Latent Heat Effects Research Articles

Novel microstructural features of selective laser melted lattice struts fabricated with single point exposure scanning

Single point exposure scanning strategy is a largely unexplored selective laser melting (SLM) technique to fabricate lattice structures without an STL file. In this work, we used a series of >50 sets of processing parameters to systematically study the SLM fabrication of vertical struts made of Ti-6Al-4 V. In addition, the effects of (partial) re-melting and latent heat on hardness and developed microstructure were investigated. We demonstrate that the strut dimensions could be controlled by the processing parameters with higher energy inputs, resulting in larger strut diameters up to a saturation point (i.e. 520 μm corresponding to 0.5 J energy). The single point exposure method yielded keyhole shaped pores that were up to 4 times smaller than those observed, typically when the hatching and contour technique is used. Transmission electron microscopy (TEM) images revealed ultrafine (˜200–300 nm) and homogeneous microstructure in the double-melted specimens as compared to the classic microstructure of SLM Ti6Al4V observed in the single melted strut: hierarchical α'-laths with varying sizes (0.1–1 μm). Finally, we investigated the texture and identified the retained β phase, which enabled us to check the Burgers orientation relationship (BOR) between α' and β phases. This is the first attempt to systematically study the microstructural features resulting from the single point exposure SLM technique for lattice structures made from Ti6Al4V, and exhibits the processability window that could be used to engineer the microstructure of such structures.

Potential Vorticity Diagnostics to Quantify Effects of Latent Heating in Extratropical Cyclones. Part II: Application to Idealized Climate Change Simulations

Abstract It is still debated how enhanced cloud-condensational latent heating (LH) in a warmer and moister climate may affect the dynamics of extratropical cyclones. In this study, a diagnostic method that explicitly quantifies the contribution of LH to the lower-tropospheric cyclonic potential vorticity (PV) anomaly is used to investigate the effects of stronger LH on the dynamics, intensity, and impacts of cyclones in two conceptually different sets of idealized climate change simulations. A first set of regional surrogate climate change simulations of individual moderate to intense Northern Hemisphere cyclones in a spatially homogeneously 4-K-warmer climate reveals that enhanced LH can largely but not exclusively explain the substantially varying increase in intensity and impacts of most of these cyclones. A second set of idealized aquaplanet GCM simulations demonstrates that the role of enhanced LH becomes multifaceted for large ensembles of cyclones if climate warming is additionally accompanied by changes in the horizontal and vertical temperature structure: cyclone intensity increases with warming due to the continuous increase in LH, reaches a maximum in climates warmer than present day, and decreases beyond a certain warming once the increase of LH is overcompensated by the counteracting reduction in mean available potential energy. Because of their substantially stronger increase in LH, the most intense cyclones reach their maximum intensity in warmer climates than moderately intense cyclones with weaker LH. This suggests that future projections of the extreme tail of the storm tracks might be particularly sensitive to a correct representation of LH.

Thermoregulation effect analysis of microencapsulated phase change thermoregulation agent for asphalt pavement

To analyze the latent heat thermoregulation effect of the microencapsulated phase change material (Micro-PCM) on the pavement asphalt mixture, 300 mm × 300 mm × 300 mm outdoor cubic specimen made up of asphalt mixture with the Micro-PCM was prepared. By arranging a sufficient number of temperature sensors inside the specimen, a real-time monitoring system was established to record the temperature variations of the specimen. Two indices, the latent heat accumulated temperature value (LHATV) and latent heat thermoregulation index (LHTI) were proposed to evaluate the latent heat thermoregulation performance of the Micro-PCM under heating and cooling processes. The results showed that the solar radiation and air flow conditions were the important factors affecting the latent heat effect of the Micro-PCM. The responses of the heat transfer process of the Micro-PCM varied at different locations inside the specimen, which caused a difference in the latent heat efficiency. Meanwhile, under the conditions where the ambient temperature changed rapidly, the phase change response inside the specimen would be relatively lagged, the process of latent heat storage was hindered, and the heat couldn’t be completely converted to the latent form. It can be conclude that the excessive heating and cooling rates will affect the process of latent heat, the thermoregulation efficiency of the Micro-PCM can be maintained at a high level under the appropriate variable temperature conditions, a medium temperature range and time span. Under these conditions, the Micro-PCM can exert an effective latent heat thermoregulation function to asphalt mixture.

Effect of Latent Heat of Aluminum Alloys on Bonding between Strips in Clad Strip Cast by a Twin-Roll Caster

This study shows that the latent heat of the aluminum alloy in an overlay strip is the key factor affecting the bonding quality of clad strips fabricated by a vertical-type tandem twin-roll caster. Three-layer clad strips, for which the base strip was 3003 aluminum alloy and the overlay strip was Al-1%Si, Al-2%Si, Al-11%Si (4045), Al-2%Mg, and Al-4.5%Mg (5182), respectively, were cast. The 4045 overlay strip bonded to the base strip. However, overlay strips made of the other alloys did not bond to the base strip. The latent heat of Si is much higher than that of Al, which in turn is higher than that of Mg. Therefore, the latent heat of the 4045 alloy was higher than that of the other alloys. The high latent heat of the 4045 alloy allowed it to heat the base strip to a temperature at which bonding was possible.

Challenging the Greenhouse Effect Specification and the Climate Sensitivity of the IPCC

The greenhouse effect concept has been developed to explain the Earth’s elevated temperature. The prevailing theory of climate change is the anthropogenic global warming theory, which assumes that the greenhouse (GH) effect is due to the longwave (LW) absorption of 155.6 Wm-2 by GH gases and clouds. The actual warming increase to 33°C of the Earth’s surface temperature according to the present GH effect definition is the infrared downward LW radiation of 345.6 Wm-2 emitted by the atmosphere. The atmosphere’s temperature is the key element behind this radiation. According to the energy laws, it is not possible that the LW absorption of 155.6 Wm-2 by the GH gases could re-emit downward LW radiation of 345.6 Wm-2 on the Earth’s surface. In this study, the GH effect is 294.5 Wm-2, including shortwave radiation absorption by the atmosphere and the latent and sensible heating effect. This greater GH effect is a prerequisite for the present atmospheric temperature, which provides downward radiation on the surface. Clouds’ net effect is 1% based on the empirical observations. The contribution of CO2 in the GH effect is 7.3% corresponding to 2.4°C in temperature. The reproduction of CO2 radiative forcing (RF) showed the climate sensitivity RF value to be 2.16 Wm-2, which is 41.6% smaller than the 3.7 Wm-2 used by the IPCC. A climate model showing a climate sensitivity (CS) of 0.6°C matches the CO2 contribution in the GH effect, but the IPCC’s climate model showing a CS of 1.8°C or 1.2°C does not.

A non-isothermal phase field study of the shape memory effect and pseudoelasticity of polycrystalline shape memory alloys

In this paper, a non-isothermal phase field (PF) model is proposed to investigate the shape memory effect (SME) and pseudoelasticity (PE) of polycrystalline shape memory alloys (SMAs) with consideration of the latent heat effect. The latent heat release and absorption accompanying the phase transformation processes are explicitly considered by coupling the phase field evolution with latent heat conduction. A modified Gibbs free energy function is proposed to accommodate the continuously varying temperature. It is shown that the SME and PE of polycrystalline SMAs under different ambient temperatures can be well characterized with the proposed PF model within a unified framework. The PF simulation results are in accordance with the previously reported experimental results. The influences of various factors such as the ambient temperature, grain size, crystal orientation, and latent heat effect on the phase transformation process and mechanical responses as well as the temperature evolution of SMAs are systematically discussed by conducting PF simulations. Some important implications for the devise of elastocaloric cooling devices are provided.

Numerical Simulation of Residual Stress in P91 Repair Welding Incorporating Martensitic Transformation

The type IV cracking is one of the main reasons for service failure. The repair welding is implemented to solve this problem. The residual stress in P91 repair welding incorporating martensitic transformation (MT) is acquired through finite element simulation. In the simulation, the ABAQUS and the user subroutines FILM, DFLUX, HETVAL, USDFLD, UEXPAN and UHARD are adopted. The effect of MT latent heat on temperature and the effects of the volume expansion, the yield strength change and the transformation plasticity on stress are considered. The results show that there is full MT in the repair welding area and the old welding area. The MT latent heat makes the temperature of the repair welding area increase. The residual stress of the repair welding area decreases because MT relieves the thermal stress. Before repair welding, the residual stress distribution is M-shape, which is consistent with the experimental results. After repair welding, the residual stress of repair welding area decreases and the residual stress of old welding area increases.

Effects of Cloud Microphysical Latent Heat on a Heavy Rainstorm in Beijing

The latent heat produced by cloud microphysical processes can greatly affect the thermal and dynamic structure of the atmosphere, as well as the development and evolution of clouds and precipitation. In this study, to examine the consequences of different kinds of latent heat produced by microphysical processes, four sensitivity tests were conducted based on the control simulation results of a heavy rainstorm occurred in Beijing on 21 July 2012 using the Weather Research and Forecasting Model (WRF). Without the latent heat absorption of evaporation, the convective cloud system developed stronger, and the accumulated precipitation amount increased. Without the latent heat release of deposition, the transit time of the surface front was delayed; in addition, the convective cloud system developed weakly. The accumulated conversion amounts of microphysical processes and the accumulated rainfall amount in the deposition adiabatic test were far less than those in the other tests. Without the latent heat of melting and freezing, the convective cloud system did not change substantially, and there was only a minor effect on precipitation. Hydrometeor production exhibited some changes related to precipitation in the five tests. The latent heat produced by the convective system varied substantially in the five tests with a change in the latent heat budget.

METHODS OF PRESERVATION OF FRUIT

The aim of this paper is to demonstrate that procedures and methods of conservation are very important for the production of good and quality fruit products. The use of preserving methods is essential in order to preserve the quality for a long period of time in most fruit products. Conservation methods are divided into three groups: physical, chemical and biological methods. In these methods, the temperature and the quality of the raw materials are very important. In order to obtain various fruit juices, pulps, various fruit products, all the conditions and in particular the method, method, temperature and conservation conditions must be taken into account. The most common and most used methods are pasteurization, sterilization, drying and freezing. In the pasteurisation method, latent heat and air effect must be taken into account, which directly affect the quality of the products obtained by this method.

Determination of Optimum Hot-Water Temperatures for PCM Radiant Floor-Heating Systems Based on the Wet Construction Method

Owing to use of mortar, which demonstrates low heat storage and discharge performance, conventional radiant floor-heating systems, based on the wet construction method and hot-water circulation, consume large amounts of energy. This study proposes a new type of radiant floor-heating system that is capable of reducing energy consumption via use of the latent heat of a phase change material (PCM), whereby the phase change, which occurs within, is induced by the thermal energy supplied by hot water. Simulation analyses revealed that hot-water supply temperatures, required to maintain the floor-surface and indoor-air temperatures at the set point using PCM latent heat, were in the range 40–41 °C. At supply water temperatures measuring less than 39 °C or exceeding 42 °C, the latent-heat effect of the phase change of the PCM tended to fail, and the corresponding floor-surface temperature assumed a value different from that corresponding to the set point. By contrast, supply temperatures in the range 40–41 °C resulted in return temperatures measuring approximately 27.4–27.5 °C, which in turn corresponded to an indoor air temperature of 21.6–22.6 °C that was stably maintained within ±0.6 °C of the 22 °C set-point temperature.

The Influences of Orography and Ocean on Track of Typhoon Megi (2016) Past Taiwan as Identified by HWRF

AbstractTyphoon Megi (2016) headed northwestward toward Taiwan with southward deflection near landfall. In this study, Hurricane Weather Research and Forecast system (HWRF) was used to investigate the mechanism of the track changes over free ocean and track deflection near landfall. HWRF simulations using more realistic Hybrid Coordinate Ocean Model sea surface temperature (SST) analysis improve the northward biased track compared with that using Global Forecast System SST, due to the initial cooler SST below the storm path. The initial warmer Global Forecast System SST leads to a northward track shifting with an overintensified typhoon. As the Princeton Ocean Model is coupled, the SST over South China Sea becomes warmer leading to a northward track shifting compared to a southward shifting induced by the upper ocean cooling due to the typhoon‐ocean interactions in the vicinity of the typhoon. Regardless of track shifting, southward deflection near landfall is mainly controlled by orographic effects of the Central Mountain Range (CMR). Cyclonic northerly is enhanced to the west of the typhoon center ahead and over the CMR that results in southward deflection. Diagnostics of potential vorticity (PV) tendency budget indicates that southward deflection can be explained by the southeastward tendency of latent heating effects near landfall. The combined effects of latent heating and cyclonic rotation of positive wave numer‐1 (WN‐1) potential vorticity vertical advection dominate the southward deflection when the typhoon is closer to Taiwan. Furthermore, the typhoon movement near landfall is slowed down mainly due to WN‐1 negative vertical differential latent heating over the northern CMR.

Diurnal variation in the intensity of nascent Tibetan Plateau vortices

Tibetan Plateau vortices (TPVs) are major rain‐producing systems forming over the Tibetan Plateau, and the ones moving off the plateau can trigger heavy rainfall over eastern China. The survival probability of a nascent TPV is closely related to its intensity, which is important in the prediction of the precipitation over and to the east of the Tibetan Plateau. In this study, diurnal variation of the intensity of nascent TPVs (ITPV) occurring in four local time periods (hours 00–06 LT, 06–12 LT, 12–18 LT, 18–00 LT; LT = UTC + 6 h) during May–August of 2000–2016 was investigated. The average ITPV shows a robust diurnal variation, with the maximum from evening to midnight (18–00 LT) and minimum from morning to noon (06–12 LT). In 18–00 LT, the ratios of the strong and weak TPVs are 46 and 22.2%, respectively, while those in 06–12 LT are 26.3 and 42.4%. The strong TPVs occurring in 18–00 LT are mainly located over the western and central Tibetan Plateau, while in 06–12 LT over the central and eastern Tibetan Plateau. The dynamic and thermodynamic processes associated with the diurnal variation of ITPV are studied, revealing the important roles of large‐scale circulations and condensational latent heat related to precipitation. In 18–00 LT, the strongest convergence at 500 hPa, divergence at 200 hPa, and the accordingly strongest ascending motion, as well as the largest amount of net water vapour budget are observed, benefiting the precipitation and the related latent heat release. On the contrary, the situations in 06–12 LT result in little latent heat release. The diagnosis of potential vorticity budget further verifies the important effect of condensational latent heating on ITPV.

Characteristics of Water‐Heat Exchanges and Inconsistent Surface Temperature Changes at an Elevational Permafrost Site on the Qinghai‐Tibet Plateau

AbstractIncrease of surface temperatures has long been recognized as an unequivocal response to radiative forcing and one of the most important implications for global warming. However, it remains unclear whether the variation of ground surface temperature (GST) and soil temperatures is consistent with simultaneous changes of the near‐surface air and land (or skin) surface temperatures (Ta and LST). In this study, a seven‐year continuous observation of GST, Ta, and surface water and heat exchange was carried out at an elevational permafrost site at Chalaping, northeastern Qinghai‐Tibet Plateau. Results showed a distinct retarding of warming on the ground surface and subsurface under the presence of dense vegetation and moist peat substrates. Mean annual Ta and LST increased at noteworthy rates of 0.22 and 0.32 °C/a, respectively, while mean annual GST increased only at a rate of 0.057 °C/a. No obvious trends were detected for the four radiation budgets except the soil heat flux (G), which significantly increased at a rate of 0.29 W · m−2 · a−1, presumably inducing the melting of ground ice and resulted in much higher moisture content through the summers of 2015 and 2016 than preceding years and subsequent 2017 at the depths between 80 and 120 cm. However, no noticeable immediate variations of soil temperatures occurred owing to the large latent heat effect (thermal inertia) and the extending zero‐curtain period. We suggest that a better protected eco‐environment, particularly the surface vegetation, helps preserving the underlying permafrost, and thus to mitigates the potential degradation of elevational permafrost on the Qinghai‐Tibet Plateau.

Thermal Modeling of Temperature Distribution in Metal Additive Manufacturing Considering Effects of Build Layers, Latent Heat, and Temperature-Sensitivity of Material Properties

A physics-based analytical model is proposed in order to predict the temperature profile during metal additive manufacturing (AM) processes, by considering the effects of temperature history in each layer, temperature-sensitivity of material properties and latent heat. The moving heat source analysis is used in order to predict the temperature distribution inside a semi-infinite solid material. The laser thermal energy deposited into a control volume is absorbed by the material thermodynamic latent heat and conducted through the contacting solid boundaries. The analytical model takes in to account the typical multi-layer aspect of additive manufacturing processes for the first time. The modeling of the problem involving multiple layers is of great importance because the thermal interactions of successive layers affect the temperature gradients, which govern the heat transfer and thermal stress development mechanisms. The temperature profile is calculated for isotropic and homogeneous material. The proposed model can be used to predict the temperature in laser-based metal additive manufacturing configurations of either direct metal deposition or selective laser melting. A numerical analysis is also conducted to simulate the temperature profile in metal AM. These two models are compared with experimental results. The proposed model also well captured the melt pool geometry as it is compared to experimental values. In order to emphasize the importance of solving the problem considering multiple layers, the peak temperature considering the layer addition and peak temperature not considering the layer addition are compared. The results show that considering the layer addition aspect of metal additive manufacturing can help to better predict the surface temperature and melt pool geometry. An analysis is conducted to show the importance of considering the temperature sensitivity of material properties in predicting temperature. A comparison of the computational time is also provided for analytical and numerical modeling. Based on the obtained results, it appears that the proposed analytical method provides an effective and accurate method to predict the temperature in metal AM.

Effects of martensitic transformation on residual stress of P91 welded joint

The new method considering thermo-metallurgical and thermo-mechanical relationship of P91 welded joint was proposed in this paper by using the ABAQUS. In this new method, we developed a whole set of programs by using subroutines to do the calculations and consider the martensitic transformation (MT) effects. Firstly, the effect of MT latent heat on temperature field was considered. Then on the basis of the temperature field, the residual stress was calculated by considering the effects of volume expansion, the yield strength change and the transformation plasticity due to MT. The results show that the MT latent heat makes the temperature increase, which is consistent with the conclusion in the literature. The martensite microstructure is concentrated in weld bead and heat affected zone. The residual stress distribution is M-shape when the effects of MT are considered, which is consistent with the experimental results. The volume expansion makes the residual stress decrease a lot, the yield strength change makes the residual stress increase a little and the transformation plasticity has the ‘relaxation effect’. The volume expansion, the yield strength change and the transformation plasticity’s effects on residual stress decrease in turn.

Non-hysteretic first-order phase transition with large latent heat and giant low-field magnetocaloric effect

First-order magnetic transitions (FOMTs) with a large discontinuity in magnetization are highly sought in the development of advanced functional magnetic materials. Isosymmetric magnetoelastic FOMTs that do not perturb crystal symmetry are especially rare, and only a handful of material families, almost exclusively transition metal-based, are known to exhibit them. Yet, here we report a surprising isosymmetric FOMT in a rare-earth intermetallic, Eu2In. What makes this transition in Eu2In even more remarkable is that it is associated with a large latent heat and an exceptionally high magnetocaloric effect in low magnetic fields, but with tiny lattice discontinuities and negligible hysteresis. An active role of the Eu-5d and In-4p states and a rather unique electronic structure borne by In to Eu charge transfer, altogether result in an unusual exchange mechanism that both sets the transition in motion and unveils an approach toward developing specific magnetic functionalities ad libitum.

Investigation on flow and heat transfer characteristics of ice slurry without additives in a plate heat exchanger

Ice slurry without additives plays a positive role in direct contact food and medical protective cooling applications, as we all now there are not adequate research on the flow and heat transfer characteristics of ice slurry without additives. Thus, experiments are conducted to determine the flow and heat transfer characteristics of 0–20 wt% ice slurry without additives through a plate heat exchanger (PHE) in present research. The results indicate that the pressure drop of ice slurry is about 5.5–61.0 kPa as the flow rate increased from 0.414 to 1.1 m3/h, it is about 1.2–1.6 times of that of chilled water. The pressure drops of ice slurry could be presented as a function of flow rate, ice fraction and Reynolds number, which are greater than that of the chilled water. The flow rate has a greater impact than ice fraction on pressure drop, which has an increment of 20% as the flow rates varying from 0.414 to 1.270 m3/h. The pressure drop of melting ice slurry is much smaller than that without heat exchanging, and it has no significant change as ice fraction decreases from 5% to 20% during heat exchanging. Based on the experimental results, the flow friction factor correlation is developed, and the local heat transfer correlation for ice slurry is also established with consideration of effect of latent heat on the heat transfer. In addition, the heat transfer analysis shows that the overall heat transfer coefficient of heat exchanger increases with the increase of flow rate. The flow rate plays a more important role than ice fraction in determining the overall heat transfer coefficient. The overall heat transfer coefficient and cooling duty increase with the of increase inlet water temperature and flow rate. And cooling duty has about 18.5–32.6% increment as the ice fraction varies from 0 to 5 wt%, but its increment is very small as the ice fraction is between 5 wt% and 20 wt%.

Coupled cooling method and application of latent heat thermal energy storage combined with pre-cooling of envelope: Temperature control using phase-change chair

A latent heat thermal energy storage system is a safe, stable, and reliable method of controlling the room temperature. However, this system is difficult to fit in some harsh environments such as a mine refuge chamber where the temperature is high. In this article, a new coupled cooling method implementing a phase change chair (PCC) is proposed, which is not only suitable for harsh environments, but also saves valuable living space. A new PCC model and a simplified coupled heat transfer model considering the air, surrounding rock, PCC, and heat source are established. The effects of melting temperature, latent heat, thermal conductivity, and thickness of PCC were systematically investigated. The analysis results indicated that: (i) the coupled cooling method based on the PCC could effectively control the temperature in 40 h. (ii) under the given operating conditions, the optimal melting temperature is approximately 27 °C, and the thermal conductivity of PCC is 0.6 W/m K. (iii) increasing the latent heat and the thickness of PCC has a similar effect on temperature control. For every 30 kJ/kg increase in the latent heat or 0.01 m increase in the thickness, the control time increases by 4.5 h, but the effect gradually decreases.

Determination of soil ground heat flux through heat pulse and plate methods: Effects of subsurface latent heat on surface energy balance closure

The soil heat flux plate method is popularly applied in surface energy balance studies. Previous studies have shown that impervious plate blocks the flow of water and vapor within soil. Soil heat flux is generally commonly measured below surface, and its exact constitution is required in calculating surface energy balance. When subsurface evaporation occurs, subsurface latent heat sink constitutes an important proportion of the apparent ground heat flux. However, the plate method fails to detect such occurrence. In aboveground meteorological measurement, evaporated vapor moving out of soil profile is also being detected and the subsurface latent heat sink is recognized as part of turbulent latent heat flux. Thus, caution should be exercised when excluding the potential error from double counting of subsurface latent heat sink in surface energy balance evaluation. In this study, two common combination methods were used to determine the ground heat flux without latent heat sink (G0). One method is a combination of gradient-based heat pulse measurements and calorimetric method (GradC), and the other method is a combination of plate measurements at shallow depths and calorimetric method (PlateC). Results demonstrated that, in contrast to the PlateC method, the GradC method minimized the disturbance in soil structure and reduced the disruption in heat and water flow. Furthermore, the estimated G0 from the PlateC method was only 49.2% of that of the GradC method during daytime. Moreover, surface energy balance closure (EBC) was evaluated using the estimated G0 and aboveground turbulent energy flux data. In comparison with the PlateC method, the GradC method improved the surface EBC from 79.3% to 87.7% during daytime. In summary, accurate knowledge on the composition of ground heat flux and the location of water evaporation is necessary to calculate surface energy balance during micro-meteorology measurements.

Ground surface temperature reconstruction for the last 500 years obtained from permafrost temperatures observed in the SHARE STELVIO Borehole, Italian Alps

Abstract. Here we present the results of the inversion of a multi-annual temperature profile (2013, 2014, 2015) of the deepest borehole (235 m) in the mountain permafrost of the world located close to Stelvio Pass in the Central Italian Alps. The SHARE STELVIO Borehole (SSB) has been monitored since 2010 with 13 thermistors placed at different depths between 20 and 235 m. The negligible porosity of the rock (dolostone, < 5 %) allows us to assume the latent heat effects are also negligible. The inversion model proposed here is based on the Tikhonov regularization applied to a discretized heat equation, accompanied by a novel regularizing penalty operator. The general pattern of ground surface temperatures (GSTs) reconstructed from SSB for the last 500 years is similar to the mean annual air temperature (MAAT) reconstructions for the European Alps. The main difference with respect to MAAT reconstructions relates to post Little Ice Age (LIA) events. Between 1940 and 1989, SSB data indicate a cooling of ca. 1 °C. Subsequently, a rapid and abrupt GST warming (more than 0.8 °C per decade) was recorded between 1990 and 2011. This warming is of the same magnitude as the increase in MAAT between 1990 and 2000 recorded in central Europe and roughly doubling the increase in MAAT in the Alps.