1. OPERATIONAL ATMOSPHERIC CHEMISTRY MONITORING MISSIONS CAPACITY ESA contract no. 17237/03/NL/GS GEOPHYSICAL DATA REQUIREMENTS Michiel van Weele, KNMI Final presentation June 2, 2005

2. Overview Data Requirements Objectives and Strategy to Geophysical Data Requirements Relations to IGACO and other available requirements Sampling and coverage; atmospheric domains Spatial resolution and revisit time Uncertainty Measurement Strategy: Ozone Layer and UV Measurement Strategy: Air Quality Measurement Strategy: Climate Geophysical Data Requirements Tables Summary

3. Objectives User Requirements per Theme: Ozone Layer and Surface UV Radiation Air Quality Climate and per User Type / Application Protocol Monitoring Near-real time data use Assessment Objectives Compile the user requirements per theme / user category and interpret in terms of a required set of observables per atmospheric domain Define a measurement strategy for the optimal combination of satellite observations, ground-based / in-situ observations and use of models

4. Strategy to Data Requirements Specify for each parameter the (threshold) resolution and revisit time requirements per atmospheric domain and on the basis of the observed spatial and temporal variability Define a measurement strategy the different role of satellite data, ground-based networks and atmospheric models for each theme/user type combination Investigate the role of data assimilation for uncertainty requirements, also in relation with the established resolution and revisit time requirements and sampling/coverage Define the auxiliary data requirements for the applications. Examine and try to understand differences with tabulated data requirements such as IGACO, GMES-GATO/BICEPS, ESA studies (ACECHEM, GeoTrope, Kyoto), Eumetsat paper on Nowcasting, and MTG requirements

5. Relations to IGACO and other Requirements IGACO data requirements have not been specified per theme/user type. Instead, distinction has been made in a group-1 (existing systems) and group-2 (next generation systems) set of observables IGACO has four themes, CAPACITY only three. The fourth theme of IGACO is the oxidising capacity, which in Capacity has been integrated in the assessment of the three other themes IGACO requirements are given on a per species and atmospheric domain basis, but the rationale behind each of the quantitative requirements has not been detailed in the IGACO report. ACECHEM and GeoTrope are compilations of data requirements for research missions and exceed operational data requirements Eumetsat Nowcasting position paper only contains requirements for <12 hours ahead MTG requirements focus on the geostationary, non-global perspective

6. Sampling and Coverage Requirements The themes (Ozone Layer, Air Quality and Climate) are all of a global nature. The target requirement for satellite observations is to get as close as possible to global coverage with near-contiguous sampling. Ground-based networks should be globally representative. For Air Quality additional focus is on the local, regional to continental scale in Europe. Threshold coverage for satellite data and surface networks contributing to Air Quality is Europe, including Turkey and Europes coastal waters as well as the closest parts of the North- Atlantic. The aim of each component to an integrated system should be to maximize its contribution, the number of independent observations mainly being limited by any of the other data requirements on, e.g., uncertainty, resolution and revisit time. The integrated system will allow data gaps in space and time, however only up to a certain extent. This will depend on the application.

7. Atmospheric domains US + M MS LS TTL US + M MS US + M MS LS FT + UTFT,UT Tropics Eq. – 30° Mid- latitudes 30° – 60° Polar region 60° – Pole FT FT + UT + LS 35 km 20 km 16 km 6 km 12 km PBL 2 km 80 km

8. Uncertainty The (assumed) uncertainty mainly determines the potential impact of observations in assimilation systems. These requirements are most quantitative and are leading. The uncertainty requirement contains a random component and a systematic component. The latter component can only be established by long-term validation with independent measurements. For ground-based and in-situ observations a representation error will contribute significantly to the overall uncertainty. Satellite observations suffer less from this error as long as the resolution is more or less comparable to the model grid size. Large numbers of independent observations from prolonged data sets with stable retrievals and limited instrumental drift will help to better characterize random and systematic components (=> mission lifetime) Spatio-temporal variations in (current) model uncertainties have not been taken into account. Model uncertainties are often related to intermittent processes and unpredictable events, which are often difficult to assign to certain locations and time periods and can not easily be used to relax requirements.

9. Spatial Resolution and Revisit Time Typically the resolution and revisit time requirements are determined by the known variability of the observable in space and time in the different atmospheric domains. Ultimate threshold is to observe some of the variability. The horizontal resolution should be typically a factor 2-3 smaller than the error correlation length (ECL) used in the assimilation of the observable. The error correlation length is typically a function of altitude and determined by physical processes. The ECL decreases from several 100 kms in the middle stratosphere to tens of kilometers in the troposphere and even smaller in the PBL. Vertical resolution requirements are related to the observed vertical gradients in the atmosphere. Requirements are most stringent in the UTLS and PBL and much less in the free troposphere and middle stratosphere and mesosphere. In principle, the revisit time requirements can also be based on required update frequencies from assimilation studies on anomaly correlations. These correlations however mainly depend on the predictability of the meteorology. Revisit time requirements are most stringent in the PBL.

10. Data Requirements per Theme and User Category Theme A: Ozone Layer and Surface UV Radiation A1. Protocol Monitoring A2. Near-real time data use A3. Assessment Theme B: Air Quality B1. Protocol Monitoring B2. Near-real time data use B3. Assessment Theme C: Climate C1. Protocol Monitoring C2. Near-real time data use C3. Assessment

11. Measurement Strategy A1 O3/UV Protocol Monitoring Role of Satellite measurements Monitoring of the global total ozone spatial distribution (<3% uncertainty for individual measurements) Contribution to the monitoring of surface UV radiation by provision of information on total ozone, solar irradiance, surface albedo, and aerosol optical depth and absorption Role of Surface network Trends in concentrations of regulated ozone depleting substances (ODS) Detection of ODS emissions and their trends Trend in Surface UV and the attribution of UV changes to ozone layer changes Validation of the satellite data Weekly surface/column observations (O3, ODS) by representative surface networks Auxiliary data Meteorology from NWP centers including surface data (dynamics, clouds, snow cover)

12. Measurement Strategy A2 O3/UV Near-real time data use Role of Satellite Measurements Forecasting of the Ozone layer and surface UV; Feed polar ozone reports Better representation of stratospheric transport, chemistry and radiation in NWP to improve (medium range) weather forecasts and stratospheric near- real time monitoring, also by improving retrievals of temperature => stratospheric distribution of major greenhouse gases (CO2, H2O, O3, CH4, N2O) and aerosols Further: tracers (B-D circulation, ST exchange), PSCs Role of surface network and in-situ operational measurements NRT validation of the satellite measurements Ozone/ radiosondes: NRT delivery of O3, H2O, p, T, wind NRT delivery of (UTLS) aircraft observations of O3, H2O, CO, HNO3, HCl Auxilary data Meteorological forecast from NWP centers including surface data (dynamics, clouds, sunshine duration, snow cover)

13. Measurement Strategy A3 O3/UV Assessment Role of Satellite measurements State of ozone layer and its evolution in time; role of dynamics, radiation, and chemistry Changes in surface UV radiation globally, per location Distribution and trends in ODS and reservoir species The role of PSCs and of denitrification The role of volcanic eruptions (SO2, aerosol, aerosol type) Short-lived species can typically be derived from long-lived species given that the chemistry is sufficiently understood (some exception: NO2, ClO etc) Role of Surface network Validation of the satellite measurements Surface UV radiation trend monitoring and attribution Concentration monitoring ODS; detection of ODS emissions Auxiliary data meteorology from NWP centers including surface data (dynamics, clouds, sunshine duration, snow cover)

14. O3 / Surface UV Radiation: Satellite Data ObservableUser(s)Domain(s) O3A1, A2, A3Stratosphere, Troposphere UV solar spectrumA1, A2, A3Top-of-Atmosphere UV aerosol optical depthA1, A2, A3Troposphere UV aerosol absorption optical depthA1, A2, A3Troposphere Spectral UV surface albedo A1, A2, A3Surface H2OA2, A3Stratosphere N2OA2, A3Stratosphere CH4A2, A3Stratosphere CO2A2, A3Stratosphere HNO3A2, A3Stratosphere Volcanic aerosolA2, A3Stratosphere CFC-11A3Stratosphere CFC-12A3Stratosphere HCFC-22A3Stratosphere ClOA3Stratosphere BrOA3Stratosphere SO2A3Stratosphere Aerosol surface densityA3Stratosphere PSCs A3Stratosphere HClA3Stratosphere ClONO2A3Stratosphere CH3ClA3Stratosphere HBrA3Stratosphere BrONO2A3Stratosphere CH3BrA3Stratosphere

15. Measurement Strategy B1 Air Quality Protocol Monitoring Role of Satellite Measurements Interpolation of surface networks in the PBL Boundary conditions for regional AQ models and tropospheric background (long-range transport) Application to inverse modeling of surface emissions (aerosols, NO2, SO2, CO, CH2O). Formaldehyde is related to VOC emissions Role of Surface Networks EU Framework Directives (surface concentrations) National Emission Ceilings (concentration monitoring to derive emissions) Gothenburg protocol on ground-level ozone Ship emissions (operational ship monitoring coastal waters) A representative network for surface concentrations and emissions in Europe Satellite and model validation, also by boundary layer profiling (LIDARS, Towers) Auxiliary data Meteorology from NWP Centers including surface data (dynamics, clouds, surface characterization) Emission inventories

16. Measurement Strategy B2 Air Quality Near-real time data use Role of Satellite Measurements Interpolation of surface network in PBL Plume transport and plume dispersion on local, regional, continental and global scale Boundary conditions to regional AQ models and tropospheric background levels Early warnings on hazards and unpredictable events Role of Surface Networks Local Air Quality monitoring of surface levels Constraints on satellite-derived aerosol types and VOC emissions from HCHO NRT ozone sonde data for ozone and relative humidity profiles CH4 trend monitoring Auxiliary data Forecast meteorology from NWP centers including NRT surface / vegetation data Emission inventories

17. Measurement Strategy B3 Air Quality Assessment Role of Satellite Measurements Global-scale oxidizing capacity components and their evolution in time (O3, CO, H2O, NOx, CH4, CH2O, UV, aerosols) Long-range transport of pollutants; tropospheric background levels Interpolation of data from surface networks input to inverse modeling of surface emissions (CO, NOx, SO2, CH2O) Isotopes of CO to distinguish between emission types Role of Surface network Assessment of surface concentrations and boundary layer pollution over Europe Concentration monitoring to derive emissions on national levels HNO3, N2O5(at night) and org. nitrates: reservoir species to constrain acid deposition and N budget Validation of satellite observations (including sondes, lidars, towers) Auxilary data Meteorology from NWP centers including surface characterisation Emission inventories

18. Air Quality: Satellite Data ObservableUser(s)Domain(s) O3B1, B2, B3PBL/Troposphere NO2 B1, B2, B3PBL/Troposphere COB1, B2, B3PBL/Troposphere SO2B1, B2, B3PBL/Troposphere CH2OB1, B2, B3PBL/Troposphere Aerosol ODB1, B2, B3PBL/Troposphere Aerosol TypeB1, B2, B3PBL/Troposphere H2OB2, B3PBL/Troposphere HNO3B2, B3PBL/Troposphere N2O5B2, B3PBL/Troposphere PAN / Org. nitratesB2, B3PBL/Troposphere Surface UV albedoB2, B3Surface

19. Measurement Strategy C1 Climate Protocol Monitoring Role of Satellite Measurements Concentration monitoring for inverse modeling of emissions of CH4, CO2, CO and NO2 Global concentration distributions of the mentioned gases, O3 and aerosols Role of Surface network Greenhouse gases trend monitoring (CO2, CH4, N2O, SF6, CF4, HFCs Weekly surface concentrations and total columns from a representative network. Validation of satellite measurements Concentration monitoring for inverse modeling of surface emissions of CH4, CO2, CO and NO2 Tropospheric O3: sondes, lidar and surface data; Tropospheric aerosol optical depth and aerosol absorption optical depth Trend monitoring for ozone depleting substances ODS with climate forcing: (H)CFCs. Auxiliary data Meteorology from NWP centers including surface data Emission inventories and estimates on sinks

20. Measurement Strategy C2 Climate Near-real time data use Role of Satellite Measurements For use in assimilation at NWP centers to improve on stratospheric elements H2O, O3, stratospheric tracers, and information on aerosols and cirrus Climate monitoring (delivery time ~weeks – months) Validation of climate and NWP models (present-day climate reconstructions) Role of Surface network NRT validation of satellite observations Evolution of long-lived greenhouse gases In-situ observations in the PBL of CO2 NRT delivery of ozone sonde / Lidar data: O3, H2O Auxiliary data Forecast meteorology from NWP centers including surface data

21. Measurement Strategy C3 Climate Assessment Role of Satellite Measurements Assessment radiative forcing and its changes over time, including volcanic eruptions and solar cycle: GHGs, aerosol OD, aerosol absorption, SO2, cirrus) Assessment of stratospheric H2O budget and H2O trend monitoring The role of the ozone layer evolution on climate change: CFCs, Cly, ClO, HNO3 The role of the oxidizing capacity of the troposphere for climate change (CH4, CO, O3, H2O, NOx, UV) The role of a changing B-D circulation on climate change: tracers Concentration monitoring for inverse modeling of GHG & precursor emissions Role of Surface network Validation of satellite observations Ozone sonde/LIDAR network for trends in strat. profiles of long-lived gases Radiosonde/GPS network for H2O and T Aerosol network UTLS operational aircraft observations of O3, H2O, CO, NOx Auxiliary data Meteorology from ECMWF analyses, including surface data

22. Climate: Satellite Data ObservableUser(s)Domain(s) CH4C1PBL, Troposphere CO2C1PBL, Troposphere COC1PBL, Troposphere NO2C1PBL, Troposphere O3C1PBL, Troposphere Aerosol ODC1PBL, Troposphere Aerosol absorption ODC1PBL, Troposphere H2OC2, C3Troposphere, Stratosphere O3C2, C3Troposphere, Stratosphere CH4C2, C3Stratosphere CO2C2, C3Stratosphere N2OC2, C3Stratosphere Aerosol optical propertiesC2, C3Stratosphere Cirrus optical propertiesC2, C3Troposphere HNO3C3Troposphere, Stratosphere NO2C3Stratosphere SF6C3Stratosphere Cl compoundsC3Stratosphere N2O5C3Stratosphere PANC3Troposphere CO, HCs, CH2O,H2O2C3Troposphere

23. Data Requirements Table Format A1S: Ozone Layer; Protocol Monitoring; Satellite data Data product + Driver Height Range(s) Hor. Resolution (target/threshold) Vert. Resolution (target/threshold) Revisit time (target /threshold) Uncertainty (threshold) + Similar Tables for A1-G, A2-S, A2-G, ….C3-S, C3-G (18 Tables in total)

24. Summary This work has drawn from several earlier requirement studies, but it has never been done before in such a comprehensive way with focus on atmospheric composition and for operational applications Geophysical Data Requirements have been tabulated per theme and within each theme per user type Per data product and product type (column, profile) resolution, revisit time and uncertainty have been tabulated, for each atmospheric domain Based on the definition of drivers per application a measurement strategy has been proposed for satellites, ground-based/in-situ data and auxiliary data, including models The tables, traceable to the user requirements, served as input for the analysis of existing/planned missions and networks, and for the definition of instrument requirements for new mission concepts