17:15 〜 18:45
[AAS01-P03] Development of algorithms for cloud detection and Doppler Velocity unfolding using 94-GHz cloud radar
キーワード：cloud radar, cloud detection, Doppler velocity, reflectivity, velocity unfolding
Clouds play a crucial role in influencing Earth's radiation budget through the absorption and reflection of thermal radiation. The study of clouds is essential for understanding their macro- and microphysics, impacting both the climate and the Earth's water cycle. Cloud profiling radar (CPR) has proven effective in cloud studies; however, the data often includes contaminants, leading to misclassifications in cloud masks. This paper proposes an improved cloud detection method for the 94-GHz W-band radar (HG-SPIDER), utilized in Japan. The method combines signal power and a spatial filter to improve the accuracy of cloud and hydrometeor detection while mitigating other contaminations. This novel approach outperforms traditional cloud detection method based on constant noise threshold.
Additionally, accurate Doppler velocity measurements are vital for target discrimination and improving the precision of cloud microphysics systems. Velocity folding, a common issue in radar measurements, occurs when the phase shift between radar pulses exceeds the Nyquist velocity, impacting data accuracy. To address this, a novel velocity unfolding methodology is introduced, leveraging both reflectivity (Z) and Doppler velocity (V). The process involves three stages: identifying folded velocity pixels, establishing the relationship between Z and V, and assigning weights to Z for correcting aliased velocity pixels. The corrected Doppler velocity by HG-SPIDER is validated against Doppler Wind Lidar (DWL) datasets, demonstrating good agreement between HG-SPIDER and DWL; and a comparison of HG-SPIDER velocity with that of WPR is planned. Furthermore, the outcomes of the new technique are compared with those of the conventional method, which relies on a fixed velocity threshold, highlighting the superior/improved performance of the proposed approach.
The methods developed in this study are planned to be implemented in EarthCARE L2 algorithms for CPR.
Additionally, accurate Doppler velocity measurements are vital for target discrimination and improving the precision of cloud microphysics systems. Velocity folding, a common issue in radar measurements, occurs when the phase shift between radar pulses exceeds the Nyquist velocity, impacting data accuracy. To address this, a novel velocity unfolding methodology is introduced, leveraging both reflectivity (Z) and Doppler velocity (V). The process involves three stages: identifying folded velocity pixels, establishing the relationship between Z and V, and assigning weights to Z for correcting aliased velocity pixels. The corrected Doppler velocity by HG-SPIDER is validated against Doppler Wind Lidar (DWL) datasets, demonstrating good agreement between HG-SPIDER and DWL; and a comparison of HG-SPIDER velocity with that of WPR is planned. Furthermore, the outcomes of the new technique are compared with those of the conventional method, which relies on a fixed velocity threshold, highlighting the superior/improved performance of the proposed approach.
The methods developed in this study are planned to be implemented in EarthCARE L2 algorithms for CPR.