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Estimation of the Melting Layer from a Micro Rain Radar (MRR) data at the Cloud Physics Observation System (CPOS) site at Daegwallyeong Weather Station
根据大关岭气象站云物理观测系统 （CPOS） 站点的微雨雷达 （MRR） 数据估算熔化层

Joo-Wan Cha 1 , 2 1 , 2 ^(1,2){ }^{1,2}, Seong Soo Yum 1 1 ^(1){ }^{1}, Ki-Ho Chang 2 2 ^(2){ }^{2} and Sung Nam Oh 2 2 ^(2){ }^{2}
Joo-Wan Cha 1 , 2 1 , 2 ^(1,2){ }^{1,2} 、 Seong Soo Yum 1 1 ^(1){ }^{1} 、 Ki-Ho Chang 2 2 ^(2){ }^{2} 和 Sung Nam Oh 2 2 ^(2){ }^{2} 1 1 ^(1){ }^{1} Dept. of Atmospheric Sciences, Yonsei University
1 1 ^(1){ }^{1} 延世大学大气科学系 2 2 ^(2){ }^{2} Remote sensing Lab. METRI/KMA
2 2 ^(2){ }^{2} 遥感实验室 METRI/KMA

(Manuscript received 9 December 2006; in final form 2 February 2007)
（手稿于 2006 年 12 月 9 日收到;最终形式于 2007 年 2 月 2 日收到）

Abstract  抽象

For the first time in Korea, monthly mean melting layer height data measured by a Micro Rain Radar (MRR) is presented. Measurements are made at the Cloud Physic Observation System (CPOS) site at Daegwallyeong Weather Station ( 37 ∘ 41 N 37 ∘ 41 N 37^(@)41N37^{\circ} 41 \mathrm{~N}, 128 ∘ 46 E , 842 m ASL 128 ∘ 46 E , 842 m ASL 128^(@)46E,842mASL128^{\circ} 46 \mathrm{E}, 842 \mathrm{~m} \mathrm{ASL} ), located in Gangwon Province. An easy method is introduced to estimate the melting layer height from the MRR rain rate data in association with the bright band regions. This method seems to be reliable: for the carefully selected 20 cases, estimated freezing heights (the top of melting layer) from the MRR data match really well with those from the radiosonde data measured at Sokcho Weather Station. The melting layer height varied approximately between 3000 m to 4000 m for the year 2005 except January and December, when the melting layer heights were lower than 2000 m . It is also demonstrated that the MRR can be used to investigate the vertical structure of precipitation particle size distributions.
在韩国，首次提供了由微雨雷达 （MRR） 测量的月平均熔化层高度数据。测量是在位于江原道的大关岭气象站 （ 37 ∘ 41 N 37 ∘ 41 N 37^(@)41N37^{\circ} 41 \mathrm{~N} ， 128 ∘ 46 E , 842 m ASL 128 ∘ 46 E , 842 m ASL 128^(@)46E,842mASL128^{\circ} 46 \mathrm{E}, 842 \mathrm{~m} \mathrm{ASL} ） 的云物理观测系统 （CPOS） 站点进行的。引入了一种简单的方法，从与亮带区域相关的 MRR 降雨速率数据中估计熔化层高度。这种方法似乎是可靠的：对于精心挑选的 20 个案例，MRR 数据中估计的冻结高度（熔化层顶部）与束草气象站测量的无线电探空仪数据中的估计非常吻合。2005 年的熔化层高度大约在 3000 m 到 4000 m 之间变化，但 1 月和 12 月除外，当时熔化层高度低于 2000 m。研究还表明，MRR 可用于研究沉淀物粒度分布的垂直结构。

Key words: Micro Rain Radar, Melting Layer, Bright Band, Rain Rate, Precipitation Particle Size Distribution
关键词： 微雨雷达， 熔化层， 亮带， 降雨速率， 降水粒径分布

1. Introduction  1. 引言

Micro Rain Radar (MRR), a vertically point Doppler radar, is a very useful instrument to measure vertical profiles of precipitation particle size distributions and structures (Löffler-Mang and Kunz, 1999). One of the applications of an MRR is to estimate the melting layer height and depth. Melting layer is shown by a bright band (BB), a layer of enhanced radar reflectivity resulting from the difference in the dielectric factor for ice and water and the aggregation of ice particles as they descend and melt. The top of a melting layer is the melting level (or freezing height), commonly accepted as the altitude of the 0 ∘ C 0 ∘ C 0^(@)C0^{\circ} \mathrm{C} isotherm surface (Glickman, 2000). The existence of a melting layer leads to overestimation of precipitation
微型降雨雷达 （MRR） 是一种垂直点多普勒雷达，是测量降水粒度分布和结构垂直剖面的非常有用的仪器（Löffler-Mang 和 Kunz，1999 年）。MRR 的应用之一是估计熔化层的高度和深度。融化层由亮带 （BB） 表示，这是由于冰和水的介电因数不同以及冰粒子在下降和融化时聚集而形成的增强雷达反射率层。熔化层的顶部是熔化水平（或冻结高度），通常被认为是 0 ∘ C 0 ∘ C 0^(@)C0^{\circ} \mathrm{C} 等温线表面的高度（Glickman，2000 年）。熔化层的存在导致对降水的高估
intensities (Rico-Ramirez et al., 2005) since they are calculated simply by the reflected power. To solve the problem, several algorithms have been proposed to correct the effect of BB and the variation of the vertical profile of reflectivity (e. g., Song and Marwitz, 1989; Kitchen et al., 1994; Hardaker et al., 1995; Gray et al., 2002; Neiman et al., 2002) using singlepolarization reflectivity measurements.
强度（Rico-Ramirez et al.， 2005），因为它们只是通过反射功率计算的。为了解决这个问题，已经提出了几种算法来校正 BB 的影响和反射率垂直轮廓的变化（例如，Song 和 Marwitz，1989 年;Kitchen et al.， 1994;Hardaker 等人，1995 年;Gray 等人，2002 年;Neiman et al.， 2002）使用单偏振反射率测量。
Knowledge of the characteristics of melting layer is very useful to weather forecasters in predicting and monitoring the snow level, defined as the lowest level in a melting layer where snow or ice completely changes to rain. This information can also be useful to road maintenance workers, hydrologists, emergency managers, aviators and the ski industry (White et al., 2002). More importantly, the information of the freezing height and the melting layer are critically important in making decision to do seeding experiment or not and in establishing an optimal seeding strategy that may lead to most profitable output.
了解融化层的特性对于天气预报员预测和监测雪量非常有用，雪量定义为融雪层中雪或冰完全变为雨的最低水平。这些信息对道路维护工人、水文学家、应急管理人员、飞行员和滑雪行业也很有用（White et al.， 2002）。更重要的是，凝固高度和熔融层的信息对于决定是否进行晶种实验以及建立可能导致最有利可图产出的最佳晶种策略至关重要。
The main topic of this study is to introduce the method to estimate the freezing height and the melt-
本研究的主要主题是介绍估计凝固高度和熔融 -
ing layer depth, the altitude interval throughout which ice-phase precipitation melts as it descends, from the MRR output product. This study is the first attempt in Korea to estimate the monthly variation of the melting layer height and depth using the MRR output product.
ing 层深度，即冰相降水在下降时融化的高度间隔，来自 MRR 输出产品。这项研究是韩国首次尝试使用 MRR 输出产品估计熔化层高度和深度的月度变化。

2. Measurements  2. 测量

a. Measurement location and time
一个。测量位置和时间

The MRR measurements are made at the Cloud Physic Observation System (CPOS) site at Daegwallyeong Weather Station ( 37 ∘ 41 N , 128 ∘ 46 E , 842 m 37 ∘ 41 N , 128 ∘ 46 E , 842 m (37^(@)41(N),128^(@)46E,842(m):}\left(37^{\circ} 41 \mathrm{~N}, 128^{\circ} 46 \mathrm{E}, 842 \mathrm{~m}\right. ASL) in Gangwon Province. The MRR is one of several instruments that installed at the CPOS site for continuous measurements of cloud microphysical parameters, including a Forward Scattering Spectrometer Probe (FSSP), a microwave radiometers, and a distrometer. The CPOS site is established as a strategic site to measure basic cloud microphysics over the mountainous region in Gangwon Province, the ultimate purpose of which is to provide valuable information for feasibility studies of orographic cloud seeding experiments in Korea. This study analyzes the MRR data in 2005. The radiosonde site (Sokcho
MRR 测量是在江原道大关岭气象站 ( 37 ∘ 41 N , 128 ∘ 46 E , 842 m 37 ∘ 41 N , 128 ∘ 46 E , 842 m (37^(@)41(N),128^(@)46E,842(m):}\left(37^{\circ} 41 \mathrm{~N}, 128^{\circ} 46 \mathrm{E}, 842 \mathrm{~m}\right. ASL） 的云物理观测系统 （CPOS） 站点进行的。MRR 是安装在 CPOS 现场的用于连续测量云微物理参数的几台仪器之一，包括前向散射光谱仪探头 （FSSP）、微波辐射计和分布计。CPOS 站点是作为测量江原道山区基本云微物理学的战略站点而建立的，其最终目的是为韩国地形云播种实验的可行性研究提供有价值的信息。本研究分析了 2005 年的 MRR 数据。无线电探空仪站点（束草
Weather Station, 38 ∘ 28 N , 128 ∘ 52 E , 17.6 m ASL 38 ∘ 28 N , 128 ∘ 52 E , 17.6 m ASL 38^(@)28N,128^(@)52E,17.6mASL38^{\circ} 28 \mathrm{~N}, 128^{\circ} 52 \mathrm{E}, 17.6 \mathrm{~m} \mathrm{ASL} ) is located about 50 km northeast to the CPOS site.
气象站） 38 ∘ 28 N , 128 ∘ 52 E , 17.6 m ASL 38 ∘ 28 N , 128 ∘ 52 E , 17.6 m ASL 38^(@)28N,128^(@)52E,17.6mASL38^{\circ} 28 \mathrm{~N}, 128^{\circ} 52 \mathrm{E}, 17.6 \mathrm{~m} \mathrm{ASL} 位于 CPOS 站点东北约 50 公里处。

b. Measurement principles
b.测量原理

MRR is a vertically pointing FM-CW Doppler radar manufactured by MEteorologische messTEchniK GmbH (METEK), a German company. The specification of the MRR installed at the CPOS site is in Table 1. Conventional weather radars use the pulse radar mode while MRR uses a frequency modulated gunn-diode-oscillator with integrated mixing diode. Thus an MRR can measure precipitation particle size distributions. The CW-operation makes optimum use of the available transmit power. Thus a stable and reliable Gunn oscillator with only 50 mW output power can be used for transmitter. The retrieval of range-resolved Doppler spectra follows the method described by Strauch (1976). The MRR output products include the vertical structure of the radar reflectivity ( Z Z ZZ in dBZ ), liquid water content (LWC in g / m 3 g / m 3 g//m^(3)\mathrm{g} / \mathrm{m}^{3} ), rain rate ( RR in mm / h mm / h mm//h\mathrm{mm} / \mathrm{h} ), and falling velocity ( v v vv in m / s m / s m//s\mathrm{m} / \mathrm{s} ). Briefly how the output products are obtained is explained below.
MRR 是由德国公司 MEteorologische messTEchniK GmbH （METEK） 制造的垂直指向 FM-CW 多普勒雷达。表 1 中介绍了安装在 CPOS 站点的 MRR 的规格。传统的天气雷达使用脉冲雷达模式，而 MRR 使用带有集成混频二极管的调频耿氏二极管振荡器。因此，MRR 可以测量沉淀物粒度分布。CW 作充分利用了可用的发射功率。因此，输出功率仅为 50 mW 的稳定可靠的 Gunn 振荡器可用于发射器。距离分辨多普勒光谱的检索遵循 Strauch （1976） 描述的方法。MRR 输出产品包括雷达反射率 （ Z Z ZZ in dBZ ）、液态水含量 （LWC in g / m 3 g / m 3 g//m^(3)\mathrm{g} / \mathrm{m}^{3} ）、降雨率 （ RR in mm / h mm / h mm//h\mathrm{mm} / \mathrm{h} ） 和下落速度 （ v v vv in m / s m / s m//s\mathrm{m} / \mathrm{s} ） 的垂直结构。下面简要说明如何获得输出产品。
The rain rate (RR) is obtained by integration over the precipitation particle size distribution:
降雨率 （RR） 是通过对降水粒度分布进行积分获得的：
Table 1. The specification of the MRR at the CPOS site.
表 1.CPOS 站点的 MRR 规范。
Specification  规范 MRR
Transmit frequency  发射频率 24 GHz (K-band)  24 GHz（K 波段）
Transmit power  发射功率 50 mW  50 毫瓦
Receiver-Transmitter Antenna
接收器-发射天线		 offset -parabolic, 0.6 m diameter
偏移 - 抛物线形，直径 0.6 m
Beam Width  光束宽度 1-way, 3 dB  1 分频，3 dB
Modulation:  调制：

调频连续波
Frequency modulated
continuous wave
Frequency modulated continuous wave| Frequency modulated | | :--- | | continuous wave |
Height resolution  高度分辨率 35 ∼ 200 m 35 ∼ 200 m 35∼200m35 \sim 200 \mathrm{~m}
Averaging time  平均时间 10 ∼ 3600 s 10 ∼ 3600 s 10∼3600s10 \sim 3600 \mathrm{~s}
Height range  高度范围 29 range gates from 2 X range resolution to 30 X range resolution
29 个范围门，范围分辨率从 2 倍到 30 倍范围分辨率
Measured variables  测量变量 average power spectra of the receiving signal with 2048 lines resolution
接收信号的平均功率谱，分辨率为 2048 线
Interface  接口 RS232 9600 ∼ 57600 9600 ∼ 57600 9600∼576009600 \sim 57600 Baud  RS232 9600 ∼ 57600 9600 ∼ 57600 9600∼576009600 \sim 57600 波特率
Power supply  电源 24 VDC / 10 W 24 VDC / 10 W 24VDC//10W24 \mathrm{VDC} / 10 \mathrm{~W}
Weight  重量 12 kg  12 千克
Dimensions  尺寸 0.6 m 3 0.6 m 3 0.6m^(3)0.6 \mathrm{~m}^{3}
Specification MRR Transmit frequency 24 GHz (K-band) Transmit power 50 mW Receiver-Transmitter Antenna offset -parabolic, 0.6 m diameter Beam Width 1-way, 3 dB Modulation: "Frequency modulated continuous wave" Height resolution 35∼200m Averaging time 10∼3600s Height range 29 range gates from 2 X range resolution to 30 X range resolution Measured variables average power spectra of the receiving signal with 2048 lines resolution Interface RS232 9600∼57600 Baud Power supply 24VDC//10W Weight 12 kg Dimensions 0.6m^(3)| Specification | MRR | | :--- | :--- | | Transmit frequency | 24 GHz (K-band) | | Transmit power | 50 mW | | Receiver-Transmitter Antenna | offset -parabolic, 0.6 m diameter | | Beam Width | 1-way, 3 dB | | Modulation: | Frequency modulated <br> continuous wave | | Height resolution | $35 \sim 200 \mathrm{~m}$ | | Averaging time | $10 \sim 3600 \mathrm{~s}$ | | Height range | 29 range gates from 2 X range resolution to 30 X range resolution | | Measured variables | average power spectra of the receiving signal with 2048 lines resolution | | Interface | RS232 $9600 \sim 57600$ Baud | | Power supply | $24 \mathrm{VDC} / 10 \mathrm{~W}$ | | Weight | 12 kg | | Dimensions | $0.6 \mathrm{~m}^{3}$ |
R R = π 6 ∫ 0 ∞ N ( D ) D 3 v ( D ) d D R R = π 6 ∫ 0 ∞   N ( D ) D 3 v ( D ) d D RR=(pi)/(6)int_(0)^(oo)N(D)D^(3)v(D)dDR R=\frac{\pi}{6} \int_{0}^{\infty} N(D) D^{3} v(D) d D
The precipitation particle size distribution ( N ( D ) ) ( N ( D ) ) (N(D))(N(D)) is given
给出了沉淀粒径分布 ( N ( D ) ) ( N ( D ) ) (N(D))(N(D))
N ( D ) = η ( D ) σ ( D ) N ( D ) = η ( D ) σ ( D ) N(D)=(eta(D))/(sigma(D))N(D)=\frac{\eta(D)}{\sigma(D)}
where D D DD is raindrop diameter, σ ( D ) σ ( D ) sigma(D)\sigma(D) is the backscattering cross-section, and η ( D ) η ( D ) eta(D)\eta(D) is the spectral reflectivity as a function of D D DD, which is related to v v vv, as
其中 D D DD 是雨滴直径， σ ( D ) σ ( D ) sigma(D)\sigma(D) 是背向散射截面， η ( D ) η ( D ) eta(D)\eta(D) 是光谱反射率与 D D DD 的函数关系，如 v v vv 。
η ( D ) = η ( v ) ∂ ( v ) ∂ ( D ) η ( D ) = η ( v ) ∂ ( v ) ∂ ( D ) eta(D)=eta(v)(del(v))/(del(D))\eta(D)=\eta(v) \frac{\partial(v)}{\partial(D)}
where η ( v ) η ( v ) eta(v)\eta(v) is the spectral volume reflectivity as a function of v v vv. The falling velocity is estimated by the spectra volume reflectivity,
其中 η ( v ) η ( v ) eta(v)\eta(v) 是光谱体积反射率与 的函数关系。 v v vv 下落速度由光谱体积反射率
v = λ 2 ∫ 0 ∞ η ( f ) f d f ∫ 0 ∞ η ( f ) d f v = λ 2 ∫ 0 ∞   η ( f ) f d f ∫ 0 ∞   η ( f ) d f v=(lambda)/(2)(int_(0)^(oo)eta(f)fdf)/(int_(0)^(oo)eta(f)df)v=\frac{\lambda}{2} \frac{\int_{0}^{\infty} \eta(f) f d f}{\int_{0}^{\infty} \eta(f) d f}
where λ λ lambda\lambda is wavelength.
其中 λ λ lambda\lambda 是波长。
The relation between falling velocity and drop diameter has been expressed by appropriated analytical form by Atlas et al. (1973)
下落速度和液滴直径之间的关系由 Atlas 等人 （1973） 用适当的分析形式表示
v ( D ) = 9.65 − 10.3 ∗ Exp ( − 0.6 D ) v ( D ) = 9.65 − 10.3 ∗ Exp ( − 0.6 D ) v(D)=9.65-10.3**Exp(-0.6D)v(D)=9.65-10.3 * \operatorname{Exp}(-0.6 \mathrm{D})
where 0.109 mm ≤ D ( mm ) ≤ 6 mm 0.109 mm ≤ D ( mm ) ≤ 6 mm 0.109mm <= D(mm) <= 6mm0.109 \mathrm{~mm} \leq \mathrm{D}(\mathrm{mm}) \leq 6 \mathrm{~mm}.  其中 0.109 mm ≤ D ( mm ) ≤ 6 mm 0.109 mm ≤ D ( mm ) ≤ 6 mm 0.109mm <= D(mm) <= 6mm0.109 \mathrm{~mm} \leq \mathrm{D}(\mathrm{mm}) \leq 6 \mathrm{~mm} .
The Z Z ZZ and LWC are defined by the precipitation particle size distribution,
和 Z Z ZZ LWC 由沉淀粒径分布
Z = ∫ 0 ∞ N ( D ) D 6 d D Z = ∫ 0 ∞   N ( D ) D 6 d D Z=int_(0)^(oo)N(D)D^(6)dDZ=\int_{0}^{\infty} N(D) D^{6} d D
L W C = ρ w π 6 ∫ 0 ∞ N ( D ) D 3 d D L W C = ρ w π 6 ∫ 0 ∞   N ( D ) D 3 d D LWC=rho_(w)(pi)/(6)int_(0)^(oo)N(D)D^(3)dDL W C=\rho_{w} \frac{\pi}{6} \int_{0}^{\infty} N(D) D^{3} d D
where ρ w ρ w rho_(w)\rho_{w} is the density of water.
其中 ρ w ρ w rho_(w)\rho_{w} 是水的密度。
To estimate the impact of using Mie theory for computing the backscatter cross-section (Löffler-Mang and Kunz, 1999), the backscattering cross-section σ Mie σ Mie  sigma_("Mie ")\sigma_{\text {Mie }} of a dielectric sphere for a plane electromagnetic wave is given by
为了估计使用 Mie 理论计算反向散射截面的影响（Löffler-Mang 和 Kunz，1999 年），平面电磁波的介电球的反向散射截面 σ Mie σ Mie  sigma_("Mie ")\sigma_{\text {Mie }} 由下式给出
σ M i e = λ 2 4 π | ∑ n = 1 ∞ ( − 1 ) n ( 2 n + 1 ) ( a n − b n ) | 2 σ M i e = λ 2 4 π ∑ n = 1 ∞   ( − 1 ) n ( 2 n + 1 ) a n − b n 2 sigma_(Mie)=(lambda^(2))/(4pi)|sum_(n=1)^(oo)(-1)^(n)(2n+1)(a_(n)-b_(n))|^(2)\sigma_{M i e}=\frac{\lambda^{2}}{4 \pi}\left|\sum_{n=1}^{\infty}(-1)^{n}(2 n+1)\left(a_{n}-b_{n}\right)\right|^{2}
where a n a n a_(n)a_{n} an b n b n b_(n)b_{n} are derived from Bessel and Hankel function.
其中 a n a n a_(n)a_{n} an b n b n b_(n)b_{n} 派生自 Bessel 和 Hankel 函数。
The vertical resolution is 200 m for the first two months in 2005 (January and February) and 150 m for the rest of the year. Time resolution of the MRR observation is 1 min .
2005 年前两个月（1 月和 2 月）的垂直分辨率为 200 米，其余时间为 150 米。MRR 观测的时间分辨率为 1 min。
Fig. 1. Schematic diagram that shows how to estimate of the melting layer from MRR data.
图 1.显示如何从 MRR 数据估计熔化层的示意图。
  1. Corresponding Author: Joo-Wan Cha, Dept. of Atmospheric sciences, Yonsei University, 134 Shinchon-dong, Seodaemun-gu, Seoul, Korea.
    通讯作者：Joo-Wan Cha，延世大学大气科学系，韩国首尔市西大门区新村洞 134 号。
    Phone : +82-2-2123-7613, Fax : +82-2-365-5163
    电话 ： +82-2-2123-7613， 传真 ： +82-2-365-5163
    E-mail: jwcha@yonsei.ac.kr
    电子邮件： jwcha@yonsei.ac.kr