Table 2.
Summary of model performance statistics over the period 2010–2017 for the national, provincial and site-specific models showing the range of R2, root mean squared error (RMSE) and mean absolute error (MAE) for the years included.
| Model Building | Spatial LOLO CV | Temporal LTO CV | Data Availability | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| R2 (Range) |
RMSE (Range) |
MAE (Range) |
R2 (Range) |
RMSE (Range) |
MAE (Range) |
R2 (Range) |
RMSE (Range) |
MAE (Range) |
No of Unique Sites | Years | |
| National | 0.77–0.79 | 12.1–16.76 | 8.69–11.38 | 0.11–0.35 | 17.72–29.47 | 13.62–23.65 | 0.77–0.79 | 12.31–16.43 | 8.85–11.39 | 20–44 | 2010–2017 |
| Provincial * | |||||||||||
| Mpumalanga | 0.73–0.81 | 14.03–19.35 | 9.63–12.13 | 0.39–0.69 | 22.06–36.21 | 13.5–29.59 | 0.73–0.78 | 13.55–19.21 | 9.85–12.01 | 5–17 * | 2010–2017 |
| Gauteng | 0.49–0.79 | 10.34–23.36 | 9.24–16.75 | 0.26–0.52 | 19.72–34.25 | 15.69–29.42 | 0.52–0.79 | 15.11–23.43 | 9.94–16.87 | 6–18 * | 2010–2017 |
| Western Cape | 0.29–0.71 | 6.74–8.73 | 5.11–6.72 | 0.35–0.54 | 7.38–11.22 | 5.76–8.86 | 0.44–0.66 | 6.66–23.29 | 5.18–17.92 | 1–11 * | 2010–2017 |
| KwaZulu-Natal | 0.55–0.79 | 7.36–9.53 | 5.29–8.11 | 0.29–0.57 | 8.54–19.95 | 6.95–16.82 | 0.47–0.78 | 7.37–10.71 | 5.46–8 | 3–6 * | 2010–2017 |
| Site-specific ** | |||||||||||
| Beliville | 0.42–0.47 | 5.81–9.16 | 4.51–7.26 | NA | NA | NA | 0.45–0.49 | 5.67–9.02 | 4.45–7.03 | NA | 2012, 2013, 2015–2017 |
| Bodibeng | 0.54–0.63 | 16.89–19.42 | 13.61–15.07 | NA | NA | NA | 0.57–0.67 | 16.36–18.91 | 13.32–14.87 | NA | 2012–2013 |
| Brackenham | 0.41–0.49 | 8.06–8.95 | 6.31–7.10 | NA | NA | NA | 0.46–0.49 | 7.81–8.95 | 6.25–7.15 | NA | 2011, 2015–2017 |
| Booysens | 0.45–0.67 | 22.13–22.82 | 17.99–20.77 | NA | NA | NA | 0.5–0.71 | 22.10–25.74 | 17.87–20.53 | NA | 2012,2014 |
| Camden | 0.38–0.62 | 10.64–23.27 | 8.69–17.85 | NA | NA | NA | 0.39–0.65 | 10.29–22.43 | 9.61–17.15 | NA | 2013, 2015, 2017 |
| CBD | 0.38–0.59 | 6.35–9.55 | 4.93–7.45 | NA | NA | NA | 0.41–0.64 | 6.28–9.23 | 4.98–7.21 | NA | 2011–2013, 2015–2017 |
| City Hall | 0.45 | 10.29 | 7.69 | NA | NA | NA | 0.48 | 9.78 | 7.43 | NA | 2010 |
| Elandsfontein | 0.39–0.52 | 11.72–12.49 | 9.38–9.68 | NA | NA | NA | 0.45–0.57 | 11.17–11.79 | 8.99–9.38 | NA | 2016–2017 |
| Ermelo | 0.48–0.76 | 9.20–18.96 | 7.69–15.31 | NA | NA | NA | 0.51–0.77 | 9.12–19.98 | 7.54–13.89 | NA | 2010–2016 |
| Etwatwa | 0.63 | 24.03 | 18.74 | NA | NA | NA | 0.69 | 23.78 | 18.56 | NA | 2012 |
| Ferndale | 0.68–0.74 | 3.63–5.42 | 2.84–3.92 | NA | NA | NA | 0.65–0.77 | 3.49–5.38 | 2.76–3.88 | NA | 2010–2012 |
| Foreshore | 0.32–0.49 | 5.29–9.76 | 4.1–7.22 | NA | NA | NA | 0.33–0.49 | 5.27–9.58 | 4.13–7.08 | NA | 2011–2013,2015–2017 |
| Gangles | 0.48–0.74 | 11.86–13.4 | 9.22–10.11 | NA | NA | NA | 0.51–0.75 | 11.23–11.88 | 8.96–9.71 | NA | 2010, 2011, 2013,2014 |
| Germiston | 0.42 | 19.65 | 14.96 | NA | NA | NA | 0.44 | 19.07 | 14.79 | NA | 2011 |
| George | 0.55–0.56 | 7.09–8.41 | 5.49–6.56 | NA | NA | NA | 0.58 | 6.95–8.12 | 5.39–6.34 | NA | 2010, 2013 |
| Goodwood | 0.46–0.57 | 6.77–8.78 | 5.26–8.24 | NA | NA | NA | 0.49–0.59 | 6.60–8.49 | 5.29–7.80 | NA | 2011–2012, 2014–2016 |
| Grootvlei | 0.41–0.44 | 10.76–11.32 | 8.70–8.87 | NA | NA | NA | 0.42–0.49 | 10.65–11.12 | 8.63–8.82 | NA | 2011, 2013 |
| Hendrina | 0.39–0.71 | 11.12–17.02 | 8.32–13.62 | NA | NA | NA | 0.43–0.74 | 11.18–16.56 | 8.36–12.96 | NA | 2010–2012,2015–2016 |
| Middleburg | 0.67–0.81 | 7.81–19.25 | 6.08–14.73 | NA | NA | NA | 0.70–0.82 | 7.49–18.63 | 5.92–14.25 | NA | 2010–2016 |
| Olievenhoutbosch | 0.57 | 34.23 | 27.01 | NA | NA | NA | 0.59 | 34.16 | 26.98 | NA | 2012 |
| Orange Farm | 0.45–0.69 | 10.78–19.81 | 8.57–15.56 | NA | NA | NA | 0.49–0.71 | 10.23–19.49 | 8.28–15.62 | NA | 2010,2017 |
| Rosslyn | 0.55–0.61 | 5.91–11.49 | 4.77–9.30 | NA | NA | NA | 0.52–0.67 | 5.86–11.05 | 4.47.8.93 | NA | 2012–2014 |
| Secunda | 0.63–0.77 | 7.73–25.21 | 5.86–19.96 | NA | NA | NA | 0.67–0.77 | 7.47–24.64 | 5.75–19.7 | NA | 2010–2013 |
| Witbank | 0.72–0.83 | 9.21–22.33 | 7.63–17.27 | NA | NA | NA | 0.73–0.83 | 8.79–21.87 | 7.34–16.75 | NA | 2010,2013–2016 |
| Komati | 0.45–0.83 | 8.52–28.02 | 6.61–21.51 | NA | NA | NA | 0.46–0.84 | 8.29–27.11 | 6.5–20.91 | NA | 2011–2012,2014–2017 |
| Leandra | 0.29–0.36 | 6.63–14 | 4.86–10.38 | NA | NA | NA | 0.35–0.4 | 6.35–13.64 | 4.81–10.31 | NA | 2011–2012 |
| Newtown | 0.43 | 22.07 | 17.52 | NA | NA | NA | 0.47 | 21.68 | 17.27 | NA | 2012 |
| Phola | 0.54–0.65 | 22.44–28.89 | 17.83–22.55 | NA | NA | NA | 0.57–0.65 | 22.02–28.88 | 17.48–22.72 | NA | 2013–2014,2016–2017 |
| Stellenbosch | 0.35–0.56 | 6.34–7.31 | 4.85–5.67 | NA | NA | NA | 0.37–0.61 | 6.26–7.14 | 4.83–5.62 | NA | 2012–2013 |
| Tableview | 0.36–0.4 | 5.63–7.04 | 4.43–5.81 | NA | NA | NA | 0.38–0.43 | 5.54–7 | 4.31–5.6 | NA | 2011–2013 |
| Tembisa | 0.71 | 17.78 | 14.09 | NA | NA | NA | 0.73 | 17.35 | 13.89 | NA | 2011 |
| Thokoza | 0.56 | 41.30 | 29.22 | NA | NA | NA | 0.57 | 40.25 | 28.76 | NA | 2011 |
| Wallacedene | 0.47–0.51 | 5.53–11.26 | 4.28–8.9 | NA | NA | NA | 0.47–0.54 | 5.52–10.82 | 4.29–8.69 | NA | 2012, 2015–2017 |
| Wattville | 0.52 | 39.10 | 29.09 | NA | NA | NA | 0.57 | 37.16 | 28.57 | NA | 2012 |
| Club | 0.59–0.67 | 11.01–14.87 | 8.76–11.86 | NA | NA | NA | 0.62–0.69 | 10.7–14.88 | 8.55–11.99 | NA | 2012–2014, 2016–2017 |
| Ekandustria | 0.46–0.59 | 11.14–16.83 | 8.88–13.09 | NA | NA | NA | 0.50–0.64 | 10.58–16.43 | 8.5–12.83 | NA | 2013–2014 |
| Embalenhle | 0.56–0.73 | 16.48–22.18 | 11.34–14.69 | NA | NA | NA | 0.59–0.73 | 13.31–22.18 | 11.03–17.86 | NA | 2012,2014,2016–2017 |
| Verkykkop | 0.44–0.49 | 6.63–9.71 | 5.53–7.88 | NA | NA | NA | 0.47–0.48 | 6.56–9.49 | 5.33–7.72 | NA | 2013,2016–2017 |
| Randwater | 0.32–0.73 | 12.99–15.99 | 9.82–15.83 | NA | NA | NA | 0.36–0.75 | 12.08–15.63 | 9.57–12.19 | NA | 2013–2017 |
| Esikhaweni | 0.43–0.58 | 9.07.9.45 | 7.36–7.4 | NA | NA | NA | 0.44–0.60 | 8.95–9.35 | 7.17 | NA | 2016–2017 |
| Chicken Farm | 0.44 | 13.14 | 10.44 | NA | NA | NA | 0.48 | 12.71 | 10.21 | NA | 2017 |
| Kwazamokuhle | 0.65 | 18.10 | 14.44 | NA | NA | NA | 0.67 | 17.10 | 13.84 | NA | 2017 |
| Kriel Village | 0.62 | 17.27 | 13.55 | NA | NA | NA | 0.66 | 16.89 | 13.41 | NA | 2017 |
| Bosjesspruit | 0.51 | 13.05 | 10.44 | NA | NA | NA | 0.55 | 12.58 | 10.27 | NA | 2017 |
* The provincial models included all possible sites with PM10 observation; ** The sites models included the monitoring stations with at least 70% annual PM10 observation. NA: Not applicable. These are individual site models—Spatial cross-validation (CV) cannot be perform for models with less than two sites. LOLO: Leave one location out spatial cross-validation; LTO: Leave time out temporal cross-validation. Range: The minimum and maximum values of the statistics metrics from the models across 2010.