Thermal effects on vertical displacement of GPS stations in China

The temperature of GPS concrete pillar can be influenced by the surface air temperature changes. For the above ground and underground parts of the GPS concrete pillar, both inner temperatures vary with the surface air temperature changes by heat conduction effects. The temperature change of GPS concrete pillar will cause a vertical displacement of the GPS antenna. The annual amplitude of GPS vertical displacement induced by the temperature change of underground concrete pillar can reach to 1 mm in China, and exceeds 0.5 mm in the area north of Changjiang River. The maximum annual amplitude of GPS vertical displacement induced by the temperature change in both above- and under-ground parts of GPS concrete pillar is 2. 8 mm for the 23 GPS stations of the Crustal Movement Observation Network of China (CMONOC). Meanwhile, the annual amplitudes of 13 GPS stations exceed 1 mm in the 23 GPS stations of the CMONOC. Thus, thermal effects on the GPS vertical displacement are a very important factor to explain the annual variations of GPS vertical displacement.