Behavior of the Temperature Structure Parameter in a Desert Basin

Abstract

Measurements of the optical refractive index structure coefficient Cn2 and the temperature structure coefficient CT2 were made over the Tularosa Basin of south central New Mexico using both tower and aircraft mounted instruments. The height dependence of CT2 agrees reasonably well with the predictions of similarity theory in the daytime. However, the nighttime profiles disagree significantly from the surface-layer predictions for z/L > 0.05. Two factors can explain this disagreement: 1) for strong stabilities, the boundary layer is not fully turbulent, and 2) in the absence of strong synoptic forcing, mountain drainage flows may modify the profiles. The magnitude of CT2 during the daytime is found to be closely correlated with the difference in temperature between the surface and the air; in addition, there is a small dependence on wind speed. Measurements of CT2 through the depth of the convective mixing layer during the day agree closely with the model of Kaimal et al. (1976). These results imply that a single measurement or estimate of CT2 in the surface layer can be used to estimate the average profile of CT2 up to the inversion height during the day.