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QA flagging of clouds and atmospheric anomalies Fast UV simulation tool - FastRT Ola Engelsen Norwegian Institute for Air Research (NILU)

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Presentation on theme: "QA flagging of clouds and atmospheric anomalies Fast UV simulation tool - FastRT Ola Engelsen Norwegian Institute for Air Research (NILU)"— Presentation transcript:

1 QA flagging of clouds and atmospheric anomalies Fast UV simulation tool - FastRT Ola Engelsen Norwegian Institute for Air Research (NILU)

2 CheckUVSpec Print & Exit Flexstor Data Compute bands Too low? Too high? Snow/ Br.Cl? Clouds? Cloudy throughout? Clear throughout? Cloud H 2 O Aerosol OD ShicRIVM yes no yes no yes no yes no yes no yes no

3 Fastrt UV simulation tool Few milliseconds running time Accuracy comparable to UV measurements Large variety of biological action spectra Ozone Slitfunction Aerosol optical depth Cloud liquid water column Surface albedo / type Broken clouds

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6 FastRT error analysis Clear sky: max 4%, mean error 1%, st. dev. 1%. Turbid sky: max 18%, mean 3%, st.dev. 4%. Cloudy: max 35%, mean 8%, st. dev. 9%. CheckUVSpec QA tests: max 1%.

7 Flexstor data extraction Extract following information: Wavelengths Irradiances Slitfunction Ozone column, if available Snow cover info, if available Location Times Compute solar zenith angles Check correctness of input QA-flagging

8 Compute bands Add n irradiances band1 and band2 The spectral location of band 1 and 2 depend on instrument, nominally 330nm and 390nm If slitfunction is available n = 3, otherwise 9 QA-flagging

9 Too low? Flag if band 2 irradiance is lower than simulation for very thick clouds (> 4000 g/m2) QA-flagging

10 Too high? band 2 > thick trapping clouds above snow Thick cloud Snow Sun Clear sky downward total transmittance QA-flagging

11 Snow/Broken Clouds? Snow + broken clouds > band 2 > Clear sky QA-flagging

12 Clouds? Thick clouds < band 2 < 5km visib. QA-flagging

13 Clear throughout? No if: band1 / band2 < simulated (clear band1 / clear band2 ) QA-flagging

14 Cloudy throughout? No if: band1 / band2 > simulated (thick cloud band1 / thick cloud band2 ) QA-flagging

15 Cloud H 2 O? Search for cloud thickness scenario which best fits band 2 QA-flagging

16 Aerosol OD (optical depth)? Search for aerosol optical depth scenario which best fits band 2 QA-flagging

17 ShicRIVM QC/QA of solar spectral UV measurements and standardized spectral data-analysis 6 quality flags: Shift_1 Shift_2 Start_irradiance Spike+local_shape Transmission_2 Scan_variability_2 Code and documentation: ftp.rivm.nl:/outgoing/shicrivm /shic QA-flagging


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