Publication Abstracts

Tselioudis and Grise 2020

Tselioudis, G., and K. Grise, 2020: Midlatitude cloud systems. In Clouds and Climate: Climate Science's Greatest Challenge. A.P. Siebesma, S. Bony, C. Jakob, and B. Stevens, Eds., Cambridge University Press, pp. 279-296.

In contrast to the tropics and subtropics, the rniddle latitudes are characterised by large meridional temperature gradients, created as a consequeoce of differential radiative heating between high and low latitudes. These meridional temperature gradients often concentrate in relatively narrow baroclinic zones that become unstable to wave-like perturbations called baroclinic eddies, or more commonly baroclinic storms or mid-latitude cyclones. Baroclinic storms constitute the primary source of poleward energy transport at mid latitudes. which is accomplished through contrasting transports of warm air masses polewards (warm fronts) and cold air masses equatorwards (cold fronts). Baroclinic storms also flux momentum into mid-latitude regions, driving a region of enhanced westerly winds from the surface to the upper troposphere called the eddy-driven jet stream.

Baroclinic storms are the primary source of mid-latitude cloud formation and thus play an important role in detemining the radiative and hydrologic budgets in mid-latitude regions. High clouds of various vertical extents tend to form in the uplift regimes of the warm and cold fronts associated with the baroclinic storms, while low cloud decks often form in the subsidence regimes of the cold air masses that foUow a cold frontal passage. As a result, the mid-latitude cloud field encompasses almost the full range of cloud types, and the appearance of particular cloud types can be viewed as a tracer of mid-latitude dynamic regimes. Because the clouds in the vicinity of the warm and cold fronts tend to be opticaUy thick and often have tops in upper tropospheric layers, they produce substantial short- and long-wave radiative signatures. Section 1.2.1 and Chapter 4 provide a detailed review of the short- and long-wave radiative signatures of clouds. Briefly, the large optical depth of the clouds in the vicinity of the fronts promotes the reflection of incident solar radiation (a sbort-wave cooling effect), vhereas the cold cloud-top temperatures promote the reduction of outgoing long-wave radiation to space (a long-wave warming effect). In contrast, the low cloud decks in mid-latitude cold air regimes have primarily a short-wave cooling effect, as their cloud-top temperature differs little from the underlying surface temperature.

These short-wave cooling and long-wave warming effects make mid-latitude clouds a key contributor to the global radiative budget and thus a potential source of significant radiative feedbacks in climate change situations (Chapter 13). Changes in the climate system, such as a climate warming, could affect meridional temperature gradients as well as the moisture availability of the atmosphere, which, through latent heat release, constitutes an additional energy source for baroclinic storms. Consequently, significant changes in the track and strength of baroclinic storms could occur with climate warming, and these changes would alter the mid-latitude cloud field and produce radiative and hydrologic climate feedbacks. At the same time, altered cloud fields through their radiative effects and latent heat release have the ability to change temperature gradient patterns which in return can alter the characteristics of the mid-latitude atmospheric circulation. The examination of mid-latitude cloud processes and feedbacks, therefore, requires a detailed understanding of the relationships between the dynamical features of baroclinic storms and the properties of the clouds that they produce.

This chapter will examine in detail the relationships between cloud properties and atmospheric dynamics in mid-latitude regions. Cloud structures aud formation mechanisms in baroclinic storms will be examined first, with an emphasis on the latest satellite retrievals of cloud properties. Next, the climatologies of mid-latitude clouds and their radiative properties will be discussed. Then, the interactions of the mid-latitude atmospheric circulation with clouds and their radiative properties will be examined, including an examination of the effects of clouds on the mid-latitude circulation. Finally, the chapter will address how mid-latitude clouds may be aftected in as well as affect a changing climate.

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BibTeX Citation

  author={Tselioudis, G. and Grise, K.},
  editor={Siebesma, A. P. and Bony, S. and Jakob, C. and Stevens, B.},
  title={Midlatitude cloud systems},
  booktitle={Clouds and Climate: Climate Science's Greatest Challenge},
  publisher={Cambridge University Press},

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RIS Citation

ID  - ts06300k
AU  - Tselioudis, G.
AU  - Grise, K.
ED  - Siebesma, A. P.
ED  - Bony, S.
ED  - Jakob, C.
ED  - Stevens, B.
PY  - 2020
TI  - Midlatitude cloud systems
BT  - Clouds and Climate: Climate Science's Greatest Challenge
SP  - 279
EP  - 296
PB  - Cambridge University Press
ER  -

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