CRITICAL REVIEW OF THE ATMOSPHERIC COMPOSITION OBSERVING CAPABILITIES FOR MONITORING AND FORECASTING

Monitoring of atmospheric composition covers applications related to evaluating distributions and changes in atmospheric composition, both temporally and spatially, on regional to global scales. Such applications support scientific assessments and process studies and require measurement reproducibility, small data uncertainty, long-term stability, and global or regional data representativeness, while efficient data delivery can help ensure timely access to the observations. These monitoring applications include support for treaty monitoring, the assessment of trends in composition and emissions/fluxes, the early detection of unexpected anomalies in composition, and the production of climatologies and re-analyses. Data are often used in products such as the WMO Global Atmosphere Watch Ozone and Greenhouse Gas Bulletins and the State of Climate Services for Health report, and they provide the Essential Climate Variables related to atmospheric composition for the Global Climate Observing System.

Forecasting atmospheric composition changes and their induced environmental phenomena covers forecasting applications from global to regional scales, with horizontal resolutions like global Numerical Weather Prediction (approx. 10 km and coarser), and with stringent timeliness requirements; near-real-time. The uncertainty of these forecasted atmospheric composition changes can be higher than in the case of monitoring. These applications include support for operations such as air quality and chemical weather forecasts, sand and dust storm warnings, wildfire plume dispersion, and haze-fog prediction. There are clear connections and synergies with many of the Numerical Weather Prediction applications. Although the new guidelines of the Rolling Review of Requirements have created new categorizations of the application areas, it is important to highlight that the requirements for monitoring and forecasting are different. This report will consider both application areas, noting that there are similarities in the observational requirements, but that these may vary depending on the application area.

This document provides a holistic vision of the gaps in observations for all the focal areas of the Global Atmosphere Watch Programme: aerosols, long-lived greenhouse gases, stratospheric ozone and vertical ozone profiles, reactive gases including tropospheric ozone, NOx, CO, VOCs and SO2, total atmospheric deposition, and UV radiation. The variables covered by this document are part of the list of variables included in the application 2.6 of the Observing Systems Capability Analysis and Review Tool: Atmospheric Composition Forecasting and Monitoring. That database is the official repository of requirements for the observation of geophysical variables in support of WMO Programmes and Co-sponsored Programmes.