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Multi-decadal Downlift in Eastern North Atlantic Subtropical Stratocumulus
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  • Juan Carlos Guerra García,
  • Judit Carrillo,
  • Hugo Rodriguez,
  • Silvia Alonso-Pérez
Juan Carlos Guerra García
Universidad de La Laguna

Corresponding Author:[email protected]

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Judit Carrillo
University of La Laguna
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Hugo Rodriguez
Universidad de La Laguna
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Silvia Alonso-Pérez
Universidad de La Laguna
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Abstract

The height of stratocumulus clouds (Sc) in the Northeast Atlantic, off the coast of Africa in the Central Macaronesian region, has been examined over the past two decades. We analyzed a dataset of sounding and surface meteorological data from the islands of Madeira and Tenerife to investigate cloud base height (CBH) and cloud top height (CTH) using the lifting condensation level and the height of the trade wind inversion base as proxies. The results of a Mann-Kendall analysis indicate a statistically significant downward trend in the height of the Sc boundaries at both locations. This trend is particularly pronounced towards the northern end of the Central Macaronesian region (Madeira), where the decrease is more than double that the observed at the southern end (Tenerife). The decrease in CTH is consistent with the observed increase in subsidence at the 850 hPa level over the last two decades, which may be related to the observed expansion and intensification of the Azores High (AH). The observed change in the CBH can be attributed to an increase in the moisture content of the air, in line with the observed changes in the regional and local sea surface temperature. However, it cannot be ruled out that changes in the AH, also evidenced by the observed trend in surface pressure at Central Macaronesia, have altered the moisture transport patterns. While the observed changes in the Sc may have significant implications for regional climatic conditions, the most imminent effects are on the height distribution of cloud forests.
10 Jul 2024Submitted to ESS Open Archive
14 Jul 2024Published in ESS Open Archive