5:15 PM - 6:45 PM
[AAS01-P04] Analyses of vertical motion using Wind Profiler for interpretating Doppler velocity by EarthCARE CPR
The CPR (94 GHz) onboard EarthCARE satellite will provide the first Doppler velocity measurements in vertical direction for the first time from space. The 1.3GHz-Wind Profilers (WPR) operated by the Japan Meteorological Agency are located at 33 sites across Japan. It is expected that the network of WPR offers great opportunities for validation of the CPR. Different scattering mechanisms are expected between cloud radar and WPR due to the different frequencies, leading to the possible differences in measured Doppler velocity for the same target. Magnitude of Doppler velocity measured by the vertical pointing cloud radars and precipitation radars are mainly affected by the falling speed of clouds and precipitation particles and the vertical air motion, whereas the WPR signal is affected by Bragg scattering and clouds and precipitation particles. Due to the different nature, WPR can provide Doppler information in clear sky, precipitation, and cloud regions.
In this study, long-term analyses of Doppler velocities observed by the 1.3GHz-WPR were conducted. WPR measures vertical and horizontal Doppler velocity and signal-to-noise ratio (SNR) in the range from about 5 km to 10 km from about 291 m above the ground surface. WPR data acquired on Minamidaito Island and Yonaguni Island showed that upward velocity was frequently observed during clear day, and mean value of the SNR in the clear areas was around 40 dB. On the other hand, Doppler velocity in precipitation areas was mostly below -4.0 m/s (hereafter negative sign indicates downward flow). The Doppler velocity in clouds above precipitation regions was approximately −1.0 m/s. The SNR in the precipitation area was 60 to 70 dB, while the cloud area was mostly 45 to 50 dB. The presence of a melting layer was also confirmed. Statistics on Doppler velocities from May to October in 2018-2021 and February to July in 2023 showed that the frequency distribution of the Doppler velocity was similar regardless of region. The distributions were bimodal and the values mostly ranged from -12.0 m/s to 6.0 m/s.
We have developed a method to identify precipitation, clouds, melting layers, and clear areas from Doppler velocity and SNR. Next, according to the identify method results, we analyzed the relationship between SNR and Doppler velocity. The analyses of the relationship between SNR and Doppler velocity showed that downward velocity increases as SNR increases. Doppler velocity and SNR of rainfall particles range from -2.0m/s to -10.0m/s and 20dB to 90dB, respectively. The values of melting layer were between -1.0m/s to -5.0m/s for Velocity and 30dB to 80dB for SNR, respectively. The velocity and SNR in Clouds range from 0.2m/s to -2.0m/s and between 30dB to 60dB, respectively. These statistical analyses will be helpful to evaluate Doppler observations of EarthCare CPR.
(Acknowledgment) The WPR data were provided by the Japan Meteorological Agency's project to promote research to elucidate the mechanism of linear precipitation zones and to improve forecasting technology.
In this study, long-term analyses of Doppler velocities observed by the 1.3GHz-WPR were conducted. WPR measures vertical and horizontal Doppler velocity and signal-to-noise ratio (SNR) in the range from about 5 km to 10 km from about 291 m above the ground surface. WPR data acquired on Minamidaito Island and Yonaguni Island showed that upward velocity was frequently observed during clear day, and mean value of the SNR in the clear areas was around 40 dB. On the other hand, Doppler velocity in precipitation areas was mostly below -4.0 m/s (hereafter negative sign indicates downward flow). The Doppler velocity in clouds above precipitation regions was approximately −1.0 m/s. The SNR in the precipitation area was 60 to 70 dB, while the cloud area was mostly 45 to 50 dB. The presence of a melting layer was also confirmed. Statistics on Doppler velocities from May to October in 2018-2021 and February to July in 2023 showed that the frequency distribution of the Doppler velocity was similar regardless of region. The distributions were bimodal and the values mostly ranged from -12.0 m/s to 6.0 m/s.
We have developed a method to identify precipitation, clouds, melting layers, and clear areas from Doppler velocity and SNR. Next, according to the identify method results, we analyzed the relationship between SNR and Doppler velocity. The analyses of the relationship between SNR and Doppler velocity showed that downward velocity increases as SNR increases. Doppler velocity and SNR of rainfall particles range from -2.0m/s to -10.0m/s and 20dB to 90dB, respectively. The values of melting layer were between -1.0m/s to -5.0m/s for Velocity and 30dB to 80dB for SNR, respectively. The velocity and SNR in Clouds range from 0.2m/s to -2.0m/s and between 30dB to 60dB, respectively. These statistical analyses will be helpful to evaluate Doppler observations of EarthCare CPR.
(Acknowledgment) The WPR data were provided by the Japan Meteorological Agency's project to promote research to elucidate the mechanism of linear precipitation zones and to improve forecasting technology.