《高度的相关性分析datafroms波段雷达天顶指向新加坡》由会员分享，可在线阅读，更多相关《高度的相关性分析datafroms波段雷达天顶指向新加坡（7页珍藏版）》请在金锄头文库上搜索。
1、42 HEIGHT-CORRELATION ANALYSIS OF DATA FROM AN S-BAND ZENITH-POINTING RADAR IN SINGAPORE M. Thurai1*, V. N. Bringi1, Y. H. Lee2, L. S. Kumar2, J. D. Eastment3, and D. Ladd3 1Dept. of ECE, Colorado State University, Fort Collins, Colorado, USA 2School of Engineering, Nanyang Technological University,
2、 Singapore 3STFC Rutherford Appleton Laboratory, Chilton, Didcot, Oxon, UK 1, INTRODUCTION Information on height correlation of radar reflectivity (and rain rate) is useful for retrieving rain rates from satellite radar measurements. Due to surface back scatter “leakage” into range gates close to th
3、e surface (range-time sidelobes), the retrieval algorithms need to extrapolate from aloft (around 2 km height) to surface level, or what is termed as “near surface rain rate”. At present, the development of GPM retrieval algorithms for dual-wavelength radars is on-going, and in some cases, the algor
4、ithms require a priori constraints on the vertical covariances which need to be embedded in the algorithms in order to remove some of the unrealistic ambiguities that are present in the radar measurements (Tanelli, private communication). This paper presents height-correlations of radar reflectivity
5、 determined from a zenith-pointing S-band radar in Singapore. The radar was deployed in early 1998 and was operational for 4 years (Thurai et al., 2003). Figure 1 shows the radar location. Disdrometers, rain gauges, and several other instrumentations were also collocated at the radar site. From the
6、recorded events, several examples of stratiform and convective events have been chosen to determine the height correlations of radar reflectivity and rainfall rates, the latter using the appropriate Z-R relationships determined from a collocated JWD disdrometer. 2. INSTRUMENTATION AND DATA An overvi
7、ew of the radar hardware can be found in Thurai et al., (2003), and details of a similar system which was deployed in another tropical location can be found in Eastment et al., (1998). *Corresponding author: M. Thurai, Dept. of ECE, Colorado State University, Fort Collins, CO 80523. email: merhalaen
8、gr.colostate,edu The radar uses a 3 m-diameter dish antenna equipped with a dual-polarization (horizontal and vertical) feed. The antenna has a gain of 36.5 dBi, a 3- dB beamwidth of 2.3, and an integrated cross- polar isolation of around 25 dB. The transmitter uses a magnetron of 600 kW peak output
9、 power, operating at 3028 MHz. The radar operates at a PRF of 625 Hz with a pulse-length of 0.5 s. The ADC bank samples co- and cross-polar log video, co-polar I and Q, transmit-pulse I and Q, and transmitted power at a rate of 2 MHz. Transmitted polarization is always horizontal, with simultaneous
10、reception of horizontally and vertically polarized returns. The above parameters result in a maximum unambiguous range of 240 km, a maximum unambiguous velocity of around 15.5 m/s, and a range-resolution of 75 m. Data were generally recorded with an instrumented range of 0 to 45 km, and the number o
11、f pulses used is 64 or 256 in the vertically-pointing mode. The unique feature of these operating parameters is that a vertical profile of data is acquired in 0.1-0.4 s (as compared with VHF/UHF profilers which can take up to several minutes). Thus very high resolution is obtained both temporally an
12、d spatially, and in particular, for computing the vertical correlations of Z (Section 4). The Z, LDR, Doppler mean velocity (v) and spectral width (w) are recorded for each height-profile. Data from a collocated disdrometer (JWD) have been used to establish calibration as well as to determine suitab
13、le Z-R relations to determine rainfall rates from the radar measurements. (A comprehensive analysis of the disdrometer data has been published elsewhere, e.g. Kozu et al. 2006). 3. STRATIFROM AND CONVECTIVE EVENTS An example of a stratiform event is shown in Fig. 2 and an example of a convective eve
14、nt, followed by mixed and stratiform rain is shown in Fig. 3. In both cases, the top 3 panels show the height versus time series color-filled plots for (a) Z, (b) LDR, and (c) v. The melting layer is clearly visible at around 4.5 km in all 3 plots in Fig. 2, and especially so in the LDR plot. Fig. 1
15、: Map showing the radar location (red mark). The radar bright-band is also evident in Fig. 3, but only after 19:00. Between 19:30 and 20:30, the bright- band thickness is noticeably larger (than in Fig. 2(a) as is its reflectivity values and its height appears to be somewhat lowered, as seen more cl
16、early in LDR. The reflectivity in the rain region below is also larger, and LDR in rain appears to be detectable during this time period also. At some certain gates there appears clutter contamination (e.g. at around 3.5 km) perhaps due to near-by building scatter via the antenna sidelobes. The Doppler mean is particularly affected by such clutter (as expected). The 1-minute DSDs from t
