Oscillations in lowest-level wind speeds over some land regions

Over certain areas (e.g. the Amazon), E3SMv1 produces wild oscillations in the surface winds, causing the winds to largely "turn off" or "blink" every other time step. This appears to be a numerical instability caused by only doing land-atmosphere coupling every half hour in the default model configuration (at least at ne30np4 resolution). The instability seems to result from a tug-of-war between the surface stresses (which can rapidly reduce the surface wind speed) and dynamics (which are pushing to increase or maintain the wind speed in the boundary layer).

This looks quite bad when observing the winds over short time spans, because the boundary layer winds are dominated by high frequency noise. However, it's unclear how much this issue affects the model climate. The rapid pulsing of the winds does affect other surface fluxes, e.g. by increasing evaporation over the affected areas.

This issue is a regression from CAM5, which addressed this kind of instability using the implicit surface stress ("ISS") option, described on page 106/107 of [the CAM5 model description](https://www.cesm.ucar.edu/models/cesm1.0/cam/docs/description/cam5_desc_save.pdf). This option was only implemented for the older CAM turbulence schemes, however, and not for CLUBB (which I believe uses its own implicit solver for propagating the effects of the surface stresses upwards).

There is another way to get rid of these oscillations, which is to set `sfc_flux_avg = 1` in the atmosphere model namelist. This smooths out surface fluxes (latent and sensible heat, as well as the surface stresses) by smearing them out over a ~2 hour timescale, which is similar to how CAM5's ISS scheme handled the surface stresses.

While this gets rid of the instability, smearing the effect of incoming fluxes over a few hours may not be an ideal solution. There may be some other way to improve the land-atmosphere coupling that avoids adding this kind of explicit smoothing.

Start by reproducing the oscillations in the default E3SMv1 configuration at ne30np4 over an affected land region, then compare behavior with the atmosphere namelist setting sfc_flux_avg = 1. Review the CAM5 implicit surface stress description and the CLUBB coupling context. Done means identifying and validating a land-atmosphere coupling approach that removes the instability without relying solely on multi-hour flux smoothing.

Written by the indexing model from the issue text.