Improvement of vertical and residual velocities in pressure or hybrid sigma-pressure coordinates in analysis data in the stratosphere

[摘要] Stratospheric vertical winds from analysis datain pressure (p) or hybrid pressure (σ-p) coordinates,for use in e.g. chemical transport models(CTMs) or trajectory models,often suffer both from excessivenoise and errors in their mean magnitude, which in turncan introduce errors in important dynamical quantities like vertical mixingor constituent transport with the residual circulation. Sincevertical velocities cannot be measured directly, they areinferred from other quantities, typically from horizontal wind divergence,that is the mass continuity equation.We propose a method to calculate the vertical wind field from thethermodynamic energy equation in p or σ-p vertical coordinatesthat substantially reduces noise andoverestimation of the residual circulation. It is completelyequivalent to the approach using potential temperature (θ) as a verticalcoordinate and diabatic heating rates as vertical velocities, which hasalready been demonstrated to give superior results to the continuity equation.It provides a quickly realizable improvement of the vertical winds,when a change of the vertical variable would cause an inadequate effort(e.g. in CTMs).The method is only applicable for stably stratified regions likethe stratosphere.

[学科分类] 大气科学