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    Clouds Bases

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    • ivo
      ivo Administrator @Gkikas LGPZ last edited by

      @Gkikas-LGPZ this is important info thank you

      Gkikas LGPZ 1 Reply Last reply Reply Quote 1
      • idefix37
        idefix37 Sailor Moderator @Gkikas LGPZ last edited by idefix37

        @Gkikas-LGPZ
        OK your example in Nuremberg seems to demonstrate that ICON 0°C isotherm is MSL, which is confirmed by the Ref. Manual.

        But how do you explain that this morning in Greece ICON shows on Windy a Freezing « altitude » at 0m in mountains of 1800m alt. approx. and, at close distance, in low land of 100m alt. approx., a Freezing « altitude » at 1300m.

        E8F2FBF6-81FC-4090-947A-A9CEB595A9CC.jpeg

        Switching to ECMWF we see the same figures at same places, but just with a lower resolution map.
        For me both ICON and ECMWF on Windy seem to display a Freezing HEIGHT AGL.

        Gkikas LGPZ 1 Reply Last reply Reply Quote 0
        • Gkikas LGPZ
          Gkikas LGPZ Moderator @idefix37 last edited by

          @idefix37
          It seems that you are right!
          So, I can give you those two explanations:

          1. DWD ICON ref. manual is wrong
            919531ff-c6fd-4e4a-a90f-cb4eb873cc08-εικόνα.png

          2. Windy uses a different parameter!

          I hope Windy team will investigate that.

          Gkikas LGPZ 1 Reply Last reply Reply Quote 1
          • Gkikas LGPZ
            Gkikas LGPZ Moderator @ivo last edited by Gkikas LGPZ

            @ivo
            Please check if Windy uses HZEROLOC parameter for frz. alt.(ICON).
            Read the comments above.

            1 Reply Last reply Reply Quote 0
            • Gkikas LGPZ
              Gkikas LGPZ Moderator @Gkikas LGPZ last edited by Gkikas LGPZ

              @Tomber42
              You speak German fluently. Isn't it?
              I'd be grateful if you ask DWD if there is a mistake in their reference manual
              https://www.dwd.de/SharedDocs/downloads/DE/modelldokumentationen/nwv/icon/icon_dbbeschr_aktuell.html
              (description of HZEROCL, Table 7.5, page 46 on Ref. Manual version 1.2.6).
              Above msl or above surface?

              1 Reply Last reply Reply Quote 0
              • Tomber42
                Tomber42 Moderator last edited by

                I'm at vacation tomorrow, so I write a text for you here and you can send it to dwd

                Sehr geehrte Damen und Herren,
                Ich hätte eine Frage zur Dokumentation des Icon Modell. In der Doku "insert link to dokument " sprechen Sie bei der Beschreibung von HZEROCL, Tabelle 7.5, Seite 46,Version 1.2.6 von MSL oder über Grund Höhe?

                Mit freundlichen Grüßen
                "your name"

                Greetings from Tomber

                Gkikas LGPZ 1 Reply Last reply Reply Quote 1
                • Gkikas LGPZ
                  Gkikas LGPZ Moderator @Tomber42 last edited by Gkikas LGPZ

                  @Tomber42
                  @idefix37
                  @ivo

                  DWD answered:
                  " the freezing level (HZEROCL) is provided in m ASL,
                  but it is set to zero (rather than the height of the model topography)
                  if the freezing level is at the surface.

                  However, I see that this should be changed in our diagnostic
                  calculation, as well as the scanning direction (which should be top-down
                  rather than bottom-up) in order to detect the uppermost freezing level."

                  So, dear idefix37, I think it answers your/our question!

                  btw how does AROME handle the subject?

                  idefix37 1 Reply Last reply Reply Quote 0
                  • idefix37
                    idefix37 Sailor Moderator @Gkikas LGPZ last edited by idefix37

                    @Gkikas-LGPZ said in Clouds Bases:

                    @Tomber42
                    @idefix37
                    @ivo

                    I think it answers your/our question!

                    btw how does AROME handle the subject?

                    Yes, I think... but to clarify the "Freezing altitude" layer on Windy, should we understand that this level is counted as Altitude above sea level, but when this level intersects terrain located at a higher altitude , then this level is measured in relation to the ground itself, as Height above the ground.
                    So this layer should be called FREEZING LEVEL, as sometime it is measured as ALTITUDE above sea level (asl), sometime as HEIGHT above ground.

                    In Windy, if you check the Freezing level with AROME it switches to ECMWF. So this layer is not available with this model

                    In the example below (left map) the Freezing level is at 2400m in West of the Alps and at 0m just above the high summits, as described here above for ICON.
                    On same locations, the Freezing altitude from AROME data on Meteociel (Right map) is shown at 2700-2600m even when this altitude intersects mountains at 3000 or 4000m.

                    8391598B-3576-493D-B977-4FB8A3919388.jpeg

                    So there are different ways to display the Freezing level as we could try to summarise with this sketch:

                    EDCC022F-6819-4D8F-BAFC-52F7277E3963.jpeg

                    I am more familiar with Freezing altitude asl, which is much more precise for outdoors activity in mountains. The Height above ground is too coarse due to the low altitude resolution of the orographic model integrated in the model itself.

                    Anyway, at least, it clarifies the way how this layer must be interpreted...

                    Thanks for your investigation

                    Alain

                    1 Reply Last reply Reply Quote 1
                    • dirk001
                      dirk001 @TZ last edited by

                      @TZ Hi there, I just checked this old post and it seems like Windy cloud base can still be < 50% cloud cover so you never changed over to ECMWF Ceiling? or am I missing something here in New Zealand? Lots of days when cloud base green around 2000m but cloud cover only say 20%.

                      1 Reply Last reply Reply Quote 0
                      • J
                        jpsurin @TZ last edited by

                        @TZ yes ceiling is really useful for pilots . it would be great to have this parameter available.

                        TZ 1 Reply Last reply Reply Quote 1
                        • TZ
                          TZ Administrator @jpsurin last edited by

                          @jpsurin It is already available as "Cloud base" layer.

                          1 Reply Last reply Reply Quote 0
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