# Measuring Gas Flaring in Russia with Multispectral VIIRS Nightfire
## 4 Discussion
### Seasonality in Observation and Effect of COVID-19 Pandemic on Gas Flaring
It corresponds to a large four flaring stack facility on a recently commissioned Novoportovskoye oil field at high latitudes with  
Figure 14: Preliminary analysis of VIIRS Active Fire Product (VAFP) [63] Fire Radiative Power (_FRP_) estimates for the hotspots detected within VIIRS Nightfire gas flare contours located in Russia in 2019. (**a**) Plot of VAFP annual weighted monthly mean _FRP_ (_FRP\({}_{\text{WMM}}\)_; in MW) vs. VIIRS Nightfire annual Radiant Heat (_RH_; in MW) (N.b. _RH_ from Equation (2) is used instead of _RH’_ from Equation (4).) Note that the point ID7117 is considered an outlier and is thus excluded from the resulting correlation. (**b**) Plot VAFP monthly _FRP\({}_{\text{WMM}}\)_ (MW) vs. VIIRS Nightfire monthly _RH_ (MW) for gas flares that remain confidently detectable with Nightfire in June (roughly latitudes < 55\({}^{\circ}\)N). (**c**) Plot night-time vs. daytime monthly VAFP _FRP\({}_{\text{WMM}}\)_ (MW) in August and September. (**d**) Histogram monthly day and night-time distribution of raw (non-weighted) _FRP_ (in GW) and graph VAFP detection tally within VIIRS Nightfire gas flare contours. no Nightfire observations available in the May-July period. As noted in Section 4.2, such large flaring facilities may be underestimated with Nightfire, while still being correctly estimated with _FRP_ data; however, to our knowledge, no reported flaring volume data are publicly available for the field to affirm this speculation. With this observation excluded, a stronger correlation (R\({}^{2}\) = 0.95) is observed. For the purposes of filling the summertime gaps in Nightfire observations, monthly VAFP estimates are required instead. Initial unfiltered correlation is not as strong as the annual one (R\({}^{2}\) = 0.73). This can be explained with the presence of increased summer daytime sensitivity of VAFP coinciding with gaps in Nightfire observations, rough estimate of detection frequency applied in _FRP\({}_{WMM}\)_, or the possible seasonal discrepancy in _FRP_ estimates between summer and wintertime observations due to different background brightness and reflectance qualities. To remedy this, a smaller sample (171 Nightfire contours) of flares which remain confidently detectable with Nightfire in June (i.e., roughly with latitude < 55\({}^{\circ}\)N) was selected, which results in a strong correlation (R\({}^{2}\) = 0.88), as shown in Figure 14b. It is worth noting, however, that most of these flares are relatively small compared with the flares in northern regions. To observe the correlation between day and night-time observation, in Figure 14c, only August and September observations for all flares were selected. These months were chosen to represent the summer season (i.e., low chance of snow cover presence), while at the same time having Nightfire estimates available. Although the correlation is strong (R\({}^{2}\) = 0.89), the non-1:1 ratio should be acknowledged. There are other known and observed limitations characterizing the presented data:  
* In Active Fire Detection algorithm, winter daytime pixels containing gas flares may be omitted based on the high reflectance of snow cover of the surrounding pixels combined with low background temperatures. This, combined with lower daylight length, can be the explanation for almost non-existent daytime _FRP_ estimates in the winter season as seen in Figure 14d, which presents raw _FRP_ data. Compared with Nightfire _RH_, overall _FRP\({}_{WMM}\)_ estimates tend to be lower in winter (Figure 14b, blue markers), and, as is later seen in Figure 14d, despite a shorter night-time period, the tally of night-time detections is higher in summer while _FRP_ estimates remain stable. As such, it is possible that winter season observations should be ignored, given that the aim of applying _FRP_ estimates is to fill the summertime gaps in observations. * As _FRP_ itself is retrieved based on wildfire experimental characteristics [66], it may also underestimate the radiative power emitted by higher temperature gas flares.