Correcting global solar ultraviolet spectra recorded by a brewer spectroradiometer for its angular response error.

Area of Science:

• Atmospheric Science
• Spectroradiometry
• Radiative Transfer

Background:

• Brewer spectroradiometers are crucial for measuring global UV spectral irradiance.
• Deviations in the instrument's angular response introduce errors in spectral measurements.
• Accurate UV measurements are vital for atmospheric research and climate studies.

Purpose of the Study:

• To develop and validate a methodology for correcting angular response errors in Brewer MKIII spectroradiometer UV spectral measurements.
• To ensure the applicability of the correction methodology to other operational Brewer spectroradiometers.
• To quantify the uncertainties associated with the correction methodology.

Main Methods:

• Characterizing the deviation of the Brewer MKIII spectroradiometer's angular response from an ideal cosine response.
• Developing a correction factor based on the angular response deviation.
• Applying the correction to global spectral UV measurements.
• Comparing corrected measurements with uncorrected data, collocated spectroradiometer measurements, and model calculations.

Main Results:

• The methodology effectively corrects for angular response errors in UV spectral measurements.
• Cosine correction factors varied between 2% and 7%, depending on wavelength and aerosol loading.
• Uncertainties in the calculated correction factors were small, ranging from approximately 0.2% to 2%.

Conclusions:

• The presented methodology significantly improves the accuracy of global UV spectral measurements from Brewer spectroradiometers.
• The correction is applicable to various Brewer instruments, enhancing data consistency across different measurement sites.
• The validated method provides more reliable UV spectral data for atmospheric research and monitoring.