QA flagging of clouds and QA flagging of clouds and atmospheric anomaliesatmospheric anomalies

Fast UV simulation tool - Fast UV simulation tool - FastRTFastRT

Ola EngelsenOla Engelsen

Norwegian Institute for Air Norwegian Institute for Air ResearchResearch

(NILU)(NILU)

OutlineOutline

• QA software CheckUVSpec• FastRT UV simulation tool• Applications of FastRT• Status of NPI tasks

CheckUVSpecCheckUVSpec

Print &Exit

FlexstorData

Computebands

Toolow?

Toohigh?

Snow/Br.Cl?

Clouds?Cloudy

throughout?

Clearthroughout?

CloudH2O

AerosolOD

ShicRIVM

yes

no

yes

no

yes

no

yes

no

yes

no

yes

no

no

Fastrt UV simulation toolFastrt 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

FastRT error analysisFastRT 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%.

Vitamin D doserate @ noonVitamin D doserate @ noon

Cod egg mortality – monthly dosesCod egg mortality – monthly doses

Recent workRecent work

• Installed QA flagging tool at database• Updated ”LAP review of cloud flagging”• Documentation of FastRT, incl. error analysis• Installed interactive FastRT and downloadables

on http://zardoz.nilu.no/~olaeng/fastrt/fastrt.html

• CheckUVSpec QA tool available at http://

zardoz.nilu.no/~olaeng/CheckUVSpec/CheckUVSpec.html

Remaining workRemaining work

All required milestones and deliverables are completed, but:

• New FastRT scheme for coupling clouds, aerosols and ozone

• Make CheckUVSpec extract atmospheric visibility?

• Make CheckUVSpec handle broadband data?• Publications

The End

Flexstor data extractionFlexstor data extraction

Extract following information:• Wavelengths• Irradiances• Slitfunction• Ozone column, if available• Snow cover info, if available• Location• Times• Compute solar zenith anglesCheck correctness of input

QA-flagging

Compute bandsCompute 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

Too low?Too low?

• Flag if band 2 irradiance is lower than simulation for very thick clouds (> 4000 g/m2)

QA-flagging

Too high?Too high?

band 2 > thick trapping clouds above snow

Thick cloud Thick cloud

Snow

Sun

Clear sky downward totaltransmittance

QA-flagging

Snow/Broken Clouds?Snow/Broken Clouds?

Snow + broken clouds > band 2 > Clear sky

QA-flagging

Clouds?Clouds?

• Thick clouds < band 2 < cloudless @ 5km visib.

QA-flagging

Clear throughout?Clear throughout?

No if:

band1 / band2 < simulated (clearband1 / clearband2)

QA-flagging

Cloudy throughout?Cloudy throughout?

No if:

band1 / band2 > simulated (thick cloudband1 / thick cloudband2)

QA-flagging

Cloud HCloud H22O?O?

Search for cloud thickness scenario which best fits band 2

QA-flagging

Aerosol OD (optical depth)?Aerosol OD (optical depth)?

Search for aerosol optical depth scenario which best fits band 2

QA-flagging

ShicRIVMShicRIVM

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/shicrivmwww.rivm.nl/en/millieu/risicos_stoffen/

nietioniserende_straling/shic

QA-flagging