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This paper investigates the surface-layer processes associated with the morning transition from nighttime downslope winds to daytime upslope winds over a semi-isolated massif. It provides an insight into the characteristics of the transition and its connection with the processes controlling the erosion of the temperature inversion at the foot of the slope. First, a criterion for the identification of days prone to the development of purely thermally driven slope winds is proposed and adopted to select five representative case studies. Then, the mechanisms leading to different patterns of erosion of the nocturnal temperature inversion at the foot of the slope are analyzed. Three main patterns of erosion are identified: the first is connected to the growth of the convective boundary layer at the surface, the second is connected to the descent of the inversion top, and the third is a combination of the previous two. The first pattern is linked to the initiation of the morning transition through surface heating, and the second pattern is connected to the top-down dilution mechanism and so to mixing with the above air. The discriminating factor in the determination of the erosion pattern is identified in the partitioning of turbulent sensible heat flux at the surface. Significance Statement The purpose of this study is to improve our understanding of the thermally driven slope circulations with a focus on the unsteady processes associated with the morning transition and the erosion patterns of the nocturnal temperature inversion, so far in the literature less investigated and understood than the evening transition. Understanding this diurnal process will advance our abilities to model it and to improve the accuracy of weather forecasting in complex terrain.

This study uses advanced numerical and diagnostic methods to evaluate the atmospheric energy budget with the fifth major global reanalysis produced by ECMWF (ERA5) in combination with observed and reconstructed top of the atmosphere (TOA) energy fluxes for the period 1985–2018. We assess the meridional as well as ocean–land energy transport and perform internal consistency checks using mass-balanced data. Furthermore, the moisture and mass budgets in ERA5 are examined and compared with previous budget evaluations using ERA-Interim as well as observation-based estimates. Results show that peak annual mean meridional atmospheric energy transports in ERA5 (4.58 ± 0.07 PW in the Northern Hemisphere) are weaker compared to ERA-Interim (4.74 ± 0.09 PW), where the higher spatial and temporal resolution of ERA5 can be excluded as a possible reason. The ocean–land energy transport in ERA5 is reliable at least from 2000 onward (~2.5 PW) such that the imbalance between net TOA fluxes and lateral energy fluxes over land are on the order of ~1 W m−2. Spinup and spindown effects as revealed from inconsistencies between analyses and forecasts are generally smaller and temporally less variable in ERA5 compared to ERA-Interim. Evaluation of the moisture budget shows that the ocean–land moisture transport and parameterized freshwater fluxes agree well in ERA5, while there are large inconsistencies in ERA-Interim. Overall, the quality of the budgets derived from ERA5 is demonstrably better than estimates from ERA-Interim. Still some particularly sensitive budget quantities (e.g., precipitation, evaporation, and ocean–land energy transport) show apparent inhomogeneities, especially in the late 1990s, which warrant further investigation and need to be considered in studies of interannual variability and trends.

The spatial heterogeneity and temporal variation of soil moisture and surface heat fluxes are key to many geophysical and environmental studies. It has been demonstrated that they can be mapped by assimilating soil thermal and wetness information into surface energy balance models. The aim of this work is to determine whether enhancing the spatial resolution or temporal sampling frequency of soil moisture data could improve soil moisture or surface heat flux estimates. Two experiments are conducted in an area mainly covered by grassland, and land surface temperature (LST) observations from the Geostationary Operational Environmental Satellite (GOES) mission are assimilated together with either an enhanced L-band passive soil moisture product (9 km, 2–3 days) from the Soil Moisture Active Passive (SMAP) mission or a merged product (36 km, quasi-daily) from the SMAP and the Soil Moisture Ocean Salinity (SMOS) mission. The results suggest that the availability of soil moisture observations is increased by 41% after merging data from the SMAP and the SMOS missions. A comparison with results from a previous study that assimilated a coarser SMAP soil moisture product (36 km, 2–3 days) suggests that enhancing the temporal sampling frequency of soil moisture observations leads to improved soil moisture estimates at both the surface and root zone, and the largest improvement is seen in the bias metric (0.008 and 0.007 m3 m−3 on average at the surface and root zone, respectively). Enhancing the spatial resolution, however, does not significantly improve soil moisture estimates, particularly at the surface. Surface heat flux estimates from assimilating soil moisture data of different spatial or temporal resolutions are very similar.

International audience; Sea surface temperature in the central-eastern equatorial Atlantic has a seasonal cycle far bigger than that of the Pacific, but interannual anomalies smaller than those of the Pacific. Given the amplitude of seasonal SST variability, one wonders whether the seasonal cycle in the Atlantic is so dominant that it is able to strongly influence the evolution of its interannual variability. In this study, interannual upper-ocean variability within the tropical Atlantic is viewed from an energetics perspective, and the role of ocean dynamics, in particular the role of ocean memory, within zonal mode events is investigated. Unlike in the Pacific where seasonal and interannual variability involve distinctly different processes, the results suggest that the latter is a modulation of the former in the Atlantic, whose seasonal cycle has similarities with El Niño and La Niña in the Pacific. The ocean memory mechanism associated with the zonal mode appears to operate on much shorter time scales than that associated with the El Niño-Southern Oscillation, largely being associated with interannual modulations of a seasonally active delayed negative feedback response. Differences between the El Niño-Southern Oscillation and the zonal mode can then be accounted for in terms of these distinctions. Anomalous wind power over the tropical Atlantic is shown to be a potential predictor for zonal mode events. However, because zonal mode events are due to a modulation of seasonally active coupled processes, and not independent processes operating on interannual time scales as seen in the Pacific, the lead time of this potential predictability is limited.

In this study, attention has been focused on the climatology of some variables linked to the turbulent exchanges of heat and water vapor in the surface layer during a summer monsoon in Korea. In particular, the turbulent fluxes of sensible and latent heat, the hydrologic budget, and the soil temperatures and moistures have been analyzed. At large scale, because the measurements of those data are not only fragmentary and exiguously available but also infeasible for the execution of climatologic analyses, the outputs of a land surface scheme have been used as surrogate of observations to analyze surface layer processes [this idea is based on the methodology Climatology of Parameters at the Surface (CLIPS)] in the Korean monsoonal climate. Analyses have been made for the summer of 2005. As a land surface scheme, the land surface process model (LSPM) developed at the University of Torino, Italy, has been employed, along with the data collected from 635 Korean meteorological stations. The LSPM predictions showed good agreement with selected observations of soil temperature. Major results show that, during the rainfall season, soil moisture in the first tenths of centimeters frequently exceeds the field capacity, whereas most of the rainfall is “lost” as surface runoff. Evapotranspiration is the dominant component of the energy budget, sometimes even exceeding net radiation, especially during the short periods between the precipitation events; in these periods, daily mean soil temperatures are about 28°C or even more. The Gyeonggi-do region, the metropolitan area surrounding Seoul, shows some particularities when compared with the neighboring regions: solar radiation and precipitations are lower, causing high values of sensible heat flux and soil temperatures, and lower values of latent heat flux and soil moistures.