Almost one year of TROPOMI/S5P total ozone column data: global ground-based validation

Póster presentado en: ATMOS 2018, celebrado en Salzburgo (Austria) del 26 al 29 de noviembre de 2018.In this work we present the validation results of almost one year of TROPOMI Near Real Time (NRTI) and OFFLine (OFFL) data against ground-based quality-assured Brewer and Dobson total ozone column (TOC) measurements deposited in the World Ozone and Ultraviolet Radiation Data Center (WOUDC). Additionally, comparisons to Brewer measurements from the European Brewer Network (EUBREWNET) and the Canadian Network are performed, as well as to twilight zenith-sky measurements obtained with ZSL-DOAS (Zenith Scattered Light Differential Optical Absorption Spectroscopy) instruments, that form part of the SAOZ network (Système d'Analyse par Observation Zénitale) of the Network for the Detection of Atmospheric Composition Change (NDACC). Through the comparison of the TROPOMI measurements to the total ozone ground-based measurements from stations that are distributed globally, as the background truth, the dependence of the new instrument on latitude, cloud properties, solar zenith and viewing angles, among others, is examined. Validation results show that the mean bias and the standard deviation of the percentage difference between TROPOMI and QA ground TOC meet the product requirements

TROPOMI/S5P total ozone column data: global ground-based validation and consistency with other satellite missions

In this work, the TROPOMI near real time (NRTI) and offline (OFFL) total ozone column (TOC) products are presented and compared to daily ground-based quality-assured Brewer and Dobson TOC measurements deposited in the World Ozone and Ultraviolet Radiation Data Centre (WOUDC). Additional comparisons to individual Brewer measurements from the Canadian Brewer Network and the European Brewer Network (Eubrewnet) are performed. Furthermore, twilight zenith-sky measurements obtained with ZSL-DOAS (Zenith Scattered Light Differential Optical Absorption Spectroscopy) instruments, which form part of the SAOZ network (Système d'Analyse par Observation Zénitale), are used for the validation. The quality of the TROPOMI TOC data is evaluated in terms of the influence of location, solar zenith angle, viewing angle, season, effective temperature, surface albedo and clouds. For this purpose, globally distributed ground-based measurements have been utilized as the background truth. The overall statistical analysis of the global comparison shows that the mean bias and the mean standard deviation of the percentage difference between TROPOMI and ground-based TOC is within 0 –1.5 % and 2.5 %–4.5 %, respectively. The mean bias that results from the comparisons is well within the S5P product requirements, while the mean standard deviation is very close to those limits, especially considering that the statistics shown here originate both from the satellite and the ground-based measurements.This research has been supported by the European Space Agency “Preparation and Operations of the Mission Performance Centre (MPC) for the Copernicus Sentinel-5 Precursor Satellite” (contract no. 4000117151/16/1-LG)

Evolution of Ozone above Togo during the 1979-2020 Period

International audienceThe objective of this paper is to estimate the trend of the Total Ozone Column (TOC) over Togo. A Multi-Sensor Reanalysis-2 (MSR-2) of the TOC over the entire territory of Togo was used. A Multiple Linear Regression (MLR) method has been applied to retrieve the interannual contributions of different forcings and the long-term variability. It was found that the Annual Oscillation (AnO), the Quasi Biennial Oscillation at 30 mb (QBO30), the Solar Flux (SF), and the El Niño–Southern Oscillation (ENSO) has a statistically significant influence on the interannual variability of the TOC. The strongest contribution (22 ± 1.4 DU) is allocated to the AnO while the weakest (<1 DU) is attributed to the Semi-Annual Oscillations (SAnO). Before the peak year of the Equivalent Effective Stratospheric Chlorine (EESC) in the tropics in 1997, the trend is negative (−0.3% ± 0.9% per decade) and is not statistically significant. After the peak year, a statistically significant positive trend is observed. The trend of the TOC is 0.6% ± 0.2% per decade. The monthly TOC trend over Togo is positive and statistically significant during the rainy season (particularly during the monsoon period) except in April, unlike during the harmattan period (DJF), where the trend is not significan

Evolution of Ozone above Togo during the 1979–2020 Period

International audienceThe objective of this paper is to estimate the trend of the Total Ozone Column (TOC) over Togo. A Multi-Sensor Reanalysis-2 (MSR-2) of the TOC over the entire territory of Togo was used. A Multiple Linear Regression (MLR) method has been applied to retrieve the interannual contributions of different forcings and the long-term variability. It was found that the Annual Oscillation (AnO), the Quasi Biennial Oscillation at 30 mb (QBO30), the Solar Flux (SF), and the El Niño–Southern Oscillation (ENSO) has a statistically significant influence on the interannual variability of the TOC. The strongest contribution (22 ± 1.4 DU) is allocated to the AnO while the weakest (<1 DU) is attributed to the Semi-Annual Oscillations (SAnO). Before the peak year of the Equivalent Effective Stratospheric Chlorine (EESC) in the tropics in 1997, the trend is negative (−0.3% ± 0.9% per decade) and is not statistically significant. After the peak year, a statistically significant positive trend is observed. The trend of the TOC is 0.6% ± 0.2% per decade. The monthly TOC trend over Togo is positive and statistically significant during the rainy season (particularly during the monsoon period) except in April, unlike during the harmattan period (DJF), where the trend is not significant

Transport of aerosol to the Arctic: analysis of CALIOP and French aircraft data during the spring 2008 POLARCAT campaign

International audienceLidar and in situ observations performed during the Polar Study using Aircraft, Remote Sensing, Surface Measurements and Models, Climate, Chemistry, Aerosols and Transport (POLARCAT) campaign are reported here in terms of statistics to characterize aerosol properties over northern Europe using daily airborne measurements conducted between Svalbard and Scandinavia from 30 March to 11 April 2008. It is shown that during this period a rather large number of aerosol layers was observed in the tropo-sphere, with a backscatter ratio at 532 nm of 1.2 (1.5 below 2 km, 1.2 between 5 and 7 km and a minimum in between). Their sources were identified using multispectral backscatter and depolarization airborne lidar measurements after careful calibration analysis. Transport analysis and comparisons between in situ and airborne lidar observations are also provided to assess the quality of this identification. Comparison with level 1 backscatter observations of the space-borne Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) were carried out to adjust CALIOP multispectral observations to airborne observations on a statistical basis. Recalibration for CALIOP daytime 1064 nm signals leads to a decrease of their values by about 30 %, possibly related to the use of the version 3.0 calibration procedure. No recalibra-tion is made at 532 nm even though 532 nm scattering ratios appear to be biased low (−8 %) because there are also significant differences in air mass sampling between airborne and CALIOP observations. Recalibration of the 1064 nm signal or correction of −5 % negative bias in the 532 nm signal both could improve the CALIOP aerosol colour ratio expected for this campaign. The first hypothesis was retained in this work. Regional analyses in the European Arctic performed as a test emphasize the potential of the CALIOP spaceborne lidar for further monitoring in-depth properties of the aerosol layers over Arctic using infrared and depolarization observations. The CALIOP April 2008 global distribution of the aerosol backscatter reveal two regions with large backscatter below 2 km: the northern Atlantic between Greenland and Norway, and northern Siberia. The aerosol colour ratio increases between the source regions and the observations at latitudes above 70 • N are consistent with a growth of the aerosol size once transported to the Arctic. The distribution of the aerosol optical properties in the mid-troposphere supports the known main transport pathways between the mid-latitudes and the Arctic

Arctic aerosol measurements and transport in the frame of the Ice-Atmosphere-Ocean Observing System (IAOOS) project.

International audienceA new observational network is being developed for ocean-ice-atmosphere climate survey over the Arctic Ocean, in the frame of the French IAOOS Equipex project, to better understand the role of aerosols and clouds in the Arctic. Automated backscatter microlidar measurements have allowed to profile aerosols and clouds in the low and mid- troposphere during first campaigns, and to retrieve aerosol optical properties in complement to CALIPSO and IASI observations. Measurements taken end during spring 2014 close to the North Pole and end of winter 2015 north of Svalbard show large occurrence of aerosol and haze layers both from ground and space observations. Analysis of trajectories have been done to link more closely both observations types and better identify aerosol sources. Observations are presented and first results are discussed

Evaluation of modeled vertical aerosol distributions over Europe using in-situ and satellite data

As part of the EU ECLIPSE project, which aims to quantify the climate impact of short-lived climate forcers (SLCFs), including aerosols, black carbon and ozone, regional models are being used to evaluate global model performance for specific case studies. Here, we present results using regional WRF-Chem simulations run with different aerosol schemes over Europe. Results are compared to satellite data and field campaigns which took place in spring and summer 2008. The aim is to evaluate the ability of the models to simulate the aerosol physical, chemical and optical properties, with a focus on pollution layers over source regions and during transport downwind. The radiative impact of such layers over Europe is also examined as a function of their relative positions to clouds. The WRF-Chem regional model was run using MOZART gas phase chemistry and different aerosol schemes and evaluated against the measurements. The model was run using anthropogenic and fire emissions for 2008, while boundary conditions were specified using the fields from a global chemical transport model. The radiative impact of pollution aerosol layers has already been investigated but less is known about the influence of vertical layering in the atmosphere. Such layers might have different radiative impacts whether they are below or above clouds and in that sense, a better understanding of their spatial extent is critical. Information about pollution aerosol layers and clouds optical properties and positions over Europe are determined using satellite-based remote-sensing measurements (CALIPSO lidar). The radiative impact of these layers has been evaluated and compared to the observations. In addition to satellite observations, data providing information on aerosol physical, optical and chemical properties from 2008 measurements campaigns over Europe (e.g., EUCAARI and POLARCAT-France) have been used to evaluate the simulations. In this study, we assess, for exemple, aerosol total number concentrations and size distributions simulated by the model. The aerosol aging is also evaluated bu examining the ratio between elementary and organic carbon (EC:OC), while the aerosol origins and sources are investigated using Lagrangian back-trajectories and observed chemical compositions, respectively. Specific attention is given to the simulation of observed pollution aerosol layers identified by CO and aerosol total number concentration enhancements

Impact of the COVID-19 pandemic related to lockdown measures on tropospheric NO₂ columns over Île-de-France

International audienceThe evolution of NO2 , considered as proxy for air pollution, was analyzed to evaluate the impact of 1 st lockdown 10 (March 17 th-May 10 th 2020) over île-de-France region (Paris and surroundings). Tropospheric NO2 columns measured by two UV-Visible SAOZ spectrometers were analyzed to compare the evolution of NO 2 between urban and suburban sites during the lockdown. The urban site is the observation platform QUALAIR (48°50'N/2°21'E) on the Pierre et Marie Curie Campus of Sorbonne University in the center of Paris. The suburban site is located at Guyancourt (48°46'N/2°03'E), University of Versailles Saint Quentin, 24 km southwest of Paris. Tropospheric NO2 columns above Paris and Guyancourt 15 have shown similar values during the whole lockdown period from March to May 2020. One decade datasets were filtered to consider air masses at both sites with similar meteorological conditions. The median NO2 columns, as well as the surface measurements of AIPARIF (Air Quality Observatory in Ile de France) during the lockdown period in 2020 were compared to the extrapolated values estimated from a linear trend analysis for the 2011-2019 period at each station. Negative NO 2 trends of-1.5 Pmolec cm-2 yr-1 (~-6.3 % yr-1) are observed from the columns and of-2.2 µg m-3 yr-1 (~-3.6 % yr-1) from the surface 20 concentration. The negative anomaly in tropospheric columns in 2020 attributed to lockdown (and related emission reductions) was found to be 56% at Paris and 46% at Guyancourt, respectively. Similar anomaly was found in the data of surface concentrations, amounting for 53% and 28% at the urban and suburban sites, accordingly

Evaluation of modelled aerosol distributions in the Artic using CALIOP

International audienceAs part of the EU-ECLIPSE project, a set of global and regional chemistry and transport models have performed simulations predicting atmospheric distributions of aerosols both globally and in the Arctic region. Here, model accuracy has been evaluated using satellite observations in the Arctic. All models used the same anthropogenic (ECLIPSEv4a), biogenic (MEGAN), and biomass burning (GFED-v3) emissions. Aerosol data derived from the spaceborne CALIOP lidar are used to evaluate models over the entire Arctic region during spring and summer 2008. Monthly mean results from the ECLIPSE models are compared with vertical distributions of attenuated scattering ratio at 532 nm from CALIOP averaged using a 3°x5° grid over a region covering 30° N to 82° N. This new product (Ancellet et al., 2014), based on CALIOP level 1 backscatter signals filtered using CALIPSO level 2 cloud masks, is not affected by errors associated with a lidar signal inversion.Modelled aerosol distributions are shown to overestimate aerosols in mid-latitude source regions and underestimate aerosols in the lower Arctic troposphere (0-2km), compared to CALIOP satellite data despite the fact that models use the new ECLIPSE emissions that include improved representations of Russian flaring and domestic wood burning. . During April 2008, lower aerosol levels are observed over the Arctic near the surface compared to the free troposphere. Intense fires over Siberia and western Russia/eastern Europe coupled with transport of Asian emissions into the Arctic free troposphere during spring 2008 led to enhanced aerosol concentrations aloft at this time of year. The models have problems simulating enhanced aerosols aloft during spring 2008. In general, observed aerosol levels are lower during the summer months due to more efficient scavenging processes and less efficient transport of polluted air masses into the Arctic at this time of year. All the ECLIPSE models have too little aerosol in the Arctic in July 2008 pointing to aerosol lifetimes that are too short or suggesting that vertical transport in the models may not be efficient enough.Discrepancies point to remaining uncertainties in emissions as well as deficiencies in global model transport processes and uncertainties in wet scavenging of aerosols during transport to the Arctic