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CSU -- Compact Microwave Radiometer Network
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Please contact Prof. Steven Reising at Steven.Reising@ColoState.edu
Emerging Technologies
Quantitative precipitation forecasting is currently limited by the paucity of observations on sufficiently fine temporal and spatial scales. In particular, convective storms have been observed to develop in regions of strong and rapidly evolving moisture gradients that vary on sub-meso γ scales (<2-5 km). Therefore, measurements of water vapor aloft with high time resolution and sufficient spatial resolution have the potential to improve forecast skill for the initiation of convective storms. Such measurements may be used for assimilation into and validation of numerical weather prediction (NWP) models. Conventional measurements of water vapor density profiles are obtained using in-situ probes on-board weather balloons, including radiosondes, which have excellent vertical resolution but are severely limited in temporal sampling and horizontal coverage. Therefore, high spatial resolution moisture measurements with rapid revisit times are needed to improve the prediction of convective storm initiation. To obtain high-resolution measurements of humidity in the troposphere, the Microwave Systems Laboratory at Colorado State University has developed, fabricated, tested and deployed the Compact Microwave Radiometer for Humidity Profiling (CMR-H) [1]. For ground-based deployment, a coordinated sensor network consisting of a number of CMR-Hs can produce 3-D images of atmospheric humidity in the region. In terms of sensor design, CMR-H takes advantage of the latest microwave integrated circuit technology developed for satellite communications to achieve small size (9” x 7” x 6”), light weight (13 lbs.) and low power consumption (25-50 W, depending on the season of the year). These features make the CMR-H convenient for low-cost deployment, not only on the ground, but also on a variety of airborne measurement platforms. The CMR-H has successfully performed field measurements at NCAR’s Mesa Laboratory during the Refractivity Experiment for H2O Research and Collaborative operational Technology Transfer (REFRACTT 2006). CMR-H was mounted atop a pan-tilt positioner and is capable of scanning at the rate of 7º/sec in elevation and 25º/sec in azimuth. A single CMR-H is capable of providing integrated precipitable water vapor (PWV) with a resolution of 0.1 mm as well as water vapor density profiles with high spatial and temporal resolution. The availability of these microwave radiometers enables the deployment of a sufficient number of scanning microwave radiometers to form a remote sensor network. In such a network, each CMR-H performs a complete volumetric scan, and multiple sensors measure the same atmospheric volumes from different perspectives. The brightness temperatures from multiple scanning compact microwave radiometers were combined to retrieve the 3-D water vapor field. This new retrieval technique combines algebraic tomographic reconstruction, Bayesian optimal estimation and Kalman filtering to retrieve the 3-D water vapor field as a function of time [2]. An Observation System Simulation Experiment (OSSE) was performed in order to evaluate the capabilities of a network of scanning microwave radiometers to retrieve the 3-D distribution of water vapor in the troposphere. To accomplish this, the 3-D water vapor output from a fine-resolution Weather Research and Forecast (WRF) numerical weather prediction model was compared with retrievals from synthetic brightness temperatures. OSSE results show that the 3-D water vapor density field can be retrieved with an accuracy of about 15-20% at all altitudes studied above ground level [2]. Two field experiments were performed to demonstrate the capability of algebraic reconstruction tomography to retrieve 3-D water vapor fields from radiometer network observations with multiple radiometers measuring overlapping atmospheric volumes. The first field experiment consisted of measurements using three ground-based microwave radiometers deployed in an equilateral triangle at the Atmospheric Radiation Measurement (ARM) Southern Great Plains (SGP) site in Billings, OK, USA during August 2008. The ARM-SGP deployment was sponsored by Ball Aerospace & Technologies Corp., with complementary funding from the National Science Foundation for CMR-H fabrication. Brightness temperatures measured by the three-station radiometer network were used to retrieve the 3-D water vapor density in the region with a 0.5-km horizontal and vertical resolution, as well as 10-15 minute temporal resolution [2]. The second field experiment involved the deployment of the three-radiometer network in a triangular topology in Rome, Italy. The 3-D water vapor field was retrieved with the same spatial and temporal resolution as during the ARM-SGP experiment. This work was performed as part of the European Space Agency project entitled Mitigation of Electromagnetic Transmission errors induced by Atmospheric Water Vapor Effects (METAWAVE).
Steven C. Reising
Colorado State University
1373 Campus Delivery Electrical and Computer Engineering Fort Collins, CO 80523-1373
DeveloperSteven C. Reising, Colorado State University
Development SectorAcademia
R&D ProgramYes
Years Till Available<3
Investment Required$100k-$1M
Projected ApplicationRemote Sensing of 3-D Humidity Field
Unit Cost$10k-$100k
Key RisksAvailability of R&D investment
Ease of Useunattended
1. Iturbide-Sanchez, F., S. C. Reising and S. Padmanabhan, "A Miniaturized Spectrometer Radiometer Based on MMIC Technology for Tropospheric Water Vapor Profiling," IEEE Trans. Geosci. Remote Sensing, vol. 45, no. 7, pp. 2181-2194, July 2007. 2. Padmanabhan, S., S. C. Reising, J. Vivekanandan and F. Iturbide-Sanchez, "Retrieval of Atmospheric Water Vapor Density With Fine Spatial Resolution Using Three-Dimensional Tomographic Inversion of Microwave Brightness Temperatures Measured by a Network of Scanning Compact Radiometers," IEEE Trans. Geosci. Remote Sensing, in press, Nov. 2009 issue.
Field Deployable
9 Oct 2009 19:43