Site-testing at Muztagh-ata site III: temperature inversion in surface-layer atmosphere

Abstract

In this article, we present detailed seasonal, monthly and daily statistics of temperature difference in the surface layer at the Muztagh-ata site based on the temperature measurements at two heights of 2m and 6m. We find that temperature inversion occurs frequently at our site during nighttime, especially during the cold season. Strong temperature inversion always represents stable atmospheric turbulence, which is crucial for an optical observatory. By analyzing the behavior of temperature inversion and its correlation with wind and cloud amount, one conclusion can be made that radiation inversion is the main reason for the existence of temperature inversion in the surface-layer at the Muztagh-ata site.

Data processing and data products from 2017 to 2019 campaign of astronomical site testing at Ali, Daocheng and Muztagh-ata

“…A consistency test between French DIMMs was conducted at the Xinglong Observatory by Wang et al (2020), and the average difference in the measurements is 0.075 arcsec. The French and NIAOT DIMM consistency test was conducted at the top of an 11 m tower at the Muztagh-ata site by Xu et al (2020b), and the median value of the French DIMM is a little higher than that of the NIAOT DIMM by 0.01 arcsec, approximately within the measurement error. The French and Ali DIMM consistency test was conducted at the Ali site by , and the median value of French DIMM is lower than the Ali DIMM by 0.06 arcsec.…”

“…The operation height of DIMM is important to avoid near-ground turbulence, which has been tested independently by the operation teams at Muztagh-ata and Ali. From 2017 June 23 to 2017 November 14, Xu et al (2020b) deployed the NIAOT DIMM on the ground with the French DIMM on the 11 m tower at the Muztagh-ata site. The median value from the NIAOT DIMM was 0.97 arcsec and that from the French DIMM was 0.79 arcsec from the 11 m tower.…”

“…We can roughly estimate from the histograms that the reinforcement of the tower has a positive impact on the improvement of the seeing measurement. More detailed analysis about the relationship between the seeing and wind speed of prevailing wind direction in Muztaghata was finished by Xu et al (2020b). He found the median seeing value manifests an initial drop until the wind speed 3.…”

Forecast of Observing Time Delay of Strongly Lensed Quasars with the Muztagh-Ata 1.93 m Telescope

“…Our purpose is to discuss the capability of measuring TDSL with the Muztagh-Ata 1.93 m telescope, rather than to give prediction for a specific target. Based on the field measurements at the Muztagh-Ata site Xu et al (2020aXu et al ( , 2020bXu et al ( , 2020c, we believe 200 observable days per season (i.e., per year) is reasonable number for our simulations. In order to demonstrate the robustness of measuring TDSL with 1.93 m telescope, here we consider several cadences as well as observation campaign length.…”

Site-testing at Muztagh-ata site. IV. Precipitable Water Vapor

“…A multi-year on-site study of the characteristics of Muztaghata site has proved its excellent optical observation conditions. In former papers, we showed the optical astronomical observing conditions such as atmospheric parameters, sky brightness, seeing and inversion layer in the near-ground atmosphere of Muztagh-ata site (Xu et al 2020b(Xu et al , 2020c(Xu et al , 2020a. This manuscript mainly focus on discussing the PWV of the site.…”