noctilucent clouds over the daugava river in riga, latvia on june night

blue daugava river kipsala latvia nlc riga astronomy atmosphere atmospheric background beautiful bright calm water city dark dawn dusk evening glow high indusial landscape light luminescence mesosphere mesospheric midnight nature night scape people noctilucent clouds nordic outdoors phenomena polar port rare reflection scenic shining silver sky space stars summer tranquil twilight weather yachts