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Observation of Noctilucent Clouds in Austria

(English Summary)

(k.kaiser@mail.asn-linz.ac.at)

Short descriptions of the years with NLC-observations: 

1995 - 1996 - 1997 - 1998 - 1999 - 2000 - 2001 - 2002 - 2003 - 2004 - 2005 - 2006 - 2007 - 2008

Survey of NLC-pictures:

1995, 1997, 1998, 1999, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008

 

nlc153-22mi.JPG (9504 Byte)

Is it possible to see the midnight dawn in Austria? During the days of solstice I decided to search for the midnight dawn on top af the look-out tower at the Moldaublick (1020 m, 48° 42´N, 13° 58´ E). This mountain is situated in the Austrian part of the Bohemian Forest near the boarder to Czechoslovakia. I´m shure that this peak is one of the best sites for observation because there are only few small villages beyound the border, so light pollution is minimized.

Midnight dawn and the first Noctilucent Cloud

The evening of June 29th, 1995 seemed ideal for my observation: Only some cumuli, which would dissolve, no moonlight and comfortable temperature. At 2030 UT a fabulous night began: Marvellous dark sky, shooting stars, satellites and the diminishing brightness of the dawn on the horizon. I was able to see the rest of the dawn till 2230 UT! In my camera I used an ISO 1000/36° colour slidefilm and indeed the horizon in the north direction was brightened at 2300 UT! At 0030 UT, when dawn had already proceeded , I wanted to complete the observation with a last view at the brightening horizon. What a big surprise: Using my field-glass I recognized the typical shapes of Noctilucent Clouds - bands and waves - "my" first NLC, maybe at the south coast of the Baltic Sea in 500 km distance! The brightness and the extension of the cloud increased in the next 30 minutes. It was an unforgetable event! Unfortunately this remained a single sighting until 1997. I was told that this cloud was perhaps the first  NLC that was photographed in Austria ! Times of observations during the year 1995.

1996: No NLC´s were visible in Austria. Times of observations 1996.

Highlights of the year 1997: On the evening of June 9th, 1997 I got a call from Chemnitz (a town in Germany, 200 km northwest of Schlägl) that bright NLC´s were visible. Unfortunately low clouds moved over the Bohemian Forest. On the next morning the sky was clear and a wonderful Noctilucent Cloud was visible. During the following weeks I searched for the clouds on every clear evening and morning and succeeded on 5 more days. Unexpected were the vertical and horizontal extensions: Some clouds reached a height of 15° and a width of 59°! Times of observations 1997.

In the year 1998 I searched for NLC´s 25 times from June 6th till July 21st, but only on June 23rd I saw faint bands on the NNW horizon between low dark clouds. The observation on this day especially showed that in southern latitudes it is not easy to find NLC´s if their brightness and vertical extension are very low. An inexperienced observer could easily overlook the phenomenon.

In the year 1999 I saw the first NLC in the evening of June 22nd. In the night of the 2nd to the 3rd of July the activity of the Noctilucent Clouds reached its peak during my five years of observation: The first bands and waves where visible in the evening in Schlägl. The following morning at the Moldaublick I rejoiced at "my" most beautiful, brightest and richest structured NLC´s with veils, bands and waves! I was very impressed by the shape changing so quickly during the 60 minutes of my observation! Times of observations during the year 1999.

2000: During this year no NLC´s were visible in Austria. Times of observations during this year.

2001: Only on June 27th I watched a NLC this year. Only some minutes I could view the cloud with my field-glass because of high Cirrus, Cirrostratus and Altocumulus. Other successful observations during this night were made in England, Scottland, Finland and East-Germany (Frankfurt an der Oder). My observation-intervals during 2001.

2002: 2002 was one of the worst years for NLC-observers in Europe. Only few observations where made in May and June, a little bit more in July. I have to say that in the northern parts of Central Europe and on the British Islands the weather conditions did not allow a continuous search. But in Austria the meteorological situation was perfect. Not before my 33rd observation-interval I succeeded: On  July 6th a very extended NLC was visible - maximum elevation 50°, horizontal dimension 90°! The cloud was clearly structured with veils, bands, waves and quickly changing whirls. I think no one else has observed that cloud this morning. North-north-west of this extended NLC there was a second, a much smaller and fainter one, only few degrees above the horizon. Another NLC appeared in the evening of July 9th within cirrus near the north-western horizon. 

2003: During the night from 20th to 21st of June NLC´s where watched  by some observers in Central Europe. This year my observation campagne started in the evening of June 21st and next morning I already succeeded. It was a remarkable cloud because of its extensive expansion in azimuth: 050° to 112°! The NLC showed small veils, fine waves and a lot of bands. I had to finish my Austrian observations on July 1st due to travelling from Denmark to Iceland by ferry. On July 6th a Noctilucent Cloud appeared in the evening sky over the North Sea. Observation-intervals during 2003.

2004: The first NLC this year did not appear before the 23rd observation intervall on July 7th. A cloud with a lot of long bands was seen in the north-west direction. On the next day it was possible to watch Noctilucent Clouds in the morning and evening. The conditions for their developing must have been excellent in the upper atmosphere for a long time - many observations were made in widespread northern areas in these days. The last NLC of this year appeared in the evening hours of July 11th - maybe the most faintest cloud I have ever watched and photographed during my 10 years of observations! It's most remarkable that in this season we can read about NLC-descriptions from the Czech Republic (Prague: 1st/2nd July; Jesenik: 3rd/4th July)! Observation-intervals during 2004.

2005: In the northern areas of Central Europe the NLC season has not started before the night of the 10th to 11th of June. First observations were reported from northern parts of Germany and Denmark. During the following days a lot of NLC´s were mentioned in www-forums. In Austria the first Noctilucent Cloud was watched on the evening of June 19th, the next during the morning hours of June 23rd. One of the most impressive clouds was visible on July 18th with a horizontal extension of about 90°, but only with a maximum elevation of 8°. Some German observers took beautiful images; so it is possible to compare the sightings from Austria and Germany. The fourth NLC was visible in the early morning of July 20th. This year some observations of Noctilucent Clouds were possible from a latitude lower than 50°N (Odenwald and Wendelstein in Germany). It was the first time that a NLC was seen from the northern parts of Lower Austria (evening of 10th of June 2005). Sorry, there is no picture available. Observation-intervals during 2005.

2006: The NLC-season 2006 is one of the best in Austria I have ever had. In my country it started during the night of the 7th to 8th of June. A Noctilucent Cloud with unincredible extension was watched during the morning hours of 13th of June: I observed faint structures of the cloud near the horizon in south direction! An astronomer in Lower Austria took some images too. It is nice to compare the structures of the cloud from different places. There are very nice pictures that were taken in Churáňov in the southern parts of the Czech Republic. This cloud was visible in northern Italy: Rocca Malatina (Emilia-Romagna; 44,4° N) and Venice too! The brightest Noctilucent Cloud I had ever observed was visible in the morning of July 14th. The last NLC of the year was watched in the evening hours of July 22nd. No other observation of Noctilucent Clouds was reported on that day in Central Europe. Observation-intervals during 2006.

2007: On June 3rd the first  "German" NLC of this season was visible to observers in northern parts of the country. In Austria the first Noctilucent Clouds were watched on June 15th and 17th during the evening hours in Vienna. More observations in Vienna: in the morning of June 24th and July 1st, during evening hours of June 28th, 29th and July 13th. In Schlägl I took images of 5 different clouds during the morning hours of June 24th, 29th and July 1st and 14th and in the evening of July 13th. The most spectacular phaenomenon of the year 2007 occured in the morning of June 24th: horizontal extension of the NLC - 118°, maximum elevation - 40°, brightness - 4! An Italian observer took images of this cloud at the very low latitude of 43,8°N at Verghereto (northern Italy)! A big surprise was the observation of an NLC at Palmela, Portugal, at the very low latitude of 38° 34' during nighthours of June 29th/30th 2007. This year more people kept watch for Noctilucent Clouds in Austria. Together we took images of 9 different NLC´s!  Observation-intervals during 2007.

2008: The first NLCs of Central Europe were watched during the morning hours of June 13th in northern parts of Germany and The Netherlands. This year Austrian observers watched Noctilucent Clouds only on 2 days: in the morning hours of July 2nd and during the evening of July 21st. The second cloud was visible in Vienna too. This year observers got informations of sightings from Turkey (40° 31' N - July 12th/13th 2008) and Spain (41,67° N - July 13th/14th 2008)! Have a look at the images on this website: Noctilucent Cloud Observers' Homepage. There are also some reports of Noctilucent Clouds that were visible in Hungary. Very interesting for NLC observers are some webcams in the Czech Republic: It is possible to search for NLCs in the video archive - both Austrian observations are recorded! Observation-intervals during 2008.

 

Retrospect and outlook

Looking back at more than ten years of very successful observation I ask why NLC´s are very seldom seen at latitudes lower than 50°. Reasons for this could be:

It would be desirable if more observers looked out for NLC´s in the more southern latitudes during the next years because I´m sure they are not as rare a phenomenon as we have suspected.

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Summary of the "Austrian" NLC-observations

Datum Beobachtungsintervall (UT) Horizontalausdehnung in ° Höhe des Wolkenoberrandes in ° Beobachtungsort * Helligkeit ** Formen ***
30.06.95 0045 - 0135 37 8 Moldaublick 2 II
10.06.97 0055 - 0200 25 6 Moldaublick 2 II, III
11.06.97 0045 - 0130 20 3 Schlägl 1 II
15.06.97 2000 - 2105 52 15 Schlägl 2 II, III
16.06.97 0045 - 0145 >40 15 Schlägl 2 II ****
21.06.97 0040 - 0145 26 12 Schlägl 2 II, III
08.07.97 2000 - 2055 59 10 Schlägl 1 II
23.06.98 0100 - 0200 18 4 Schlägl 1 II
22.06.99 2040 - 2100 34 5 Schlägl 2 II
02.07.99 2015 - 2045 11 11 Schlägl 2 II, III
03.07.99 0100 - 0200 41 10 Moldaublick 2 bis 3 I, II, III
27.06.01 2005 - 2050 2 3 Schlägl 1 II
06.07.02 0105 - 0220 105 ***** 50 Schlägl 2 I, II, III, IV
09.07.02 1955 - 2110 7 3 Schlägl 1 II
22.06.03 0100 - 0205 62 15 Schlägl 2 I, II, III
07.07.04 2025 - 2100 25 5 Schlägl 1 II
08.07.04 0045 - 0140 15 2 Moldaublick 1 II, III
08.07.04 2025 -2110 18 5 Neudorf bei Halsach 1 II, III
11.07.04 2005 - 2100 5 5 Schlägl 1 II, III
19.06.05 2005 - 2110 25 5 Schlägl 2 I, II, III
23.06.05 0110 - 0205 40 20 Schlägl 2 I, II, III
18.07.05 0115 - 0215 90 8 Schlägl 2 I, II, III
20.07.05 0115 - 0225 27 8 Schlägl 1 II, III
08.06.06 0105 - 0155 31 8 Schlägl 2 I, II, III
13.06.06 0105 - 0220 200 42 Schlägl 3 I, II, III, IV, V
14.07.06 0120 - 0250 126 45 Schlägl 4 I, II, III, IV, S
22.07.06 1955 - 2030 60 10 Schlägl 2 I, II, III
24.06.07 0105 - 0220 118 40 Schlägl 4 I, II, III, S
29.06.07 0115 - 0200 1 8 Schlägl 1 II ****
01.07.07 0110 - 0200 26 8 Schlägl 1 II
13.07.07 2010 - 2050 57 15 Schlägl 2 bis 3 I, II, III, S
14.07.07 0115 - 0155 33 8 Schlägl 2 I, II, S
02.07.08 0115 - 0150 102 10 Schlägl 2 I, II, III
21.07.08 1940 - 2045 42 10 Schlägl 2 I, II
             

* Moldaublick: 48° 42` N; 13° 58´ E; Neudorf bei Haslach: 48° 33' N; 14° 03' E; Schlägl: 48° 38´ N; 13° 58´ E

** 1: NLC very weak; 2: clearly detected; 3: clearly visible; 4: very bright; 5: extremely bright

*** I: veil; II: bands; III: waves; IV: whirls; S: NLC with bright "knots"; V: NLC with net-like structure

**** Observation was impaired by clouds

***** Whole area of two separated clouds

Summary: Times of observations

Survey of NLC-pictures: 1995, 1997, 1998, 1999, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008

References:

Filling, H. (1998): Leuchtende Nachtwolken, Mitt. Arb.kr. Geschichte der Geophysik DGG/Deutsche Geophysikalische Gesellschaft, Bd. 17, p. 52 - 63

Gadsden, M., Schröder, W. (1989): Noctilucent Clouds, Springer-Verlag, Heidelberg

Kaiser, K. (1995): Helle Sommernacht in Österreich mit Überraschung, Mitt. Arb.kr. Meteore 20/8, p. 15-16

     -          (1995): Leuchtende Nachtwolke von Österreich aus beobachtet, Sterne und Weltraum 34/12, p. 922

     -          (1998): Beobachtung Leuchtender Nachtwolken von Österreich aus, Astro Info 139, p. 61- 62

     -          (1998): Leuchtende Nachtwolken im Sommer 1997 von Österreich, Meteoros 1/2, p. 49

     -          (2003): Beobachtung Leuchtender Nachtwolken in Österreich, Jahresbericht BG/BRG Rohrbach 2002/2003, p. 96 - 100

     -          (2005): Beobachtung Leuchtender Nachtwolken in Österreich im Zeitraum 1995 bis 2002, Lectures in Geophysics and Physics, Bd. 6/2, p. 46 - 51

Minnaert, M. (1992): Licht und Farbe in der Natur, Birkhäuser Verlag Basel-Boston-Berlin

Neckel, Th. (1998): Leuchtende Nachtwolken in der Nacht vom 9. zum 10. Juni 1997, Sterne und Weltraum 37/7, p. 666 - 669

Rendtel, J. (1995): Leuchtende Nachtwolken 1995 - eine erste Zusammenfassung, Mitt. Arb.kr. Meteore 20/11, p. 17-18

     -            (1996): Leuchtende Nachtwolken 1996 (III), Mitt. Arb.kr. Meteore 21/8, p. 127-131

     -            (1998): Beobachtung Leuchtender Nachtwolken 1997, Meteoros 1/2, p. 43-49

     -            (1998): Leuchtende Nachtwolken im Mai, Juni, Juli, August 1998, Meteoros 1/6-10, p.130-131, 150-151, 169-170, 186

     -            (1999): Leuchtende Nachtwolken im Mai, Juni, Juli, August 1999, Meteoros 2/6-9, p. 99-100, 122-123, 145-146

Schlegel, K.(2001): Vom Regenbogen zum Polarlicht, Spektrum Akademischer Verlag, Heidelberg-Berlin

Schröder, W. (1998): Noctilucent Clouds/Leuchtende Nachtwolken, Science Edition/IAGA, Bremen

Links:

Noctilucent Cloud Observers' Homepage (Tom McEwan)
Noctilucent Cloud Observers‘ Forum
Noctilucent Clouds Homepage (University of Colorado)
NLC-sites, Arbeitskreis Meteore e.V. (Deutschland)
NLC-Seite von Ole Skov Hansen (Dänemark)
NLC-Seite von Tomas Trzicky (Tschechien)
NLC-Seite von Tom Eklund  (Finnland)
NLC-Seite von Alexander Wünsche (Deutschland)
NLC-Seite von Mats Mattsson (Schweden)
NLC-Seite von Rainmaker (Deutschland)
NLC-Seite von Matthias Juchert (Deutschland, Österreich)
NLC Kamera Netzwerk des Leibniz-Instituts für Atmosphärenphysik e.V. an der Universität Rostock (IAP).

 

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