  Radio Frequency Interference (RFI) is unwanted noise that swamps the desired
astronomical signal. Radio astronomers have always had to deal with RFI
detection and excision around telescope sites, but little has been done to
understand the full scope, nature and evolution of RFI in a unified way. We
undertake this for the MeerKAT array using a probabilistic multidimensional
framework approach focussing on UHF-band and L-band data. In the UHF- band, RFI
is dominated by the allocated Global System for Mobile (GSM) Communications,
flight Distance Measuring Equipment (DME), and UHF-TV bands. The L-band suffers
from known RFI sources such as DMEs, GSM, and the Global Positioning System
(GPS) satellites. In the "clean" MeerKAT band, we noticed the RFI occupancy
changing with time and direction for both the L-band and UHF band. For example,
we saw a significant increase (300% increase) in the fraction of L-band flagged
data in November 2018 compared to June 2018. This increase seems to correlate
with construction activity on site. In the UHF-band, we found that the early
morning is least impacted by RFI and other outliers. We also found a dramatic
decrease in DME RFI during the hard lockdown due to the COVID-19 pandemic. The
work presented here allows us to characterise the evolution of RFI at the
MeerKAT site. Any observatory can adopt it to understand the behaviour of RFI
within its surroundings.
