Direct Thermal Verification of Symmetric Baroclinic Instability

Direct temperature measurements are reported for two rotating annulus experiments. One shows the flow pattern interpreted by Stone et al. as a manifestation of symmetric baroclinic (inertial) instability, and the other shows the flow pattern typical of baroclinic waves. The mean value of the Richardson number in the former experiment is found to he 0.62. This value agrees with theoretical expectations for a symmetric haroclinic instability regime and thus verifies the original interpretation of the flow pattern. The mean value of the Richardson number in the baroclinic wave experiment is 83. In the symmetric instability experiment the thermal fields and Richardson number are not steady, but show a cyclic variation.