Assessments of Ali, Dome A, and Summit Camp for Mm-wave Observations Using MERRA-2 Reanalysis

TL;DR

This study evaluates five potential mm-wave observation sites using MERRA-2 reanalysis data, identifying Dome A as the best site and highlighting Ali and Summit Camp as promising locations with comparable conditions to established sites.

Contribution

First comprehensive assessment of multiple high-altitude sites for mm-wave observations using MERRA-2 data, providing new insights into their atmospheric suitability.

Findings

Dome A has the lowest PWV and fluctuations, making it the best site.

Ali's higher elevation site is comparable to Cerro Chajnantor in transmission.

Summit Camp's conditions are similar to Cerro Chajnantor, despite more liquid water clouds.

Abstract

The latest MERRA-2 reanalysis of the modern satellite measurements provides unprecedented uniformity and fidelity for the atmospheric data. In this paper, these data are used to evaluate five sites for millimeter-wave (mm-wave) observations. These include two established sites (South Pole and Chajnantor, Atacama), and three new sites (Ali, Tibet; Dome A, Antarctica; and Summit Camp, Greenland). Atmospheric properties including precipitable water vapor (PWV), sky brightness temperature fluctuations, ice and liquid water paths are derived and compared. Dome A emerges to be the best among those evaluated, with PWV and fluctuations smaller than the second-best site, South Pole, by more than a factor of 2. It is found that the higher site in Ali (6,100 m) is on par with Cerro Chajnantor (5,612 m) in terms of transmission and stability. The lower site in Ali (5,250 m) planned for first stage of observations at 90/150GHz provides conditions comparable to those on the Chajnantor Plateau. These analyses confirm Ali to be an excellent mm-wave site on the Northern Hemisphere that will complement well-established sites on the Southern Hemisphere. It is also found in this analysis that the observing conditions at Summit Camp are comparable to Cerro Chajnantor. Although it is more affected by the presence of liquid water clouds.