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(Joshua Wurman) $@H/I=MW;]!'(J
The Doppler On Wheels (DOW) mobile radars were used in the Radar Observations of Tornadoes And Thunderstorms Experiment (ROTATE) in 1998. Three tornadoes were observed. One was observed by both DOWs, permitting dual-Doppler retrievals. One was observed intermittently for over 30 minutes as it intensified into a violent tornado. The tornado was observed as it destroyed the town of Spencer, South Dakota, killing 6 and injuring 50% of the population. Winds of 115 m/s were observed, representing the highest ever recorded near the ground. Sub tornado structures, possibly indicating multiple-vortex structure were observed. A third tornado was observed from extremely close range as the center of rotation passed within 170 m of a DOW, with the outer flow region passing through the radar. At the center of the tornado the radar beamwidth was only 3 m (though radar gates were 38 m), constant elevation observations were repeated every 12-14 s. The DOW radars intercepted hurricanes Bonnie (North Carolina) and Georges (Mississippi) as the eyes passed onshore. Dual-Doppler data were retrieved in George with a baseline of 14 km. Small scale structures and wind streaks that had been recently discovered in hurricane Fran (1996, North Carolina) were observed.
(Seelye Martin) $@H/I=MW;]!'(J
Using remote sensing and oceanographic data, we describe the properties of the northern Okhotsk polynyas, which occur on the northwest shelf between Ayun and Okhotsk City, on the northern shelf between Okhotsk City and Magadan, and in Shelikhov Bay. In the satellite analysis, we use a passive microwave algorithm to derive for each polynya the area of thin ice and open water, and a heat flux algorithm to derive the ice and brine production. From our analysis, the NWS polynya is the dominant ice and brine producer, contributing on average about 55% of the total production. Shelikhov Bay is the second largest producer with about 25% of the total, and the northern shelf produces the final 20%. For our observational period, we found that the total polynya productivity varied by a factor of two, and that of the dominant NWS polynya varied by a factor of three. The source of the NWS variability is due to the winter-averaged angle at which the surface pressure isobars intersect the NWS coast. When the isobars are parallel to the coast, there is little offshore transport. When the isobars are at an angle such that there is an offshore flow, the polynya size and ice production are much larger, so that a small change in angle yields a large change in ice and brine production. For the 1996 and 1997 winters, we also compare satellite estimates of polynya ice and brine production with Russian CTD surveys provided by Gladyshev. For Shelikhov Bay, the surveys show that this region produces large amounts of dense water, which flows into the Tinro Basin. For the northern and northwest shelves, the observations show that much of the generated dense water circulates on the shelf around to the east to enter the East Sakhalin Current. Our satellite estimates show that the total polynya ice production for 1996 and 1997 was respectively 230 and 120 cubic kilometers, with the NWS contributing 60 - 70% of the total. For the same years, ship survey estimates of ice production yield comparable values of 210 and 130 cubic kilometers in 1996 and 1997. This agreement suggests that the satellite observations provide reasonable estimates of the ice and brine production, and can be used to monitor the polynya response to changes in regional climate.
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