Refractive atmospheric conditions at low altitudes can have a significant impact on electromagnetic signals propagating at low grazing angles in many coastal regions. Refractivity from clutter (RFC) is a technique that refers to the estimation of an atmospheric refractivity profile from radar sea clutter returns. The RFC algorithm obtains the simulated clutter pattern that has the best fit to the collected radar data. RFC is traditionally performed with the minimum range not starting before 10 km. This is because there are large fluctuations in the grazing angle of an electromagnetic signal when an evaporation duct is present. This paper proposes using a commercial Koden MDS-63R marine radar architecture converted for increased sea clutter sensitivity and implementing a modified version of the Georgia Institute of Technology (GIT) model to perform RFC inversions starting on the first kilometer of the returned clutter power. Radar data for testing the procedure was collected in Southern California at Pt. Mugu from September to October 2017 as part of the coupled Air-Sea Processes and EM ducting research (CASPER) West Campaign. Validation data was also collected during the campaign and consist of buoy in situ bulk measurements of air temperature, humidity, wind speed, and sea surface temperature.