The Feasibility of Radar-Based Remote Sensing of Barometric Pressure Final Report

This study assesses the feasibility of radar-based remote sensing of barometric pressure of the air at the sea surface. Currently, sea surface barometric pressure measurements can only be obtained from in situ observations including buoy and dropsonde measurements, which are sparse in spatial coverage and expensive to implement. There are no operational remote sensing methods available even in experimental stages. The proposed technology is to use differential absorption radar working at the 50-56 GHz O2 bands to fill the observational gap. The numerical simulation results for homogeneous sea surface backgrounds show that with an airborne radar working at these O2 absorption bands, the rms errors of the instantaneous radar surface pressure estimates with 15 dB signal-to-noise ratios can be as low as 4–7 mb. With multiple measurements over an area about 10 km the uncertainty in radar sea surface pressure estimates would drop to about 1 mb which is similar to conventional in situ buoy measurements. A radar system that covers the O2 absorption wavelengths over the ocean will have great potential for weather observations and other meteorological applications, especially for forecasts of hurricanes. Case studies show that with the capability of remotely sensed sea surface barometric pressure data, the errors of hurricane center pressure, the most important indicator of hurricane intensity, in weather prediction models would reduce from about 48 mb to about 1.5 mb. The increased accuracy is about 1/3 of whole range of possible variations of hurricane center pressure. The uncertainties in the weather model predicted landfall positions or tracks of hurricanes also shrink greatly from ~350 km to within 100 km. Based on conventional radar system design and radar engineering models, our assessment clearly illustrates that it is realistic to develop our proposed airborne radar system with existing technology. That is, all major subsystems of the proposed instrument could be built using available Commercial Off The Shelve (COTS) components. An investment would be required to integrate and test the whole instrument as well as to install it onto the aircraft or UAV. The Technology Readiness Level (TRL) assessment before this feasibility analysis was based upon the basic principle and technology concept and resulted in TRL 2. The current analysis and assessment, especially the analytical results of the O2-band radar, applications, sea surface air pressure retrievals, and airborne radar system designs, advances the O2-band radar technology to TRL 3. Finally, a roadmap for further studies on the radar system to advance the TRL to higher levels, such as 6 and higher, is shown in this report.