MÉRA: Met Éireann ReAnalysis Global Shortwave Radiation

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1 MÉRA: Met Éireann ReAnalysis Global Shortwave Radiation Emily Gleeson, Met Éireann Kristian Pagh Nielsen, DMI Eoin Whelan, Met Éireann Special thanks to the ALADIN- HIRLAM consortium

2 Some facts about MÉRA Regional Reanalysis Ireland, UK, Northern France 900 TB data 12.5 million computer hours Data freely available to all 2

3 Overview The MÉRA Reanalysis Some basic statistical checks The clear sky index (CSI) Variability index (VI) Next steps 3

4 HARMONIE-AROME vs ERA-Interim Orography 2.5 km 79 km 5

5 HIRLAM & ALADIN Consortia 6

6 HARMONIE-AROME configuration 7

7 Summary of Model Output 8

8 HARMONIE-AROME Forecast Model ALADIN dynamical core Mainly MESO-NH physics SURFEX Surface Papers: Bengtsson et al 2017, Monthly Weather Review. Seity et al.,

9 Physics Parametrizations Shortwave radiation: Morcrette IFS cycle 25R1 6 bands, Tegen aerosol climatology ECMWF 10

10 Overview The MÉRA Reanalysis Some basic statistical checks The clear sky index (CSI) Variability index (VI) Next steps 11

11 35-year time series of BIAS/STDEV 7 original stations 24-hour averages 12

12 7 original stations 24-hour averages BIAS by day of year 13

13 Current Radiation Network Automatic stations Autosol for the 7 original stations 15

14 Hourly resolution 20 stations BIAS by day of year 16

15 Hourly resolution Sample station BIAS by hour of day 17

16 Biases 18

17 Rare clear day 19

18 Overview The MÉRA Reanalysis Some basic statistical checks The clear sky index (CSI) Variability index (VI) Next steps 20

19 Clear Sky Index (CSI) The index is the ratio of global shortwave irradiance divided by the maximum possible global shortwave irradiance which is dependent on the location, date and time. Used clear sky model equation from HIRLAM and an atmosphere of 2.5 g/cm 2 cloud water load CSI =0 overcast CSI = 1 clear sky or 100% thin cloud CSI: = 1 21

20 Clear Sky Index (CSI) The index is the ratio of global shortwave irradiance divided by the maximum possible global shortwave irradiance which is dependent on the location, date and time. Used clear sky model equation from HIRLAM and an atmosphere of 2.5 g/cm 2 cloud water load CSI =0 overcast CSI = 1 clear sky or 100% thin cloud CSI: =

21 Clear Sky Index (CSI) The index is the ratio of global shortwave irradiance divided by the maximum possible global shortwave irradiance which is dependent on the location, date and time. Used clear sky model equation from HIRLAM and an atmosphere of 2.5 g/cm 2 cloud water load CSI =0 overcast CSI = 1 clear sky or 100% thin cloud CSI: =0 23

22 All stations incl. Hourly CSI values Clear Sky Index (CSI) 24

23 Overview The MÉRA Reanalysis Some basic statistical checks The clear sky index (CSI) Variability index (VI) Next steps 25

24 Variability Index (VI) VI = n k=2 n k=2 (GHI k GHI k 1 ) 2 + t 2 (SBOA k SBOA k 1 ) 2 + t 2 Stein et al., 2012 Used hourly averaged SW (obs and MÉRA) GHI = global horizontal irradiance (W/m 2 ) averaged over t=60 min SBOA = SW irradiance at the surface (bottom of atmosphere) As t=60 min is used rather than 1 minute data, final answer is scaled by multiplying by sqrt(60) 26

25 Variability Index (VI) VI: 0-5 range Low variability e.g. stratus Daily CSI Obs & MÉRA 27

26 Variability Index (VI) VI: 5-10 range Clear days incl Obs & MÉRA 28

27 Variability Index (VI) VI: >10 range Medium variability e.g. cumulous Obs & MÉRA 29

28 Overview The MÉRA Reanalysis Some basic statistical checks The clear sky index (CSI) Variability index (VI) Next steps 30

29 Next steps Comparisons with ECMWF forecasts Satellite data: MSGCPP (KNMI) Apply the variability index to experiments using improved radiation scheme and other domains Use SW to verify clouds operationally 31

30 Is MÉRA useful? 32

31 Gleeson et al., ASR, 2017 Whelan et al., submitted to QJRMS 33

32 Poster: P59 Comparison of surface solar irradiance measurements over Ireland: Satellite data, in-situ observations and high resolution regional re-analysis model data. by Willemien Phelan Friday Sept 8 th poster session 35

33 Questions? Sinéad Duffy Casement Aerodrome Christmas morning C 36