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ATD Achievements - Developments Select from: Facilities Data and Network Services Design and Fabrication

Facilities Select from: Advanced Observing Systems Ground-Based Observing Systems Airborne Observing Systems

Advanced Observing Systems: APOL - Select From: CO2 Isotropic Ratio Instrument Airborne DFG Instrument Airborne TDLAS System

The joint ATD/ACD Analytical Photonics & Optoelectronics Laboratory (APOL) addresses the development and employ of new advanced technologies, instruments, and advanced algorithms for improved ground-based and airborne measurements of various trace gases, which supports NCAR's Upper Troposphere/Lower Stratosphere Initiative. Specific achievements of APOL this past year include:

1. continued development of a high precision CO2 isotopic ratio instrument based upon difference frequency generation (DFG);
2. continued development of a rugged, light-weight, high performance DFG instrument for airborne measurements of formaldehyde (CH2O); and
3. continued improvements (both hardware and software) to a liquid-nitrogen cooled lead-salt tunable diode laser absorption spectrometer (TDLAS) for airborne measurements of CH2O

CO2 isotopic ratio instrument based upon difference frequency generation (DFG)

Figure 1(left) illustrates a modified version of the optical setup shown last year, has been constructed and a number of tests have been carried out. This new setup allows the sample and reference beams to make two traversals of the absorption cells for improved measurement precision. As discussed in our previous ASR, the absorption signals from the two cells containing the sample gas and an isotopic reference standard are rapidly compared using on-line fitting analysis. The fitting procedures have been developed and wait further testing on CO2 absorption features.

Figure 2 shows the design of the inlet system, which represents the second major task associated with high precision CO2 measurements. This system, which is in the testing phase, allows us to introduce various combinations of reference standards and ambient samples to the absorption cells under closely matched conditions of pressure and flow. Other studies frequently do not take such precautions.

Airborne DFG Instrument for the Measurement of CH2O (formaldehyde)

The APOL group has been actively involved in a long-term effort to carry out ever more accurate and precise measurements of CH2O (formaldehyde) throughout the troposphere and lower stratosphere. The present instrument sensitivity needs to be further improved for routine CH2O measurements in the background atmosphere, particularly in the upper troposphere/lower stratosphere where CH2O decomposition becomes a major source of reactive hydrogen radicals. In addition, the instrument is large and requires periodic operator intervention. To address this critical need as well as the need to develop smaller, lighter, and autonomous-operation instruments for future HIAPER campaigns, the APOL group has been developing a new high performance airborne CH2O instrument based upon difference frequency generation (DFG). However, for size comparison purposes, we show in Figures 3 (above left, click for larger image) and 4 (left - click for larger image) our present airborne TDLAS system and the compact new DFG system. The Herriott absorption cells in both systems are approximately the same size. With this in mind, a comparison of these two figures immediately reveals that the DFG system is significantly smaller than the TDLAS system; the DFG-Herriott cell configuration in Fig. 4 has replaced the entire optical setup of the TDLAS system in Fig. 3. A further advantage of the DFG system is that no liquid cryogens are required, in stark contrast to our present TDLAS system. Although laboratory tests with the new DFG system are not yet complete, evidence strongly indicates that this new system will ultimately achieve higher performance than our TDLAS system for CH2O and other molecules.

Airborne TDLAS System Hardware and Software

Despite the significant progress achieved in the DFG development, the laboratory prototype system has not yet been tested on airborne platforms. Rather than risk flying such a system for the first time during a critical field mission, we decided to pursue the more prudent course of action by employing the TDLAS system during the 2004 summer INTEX-NA study. However, numerous small modifications were implemented to this system this past year to further improve the system robustness, reliability, and performance. Many of these modifications, which are too numerous to list here, focused on improving the optical-mechanical stability of the system. In addition, numerous software changes were also implemented for improved performance, reliability, and enhanced data quality assurance.

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Ground-Based Observing Systems - Select From: Remote Sensing Sounding Systems Surface Flux Systems

Remote Sensing -
REAL | S-Pol | Rapid DOW | NEXRAD

REAL (Raman-shifted Eyesafe Aerosol Lidar)

REAL had its first prototype demonstration last spring at the Pentagon in Washington DC. ATD collected eye-safe scanning backscatter data (at 1.5 microns) over a wide variety of weather conditions on 9 days, from pouring down rain to severe clear. Much time was spent making sector Plan-Position Indicator (PPI) scans over the Pentagon and surrounding region and Range Height Indicator (RHI) were also collected to show the vertical structure. In all, ATD over 10,000 quick-look images on 9 CDs and half dozen DLTs containing the raw data. The images are rich with fascinating features--things that are almost never visible to the naked eye. The animations of the images, which are available online, are even more powerful because they reveal the advection and dispersion of the features--and promise the ability someday to obtain the vector wind field by tracking methods. Similar data taken from the Foothills Lab site is available for viewing.

S-Pol (S-band Dual Polarization Doppler Radar)

S-Pol has seen some major modifications during FY04 and has been deployed on two major field projects: Winter Icing Storms Project 2004 (WISP04) and North American Monsoon Experiment (NAME). FY04 development activities for the S-Pol have been highlighted here.

Rapid DOW

This year ATD continued collaborations with Center for Severe Weather Research (CSWR) for the completion of the Rapid Dow truck-mounted radar operated by CSWR the under a collaborative agreement with NCAR. This radar is unique because of its use of six, frequency-steered beams utilizing a flat plate antenna. The multiple beams allow volume data acquisition of short lifetime phenomenon, such as tornados and detailed hurricane eyewall structures. Work did not proceed as well as hoped because of staffing and field project conflicts. Plans continue to be made for the completion of this radar.

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NEXRAD (NEXt Generation RADar)

The NEXRAD data quality project is funded by the Radar Operations Center (ROC) of Norman OK. The purpose of the project is to increase the data quality of the National Weather Service's NEXRAD radars. The work at NCAR has primarily focused on two areas:

1. range-velocity (RV) ambiguity mitigation
2. radar echo classification (e.g., anomalous propagation (AP) clutter and precipitation).

During FY04, ATD continued to develop new and improved software tools for the analysis and verification of a RV and AP mitigation algorithms

The RV mitigation technique involves the phase coding of the transmit pulses and the subsequent recohering of the received echoes. Phase coding the transmit pulses of weather radar makes possible the separation of multi trip echoes, thereby extending the unambiguous range of the radar while not compromising the unambiguous velocity. To accomplish this in real time, a SIGMET RVP8 processor was installed in S-Pol in May of 2003. Data has been gathered, processor problems have been identified and SIGMET has implemented improvements to their hardware. ATD has continued to take data with RVP8 in 2004 and has performed data analysis.

In June of 2004 ATD delivered to the ROC a phase coding algorithm/software (with cooperation of NSSL) called the SZ-2 algorithm. The SZ-2 algorithm will be used at the lowest tilt angles of the NEXRAD radars and is scheduled to be deployed on the NEXRAD radars in 2005.

Range-Velocity Ambiguity Mitigation

The following data were gathered by S-Pol at 0.5 degree elevation on 28 March 2004 using RVP8 at the Marshall field site near Boulder, CO. A long PRT scan (PRT=3.125ms) was followed by a short PRT scan (PRT=0.8ms) separated by about 30 seconds. The unambiguous range for the long PRT is 468km (i.e., no folded echoes) while the unambiguous range for the short PRT is about 120km.

Figure 1 (left, click for full-sized image) shows the ``power'' from the long PRT scan. The dark lines show the borders of the first, second and third trip regions for the short PRT scan.

Figure 2 (left, click for full-sized image) shows the SZ-2 recovered velocity without censoring while Fig.3 (below left, click for full-sized image) shows the SZ-2 recovered velocity with censoring applied.

At 120km in the beginning of the second trip in Figure 2 (above left), leakage from the strong first trip ground clutter echoes causes the seen ring. The white areas of the censored image (Fig 3, left) are due to the SNR threshold of 3dB. The purple areas indicate poor quality data identified by the SZ-2 algorithm.

In sharp contrast, Figure 4 (left, click for full-sized image) shows the same velocity field of Fig. 1 but with the current NEXRAD WSR-88D censoring algorithm applied and as can be seen, much more velocity data is censored. Thus, the SZ-2 phase coding algorithm can greatly increase the amount and quality of the velocity data viewed by NWS weather forecasters. For more in depth description of the NEXRAD activities see the EOL/NCAR NEXRAD webpage.

Anomalous Propagation Clutter Mitigation

The ATD Anomalous Propagation (AP) clutter mitigation scheme consists of a fuzzy logic-based radar echo classifier as well as a reflectivity and radial velocity compensation algorithm. The radar echo classifier (REC) detects AP ground clutter echoes and precipitation echoes. The compensation algorithms correct the bias in the reflectivity and radial velocity fields that exist from the application of the ground clutter filter. Output from the REC ensures that the compensation algorithms are only applied to precipitation echoes. The AP clutter mitigation scheme has been deployed on each S-POL field experiment since STEPS in 2000, including the North American Monsoon Experiment (NAME) in July and August of 2004.

The REC AP clutter Detection Algorithm (APDA) was deployed on the National Weather Service WSR-88D radar network in the Open Radar Product Generation (ORPG) in September 2002. During 2004, the ORPG Enhanced Precipitation Preprocessing (EPRE) algorithm was modified to use the APDA algorithm to remove ground clutter contamination before radar-derived rainfall estimates are calculated. Further, the ORPG Common Operations and Development Environment (CODE) software has been installed at ATD. This package facilitates the transition of radar algorithms from research to operational status on the WSR-88D. At ATD, the CODE is being used not only to enhance the current operational implementation of the REC AP Detection Algorithm, but also to implement the REC Precipitation Detection Algorithm (PDA) and the reflectivity compensation algorithm. Both are planned for deployment in the WSR-88D radar network beginning in 2005. The PDA and the reflectivity compensation algorithm will be added to EPRE to further enhance rainfall estimates, at a future date.

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Sounding Systems -
Integrated Sounding System | TAOS | GPS Dropsonde | Driftsonde | GAUS

ISS/MISS/MAPR (Integrated Sounding System)

Integrated Sounding System components received some timely modernization and added capabilities which were valuable during two FY04 field deployments. Three ISS participated in the North American Monsoon Experiment (NAME) (Sonora and Baja, Mexico), and two ISS (MISS and MAPR) were deployed to the Sierra Rotors project in California. FY04 development activities for the ISS have been highlighted here.

TAOS (Tethered Atmospheric Observing System)

In FY '04 TAOS participated in two projects, the Hudson Valley Ambient Meteorology Study (HVAMS) and the North American Monsoon Experiment (NAME). For HVAMS, night flights were made in the Hudson River Valley south of Albany, NY during the month of October. Data was collected during calm cool wet evenings in support of an effort to understand CO2 processes. A user’s sensor was included on the flight train and for the first time CO2 was measured using TAOS.

GPS Dropsonde

The 8-year old GPS Dropsonde system is currently used on over 20 aircraft throughout the world supporting both scientific research and operational needs. FY04 development activities for the Dropsonde have been highlighted here.

Driftsonde

In FY04, development efforts began for integrating the Vaisala RS-92 radiosonde into Driftsonde (left) replacing the current NCAR GPS Dropsonde that has been used for past Driftsonde flight tests. The RS-92 sonde will reduce costs and the weight of the system or allow for a large sonde payload. This work has been comprised of testing the RS-92 algorithms and developing receiving hardware specifically for the RS-92. and testing RS-92 software libraries on the Driftsonde main computer processor. Other work has been in the evaluation and testing of GPS receiver to be used in a Wind only sonde. System analysis of a Super pressure balloon was performed to look at the future replacement of the zero-pressure balloon.

GPS Advanced Upper-air Sounding System (GAUS)

The new ATD GPS Advanced Upper-air Sounding System (GAUS) is under development to replace the venerable GPS LORAN Atmospheric Sounding System (GLASS). The last project for the tried and true GLASS system was the North American Monsoon Experiment (NAME). GAUS incorporates Vaisala RS92 next generation radiosonde, has portability, built-in test capability and flexibility for multiple channel operations, and delivers users final processed data with high precision and additional GPS position data. Vaisala RS92 radiosonde promises to deliver high quality wind measurements from the ground with code-correlating GPS technology, as well as pressure, temperature and humidity measurements all transmitted digitally to the receiving station. Digital technology will reduce missed data due to noise and increase overall reliability in the system. Vaisala RS92 provides much better humidity measurement with the heated twin-sensor design and the new reconditioning procedure before launch. A prototype GAUS has been deployed in TELEX and proven to be successful.

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Surface Flux Systems -
Integrated Surface Flux Facility | AIRCOA | Adaptive Sensor Array

ISFF (Integrated Surface Flux Facility)

The ISFF is designed to study exchange processes between the atmosphere and Earth's surface. This includes the direct measurement of fluxes of momentum, sensible and latent heat, trace gases, and radiation as well as standard atmospheric and surface variables. FY04 development activities for the ISFF have been highlighted here.

Autonomous Inexpensive Robust CO2 Analyzer (AIRCOA)

In support of the CME deployment and future experiments to measure local and regional CO2 variations, ATD developed an autonomous, inexpensive, and robust CO2 analyzer, (AIRCOA). ATD's B. Stephens constructed 4 AIRCOA units after initial design testing and deployed three of these in the field during the CME campaign. The figure at the left shows two AIRCOA units at the Willow Site of the project. These units measure CO2 concentrations at 6 levels on a tower, producing individual measurements every 2.5 minutes precise to 0.1 ppm CO2 and closely tied to the WMO CO2 scale. A key component in the robustness of these analyzers is near real-time data processing with extensive automated diagnostic tests to verify normal operation, with new results available from a web interface every day

ASA (Adaptive Sensor Array)

Progress on ASA (formerly ISA) continued this year with the deployment of a prototype system. FY04 development activities for the ASA have been highlighted here.

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Airborne Observing Systems - Select From: HIAPER C-130 Airborne Remote Sensing

HAIPER

In FY04, modifications to the GV were completed by Gulfstream and Lockheed. These modifications included the installation of three under wing hard points on each wing, three 20.5-inch diameter view ports (two up-looking and one down-looking), several fuselage hard points and aperture plates, cabin attachment points (seat rails), and research power and signal wiring. High pressure testing of the modified fuselage was successfully conducted in September and preparations were made for ferrying of the aircraft from Greenville, SC to Savannah, GA for interior and exterior completion at the Savannah Air Center. The figure to the left shows the newly-modified GV receiving final placement of the NSF and NCAR logo templates on the fuselage.

Over the past year, the various HIAPER infrastructure subgroups made significant progress toward the development of critical research systems for the aircraft. The data acquisition system development group – headed by Mike Spowart and Dick Friesen of the HPO – has led the effort to develop a next generation data system that is faster, smaller, lighter, and consumes less power than the current NSF/NCAR C-130 system. The new GV data system is built around a PC-104 (ISA bus) architecture and will continue to provide all of the standard digital interfaces supported by the C-130 system. Older, non-standard digital interfaces (e.g., the PMS probe 2D interface) will be discontinued and replaced by a new USB interface. Construction of the data sampling modules (DSMs) to be used to acquire data from instrumentation mounted on the aircraft was completed in FY04, as was environmental testing of the DSM prototype. Chris Webster and Mike Daniels continued to oversee the effort to develop new data visualization and access software for the GV. Software engineers from throughout ATD contributed time and expertise to this software development effort, resulting in the creation of several prototype display packages by the conclusion of FY04.

Other HIAPER infrastructure preparation efforts undertaken during FY04 included the award of subcontracts for installation of the intercommunication system (ICS) and SATCOM systems and an Airborne Flight Information System (AFIS) on the GV. The ICS installation will be performed by Garrett Aviation and Savannah Air Center personnel during the aircraft interior and exterior completion time period, and Atlas Telecom will undertake installation of the SATCOM systems and the AFIS following the delivery of the GV to UCAR/NCAR.

In July, two of the ATD pilots – Henry Boynton and Lowell Genzlinger – completed an intensive flight simulator training course in Savannah, GA to receive their credentials to pilot the GV. Additionally, a number of ATD personnel traveled to July during this same month to participate in an “all hands” training program for the aircraft. This latter series of classes provided the participants with the opportunity to learn about emergency and safety procedures for the aircraft and to take part in a drill involving the evacuation of the smoke-filled cabin of a life-size GV cabin model into water. ATD maintenance team members Bob Beasley, Brent Kidd, and Jim Nolan began the GV maintenance training program in September and will complete the course in early October.

Jeffco Hangar

Work commenced on expanded hangar facilities at Jeffco shortly after the start of FY 04. Excavation of the site was completed by January 2004. Underground utility and foundation work was accomplished during February and March. The steel building was delivered in mid-April. Erection of the building started shortly thereafter and continued through the summer. By the end of FY 04, the hangar building was complete. 2 items, sealing and coating the hangar floor and some landscape work remained to be finalized before the project could be called finished. It is expected that both items will be done before the arrival of HIAPER.

C-130

In the past few years, the NCAR C-130 aircraft has been put to the test on a couple of demanding air-sea interaction experiments that involve extensive low-level flight legs in quiescent conditions (e.g. DYCOMS-II and EPIC) to measure turbulent momentum flux. Careful examination of these data sets by Marie Lothon (visitor to MMM and ATD) and Donald Lenschow, as well as EPIC scientists (Chris Bretherton and Charlie Cornish, University of Washington, Seattle) and Steve Esbensen (Oregon State University, Corvallis) revealed modulation of the momentum flux by the aircraft heading and inertial subrange spectra of the velocity components that departed somewhat from theoretical predictions. In an effort to improve the quality of the velocity measurements, ATD undertook an inflight "trailing cone" calibration of the static pressure measurement under the direction of Allen Schanot. Lothon and Lenschow applied the new calibration to the DYCOMS-II data and found a considerable improvement in the momentum flux measurement. Lenschow has also been collaborating with Bjorn Stevens and Verica Savic-Jovcic (University of California, Los Angeles) on the use of wind measurements from 60 km diameter circles in DYCOMS-II for estimating divergence and vorticity in the marine stratocumulus-capped boundary layer. They found that the standard procedures used for calibrating the air motion system are not adequate for this demanding application. They are working on a protocol that should extend the capabilities of the system to these measurements.

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Remote Sensing Systems

SABL (Scanning Aerosol Backscatter Lidar)

SABL was deployed on the C-130 in two field campaigns and received significant improvements in FY04. Specifically, the field campaigns were AIRS II and Ocean Waves. FY04 development activities for SABL have been highlighted here.

NCAR CO2 and O2 Calibration Facility

ATD has completed assembly of primary components of the NCAR CO2 and O2 Calibration Facility. These include a box to hold 25 large high-pressure gas cylinders oriented horizontally and insulated as necessary to prevent fractionation, a control module to selectively deliver pressure-regulated gases from these cylinders to a cryogenic drier and the concentration instrumentation, a high-precision commercial CO2 analyzer, a repackaged version of the RAF Oxygen Analyzer (ROXAN), and a suite of long-term (~20 years) calibration standards tied to Scripps Institution of Oceanography and NOAA CMDL WMO calibration scales. ATD used this facility to calibrate over 30 CO2 reference cylinders used in the CME and ACME campaigns.

Data and Network Services

In FY 2004, ATD completed migration to the Active Directory client/server architecture for the Windows desktops, which will enhance computer reliability, facilitate remote management and create a more secure environment. RDP improved ATD data accessibility by connecting ATD to the UCAR Data Portal pilot program. RDP also began building a metadata database, using HIAPER as its first platform, to electronically manage descriptive data for our holdings. When completed, this metadata database will facilitate automation, electronic documentation and consistency for all aspects of ATD metadata. Our data can connect to digital libraries, online analysis tools and data catalogs and our community will see improved data quality since we can better track dataset history, calibration and documentation through the use of this infrastructure.

In preparation for future deployments, ATD collaborated with Unidata and JOSS to bring new capabilities to the RDCC. Chief among these are the use of Unidata's Integrated Data Viewer (IDV) to display S-Pol Radar data, GOES 1km satellite data, aircraft tracks and sounding data into one integrated three dimensional display for future projects. In addition to the operational goals of providing an extraordinary level of real-time data and communication services, ATD's FY04 preparations served an educational purpose - that of creating tutorials regarding the analysis of atmospheric data that will be used by students in the atmospheric sciences.

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Design and Fabrication

Purchase of a new 4-axis machining center occurred in the second quarter of FY 2004. This new machine tool increases the physical size capability, accuracy and productivity of machined parts produced by the group. DFS supported a number of major projects as well as numerous small projects.

Some of the major projects were:

• Sunrise balloon borne solar telescope;
• Driftsonde;
• HIAPER infrastructure and instrumentation development;
• S-Pol deployments and improvements;
• APOL developments;
• Eye safe Lidar (REAL) developments;
• Water vapor DIAL developments;
• and a Laser induced fluorescence inlet.

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Table of Contents | Director's Message | Executive Summary | ATD Achievements
Education and Outreach | Community Service | Awards | Publications | People | ASR 2004 Home