Noctilucent Clouds Modulated by Strong 5-day Planetary Wave in 2025: Amplitudes, Phases and Altitudes Based on Ground-Based Observations and Satellite Temperature Data

TL;DR

This study investigates the 2025 summer noctilucent clouds at 55-60N, revealing a unique 5-day planetary wave influence on their occurrence, altitude, and phase lag, based on ground and satellite data.

Contribution

It identifies a strong 5-day planetary wave as the driver of NLC variability in 2025, with detailed analysis of wave evolution and NLC-altitude relationships.

Findings

A 5-day planetary wave was twice as strong as previous observations.

NLC occurrence lagged behind temperature minima by a positive phase.

2025 showed unprecedented planetary wave amplitude and NLC response.

Abstract

During the summer season of 2025, noctilucent clouds (NLC) were observed at the latitudes 55-60N from the late May until the late August. A distinct 5-day periodicity in their occurrence emerged following the summer solstice. Analysis of EOS Aura/MLS satellite data revealed that this effect was driven by a westward 5-day planetary wave, the amplitude of which was twice that of any previous northern summer since the start of the EOS Aura measurements in 2005. This study details the evolution of this exceptional planetary wave throughout the summer. Furthermore, NLC altitudes were determined via triangulation and colorimetry and were compared with MLS temperature profiles, enabling the determination of a mean positive phase lag for NLC occurrence relative to the temperature minimum.