Estimation of global horizontal irradiance in China using a deep learning method

Figures & data

Figure 1. Spatial distribution of selected sites of e CERN

Figure 2. The structure of an ordinary DBN and diagram of a restricted Boltzmann machine. (a) A simple structure of a DBN; (b) A simple structure of a RBM

Table 1. Characteristics of LUT for a clear sky

Input parameter	Abbreviation	Quantity	Value range
Solar zenith angle	SZA	°	2:2:88
Total column water vapour	TCWV	g cm^−2	0:0.25:2
Altitude	H	km	0:0.5:4
Surface Albedo	SA	1	0:0.1:0.6
Aerosol optical thickness	AOT	1	0:0.1:2.5
Single scattering albedo	SSA	1	0.7:0.1:1
Angstrom exponent	AE	1	0.2:0.2:2

Note: The three parameters in Value range are minimum, step and maximum value, respectively.

Table 2. Characteristics of LUT for a cloudy sky: both for water cloud and ice cloud

Input parameter	Abbreviation	Quantity	Value range
Cloud phase	CLP	–	Ice cloud/Water cloud
Solar zenith angle	SZA	°	2:2:88
Total column water vapour	TCWV	g cm^−2	0:0.25:2
Altitude	H	km	0:0.5:4
Surface Albedo	SA	1	0:0.1:0.6
Cloud optical thickness	COT	1	0.5 for 0:10. 2 for 10:80
Cloud effective radius	CER	µm	2:10:80

Figure 3. The flow chart for the whole estimate

Figure 4. (a) Sensitivity of GHI to SZA: Clear: AOT = 0.1, SA = 0.1; Water cloud: COT = 10, CER = 8 μm, SA = 0.1; Ice cloud: COT = 10, CER = 32 μm, SA = 0.1; (b) Sensitivity of GHI to AOT: SA = 0.1; (c) Sensitivity of GHI to CTWV: AOT = 0.1, SA = 0.1; (d) Sensitivity of GHI to COT: Water cloud: SZA = 30°, CER = 8 μm, SA = 0.1; Ice cloud: SZA = 30°, CER = 32 μm, SA = 0.1; (e) Sensitivity of GHI to CER: Water cloud: SZA = 30°, COT = 10,SA = 0.1; Ice cloud: SZA = 30°, COT = 10, SA = 0.1 (f). Sensitivity of GHI to SA: Clear: SZA = 30°, AOT = 0.1; Water cloud: COT = 10, CER = 8 μm, Ag = 0.1; Ice cloud: COT = 10, CER = 32 μm

Figure 5. Comparison of the normalized calculation efficiency of different methods (SBDART results is set as a baseline. Xeon (R) E5-2640 processor and RAM 16 GB)

Figure 6. Estimated GHI (w m⁻²) at 03:00 UTC on chosen days: (a) 21 August 2018; (b) 25 August 2018; (c) 1 November 2018; (d) 4 November 2018

Figure 7. Estimated GHI (w m⁻²) at 06:00 UTC on chosen days: (a) 21 August 2018; (b) 25 August 2018; (c) 1 November 2018; (d) 4 November 2018

Figure 8. Real colour images from Himawari-8 at 03:00 UTC on chosen days: (a) 21 August 2018; (b) 25 August 2018; (c) 1 November 2018; (d) 4 November 2018

Table 3. Summary statistics of the validation results

	Clear sky			Cloudy sky			All sky
	MAE (w m^−2)	NMAE (%)	RMSE (w m^−2)	MAE (w m^−2)	NMAE (%)	RMSE (w m^−2)	MAE (w m^−2)	NMAE (%)	RMSE (w m^−2)
Summer case	27.61	4.61	33.90	45.38	10.68	87.42	45.00	8.02	73.52
Winter case	34.48	7.09	45.60	37.16	9.73	60.88	35.98	8.73	54.68

Figure 9. Validation results at the chosen CERN sites over China: summer clear case is on upper left; winter clear case is on upper right; summer cloud case is located on bottom left; winter cloud case is located on bottom right. (a) If cloud = No & Season = Summer; (b) If cloud = No & Season = Winter; (c) If cloud = Yes & Season = Summer; (d) If cloud = Yes & Season = Winter. Note that subfigures (a) and (b) share the same y-axis lables, as well as (c) and (d). And (a) and (c), (b) and (d) share the same x-axis labels respectively