CO2 enhancements associated with Convective Cold Pools at the Amazon Tall Tower Observatory (ATTO)

Convective cold pools (CCPs) can strongly disturb the planetary boundary layer (PBL) through their strong outflow winds and associated turbulence. At the Amazon Tall Tower Observatory (ATTO) in central Amazonia, CCPs occur nearly daily and routinely perturb the PBL. Since the Amazon forest is a crucial component of the global carbon cycle, understanding how recurring CCP-induced circulations and turbulence modulate diurnal CO₂ dynamics is paramount. Using a dataset of 410 CCP events detected at ATTO between August 2021 and December 2023, we investigate whether CCPs systematically modify CO₂ concentrations and whether the magnitude of the response depends on CCP intensity and pre-CCP PBL stability. Events were classified by intensity and pre-CCP PBL stability, while accounting for the forest’s diurnal respiration–photosynthesis cycle. Composite time-height analyses reveal a coherent CO₂ response across all classifications, with abrupt increases throughout the tower depth within about 10 min of gust-front arrival. The magnitude of the CO₂ response is more strongly related to pre-CCP stability than CCP intensity, with the largest enhancements occurring under stable conditions, whereas CCP intensity primarily controls persistence. The canonical gust-front dynamical structure, characterized by a leading updraft followed by trailing subsidence and enhanced turbulence, is evident in the composite wind and temperature fields, coinciding with the observed CO₂ enhancements. Furthermore, vertically integrated CO₂ anomalies per unit area increase following CCP arrival across all classifications, indicating a net increase in CO₂ within the observed atmospheric column and suggesting that propagating CCPs transport CO₂-rich air into the column. Overall, CCPs act as an efficient mechanism for CO₂ redistribution within the Amazon PBL. These findings highlight the role of CCP dynamics in modulating biosphere–atmosphere exchanges and provide new insights into the coupling between deep convection and the tropical forest carbon cycle.