DFT-based spectral moments estimators for spaceborne Doppler precipitation radars

Tanelli, Simone; Im, E.; Facheris, Luca; Smith, Eric A.

doi:10.1117/12.467754

Cited by 10 publications

(22 citation statements)

References 8 publications

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“…For narrow spectra (e.g.,w N < 0.1) and large M (e.g., M>1000), this algorithm provides unbiased estimates of the first spectral moment with the corresponding standard deviations comparable to those obtained by DFT-Z. However, this algorithm is more sensitive to w N than DFT-Z and DFT-ZN 8 .…”

Section: Standard Spectral Moments Estimatorsmentioning

confidence: 78%

<title>Spaceborne Doppler precipitation radar: system configurations and performance analysis</title>

Tanelli

2004

SPIE Proceedings

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Knowledge of the global distribution of the vertical velocity of precipitation is important in the study of energy transportation in the atmosphere, the climate and weather. Such knowledge can only be directly acquired with the use of spaceborne Doppler precipitation radars (DPR). Although the high relative speed of the radar with respect to the rainfall particles introduces significant broadening in the Doppler spectrum, recent studies have shown that the average vertical velocity can be measured to acceptable accuracy levels by appropriate selection of radar parameters. Furthermore, methods to correct for specific errors arising from non-uniform beam filling (NUBF) effects and pointing uncertainties have recently been developed. In this paper we will present the results of the trade studies on the performances of a spaceborne Doppler radar with different system parameters configurations. Particular emphases will be placed on the choices of: 1) the PRF vs. antenna size ratio, 2) the observational strategy, 3) the operating frequency; and 4) processing strategy. The results show that accuracies of 1 m/s or better can be achieved with the currently available technology. DOPPLER VELOCITY MEASUREMENTS FROM SPACEBORNE RADARDoppler velocity measurements require coherent processing of the radar signal. It follows that two consecutive radar echoes must be correlated in order to allow the measurement of the relative phase shift (and therefore of the Doppler frequency shift) without ambiguity.A Doppler radar transmitting one pulse every T S seconds can measure without ambiguity the Doppler velocity of a single target in the range ±v m where v m is the Nyquist limit imposed by the finite sampling:(1) where is the radar operating wavelength and PRF = 1/T S is the Pulse Repetition Frequency. A Precipitation Radar measures the echo returned by the distributed target consisting of all hydrometeors within a radar volume of resolution, therefore, in general, the Doppler signal is described through its Doppler velocity spectrum P(v) which can be expressed as:[ ] ( ) + = r r r r p r p

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Section: Standard Spectral Moments Estimatorsmentioning

confidence: 78%

<title>Spaceborne Doppler precipitation radar: system configurations and performance analysis</title>

Tanelli

2004

SPIE Proceedings

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“…The data processing flow chart is shown in Fig.3(a) [7]. We suppose that the power spectrum of each APR-2 data matches the Gaussian Model.…”

Section: Results and Analysismentioning

confidence: 99%

Data Simulation of Geostationary Space-borne Precipitation Radar Based on APR-2 Data

Hou¹,

Li²,

Tang³

et al. 2016

dtetr

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Abstract. Due to the importance of some function and performance vertification for the future geostationary space-borne precipitation radar (GSPR), a data simulation method based on the second airborne precipitation radar(APR-2) is introduced in this paper. In this method, the low resolution volume of GSPR is divided into finer resolution sub-volumes which are matched with the resolution of the APR-2 data, and the Doppler spectrums of each resolution volume of GSPR are constructed from the Gaussian shape and their intensity, average frequency and spectrum width are decided by the reflectivity and Doppler frequency of APR-2 data. Results indicate that the simulation method is feasible and simulation data can show some characteristics of GSPR echoes.

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“…For a Gaussian circular antenna pattern, and only in case of very weak vertical wind shears, Eq. (3) reduces to (Tanelli et al 2002a)…”

Section: Spectral Width and Coherency Time For Spaceborne Doppler Radarsmentioning

confidence: 97%

“…The larger radar beamwidth at 35 GHz is likely to cause larger velocity biases due to Nonuniform Beam Filling (NUBF; Tanelli et al 2002a;Schutgens 2008;, manuscript submitted to J. Atmos. Oceanic Technol.).…”

Section: Introductionmentioning

confidence: 99%

Polarization Diversity for Millimeter Spaceborne Doppler Radars: An Answer for Observing Deep Convection?

Battaglia

Tanelli

Kollias

2013

Journal of Atmospheric and Oceanic Technology

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Spaceborne Doppler radars have the potential to provide key missing observations of convective vertical air motions especially over the tropical oceans. Such measurements can improve understanding of the role of tropical convection in vertical energy transport and its interaction with the environment. Several millimeter wavelength Doppler radar concepts have been proposed since the 1990s. The Earth Clouds, Aerosols, and Radiation Explorer (EarthCARE) Cloud Profiling Radar (CPR) will be the first Dopplerized atmospheric radar in space but has not been optimized for Doppler measurements in deep convective clouds.The key challenge that constrains the CPR performance in convective clouds is the range-Doppler dilemma. Polarization diversity (PD) offers a solution to this constraint by decoupling the coherency (Doppler) requirement from the unambiguous range requirement. Careful modeling of the radar signal depolarization and its impact on radar receiver channel cross talk is needed to accurately assess the performance of the PD approach.The end-to-end simulator presented in this work allows reproduction of the signal sensed by a Doppler radar equipped with polarization diversity when overpassing realistic three-dimensional convective cells, with all relevant cross-talk sources accounted for. The notional study highlights that multiple scattering is the primary source of cross talk, highly detrimental for millimeter Doppler velocity accuracy. The ambitious scientific requirement of 1 m s 21 accuracy at 500-m integration for reflectivities above 215 dBZ are within reach for a W-band radar with a 2.5-m antenna with optimal values of the pulse-pair interval between 20 and 30 ms but only once multiple scattering and ghost-contaminated regions are screened out. The identification of such areas is key for Doppler accuracies and can be achieved by employing an interlaced pulse-pair mode that measures the cross and the copolar reflectivities. To mitigate the impact of attenuation and multiple scattering, the Ka band has been considered as either alternative or additional to the W band. However, a Ka system produces worse Doppler performances than a W-band system with the same 2.5-m antenna size. Furthermore, in deep convection it results in similar levels of multiple scattering and therefore it does not increase significantly the depth of penetration. In addition, the larger footprint causes stronger nonuniform beam-filling effects. One advantage of the Ka-band option is the larger Nyquist velocity that tends to reduce the Doppler accuracies. More significant benefits are derived from the Ka band when observing precipitation not as intense as the deep convection is considered here.This study demonstrates that polarization diversity indeed represents a very promising methodology capable of significantly reducing aliasing and Doppler moment estimate errors, two main error sources for Doppler velocity estimates in deep convective systems and a key step to achieving typical mission requirements for convection-oriented millimeter r...

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DFT-based spectral moments estimators for spaceborne Doppler precipitation radars

Cited by 10 publications

References 8 publications

<title>Spaceborne Doppler precipitation radar: system configurations and performance analysis</title>

<title>Spaceborne Doppler precipitation radar: system configurations and performance analysis</title>

Data Simulation of Geostationary Space-borne Precipitation Radar Based on APR-2 Data

Polarization Diversity for Millimeter Spaceborne Doppler Radars: An Answer for Observing Deep Convection?

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