AN EVALUATION OF THE TEMPERATURE, WATER-VAPOR, AND VERTICAL VELOCITY STRUCTURE OF AIRCRAFT CONTRAILS

Measurements made in contrails formed in the wake of a Lear 35 have be en analyzed with respect to their temperature, water vapor, and vertic al velocity structure. The National Center for Atmospheric Research (N CAR) Sabreliner traversed the Lear's wake at distances varying from 15 0 m to 5 km and penetrated the contrails 243 times over the course of seven flights. The width of the plume is documented as a function of t he distance between the leading and chase aircraft and the temperature , humidity and vertical motion components inside the plume have been a nalyzed and compared with a three dimensional wake vortex model. The a nalysis shows that the width increases very little within the first 5 km, in agreement with the vortex model. The increases in temperature a nd water vapor in the contrail 500 m from the exhaust were approximate to 0.6 degrees and 8 ppmv, respectively. The vertical velocity change across the contrail was approximate to 4 m s(-1). The agreement betwe en observations and model predictions is quite good in comparisons of temperature. The model predicts larger water vapor mixing ratios, but the differences can be explained within the expected measurement uncer tainties and lack of particle condensation in the vortex model. The mo del predicts larger excursions in vertical velocity but the trends are in excellent agreement between model and observations.