Tibet's Ali: Asia's Atacama?

TL;DR

This study evaluates the astronomical observation potential of Ngari's Ali region in Tibet using 31 years of climate data, finding conditions comparable to top global observatories and suggesting high-altitude sites could offer exceptional observing conditions.

Contribution

It provides a comprehensive astroclimatological assessment of Ngari's Ali region, highlighting its potential as a premier astronomical site comparable to Atacama.

Findings

Ali Observatory has 57% photometric nights

Median atmospheric seeing is 0.8 arcseconds

Precipitable water vapor is 2.5 mm

Abstract

The Ngari (Ali) prefecture of Tibet, one of the highest areas in the world, has recently emerged as a promising site for future astronomical observation. Here we use 31 years of reanalysis data from the Climate Forecast System Reanalysis (CFSR) to examine the astroclimatology of Ngari, using the recently-erected Ali Observatory at Shiquanhe (5~047~m above mean sea level) as the representative site. We find the percentage of photometric night, median atmospheric seeing and median precipitable water vapor (PWV) of the Shiquanhe site to be $57\%$, $0.8"$ and 2.5~mm, comparable some of the world's best astronomical observatories. Additional calculation supports the Shiquanhe region as one of the better sites for astronomical observations over the Tibetan Plateau. Based on the studies taken at comparable environment at Atacama, extraordinary observing condition may be possible at the few vehicle-accessible 6~000~m heights in the Shiquanhe region. Such possibility should be thoroughly investigated in future.