Accurate estimation of the timing of intensive spring leaf growth initiation at mid and high latitudes is crucial for improving the predictive capacity of biogeochemical and Earth system models. In this study, we focus on the modeling of climatological onset of spring leaf growth in Central Europe and use three spring phenology models driven by three meteorological datasets. The MODIS-adjusted NDVI3g dataset was used as a reference for the period between 1982 and 2010, enabling us to study the long-term mean leaf onset timing and its interannual variability (IAV). The performance of all phenology model–meteorology database combinations was evaluated with one another, and against the reference dataset. We found that none of the constructed model–database combinations could reproduce the observed start of season (SOS) climatology within the study region. The models typically overestimated IAV of the leaf onset, where spatial median SOS dates were best simulated by the models based on heat accumulation. When aggregated for the whole study area, the complex, bioclimatic index-based model driven by the CarpatClim database could capture the observed overall SOS trend. Our results indicate that the simulated timing of leaf onset primarily depends on the choice of model structure, with a secondary contribution from the choice of the driving meteorological dataset.
<p>Plant phenology focuses on the annual repetitive development phases of the terrestrial vegetation. Since the date of the onset and the cessation of vegetation growth define the possible time period for photosynthesis, plant phenology strongly affects the carbon cycle of the ecosystems. Phenology has a serious impact on the climate system through the carbon-, water- and energy cycle. Observations indicate changes in the phenological cycle of the vegetation worldwide that are clear indicators of climate change. Warming climate can be associated with more intense carbon uptake, but it can also negatively affect production. Current studies clearly indicated that the phenological cycle is not properly represented in the Earth System Models which means that further research is needed.</p><p>Meteorological variables affecting the state of the environment, such as temperature and precipitation, also play a key role in the development of vegetation. Phenology models of different complexity were developed to quantify the timing of the onset of vegetation growth based on meteorological data. The sensitivity of the models to the source meteorological datasets is rarely studied. The aim of the present study is to quantify the sensitivity of widely used phenology models to the selection of the driving meteorological dataset.</p><p>Two phenology models were used to evaluate the different databases. One is the so-called Growing Degree Day (GDD) method, which calculates the onset date based on the degree day logic. The GDD model is further divided into simple thermal forcing model and thermal model, where the latter includes chilling requirement as well. The second method uses minimum temperature, photoperiod and vapor pressure deficit and calculates a so-called Growing Season Index (GSI) which is used to estimate onset date</p><p>Considering the meteorological data, three different datasets were used. The ERA5 is a reanalysis database, which is the product of the European Centre for Medium-Range Weather Forecasts (ECMWF). The CarpatClim and the FORESEE (Open Database&#160;FOR&#160;ClimatE&#160;Change-Related Impact&#160;Sudies in CEntral&#160;Europe) are observation based, gridded datasets for the larger Carpathian Region (Central Europe). &#160;</p><p>In any modelling exercise aiming at simulating the stages of phenology, observations are essential. In the present study the phenological observation data is originating from satellite data and field observations. The first means the third generation Normalized Vegetation Index (NDVI3g) disseminated by GIMMS (Global Inventory Modeling and Mapping Studies), and the latter means the PEP725 phenology dataset and field observations from the botanical garden of E&#246;tv&#246;s Lor&#225;nd University, located in Budapest.</p>
The purpose of this study is to provide an overview of the science and development of atmospheric energetics, its so far matured parts to date, and the direction of the researches. However, we restrict ourselves to the discussion of the very basic results of the researches to reveal the parts the introduction of which can be suggested into the compulsory education of the future meteorologist. This became feasible especially due to the rapid development of the personal computer that makes possible the calculation of the atmospheric energies for students by using their own laptops, so this field of meteorology now can be a tactile reality for them. The founder of atmospheric energetics was Lorenz, who formulated for a global, dry atmosphere the concept of available potential energy, which is the difference between the current energy state of the atmosphere and a reference state with minimum energy. His basic results concerning the global description of atmospheric energetics have already become part of the university curriculum. It is important to be able to describe the energy balance of the atmosphere both locally as well as globally, for which the introduction of enthalpy and exergy seemed appropriate. The advantage of examining the dry atmosphere is that significant simplifications can be applied, but the atmosphere is finally moist, so research has also started in this direction, first with a global and then with a local approach. The key is to find the reference state, which is a complex, computationally demanding task. In this paper, we focus on the most important steps of this process and concentrate on the thermodynamic basis of the new concepts.
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