Comparative performance analysis of climate re-analysis approaches in Angola

Figures & data

Figure 1. Angola geography, provincial capitals and main rivers.

Table 1. Number of monitoring stations with records collected for the current research.

No. of hydrological years with complete records	No. of precipitation monitoring stations	No. of temperature monitoring stations	No. of evaporation monitoring stations
>40	11	2	1
>30 and ≤40	26	2	3
>20 and ≤30	107	20	24
>10 and ≤20	201	57	62
>5 and ≤10	119	42	45

Figure 2. Locations of (a) precipitation, (b) temperature and (c) evaporation monitoring stations used in the study. The vertical lines show the transects used in Figures 4, 8 and 12.

Table 2. Summary of the global atmospheric re-analysis exercises used.

Exercise	Time range	Global model resolution	Assimilation scheme and model vintage	Available time step(s)	Publicly available dataset resolution
NCEP r1	1948–present	T62 L28	3D-Var /1995	Sub-daily, Daily, Monthly	2.5° × 2.5°
ECMWF ERA 40	1957–2002	T159 L60	3D-Var /2004	Sub-daily, Monthly	2.5° × 2.5°
JRA 55	1958–2012	T319 L60	4D-Var /2009	Sub-daily, Monthly	1.25° × 1.25°

Figure 3. Mean annual precipitation maps for 1959/60–1973/74 obtained by co-kriging interpolation from ground observation measurements and re-analysis estimates (values in mm).

Figure 4. North–south transect of mean annual precipitation of the 1959/60–1973/74 record obtained at longitudes 13°50ʹE, 17°35ʹE and 20°20ʹE.

Figure 5. Annual precipitation and seasonal precipitation values obtained from the re-analysis datasets against in situ records for 1959/60–1973/74. Each point represents a monitoring site and one year or season (values in mm).

Figure 6. Performance indicators of annual precipitation estimates from ERA-40, NCEP-r1 and JRA-55 re-analysis exercises using the period 1959/60–1973/74. Each point represents a monitoring site.

Table 3. Performance indicators of annual precipitation and seasonal precipitation values obtained from the re-analysis datasets and the ensemble means of the re-analysis against in situ records for the period 1959/60–1973/74.

	Annual precipitation				Dry season precipitation				Wet season precipitation
	ERA-40	NCEP-r1	JRA-55	AVG	ERA-40	NCEP-r1	JRA-55	AVG	ERA-40	NCEP-r1	JRA-55	AVG
r	57.5	59.0	52.1	61.5	58.2	71.2	39.2	67.1	55.2	55.6	48.3	58.4
Bias	−181	−291	−105	−192	27	−16	−21	−4	−83	−275	−82	−182
RMSE	427	476	471	412	57	39	54	37	468	463	468	405
NSE	−2.31	−3.12	−3.03	−2.09	−3.47	−1.10	−3.02	−0.87	−3.15	−3.06	−3.15	−2.10

Figure 7. Mean temperature map for 1959/60–1973/74 obtained by co-kriging interpolation from ground observation measurements and re-analysis estimates.

Figure 8. North–south transect of average temperature of the 1959/60–1973/74 record obtained at longitudes 13°50ʹE, 17°35ʹE and 20°20ʹE.

Figure 9. Mean temperature values obtained from the re-analysis datasets against in situ records for 1959/60–1973/74. Each point represents a monitoring site and one year or season (values in °C).

Figure 10. Performance indicators of mean temperature estimates from ERA-40, NCEP-r1 and JRA-55 re-analysis exercises for 1959/60–1973/74. Each point represents a monitoring site.

Table 4. Performance indicators of mean surface air temperature values obtained from the re-analysis datasets and the ensemble means of the re-analysis against in situ records for the period 1959/60–1973/74.

	Mean annual surface air temperature				Mean dry season surface air temperature				Mean wet season surface air temperature
	ERA-40	NCEP-r1	JRA-55	AVG	ERA-40	NCEP-r1	JRA-55	AVG	ERA-40	NCEP-r1	JRA-55	AVG
r	42.9	55.5	70.5	72.3	52.7	64.9	68.5	68.9	44.0	51.7	72.0	61.5
Bias	0.2	0.1	0.9	0.4	0.6	0.3	1.4	0.7	0.03	0.00	0.66	0.23
RMSE	2.3	2.1	2.0	2.0	2.2	1.9	2.3	2.1	2.4	2.3	2.0	2.1
NSE	−9.2	−5.9	−5.9	−5.0	−5.3	−4.0	−6.6	−3.7	−9.2	−6.8	−4.8	−5.2

Figure 11. Mean annual evaporation map for 1959/60–1973/74 obtained by co-kriging interpolation from ground observation measurements and re-analysis estimate (values in mm).

Figure 12. North–south transect of mean annual evaporation of the 1959/60–1973/74 record obtained at longitudes 13°50ʹE, 17°35ʹE and 20°20ʹE.

Figure 13. Annual evaporation values and seasonal evaporation values obtained from the re-analysis datasets against in situ records for 1959/60–1973/74. Each point represents a monitoring site and one year or season (values in mm).