The Analytical Objective Hysteresis Model (AnOHM v1.0): methodology to determine bulk storage heat flux coefficients
- 1Department of Meteorology, University of Reading, Reading, RG6 6BB, UK
- 2Department of Hydraulic Engineering, Tsinghua University, Beijing 100084, China
- 3State Key Laboratory of Hydro-Science and Engineering, Tsinghua University, Beijing 100084, China
- 4School of Sustainable Engineering and the Built Environment, Arizona State University, Tempe, AZ 85287, USA
- 5Global Change Research Group, Department of Biology, San Diego State University, San Diego, CA 92182, USA
- 6Department of Environment, Earth and Ecosystems, The Open University, Milton Keynes, MK7 6AA, UK
Abstract. The net storage heat flux (ΔQS) is important in the urban surface energy balance (SEB) but its determination remains a significant challenge. The hysteresis pattern of the diurnal relation between the ΔQS and net all-wave radiation (Q∗) has been captured in the Objective Hysteresis Model (OHM) parameterization of ΔQS. Although successfully used in urban areas, the limited availability of coefficients for OHM hampers its application. To facilitate use, and enhance physical interpretations of the OHM coefficients, an analytical solution of the one-dimensional advection–diffusion equation of coupled heat and liquid water transport in conjunction with the SEB is conducted, allowing development of AnOHM (Analytical Objective Hysteresis Model). A sensitivity test of AnOHM to surface properties and hydrometeorological forcing is presented using a stochastic approach (subset simulation). The sensitivity test suggests that the albedo, Bowen ratio and bulk transfer coefficient, solar radiation and wind speed are most critical. AnOHM, driven by local meteorological conditions at five sites with different land use, is shown to simulate the ΔQS flux well (RMSE values of ∼ 30 W m−2). The intra-annual dynamics of OHM coefficients are explored. AnOHM offers significant potential to enhance modelling of the surface energy balance over a wider range of conditions and land covers.