Using Loon to Comprehensively Observe Gravity Wave Properties
Isabella Dula Razzolini, Stanford University
Between 2013 and 2020, Project Loon launched thousands of super
pressure stratospheric balloons to provide internet access to under-
served areas. Loon is the largest set of in-situ atmospheric
observations and is platform for observing wave fluctuations in the
lower stratosphere. Wavelet analysis on velocity fluctuations measured
from the balloons quantifies the strength and global spectra of Gravity
Wave (GW) momentum fluxes, a key input towards constraining GW
parameterizations within climate models to generate realistic
circulation. Horizontal GW properties, such as the wavelength structure
and phase speeds, are also valuable in parameterizations of GWs in
climate models. This project aims to study the subset of Loon balloons
consisting of balloon groups coincident in time and space. Given a
coincident pair of balloons within a group, a cross-spectral analysis can
be performed on their respective wavelet signals. Regions of strong
coherence identify whether the balloons are travelling through the
same GW packet. The phase offset between two GW signals at the
same time is a linear combination of the GW wavenumbers and the
distance between balloons. Least squares regression on the
measurements of all balloon pair combinations within a group can
directly estimate the wavenumbers of the observed GW. These
estimates are also used to compute GW phase speed, group velocity,
and propagation direction, providing a comprehensive measurement of
the wave. This work performs a set of measurements of atmospheric
GWs using a novel method. Results can further constrain GW
parameterizations and provide insight into global distributions of GW
properties.