Test results of Array Type HF Radar in the eastern coast of Korea

Transcription

1 Test results of Array Type HF Radar in the eastern coast of Korea Seung Bea Choi 1, Hyeon Seong Kim 1, Jong Yoon Moon 1, Kang Ho Lee 1, Isamu Ogasawara 2 and Matthias Kniephoff 3 1 Marine Information Technology, Corp., Seoul, Korea (ace8978@hanmail.net) 2 Kokusai Kogyo Co., Ltd., Tokyo, Japan (isamu_ogasawara@kk-grp.jp) 3 Helzel Messtechnik GmbH, Kaltenkirchen, Germany (kniephoff@helzel.com) Key words: HF Radar, Array Type, Ocean remote sensing, WERA Abstract: In the eastern coast of Korea, damages on human and properties have been caused by abnormally heaving seas, tsunamis and hurricane-induced waves, and thus the necessity to observe waves with high spatial and temporal resolution was raised. Accordingly, to establish systems for observing and forecasting wide areas of sea surfaces including wave parameters, array type HF radar were introduced to Imwon Port (Site 1) in Samcheok-si and Hujeong Beach (Site 2) in Uljin-gun in the mid-eastern coast for the first time in Korea. This paper reports the installed system of the array type HF radar and shows preliminary test results of wave and current observation and introduces future plans. 1. Introduction To get current and wave vector data from ocean radar a pair of HF radar stations need always to be installed. The array type radar has a typical angular field view of 120 for current mapping, and 90 for wave mapping. Within the overlap of coverage from both stations vector data can be derived. The detection range of these ocean radar systems strongly depend on the operation frequency. The array type system that was firstly introduced into Korea by our company is a short range, high resolution 8-channel WERA (Fig. 1). The two sites operate alternatively for 15 minutes, providing a complete new data set every 30 minutes. (a) (b) (c) Fig. 1 (a) Location of HF radar installation sites in the eastern coast of Korea, (b) mimetic diagram of the Site 1 and (c) the Site 2.

2 2. System These WERAs (WavE RAdar) are developed in 2000 by Helzel Messtechnik GmbH, in Germany that used a frequency of MHz (Helzel, 2012). The WERA system is operating in a frequency modulated continuous wave mode (FMcw; Gurgel et al., 1999). Each site has a 8 channel system consisting of a transmitter array (Fig. 2 a and c) and 8 receiver antennas (Fig 2 b and d). Center beam azimuth is 95.8 in the Site 1, and 37.3 in the Site 2 and direction ranges are within ±60 from the central beam angle. (a) (b) (c) (d) Fig. 2 HF radar installed at the coast of the East Sea. (a) Tx antenna and (b) Rx antenna installed at Imwon Port (Site1) in Samcheok-si, (c) Tx antenna and (d) Rx antenna installed at Hujeong Beach in Uljin-gun (Site2) Actually we set to measure wave and current in the 30 minutes intervals (The data measuring time intervals can be changed by setting). Each site was set to observed wave field within the range up to 25 km and current field within the range up to 50 km and used a bandwidth of 150 khz to have a range resolution of 1 km intervals (Table 1). Fig. 3 shows samples of wave and current distribution that were measured in March 20, 2012 with the aforementioned setting.

3 Table 1. Information of WERA system installed in the east coast of Korea (a) :45(UTC) Current Map (b) :45(UTC) Wave Map (c) :15(UTC) Current Map (d) :15(UTC) Wave Map Fig. 3 Samples of wave and current distribution (March 20, 2012) 3. Preliminary Results Using HF radar data for 6 days from March 20 to 26, 2012, current velocity and direction, significant wave height and direction was monitored in the selected four points (Fig. 4) and was plotted as time series in Fig. 5. Current speed and direction in near shore point P1 showed a diurnal variation. This result is correspondent to that diurnal tidal current is dominant in the East Sea. However, the current speed and direction in the offshore points P3 and P4 showed comparably small variations. We

4 believed the oceanic current (East Korea Warm Current, a branch of Tsushima Warm Current) might be stronger than the tidal current in the offshore region such that the current direction is not changed by the oscillating tidal currents. This preliminary test run of array type HF radar installed in the middle coast of the East Sea for the first time in Korea indicates that wave and current data were successfully measured. Fig. 4 Regions where the Sample Data were extracted (a) Time series data from points P1 (b) Time series data from points P2 (c) Time series data from points P3 (d) Time series data from points P4 Fig. 5 Time series data from points P1- P4 (March 20-26, 2012)

5 4. Future plan In the future, ground trusting observation instruments such as wave-height meters (TWR- 2050), ADCP and RCM9 should be deployed to verify the radar measurements of waves and currents. References Gurgel, K.-W., G. Antonischki, H.-H. Essen and T. Schick, Wellen Radar (WERA), a new ground-wave based HF radar for ocean remote sensing. Coastal Engineering, VOL 37, NOS. 3-4, ISSN , pp Helzel, T History and Characteristics WERA ocean sensor.