annuncio

Comprimi
Ancora nessun annuncio.

Swiss frost hollows: kaltluftseen.ch

Comprimi
X
 
  • Filtro
  • Ora
  • Visualizza
Elimina tutto
nuovi messaggi

  • Swiss frost hollows: kaltluftseen.ch

    Abbiamo il piacere di ospitare nel nostro forum alcune rilevazioni e commenti da parte di un project manager di Meteo Swiss, il Sig. Stephan Vogt.

    Eccezionalmente questo thread sarà in lingua inglese in modo da poter condividere le nostre conoscenze ed informazioni.

    Stephan ha un sito per il suo progetto: https://kaltluftseen.ch/

    Benvenuto a Stephan

    We have the pleasure to host in our forum some temperatures reporting and comments by a project manager from Meteo Swiss, Mr.. Stephan Vogt.


    Exceptionally this thread will be in English so that we can share our knowledge and information.

    Stephan has a web site for his project: https://kaltluftseen.ch/

    Welcome to Stephan
    La temperatura rilevata nelle “frost hollow” come la matematica non è un’opinione, chiedilo agli abitanti di Oymyakon

    Stazione meteo Levico Terme, quota 490 metri


    Stazione meteo Compet, quota 1390 metri

  • #2
    Welcome Stephan!

    I've already gone through your website, very nice job! I'll be waiting to read some news about the frost hollows you're currently monitoring soon

    Riccardo
    Davis Vantage PRO 2 - Volpago del Montello (170mslm)
    Monitoraggio dei siti freddi del Montello (Valle di Piero Gobbo) e dei colli Berici (Busa Maran)
    Tutti i dati su: http://montellometeo.altervista.org

    Commenta


    • #3
      Onorevoli colleghi!

      Mille grazie per l’opportunità di beneficiare della vostre esperienza!

      Unfortunately my Italian is more or less inexistant, so I appreciate your offer to share our experiences in English. As already mentioned, I'm working at MeteoSwiss in the Data Integration departement but my activities in the field of frost hollows is done on a completely private basis.

      I found this forum while serching for literature on frost hollows. "Le fabbriche naturali del freddo" by Bruno Renon was an inspiration for my work and as far as I understood and learned your group managed it to create a group of passionates which ist helping to run your unique measurement network. I wish you all the best in your activities!

      So far I run two stations in the north eastern part of Switzerland in the Alpstein massif. Perhaps you know Säntis (2502 m) which its famous mountain weather station.

      My first station at Lake Sämtis is running since April 2, 2016. It is situated in one of the deepest sinkholes in Switzerland (~70m):

      Here is a link to the topographic map of Switzerland: https://map.geo.admin.ch/?topic=ech&lang=de&bgLayer=ch.swisstopo.pixelkarte-farbe&layers=ch.swisstopo.zeitreihen,ch.bfs.gebaeu de_wohnungs_register,ch.bav.haltestellen-oev,ch.swisstopo.swisstlm3d-wanderwege&layers_visibility=false,false,false,fal se&layers_timestamp=18641231,,,&X=237391&Y=752292& zoom=7&crosshair=marker

      First results show that this frost hollow has a clear saisonality due to the presence of a lake. In addition it is very vulnerable to Föhn (downstream of the Rhine valley), resulting in remarkable temperature jumps. The Sky View factor is not optimal (0.84 - 0.87 at the ground).

      I have the luck that there is a webcam installed on a nearby mountain which provides insights into the frost hollow. it allows to derive additional information (presence of snow, lake frozen?) and form time to time there are beautiful pictures available like this one:



      My second station is in the western part of the Alpstein in the village of Alt St. Johann in the Gräppelen valley. The Hintergräppelen sinkhole is slightly higher (~1290m on the ground), a little bit more than 40 m deep and has a higher Sky View Factor (>0.9) in the lower areas of the sinkhole:

      Note: in transparent blue, the contributing area to the frost hollow is marked.

      Mainly due to the better Sky View Factor the minimal temperatures are some 6 - 9 K lower than at Lake Sämtis:



      On January 6, I recorded the so far lowest temperature in Hintergräppelen with a handheld thermometer. I managed it to take a picture at -34.9 °C but I could read -35.8 °C as minimum:



      Due to the low temperature I was not able to collect the data from the logger (the notebook was not working any more...). This value is lower than any other station in Switzerland for the morning of January 6. Of course this value has to be regarded carefully and I plan to visit my stations on the next weekend. This will allow me to receive a reference for the temperatures taken with the handheld thermometer.

      So far from my side at the moment...

      Best regards and thanks again for your warm welcome!

      Stephan
      File allegati

      Commenta


      • #4
        Thanks to share with us your experience. I Think you could find many iter experience and stories in this forum from 2008. I Hope that we Can create a Great discussion in English. If you have any question about our instruments or equipment or type of logging temperature..we Will help you to improve your sinkhole adventure. Thanks to join us!!
        ...dal caldo sahariano, passando per la mitica brezza, arrivando al freddo dolinatore...

        Commenta


        • #5
          Hi Stephan,
          according to the cartographic data of Lake Sämtis site (seen in the map you pointed out before) it is not a real concave area, as revealed by the presence of the outflowing stream from the lake. It seems, instead, a flat plain at the bottom of a glacial valley, is it correct? So it could explain why you didn't measure, until now, very low temperatures there (clearly less cold than Hintergräppelen).

          Commenta


          • #6
            Dear Bruno, Lake Sämtis is an entirely closed frost hollow, about 70 m deep. Just one quick link: http://www.appenzellerlinks.ch/Appen...emtisersee.htm

            More this evening...

            Regards, Stephan

            Commenta


            • #7
              This picture should clarify your question: http://kaltluft.myhostpoint.ch/pics/...e-1024x724.jpg

              Commenta


              • #8
                Oh, excuse me Stephan, you’re right…
                I had a quick look to the map and seemed that there was a tributary (inflowing) stream of the lake on the right (East) and an outflowing stream on the left (West). Instead there are two tributary streams.
                70 m deep…such an impressive frost hollow! I’m curious to see its performances in these weeks, with frozen lake and a good snow cover

                Commenta


                • #9
                  Lake Sämtis is indeed a rather special frost hollow. It has a glacial origin and the ground has been sealed with loamy morain material. Just after the last ice age the entire sink hole was filled up with water. The lake drained superficially in north eastern direction. Over the time carstic processes resulted in sub-terrain drainage - and this may be unexpected - in eastern direction into the Rhine valley. This has been shown with tracer experiments in the early twentieth century.

                  Another special aspect is the fact that the contribution superficial catchement of Lake Sämtis comprises two upstream sinkholes (no dataloggers present up to now...). Here is one picture from Lake Fälen (one of these upstream sinkholes) taken in December 2016, when exceptionally no snow was present. Black ice formed on the lake and the cold air pool is marked with rime:


                  reference: https://www.facebook.com/chrisbufoto...74463275970772

                  My last visit to download data from the logger @ Lake Sämtis was on November 20, 2016. We had a short period in November with winter conditions where the temperature dropped to -13.3 °C - which was a bit disappointing... The sinkhole was covered with snow and black has formed for the first time of the year, but every thing melted away after a few days.

                  The best radiation properties are of course present when the lake is covered with ice AND snow: the radiation properties are then identical with the snow covered land surface. If you have snow on the land surface and black ice on the lake, radiation properties are different and I assume that a certain air circulation starts - which is not favourable for very low temperatures. Of course this circulation is reduced compared with an open water situation - but how big is the difference between "black ice" vs. "snow covered ice"? I'm looking foreward to my field trip this weekend: New data - new insights... Do you have frost hollows including a lake on the ground? What are your experience with this kind of frost hollows?

                  Commenta


                  • #10
                    It is a really interesting matter, Stephan...
                    We have monitored for 5-6 years (2006-2011) a frost hollow (Lago di Fosses, that means Fosses Lake) with a lake at its bottom (2142 m), but smaller than Lake Sämtis.
                    Its absolute minimum temperature was -37.5°C (January 4th 2009)


                    Honestly I've never focused on this matter, I sholud examine better the data to understand better the effect of the lake at the begin of the winter.
                    I'll tell my opinion this evening about the role of "black ice" and "snow coverd ice".

                    Meanwhile, Lake Sämtis frost hollow is in perfect ground/snow cover conditions for very low temperatures in these days...
                    Here the situation this morning, at 8am (on the right the Lago di Fosses frost hollow)
                    File allegati

                    Commenta


                    • #11
                      I have examined the data of Lago di Fosses from October to December in the period when the data logger worked (with snow, without snow, before and after days with temperatures below -10°C when the lake could has been frozen) but I have found nothing of interesting.
                      In fact it is not easy to analyze and understand the few cases with snow at ground and "black ice" on the lake.
                      About you theory of the air circulation triggered by the difference of radiation balance between the frozen lake (without snow) and the surrounding meadows covered by snow, I think it is credible, but it is probably very weak and not so strong to influence the radiation cooling of that huge frost hollow.
                      But, you know, we should do an accurate monitoring of temperatures and winds there, to have the answer.

                      Anyway, I'm looking forward to hearing your news from Lake Sämtis!

                      Commenta


                      • #12
                        Dear all

                        I visited my two stations in the frost hollows in the Alpstein. More details later, just the highlights:



                        -38.2 °C @ Hintergräppelen and -33.4 °C @ Lake Sämtis on January 6...

                        Best regards, Stephan

                        Commenta


                        • #13
                          Originariamente inviato da Stephan Visualizza il messaggio
                          Dear all

                          I visited my two stations in the frost hollows in the Alpstein. More details later, just the highlights:



                          -38.2 °C @ Hintergräppelen and -33.4 °C @ Lake Sämtis on January 6...

                          Best regards, Stephan
                          Amazing results! The Hintergräppelen one, especially, is very significative due to its modest altitude.

                          Great job Stephan

                          Sent from my Nexus 5 using Tapatalk
                          Davis Vantage PRO 2 - Volpago del Montello (170mslm)
                          Monitoraggio dei siti freddi del Montello (Valle di Piero Gobbo) e dei colli Berici (Busa Maran)
                          Tutti i dati su: http://montellometeo.altervista.org

                          Commenta


                          • #14
                            Dear all

                            Here is the monthly overview for Hintergräppelen, updated until January 22:

                            Commenta


                            • #15
                              Dear Stephan,

                              Hintergräppelen is definitely a good frost hollow, also considering, as Gasgallo said, it is located at middle elevation.
                              The data of January 6th are very interesting:

                              1 - after a cloudy and/or windy night, since 4am the temperature suddenly dropped due to the clearing up and/or to the calming of the wind and this strong cooling continued until 9-9.30am

                              2 - since 10am the temperature has increased but slighty, in fact the maximum was -29.5°C (the heat's release of snow was probably strong during the sunny hours too)

                              3 - as soon as the sun began to go down the temperature has begun to drop continuosly (already -36°C at 6pm) until late evening, when the cooling stopped (minimum temperature of the night was -38.2°C around 9-10pm). In fact all night long temperature remained stable between 37.0°C and 37.4°C. This has been probably caused by a considerable mild and dry advection above the frost hollow, especially between 1500 and 2500 m. Milder air aloft could have increase the downward longwave radiation of the sky, that would have block the further cooling of airmass enclosed in the hollow.

                              Are you agree with me?

                              Commenta

                              Sto operando...
                              X