GATNDOR is a research team supporting the development and implementation of GRUAN on scientifically sound foundations. The team performs focused, short-term research to address specific topics identified by the GRUAN science and management community. GATNDOR efforts are coordinated with those other GRUAN Task Teams and with national GCOS programs when appropriate.
Under the auspices of the GCOS (Global Climate Observing System) AOPC (Atmospheric Observation Panel for Climate) Working Group on Atmospheric Reference Observations, a research team will identify and carry out a series of well-defined, limited-scope retrospective analyses of existing observations from established stations that are potential GRUAN (GCOS Reference Upper Air Network) sites, other complementary observations, metadata, and model simulations. The unifying purpose of this series of studies will be to obtain insight from existing information for optimizing the design and implementation of the GRUAN observational program to meet its scientific goals.
At the 1st GRUAN Implementation and Coordination Meeting (ICM-1) in Norman, Oklahoma, in March 2009, an initial research team of four interested volunteers was formed. It included Reinout Boers, Tom Gardiner, Dian Seidel (chair), and Junhong Wang. A preliminary brainstorming session following the meeting, and a team conference call in April 2009, identified an initial set of five research topic areas.
- Topic 1: Collocation of Observations
- Topic 2: Management of Change
- Topic 3: Scheduling Protocol
- Topic 4: Quantifying the Value of Complementary Observations
- Topic 5: Network Configuration
The team held quarterly conference calls to discuss ideas, progress, impediments, and plans.
At ICM-2, in March, 2010 in Payerne, the team reported progress on Topics 1 and 2 and plans for Topic 3. Topics 4 and 5 were placed “on the back burner” for future work. For details, see the GRUAN web page devoted to the agenda of the Payerne 2010 meeting. GATNDOR presentations are in Session 4.
Discussions at ICM-2 resulted in the formation of several new GRUAN Task Teams to address high priority GRUAN needs. One new Task Team was given responsibility for recommending a GRUAN observing schedule protocol, GATNDOR Topic 3. At a lunchtime meeting of all interested ICM-2 participants, these goals were set for the following year:
- Expand the membership of GATNDOR
- Forge stronger links between GRUAN/GATNDOR and the satellite community
- Submit a paper to a peer-reviewed journal on Topic 1
- Present preliminary results to ICM3 on Topics 2, 4 and 5
This work plan outlines how these goals are to be pursued.
At ICM-3, end of February – early March 2011 in Queenstown, NZ, the team reported progress and achieved results on all the Topics. Moreover, a new sub-topic to be developed in the frame of Topic 1 has been identified and presented to the GRUAN community. The sub-topic will be related to the design of a tool for evaluation of instrumental co-location mismatch for GRUAN sites and Franz Immler will lead the investigation of this issue.
Discussions at GATNDOR side meeting, during the break-out session of ICM-3 on March 2, identified the main results to be released before ICM-4 by means of tools, recommendations and strategies provided to the GRUAN stations. Below, all the topics are described according to their work progress and the mentioned deliverables that also represent the core of 2011-2012 work plan. Deliverables will be made available to the GRUAN community though peer-reviewed papers reporting the outcome of proposed investigation.
During the side meeting it has been also reiterated that principle membership is by no means exclusive; interested scientists are welcome to participate and are encouraged to contact the chair. However, contributions from new collaborators should be well focused to urgently address a few research questions/themes, identified as possible new topics to investigate in the frame of GATNDOR or to be addressed in the enlarged GRUAN community:
- Are error covariance matrices mandatory/useful for providing vertically correlated uncertainties when derived products are considered?
- Use of GRUAN data in order to show their value (as soon as the reprocessing of historical radiosounding data will be available) through the investigation of appropriate scientific topics.
- Validating weather and climate models and re-analysis products using GRUAN data;
- Plan for a network design workshop in order to put together all the expertise already existing in this field.
No volunteers have been identified to address these issues.
A closer cooperation among different topics will be fostered in order to address common goals. For example, scientists working on Topic 2 and 3 will collaborate on the management of change for complementary measurements (lidar, microwave, ….). Moreover, GRUAN Task Team 5 on Ancillary Measurements offers its support. However, a closer cooperation between GATNDOR and TT5 will be established.
Funding perspectives have been also discussed. “MarieCurie” funding scheme of EU and a “medium term trust fund” solution have been proposed: both solutions will be discussed during the quarterly teleconference. Currently GATNDOR work is carried out entirely on voluntary basis.
Based on recruitment at ICM-2, ICM-3 and outreach by GATNDOR team members, the current GATNDOR team is listed here. These individuals are responsible for specific GATNDOR projects and collaborate with a wider community to meet GATNDOR goals.
School of Engineering and Applied Sciences
Cambridge, MA 02138 (USA)
Expertise: sensor calibration, satellite remote sensing, radiative transfer, collocation of observations, management of change (especially for remotely sensed and in situ measurements of the same variable)
Principal Research Scientist
Environmental Measurements Group
National Physical Laboratory
Hampton Rd Teddington Middlesex UK TW11 0LW
Tel: +44 20 8943 7143 Fax: +44 20 8614 0455
Expertise: measurement uncertainties for atmospheric sensors, optical sensing of atmospheric constituents (in particular Fourier Transform spectrometers, laser absorption spectrometers, and differential absorption lidar), and uncertainties in long-term trends.
Deutscher Wetterdienst (DWD) / German Meteorological Service
Meteorological Observatory Lindenberg / Richard Aßmann Observatory, Am Observatorium 12
15848 Tauche OT Lindenberg, Germany
Phone: +49 (0)331677 60 170
Fax: +49 (0)331677 60 280
Expertise: measurement uncertainties of radiosondes, intercomparison evaluation, lidar remote sensing of aerosol, clouds and water vapor.
Fabio Madonna (chair)
Istituto di Metodologie per l’Analisi Ambientale
C.N.R. – I.M.A.A.
Contrada S. Loja
Tito Scalo zona industriale
I-85050 Potenza, Italy
Phone: +39 0971 427252
Fax: +39 0971 427271
Expertise: Lidar and microwave remote sensing, Integration of active and passive remote sensing techniques
NOAA Air Resources Laboratory (R/ARL)
1315 East West Highway
Silver Spring, MD 20910 USA
Phone: +1-301-713-0295 ext. 126
Expertise: climate variability and change, data quality and continuity, radiosonde observations and metadata, upper-air temperature trends.
Junhong (June) Wang
P.O. Box 3000
Boulder, CO 80307-3000 USA
Expertise: radiosonde observations, data quality and climatology, GPS observations and application, water vapor measurements and variability, upper-air sounding instruments and data quality.
Greenbelt, MD 20771 USA
office +1 301 614 6703
lab +1 301 614 6775
ALVICE +1 301 614 6515
fax +1 301 614 5492
Expertise: water vapor measurements and instrumentation; particularly lidar and balloon-borne sensors, satellite retrieval and radiance validation, aerosol and cloud studies using lidar
Below are descriptions of three GATNDOR topics. For simplicity and flexibility we have dispensed with the previous topic numbers. The titles are:
- Atmospheric Variability and co-location
- Management of Change
- Quantifying the Value of Complementary Observations
Title: Atmospheric Variability and co-location
Research Question: comparison of atmospheric observations measured with different techniques at the same site are generally not taken at exactly the same time and the exactly same spot (quasi-redundant). The (natural) variability in the temporal and spatial frame given by the dislocation of the two measurements limits the accuracy of the comparison of these measurements. Based on this variability and the (inherent) uncertainties of the instruments a definition can be derived to what extend quasi-redundant measurements can be considered co-located.
Approach: Based on model or measurement data the variability of temperature and humidity in the temporal and spatial range that is typical for the dislocation of two quasi-redundant measurements (e.g. lidar and radiosonde) is established.. A formalism, or tool, will be developed that answers the question whether or not two measurements can be considered co-located, based on the variability of the measurand and the measurement uncertainties of the instruments.
Previous Relevant Work: This project builds on earlier GATNDOR and GRUAN research to quantify individual components of the overall profile uncertainty. One study (Sun et al., J. Geophys. Res., 2010) presented a methodology for estimating uncertainty in one observation given a second “reference” observation. That study also quantified the effects of time and space collocation mismatch on temperature, humidity and refractivity profiles. A second study (Seidel et al., J. Geophys. Res., 2011) developed a global climatology of radiosonde balloon drift distance and rise rate, with particularly attention to GRUAN sites, for use in quantifying uncertainty associated with collocation. A third paper (Immler et al., Atmos. Meas. Tech., 2010) presented a framework for characterizing overall measurement uncertainty in GRUAN data products.
Results available by ICM-4:
- Tool for evaluating overall uncertainty of GRUAN atmospheric profile measurements
- Draft of a related manuscript
Team Lead: Franz Immler (DWD, Lindenberg)
Possible Collaborators: Bomin Sun, Tony Reale, Michael Pettey (NOAA/NESDIS) and Dian Seidel (NOAA/ARL)
Start Date and Estimated Project Duration: Spring 2011 + 2 years
Title: Management of Change
Research Question: To provide scientific bases to develop operational practices in better managing changes at GRUAN sites from one instrument type to another and to accurately merge the two data segments to create a homogeneous time series.
Approach: The study makes use of dual-sonde data collected at GRUAN sites in the past either continuously or at times when changes were made. The focus has been on the 13-year (1998-2010) Lindenberg dual-sonde data. In the future we plan to include the dual-sonde data from Tateno and possibly Payerne too. Specifically the project will include three parts. The first part is to analyze the Lindenberg data to show that what information is needed to document and identify changes.. The second one is to provide insights on the amount of overlap dual-sonde data required to minimize the discontinuity introduced by the changes by implementing the approach developed by Peterson and Durre (2002) to the Lindenberg dual-sonde data. The third one is to analyze the dual-sonde data collected at Lindenberg and Tateno in Japan to show several approaches for quantifying and adjusting changes in order to prepare a homogenized radiosonde climate record. . In the future, the study can be expanded to learn the value of long-term, independent and co-incident measurements in management of change.
Work completed: We have conducted some analyses on the 13-year (1998-2010) Lindenberg radiosonde record and explored methods to document, identify and adjust changes made during the period. Initial findings were that detailed metadata, 4-times daily sampling and independent dual sonde data are proved very useful to document and identify changes. The GRUAN “consistency test” (Immler et al. 2010) is useful to quantitatively identify change points. It is found that about 200 dual sonde flights a year are needed to accurately assess the bias between old and new sondes when the station plans to switch from one type of sonde to another one. These flights should cover day and night and the entire annual cycle. Five approaches are shown promising to quantify and adjust changes (i.e., homogenize the data record), including using independent and redundant measurements, correcting known errors and biases using prior work, developing correction schemes to either old or new sonde data using dual sonde data, and using statistical methods.
Previous Relevant Work: Immler et al. (2010); Seidel and Free (J. Climate 2006); Peterson and Durre (2002, “A climate continuity strategy for the radiosonde replacement system transition”)
Team Lead: Junhong Wang
Deliverables available by ICM-4:
- Quantitative assessment and provision of a sampling strategy (based upon Lindenberg, Tateno, Payerne stations)
- Optimal strategy for managing the change
Possible Collaborators: Aiguo Dai (NCAR/CGD), Fraz Immler (GRUAN Lead Center), Hakaru Mizuno (JMA), Tom Peterson (NOAA/NCDC), Peter Thorne (NOAA/NCDC), Holger Voemel (GRUAN Lead Center)
Start Date and Estimated Project Duration: Spring 2011 + 1 years
Title: Quantifying the Value of Complementary Observations
Research Question: How much is measurement uncertainty reduced by having redundant or complementary measurements of a given variable?
Approach: This topic aims to estimate uncertainty of vertical profiles of both temperature and moisture using data from highly-instrumented GRUAN sites (e.g., ARM site, Beltsville, Cabauw, Lindenberg, Potenza) and to quantify the error reduction resulting from increasing redundancy of measurements. This requires the assessment of the uncertainty of the temperature and moisture vertical profiles retrieved using each of the considered techniques and then the investigation of possible sensors’ synergies to reduce the uncertainty. The investigation will be carried out focusing on the most common instruments at the considered GRUAN sites: for temperature, radiosoundings and microwave profilers; for moisture, radiosoundings, Raman lidars, microwave profilers, and GPS receivers.
The quantification of the value added by complementary observations will be assessed with respect to the following issues:
- Sensor calibration/inter-calibration (here the ARM Value Added Products could be considered as a model)
- Identification of possible biases
- Representativeness of measurements
- Quality control/assurance with a focus on instrument performance in different meteorological conditions.
The evaluation shall start from a detailed review of the existing literature, for identifying what has been already assessed for each measuring technique.
The assessment will be carried out:
- performing intercomparison of co-located measurements;
- elaborating Bayesian approaches for evaluating the impact of different error sources and information content with respect to the required representativeness and sensitivity to climate changes;
- comparing time structure functions of each technique for assessing the benefits of using combinations of instruments/parameters for the investigation of climate variability.
Satellite observations and model outputs may be used for supporting the evaluation scheme.
The final outcome of this investigation is the provision of recommendation on the optimal observation strategy to use at GRUAN sites for supporting GRUAN strategy, increasing accuracy of measured parameters through redundancy and reducing profiling uncertainty.
- summary of the detailed review of the relevant literature for the topic;
- statistics from intercomparison of co-located measurements to qualitatively assess value of lidar and microwave radiometer in reducing radiosounding uncertainty.
- preliminary frame of the sensor calibration/inter-calibration procedure for reducing uncertainty.
Previous Relevant Work: Wang and Young (2005)
Team Lead: Fabio Madonna
Possible Collaborators: Nico Cimini (IMAA), Belay Demoz (Howard University), Jürgen Güldner (DWD), Rigel Kivi (FMI), Seth Gutman (NOAA)
Start Date and Estimated Project Duration: Spring 2011 + 1 years
Results available by ICM-4:
- Recommendations for an optimal observation strategy related to GRUAN phase 1 and 2.
- Recommendations for the equipment to operate/acquire at the GRUAN sites.