Simultaneous observations of reflection echoes and refractive index gradient in the troposphere and lower stratosphere
Simultaneous observations of reflection echoes and refractive index gradient in the troposphere and lower stratosphere
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对流层和平流层低层反射回波和折射率梯度的同时观测
DOI：
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发表时间：
1988
期刊：
影响因子：
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通讯作者：
S. Fukao
中科院分区：
文献类型：
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作者：
T. Tsuda;P. May;Toru Sato;S. Kato;S. Fukao
通过同时观测平流层和对流层的垂直回波功率和温度廓线，研究了平流层下层晴空回波的一些特征。垂直回波功率由中高层大气（MU）雷达（35°N, 136°E）每隔75 m进行过采样，高度分辨率为150 m。在雷达观测期间，在MU雷达站发射了一个探空仪，测量温度、湿度和压力，高度分辨率为几十米，由此确定了广义势折射率的平均梯度M。在对流层下层（海拔10 km以下），由于湿度的作用，M增强了约10 ~ 20 dB，其精细结构主要由湿度垂直梯度决定。对流层回波功率随时间高度变化较大，可能与湿度廓线的快速变化有关。另一方面，在对流层上层（海拔10 km以上）和平流层，M的垂直结构主要由Brunt-Vaisala频率和空气密度决定，前者决定M的精细垂直结构，后者决定M在尺度高度约为7 km时的逐渐减小。实测的M2剖面与雷达高度分辨率为150 m的垂直回波功率剖面吻合良好。即反射系数的垂直结构主要由M2决定，因此3-m尺度波动的能量密度E（2k）似乎随高度均匀分布。强反射层的垂直间距通常在500 m到几公里之间，这与Brunt-Vaisala频率剖面中波动的主要垂直尺度相对应。强反射层的垂直分布似乎以斜率为- 3、垂直尺度为几公里的重力波饱和垂波数谱为主。
We have studied some characteristics of clear air echoes in the lower stratosphere and troposphere from simultaneous observations of vertical echo power and temperature profiles. The vertical echo power has been oversampled every 75 m with a height resolution of 150 m by the middle and upper atmosphere (MU) radar (35°N, 136°E). During the radar observations a radiosonde was launched at the MU radar site in order to measure temperature, humidity, and pressure with a height resolution of a few tens of meters, from which the mean gradient of generalized potential refractive index, M, was determined. In the lower troposphere (below 10 km altitude), M is enhanced owing to humidity by about 10–20 dB, and its fine structure is mainly determined by the vertical gradient of humidity. The relatively large time-height variation of tropospheric echo power seems to be attributed to rapid changes in the humidity profile. On the other hand, in the upper troposphere (above 10 km altitude) and stratosphere the vertical structure of M is mainly determined by the Brunt-Vaisala frequency and air density, where the former determines fine vertical structure of M and the latter the gradual decrease in M with a scale height of about 7 km. The measured M2 profile agrees well with the vertical echo power profile down to the radar height resolution of 150 m. That is, the vertical structure of the reflection coefficient is mainly determined by M2, and therefore the energy density of 3-m scale fluctuations E(2k) seems to be distributed uniformly with height. The vertical spacing of intense reflection layers usually ranges from 500 m to a few kilometers, which corresponds to the dominant vertical scale of fluctuations in the Brunt-Vaisala frequency profile. The vertical distribution of intense reflection layers seems to be explained by a predominance of a saturated vertical wave number spectrum of gravity waves with a slope of −3 and a dominant vertical scale of a few kilometers.