On 5th of May, at around 6 UTC, a blaze started at the ECO-X rubbish depot in Pomezia, a municipality in the Metropolitan City of Rome (41°41′N, 12°30′E). The fire was active for about two days and the cloud of smoke was visible from several kilometres away. Both the fire service and the local health authority of Pomezia, warned locals to keep windows closed in homes, schools, offices, and health and social care structures, keep animals inside, and to avoid all unnecessary travel.
Observations from remote sensing instruments operated in the context of European Space Agency (ESA) projects, revealed that the smoke plume was transported over Rome and in the Tiber Valley on May 5 and 6. In particular, data from the two PANDORA instruments #115 and #117 (http://pandonia.net/) showed statistically significant increases of nitrogen dioxide (NO2) and formaldehyde (HCOH). Specifically, PANDORA #115 is located at CNR-ISAC, in a semi-rural environment South-East Rome, while PANDORA #117 is operated at Physics Department of Sapienza University, i.e. in a urban environment close to Rome centre. The PANDORA data analysis for this specific case has been performed by LuftBlick team, and used as test case for the development of new retrieval algorithms.
The two PANDORAs #115 and #117 are part of a suite of atmospheric remote sensing instruments operated in synergy to form a satellite products validation “super-site”, called Boundary layer Air Quality-analysis Using Networks of INstruments (BAQUNIN). BAQUNIN is funded by ESA within its Atmospheric Composition Cal/Val framework and is one of the “IDEAS+” contract activities. The super-site instrumental suite comprises, among others, elastic and Raman LIDARs (LIght Detection And Ranging, aerosol and water vapour profiling), sun photometers (e.g. AERONET https://aeronet.gsfc.nasa.gov/, SKYNET http://atmos2.cr.chiba-u.jp/skynet/, PANDONIA http://pandonia.net/) and SODARs (SOund Detection And Ranging, wind profiling in the atmospheric boundary layer).
The two animations show the time evolution of the NO2 and HCOH tropospheric columns. The tropospheric column is the amount of species integrated between the surface and the tropopause (about 10 km altitude).

This quantity is most suitable for the detection of pollution events, which usually impact the lowest portion of the atmosphere.
Each frame of the animations displays the following panels:

1. Upper left: time evolution of NO2(HCOH) tropospheric column from PANDORA #115 (red line) for the 5th of May. The black line is the average of same quantity using data from 4th and 7th of May, considered as reference values for “clean days”.

2. Upper right: same as left panel but for PANDORA #117 (blue line).

3. Lower Left: time evolution of the difference between NO2(HCOH) values of May 5th and the “clean day” reference. This quantity indicates if a statistically significant difference is observed. Red line refers to PANDORA #115 (CNR-ISAC), blue line to OPANDORA #117 (Rome centre).

4. Lower right: the map reports the position of the two PANDORAs and of ECO-X, the PANDORA viewing directions when operating in “direct sun” mode, and the position of the air parcels that, starting from 6:00 UTC (8am local time), are injected in the atmosphere and are subsequently transported (or “advected”) away from the sources by the wind. The colour of the filled circles indicate the approximate altitude of the related air parcel. The trajectories are computed using the Weather Research Forecasting model (http://www.wrf-model.org/index.php) wind products using a simple advection scheme.

It can be clearly seen that the tropospheric amounts of NO2 and HCOH are significantly higher with respect to the reference values. In particular, the air parcel trajectories, estimated from atmospheric model simulation, confirm that the smoke plume was reaching the two PANDORAs at the time when the increase in concentration is observed.
The analysis of all super-site data acquired during the event is on-going, however this exercise demonstrates that the BAQUNIN instrumental set-up is providing high quality and very significant information on air quality of the Rome area. This capacity will be fully exploited when BAQUNIN will operate in synergy with the next to fly SENTINEL-5p mission (https://sentinel.esa.int/web/sentinel/missions/sentinel-5p), which will produce atmospheric chemistry products at relatively high spatial resolution.

 

Authors:

S. Casadio ⁽¹⁾, A.M. Iannarelli ⁽¹⁾, E. Cadau ⁽²⁾, M. Cacciani ⁽³⁾, M. Campanelli ⁽⁴⁾, the PANDONIA TEAM ⁽⁵⁾

Affiliations:

(1) SERCO spa (https://www.serco.eu/index.php/19-public-website/contact )

(2) Sardegna Clima Onlus (http://www.sardegna-clima.it/)

(3) Physics Department, University of Rome “Sapienza” (https://g24ux.phys.uniroma1.it/)

(4) CNR-ISAC (http://www.isac.cnr.it/)

(5) LuftBlick (http://luftblick.at/)