In this study, we have taken advantage of a variety of imaging systems onboard different spacecraft (Table 1 and Figure 3):

 VMC (Visual Monitoring Camera) (Ormston et al., 2011; Sánchez-Lavega et al. 2018a), on board MEX, is a low resolution RGB color camera that usually observes from the apoapsis of the MEX orbit at 10500km (Details on the orbit and VMC  operations can be found in Ravanis et al., 2020). Images are usually taken in a series covering several minutes, enabling the measurement of atmospheric motions from the tracking of clouds and dust features (Hernández-Bernal et al., 2019).
 HRSC (High Resolution Stereo Camera) (Jaumann et al., 2007) on board MEX is a high resolution pushbroom camera that takes images in 9 different channels at different altitudes along the highly elliptical orbit.
 OMEGA (Observatoire pour la Minéralogie, l'Eau, les Glaces et l'Activité) (Bibring et al. 2004) on board MEX, is an imaging spectrometer that takes images simultaneously in several spectral bands.
 IUVS (Imaging Ultraviolet Spectrograph) (McClintock et al., 2015, Connour et al. 2019) on board MAVEN, is a scanning-slit spectrograph that takes composite false color UV images of Mars. IUVS acquires data during nearly every MAVEN orbit with a cadence of  ~4.5 hours, enabling it to image recurring phenomena.
 MCC (Mars Colour Camera) (Arya et al. 2015) on board ISRO (Indian Space Research Organization) MOM, is an RGB color camera that acquires images at different altitudes from a highly elliptical orbit, usually with high resolution.
 VIS (Visual Imaging System) (Wellman et al., 1976) on board Viking 2 orbiter was a single channel visible camera of high resolution. Viking orbiters were in highly elliptical non sun-synchronous orbits.
 MARCI (Mars Color Imager) (Bell et al., 2009) on board MRO is a pushbroom camera that observes Mars during the afternoon from an afternoon sun-synchronous orbit, achieving high-resolution coverage of the whole planet every Martian sol. As MARCI only observes during the afternoon, it has never imaged the AMEC itself, therefore we use MARCI for support in the understanding of the AMEC daily cycle (section 4).
This includes all current missions in non sun-synchronous orbits, except TGO. We have excluded TGO since its only camera, CASSIS (Colour and Stereo Surface Imaging System), has a narrow field of view and thus it is not likely to have imaged the AMEC.

[Figure: Figure 2. Seasonal coverage of Arsia Mons observations by different instruments. Colored points represent single observations and arrows represent periods with continuous observations (at least every few sols). Only observations between 5 and 10 LTST (Local True Solar Time) are included. Positive observations (i.e. with the AMEC present) are indicated by the background colour. Flat colored areas indicate continuous observations, and striped areas infer the probable minimum duration of the phenomenon. Single positive observations are indicated by a small striped area. The actual duration of the phenomenon is very likely longer than shown here for most MYs, as few suitable observations are available before MY34, and they are all positive. This figure will be discussed again in section 7 as part of the interannual comparison. Refer to tables S1-S6 in the supporting material for further details.]