Paper+Summary

**This page provides summary of some of the highlighted papers discussed in the cloud reading group.**
1. Sept. 12, Adeyemi Adebiyi, Paper -- Presented slides --

The author used temperature data from AIRS and GDAS model and compare the vertical changes with MODIS aerosol optical depth. They found that heating occurs within the Sahara Air Layer and cooling above and below it. BY excluding the influence of geographic memory and retrieval artifact, they focus on disentagling the effect of meteorology from aerosol radiative effect. This was performed by taking del-ß = ß_obs - ß_model with the assumption that ß_model incorporate necessary "physics". ß is the change in temperature with aerosol optical depth. Hence del-ß was interpreted as the aerosol radiative heating signature which gives about 2-4K at the dust layer.

The CPRG, however, suggest that GDAS model might indirectly have assimilated the AIRS data, therefore rendering the observed change in del-ß questionable. They recommended that such study may be performed with and without the supposed, indirectly assimilated AIRS data within the GDAS model. The difference might provide more light and probably a better interpretation of the heating profile.

2. October 2, Arun Chandra, Paper -- Presented slides --

The author uses the Dutch Atmospheric Large-Eddy simulation model to investigate the role of positive feedback, as well as evaporation in sub-cloud layer, during the transition between shallow to deep convection. They do this, by confining themselves to cases with prescribed initial relative humidity profile and no wind shear. They found that in experiments where cold pools formation are suppressed, deepest clouds which corresponds to the heaviest precipitation are suppressed. They also found that the properties and organization of the subcloud layer is important in the deep cloud formation but it however does not correlate with the exit height of the system.

3. November 13, Zhujun Li: -- C. Rio et al., 2013: "Control of deep convection by sub-cloud lifting processes: the ALP closure in the LMDZ5B general circulation model" , 2009: "Shifting the diurnal cycle of parameterized deep convection over land"

The authors developed a new parameterization to correct for the inaccuracy in the time of initiation of continental thunderstorm in General Circulation Models. Inotherwords, triggering and closure mechanisms were introduced to better relate the deep convection occurrence and intensity to lifting effects of the sub-grid sub-cloud process through two parameters: The available lifting energy(ALE) and the available lifting power(ALP). These parameters are controlled by the thermals and gust(wake) in the boundary layer.

A conceptual 1-D model can be viewed as a shallow cumulus initiated by thermals in the boundary layer and entrainment at the BL-top. This contributes to the pre-conditioning of deep convection by gradual deepening of the boundary layer. Once deep convection is formed, the evaporation of the precipitation in unsaturated downdrafts leads to developments of cold pool under the convective system. The cold pool spreads out to initiate lifting air at the edge which also contribute to maintain the deep convection. Given this model, the new parameterization leads to the delay of the deep convection until the Convective INhibition(CIN) is overcome by the thermal ALE, whereby shallow convection suddenly switch to deep convection. Afterwards, addition of cold-pool ALE helps to keep the deep convection active, while ALP intensifies it.