The effect of leads in Arctic sea ice on clouds is a potentially important climate feedback. We use observations of clouds and leads from the Ice, Cloud, and Land Elevation Satellite-2 (ICESat-2) to study the effects of leads on clouds. Both leads and clouds are strongly forced by synoptic weather conditions, with more clouds over both leads and sea ice at lower sea level pressure. Contrary to previous studies, we find the overall lead effect on low-level cloud cover is –0.02, a weak cloud dissipating effect in cold months, after the synoptic forcing influence is removed. This is due to compensating contributions from the cloud dissipating effect by newly frozen leads under high pressure systems and the cloud enhancing effect by newly open leads under low pressure system. The lack of proper representation of lead effect on clouds in current climate models and reanalyses may impact their performance in winter months, such as in sea ice growth and Arctic cyclone development.

Low‐level wind jets (LLJs) and strong surface winds are frequently observed near the sea ice edge in the presence of strong thermal contrast between open water and sea ice. Two LLJ cases near the sea ice edge in the Beaufort Sea are examined using dropsonde observations made from Seasonal Ice Zone Reconnaissance Survey flights. Ensembles of Polar Weather Research and Forecast simulations with and without sea ice demonstrate the contribution of the surface thermal contrast to the boundary layer structure, the LLJ, and surface ice edge jets. Because the surface temperature contrast only influences the lower most hundreds of meters in the atmospheric boundary layer, its contribution to the temperature gradient and wind speed at the level of the LLJ is limited. The sea ice does strengthen the LLJ by extending the LLJ northward over sea ice and increasing the maximum LLJ wind speeds by up to 13% and as much as 29% further north at a lower altitude. However, the primary reason for the observed strong winds in these two cases are the synoptic interactions between anticyclones and approaching cyclones. The effect of the surface thermal contrast on surface winds is controlled by a separate mechanism. The cold and stable boundary layer over sea ice prevents the momentum transport from the LLJ to the surface. This leads to weaker surface winds over sea ice and confines the strong surface winds close to the sea ice edge. This mechanism contributes to the frequent occurrence of the surface "ice edge jets."

176th Meeting of the Acoustical Society of America 5-9 November 2018, Victoria, BC, Canada.

Our goal is an office-based, handheld ultrasound system to target, detach, break, and/or expel stones and stone fragments from the urinary collecting system to facilitate natural clearance. Repositioning of stones in humans (maximum 2.5 MPa, and 3-second bursts) and breaking of stones in a porcine model (maximum 50 cycles, 20 Hz repetition, 30 minutes, and 7 MPa peak negative pressure) have been demonstrated using the same 350-kHz probe. Repositioning in humans was conducted during surgery with a ureteroscope in the kidney to film stone movement. Independent video review confirmed stone movements (≥ 3 mm) in 15 of 16 kidneys (94%). No serious or unanticipated adverse events were reported. Experiments of burst wave lithotripsy (BWL) effectiveness on breaking human stones implanted in the porcine bladder and kidney demonstrated fragmentation of 7 of 7 stones on post mortem dissection. A 1-week survival study with the BWL exposures and 10 specific pathogen-free pigs, showed all findings were within normal limits on clinical pathology, hematology, and urinalysis. These results demonstrate that repositioning of stones with ultrasonic propulsion and breaking of stones with BWL are safe and effective.