Download United Kingdom

UNITED KINGDOM
1. OBSERVATIONAL ACTIVITIES
1.1. Column measurements of ozone and other gases/variables relevant to ozone loss
The UK Government Department for Environment, Food and Rural Affairs (Defra) funds an ongoing monitoring programme that records total values of stratospheric ozone at two UK locations.
Measurements with a Dobson instrument are taken at the Lerwick Observatory in the Shetland
Islands (N of Scotland) and a Brewer spectrophotometer is used at the Reading site in Berkshire
(S England).The latter site replaced the Camborne Observatory site in Cornwall at the end of 2003,
where a Dobson instrument had been used for ozone measurements. The spectrophotometers
sample the ozone column at frequent intervals throughout the day to produce daily mean values,
except for when weather conditions prevent values from being recorded and during the winter at
Lerwick when the sun is too low in the sky.
Column ozone measurements are also made at the University of Manchester (N England) using a
Brewer instrument. These are also made available to the above monitoring programme (but are
separately funded) and similarly submitted to the World Ozone and Ultraviolet Radiation Data
Centre (WOUDC).
Measurements using a Systeme D'Analyse par Observations Zenithale (SAOZ) instrument are
made in Aberystwyth. These measurements have not been processed for over two years. The
University of Manchester are looking to bring them into the ozone and UV monitoring project over a
period of time depending on their resource availability.
The British Antarctic Survey (BAS) continues total column ozone measurements at Halley with a
Dobson spectrophotometer, and supports those made at Vernadsky (Ukraine). BAS also continues
total ozone and nitrogen dioxide (NO2) column measurements at Rothera with a SAOZ
spectrometer and commenced such measurements at Halley on 30th January 2013. A radiosonde
programme continues at both Halley and Rothera. The Met Office funds the Halley radiosonde
program, while BAS covers the cost of the gas. BAS covers the main cost of the Rothera
radiosonde program.
The UK Met Office lent Dobson #35 to the South African Weather Service in June 2006, and it has
remained on loan to the South African Weather Service. Dobson 35 is currently fully operational at
the Irene Operational unit standing in for Dobson 89 which required maintenance. The data are
being prepared to be submitted to WOUDC in place of 89 for 2013. It is still the intention to install
Dobson 35 at the Cape Point Facility when renovations are complete.
It is hoped that South African Weather Service will be hosting the African Dobson Inter comparison
during 2014 in which Dobson 35 will also participate.
1.2. Profile measurements of ozone and other gases/variables relevant to ozone loss
High frequency, real time in situ measurements of the principal halocarbons and radiatively active
trace gases have been made at Mace Head on the West coast of Ireland since 1987. These
measurements form a key part of the international Advanced Global Atmospheric Gases
Experiment (AGAGE) measurement programme. For about 70% of the time Mace Head monitors
clean westerly air that has travelled across the North Atlantic Ocean. For the remaining time, Mace
Head receives substantial regional scale pollution in air that has travelled from the industrial
regions of Europe. The site is therefore ideally situated to record trace gas concentrations
associated with both the Northern Hemisphere background levels and with the more polluted air
arising from Europe.
Using the Mace Head data, coupled with a Lagrangian dispersion model that determines the
history of the air arriving at Mace Head at the time of each observation, estimates of the midlatitude Northern Hemisphere baseline concentrations are made for each trace gas, see Figure 1
1
below for the surface ozone trend at Mace Head. By removing the underlying baseline trends from
the observations and by modelling where the air passed over on a regional scale on route to Mace
Head, an iterative best-fit technique can then search for a regional emission map that generates a
time-series
that
most
accurately
mimics
the
Mace
Head
observations
(www.metoffice.gov.uk/atmospheric-trends).
Figure 1 Surface ozone as measured at Mace Head; Top plot: monthly and annual mixing ratios;
Middle plot: annual growth rate using 2 methods; Lower plot: mean seasonal cycle.
The UK Department for Energy and Climate Change has expanded the atmospheric observation
network (UK DECC network) to include three additional sites in the UK, Angus north of Dundee;
Tacolneston near Norwich, and Ridge Hill near Hereford. These sites significantly increase the
spatial and temporal resolution for the interpretation work, enabling UK emission estimates to be
2
made from atmospheric observations as well as decreasing the uncertainties associated with the
UK estimates.
Analysis of the atmospheric observation data also identifies sources of and trends in ozone
formation from different areas, including comparison of observed data with expected trends, to
identify any new substances with ozone depleting or radiative forcing properties. DECC are
engaged in EU and global networks where the possible use and analysis of any data coming from
other sites remains under review.1
1.3. UV measurements
1.3.1. Broadband measurements
The solar UV index is measured at nine sites (from 50 to 60° N) across the UK by the Centre for
Radiation, Chemical and Environmental Hazards of Public Health England (PHE). A tenth site is
located at Thule in Greenland, which is operated in conjunction with the Danish Meteorological
Institute. The Department of Health provides support for this UV monitoring work, which provides
information for the Global Solar UV Index in association with World Health Organisation (WHO),
World Meteorological Organization (WMO), United Nations Environment Programme (UNEP) and
the International Commission on Non-Ionizing Radiation Protection.
1.3.2. Narrowband filter instruments
Since the 8th Ozone Research Managers meeting we have become aware that there is a Groundbased Ultraviolet (GUV) instrument routinely in use at Manchester.
1.3.3. Spectroradiometers
A spectroradiometer is co-located with the Brewer spectrophotometer in Reading, funded as part of
the Defra monitoring programme. The Bentham DM150 UV spectroradiometer has been in place
since 1993, and is regularly calibrated in situ. The instrument takes measurements from 290nm to
500nm at 0.5nm resolution at half-hour periods during daylight hours, every day of the year.
A multi-filter radiometer is also co-located with the Brewer spectrophotometer at the University of
Manchester, which provides one minute averages in each of the five narrow wavebands (305, 313,
320, 340, 380nm). Apart from calibration periods, the Manchester instrument has been in
continuous operation since 1997. Data are submitted to WOUDC alongside the ozone data series.
The BAS made spectral measurements of UV using a Bentham spectroradiometer at Rothera from
09/02/1997 until 2012, the data record stops at 12/3/2012.
Spectral UV measurements are carried out at the PHE site at Chilton. Two portable spectral
measurement systems have been developed for temporary deployment during extreme weather,
atmospheric events or at locations where large numbers of people gather outside during the UK
summer.
1.4. Calibration activities
Regular calibrations have been carried out on both Met Office Dobson instruments and the
Reading Brewer spectrophotometer. The current recommendation is to re-calibrate Brewer
Spectrophotometers every two years. Dobson Spectrophotometers are now recommended to be
re-calibrated every 4 or 5 years depending on their condition. Dobson #41 is being re-calibrated
after 5 years for that reason.
An intercomparison took place with Dobson #32 in 2011. The change of calibration detected at the
initial intercomparison was too small to require any revision of data since the previous
1
https://www.gov.uk/government/publications/uk-greenhouse-gas-emissions-monitoring-and-verification
http://www.metoffice.gov.uk/atmospheric-trends/
3
intercomparison. The final intercomparison showed that the instrument was in good condition with
no significant ozone airmass Mu dependence. Dobson #41 was taken to Hohenpeissenberg for
international inter-comparison in June 2009 and was found to be performing well. The next
intercomparison of Dobson #41 is planned for 2014 at Hohenpeissenberg.
Brewer #075 was re-calibrated in 2011 at El Arenosillo with a new filter after further technical
problems. Subsequent calibration at El Arenosillo in 2013 showed instrument extremely stable in
good working order.
2. RESULTS FROM OBSERVATIONS AND ANALYSIS
The long-term annual mean trend in ozone for the Lerwick site, and a combined southern
England trend from the Camborne (up to 2003) and Reading (2003 onwards) are given in Figure 2.
Smedley et al., (20112), analysed the trend data from these sites and demonstrated that the year at
which total ozone stopped decreasing over the UK was 1993, by which time statistically significant
reductions of 4.8% per decade for southern England and 5.8% per decade for Lerwick were
observed. These rates of decrease are at the upper end of the range in comparison with other
European ozone trends before the mid-1990s.
From 1993 to the present the data did not show any significant trend to 2008, although small
average increases were noted. A more recent analysis following the methodology in Smedley et
al., (2010) but including data up to 2013 now shows an upward trend of 2.0% (only significant at
the 10% level). In part that there is now a observable trend since 1993 is due to higher ozone
column values in 2010, which was on average some 7.6% larger than the 1993-2013 mean.
Figure 2 Total ozone trends for Lerwick and combined southern England
The data from the monitoring programme have also been analysed seasonally. Table 1 shows that
a significant decline at Lerwick since 1978 is seen in the annual mean, Spring and Autumn for both
single and multiple regression analysis. There are no significant changes at Reading since 2003.
Multiple regression has a large impact on seasonal trends at Reading because of the shorter
2
Smedley A. R. D., Rimmer J. S., Moore D., Toumi R., Webb A. R. (2011) Total ozone and surface UV trends in the United Kingdom: 1979 to 2008. I J
Clim DOI: 10.1002/joc.2275
4
record. The autumn decline is somewhat surprising as this is before the seasonal chemical ozone
depletion (Winter/Spring). We are investigating different statistical techniques to test the autumn
trend.
Table 1 Column ozone trend in Dobson Unit (DU) per year with standard errors. Numbers in bold are
significant at the 95% confidence level (P<0.05) SR: single regression; MR: multiple regression.
Lerwick since 1978 and Reading since 2003 and both to November 2013.
Annual3
(to 2012)
Winter4 (DJF)
(to 2013)
Lerwick -SR
Spring
Summer
Autumn
(MAM)
(JJA)
(SON)
(to 2013)
(to 2013)
(to 2013)
-0.59 +/- 0.18 -0.21 +/- 0.50 -0.75 +/- 0.27 -0.16 +/- 0.14 -0.47 +/- 0.18
Lerwick- MR
-0.50 +/- 0.19 -0.18 +/- 0.51 -0.57 +/- 0.22 -0.16 +/- 0.12 -0.35+/-0.16
Site
Reading –SR +0.59 +/- 1.16 +0.90 +/- 2.12
+0.57 +/1.28
+0.49 +/- 0.61 +0.85 +/- 1.03
Reading –MR -0.53 +/- 1.16 -1.03 +/- 1.48
+0.42 +/1.11
+0.30 +/- 0.64 0.00 +/- 0.65
Low ozone events observed by the Defra monitoring programme are reported in near real-time.
There appear to be long-term decadal cycles of the ratio of high and low ozone events. We have
not identified a cause for this but it is consistent with shifting patterns of tropospheric indicators,
such as the North Atlantic Oscillation (NAO), which also remain unexplained. The cycles are out of
phase. In this decade we are experiencing relatively more high/low event ratios in Reading and
Lerwick. However, 2012 was a year of typical number high and low events compared to the 20
year moving average. The low events defined as a departure of more than two standard deviations
below the long-term monthly mean value since 2011 are show in the Table 2.
Table 2 shows days that meet the Low Ozone Event criteria since 2011
Lerwick date of departure
16-Oct-13
15-Oct-13
23-Apr-13
27-Mar-12
26-Mar-12
15-Feb-12
31-Jan-12
09-Apr-11
30-Mar-11
29-Mar-11
28-Mar-11
27-Mar-11
3
4
Reading date of departure
16-Mar-14
06-Mar-14
21-Sep-13
25-Apr-13
24-Apr-13
23-Apr-13
27-Jun-12
28-Mar-12
24-Feb-12
23-Feb-12
16-Feb-12
18-Jan-12
14-Jan-12
27-Dec-11
26-Dec-11
Annual is to 2012 only
Winter (DJF) season includes December of preceding year e.g. winter 2013 is December 2012 to February 2013.
5
Lerwick date of departure
Reading date of departure
25-Dec-11
23-Dec-11
08-Oct-11
27-Jun-11
09-Apr-11
06-Apr-11
31-Mar-11
The UV monitoring results from the Defra programme were also assessed in the Smedley et al.
paper, which found no significant trend between 1993 and 2008 in the daily totals of UV, but an
increase of 6% per decade was seen in the mid-day values of the UV index. This, combined with a
lack of correlation between ozone and UV anomalies suggested that changes in cloud cover were
the cause. Re-assessing the UV data series to include data up to 2013, shows there is no longer a
significant trend in the mid-day values of UV index, due to a general decrease in daily peak values
since 2008.
It should be noted that despite the long-term data produced by the UK total ozone and spectral UV
records, in order to clearly observe significant trends since the mid-1990s several more years of
high quality data are necessary.
3. THEORY, MODELLING AND OTHER RESEARCH
Polar stratospheric clouds (PSCs) play a crucial role in controlling polar stratospheric ozone
depletion. Temperature fluctuations induced by mountain waves are an important source of PSCs.
However, this formation mechanism is usually missing in chemistry-climate models because the
temperature fluctuations are neither resolved nor parameterised, suggesting that models
underestimate the related polar ozone loss. To remedy this, scientists at the BAS have inserted a
mountain wave parameterisation scheme (which computes the temperature fluctuations due to
unresolved (sub-grid scale) mountain waves) into the chemistry-climate model configuration of the
UK Met Office Unified Model. Having firstly validated the parameterised temperature fluctuations,
the scientists showed that passing the parameterised mountain wave cooling to the PSC scheme
of the chemistry-climate model caused around 20% more PSCs over the Antarctic Peninsula at 21
km compared to a control simulation.
4. DISSEMINATION OF RESULTS
4.1. Data reporting
The ozone monitoring data from Lerwick and Reading are processed daily by local operators prior
to being quality checked and disseminated. A number of checks are performed to ensure the
integrity of these data, including comparison of daily results with the Ozone Monitoring Instrument
OMI satellite measurements and the nearest ground-based measurements.
Results
are
disseminated
by
uploading
to
a
dedicated
website
(http://ukair.defra.gov.uk/research/ozone-uv) and issuing results to the WOUDC Real-time Mapping Centre.
Monthly data are submitted to the WOUDC for inclusion on their archive.
Both total ozone and multi-filter UV data from the Manchester site are submitted regularly to the
WOUDC.
Level 0 and Level 1 ozone data from Halley are submitted to the WOUDC by the BAS.
Observations are reported in real-time using CREX (Character form for the Representation and
6
EXchange of data) on the Global Telecommunications System (GTS) from Halley, Rothera and
Vernadsky. Quality controlled ozone observations are submitted by BAS to the WMO on a weekly
basis.
4.2. Information to the public
Ozone monitoring results from the Lerwick, Reading and Camborne sites are publically available
on
the
Defra
UK-AIR
website,
along
with
relevant
reports
(http://ukair.defra.gov.uk/research/ozone-uv/). Broadband UV Index graphs produced by Public Health
England are currently not displayed to the public, however Defra are working with PHE to integrate
this data onto the Defra website. Public health messages continue to be issued in collaboration
with Defra and the UK Met Office at times of higher than expected levels of UV Index.
5. PROJECTS AND COLLABORATION
The UK Met Office
The UK Met Office has previously applied its ozone data assimilation scheme to infer chemical
polar ozone loss and to examine phenomena such as low ozone events in the southern summer
stratosphere. Studies on the impact of the representation of stratospheric ozone on extended
range tropospheric forecasts were also carried out in collaboration with Imperial College London
and European partners. A Met Office representative co-leads the World Climate Research
Programme Stratospheric Processes and their Role in Climate WCRP SPARC Data Assimilation
Working Group.
The UK Met Office Hadley Centre (MOHC) is working on the modelling of stratospheric and
tropospheric ozone and their relationship to long- and near-term climate change, as part of its joint
DECC/Defra funded MOHC Programme and the EU FP7 StratoClim project. The MOHC is
participating in the WCRP's SPARC Chemistry-Climate Modelling Initiative (CCMI) activity which
coordinates the multi-model evaluation of models and projections of stratospheric ozone recovery
and its interaction with climate-change.
The MOHC has further developed its whole-atmosphere chemistry and aerosol model, United
Kingdom Chemistry and Aerosols (UKCA), in collaboration with the Universities of Cambridge,
Leeds and Oxford. These developments represent a significant step change in modelling capability
since the 5th assessment report (AR5) of the Intergovernmental Panel on Climate Change (IPCC).
In particular, UKCA models gas-phase chemistry and aerosols in both the troposphere and
stratosphere, and photolysis rates are calculated interactively and respond to changes in aerosols
and ozone column. These improvements ensure that responses to climate change are well
modelled and that the role of ozone and aerosols in climate change can be more accurately
assessed. This configuration of UKCA, along with the land surface component Joint UK Land
Environment Simulator (JULES), will form an important and underpinning component of the joint
NERC/Met Office next-generation Earth System Model, UKESM1.
The Natural Environment research Council
The UK Natural Environment Research Council (NERC) supports national capability and funds a
number of research programmes relating to stratospheric ozone:
The CLEARFOGG (Checking Layers of the
Earth’s Atmosphere For halogenated Ozone-depleting and Greenhouse Gases) project, completed
in 2011, performed a systematic screening of various layers in the Earth’s atmosphere for unknown
halocarbons, and determined the influence of these halocarbons on stratospheric ozone depletion.
The Southern hemisphere climate change in an era of ozone recovery project, completed in 2011,
used state of the art climate modelling to derive a range of predictions of future climate change
which take account of our uncertainty in future ozone change, particularly focussing on the
southern hemisphere and the Antarctic ozone hole.
7
The SOLCLI consortium ran a 4-year coordinated study from 2007 to 2011, on the influences of
solar variability on atmospheric composition and climate. The consortium was led by Imperial
College, with partners at the Universities of Cambridge, Leeds and Reading and the BAS and with
collaborators in Germany, Japan, the USA and the UK Met Office. Study topics included: variability
over the past 150 years in solar spectral irradiance; detection of solar signals throughout the lower
and middle atmosphere; response of stratospheric composition, specifically ozone, to varying UV;
mechanisms for stratosphere-troposphere dynamical coupling; and better representation of solar
effects in climate models.
The NERC-funded Co-ordinated Airborne Studies in the Tropics (CAST) project (2012-2016) will
study the Tropical Tropopause Layer (TTL) over the Pacific Ocean and South East Asia. The TTL
is a crucial region for chemistry/climate interactions and is the main route by which very short-lived
halogen species, which represent a large uncertainty in future stratospheric ozone evolution, enter
the stratosphere. CAST aims to improve knowledge of the budgets of these gases and of their
chemical transformation and transport through the TTL, including the role of convective transport
into the TTL and the subsequent routes for transport from the TTL to the lower stratosphere.
Improving representation of these processes in global chemistry/climate models is a key aim
Further NERC-funded research projects relating to stratospheric ozone include: the impact of the
representation of ozone on tropospheric weather forecasts; multi-scale modelling of mesospheric
metals, and the impact of the mesosphere on stratospheric ozone and climate; interactions of the
lower stratosphere with the tropospheric chemistry/climate system (including recovery scenarios
for stratospheric ozone); producing a century-long record of trace gases in the northern
hemisphere from the North Greenland EEMian ice core drilling project in Greenland; and
determining the impact of energetic electrons on polar stratospheric ozone.
The University of Manchester
The University of Manchester is represented on the WMO Brewer sub-committee, and has been
active in discussions and final decisions on the effective changeover of ozone absorption
coefficients Absorption Cross Sections of Ozone (ACSO) committee, and the need for a reliable
historical dataset on ozone profiles (SPARC/IGACO/IO3C/NDACC), required for trend analysis in
the presence of climate and circulation changes. In 2012, John Rimmer made a successful bid for
funds from the European COST Office to bring all the European Brewer Ozone Spectrophotometer
stations together in a formal network. COST Action ES1207 was launched in April 2013
(http://www.eubrewnet.org/cost1207/).
The University of Cambridge
In accordance with Decision XXIII-13 of the Montreal Protocol on Substances that Deplete the
Ozone Layer, an assessment of the state of understanding on the science of the ozone layer will
be prepared by the Scientific Assessment Panel (SAP) and will be considered by the Parties in
2015. The University of Cambridge provides one of the four international co-chairs for the SAP.
6. FUTURE PLANS
Defra does not have any plans at present to provide direct government funding for any additional
ozone, UV or ozone depleting substances (ODS) monitoring sites in the UK. Defra is keeping
future research needs for policy development on stratospheric ozone under review.
NERC continues to support BAS and NCAS national capability to monitor ozone and model
chemistry and climate. Funding support for new research projects on ozone will be considered
through usual processes.
7. NEEDS AND RECOMMENDATIONS
8
International agreement needs to be reached on the form of zenith polynomial for use in Dobson
zenith sky measurements.
COST Action ES1207 aims to provide harmonisation and consistency across Brewer monitoring
stations throughout Europe and near neighbours. Other international agencies (NOAA, IOS, WMO,
ESA) are also collaborating. This will bring uniformity to calibration and characterisation protocols,
data reduction algorithms and a unified quality assurance scheme including near real time data.
Data end users and stakeholders (ozone, UV and aerosol optical depth (AOD) are encouraged to
contact the Chair (John Rimmer, University of Manchester) to discuss interaction.
Maintenance of long time-series remains essential, especially for trend analysis and ground
truthing of satellite data.
Further work to model emissions of trace gases and ODS will be beneficial for assessing
emissions inventories.
9