Environmental Effects On Continuous GPS Station Time Series

Environmental factors will cause a deformation of the earth surface. From the past study, the environment will cause dozens of millimeters in vertical displacement of the earth surface. The environmental impact on horizontal displacement is only 1/10 to 1/3 of that on vertical displacement. The impact of environmental factors on the station has seriously polluted the GPS time accuracy, so the environmental factors must be removed from the station displacement time series in the high precision space geodesy field.Based on the theory of elasticity of the earth’s surface loading, convolution integration was proceeded between environmental factors and station GPS data including the latest atmosphere, non-tidal ocean, temperature and the land-water data:In order to analyze the 24 stations’vertical and horizontal movement in the crustal movement monitoring network of China caused by the environmental factors, the spherical harmonic function approach or green’s function loading approach are used. Analysis of environmental factors correction and local meteorological factors in the six stations of Shandong province was made; and then, the displacements of the seasonal variation characteristics was analyzed by comparing the GPS data before or after the environmental factors were corrected.Research shows that:the effect of environmental factors on the GPS vertical displacements is significant and on the horizontal displacement is small that can even be neglected. Vertical displacement on the stations caused by atmospheric loading influence can be up to 16 millimeters,4 millimeters by non-tidal ocean influence, within 1 millimeter by the temperature change influence, within 7 millimeters by atmospheric humidity, and 5 millimeters by groundwater influence in Shandong province. The effect of environmental factors on the station’s vertical displacement shows obvious cycle characteristics, which is consistent with the seasonal variation characteristics in our country. Phase in anniversary appear in August or September by atmospheric loading influence, non-tidal ocean influence. Phase in semi-anniversary appear in December or January by temperature change influence, atmospheric humidity change influence, land-water loading influence, underground water change influence. From the result, we can see that the environmental influence can be 80 percents of errors on the vertical displacement on the stations in Shandong province. And comparing the GPS data after the merger of correction value with the original, we can find that there are some deviations. The reasons are multi-faceted and complex. In this paper, we will try to probe them.There are two main innovations. The first one is that the latest environmental dataset are used on the stations’displacement study and the results can be used to explain how much degree GPS observation reflects the crustal deformation, so as to provide references for the GPS data processing. The second one is that research of local meteorological factors affect on vertical displacement of the GPS stations was proposed for the first time in Shandong province, and the research results can provide some references for other regions.