GRUAN Analysis Team for Network Design and Operations Research

GRUAN Analysis Team for Network Design and Operations Research

This post provides basic information about the GRUAN Analysis Team for Network Design and Operations Research. The team was an (unexpected) outcome of the 1st GRUAN Implement and Coordination Meeting (ICM1) in Norman, Oklahoma, in March 2009. As an informal and new team, its work plan is flexible and current projects are in preliminary stages; this post is meant as an initial report for the GRUAN community. The team will provide a more thorough report on its activities and plans at the 2nd GRUAN Implement and Coordination Meeting in Payerne, Switzerland, in March 2010.

Scope and Concept
The small, ad hoc, international research team performs focused, short-term scientific analyses to address specific topics identified by the GRUAN science and management community. Under the auspices of the AOPC Working Group on Atmospheric Reference Observations, the 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, and other observations. The unifying purpose of this series of studies will be to obtain insight from past observations for optimizing the design and implementation of the GRUAN observational program. Scientific results of these studies should be published in peer-reviewed journals.

Core Research Team
Reinout Boers (KNMI, De Bilt, Netherlands)
Tom Gardiner (NPL,Teddington, UK)
Dian Seidel (chair, NOAA, Silver Spring, USA)
Junhong Wang (NCAR, Boulder, USA)

Research Topics

In April 2009, the core team identified the follow set of five research topics, to address specific issues and questions raised at ICM1.

Topic 1: Collocation of Observations
Research Question: How far apart can measurement systems be and yet be considered to effectively sample the same atmospheric column? How far apart can sub-sites be and still be considered a single GRUAN site?
Approach: Examine typical horizontal displacements of radiosondes from the ground launch location to define the width of a typical column sampled by a balloon-borne system. Assemble statistical climatology of such displacements, considering the effects of station location, season, and height. Perform global analysis and targeted analysis of GRUAN candidate sites. Use results to infer tolerable displacement of other ground based measurements (e.g. radiometers, lidars) and potential for comparison with satellite observations.
Team Lead: Dian Seidel

Topic 2: Management of Change
Research Question: To better manage changes from one instrument type to another and to accurately merge the two data segments to create a homogeneous time series, what co-incident, independent (i.e. redundant) measurements, how much and what kind of associated metadata, and how much overlap between old and new instruments are needed?
Approach: Using long time series from stations with reliable metadata and redundant measurements, and where instrument overlaps were part of the measurement protocol, attempt to identify bias adjustments using objective statistical methods and verify them using metadata and redundant observations. Determine the usefulness of redundant observations in homogenizing the time series. Determine whether archived metadata are sufficient for identifying instrument changes and explaining abrupt or otherwise suspicious changes in the time series. Determine the sensitivity of the adjustment to period of overlap by using less than the complete overlapping set of observations. Three-part study including: 1. intercomparisons of long-term, independent and co-incident measurements; 2. analysis of long-term time series of temperature and humidity at candidate sites; 3. analyses of available dual sonde data.
Team Lead: Junhong Wang

Topic 3: Scheduling Protocol
Research Question: How frequent must profile measurements be made to adequately characterize long-term changes?
Approach: Using data from a station with a long record of high-temporal-resolution observations of temperature and moisture profiles, subsample the data according to various balloon launch protocols to determine if resulting long-term changes are consistent with those from the complete record. Test number of observations per month, and various approaches to sampling the diurnal cycle.
Team Leads: Tom Gardiner and Reinout Boers

Topic 4: 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: Using data from a highly-instrumented location (e.g., ARM site, Lindenberg), and looking at vertical profiles of both temperature and moisture, estimate uncertainty of typical profiles based on individual profiling systems separately, and in various combinations. Quantify error reduction with increasing redundancy of measurements. A model for this approach may be the ARM Value Added Products.
Team Lead: To be determined

Topic 5: Network Configuration
Research Question: Where and how many GRUAN stations are needed to adequately characterize long-term climate changes?
Approach: Since GRUAN sites will be limited in number, the network configuration should be optimized for climate monitoring. What are the right places, and how far apart can they be to avoid redundant sampling of climate regimes and yet obtain adequate global sampling? Work would involve analysis of spatial information of relevant climate variables to assess variability between neighboring stations using statistical criteria. The hope is that this would lead to a quantification of a minimum number of stations, and their recommended placement, to characterize long-term change.
Team Lead: To be determined

To date, the team has no dedicated support. Projects are undertaken that are consistent with the larger research agendas of the involved scientists’ home institutions.

Working Arrangements
Work is performed largely remotely. The core research team holds quarterly conference calls to plan projects and update colleagues on their status. Person-to-person meetings have been arranged in conjunction with other travel plans. Team members work with other colleagues in their home institutions and elsewhere to accomplish project goals.


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