The dynamical influence of large‐scale heat sources and sinks on the quasi‐stationary mean motions of the atmosphere

Abstract

SUMMARYThe classical convective theory for the influence of large-scale zonally asymmetric heating and cooling on the quasi-stationary mean motions is re-examined and shown to be inconsistent with observation. Scale considerations indicate that the classical mechanism cannot be applied to heating on a scale larger than that responsible for "sea-breezes. In analogy with the theory of orographically produced stationary disturbances, heat sources and sinks of planetary dimensions produce quasi-static and quasi-geostrophic pertuilxitions. A thermally active mode! is constructed in which all motions except those of large scale are filtered out a priori. The small perturbations produced by an idealized large-scale distribution of heat sources and sinks acting on a horizontally uniform baroclinic zonal current confined between rigid horizontal planes are then studied. The influence of surface friction is taken into account. Calculations are also performed on a model with no friction and on the assumption that entropy is adverted horizontally. The results generally show good agreement with those for the more general model. When the stratosphere is taken into account, the disturbances in the upper troposphere are reduced in magnitude. The conditions for resonance in the absence of friction are determined. The passage through the resonant state is shown to modify significantly the character of the motions. The observed normals are discussed at some length in light of the theoretical computations. It is found that the magnitude and spatial distribution of the model disturbances display substantial correspondence with observation when allowance is made for orographic effects. Finally a method is suggested for quantitatively deducing the three-dimensional field of non-adiabatic heating and cooling from the observed normal maps by dynamical considerations.

Local and Remote Responses to Excessive Snow Mass over Eurasia Appearing in the Northern Spring and Summer Climate

“…The negative height anomaly over east Asia can be explained as a local response to the increased diabatic cooling over and around the Tibetan Plateau (see Table 1 and Fig. 8) and the increase of diabatic heating over the north Pacific near the east coast of Asia, as theoretically pointed out by Smagorinsky (1953). Interestingly, the same type of anomaly pattern was obtained in the observed anomaly pattern for April, relevant to the anomalous snow cover over central Asia .…”

Impact of observed North Atlantic multidecadal variations to European summer climate: a linear baroclinic response to surface heating

“…Even though a direct link of the AMV to the SNAO is still controversial. In addition to the summer North Atlantic Oscillation (SNAO), an alternative atmospheric response could be the baroclinic atmospheric response to shallow diabatic heating anomalies in the extra-tropics (Smagorinsky 1953;Hoskins and Karoly 1981;Kushnir 1994). Such diabatic heating can result from AMV-related surface heat fluxes as recently shown in the analysis of observations (Gulev et al 2013).…”

Multidecadal and interannual changes of stationary Rossby waves

“…Stationary Rossby Waves (SRW) are forced by irregularities on the Earth's surface such as orography (Charney and Eliassen, 1949) and land-sea thermal contrasts (Smagorinsky, 1953). These waves control the regional climate and, therefore, changes in SRW might be connected to regional climate change.…”