  The Atacama Desert has long been established as an excellent site for
submillimeter observations. Yet identifying potentially optimal locations for a
new facility within this region can require long field campaigns that rely on
the construction of weather stations and radiometer facilities to take data
over sufficiently long timescales. Meanwhile, high-level remote sensing data
products from satellites have generally only been available at >25 km
resolution, limiting their utility for astronomical site selection. We aim to
improve and expedite the process of site selection through the use of
km-resolution satellite data. We analyze the daytime precipitable water vapor
(PWV) values inferred using near-IR measurements from the MODIS Aqua and Terra
satellites, comparing the level-2 satellite products to those from existing
ground-based measurements from the radiometer at the Atacama Pathfinder
Experiment (APEX) site. Since the APEX radiometer data has been extensively
tested and compared to atmospheric transmission models, particularly in low-PWV
conditions of interest for astronomy, we use these data to provide a
re-calibration of the MODIS data for the entire region. After re-calibration,
the satellite data allow mapping of the PWV across the region, and we identify
several promising sites. We demonstrate a potentially powerful method for
siting new facilities such as AtLAST and extensions to global very long
baseline interferometry networks like the EHT. Further, our findings identify a
trend in both the APEX and MODIS data, and indicate that the PWV has increased
moderately over the past two decades. We verify this trend exists in the
Coupled Model Intercomparison Project Phase 6 (CMIP6) climate models, and show
that it is worse in the case of greater increase in the average global
temperature.
