Critical Test of the Validity of Monin–Obukhov Similarity during Convective Conditions

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Abstract
A recent study of convective boundary layer characteristics performed with large eddy simulation technique (LES) has demonstrated unexpected influence of the depth of the boundary layer on surface layer characteristics. The present study tests some of the predictions from these simulations with field measurements from a summertime experiment in Sweden, which includes in addition to regular surface layer data also airborne measurements and numerous radio soundings, which enable accurate determination of boundary layer depth. It is found that the measurements strongly support most of the conclusions draws from the LES study and give additional information over a wider stability range. Thus, the normalized wind gradient ϕm is found to depend on both z/L, where z is height above the ground and L is the Monin–Obukhov length, and zi/L, where zi is the height of the convective boundary layer. This additional dependence on zi/L explains much of the scatter between experiments encountered for this paramet... Abstract A recent study of convective boundary layer characteristics performed with large eddy simulation technique (LES) has demonstrated unexpected influence of the depth of the boundary layer on surface layer characteristics. The present study tests some of the predictions from these simulations with field measurements from a summertime experiment in Sweden, which includes in addition to regular surface layer data also airborne measurements and numerous radio soundings, which enable accurate determination of boundary layer depth. It is found that the measurements strongly support most of the conclusions draws from the LES study and give additional information over a wider stability range. Thus, the normalized wind gradient ϕm is found to depend on both z/L, where z is height above the ground and L is the Monin–Obukhov length, and zi/L, where zi is the height of the convective boundary layer. This additional dependence on zi/L explains much of the scatter between experiments encountered for this paramet...