Typhoon 9707 observations with the MU radar and L-band boundary layer radar

International audienceTyphoon 9707 (Opal) was observed with the VHF-band Middle and Upper atmosphere (MU) radar, an L-band boundary layer radar (BLR), and a vertical-pointing C-band meteorological radar at the Shigaraki MU Observatory in Shiga prefecture, Japan on 20 June 1997. The typhoon center passed about 80 km southeast from the radar site. Mesoscale precipitating clouds developed due to warm-moist airmass transport from the typhoon, and passed over the MU radar site with easterly or southeasterly winds. We primarily present the wind behaviour including the vertical component which a conventional meteorological Doppler radar cannot directly observe, and discuss the relationship between the wind behaviour of the typhoon and the precipitating system. To investigate the dynamic structure of the typhoon, the observed wind was divided into radial and tangential wind components under the assumption that the typhoon had an axi-symmetric structure. Altitude range of outflow ascended from 1?3 km to 2?10 km with increasing distance (within 80?260 km range) from the typhoon center, and in-flow was observed above and below the outflow. Outflow and inflow were associated with updraft and downdraft, respectively. In the tangential wind, the maximum speed of counterclockwise winds was confirmed at 1?2 km altitudes. Based on the vertical velocity and the reflectivity obtained with the MU radar and the C-band meteorological radar, respectively, precipitating clouds, accompanied by the wind behaviour of the typhoon, were classified into stratiform and convective precipitating clouds. In the stratiform precipitating clouds, a vertical shear of radial wind and the maximum speed of counterclockwise wind were observed. There was a strong reflectivity layer called a ?bright band' around the 4.2 km altitude. We confirmed strong updrafts and down-drafts below and above it, respectively, and the existence of a relatively dry layer around the bright band level from radiosonde soundings. In the convective precipitating clouds, the regions of strong and weak reflectivities were well associated with those of updraft and downdraft, respectively

Combined wind profiler-weather radar observations of orographic rainband around Kyushu, Japan in the Baiu season

International audienceA special observation campaign (X-BAIU), using various instruments (wind profilers, C-band weather radars, X-band Doppler radars, rawinsondes, etc.), was carried out in Kyushu (western Japan) during the Baiu season, from 1998 to 2002. In the X-BAIU-99 and -02 observations, a line-shaped orographic rainband extending northeastward from the Koshikijima Islands appeared in the low-level strong wind with warm-moist airs. The weather radar observation indicated that the rainband was maintained for 11h. The maximum length and width of the rainband observed in 1999 was ~200km and ~20km, respectively. The rainband observed in 2002 was not so developed compared with the case in 1999. The Froude number averaged from sea level to the top of the Koshikijima Islands (~600m) was large (>1), and the lifting condensation level was below the tops of the Koshikijima Islands. Thus, it is suggested that the clouds organizing the rainband are formed by the triggering of the mountains on the airflow passing over them. The vertical profile of horizontal wind in/around the rainband was investigated in the wind profiler observations. In the downdraft region 60km from the Koshikijima Islands, strong wind and its clockwise rotation with increasing height was observed below 3km altitude. In addition, a strong wind component perpendicular to the rainband was observed when the rainband was well developed. These wind behaviors were related to the evolution of the rainband

Metallic Cylinder Reflected Power Measurement For 93.1GHz Frequency Modulated Continuous Wave Radar Calibration

A metallic cylinder is one of the best materials and shapes to calibrate a radar system performance. The measurement of a 4cm diameter and 3cm-height metallic cylinder as a target has been presented for the analysis at the millimeter-wave (mm-wave) spectrum. This experiment was conducted in a real airport environment at Kuala Lumpur International Airport considering clear sky conditions. The measurement was carried out at 93.1 GHz which uses Frequency Modulated Continuous Wave (FMCW) radar to consistently detect the target. The radar cross-section (RCS) of the metallic cylinder is measured with respect to the angle of runway pavement. It is found that the measurements exhibited smaller RCS value with an average of –43.47 dBsm at a longer range compared to –30.16 dBsm at a shorter range with a total change of 13.31 dBsm. The reflectivity characteristics of the radar target, theoretical measurement of the metallic cylinder, its incident angle from the radar target, and measurement evaluation are presented in this paper

Metallic Cylinder Reflected Power Measurement For 93.1GHz Frequency Modulated Continuous Wave Radar Calibration

A metallic cylinder is one of the best materials and shapes to calibrate a radar system performance. The measurement of a 4cm diameter and 3cm-height metallic cylinder as a target has been presented for the analysis at the millimeter-wave (mm-wave) spectrum. This experiment was conducted in a real airport environment at Kuala Lumpur International Airport considering clear sky conditions. The measurement was carried out at 93.1 GHz which uses Frequency Modulated Continuous Wave (FMCW) radar to consistently detect the target. The radar cross-section (RCS) of the metallic cylinder is measured with respect to the angle of runway pavement. It is found that the measurements exhibited smaller RCS value with an average of –43.47 dBsm at a longer range compared to –30.16 dBsm at a shorter range with a total change of 13.31 dBsm. The reflectivity characteristics of the radar target, theoretical measurement of the metallic cylinder, its incident angle from the radar target, and measurement evaluation are presented in this paper

Line of sight visibility analysis for foreign object debris detection system

It is challenging to monitor busy airports' runway through visual inspection to precisely detect foreign object debris. Currently, many technologies for the detection of foreign object debris are available. It has been investigated that millimeter-wave radar technology's detection capability can be one of the most effective techniques for detecting foreign object debris as it is weather-resilient. However, the positioning and height of a millimeter-wave radar pole covering the runway area, considering the existing runway infrastructure, are challenging. The task involves finding the appropriate placement and optimum height. This paper presents a novel method of line of sight visibility for placement and height of radar pole using human factor research to ensure that each point on the runway is visible from various heights of the millimeter-wave radar pole to the runway locations. Kuala Lumpur International Airport, Malaysia runway 32L/14R, has used a case study to test the visibility analysis. The visual analytic test's successful results for different millimeter-wave radar pole locations and viewing heights under a visible and invisible line of sight conditions on the runway have been verified in the field experiment