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Original Temperatures: HISTALP

Posted by Frank Lansner (frank) on 23rd December, 2013
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The Austrian ZAMG website “HISTALPS” (http://www.zamg.ac.at/histalp) presents their versions of Alpine temperature data online for Austria and several nearby areas.

  
Fig 1

This is how some of the Austrian temperature series are presented by ZAMG/HISTALP. All (not only the datasets shown here) show recent years warmer than for example the warm periods around 1930-60, typically 0,5 – 1 K or more.

For all areas analysed in the ORIGINAL TEMPERATURES project we see that temperature stations in valleys or locations in shelter of ocean air (“OAS” areas) show little or no warming since the last warm period 1930-60.
Is it true when ZAMG / HISTALP claim there are no such temperature stations with little or no heat trend since the last warm peak around before 1930-60 in the entire Alp area and surrounding areas?

 
In the following, HISTALP versions of temperature data will be held against original versions from the meteorological yearbooks.

Fig 2

Some temperature stations from Alpine OAS areas. HISTALP versions (red) vs. Original (blue) from the Austrian meteorological year books. HISTALP show colder temperature data than shown in meteorological yearbooks 1940-70.

  
Fig 3

In the 2 last examples - Sonnblick and Villacher Alpe –the stations are OAA (Ocean Air affected) since the locations are located on mountains peaks.
These areas typically have more heat trend in original data and HISTALPS rarely change such data much.
  

Fig 4

From the DWD-file of German temperature data (see ORI-TEMPS GERMANY) 2 temperature stations are so far inside the mountain area of the Alps that they too display the typical OAS (Ocean Air Shelter) patterns of strong cooling in the mid 20´the century.
Again, the Original Austrian temperature data for such sites appears to be supported.

 
Fig 5

Some nearby Swiss OAS valley temperature stations close to Austria show pretty strong temperature decline around 1950-80.

HISTALP suggests that also a row of stations surrounding the Alps show warming, even in areas that are in shelter of ocean air. For example the South German Ocean air shelter area (See “B13” in ORI-TEMPS Germany) is represented in HISTALP by the stations Ulm and Augsburg:
 

Fig 6

Elevations around Ulm and Augsburg show that these location in a rather good shelter against the winds from the Atlantic, so we should expect little or no warming trend in temperature data.

    
Fig 7

From original German meteorological yearbooks it can be confirmed, that the shown German temperature data “DWD file” represents original data. For both Ulm and Augsburg we can see that the HISTALP staff has added around 1,2 – 1,4 K to the heat trend. The ECA Augsburg is also adjusted, but only with 0,1 K , and then as is sometimes the case, the German ECA data is cut of before 1947.

Hungary

  
Fig 8

2 Hungarian stations very near the Austrian border, Magyarovar and Szombathely also got a little “Homogenization” from the HISTALP crew. Then one station, Pecs, deeper into Hungarian territory, one of the best sheltered areas against ocean air in Europe. 
 
Fig 9

The drop in temperatures represented by the Pecs station 1934-1984 is common for this area, but nine the less, the staff at HISTALP have another viewpoint on this.
Slovenia

 
Fig 10

HISTALP use the Slovenian station Kocevje, but again, HISTALP has reduced temperatures of earlier decades.

 
Fig 11

HISTALP also show the urban station Ljubljana, capital of Slovenia, and on the illustration above we see Ljubljana temperature trend in comparison with original station data from the same area.

In context with Swiss temperature data ZAMG writes ont the HISTALP site:
“Due to legal issues the homogenised HISTALP Datasets for Switzerland are only available on request and with the explicit permission from MeteoSwiss. If you are interested get into contact with us for more details. “
So I cant download the HISTALP versions of Swiss data, but we can then instead make graphical comparisons:
First a few stations in valleys sheltered fairly well against ocean air.
 
Fig 12

The ECA version does not confirm the ZAMG version. The ECA version matches original data.
 
Fig 13

The ECA version does not confirm the ZAMG version. The ECA version matches original data.

And then a few stations exposed to ocean air:
 
Fig 14

For this Ocean Air Affected station with a stronger warm trend in original data, ZAMG chose not to change data. There are several of such stations used by ZAMG/HISTALP.
 
Fig 15

Davos is highly elevated, but still it is located in a valley and thus some signs of ocean air shelter location are visible in the temperature trends: In original data we see a stronger decline from 1950. ZAMG has removed the warmer temperatures before 1980.

 
Fig 16

Finally I noticed the French Dijon station that is located brilliantly in shelter of ocean air. For this station ECA only show back to 1960, but it is sufficient to reveal that ZAMG have changed Dijon data too.

Data Homogenizing or Data Pasteurizing ?
Do ZAMG/HISTALP Homogenize data from stations in ocean air shelters, stations with not so warm temperature trends? Or do they simply pasteurize (warm treat) data?
 

Last changed: 25th December, 2013 at 17:30:01

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