Greg Bodeker Peter Thorne and Ruud Dirksen Presented at the GRUANGCOSWIGOS meeting Geneva 17 and 18 November 2015 Providing reference quality data GRUAN is designed to provide reference quality data for ID: 793294
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Slide1
Benefits accruing from GRUAN
Greg Bodeker, Peter Thorne and Ruud DirksenPresented at the GRUAN/GCOS/WIGOS meeting,Geneva, 17 and 18 November 2015
Slide2Providing reference quality data
GRUAN is designed to provide reference quality data for:Climate change detection and attribution: long‐term stability and homogeneity
of essential
to robustly detect and attribute changes in
the climate
of the free atmosphere.
Satellite
community:
GRUAN
data are
used to validate
satellite‐based measurements
and
provide input to
radiative transfer calculations
to improve
and evaluate
retrievals.
A
tmospheric
process studies community:
provides
high precision and high
vertical resolution
measurements with defined
uncertainties to
aid
deeper
understanding of the processes
affecting the
atmospheric column
.
NWP
community:
GRUAN data are used to verify
NWP model outputs, and
validate
and
correct other data
being assimilated into NWP models.
GRUAN measurements themselves can be assimilated into NWP models.
Slide3Conducting research
The success of GRUAN is contingent on operating at the highest possible standard →
best achieved through
research
published in the
international peer-reviewed
literature for scrutiny by the global community
.
As GRUAN best practices are disseminated across the GOS, GRUAN research underpins the operation of the GOS in general.
Conducting this research entrains expertise from outside the typical monitoring community.
Research conducted within GRUAN strengthens the scientific foundations of the GOS e.g. by contributing to CIMO Guidelines and other GOS prescriptive documentation.
Slide4Research example 1
Contributions of different uncertainty terms to the total uncertainty estimate for the GRUAN temperature correction. Total uncertainty
is
Dirksen
, R.J.; Sommer, M.;
Immler
, F.J.; Hurst, D.F.;
Kivi
, R., et al., Reference quality upper-air measurements: GRUAN data processing for the Vaisala RS92 radiosonde,
Atmos. Meas. Tech., 7, 4463-4490, 2014.
the geometric sum of the squared individual uncertainties. Correction model is the estimated vertically resolved error on the temperature based on the estimated actinic flux. Error is subtracted from measured temperature profile to produce the corrected ambient temperature.
Slide5Research example 2
Simultaneous solar shortwave radiation, thermal longwave radiation, and air temperature measurements with radiosondes from the Earth’s surface to 35 km altitude during both daytime and night-time.Under
sun-shaded and unshaded conditions, solar radiation produces a radiative heating of about 0.2 K near the surface which linearly increases to about 1 K at 32
km.
Philipona
, R.;
Kräuchi
, A. and
Brocard
, E., Solar and thermal radiation profiles and radiative forcing measured through the atmosphere,
Geophys. Res. Lett., 39, 2012.
Slide6Research example 3
Wang et al. correction scheme proven useful for correcting historical radiosonde data → led to a reduction in mean biases and better agreement with independent measurements. Also used to validate pre-flight corrections applied in the Vaisala ground-station software.
Wang
, J.; Zhang, L.; Dai, A.;
Immler
, F.; Sommer, M., et al., Radiation Dry Bias Correction of Vaisala RS92 Humidity Data and Its Impacts on Historical Radiosonde Data,
J. Atmos. Oceanic Technol.
, 30, 197-214, 2013.
Lindenberg: Monthly-mean
PW difference between 1200 and 0000 UTC from the
GPS (blue
) and radiosonde data before (black) and after (red) the
radiation bias correction.
Slide7Research example 4
Under most optimistic scenario (no measurement uncertainty), at least 12 years of daily observations needed at SGP to detect trend.Trend detection times at 200 hPa much more sensitive to the frequency of measurements than to the random measurement uncertainties.
Whiteman
, D.N.;
Vermeesch
, K.C.; Oman, L.D. and Weatherhead, E.C., The relative importance of random error and observation frequency in detecting trends in upper tropospheric water
vapor
,
J.
Geophys. Res., 116, D21118, doi:21110.21029/22011JD016610, 2011.
N
umber
of years to detect a trend in upper
tropospheric water
vapour
concentration versus the
total uncertainty
in the
measurements. Range
of
natural water
vapor
variability,
σ
A
,
is 0.56 to 0.75.
Slide8Research example 5
Seidel, D.J.; Sun, B.; Pettey, M. and Reale, A., Global radiosonde balloon drift statistics, J. Geophys. Res., 116, D07102, doi:07110.01029/02010JD014891, 2011.Frequency
of balloon drift distances
at 50
hPa for
14 GRUAN sites. Colour
key indicates the percentage
of winds from each of four
directions.
Slide9Research example 6
Madonna, F., M. Rosoldi, J. Güldner, A. Haefele, R. Kivi, M. P. Cadeddu, D. Sisterson, and G. Pappalardo, 2014: Quantifying the value of redundant measurements at GRUAN sites. Atmos. Meas. Tech., 7, 3813-3823, doi:10.5194/amt-7-3813-2014.
C
onditional
entropy retrieved
for possible
combinations of instruments measuring integrated water
vapour at SGP site over
2010-2012. Lower values
describe
instrument combinations that more fully characterize the measurand in the atmospheric
column.
Random
uncertainties
can be
strongly reduced by including complementary
measurements.
Can
be applied to the study of other climate variables and used to select the best ensemble of instruments at a given GRUAN
site.
Slide10Change Management
GRUAN will play a key role in the management of the change from Vaisala RS92 radiosondes to other radiosonde types as production of the RS92 radiosonde is discontinued.Protocols on how such changes should be managed:Assessing impacts prior to implementation via quantitative assessment.
Overlap period between new and old measurement system.
Embracing change.
Change event notification.
Justification of change.
Validating impacts using
independent, redundant
measurements.
Change from old to
new measurement system
introduces new sources
of
uncertainty
→
must
be captured
in new
uncertainty
estimate.
Managing change is essential to maintaining network homogeneity
.
Data reprocessing
→
changes often necessitate data reprocessing.
Monitoring for unplanned changes.
Use of models to detect systematic biases between old and new measurement systems.
Involvement of manufacturers in change management.
Slide11Managing the change away from RS92 (1 of 2)
This is a challenge not just for GRUAN but for the wider WIGOS / GOS / WMO.This is not just about RS92→
RS41. GRUAN is working to ensure competition in the marketplace.
GRUAN will address this change as a network and
not as a set of individual sites
.
GRUAN can play a key role as a result of its emphasis on redundant measurement systems.
GRUAN can also provide laboratory facilities (e.g. at the Lead Centre) to understand sonde differences.
All research conducted on how to ensure homogeneity of the data record, as sites change from RS92 to other radiosondes, will be disseminated to NMSs and in particular to GUAN sites
→
exactly how best to do this is something we should discuss today and tomorrow.
Slide12Managing the change away from RS92 (2 of 2)
Dual flights will be conducted at a number of GRUAN sites (sharing the burden) to understand any biases between RS92 and replacement radiosondes → the Lead Centre is in the process of defining how we synthesize the results through a GRUAN-wide strategy.For multiple sites in the same climate zone:
O
ne
site to perform
a full intercomparison over an
extended
period (2
years) of weekly intercomparison measurements, 50-50 distribution
day-night.
O
ther
sites in that climate zone
perform several
week-long intercomparison campaigns of ~10 soundings, evenly distributed over the year to cover various seasons
.
Paper currently in discussion in
Atmospheric Measurement Techniques
Slide13Disseminating best practice across the GOS
GRUAN defines a standard of operation designed for one primary purpose → to produce reference measurements.A key attribute of GRUAN is sharing knowledge and expertise across the network →
this is needed to achieve network homogeneity.
Having representation from CIMO, CBS, CCL and CAS in GRUAN governance provides a mechanism for best practices developed in GRUAN to be disseminated across the wider GOS.
GRUAN needs to play a more active role in contributing to documentation developed by CIMO, CBS, CCL and CAS.
GRUAN can provide some leadership by example e.g. an aspirational standard of operation for GUAN sites.
Slide14Linking communities
Brings research and operations together: GRUAN has a ‘split personality’ with both strong research facets, and the inclusion of sites that are more ‘research’ sites, and strong operational facets, with the inclusion of purely operational (NMHS) sites in the network. Bringing together these often disparate communities enhances both.GRUAN provides an example of WIGOS in action.Links the measurement community to the metrology community.
Brings users and producers of data together
→
connections to SPARC, GAW, SHADOZ and NDACC.
Brings instrument manufacturers on board.