67 Scaling of Temperature and Liquid Water Content in Cloudy Marine Boundary Layer Duringphysics of Stratocumulus Top Research Campaign

Monday, 9 July 2018
Regency A/B/C (Hyatt Regency Vancouver)
Szymon P. Malinowski, University of Warsaw, Warsaw, Poland

Scaling behavior of small-scale temperature (T) and liquid water content (LWC) fluctuations in
stratocumulus topped marine boundary layer (MBL) was analyzed using data from aircraft
measurements collected over the Pacific Ocean during the Physics of Stratocumulus Top (POST)
research campaign in summer of 2008.
As an extension of the past studies for scale-invariant properties of MBL clouds, the authors
studied the variability of scaling exponents with height. The results showed that both LWC and T
have two distinct scaling regimes: the first over a range from about 1–5 m to at least 7 km,
and the second one from about 0.1–1 to 1–5 m. For the large-scale regime, fluctuations of LWC and
T are multifractal. Scaling exponents and the scale break vary with height, most significantly in the
cloud-top region. For example, LWC spectral exponent increases from 1.42 at cloud base to 1.58 at
cloud top, while scale break decreases from ~5 m at cloud base to 0.8 m at cloud top.
Following earlier studies we describe T and LWC fluctuations with bifractal parameters (H1, C1),
where H1 is the Hurst exponent characterizing nonstationarity (smoothness of data) and C1 is the
intermittency parameter. For LWC bifractal parameters increase from (0.14, 0.02) at cloud base to
(0.33, 0.1) at cloud top while maintaining a statistically significant linear relationship C1≈0.4H1-
0.04 in MBL clouds. From near surface to cloud top, (H1, C1) for T also increase with height, but
above cloud top H1 increases while C1 decreases with height.
The results suggest the existence of three turbulence regimes: near the surface, in the middle of the
boundary layer, and in the cloud-top region, which need to be distinguished.
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