Solar spectral irradiance measurements above and in-canopy (SLOCS and CloudRoots Amazonia, 2022)

Shedding Light On CloudRoots

Solar spectral irradiance measurements made with the sensors produced within the Shedding Light On Cloud Shadows (SLOCS) project, deployed at the CloudRoots Amazonia 2022 campaign. 

Dataset contents

• Level 0 (raw): the raw data as it comes from the instruments
• Level 1 (L1): data in NetCDF format with metadata, quality control, homogenized factory calibration (counts bin-1 dt-1)
• Level 2 (L2): calibrated L1 data in W m-2 nm-1
• extras: this folder includes reference calibration spectra and data quality quicklooks

Data is available at 1 Hz (resampled) and 10 Hz (native) resolution. 10 Hz resolution is compressed using NetCDF compression with gzip level 5 (uncompressed is 1.13 GB per date).

Data quality and uncertainty

Please note this dataset is in version 0.1.0, meaning you should use the dataset with caution. Not all unphysical data may have been flagged as such, and spectral calibration is an estimate based on a simple modelled spectrum. This modelled spectrum is a standard tropical atmosphere without aerosols, and is not run with observed profiles except an ERA5 estimate of total column water vapour. Please refer to 'extras' for technical validation of the spectral calibration method, and LibRadtran input/output files.

A production (1.0) version will be released as soon data is fully validated.

Lower-end uncertainty can be estimated by looking at the sensor to sensor spread at wavelength level during the calibration measurements. In the calibration phase, all sensors were co-located and homogenized at wavelength level. The 13:50 to 14:10 UTC time on August 7 is the reference frame for spectral calibration. 

Other sources of uncertainty are difficult to quantify due to measurements taking place in a very heteregeneous forest. These uncertainties relate primarily to the less-than-perfect placement of sensors on the towers in comparison to the reference calibration phase. 

Sensor 18 is only available in raw data or calibrated data. Precalibration (homogenizing) is not possible given its deviating spectral filter set compared to the others (sensor version 3b vs. 3a). 

Technical information

• The NetCDF files comply with CF1.7 where applicable.
• Metadata include sensor location (altitude relative to ground and sea level, lat, lon). 
• Code for processing raw data to NetCDF available at https://zenodo.org/records/10159129
• Calibration of raw sensor units to spectral irradiance is done using a reference clear-sky spectrum simulated with LibRadtran. Settings and output is included in "extras".

More information

• SLOCS project homepage
• CloudRoots project homepage
• 2022 campaign reference paper is in preparation
• See 'related works' for the instrument reference paper