Abstract
During an exceptionally warm September in 2016, unique and stable weather conditions contributed to a heat wave over Poland, allowing for observations of aerosol optical properties, using a variety of ground-based and satellite remote sensors. The data set collected during 11–16 September 2016 was analysed in terms of aerosol transport (HYbrid Single-Particle Lagrangian Integrated Trajectory model (HYSPLIT)), aerosol load model simulations (Copernicus Atmosphere Monitoring Service (CAMS), Navy Aerosol Analysis and Prediction System (NAAPS), Global Environmental Multiscale-Air Quality (GEM-AQ), columnar aerosol load measured at ground level (Aerosol Robotic NETwork (AERONET), Polish Aerosol Research Network (PolandAOD)) and from satellites (Spinning Enhanced Visible and Infrared Imager (SEVIRI), Moderate Resolution Imaging Spectroradiometer (MODIS)), as well as with 24/7 PollyXT Raman Lidar observations at the European Aerosol Research Lidar Network (EARLINET) site in Warsaw. Analyses revealed a single day of a relatively clean background aerosol related to an Arctic air-mass inflow, surrounded by a few days with a well increased aerosol load of differing origin: pollution transported from Germany and biomass burning from Ukraine. Such conditions proved excellent to test developed-in-house algorithms designed for near real-time aerosol optical depth (AOD) derivation from the SEVIRI sensor. The SEVIRI AOD maps derived over the territory of Poland, with an exceptionally high resolution (every 15 min; 5.5 × 5.5 km2), revealed on an hourly scale, very low aerosol variability due to heat wave conditions. Comparisons of SEVIRI with NAAPS and CAMS AOD maps show strong qualitative similarities; however, NAAPS underestimates AOD and CAMS tends to underestimate it on relatively clean days (<0.2), and overestimate it for a high aerosol load (>0.4). A slight underestimation of the SEVIRI AOD is reported for pixel-to-column comparisons with AODs of several radiometers (AERONET, PolandAOD) and Lidar (EARLINET) with high correlation coefficients (r2 of 0.8–0.91) and low root-mean-square error (RMSE of 0.03–0.05). A heat wave driven increase of the boundary layer height of 10% is accompanied with the AOD increase of 8–12% for an urban site dominated by anthropogenic pollution. Contrary trend, with an AOD decrease of around 4% for a rural site dominated by a long-range transported biomass burning aerosol is reported. There is a positive feedback of heat wave conditions on local and transported pollution and an extenuating effect on transported biomass burning aerosol. The daytime mean SEVIRI PM2.5 converted from the SEVIRI AODs at a pixel representative for Warsaw is in agreement with the daily mean PM2.5 surface measurements, whereby SEVIRI PM2.5 and Lidar-derived Ångström exponent are anti-correlated.
Highlights
There is a recognized potential for applications at a regional-scale of such controversial measures as injections of sulphate aerosols into the stratosphere, with an aim at offsetting the impacts of heat waves [1]
The goals of this paper are to demonstrate the capability of a developed-in-house algorithm to provide high temporal and spatial resolution Spinning Enhanced Visible and Infrared Imager (SEVIRI) Aerosol Optical Depth (AOD) maps over Poland in near real-time, as well as to demonstrate the capacity of using the Raman Lidar derived AOD for validation purposes of satellite derived AOD, to compare the SEVIRI AOD with the AOD obtained with other measurements and model outputs, and to draw conclusions on any mutual effects of heat wave conditions on local and long-range transported air pollution and biomass burning smoke over Poland
The SEVIRI AOD was found to be slightly underestimated in comparison to radiometric observations, which can at least be partly attributed to the surface properties during the chosen reference day (15 September), having not been as clean as necessary or expected
Summary
There is a recognized potential for applications at a regional-scale of such controversial measures as injections of sulphate aerosols into the stratosphere, with an aim at offsetting the impacts of heat waves [1]. The high temperatures during heat wave events can favor the development of intense local forest fires. These can cause an increase in the aerosol amount over the areas affected by the heat wave and have a large impact on aerosol properties normally observed [5]. The mutual effects (if any) of long-range transported forest, peatland or grass fire’s aerosols on heat waves have not been undertaken far
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