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To better understand the influence of the activity cycle on the solaratmosphere, we report the time variation of the radius observed at 37 GHz($\lambda$=8.1 mm) obtained by the Mets\"ahovi Radio Observatory (MRO) throughSolar Cycles 22 to 24 (1989-2015). Almost 5800 maps were analyzed, however, dueto instrumental setups changes the data set showed four distinct behaviors,which requested a normalisation process to allow the whole interval analysis.When the whole period was considered, the results showed a positive correlationindex of 0.17 between the monthly means of the solar radius at 37 GHz and solarflux obtained at 10.7 cm (F10.7). This correlation index increased to 0.44,when only the data obtained during the last period without instrumental changeswere considered (1999-2015). The solar radius correlation with the solar cycleagrees with the previous results obtained at mm/cm wavelengths (17 and 48 GHz),nevertheless, this result is the opposite of that reported at submillimetrewavelengths (212 and 405 GHz).

The Solar Radius at 37 GHz through Cycles 22 to 24