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The accuracy of PTRMM was evaluated by comparison with the time series of POBS from 160 meteorological stations in the YRB. Figure 2 shows that the resulting value of r for the match between PTRMM and POBS was greater than 0.9 at 67% of stations, which indicates that PTRMM reproduces reasonably well POBS across over 2/3 of the YRB. was lower than 10 mm/month at 74% of stations. As given in Figure 3, the YRB value of 4.4 mm/month indicates that TRMM over-estimated ground-based precipitation. At annual time steps, was 54.3 mm/yr for the YRB (shown in Table 2), accounting for 5% of the corresponding POBS. in the middle reaches of the YRB was larger than that in the upper reaches of the YRB at both monthly and annual steps. Scheel et al. (2011) reported that precipitation is higher in the lower latitude and altitude areas (e.g., the monthly POBS averages 72.8 and 107.1 mm/month in the upper and middle reaches, respectively), which tended to lead to larger . Nonetheless, for the two sub-basins was lower than 8% of the corresponding POBS, and therefore PTRMM is considered to be reliable for application to the YRB at monthly and annual time steps.
Table 2

Error statistics of satellite products in the YRB

Error
BasinTime stepsPOBSab
YRB Monthly (mm/month) 88.9 6.0 10.3 15.3 19.4 21.4 18.1 
Annual (mm/yr) 1066.2 54.3 51.9 76.7 141.2 152.5 
Upper reaches of the YRB Monthly (mm/month) 72.8 5.5 12.5 16.2 21.2 26.0 20.4 
Annual (mm/yr) 873.5 47.5 25.2 56.2 182.4 183.2 
Middle reaches of the YRB Monthly (mm/month) 107.1 8.0 9.5 24.1 27.1 25.5 20.5 
Annual (mm/yr) 1284.6 65.9 84.5 109.8 89.0 110.1 
Error
BasinTime stepsPOBSab
YRB Monthly (mm/month) 88.9 6.0 10.3 15.3 19.4 21.4 18.1 
Annual (mm/yr) 1066.2 54.3 51.9 76.7 141.2 152.5 
Upper reaches of the YRB Monthly (mm/month) 72.8 5.5 12.5 16.2 21.2 26.0 20.4 
Annual (mm/yr) 873.5 47.5 25.2 56.2 182.4 183.2 
Middle reaches of the YRB Monthly (mm/month) 107.1 8.0 9.5 24.1 27.1 25.5 20.5 
Annual (mm/yr) 1284.6 65.9 84.5 109.8 89.0 110.1 

aCalculated between ETMODIS and the average values of the four GLDAS datasets.

bEstimated by the GRACE measurement error and leakage error.

Figure 2

Spatial distribution of the relationship between TRMM precipitation and observed precipitation from 2003 to 2012 for the YRB. The red dots are correlation coefficient r. Background colours represent TRMM precipitation error , interpolated from 160 meteorological stations. The value in brackets is the number of stations out of 160 in the corresponding categories. Please refer to the online version of this paper to see this figure in colour: http://dx.doi.org/10.2166/nh.2016.138.

Figure 2

Spatial distribution of the relationship between TRMM precipitation and observed precipitation from 2003 to 2012 for the YRB. The red dots are correlation coefficient r. Background colours represent TRMM precipitation error , interpolated from 160 meteorological stations. The value in brackets is the number of stations out of 160 in the corresponding categories. Please refer to the online version of this paper to see this figure in colour: http://dx.doi.org/10.2166/nh.2016.138.

Figure 3

(a) Monthly averages of TRMM precipitation and observed precipitation in the YRB for 2003–2012 and (b) scatter plot of monthly TRMM precipitation and observed precipitation from 2003 to 2012. ** indicates that the relationship is significant at the level of 0.05 by T-test.

Figure 3

(a) Monthly averages of TRMM precipitation and observed precipitation in the YRB for 2003–2012 and (b) scatter plot of monthly TRMM precipitation and observed precipitation from 2003 to 2012. ** indicates that the relationship is significant at the level of 0.05 by T-test.

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