P3.7

Estimation of Liquid Water Contents by the Dual-frequency Cloud Radar

Toshio Wakayama, Mitsubishi Electric Corporation, Kamakura, Kanagawa, Japan; and T. Fujisaka, K. Hata, S. Watanabe, K. Iwanami, R. Misumi, and M. Maki

1. Introduction

The dual-frequency cloud radar, a part of Mobile Multi-parameter Radar System we have recently developed, uses a single Cassegrain antenna with 2 m diameter both for the Ka-band and the W-band subsystems. Therefore, the Ka-band radar and the W-band radars can observe the same direction. In order to utilize this characteristic, we plan to measure liquid water contents (LWC) of clouds by the dual-wavelength method.

2. The dual-wavelength method

Attenuation of a millimeter-wavelength radio wave by a cloud is relatively high, and therefore compensation of the attenuation is one of the major problems of millimeter-wavelength meteorological radars. Since attenuation by clouds is proportional to the LWC, and the attenuation coefficient depends on a radio frequency, the LWC can be estimated from the ratio of echo powers observed with two wavelengths.

3. Results of simulations

Table 1 is the specification of the radar model used in the computer simulations, which is based on the actual radar system. The meteorological model consists of 2 horizontal layers; layer 1 is a clear-air layer and layer 2 is a cloud layer.

Figure 1 is a result of computer simulation. LWC is 0.5 g/m³ and the height of the cloud bottom is 1km in this simulation case. Figure (d) is a distribution of estimated LWC, and figure (e) is a standard deviation of the estimation. From this figure, LWC is accurately estimated up to 2.2 km altitude and 1km horizontal range.

4. Conclusion