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Building from the result of study I, this study tests how people's past tracking money/ spending/ other self-monitor behaviors (credit card/ cash) impact the willingness to pay with different payment methods, and how given different payment methods impact people's general willingness to pay.

Patterns of stable isotopes of water (18O and 2H) in precipitation have been used as tracers for analyzing environmental processes which can be changed by factors such as the topography or meteorological variables. In this study, we investigated the isotopic data in precipitation for one year in the low mountain range of North Hesse, Germany, and analyzed mainly for altitude, rainfall amount, and air temperature effects on a regional scale. The results indicate that the isotopic composition expressed an altitude effect with a gradient of −0.14‰/100 m for δ18O, −0.28‰/100 m for δ2H and 0.83‰/100 m for Deuterium excess. Patterns of enrichment during warmer months and depletion during colder months were detected. Seasonal correlations were not consistent because the altitude effect was superimposed by other processes such as amount and temperature effects, vapor origins, orographic rainout processes, moisture recycling, and sub-cloud secondary evaporation. Precipitation was mostly affected by secondary evaporation and mixing processes during the summer while depleted moisture-bearing fronts and condensation were more responsible for isotope depletion during winter. In autumn and spring, the amount effect was more prominent in combination with moisture recycling, and large-scale convective processes. The altitude effect was also detected in surface water. The investigated elevation transect with multiple stations provided unique insights into hydrological and climatic processes of North Hesse on a regional scale. The spatial heterogeneity and mixing of different processes suggest that multiple rainfall stations are required when rainfall isotopes serve as forcing data for hydrological applications such as transit time assessments in complex terrains.

Monitoring studies are necessary to better understand the hydrological processes affecting the isotopic signature of cave waters, which are ultimately recorded in speleothems that are used as paleoclimate archives. This research examines changes in the isotopic composition (δ18O and δ2H) of precipitation as it infiltrates through the epikarst and into the Jumandy cave, located in the western Amazon Basin (Ecuador). Meteorological and hydrological parameters were monitored outside and inside the cave, and isotope analyses were carried out in waters from rainfall, an underground river, and drip-water at two sampling sites in the cave between April 2019 and February 2020. At monthly timescale, the rainfall weighted isotopic composition monitored at our stations was strongly correlated with the mean precipitation amount. However, when considered at weekly time-steps, the correlation is only moderate. This implies that the variation of the isotopic composition in the study area cannot be interpreted exclusively as an amount effect. Isotopic values and back-trajectory modeling show that the isotopic signature was affected by the moisture source effect associated with upstream rainout. The moisture flux is dominantly from an east to northeast direction and moisture mainly originates over the Atlantic Ocean, passing through the Amazon Basin. A significant fraction of moisture is associated with local sources within the Amazon Basin. This aspect is confirmed by d-excess values of rainfall and the Local Meteoric Water Lines (LMWLs) that indicate an influence of the high evapotranspiration rate of the Amazon region on the isotopic composition of local rainfall. The infiltrated water resides for about three weeks in the epikarst and then precipitates forming speleothems (residence time). However, this short residence time needs to be confirmed with a longer monitoring period. Despite the different magnitudes of the dripping rates, the isotopic values at the two monitored sites are similar. This suggests that the dripping discharge rate is affected by the karst structure, but the isotopic signature reflects the mixing of individual rainfall events above the cave. Therefore, ẟ18O in speleothems from these caves is mainly recording short-term precipitation changes linked to regional and large-scale atmospheric circulation.

Stable isotopes in precipitation and spring water were observed in a low mountain region, because seasonal variability in isotope altitude and amount effects based on their simultaneous observations in low latitude area have not been studied so much. Seasonal variability in spatial averages of monthly δ

The stable isotopes of oxygen and hydrogen in precipitation are widely used to track processes occurring within the hydrological cycle and understand regional atmospheric patterns that influence a specific area. Moreover, the oxygen isotopic composition of continental carbonates is extensively used for palaeohydrological reconstruction. Nevertheless, few comprehensive investigations have been performed in the Western Mediterranean to analyze the statistical relationships between oxygen and hydrogen stable isotopes in precipitation and meteorological variables. For understanding the factors that regulate the rainfall stable isotopic signature at present day in this area of Mediterranean region we selected the Tuscany region (central Italy), due to its considerable climatic seasonality, complex morphology and orography. Tuscany is affected by both Atlantic atmospheric disturbances from NW and moist air masses originated in the Mediterranean, and also by the secondary cyclogenesis center of the Gulf of Genoa, the most active in the entire Mediterranean. The ideal position of the Tuscany region thus offers the opportunity to investigate the complex influence of moisture sources on the rainfall isotopic composition. Moreover, in this region many hydrogeological and palaeohydrological studies were performed and require a more precise and quantitative interpretation. In this work, 644 isotope monthly data (δ18O, δ2H, and deuterium excess) of precipitation collected in 12 sites through Tuscany from 1971 to 2018 were gathered in a database. Then, only sites whose monthly data covered almost one year were considered for processing, resulting in 553 precipitation samples archived along with monthly mean temperature and rainfall amount. In this framework, the LMWL for Tuscany was determined by applying different regression techniques and statistical analyses were performed to define the influence of meteorological and geographical variables on the rainfall isotopic composition. The outcomes point out the variations of rainfall isotopic signature as result of several climate and geographical variables than a univocal proxy for both local temperature and precipitation amount. The Atlantic and Mediterranean moisture sources differently contribute for generating the observed isotopic variability, and their influence may seasonally change. Overall, the temperature and amount effect allow to explain the 50% of the isotopic variability, but temperature appears to be more important. These local effects are more pronounced during the periods with low rainfall (spring and summer), whereas the large-scale processes (moisture origin, trajectories, and rainout) are prevailing in winter and autumn. The altitude effect is the main driver of isotopic spatial variability. The deuterium excess parameter is revealed to be a very complex but useful signal for disentangling the different contribution of Atlantic and Mediterranean sources in Tuscan precipitation, even if it is sometime misused.

The unusual winter storm event of March 2016 brought excess rainfall in the Central part of Mexico and this study attempts to determine the moisture sources by characterizing the rainwater isotopes (δ18O, δ2H) and understanding their monthly spatial variations. Rainwater samples from six different stations (Agua Blanca, Molango, Mexico City, Pachuca, Tula and Tulancingo) of Mexico were sampled in March, April and May 2016. Enriched isotopic signatures in Tulancingo during March exhibited a mixture of moisture sources in which the predominant source was from the North followed by the Gulf of Mexico, while the depleted isotopic levels in Pachuca and Tula moisture from the recycling of inland vapour. However, the isotopic characterization in the month of April presented no much variations in δ18O values irrespective of the station (−2.31 to −2.56‰), signifying that the prime moisture source is mainly from the inland sources and migrated from the central parts to the Gulf of Mexico. In contrast, the inland migration of the vapour source from Gulf of Mexico was witnessed in May with both the continental and the amount effect. However, the enriched δ18O values in Tulancingo and Agua Blanca in May were found to be −0.84‰ and −1.44‰ respectively, with significant lesser d-excess values.

Environmental isotope tracers were applied in the Upper Crocodile River Basin, Johannesburg, South Africa, to understand the groundwater recharge conditions, flow mechanisms and interactions between surface and subsurface water. Stable isotope analysis indicated that recharge into the fractured quartzite aquifer occurs through direct mechanisms. The high variability in the stable isotope signature of temporal samples from Albert Farm spring indicated the importance of multiple samples for groundwater characterization, and that using a single sample may be yielding biased conclusions. The observed inverse relationship between spring discharge and isotope signature indicated the traces of rainfall amount effect during recharge, thereby suggesting piston groundwater flow. It is deduced that a measured discharge value can be used in this relationship to calculate the isotopic signature, which resembles effective rainfall. In the shallow alluvial deposits that overlie the granitic bed-rock, piezometer levels and stable isotopes revealed an interaction between Montgomery stream and interflow, which regulates streamflow throughout the year. This suggests that caution should be taken where hydrograph separation is applied for baseflow estimates, because the stream flow that overlies such geology may include significant interflow. The hydrochemistry evolution was observed in a stream fed by karst springs. As pH rises due to CO2 degassing, CaCO3 precipitates, thereby forming travertine moulds. The values of saturation indices that were greater than zero in all samples indicated supersaturation by calcite and dolomite and hence precipitation. Through 14C analysis, groundwater flow rate in the karst aquifer was estimated as 11 km/year, suggesting deep circulation in karst structures.

Many studies of Quaternary climate make use of terrestrial stable isotope records which are interpreted based on seasonal patterns of stable isotopes in modern precipitation. Multi-decade records of isotopes in rainfall allow testing of the assumed behavior of isotope signals used for this interpretation on multi-year to decadal scales. A 32-year record of stable O and H isotopes in precipitation in Tucson, Arizona permits a detailed examination of stable isotope amount effects, at time scales ranging from individual events to decades, in a location with summer monsoonal and winter frontal rainy seasons. Amount effects are weak to non-existent in Tucson at seasonal and longer time scales, and are not useful for discriminating either wetter or drier rainy seasons or wetter or drier decades. Amount effects are also weak to non-existent in published data for annual and multi-year amount-weighted averages for monsoonal precipitation in New Delhi and Hong Kong, but an annual amount effect appears to be present on Guam (U.S. Territory). In addition, site-specific amount effects do not correlate with measures of regional monsoon intensity. This data analysis challenges the general validity of paleoclimate reconstructions based on short-term (sub-annual) relationships observed in precipitation isotope data when applied to long-term records such as speleothem studies.

Aiming at assessing the ecological stress of land urbanization comprehensively, three perspectives are considered and combined, i.e. the amount effect with the proportion of construction lands as the indicator, the intensity effect per the density of environmental pollutant emissions, and the location effect based on their spatial distribution in the heterogeneous landscape. The quantitative results of Southern Jiangsu case in Eastern China show the single-perspective ecological stress are spatially different; the proportion effect is higher in city propers which are more densely populated and industrialized. However, the intensity effect is more significant for units along the Yangtze river where heavy industries are gathered, while the location effect is higher in “ecologically suitable” regions. As the integration of proportion, intensity, and location effects, the comprehensive stress differs across Southern Jiangsu and are also different with the single-perspective results. Dominant stressors of each unit are spatially distinct, which benefits policy-makers in targeting their objectives as per primary influencing factors. It is concluded that the comprehensive assessment could efficiently reveal the spatial differentiation of the ecological effects of land urbanization and also the differentiated role of different factors for each unit.

In everyday life, many probabilistic situations may be characterized as probabilistic waiting. A gambler, for example, bets repeatedly at the racetrack, the casino, or the card table. The gambler may not win on the first try, but if a gamble is repeated enough times, a win is almost certain to occur eventually. If repeated gambles are structured as strings of losses ending in a win (probabilistic waiting) and the amount won is discounted by the delay caused by the series of losses, then strings with many losses will be discounted more than those with fewer losses, thereby causing subjective value of the series of gambles as a whole to increase. The current study used the opposite effect that amount has on the degree of delay and probability discounting as a marker to determine whether people evaluate situations involving probabilistic waiting as they evaluate situations involving delayed outcomes or as situations involving probabilistic outcomes. We find that the more likely a probabilistic waiting situation is to end in reward (e.g., a gamble is repeated indefinitely until reward is obtained), the more that situation conforms to delay discounting; the less likely a probabilistic waiting situation is to end in reward (e.g., a fixed, small number of gambles), the more that situation conforms to probability discounting. We argue that the former situation is applicable to pathological gambling, and that people with steep delay discount functions would therefore be more likely to have gambling problems. Copyright © 2015 John Wiley & Sons, Ltd.

The amount effect of delay discounting (by which the value of larger reward amounts is discounted by delay at a lower rate than that of smaller amounts) strictly implies that value functions (value as a function of amount) are steeper at greater delays than they are at lesser delays. That is, the amount effect and the difference in value functions at different delays are actually a single empirical finding. Amount effects of delay discounting are typically found with choice experiments. Value functions for immediate rewards have been empirically obtained by direct judgment. (Value functions for delayed rewards have not been previously obtained.) The present experiment obtained value functions for both immediate and delayed rewards by direct judgment and found them to be steeper when the rewards were delayed--hence, finding an amount effect with delay discounting.

Four GNIP sites, Hong Kong, Kunming, Shijiazhuang and Urumqi with relatively complete tritium records, have been selected to determine the characteristics of tritium in precipitation in different climatic and geographical regions in China. The highest concentration, 559 TU, was measured at Hong Kong in April 1963 and resulted from Soviet thermonuclear testing. During 1985–2004, tritium values decreased substantially due to the radioactive decay and the vapor exchange between the atmosphere and ocean. During this period, tritium concentrations tended to be much higher in inland regions than in coastal regions. This difference may be explained by the continental effect and the inland continental thermonuclear testing. Stratosphere-to-troposphere exchange is the important driver for the timing of tritium seasonal peak at Urumqi and Kunming, but this mechanism is less pronounced at Hong Kong and Shijiazhuang. This offset indicates that the complex stratosphere–troposphere exchange process appears to be neither seasonally nor geographically uniform. The amount effect was only observed at the Hong Kong, indicating different tritium sources than at the other locations. Therefore, air masses influencing tritium in precipitation are more complex in inland region than in coastal region.

Several studies have examined discounting by pigeons and rats using concurrent-chains procedures, but the results have been inconsistent. None of these studies, however, has established that discounting functions derived from estimates of indifference points can be obtained with a concurrent-chains procedure, so their validity remains in doubt. The present study used a concurrent-chains procedure within sessions combined with an adjusting-amount procedure across sessions to determine the present, subjective values of food reinforcers to be obtained after a delay. Discounting was well described by the hyperbolic discounting function, suggesting that the concurrent-chains procedure and the more typical adjusting-amount procedure are measuring the same process. Consistent with previous studies with rats and pigeons using adjusting-amount procedures, no significant effect of the amount of the delayed reinforcer on the degree of discounting was observed, suggesting that the amount effect may be unique to humans although consistent with the view that animals' choices are controlled by the relative, rather than the absolute, value of reinforcers.

This paper is based on the neural network nonlinear mapping characteristics. The involute gear tooth number, modulus and their relationship model of cutting the amount effect are established respectively. Through MATLAB simulation gets the relation curve between the number of teeth and modulus. These curves can intuitive reflect the tooth number and modulus effects on cutting amount change, which provides valuable theoretical reference for the design of the involute gear.

In the present study, linear correlations between weighted-average annual precipitation oxygen isotopes ( δ 18Op) and annual precipitation amount (original data from five Chinese and three Indian GNIP stations, respectively) demonstrated that: 1) correlation between δ 18Op and annual precipitation amount is insignificant in southern China, so the significance of relevant geological proxy records as indicators of variations in past precipitation amount is limited in this area; 2) overall, negative correlations between δ 18Op and annual precipitation amount at the four stations in the Indian monsoon region are much more significant than those for the four stations in the East Asian monsoon region. This indicates that δ 18Op in the Indian monsoon region is probably controlled by an interannual amount effect, and δ 18Op in the East Asian monsoon region may be strongly influenced by variations in Indian summer monsoon intensity via the Raleigh fractionation effect.

A stable water isotopologue-enabled cloud-resolving model was used to investigate the cause of the amount effect on the seasonal (or longer) time scales. When the total water (vapor and condensed phase) budget of the precipitating column of air is considered, our results indicate that as convection becomes stronger and the precipitation rate increases, the δD of precipitation (δDp) depends on the isotopic composition of the converged vapor more than that of surface evaporation. Tests with disabled fractionation from rain evaporation demonstrate that this mechanism does not account for the amount effect as has been previously suggested. If the isotopic content of converged vapor is made uniform with height with a value characteristic of surface evaporation, the amount effect largely disappears, further supporting the dominance of converged vapor in changes to the δDp signal with increasing precipitation. δDp values were compared to the water budget term EP, where P is precipitation and E is evaporation. Results from this comparison support the overall conclusion that moisture convergence is central in determining the value of δDp and the strength of the amount effect in steady state.

Using data from Lending Club and Prosper, the two largest peer-to-peer lenders in the U.S., we provide evidence of the winner's curse in the online personal lending market. Borrowers who were rejected by a competitor are twice as likely to default as borrowers who were not rejected, conditional on receiving the same contract. Borrowers are also more likely to default when offered higher interest rates or smaller loan amounts by a competitor. Surprisingly, the loan amount effect is larger than the interest rate effect, and loan amount is a more closely related to lender choice.

The urethane reaction of o-hydroxybenzyl alcohol with phenyl isocyanate was monitored with in situ FT-IR. Dibutyltin dilaurate was used as catalyst and its amount effect was investigated. It was found that there was an obvious induction period before reaction began. It was interesting that the time of induction period climbed up and then declined with the increase of dibutyltin dilaurate. When the concentration of dibutyltin dilaurate reached 9.58 × 10−5 mol/L, the induction period disappeared completely and hereafter did not appear any more. Furthermore, the urethane reaction kinetics was studied. When the concentration of dibutyltin dilaurate increased, the reaction rate of phenolic group (k1) increased sharply, but the reaction rate of alcoholic group (k2) appeared of little change on the whole. k1 increased about 20-fold, yet k2 increased about 2-fold when the concentration of dibutyltin dilaurate varied from 9.58 × 10−6 mol/L to 1.92 × 10−4 mol/L, which made the value of k1/k2 enlarge.

Although root development is critical in the establishment of turfgrass sod, there appears to be no information on the response of root development during sod establishment to the frequency and amount of irrigation. Two alternate hypotheses for the root development response are that 1) frequent and high amounts of irrigation are needed to support sod growth and root development; and 2) deficit irrigation encourages more rapid and deeper rooting. The objective of this study was to observe root development of four warm-season turfgrasses subjected to various frequencies and amounts of irrigation. Root extension of the grasses was observed directly in soil contained in 90-cm tall, clear acrylic columns. No difference in root development was observed for any of the grasses among irrigation frequency treatments of daily, twice weekly, and once weekly. There were differences in response to the amount of irrigation. Zoysiagrass root development was maximal at the full amount of irrigation (35 mm per week). On the other hand, St. Augustinegrass, bermudagrass, and bahiagrass required deficit irrigation of only 13 mm water per week to achieve full root development. The results of this study showed that each of the two hypotheses were appropriate depending on the specific species.

The purpose of the study was to test hypotheses regarding a form of social discounting in which the subjective value of a reward decreases as a function of the number of people it is shared with. Based on evolutionary theory, individuals’ social discounting rates were expected to depend on both reward amount and the type of relationship with the people with whom the reward would be shared. As predicted, smaller amounts were discounted less steeply than larger ones, and social discounting was steepest when sharing with strangers and shallowest when sharing with family. The effect of the type of social relationship is consistent with Hamilton’s inclusive fitness theory. The shallower discounting of smaller rewards may be adaptive when resources are limited; alternatively, this finding may be due to the degree of disappointment that is anticipated if the reward is unfairly shared, assuming that the disappointment increases with the size of the reward being withheld by the group.

Using the isotope enabled ECHAM4, GISS E, HadCM3 and MUGCM GCMs, the spatial distribution of mean δ18O in precipitation, the mean seasonality (JJA-DJF) and the correlations of δ18O in precipitation with temperature and precipitation amount are analyzed. The simulation results reproduce well the stable isotopic features by the GNIP observations. Over the East Asia, the distribution of δ18O in precipitation is of marked latitude effect and altitude effect. The largest seasonality of δ18O in precipitation appears in the eastern Siberia controlled by cold high pressure, and the smallest one in the Western Pacific controlled by the subtropical high. The comparatively weak seasonality appears in middle latitudes where oceanic and continental air masses interact frequently. Temperature effect occurs mainly in mid-high-latitude and inlands. The higher the latitude is, the closer to inland is, and then the stronger the temperature effect is. Amount effect occurs mainly in low-mid latitudes and monsoon areas, with the strongest effect in low-latitude coasts or islands. A significant difference between simulations and observations is that the standard deviation of GCMs statistics is greater than that of GNIP statistics. On the contrary, as comparing parallelly time series at single station, the standard deviations of GCMs simulations is smaller than that of GNIP observations.

Studies on probabilistic discounting typically involve choosing between two outcomes of the same sign (i.e., positive or negative). Commonly, participants are given a choice between a smaller, certain gain and a larger, but uncertain gain, or (less commonly) the options may be a certain, smaller loss and an uncertain, but larger loss. In contrast, participants in this study had to make yes/no decisions as to whether they would accept a financial offer involving a combination of both a gain and a loss. This offer could be either a certain gain which, when accepted, could bring an uncertain larger loss, or a certain loss which, when accepted, could bring an uncertain larger gain. Despite the substantial differences between the alternatives posed in the present study and those in typical discounting studies, the same hyperboloid discounting function that describes the choice between certain and uncertain gains also accurately described choice in the situations presented in the present study. In addition, steeper discounting was observed with a larger uncertain gain than with a smaller uncertain gain. No amount effect was revealed with uncertain losses.

Migrant remittances from the United States to Mexico have grown at an impressive rate in recent years. Using a decomposition technique, I attribute the growth in remittances, for the 1990-2004 period and subperiods within it, to a migration effect, a remitting propensity effect and an average amount effect. Results show that while migration growth was the main force driving remittance growth for most of the 1990s, in the new century remittance growth cannot be simply attributed to migration growth. Mexican migrants are becoming more likely to remit and are remitting larger amounts. This reflects both a change in the composition of the Mexican population in the United States and new modes of immigrant incorporation, consistent with the assimilation and the transnational narratives. Macroeconomic oscillations play an important role in explaining remittance growth as well.

Understanding the main controls on stable isotope variations in precipitation is fundamental for the interpretation of the hydrological cycle. However, spatio-temporal variations in delta O-18(p) are poorly known in Morocco. Herein, we explore the relative influence of meteorological variables, spatial and orographic (attitudinal) effects, atmospheric circulation and moisture sources on precipitation stable isotopes in Morocco. Precipitation events and two-years-long monthly records from 17 rain-gauge stations in Morocco are investigated and compared in this study to global gridded records of monthly and annual stable isotopes in precipitation. We highlight that the main spatial controls on precipitation stable isotopes are the topography and the distance from marine source. The most depleted mean annual isotopes are located in the High Atlas Mountains (delta O-18(p) = -9.56 parts per thousand and delta H-2(p) = -59.3 parts per thousand), while the most enriched isotope ratios exist in southwestern Morocco (delta O-18(p) = -2.35 parts per thousand and delta H-2(p) = -7.47 parts per thousand). The well-constrained relationship between delta O-18(p) and altitude describes a gradient of 0.11-0.18 parts per thousand, per 100 m. The seasonal variation is expressed by a general enrichment that reaches -4.8 parts per thousand during the dry season, related to the recycled vapor contained within the summer precipitation. Notwithstanding the scarcity of temperature and precipitation measurements, the amount effect is observed in multiple stations during several rain events and precipitation seems to have more influence on delta O-18(p) than temperature. Backward moisture trajectories indicate a distinct depletion in delta O-18(p) in extreme events originating from the Atlantic Ocean. The presence of a rain shadow effect is also revealed on the lee side of High Atlas Mountains, southeastern Morocco.

The δ 18O variations in an 80.36 m ice core retrieved in the accumulation zone of the East Rongbuk Glacier, Mount Qomolangma (Everest), is not consistent with changes of air temperature from both southern and northern slopes of Himalayas, as well as these of the temperature anomalies over the Northern Hemisphere. The negative relationship between the δ 18O and the net accumulation records of the ice core suggests the “amount effect” of summer precipitation on the δ 18O values in the region. Therefore, the δ 18O records of the East Rongbuk ice core should be a proxy of Indian Summer Monsoon intensity, which shows lower δ 18O values during strong monsoon phases and higher values during weak phases.

There is no temperature effect in the southern Tibetan Plateau and South Asia to the south of the Tanggula Mountains. Amount effect has been observed at a few sampling stations accounting for about a half of the statistical stations. There is notable temperature effect in the middle and northern Tibetan Plateau and its adjacent Central Asia to the north of the Tanggula Mountains. Because vapor directly originates from low-latitude oceans, the relative heavy δ18O with small variation characterizes the rainfall in South Asia. A sharp depletion of the stable isotopic compositions in precipitation takes place from Kyangjin on the southern slope of the Himalayas to the Tanggula Mountains in the middle plateau. From the Tanggula Mountains to the northern Tibetan Plateau, the δ18O in precipitation increases with increasing latitude.

[1] The global increase in atmospheric CO2 since the preindustrial era has not been accompanied by a long-term trend in the CO18O/CO2 ratio (denoted as δCa), though many monitoring stations around the world observed a downward excursion in δCa (of about 0.1‰ y−1) after 1992/1993 that lasted for 5–6 years. A number of studies have suggested that the interannual variation, seasonal cycle, and spatial structure of δCa depend on terrestrial ecosystem fluxes. The δCa budget is evaluated to identify meteorological variables that could potentially influence the observed interannual δCa variations. Using global data sets, time series of relative humidity, 18O composition of precipitation (δWP), air temperature, precipitation, and solar radiation were correlated with Mauna Loa δCa variations. Observed δCa negatively correlated with relative humidity in tropical and middle- and high-latitude regions, and we estimated that observed relative humidity variations drove a 0.14‰ decrease in δCa during the mid-1990s. Similar variations in precipitation rates were also found within the tropics that suggest positive correlations between δWP and δCa consistent with an amount effect (δWP decreases as precipitation increases). The decrease in δWP during the 1990s was estimated to decrease δCa by as much as 0.48‰. In contrast to previous work, little evidence was found that would suggest carbon flux anomalies as the primary driver of interannual δCa variations. We conclude that interannual δCa variations were driven primarily by isotope hydrology and relative humidity, and that δCa can be exploited as a new constraint on hydrological cycle variations at a variety of scales.

Stable isotopes in precipitation, both liquid (rain) and solid (snow), can be suitable tracers for hydrological cycles because their concentrations reflect the cumulative record of physical phase changes. Distribution of stable isotopes in precipitation over High-Asian monsoon regions, including Yunnan Plateau is investigated. It has two noticeable features: firstly, the stable isotopes in precipitation distinctly decrease; and secondly, the stable isotopes in precipitation demonstrate smaller concentrations during rainy seasons and higher values during dry seasons. These features were found by the MUGCM simulation developed in the Melbourne Univertisty. Quantitative effect of the stable isotopes in precipitation takes place at different time scales, i.e. in diurnal, monthly or annual variations. Relative to observations, the simulated δ¹⁸O in precipitation shows stronger dependence on precipitation. In the diurnal course, the simulated regression equations of δ¹⁸O in precipitation versus precipitation amount are in good agreement with the observed values at Tengchong and Simao, except that the simulated δ¹⁸O/P curve slope is slightly smaller than the observed one at Mingzi. In the monthly and annual courses both, the simulated and observed δ¹⁸O/P slopes are smaller than it is in the diurnal course. For individual station, the local meteoric water line (LMWL) is simulated well at Mengzi and Tengchong. However, the simulated result does not reproduce truly the observed relationship between δD and δ¹⁸O in precipitation at Simao and Kunming where the LMWL inclination is larger 8.0, and a shift along the y-axis higher 10.0. In addition, all simulated LMWL slopes are higher the observed ones at four stations, suggesting that the GCM can overestimate the decreasing of Hydrogen Deuterium Oxide and, thus, underestimate the second-order parameter, i.e. the deuterium excess, in a particular region Yunnan.

This chapter outlines the current understanding of the factors affecting δ 18 O p , formalizes this understanding in mathematical models and then, describes potential applications of the technique. The oxygen isotope ratio of soil water taken up by a plant depends, to a first approximation, on the temperature of droplet formation for rain and snow falling at the site. Precipitation becomes more depleted in 18 O as temperature decreases at higher latitudes and altitudes. There is also an amount effect, with high precipitation sites having more depleted water than would be expected from site temperatures. The temperature dependence of δ 18 O of precipitation (618Or), and its record of variation in plant tissue have been recognized for some time, and prompted Libby et al. to suggest that it may be possible to use cellulose from annual tree rings as “isotopic thermometers.”

To observe the altitude effect on the deuterium content of precipitation, two sampling projects were conducted to collect precipitation waters. One is long term sampling by simple rain gauges installed along mountain slopes. Another is simultaneous daily precipitation sampling at two different altitudes.Both of them have sufficient altitude differences, about 1000 m for each.The result could not be explained either by the depletion or by the enrichment of heavy isotopes in the precipitation caused by altitude.It can be regarded as some kind of precipitational amount effect, but still the whole process cannot be grasped.

The deuterium/hydrogen ratios, expressed in terms of δD, of precipitation at Mohonk Lake, New York, from 118 individual storms during the six summers 1977–1982 have been measured and considered in light of the concurrent meteorological conditions. The so-called amount effect of Dansgaard—summers with above average precipitation totals tend to have below average δD values is observed at Mohonk Lake and is also registered in the tree ring cellulose of water-stressed Eastern White Pine. A similar amount effect is also observed for individual events and can be explained in terms of differences between convective and cyclonic precipitation. Stable cyclonic precipitation has much lower δD values (−64.8) but much greater amounts (3.77 cm) on average than purely convective storms (δD = −27.2, 1.30 cm). The seasonal amount effect is related to the fact that during the 6-year observational period, wetter than normal summers at Mohonk Lake also had a higher than normal percentage of stable cyclonic precipitation and a lower than normal percentage of purely convective precipitation.