Local monitoring of atmospheric transparency from the NASA MERRA-2 global assimilation system

TL;DR

This paper explores using NASA's MERRA-2 reanalysis data to monitor atmospheric transparency at astronomical sites, providing detailed temporal and spatial variability analysis relevant for improving observational accuracy.

Contribution

It demonstrates the application of MERRA-2 data for site-specific atmospheric transparency monitoring in astronomy, highlighting its potential for real-time correction.

Findings

MERRA-2 provides detailed atmospheric parameters for two observatory sites.

Temporal variability of atmospheric constituents over eight years is characterized.

Spatial gradients of key atmospheric variables are analyzed for their impact on transparency.

Abstract

Ground-based astronomy has to correct astronomical observations from the impact of the atmospheric transparency and its variability.The current objective of several observatories is to achieve a sub-percent level monitoring of atmospheric transmission. A promising approach has been to combine internal calibration of the observations with various external meteorological data sources, upon avail-ability and depending on quality. In this paper we investigate the use of the NASA Modern-Era Retrospective Analysis for Research and Applications, version 2 (MERRA-2) which is a general circulation model (GCM) and data assimilation system that renders freely available for any given site, at any time, all the parameters constraining atmospheric transmission. This paper demonstrates the extraction of the relevant atmospheric parameters for optical astronomy at two sites: Mauna Kea in Hawaii and Cerro Tololo InternationalObservatory in Chile. The temporal variability for the past eight years (annual, overnight and hourly), as well as the spatial gradients of ozone, precipitable water vapor, and aerosol optical depth is presented and their respective impacts on the atmospheric transparency is analyzed.