The High- Definition Sounding System (HDSS) is an automated system deploying the expendable digital dropsonde (XDD) designed to measure wind and pressure-temperature-humidity (PTH) profiles, and skin sea surface temperature (SST) within and around tropical cyclones (TCs) and other high-impact weather events needing high sampling density. Three experiments were conducted to validate the XDD.On two successive days off the California coast, 10 XDDs and 14 Vaisala RD-94s were deployed from the navy's Center for Interdisciplinary Remotely-Piloted Aircraft Studies (CIRPAS) Twin Otter aircraft over offshore buoys. The Twin Otter made spiral descents from 4 km to 60 m at the same descent rate as the sondes. Differences between successive XDD and RD-94 profiles due to true meteorological variability were on the same order as the profile differences between the spirals, XDDs, and RD-94s. XDD SST measured via infrared microradiometer, referred to as infrared skin SST (SSTir), and surface wind measurements were within 0.5 degrees C and 1.5ms(-1), respectively, of buoy and Twin Otter values.A NASA DC-8 flight launched six XDDs from 12 km between ex-TC Cosme and the Baja California coast. Repeatability was shown with good agreement between features in successive profiles. XDD SSTir measurements from 18 degrees to 28 degrees C and surface winds agreed well with drifting buoy- and satellite-derived estimates.Excellent agreement was found between PTH and wind profiles measured by XDDs deployed from a NASA WB-57 at 18-km altitude offshore from the Texas coast and NWS radiosonde profiles from Brownsville and Corpus Christi, Texas. Successful XDD profiles were obtained in the clear and within precipitation over an offshore squall line.

A mobile, phased-array Doppler radar, the Mobile Weather Radar, 2005 X-band, Phased Array (MWR-05XP), has been used since 2007 to obtain data in supercells and tornadoes. Rapidly updating, volumetric data of tornadic vortex signatures (TVSs) associated with four tornadoes are used to investigate the time-height evolution of TVS intensity, position, and dissipation up through storm midlevels. Both TVS intensity and position were highly variable in time and height even during tornado mature phases. In one case, a TVS associated with a tornado dissipated aloft and a second TVS formed shortly thereafter while there was one continuous TVS near the ground. In a second case, the TVS associated with a long-lived, violent tornado merged with a second TVS (likely a second cyclonic tornado) causing the original TVS to strengthen. TVS dissipation occurred first at a height of ~1.5 km AGL and then at progressively higher levels in two cases; TVS dissipation occurred last in the lowest 1 km in three cases examined. Possible explanations are provided for the unsteady nature of TVS intensity and a conceptual model is presented for the initial dissipation of TVSs at ~1.5 km AGL.

Observations from a hybrid phased-array Doppler radar, the Mobile Weather Radar, 2005 X-band, Phased Array (MWR-05XP), were used to investigate the vertical development of tornadic vortex signatures (TVSs) during supercell tornadogenesis. Data with volumetric update times of approximate to 10 s, an order of magnitude better than that of most other mobile Doppler radars, were obtained up to storm midlevels during the formation of three tornadoes. It is found that TVSs formed upward with time during tornadogenesis for two cases. In a third case, missing low-level data prevented a complete time-height analysis of TVS development; however, TVS formation occurred first near the ground and then at storm midlevels several minutes later. These results are consistent with the small number of volumetric mobile Doppler radar tornadogenesis cases from the past approximate to 10 years, but counter to studies prior to that, in which a descending TVS was observed in roughly half of tornado cases utilizing Weather Surveillance Radar-1988 Doppler (WSR-88D) data. A comparative example is used to examine the possible effects relatively long WSR-88D volumetric update times have on determining the mode of tornadogenesis.

During the Second Verification of the Origins of Rotation in Tornadoes Experiment (VORTEX2), in the spring of 2010, a mobile and pulsed Doppler lidar system [the Truck-Mounted Wind Observing Lidar Facility (TWOLF)] mounted on a truck along with a mobile, phased-array, X-band Doppler radar system [Mobile Weather Radar-2005 X-band, phased array (MWR-05XP)] was used to complement Doppler velocity coverage in clear air near the radar-lidar facility and to provide high-spatial-resolution vertical cross sections of the Doppler wind field in the clear-air boundary layer near and in supercells. It is thought that the magnitude and direction of vertical shear and possibly the orientation and spacing of rolls in the boundary layer have significant effects on both supercell and tornado behavior; MWR-05XP and TWOLF can provide data that can be used to measure vertical shear and detect rolls. However, there are very few detailed, time-dependent and spatially varying observations throughout the depth of the boundary layer of supercells and tornadoes.This paper discusses lidar and radar data collected in or near six supercells. Features seen by the lidar included gust fronts, horizontal convective rolls, and small-scale vortices. The lidar proved useful at detecting high-spatial-resolution, clear-air returns at close range, where the radar was incapable of doing so, thus providing a more complete picture of the boundary layer environment ahead of supercells. The lidar was especially useful in areas where there was ground-clutter contamination. When there was precipitation and probably insects, and beyond the range of the lidar, where there was no ground-clutter contamination, the radar was the more useful instrument. Suggestions are made for improving the system and its use in studying the tornado boundary layer.

A mobile X-band, phased-array Doppler radar was acquired from the U.S. Army by the Center for Interdisciplinary Remotely Piloted Aircraft Studies (CIRPAS) at the Naval Postgraduate School and adapted for meteorological use by ProSensing, Inc. The radar was used during field experiments conducted in the Southern Plains by faculty and students from the School of Meteorology at the University of Oklahoma during the spring storm seasons of 2007 and 2008. During these field experiments, storm-scale, rapid-scan, volumetric, Doppler-radar observations were obtained in tornadic and nontornadic supercells, quasilinear mesoscale convective systems, and in both boundary layer-based and elevated ordinary convective cells. A case is made for the use of the radar for studies of convective weather systems and other weather phenomena that evolve on time scales as short as tens of seconds.

Tornadoes and many severe convective storms evolve on very short time scales (~ 10 s), owing to very high horizontal wind speeds and vertical velocities. This paper documents the formation of a tornado in the U. S. using a mobile, rapidly scanning, Doppler radar. This radar, the MWR-05XP (Meteorological Weather Radar, 2005, X-band, Phased Array), electronically scans in elevation and azimuth over limited sectors, and mechanically in azimuth at high speed. While the radar scans electronically in elevation, the attitude of its beam is held nearly fixed in space because it electronically back scans in azimuth at the same rate as it mechanically scans. Back scanning in azimuth is accomplished by frequency hopping, while scanning in elevation is accomplished by changing the phase delay.

Measurements of solar and infrared irradiance by instruments rigidly mounted to an aircraft have historically been plagued by the introduction of offsets and fluctuations into the data that are solely due to the pitch and roll movements of the aircraft. The Stabilized Radiometer Platform ( STRAP) was developed to address this problem. Mounted on top of an aircraft and utilizing a self-contained, coupled Inertial Navigation System-GPS, STRAP actively keeps a set of uplooking radiometers horizontally level to within +/- 0.02 degrees for aircraft pitch and roll angles of up to approximately +/- 10 degrees. The system update rate of 100 Hz compensates for most pitch and roll changes experienced in normal flight and in turbulence. STRAP was mounted on a Twin Otter aircraft and its performance evaluated during normal flight and during a series of flight maneuvers designed to test the accuracy, range, and robustness of the platform. The measurements from an identical pair of solar pyranometers-one mounted on STRAP and the other rigidly mounted nearby directly to the aircraft-are compared to illustrate the accuracy and capability of the new platform. Results show that STRAP can keep radiometers level within the specified pitch and roll range, that it is able to recover from flight maneuvers outside of this range, and that it greatly increases the quantity of useful radiometer data from any given flight. Of particular note, STRAP now allows accurate measurements of the downwelling solar irradiance during spiral ascents or descents of the aircraft, greatly expanding the utility of aircraft radiometer measurements.

he ocean sciences community is currently engaged in the process of defi ning new facilities that will support oceanographic research, education, and monitoring efforts for the next several decades.New research vessels, drilling ships, coastal and deep-ocean observing systems, satellites, and submersibles will be designed to increase ocean access in terms of geographical coverage, depth, temporal continuity, and resolution of events.Aircraft may be largely overlooked facilities that are capable of providing observations and data in ways that satisfy many research goals, and they should be considered an important component in the future mix of oceanographic facilities.Aircraft are capable of greater speed, and therefore greater range and spatial coverage during a short time period when compared to surface and subsurface ocean research platforms.Such speed and range attributes lead to better synoptic coverage of oceanic and atmospheric variability.Aircraft-mounted sensors provide data with much of the appeal of the aerial view provided by satellites, but with much greater specifi city, spatial and temporal resolution, and scheduling fl exibility, and they can provide resolution adaptable to phenomena of interest.Aircraft are ideal for both fast-response investigations and routine, long-term measurements, and they naturally combine atmospheric measurements with oceanographic measurements on similar temporal and spatial scales.Aircraft surveys reach across a wide range of environmental and geographic conditions.

In June 1994 the Monterey Area Ship Track (MAST) experiment was conducted off the coast of California to investigate the processes behind anthropogenic modification of cloud albedo. The motivation for the MAST experiment is described here, as well as details of the experimental design, Measurement platforms and strategies are explained, and a summary of experiment operations is presented The experiment produced the largest dataset to date of direct measurements of the effects of ships on the microphysics and radiative properties of marine stratocumulus clouds as an analog for the indirect effects of anthropogenic pollution on cloud albedo.