Strategic Priority: Developing new instrumentation

Development of a COronal Solar Magnetism Observatory (COSMO)

Driven by society's need to understand the origins of space weather, NCAR scientists at the High Altitude Observatory, along with colleagues at the University of Hawaii and the University of Michigan, plan to build the Coronal Solar Magnetism Observatory (COSMO). The facility will take continuous synoptic measurements of the entire corona in order to understand solar eruptive events that drive space weather and to investigate long-term and solar-cycle phenomena. The primary instrument will consist of a 1.5-m coronagraph with two detector systems: a narrow-band filter polarimeter and a spectropolarimeter. Supporting instruments are a white-light coronagraph to record the evolution of the electron scattered corona (K-corona) and a chromosphere and prominence magnetometer. This new facility will replace the current NCAR Mauna Loa Solar Observatory which has been collecting synoptic coronal data for over 40 years in support of the solar and heliospheric community.

In order to demonstrate the feasibility of measuring coronal magnetic fields, prototype instruments have been developed over the past 5 years at NCAR and the University of Hawaii. The Coronal Multi-channel Polarimeter (CoMP) instrument, which was built at NCAR/HAO, is a prototype of the COSMO coronal magnetometer. In 2007, the CoMP enabled a scientific breakthrough by imaging, for the first time, Alfven waves in the solar corona. These waves were found in observations of the Doppler shift of coronal plasma in the FeXIII emission line at 1074.7 nm. These waves are important in that they can transport energy from the turbulent photosphere out into the solar corona and could explain why the solar corona is heated to a temperature of 1 million degrees.

The major planned activity from last year for FY07 was the submission of a proposal to the NSF/ATM Mid-Size Infrastructure (MSI) account. In September 2007, the announcement of opportunity for the MSI was released with a deadline for submission of proposals in June 2008. Our plans for 2008 include continued observations of coronal magnetism with CoMP, and the submission of a proposal to the MSI account for the construction of the COSMO facility. Construction of the facility will require 5 years. Following completion, the COSMO facility will provide a continuous set of observations of coronal magnetism in near real-time.

Planning for COSMO has been assisted by a Scientific Advisory Panel of community members who have set the scientific requirements for the facility. Operation of the facility will continue to be guided by the Scientific Advisory Panel which will insure that the facility will continue to meet the needs of the solar and heliospheric community which it serves.

The development of the CoMP instrument was supported by the NSF through the NCAR Strategic Initiative Fund and HAO base funds.

return to top

High-performance Instrumented Airborne Platform for Environmental Research (HIAPER) instrumentation

PI: Andrew Weinheimer (UCAR/NCAR) Estimated Completion: 2008

NO-NOy Instrument - Two-channel instrument for the in situ measurement of NO (nitric oxide) and NOy (total reactive nitrogen).

This two-channel chemiluminescence instrument will obtain ~1-sec in situ measurements of NO and NOy. Several components of the overall system have been built and tested. Plans for early FY2008 are to complete the development with (1) reconstruction of the main instrument module and modification of other existing components, (2) inlet design and fabrication, (3) CO containment vessel fabrication, (4) configuration into a GV rack, and (5) certification of the entire installation. This will be completed early in FY2008, in preparation for HEFT test flights, so that the instrument will be flight-tested and ready for deployment on the GV in START08.

PI: Teresa Campos (UCAR/NCAR) Estimated Completion: 2008

Fast Ozone Instrument - Quantification of ozone mixing ratios at 5 Hz using the method of chemiluminescent reaction of ozone with nitric oxide.

A preliminary instrument package constructed in FY2006 by ACD scientists included a prototype detection module and some components designed and certified as part of the HAIS O3 instrument development. This fast ozone instrument was deployed on the GV during the T-REX campaign. In FY2007 techniques were developed for frequency-response testing and laboratory tests were conducted on the prototype detection module, prior to final design and construction of the new module. Additionally the prototype was operated in a high-frequency configuration on the C130 during PASE to demonstrate fast response in flight. The new module will be completed early in FY2008 for HEFT test-flights, where it will join previously built and certified components of the HAIS system. Following the HEFT tests, the HAIS O3 instrument development will be complete, and the instrument will fly on the GV in START08.

PI: Eric Apel (UCAR/NCAR) Estimated Completion: 2008

Trace Organic Gas Analyzer (TOGA) - In situ measurements of oxygenated volatile organic compounds (OVOCs), non-methane hydrocarbons (NMHCs), and halocarbons.

The Trace Organic Gas Analyzer (TOGA) will be completed in FY 08. It will have the unique capability of simultaneously measuring, with one instrument, a suite of organic compounds that play important functions in many areas of atmospheric chemistry. Several of the compounds are precursors or intermediates in atmospheric oxidation sequences. Others are indicators or tracers of different anthropogenic and biogenic processes. The compounds that TOGA will measure consist of a series of hydrocarbons, oxygenated compounds, halocarbons (including HCFCs and CFCs), and a few nitrogen and sulfur containing compounds. These species are identified in the HIAPER Advisory Committee Report as high priority. These measurements are possible due to the very recent development of new fast gas chromatographs. A prototype of this instrument was flown on the NSF/NCAR C-130 during MIRAGE and INTEX-B.

PI: Rick Shetter (UCAR/NCAR) Estimated Final Acceptance: March 2008

HIAPER Atmospheric Radiation Package (HARP) - Spectrally resolved actinic flux and stabilized platform irradiance measurements.

Shetter and three co-investigators, Barry Lefer (University of Houston), Manfred Wendisch (Leibniz Institute for Tropospheric Research, Germany), and Peter Pilewski (CU), will provide state-of-the-art radiation instrumentation for the HIAPER aircraft. The instruments include down and up-welling wavelength dependent actinic flux spectroradiometers and down and up-welling horizontally stabilized wavelength dependent irradiance spectroradiometers. The actinic flux spectroradiometers will provide actinic flux data from 280 to 680 nm with data frequencies ranging from 0.1 to 1 Hz. The irradiance instruments will provide flat plate irradiance from 300 to 2400 nm with data frequencies of 1 Hz. The irradiance optical collectors will be mounted on actively stabilized platforms to maintain horizontal stability to 0.1 degree up to aircraft pitch and roll angles of 6 degrees. The actinic flux and irradiance spectroradiometers and optical collectors were flown successfully on the PACDEX mission. The stabilized platform design has been approved, fabrication completed, and final acceptance flight testing will be performed in February 2008.

PI: Greg Huey (Georgia Institute of Technology), CoPI David Hanson Estimated Completion: 2008

Chemical Ionization Mass Spectrometer (CIMS) - Measurements of nitric acid, pernitric acid, hydrochloric acid, bromine oxide, and sulfur dioxide in standard CIMS (negative ion) mode, and measurements of organics such as methanol, acetaldehyde, acetonitrile, and acetone in CIMS positive ion mode.

A CIMS capable of measurements in two basic configurations will be constructed for HIAPER. In one configuration the instrument will measure nitric acid, pernitric acid, in real time. Other species such as bromine oxide and chlorine nitrate may be available after post-flight data processing. The second configuration will allow measurements of organic compounds such as methanol, acetaldehyde, and acetone. Data will be reported from one to three second time intervals. FY 2008 plans are to complete fabrication and begin certification.

return to top

Analysis of data from Hinode

FY2007 marks a milestone for solar science with the first year of operation of the joint Japan/US/UK Hinode satellite. ESSL's High Altitude Observatory has been involved in the Hinode program since its inception over a decade ago. NCAR contributed to the spectacular success of Hinode in several crucial ways. Spurred by the success of the ground-based Advanced Stokes Polarimeter and drawing on its experience in precision spectro-polarimetry over more than three decades, HAO scientists and engineers participated in the design, construction, and calibration of the focal plane instrument package for the Hinode 50-cm Solar Optical Telescope (SOT). The SOT Spectro-Polarimeter is providing the world scientific community with its first high-resolution, continuous quantitative measurements of the magnetic field vector in the solar atmosphere. Through the efforts sponsored by the NCAR Strategic Initiative "Community Spectro-Polarimetric Analysis Center" ESSL has provided the data reduction and analysis tools for the Hinode spectro-polarimetric data. These quantitative measurements are fundamental to the exploration and understanding of the solar magnetic activity that controls the space environment of Earth. The data gathered from this instrument during the past year have already yielded dozens of major scientific discoveries regarding the physical processes underlying the dynamical solar magnetic field and its influence on variability of the Sun. For example, HAO scientists, in collaboration with scientists from around the world, have reported on Alfvénic waves in the chromosphere that may be responsible for heating and acceleration of the solar wind, the discovery of ubiquitous small-scale horizontal fields in the solar photosphere perhaps resulting from a local dynamo in the upper convective layers of the Sun, and the evolution of the magnetic fields leading up to the large solar flares of December, 2006. In addition to science analysis of the data, HAO scientists participate in the planning of the daily 24/7 operation of Hinode, and provide maintenance and updates of the data reduction software for the Hinode Spectro-Polarimeter. This major effort is a benefit for the entire community: the calibrated Hinode data are made available immediately via the web. In the first year of operation, demand for data from the Hinode SOT has been extremely high. Operations often include coordinated observations with ground-based observatories and other spacecraft, many of which are proposed by the community outside of the core Hinode Science Team. ESSL expects to continue its participation in Hinode operations, data analysis, and science during the 3-year lifetime of the mission, and perhaps beyond that if the mission life is extended.

return to top

High Resolution Dynamics Limb Sounder (HIRDLS)

The High Resolution Dynamics Limb Sounder (HIRDLS) is a 21 channel infrared limb scanning radiometer, jointly developed by ACD, the University of Colorado, and the Physics Department of Oxford University. It is designed to make observations of temperature, O 3 , H 2 O, and 8 other trace species, as well as PSC's, aerosols and cirrus clouds, from the upper troposphere to the mesosphere, with higher vertical resolution than has previously been available from space observations. NASA funded the U.S. share of the HIRDLS development. When HIRDLS was launched on the Aura spacecraft in July 2004, a thin plastic film from inside HIRDLS came loose and obstructed most of the instrument's aperture, limiting the view to the atmosphere to a small fraction of the width of the optical beam. Attempts to shake it off were unsuccessful. However, enough had been learned for the team, led by John Gille, the U.S. PI, and John Barnett (Oxford), the U.K. PI, to propose that they be allowed to show they could make use of the signals that could be seen through the partial aperture. These efforts have demonstrated that there is recoverable atmospheric information in the signals, and initial results for temperature, ozone, PSC's and cirrus were very encouraging. Based on these results, NASA approved the continuation of the HIRDLS effort.

The next steps were to correct the measured signals to make them as close as possible to the expected radiances. The major efforts this year were to improve and refine the correction algorithms, make them more robust, and if possible develop a physical basis for them that would assure that they would work under all conditions. The 3 required corrections are the removal of spurious oscillations from the signal (due to mechanical oscillation of the plastic), correction for the reduced viewing area, and subtraction of the infrared signal from the plastic itself.

A key method for determining these corrections is to have the spacecraft pitch by ~5°, so that HIRDLS looks above the atmosphere and measures signals only from the plastic film, thus allowing their characteristics to be determined. This year the ACD HIRDLS team coordinated 3 of these pitch maneuvers. The initial development of these algorithms was described last year, but continued work to improve the estimate of the reduced viewing area, and especially subtraction of the signal from the plastic film. The latter is the biggest difficulty at this time. In addition, the calibration coefficients, radiance sample geolocation, and improved cloud location were incorporated in the operational processing code. This has resulted in the production of Version 2.04.09 data, and release of global temperature, ozone, nitric acid and aerosol/cirrus data to the community. These data have been demonstrated to be of high quality by an extensive validation process. For example, the HIRDLS temperatures were compared to U.K. Meteorological Office high resolution data from radiosondes for 9 widely distributed stations, and for all data available from January 2005 until August 2007. The 2 HIRDLS retrievals for two of the stations, Gibralter and St. Helena show very good agreement with the sonde and with each other. These also illustrate the fidelity with which the HIRDLS retrievals track the smaller scale variations of the sondes above 200 hPa. Five papers have been submitted for an Aura special issue. A presentation on stratosphere-troposphere exchange was given at the AMS Middle Atmosphere meeting.

The NCAR part of the team hosted a meeting of the HIRDLS science team in January, and attended one hosted by Oxford in June. The team reviewed the correction algorithms and approaches, presented results of HIRDLS validation comparisons with other data, and discussed future plans.

In the next year the algorithms to correct the radiances will be improved to allow additional species to be recovered. Emphasis will be on improved estimation of the partial view area and the signal from the plastic. In parallel, emphasis will be placed on the use of the released data for scientific studies, especially of gravity waves, and UT/LS processes, notably strat-trop exchange. In particular, we expect to be heavily involved in the START08 experiment.

return to top

Measurement Of Pollution In The Troposphere (MOPITT)

The daily operational processing of Measurement Of Pollution In The Troposphere (MOPITT) instrument raw counts into the final retrieved geophysical products, delivery of products to NASA for free public access, and user education and support, constitutes a major service to the scientific community. MOPITT is also unique in providing the community with the longest continuous validated global CO data product. Scientific results have been presented worldwide at numerous scientific meetings and show a documented strong presence on the Internet. MOPITT data distribution, publications, literature citations, and conference presentations are all showing strong upward trends, indicating mounting demand and scientific interest. Other sectors of government have shown increasing interest in the way in which global observations of pollution might provide useful information with respect to air quality (EPA and NOAA) and agricultural production (NARSTO and USDA).

The MOPITT data processing algorithms continue to be developed for the next data version 4. Enhancements will include: (1) a new forward model with improved description of the MOPITT gas correlation cells; (2) a new description of the retrieval a priori surface emissivity; (3) a new seasonally and geographically variable CO retrieval a priori; and (4) the use of an assumed log-normal variability for CO volume mixing ratio in the new retrieval algorithm.

The NASA 'Terra' satellite (the host platform for MOPITT) mission was subjected to the NASA Senior Review process in FY07. Preparations for the Review involved extensive discussions among the five instrument Science Teams (and Terra Project Scientist) and thorough documentation of the scientific value and exploitation of all of the Terra data products. The Senior Review Panel strongly endorsed continuation of the Terra mission, finding that many products from the Terra instruments were critical to national objectives. Continued funding for MOPITT has been approved for FY08 and FY09, with an endorsement for FY10 and FY11 as well. Among the five Terra instruments, MOPITT was the only instrument recommended for 'Enhanced Mission' funding, over and above the funding required for 'Basic Continuation.' The added funding will enable the MOPITT team to enhance the MOPITT product for CO in the boundary layer.

During FY07, the NCAR MOPITT team supported two field campaigns with near-real-time satellite imagery. In the Spring of 2007, the Pacific Dust Experiment ('PACDEX') experiment was coordinated by NCAR's Environmental Observing Laboratory (EOL) to probe the effect of the mixed dust-pollution plume originating in Asia on Pacific Ocean cloud systems and the associated radiative forcing. In July, the Tropical Composition, Cloud and Climate Coupling ('TC4') experiment was conducted from Costa Rica to study the chemical, dynamic, and physical processes occurring in the tropical upper troposphere and tropopause transitional layer in the Eastern Pacific. For both experiments, 'Rapid-Response' MOPITT data were processed at NCAR and made available on campaign-specific websites. These products were then accessed in the field to complement model forecasts for daily flight planning.

MOPITT products are also being routinely exploited in the analysis phase of earlier field campaigns. For example, in support of the INTEX-B (Intercontinental Chemical Transport Experiment) field experiment that took place in Spring, 2006, ACD scientists are exploiting MOPITT data to analyze the inter-annual variability in transpacific transport of pollution. For this purpose they are combining multi-year satellite observations of MOPITT CO and MODIS aerosol optical depth with model simulations using the chemistry transport model MOZART (Model for Ozone and Related Chemical Tracers). MOPITT and MODIS data show that 2006 was a typical year and not subject to special events such as seen in other years. Model simulations with a time constant emission scenario estimate that about one third of the variability seen in MOPITT CO is due to changes in meteorology, the remainder is attributed to emission changes.

Conversely, in-situ vertical profiles acquired during the earlier INTEX-A campaign (conducted during the summer of 2004 over North America) were recently used to support continuing MOPITT validation efforts. On average, the MOPITT CO retrievals appear biased slightly high for these North America locations. On average, it is estimated that MOPITT is 7-14% high at 700 hPa and ~3% high at 350 hPa. These results are consistent with previous validation results and are generally within the design criteria of 10% accuracy.

Many users of MOPITT data are mainly interested in CO concentrations in the lower troposphere. Unfortunately, the sensitivity of MOPITT observations (and other satellite instruments based on thermally-emitted infrared radiation) to this part of the atmosphere is often quite weak. However, recent work in the MOPITT team demonstrates that over land, the sensitivity of MOPITT observations to CO in the lower troposphere is highly variable and, in arid regions, comparable to the sensitivity to CO in higher layers. This analysis, based on both simulated and operational weighting functions and averaging kernels, demonstrates that the potential of MOPITT products for characterizing surface-based CO emissions is much greater than was previously believed. The Figure below compares global patterns of MOPITT sensitivity to CO in the lower and middle troposphere. Regions shown in yellow, orange and red in the top panel indicate areas where useful sensitivity to lower-tropospheric CO can be expected.

Plans for FY08 include development and testing of a new processor to replace the current 'Version 3' MOPITT product. In addition to the algorithm enhancements noted above, the new processor will incorporate features to compensate for slowly drifting instrument parameters which have recently come to light. The MOPITT team also plans to continue supporting field campaigns during FY08, including the ARCTAS (Arctic Research of the Composition of the Troposphere from Aircraft and Satellites) campaign scheduled for Spring, 2008. In addition to providing near-real-time imagery, support for ARCTAS will include production of experimental CO products optimized for Arctic conditions. The MOPITT Science Team will continue to evaluate operational products both in the context of traditional validation (e.g., using in-situ data from aircraft) and in comparison to models.

This work is funded by NASA and NSF/NCAR.

return to top

Atmospheric chemistry instrumentation

ACD scientists are involved in ongoing efforts to develop, improve, operate, and maintain a large number of instruments designed to measure trace gases, radicals, optical properties, and aerosols in the atmosphere.

A suite of instruments measure trace gases and radicals that are required for studies of photochemistry including O3, NOx, NOy, PANs, HOx, RO2, H2SO4, HNO3, and NH3. Ozone, NOx, and NOy are measured by by chemiluminescence instruments. The remaining species are measured by chemical ionization mass spectroscopy (CIMS) techniques. All of these instruments flew on the NSF/NCAR C-130 during MIRAGE and INTEX-B. Many of them have also been used on other aircraft and in ground based studies. Various instruments are being developed or modified specifically to be operated on the NSF/NCAR GV aircraft, including a 2-channel NO-NOy instrument, a fast-time resolution ozone instrument, a gas chromatograph/mass spectrometer system to measure VOC (TOGA), a HOx/ROx CIMS system, and a PANs CIMS instrument. Various other instrument improvements are planned for FY2008 to increase reliability and provide better precision and accuracy, as well as lower limits of detection.

Improvements continue to be made on CIMS instrumentation for measurement of HO2 and RO2. We have successfully developed a method to quantify HO2 and HO2+RO2 within one minute on aircraft platforms. Deployment during the PASE campaign this year demonstrated the improvement performance. Our development of a method for gas-phase ammonia continued this year, including successful collection of data during PASE. We are in the process of downsizing and automating our HOx (OH, HO2 and RO2) instrumentation for installation on the NSF/NCAR G-V.CA

ACD scientists also maintain and deploy a suite of Community Aircraft Instruments which can be requested from EOL through the NSF Facility request (LAOF) process. ACD's CARI group is responsible for these instruments and they are described in the Community Instrument section of this report.

Another set of instruments use optical techniques for measurement of actinic flux and column measurements of a number of gases. These actinic flux measurements are key to understanding the radical production in photochemistry. The CCD Actinic Flux Spectroradiometer (CAFS) instruments determine wavelength dependent actinic flux from 280-640 nm. The aircraft instrument package includes two independent, but time synchronized (IRIG-B) spectroradiometer systems to measure the up- and down-welling fluxes in a 1-6 second spectral acquisition times. Summing these produced the spherically integrated actinic flux. The actinic flux measurements in combination with the absorption cross section and quantum yield molecular data are used to calculate in situ photolysis of 23 important photochemical species, including O3, NO2, HONO, CH2O, H2O2, CH3OOH, HNO3, PAN, CH3NO3, CH3CH2NO3, and CH3COCH3. The solid state, CCD Actinic Flux Spectroradiometers (CAFS) instruments were deployed successfully on HIAPER during the PACDEX mission and the NASA WB-57 and DC-8 platforms during Tropical Composition, Cloud and Climate Coupling (TC4) experiment.

The CAFS measurements of up- and down-welling flux were used in conjunction with radiative transfer calculations to obtain the direct solar beam fraction of the measured flux as a function of wavelength. The ozone absorption of the direct beam was determined to obtain the total ozone column abundances above the aircraft.

During MIRAGE, ground based column measurements of a number of gases of interest in an urban plume environment, including CO, H2O, NH3 and C2H4 were made using a .06cm -1 resolution Fourier transform spectrometer. High resolution spectra of atmospheric infrared absorption were recorded and infrared spectra were fit to retrieve column amounts, and some vertical profiles.

Another suite of instruments have been developed to measure organic compounds from aircraft and ground based sites. The aircraft instruments are based on gas chromatography/mass spectrometry and proton transfer mass spectrometry and were designed to measure key organic compounds, including VOCs, in-situ, with high accuracy and precision. Both instruments were flown on the NSF/NCAR C-130 during MIRAGE and INTEX-B. Ground based systems are designed to measure fluxes of key organic compounds, including isoprene, from towers and tethered balloons. Analytical systems for these measurements are based on gas chromatography/mass spectrometry and gas chromatography/flame ionization detection.

During 2007 the Ultrafine Aerosols group has optimized their techniques for observing carboxylic acids in atmospheric nanoparticles using Thermal Desorption Chemical Ionization Mass Spectrometry (TDCIMS), so it is now possible to detect the parent ion of a large range of these potentially important species. Figure 2 shows a sensitivity analysis for the instrument for carboxylic acids with three to eight carbon atoms. For reference, 1 pg of collected aerosol is commonly considered to be the detection limit for the instrument for pure compounds. Thus Figure 2 shows that the TDCIMS is close to performing at the necessary sensitivity. Further developments in these techniques with other species expected in atmospheric nanoparticles are planned in 2008.

return to top

Community Spectro-Polarimetric Analysis Center (CSAC)

The Community Spectro-Polarimetric Analysis Center is an NCAR Strategic Initiative to provide a suite of community resource of tools for analysis of precision polarization data from remote sensing of magnetic fields in the solar atmosphere. The tools being provided range from data reduction/calibration utilities to extraction of measures of the magnetic field vector (and associated thermodynamic properties) for display and presentation of the fields. The addition of one FTE to CSAC in mid-FY07 brought the level of critical software support up to close to that envisioned at the outset, and significant progress has been made this year.

CSAC has contributed data reduction/calibration software to two ground-based spectro-polarimetric instruments available to the community: the Diffraction-Limited Spectro-Polarimeter at the National Solar Observatory, and the Spectro-Polarimeter at the Swedish Solar Observatory on La Palma, Canary Islands, Spain. Importantly, this software has been adapted to process data from the Spectro-Polarimeter on the Hinode satellite. CSAC also has now completed the workhorse MERLIN data analysis package that performs the critical process of extraction of the magnetic field vector from the observed polarization spectra. This is the first such package that is composed for distribution to the community: the software is portable, carefully documented, computationally efficient, and modular so that it may be adapted for other purposes. MERLIN will be used to provide bulk processing of data from the Hinode Spectro-Polarimeter, thereby providing the first large-scale database of precision measures of the solar magnetic field vector to a wider community that is not highly versed in the complexity of analysis of spectro-polarimetric data.

Other components of CSAC include the exploration of advanced techniques for data analysis and display. A new, fast analysis technique based on artificial neural networks has been completed, and tested as an initialization of the MERLIN least-squares fitting routine. Although this technique gives accurate results for a high percentage of solar conditions, it still does not provide the best guess possible that has been achieved by the standard, but much slower, genetic algorithm initialization. In the coming year CSAC will implement a code (LILIA) that extracts a more detailed physical characterization of the magnetic structure of the solar atmosphere, adapt the AZAM utility for display of results from MERLIN and assist in resolving an inherent ambiguity in the inferred azimuth of the magnetic field, and begin implementation of inversion procedures for the analysis of chromospheric magnetic fields, e.g. from the Prominence Magnetometer.

return to top

Instrument and experimental meteorology

A central issue in the cloud physics community is that after three decades of measuring particle size distributions we are not yet able to accurately measure the concentrations of ice crystals in clouds. In articles submitted during the past year, the MMM Physical Meteorology Group (PMG) has shown that past and recent measurements from a wide range of instruments that measure size distributions and integrated products such as the volume extinction coefficient have been seriously in error. For example, the total concentrations of ice crystals are overestimated up to an order of magnitude, and the volume extinction coefficient factors of two to four. The cause of these overestimates is the shattering of large particles that impact the leading edge of the probes, with the resulting fragments passing through the probe’s inlets and being measured as real particles. Over prediction of ice concentrations in climate models leads to smaller, more slowly falling crystals that do not sublimate readily in the middle troposphere through to the lower stratosphere so that ice cloud albedos are significantly overestimated. This can result in significant errors in the earth’s net radiation budget.

The PMG has acquired a new probe that has been designed to rectify deficiencies with earlier probes. The small ice detector (SID-2) probe, an open path instrument that sizes in the range 1 to 60 microns, has been flown on the HIAPER G-5 aircraft during the Pacific Dust Experiment (PacDEx) in April and May, 2007. Although there were some instrument malfunctions during the field program, excellent SID-2 data were acquired.

To improve knowledge of ice formation mechanisms and to better quantify the ice concentrations in clouds we have organized the Ice in Clouds Experiment (ICE-L [layer]) to take place in November and December 2007. This field program, involving two-dozen university and NCAR investigators, will use the NCAR C130 to characterize the composition of ice nuclei, the thermodynamic conditions for first and subsequent ice formation, and the radar and lidar signatures of the ice particles. We will use the SID-2 probe together with many improved and new particle probes to quantify the concentrations and size distributions of hydrometeor populations.

The ICE-L research flights will include repeated penetrations through mountain-induced lenticular clouds. These clouds are quasi-steady state and form the foundation for a laboratory-like setting. Repeated penetrations at multiple levels are designed to achieve the goals of the project (see figure). Precipitating layer (upslope) clouds will also be targeted by ICE-L. The goals are likewise to identify ice production processes but a main difference is that the ice nuclei may derive from the surface and ice formation is likely to occur at cloud top and with warmer temperatures than for lenticular clouds.

return to top

Development of instrumentation for the Solar Dynamics Observatory (SDO)

The Helioseismic and Magnetic Imager (HMI)is one of the primary instruments to be flown on board NASA's Solar Dynamics Observatory spacecraft which is scheduled to launch in late 2008. The HMI will make images of the Sun with 4096 by 4096 pixel detectors in wavelengths around the Fe spectrum line at 617.3 nm in various polarization states. These will allow us to construct images of the velocity and magnetic fields over the entire solar surface with a spatial resolution of 2 arcseconds at a cadence of 90 seconds. The instrument development is led by researchers at Stanford University and the instrument is being constructed by Lockheed. Our role at HAO is assist with the calibration of the instrument and to develop tools to convert the observations into physical parameters such as the magnetic field strength and orientation. One challenging aspect will be to analyze the enormous volume of data in real time. In 2007, we developed and implemented a computer code which can determine magnetic field parameters from polarization measurements faster than any previous code. Next year we will complete a production version of this code which will be incorporated into the HMI processing pipeline.

return to top

Fundamental Physics of Radiative Processes

Almost everything we know about the Sun comes from our interpretation of its radiative output. The study of the intensity and polarization of the radiation that we receive from solar regions allows us to infer the thermo-dynamical and magnetic properties of the emitting plasma, if we are able to formulate adequate models of the origin and transport of polarized radiation in the solar atmosphere. In the deeper and denser layers of the visible atmosphere (photosphere), plasma collisions typically ensure that, at each point in the plasma, the ratio of radiation emissivity to absorptivity (source function) is only determined by the local thermal properties of the plasma (local thermodynamic equilibrium, or LTE). Under these special conditions, the mechanisms for the production and transport of polarized radiation are very well understood, and reliable models have been available for at least half a century.

As we move outward in the solar atmosphere (chromosphere and corona), the plasma density rapidly decreases, while at the same time the radiation becomes increasingly anisotropic. Both conditions determine significant departures from LTE, as the atomic equilibrium is now driven mainly by optical pumping by the underlying photospheric radiation. These are also the regions of the solar atmosphere where the topology of the magnetic fields that permeate the heliosphere - finally interacting with the Earth's magnetosphere - takes shape. So the development of adequate models of polarized radiative transfer in these regions, in order to determine the correct magnetic boundary conditions of the heliosphere, is of primary importance for our understanding of solar drivers of Space Weather.

FY07 achievements

1) The inversion of spectro-polarimetric data in one solar filament (i.e., a prominence during its transit over the solar disk) observed in an active region has revealed the presence of magnetic fields in excess of 700 G. These large fields - more than one order of magnitude larger than the observed magnetic strengths in quiet-Sun filaments - pose important questions on the magneto-hydrodynamic stability of these structures.

2) We demonstrated that broadband scattering polarization in hydrogen lines can be produced in a magnetized plasma even in the absence of anisotropic irradiation, due to the presence of micro-turbulent electric fields in plasmas. This result forces a complete revision of the use of hydrogen lines for magnetic diagnostics - in solar structures as well as in laboratory plasmas - and the questioning of results old and new in solar magnetism that have been obtained with these lines (e.g., the measurement of magnetic fields in prominences using the Balmer series of hydrogen).

3) We initiated a study of multi-level effects in the formation of the two well-known Fe I lines at 630 nm, which was motivated by recent spectro-polarimetric observations of these lines in chromospheric emission with the SOT instrument on board Hinode. We were able to prove that these multi-level effects explain the surprising finding that the polarization of these lines by scattering appears to be radially oriented, rather than tangential to the solar limb as one would have expected.

FY08 plans

1) To work on the radiative transfer modeling in a realistic solar atmosphere of the Na I doublet at 589 nm, with the goal of resolving the long standing "enigma" concerning the complicated shape of the linear polarization profile of these lines, produced by scattering near the solar limb.

2) To progress on the theory of the polarized line formation in the presence of coherent scattering (partial redistribution in frequency).

3) To devise plasma diagnostic techniques exploiting the polarization effects of micro-turbulent electric fields on hydrogen lines (e.g., the role of electric-induced dichroism in optically thick plasmas).

4) To refine the atmospheric model adopted for the simulation of the chromospheric Fe I Hinode observations, and to reach a better understanding of the interplay between multi-level effects in Fe I and magnetic fields, in order to assess the diagnostic potential of Fe I limb emission for chromospheric magnetism.

return to top

Virtual remote sensing facility

Growing out of the remote sensing plan whitepaper and later discussions, a new NCAR Program in Atmospheric Composition Remote Sensing and Prediction (ACRESP) is now getting underway that will build on current satellite missions and expertise and leadership in satellite remote sensing science (ACD), Earth System modeling (ESSL), and data assimilation (ESSL/CISL). As outlined in the initial whitepaper, the core of the ACRESP Program will be the development of the Satellite Observation Simulator and Assimilation System (SOSAS). This is envisioned as a community facility for investigations in 3 main interrelated areas:

1. Observation System Simulation Experiments (OSSEs) for the quantitative evaluation of different conceptual satellite measurements for answering specific science questions
2. Evaluation of Earth system model performance with respect to existing satellite observations
3. Remote sensing of air quality with an assimilation capability for cross-scale observations within an Earth system model for tropospheric air quality "chemical weather" forecasts and field campaign design

Observation System Simulation Experiments (OSSE) studies are a practical way of planning science-driven missions with a traceability matrix providing a rational chain of science requirements leading to measurement requirements and onto instrument requirements. The experiment involves the following basic steps: (1) to answer a specific scientific question, a conceptual instrument simulator is constructed; (2) the simulator samples an appropriate model atmosphere "truth" to produce a retrieved product with associated errors and measurements characteristics; (3) the simulated product is assimilated into climatology background "distorted" atmosphere(s); and (3) a quantitative evaluation is performed of how quickly this assimilation is brought back to "truth". This helps answer the question of whether or not the simulated observation will be useful in meeting the measurement goal and addressing the driving scientific question.

ACD scientists are developing an OSSE to evaluate retrievals of planetary boundary layer carbon monoxide (CO) concentration for air quality studies. This quantity provides useful information on pollution transport and ozone chemistry, and is probably the leading candidate trace gas for which the boundary layer concentration can be determined from space. This activity builds on Terra/MOPITT experience and uses a multi-spectral simulation and retrieval for independent information on CO concentration in the boundary layer, lower free troposphere and upper troposphere. This activity currently uses the MOZART and CAM models and the DART assimilation scheme, and will soon move to finer horizontal resolution using the WRF-Chem framework. A longer-term goal of the ACRESP OSSE activity is to develop a community facility at NCAR. This would be used by researchers from the universities and agency centers for building and testing instrument simulators as part of the proposal and design of the next generation of satellite instruments.

As a parallel activity of the first stage of the NCAR ACRESP Program, ACD scientists are developing an air quality "chemical weather" forecasting capability based on existing satellite observations as part of SOSAS. Chemical weather is a priority research theme for ESSL. The characterization of global and regional scale air quality involves field campaigns, chemical transport modeling, and remote sensing. The goal is a scientific and observing framework analogous to that used for weather forecasting with a model assimilation of observations from satellite, aircraft and surface platforms to derive a 4-dimensional view (3 spatial plus temporal) of the physical state of the atmosphere.

This analysis will be used in air quality basic research: the quantification of emissions of ozone and aerosol precursors and the examination of the long-range transport of pollutants extending from regional to global scales. The general tools and methodologies developed will also be used for studies examining the connections between climate change and regional air quality, and the roles of anthropogenic and natural processes in changing atmospheric composition. The predictive capability will provide a powerful tool to support field campaign activities such as those involving HAIPER chemical instrumentation. There also exists the possibility of demonstrating schemes for future operational applications elsewhere in the community related to air quality management and health advisories.

Increasingly, there is interest in accessing finer spatial scales to quantify both the wider impact of local pollution sources such as wildfires and mega-cities and assessing the contribution of transported pollution. Work is underway on a detailed chemical weather case study for the MIRAGE and INTEX-B spring 2006 period. This involves global model simulations using analyzed meteorology and the best possible chemical sources with fire emissions based on satellite fire products. A nested regional model simulation concentrating on Mexico and parts of the INTEX-B Pacific region are also being performed using WRF-Chem.

During the Spring 2006 INTEX-B and MIRAGE field campaigns, a near-real-time assimilation of MOPITT data into MOZART and CAM was used to initialize a 3-day forecast of the CO distribution. This forecast was used to identify suitable pollution plumes for sampling in subsequent aircraft flights. This analysis used the extended Kalman filter and ensemble Kalman filter data assimilation techniques. Building on this experience, assimilation of other available satellite data sets such as Terra/Aqua/MODIS aerosol optical depth, ENVISAT/SCIAMACHY and Aura/OMI NO2, OMI O3 tropospheric column, and Aura/TES CO and O3 are being explored. This exercise will impose constraints on the modeled chemical fields and can be evaluated in comparison with actual MIRAGE and INTEX-B field measurements.

This work will involve the collaborative efforts between ACD and the DART initiative in IMAGe, and the community MIRAGE and INTEX-B science teams. The success in forecasting the location of pollution plumes during INTEX-B also suggests that the techniques that will be developed will be of great use in future field campaign design and flight planning involving HIAPER. The ACRESP team will also aim to foster collaboration with other efforts in the development of chemical weather forecast capability both within U.S. Universities, NOAA and NASA, and internationally, particularly with the GEMS project in Europe.

The first stage of the ACRESP Program will develop the SOSAS capability in modeling and measurement of air quality, with parallel and related efforts on air quality satellite instrument OSSEs and chemical weather forecasts using existing satellite observations. Funding for these activities has been provided by NSF/NCAR and NASA.

return to top

Analysis Of Data From TIMED and COSMIC

HAO scientists have conducted several studies using data from the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) program in the last year. Two of them are highlighted here. Lei et al., (2007) conducted a verification study for COSMIC electron density profiles. Figure 1 shows comparisons between COSMIC observations and measurements by the Millstone Hill Incoherent scatter radar. Comparisons between these and other ground-based observations demonstrate the validity and global coverage of COSMIC ionospheric measurements. Lei et al., also compared COSMIC data with the NCAR TIE-GCM and with empirical models. Their main conclusions were that the comparisons were generally good, but that features such as the north-south asymmetry and longitudinal variation of the equatorial anomaly that are seen in the COSMIC data and the TIE-GCM simulations were not fully captured by empirical models.

Zeng et al. (2007) have used COSMIC data, the NCAR TIE-GCM and the IRI model to study the annual anomaly in F2 region electron density. Figure 2 shows that this anomaly is well represented in both the NCAR TIE-GCM results and the COSMIC data and that the two are mostly in agreement in terms of both morphology and amplitude. TIE-GCM simulations show that changes in solar EUV radiation between the December and June solstices, the displacement of the geomagnetic axis from the geographic axis, and tides from the lower atmosphere are the primary processes causing the annual asymmetry and its associated longitudinal and local time variations.

Additional causes of ionospheric variability due to persistent global weather patterns seen in results from the IMAGE satellite and COSMIC data have been described by Hagan et al. [2007]. Because of the potential importance of the eastward-traveling wavenumber-3 component of the nonmigrating diurnal tide for this effect, data from the TIMED Doppler Interferometer (TIDI) was examined by Wu et al. [2007] to study tidal variability. Figure 3 shows the variation in amplitude of the nonmigrating E3 component in four years that suggest that this tidal component is enhanced during the eastward phase of the QBO (2002 and 2004) compared to its westward phase, which could be an important element of interannual variation in the thermosphere-ionosphere system.

return to top

Development of the Sunrise balloon mission

The dynamo-generated fields that emerge from the interior in the form of rope-like concentrations of magnetic flux play a pivotal role in the production of the Sun's activity and radiative variability. The flux eruption process drives the magnetic evolution of the corona and leads to conditions that are conducive to the onset of coronal mass ejections, expulsions of plasma and fields from the Sun that can disturb the Earth's magnetosphere and upper atmosphere and cause disruptive geomagnetic storms. Magnetic flux concentrations of all size scales in the photosphere can affect the flow of energy in the surface layers of the Sun, causing variability of the solar irradiance. Sunrise is a project whereby a balloon-borne, 1-meter telescope will be used to observe the Sun from an altitude sufficiently high that the distorting effects of the Earth's atmosphere are small. Sunrise will permit researchers to study the structure and dynamics of the magnetic field in the solar atmosphere on small spatial scales for extended time periods.

In FY07, an important milestone in the Sunrise balloon-borne solar telescope project was reached with the completion of the construction of the balloon gondola at NCAR. This design and fabrication effort was a joint undertaking of ESSL's HAO and EOL. The sophisticated gondola will carry a 1 m aperture telescope to stratospheric altitudes where it will be used to acquire the highest spatial resolution solar observations ever obtained. The Sunrise project is an international collaborative effort, consisting of HAO (USA), the Max-Planck-Institut fur Sonnensystemforschung (Germany), the Kiepenheuer-Institut fur Sonnenphysik (Germany), the Instituto de Astrofisica de Canarias (Spain), the Lockheed Martin Solar & Astrophysics Laboratory (USA), the University of Utrecht (The Netherlands), and the University of Chicago (USA).

Recently, the Sunrise gondola, equipped with a 26.2 cm test telescope, was flown out of NASA's High Altitude Balloon Facility at Fort Sumner, New Mexico for a 10 hour test flight. The flight was successful, with data on the performance of the pointing system of the gondola taken as well series of pictures of the Sun. The landing was smooth, with little resulting damage to the equipment. Preliminary data analysis has led to the decision to go ahead with the preparation of a multi-day science flight in 2009 out of Kiruna, Sweden.

Press Releases:

Balloon test flight hailed - Denver Post
NCAR Finds Success With Solar Telescope - CBS 4
A really big balloon to see the sun like never before - 9 News
Science Daily

return to top