山基GPS掩星与自动气象站观测结果比较

Comparison between mountain-based GPS occultation observations and results from automatic weather station

山基GPS掩星技术可以精确获得低层大气折射率信息,其观测原理是：在高山的山顶安装GPS接收机,跟踪GPS卫星的低仰角和负仰角信号,通过载波相位的变化求出大气折射造成的弯曲角剖面,从而利用科学反演方法获得观测点高度以下的大气折射率剖面.为了对山基掩星测量数据进行验证,2005年8月1日-29日,在河北雾灵山（40.60°N,117.48°E,2118m）开展了为期一个月的山基GPS掩星观测与其他探测的对比实验.实验所用的JAVAD双频GPS接收机共工作576小时,接收机朝南观测,记录到山基掩星事件1136次,其中上升掩星621次,下降掩星515次.实验期间,在雾灵山顶利用自动气象观测仪每天24小时观测当地的温度、湿度和气压,由此可计算大气折射率.本文利用雾灵山GPS掩星实验所获得的观测数据,成功反演得到大气折射率剖面,并将所得接收机高度的折射率与雾灵山顶自动气象站观测结果进行比对,分析结果表明：山基GPS掩星和自动气象站观测结果是一致的.山基GPS掩星观测可为低层大气环境监测提供大量数据,具有潜在的应用前景.

Mountain-based GPS occuhation technique can measure the profile of the lower atmospheric refractivity exactly, its observation theory is to install the GPS receiver at the top of high mountain and receive the radio signals of GPS satellites with very low elevations and negative elevations, and we can obtain the profile of the bending angle due to atmospheric refraction through the change of carrier wave＇s phase, then the refractivity profile below the altitude in which the receiver is located can be retrieved by using some inversion method. An mountain-based GPS occultation observation experiment of one month was performed at Mt. WuLing（40.60°N, 117,48°E, 2118m） in HeBeiprovince during August 1-29, 2005. TheJAVAD receiver we used has worked for about 576 hour, and theJAVAD receiver is installed towards south. Totally 1136 occultation events were recorded. Out of the total occultation events, 621 events are rising occultation events and 515 events are setting occultation events. During the experiment, the automatic weather station at the top of Mt. WuLing can observe the local temperature, humidity and pressure all day, from which we can calculate the atmospheric refractivity. In this paper, we retrieved the atmospheric refractivity success fully using the observation data of mountain based GPS occultation observation experiment at Mt. WuLing, and then compared the refractivity of the altitude in which the receiver is located with the result of automatic weather station. The result illustrates a good agreement in mountain-based GPS occultation and automatic weather station. Mountainbased occultation observations provide a lot of refractivity data for monitoring lower atmospheric environment. This novel technique has potential applications.