Monday, 24 October 2005
Alvarado F and Atria (Hotel Albuquerque at Old Town)
It is getting more important to know the global environment and the global change of climate for the human beings. It is necessary to know balance of solar energy coming to the Earth and cycle of water for the comprehension. One of the most significant features to know them is cloud. Information on 3-dimensional structures of clouds, sizes and distribution of cloud particles, and so on are desirable to solve role of clouds. Observations of clouds with radars in millimeter wave ranges would be most powerful method to derive the information rather than other wavelengths. Low power and high sensitivity cloud profiling FM-CW radars are developed at 95 GHz. We make use of FM-CW type radars, which transmit frequency-modulated continuous wave (FM-CW). Millimeter wave at 95 GHz is used to realize high sensitivity to small cloud particles. An FM-CW type radar would realize similar sensitivity with much smaller output power to a traditional pulse type radar because of its continuous observations in time. Two 1m-diameter parabolic antennas separated by 1.4m each other are used for transmitting and receiving the wave. The direction of the antennas is fixed at the zenith. The radar is designed to observe clouds between 0.3 and 15 km in height with a resolution of 15 m. Using the facility, test observations for sensitivity by comparing with a pulse type radar have been done. Although the output power of the developed FM-CW radar is 3000 times lower than that of the pulse radar, both facilities obtained similar structure of clouds as shown inFig.2. The results show that the FM-CW can detect clouds with 30 dBZ at around 6km height. Long term campaign observations have been done in March to April 2003, and the facility worked well and provided good data during the campaign. Results of these observations show that the developed FM-CW radar is sensitive and stable enough to observe various types of clouds. Development of the second FM-CW radar with single antenna is now on way, and its performance will be also presented.
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