Spatial Resolution of Meteorological Radar Network Consisting of High Range and Temporal Resolution Radars

The Ku-band broadband radar (BBR) [1], [2] is a short-range (15 km) and ground-based Doppler weather radar with remarkably high range and temporal resolution (several meters and 1 min per volume scan). A weather radar network consisting of several BBRs observes multi-directionally and simultaneously hazardous small-scale weather phenomena such as tornadoes and microbursts occurring in the lower troposphere (below an altitude of 2 km) with high resolution and accuracy. In general, a weather radar network has a duplicative observational area of several radar nodes, where high signal-to-noise ratio (SNR) is accomplished by obtaining the same physical parameters (reflectivities) from several radar nodes at a desired point. In addition, the BBR network has another important advantage as shown below. Data integration of reflectivities obtained by each radar node by simply using a weighting function is equivalent to a weighting average of composite average functions (CAF) [3]. The BBR has a beam width of 3 deg, which is significantly inferior to the range resolution of several meters (the beam width of 3 deg is equivalent to a cross-range resolution of 785 m at a range of 15 km). A CAF of the BBR, which is determined by transmitting pulse, beam patterns, and so on, has a thin-plate shape, while conventional radars are like a spherical shape since the pulse and beam patterns have a comparable order of the half power width. In the BBR network, several thin-plate CAFs are crossed and an averaged CAF achieves high spatial resolution of several meters in 2D or 3D. Panel (a) in Fig. 1 shows spatial resolution of about 10 x 10 m (in which normalized power is over -3 dB) in a two-BBR network on the base scan. On the other hand, Panel (b) shows that the spherical CAFs do not achieve such a resolution improvement as in Panel (a) in spite of an equivalent volume of CAF. This presentation shows formulations of a simple weighting average of CAFs of several radar nodes through a radar equation for precipitation particles. Then simulation results about comparisons of resolution enhancements between thin-plate and spherical CAFs, and between two- and three-BBR networks, are described. Observation results of the BBR network deployed in Osaka, Japan are presented in another presentation in the conference. Fig 1. Comparison of resolution enhancements in weather radar networks. Panel (a): Improved resolution by averaging thin-plate CAFs (the BBR), Panel (b): Resolution by averaging spherical CAFs (conventional radars). [1] T. Mega, K. Monden, T. Ushio, K. Okamoto, Z. Kawasaki, and T. Morimoto, “A low-power high-resolution broad-band radar using a pulse compression technique for meteorological application,” IEEE Geosci. Remote Sens. Lett., vol. 4, no. 3, pp. 392–396, Jul. 2007. [2] E. Yoshikawa, T. Ushio, Z. Kawasaki, T. Mega, S. Yoshida, T. Morimoto, K. Imai, and S. Nagayama (2010), Development and initial observation of the high-resolution volume scanning radar for meteorological application, IEEE Trans. Geosci. Remote Sens., vol. 48, no. 8, 3225-3235. [3] R. J. Doviak and D. S. Zrnic (2007), Doppler Radar and Weather Observations, chap. 4, 65-86, Academic Press, SanDiego, CA.