Design of a new cryogenically cooled radiometer for middle atmospheric water vapor measurements:CRYOWARA

Continuous monitoring of atmospheric trace gases in the middle atmosphere presentssignificant challenges. Remote sensing instruments are essential for understanding andcharacterizing changes in atmospheric chemical composition. Although water vapor ispresent in low concentrations in the middle atmosphere, it plays a critical role as oneof the most significant greenhouse gases, profoundly influencing climate change. Watervapor is a key climate variable, important for radiative balance, and is involved in variouschemical reactions, including ozone depletion through the formation of polar stratosphericclouds.With the decommissioning of the AURA-MLS 183 GHz water vapor line, there is anincreasing need to expand the ground-based network of microwave (MW) radiometers.At the Institute of Applied Physics (IAP), within the Microwave Group (MW), we havedesigned a new cryogenically cooled radiometer to measure the emitted radiation from the22 GHz water vapor line. This instrument, called CRYOWARA, is intended to replacethe existing 22 GHz radiometer known as MIAWARA, which is currently used by theMW group at the Zimmerwald observatory in Switzerland.The primary distinction of CRYOWARA is its partially cryogenically cooled front end,which significantly reduces instrumental noise. This enhancement will enable more ac-curate water vapor retrievals at higher altitudes, further advancing the study of middleatmospheric dynamics. At the EGU 2025 conference, we will present the instrument’sdesign along with some preliminary results from the breadboard assembly.