Mean Square Slopes Of Sea Waves In Cyclone Area From Dual-Frequency Precipitation Radar And Microwave Radiometer

Abstract. This paper is to investigate the uncertainties of microwave radiometer (MWR) retrievals in snow conditions and also explore the discrepancies of MWR retrievals in zenith and off-zenith observations. The MWR retrievals were averaged in a ±15 min period centered at sounding times of 00:00 and 12:00 UTC and compared with radiosonde observations (RAOBs). In general, the MWR retrievals have a better correlation with RAOB profiles in off-zenith observations than in zenith observations, and the biases (MWR observations minus RAOBs) and root mean square errors (RMSEs) between MWR and RAOB are also clearly reduced in off-zenith observations. The biases of temperature, relative humidity, and vapor density decrease from 4.6 K, 9 %, and 1.43 g m−3 in zenith observations to −0.6 K, −2 %, and 0.10 g m−3 in off-zenith observations, respectively. The discrepancies between MWR retrievals and RAOB profiles by altitude present the same situation. Cases studies show that the impact of snow on accuracies of MWR retrievals is more serious in heavy snowfall than in light snowfall, but off-zenith observation can mitigate the impact of snowfall. The MWR measurements become less accurate in snowfall mainly due to the retrieval algorithm, which does not consider the effect of snow, and the accumulated snow on the top of the radome increases the signal noise of MWR measurements. As the snowfall drops away by gravity on the sides of the radome, the off-zenith observations are more representative of the atmospheric conditions for RAOBs.

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A new algorithm for determining mean square slopes of sea waves: a theoretical approach

Sovremennye problemy distantsionnogo zondirovaniya Zemli iz kosmosa ◽

10.21046/2070-7401-2021-18-6-73-84 ◽

2021 ◽

Vol 18 (6) ◽

pp. 73-84

Author(s):

V.Yu. Karaev ◽

◽

M.A. Panfilvoa ◽

M.S. Ryabkova ◽

Yu.A. Titchenko ◽

...

Keyword(s):

Theoretical Approach ◽

Mean Square ◽

Sea Waves

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

Journal of Applied Meteorology and Climatology ◽

10.1175/jamc-d-19-0293.1 ◽

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.

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An Initial Assessment of the Surface Reference Technique Applied to Data from the Dual-Frequency Precipitation Radar (DPR) on the GPM Satellite

Journal of Atmospheric and Oceanic Technology ◽

10.1175/jtech-d-15-0044.1 ◽

2015 ◽

Vol 32 (12) ◽

pp. 2281-2296 ◽

Cited By ~ 35

Author(s):

Robert Meneghini ◽

Hyokyung Kim ◽

Liang Liao ◽

Jeffrey A. Jones ◽

John M. Kwiatkowski

Keyword(s):

Cross Section ◽

Radar Data ◽

Single Frequency ◽

Initial Assessment ◽

Dual Frequency ◽

Precipitation Radar ◽

Frequency Method ◽

Ka Band ◽

Spaceborne Radar ◽

Ku Band

AbstractIt has long been recognized that path-integrated attenuation (PIA) can be used to improve precipitation estimates from high-frequency weather radar data. One approach that provides an estimate of this quantity from airborne or spaceborne radar data is the surface reference technique (SRT), which uses measurements of the surface cross section in the presence and absence of precipitation. Measurements from the dual-frequency precipitation radar (DPR) on the Global Precipitation Measurement (GPM) satellite afford the first opportunity to test the method for spaceborne radar data at Ka band as well as for the Ku-band–Ka-band combination.The study begins by reviewing the basis of the single- and dual-frequency SRT. As the performance of the method is closely tied to the behavior of the normalized radar cross section (NRCS or σ0) of the surface, the statistics of σ0 derived from DPR measurements are given as a function of incidence angle and frequency for ocean and land backgrounds over a 1-month period. Several independent estimates of the PIA, formed by means of different surface reference datasets, can be used to test the consistency of the method since, in the absence of error, the estimates should be identical. Along with theoretical considerations, the comparisons provide an initial assessment of the performance of the single- and dual-frequency SRT for the DPR. The study finds that the dual-frequency SRT can provide improvement in the accuracy of path attenuation estimates relative to the single-frequency method, particularly at Ku band.

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