A novel calibration approach using satellite and visibility observations to estimate fine particulate matter exposures in Southwest Asia and Afghanistan

Figures & data

Figure 1. Map showing visibility monitoring stations in Iraq study region.

Figure 2. Relationship between predicted and measured daily average visibility.

Table 1. Prediction accuracy for 10-fold cross-validation (CV) trials of Stage 1 calibration model.

Trial	CV R^2	CV R^2Spatial	CV R^2Temporal	RMSPE^a (m)
1	0.83	0.96	0.73	580.5
2	0.67	0.89	0.56	831.8
3	0.71	0.86	0.67	795.6
4	0.76	0.60	0.63	679.4
5	0.74	0.77	0.60	703.6
6	0.67	0.84	0.51	886.5
7	0.76	0.98	0.64	816.2
8	0.63	0.94	0.51	909.3
9	0.64	0.95	0.55	913.3
10	0.71	0.63	0.51	798.2
Mean	0.71	0.87	0.60	790.7

Note. m = meters, as in distance of visual range.^aRoot of the mean squared prediction errors.

Figure 3. Plot of predicted versus measured visibility averages for each of 10 CV trials.

Table 2. Prediction accuracy for 10-fold cross-validation (CV) of Stage 3 calibration model.

Site	CV R^2	CV R^2Spatial	CV R^2Temporal	RMSPE^a (m)
1	0.82	0.96	0.64	571.6
2	0.85	0.69	0.75	569.8
3	0.87	0.88	0.81	538.9
4	0.80	0.99	0.66	664.5
5	0.91	0.98	0.83	505.4
6	0.83	0.86	0.68	601.2
7	0.84	0.98	0.70	621.8
8	0.78	0.93	0.56	604.9
9	0.85	0.87	0.66	544.6
10	0.90	0.94	0.84	487.3
Mean	0.84	0.91	0.71	580.3

Note. m = meters, as in distance of visual range.^aRoot of the mean squared prediction errors.

Figure 4. Spatial pattern of 1 × 1 km PM_2.5 predictions averaged over 2 yr (2006–2007).

Figure 5. PM_2.5 monthly predictions by site and across sites during the study period.