Forecasting Stratospheric Chemistry for Copernicus

2023-2024
Since 27 June 2023, Europe’s Copernicus Atmosphere Monitoring Service’s (CAMS) forecasts the detailed chemical processes not only in the troposphere (lower 10 km of the atmosphere) but also in the ozone layer, thanks to BIRA-IASB’s contribution to the Integrated Forecasting System (IFS) of the European Centre for Medium Range Weather Forecasts (ECMWF).

We extended IFS with stratospheric chemistry modules from our own modelling and assimilation system (BASCOE) and validated the improved operational forecasts of stratospheric composition.

Extending the CAMS chemical forecasts to the stratosphere

Since 27 June 2023, global forecasts by the Copernicus Atmosphere Monitoring Service (CAMS) include not only detailed information on the troposphere but also on the stratosphere, which spans 15–50 km in altitude and contains the ozone layer that shields us from harmful UV radiation.

Each spring, a “hole” forms in the ozone layer above the Antarctic, and occasionally the Arctic. Recent years have seen major disruptions in the stratosphere due to events like

Previously, CAMS used a simplified stratospheric chemistry model, limiting its ability to capture such disruptions. Responding to user needs, the system now includes a more complete representation of stratospheric processes, improving monitoring of the ozone layer and its links to the climate crisis.

Monitoring atmospheric composition by Europe                  

CAMS provides global, real-time forecasts of atmospheric composition, supporting applications such as:

Its data reach over 200 million people daily via websites and apps. These forecasts are produced by a special configuration of the Numerical Prediction System of ECMWF (the European Center for Meteorological Weather Forecasts), which integrates both meteorology and atmospheric chemistry.

As part of CAMS, the Royal Belgian Institute for Space Aeronomy (BIRA-IASB) has implemented the modelling of stratospheric chemical processes.

A new generation of global atmospheric models

Until 2023, CAMS did not explicitly model the complex chemistry of the ozone layer. BIRA-IASB, building on its BASCOE system developed since 2002, integrated stratospheric chemistry modules into the ECMWF model.

This upgrade enables forecasts of not only ozone and stratospheric dynamics but also key chemical species like NO₂, HCl, and ClO that influence the thickness of the ozone layer. Users now benefit from more detailed insights into its evolution, shaped by both the Montreal Protocol and the currently unfolding climate crisis.

Further improvements, including aerosol-gas interactions, were implemented in the operational model on 12 November 2024.

This achievement reflects 25 years of continuous R&D at BIRA-IASB and long-term support from the European Union’s Copernicus Programme and the Belgian Federal Science Policy Office.

 

References:

Europe’s Copernicus Atmosphere Monitoring Service’s (CAMS)
Europe’s Copernicus Atmosphere Monitoring Service’s (CAMS)
Five-day forecasts maps
Five-day forecasts delivered by the new version of ECMWF/IFS CAMS global system: maps in the lower stratosphere at the pressure level 30 hPa, corresponding to an approximate altitude 22 km above ground. The date shown is 6 October 2022, as the 2022 ozone hole was one of the longest-lived of the last 40 years. The maps show temperature, ozone (O3), nitrogen dioxide (NO2), hydrogen chloride (HCl) and chlorine monoxide (ClO) to illustrate the development of the polar ozone hole.

The very low temperatures above the Antarctic lead to the development of stratospheric clouds and the chemical production of HCl, generating after the long polar night ClO, which destroys ozone. NO2 is involved in these chemical reactions and is also an important pollutant at the surface: computing its concentration in the stratosphere allows a better use of satellite observations to forecast surface pollution.
Evolution Antarctic ozone hole CAMS
Figure generated by CAMS on 15 September 2024 (and updated every day) to monitor the evolution of the Antarctic ozone hole and compare it with the previous years. The red line shows the area of the ozone hole as a function of day during the current year, the blue lines show the corresponding evolution during the two previous years, and the grey zones show the range of values encountered since satellite observations are available (1979).