出版日期: 2016-11-25点击次数：下载次数：DOI: 10.11834/jrs.201653112016 | Volumn20 | Number 6 上一篇|

FY-3C微波温度计资料的台风“威马逊”垂直结构研究

1. 南京信息工程大学 气象灾害教育部重点实验室，气候与环境变化国际合作联合实验室，气象灾害预报预警与评估协同创新中心资料同化研究与应用中心，江苏 南京 210044
2. 海南省南海气象防灾减灾重点实验室，海南 海口 570203
3. 江苏省气象局 公共服务中心，江苏 南京 210008
4. 海南省气象局 气象服务中心，海南 海口 570203
5. 民航西北空管局 气象中心, 陕西 西安 710082
 收稿日期: 2015-12-29; 优先数字出版日期: 2016-11-25 基金项目: 南京信息工程大学人才启动费（编号：S8113066001）；南海气象防灾减灾重点实验室开放基金（编号：SCSF201402）；国家自然科学基金(编号：41365005) 第一作者简介: 王祥(1983—)，男，博士，讲师，从事卫星资料研究与应用方面工作。E-mail： wangxiang@nuist.edu.cn 中图分类号: P407.7 文献标识码: A

# 关键词

Investigating the vertical structure of typhoon “Rammasun” using FY-3C MWTS measurements
WANG Xiang1,2 , REN Yifang3 , LI Xun4 , HE Xiaodong5
1.Key Laboratory of Meteorological Pisaster, Ministry of Education, Joint International Research Laboratory of Climate and Environment change, Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters, Center of Data Assimilation for Research and Application, Nanjing University of Information Science and Technology, Nanjing 210044, China
2.Key Laboratory of South China Sea Meteorological Disaster Prevention and Mitigation of Hainan Province, Haikou 570203, China
3.Meteorological Bureau in Jiangsu Province, Nanjing 210008, China
4.Hainan Meteorological Service, China Meteorological Administration, Haikou 570203, China
5.Meteorological Center, Northwest Regional Air Traffic Management Bureau of Civil Aviation of China, Xi’an 710082, China

# Abstract

Owing to the deficiency of conventional observations over oceans, particularly under typhoon conditions, numerical simulation has become the foremost approach to the study of the thermal and dynamic structures of typhoons, and the accuracy of the numerical simulation depends on the initial structure of the typhoon and the accuracy of the model. As the first operational satellite, FY-3C was successfully launched into a morning-configured orbit on September 23, 2013. The MWTS onboard the FY-3C is designed with significantly more channels, finer spatial resolution, and better sensor precision than those of FY-3A and FY-3B.Moreover, the observed radiance is insignificantly affected by non-precipitating clouds, making MWTS measurements more suitable to detect the thermal features of typhoons.Radiance in the microwave band is linearly proportional to the entire layer of atmospheric temperature. The weighting functions of all the sounding channels of MWTS are substantially steady, and atmospheric temperature at a given pressure can be expressed as a linear combination of brightness temperatures measured at certain sounding channels. In this study, a stepwise linear regression analysis with a 1% significance level is used. Under a clear-sky condition, the brightness temperatures at channels 3-10 are used to retrieve the temperatures at 21 pressure levels ranging from 100 hPa to 1000 hPa, but channels 3 and 4 are not used for retrieval under precipitation conditions. When the temperature profiles are retrieved, the tangential winds around typhoon “Rammasun” are calculated using hydrostatic equilibrium and gradient balance equations based on the retrieved temperature profiles.Under a clear-sky condition, the root-mean-square error of the retrieved temperature is 1.4 K at the most and even lower than 1.1 K in the upper troposphere and lower stratosphere. These error values are sufficiently low; thus, the thermal structure of typhoons can be monitored. Applied to the super typhoon “Rammasun”, the method excellently described the warm core eye and the temperature gradients across the eyewall. The results generated by the proposed method are more accurate than the results generated from the NCEP reanalysis data. The warm core is identified throughout the troposphere, with maximum temperatures ranging from 8 °C to 10 °C near 200 hPa; the warm core extends to the sea surface. This finding on the warm core is seemingly more realistic compared with the typical one. From the anomaly field, the radius of the typhoon eye at the sea surface is approximately 100 km, and the eye tilts outward with height. The maximum wind speed radius is approximately 80 km, and the maximum wind speed can reach up to 51 m/s.Among the most important parameters in monitoring typhoon intensity, studying typhoon inner core dynamics, and constructing the initial vortex for a typhoon simulation, the three-dimensional warm core and tangential wind features derived from FY-3C MWTS measurements are investigated in this study. Evidently, MWTS has considerable potential for improving our knowledge of typhoons and hurricanes. However, only a single typhoon case is analyzed in this study; more cases should be studied to verify the retrieval method.

# Key words

MWTS , typhoon , warm core , tangential wind

# 2 资料与台风个例介绍

## 2.1 研究资料介绍

Table 1 Channel characteristics of MWTS

 通道 中心频率/GHz 精度/K 带宽 /MHz 权重函数峰值高度/hPa 1 50.300 1.20 180 地表 2 51.760 0.75 400 地表 3 52.800 0.75 400 950 4 53.596 0.75 400 700 5 54.400 0.75 400 400 6 54.940 0.75 400 270 7 55.500 0.75 330 180 8 57.290(ƒ 0) 0.75 330 90 9 ƒ 0±0.217 1.20 78 50 10 ƒ 0±0.322±0.048 1.20 36 20 11 ƒ 0±0.322±0.022 1.70 16 12 12 ƒ 0±0.322±0.010 2.40 8 5 13 ƒ 0±0.322±0.005 3.60 3 2

## 2.2 台风“威马逊”介绍

2014年7月9日，一个低压区在楚克东部的西北太平洋面上生成，至2014-07-09 UTC 08左右加强为热带风暴。随后几天，由于环境条件好，热带风暴逐渐加强并稳定西移，在15—16日加强为台风，穿过菲律宾中部进入南海。虽然台风登陆菲律宾后有所减弱，但在进入南海后，受惠于良好的大气环境及高水温，重新组织与增强，中心气压呈下降趋势，至18日凌晨，上升为超强台风“威马逊”，中心附近最大风速52 m/s，最低气压935 hPa。当日下午3时半，“威马逊”以颠峰强度于中国海南省文昌市翁田镇沿海短暂登陆，在重创了海南后便进入海南和雷州之间的琼州海峡。 图 2给出了2014-07-18 UTC 13:53 MWTS通道1的观测亮温在台风“威马逊”周围的空间分布，台风中心在北纬20.3°，东经110.3°。总体而言，陆地的观测亮温明显高于海洋，这是由于海水的地表发射率远低于陆地引起的；再者，可以看到海南岛的西边小块区域的观测亮温也明显低于其他陆地地区(卫星云图略)，这是因为台风螺旋雨带致使MWTS通道1只能探测到螺旋雨带顶部的辐射。

# 3 反演方法与结果

## 3.1 大气温度反演方法与结果

FY-3C MWTS通道的中心频率位于50—60 GHz，处于氧气的吸收带上，氧气在大气的分布均匀而且稳定，因此MWTS各通道的权重函数的分布相当稳定；另外，MWTS各大气探测通道测得的微波辐射与大气各层的物理温度成线性关系。因而MWTS各大气探测通道的观测亮温值可以用来反演大气垂直温度廓线，具体地可以将大气各层的物理温度表示成多个大气探测通道观测亮温的线性组合( Janssen，1993)，公式如下

 \begin{aligned} T(p)={{\beta }_{0}}(p,\theta )+\sum\limits_{i=1}^{n}{{{\beta }_{i}}(p,\theta ){{T}_{\rm b}}({{\upsilon }_{i}},\theta )} \end{aligned} (1)

## 3.2 水平切向风反演方法与结果

 \begin{aligned} {{T}_{i}}=\sum{{{w}_{k}}{{T}_{k}}}/\sum{{{w}_{k}}} \end{aligned} (2)

 \begin{aligned} {{w}_{k}}=\exp [-{{({{r}_{i}}-{{r}_{k}})}^{2}}/r_{\text{e}}^{2}] \end{aligned} (3)

 $\frac{\partial \Phi (p)}{\partial \ln p}=-{{R}_{\text{d}}}{{t}_{\text{v}}}(p)$ (4)

 $F(p,r)=-\frac{\partial \Phi (p,r)}{\partial r}$ (5)

 \begin{aligned} \frac{v_{t}^{2}(p,r)}{r}+{{f}_{c}}{{v}_{t}}(p,r)-F(p,r)=0 \end{aligned} (6)

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