The Impact of the Radar-Sampling Volume on Multiwavelength Spaceborne Radar Measurements Using Airborne Radar Observations

Abstract

Multiwavelength radar observations have demonstrated great potential in improving microphysical retrievals of cloud properties especially in ice and snow precipitation systems. Advancements in spaceborne radar technology have already fostered the launch in 2014 of the first multiwavelength radar system in space, while several future spaceborne multiwavelength radar concepts are under consideration. However, due to antenna size limitations, the sampling volume of spaceborne radars is considerably larger than those achieved by surface- and airborne-based radars. Here, the impact of these large sampling volumes in the information content of the Dual-Wavelength Ratio estimates at Ka-W, Ku-Ka is investigated. High-resolution airborne multiwavelength radar observations during the Olympic Mountain Experiment (OLYMPEx) are used to perform retrievals of ice/snow characteristic particle size, such as mass-weighted particle diameter. To mimic the different satellite sampling volumes, a moving average is applied to the airborne measurements. The radar-observed variables (reflectivity and dual-wavelength ratios) and retrieved microphysical properties at the coarser resolution are compared against those at the original resolution. Our analysis indicates that future Ka-W spaceborne radar missions should take into account the impact of the radar resolution volume on the retrieval of microphysical properties and avoid footprints larger than 2–3 km.

A Dual-Frequency Radar Retrieval of Two Parameters of the Snowfall Particle Size Distribution Using a Neural Network

“…While it has been shown here that the NN retrieval performs better than the average GPM-DPR retrieval of IWC (section 3) using the APR data, the uncertainties caused by the resolution differences, radar sensitivity differences, and the source of environmental temperature information could impact the retrieval when applied to the GPM-DPR data (e.g., Pfitzenmaier et al 2019). To investigate how the radar differences impact the retrieval, the NN is applied directly to the GPM-DPR data on the 3 December 2015 (Fig.…”

10 GHz Generation with Ultra-Low Phase Noise via the Transfer Oscillator Technique

“…To minimize instabilities resulting from environmental effects, the cavities are housed within several layers of thermal and acoustic shielding and employ both passive and active vibration control to isolate the cavity length from changes due to acceleration. The room-temperature Fabry-Perot cavities (∼ 30 cm long) act as length references, that at the time of the writing of this manuscript, can support fractional length instabilities near 1 part in 10 16 . These cavities act as optical frequency filters when a laser is stabilized to one of their longitudinal optical modes, transferring the cavity length stability to frequency stability of the laser light.…”

“…These advantages help support the development of low-noise microwave flywheels derived from optical references, which are needed for realization of optical atomic time for future redefinition of the SI second 15 . Furthermore, TO-OFD may help to improve multi-frequency radar, which can provide high-resolution images for resource exploration and military ventures 16 . The TO technique may also help facilitate low-noise microwave generation from chipscale OFCs that are difficult to stabilize 17 or from highly robust polarization-maintaining linear fiber lasers [18][19][20][21] that exhibit higher intrinsic noise.…”