Trace gases exchange between the free troposphere and the planetary boundary layer in the Amazon

• Autor(a) principal: Haytzmann, Guido Giovanelli
• Data de Publicação: 2024
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Biblioteca Digital de Teses e Dissertações da USP
• Texto Completo: https://www.teses.usp.br/teses/disponiveis/43/43134/tde-03072024-160304/
• topic: Amazon; Amazônia; ATTO; ATTO; Clouds; CLP; Gases; Gases; Nuvens; PBL

Anthropogenic emissions of greenhouse gases are causing the Earths temperature to rise at an unprecedented rate. In this scenario, the Amazon rainforest stands out for its essential environmental services, such as carbon storage and regulation of global biogeochemical cycles. It is, therefore, vital to understand the key processes that keep the forest alive. Scientists have shown that Amazonian soils depend on the long-range transport of nutrients, such as phosphorus, to meet the needs of vegetation. This transport occurs through atmospheric rivers in the free troposphere. However, how these atmospheric rivers penetrate the planetary boundary layer (PBL) remains unclear. This study aims to take a first step towards filling this knowledge gap by investigating the exchange of trace gases between the free troposphere and the PBL in the Amazon region. The investigation was supported by several datasets from the Amazon Tall Tower Observatory (ATTO), which provided data on gas concentrations and meteorological parameters at different heights above and within the rainforest canopy. The study also used the recently established Campina site, which is equipped with a wide range of radars and in-situ measurements of cloud-related parameters. The combination of measurements of vertical gas profiles and atmospheric dynamics provides a unique insight into the variability of gas concentrations in the Amazon region. Two recent campaigns have been used to study the gas variability: CloudRoots during the dry season and CAFE-BRAZIL during the wet season. First, a general characterization of shallow, congestus, and deep convective clouds during the dry and wet seasons was performed. Significant differences in cloud characteristics were observed between the two seasons. The main differences are the deeper clouds during the rainy season and the role of the precipitable water vapor (PWV), which defines the cloud activity during the dry season but has similar values for all cloud types during the wet season. The variability of the gas concentration during cloud cover events was then investigated for different cloud types. A careful analysis showed that deep clouds have the greatest influence on surface concentrations of trace gases, especially O3 and CO2. A case study showed that the observed variations in these gas concentrations during a deep convective event are mainly caused by air transport from higher altitudes to the PBL. The results of this study indicated relevant differences in the processes driving CO and black carbon concentrations during the two seasons. The synoptic pattern is crucial for trace gas variability during the dry season. Finally, variability during non-rain events was investigated using model simulations from MesoNH to assess the potential contribution of convection-generated gravity waves in transporting air masses from the free troposphere into the PBL. The results indicate that gravity waves induce fluctuations in the water vapor field in the PBL. This effect could explain fluctuations in trace gas concentrations as squall lines approach.