Intercomparison between ground-based and space-borne radars echo top heights: Application to the Multi-Radar Multi-Sensor and the Global Precipitation Measurement.

Abstract

The accuracy and uncertainty of radar echo top heights estimated by ground-based radars remains largely unknown despite their critical importance for applications ranging from aviation weather forecasting to severe weather diagnosis. As the vantage point of space is more suited for the estimation of echo top heights than ground-based radars, the use of space-borne radar observations is explored as an external reference for cross-comparison. An investigation has been carried out across the conterminous United States by comparing the National Oceanic and Atmospheric Administration (NOAA)/National Severe Storms Laboratory Multi-Radar Multi-Sensor (MRMS) system to the space-based radar onboard the NASA/JAXA Global Precipitation Measurement satellite platform. No major bias was assessed between the two products. An annual cycle of differences is found, driven by an underestimation of the stratiform cloud echo top heights and an overestimation of the convective ones. The investigation of the systematic biases for different radar volume coverage pattern (VCP) shows that scanning strategies with fewer tilts and greater voids as VCP 21/121/221 contribute to overestimations observed for high MRMS tops. For VCP 12/212, the Automated Volume Scan Evaluation and Termination (AVSET) function increases the radar cone of silence, causing overestimations when the echo top lies above the highest elevation scan. However, it seems that for low echo tops, the shorter refresh rates contribute to mitigate underestimations, especially in stratiform cases.