Large-amplitude inertia-gravity wave environments: Three-dimensional structure and multiscale evolution

The goal of this research is to investigate the three-dimensional structure and multiscale evolution of the environments associated with large-amplitude inertia-gravity waves (IGWs) through composite analysis of an IGW climatology and through case study analyses.; Composite soundings are calculated in order to investigate the vertical thermal and wind structure of IGW environments. Results of these composites soundings show that the IGW vertical thermal structure is characterized by a low-level stable layer capped by a less stable upper layer in which the lapse rate approaches moist-neutral and extends to a high tropopause. Winds in the low-level stable layer generally, have an easterly component and veer to southwesterly in the less stable upper layer.; The composite structure and evolution of the three-dimensional environment is constructed using the NCEP/NCAR Reanalyses. Results show IGWs occur: to the north and west of a surface low pressure center; poleward of a frontal boundary; and under the inflection point of a short-wavelength trough/ridge couplet overhead. Two jet maxima are typically observed. One is located to the southwest on the downstream side of the trough and a second is northeast of the IGW region.; The composite evolution shows that during the 36 h prior to IGW occurrence, the short-wavelength trough/ridge couplet develops as an amplifying short-wave trough originally approaches a quasi-stationary ridge. This leads to a collapse of the downstream half-wavelength between the trough and downstream ridge and a steepening of the downstream side of the dynamic tropopause that results in large divergence, large divergence tendencies, and vigorous rising motion.; The detailed mesoscale structure and environment of a wake trough from 28 April 1996 and an IGW from 25 January 2000 are compared. Results of this comparison show that the mesoscale environments of the two cases are similar. Both feature a descending rear-inflow jet that leads to significant mid-tropospheric downward vertical motions, and adiabatic warming and drying. The mid-tropospheric drying in each case results in a significant erosion of reflectivity at the back edge of the precipitation band.