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<p>Microphysical processes are important for the development of clouds and thus Earth's climate. For example, turbulent fluctuations in the water vapor mixing ratio, <span class="inline-formula"><i>r</i></span>, and temperature, <span class="inline-formula"><i>T</i></span>, cause fluctuations in the saturation ratio, <span class="inline-formula"><i>S</i></span>. Because <span class="inline-formula"><i>S</i></span> is the driving factor in the condensational growth of droplets, fluctuations may broaden the cloud droplet size distribution due to individual droplets experiencing different growth rates. The small-scale turbulent fluctuations in the atmosphere that are relevant to cloud droplets are difficult to quantify through field measurements. We investigate these processes in the laboratory using Michigan Tech's <span class="inline-formula">Π</span> Chamber. The <span class="inline-formula">Π</span> Chamber utilizes Rayleigh–Bénard convection (RBC) to create the turbulent conditions inherent in clouds. In RBC it is common for a large-scale circulation (LSC) to form. As a consequence of the LSC, the temperature field of the chamber is not spatially uniform. In this paper, we characterize the LSC in the <span class="inline-formula">Π</span> Chamber and show how it affects the shape of the distributions of <span class="inline-formula"><i>r</i></span>, <span class="inline-formula"><i>T</i></span>, and <span class="inline-formula"><i>S</i></span>. The LSC was found to follow a single roll with an updraft and downdraft along opposing walls of the chamber. Near the updraft (downdraft), the distributions of <span class="inline-formula"><i>T</i></span> and <span class="inline-formula"><i>r</i></span> were positively (negatively) skewed. At each measuring position, <span class="inline-formula"><i>S</i></span> consistently had a negatively skewed distribution, with the downdraft being the most negative.</p>