The Second Term Site Survey in Gaomeigu, Lijiang—Determination of the Ground-height for the Telescope

As a basic work of the site survey in Gaomeigu, Lijiang, we have determined the ground-height for the telescope by using micro-thermal sensors installed on a 30m meteorological tower at No.6 site of Gaomeigu. The micro-thermal sensors are installed at three levels of the tower and can be flexibly moved along the tower in terms of measured height. The measured principle is that the variation profile of the temperature structure parameter C_T² along the ground-height determines the ground-height for the teleseope. The dada of C_T² were collected over a two-month period from November through December,2000. The ambient temperature, ground temperature, gas pressure, wind speed and direction were sampled in the same time. In order to maintain the reliability of the data, we kept micro-thermal sensors to be same sensitivity through adjusting their resistance at same ground-height. We obtained the data in 14 whole nights. The daily means of C_T²were computed for different heights. The vert ical profiles of C_T² were then obtained by data regression. The ground-height of the telescope determined is 13-15m.