Astroclimatic conditions of the Suffa Plateau: optical and radiophysical parameters

Abstract

This paper presents the results of long-term astroclimatic and atmospheric monitoring conducted at the Suffa Plateau. Located at \(39^{\circ }37^{\prime }\text{ N}\) and \(67^{\circ }56^{\prime }\) E, at an altitude of approximately 2300 m above sea level in the Turkestan Range, the Suffa Plateau is considered one of the most promising high-altitude astronomical sites in Central Asia for optical, millimeter-wave, and radio astronomical observations. The favorable astroclimatic conditions of the site are associated with its dry continental climate, relatively low precipitable water vapor (PWV), weak atmospheric turbulence, and low levels of radio-frequency interference. Optical seeing measurements obtained using a Differential Image Motion Monitor (DIMM) yielded median and mean nighttime seeing values of \(1.06^{\prime \prime }\) and \(1.11^{\prime \prime }\), respectively, indicating relatively stable optical observing conditions. Long-term radiometric observations of atmospheric absorption and transparency were carried out using the dual-channel MIAP-2 millimeter-wave radiometer operating in the 84–99 GHz (3 mm) and 132–148 GHz (2 mm) atmospheric windows. Median and mean atmospheric absorption were 0.13 and 0.14 Np in the 2 mm channel and 0.11 and 0.12 Np in the 3 mm channel. Quantitative PWV retrievals were derived exclusively from the 2 mm channel, yielding median and mean PWV values of 4.96 and 5.91 mm, respectively, while the 3 mm channel was used primarily to characterize dry atmospheric opacity and long-term atmospheric transparency. Seasonal analysis demonstrates that winter months, particularly January and February, provide the most favorable conditions for millimeter-wave observations, when atmospheric absorption decreases by approximately \(50\%\) relative to annual mean values. Additional comparison with ERA5 atmospheric reanalysis data confirms the general reliability and seasonal consistency of the radiometric PWV retrievals. The results indicate that the Suffa Plateau possesses favorable atmospheric conditions for a significant fraction of the year and represents a promising site for future optical, radio, and millimeter-wave astronomical facilities, including the RT-70 radio telescope currently under development.