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

Continuous monitoring of atmospheric trace gases in the middle atmosphere presents
significant challenges. Remote sensing instruments are essential for understanding and
characterizing changes in atmospheric chemical composition. Although water vapor is
present in low concentrations in the middle atmosphere, it plays a critical role as one
of the most significant greenhouse gases, profoundly influencing climate change. Water
vapor is a key climate variable, important for radiative balance, and is involved in various
chemical reactions, including ozone depletion through the formation of polar stratospheric
clouds.
With the decommissioning of the AURA-MLS 183 GHz water vapor line, there is an
increasing need to expand the ground-based network of microwave (MW) radiometers.
At the Institute of Applied Physics (IAP), within the Microwave Group (MW), we have
designed a new cryogenically cooled radiometer to measure the emitted radiation from the
22 GHz water vapor line. This instrument, called CRYOWARA, is intended to replace
the existing 22 GHz radiometer known as MIAWARA, which is currently used by the
MW 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 middle
atmospheric dynamics. At the EGU 2025 conference, we will present the instrument’s
design along with some preliminary results from the breadboard assembly.