Europe and the NHEurope and the NH

Phil JonesPhil JonesClimatic Research UnitClimatic Research Unit

University of East AngliaUniversity of East AngliaNorwich, UKNorwich, UK

SummarySummary

• Advantage of pressure over early Advantage of pressure over early observed variablesobserved variables

• Earlier MSLP digitization effortsEarlier MSLP digitization efforts

• CLIWOC – marine dataCLIWOC – marine data

• Pressure data enable robust Pressure data enable robust estimates of wind strength variations estimates of wind strength variations to be made over centuriesto be made over centuries

Pressure AdvantagesPressure Advantages

• Early observers with a barometer almost always Early observers with a barometer almost always knew what they were doingknew what they were doing

• Temperature, elevation and gravity adjustments Temperature, elevation and gravity adjustments can generally be taken care of quite easilycan generally be taken care of quite easily

• Time of daily observations also generally quite Time of daily observations also generally quite easy to deal with – from detailed observations easy to deal with – from detailed observations that have often been made in many locations for that have often been made in many locations for 10-year periods10-year periods

• Pressure is much easier to homogenize than early Pressure is much easier to homogenize than early temperature and precipitation measurementstemperature and precipitation measurements

1980s data digitization/analysis efforts1980s data digitization/analysis efforts• Extended monthly grids developed from station data, Extended monthly grids developed from station data,

assuming gridded datasets from the late 19th century for assuming gridded datasets from the late 19th century for parts of the NH (Europe and North America)parts of the NH (Europe and North America)

• Grids based on daily weather maps drawn from 1899 Grids based on daily weather maps drawn from 1899 onwards during WW2 (Historical Weather Mapping Project, onwards during WW2 (Historical Weather Mapping Project, HWMP), extended in Europe to 1873 using German HWMP), extended in Europe to 1873 using German operational chartsoperational charts

• Reconstruction technique is Orthogonal Spatial RegressionReconstruction technique is Orthogonal Spatial Regression• Extensions of this approach to the Arctic – illustrating Extensions of this approach to the Arctic – illustrating

problem of the ‘Arctic High’, which resulted from the chart problem of the ‘Arctic High’, which resulted from the chart analysts being told there was an Arctic High, so generally in analysts being told there was an Arctic High, so generally in the absence of data they drew onethe absence of data they drew one

• Bias introduced is up to 10hPa in northern Canada and the Bias introduced is up to 10hPa in northern Canada and the western Arctic before the 1940swestern Arctic before the 1940s

• Jones, P.D., 1987: The early twentieth century Arctic High - fact or fiction? Jones, P.D., 1987: The early twentieth century Arctic High - fact or fiction? Climate DynamicsClimate Dynamics 11, 63-75., 63-75.

1990s data digitization/analysis efforts1990s data digitization/analysis efforts

• SH and Antarctic work, also monthly station SH and Antarctic work, also monthly station pressure basedpressure based

• If monthly average MSLP available then daily/sub-If monthly average MSLP available then daily/sub-daily should be, it just will take some findingdaily should be, it just will take some finding

77 SH sites from 1991 paper, with many extending back to 1910s

2000s data digitization/analysis efforts2000s data digitization/analysis efforts

• HadSLP1 and HadSLP2HadSLP1 and HadSLP2• EMULATE – daily gridded fields from the EMULATE – daily gridded fields from the

18511851• Daily station data digitized across Europe for Daily station data digitized across Europe for

1851-1880, then combined with the maps 1851-1880, then combined with the maps from HWMP, marine MSLP data from ICOADS from HWMP, marine MSLP data from ICOADS and HadSLP2 for monthly continuityand HadSLP2 for monthly continuity

• EMULATE has had numerous uses in EMULATE has had numerous uses in synoptic climatology – and like Lamb synoptic climatology – and like Lamb weather types allows for numerous U/G and weather types allows for numerous U/G and MSc projectsMSc projects

A summer PC based on 1911-40

A summer MSLP PC based on the 1911-40 period, showing the precipitation, temperature and DTR response

Reconstructions of circulation indices from wind Reconstructions of circulation indices from wind measurements from ships’ logbooks - CLIWOCmeasurements from ships’ logbooks - CLIWOC

Reconstructions always better in the winter season/winter half year, which is unfortunately the time when there were least ships

Reduction in observation count a serious Reduction in observation count a serious issue of early ship-based data – for an issue of early ship-based data – for an atmospheric measure as opposed to SSTatmospheric measure as opposed to SST

Digitization todayDigitization today• Emphasis seems to be on Max/Min temperature and Emphasis seems to be on Max/Min temperature and

precipitation, but it is relatively easy to add in MSLPprecipitation, but it is relatively easy to add in MSLP• ECA&D and ENSEMBLES daily digitization (and ECA&D and ENSEMBLES daily digitization (and

gridding) has included MSLP, but fewer NMSs have gridding) has included MSLP, but fewer NMSs have sent long seriessent long series

• Many seem unaware of the importance of MSLP data Many seem unaware of the importance of MSLP data and the fact that it is far easier to homogenize than and the fact that it is far easier to homogenize than temperature and precipitationtemperature and precipitation

• Digitization needs to be justified and one important Digitization needs to be justified and one important user of weather data is the Insurance Industryuser of weather data is the Insurance Industry

• Windstorms are the major insurance peril in Europe, Windstorms are the major insurance peril in Europe, and claims far outweigh fluvial or coastal floodingand claims far outweigh fluvial or coastal flooding

• Daily data are vital to develop long-term trends in Daily data are vital to develop long-term trends in circulation features and provide the best means of circulation features and provide the best means of developing long series that are proxies for windinessdeveloping long series that are proxies for windiness

• Sub-daily (e.g. 3-hourly) data can be used to provide Sub-daily (e.g. 3-hourly) data can be used to provide long series of rapid deepening rates of stormslong series of rapid deepening rates of storms

Pressure Triangle approach Pressure Triangle approach developed by Hans developed by Hans AlexanderssonAlexandersson

Extension of this back to 1750 for NW Extension of this back to 1750 for NW EuropeEurope

• Daily MSLP digitized for Paris (back to 1675, Daily MSLP digitized for Paris (back to 1675, with gaps in the 1730s/1740s), London with gaps in the 1730s/1740s), London (back to 1693, but with gaps in the (back to 1693, but with gaps in the 1710s/1720s) and De Bilt (back to 1706)1710s/1720s) and De Bilt (back to 1706)

• With these three sites the triangle approach With these three sites the triangle approach will be able to put the high values seen in will be able to put the high values seen in the 1880s into a longer-term context the 1880s into a longer-term context

• Paris/London MSLP difference is also a very Paris/London MSLP difference is also a very good NAO index for the wintergood NAO index for the winter

ConclusionsConclusions

• Many long MSLP records exists, but much Many long MSLP records exists, but much is monthlyis monthly

• The daily should exist but finding it is often The daily should exist but finding it is often the problemthe problem

• Many NMSs unaware of the potential Many NMSs unaware of the potential usefulness of daily and sub-daily MSLP usefulness of daily and sub-daily MSLP datadata

• ERA-75 won’t be any better than ERA-40 ERA-75 won’t be any better than ERA-40 for the pre-1979 period if more for the pre-1979 period if more observational data are not addedobservational data are not added