Enabling Enhanced Temporal Resolution of Observations and Retrievals of Water Vapor, Clouds and Precipitation: Recent Scientific Results from the Temporal Experiment for Storms and Tropical Systems (TEMPEST) Missions

The Temporal Experiment for Storms and Tropical Systems – Demonstration (TEMPEST-D) mission demonstrated the first global observations from a multi-frequency microwave radiometer on a CubeSat, operating for nearly three years from 2018 to 2021. This NASA Earth Venture Technology mission exceeded expectations for scientific data quality, instrument calibration, radiometer stability, and mission duration. TEMPEST-D brightness temperatures were validated using scientific and operational microwave sensors, including GPM/GMI and four MHS sensors, operating at similar frequencies to TEMPEST-D channels at 87, 164, 174, 178 and 181 GHz. TEMPEST-D performance was shown to be comparable to or better than much larger operational sensors, in calibration accuracy, precision, stability and instrument noise, during its nearly 3-year mission.

Based on the success of TEMPEST-D, a nearly identical TEMPEST sensor produced for risk reduction was delivered to the U.S. Space Force and integrated with NASA/JPL’s Compact Ocean Wind Vector Radiometer (COWVR). COWVR and TEMPEST were launched on December 21, 2021, on STP-H8 for 3 years of operations on the ISS. COWVR and TEMPEST have performed coordinated observations of Earth’s oceans and atmosphere from the ISS since January 7, 2022.

Atmospheric inversion techniques have been developed to retrieve water vapor altitude profiles, as well as single-layer cloud liquid water and cloud ice water, from TEMPEST brightness temperatures, using ECMWF Reanalysis v5 (ERA5) data as an initial guess. These retrievals are enhanced through the inclusion of geostationary infrared data from GOES-16 ABI channels, increasing the number of levels and reducing the error of water vapor retrieval, particularly in the upper troposphere.

Previous studies have validated accuracy and precision of TEMPEST brightness temperatures using only clear-sky oceanic observations. Recent studies extend the validation of TEMPEST to include observations over tropical cyclones, using GPM-GMI passive microwave brightness temperatures and GPM-DPR active microwave vertical cumulative reflectivity. Such active/passive microwave observations provide a basis for development of surface rain rate estimates and retrieval of the vertical structure of precipitation from combined TEMPEST and DPR observations.