Publication Date:
2018-01-03
Description:
Satellite observations are used to study the variance scaling of temperature and water vapor in the atmosphere. A high resolution of 13.5 km at nadir, instead of 45 km as in previous Atmospheric Infrared Sounder (AIRS) studies, enables the derivation of the variance-scaling exponents down to length scales of ~ 55 km.With the variable-size circular area Monte Carlo approach the exponents can be computed instantaneously along the track of Aqua, which gives more insight into the scaling behavior of the atmospheric variables in individual Level 2 satellite granules. Scaling exponents are shown to fluctuate heavily between β = −1 and β = −3 at the larger scales, while at the smaller scales they are often closer to β = −2, and they decrease a bit for moisture at the smallest scales that are considered. Outside the tropics, the temperature large-scale variance-scaling exponent is often close to −3 due to large temperature slopes that are present along the track of Aqua, likely as a result of geostrophic turbulence. Around the tropics, this exponent is often closer to −1, because the tropical atmosphere is dominated by smaller-scale processes such as moist convection, leading to an observable reverse scale break. In contrast, water vapor is shown to have large-scale exponents often close to −3 around the tropics, because there, large-scale water vapor slopes are common along the Aqua track. Furthermore, the scale-break length scale turns out to be highly variable and shows a large spread. The presented variance-scaling results are of importance for cloud parameterization purposes.
Electronic ISSN:
1867-8610
Topics:
Geosciences
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