Dataset: Solar global irradiance from actinometric measurements and reanalysis data for Cáceres (Spain, 1913–1923) and Afumati Observatory (Bucharest, 1971–1973)

This dataset accompanies the manuscript "Solar global irradiance from actinometric measurements for Caceres (Spain) 1913–1920" submitted to Theoretical and Applied Climatology. It contains three categories of data: Historical actinometric observations from Cáceres (Spain), 1913–1923. Daily readings from an Arago-Davy actinometer (black-bulb and bright-bulb temperatures, in actinometric degrees) recorded at 16:00 local time (15:00 UTC) during 1913–1920 and at 13:00 local time (12:00 UTC) during 1923. Observations are absent for the years 1921–1922. The station is located at the former Provincial Institute of Secondary Education (39.4731° N, 6.3700° W, 460 m a.s.l.). Reanalysis of solar irradiance at Cáceres, 1905–1923. Surface downward shortwave radiation (W/m²) from ECMWF CERA-20C (ensemble mean, SSRD) and NOAA 20CRv3 (dswrf.sfc), at 3-hourly and daily resolution. Validation data at Afumati Observatory (Bucharest), 1971 and 1973. Paired daily values of ground-measured solar irradiance and CERA-20C SSRD (W/m²), used for preliminary validation of reanalysis performance (see Section 3.1 and Table 1 of the manuscript). Station Metadata Cáceres Observatory (Spain) Coordinates: 39.4731° N, 6.3700° W (39° 28′ 23″ N, 6° 22′ 12″ W) Altitude: 460 m a.s.l. Location: Terrace of the former Provincial Institute of Secondary Education, historic centre of Cáceres (UNESCO World Heritage Site since 1986) Instrument: Arago-Davy actinometer with two Tonnelot thermometers (black bulb #38135, bright bulb #38140) Observation time: 16:00 local time = 15:00 UTC (1913–1920); 13:00 local time = 12:00 UTC (1923) Afumati Observatory (Bucharest, Romania) Coordinates: 44.5001° N, 26.2128° E Altitude: 90 m a.s.l. Role: Validation site — paired ground-measured irradiance and CERA-20C reanalysis for 1971 and 1973 Reanalysis Products CERA-20C (ECMWF) Variable: Surface Solar Radiation Downwards (SSRD), parameter 169.128 Ensemble member: Ensemble mean (type=em, stream=enda) Source: ECMWF MARS archive Grid: Regridded to 1.0° × 1.0° Unit conversion: De-accumulated from J/m² per forecast step, divided by 10 800 s → W/m² Temporal note: Each 3-hourly value represents the mean irradiance over the preceding 3-hour window 20CRv3 (NOAA-CIRES-DOE) Variable: Downward Short-Wave Radiation Flux (dswrf.sfc) Source: NOAA Physical Sciences Laboratory (ftp2.psl.noaa.gov/Datasets/20thC_ReanV3/sfcFlxSI/) Grid: Native 1.0° × 1.0° Units: Natively in W/m² (no conversion needed) File Inventory File Description Period observations/caceres_actinometric_1913_1923.csv Arago-Davy actinometric readings at Cáceres 1913–1923 validation/afumati_measured_vs_cera20c_daily_1971_1973.csv Paired measured irradiance and CERA-20C at Afumati (validation) 1971, 1973 reanalysis/caceres_cera20c_ssrd_3h_1905_1923.csv CERA-20C SSRD 3-hourly at Cáceres 1905–1923 reanalysis/caceres_cera20c_ssrd_daily_1905_1923.csv CERA-20C SSRD daily at Cáceres 1905–1923 reanalysis/caceres_20crv3_dswrf_3h_1905_1923.csv 20CRv3 DSWRF 3-hourly at Cáceres 1905–1923 reanalysis/caceres_20crv3_dswrf_daily_1905_1923.csv 20CRv3 DSWRF daily at Cáceres 1905–1923 All files are in CSV format with header rows. Missing values are coded as NA. All timestamps are in UTC. Full metadata, provenance, known data quality issues, and 12 anomalous actinometric readings are documented in the included README.md.