Evaluating UVA aerosol optical depth using a smartphone camera.

Area of Science:

• Atmospheric Science
• Optical Remote Sensing
• Sensor Technology

Background:

• Consumer-grade complementary metal oxide semiconductor (CMOS) image sensors exhibit inherent sensitivity to ultraviolet A (UVA) radiation.
• Smartphone camera lenses can attenuate UVA radiation, necessitating protective and corrective optical components.
• Previous research indicates potential for CMOS sensors in atmospheric measurements, but validation is required.

Purpose of the Study:

• To evaluate the capability of a smartphone CMOS image sensor for quantifying solar UVA irradiance.
• To assess the sensor's efficacy in measuring aerosol optical depth (AOD) at specific UVA wavelengths (340 nm and 380 nm).
• To determine the accuracy and error margins of measurements using a modified smartphone sensor.

Main Methods:

• Utilized a smartphone CMOS image sensor equipped with narrow bandpass and neutral density filters.
• Conducted observations on clear, cloud-free days to measure incident solar UVA radiation.
• Analyzed sensor response to varying solar irradiance and atmospheric conditions to derive AOD.

Main Results:

• Demonstrated a quantifiable sensor response to changes in solar irradiance.
• Achieved measurement of aerosol optical depth with error margins of 5% at 380 nm and 10% at 340 nm.
• Reported under 1% error for solar irradiance measurements at 380 nm, with higher relative error at 340 nm due to scattering and signal-to-noise ratio.

Conclusions:

• Smartphone CMOS image sensors, augmented with external filters, are viable field instruments for solar UVA irradiance monitoring.
• The system can effectively measure aerosol optical depth, providing valuable data for atmospheric studies.
• This approach presents a low-cost alternative for ground-based atmospheric remote sensing.