Report
GCOS/GRUAN Implementation-Coordination Meeting (ICM-1)
Norman, OK, USA, 2-4 March 2009
HMEI was invited to attend
this meeting as an observer. HMEI Councillor, Fred Clowney from International Met
Systems attended as a HMEI representative and has supplied the
report below ,for which HMEI thanks him.
Introduction
This, the first implementation-coordination meeting for the GRUAN, focused on
establishing the methods and procedures necessary to move the network
towards operational status.
The goal of this report is to provide summary information for instrument
manufacturers that will help them understand the GRUAN requirements and
what will be necessary for instruments to be qualified for use. Papers
prepared for the meeting and copies of PowerPoint presentations are
available at the GRUAN website (www.gruan.org). Additional details can
be learned by downloading the relevant papers and presentations.
Summary
The GCOS Reference Upper Air Network was conceived in 2005 to establish
a consistent climatological record of the upper atmosphere. The
evolution of GRUAN is presented in
the attached paper to be published in
the March, 2009 Bulletin of the American Meteorological Society.
From the perspective of instrument manufacturers, the key to
understanding GRUAN is to understand the goals of climatologists and how
these will need to be reflected in the products offered to them. The
Norman conference went a long way towards defining these requirements.
1. What are the priorities of the GRUAN?
- The primary measurement priorities are temperature and water vapour in the upper troposphere and lower stratosphere (UTLS). Also required will be comprehensive surface observations and total column water vapour.
- Although remote sensing will be a critical component of the network, in-situ observations will continue to provide the most accurate, high resolution data for the foreseeable future.
-
Secondary measurement priorities are total column and vertical
profile for ozone, methane and aerosols plus cloud and radiation
parameters.
- Although instruments do not yet exist that meet all of the desired accuracies, the goal is to start now and carefully manage the change process as instruments improve (“start small, but start”). - The
GRUAN will begin with existing sites with established budgets - and
build from there.
- A GRUAN Radiosonde observation must meet the accuracy requirements defined in the document published as GCOS-112 (summary attached).
- A GRUAN observation must be accompanied by sufficient statistical and meta data to define its level of uncertainty. “Error bars” are the most commonly accepted description for this, but must be comprehensive and traceable to absolute or relative standards. However, adequate characterization does not qualify an observation unless it also meets the accuracy requirements.
- A single instrument may not be sufficient to accurately measure the entire vertical profile (especially humidity).
- Additional work is needed by an Expert Team to define the nature of the uncertainties for various instruments and the methods necessary to trace observations back to the International System of Units (SI).
- The use of remote sensors to validate or characterize in-situ observations will be a key goal of the GRUAN. Examples include Raman Lidar, GPS PWV, Microwave Radiometers, FTIR and AERI IR spectrometers. Redundancy of measurement technology, whereby each variable is measured by more than one instrument, is a key requirement of GRUAN.
- Observations may be based on Local Solar Time as opposed to the GMT used for synoptic observations.
- Definition of humidity, in terms of mixing ratios should be considered due to inconsistencies in the vapour pressure formulas used to calculate different characterizations of humidity in the low moisture regions of the UTLS, may also be needed.
- Sites should develop Calibration/Validation procedures independent from the instrument manufacturers to verify performance prior to use. Procedures that may be appropriate for operational observations may not be adequate for climatology.
- Observing processes should be systematized to reduce operator
errors. Consistent preparation of instruments and the collection of
extensive meta data will be particularly important.
- Data must be preserved in both processed and raw forms, accompanied by sufficient metadata so future researchers can understand and re-process the data long after the observers are gone. The key here is to provide sufficient documentation about what corrections were made, and what processing was done to arrive at the final data output.
- For radiosondes, pre-flight cal/val data must be retained to validate the accuracy of the sounding.
- There may be no “black boxes” used to calibrate, smooth, correct or otherwise manipulate the raw data. All processing algorithms must be documented, tested and publicly available to researchers. This is particularly important for radiation corrections applied to temperature and humidity observations.
- Data quality indicators should be included where available. Interpolations should not be used to fill in for missing data.
- Data file version numbers will be necessary for traceability.
- Only complete, processed, quality checked and error-barred data
will provided to the general scientific community. Input from the
manufacturers for complete uncertainty analysis will be needed to
complete this task.
- The GRUAN will not be a centrally managed, homogeneous network. Individual sites will have different suites of instruments and will be independently funded and managed.
- To be qualified as a GRUAN site, locations must observe the network’s observing principals and procedures.
- It is understood that individual sites will have “different
masters” and obligations besides GRUAN.
- The Lead Center (Lindenberg) will be the “glue” that binds the network together and provides day-to-day management. It will also serve as the primary test bed for processes and procedures. - Sites should be capable of conducting their own intercomparisons between related instruments (e.g. GPS PWV and radiosoundings).
- A GRUAN Manual will be commissioned to document observing
practices and procedures. This will be supplemental to the CIMO
guide and site and instrument documentation - but will be critical
to maintaining consistency across the network.
- Although it is desirable for GRUAN sites to be representative of a wide range of climate regimes, this may not be achievable due to the absence of suitable facilities and budgets in all locations.
- GRUAN will exist within the WMO Global Climate Observing System (GCOS).
- GRUAN will support the Global Space-Based Inter-Calibration System (GSICS) by working to validate satellite observations through the use of in-situ sensor launches coordinated with overpasses.
- GRUAN will request to be considered a WIGOS (WMO Integrated Global Observing System) Pilot Project. This request will be carefully defined to maximize potential benefits and the likelihood for success.
- From an operational standpoint, the GRUAN will not seek to “reinvent the wheel”. Well developed methods and procedures that are already in place at the high quality observing sites will be adopted where consistent with the GRUAN’s objectives. Examples include the DoE’s Atmospheric Radiation Measurement sites (http://www.arm.gov ) the Network for the Detection of Atmospheric Composition Change (http://www.ndsc.ncep.noaa.gov/) and the Baseline Surface Radiation Network (BSRN) (http://www.bsrn.awi.de/en/home/bsrn/).
- A GRUAN website has been established (www.gruan.org) to serve as the focus for communications, documentation and data access.
- The GRUAN Lead Center and working group will participate in WMO CIMO Intercomparisons where appropriate, including the upcoming 2010 Radiosonde Intercomparisons to be held in China. Inclusion of BQRRS instruments is desirable but probably not affordable.
- GRUAN data will be maintained at an established repository, with
the NCDC being the most likely site (http://www.ncdc.noaa.gov/oa/ncdc.html).
Several teams were established to conduct additional research and work on specific tasks.
- A team was established to draft the GRUAN Implementation Plan with a target of June 2009 for a high level document. Topics will include data dissemination, site instrument certifications, GRUAN Manual, site selection, GRUAN launch event, lessons learned from sites, expert teams, instrument co-location issues and observing procedures.
- A team was formed to develop a set of “lesons learned” from existing high quality observing sites for possible application to GRUAN. Specific research topics are being developed.
- A team was formed to define specific requirements for GRUAN observations including uncertainties and traceability, independent ground checks and processes for managing change.
- The Lead Center will continue evaluating radiation correction procedures for Radiosonde observations and will compile an inventory of instruments at prospective GRUAN sites. Links to the ARM and NCDC will be formalized.
