive increase in the midrange, 20–34 dBZ, when comparing data from periods before and after the orbit altitude was boosted in August 2001. Data from two 2-yr time periods, 1999–2000 (preboost) and 2002–03 (postboost), show statistically significant differences of 2%–3% at altitudes of 2, 4, and 10 km and for path-averaged reflectivity. The bivariate Gaussian function, used to model idealized radar response functions, has mathematical properties that indicate an increase in field-of-view (FOV) size associated with an increase in satellite altitude can be expected to result in a narrowing of observed dBZ distributions, with a resulting increase in midrange values. Numerical simulations with echo areas much smaller and larger than the TRMM PR FOV before (4.3 km) and after (5.0 km) boost are used to demonstrate basic characteristics of the observed and expected distribution changes.

scholarly journals Geographical Distribution of Variance of Intraseasonal Variations in Western Indochina as Revealed from Radar Reflectivity Data

2008 ◽  
Vol 21 (19) ◽  
pp. 5154-5161 ◽  
Author(s):  
Satoru Yokoi ◽  
Takehiko Satomura
Keyword(s):  
Geographical Distribution ◽  
Coastal Region ◽  
Radar Reflectivity ◽  
Windward Side ◽  
Synoptic Scale ◽  
Wind Anomaly ◽  
Orographic Rainfall ◽  
Intraseasonal Variations ◽  
Reflectivity Data ◽  
Reflectivity Factor

Abstract This study reveals remarkable differences in the geographical distribution of variance between two types of intraseasonal variations in daily-mean radar reflectivity data in the western part of the Indochina Peninsula. In this region, the Downa Range lies parallel to the coast and separates the inland region from the coastal region. The 30–60-day variation of reflectivity factor dominates most of the coastal region, while its variance in the inland region is less than that of background red noise with the same frequency band. Horizontal gradients in the variance are largest over the range, implying that the mountain range plays a significant role in the geographical contrast. Correlation analysis with reanalysis data shows that the variation only in the coastal region is associated with a synoptic-scale zonal wind anomaly with the same time scale, suggesting the importance of an orographic rainfall process that brings a large amount of precipitation only to the windward side of the Downa Range. In contrast, while the 10–20-day variation of reflectivity factor has larger variance in the inland region than in the coastal region, the variation in both of the regions is correlated with synoptic-scale cyclonic circulation anomaly. A possible reason for the differences between the two types is also discussed in terms of the relationship between synoptic-scale wind anomaly field and the orientation of the Downa Range.

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