Evaluation and Error Analysis of Multi-Source Precipitation Datasets during Summer over the Tibetan Plateau

By inergency On Jan 27, 2024

Figure 1.
Geographic locations of the 247 CMA meteorological stations (133 original stations and 114 new stations added post-2016) and 10 rain gauge stations across the TP.

Figure 2.
Research flowchart.

Figure 3.
Spatial pattern of mean annual summer precipitation based on the (a) 133 station observations, (b) CMFD, (c) ERA5-Land, and (d) IMERG during 2000–2018 on the TP.

Figure 4.
Spatial pattern of the difference between the (a) CMFD, (b) ERA5-Land, and (c) IMERG gridded precipitation products and the observed precipitation during the summers of 2000–2018 on the TP.

Figure 5.
Spatial pattern of summer precipitation trends based on the (a) interpolation of 133 station observations, (b) CMFD, (c) ERA5-Land, and (d) IMERG during 2000–2018 on the TP (the significant values at 95 % confidence level are represented by black dots).

Figure 6.
Temporal pattern of the regional mean annual summer precipitation during 2000–2018 on the TP (the CMFD, ERA5-Land, and IMERG data were all interpolated to the original station locations and then the mean annual values were taken for all 133 stations).

Figure 7.
Scatter plots of the annual summer precipitation for the (a) CMFD, (b) ERA5-Land, and (c) IMERG on the TP.

Figure 8.
Taylor diagram of high-resolution precipitation datasets for the summer months.

Figure 9.
Box plots of the (a) CC, (b) bias, (c) RMSE, (d) POD, (e) FAR, and (f) CSI for the CMFD, ERA5-Land, and IMERG for the summer daily scale precipitation during 2000–2018 on the TP. The black dashed line is the median value, and the red solid line is the mean value (the yellow color represents the interquartile range, the black circles represent outliers).

Figure 10.
Spatial patterns of (a–c) POD, (d–f) FAR, and (g–i) CSI for the CMFD, ERA5-Land, and IMERG at a daily scale in the summers of 2000–2018 on the TP, with reference to the original 133 stations.

Figure 11.
Spatial patterns of the (a–c) CC, (d–f) bias, and (g–i) RMSE for the CMFD, ERA5-Land, and IMERG at a daily scale in the summers of 2016–2018 on the TP, with reference to the additional 114 stations.

Figure 12.
Spatial patterns of (a–c) POD, (d–f) FAR, and (g–i) CSI for the CMFD, ERA5-Land, and IMERG at a daily scale in the summers of 2016–2018 on the TP, with reference to the additional 114 stations.

Table 1.
Evaluation metrics for the high-resolution precipitation datasets.

Evaluation Metric	Formula ¹	Perfect Value
Correlation coefficient (CC)	$CC = \frac{\sum_{i = 1}^{n} (x_{i} - \bar{x}) (y_{i} - \bar{y})}{\sqrt{\sum_{i = 1}^{n} {(x_{i} - \bar{x})}^{2}} \sqrt{\sum_{i = 1}^{n} {(y_{i} - \bar{y})}^{2}}}$	1
Relative bias (bias)	$bias = \frac{\sum_{i = 1}^{n} (x_{i} - y_{i})}{\sum_{i = 1}^{n} y_{i}} \times 100 %$	0
Root-mean-square error (RMSE)	$RMSE = \sqrt{\frac{1}{n} \sum_{i = 1}^{n} {(x_{i} - y_{i})}^{2}}$	0
Probability of detection (POD)	$POD = \frac{H}{H + M}$	1
False alarm ratio (FAR)	$FAR = \frac{F}{H + F}$	0
Critical success index (CSI)	$CSI = \frac{H}{H + M + F}$	1

Table 2.
Evaluation metrics of high-resolution precipitation datasets for summer months from 2000 to 2018.

Month	Evaluation Metric	CMFD	ERA5-Land	IMERG
Jun.	CC	0.932	0.692	0.846
	Bias (%)	2.375	56.006	8.113
	RMSE (mm/month)	19.921	71.310	30.099
Jul.	CC	0.837	0.624	0.743
	Bias (%)	4.996	58.462	15.523
	RMSE (mm/month)	34.519	90.711	46.040
Aug.	CC	0.868	0.633	0.736
	Bias (%)	5.494	61.442	16.676
	RMSE (mm/month)	28.488	80.821	43.258

Table 3.
Differences between the gridded precipitation datasets used in this study with their parameters.

Dataset	Spatio-Temporal Resolution	Temporal Coverage	Spatial Coverage	Addition
CMFD	0.1°, 3 h	1979 to 2018	China	release latency, CMA station calibration
ERA5-Land	0.1°, 1 h	1950 to present	Global land	release latency, GPCC calibration
IMERG	0.1°, 0.5 h	2000 to 2021	60°N-S	release latency, NCEP Stage IV calibration

Table 4.
Precipitation estimations at gauge stations on the Qiangtang Plateau during the summer of 2018 from the three gridded datasets.

Station	Latitude (°E)	Longitude (°N)	OBS (mm)	CMFD (mm)	ERA5-Land (mm)	IMERG (mm)
EW01	32.51	79.68	88.6	95.4	286.1	139.6
EW03	32.37	80.61	99.6	93.5	246.3	177.3
EW05	32.21	81.56	181.2	211.4	332.3	200.2
EW06	32.22	82.26	163.6	233.7	232.0	321.7
EW07	32.53	82.59	114.2	247.2	250.0	400.6
EW08	32.4	83.42	173.4	252.8	330.2	346.5
EW09	32.29	84.07	166.0	196.3	286.8	237.1
EW11	32.02	85.48	250.8	203.4	281.9	376.0
EW16	31.87	88.15	296.8	283.3	457.3	436.9
SN28	32.38	89.15	312.0	289.5	371.5	332.5