Astronomy and Astrophysics – Astronomy
Scientific paper
Dec 2004
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2004agufm.g31a0785b&link_type=abstract
American Geophysical Union, Fall Meeting 2004, abstract #G31A-0785
Astronomy and Astrophysics
Astronomy
8494 Instruments And Techniques, 3329 Mesoscale Meteorology, 3337 Numerical Modeling And Data Assimilation, 1206 Crustal Movements: Interplate (8155), 1243 Space Geodetic Surveys
Scientific paper
We investigate the utility of a mesoscale weather model for mitigating atmospheric errors in InSAR-derived displacement fields associated with volcanotectonic phenomena at Mauna Loa and Kilauea volcanoes on the Island of Hawaii. The MM5 (NCAR-Penn State Mesoscale Model Version 5) forecast is run twice daily for the island of Hawaii by the Mauna Kea Weather Center in support of Mauna Kea's astronomical observatories. MM5 has a 60-hour forecast window and the forecast fields are output in 3-hour increments. A high-resolution analysis that incorporates weather observations from National Weather Service and satellite-derived winds from the University of Wisconsin, provides the initial conditions for MM5. In turn, MM5 produces predictions of thermodynamic properties of the atmosphere, including temperature, pressure, and moisture fields at a 3 km horizontal resolution. The vertical resolution is density weighted with the greatest vertical resolution (10s of meters) near the surface. For any radar image acquisition there is a high-resolution 3D simulation of atmospheric water vapor valid within 1.5 hours of the acquisition time and predicted forward no more than 12 hours from the initial observations. Using MM5 forecast water vapor, we create line-of-sight delay maps that can be either directly removed from InSAR differential pairs or used to create synthetic radar interferograms that can be compared with the observed interferogram. We analyze Envisat ASAR radar data collected during 2003-2004 and find, qualitatively, that contours of excess path delay in MM5 model runs often closely mimic both topographic contours and fringes observed in differential interferograms which have had topographic phase removed. Over periods of days, the delays can vary in magnitude and spatial scale by 10s of mms and 10s of kms, respectively. Individual models can predict peak delays associated with moist layer inversions of order ~20 mm around the summits of Mauna Loa and Kilauea, both active volcanoes. Similar delays are also associated with the inactive Mauna Kea summit. These results are particularly pertinent for using InSAR to track accurately the history of summit-related magmatic phenomena between scene acquisitions. The path delays would introduce a significant atmosphere-related bias if included in a deformation analysis. To validate the technique, we compare total delays and precipitable water data from more than 20 continuous GPS (CGPS) sites with those estimated by the MM5 model. We investigate the technique's efficacy by inverting InSAR-derived line-of-sight displacement fields for the time-varying characteristics of a shallow magma chamber below Mauna Loa's summit caldera. Finally, we compare these results with independent inversion of summit CGPS data.
Brooks Benjamin A.
Businger Steven
Cherubini Tiziana
Foster John Jr.
Miklius Asta
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