1. General overview

The IAGOS Footprints Service allows a user to explore tropospheric vertical profiles of carbon monoxide mixing ratios (measured by IAGOS) in conjunction with source attribution data (calculated using the SOFT-IO model, cf. Sauvage et al.: Source attribution using FLEXPART and carbon monoxide emission inventories: SOFT-IO version 1.0, Atmos. Chem. Phys., 17, 15271-15292, https://doi.org/10.5194/acp-17-15271-2017, 2017). 

The profiles are over airports visited by commercial aircrafts equipped with IAGOS’ instruments. The SOFT-IO model is based on the coupling of FLEXPART backward footprint (with the receptor points located along the profile) with emission inventory databases:

• GFAS v1.2 (for biomass burning emissions)
• CAMS-GLOB-ANT v5.3 (for anthropogenic emissions).

The service provides a visualisation of the above-mentioned data and data download will be available by the end of April 2024. 

2. User input

In the service, a user can choose:

• an airport, either from the dropdown list (see Legend 1 on Figure 1) or by clicking on the map (7)
• vertical layer (2):
  • lower troposphere (LT) – below 3 km a.s.l.
  • free troposphere (FT) – between 3 km and 8 km a.s.l
  • upper troposphere (UT) – above 8 km a.s.l.

• an emission inventory database used by SOFT-IO: GFAS, CAMS-GLOB-ANT or both, see (3)
• one of 14 emission regions (as defined by GFED), or the total of all regions (4)
• date and time of a profile over the chosen airport with IAGOS measurements of CO mixing ratios; this can be set up by clicking on the time-series plot (5) or using the navigation buttons (6).

Any change in the user input automatically updates the plots which depend on the input changed.

3. Visualised data

The data presented to the user in the form of 4 plots depend on the choice of

• an airport
• a vertical layer
• an emission inventory database
• an emission region
• a date and time of a profile

(see 2. User Input for details).

3.1. Time-series

Given the airport, a certain number of vertical profiles with IAGOS measurements of carbon monoxide mixing ratios are available. Each vertical profile has an associated date and time, and thus averaging the CO mixing ratios within the chosen vertical layer (LT, FT or UT) leads to time-series data which is presented on the plot (see Legend 1 on Figure 2). Usually, the majority of the time-series is derived from IAGOS level 2 data (L2 – final quality controlled observational data), but the most recent part of the time-series can be derived from IAGOS level 1 data (L1 –  intermediate observational data), see (2).

The time-series plot of CO mixing ratios is accompanied with the plot (3). It shows the data calculated by the SOFT-IO model (cf. Sauvage et al.: Source attribution using FLEXPART and carbon monoxide emission inventories: SOFT-IO version 1.0, Atmos. Chem. Phys., 17, 15271-15292, https://doi.org/10.5194/acp-17-15271-2017, 2017). Briefly, the data consist of CO contribution (in ppb) to the receptor located over the airport within the vertical layer from emissions reported in the emission inventory database coming from the region. 

Finally, the vertical dashed line (4) crossing both time-series plots indicates the date and time of the chosen vertical profile, which details are presented on the two other plots.

3.2. Vertical profile

For a given vertical profile (identified by the airport and date and time), the plots (see Figure 3) of the observed CO mixing ratios (1) and modelled CO contribution (2), as functions of ppb of CO by altitude, are available. In case there is sufficient amount of CO observations for the airport within a 5 year window around the profile’s date and time, a 5-year mean and standard deviation vertical profile of observed CO mixing ratios (3) is shown.

CO contribution plot (2) has a form of area plot of ppb of CO by altitude. Apart from the total CO contribution – SOFT-IO TOTAL (4) – to the receptor point (identified on the profile by its altitude), also a repartition of the total into geographical regions and/or emission type is shown (5). In a typical situation when only a few geographical regions provide a non-negligible contribution, these regions can be filtered using the controller shown in (6).

3.3. Footprint

The 10-day backward footprint (see Legend 1 on Figure 4) with an origin at the receptor (2) (whose location is determined by the airport (3) and the vertical layer (LT, FT or UT) (4), and time is determined by time and date (5)), is shown in a form of a heat map. The footprint (residence time) is calculated by FLEXPART (Lagrangian transport and dispersion model, https://www.flexpart.eu/) on a 4-dimensional grid (longitude / latitude / height for the space dimensions and backward simulation time). This footprint is subsequently used by SOFT-IO model to calculate CO contribution to the receptor point based on the given emission inventory database. For the visualisation purposes, the footprint is integrated along height and time dimensions and normalised by surface element, and thus leading to a longitude / latitude scalar field being the residence time in a total air column during a 10-day period.

The heat map, which visualises the residence time, can be tailored by the user by choosing:

• the scale (linear, power, logarithmic) (6),
• a threshold of cut-off small values of the residence time (7).

4. Interactive features of the plots

Each plot comes with several interactive features:

• Using the figure controller (see Legend 1 on Figure 5) the user can zoom or pan onto an area of interest, reset view or download the figure (by clicking on the camera icon).
• Clicking on the legend marker (e.g. (2)) allows to hide or show the corresponding plot element.
• A drag-and-drop gesture over the x- or the y-axis shifts the axis, while a scrolling gesture changes the axis’ scale (does not apply to the map).
• Double-clicking on an annotation item (title, axis annotation, legend items, see the underlined elements of the plot on Figure 5, e.g. (3)) allows for the annotation edit, which can be useful before eventual figure download.