Atmospheric composition forecasts produced operationally by the Copernicus Atmosphere Monitoring Service (CAMS), which is implemented by ECMWF on behalf of the EU, can on request be provided in the form of tailor-made, detailed plots on a dedicated web page to support scientific field campaigns. ECMWF provided such a service even before CAMS was created in 2014, and to date more than 30 field campaigns have been supported in this way.
Enhancing our knowledge of trace gases and aerosols in the atmosphere is key to tackling air pollution, responding to climate change and improving the simulation of feedbacks between weather and atmospheric composition. Aircraft campaigns make an important contribution to this endeavour by observing trace gases and aerosols in situ. It is important for these campaigns to define their flight routes in a timely manner. CAMS forecasts provide valuable advance information on pollutant or desert dust plumes to support the flight route planning.
The CAMS flight campaign support service (FCSS) is a special service for the scientific community. Principal investigators of interested campaigns can request a choice of parameters, geographical areas, levels and vertical cross-section lines by filling in an online form. Each day for the duration of the campaign, the requested plots (typically several hundred) are produced and presented on the CAMS website shortly after the forecast is completed.
A further challenge such campaigns face is the timely attribution of observed concentration patterns to associated sources. To help with this, the CAMS FCSS runs an additional forecast suite that includes hypothetical tracers with a prescribed atmospheric residence time, which are injected over predefined regions to indicate the origin of observed plumes. Most commonly, anthropogenic or biomass burning emissions of carbon monoxide are used as the emissions of the hypothetical tracer. The source areas can be continental in scale, such as North America, but local hotspots such as the Ruhr area in Germany have also been requested and have proven to be valuable for campaign planning. The tracers often show the predicted transport patterns more clearly than the forecast for the actual concentration fields. Another tracer used in the CAMS system, stratospheric ozone, identifies intrusions of dry and ozone-rich air into the troposphere. If CAMS is involved in the campaign planning at an early stage, more complex tracers can be implemented. For example, a tracer to track oceanic emissions of short-lived halocarbons and a tracer of the nitrogen oxides emitted from lightning were included in the forecasts for the CAST/CONTRAST/ATTREX campaigns.
The first time the service was provided was back in 2008 for the POLARCAT/ACTRIS campaigns, which investigated the long-range transport of pollutants into the Arctic. Several subsequent campaigns supported by the service observed the pollutant plumes resulting from biomass burning and anthropogenic emissions (e.g. SAMBA and EMeRGe).
As Prof. John Burrows, principal investigator of the EMeRGe campaigns, explains: “The CAMS 5‑day forecast input was used by the flight planning group to prepare the flight tracks to catch the plumes from mega-cities and biomass burning on a daily basis. Gas samples taken have shown that HALO aircraft intercepted the pollution plumes very successfully.”
Other campaigns have aimed to measure aerosol composition and its interaction with radiation and clouds (e.g. ICE-D and W-CAN). Outflow patterns of desert dust and its impact on local weather have also been studied (e.g. FENNEC and DACCIWA). Yet other campaigns (e.g. ACTRIS and HIPPO) have focused on the long-range gradient and distribution of long-lived greenhouse gases and on exchange processes between the stratosphere and the troposphere.
CAMS can in turn use the observations made during the campaigns to evaluate its forecasts and analyses. This targeted evaluation complements the routine evaluation of CAMS products. As transport processes play a big role in weather forecasts, tracer observations can also help to evaluate meteorological aspects in ECMWF’s Integrated Forecasting System (IFS).
For more information on the CAMS flight campaign support service, see: https://atmosphere.copernicus.eu/scientific-field-campaign-support