Presenter: Bryce Harrop

Title: Conservation of dry air, water, and energy in CAM (and EAM) and its impact on tropical rainfall

Abstract: For the Community Atmosphere Model (CAM), and any other model using an artificially fixed moist pressure as its vertical coordinate for physics parameterizations, an adjustment must be made to conserve dry air mass and water content. This adjustment in CAM exposes an inconsistency in how CAM's energy budget incorporates water, which breaks energy conservation. The energy error associated with the adjustment results from the net change in water vapor, and is largest in regions with heavy precipitation where the energy sink reaches as high as 40~W/m$^2$ in the annual mean. The energy error is shown to result from missing energy fluxes associated with condensed phases of water. The impact of this energy error on the simulated climate is tested by reformulating the adjustment routine to resolve the inconsistency in the energy budget at the expense of physical realism. Comparing simulations with CAM6 using the default and this alternative adjustment configuration shows that precipitation, particularly its variability, is highly sensitive to the energy budget formulation. Changes in equatorial waves between the default and experimental configuration are as large as those between parameterized and super-parameterized deep convection in the model. Not only does this experiment serve as an illustrative example of the sensitivity of the hydrological cycle to choices in the treatment of energy, it also acts as a platform to advocate for including the thermal energy carried by water in global models moving forward.

Date

10 Dec 2020

Time

PT: 8:30 am
ET: 11:30 am

Call Info

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Attendees

Presentation

Time	Title	Presenter	Presentation	Recording	Notes
30 min	Conservation of dry air, water, and energy in CAM (and EAM) and its impact on tropical rainfall	Bryce Harrop	Harrop_20201210_AllHandsWebinar.pptx	MP4 Movie (on the E3SM YouTube Channel)

Time

Title

Presenter

Presentation

Recording

Notes

30 min

Conservation of dry air, water, and energy in CAM (and EAM) and its impact on tropical rainfall

Bryce Harrop

Harrop_20201210_AllHandsWebinar.pptx

MP4 Movie (on the E3SM YouTube Channel)

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