Algorithm Development for Column Water Vapor Retrieval Using the SAM Sensor

Joshua Bruce Williams, Utah State University


To understand and model the energetics of the Sun-Earth connection, measurements of specific atmospheric molecules are beneficial. The objective is to formulate an algorithm to derive temporally varying atmospheric water vapor concentrations as functions of altitude, latitude, and longitude from solar irradiance absorption measurements. The Visidyne SAM (Sun and Aureole Measurement) instrument, which studies the size and distribution of cloud particles, was used to obtain the experimental data. By introducing a spectrometer to the SAM instrument, column water vapor is produced as part of the data product. A new model optimized algorithm is developed and tested versus existing algorithms. Through a least-squares analysis, the new algorithm showed an improvement of a factor of 23 over the industry standard. A test was also conducted to determine which water absorption bandpass produces the smallest error. Through these tests a model optimized algorithm has been produced.