The Atmospheric Boundary Layer over Santiago Valley at the Foot of the Andes in Central Chile Characterized with Three Years of AMDAR Observations

The global Aircraft Meteorological DAta Relay (AMDAR) programme is a World Meteorological Organization (WMO) effort to collect meteorological data gathered by commercial aircrafts around the world and make it available to meteorological services (1). It has greatly expanded the global availability of upper air observations beyond the historical global radiosonde network. In year 2017 the South-American LATAM airline joined AMDAR with funding of the U.S. AMDAR/MDCRS program (2,3). As a result, the availability of vertical profiles of meteorological variables in many sites of the region increased dramatically. In this work we present the 2017-2019 climatology of the lower troposphere in the Santiago valley in central Chile. AMDAR data for the international airport of Santiago has produced for the first time almost continuous upper-air information for a valley subjected to serious air pollution problems during winter. We center the analysis in the description of the stability and winds in the boundary layer, a region where the alternative sources of information (numerical models) have significant problems. In the stability climatology, a conspicuous secondary maximum of inversions frequency is observed detached from the surface, pointing to a mechanism distinct from that of surface cooling. In terms of winds, the observations show clearly the recurrence of a northerly flow above the SW winds of the daytime boundary layer. This climatology is a first step towards a better understanding of the dynamics of this valley atmospheric boundary layer.

Acknowledgments

This work is partially funded by FONDECYT Project 1170214 of the Chilean CONICYT agency.

Ref.1:

https://www.wmo.int/pages/prog/www/GOS/ABO/AMDAR/About.html

Ref. 2: https://www.wmo.int/pages/prog/www/GOS/ABO/AMDAR/AMDAR_Airlines.html#airlines_reg

Ref. 3:

https://sites.google.com/a/wmo.int/amdar-news-and-events/newsletters/volume-13-april-2017#TOC-Status-of-the-U.S.-Aircraft-Based-Observations-Programme