Abstract
The World Meteorological Organization Aircraft Meteorological Data Relay (AMDAR) programme refers to meteorological data gathered by commercial aircraft and made available to weather services. It has become a major source of upper-air observations whose assimilation into global models has greatly improved their performance. Near busy airports, AMDAR data generate semi-continuous vertical profiles of temperature and winds, which have been utilized to produce climatologies of atmospheric-boundary-layer (ABL) heights and general characterizations of specific cases. We analyze 2017–2019 AMDAR data for Santiago airport, located in the centre of a 40times 100 km^2 subtropical semi-arid valley in central Chile, at the foothills of the Andes. Profiles derived from AMDAR data are characterized and validated against occasional radiosondes launched in the valley and compared with routine operational radiosondes and with reanalysis data. The cold-season climatology of AMDAR temperatures reveals a deep nocturnal inversion reaching up to 700 m above ground level (a.g.l.) and daytime warming extending up to 1000 m a.g.l. Convective-boundary-layer (CBL) heights are estimated based on AMDAR profiles and the daytime heat budget of the CBL is assessed. The CBL warming variability is well explained by the surface sensible heat flux estimated with sonic anemometer measurements at one site, provided advection of the cool coastal ABL existing to the west is included. However, the CBL warming accounts for just half of the mean daytime warming of the lower troposphere, suggesting that rather intense climatological diurnal subsidence affects the dynamics of the daytime valley ABL. Possible sources of this subsidence are discussed.
Highlights
The global Aircraft Meteorological Data Relay (AMDAR) programme is a World Meteorological Organization effort to collect meteorological data gathered by commercial aircraft around the world and make the data available to meteorological services (Moninger et al 2003; Petersen 2016)
Our goals are: (1) to validate and utilize AMDAR data to characterize the diurnal climatology of the Santiago valley mountain boundary layer (MoBL), (2) to test whether the AMDAR data can be used to constrain the heat budget of the Santiago valley MoBL, and (3) to identify the main factors controlling that budget as suggested by the new data
As concluded by Rahn and Mitchell (2016), the AMDAR data have great potential in the characterization of the lower troposphere around the sites where it is available, especially around busy airports where almost continuous sampling is achieved. They used AMDAR data to produce a valuable climatology of the coastal atmospheric boundary layer (ABL) in California and a qualitative discussion of the mechanisms behind it
Summary
The global Aircraft Meteorological Data Relay (AMDAR) programme is a World Meteorological Organization effort to collect meteorological data gathered by commercial aircraft around the world and make the data available to meteorological services (Moninger et al 2003; Petersen 2016). Other more specific uses of AMDAR data in ABL studies include the evaluation of their performance to detect inversion and shear layers at an airport (Drüe et al 2010) or the sensitivity of the ABL to heat waves (Zhang et al 2020b) Despite these efforts, the use of AMDAR data in ABL studies can still be considered as incipient, especially in more quantitative evaluations of the mechanisms affecting the ABL dynamics in specific settings. The use of AMDAR data in ABL studies can still be considered as incipient, especially in more quantitative evaluations of the mechanisms affecting the ABL dynamics in specific settings In this regard, the potential of having publicly available long-term, semi-continuous, high-resolution vertical profiles of temperature and winds near the surface has not yet been fully realized
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