Articles | Volume 18, issue 2
Research article
24 Jan 2018
Research article |  | 24 Jan 2018

Universal power law of the gravity wave manifestation in the AIM CIPS polar mesospheric cloud images

Pingping Rong, Jia Yue, James M. Russell III, David E. Siskind, and Cora E. Randall

Abstract. We aim to extract a universal law that governs the gravity wave manifestation in polar mesospheric clouds (PMCs). Gravity wave morphology and the clarity level of display vary throughout the wave population manifested by the PMC albedo data. Higher clarity refers to more distinct exhibition of the features, which often correspond to larger variances and a better-organized nature. A gravity wave tracking algorithm based on the continuous Morlet wavelet transform is applied to the PMC albedo data at 83 km altitude taken by the Aeronomy of Ice in the Mesosphere (AIM) Cloud Imaging and Particle Size (CIPS) instrument to obtain a large ensemble of the gravity wave detections. The horizontal wavelengths in the range of  ∼ 20–60 km are the focus of the study. It shows that the albedo (wave) power statistically increases as the background gets brighter. We resample the wave detections to conform to a normal distribution to examine the wave morphology and display clarity beyond the cloud brightness impact. Sample cases are selected at the two tails and the peak of the normal distribution to represent the full set of wave detections. For these cases the albedo power spectra follow exponential decay toward smaller scales. The high-albedo-power category has the most rapid decay (i.e., exponent  =  −3.2) and corresponds to the most distinct wave display. The wave display becomes increasingly blurrier for the medium- and low-power categories, which hold the monotonically decreasing spectral exponents of −2.9 and −2.5, respectively. The majority of waves are straight waves whose clarity levels can collapse between the different brightness levels, but in the brighter background the wave signatures seem to exhibit mildly turbulent-like behavior.

Short summary
There is a massive manifestation of atmospheric gravity waves (GWs) in polar mesospheric clouds (PMCs) at the summer mesopause, which serves as indicators of the atmospheric dynamics and climate change. We obtained a universal power law that governs the GW display morphology and clarity level throughout the wave population residing in PMCs. Higher clarity refers to more distinct exhibition of the features. A GW tracking algorithm is used to identify the waves and to sort the albedo power.
Final-revised paper