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		   EMULATE: land station daily MSLP series
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86 Land station daily MSLP series were included in the final gridded  MSLP
product, EMSLP3.   Two MSLP series for each of the 86 stations are provided 
here.   These correspond to the 'uncorrected' and 'corrected' series.   The  
corrections will be described in detail below.  Firstly, the format of the
files  is described. 
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1. Format

Each file is in ascii format.  There are two lines of header information.  
The first line is the station name (including the directory). 

The second line contains some important station details:  
station_number, first_year, last_year, latitude, longitude, station height

eg. For  La Coruna

  8001  1865  2002   4316   -850     58
  
The series then follows with 
year, month, day, pressure 


Notes:
* the pressure is at mean sea level and is given in hPa.
* missing MSLP values are given as   -999.90
* if there is no station number, it is given 99999
* station height is given in metres
* if no details of station height were available, we used the height given in 
  the WMO records
* if a change of height was known, we took an average of the heights. 
* latitudes are in degrees (not degree and minutes) x 100.  For example: 
  45 degrees N, 30 minutes = 45.5 x 100  => 4550
  43 degrees N, 15 minutes = 45.25 x 100 => 4525
* longitudes are in degrees (not degrees and minutes) x 100.  West is denoted  
  by negative values.  For example, 
  30 degrees E, 12 minutes = 30.2 x 100 => 3020
  10 degrees W, 55 minutes = -10.92 x 100 => -1092

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2. 'Uncorrected' Series 
These files are denoted by the file ending : .ts.asc 
For example for Malta the filename is: 

emulate_malta.ts.asc

Although they are classed here as 'uncorrected', many of these stations have 
undergone considerable quality control (eg. WASA, IMPROVE stations, Durham
etc).  We call them 'uncorrected', because we (at the Hadley Centre)  have
applied minimal corrections - they are  basically in the form that we received
the data in.  Minimal corrections refer to  correcting  typos, calculating the
daily average, filling in missing data points in a couple of stations (using a
different source) and reducing Hohenpeissenberg, Jena, Milan and Athens to mean
sea level. 

As other groups have spend considerable time working on these series  (a big
thanks to David Lister, Manola Brunet-India, Anders Moberg etc), it is 
appropriate to give the main point of contact for each of these 'uncorrected'
series.   The name given below does not always correspond to the original
source of the data,  however they can probably point you in the right
direction! 


aberdeen:  WASA & R. Allan             london : Rob Allan
alexandria:  R. Allan                  lugansk: D. Lister
algiers:  R. Allan                     lund: WASA
ammasalik: WASA                        lyon: R. Allan
angra:  R. Allan                       madrid: M. Brunet-India
archangel: D. Lister                   malta: D. Lister 		     
armagh: R. Allan                       milan: IMPROVE
astrakhan: D. Lister                   montreal: V. Slonosky
athens: R. Allan & D. Founda           moscow: D. Lister
baghdad: R. Allan                      nikolaef: D. Lister
barcelona: M. Brunet-India             nordby: WASA & A. Moberg
beirut: R. Allan                       oksoyfyr: WASA & A. Moberg
bergen: WASA & A. Moberg               orenburg: D. Lister
bermuda: D. Lister                     padua: IMPROVE
biarritz: R. Allan                     palermo: M. Barriendos
biskra: R. Allan                       paris: M. Barriendos
bodo: WASA & O. Nordli & D. Lister     plymouth: R. Allan
brest: R. Allan                        potsdam: WASA
cadiz: M. Brunet-India & IMPROVE       prague: D. Lister
corfu: D. Lister                       providence: D. Lister
debilt: T. Brandsma                    reykjavik: P. Jones
diarbekir: R. Allan                    riga: D. Lister
durham: D. Lister                      rochefort: R. Allan
fao: R. Allan                          rome: R. Allan
funchal: R. Allan                      scutari: D. Lister
galway: R. Allan (K. Hickey)           sevastopol: D. Lister
gibraltar: M. Rodwell & D. Wheeler     sibiu: D. Lister
godthaab: R. Allan                     stjohns: V. Slonosky
goteborg: WASA & A. Moberg             stockholm: WASA & A. Moberg
halifax: D. Lister & V.Slonosky        stornoway: R. Allan
hammerodde: WASA                       stpetersburg: D. Lister
haparanda: WASA & A. Moberg            stykkisholmur: WASA
harnosand: WASA                        tenerife: M. Brunet-India
helsinki: WASA                         tiflis: D. Lister
hohenpeissenberg:  J. Jacobeit         torshavn: WASA & A. Moberg
jena: T. Ansell & F. Gerstengarbe      toulon: R. Allan
kazan: D. Lister                       uppsala: WASA & A. Moberg
kem: D. Lister                         valentia: WASA & R. Allan
kiev: D. Lister                        vardo: O. Nordli & D. Lister 
kostroma: D. Lister                    vestervig: WASA	
lacoruna: M. Brunet-India              visby: WASA & A. Moberg
lesina: R. Allan                       wilna: D. Lister
lisbon: R. Allan                       zagreb: L. Srnec
 
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3. 'Corrected'

These files are denoted by the file ending : .ts.diurnal.adj.asc
For example for Malta the filename is :
emulate_malta.ts.diurnal.adj.asc

Firstly we apply a correction for the diurnal  and semi diurnal oscillation.  We
use the phase and amplitude fields (seasonal)  calculated by Dai and Wang (1999)
to estimate the diurnal & semi diurnal cycle at each  station.  Observation
hours for each day of a station series have been produced  and these are then
used to determine the appropriate adjustment, given the cycle.   Due to a lack
of sufficient sub-daily data, we were unable to calculate  the diurnal and
semidiurnal cycle at each station directly.  The Dai and Wang fields are on a
5x5 degree latitude longitude grid and hence we interpolate  the nearest grid
point to our station.  It is rather a crude adjustment, however  corrections are
generally small and, as stated above, it was not possible to estimate  diurnal
waves  directly for each station in this project. 

Secondly, we adjust the series such that the monthly mean is equal to a
reference monthly mean (either the corresponding ADVICE station series, that 
interpolated from the nearest ADVICE  grid point, or from the nearest HadSLP
grid point).   Specifically, the monthly means are calculated from the daily
series and compared  to the reference ADVICE/HadSLP monthly value.  The
difference in  monthly means is then used to adjust the daily SLP values.  There
was some concern  about jumps in adjustments at the end of each month, so a
slight smoothing  was applied to the monthly adjustments.  Preference was given
to the ADVICE station  series where possible, however in some cases problems
were found with the ADVICE  station series.  In these instances, the ADVICE
gridded value was used. 

For the Canadian stations and those in the far east of the EMULATE region a
final  adjustment was required so that their daily average represented the same
24 hour  period as the other series. The Canadian stations are 5 hours behind,
the  Russian 4 hours ahead.   As only daily averages were available, we were
forced  to interpolate between the preceding (following) day and the actual day
for  the Canadian (far Russian) stations. 

These are denoted as : ts.diurnal.adj.gmt.ts

Finally after all quality control checks were performed, a number of remaining
gross  outliers were identified.  These were either corrected or replaced with
missing  values.  This effected 4 stations and these are denoted:  
ts.diurnal.adj_g_error_corr.ts.asc

eg. 
emulate_gibraltar.ts.diurnal.adj_g_error_corr.ts.asc

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4. Remaining issues

We do still have come concerns about the quality of a number of series.  To
properly  quality control 86 stations would require more than time allocated to
the whole of  the EMULATE project.  Because the data would undergo further
quality control in  the gridding procedure, we decided to proceed with the
stations series as they stood.   For research being conducted with individual
station series, we would recommend  however that some caution to be exercised. 

Any feedback would be extremely useful!


Tara Ansell

tara.ansell@metoffice.com
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5. References

Dai, A. and Wang, J. (1999) 'Diurnal and Semidiurnal Tides in Global Surface
Pressure Fields', J. Atmos. Sci., 56, 3874-3891

