Seminário do Departamento de Ciências Atmosféricas
Tema: Physical Controls on Tropical CO2-Exchange Across Convective Regimes in ECMWF-IFS
Apresentação: Vincent S. de Feiter (Meteorology and Air Quality Section, Wageningen University, Netherlands)
The diurnal cycle and vertical exchange of CO2 are governed by surface and atmospheric processes operating across a wide range of spatial and temporal scales. Over tropical regions such as the Amazon rainforest, particularly distinct shallow-to-deep convective regimes are anticipated to significantly modulate the diurnal cycle (6:00 – 18:00), influencing both the lateral transport of CO2 over the rainforest and its vertical exchange between the surface and free troposphere aloft. Yet, the precise role of convection, particularly during the transition from clear-to-cloudy conditions, remains poorly understood and insufficiently quantified. Accurately representing the role of convection is essential for improving global estimates of the CO2 exchange for the Amazon rainforest under a changing climate. To address this research gap, we examine the role of convection in regulating the atmospheric CO2 exchange over the Amazon rainforest under clear-to-cloudy conditions. More specifically, using the high-resolution global storm-resolving Integrated Forecasting System (IFS) of the ECMWF across three configurations (horizontal resolutions of 25 km, 9 km (current operational resolution), and 4.4 km), we assess the various contributions and regulating processes of the diurnal CO2 budget. We construct a sensitivity in which we decompose the diurnal CO2 tendencies and vertical fluxes into contributions from turbulent diffusion, convective transport, and large-scale dynamics, isolating the role of convection. Furthermore, we formulate an analytical expression grounded in well-mixed theory to quantify the importance and sensitivity of the multi-scale processes across resolutions. In this way, we are able to identify errors that may arise when the physical controls on the CO2-exchange are misrepresented. The framework is evaluated using comprehensive observations and turbulence- and cloud-resolving large-eddy simulations from the CloudRoots-Amazon22 campaign (dry season 2022). Our findings show that under clear-to-shallow convective conditions at ATTO, three diurnal regimes can be distinguished and that shallow clouds actively organise the vertical turbulent exchange at cloud scales, ventilating CO2 to altitudes up to twice the boundary-layer depth and modulating its vertical distribution until late afternoon. The ECMWF-IFS reproduces the diurnal evolution and vertical structure of temperature, humidity, and wind across resolutions. However, larger uncertainties remain in the representation of CO2 exchange on both time and space, highlighting the sensitivity of simulated CO2 and the timing and organisation of convection, motivating ongoing efforts to disentangle the multi-scale and role of shallow-to-deep convective processes in controlling the CO2-exchange over the Amazon rainforest.
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