14 research outputs found
The role of subsidence in a weakly unstable marine boundary layer: a case study
The diurnal evolution of a cloud free, marine boundary layer is studied by
means of experimental measurements and numerical simulations. Experimental
data belong to an investigation of the mixing height over inner Danish
waters. The mixed-layer height measured over the sea is generally nearly
constant, and does not exhibit the diurnal cycle characteristic of boundary
layers over land. A case study, during summer, showing an anomalous
development of the mixed layer under unstable and nearly neutral atmospheric
conditions, is selected in the campaign. Subsidence is identified as the main
physical mechanism causing the sudden decrease in the mixing layer height.
This is quantified by comparing radiosounding profiles with data from
numerical simulations of a mesoscale model, and a large-eddy simulation
model. Subsidence not only affects the mixing layer height, but also the
turbulent fluctuations within it. By analyzing wind and scalar spectra, the
role of subsidence is further investigated and a more complete interpretation
of the experimental results emerges
Increased Amazon carbon emissions mainly from decline in law enforcement
The Amazon forest carbon sink is declining, mainly as a result of land-use and climate change. Here we investigate how changes in law enforcement of environmental protection policies may have affected the Amazonian carbon balance between 2010 and 2018 compared with 2019 and 2020, based on atmospheric CO2 vertical profiles, deforestation and fire data, as well as infraction notices related to illegal deforestation. We estimate that Amazonia carbon emissions increased from a mean of 0.24â±â0.08âPgCâyearâ1 in 2010â2018 to 0.44â±â0.10âPgCâyearâ1 in 2019 and 0.52â±â0.10âPgCâyearâ1 in 2020 (± uncertainty). The observed increases in deforestation were 82% and 77% (94% accuracy) and burned area were 14% and 42% in 2019 and 2020 compared with the 2010â2018 mean, respectively. We find that the numbers of notifications of infractions against flora decreased by 30% and 54% and fines paid by 74% and 89% in 2019 and 2020, respectively. Carbon losses during 2019â2020 were comparable with those of the record warm El Niño (2015â2016) without an extreme drought event. Statistical tests show that the observed differences between the 2010â2018 mean and 2019â2020 are unlikely to have arisen by chance. The changes in the carbon budget of Amazonia during 2019â2020 were mainly because of western Amazonia becoming a carbon source. Our results indicate that a decline in law enforcement led to increases in deforestation, biomass burning and forest degradation, which increased carbon emissions and enhanced drying and warming of the Amazon forests