Latent heat

About: Latent heat is a research topic. Over the lifetime, 13503 publications have been published within this topic receiving 302811 citations.

Modeling canopy-induced turbulence in the Earth system: a unified parameterization of turbulent exchange within plant canopies and the roughness sublayer (CLM-ml v0)

Abstract: . Land surface models used in climate models neglect the roughness sublayer and parameterize within-canopy turbulence in an ad hoc manner. We implemented a roughness sublayer turbulence parameterization in a multilayer canopy model (CLM-ml v0) to test if this theory provides a tractable parameterization extending from the ground through the canopy and the roughness sublayer. We compared the canopy model with the Community Land Model (CLM4.5) at seven forest, two grassland, and three cropland AmeriFlux sites over a range of canopy heights, leaf area indexes, and climates. CLM4.5 has pronounced biases during summer months at forest sites in midday latent heat flux, sensible heat flux, gross primary production, nighttime friction velocity, and the radiative temperature diurnal range. The new canopy model reduces these biases by introducing new physics. Advances in modeling stomatal conductance and canopy physiology beyond what is in CLM4.5 substantially improve model performance at the forest sites. The signature of the roughness sublayer is most evident in nighttime friction velocity and the diurnal cycle of radiative temperature, but is also seen in sensible heat flux. Within-canopy temperature profiles are markedly different compared with profiles obtained using Monin–Obukhov similarity theory, and the roughness sublayer produces cooler daytime and warmer nighttime temperatures. The herbaceous sites also show model improvements, but the improvements are related less systematically to the roughness sublayer parameterization in these canopies. The multilayer canopy with the roughness sublayer turbulence improves simulations compared with CLM4.5 while also advancing the theoretical basis for surface flux parameterizations.

Accuracy of bulk-method-determined flux, stability, and sea surface roughness

Abstract: This paper discusses the various uses of bulk-method-determined fluxes and the inherent difficulties of making flux measurements over the ocean. The accuracy of eddy correlation, profile, dissipation, and bulk flux methods is compared. We conclude that there are four principal sources of uncertainty in bulk flux determinations made using ship data: the accuracy of the flux measurements used to develop the bulk method, the variations resulting from the use of different bulk coefficient schemes, the accuracy of the meteorological sensors, and the distortion of the measurements produced by the ship. This paper also describes previously published analyses of each of these uncertainty sources and compares the relative importance of those sources. Finally, the results are combined to estimate the overall accuracy of the method. Our analysis determined that the average accuracy of the bulk method ranges from 35% to 105% for stress magnitudes of 0.025–1.0 N/m2, 35–220% for sensible heat flux magnitudes of 5–150 W/m2, 40–215% for latent heat flux magnitudes of 10–300 W/m2, 85% to > 1000% for Monin-Obukhov stability magnitudes at 10 m of 0.001–10, and 160% to > 1 × 104% for roughness length magnitudes of 10−5–10−2 m. The results of the analysis are presented graphically and in tabular and polynomial forms to facilitate their use by those wishing to test the sensitivity of their work to the typical average uncertainty of bulk method flux, stability, and sea surface roughness determinations.

Diurnal and inter-monthly variation of land surface heat fluxes over the central Tibetan Plateau area

Abstract: The energy and water cycle over the Tibetan Plateau play an important role in the Asian monsoon system, which in turn is a major component of both the energy and water cycles of the global climate system. Using field observational data observed from the GAME/Tibet (GEWEX (Global Energy and Water cycle Experiment) Asian Monsoon Experiment on the Tibetan Plateau) and the CAMP/Tibet (CEOP (Coordinated Enhanced Observing Period) Asia-Australia Monsoon Project (CAMP) on the Tibetan Plateau), some results on the local surface energy partitioning (diurnal variation, inter-monthly variation and vertical variation etc.) are presented in this study. The study on the regional surface energy partitioning is of paramount importance over heterogeneous landscape of the Tibetan Plateau and it is also one of the main scientific objectives of the GAME/Tibet and the CAMP/Tibet. Therefore, the regional distributions and their inter-monthly variations of surface heat fluxes (net radiation flux, soil heat flux, sensible heat flux and latent heat flux) are also derived by combining NOAA-14/AVHRR data with field observations. The derived results were validated by using the ground truth, and it shows that the derived regional distributions and their inter-monthly variations of land surface heat fluxes are reasonable by using the method proposed in this study. Further improvement of the method and its applying field were also discussed.