1,415 research outputs found
Understanding decreases in land relative humidity with global warming: conceptual model and GCM simulations
Climate models simulate a strong land-ocean contrast in the response of
near-surface relative humidity to global warming: relative humidity tends to
increase slightly over oceans but decrease substantially over land. Surface
energy balance arguments have been used to understand the response over ocean
but are difficult to apply over more complex land surfaces. Here, a conceptual
box model is introduced, involving moisture transport between the land and
ocean boundary layers and evapotranspiration, to investigate the decreases in
land relative humidity as the climate warms. The box model is applied to
idealized and full-complexity (CMIP5) general circulation model simulations,
and it is found to capture many of the features of the simulated changes in
land relative humidity. The box model suggests there is a strong link between
fractional changes in specific humidity over land and ocean, and the greater
warming over land than ocean then implies a decrease in land relative humidity.
Evapotranspiration is of secondary importance for the increase in specific
humidity over land, but it matters more for the decrease in relative humidity.
Further analysis shows there is a strong feedback between changes in
surface-air temperature and relative humidity, and this can amplify the
influence on relative humidity of factors such as stomatal conductance and soil
moisture.Comment: Submitted to Journal of Climate on May 1st, 201
Interlinked dual-time feedback loops can enhance robustness to stochasticity and persistence of memory.
Multiple interlinked positive feedback loops shape the stimulus responses of various biochemical systems, such as the cell cycle or intracellular Ca2+ release. Recent studies with simplified models have identified two advantages of coupling fast and slow feedback loops. This dual-time structure enables a fast response while enhancing resistances of responses and bistability to stimulus noise. We now find that (1) the dual-time structure similarly confers resistance to internal noise due to molecule number fluctuations, and (2) model variants with altered coupling, which better represent some specific biochemical systems, share all the above advantages. We also develop a similar bistable model with coupling of a fast autoactivation loop to a slow loop. This model\u27s topology was suggested by positive feedback proposed to play a role in long-term synaptic potentiation (LTP). The advantages of fast response and noise resistance are also present in this autoactivation model. Empirically, LTP develops resistance to reversal over approximately 1h . The model suggests this resistance may result from increased amounts of synaptic kinases involved in positive feedback
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