7 research outputs found

    East Australian cyclones and air‐sea feedbacks

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    The importance of resolving mesoscale air-sea interactions to represent cyclones impacting the East Coast of Australia, the so-called East Coast Lows (ECLs), is investigated using the Australian Regional Coupled Model based on NEMO-OASIS-WRF (NOW) at urn:x-wiley:2169897X:media:jgrd57355:jgrd57355-math-0001 resolution. The fully coupled model is shown to be capable of reproducing correctly relevant features such as the seasonality, spatial distribution and intensity of ECLs while it partially resolves mesoscale processes, such as air-sea feedbacks over ocean eddies and fronts. The mesoscale thermal feedback (TFB) and the current feedback (CFB) are shown to influence the intensity of northern ECLs (north of urn:x-wiley:2169897X:media:jgrd57355:jgrd57355-math-0002), with the TFB modulating the pre-storm sea surface temperature by shifting ECL locations eastwards and the CFB modulating the wind stress. By fully uncoupling the atmospheric model of NOW, the intensity of northern ECLs is increased due to the absence of the cold wake that provides a negative feedback to the cyclone. The number of ECLs might also be affected by the air-sea feedbacks but large interannual variability hampers significant results with short term simulations. The TFB and CFB modify the climatology of sea surface temperature (mean and variability) but no direct link is found between these changes and those noticed in ECL properties. These results show that the representation of ECLs, mainly north of urn:x-wiley:2169897X:media:jgrd57355:jgrd57355-math-0003, depend on how air-sea feedbacks are simulated. This is particularly important for atmospheric downscaling of climate projections as small-scale sea surface temperature interactions and the effects of ocean currents are not accounted for

    Full‐Depth Global Estimates of Ocean Mesoscale Eddy Mixing From Observations and Theory

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    Mixing by mesoscale eddies profoundly impacts climate and ecosystems by redistributing and storing dissolved tracers such as heat and carbon. Eddy mixing is parameterized in most numerical models of the ocean and climate. To reduce known sensitivity to such parameterizations, observational estimates of mixing are needed. However, logistical and technological limitations obstruct our ability to measure global time‐varying mixing rates. Here, we extend mixing length theory with mean‐flow suppression theory, and first surface modes, to estimate mixing from readily available observational‐based climatological data, of salinity, temperature, pressure, and eddy kinetic energy at the sea surface. The resulting full‐depth global maps of eddy mixing can reproduce the few available direct estimates and confirm the importance of mean‐flow suppression of mixing. The results also emphasize the significant effect of eddy surface intensification and its relation to the vertical density stratification. These new insights in mixing dynamics will improve future mesoscale eddy mixing parameterizations

    On the use of indices to study extreme precipitation on sub-daily and daily timescales

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    While there are obstacles to the exchange of long-term high temporal resolution precipitation data, there have been fewer barriers to the exchange of so-called 'indices'. These are derived from daily and sub-daily data and measure aspects of precipitation frequency, duration and intensity that could be used for the study of extremes. This paper outlines the history of the rationale and use of these indices, the types of indices that are frequently used and the advantages and pitfalls in analysing them. Moving forward, satellite precipitation products are now showing the potential to provide global climate indices to supplement existing products using longer-term in situ gauge records but we suggest that to advance this area differences between data products, limitations in satellite-based estimation processes, and the inherent challenges of scale need to be better understood.Open access article.This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]
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