Negative or positive cloud optical depth feedback?

Why is longwave cloud feedback positive?

[1] Longwave cloud feedback is systematically positive and nearly the same magnitude across all global climate models used in the Intergovernmental Panel on Climate Change Fourth Assessment Report (AR4). Here it is shown that this robust positive longwave cloud feedback is caused in large part by the tendency for tropical high clouds to rise in such a way as to remain at nearly the same tempera...

Positive and Negative Cloud-to Ground Lightning*

Positive cloud-to ground lightning (+ CGL) occurs in a minor fraction of all thunderstorms [1]. We propose that the microscopic mechanism is the same as in the more common negative CGL, whereas the different polarity is due to the macroscopic cloud dynamics [2]. The origin of collisional charging involves three stages in the basic process [3]. In the first stage kinetic roughening of the surfac...

Positive Feedback Promotes Oscillations in Negative Feedback Loops

A simple three-component negative feedback loop is a recurring motif in biochemical oscillators. This motif oscillates as it has the three necessary ingredients for oscillations: a three-step delay, negative feedback, and nonlinearity in the loop. However, to oscillate, this motif under the common Goodwin formulation requires a high degree of cooperativity (a measure of nonlinearity) in the fee...

Positive Woman or Negative Man?

Measurement of aerosol optical depth and sub-visual cloud detection using the optical depth sensor (ODS)

A small and sophisticated optical depth sensor (ODS) has been designed to work in the atmosphere of Mars. The instrument measures alternatively the diffuse radiation from the sky and the attenuated direct radiation from the Sun on the surface. The principal goals of ODS are to retrieve the daily mean aerosol optical depth (AOD) and to detect very high and optically thin clouds, crucial paramete...