The systematic overestimation by climate models of the surface temperature over the eastern tropical oceans is generally attributed to an insufficient oceanic cooling or to an underestimation of ...stratocumulus clouds. We show that surface evaporation contributes as much as clouds to the dispersion of the warm bias intensity in a multimodel simulations ensemble. The models with the largest warm biases are those with the highest surface heating by radiation and lowest evaporative cooling in atmospheric simulations with prescribed sea surface temperatures. Surface evaporation also controls the amplitude of the surface temperature response to this overestimated heating, when the atmosphere is coupled to an ocean. Evaporation increases with temperature both because of increasing saturation humidity and of an unexpected drying of the near‐surface air. Both the origin of the bias and this temperature adjustment point to the key role of near‐surface relative humidity and its control by the atmospheric model.
Key Points
Surface evaporation biases contribute as much as cloud biases to the warm bias intensity
Biases in surface humidity explain most of the evaporation biases over the eastern tropical oceans
Evaporation and relative humidity control the response of the surface temperature to heat fluxes
•Soil and atmospheric water stresses’ effect on cacao’s transpiration are independent.•Atmospheric stress reduced the canopy density by one third regardless of irrigation.•An extra third of the ...canopy density was lost due to soil water stress in the control.•Soil moisture and air vapour pressure are the key drivers of cacao sap velocity.•Cacao transpiration may be more limited by root uptake than canopy conductivity.
In West Africa, Harmattan-induced atmospheric and soil droughts represent seasonally recurring hazards for Theobroma cacao L. agro-ecosystems. Under the influence of the Harmattan winds, precipitation is impaired and air humidity and temperature reach stressful levels. Climate change is causing an increase in temperature that will drive up the evaporative power of the atmosphere, risking to harshen both the soil and atmospheric stress. This would further threaten the viability of cacao cultivation in this region. To characterize the response of cacao trees to atmospheric and soil drought, we monitored two sub-plots, with and without irrigation, throughout one Harmattan season (November 2019 - March 2020) in the Eastern region in Ghana. For both treatments we recorded: sap flow velocity, photosynthetic active radiation (PAR) above and below the canopy, soil moisture, temperature, air humidity and daily precipitation. Leaf area index (LAI) was estimated from PAR measurements. To characterize drought responses of mature cocoa trees during the day and at the seasonal scale, we developed two boosted regression trees models (BRT) with the environmental variables measured. The atmospheric component of Harmattan-induced drought was found to affect the canopy to a similar extent as soil water stress, both causing a decline in LAI of 33%. This study confirmed the importance of soil drought but highlighted as well the crucial role of atmospheric drought for this species’ transpiration control. Soil and atmospheric water stresses did not have a synergistic effect on transpiration under the studied conditions. The BRT models identified LAI as one of the most influential drivers for sap velocity, which, in turn was sensitive to the interactive effect of both atmospheric and soil drought. Our results highlight that not only reduced precipitation but also increasing atmospheric drought is likely to negatively impact on cacao production in West Africa under increasingly dry conditions imposed by the influence of the Harmattan winds.
Ocean‐atmosphere interactions represent a key component of the hydrological cycle in tropical regions and their variability has profound influences on low‐latitude climate. In order to evaluate how ...climate models represent these fluxes while taking into account the observational uncertainties, we assemble a comprehensive database of 14 climatological surface flux products, including in situ‐based, satellite, hybrid, and reanalysis data sets. We find that the large observational uncertainties are reflected in the climatological magnitudes, as well as in the spatial patterns and seasonal variations and that, for the most part, they do not carry specific signatures of product type. This data ensemble allows us to draw several conclusions on the current representation of the intertropical turbulent air‐sea fluxes in the atmospheric component of the Intitut Pierre Simon Laplace‐Coupled Model 5A, when forced by observed sea surface temperatures. Despite significantly underestimated near‐surface wind speeds over the entire tropical oceans domain, the atmospheric model produces generally well represented zonal and meridional wind stress values, and only weak biases in the spatial patterns and seasonality. The simulated latent heat flux develops a bias pattern matching that of the wind speed, but with no systematic underestimation. Compared to the same reference, the sensible heat flux is overestimated over the entire region of interest, in response to a significant overestimation of the sea‐air temperature contrast. The observational ensemble and analyses presented in this paper offer a good framework for large‐scale model surface flux evaluation.
Key Points
Database of 14 turbulent air‐sea flux products is assembled for model evaluation
Proposed methodology is suited for systematic large‐scale model evaluation
Robust biases in state variables do not result in robust biases in IPSL fluxes
Turbulent momentum and heat (sensible heat and latent heat) fluxes at the air–sea interface are key components of the whole energetic of the Earth’s climate. The evaluation of these fluxes in the ...climate models is still difficult because of the large uncertainties associated with the reference products. In this paper we present an objective metric accounting for reference uncertainties to evaluate the annual cycle of the low latitude turbulent fluxes of a suite of IPSL climate models. This metric consists in a Hotelling
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test between the simulated and observed field in a reduce space characterized by the dominant modes of variability that are common to both the model and the reference, taking into account the observational uncertainty. The test is thus more severe when uncertainties are small as it is the case for sea surface temperature (SST). The results of the test show that for almost all variables and all model versions the model-reference differences are not zero. It is not possible to distinguish between model versions for sensible heat and meridional wind stress, certainly due to the large observational uncertainties. All model versions share similar biases for the different variables. There is no improvement between the reference versions of the IPSL model used for CMIP3 and CMIP5. The test also reveals that the higher horizontal resolution fails to improve the representation of the turbulent surface fluxes compared to the other versions. The representation of the fluxes is further degraded in a version with improved atmospheric physics with an amplification of some of the biases in the Indian Ocean and in the intertropical convergence zone. The ranking of the model versions for the turbulent fluxes is not correlated with the ranking found for SST. This highlights that despite the fact that SST gradients are important for the large-scale atmospheric circulation patterns, other factors such as wind speed, and air–sea temperature contrast play an important role in the representation of turbulent fluxes.
The paper presents a study on four species of aromatic plants: a native species from the spontaneous flora of the Republic of Moldova (Nepeta cataria L.), a species to be introduced (Nepeta racemosa ...Lam.) and two non-native species (Nepeta melissifolia Lam., Nepeta grandiflora M. Bieb.); little research has been conducted on these species, but they are therapeutically valuable. The genus Nepeta L. is one of the largest and most important genera in the family Lamiaceae, subfamily Nepetoideae. The studies aimed at their evaluation and characterization from a bio-ecological and phytochemical aspect, in order to highlight the biomorphological peculiarities, the essential oil content and the possibility of using them in aromatherapy, perfumery, phytotherapy and gastronomy. The research highlighted the high adaptive potential and the prospects of cultivation of these species under the pedoclimatic conditions of the Republic of Moldova.
Despite decades of efforts and improvements in the representation of processes as well as in model resolution, current global climate models still suffer from a set of important, systematic biases in ...sea surface temperature (SST), not much different from the previous generation of climate models. Many studies have looked at errors in the wind field, cloud representation or oceanic upwelling in coupled models to explain the SST errors. In this paper we highlight the relationship between latent heat flux (LH) biases in forced atmospheric simulations and the SST biases models develop in coupled mode, at the scale of the entire intertropical domain. By analyzing 22 pairs of forced atmospheric and coupled ocean-atmosphere simulations from the CMIP5 database, we show a systematic, negative correlation between the spatial patterns of these two biases. This link between forced and coupled bias patterns is also confirmed by two sets of dedicated sensitivity experiments with the IPSL-CM5A-LR model. The analysis of the sources of the atmospheric LH bias pattern reveals that the near-surface wind speed bias dominates the zonal structure of the LH bias and that the near-surface relative humidity dominates the east–west contrasts.
The study has been focused on the field of introduction, conservation and use of aromatic and medicinal plants, which represent inexhaustible sources of raw materials for the pharmaceutical, cosmetic ...and food industries. The article describes the results of the evaluation of the prospects for the introduction of 4 species of the genus Agastache Gronov: Agastache foeniculum ( Pursh) Kuntze, Agastache rugosa (Fisch & C. A Mey.) O. Kuntze, Agastache urticifolia (Benth.) Kuntze, Agastache nepetoides L., species that have not been studied in much detail, but of high therapeutic value. The studies focused on the bio-ecological and phytochemical research on the plants, in order to highlight the biomorphological peculiarities, the essential oil content and the possibility of using them in various branches of the national economy. Far from being an exhausted source of remedies, natural products continue to provide low molecular weight compounds with important biological properties that can be used for pharmaceutical purposes.
The phenomenon known as stand-up comedy emerged in the late 1970s when the first live shows of this type were introduced to the public. This type of humour, which relies on ingenuity, contains a ...variety of topics used by comedians, such as their everyday life, religion, politics or racism. These are just a few of the topics usually employed in order to create comedy. It is curious how a serious matter such as racism, for example, can be used to trigger laughter. Eddie Griffin, an African American stand-up comedian, uses this type of topics in almost all of his shows. More than one question come to mind: Why should comedians use racism in this type of discourse? Can it be funny? Are there any special techniques applied when dealing with such a sensitive subject? Can the humour be preserved if the written version of such a show is translated? The present paper aims at finding some answers to these questions and, to this end, looks for textual evidence in Eddie Griffin’s 2011 comedy show You Can Tell ‘Em I Said It.
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