ISSN 1000-0526
CN 11-2282/P
CN 11-2282/P
Archive > Volume 50 Issue 3 > 2024,50(3):291-302. DOI:10.7519/j.issn.1000-0526.2023.122001 Prev Next
Analysis of Precipitation Echoes from Ka-Band Millimeter Wave Cloud Radar on the Southeast Margin of the Tibetan Plateau
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Abstract:
This article analyzes the vertical variation patterns of the echo intensity (Z), radial velocity (Vr), and velocity spectral width (Sw) of the cloud radar before and after two precipitation processes, using high-resolution vertical observation data obtained from the newly built Ka-band millimeter wave cloud radar at Lijiang Station, combined with minutely data from ground automatic weather stations and raindrop spectra at the same site, conventional sounding data, and intensity echoes from nearby C-band weather radar. Analysis shows that during weak precipitation, the vertical variation of cloud radar Z is not significant, but there is a clear boundary layer (melting layer) at a slightly lower position of the 0℃ layer for Vr and Sw values. After particles pass through the melting layer, Vr and Sw rapidly increase. This change is mainly caused by the phase state of particles changing from solid to liquid. The height of the bright band in the 0℃ layer can be identified by the position of the sudden changes in Vr and Sw values.From the time-height maps of C-band weather radar echo intensity, profile, and cloud radar position, we can see a significant difference in intensity and height between the echoes of drizzle and light rain. The height of the echoes of drizzle is lower and weaker than that of light rain. Compared to cloud radar, C-band radar cannot observe higher clouds and weak precipitation echoes at longer distances. Due to the different scattering of electromagnetic waves of different wavelengths by the same particle, the Z changes observed in the vertical direction by the two radars are different. Compared with weak precipitation echoes, during strong precipitation cloud radar shows a gap in Z, Vr has a significant positive value above the 0℃ layer (Vr for weak precipitation is negative), and Sw becomes larger above the 0℃ layer (during weak precipitation, Sw values are smaller above the 0℃ layer and larger below the 0℃ layer). During heavy rainfall, from the C-band radar echo intensity time-height map, the vertical direction echo intensity changes significantly, and at the same time, the variation of echo intensity from ground to air gradually decreases. The intensity of the same altitude layer also varies at different times, and the echo during the rain attenuation gap period of cloud radar is significantly stronger than that in other periods. The case study shows that if precipitation occurs with an intensity of less than 0.3 mm per minute, cloud radar can observe complete cloud information; if precipitation with a minimum rainfall intensity of 0.5 mm or more occurs, cloud radar will experience severe rain attenuation and cannot observe complete cloud information
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