Another Very Important Paper Which Illustrates Major Problems With Using Minimum Land Temperatures As Part Of The Diagnosis of Global Warming and Cooling: “Vertically Integrated Sensible-Heat Budgets For Stable Nocturnal Boundary Layers By Nakamura and Mahrt 2006

There is further evidence with respect to major issues in using minimum 2m temperatures as part of the diagnosis of climate system heat changes (i.e. global warming and cooling). [thanks to Jielun Sun for alerting us to it!].

It is

Nakamura, R. and L. Mahrt, 2006: Vertically integrated sensible-heat budgets for stable nocturnal boundary layers. Q. J. R. Meteorol. Soc. (2006), 132, pp. 383–403 doi: 10.1256/qj.05.50.

The abstract reads

“The stable nocturnal boundary layer is commonly viewed or modelled as a balance between the temperature tendency (cooling) and vertical heat-flux divergence. Sometimes the radiative-flux divergence is also included. This perspective has dictated the design of field experiments for investigating stable nocturnal boundary layers. Tower-based micrometeorological data from three field campaigns are analysed to evaluate the vertically integrated sensible-heat budget for nocturnal stable conditions. Our analysis indicates frequent occurrence of large imbalance between the temperature tendency and vertical heat-flux divergence terms. The values of the radiative-flux divergence are generally too small and sometimes of the wrong sign to explain the residual. An analysis of random flux errors and uncertainties in the tendency term indicate that such errors cannot explain large imbalances, suggesting the importance of advection of temperature or possibly the divergence of mesoscale fluxes. The implied role of advection is consistent with circumstantial evidence. Even weak surface heterogeneity can create significant horizontal gradients in stable boundary layers. However, it is shown that existing field data and observational strategy do not allow adequate evaluation of advection and mesoscale flux divergence terms.”

As the authors write in the conclusions,

Even weak surface heterogeneity may induce important horizontal variations in the very stable boundary layer, and new approaches for measuring horizontal variation of temperature and fluxes are required.”

Thus minimum temperatures over land are very sensitive to their immediate local environments. Their use to characterize minimum temperatures  as being spatially representative over a larger area, such as used to diagnose global warming and cooling,  are not appropriate.