Time-lapse photography of clouds and other phenomena in the sky

Martin Setvak
 

Gallery 2020
 

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My recent timelapsing gear consists of two APS-C cameras: Samsung NX500 (with Samyang 12mm F2.0 NCS CS and Samyang 8mm F2.8 UMC Fisheye II lenses) and Ricoh GXR camera with its A16 (24-85mm) zoom unit. Comments on why I use these cameras can be found in the Introduction to time-lapse photography page, and my typical settings and additional comments on timelapsing with Ricoh cameras are here. Notes on timelapsing with the Samsung NX500 can be found here.   All the times below are given in UTC (GMT).  

Sources of satellite and other meteorological data used below: CHMI, EUMETSAT, NOAA CLASS and Copernicus.

Note: movie files below, which are stored as .mkv (encrypted here as x265 RGB) are identical to those stored as .mp4 (here encrypted as standard x264 YUV420p High), but should have somewhat better quality, namely in transitions of the blue sky (around sunset and sunrise). However, to play these, you will most likely have to do so outside of your browser, either using a system movie player, or one of the external ones (e.g. MPC-HC or VLC).
 



2020-02-17   07:15 - 08:42 UTC  (1h 27m)
Ricoh GXR-A16,  interval 5 seconds, speed 150x

20200217_0715-0842utc_Praha-Libus_1920x1080.mp4  (88 MB)
20200217_0715-0842utc_Praha-Libus_1920x1080_x265.mkv  (115 MB, H.265)

Helmholtz cloud waves, Praha - Libuš.    Waves in low clouds, which were formed by strong wind shear at levels around 2 km. Contrary to more frequent orographic waves, which form downwind of mountain ridges or islands and typically are quasi-steady or move very slowly, these wind shear-induced waves propagated very quickly in an eastward direction, even faster than the cloud base underneath. The wind shear can be nicely seen e.g. in this wind profiler plot from Temelín (south Bohemia, lower panel), and cloud height can be retrieved from the ceilometer plot from the same location (upper panel). The cloud height at the location from which the timelapse was taken (Praha-Libuš) can be seen in this ceilometer plot  (no wind profiler there). In both plots, the vertical lines outline the period of the timelapse sequence. The traditional sounding plot from Praha-Libuš from 06 UTC and 12 UTC shows that at levels near 2 km there was no significant inversion. Source of these plots: CHMI and EUMETNET e-Profile

The appearance of these waves from above can be seen in satellite imagery at higher pixel resolution. In this Meteosat-10 (MSG-3) HRV band image (at resolution of about 1x2 km for this region) from the beginning of the timelapse sequence, the individual waves can be resolved. The red dot indicates the location of Praha-Libuš (from where the timelapse was taken), the green dot marks location of Temelín, and the sector outlines the horizontal range and direction of the timelapse. In this Meteosat-10 HRV loop (taken at 5 minute rapid scan mode) the sector also marks the timelapse interval. Despite the fact that the waves can be resolved in the HRV images, their motion can't be resolved in the loop due to their fast eastward propagation. Somewhat better resolution is available in this Metop-B AVHRR 1 km image, captured at the end of the timelapse series. However, the clearest image of these waves was recorded about 30 minutes later by the Sentinel-3B satellite with its OLCI instrument at 300 m resolution, shown here in the RGB composite image of bands 8, 6 and 4. From this image it is possible to retrieve the wavelength of these waves, which ranges from about 2 km near Praha (red dot), up to about 4 km in the other more distant regions. From the timelapse series it is possible to estimate the period of these waves, reaching about 85 seconds. 

The timelapse series, unfortunately terminated by the memory card capacity, was captured from my office window at the CHMI Observatory Praha-Libuš, Czech Republic, with a southwestward view.

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