GCOS Implementation Plan - WMO

Implementation Plan for the Global Observing System for Climate in Support of the UNFCCC
(2010 Update)
Meteorology, Ionosphere and Climate) fleet of satellites provides real-time data and the GNSS
Receiver for Atmospheric Sounding (GRAS) instrument is the first of a series of operational RO
instruments. Real-time use of the data has been established and a positive impact on Numerical
Weather Prediction (NWP) has been demonstrated. Climate applications are being developed by
providing consistent time series of bending angles and refractivity profiles. The introduction of other
GNSS offers opportunities for further improvement in coverage of RO data.
Action A21 [A20 IP-04]
Action: Ensure the continuity of the constellation of GNSS RO satellites.
Who: Space agencies.
Time-Frame: Ongoing; replacement for current COSMIC constellation needs to be approved
urgently to avoid or minimise a data gap.
Performance Indicator: Volume of data available and percentage of data exchanged.
Annual Cost Implications: 10-30M US$ (Mainly by Annex-I Parties).
ECV – Upper-air Wind Speed and Direction
The WWW/GOS radiosonde network is the backbone of global upper-air wind observations.
Observations from commercial aircraft are also becoming more plentiful. A further source of wind
information is the cloud motion vectors obtained by tracking cloud elements between successive
satellite observations and assigning their height by estimating their temperature to provide “satellite
winds” over the ocean. Multi-angular instruments can add value to such estimates, since height
information is derived from the parallax in the data and does not involve assumptions about
temperature profiles. These data are part of the WWW/GOS designed for weather forecasting and will
have application for climate through their incorporation in reanalysis.
The ADM/Aeolus mission has been developed to pioneer wind-lidar measurement from space. If the
data from this mission demonstrate significant value for climate purposes, careful and prompt
consideration will need to be given to the implementation of follow-on missions (see also Action A11).
ECV – Upper-air Water Vapour
Water vapour is a key gas in the atmosphere since it is both radiatively and chemically active. It is the
strongest of the greenhouse gases (GHGs) on the planet, though largely influenced indirectly rather
than directly by anthropogenic activity. In the upper troposphere and lower stratosphere, it is a key
indicator of convection and radiative forcing. In the stratosphere, water vapour is a source gas for OH
which is chemically active in the ozone budget. There is recent evidence that the Brewer Dobson
circulation is changing in the Tropics due to climate change, which alters the balance of water vapour
in the Upper Troposphere (UT) and Lower Stratosphere (LS) markedly and has a strong feedback on
climate change.
Broad-scale information on tropospheric water vapour is routinely provided by operational passive
microwave, infrared and UV/VIS satellite instruments. Infrared instruments have more recently been
enhanced by high spectral resolution infrared sounders. UV/VIS instruments provide additional
information for total column water vapour.
Data assimilation can be used to improve the consistency of water vapour, cloud and precipitation
estimates. Data from GPS receivers are used operationally to observe continuous total column water
vapour (via atmospheric refractivity), and the data should be freely exchanged for climate purposes.
Collocating GPS receivers at GRUAN sites is important.
The capability to observe continuous total column water vapour data from ground-based GPS
receivers is well-established and these data are exchanged and used operationally in NWP centres.
The network of GPS receivers should be extended across all land areas to provide global coverage.
Several other Actions already call for continuity of the required instruments. Requirements for stable
operation and processing, as expressed in Action A8 for precipitation, apply for water vapour. Global
high vertical resolution measurements of H 2 O in the UT/LS by limb observations are also essential.
The required limb sounding also yields invaluable information on ozone and other chemical
composition variables. Action A26 in section 4.3 calls for the required measurements.
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