Solar irradiance measurements from a research aircraft

Area of Science:

• Atmospheric Science
• Solar Physics
• Radiometry

Background:

• Accurate solar constant and spectral irradiance data are crucial for climate modeling and understanding Earth's energy balance.
• Atmospheric absorption and variability introduce significant uncertainties in ground-based measurements.

Purpose of the Study:

• To obtain precise measurements of the solar constant and solar spectral irradiance.
• To minimize atmospheric interference by conducting observations above the majority of the atmosphere.
• To establish a revised solar spectral irradiance curve for zero air mass conditions.

Main Methods:

• Aircraft-based measurements were conducted at an altitude of 11.58 km.
• A wide range of solar zenith angles was covered over six flights, totaling more than 14 hours of observation.
• Nine different instruments with complementary measuring techniques and wavelength ranges were utilized and cross-calibrated.

Main Results:

• A new value for the solar constant was determined to be 135.1 mW cm(-2).
• A revised solar spectral irradiance curve for zero air mass was generated.
• Data from multiple instruments provided a comprehensive spectral coverage and validation.

Conclusions:

• The study provides a more accurate determination of the solar constant, essential for climate studies.
• The revised solar spectral irradiance curve offers improved data for atmospheric and solar research.
• Aircraft-based measurements above most atmospheric interference are vital for precise solar radiation determination.