## 3 Results
Figure 4: Data collected from 0600 Sunday, 4 April to 0600 Monday, 5 April (local time). Figure 3: Periods of stable conditions (where the air temperature at the upper location was warmer than the lower location) were accompanied by offshore flow events. In the bottom diagram, the arrows correspond to the wind velocity direction. As show in the inset figure on the right, onshore flow occurs when the arrows point towards the lower right, whereas offshore flow occurs when the arrows point to the upper left. The fourth plot of Figure 4 is the temperature difference between the upper and lower hygrometers. Here we see an expected trend of the lower temperature readings being greater than the temperature measured by the upper sensor due to its proximity to the heat-absorbing surface. Overnight, we reach a point of inflection as the ground cools and is momentarily at equilibrium with the temperature of the air at the higher elevation, shown with the solid black line plotted. As we enter the post-midnight hours, the ground is now cooler than the air at the higher elevation. It is also important to note that--as expected--the \(C_{n}^{2}\) values of both sonics tend to be higher during periods of large negative temperature differences and tend to be lower during neutral conditions (i.e., when the temperature difference is zero). Other instances such as these will be further explored when we compare our results to NAVSLaM estimates. In the final plot of Figure 4, we have the slopes of the best line fit to the PSDs of both sonic anemometers; the expected value of \(-5/3\) slope was plotted as a solid black line. This plot was used to ensure that the probing frequency window (1 to 5 Hz) was sufficient to capture frequencies within the inertial subrange, as previously discussed. In the early morning hours of April 4 th, the slope deviates drastically from the expected value of \(-5/3\); simultaneously, both sonic anemometers indicate a \(C_{n}^{2}\) value of \(\sim 10^{-16}\) m\({}^{-2/3}\). This may indicate that the sonics are approaching the noise floor which occurs when \(C_{n}^{2}\approx 10^{-16}\) m\({}^{-2/3}\); smaller values than this are difficult for these sonics to measure. We noted another strong deviation from the \(-5/3\) slope just before 2000 on the night of the fourth. This also may be attributed to the sonics approaching their noise floors. After analyzing the collected data from the sonic anemometers for the remaining days of the experiment, we then compared these results with estimates produced by the two-level version NAVSLaM. The inputs to NAVSLaM are listed in Table 1, along with the corresponding instrument used to determine that input. Wind speed, air temperature, and relative humidity were recorded at two different heights, as described earlier and as required by this version of NAVSLaM. The outputs of NAVSLaM include \(C_{n}^{2}\) as a function of height above the surface. The sonic \(C_{n}^{2}\) estimates were compared to the NAVSLaM outputs at the corresponding heights. Figure 5 shows the \(C_{n}^{2}\) estimates produced by NAVSLaM overlayed on plots from the sonics from 0700 Tuesday, 6 April to 0800 Wednesday, 7 April. Again, values measured by the two CSAT3 sonic anemometers are shown in blue (upper sonic) and orange (lower sonic). The green curves in the first two plots represent the NAVSLaM \(C_{n}^{2}\) estimates at the corresponding heights of the sonics (4.4 m above the ground for the upper sonic and 1.2 m for the lower sonic). Additionally, the first two plots contain colored circles along the horizontal axis which represent various diagnostic errors recorded by the CR6 Datalogger. Most of the errors recorded were due to low battery warnings in which slow scans would be occasionally skipped; however, full data scans were still conducted and saved to the