The realization of polar specific humidity inversions and surface processes in reanalyses

Abstract:

We will present an all-sky climatology derived from reanalyses of specific humidity inversions, a quite prevalent phenomenon in both polar regions. All produce increased frequency of humidity inversions in monthly mean profiles over the polar regions. According to the climatology, humidity inversions in the polar regions are the most persistent in winter and strongest in summer or autumn. An advantage of using the reanalyses is that they can be used to test previous hypotheses about how these inversions form or are maintained. For instance, MERRA is unique in that it provides humidity tendencies due to various processes. We will show from such tendencies averaged over humidity inversions in the polar regions that the most influential processes are dynamics, moist processes, and turbulence. Of dynamical processes, local advection may not be as important as humidity fluxes into the polar regions. Over the Arctic, winter humidity inversions are near-surface associated with temperature inversions, while summer inversions are more likely associated with cloud-top processes when clouds are very persistent.

We will also present an evaluation of surface processes over Arctic land, ocean, and sea ice in the reanalyses by comparing to global datasets and station data. For the most part, near-surface quantities and surface fluxes are better represented over land than over the oceans and sea ice. We will use the insights developed from these assessments of surface and near-surface processes in reanalyses to evaluate the Regional Arctic System Model (RASM) and global climate models.