Abstract The three dimensional distribution of water vapour around mountainous terrain can be highly variable. This variability can in turn affect local meteorological processes and geodetic techniques to measure ground surface motion. We demonstrate this general problem with the specific issues of a small tropical island, Montserrat. Over a period of 17 days in December 2014 we made observations using InSAR and GPS techniques, together with concurrent atmospheric models using the WRF code. Comparative studies of water vapour distribution and its effect on refractivity were made at high spatial resolution (300 m) over short distances (~10 km). Our results show that model simulations of the observed differences in water vapour distribution using WRF is insufficiently accurate. We suggest that better use could be made of the knowledge and observations of local water vapour conditions at different scales, specifically the Inter Tropical Convergence Zone (ITCZ), the trade wind fields and the mountain flow (~30 m) perhaps using eddy simulation. The annual perturbations of the ITCZ show that the range of humidity is approximately the same expressed as the differential phase of InSAR imaging (~100 mm). Trade wind direction and speed are particularly important at high wind speeds driving vigorous asymmetrical convection over the island's mountains. We also show that the slant angles of radar can follow distinct separate paths through the water vapour field. Our study is novel in demonstrating how synoptic-scale features and climate can advise the modelling of mesoscale systems and sub-seasonal InSAR imaging on tropical islands.

中文翻译：

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使用 InSAR 和大地测量观测大气模型绘制山区热带岛屿上的水汽变化

摘要 山区周围水汽的三维分布变化很大。这种可变性反过来会影响当地的气象过程和测量地表运动的大地测量技术。我们通过一个热带小岛蒙特塞拉特的具体问题来证明这个普遍问题。在 2014 年 12 月的 17 天里，我们使用 InSAR 和 GPS 技术以及使用 WRF 代码的并发大气模型进行了观测。在高空间分辨率 (300 m) 下短距离 (~10 km) 对水蒸气分布及其对折射率的影响进行了比较研究。我们的结果表明，使用 WRF 对观察到的水汽分布差异的模型模拟不够准确。我们建议可以更好地利用不同尺度的当地水汽条件的知识和观察，特别是热带辐合带 (ITCZ)、信风场和山流 (~30 m)，也许使用涡流模拟。ITCZ 的年度扰动表明，湿度范围与 InSAR 成像的微分相位（~100 mm）大致相同。信风的方向和速度在高风速下尤其重要，在岛上的山脉上驱动着强烈的不对称对流。我们还表明，雷达的倾斜角可以沿着不同的独立路径穿过水汽场。