Water Vapor Input Research Articles

Water Vapor from Western Eurasia Promotes Precipitation during the Snow Season in Northern Xinjiang, a Typical Arid Region in Central Asia

Atmospheric water vapor plays an important role in the water cycle, especially in arid Central Asia, where precipitation is invaluable to water resources. Understanding and quantifying the relationship between water vapor source regions and precipitation is a key problem in water resource research in typical arid Central Asia, Northern Xinjiang. However, the relationship between precipitation and water vapor sources is still unclear of snow season. This paper aimed at studying the role of water vapor source supply in the Northern Xinjiang precipitation trend, which was investigated using the Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model. The results showed that the total water vapor contributed from Western Eurasia and the North Polar area presented upward trends similar to the precipitation change trend, which indicated that the water vapor contribution from the two previous water vapor source regions supplied abundant water vapor and maintained the upward precipitation trend from 1980 to 2017 in Northern Xinjiang. From the climatology of water vapor transport, the region was controlled by midlatitude westerlies and major water vapor input from the western boundary, and the net water vapor flux of this region also showed an annual increasing trend. Western Eurasia had the largest moisture percentage contribution to Northern Xinjiang (48.11%) over the past 38 years. Northern Xinjiang precipitation was correlated with water vapor from Western Eurasia, the North Polar area, and Siberia, and the correlation coefficients were 0.66, 0.45, and 0.57, respectively. These results could aid in better understanding the water cycle process and climate change in this typical arid region of Central Asia.

Analysis of the Contribution of Water Vapor from the Arabian Sea to the Local Rainstorm Process in Southern Xinjiang

In order to investigate the water vapor sources of summer precipitation in southern Xinjiang, especially Hotan area. Based on NCEP FNL 1°*1° analysis data and Xinjiang meteorological bureau area numerical operation prediction, a local precipitation event in southern Xinjiang on June 26 was analyzed, and the results showed that the water vapor involved in this process originated from the northwestern Gangetic Plain and was transported along the Indus River plain and over the northwestern end of the mountains. Driven by the Iranian low-pressure trough, water vapor at 500 hPa was transported across the northwestern end of the Gangdise Mountains, past Georgoli Peak, and northwest over the Kunlun Mountains to arrive in southern Xinjiang. And a zonal profile was made along the northern foothills of the Kunlun Mountains (latitude 36°N), and the width was limited to the longitude range [70°E, 80°E] and the height range [500 hPa, 300 hPa] according to the water vapor channel scope of the process. In the first 24 hours after the end of the precipitation process, the total water vapor input and transmission amount was more than 3*107kg. That is, the water vapor transmitted over the preceding 24 hours far exceeded the precipitation during the precipitation event. So, under the combined influence of the Iranian vortex and equatorial vortex, moisture from the Arabian Sea at heights above 500 hPa can directly cross the Indus River plain traverse the Qinghai-Tibet Plateau and reach the southern region of Xinjiang. Therefore, the southern upper air passage is an important water vapor source in southern Xinjiang. Under appropriate conditions, it can cause short-term local heavy rainfall and lead to secondary meteorological disasters such as debris flow.

Maize yield under a changing climate: The hidden role of vapor pressure deficit

Temperatures over the next century are expected to rise to levels detrimental to crop growth and yield. As the atmosphere warms without additional water vapor input, vapor pressure deficit (VPD) increases as well. Increased temperatures and accompanied elevated VPD levels can both lead to negative impacts on crop yield. The independent importance of VPD, however, is often neglected or conflated with that from temperature due to a tight correlation between the two climate factors. We used a coupled process-based crop (MAIZSIM) and soil (2DSOIL) model to gain a mechanistic understanding of the independent roles temperature and VPD play in crop yield projections, as well as their interactions with rising CO2 levels and changing precipitation patterns. We found that by separating out the VPD effect from rising temperatures, VPD increases had a greater negative impact on yield (12.9 ± 1.8%, increase in VPD associated with 2 °C warming) compared to that from warming (8.5 ± 1.4%, the direct effect of 2 °C warming). The negative impact of these two factors varied with precipitation levels and influenced yield through separate mechanisms. Warmer temperatures caused yield loss mainly through shortening the growing season, while elevated VPD increased water loss and triggered several water stress responses such as reduced photosynthetic rates, lowered leaf area development, and shortened growing season length. Elevated CO2 concentrations partially alleviated yield loss under warming or increased VPD conditions through water savings, but the impact level varied with precipitation levels and was most pronounced under drier conditions. These results demonstrate the key role VPD plays in crop growth and yield, displaying a magnitude of impact comparative to temperature and CO2. A mechanistic understanding of the function of VPD and its relation with other climate factors and management practices is critical to improving crop yield projections under a changing climate.

Delayed impacts of the IOD: cross-seasonal relationships between the IOD, Tibetan Plateau snow, and summer precipitation over the Yangtze–Huaihe River region

Significant anomalous signals are found during the ensuing summer after the Indian Ocean Dipole (IOD) forcing mode dissipates over the tropical Indian Ocean. These signals manifest as increased summer precipitation over the Yangtze–Huaihe River (YHR) region associated with abnormal water vapor convergence contributed mainly by southerly water vapor input along the western flank of an anomalous anticyclone over the subtropical western North Pacific (WNP). The mechanism of these delayed impacts of the IOD is investigated and summarized as a relationship between the IOD, Tibetan Plateau (TP) snow, and summer precipitation. The evolution of the moisture circulation response to the IOD reveals that the IOD can modulate the precipitation over the TP during winter and deepen the snow distribution over the southern TP. Anomalous snow conditions over the TP are a likely capacitor of the delayed effect of the IOD in that they can exert further influence on the ensuing summer monsoon. The influence of deeper snow over the southern edge of the TP on summer precipitation is confirmed: (1) the melting of excessive snow over the TP can lead to a weakened thermal land-sea contrast and weakened Asian summer monsoon westerlies; (2) easterly anomalies can further induce divergence over the WNP, meanwhile stimulating a Pacific-Japan teleconnection pattern; and (3) the anomalous anticyclone over the WNP strengthens the subtropical high and benefits southerly water vapor input to the YHR, while the anomalous cyclone dominates Japan. In between, the subtropical upper-level westerly jet accelerates, and the divergence at its right entrance can enhance the ascending vertical motion over the YHR, which is also favourable for precipitation.

Three dimensional structure of atmospheric water vapor transportation and its relationship with the summer flood/drought situations over Huaihe River Basin

Using the observational and JRA-25 reanalysis datasets, three dimensional structure of water vapor transportation and its relationships with the summer flood/drought situations are investigated in summer time over the Huaihe River Basin (HRB) in eastern China. Results show that there exist major net water vapor input from the western and southern boundaries and net water vapor output in the eastern and northern ones. The water vapor transported from the Bay of Bengal and the South China Sea regions are critical to the precipitation in the HRB region. A typical flood has close relationships with positive anomaly of the transported water vapor from the Bay of Bengal. For a typical drought year, water vapor transported from the Bay of Bengal, as well as the South China Sea, are greatly reduced. And the contribution of the South China Sea is relatively large. Water vapor transported by the tropical westerly also plays a key role in the summer precipitation of the HRB area. Results suggested that the region of the southeast of the Tibet Plateau plays a key role as “transfer post”.

Simulated precipitation changes in Central Asia since the Last Glacial Maximum

The availability of freshwater has been and remains a crucial concern in westerlies-dominated arid Central Asia. Understanding precipitation changes in this area and the underlying mechanisms, therefore, is of great importance. This study explores precipitation changes in Central Asia (35°–50° N and 50°–70° E) since the Last Glacial Maximum (LGM) and their control factors using results from the “Simulation of Transient Climate Evolution over the last 21,000 years”. Transient simulations reveal that a wet climate occurred during the LGM, the Bølling-Allerød warm period, and the middle Holocene, and a dry climate occurred during Heinrich event 1, the Younger Dryas, and the early Holocene in this area. Model results are in good agreement with proxy records since the last deglaciation. These changes were mainly controlled by Earth's orbital parameters, meltwater discharges into the oceans and continental ice sheets. The contribution of GHG concentrations to precipitation changes was minor. External forcing factors influenced the precipitation mainly through affecting the water vapor input from the North Atlantic and Mediterranean Sea, and vertical motions of the atmosphere over Central Asia. The North Atlantic Oscillation was an important atmospheric bridge connecting the external forcings to precipitation changes in Central Asia. There were complex relationships between precipitation changes in Central Asia and East Asia since the LGM due to the differences of the dominating factors.

Simulating the hydrological response of a small tropical forest watershed (Mata Atlantica, Brazil) by the AnnAGNPS model

Given the intrinsic hydrological cycle made of large input of water vapour and intense precipitation producing large volumes of water and sediment, modelling runoff and water losses in humid tropical watersheds is important for forest and water resources management. For instance, reliable simulations of the water cycle in such environments are a prerequisite for predictions of water quality, soil erosion and the climate change effects on water resources. The distributed parameter, physically based, continuous simulation, daily time step AnnAGNPS model, was implemented in almost completely forested (98% of its area, 0.56 km2) Cunha watershed (Brazil) to assess its capability to simulate hydrological processes under tropical conditions. The simulated surface runoff was compared to 4-year observations with statistical indices on several time scales. The model, running with default CN of forest, showed poor predictions of runoff. After increasing CN from 63 to 72 by calibration, the runoff prediction capability of AnnAGNPS was satisfactory on annual, seasonal and monthly scales, while daily runoff predictions were less accurate. Modelling water losses at event scale showed that the effect of forest vegetation on water retention during a single precipitation was more limited than for longer periods (months, seasons and years), since evapo-transpiration and interception account for small shares (>20%) of total precipitation.This study demonstrated that the AnnAGNPS model has reliable runoff prediction capacity in tropical forest watersheds at the annual and seasonal scales (E > 0.73), whereas daily runoff simulations are less accurate (E = 0.44). The use of this model may prove an important tool for water resource and territory management in tropical rainforests.

Photocatalytic property of titanium dioxide thin films deposited by radio frequency magnetron sputtering in argon and water vapour plasma

The present work is investigating the photocatalytic activity of TiO2 thin films deposited by radiofrequency magnetron sputtering of a pure TiO2 target in Ar and Ar/H2O (pressure ratio 40/3) plasmas. Optical absorption, structure, surface morphology and chemical structure of the deposited films were comparatively studied. The films were amorphous and included a large amount of hydroxyl groups (about 5% of oxygen atoms were bounded to hydrogen) irrespective of the intentional content of water in the deposition chamber. Incorporation of hydroxyl groups in the film deposited in pure Ar plasma is explained as contamination of the working gas with water molecules desorbed by plasma from the deposition chamber walls. However, intentional input of water vapour into the discharge chamber decreased the deposition speed and roughness of the deposited films. The good photocatalytic activity of the deposited films could be attributed hydroxyl groups in their structures.

Tropical cyclogenesis and vertical shear in a moist Boussinesq model

AbstractTropical cyclogenesis is studied in the context of idealized three-dimensional Boussinesq dynamics with perhaps the simplest possible model for bulk cloud physics. With low-altitude input of water vapour on realistic length and time scales, numerical simulations capture the formation of vortical hot towers. From measurements of water vapour, vertical velocity, vertical vorticity and rain, it is demonstrated that the structure, strength and lifetime of the hot towers are similar to results from models including more detailed cloud microphysics. The effects of low-altitude vertical shear are investigated by varying the initial zonal velocity profile. In the presence of weak low-level vertical shear, the hot towers retain the low-altitude monopole cyclonic structure characteristic of the zero-shear case (starting from zero velocity). Some initial velocity profiles with small vertical shear can have the effect of increasing cyclonic predominance of individual hot towers in a statistical sense, as measured by the skewness of vertical vorticity. Convergence of horizontal winds in the atmospheric boundary layer is mimicked by increasing the frequency of the moisture forcing in a horizontal subdomain. When the moisture forcing is turned off, and again for zero shear or weak low-level shear, merger of cyclonic activity results in the formation of a larger-scale cyclonic vortex. An effect of the shear is to limit the vertical extent of the resulting emergent moist vortex. For stronger low-altitude vertical shear, the individual hot towers have a low-altitude vorticity dipole rather than a cyclonic monopole. The dipoles are not conducive to the formation of larger-scale vortices, and thus sufficiently strong low-level shear prevents the vortical-hot-tower route to cyclogenesis. The results indicate that the simplest condensation and evaporation schemes are useful for exploratory numerical simulations aimed at better understanding of competing effects such as low-level moisture and vertical shear.

Long-term Change in Summer Water Vapor Transport over South China in Recent Decades

This article investigated the long-term variation of the boreal summer (JJA) moisture circulation over South China (SC). The total precipitable water (TPW) and moisture convergence over SC have increased obviously, such trend is not a local phenomenon, but the result of large-scale circulation anomaly. In the past few decades, the water vapor transport from southern hemisphere and subtropical western Pacific is strengthened, while the northward transport over East Asia is weakened, leading enhanced moisture convergence over the Philippines and adjacent region. The net flux of SC shows no significant shift in the end of the 1970s which is widely acknowledged as ‘‘climate shift’’, but ascends remarkably after the early 1990s. This doesn’t mean the moisture circulation over SC experiences no variation with the ‘‘climate shift’’. In fact, the relationship between total net flux with budgets of four boundaries had been modified in the end of the 1970s. The correlation of the net flux is highly negative with the budget of north boundary, and positive with the budget of west and east boundaries before 1979/80, but only highly positive with the budget of south boundary after 1979/80. This modification is closely related to the north-south migration of western Pacific subtropical high (WPSH). Before 1979/80, the ridge of WPSH lies northward, resulting in stronger output of water vapor via the north boundary which may probably lead to the significant correlation between flux of north boundary and net flux. After 1979/80, the ridge of WPSH shifts southward, inducing stronger water vapor input through the south boundary, which is probably the causation of significant correlation between flux of south boundary and net flux.

Investigating sublimation and the effect of an imaging gas in a VPSEM

In this paper we present an investigation into the possible link between the pressure of the gas in the surrounding environment and the rate of ice sublimation in a VPSEM (variable pressure scanning electron microscope). Although this is mainly significant to an electron microscopist working in a variable pressure environment, it is relevant to people working at low pressures who wish to have control over the rate of sample dehydration where the input of water vapour is not a viable alternative.

Performance and analysis of the constructed analogue method applied to U.S. soil moisture over 1981–2001

We have conducted an experiment to assess the real time skill in monthly and seasonal predictions based solely on patterns of antecedent hydrological information over the United States. The hydrological information is contained in a proxy for soil moisture at 102 locations over the lower 48 states. This soil moisture is calculated over the years 1931 to present from a local hydrological equation taking monthly precipitation (P) and temperature (T) as input, and producing soil moisture (w), evaporation (E), runoff (R), and loss to groundwater (G) as output. The initial condition (IC) for the forecast procedure is soil moisture over the United States at the end of the month (w30). We constructed an analogue to the w30 fields, i.e., made linear combinations of soil moisture fields at the same time of year in years past to reproduce the IC to within a small tolerance. The coefficients assigned to the years past are then made to persist, and the subsequent development in the historical years is linearly combined to form a forecast. This method has been running at CPC in real time since 1998, and we added 1981–1997 in “retroactive real time” mode to form a large enough sample. In total, we considered both seasonal and monthly forecasts at leads of −1 to +6 months for 1981–2001, for the elements w30, E, T, and P. From the outset, we wanted to investigate nonlocal forecast methods, considering local effects, on evaporation and temperature mainly, as being established already and well documented [Huang et al., 1996]. In a nonlocal method we entertain the possibility of precipitation (the response) falling downstream of a soil moisture anomaly (forcing). We found that we have about a 0.6 correlation in forecasting monthly soil moisture with a lead of one month (i.e., July at the end of May). This figure is higher in spring and somewhat lower in the early fall. The capability to forecast evaporation anomalies is very seasonal. During the cold half of the year, when E anomalies resemble T anomalies, the correlation is only 0.2–0.3, but in summer, when E anomalies resemble w anomalies, the skill of forecasts goes up to 0.6. We thus have some insight into patterns of anomalous water vapor input from the land surface into the lower atmosphere on a continental scale. Skill of forecasting T is modest, reaching 0.2–0.3 in many months and seasons, but there is no clear seasonal dependence that relates to the presumed physics of land atmosphere interactions. Skill in forecasting P is quite low, barely 0.1 in correlation, but +ve in all months and seasons. We did alternative experiments where the constructed analogue was built on E, T, or P instead of w and verified the forecast of all elements likewise. We found initial w to be the best for forecasting w itself and indeed for forecasting the other fields as well! This is important testimony that soil moisture is indeed the key, as has been suspected by many for ages.

Validation of the Labeled-Water Method for Estimating Food Consumption in Nestling Herons

AbstractAccurate measurements of food consumption by young birds are of great value in a variety of ecological studies, but traditional measurement methods are problematic and prone to high error. In animals that obtain their water primarily through food, it is possible to estimate food consumption from measurements of water influx rate, using radioactively labeled water (3H2O), and diet water content. We evaluated that method by comparing actual food consumption with simultaneous estimates of food consumption based on the labeled-water method in captive-reared nestling Tricolored Herons (Egretta tricolor). There was good agreement. The average error in the isotope method was −2% (SD = 8%), and that difference was not statistically significant. An errors analysis indicated that the accuracy of this method is sensitive to determinations of dietary water content and animal body water content, and to estimates of rates of metabolic water production and unidirectional water vapor input.

VALIDATION OF THE LABELED-WATER METHOD FOR ESTIMATING FOOD CONSUMPTION IN NESTLING HERONS

Abstract Accurate measurements of food consumption by young birds are of great value in a variety of ecological studies, but traditional measurement methods are problematic and prone to high error. In animals that obtain their water primarily through food, it is possible to estimate food consumption from measurements of water influx rate, using radioactively labeled water (3H2O), and diet water content. We evaluated that method by comparing actual food consumption with simultaneous estimates of food consumption based on the labeled-water method in captive-reared nestling Tricolored Herons (Egretta tricolor). There was good agreement. The average error in the isotope method was −2% (SD = 8%), and that difference was not statistically significant. An errors analysis indicated that the accuracy of this method is sensitive to determinations of dietary water content and animal body water content, and to estimates of rates of metabolic water production and unidirectional water vapor input.

Validation of the Doubly Labeled Water Method (3HH18O) for Measuring Water Flux and CO2 Production in the Tropical Hummingbird Amazilia saucerottei

We validated the doubly labeled water (DLW) method for a tropical hummingbird (Amazilia saucerottei) in a humid environment. We compared daily water influx and energy intake, expenditure, and storage using two independent techniques: the DL W method (using 3HH18O [HTO-18] with and without fractionation corrections) and a gravimetric method. Uncorrected DLW values differed significantly from gravimetric values, with water influx 4.5 % lower, energy intake 4.6 % lower, and energy expenditure 15.1 % higher than for the gravimetric method. In contrast, the corrected DLW values were statistically equivalent to the gravimetric values, with differences ranging from 1.5 % lower to 0.1 % higher. This suggests that physical fractionation of isotopes during evaporative water loss was appreciable but that corrections based on published fractionation constants yielded highly accurate DLW estimates. We conclude that two potential problems in using the DLW method on tropical hummingbirds, water vapor input from humid air and dynamic biological effects from high rates of water turnover and energy metabolism, did not contribute significant error to DLW estimates corrected for fractionation.

Major Northern Hemisphere deglaciation caused by a moisture deficit 140 ka

A variety of marine evidence indicates that much of the deglacial activity that ended the Illinoian glaciation occurred under cold climate conditions prior to the glacial termination 2 warming at 127 ka in the {delta}{sup 18}O deep-sea core record. This anomalous deglaciation is explained by a reduction of water-vapor input to the ice sheets caused by weaker summer atmospheric circulation due to a known smaller latitudinal insolation gradient associated with Earth's orbital variations. A major factor in the eventual marine and atmospheric warming of termination 2 was the formation of unusually warm deep water in the eastern North Atlantic and its circulation to Antarctica, with the probable consequence that the marine-based West Antarctic ice sheet melted, resulting in a eustatic sea level 6 m higher than present.

Remote sensing of snow

Snow is a variable resource that, after being deposited on the Earth's land surface, subsequently serves as a source of water vapor input to the atmosphere through the processes of sublimation and evaporation and as a source of water to the soil and river systems when melting occurs. When the snow is deposited on a land surface, it also markedly changes the albedo and the radiation balance. Therefore snow cover represents a changing atmospheric output that is a function of variability in the Earth's climate, and it is also a boundary condition that affects meteorology and climate through the changes that it makes in the radiation balance and the water vapor input to the atmosphere. Thus it is important to have an active snow cover‐monitoring program that will describe the spatial and temporal variability of the snow cover over land areas.

Computer analysis of the efficacy of evaporative cooling for glasshouses in high energy environments

Theoretical analysis of the efficacy of direct, single-stage evaporative cooling of glasshouses demonstrates how much temperatures in glasshouses can be reduced below those of the outside air. The analysis provides information on diurnal trends in glasshouse temperatures under specified radiant energy and outside temperature conditions. Increasing ventilation rates result in increased temperature reduction, but the increase is non-linear with air throughput rates. There is some input of water vapour due to humidification of the input air but transpiration from the crop contributes much more. The equations presented are relatively simple but can easily be expanded if necessary. They can be used for analysis of the effects of ventilation with uncooled air.