Search

The National Oceanic and Atmospheric Administration's (NOAA's) Air Resources Laboratory (ARL), using the NOAA Twin Otter aircraft, made meteorological and chemical measurements during 21 flights in May 2002 in and around the Tampa Bay, Florida area as part of the Bay Region Atmospheric Chemistry Experiment (BRACE). One or more vertical profiles were flown during each flight both over land and over the Gulf of Mexico. NOAA's Environmental Technology Laboratory (ETL; now part of NOAA's Earth System Research Laboratory (ESRL)) deployed three surface-based 915-MHz radar wind profilers equipped with radio acoustic sounding systems (RASS) at Ruskin, Sydney, and St. Petersburg. The National Weather Service Office in Tampa (NWS/TBW) released rawinsondes twice daily from the Ruskin site. The measurements of temperature, dew point, potential temperature, ozone, and condensation nuclei acquired during the aircraft profiles are analyzed, and in combination with the profiler and sounding data, are used to determine the structure of the boundary layer over the Tampa Bay region and the temporal and spatial changes that occurred in that structure during representative flights.

An assessment of Advanced Microwave Scanning Radiometer Earth Observing System (AMSR-E) sea ice concentrations under winter conditions using ice concentrations derived from Landsat-7 Enhanced Thematic Mapper Plus (ETM+) imagery obtained during the March 2003 Arctic sea ice validation field campaign is presented. The National Oceanic and Atmospheric Administration Environmental Technology Laboratory's Airborne Polarimetric Scanning Radiometer Measurements, which were made from the National Aeronautics and Space Administration P 3B aircraft during the campaign, were used primarily as a diagnostic tool to understand the comparative results and to suggest improvements to the AMSR-E ice concentration algorithm. Based on the AMSR-E/ETM+ comparisons, a good overall agreement with little bias (~1%) for areas of first year and young sea ice was found. Areas of new ice production result in a negative bias of about 5% in the AMSR-E ice concentration retrievals, with a root mean square error of 8%. Some areas of deep snow also resulted in an underestimate of the ice concentration (~10%). For all ice types combined and for the full range of ice concentrations, the bias ranged from 0% to 3%, and the rms errors ranged from 1% to 7%, depending on the region. The new-ice and deep-snow biases are expected to be reduced through an adjustment of the new-ice and ice-type C algorithm tie points

We discuss the performances of a set of four microwave water vapor radiometers operating in the 20-30-GHz band during a field experiment, with an emphasis on calibration and achievable accuracy. The field experiment was conducted at the Department of Energy's Atmospheric Radiation Measurement Program's field site in north central Oklahoma, and was focused on clear-sky water vapor measurements by both radiometers and radiosondes. A comparison between two published radiometric tip curve calibration procedures is presented, and these procedures are applied to measurements from two nearly identical instruments placed a few meters apart. Using the instantaneous tip cal method of the Environmental Technology Laboratory, the brightness temperature measurements for the two identical instruments differed by less than 0.2 K over a 24-h period. Results from reference load cryogenic tests and brightness temperature cross comparisons have shown differences within 0.7 K. In addition, we compare radiometric measurements with calculations of brightness temperature based on the Rosenkranz absorption model and radiosonde observations. During the experiment, both Vaisala-type RS80 and RS90 humidity sensors were used. Our comparisons demonstrate the improvements achieved by the new Vaisala RS90 sensors in atmospheric humidity profiling, which reduce or eliminate the "dry bias" problem.

During June‐July 1999, the NOAA R/V Ron H. Brown(RHB) sailed from Australia to the Republic of Nauru where the Department of Energy’s Atmospheric Radiation Measurement (ARM) Program operates a long-term climate observing station. During July, when the RHB was in close proximity to the island of Nauru, detailed comparisons of ship- and island-based instruments were possible. Essentially identical instruments were operated from the ship and the island’s Atmospheric Radiation and Cloud Station (ARCS)-2. These instruments included simultaneously launched Vaisala RS80-H radiosondes, the Environmental Technology Laboratory’s (ETL) Fourier transform infrared radiometer (FTIR), and ARM’s atmospheric emitted radiance interferometer (AERI), as well as cloud radars/ceilometers to identify clear conditions. The ARM microwave radiometer (MWR) operating on Nauru provided another excellent dataset for the entire Nauru99 experiment. The calibration accuracy was verified by a liquid nitrogen blackbody target experiment and by consistent high quality tipping calibrations throughout the experiment. Comparisons were made for calculated clear-sky brightness temperature (Tb) and for precipitable water vapor (PWV). These results indicate that substantial errors, sometimes of the order of 20% in PWV, occurred with the original radiosondes. When a Vaisala correction algorithm was applied, calculated Tbs were in better agreement with the MWR than were the calculations based on the original data. However, the improvement in Tb comparisons was noticeably different for different radiosonde lots and was not a monotonic function of radiosonde age. Three different absorption algorithms were compared: Liebe and Layton, Liebe et al., and Rosenkranz. Using AERI spectral radiance observations as a comparison standard, scaling of radiosondes by MWR data was compared with both original and corrected soundings.

An algorithm to compute the magnitude of humidity gradient profiles from the measurements of the zeroth, first, and second moments of wind profiling radar (WPR) Doppler spectra was developed and tested. The algorithm extends the National Oceanic and Atmospheric Administration (NOAA)/Environmental Technology Laboratory (ETL) Advanced Signal Processing System (SPS), which provides quality control of radar data in the spectral domain for wind profile retrievals, to include the retrieval of humidity gradient profiles. The algorithm uses a recently developed approximate formula for correcting Doppler spectral widths for the spatial and temporal filtering effects. Data collected by a 3-beam 915-MHz WPR onboard the NOAA research vessel Ronald H. Brown (RHB) and a 5-beam 449-MHz WPR developed at the ETL were used in this study. The two datasets cover vastly different atmospheric conditions, with the 915-MHz shipborne system probing the tropical ocean atmosphere and the 449-MHz WPR probing continental win...

Airborne wind observations collected by the National Oceanic and Atmospheric Administration's (NOAA) WP-3D aircraft are compared with the winds retrieved by the NOAA/Environmental Technology Laboratory's ground-based scanning Doppler lidar within the Wipp Valley during the Special Observing Period of the Mesoscale Alpine Programme. Comparisons are performed along individual flight tracks and over an aggregated dataset consisting of all pairs of WP-3D and lidar observations that were approximately coincident in time and space. The impact of several different quality-control thresholds on the root mean square (r.m.s.) difference between the two observations is explored. The overall quality-controlled r.m.s. difference between radial wind speeds measured by each platform was 3.0 m s−1, with larger r.m.s. errors in the region up valley from the lidar than in the region down valley. A bias was also evident, in which the wind speeds from the WP-3D exceeded those from the lidar; this bias was small down valley (0.4 m s−1) and much larger up valley (2.4 m s−1). Copyright © 2003 Royal Meteorological Society.

A NOAA/Environmental Technology Laboratory Doppler lidar measured the life cycle of the land- and sea-breeze system at Monterey Bay, California, in 1987, during the Land–Sea Breeze Experiment (LASBEX). On days with offshore synoptic flow, the transition to onshore flow (the sea breeze) was a distinct process easily detected by lidar. Finescale lidar measurements showed the reversal from offshore to onshore flow near the coast, its gradual vertical and horizontal expansion, and a dual structure to the sea-breeze flow in its early formative stages. Initially, a shallow (

An approach is suggested to relate measurements of radar depolarization ratios and aspect ratios of predominant hydrometeors in nonprecipitating and weakly precipitating layers of winter clouds. The trends of elevation angle dependencies of depolarization ratios are first used to distinguish between columnar-type and plate-type particles. For the established particle type, values of depolarization ratios observed at certain elevation angles, for which the influence of particle orientation is minimal, are then used to estimate aspect ratios when information on particle effective bulk density is assumed or inferred from other measurements. The use of different polarizations, including circular, slant-45° linear, and two elliptical polarizations, is discussed. These two elliptical polarizations are quasi-circular and quasi-linear slant-45° linear, and both are currently achievable with the National Oceanic and Atmospheric Administration Environmental Technology Laboratory’s Ka-band radar. In compari...

The need for a reliable, low-cost observing system to measure water vapor in the atmosphere is incontrovertible. Experiments have shown the potential for using Global Positioning System (GPS) receivers to measure total precipitable water vapor accurately at different locations and times of year and under all weather conditions. The National Oceanic and Atmospheric Administrations’s (NOAA) Forecast Systems Laboratory (FSL) and Environmental Technology Laboratory (ETL), in collaboration with the University NAVSTAR Consortium, University of Hawaii, Scripps Institution of Oceanography, and NOAA’s National Geodetic Survey (NGS) Laboratory, are addressing this need by developing a ground-based water vapor observing system based on the measurement of GPS signal delays caused by water vapor in the atmosphere. The NOAA GPS Integrated Precipitable Water Vapor (NOAA GPS–IPW) network currently has 35 continuously operating stations and is expected to expand into a 200-station demonstration network by 2004. T...

During the past decade, the U.S. Department of Energy (DOE), through the Atmospheric Radiation Measurement (ARM) Program, has supported the development of several millimeter-wavelength radars for the study of clouds. This effort has culminated in the development and construction of a 35-GHz radar system by the Environmental Technology Laboratory (ETL) of the National Oceanic and Atmospheric Administration (NOAA). Radar systems based on the NOAA ETL design are now operating at the DOE ARM Southern Great Plains central facility in central Oklahoma and the DOE ARM North Slope of Alaska site near Barrow, Alaska. Operational systems are expected to come online within the next year at the DOE ARM tropical western Pacific sites located at Manus, Papua New Guinea, and Nauru. In order for these radars to detect the full range of atmospheric hydrometeors, specific modes of operation must be implemented on them that are tuned to accurately detect the reflectivities of specific types of hydrometeors. The set...

During a month-long experiment near San Clemente Island, California, the San Clemente Ocean Probing Experiment (SCOPE), unusual radar echoes were observed from an X-band Doppler radar operated by the National Oceanic and Atmospheric Administration Environmental Technology Laboratory from a cliff 573 m above mean sea level. These radar images were often obtained whenever a strong marine inversion was observed below the level of the radar. The unusual characteristics of the specific event analyzed here were the observed wavelength of the periodic pattern, about 2 km, and its lack of movement during the 15-min period during which specific features of the pattern, for example, the “wave” crest, could be identified. Several explanations were considered but rejected because of their conflict with the observations and known characteristics of ocean waves. The simplest explanation consistent with all of the observations was that of microwave propagation through a marine inversion which was supporting a low-amplitude standing wave in the lee of the island. The plausibility of this hypothesis was supported by a simple ray-trace calculation that simulated propagation through an analytical two-dimensional field of modified refractive index that represented the essential characteristics of the observed refractive index profile.

In 1992 the atmospheric lidar remote sensing groups of the National Aeronautics and Space Administration Marshall Space Flight Center, the National Oceanic and Atmospheric Administration/Environmental Technology Laboratory (NOAA/ETL), and the Jet Propulsion Laboratory began a joint collaboration to develop an airborne high-energy Doppler laser radar (lidar) system for atmospheric research and satellite validation and simulation studies. The result is the Multi-center Airborne Coherent Atmospheric Wind Sensor (MACAWS), which has the capability to remotely sense the distribution of wind and absolute aerosol backscatter in three-dimensional volumes in the troposphere and lower stratosphere. A factor critical to the programmatic feasibility and technical success of this collaboration has been the utilization of existing components and expertise that were developed for previous atmospheric research by the respective institutions. For example, the laser transmitter is that of the mobile ground-based Do...

A scanning 5-mm-wavelength (60 GHz) radiometer was deployed during two recent experiments. The first was in September–October in 1995 when the Environmental Technology Laboratory conducted the Coastal Ocean Probing Experiment off the Oregon coast. During this experiment the scanning radiometer was deployed on the Floating Instrument Platform, a research vessel operated by the Scripps Institution of Oceanography. Ground truth for the radiometer was provided by two independent in situ and infrared measurements of the ocean surface temperature; ground truth for air temperature was also provided by two in situ measurements at 0.5 and 12 m above the ocean surface. The second experiment was during September 10–30, 1996, at the Department of Energy's Atmospheric Radiation Measurement Program's Cloud and Radiation Testbed site near Lamont, Oklahoma. Here ground truth for derived quantities consisted of 3-hourly radiosonde releases and measurements at 25 and 60 m from a meteorological tower. The results of the experiments indicate that the scanning radiometer yields accuracies of the order of 0.4°C rms for sea-air temperature difference and accuracies in temperature of better than 0.7°C rms at altitudes below 60 m.

Ice cloud microphysical parameters derived from a remote sensing method that uses ground-based measurements from the Environmental Technology Laboratory’s Ka-band radar and an IR radiometer are compared to those obtained from aircraft sampling for the cirrus priority event from the FIRE-II experiment. Aircraft cloud samples were taken not only by traditional two-dimensional probes but also by using a new video sampler to account for small particles. The cloud parameter comparisons were made for time intervals when aircraft were passing approximately above ground-based instruments that were pointed vertically. Comparing characteristic particle sizes expressed in terms of median mass diameters of equal-volume spheres yielded a relative standard deviation of about 30%. The corresponding standard deviation for the cloud ice water content comparisons was about 55%. Such an agreement is considered good given uncertainties of both direct and remote approaches and several orders of magnitude in natural v...

The remote sensing method for retrieving vertical profiles of microphysical parameters in ice clouds from ground-based measurements taken by the Doppler radar and IR radiometer was applied to several cloud cases observed during different field experiments including FIRE-II, ASTEX, and the Arizona Program. The measurements were performed with the NOAA Environmental Technology Laboratory instrumentation. The observed ice clouds were mostly cirrus clouds located in the upper troposphere above 5.6 km. Their geometrical thicknesses varied from a few hundred meters to 3 km. Characteristic cloud particle sizes expressed in median mass diameters of equal-volume spheres varied from about 25 μm to more than 400 μm. Typically, characteristic particle sizes were increasing toward the cloud base, with the exception of the lowest range gates where particles were quickly sublimating. Highest particle concentrations were usually observed near the cloud tops. The vertical variability of particle sizes inside an individual cloud could reach one order of magnitude. The standard deviation of the mean profile for a typical cloud is usually factor of 2 or 3 smaller than mean values of particle characteristic size. Typical values of retrieved cloud ice water content varied from 1 to 100 mg m−3; however, individual variations were as high as four orders of magnitude. There was no consistent pattern in the vertical distribution of ice water content except for the rapid decrease in the vicinity of the cloud base. The relationships between retrieved cloud parameters and measured radar reflectivities were considered. The uncertainty of estimating cloud parameters from the power-law regressions is discussed. The parameters of these regressions varied from cloud to cloud and were comparable to the parameters in corresponding regressions obtained from direct particle sampling in other experiments. Relationships between cloud microphysical parameters and reflectivity can vary even for the same observational case. The variability diminishes if stronger reflectivities are considered. A procedure of “tuning” cloud microphysics–reflectivity regressions for individual profiles is suggested. Such a procedure can simplify the radar–radiometer method and make it applicable for a broader range of clouds.

The NOAA Environmental Technology Laboratory air–sea interaction group and collaborators at the Woods Hole Oceanographic Institution have developed a seagoing measurement system suitable for mounting aboard ships. During its development, it was deployed on three different ships and recently completed three cruises in the Tropical Ocean Global Atmosphere Coupled Ocean–Atmosphere Response Experiment as well as two cruises off the west coast of the United States. The system includes tower-mounted micrometeorological sensors for direct covariance flux measurements and a variety of remote sensors for profiling winds, temperature, moisture, and turbulence. A sonic anemometer/thermometer and a fast-response infrared hygrometer are used for turbulent fluxes. Winds are obtained from a stabilized Doppler radar (wind profiler) and a Doppler sodar. Returned power and Doppler width from these systems are used to deduce profiles of small-scale turbulence. A lidar ceilometer and a microwave radiometer are used ...

Observations taken during the February 1991 Atmospheric Studies in Complex Terrain (ASCOT) Winter Validation Study are used to describe the wind field associated with a terrain-forced mesoscale vortex and thermally forced canyon drainage flows along the Front Range of northeastern Colorado. A case study is presented of the night of 6/7 February 1991 when a weak vortex formed and propagated through the ASCOT domain. The NOAA/ERL Environmental Technology Laboratory Doppler lidar, one of an ensemble of instruments participating in the ASCOT field experiment, obtained high-resolution measurements of the structure of both the vortex and the canyon drainage flows. The lidar observations documented the kinematic and structural changes in the cyclone and their relationship to a drainage jet exiting a nearby canyon. Lidar analyses clearly show the layering and stratification present during this case, specifically the drainage jet flowing under the cyclone. A period of strong intensification of the drainag...

The System Demonstration and Integration Division of the Environmental Technology Laboratory and the Battlefield Environment Directorate of the U.S. Army Research Laboratory have designed and built the Mobile Profiler System (MPS).The MPS is an integrated system of ground-based and satellite-borne remote sensors that measure nearly continuous wind and temperature profiles from the surface up through the troposphere. Ground-based sensors include a 924-MHz phased-array wind and temperature profiler, a four-channel microwave radiometer, a surface meteorological tower, and a balloon sounding system. Although MPS was initially developed for military applications, the nonmilitary environmental applications are numerous and significant. This paper provides an overview of the instrumentation, software networking, data processing, data integration, and near real-time data display capabilities currently incorporated into the MPS. Initial results from the first field tests (Los Angeles Free-Radical Study, 3...

Simulations of the 9 January 1989 Colorado Front Range windstorm using both realistic three-dimensional (3D) orography and a representative two-dimensional (2D) east–west cross-sectional orography are presented. Both Coriolis forcing and surface friction (drag law formulation) were included for all experiments. The model results were compared with analyses of Doppler lidar scan data available from the surface to 4 km MSL provided by the Environmental Technology Laboratory of the National Oceanic and Atmospheric Administration (NOAA). The fully three-dimensional simulations with realistic orography used time-dependent inflow boundary conditions. These experiments were designed, in part, to assess the ability of mesoscale models to predict the onset and general characteristics of downslope windstorms. The present experiments highlight the sensitivity of wind storm onset and positioning of surface gusts to both model resolution and surface physics, which is in agreement with previous findings. These...

The fine-scale horizontal variations of water vapor and cloud liquid water are of importance to climate, meteorology, and satellite validation/calibration. The Environmental Technology Laboratory of NOAA has developed a dual-frequency upward- (and downward-) looking radiometer at 23.87 and 31.65 GHz to measure the integrated amounts of water vapor and cloud liquid above an aircraft. Two experiments involving the NOAA WP-3D (tail number N43RF) were conducted in the Oklahoma-Texas region during April 1 to June 15, 1995. The first, the Verification of the Origin of Rotation in Tornadoes Experiment (VORTEX), focused on obtaining detailed observations of mesocyclones and their potential for developing into tornadoes. The second, sponsored by the Department of Energy's Atmospheric Radiation Program, was to obtain detailed aircraft observations of cloud liquid and water vapor to correlate with short- and long-wave radiation measurements. The almost mutually exclusive goals of the two experiments allowed shared use of NOAA WP-3D aircraft throughout the entire April-June period. During VORTEX, the radiometer was operated on all WP-3D flights; of particular interest were several flights flown in zig zag flight patterns through mesoscale moisture fronts known as "dry lines". Through the sharp boundaries of dry lines, strong horizontal gradients in moisture can occur. Several of the dry line cases were observed, and examples are shown.

During September-October in 1995, the Environmental Technology Laboratory (ETL) conducted the Coastal Oceans Probing Experiment COPE off the Oregon coast. During this experiment, a 5-mm scanning radiometer was deployed on a research vessel. In this report, a summary of the obtained results is presented.

A multiband Polarimetric Scanning Radiometer (PSR) was integrated onto the NASA DC-8 aircraft (N717NA) and flown from August through September of 1998 during the third Convection and Moisture Experiment (CAMEX3) and Texas-Florida Under-flight (TEFLUN-B) campaign. The PSR is a unique conically-scanned imaging radiometer with channels at 10.7, 18.7, 21.5, 37.0 and 89.0 GHz, measuring both vertical and horizontal polarizations at each of these frequencies. These channels correspond to several key bands of the DMSP (Defense Meteorological Satellite Program) SSM/I (Special Sensor Microwave Imager) and the NASA TRMM (Tropical Rainfall Measuring Mission) TMI (TRMM Microwave Imager). The PSR was developed by Georgia Institute of Technology and the NOAA Environmental Technology Laboratory. It is the first airborne imaging radiometer to provide a research quality set of high spatial resolution multiband polarimetric microwave imagery within and around a hurricane. A nonlinear statistical emission algorithm was developed for rain rate retrieval, similar to that described by Skofronick-Jackson and Gasiewski (1995). We use the PSR/A 10.7 GHz channels of horizontal and vertical polarization because of their predominantly monotonic response to near-surface rain rate from 0 to /spl sim/50 mm/hr. An initial comparison of the PSR retrieved rain rate to coincidently observed rain rate retrieved using NASA JPL's Airborne Rain Mapping Radar (ARMAR) shows favorable agreement over at least an order of magnitude in rain rate intensity. Discrepancies are within the standard deviations of the PSR retrieval algorithm and can be explained by differences in the observation geometries of the sensors and by differences in the physical measurement principals between the two instruments. Further comparison of the PSR rain rate retrieval with the TMI level 2A12 rain rate product is similarly favorable. Some discrepancies can be explained by the differences in spatial resolution of the two passive microwave instruments and the different nature of the two retrieval algorithms. Despite these differences, the correlation coefficient between the TMI and the PSR coincidentally observed rain rates is 0.92 and 0.91 for PSR horizontal and vertical channels (respectively), for rain rates from /spl sim/1 to /spl sim/16 mm/hr.

Tomography has been widely used in many fields of science, medicine and technology for remote sensing of different media. Acoustic tomography of the atmosphere allows one to reconstruct the three-dimensional temperature and velocity fields and to monitor their evolution in time. It was first employed in the 1990s. In this paper, we overview arrays for acoustic tomography of the atmosphere which have been employed so far. Furthermore, we describe an acoustic tomography array which is proposed to be built at the NOAA Environmental Technology Laboratory. The array will allow us to remotely measure the temperature and velocity fields in a volume with the size of about 40 m/spl times/40 m/spl times/6 m, located at several meters above the ground. No currently existing meteorological instrumentation allows one to do such measurements. The temperature and velocity fields which will be reconstructed with the use of this array are important for many applications: boundary layer meteorology; propagation of acoustic and electromagnetic waves in the atmosphere; experimental verification of large eddy simulation and direct numerical simulation; etc.

[1] A system of two scanning radiometers has been developed by the National Oceanic and Atmospheric Administration/Environmental Technology Laboratory and deployed on the NOAA R/V Ronald H. Brown during the Nauru99 cruise in the tropical western Pacific in June and July 1999. The system is composed of a high-quality temperature sensor and two independent, vertically scanning radiometers, measuring atmospheric and oceanic emission in the microwave (MW), and infrared (IR) regions. Both radiometers measure emission from a uniformly mixed atmospheric gas: oxygen for MW (60 GHz) and carbon dioxide for IR (14.2 μm). The high atmospheric absorption at these frequencies allows one calibration point from the horizontal atmospheric view using the in situ temperature sensor measurements as a reference. The signal at all other scan angles is scaled relative to that at the horizontal, resulting in a differential technique that is independent of calibration offset. This technique provides continuous and accurate estimates of boundary layer air temperature profile and air/sea temperature difference. The main advantage of this technique is that the water skin temperature can be measured at different optical depths without disturbing the skin layer (magnitude order of microns). We first compare radiometric data collected during the experiment with simulations obtained by atmospheric and oceanic radiative transfer models. We then use statistical inversion techniques to estimate air temperature profiles from upward looking measurements, based on an a priori data set of about 1500 ship-based radiosonde observations. For the “well-posed” problem of air/sea temperature difference estimation, we apply a physical retrieval algorithm to the downward looking measurements, accounting for air attenuation and sea surface roughness. Then we show retrieval results and evaluate the achieved accuracy. Finally, we compare radiometric estimates with in situ measurements, discussing similarities and discrepancies.

Passive ocean-viewing microwave radiometers produce promising results for measuring the near-surface wind vector by measuring the thermal emission from the combined rough surface and atmosphere. The brightness temperature variations of the rough ocean surface provide the necessary information for determining the near ocean surface wind speed and direction. Ocean wind direction measurements have only recently been obtained by microwave radiometers. These recent wind direction measurements showed that ocean brightness temperature variations with respect to azimuth angle (wind direction) varied by a few Kelvin. All these radiometers measured the azimuthal dependence of vertically- and horizontally-polarized ocean brightness temperatures. Brightness temperature measurements at other polarization states (four Stokes parameters) are also sensitive to near surface ocean wind direction. This paper focuses on a nonpolarimetric aircraft-based dual-frequency dual-polarized microwave radiometer that was developed at the Environmental Technology Laboratory (ETL) of the National Oceanic and Atmospheric administration (NOAA). The lower frequency at 23.87 GHz is horizontally-polarized with respect to the aircraft's flight direction and the 31.65 GHz frequency is vertically-polarized to that direction. This radiometer was one of several instruments deployed in ETL's first Advanced Sensor Applications Program (ASAP) experiment. This experiment was named the San Clements Ocean Probing Experiment (SCOPE). The main purpose of the airborne microwave radiometer was to determine if it could measure azimuthal-dependent brightness temperature variations from a rough ocean surface, and thus infer the near-surface wind vector. Furthermore, in order to gain a better understanding on the potential of the NOAA dual-frequency radiometer for near-surface wind vector determination, the SCOPE radiometer measurements are compared with a new combined atmospheric and two-scale ocean surface model.

A previous radio-meteorological experiment conducted along the coast of southern California showed a high correlation between UHF signals and the base of the elevated temperature inversion. A reanalysis of this experimental data with a recently developed hybrid propagation model confirmed this correlation and a method to remotely sense the refractive structure was proposed. An experiment called Variability of Coastal Atmospheric Refractivity (VOCAR) was designed under a larger program called Coastal Variability Analysis, Measurements, and Prediction. VOCAR is a multi-year experimental effort to investigate the variability of atmospheric refractivity with emphasis on the coastal zone. The experiment is being conducted by the Naval Command, Control and Ocean Surveillance Center RDT & E Division jointly with the Naval Air Warfare Center Weapons Division, Point Mugu, CA, the Naval Research Laboratory (Washington, DC and Monterey), and the Naval Postgraduate School. In addition, the National Oceanic and Atmospheric Administration Environmental Technology Laboratory, Penn State University Applied Research Laboratory, and Johns Hopkins University Applied Physics Laboratory participated in the intensive measurement phase of VOCAR. The objectives of VOCAR are to provide an assessment capability for horizontally varying refractivity conditions in a coastal environment and to develop a remote sensing capability. The propagation measurements being made during VOCAR consist of monitoring signal strength variations of VHF/UHF transmitters in the southern California coastal region. Corresponding meteorological measurements are made during routine, special, and intensive observation periods. Measurements began in May 1993 and will be conducted periodically through 1994. >

An experiment was conducted to measure low amounts of total-column precipitable water vapor (PWV). Extremely dry conditions commonly occur in polar regions during the winter months. Accurate measurements of the PWV during such dry conditions are needed to improve our understanding of the regional radiation energy budgets. D. C. Jones et al. (1998) have shown that the strength associated with the 183 GHz water vapor absorption line makes radiometry in this frequency regime promising for measuring low amounts of PWV. However, retrievals using these frequencies are complicated by uncertainties in absorption models and the fact that these frequencies also respond to the vertical temperature distribution as well as to liquid and ice clouds. NASA Goddard Space Flight Center and NOAA Environmental Technology Laboratory conducted an experiment to investigate millimeter wave measurements for making ground-based estimates of PWV during dry conditions. The experiment was conducted at the DOE's North Slope of Alaska/Adjacent Arctic Ocean Cloud and Radiation Testbed site located just outside Barrow, Alaska. NASA and NOAA deployed a suite of radiometers covering 28 channels in the frequency range of 20 GHz up to 340 GHz including 8 channels around the 183 GHz water vapor absorption line.

Measurements of the sea-air temperature difference using a 5-mm wavelength scanning radiometer were made previously from a ship. It was shown that groundbased scanning observations in the oxygen absorption band allow the measurement of the water skin-air temperature difference with an accuracy of about O.1K. Changes in the air temperature gradient of less than 0.005 K/m in the 20-200 meter altitude layer are detectable. A similar scanning radiometer was built in the Environmental Technology Laboratory in 1997. In 1999, the radiometer was modified to include an internal reference load, ferrite switch, step motor, and computer motor control. The instrument was mounted in the wing tip of a Twin-Otter airplane and deployed during the Shoaling Waves Experiment. This experiment was conducted near the East Coast of North Carolina during the fall 1999. The radiometric observations were supported by meteorological buoy data. In contrast to ground-based observations airborne observations of sea-air temperature have some features that increase the measurement errors. It is not possible to average the data during the airplane flights as long as can be done with ship observations. Another important feature is the influence of the atmosphere layer below the aircraft. For flying at an altitude of 300 m, water temperature differences of few tenths of degree can be seen, but it is difficult to measure air temperature in the layers nearest to sea surface. In the report, the authors describe the measurement technique and results of the airborne measurements of the sea-air temperature difference.

The objective of the project reported is to develop and commercialize unattended lidar systems that will continuously monitor the vertical profiles of ozone and particulate matter and provide near-real-time results to investigators. The systems must be affordable in multiple units, and they must have a low operating cost, so that networks of the unattended ozone lidars can be deployed in polluted cities. Such lidars will be useful for both long-term monitoring and for intensive campaigns. The work reported is a joint project of the Electro-Optics Laboratory of the Georgia Tech Research Institute (GTRT) and the Environmental Technology Laboratory (ETL) of NOAA.

A systematic study was undertaken to develop a glass composition to demonstrate the vitrification flowsheet of the Idaho National Engineering and Environmental Laboratory's sodium bearing waste (SBW) using the latest WM-180 tank composition. Although the previous study did not restrict waste loadings (WLs) based on the potential to form a segregated salt layer, avoiding its development in a melter is beneficial and was the primary focus from the glass-formulation perspective. The testing results described in this report were aimed at providing a candidate glass composition for use in a scaled melter demonstration of direct vitrification of WM-180 in the Research Scale Melter (RSM) at Pacific Northwest National Laboratory and the EV-16 melter at the Clemson Environmental Technology Laboratory.

Both during September 15-30, 1996 and September 15-October 5, 1997, the Environmental Technology Laboratory (ETL) participated in experiments at the Southern Great Plains (SGP) Cloud and Radiation Testbed (CART) site that was designed to study many of the ways that ARM is measuring water vapor. Because of some inconsistencies between ETL and ARM Microwave radiometers (MWR) during these experiments, called the Water Vapor Intensive Operating Periods (WVIOPs), we applied to both sets of data a newly developed correction algorithm for tipping curve calibration. We found that this algorithm reduces the differences between the radiometers, there are still some unexplained features of scanning ARM MWR data. Measurements of water vapor at the North Slope of Alaska and Adjacent Arctic Ocean (NSA/AAO) CART site in Barrow, Alaska, area potential problem because of the difficulty of radiosondes to measure low amounts of vapor during cold and extremely dry conditions. The applicability of MWR scaling to radiosondes is questionable because of the low sensitivity of these instrument during dry conditions. It has been suggested by the ARM Instantaneous Radiative Flux Working Group and others that measurements of brightness temperature around 183 GHz could be used to scale radiosondes during the coldest and driest periods.more » However, the millimeter wavelengths are vulnerable to cloud effects from both liquid and ice. During March 1999, we participated in the joint NASA/NOAA Millimeter wave Arctic Experiment to evaluate microwave and millimeter wave radiometers during extremely cold conditions. ETL tested, both in an experiment at the Boulder Atmospheric Observatory and during the two Water Vapor Intensive Operating Periods in 1996 and 1997, a 5-mm scanning radiometer that measures low-altitude temperature profiles; both profiles of lapse rate and absolute temperature can be measured with the instrument. Results of these tests were published in the open literature. In addition, the ETL scanning radiometer was operated at the NSA/AAO in March 1999.« less

Both during September 15-30, 1996 and September 15-October 5, 1997, the Environmental Technology Laboratory (ETL) participated in an experiment at the Southern Great Plains (SGP) Cloud and Radiation Testbed (CART) site that was designed to study many of the ways that ARM is measuring water vapor. These experiments, called the Water Vapor Intensive Operating Periods (WVIOPs), produced some results of significant importance to ARM water vapor measurements. We have spent the major portion of this years activities in analyzing results of these experiments, and improving algorithms for improving the measurement of precipitable water vapor (PWV) from instruments available at ARM. The most important ARM instrument for this measurement continues to be the Microwave Radiometer (MWR). Measurements of water vapor at the North Slope of Alaska and Adjacent Arctic Ocean (NSA/AAO) CART site in Barrow, Alaska, area potential problem because of the difficulty of radiosondes to measure low amounts of vapor during cold and extremely dry conditions. The applicability of MWR scaling to radiosondes is questionable because of the low sensitivity of these instrument during dry conditions. It has been suggested by the ARM Instantaneous Radiative Flux Working Group and others that measurements of brightness temperature around 183 GHz could bemore » used to scale during the coldest and driest periods. However, the millimeter wavelengths are vulnerable to cloud effects from both liquid and ice. We have participated in the planning and will participate in the Millimeter wave Arctic Experiment that will evaluate microwave and millimeter wave radiometers during extremely cold conditions. ETL has tested, both in an experiment at the Boulder Atmospheric Observatory and during the two Water Vapor Intensive Operating Periods in 1996 and 1997, a 5-mm scanning radiometer that measures low-altitude temperature profiles; both profiles of lapse rate and absolute temperature can be measured with the instrument. The technique and algorithms were developed for continental conditions and produced excellent agreement with in situ data. Due ETL recommendations, an instrument of this type was purchased and will be deployed in the NSA. During this year, we have developed algorithms for this instrument in the NSA and to blend the data with other sources of temperature information, such as Radio Acoustic Sounding Systems (RASS). In addition, we conducted an extensive analysis of the data from this instrument, and compared the data with a variety of in situ ground truth.« less

During September 15 to October 5, 1997, an intensive experiment to measure atmospheric water vapor was conducted at the Department of Energy's Atmospheric Radiation Measurement Program's Cloud and Radiation Testbed (CART) site in north central Oklahoma. This experiment was called the 1997 Water Vapor Intensive Operating Period (WVIOP'97). Among the goals of WVIOP'97 was the comparison of different methods of measuring precipitable water vapor (PWV). This paper focuses on the inter-comparison of PWV measurements by ground-based microwave radiometers, Global Positioning System-PWV instruments (GPS-PWV), and by radiosondes. For this experiment 3-hourly radiosondes for in situ measurements were deployed. Microwave radiometric measurements of water vapor in the zenith direction were made by two independent radiometers that produce PWV and cloud liquid path from brightness temperature T/sub b/ measurements. These radiometers were operated by the Environmental Technology Laboratory and operate at the frequency pairs of (20.6, 31.65 GHz) and (23.87, 31.65 GHz). The calibration of the instruments was achieved by the so-called "tip cal" method and their data, in terms of derived PWV are compared. Two independent GPS-PWV instruments were also operated 9 km apart and, in addition, two different processing algorithms were applied to the data from each of these instruments.

A transportable ground-based differential absorption lidar specifically designed for ozone and aerosol profiling in the lower troposphere was developed at the National Oceanic and Atmospheric Administration/Environmental Technology Laboratory (NOAA/ETL). The NOAA/ETL ozone lidar has the unique capability of measuring vertical profiles of ozone concentration from near the surface up to 3 km, and measuring vertical profiles of aerosol from the surface to about 10 km. The innovative hardware design and improved signal processing techniques make the system efficient, compact, and easily transportable. A recently implemented 2D scanning system provides the capability of measuring ozone concentrations and aerosol in a vertical plane. The lidar has been deployed in seven field experiments in California, Illinois, and Boulder, Colorado since summer 1993. Lidar observations of vertical profiles of ozone concentrations and ozone advection fluxes in Southern California during high ozone season revealed interesting structures of ozone distributions in the Los Angeles urban area, and near the Cajon Pass which is a major corridor of ozone transport from Los Angeles to the Mojave Desert.

The Environmental Technology Laboratory (ETL) High Resolution Doppler Lidar (HRDL) was developed to provide higher spatial, temporal, and velocity resolution, and more reliable performance, than was previously obtainable with C02 laser based technology. The improved performance is needed to support continued advancement of boundary layer simulation models and to facilitate high resolution turbulent flux measurements. HRDL recently operated from a ship during the Marine Boundary Layer Experiment and demonstrated simultaneously 5 cm/s velocity resolution and 30 m range resolution. Program objectives, technology and performance are discussed.

The NOAA Environmental Technology Laboratory (ETL) and the NCAR Atmospheric Technology Division (ATD) participated in the 1995 Southern Oxidants Study (SOS) Nashville summer intensive campaign. The airborne UV-DIAL ozone lidar operated jointly by these laboratories was deployed as part of the large suite of instruments used in this study.

The U.S. Department of Energy (DOE) has prepared an environmental assessment (EA) on the proposed Processing and Environmental Technology Laboratory (PETC) at Sandia National Laboratories/New Mexico (SNL/NM). This facility is needed to integrate, consolidate, and enhance the materials science and materials process research and development (R&D) currently in progress at SNL/NM. Based on the analyses in the EA, DOE has determined that the proposed action is not a major Federal action significantly affecting the quality of the human environment within the meaning of the National Environmental Policy Act (NEPA) of 1969. Therefore, an environmental impact statement is not required, and DOE is issuing this Finding of No Significant Impact (FONSI).

A very compact, transportable differential absorption lidar (DIAL) for ozone and aerosol profiling in the lower troposphere (from near surface to about 3 km) has been developed at the National Oceanic and Atmospheric Administration's Environmental Technology Laboratory. The ozone lidar has been employed in two field experiments in California. the first was in intercomparison experiment of the lidar and an airborne ozone analyzer carried out in the Sacramento valley of northern California during July 1993. The second field experiment involving the ozone lidar was the Free Radical Study, carried out in the Los Angeles basin during September 1993, where the highest ozone episode of the year was observed during the experiment. The system will be described and examples of ozone profiles during the high- ozone episode in inland Los Angeles will be shown.

A very compact, transportable differential absorption lidar (DIAL) for ozone and aerosol profiling in the lower troposphere (from near surface to about 3 km) has been developed at the National Oceanic and Atmospheric Administration's Environmental Technology Laboratory. The ozone lidar has been employed in two field experiments in California. The first was an intercomparison experiment of the lidar and an airborne ozone analyzer carried out in the Sacramento valley of northern California during July 1993. The second field experiment involving the ozone lidar was the Free Radical Study, carried out in the Los Angeles basin during September 1993, where the highest ozone episode of the year was observed during the experiment. The system will be described and examples of ozone profiles taken during the high ozone episode in inland Los Angeles will be shown.

The atmospheric lidar remote sensing groups of NOAA Environmental Technology Laboratory, NASA Marshall Space Flight Center, and Jet Propulsion Laboratory have developed and flown a scanning, 1 Joule per pulse, CO2 coherent Doppler lidar capable of mapping a three-dimensional volume of atmospheric winds and aerosol backscatter in the planetary boundary layer, free troposphere, and lower stratosphere. Applications include the study of severe and non-severe atmospheric flows, intercomparisons with other sensors, and the simulation of prospective satellite Doppler lidar wind profilers. Examples of wind measurements are given for the marine boundary layer and near the coastline of the western United States.

In another case of military swords being turned into scientific plowshares, two American researchers have used radar systems once designed to detect Soviet planes during the Cold War to map open-ocean currents instead. In the name of science, Thomas Georges and Jack Harlan of NOAA's Environmental Technology Laboratory borrowed some time last summer on the U.S. Navy's over-the-horizon (OTH) radar systems in both Virginia and Texas. Training the radars on the waters off of the southern coast of Florida, the researchers gathered enough data to deduce the surface motion of two 70,000 km2 swatches of the Caribbean Sea and Gulf of Mexico. By bouncing 5–28 MHz radio waves off the ionosphere down to the sea surface and back, the researchers were able to derive the characteristics of the ocean surface from Bragg backscatter resonance.