As the COVID-19 pandemic unfolded, questions arose as to whether the pandemic would amplify or pacify tropical deforestation. Early reports warned of increased deforestation rates; however, these studies were limited to a few months in 2020 or to selected regions. To better understand how the pandemic influenced tropical deforestation globally, this study used historical deforestation data (2004–2019) from the Terra-i pantropical land cover change monitoring system to project expected deforestation trends for 2020, which were used to determine whether observed deforestation deviated from expected trajectories after the first COVID-19 cases were reported. Time series analyses were conducted at the regional level for the Americas, Africa and Asia and at the country level for Brazil, Colombia, Peru, the Democratic Republic of Congo and Indonesia. Our results suggest that the pandemic did not alter the course of deforestation trends in some countries (e.g., Brazil, Indonesia), while it did in others (e.g., Peru). We posit the importance of monitoring the long-term effects of the pandemic on deforestation trends as countries prioritize economic recovery in the aftermath of the pandemic.
<p>Atmospheric boundary layer (ABL) dynamics severely impact the horizontal transport of pollutants as well as their vertical dilution. Despite this, observations of vertical wind profiles and the ABL height are still rare, particularly in cities. Thanks to recent technological advances compact ground-based remote sensing instruments are now available to monitor the heterogeneous urban atmosphere across dense sensor networks. In urban settings, Doppler wind lidars (DWL) and automatic lidars and ceilometers (ALC) are particularly useful as they operate continuously and automatically with very low maintenance under all weather conditions. Thanks to those novel profiling instruments, high-resolution (time and vertical) wind information as well as aerosol backscatter profiles can be recorded.</p> <p>Based on the RI-URBANS (and ICOS-cities) pilot city of Paris, France, we demonstrate what advanced products can be derived using different detailed algorithms, including vertical profiles of horizontal wind and turbulence, boundary layer heights based on aerosol or turbulence indicators, as well as low-level jet characteristics. In Paris, RI-URBANS is embedded in the PANAME initiative that coordinates the synergy between numerous projects that are investigating the urban atmosphere. Clear measurement standards, careful quality control and advanced processing algorithms are required to ensure harmonised products are obtained from the diverse sensor networks that involve instruments of different models from various manufacturers with respective capabilities and limitations.</p> <p>Using the synergy of the different ABL products obtained in the Paris region, it is investigated how the urban boundary layer interacts with the synoptic scale flow, the underlying topography and the urban surface. A combination of wind direction, atmospheric stability and terrain clearly affect shallow boundary layer heights and the low-level jet characteristics. But also spatial variations across the region are registered during deep convective boundary layer development.</p>
<p>Air quality and meteorology in urban environments are strongly affected by dynamical and turbulent processes occurring in the atmospheric boundary layer. These are largely driven by the interaction between the surface and the atmosphere, including the exchange of momentum, heat, moisture, and various gases and aerosols. Vertical ventilation, horizontal advection, and atmospheric stratification are key processes.</p><p>To improve the understanding of the exchange processes in the urban atmosphere and to assess the implications of spatial variations in surface roughness, spatially resolved vertical profiles of the horizontal wind are required. In this work, we are implementing a novel &#8220;volume wind processing&#8221; approach to retrieve horizontal wind information on a 3D spatial grid from observations of a scanning Doppler wind lidar (Vaisala Windcube 400s). Deployed on the rooftop of a tall building in downtown Paris, France, the Doppler lidar is operated with a series of scan strategies to monitor the vertical and horizontal variations of the mean wind field across the city center.</p><p>In order to quantify the performance of the volume wind processing, an evaluation measurement campaign was performed combining measurements at the Vaisala measurement site and the SIRTA atmospheric observatory (Paris-Saclay) located 3.5 km from each other. The Windcube 400s, located on the Vaisala site, gathered measurements based on different scan patterns (full or sector (>30&#176;) Plan-position Indicator (PPI)), from which wind profiles were retrieved using the volume wind processing. These retrievals were then compared to vertical wind profiles obtained from a previously validated and calibrated Doppler lidar (WLS70) running in a vertical profiling mode located at SIRTA. The comparison is performed over a 30-days period. We found a mean difference (Volume Wind &#8211; Vertical Stare) of -0.69 m/s and a standard deviation of 1.32 m/s for 10-min averaged profiles.</p><p>The ongoing work consists of identifying the sources of uncertainty in the volume wind processing and improving the quality of the retrievals by improving quality control procedures. High-quality wind profile products will then be available for research on the spatial variability of the wind speed profiles, in order to determine the influence of the surface roughness on exchange processes in the Paris urban atmosphere.</p>
<p>Air quality and meteorology in urban environments are strongly affected by dynamical processes occurring in the atmospheric boundary layer. Vertical ventilation, horizontal advection, and atmospheric stratification, largely driven by surface-atmosphere exchanges influence the transport of momentum, heat, moisture, gases, and aerosols.</p><p>To improve the understanding of these exchange processes in the urban atmosphere and the implications of spatial variations in topography, surface roughness, and surface cover; the 3-dimensional wind field is studied. In this work, we are reporting results of the novel &#8220;volume wind processing (VW)&#8221; software to retrieve horizontal wind information on a 3D spatial grid from observations of a single scanning Doppler wind lidar (Vaisala Windcube 400s). In the framework of the PANAME initiative (PAris region urbaN Atmospheric observations and models for Multidisciplinary rEsearch), the Doppler wind lidar is deployed on the rooftop of a tall building in central Paris, France, for the duration of two years. It is set to perform a series of scan strategies to monitor the vertical and horizontal variations of the mean wind field across the city center.</p><p>In addition to classical vertical wind profiling at the location of the lidar in Doppler Beam Swinging mode (DBS), 2D maps of horizontal wind speed are obtained from zero-elevation Plan Position Indicator (PPI) scans to assess spatial heterogeneity of the wind field. Further, the VW provides vertical profiles of horizontal wind to be derived at large distances (up to 7km) from the sensor using sector PPI scans at multiple elevation angles. It is the objective of this work to quantify the uncertainties in the VW products, to optimize the scan strategies considering spatial and temporal variations of the wind field, and to finally demonstrate their potential for a variety of applications.</p><p>Observations describing the horizontal and vertical variations in wind speed and direction, at high spatial resolution and continuous temporal coverage, are expected to greatly advance the process of understanding the urban atmosphere dynamics. These new generation data are also valuable for the evaluation of numerical simulations (weather and air quality), the quantification of wind energy resources, air traffic (e.g., drones) and sustainable urban design.</p>
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