Dean Lauritsen

Testing a mobile version of a Cross-Chain LORAN Atmospheric (M-CLASS) Sounding System

Abstract We have Rested the NCAR Cross-Chain LORAN Atmospheric Sounding System (CLASS) in a fully mobile configuration, which we call M-CLASS. The sondes use LORAN-C navigation signals to allow calculation of balloon position and horizontal winds. In nonstormy environments, thermodynamics and wind data were almost always of high quality. Besides providing special soundings for operational forecasts and research programs, a major feature of mobile ballooning with M-CLASS is the ability to obtain additional data by flying other instruments on the balloons. We flew an electric field meter, along with a sonde, into storms on 8 of the initial 47 test flights in the spring of 1987. In storms, pressure, temperature, humidity, and wind data were of good quality about 80%, 75%, 60%, and 40% of the time, respectively. In a flight into a mesocyclone, we measured electric fields as high as −135 kV/m (at 10 km MSL) in a region of negative charge. The electric field data from several storms allow a quantitative assessm...

A Long-Term, High-Quality, High-Vertical-Resolution GPS Dropsonde Dataset for Hurricane and Other Studies

AbstractA GPS dropsonde is a scientific instrument deployed from research and operational aircraft that descends through the atmosphere by a parachute. The dropsonde provides high-quality, high-vertical-resolution profiles of atmospheric pressure, temperature, relative humidity, wind speed, and direction from the aircraft flight level to the surface over oceans and remote areas. Since 1996, GPS dropsondes have been routinely dropped during hurricane reconnaissance and surveillance flights to help predict hurricane track and intensity. From 1996 to 2012, NOAA has dropped 13,681 dropsondes inside hurricane eye walls or in the surrounding environment for 120 tropical cyclones (TCs). All NOAA dropsonde data have been collected, reformatted to one format, and consistently and carefully quality controlled using state-of-the-art quality-control (QC) tools. Three value-added products, the vertical air velocity and the radius and azimuth angle of each dropsonde location, are generated and added to the dataset. As ...

Targeted Dropwindsondes in Complex Terrain

Abstract The dropwindsonde (or dropsonde) is a frequently utilized tool in geophysical research and its use over ocean and flat terrain is a reliable and well-established practice. Its use in complex terrain, however, is complicated by signal acquisition challenges that can be directly related to the ground target location, local relief, and line of sight to flight tracks relevant to the observation sought. This note describes a straightforward technique to calculate the theoretical altitude above ground to which a ground-targeted dropsonde will provide data for a given airborne platform. It is found that this height HCq can be calculated from expected airborne platform horizontal velocity Uag, mean dropwindsonde vertical velocity Ws, the relevant barrier maximum HB, and the horizontal distance from the target area to the barrier maximum DB. Here, HCq is found to be weakly dependent on release altitude through Ws. An example from the Terrain-induced Rotor Experiment (T-REX) is used to show that for modern...

A reference radiosonde system for climate and weather research: IHOP experience

Global radiosonde data are required by meteorological analysis centers for initializing numerical prediction models for weather forecasting, and represent an increasingly valuable resource for studies of climate change and in the development, calibration and validation of retrieval techniques for atmospheric temperature and water vapor profiles from satellite. Unfortunately, the usefulness of radiosonde data is limited by sensor accuracy, by data reporting practices, and by the fact that sonde and sensor types vary by location and with time. Numerous studies and reports have called for a reference sonde to serve as a transfer standard to compare and connect data from past, present and future sonde systems. We are working on developing a reference radiosonde system at the Atmospheric Technology Division (ATD) at NCAR. The reference radiosonde system will carry the best sensors, have a flexible infrastructure to host multiple and different user-provided sensors and will be recoverable to reduce costs. The first version of the reference radiosonde system was deployed in the Oklahoma panhandle and Dodge City, KS (NWS radiosonde site) during the International H2O Project (IHOP_2002). A total of sixteen reference sondes were launched during IHOP either with Vaisala RS80 or Sippican (VIZ) radiosondes. The humidity data from the reference humidity sensor (Snow White, SW) are compared with Vaisala and VIZ data. The comparisons show that (a) VIZ carbon hygristor fails to respond to humidity changes in the upper troposphere, (b) the carbon hygristor inside the reference sonde has slower response than that inside NWS VIZ sonde, (c) Vaisala RS80-H agrees with SW very well in the middle and lower troposphere, and (d) SW can detect cirrus clouds near the tropopause and possibly estimate their ice water content (IWC). The climate impacts of these results are also discussed.