Hydrologically transported dissolved organic carbon influences soil respiration in a tropical rainforest

NASA Astrophysics Data System (ADS)

Zhou, Wen-Jun; Lu, Hua-Zheng; Zhang, Yi-Ping; Sha, Li-Qing; Schaefer, Douglas Allen; Song, Qing-Hai; Deng, Yun; Deng, Xiao-Bao

2016-10-01

To better understand the effect of dissolved organic carbon (DOC) transported by hydrological processes (rainfall, throughfall, litter leachate, and surface soil water; 0-20 cm) on soil respiration in tropical rainforests, we detected the DOC flux in rainfall, throughfall, litter leachate, and surface soil water (0-20 cm), compared the seasonality of δ13CDOC in each hydrological process, and δ13C in leaves, litter, and surface soil, and analysed the throughfall, litter leachate, and surface soil water (0-20 cm) effect on soil respiration in a tropical rainforest in Xishuangbanna, south-west China. Results showed that the surface soil intercepted 94.4 ± 1.2 % of the annual litter leachate DOC flux and is a sink for DOC. The throughfall and litter leachate DOC fluxes amounted to 6.81 and 7.23 % of the net ecosystem exchange respectively, indicating that the DOC flux through hydrological processes is an important component of the carbon budget, and may be an important link between hydrological processes and soil respiration in a tropical rainforest. Even the variability in soil respiration is more dependent on the hydrologically transported water than DOC flux insignificantly, soil temperature, and soil-water content (at 0-20 cm). The difference in δ13C between the soil, soil water (at 0-20 cm), throughfall, and litter leachate indicated that DOC is transformed in the surface soil and decreased the sensitivity indices of soil respiration of DOC flux to water flux, which suggests that soil respiration is more sensitive to the DOC flux in hydrological processes, especially the soil-water DOC flux, than to soil temperature or soil moisture.

Cloud water interception and canopy water balance in the Hawaiian Islands: preliminary results and emerging patterns

NASA Astrophysics Data System (ADS)

Tseng, H.; Giambelluca, T. W.; DeLay, J. K.; Nullet, M.

2017-12-01

Steep climate gradients and diverse ecosystems make the Hawaiian Islands an ideal laboratory for ecohydrological experiments. Researchers are able to control physical and ecological variables, which is difficult for most environmental studies, by selecting sites along these gradients. Tropical montane forests, especially those situated in the cloud zone, are known to improve recharge and sustain baseflow. This is probably the result of frequent and persistent fog characteristic to these systems. During fog events, evapotranspiration is suppressed due to high humidity and reduced solar radiation. Moreover, cloud water interception by the forest canopy can produce fog drip and contribute significantly to the local water budget. Because the interception process is a complex interaction between the atmosphere and the vegetation, the effects of the meteorological conditions and canopy characteristics are equally important and sometimes hard to separate. This study aims to examine patterns in cloud water interception and canopy water balance across five tropical montane forest sites on three of the main islands of Hawaii. The sites cover a range of elevations between 1100- 2114 m, annual rainfall between 1155-3375 mm, and different dominant plant species with canopy heights ranging from 1.5 m to 30 m. We investigate the effect of climatic factors by comparing passive fog gauge measurements and other meteorological variables, then examine the differences in canopy water balance by comparing throughfall and stemflow measurements at these sites. While this study is ongoing, we present the first few months of field observations and the results of preliminary analyses. This study will improve understanding of how large-scale climate and vegetation factors interact to control cloud water interception and will inform ongoing watershed management. This is particularly important for oceanic islands such as Hawaii because they rely on precipitation entirely for water supply and are, therefore, vulnerable to impacts of altered ecohydrological functioning due to climate and land cover changes.

Spatial pulses of water inputs in deciduous and hemlock forest stands

NASA Astrophysics Data System (ADS)

Guswa, A. J.; Mussehl, M.; Pecht, A.; Spence, C.

2010-12-01

Trees intercept and redistribute precipitation in time and space. While spatial patterns of throughfall are challenging to link to plant and canopy characteristics, many studies have shown that the spatial patterns persist through time. This persistence leads to wet and dry spots under the trees, creating spatial pulses of moisture that can affect infiltration, transpiration, and biogeochemical processes. In the northeast, the invasive hemlock woolly adelgid poses a significant threat to eastern hemlock (Tsuga canadensis), and replacement of hemlock forests by other species, such as birch, maple, and oak, has the potential to alter throughfall patterns and hydrologic processes. During the summers of 2009 and 2010, we measured throughfall in both hemlock and deciduous plots to assess its spatial distribution and temporal persistence. From 3 June to 25 July 2009, we measured throughfall in one hemlock and one deciduous plot over fourteen events with rainfall totaling 311 mm. From 8 June through 28 July 2010, we measured throughfall in the same two plots plus an additional hemlock stand and a young black birch stand, and rainfall totaled 148 mm over eight events. Averaged over space and time, throughfall was 81% of open precipitation in the hemlock stands, 88% in the mixed deciduous stand, and 100% in the young black birch stand. On an event basis, spatial coefficients of variation are similar among the stands and range from 11% to 49% for rain events greater than 5 mm. With the exception of very light events, coefficients of variation are insensitive to precipitation amount. Spatial patterns of throughfall persist through time, and seasonal coefficients of variation range from 13% to 33%. All stands indicate localized concentrations of water inputs, and there were individual collectors in the deciduous stands that regularly received more than twice the stand-average throughfall.

Analysis of pesticides in surface water, stemflow, and throughfall in an agricultural area in South Georgia, USA.

PubMed

Glinski, Donna A; Purucker, S Thomas; Van Meter, Robin J; Black, Marsha C; Henderson, W Matthew

2018-06-18

To study spray drift contributions to non-targeted habitats, pesticide concentrations in stemflow (water flowing down the trunk of a tree during a rain event), throughfall (water from tree canopy only), and surface water in an agriculturally impacted wetland area near Tifton, Georgia, USA were measured (2015-2016). Agricultural fields and sampling locations were on the University of Georgia's Gibbs Research Farm, Tifton, GA. Samples were screened for more than 160 pesticides, and cumulatively, 32 different pesticides were detected across matrices. Data indicate that herbicides and fungicides were present in all types of environmental samples analyzed while insecticides were only detected in surface water samples. The highest pesticide concentration observed was 10.50 μg/L of metolachlor in an August 2015 surface water sample. Metolachlor, tebuconazole, and fipronil were the most frequently detected herbicide, fungicide, and insecticide, respectively, regardless of sample origin. The most frequently detected pesticide in surface water and stemflow samples was metolachlor (0.09-10.5 μg/L), however, the most commonly detected pesticide in throughfall samples was biphenyl (0.02-0.07 μg/L). These data help determine the importance of indirect chemical exposures to non-targeted habitats by assessing inputs from stemflow and throughfall into surface waters. Copyright © 2018 Elsevier Ltd. All rights reserved.

Spatiotemporal throughfall patterns beneath an urban tree row

NASA Astrophysics Data System (ADS)

Bogeholz, P.; Van Stan, J. T., II; Hildebrandt, A.; Friesen, J.; Dibble, M.; Norman, Z.

2016-12-01

Much recent research has focused on throughfall patterns in natural forests as they can influence the heterogeneity of surface ecohydrological and biogeochemical processes. However, to the knowledge of the authors, no work has assessed how urban forest structures affect the spatiotemporal variability of throughfall water flux. Urbanization greatly alters not only a significant portion of the land surface, but canopy structure, with the most typical urban forest configuration being landscaped tree rows along streets, swales, parking lot medians, etc. This study examines throughfall spatiotemporal patterns for a landscaped tree row of Pinus elliottii (Engelm., slash pine) on Georgia Southern University's campus (southeastern, USA) using 150 individual observations per storm. Throughfall correlation lengths beneath this tree row were similar to, but appeared to be more stable across storm size than, observations in past studies on natural forests. Individual tree overlap and the planting interval also may more strongly drive throughfall patterns in tree rows. Meteorological influences beyond storm magnitude (intensity, intermittency, wind conditions, and atmospheric moisture demand) are also examined.

Chloride cycling in two forested lake watersheds in the west-central Adirondack Mountains, New York, U.S.A.

USGS Publications Warehouse

Peters, N.E.

1991-01-01

The chemistry of precipitation, throughfall, soil water, ground water, and surface water was evaluated in two forested lake-watersheds over a 4-yr period to assess factors controlling C1- cycling. Results indicate that C1- cycling in these watersheds is more complex than the generally held view of the rapid transport of atmospherically derived C1- through the ecosystem. The annual throughfall Cl- flux for individual species in the northern hardwood forest was 2 to 5 times that of precipitation (56 eq ha-1), whereas the Na+ throughfall flux, in general, was similar to the precipitation flux. Concentrations of soil-water Cl- sampled from ceramic tension lysimeters at 20 cm below land surface generally exceeded the Na+ concentrations and averaged 31 ??eq L-1, the highest of any waters sampled in the watersheds, except throughfall under red spruce which averaged 34 ??eq L-1. Chloride was concentrated prior to storms and mobilized rapidly during storms as suggested by increases in streamwater Cl- concentrations with increasing flow. Major sources of Cl- in both watersheds are the forest floor and hornblende weathering in the soils and till. In the Panther Lake watershed, which contains mainly thick deposits of till( > 3 m), hornblende weathering results in a net Cl- flux 3 times greater than that in the Woods Lake watershed, which contains mainly thin deposits of till. The estimated accumulation rate of Cl- in the biomass of the two watersheds was comparable to the precipitation Cl- flux.The chemistry of precipitation, throughfall, soil water, ground water, and surface water was evaluated in two forested lake-watersheds over a 4-yr period to assess factors controlling Cl- cycling. Results indicate that Cl- cycling in these watersheds is more complex than the generally held view of the rapid transport of atmospherically derived Cl- through the excosystem. The annual throughfall Cl- flux for individual species in the northern hardwood forest was 2 to 5 times that of precipitation (56 eq ha-1), whereas the Na+ throughfall flux, in general, was similar to the precipitation flux. Concentrations of soil-water Cl- sampled from ceramic tension lysimeters at 20 cm below land surface generally exceeded the Na+ concentrations and averaged 31 ??eq L-1, the highest of any waters sampled in the watersheds, except throughfall under red spruce which averaged 34 ??eq L-1. Chloride was concentrated prior to storms and mobilized rapidly during storms as suggested by increases in streamwater Cl- concentrations with increasing flow. Major sources of Cl- in both watersheds are the forest floor and hornblende weathering in the soils and till. In the Panther Lake watershed, which contains mainly thick deposits of till (> 3 m), hornblende weathering results in a net Cl- flux 3 times greater than that in the Woods Lake watershed, which contains mainly thin deposits of till. The estimated accumulation rate of Cl- in the biomass of the two watersheds was comparable to the precipitation Cl- flux.

THE ROLE OF PRE-EVENT CANOPY STORAGE IN THROUGHFALL AND STEMFLOW USING ISOTOPIC TRACERS

EPA Science Inventory

Stable isotopes can be a valuable tool for tracing the redistribution, storage, and evaporation of water associated with canopy interception of rainfall. Isotopic differences between throughfall and rainfall have been attributed to three mechanisms: evaporative fractionation, iso...

Wet season water distribution in a tropical Andean cloud forest of Boyacá (Colombia) during the dry climate of El Niño

NASA Astrophysics Data System (ADS)

Garcia-Santos, G.; Berdugo, M. B.

2010-07-01

Fog has been demonstrated as the only source of moisture during the dry climate of El Niño in the tropical Andean cloud forest of Boyacá region in Colombia, yet its importance for the forest is virtually unknown. We assessed fog water distribution during the wet season inside the forest and outside in a practically deforested area. Water intercepted by plant was measured at different vertical stratus. Soil moisture in the first centimetres was also measured. During the anomalous drier wet season there was lack of rainfall and the total recorded cloud water was lower compared with the same period during the previous year. Our results indicated that the upper part of the forest mass intercepts most of the fog water compared with lower stratus when the fog event starts. However upper most stratus became rapidly drier after the event, which is explained because water is released to the atmosphere due to high heat atmosphere-leaves interface fluctuations caused by wind and solar radiation, flows towards a different water potential and drips from the leaves. Low amount of fog dripped from tree foliage into the soil, indicating a large water storage capacity of the epiphyte and bryophyte vegetation. Despite the small amount of throughfall, understory vegetation and litter remained wet, which might be explained by the water flowing through the epiphyte vegetation or the high capacity of the understory to absorb moisture from the air. Soil water did not infiltrate in depth, which underlines the importance of fog as water and cool source for seedling growth and shallow rooted understory species, especially during drier conditions.

Throughfall under a teak plantation in Thailand: a multifactorial analysis on the effects of canopy phenology and meteorological conditions

NASA Astrophysics Data System (ADS)

Tanaka, N.; Levia, D. F., Jr.; Igarashi, Y.; Nanko, K.; Yoshifuji, N.; Tanaka, K.; Chatchai, T.; Suzuki, M.; Kumagai, T.

2014-12-01

Teak (Tectona grandis Linn. f.) plantations cover vast areas throughout Southeast Asia and are of great economic importance. This study has sought to increase our understanding of throughfall inputs under teak by analyzing the abiotic and biotic factors governing throughfall amounts and throughfall ratios in relation to three canopy phenophases (leafless, leafing, and leafed). There is no rain during the brief leaf senescence phenophase. Daily data was available for both throughfall volumes and depths as well as leaf area index. Detailed meteorological data were available in situ every ten minutes. Leveraging this high-resolution field data, we employed boosted regression trees (BRT) analysis to identify the primary controls on throughfall amount and ratio during each of the three canopy phenophases. Whereas throughfall amounts were always dominated by the magnitude of rainfall (as expected), throughfall ratios were governed by a suite of predictor variables during each phenophase. The BRT analysis demonstrated that throughfall ratio in the leafless phase was most influenced (in descending order of importance) by air temperature, rainfall amount, maximum wind speed, and rainfall intensity. Throughfall ratio in the leafed phenophase was dominated by rainfall amount which exerted 54.0% of the relative influence. The leafing phenophase was an intermediate case where rainfall amount, air temperature, and vapor pressure deficit were most important. Our results highlight the fact that throughfall ratios are differentially influenced by a suite of meteorological variables during leafless, leafing, and leafed phenophases. Abiotic variables (rainfall amount, air temperature, vapor pressure deficit, and maximum wind speed) trumped leaf area index and stand density in their effect on throughfall ratio. The leafing phenophase, while transitional in nature and short in duration, has a detectable and unique impact on water inputs to teak plantations. Further work is clearly needed to better gauge the importance of the leaf emergence period to the stemflow hydrology and forest biogeochemistry of teak plantations.

A comparison of winter mercury accumulation at forested and no-canopy sites measured with different snow sampling techniques

USGS Publications Warehouse

Nelson, S.J.; Johnson, K.B.; Weathers, K.C.; Loftin, C.S.; Fernandez, I.J.; Kahl, J.S.; Krabbenhoft, D.P.

2008-01-01

Atmospheric mercury (Hg) is delivered to ecosystems via rain, snow, cloud/fog, and dry deposition. The importance of snow, especially snow that has passed through the forest canopy (throughfall), in delivering Hg to terrestrial ecosystems has received little attention in the literature. The snowpack is a dynamic system that links atmospheric deposition and ecosystem cycling through deposition and emission of deposited Hg. To examine the magnitude of Hg delivery via snowfall, and to illuminate processes affecting Hg flux to catchments during winter (cold season), Hg in snow in no-canopy areas and under forest canopies measured with four collection methods were compared: (1) Hg in wet precipitation as measured by the Mercury Deposition Network (MDN) for the site in Acadia National Park, Maine, USA, (2) event throughfall (collected after snowfall cessation for accumulations of >8 cm), (3) season-long throughfall collected using the same apparatus for event sampling but deployed for the entire cold season, and (4) snowpack sampling. Estimates (mean ?? SE) of Hg deposition using these methods during the 91-day cold season in 2004-2005 at conifer sites showed that season-long throughfall Hg flux (1.80 ??g/m2) < snowpack Hg (2.38 ?? 0.68 ??g/m2) < event throughfall flux (5.63 ?? 0.38 ??g/m2). Mercury deposition at the MDN site (0.91 ??g/m2) was similar to that measured at other no-canopy sites in the area using the other methods, but was 3.4 times less than was measured under conifer canopies using the event sampling regime. This indicates that snow accumulated under the forest canopy received Hg from the overstory or exhibited less re-emission of Hg deposited in snow relative to open areas. The soil surface of field-scale plots were sprayed with a natural rain water sample that contained an Hg tracer (202Hg) just prior to the first snowfall to explore whether some snowpack Hg might be explained from soil emissions. The appearance of the 202Hg tracer in the snowpack (0-64% of the total Hg mass in the snowpack) suggests that movement of Hg from the soil into the snowpack is possible. However, as with any tracer study the 202Hg tracer may not precisely represent the reactivity and mobility of natural Hg in soils. ?? 2007 Elsevier Ltd. All rights reserved.

Land-Atmosphere Coupling in the Multi-Scale Modelling Framework

NASA Astrophysics Data System (ADS)

Kraus, P. M.; Denning, S.

2015-12-01

The Multi-Scale Modeling Framework (MMF), in which cloud-resolving models (CRMs) are embedded within general circulation model (GCM) gridcells to serve as the model's cloud parameterization, has offered a number of benefits to GCM simulations. The coupling of these cloud-resolving models directly to land surface model instances, rather than passing averaged atmospheric variables to a single instance of a land surface model, the logical next step in model development, has recently been accomplished. This new configuration offers conspicuous improvements to estimates of precipitation and canopy through-fall, but overall the model exhibits warm surface temperature biases and low productivity.This work presents modifications to a land-surface model that take advantage of the new multi-scale modeling framework, and accommodate the change in spatial scale from a typical GCM range of ~200 km to the CRM grid-scale of 4 km.A parameterization is introduced to apportion modeled surface radiation into direct-beam and diffuse components. The diffuse component is then distributed among the land-surface model instances within each GCM cell domain. This substantially reduces the number excessively low light values provided to the land-surface model when cloudy conditions are modeled in the CRM, associated with its 1-D radiation scheme. The small spatial scale of the CRM, ~4 km, as compared with the typical ~200 km GCM scale, provides much more realistic estimates of precipitation intensity, this permits the elimination of a model parameterization of canopy through-fall. However, runoff at such scales can no longer be considered as an immediate flow to the ocean. Allowing sub-surface water flow between land-surface instances within the GCM domain affords better realism and also reduces temperature and productivity biases.The MMF affords a number of opportunities to land-surface modelers, providing both the advantages of direct simulation at the 4 km scale and a much reduced conceptual gap between model resolution and parameterized processes.

Temporal sequencing of throughfall drop generation as revealed by use of a large-scale rainfall simulator

NASA Astrophysics Data System (ADS)

Nanko, K.; Levia, D. F., Jr.; Iida, S.; SUN, X.; Shinohara, Y.; Sakai, N.

2017-12-01

Scientists have been interested in throughfall drop size and its distribution because of its importance to soil erosion and the forest water balance. An indoor experiment was employed to deepen our understanding of throughfall drop generation processes to promote better management of forested ecosystems. The indoor experiment provides a unique opportunity to examine an array of constant rainfall intensities that are ideal conditions to pick up the effect of changing intensities and not found in the fields. Throughfall drop generation was examined for three species- Cryptomeria japonica D. Don (Japanese cedar), Chamaecyparis obtusa (Siebold & Zucc.) Endl. (Japanese cypress), and Zelkova serrata Thunb. (Japanese zelkova)- under both leafed and leafless conditions in the large-scale rainfall simulator in the National Research Institute for Earth Science and Disaster Resilience (Tsukuba, Japan) at varying rainfall intensities ranging from15 to 100 mm h-1. Drop size distributions of the applied rainfall and throughfall were measured simultaneously by 20 laser disdrometers. Utilizing the drop size dataset, throughfall was separated into three components: free throughfall, canopy drip, and splash throughfall. The temporal sequencing of the throughfall components were analyzed on a 1-min interval during each experimental run. The throughfall component percentage and drop size of canopy drip differed among tree species and rainfall intensities and by elapsed time from the beginning of the rainfall event. Preliminary analysis revealed that the time differences to produce branch drip as compared to leaf (or needle) drip was partly due to differential canopy wet-up processes and the disappearance of branch drips due to canopy saturation, leading to dissimilar throughfall drop size distributions beneath the various tree species examined. This research was supported by JSPS Invitation Fellowship for Research in Japan (Grant No.: S16088) and JSPS KAKENHI (Grant No.: JP15H05626).

Spatial patterns of throughfall isotopic composition at the event and seasonal timescales

NASA Astrophysics Data System (ADS)

Allen, Scott T.; Keim, Richard F.; McDonnell, Jeffrey J.

2015-03-01

Spatial variability of throughfall isotopic composition in forests is indicative of complex processes occurring in the canopy and remains insufficiently understood to properly characterize precipitation inputs to the catchment water balance. Here we investigate variability of throughfall isotopic composition with the objectives: (1) to quantify the spatial variability in event-scale samples, (2) to determine if there are persistent controls over the variability and how these affect variability of seasonally accumulated throughfall, and (3) to analyze the distribution of measured throughfall isotopic composition associated with varying sampling regimes. We measured throughfall over two, three-month periods in western Oregon, USA under a Douglas-fir canopy. The mean spatial range of δ18O for each event was 1.6‰ and 1.2‰ through Fall 2009 (11 events) and Spring 2010 (7 events), respectively. However, the spatial pattern of isotopic composition was not temporally stable causing season-total throughfall to be less variable than event throughfall (1.0‰; range of cumulative δ18O for Fall 2009). Isotopic composition was not spatially autocorrelated and not explained by location relative to tree stems. Sampling error analysis for both field measurements and Monte-Carlo simulated datasets representing different sampling schemes revealed the standard deviation of differences from the true mean as high as 0.45‰ (δ18O) and 1.29‰ (d-excess). The magnitude of this isotopic variation suggests that small sample sizes are a source of substantial experimental error.

Comparison of throughfall chemistry in a mature hemlock forest and an early-successional deciduous forest resulting from salvage logging in Whately, Massachusetts

NASA Astrophysics Data System (ADS)

Zukswert, J. M.; Rhodes, A. L.; Dwyer, C. H.; Sweezy, T.

2012-12-01

Removal of foundation species as a result of disturbance events such as exotic species invasions can alter community composition and ecosystem function. The current hemlock woolly adelgid (Adelges tsugae) infestation in eastern North America that threatens the eastern hemlock (Tsuga canadensis), a foundation species, has motivated salvage logging efforts. Ecological succession resulting from salvage logging of hemlock would eventually produce a deciduous hardwood forest. The chemistry of throughfall beneath a mature hemlock forest canopy is expected to be more acidic than throughfall from a mature deciduous forest canopy because hemlock foliage releases more organic acids and fewer base cations. The chemical composition of throughfall during the early successional transition from hemlock to deciduous is less understood. We hypothesize that throughfall chemistry in a deciduous forest consisting primarily of juvenile trees may be more similar to direct precipitation because leaf area index is smaller. Differences between hemlock throughfall and direct precipitation may be larger due to the denser canopy of these mature trees. We compared the chemical composition of precipitation, hemlock throughfall, and black birch throughfall for 26 precipitation events from 4 March to 30 July 2012. The black birch (Betula lenta) forest patch resulted from salvage logging of hemlocks twenty years ago at the MacLeish Field Station in Whately, MA. From the three plots we measured the volume of water collected and pH, acid neutralizing capacity, dissolved organic carbon (DOC), and concentrations of cations (Ca2+, K+, Na+, Mg2+, NH4+), anions (Cl-, NO3-, SO42-), and dissolved silica. Precipitation totaled 405 mm during the course of the study. Throughfall totaled 347 mm in the black birch plot and 315 mm in the hemlock plot. The proportion of precipitation passing through the forest canopy was smaller in hemlock throughfall than black birch throughfall during small precipitation events (depth < 10 mm), but appeared comparable in larger events. Before leaf emergence, differences between base cation and DOC deposition were not significant (p>0.05, n = 5) for throughfall and direct precipitation. After leaf emergence, base cation and DOC deposition was significantly (p<0.05, n = 21) greater in throughfall than direct precipitation. Additionally, K+, Mg2+, and DOC deposition were significantly greater in hemlock throughfall than black birch throughfall. Black birch throughfall had significantly less H+ deposition than direct precipitation, which suggests that the black birch canopy appears to neutralize the acidity of the precipitation. H+ deposition in hemlock throughfall, however, was not significantly different than precipitation, which could be due to its higher DOC. These results suggest that the successional stage of a deciduous forest canopy has an effect on throughfall chemistry. Lower deposition of base cations prior to and during this juvenile stage could affect soil chemistry by increasing soil acidity and lowering base saturation.

The role of pre-event canopy storage in throughfall and stemflow by using isotopic tracers

Treesearch

S.T. Allen; J.R. Brooks; R.F. Keim; B.J. Bond; J.J. McDonnell

2014-01-01

Stable isotopes can be a valuable tool for tracing the redistribution, storage, and evaporation of water associated with canopy interception of rainfall. Isotopic differences between throughfall and rainfall have been attributed to three mechanisms: evaporative fractionation, isotopic exchange with ambient vapor, and temporal redistribution. We demonstrate the...

Molecular and optical properties of tree-derived dissolved organic matter in throughfall and stemflow from live oaks and eastern red cedar

NASA Astrophysics Data System (ADS)

Stubbins, Aron; Silva, Leticia M.; Dittmar, Thorsten; Van Stan, John T.

2017-03-01

Studies of dissolved organic matter (DOM) transport through terrestrial aquatic systems usually start at the stream. However, the interception of rainwater by vegetation marks the beginning of the terrestrial hydrological cycle making trees the headwaters of aquatic carbon cycling. Rainwater interacts with trees picking up tree-DOM, which is then exported from the tree in stemflow and throughfall. Stemflow denotes water flowing down the tree trunk, while throughfall is the water that drips through the leaves of the canopy. We report the concentrations, optical properties (light absorbance) and molecular signatures (ultrahigh resolution mass spectrometry) of tree-DOM in throughfall and stemflow from two tree species (live oak and eastern red cedar) with varying epiphyte cover on Skidaway Island, Savannah, Georgia, USA. Both stemflow and throughfall were enriched in DOM compared to rainwater, indicating trees were a significant source of DOM. The optical and molecular properties of tree-DOM were broadly consistent with those of DOM in other aquatic ecosystems. Stemflow was enriched in highly colored DOM compared to throughfall. Elemental formulas identified clustered the samples into three groups: oak stemflow, oak throughfall and cedar. The molecular properties of each cluster are consistent with an autochthonous aromatic-rich source associated with the trees, their epiphytes and the microhabitats they support. Elemental formulas enriched in oak stemflow were more diverse, enriched in aromatic formulas, and of higher molecular mass than for other tree-DOM classes, suggesting greater contributions from fresh and partially modified plant-derived organics. Oak throughfall was enriched in lower molecular weight, aliphatic and sugar formulas, suggesting greater contributions from foliar surfaces. While the optical properties and the majority of the elemental formulas within tree-DOM were consistent with vascular plant-derived organics, condensed aromatic formulas were also identified. As condensed aromatics are generally interpreted as deriving from partially combusted organics, some of the tree-DOM may have derived from the atmospheric deposition of thermogenic and other windblown organics. These initial findings should prove useful as future studies seek to track tree-DOM across the aquatic gradient from canopy roof, through soils and into fluvial networks.

Gross rainfall amount and maximum rainfall intensity in 60-minute influence on interception loss of shrubs: a 10-year observation in the Tengger Desert.

PubMed

Zhang, Zhi-Shan; Zhao, Yang; Li, Xin-Rong; Huang, Lei; Tan, Hui-Juan

2016-05-17

In water-limited regions, rainfall interception is influenced by rainfall properties and crown characteristics. Rainfall properties, aside from gross rainfall amount and duration (GR and RD), maximum rainfall intensity and rainless gap (RG), within rain events may heavily affect throughfall and interception by plants. From 2004 to 2014 (except for 2007), individual shrubs of Caragana korshinskii and Artemisia ordosica were selected to measure throughfall during 210 rain events. Various rainfall properties were auto-measured and crown characteristics, i.e., height, branch and leaf area index, crown area and volume of two shrubs were also measured. The relative interceptions of C. korshinskii and A. ordosica were 29.1% and 17.1%, respectively. Rainfall properties have more contributions than crown characteristics to throughfall and interception of shrubs. Throughfall and interception of shrubs can be explained by GR, RI60 (maximum rainfall intensities during 60 min), RD and RG in deceasing importance. However, relative throughfall and interception of two shrubs have different responses to rainfall properties and crown characteristics, those of C. korshinskii were closely related to rainfall properties, while those of A. ordosica were more dependent on crown characteristics. We highlight long-term monitoring is very necessary to determine the relationships between throughfall and interception with crown characteristics.

Variation in throughfall deposition across a deciduous beech (Fagus sylvatica L.) forest edge in Flanders.

PubMed

Devlaeminck, Rebecca; De Schrijver, An; Hermy, Martin

2005-01-20

Throughfall deposition and canopy exchange of acidifying and eutrophying compounds and major base cations were studied by means of throughfall analysis in a deciduous beech (Fagus sylvatica L.) forest edge in Belgium over a period of 1 year. Throughfall fluxes of Cl(-), NH(4)(+) and Na(+) were significantly elevated at the forest edge compared to the forest interior. As no edge effect on throughfall water volume could be detected, the observed edge enhancement effects were mainly due to dry deposition and canopy exchange patterns. Indeed, there was an elevated dry deposition of Cl(-), Na(+), K(+), Ca(2+) and Mg(2+) up to 50 m from the field/forest border. Within the forest, throughfall and dry deposition of SO(4)(2-) were highly variable and no significant differences were observed between the forest edge and the forest interior. Leaching of K(+) and Ca(2+) was reduced in the forest edge up to a distance of 30 m from the border. The measured nitrogen and acidic depositions far exceeded the current Flemish critical loads with respect to the protection of biodiversity in forests, especially at the forest edge. This points to an urgent need for controlling emissions as well as the need to consider the elevated deposition load in forest edges when calculating the critical loads in forests.

Implication of Intrastorm Rainfall-Canopy Interaction on Interception Performance of Broadleaf Evergreen Shrubs in an Ultra-Urban Setting

NASA Astrophysics Data System (ADS)

Yerk, W.; Montalto, F. A.

2015-12-01

Because of its ability to intercept a portion of rainfall, vegetated canopies can play substantial role in modulating the urban hydrological cycle. However, canopy interception research has historically been focused to forest canopies. The goal of our research is to quantify rainfall partitioning by isolated evergreen shrub canopies in an ultra-urban setting. The three year field experiment involved three exemplars of cherry laurel (Prunus laurocerasus 'Otto Luyken'.) Ten rain gauges positioned under each plant were used to measure throughfall with a sampling frequency of five seconds. A number of specific techniques were implemented to minimize error associated with the gauges, e.g., splash-in, splash-out and excessive wetting. The cumulative throughfall deficit (i.e., gross precipitation minus throughfall within the canopy projected area and minus stemflow) for the periods of August-December 2013, April-December 2014 and April-July 2015 was 39%. Spatial variability of throughfall was large (coefficient of variation up to 1.5.) Stable areas of preferential throughfall flux were observed. Stemflow showed a high variability (1.4 - 24%) between rain events. The relationship between throughfall and precipitation intensity was strongly linear (adjusted coefficient of determination R2 0.79) throughout the entire range of observed rainfall intensities. The overall ratio of throughfall to precipitation intensity was 0.48:1. The observations suggest that reduction of throughfall intensity by the canopy during a rainstorm determines the aggregate interception depth. In contrast, the amount of water stored on the canopy and evaporated between and after rain events contributes minimally to interception loss. Penman-Monteith estimates of wet canopy evaporation cannot account for the throughfall deficit. Lateral displacement of microdrops beyond the canopy projected area is another phenomenon that will be discussed and most recent observations of an extended gauge network will be presented.

Throughfall reduction and nutrient availability effects on carbon balance in loblolly pine plantations in the southeastern United States

NASA Astrophysics Data System (ADS)

Bracho, R. G.; Vogel, J.; Jokela, E. J.; Cucinella, J.; Noormets, A.; Laviner, M. A.; Gonzalez-Benecke, C. A.; Samuelson, L. J.; Markewitz, D.; Will, R.; Meek, C.; Seiler, J.; Strahm, B. D.; McElligott, K.; Martin, T.

2016-12-01

Planted loblolly pine covers over 11 million hectares in the southeastern United States. Occurring across a range of climatic conditions, these pine plantations are critical for the regional economy and offset a significant fraction of anthropogenic CO2 emissions. Loblolly pine productivity has been enhanced through genetic improvement and intensive silviculture. However, climate projections forecast higher air temperature and more variable precipitation patterns for the region. A critical question is how silvicultural practices will interact with projected climate change to affect loblolly pine carbon balance. A fertilization by throughfall reduction experiment was established in the spring of 2012 at four loblolly pine plantations at the margins of the natural range of the specie (Florida FL, Georgia GA, Oklahoma OK and Virginia VA). Net primary productivity (NPP) was estimated from repeated tree inventories and net ecosystem productivity (NEP) as the difference between NPP and heterotrophic respiration (RH). Soil respiration (RS) and RH were measured simultaneously several times during the experiment. Throughfall reduction significantly decreased surface soil water content at all sites. After four years of treatment, fertilization increased NPP at all sites and throughfall reduction had a negative effect on NPP at the GA and OK sites. The combination fertilization x throughfall reduction did not have a significant effect on NPP. RS and RH were, in general negatively affected by fertilization and throughfall reduction with differential responses between sites, leading to significant NEP increases under fertilization, while throughfall reduction increased NEP at FL and VA due to no effect on NPP and negative effect on RS. Fertilization offset the negative effect of throughfall reduction on NEP in the fertilization x throughfall reduction treatment. All sites were significant carbon sinks, accumulating from 3.5 to 24 Mg C ha-1 in a 3 year period under a range of climatic conditions, age and treatments.

Effects of fertilization and three years of throughfall reduction on leaf physiology of loblolly pine

Treesearch

Charles J. Pell; Lisa J. Samuelson

2016-01-01

Climate models project decreased soil water availability in the southeastern United States, which may impact loblolly pine (Pinus taeda L.) productivity. In conjunction with an interdisciplinary project known as PINEMAP, the objective of this study was to investigate the interactive effects of fertilization and a 30 percent reduction in throughfall on physiological...

Quantifying interception associated with new urban vegetation canopies

NASA Astrophysics Data System (ADS)

Yerk, W.; Montalto, F. A.

2013-12-01

Interception of precipitation by vegetation canopies has long been recognized as an important component of the hydrologic cycle, though most research has been in closed or sparse canopy forests. Much less work has been published on interception by urban vegetation, and especially associated with the low growing shrubs commonly installed in green infrastructure program. To inform urban watershed model with vegetation-specific interception data, a field experiment was designed to directly measure canopy throughfall associated with two shrub species commonly included in urban greening programs. Data was collected at a high (e.g. five second) sampling frequency. A non-parametric Kruskal-Wallis test performed on data collected between August and October of 2012 demonstrated statistically significant (p= 0.0011) differences in recorded throughfall between two species (94% for Itea virginica, 86% for Cornus sericea). Additionally, the results suggested that the relationship of throughfall to rainfall intensity varied by species. For Itea, the ratio of throughfall to precipitation intensity was close to 1:1. However, for Cornus, the throughfall rate was on average slower (or 0.85 of the precipitation intensity). An improved and expanded set-up installed in 2013 added two additional species (Prunus laurocerasus and Hydrangea quercifolia). The 2013 results confirm interspecies differences in both throughfall amount, and in the relationship of throughfall rate to precipitation intensity. The results are discussed with respect to droplet splashing and enhanced evaporation within the canopy. Both years' findings suggest that the quantity of water intercepted by vegetation canopies exceeds the canopy storage capacity, as assumed in many conventional hydrologic models.

Tracing hydrologic pathways using chloride at the Panola mountain research watershed, Georgia, USA

USGS Publications Warehouse

Peters, N.E.; Ratcliffe, E.B.

1998-01-01

An analysis of chloride (Cl-) concentrations and fluxes at the 41 ha Panola Mountain Research Watershed indicates that Cl- may be used effectively to differentiate 'new' and 'old' water flow through the hillslope and their respective contributions to streamwater. Rainfall and throughfall, the 'new' water inputs, are marked by low Cl- concentrations (30 ??eq L-1). Timing of soil water transport is not sufficiently rapid to suggest that soil water from this hillslope site (20 m from the stream) contributes to streamwater during individual rainstorms. The source of streamflow, therefore, must be a combination of channel interception, overland flow and soil water from nearchannel areas, and run off from a 3 ha bedrock outcrop in the headwaters Groundwater contribution to streamflow was estimated using Cl- concentrations of throughfall and groundwater as the two end members for a two-component hydrograph separation. For the study period, groundwater contributed 79% of the streamflow and from 1985 to 1995, contributed 75% of the streamflow. Rainfall was the source of 45% of the Cl- flux from the watershed in the long term; the remaining Cl- is hypothesized to be derived from dry deposition, consistent with the enrichment noted for throughfall. At peak flow during individual rainstorms, 'new' water can contribute 95% of the runoff.

Gross rainfall amount and maximum rainfall intensity in 60-minute influence on interception loss of shrubs: a 10-year observation in the Tengger Desert

PubMed Central

Zhang, Zhi-Shan; Zhao, Yang; Li, Xin-Rong; Huang, Lei; Tan, Hui-Juan

2016-01-01

In water-limited regions, rainfall interception is influenced by rainfall properties and crown characteristics. Rainfall properties, aside from gross rainfall amount and duration (GR and RD), maximum rainfall intensity and rainless gap (RG), within rain events may heavily affect throughfall and interception by plants. From 2004 to 2014 (except for 2007), individual shrubs of Caragana korshinskii and Artemisia ordosica were selected to measure throughfall during 210 rain events. Various rainfall properties were auto-measured and crown characteristics, i.e., height, branch and leaf area index, crown area and volume of two shrubs were also measured. The relative interceptions of C. korshinskii and A. ordosica were 29.1% and 17.1%, respectively. Rainfall properties have more contributions than crown characteristics to throughfall and interception of shrubs. Throughfall and interception of shrubs can be explained by GR, RI60 (maximum rainfall intensities during 60 min), RD and RG in deceasing importance. However, relative throughfall and interception of two shrubs have different responses to rainfall properties and crown characteristics, those of C. korshinskii were closely related to rainfall properties, while those of A. ordosica were more dependent on crown characteristics. We highlight long-term monitoring is very necessary to determine the relationships between throughfall and interception with crown characteristics. PMID:27184918

Concentration levels of new-generation fungicides in throughfall released by foliar wash-off from vineyards.

PubMed

Pérez-Rodríguez, P; Soto-Gómez, D; Paradelo, M; López-Periago, J E

2017-12-01

The presence of agricultural pesticides in the environment and their effects on ecosystems are major concerns addressed in a significant number of articles. However, limited information is available on the pesticide concentrations released from crops. This study reports losses of new-generation fungicides by foliar wash-off from vineyards and their potential impact on the concentrations of their main active substances (AS) in surface waters. Two experimental plots devoted to vineyards were treated with various combinations of commercial new-generation fungicide formulations. Then, up to sixteen throughfall collectors were installed under the canopy. Concentrations of sixteen different AS in throughfall were determined along nine rainfall episodes. Concentrations in throughfall far exceeded the maximum permissible levels for drinking water established by the European Union regulations. Dynamics of fungicide release indicated a first-flush effect in the wash-off founding the highest concentrations of AS in the first rain episodes after application of the fungicides. This article shows that foliar spray application of commercial formulations of new-generation fungicides does not prevent the release of their AS to soil or the runoff. Concentration data obtained in this research can be valuable in supporting the assessment of environmental effects of new-generation fungicides and modeling their environmental fate. Copyright © 2017 Elsevier Ltd. All rights reserved.

Pre-exposure to drought increases the resistance of tropical forest soil bacterial communities to extended drought

PubMed Central

Bouskill, Nicholas J; Lim, Hsiao Chien; Borglin, Sharon; Salve, Rohit; Wood, Tana E; Silver, Whendee L; Brodie, Eoin L

2013-01-01

Global climate models project a decrease in the magnitude of precipitation in tropical regions. Changes in rainfall patterns have important implications for the moisture content and redox status of tropical soils, yet little is known about how these changes may affect microbial community structure. Specifically, does exposure to prior stress confer increased resistance to subsequent perturbation? Here we reduced the quantity of precipitation throughfall to tropical forest soils in the Luquillo Mountains, Puerto Rico. Treatments included newly established throughfall exclusion plots (de novo excluded), plots undergoing reduction for a second time (pre-excluded) and ambient control plots. Ten months of throughfall exclusion led to a small but statistically significant decline in soil water potential and bacterial populations clearly adapted to increased osmotic stress. Although the water potential decline was small and microbial biomass did not change, phylogenetic diversity in the de novo-excluded plots decreased by ∼40% compared with the control plots, yet pre-excluded plots showed no significant change. On the other hand, the relative abundances of bacterial taxa in both the de novo-excluded and pre-excluded plots changed significantly with throughfall exclusion compared with control plots. Changes in bacterial community structure could be explained by changes in soil pore water chemistry and suggested changes in soil redox. Soluble iron declined in treatment plots and was correlated with decreased soluble phosphorus concentrations, which may have significant implications for microbial productivity in these P-limited systems. PMID:23151641

Organic carbon fluxes in stemflow, throughfall and rainfall in an olive orchard

NASA Astrophysics Data System (ADS)

Lombardo, L.; Vanwalleghem, T.; Gomez, J. A.

2012-04-01

The importance of rainfall distribution under the vegetation canopy for nutrient cycling of forest ecosystems has been widely studied (e.g. Kolkai et al., 1999, Bath et al., 2011). It has been demonstrated how throughfall and stemflow reach the soil as chemically-enriched water, by incorporating soluble organic and inorganic particles deriving from plant exudates and from atmospheric depositions (dryfall and wetfall) present on the surfaces of the plant (leaves, bark, fruits). Dissolved (DOC) and particulate (POC) organic carbon inputs from stem- and canopy-derived hydrologic fluxes are small but important components of the natural carbon cycle. DOC has also the capability to form complexes that control the transport and solubility of heavy metals in surface and ground waters, being composed for the most part (75-90%) of fulvic, humic or tanninic compounds, and for the resting part of molecules like carbohydrates, hydrocarbons, waxes, fatty acids, amino and hydroxy acids. However, very little data is available for agricultural tree crops, especially olive trees. In this sense, the objective of this work is to investigate the concentration and fluxes of organic carbon in rainfall, throughfall, and stemflow in a mature olive orchard located in Cordoba, in Southern Spain and to relate them to rainfall characteristics and tree physiology. The measurements started in October 2011. Four high density polyethylene bottles with 18-cm-diameter polyethylene funnels for throughfall collection were placed beneath the canopy of each of the three selected olive trees; four more collectors were placed in open spaces in the same orchard for rainfall sampling. Stemflow was collected through PVC spiral tubes wrapped around the trunks and leading into collection bins. The throughflow sampling points were chosen randomly. Total and dissolved organic carbon concentrations in unfiltered (TOC) and filtered (0.45 µm membrane filter, DOC) collected waters were measured using a TOC analyzer with a high temperature combustion system and infrared detection of the evolved CO2. The difference in concentration between TOC and DOC defined the POC concentration. Leaf area density (LAD) and leaf area index (LAI) of olive trees were calculated using the LAI-2000 plant canopy analyzer (PCA) (Li-Cor). Stemflow and throughfall resulted both influenced by the characteristics of precipitations (amount, time of the year), canopy volume and leaf characteristics, with stemflow showing, in average, higher DOC and POC concentration values compare to throughfall. Throughfall resulted between 4 and 17 times more concentrated DOC than rainfall, but highlighted a high site-specific variability related to the canopy architecture.

Implication of Intrastorm Rainfall-Canopy Interaction on Interception Performance of Broadleaf Evergreen Shrubs in Urban Setting

NASA Astrophysics Data System (ADS)

Yerk, W.; Montalto, F. A.

2014-12-01

Because of its ability to intercept a portion of rainfall, vegetated canopy has a significant influence on the urban hydrological cycle. In turn, urban watersheds, characterized by large impervious areas, have an enormous and often adverse impact on receiving waters. However, most historical interception research has been dedicated to forest canopies. The goal of our research was to quantify rainfall partitioning by isolated evergreen canopies in an urban setting. Two years of the field experiment involved three exemplars of Cherry Laurel (Prunus laurocerasus'Otto Luyken'.) Each plant had ten rain gauges to measure throughfall with a five second sampling frequency. A number of preventive techniques were introduced to minimize the gauges' errors (e.g., splash-in, splash-out and excessive wetting.) Leaf area index was measured manually. We estimated the canopy storage capacity to be less than 0.5 mm. An on-site automated weather station provided meteorological data. Cumulative interception loss for the periods of August-December 2013 and April-July 2014 was 51%. Phenological change did not show a stable pattern of influence on throughfall depths. Measurements in May and July 2014 showed a high variability of stemflow (2-16%) between rain events. Throughfall and precipitation intensities (mm/hr) expressed strong linear relationships (adjusted coefficient of determination R20.79) for the entire range of observed rainfall intensities. The ratio of throughfall to precipitation intensity was 0.49:1. The observations suggest that reduction of throughfall intensity by the canopy during a rainstorm determines the bulk of interception depth. In contrast, the amount of water stored on the canopy and evaporated between and after rain events contributes minimally to interception. Simulations of potential evaporation based on the Penman-Monteith method revealed a serious underestimation of evaporation from the wet canopy surfaces during the rain events. Mechanisms other than heat balance models of potential evaporation from a still water surface are being discussed in order to explain large intrastorm evaporation from within an isolated canopy.

Tracing hydrologic pathways at the Panola Mountain research watershed, Georgia, USA

USGS Publications Warehouse

Peters, N.E.; Ratcliffe, E.B.

1997-01-01

An analysis of Cl- concentrations and fluxes at the Panola Mountain Research Watershed indicates that Cl- may be effectively used to differentiate 'new' and 'old' water flow through the hillslope and their respective contributions to streamwater. Rainfall and throughfall, the 'new' water inputs, are marked by low Cl- concentrations (15 ??eq 1-1). Stormwater moves rapidly to depth along preferred pathways in a deciduous forest hillslope, as evidenced by low concentrations (20 ??eq 1-1) in mobile soil water from zero-tension stainless-steel pan lysimeters. 'Old' waters, matrix soil waters and groundwater, typically have high concentrations (20 ??eq 1-1). Timing of soil water transport is not sufficiently rapid to suggest that soil water from the hillslope contributes to streamwater for an individual rainstorm. The source of streamflow, therefore, must be a combination of channel interception, runoff from near-channel areas, and runoff from a 3-ha bedrock outcrop in the headwaters. Groundwater contribution to streamflow was estimated using Cl- concentrations of throughfall and groundwater as the two end members for a two-component hydrograph separation. For the study period, groundwater contributed 79% of the runoff and from 1985 to 1995, contributed 75% of the runoff. Rainfall was the source of 45% of the Cl- flux from the watershed in the long term; the remaining Cl- is hypothesized to be derived from dry deposition, consistent with the enrichment noted for throughfall. At peak flow during individual rainstorms, 'new' water can contribute 95% of the runoff.

Throughfall patterns of a Subtropical Atlantic Forest in Brazil

NASA Astrophysics Data System (ADS)

Macedo Sá, João Henrique; Borges Chaffe, Pedro Luiz; Yuimi de Oliveira, Debora; Nery Giglio, Joana; Kobiyama, Masato

2017-04-01

The interception process is responsible for the spatial and temporal redistribution of the precipitation that reaches the ground. This process is important especially in forested areas since it influences recycling of moisture from the air and also the amount of water that effectively reaches the ground. The contact of the precipitation with the canopy influences on the water quality, increasing the concentration of various nutrients in the throughfall (Tf) and stemflow (Sf). Brazil, only about 8% of the original Atlantic Forest cover remains. That is an important biome and little is known about the characteristics of rainfall interception of this forest. The total interception loss in forested areas is usually formulated as the gross precipitation (P) minus the sum of the throughfall (Tf) and the stemflow (Sf). The stems characteristics influence on Sf, meanwhile, the value of Tf strongly depends on the canopy and leaf structures. Because of the complex structure of the canopy, these characteristics are usually expressed by the simpler Leaf Area Index (LAI) or the Canopy Cover Fraction (CCF). The Araponga river experimental catchment (ARA) with 5.3 ha is on the northern plateau of Santa Catarina State, southern Brazil. It is an area completely covered by secondary subtropical Atlantic Forest, the regional climate is the Köppen Cfb type, i.e., temperate climate without dry season and with warm summer (the mean temperature of the hottest month is always under 22°C). The objectives of the present study were (i) to evaluate the spatial and temporal variation of canopy cover; (ii) to influence of the interception process on the precipitation quality; and (iii) to explore the relation between canopy cover and throughfall. Inside the catchment, 9 Tf gauges were installed 40 cm above the soil surface in order to include the interception by shrub. 28 hand-made gauges were installed on a circular area of 3 m radius to analyze the spatial variability of throughfall. During 3 year in 2012 to 2014, digital images were taken every month with a camera installed horizontally 25 cm above the soil surface at each Tf gage. The total incident rainfall was 4624 mm, the throughfall volume was 3538 mm or 76% of incident rainfall. CCF and LAI ranged from 70 to 90% and from 3 to 5.5 m2/m2, respectively. We could not find any satisfactory relationship between Tf and canopy parameters (CCF and LAI). The analysis shows the significant difference in the water quality of the precipitation that reaches the ground after being intercepted. There was no significant relationship between the physicochemical parameters and the canopy cover fraction. The results indicate that the distribution of throughfall is not homogeneous, its spatial variation is not linked to any of the calculated parameters.

Temporal Dynamics in the Concentration, Flux, and Optical Properties of Tree-derived Dissolved Organic Matter (Tree-DOM) in an Epiphyte-laden Oak-cedar Forest.

NASA Astrophysics Data System (ADS)

Whitetree, A.; Van Stan, J. T., II; Wagner, S.; Guillemette, F.; Lewis, J.; Silva, L.; Stubbins, A.

2017-12-01

Studies on the fate and transport of dissolved organic matter (DOM) along the rainfall-to-discharge flow pathway typically begin in streams or soils, neglecting the initial enrichment of rainfall with DOM during contact with plant canopies. However, rain water can gather significant amounts of tree-derived DOM (tree-DOM) when it drains from the canopy, as throughfall, and down the stem, as stemflow. We examined the temporal variability of event-scale tree-DOM concentrations, yield, and optical (light absorbance and fluorescence) characteristics from an epiphyte-laden Quercus virginiana-Juniperus virginiana forest on Skidaway Island, Savannah, Georgia (USA). All tree-DOM fluxes were highly enriched compared to rainfall and epiphytes further increased concentrations. Stemflow DOC concentrations were greater than throughfall across study species, yet larger throughfall water yields produced greater DOC yields versus stemflow. Tree-DOM optical characteristics indicate it is aromatic-rich with FDOM dominated by humic-like fluorescence, containing 10-20% protein-like (tryptophan-like) fluorescence. Storm size was the only storm condition that strongly correlated with tree-DOM concentration and flux; however, throughfall and stemflow optical characteristics varied little across a wide range of storm conditions (from low magnitude events to intense tropical storms). Annual tree-DOM yields from the study forest (0.8-46 g-C m-2 yr-1) compared well to other yields along the rainfall-to- discharge flow pathway, exceeding DOM yields from some river watersheds.

Coastal Fog Sustains Summer Baseflow in Northern Californian Watershed

NASA Astrophysics Data System (ADS)

Chung, M.; Dufour, A.; Leonardson, R.; Thompson, S. E.; Dawson, T. E.

2015-12-01

The Mediterranean climate of Northern California imposes significant water stress on ecosystems and water resources during the dry summer months. During summer, frequently the only water inputs occur as occult precipitation, in the form of fog and dew. In this study, we characterized the role of coastal fog, a dominant feature of Northern Californian coastal ecosystems and a widespread phenomenon associated with deep marine upwelling in west coast, arid, and Mediterranean climates worldwide. We monitored fog occurrence and intensity, throughfall following canopy interception of fog, soil moisture, streamflow, and meteorological variables, and made visual observations of the spatial extent of fog using time-lapse imagery in Upper Pilarcitos Creek Watershed (managed by San Francisco Public Utilities Commission as part of the San Francisco area water supply). We adopted a stratified sampling design that captured the watershed's elevation gradient, forest-edge versus interior locations, and different vegetation cover. The point-scale observations of throughfall inputs and transpiration suppression, estimated from the Penman equation, were upscaled using such watershed features and the observed fog "footprint" identified from the time-lapse images. When throughfall input and fog-induced transpiration suppression were incorporated into the operational watershed model, they improved estimates of summer baseflow, which remained persistently higher than could be explained without the fog effects. Fog, although providing relatively small volumetric inputs to the water balance, appears to offer significant relief of water stress throughout the terrestrial and aquatic components of the coastal Californian ecosystem and thus should be accounted for when assessing water stress availability in dry ecosystems.

The canopy interception-landslide initiation conundrum: insight from a tropical secondary forest in northern Thailand

NASA Astrophysics Data System (ADS)

Sidle, Roy C.; Ziegler, Alan D.

2017-01-01

The interception and smoothing effect of forest canopies on pulses of incident rainfall and its delivery to the soil has been suggested as a factor in moderating peak pore water pressure in soil mantles, thus reducing the risk of shallow landslides. Here we provide 3 years of rainfall and throughfall data in a tropical secondary dipterocarp forest characterized by few large trees in northern Thailand, along with selected soil moisture dynamics, to address this issue. Throughfall was an estimated 88 % of rainfall, varying from 86 to 90 % in individual years. Data from 167 events demonstrate that canopy interception was only weakly associated (via a nonlinear relationship) with total event rainfall, but not significantly correlated with duration, mean intensity, or antecedent 2-day precipitation (API2). Mean interception during small events (≤ 35 mm) was 17 % (n = 135 events) compared with only 7 % for large events (> 35 mm; n = 32). Examining small temporal intervals within the largest and highest intensity events that would potentially trigger landslides revealed complex patterns of interception. The tropical forest canopy had little smoothing effect on incident rainfall during the largest events. During events with high peak intensities, high wind speeds, and/or moderate-to-high pre-event wetting, measured throughfall was occasionally higher than rainfall during large event peaks, demonstrating limited buffering. However, in events with little wetting and low-to-moderate wind speed, early event rainfall peaks were buffered by the canopy. As rainfall continued during most large events, there was little difference between rainfall and throughfall depths. A comparison of both rainfall and throughfall depths to conservative mean intensity-duration thresholds for landslide initiation revealed that throughfall exceeded the threshold in 75 % of the events in which rainfall exceeded the threshold for both wet and dry conditions. Throughfall intensity for the 11 largest events (rainfall = 65-116 mm) plotted near or above the intensity-duration threshold for landslide initiation during wet conditions; 5 of the events were near or above the threshold for dry conditions. Soil moisture responses during large events were heavily and progressively buffered at depths of 1 to 2 m, indicating that the timescale of any short-term smoothing of peak rainfall inputs (i.e., ≤ 1 h) has little influence on peak pore water pressure at depths where landslides would initiate in this area. Given these findings, we conclude that canopy interception would have little effect on mitigating shallow landslide initiation during the types of monsoon rainfall conditions in this and similar tropical secondary forest sites.

Effects of rainfall partitioning in the seasonal and spatial variability of soil water content in a Mediterranean downy oak forest

NASA Astrophysics Data System (ADS)

Garcia-Estringana, P.; Latron, J.; Molina, A. J.; Llorens, P.

2012-04-01

Rainfall partitioning fluxes (throughfall and stemflow) have a large degree of temporal and spatial variability and may consequently lead to significant changes in the volume and composition of water that reach the understory and the soil. The objective of this work is to study the effect of rainfall partitioning on the seasonal and spatial variability of the soil water content in a Mediterranean downy oak forest (Quercus pubescens), located in the Vallcebre research catchments (42° 12'N, 1° 49'E). The monitoring design, started on July 2011, consists of a set of 20 automatic rain recorders and 40 automatic soil moisture probes located below the canopy. One hundred hemispheric photographs of the canopy were used to place the instruments at representative locations (in terms of canopy cover) within the plot. Bulk rainfall, stemflow and meteorological conditions above the forest cover are also automatically recorded. Canopy cover, in leaf and leafless periods, as well as biometric characteristics of the plot, are also regularly measured. This work presents the first results describing throughfall and soil moisture spatial variability during both the leaf and leafless periods. The main drivers of throughfall variability, as canopy structure and meteorological conditions are also analysed.

Loblolly pine productivity and water relations in response to throughfall reduction and fertilizer application on a poorly drained site in northern Florida

DOE PAGES

Wightman, Maxwell G.; Martin, Timothy A.; Gonzalez-Benecke, Carlos A.; ...

2016-09-26

Loblolly pine ( Pinus taeda L.) forests are of great ecological and economic value in the southeastern United States, where nutrient availability frequently limits productivity. The impact of fertilizer application on the growth and water relations of loblolly pine has been investigated by numerous studies; however, few field experiments have examined the effects of drought. Drought is of particular interest due to the potential for climate change to alter soil water availability. In this study, we investigated the impact of fertilizer application and a 30% reduction in throughfall on loblolly pine productivity, transpiration, hydraulic conductance, and stomatal conductance. The studymore » was installed in a ten-year-old loblolly pine plantation on a somewhat poorly drained site in northern Florida. Throughfall reduction did not impact tree productivity or water relations of the trees. This lack of response was attributed to abundant rainfall and the ability of trees to access the shallow water table at this site. Fertilizer application increased basal area production by 20% and maximum leaf area index by 0.5 m2 m 2, but it did not affect whole-tree hydraulic conductance or the sensitivity of stomatal conductance to vapor pressure deficit. During the spring, when leaf area and vapor pressure deficit were high, the fertilizer-only treatment increased monthly transpiration by 17% when compared to the control. This relationship, furthermore, was not significant during the rest of the year.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lawrence, G.B.; Fernandez, I.J.; Goltz, S.M.

To provide information needed to assess the current and future status of spruce-fir forests in Maine, the Howland Integrated Forest Study (HIFS) was initiated in 1987 as part of the USDA Forest Service Forest Response Program, in conjunction with the establishment of a Mountain Cloud Chemistry Program (MCCP) monitoring site. Through this project, bulk and wet-only precipitation, dry deposition, throughfall and soil solution chemistry has been determined. This paper will focus on soil solution collected between May, 1988 and bulk precipitation collected from June through November, 1988.

Modelling hydrological conditions in the maritime forest region of south-western Nova Scotia

NASA Astrophysics Data System (ADS)

Yanni, Shelagh; Keys, Kevin; Meng, Fan-Rui; Yin, Xiwei; Clair, Tom; Arp, Paul A.

2000-02-01

Hydrological processes and conditions were quantified for the Mersey River Basin (two basins: one exiting below Mill Falls, and one exiting below George Lake), the Roger's Brook Basin, Moosepit Brook, and for other selected locations at and near Kejimkujik National Park in Nova Scotia, Canada, from 1967 to 1990. Addressed variables included precipitation (rain, snow, fog), air temperature, stream discharge, snowpack accumulations, throughfall, soil and subsoil moisture, soil temperature and soil frost, at a monthly resolution. It was found that monthly per hectare stream discharge was essentially independent of catchment area from <20 km2 to more than 1000 km2. The forest hydrology model ForHyM2 was used to simulate monthly rates of stream discharge, throughfall and snowpack water equivalents for mature forest conditions. These simulations were in good agreement with the historical records once the contributions of fog and mist to the area-wide water budget were taken into account, each on a monthly basis. The resulting simulations establish a hydrologically consistent, continuous, comprehensive and partially verified record for basin-wide outcomes for all major hydrological processes and conditions, be these related to stream discharge, soil moisture, soil temperature, snowpack accumulations, soil frost, throughfall, interception and soil percolation.

Simulated Impacts of Emerald Ash Borer on Throughfall and Stemflow Inputs of Water and Nitrogen in Black Ash Wetlands in Northern Michigan

NASA Astrophysics Data System (ADS)

Pypker, T. G.; Davis, J.; Van Grinsven, M. J.; Bolton, N. W.; Shannon, J.; Kolka, R. K.; Nelson, J.; Wagenbrenner, J. W.

2014-12-01

Emerald ash borer (Agrilus planipennis Fairmaire (EAB)) is an invasive insect that effectively kills ash trees (genus: Fraxinus) greater than 2.5 cm in diameter, resulting in near-complete stand mortality within 3-4 years. Black ash wetlands occupy approximately 270,000 ha in Michigan, and have 40 to 90% of the basal area occupied by black ash (F. nigra Marshall); hence the loss of black ash may result in dramatic changes in the canopy hydrology and nutrient deposition. We assessed the impact of a simulated EAB invasion on throughfall and stemflow quantity and nitrogen (N) content in 9 uninfected black ash wetlands located in the Upper Peninsula of Michigan. Within the 9 stands, 3 stands were left untreated ('Control'), 3 stands had all the black ash trees manually girdled ('Girdled') and 3 had all the black ash trees felled by chainsaw ('Clearcut'). We measured the quantity and inorganic-N content of throughfall using an array of randomly placed collectors (n = 16 per site). Stemflow was monitored at 2 sites (n = 12 trees) on the 3 most common tree species (black ash, yellow birch (Betula alleghaniensis Britt.) and red maple (Acer rubra L.)). Preliminary results indicate that relative to the Control, average monthly throughfall was 25% and 1% greater in the Clearcut and Girdled sites, respectively. While the loss of the ash trees resulted in greater throughfall inputs in the Clearcut sites, water table heights did not significantly change as a result of the treatments. Stemflow from live black ash trees was lower than from the yellow birch and red maple trees. As a result, we predict stemflow will increase over time as species with smoother bark and less upright branching begin replacing the black ash. Hence, the change in tree species may result in a greater concentration of inorganic-N inputs to the base of the trees, thereby altering the distribution of inorganic-N inputs into the wetland. Our preliminary results show no significant change in the total inorganic-N deposition via throughfall. Despite the severity of the disturbance that resulted from the simulated EAB infestation, preliminary results suggest that that these wetlands may show some short-term resiliency to the impacts of ash mortality, resulting in relatively unchanged hydrologic and nutrient deposition regimes.

Temporal Dynamics in the Concentration, Flux, and Optical Properties of Tree-Derived Dissolved Organic Matter in an Epiphyte-Laden Oak-Cedar Forest

NASA Astrophysics Data System (ADS)

Van Stan, John T.; Wagner, Sasha; Guillemette, François; Whitetree, Ansley; Lewis, Julius; Silva, Leticia; Stubbins, Aron

2017-11-01

Studies on the fate and transport of dissolved organic matter (DOM) along the rainfall-to-discharge flow pathway typically begin in streams or soils, neglecting the initial enrichment of rainfall with DOM during contact with plant canopies. However, rain water can gather significant amounts of tree-derived DOM (tree-DOM) when it drains from the canopy, as throughfall, and down the stem, as stemflow. We examined the temporal variability of event-scale tree-DOM concentrations, yield, and optical (light absorbance and fluorescence) characteristics from an epiphyte-laden Quercus virginiana-Juniperus virginiana forest on Skidaway Island, Savannah, Georgia (USA). All tree-DOM fluxes were highly enriched in dissolved organic carbon (DOC) compared to rainfall, and epiphytes further increased concentrations. Stemflow DOC concentrations were greater than throughfall across study species, yet larger throughfall water yields produced greater DOC yields versus stemflow. Tree-DOM optical characteristics indicate it is aromatic-rich with fluorescent DOM dominated by humic-like fluorescence, containing 10-20% protein-like (tryptophan-like) fluorescence. Storm size was the only storm condition that strongly correlated with tree-DOM concentration and flux; however, throughfall and stemflow optical characteristics varied little across a wide range of storm conditions (from low magnitude events to intense tropical storms). Annual tree-DOM yields from the study forest (0.8-46 g C m-2 yr-1) were similar to other yields from discrete down-gradient fluxes (litter leachates, soil leachates, and stream discharge) along the rainfall-to-discharge flow path.

Interception loss, throughfall and stemflow in a maritime pine stand. I. Variability of throughfall and stemflow beneath the pine canopy

NASA Astrophysics Data System (ADS)

Loustau, D.; Berbigier, P.; Granier, A.; Moussa, F. El Hadj

1992-10-01

Patterns of spatial variability of throughfall and stemflow were determined in a maritime pine ( Pinus pinaster Ait.) stand for two consecutive years. Data were obtained from 52 fixed rain gauges and 12 stemflow measuring devices located in a 50m × 50m plot at the centre of an 18-year-old stand. The pine trees had been sown in rows 4m apart and had reached an average height of 12.6m. The spatial distribution of stems had a negligible effect on the throughfall partitioning beneath the canopy. Variograms of throughfall computed for a sample of storms did not reveal any spatial autocorrelation of throughfall for the sampling design used. Differences in throughfall, in relation to the distance from the rows, were not consistently significant. In addition, the distance from the tree stem did not influence the amount of throughfall. The confidence interval on the amount of throughfall per storm was between 3 and 8%. The stemflow was highly variable between trees. The effect of individual trees on stemflow was significant but the amount of stemflow per tree was not related to tree size (i.e. height, trunk diameter, etc.). The cumulative sampling errors on stemflow and throughfall for a single storm created a confidence interval of between ±7 and ±51% on interception. This resulted mainly from the low interception rate and sampling error on throughfall.

Northern Forest DroughtNet: Initial results from a multi-year throughfall manipulation experiment in New Hampshire

NASA Astrophysics Data System (ADS)

McIntire, C.; Vadeboncoeur, M. A.; Coble, A.; Jennings, K.; Asbjornsen, H.

2016-12-01

Climate change is likely to affect the Northern Forest region through the increased frequency and severity of drought events. However, our understanding of how the Northern Forest, which is adapted to humid temperate conditions, will respond to moderate to extreme droughts is limited. Given the important role that these forests play in protecting ecosystem services and in supplying forest products, enhancing our knowledge about impacts of drought is critical to ensuring effective forest management and adaptation to climate change. The Northern Forest DroughtNet project aims to simulate a four-year severe drought by removing 55% of the incoming throughfall; thus representing the 99th percentile of annual precipitation based on historic precipitation data in Durham, NH. This is accomplished using two replicated 900 m2 throughfall removal structures consisting of a network of gutters that capture and divert incoming precipitation away from the established treatment area. Data presented here will address the ecosystem response to the drought treatment over the course of the first year of the experiment as well as validate the effectiveness and artifacts of the throughfall removal structure. Response variables of interest include soil moisture content, above and below ground biomass production, litterfall, decomposition rates, leaf water potential, foliar gas exchange, and whole tree transpiration rates. Preliminary findings provide insight into the effectiveness of using throughfall manipulation experiments in a temperate forest ecosystem to simulate an extreme drought event, as well as initial tree physiological and growth responses in relation to soil moisture availability and the implications for future climate change impacts.

Flux-based Enrichment Ratios of Throughfall and Stemflow Found to Vary Significantly within Urban Fragments and Along an Urban-to-Rural Gradient

NASA Astrophysics Data System (ADS)

Dowtin, A. L.; Levia, D. F., Jr.

2017-12-01

Throughfall and stemflow are important inputs of water and solutes to forest soils in both rural and urban forests. In metropolitan wooded ecosystems, a number of factors can affect flux-based enrichment ratios, including combustion of fossil fuels and proximity to industry. Use of flux-based enrichment ratios provides a means by which this modification of net precipitation chemistry can be quantified for both throughfall and stemflow, and allows for a characterization of the relative contributions of stemflow and throughfall in the delivery of nutrients and pollutants to forest soils. This study utilizes five mixed deciduous forest stands along an urban-to-rural gradient (3 urban fragments, 1 suburban fragment, and a portion of 1 contiguous rural forest) within a medium-sized metropolitan region of the United States' Northeast megalopolis, to determine how the size, shape, structure, and geographic context of remnant forest fragments determine hydrologic and solute fluxes within them. In situ observations of throughfall and stemflow (the latter of which is limited to Quercus rubra and Quercus alba) within each study plot allow for an identification and characterization of the spatial variability in solute fluxes within and between the respective sites. Preliminary observations indicate significant intra-site variability in solute concentrations as observed in both throughfall and stemflow, with higher concentrations along the respective windward edges of the study plots than at greater depths into their interiors. Higher flux-based stemflow enrichment ratios, for both Q. rubra and Q. alba, were also evident for certain ions (i.e., S2-, NO3-) in the urban forest fragments, with significantly lower ratios observed at the suburban and rural sites. Findings from this research are intended to aid in quantifying the spatial variability of the hydrologic and hydrochemical ecosystem service provisions of remnant metropolitan forest fragments. This research is supported in part by National Science Foundation grant Reference Number BCS-1459116.

Properties of dissolved and total organic matter in throughfall, stemflow and forest floor leachate of central European forests

NASA Astrophysics Data System (ADS)

Bischoff, S.; Schwarz, M. T.; Siemens, J.; Thieme, L.; Wilcke, W.; Michalzik, B.

2015-05-01

We present the first investigation of the composition of dissolved organic matter (DOM) compared to total organic matter (TOM, consisting of DOM, < 0.45 μm and particulate organic matter 0.45 μm < POM < 500 μm) in throughfall, stemflow and forest floor leachate of common beech (Fagus sylvatica L.) and Norway spruce (Picea abies (L.) H. Karst.) forests using solid-state 13C nuclear magnetic resonance (NMR) spectroscopy. We hypothesized that the composition and properties of organic matter (OM) in forest ecosystem water samples differ between DOM and TOM and between the two tree species. The 13C NMR results, derived from 21 samples, point to pronounced differences in the composition of DOM and TOM in throughfall solution at the beech sites, with TOM exhibiting higher relative intensities for the alkyl C region, which represents aliphatic C from less decomposed organic material compared to DOM. Furthermore, TOM shows lower intensities for lignin-derived and aromatic C of the aryl C region resulting in lower aromaticity indices and a diminished degree of humification. Across the ecosystem compartments, differences in the structural composition of DOM and TOM under beech lessened in the following order: throughfall > stemflow ≈ forest floor leachate. In contrast to the broadleaved sites, differences between DOM and TOM in throughfall solution under spruce were less pronounced and spectra were, overall, dominated by the alkyl C region, representing aliphatic C. Explanations of the reported results might be substantiated in differences in tree species-specific structural effects, leaching characteristics or differences in the microbial community of the tree species' phyllosphere and cortisphere. However, the fact that throughfall DOM under beech showed the highest intensities of recalcitrant aromatic and phenolic C among all samples analysed likely points to a high allelopathic potential of beech trees negatively affecting other organisms and hence ecosystem processes and functions.

Re-Assessing the Measurement of Fogwater Inputs to a Tropical Ecosystem

NASA Astrophysics Data System (ADS)

Burkard, R.; Eugster, W.; Holwerda, F.; Bruijnzeel, S.; Scatena, F.; Siegwolf, R.

2002-12-01

For several years the hydrological importance of the fog- and cloudwater deposition to ecosystems in the tropics has been of great interest. In earlier studies carried out in the humid tropics the amount of deposited cloudwater was estimated by indirect methods based on the physical characteristics of the utilized cloudwater collector. In the temperate climatic zone of central Europe most of the studies dealing with cloudwater focus on the additional chemical input due to cloudwater in relation to the amount of deposited rainwater. During our experiment in the Luquillo mountains of Puerto Rico the different aspects of the chemical and hydrological impacts of cloudwater deposition have been investigated. During 43 days, cloudwater fluxes were measured with an eddy covariance setup consisting of a Solent ultrasonic anemometer and a size-resolving cloud droplet spectrometer. Cloudwater samples were taken with a Caltech-type active strand cloudwater collector. Additionally, measurements of rain, throughfall and stemflow were performed. Samples of fog, rain, throughfall and stemflow were analyzed for inorganic ion and stabile isotope concentrations (δ18O and δ2H). First analysis of the hydrological input show that there exist some significant differences in the deposited amount of cloudwater as measured with our instruments in comparison with previous studies carried out at the same location: Mean liquid water content was 78.6 mg m-3 during situations with a visibility below 1000 m (84% of the entire field campaign). The deposition rate of cloudwater was 0.88 mm d-1. A mismatch was found regarding the water balance. We conclude from this that the rainfall amount and therefore also the chemical input by rain is strongly underestimated due to wind-driven rain, which is not measured by standard rain gauges. Depending on the reference value, we have to conclude that the deposition of cloudwater accounts for 6--11% of wet deposition.

BOREAS HYD-8 Throughfall Data

NASA Technical Reports Server (NTRS)

Wang, Xue-Wen; Hall, Forrest G. (Editor); Knapp, David E. (Editor); Fernandes, Richard; Smith, David E. (Technical Monitor)

2000-01-01

The Boreal Ecosystem-Atmosphere Study (BOREAS) Hydrology (HYD)-8 team made measurements of surface hydrological processes at the Southern Study Area (SSA) and Northern Study Area (NSA) Old Black Spruce (OBS) Tower Flux sites, supporting its research into point hydrological processes and the spatial variation of these processes. These data were collected during the 1994 and 1996 field campaigns. Data collected may be useful in characterizing canopy interception, drip, throughfall, moss interception, drainage, evaporation, and capacity during the growing season at daily temporal resolution. This particular data set contains the measurements of throughfall, which is the amount of precipitation that fell through the canopy. A nested spatial sampling plan was implemented to determine spatial variations of the measured hydrological processes and ultimately the impact of these variations on modeled carbon and water budgets. These data are stored in ASCII text files. The data files are available on a CD-ROM (see document number 20010000884) or from the Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC).

The role of urban forest to reduce rain acid in urban industrial areas

NASA Astrophysics Data System (ADS)

Slamet, B.; Agustiarni, Y.; Hidayati; Basyuni, M.

2018-03-01

Urban forest has many functions mainly on improving the quality of the urban environment. One of the functions is to increase pH and reduce dangerous chemical content. The aim of the research is to find out the role of vegetation density of urban forest around the industrial area in reducing the acid rain. The condition of land cover was classified into four classes which are dense, medium, sparse and open area. The water of the throughfall and stemflow was taken from each type of land cover except in the open area. Parameters measured in this study are water acidity (pH), anion content (SO4 2- and NO3 -), cation content (Ca2+, Mg2+, and NH4 +) and electrical conductivity (EC). The results indicated that urban forest vegetation was able to increase the pH of rain water from 5.42 which is in an open area without vegetation to be 7.13 and 7.32 in dense and moderate vegetation cover by throughfall mechanism, respectively. Rain water acidity also decreased through stemflow mechanism with a pH ranged from 5.92 - 6.43. Urban forest vegetation decreased sulfate content (SO42-) from 528.67 mg/l in open area to 44 - 118 mg/l by throughfall mechanism and ranged from 90 to 366.67 mg/l through stemflow mechanism. Urban forest vegetation significantly decreased the rainwater nitrate content from 27 mg/l to 0.03 - 0.70 mg/l through the mechanism of throughfall and between 1.53 - 8.82 mg/l through the stemflow mechanism. Urban forest vegetation also increased the concentration of cations (NH4+, Ca2+, Mg2+, Na+) compared with open areas. Urban forest vegetation showed increased the electrical conductivity (EC) from 208.12 μmhos/cm to 344.67 - 902.17 μmhos/cm through the through fall mechanism and 937.67 - 1058.70 μmhos/cm through the stemflow mechanism. The study suggested that urban forests play a significant role in reducing rainwater acidity and improving the quality of rainwater that reached the soil surface.

A throughfall collection method using mixed bed ion exchange resin columns

Treesearch

Mark E. Fenn; Mark A. Poth; Michael J. Arbaugh

2002-01-01

Measurement of ionic deposition in throughfall is a widely used method for measuring deposition inputs to the forest floor. Many studies have been published, providing a large database of throughfall deposition inputs to forests. However, throughfall collection and analysis is labor intensive and expensive because of the large number of replicate collectors needed and...

Acclimation of branch and leaf hydraulics in adult Fagus sylvatica and Picea abies in a forest through-fall exclusion experiment.

PubMed

Tomasella, Martina; Beikircher, Barbara; Häberle, Karl-Heinz; Hesse, Benjamin; Kallenbach, Christian; Matyssek, Rainer; Mayr, Stefan

2018-02-01

Decreasing water availability due to climate change poses the question of whether and to what extent tree species are able to hydraulically acclimate and how hydraulic traits of stems and leaves are coordinated under drought. In a through-fall exclusion experiment, hydraulic acclimation was analyzed in a mixed forest stand of Fagus sylvatica L. and Picea abies (L.) Karst. In drought-stressed (TE, through-fall exclusion over 2 years) and control (CO) trees, hydraulic vulnerability was studied in branches as well as in leaves (F. sylvatica) and end-twigs (P. abies, entirely formed during the drought period) sampled at the same height in sun-exposed portions of the tree crown. In addition, relevant xylem anatomical traits and leaf pressure-volume relations were analyzed. The TE trees reached pre-dawn water potentials down to -1.6 MPa. In both species, water potentials at 50% loss of xylem hydraulic conductivity were ~0.4 MPa more negative in TE than in CO branches. Foliage hydraulic vulnerability (expressed as water potential at 50% loss of leaf/end-twig hydraulic conductance) and water potential at turgor loss point were also, respectively, 0.4 and 0.5 MPa lower in TE trees. Minor differences were observed in conduit mean hydraulic diameter and cell wall reinforcement. Our findings indicate significant and fast hydraulic acclimation under relatively mild drought in both tree species. Acclimation was well coordinated between branches and foliage, which might be essential for survival and productivity of mature trees under future drought periods. © The Author 2017. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Time series study of concentrations of SO4(2-) and H+ in precipitation and soil waters in Norway.

PubMed

Kvaalen, H; Solberg, S; Clarke, N; Torp, T; Aamlid, D

2002-01-01

Along with a steady reduction of acid inputs during 14 years of intensive forest monitoring in Norway, the influence of acid deposition upon soil water acidity is gradually reduced in favour of other and internal sources of H+ and sulphate, in particular from processes in the upper soil layer. We used statistical analyses in two steps for precipitation, throughfall and soil water at 5, 15 and 40 cm depths. Firstly, we employed time series analyses to model the temporal variation as a long-term linear trend and a monthly variation, and by this filtered out residual, weekly variation. Secondly, we used the parameter estimates and the residuals from this to show that the long term, the monthly and the weekly variation in one layer were correlated to similar temporal variation in the above, adjacent layer. This was strongly evident for throughfall correlated to precipitation, but much weaker for soil water. Continued acidification in soil water on many plots suggests that the combined effects of anthropogenic and natural acid inputs exceed in places the buffering capacity of the soil.

Measured and modeled interactive effects of potassium deficiency and water deficit on gross primary productivity and light-use efficiency in Eucalyptus grandis plantations.

PubMed

Christina, Mathias; Le Maire, Guerric; Battie-Laclau, Patricia; Nouvellon, Yann; Bouillet, Jean-Pierre; Jourdan, Christophe; de Moraes Gonçalves, José Leonardo; Laclau, Jean-Paul

2015-05-01

Global climate change is expected to increase the length of drought periods in many tropical regions. Although large amounts of potassium (K) are applied in tropical crops and planted forests, little is known about the interaction between K nutrition and water deficit on the physiological mechanisms governing plant growth. A process-based model (MAESPA) parameterized in a split-plot experiment in Brazil was used to gain insight into the combined effects of K deficiency and water deficit on absorbed radiation (aPAR), gross primary productivity (GPP), and light-use efficiency for carbon assimilation and stem biomass production (LUEC and LUEs ) in Eucalyptus grandis plantations. The main-plot factor was the water supply (undisturbed rainfall vs. 37% of throughfall excluded) and the subplot factor was the K supply (with or without 0.45 mol K m(-2 ) K addition). Mean GPP was 28% lower without K addition over the first 3 years after planting whether throughfall was partly excluded or not. K deficiency reduced aPAR by 20% and LUEC by 10% over the whole period of growth. With K addition, throughfall exclusion decreased GPP by 25%, resulting from a 21% decrease in LUEC at the end of the study period. The effect of the combination of K deficiency and water deficit was less severe than the sum of the effects of K deficiency and water deficit individually, leading to a reduction in stem biomass production, gross primary productivity and LUE similar to K deficiency on its own. The modeling approach showed that K nutrition and water deficit influenced absorbed radiation essentially through changes in leaf area index and tree height. The changes in gross primary productivity and light-use efficiency were, however, driven by a more complex set of tree parameters, especially those controlling water uptake by roots and leaf photosynthetic capacities. © 2014 John Wiley & Sons Ltd.

Leaf Pressure Volume Data in Caxiuana and Tapajos National Forest, Para, Brazil (2011)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Powell, Thomas; Moorcroft, Paul

Pressure volume curve measurements on leaves of canopy trees from the from the Caxiuana and Tapajos National Forests, Para, Brazil. Tapajos samples were harvested from the km 67 forested area, which is adjacent to the decommissioned throughfall exclusion drought experimental plot. Caxiuana samples were harvested from trees growing in the throughfall exclusion plots. Data were collected in 2011. Dataset includes: date of measurement, site ID, plot ID, tree ID (species, tree tag #), leaf area, fresh weight, relative weight, leaf water potential, and leaf water loss. P-V curve parameters (turgor loss point, osmotic potential, and bulk modulus of elasticity) canmore » be found in Powell et al. (2017) Differences in xylem cavitation resistance and leaf hydraulic traits explain differences in drought tolerance among mature Amazon rainforest trees. Global Change Biology.« less

Manganese biogeochemistry in a small Adirondack forested lake watershed

USGS Publications Warehouse

Shanley, James B.

1986-01-01

In September and October 1981, manganese (Mn) concentrations and pH were intensively monitored in a small forested lake watershed in the west-central Adirondack Mountains, New York, during two large acidic storms (each ∼5 cm rainfall, pH 4.61 and 4.15). The data were evaluated to identify biogeochemical pathways of Mn and to assess how these pathways are altered by acidic atmospheric inputs. Concentrations of Mn averaged 1.1 μg/L in precipitation and increased to 107 μg/L in canopy throughfall, the enrichment reflecting active biological cycling of Mn. Rain pH and throughfall Mn were negatively correlated, suggesting that foliar leaching of Mn was enhanced by rainfall acidity. The pulselike input of Mn to the forest floor in the high initial concentrations in throughfall (∼1000 μg/L) did not affect Mn concentrations in soil water (< 20 μg/L) or groundwater (usually < 40 μg/L), which varied little with time. In the inlet stream, Mn concentrations remained constant at 48 μg/L as discharge varied from 1.1 to 96 L/s. Manganese was retained in the vegetative cycle and regulated in the stream by adsorption in the soil organic horizon. The higher Mn levels in the stream may be linked to its high acidity (pH 4.2–4.3). Mixing of Mn-rich stream water with neutral lake water (pH 7.0) caused precipitation of Mn and deposition in lake sediment.

Effects of silvicultural management intensity on fluxes of dissolved and particulate organic matter in 27 forest sites of the Biodiversity Exploratories

NASA Astrophysics Data System (ADS)

Michalzik, Beate; Bischoff, Sebastian; Levia, Delphis; Schwarz, Martin; Escher, Peter; Wilcke, Wolfgang; Thieme, Lisa; Kerber, Katja; Kaupenjohann, Martin; Siemens, Jan

2017-04-01

In forested ecosystems, throughfall and stemflow function as key components in the cycling of water and associated biogeochemistry. Analysing annual flux data collected from 27 intensively monitored forest sites of the Biodiversity Exploratories, we found throughfall fluxes of DOC (dissolved organic carbon) linearly related (R2 = 0.40, p < 0.001) to the silvicultural management intensity indicator (SMI) developed by Schall and Ammer (2013). The SMI combines tree species, stand age and aboveground living and dead woody biomass, thereby allowing the quantifying of silvicultural management intensities of stands differing in species composition, age, silvicultural system as they convert from one stand type into another. Throughfall fluxes of particulate organic C and N (POC and PN) and dissolved N were, however independent from those forest structural metrics as well as annual C and N stemflow fluxes, which varied greatly among management intensity classes. In this context, we suggest that canopy structure metrics are more important drivers of water and matter stemflow dynamics, than structural metrics on the level of forest stands. On the other hand, leaching losses of DOC and POC from the litter layer of forests increased significantly with increasing forest management intensity. The observed relationships revealed by intensive flux monitoring are important because they allow us to link organic matter fluxes to forest metrics of larger forested areas (e.g. derived from LiDAR imagery), and hence to model and up-scale water-bound OC dynamics to the landscape level.

Spatial and temporal variability of throughfall and soil moisture in a deciduous forest in the low mountain ranges (Hesse, Germany)

NASA Astrophysics Data System (ADS)

Chifflard, Peter; Weishaupt, Philipp; Reiss, Martin

2017-04-01

Spatial and temporal patterns of throughfall can affect the heterogeneity of ecological, biogeochemical and hydrological processes at a forest floor and further the underlying soil. Previous research suggests different factors controlling the spatial and temporal patterns of throughfall, but most studies focus on coniferous forest, where the vegetation coverage is more or less constant over time. In deciduous forests the leaf area index varies due to the leaf fall in autumn which implicates a specific spatial and temporal variability of throughfall and furthermore of the soil moisture. Therefore, in the present study, the measurements of throughfall and soil moisture in a deciduous forest in the low mountain ranges focused especially on the period of leaf fall. The aims of this study were: 1) to detect the spatial and temporal variability of both the throughfall and the soil moisture, 2) to examine the temporal stability of the spatial patterns of the throughfall and soil moisture and 3) relate the soil moisture patterns to the throughfall patterns and further to the canopy characteristics. The study was carried out in a small catchment on middle Hesse (Germany) which is covered by beech forest. Annual mean air temperature is 9.4°C (48.9˚F) and annual mean precipitation is 650 mm. Base materials for soil genesis is greywacke and clay shale from Devonian deposits. The soil type at the study plot is a shallow cambisol. The study plot covers an area of about 150 m2 where 77 throughfall samplers where installed. The throughfall and the soil moisture (FDR-method, 20 cm depth) was measured immediately after every rainfall event at the 77 measurement points. During the period of October to December 2015 altogether 7 events were investigated. The geostatistical method kriging was used to interpolate between the measurements points to visualize the spatial patterns of each investigated parameter. Time-stability-plots were applied to examine temporal scatters of each investigated parameter. The spearmen and pearson correlation coefficients were applied to detect the relationship between the different investigated parameters. First results show that the spatial variability of throughfall decreases if the total amount of the throughfall increases. The soil moisture shows a similar behavior. It`s spatial variability decreases if higher soil moisture values were measured. Concerning the temporal stability of throughfall it can be shown that it is very high during the leaf-free period, although the rainfall events have different total througfall amounts. The soil moisture patterns consists of a low temporal stability and additionally only during one event a significant correlations between throughfall and soil moisture patterns exists. This implies that other factors than the throughfall patterns control the spatial patterns of soil moisture.

The Relative Importance of Convective and Trade-wind Orographic Precipitation to Streamflow in the Luquillo Mountains, Eastern Puerto Rico

NASA Astrophysics Data System (ADS)

Scholl, M. A.; Shanley, J. B.; Occhi, M.; Scatena, F. N.

2012-12-01

Like many mountainous areas in the tropics, watersheds in the Luquillo Mountains of Puerto Rico (18.3° N) have abundant rainfall and stream discharge, but relatively little storage capacity. Therefore, the water supply is vulnerable to drought and water availability may be affected by projected changes in regional temperature and atmospheric dynamics due to global warming. To help determine the links between climate and water availability, precipitation patterns were analyzed, and stable-isotope signatures of precipitation from different seasonal weather systems were established to identify those that are most important in maintaining streamflow and groundwater recharge. Stable isotope data include cloud water, rainfall, throughfall, streamflow, and groundwater from the Rio Mameyes and Rio Icacos/ Rio Blanco watersheds. Precipitation inputs have a wide range of stable isotope values, from fog/cloud water with δ2H and δ18O averaging +3.2‰, -1.74‰ respectively, to tropical storm rain with values as low as -154‰, -20.4‰. Spatial and temporal patterns of water isotopic values on this Caribbean island are different than higher latitude, continental watersheds. The data exhibit a 'reverse seasonality', with higher isotopic values in winter and lower values in summer; and stable isotope values of stream water do not decrease as expected with increasing altitude, because of cloud water input. Rain isotopic values vary predictably with local and mesoscale weather patterns and correlate strongly with cloud altitude. This correlation allows us to assign isotopic signatures to different sources of precipitation, and to investigate which climate patterns contribute to streamflow and groundwater recharge. At a measurement site at 615 m in the Luquillo Mountains, the average length of time between rain events was 15 h, and 45% of the rain events were <2 mm, reflecting the frequent small rain events of the trade-wind orographic rainfall weather pattern. Long-term average streamflow isotopic composition indicates a disproportionately large contribution of this trade-wind precipitation to streamflow, highlighting the importance of this climate pattern to the hydrology of the watersheds. Isotopic composition of groundwater suggests a slightly higher proportion of convective precipitation, but still smaller than in total rainfall. Hydrograph separation experiments yielded information on stormflow characteristics, with quantification of contributing sources determined from water isotopes and solute chemistry. The evidence that intense convective rain events run off and light trade-wind showers appear to contribute much of the baseflow indicates that the area may undergo a change in water supply if the trade-wind orographic precipitation dynamics in the Caribbean are affected by future climate change.

Biogeochemical effects of forest vegetation on acid precipitation-related water chemistry: a case study in southwest China.

PubMed

Chen, Jing; Li, Wei; Gao, Fang

2010-10-06

The elemental composition of rainwater, throughfall, and soil solutions of a forest ecosystem in the acid rain control region of southwest China was investigated during 2007-2008 to assess the acid buffering capacity of different forest covers. A possible seasonal distribution of wet deposition was identified. Sulfur was determined as the dominant acidification precursor in this region. The chemical composition of rainfall intercepted by the forest canopy was modified substantially; generally the ion concentrations were increased by dry deposition and foliar leaching. As an exception, the concentration of NH(4)(+) and NO(3)(-) decreased in throughfall, which was probably due to the absorption of nitrogen by the leaves. Elemental concentrations in soil solutions decreased with depth. The water conservation capacity of different forests was also evaluated. The most appropriate forest vegetation for water conservation and remediation of acid precipitation in this region was explored for the sake of ecosystem management, ecological restoration and economic development.

Capturing heterogeneity: The role of a study area's extent for estimating mean throughfall

NASA Astrophysics Data System (ADS)

Zimmermann, Alexander; Voss, Sebastian; Metzger, Johanna Clara; Hildebrandt, Anke; Zimmermann, Beate

2016-11-01

The selection of an appropriate spatial extent of a sampling plot is one among several important decisions involved in planning a throughfall sampling scheme. In fact, the choice of the extent may determine whether or not a study can adequately characterize the hydrological fluxes of the studied ecosystem. Previous attempts to optimize throughfall sampling schemes focused on the selection of an appropriate sample size, support, and sampling design, while comparatively little attention has been given to the role of the extent. In this contribution, we investigated the influence of the extent on the representativeness of mean throughfall estimates for three forest ecosystems of varying stand structure. Our study is based on virtual sampling of simulated throughfall fields. We derived these fields from throughfall data sampled in a simply structured forest (young tropical forest) and two heterogeneous forests (old tropical forest, unmanaged mixed European beech forest). We then sampled the simulated throughfall fields with three common extents and various sample sizes for a range of events and for accumulated data. Our findings suggest that the size of the study area should be carefully adapted to the complexity of the system under study and to the required temporal resolution of the throughfall data (i.e. event-based versus accumulated). Generally, event-based sampling in complex structured forests (conditions that favor comparatively long autocorrelations in throughfall) requires the largest extents. For event-based sampling, the choice of an appropriate extent can be as important as using an adequate sample size.

Exploratory Water Budget Analysis of A Transitional Premontane Cloud Forest in Costa Rica Through Undergraduate Research

NASA Astrophysics Data System (ADS)

Washington-Allen, R. A.; Buckwalter, E. H.; Moore, G. W.; Burns, J. N.; Dennis, A. R.; Dodge, O.; Guffin, E. C.; Morris, E. R.; Oien, R. P.; Orozco, G.; Peterson, A.; Teale, N. G.; Shibley, N. C.; Tourtellotte, N.; Houser, C.; Brooks, S. D.; Brumbelow, J. K.; Cahill, A. T.; Frauenfeld, O. W.; Gonzalez, E.; Hallmark, C. T.; McInnes, K. J.; Miller, G. R.; Morgan, C.; Quiring, S. M.; Rapp, A. D.; Roark, E.; Delgado, A.; Ackerson, J. P.; Arnott, R.

2012-12-01

The ecohydrology of transitional premontane cloud forests is not well understood. This problem is being addressed by a NSF Research Experience for Undergraduates (REU) study at the Texas A&M University Soltis Center for Research & Education in Costa Rica. Exploratory analysis of the water budget within a 20-ha watershed was used to connect three faculty-mentored research areas in ecohydrology, climate, and soil sciences and highlight the roles of 12 undergraduate researchers from 12 different universities. The water budget model is Q = Pn - E - T + ΔG + ΔS where Q = runoff, Pn = net precipitation, E = evaporation, T = transpiration, and ΔG and ΔS are change in groundwater soil water storage, respectively. Additionally, Pn = Pg - I = Tf + Sf + D, where Pg = gross precipitation, I/ΔI = canopy interception or storage, Tf = throughfall, Sf = stemflow, and D = canopy drip. The following terms were well understood Pg (satellite = 34-mm and tower = 38.1-mm) and Q from a recently constructed v-notch weir. We moderately understand Tf + D (30.9-mm from an array of forest rain gages), ΔI (7.2-mm) related to Sf, and T (10.4-mm measured with sapflow sensors). We found that soils were clay loam to silty loam textured Andisols on saprolitic tuft with a mean potential ΔS of 398 mm H2O under laboratory conditions, but in the field the following terms are almost completely unknown and require further field studies including E, ΔG, and ΔS. Recent installation of piezometers will address ΔG. Temporal scaling of measurements to a 1-week period was a challenge as well as the construction, deployment and calibration of instruments. However, this exploration allowed us to determine measurement uncertainties in the water budget, e.g., E, and to set future areas of research to address these uncertainties.

Walker Branch Throughfall Displacement Experiment Data Report: Site Characterization, System Performance, Weather, Species Composition, and Growth (NDP-078 and 078A)

DOE Data Explorer

Cushman, Robert M. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States), Carbon Dioxide Information Analysis Center, Environmental Sciences Division; Hanson, Paul J. [Oak Ridge National Laboratory, Oak Ridge, TN (USA), Environmental Sciences Division; Todd, Donald E. [Oak Ridge National Laboratory, Oak Ridge, TN (USA), Environmental Sciences Division; Riggs, Jeffery S. [Oak Ridge National Laboratory, Oak Ridge, TN (USA), Instrumentation and Controls Division; Wolfe, Mark E. [Tennessee Valley Authority, Norris, TN (USA); O'Neill, Elizabeth G. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States), Environmental Sciences Division

2001-07-01

This numeric data package provides data sets, and accompanying documentation, on site characterization, system performance, weather, species composition, and growth for the Throughfall Displacement Experiment, which was established in the Walker Branch Watershed of East Tennessee to provide data on the responses of forests to altered precipitation regimes. The specific data sets include soil water content and potential, coarse fraction of the soil profile, litter layer temperature, soil temperature, monthly weather, daily weather, hourly weather, species composition of trees and saplings, mature tree and sapling annual growth, and relative leaf area index. Fortran and SAS(TM) access codes are provided to read the ASCII data files.

Spatial variability of throughfall in a stand of Scots pine (Pinus sylvestris L.) with deciduous admixture as influenced by canopy cover and stem distance

NASA Astrophysics Data System (ADS)

Kowalska, Anna; Boczoń, Andrzej; Hildebrand, Robert; Polkowska, Żaneta

2016-07-01

Vegetation cover affects the amount of precipitation, its chemical composition and its spatial distribution, and this may have implications for the distribution of water, nutrients and contaminants in the subsurface soil layer. The aim of this study was a detailed diagnosis of the spatio-temporal variability in the amount of throughfall (TF) and its chemical components in a 72-year-old pine stand with an admixture of oak and birch. The spatio-temporal variability in the amount of TF water and the concentrations and deposition of the TF components were studied. The components that are exchanged in canopy (H+, K, Mg, Mn, DOC, NH4+) were more variable than the components whose TF deposition is the sum of wet and dry (including gas) deposition and which undergo little exchange in the canopy (Na, Cl, NO3-, SO42-). The spatial distribution was temporally stable, especially during the leafed period. This study also investigated the effect of the selected pine stand characteristics on the spatial distribution of throughfall and its chemical components; the characteristics included leaf area index (LAI), the proportion of the canopy covered by deciduous species and pine crowns, and the distance from the nearest tree trunk. The LAI measured during the leafed and leafless periods had the greatest effect on the spatial distribution of TF deposition. No relationship was found between the spatial distribution of the amount of TF water and (i) the LAI; (ii) the canopy cover of broadleaf species or pines; or (iii) the distance from the trunks.

Hydrogeochemical data from an acidic deposition study at McDonalds Branch basin in the New Jersey Pinelands, 1983-86

USGS Publications Warehouse

Lord, D.G.; Barringer, J.L.; Johnsson, P.A.; Schuster, P.F.; Walker, R.L.; Fairchild, J.E.; Sroka, B.N.; Jacobsen, Eric

1990-01-01

Data from a 1983-86 acidic-deposition study at McDonalds Branch basin, a small (2.35-sq-mi) forested watershed in Lebanon State Forest, New Jersey include mineralogy of soil and depositional clays; physical and chemical analyses of soils; hydrologic measurements (precipitation and throughfall amounts, stream stage and discharge, and water-table altitudes); and water quality data from precipitation, throughfall, soil water, surface water, and groundwater. Site locations, collector designs, and well- construction data also are presented. The pH of bulk precipitation to McDonalds Branch basin over the sampling period (January 1985 to March 1986) ranged from 4.0 to 4.7, with a mean of approximately 4.3. Stream pH ranged from 3.2 to 4.8 and generally increased in a downstream direction. In general sulfate was the dominant anion throughout the basin. Aluminum concentrations commonly were elevated in surface and groundwaters, and were as high as 10,000 micrograms/L at one upstream site on McDonalds Branch. Dissolved organic carbon was an important component of stream waters in some locations and ranged in concentration from 1/1 to 37 mg/L. (USGS)

A throughfall collection method using mixed bed ion exchange resin columns.

PubMed

Fenn, Mark E; Poth, Mark A; Arbaugh, Michael J

2002-01-15

Measurement of ionic deposition in throughfall is a widely used method for measuring deposition inputs to the forest floor. Many studies have been published, providing a large database of throughfall deposition inputs to forests. However, throughfall collection and analysis is labor intensive and expensive because of the large number of replicate collectors needed and because sample collection and chemical analyses are required on a stochastic precipitation event-based schedule. Therefore we developed and tested a throughfall collector system using a mixed bed ion exchange resin column. We anticipate that this method will typically require only one to three samplings per year. With this method, bulk deposition and bulk throughfall are collected by a funnel or snow tube and ions are retained as the solution percolates through the resin column. Ions retained by the resin are then extracted in the same column with 2 N KCl and analyzed for nitrate and ammonium. Deposition values in throughfall from conventional throughfall solution collectors and colocated ion exchange samplers were not significantly different during consecutive 3- and 4-month exposure periods at a high (Camp Paivika; >35 kg N ha(-1) year(-1)) and a low deposition (Barton Flats; 5-9 kg N ha(-1) year(-1)) site in the San Bernardino Mountains in southern California. N deposition in throughfall under mature pine trees at Camp Paivika after 7 months of exposure was extremely high (87 and 92 kg ha-1 based on the two collector types) compared to Barton Flats (11 and 13 kg ha(-1)). A large proportion of the N deposited in throughfall at Camp Paivika occurred as fog drip, demonstrating the importance of fog deposition as an input source of N at this site. By comparison, bulk deposition rates in open areas were 5.1 and 5.4 kg ha(-1) at Camp Paivika based on the two collector types, and 1.9 and 3.0 kg ha(-1) at Barton Flats.

Fertilization intensifies drought stress: water use and stomatal conductance of Pinus taeda in a midrotation fertilization and throughfall reduction experiment

Treesearch

Eric J. Ward; Jean-Christophe Domec; Marshall A. Laviner; Thomas R. Fox; Ge Sun; Steve McNulty; John King; Asko Noormets

2015-01-01

While mid-rotation fertilization increases productivity in many southern pine forests, it remains unclear what impact such management may have on stand water use. We examined the impact of nutrient and water availability on stem volume, leaf area, transpiration per unit ground area (EC) and canopy conductance per unit leaf area (GS...

Rainfall Interception by Hardwood Forest Litter in the Southern Appalachians

Treesearch

J.D. Helvey

1964-01-01

The portion of rainfall over forest cover which does not reach mineral soil can be separated into the parts evaporated from the canopy and from the litter. Canopy interception loss is usually estimated by subtracting the sum of throughfall (water falling through tree crowns) and stemflow (water running down stems) from rainfall measured in forest openings (Hamilton...

Sampling procedures for throughfall monitoring: A simulation study

NASA Astrophysics Data System (ADS)

Zimmermann, Beate; Zimmermann, Alexander; Lark, Richard Murray; Elsenbeer, Helmut

2010-01-01

What is the most appropriate sampling scheme to estimate event-based average throughfall? A satisfactory answer to this seemingly simple question has yet to be found, a failure which we attribute to previous efforts' dependence on empirical studies. Here we try to answer this question by simulating stochastic throughfall fields based on parameters for statistical models of large monitoring data sets. We subsequently sampled these fields with different sampling designs and variable sample supports. We evaluated the performance of a particular sampling scheme with respect to the uncertainty of possible estimated means of throughfall volumes. Even for a relative error limit of 20%, an impractically large number of small, funnel-type collectors would be required to estimate mean throughfall, particularly for small events. While stratification of the target area is not superior to simple random sampling, cluster random sampling involves the risk of being less efficient. A larger sample support, e.g., the use of trough-type collectors, considerably reduces the necessary sample sizes and eliminates the sensitivity of the mean to outliers. Since the gain in time associated with the manual handling of troughs versus funnels depends on the local precipitation regime, the employment of automatically recording clusters of long troughs emerges as the most promising sampling scheme. Even so, a relative error of less than 5% appears out of reach for throughfall under heterogeneous canopies. We therefore suspect a considerable uncertainty of input parameters for interception models derived from measured throughfall, in particular, for those requiring data of small throughfall events.

Influence of canopy traits on spatio-temporal variability of throughfall in Mediterranean Downy oak and Scots pine stands

NASA Astrophysics Data System (ADS)

Llorens, Pilar; Garcia-Estringana, Pablo; Latron, Jérôme; Molina, Antonio J.; Gallart, Francesc

2014-05-01

The spatio-temporal variability of throughfall is the result of the interaction of biotic factors, related to the canopy traits, and abiotic factors, linked to the meteorological conditions. This variability may lead to significant differences in the volume of water and solutes that reach the ground in each location, and beyond in the hydrological and biogeochemical dynamics of forest soils. Two forest stands in Mediterranean climatic conditions were studied to analyse the role of biotic and abiotic factors in the temporal and spatial redistribution of throughfall. The monitored stands are a Downy oak forest (Quercus pubescens) and a Scots pine forest (Pinus sylvestris), both located in the Vallcebre research catchments (NE Spain, 42º 12'N, 1º 49'E). The study plots are representative of Mediterranean mountain areas with spontaneous afforestation by Scots pine as a consequence of the abandonment of agricultural terraces, formerly covered by Downy oaks. The monitoring design of each plot consisted of a set of 20 automatic rain recorders and 40 automatic soil moisture probes located below the canopy. 100 hemispheric photographs of the canopy were used to place the instruments at representative locations (in terms of canopy cover) within the plot. Bulk rainfall, stemflow and meteorological conditions above the forest cover were also automatically recorded. Canopy cover as well as biometric characteristics of the plots were also regularly measured. The results indicate a temporal persistence of throughfall in both stands, as observed elsewhere. However, for the oak plot the seasonal evolution of canopy traits added additional variability, with higher variability in summer and different locations of wet and dry spots depending on the season. Furthermore, this work investigates the influence of canopy structure on the spatial variability of throughfall by analysing a large set of forest parameters, from main canopy traits to detailed leaves and wood characteristics. The analysis includes the consideration of the interaction of main abiotic factors with canopy traits.

How appetizing is the dissolved organic matter (DOM) trees lose during rainfall?

NASA Astrophysics Data System (ADS)

Howard, D.; Van Stan, J. T., II; Whitetree, A.; Zhu, L.; Stubbins, A.

2017-12-01

Dissolved organic carbon (DOC) is the chemical backbone of dissolved organic matter (DOM), which is important because it drives many processes in soils and waterways. Current DOC work has paid little attention to interactions between rain and plant canopies, where rainfall is partitioned into throughfall and stemflow. Even less DOC research has investigated the effect of arboreal epiphytes on throughfall and stemflow DOC. The purpose of this study is twofold: (1) assess the degree and timing of DOC consumption by microbial communities (biolability) in throughfall and stemflow, and (2) determine whether the presence of arboreal epiphytes in the canopy affect DOC biolability. Biolability of stemflow and throughfall DOC from Juniperus virginiana (cedar) was determined by incubating samples for 14 days. Throughfall and stemflow DOC was highly biolabile with DOC concentrations decreasing by 30-60%. Throughfall DOC was more biolabile than stemflow DOC. DOC in both throughfall and stemflow from epiphyte-covered cedars was less biolabile than DOC from trees without epiphytes. The high biolability of tree-derived DOC indicates that its supply provides carbon substrates to the microbial community at the forest floor, in soils and the rhizosphere. Epiphytes appear to be important in determining the biolability of DOC and therefore the size of this carbon subsidy to the soil ecosystem.

The role of stable isotopes in understanding rainfall interception processes: a review

EPA Science Inventory

The isotopic composition of water transmitted by the canopy as throughfall or stemflow reflects important hydrologic processes occurring in the canopy. A synthesis of the literature shows that complex spatiotemporal variations of isotopic composition are created by canopy interce...

Fine-Scale Spatial Variability of Precipitation, Soil, and Plant Water Isotopes

NASA Astrophysics Data System (ADS)

Goldsmith, G. R.; Braun, S.; Romero, C.; Engbersen, N.; Gessler, A.; Siegwolf, R. T.; Schmid, L.

2015-12-01

Introduction: The measurement of stable isotope ratios of water has become fundamental in advancing our understanding of environmental patterns and processes, particularly with respect to understanding the movement of water within the soil-plant-atmosphere continuum. While considerable research has explored the temporal variation in stable isotope ratios of water in the environment, our understanding of the spatial variability of these isotopes remains poorly understood. Methods: We collected spatially explicit samples of throughfall and soil water (n=150 locations) from a 1 ha plot delineated in a mixed deciduous forest in the northern Alps of Switzerland. We complemented this with fully sunlit branch and leaf samples (n = 60 individuals) collected from Picea abies and Fagus sylvatica between 14:00 and 16:00 on the same day by means of a helicopter. Soil and plant waters were extracted using cryogenic vacuum distillation and all samples were analyzed for δ18O using an isotope ratio mass spectrometer. Results: The mean δ18O of throughfall (-3.3 ± 0.8‰) indicated some evaporative enrichment associated with passage through the canopy, but this did not significantly differ from the precipitation collected in nearby open sites (-4.05‰). However, soil was depleted (-7.0 ± 1.8‰) compared to throughfall and there was no significant relationship between the two, suggesting that the sampling for precipitation inputs did not capture all the sources (e.g. stream water, which was -11.5‰) contributing to soil water δ18O ratios. Evaporative enrichment of δ18O was higher in leaves of Fagus (14.8 ± 1.8‰) than in leaves of Picea (11.8 ± 1.7‰). Sampling within crowns of each species (n = 5 branches each from 5 individuals) indicated that variability in a single individual is similar to that among individuals. Discussion: Stable isotopes of water are frequently engaged for studies of ecohydrology, plant ecophysiology, and paleoclimatology. Our results help constrain the variability within different water sources across space (e.g. when vizualized as isoscapes), as well as the extent of fractionation among those sources as water moves through the critical zone. In doing so, we also provide insight into how environment shapes this fine-scale variation in order to inform future applications of water isotopes.

The release of water from forest snowpacks during winter

Treesearch

Harold F. Haupt

1972-01-01

In the northern Rocky Mountains, in Idaho, data collected during three winters demonstrate why there is always less snow beneath the canopy of a cedar-hemlock forest than in the adjacent small openings. The author presents as evidence the differential release of water, which originates in the canopy as throughfall-drip, thus accounting for part of the deficiency in...

Considerations for throughfall chemistry sample-size determination

Treesearch

Pamela J. Edwards; Paul Mohai; Howard G. Halverson; David R. DeWalle

1989-01-01

Both the number of trees sampled per species and the number of sampling points under each tree are important throughfall sampling considerations. Chemical loadings obtained from an urban throughfall study were used to evaluate the relative importance of both of these sampling factors in tests for determining species' differences. Power curves for detecting...

[Characteristics of rainfall interception by Caragana korshinskii and Hippophae rhamnoides in Loess Plateau of Northwest China].

PubMed

Jian, Sheng-Qi; Zhao, Chuan-Yan; Fang, Shu-Min; Yu, Kai; Wang, Yang; Liu, Yi-Yue; Zheng, Xiang-Lin; Peng, Shou-Zhang

2012-09-01

From May to October 2011, an investigation was conducted on the effects of rainfall and its intensity on the canopy interception, throughfall, and stemflow of Caragana korshinskii and Hippophae rhamnoides, the main shrub species commonly planted to stabilize soil and water in the Anjiagou catchment of Loess Plateau. A total of 47 rainfall events were observed, most of which were featured with low intensity, and the total amount and average intensity of the rainfalls were 208.9 mm and 2.82 mm x h(-1), respectively. As a whole, the rainfall events of 2-10 mm and 0.1-2 mm x h(-1) had the highest frequency. The canopy interception, throughfall, and stemflow of C. korshinski were 58.5 mm (28%), 124.7 mm (59.7%), and 25.7 mm (12.3%), while those of H. rhamnoides were 17.6 mm (8.4%), 153. 1 mm (73.3%), and 38.2 mm (18.3%), respectively. Regression analysis showed that the canopy interception, throughfall, and stemflow of the two shrub species all had significant positive correlations with the rainfall amount, and had exponent or power correlations with the rainfall amount and the maximum rainfall intensity in 10 minutes.

A Review and Evaluation of Forest Canopy Epiphyte Roles in the Partitioning and Chemical Alteration of Precipitation

NASA Astrophysics Data System (ADS)

Van Stan, J. T., II; Pypker, T. G.

2015-12-01

Interactions between precipitation and forest canopy elements (bark, leaves, and epiphytes) control the quantity, spatiotemporal patterning, and the chemical concentration, character and constituency of precipitation to soils. Canopy epiphytes are an element that exerts a range of storm-related hydrological and biogeochemical effects due to their diversity of morphological traits and nutrient acquisition mechanisms. We reviewed and evaluated the state of knowledge regarding epiphyte interactions with precipitation partitioning (into interception loss, throughfall, and stemflow) and the chemical alteration of net precipitation fluxes (throughfall and stemflow). As epiphyte species are quite diverse, this review categorized findings by common paraphyletic groups: lichens, bryophytes, and vascular epiphytes. Of these groups, vascular epiphytes have received the least attention and lichens the most. In general, epiphytes decrease throughfall and stemflow and increase interception loss. Epiphytes alter the spatiotemporal pattern of throughfall and increase the overall latent heat fluxes from the canopy. Epiphytes alter biogeochemical processes by impacting the transfer of solutes through the canopy; however, the change in solute concentration varies with epiphyte type and chemical species. We discuss several important knowledge gaps across all epiphyte groups. We also explore innovative methods that currently exist to confront these knowledge gaps and past techniques applied to gain our current understanding. Future research addressing the listed deficiencies will improve our knowledge of epiphyte roles in water and biogeochemical processes coupled within forest canopies—processes crucial to supporting microbe, plant, vertebrate and invertebrate communities within individual epiphytes/epiphyte assemblages, host trees, and even the forest ecosystem as a whole.

Shifts in controls on the temporal coherence of throughfall chemical flux in Acadia National Park, Maine, USA

USGS Publications Warehouse

Nelson, Sarah J.; Webster, Katherine E.; Loftin, Cynthia S.; Weathers, Kathleen C.

2013-01-01

Major ion and mercury (Hg) inputs to terrestrial ecosystems include both wet and dry deposition (total deposition). Estimating total deposition to sensitive receptor sites is hampered by limited information regarding its spatial heterogeneity and seasonality. We used measurements of throughfall flux, which includes atmospheric inputs to forests and the net effects of canopy leaching or uptake, for ten major ions and Hg collected during 35 time periods in 1999–2005 at over 70 sites within Acadia National Park, Maine to (1) quantify coherence in temporal dynamics of seasonal throughfall deposition and (2) examine controls on these patterns at multiple scales. We quantified temporal coherence as the correlation between all possible site pairs for each solute on a seasonal basis. In the summer growing season and autumn, coherence among pairs of sites with similar vegetation was stronger than for site-pairs that differed in vegetation suggesting that interaction with the canopy and leaching of solutes differed in coniferous, deciduous, mixed, and shrub or open canopy sites. The spatial pattern in throughfall hydrologic inputs across Acadia National Park was more variable during the winter snow season, suggesting that snow re-distribution affects net hydrologic input, which consequently affects chemical flux. Sea-salt corrected calcium concentrations identified a shift in air mass sources from maritime in winter to the continental industrial corridor in summer. Our results suggest that the spatial pattern of throughfall hydrologic flux, dominant seasonal air mass source, and relationship with vegetation in winter differ from the spatial pattern of throughfall flux in these solutes in summer and autumn. The coherence approach applied here made clear the strong influence of spatial heterogeneity in throughfall hydrologic inputs and a maritime air mass source on winter patterns of throughfall flux. By contrast, vegetation type was the most important influence on throughfall chemical flux in summer and autumn.

The role of stable isotopes in understanding rainfall ...

EPA Pesticide Factsheets

The isotopic composition of water transmitted by the canopy as throughfall or stemflow reflects important hydrologic processes occurring in the canopy. A synthesis of the literature shows that complex spatiotemporal variations of isotopic composition are created by canopy interception. As a whole, the studies suggest a set of controlling factors including fractionation, exchange among liquid and vapor phase water, and spatiotemporal redistribution along varying canopy flowpaths. However, our limited understanding of physical processes and water routing in the canopy limits the ability to discern all details for predicting interception isotope effects. We suggest that the isotopic composition of throughfall and stemflow may be the key to improve our understanding of water storage and transport in the canopy, similar to how isotopic analysis contributed to progress in our understanding of watershed runoff processes. While interception isotope effects have largely been studied under the premise that they are a source of error, previous works also indicate a wide range of possible interactions that intercepted water may have with the canopy and airspace. We identify new research questions that may be answered by stable isotopes as a path forward in examining and generalizing small-scale interception processes that could facilitate integration of interception into watershed ecohydrological concepts. Evaporation from forest canopies (interception loss) is a prominent

The water balance components of Mediterranean pine trees on a steep mountain slope during two hydrologically contrasting years

NASA Astrophysics Data System (ADS)

Eliades, Marinos; Bruggeman, Adriana; Lubczynski, Maciek W.; Christou, Andreas; Camera, Corrado; Djuma, Hakan

2018-07-01

Pines in semi-arid mountain environments manage to survive and thrive despite the limited soil water, due to shallow soil depths, and overall water scarcity. This study aims to develop a method for computing soil evaporation, bedrock water uptake and transpiration from a natural, open forest, based on sap flow (Heat Ratio Method), soil moisture and meteorological observations. The water balance of individual trees was conceptualized with a geometric approach, using canopy projected areas and Voronoi (Thiesen) polygons. The canopy approach assumes that the tree's root area extent is equal to its canopy projected area, while the Voronoi approach assumes that the tree roots exploit the open area that is closer to the tree than to any other tree. The methodology was applied in an open Pinus brutia forest (68% canopy cover) in Cyprus, characterized by steep slopes and fractured bedrock, during two hydrologically contrasting years (2015 wet, 2016 dry). Sap flow sensors, soil moisture sensors, throughfall and stemflow gauges were installed on and around eight trees. Rainfall was 507 mm in 2015 and 359 mm in 2016. According to the canopy approach, the sum of tree transpiration and soil evaporation exceeded the throughfall in both years, which implies that the trees' bedrock water uptake exceeds the surface runoff and drainage losses. This indicated that trees extend their roots beyond the canopy-projected areas and the use of the Voronoi polygons captures this effect. According to the stand scale water balance, average throughfall during the two years was 81% of the rainfall. Transpiration was 61% of the rainfall in 2015, but only 32% in 2016. On the contrary, the soil evaporation fraction increased from 26% in 2015 to 35% in the dry year of 2016. The contribution of bedrock water to tree transpiration was 77% of rainfall in 2015 and 66% in 2016. During the summer months, trees relied 100% on the uptake of water from the fractured bedrock to cover their transpiration needs. Average monthly transpiration areas ranged between 0.1 mm d-1 in October 2016 and 1.7 mm d-1 in April 2015. This study shows that bedrock uptake could be an essential water balance component of semi-arid, mountainous pine forests and should be accounted for in hydrologic models.

Variation characteristics of nitrogen concentrations through forest hydrologic subcycles in various forests across mainland China.

PubMed

Sun, Suqi; Wang, Yunqi; Wang, Yujie; Zhang, Huilan; Yu, Lei; Liu, Yong; Zhu, Jinqi

2015-01-01

Increased anthropogenic nitrogen emissions and more severe environmental issues (e.g. air pollution, soil acidification, and plant nutrient imbalances) are striking forest ecosystems. Data on NH4+ and NO3- concentrations in throughfall and stemflow were collected to estimate variation characteristics of nitrogen concentrations through forest hydrological processes across China. A typical study was carried out in the three forest types in the Jinyun Mountain region of Chongqing, from May to October 2012. Nitrogen concentrations in throughfall and stemflow are higher than those in atmospheric precipitation. DIN concentrations in atmospheric precipitation, throughfall, and stemflow, across China and in the Jinyun Mountain region, were 2.18 and 1.51, 3.19 and 3.88, and 5.14 and 3.92 mg N L(-1), respectively. NH4+ concentration was higher than NO3- concentration, suggesting NH4+ is the dominant nitrogen component in China. Additionally, across China, a linear relationship existed between DIN and NH4+, and between DIN and NO3- in atmospheric precipitation. DIN concentrations in throughfall and stemflow changed with the observed changes in precipitation, and DIN concentrations in precipitation positively correlated with those in throughfall and in stemflow were also observed. Moreover, average DIN concentrations in throughfall and stemflow varied in different forest types, resulting from differences in forest canopy structures and tree species characteristics. In the Jinyun Mountain region, both throughfall and stemflow DIN concentrations were the highest in the mixed broadleaved/coniferous forest, followed by evergreen broadleaved forest, and the lowest in moso bamboo forest. Monthly variations of NH4+ and NO3- concentrations, in throughfall and stemflow, were observed in the Jinyun Mountain region.

The Effects of Urbanization on Atmospheric Nitrogen Deposition and Nitrate Removal Capacity of Urban Wetlands

NASA Astrophysics Data System (ADS)

Stander, E. K.; Ehrenfeld, J. G.

2006-12-01

Wetlands are increasingly being used as management tools to combat the widespread problem of excess nitrogen in surface waters of the United States. This is particularly true in urban or urbanizing watersheds. However, due to hypothesized higher rates of atmospheric nitrogen deposition and altered hydrology in the urban context, urban wetlands may actually be acting as sources of nitrate to receiving bodies of water. Fourteen palustrine, forested wetlands in northeastern New Jersey, the most urban part of the state, were sampled for hydrology and rates of nitrogen cycling processes. One autowell in each site recorded water table measurements four times daily. In situ rates of net nitrogen mineralization and nitrification were measured monthly during the same time period using the static core technique. Denitrification rates were measured monthly in laboratory incubations using the acetylene block technique. Additionally, in nine of the 14 sites, which represent a gradient of urban intensity from very urban to less urban, we measured inorganic nitrogen in throughfall and leachate on a weekly basis. Throughfall collectors and lysimeters to 50cm depth were installed in three locations in each of the nine sites. Throughfall and leachate samples were analyzed for 15N and 18O isotopes to distinguish between atmospheric versus nitrification sources of nitrate in soil leachate. Hydrographs demonstrated that many sites have water table depths below 30 cm (i.e., below the biologically active zone) for long periods of time. Many wetlands display uncharacteristically flashy hydrographs. Wetlands with dry or flashy hydrographs had higher rates of nitrification and lower rates of denitrification than wetlands with more normal hydrology. Rates of atmospheric N deposition were higher in wetlands located in municipalities with higher population densities. Population density, however, was not a good predictor of nitrification or denitrification rates. Results from the isotopic analysis are forthcoming.

Hydrological Components of a Young Loblolly Pine Plantation on a Sandy Soil with Estimates of Water Use and Loss

Treesearch

Deborah A. Abrahamson; Phillip M. Dougherty; Stanley J. Zarnoch

1998-01-01

Fertilizer and irrigation treatments were applied in a 7- to l0-year-old loblolly pine (Pinus taeda L.) plantation on a sandy soil near Laurinburg, North Carolina. Rainfall, throughfall, stemflow, and soil water content were measured throughout the study period. Monthly interception losses ranged from 4 to 15% of rainfall. Stemflow ranged from 0.2...

Comparative water fluxes through leaf litter of tropical plantation trees and the invasive grass Saccharum spontaneum in the Republic of Panama

NASA Astrophysics Data System (ADS)

Park, Andrew; Friesen, Patrick; Serrud, Aneth Aracelly Sarmiento

2010-03-01

SummaryThe hydrological properties of leaf litter layers remain relatively unexplored, especially in tropical vegetation communities. In this paper we explore the hydrological dynamics of litter samples from reforestation plots of tropical hardwoods and the invasive sugar cane Saccharum spontaneum, which these trees were planted to replace. Water holding capacity (WHC) and drying rates were compared under controlled conditions, and throughfall interception, drainage and calculated evaporation were measured in two field experiments (A and B) conducted with different sets of samples. The WHC of samples varied from 3.4 to 6.5 mm in experiment A, and from 1.6 to 7.1 mm in experiment B. Drainage through the litter samples averaged 78.3 ± 34.4% and 61.2 ± 34.70% TF in experiments A and B, respectively. Daily water storage was 70.8 ± 14.25% of total WHC in experiment A and 78.6 ± 25.35% of total WHC in experiment B. Estimated evaporation averaged 34.8 ± 12.52% of WHC in experiment A and 34.3 ± 14.91% of WHC in experiment B. Although significant interspecific differences in WHC, interception of TF and evaporation were recorded, species rankings tended to be different in experiments A and B. The exception was litter from the leguminous tree Gliricidia sepium, which maintained the lowest WHC and water storage in the field in both experiments, but which evaporated water more rapidly than other species. The depth of throughfall draining through litter samples in the field was similar among all species in both experiments. Comparisons of regression slopes also showed that drainage depth increased with increasing throughfall at similar rates among species. On the other hand, both slopes and slope elevations differed among species when drainage was expressed in l kg -1. Patterns of water storage and drainage in our samples were in broad agreement with those of other studies, although WHC and litter necromass in our young tree plantations fell into the lower end of the range reported for mature Amazonian forest.

Oceans Apart: Using Stable Isotopes to Assess the Role of Fog in Two Semi-Arid Island Ecosystems

NASA Astrophysics Data System (ADS)

Schmitt, S.; Riveros-Iregui, D.; Hu, J.

2017-12-01

Fog is a significant hydrologic input in many tropical island systems, and is a water source particularly susceptible to the effects of global climate change. To better understand the role of fog as a hydrological input in two oceanic islands, we address two principal questions: 1) Do seasonal or extreme precipitation events lead to distinguishable differences in stable isotopic signatures of water inputs within and between sites and islands? 2) Does microclimatic zonation lead to distinguishable differences in isotopic signatures of meteoric inputs between different sites on a given island? To perform this analysis, meteoric water samples (fog, rain and throughfall) were collected over three sites (one windward and two leeward) and three field seasons in San Cristobal, Galapagos to ascertain the isotopic signature of each water balance input during different times of year. An additional field season of data in Ascension Island, UK, was also used to perform a comparative analysis between islands. A stable isotope mixing model was used to determine the relative proportion of surface water and groundwater that is composed of fog, and to demonstrate spatiotemporal patterns of recharge dynamics in each island system. Local meteoric water lines were generated for each site and over each field season to determine the source of hydrologic inputs (trade wind-generated orographic precipitation versus storm precipitation) and the role of locally recycled water in the overall water balance of each site. Our results will approximate potential changes in water inputs to San Cristobal and Ascension, respectively, that could be impacted by an increase in cloud base height or a change in weather patterns brought about by climate change.

Chemistry of throughfall under douglas fir and Rocky Mountain juniper. [Pseudotsuga menziesii var. glauca; Juniperus scopulorum

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hart, G.E.; Parent, D.R.

1974-01-01

Concentrations of sodium, calcium, magnesium, potassium, phosphorus and nitrate were measured in throughfall under isolated douglas fir (Pseudotsuga menziesii var. glauca) and Rocky Mountain juniper (Juniperus scopulorum) trees in northern Utah for 39 storms in 1970 and 1971. Concentrations were 3-16 times greater under the trees than in the open. Throughfall under douglas fir invariably had higher concentrations than that under juniper. Since most of the chemical input occurs as dry fallout between storms, surface area and form of the canopy are believed to be the prime factors influencing throughfall chemistry in this region. 15 references, 2 figures, 5 tables.

Drier climate and productivity of operational poplar plantation - four years of throughfall exclusion experiment

NASA Astrophysics Data System (ADS)

Orsag, M.; Fischer, M.; Trnka, M.

2016-12-01

The production of woody biomass in short rotation woody coppice (SRWC) is considered as a suitable source of renewable energy for climate conditions prevailing in central European countries. The productivity of SRWC is largely dependent on the environmental conditions and the biomass yield can be severely compromised when water supply is limited. One of the climate change consequences predicted for Central Europe is the increasing frequency and duration of drought spells as a result of increased air temperature and temporally uneven distribution of precipitation. Therefore, a small-scale rain-throughfall exclusion experiment was established in 2011 in an operational SRWC plantation (hybrid poplar NM6) in the Bohemian-Moravian highlands (Czech Republic). Three times replicated experimental block comprised a treatment with 70 % rain-throughfall exclusion (R) and an adjacent control treatment (C) of the same size (25 m2). Above-ground biomass productivity (ABP) and soil moisture patterns were measured and evaluated during growing seasons 2011-2015. We observed high heterogeneity of soil moisture among blocks, resulting in high variability in ABP. The treatment effect was more pronounced with increasing seasonal precipitation. Generally, the R treatments showed lower ABP by 8.4 %, higher mortality by 6.7 % and strong competitive relationships among neighboring trees, which led to formation of few dominant trees, comprising 30 % of the total biomass at particular plot, accounting for 50 % of the annual ABP per 25 m2 plot. Our results suggests considerable resilience of hybrid poplar NM6 to decreased soil-water availability over long-term, while keeping minimal annual ABP of about 4.5 ton hectare (dry matter).

Atmospheric deposition of nitrogen and sulfur and preferential canopy consumption of nitrate in forests of the Pacific Northwest, USA

Treesearch

Mark E. Fenn; Christopher S. Ross; Susan L. Schilling; William D. Baccus; Michael A. Larrabee; Rebecca A. Lofgren

2013-01-01

Wet,dry and throughfall deposition of N and S were measured for 2 years in three national parks in Washington State:Olympic,Mount Rainier,and North Cascades.Throughfall was measured using ion exchange resin (IER) collectors. A major objective of the study was to evaluate the effectiveness of IER throughfall measurements for monitoring deposition inputs,including...

Disturbance and long-term patterns of rainfall and throughfall nutrient fluxes in a subtropical wet forest in Puerto Rico

Treesearch

Tamara Heartsill Scalley; F.N. Scatena; C. Estrada Ruiz; W.H. McDowell; Ariel Lugo

2007-01-01

Nutrient fluxes in rainfall and throughfall were measured weekly in a mature subtropical wet forest in NE Puerto Rico over a 15-year period that included the effects of 10 named tropical storms, several prolonged dry periods, and volcanic activity in the region. Mean annual rainfall and throughfall were 3482 and 2131 mm yr

Quantifying dominance of intra-storm phase of interception process by small isolated canopies

NASA Astrophysics Data System (ADS)

Yerk, Walter; Montalto, Franco

2014-05-01

Precipitation interception by vegetation canopies has long been recognized as a major component of the hydrologic cycle; however, historically most research has been dedicated to closed or sparse canopy forests. The goal of our research was to quantify rainfall partitioning by small isolated canopies in an urban setting. The field experiment involved small forms of four shrub species (Prunus laurocerasus, Cornus sericea, Itea virginica and Hydrangea quercifolia) with crown heights 40 - 80 cm and diameters 35 - 60 cm. Each plant had ten rain gauges to measure throughfall with a sampling frequency of 5 seconds. An on-site automated weather station provided meteorological data. Leaf area index (LAI) was measured by manual counting. We estimated the canopy storage capacities of all four species to be less than 0.5 mm. The obtained data showed statistically significant differences in interception properties among all four species, except between Cornus and Itea. Cumulative interception loss for the period of August-December 2013 was 10% for Cornus, 16% for Itea, 29% for Hydrangea, and 49% for Prunus. The observations revealed a weak relationship between interception abilities and LAI for all four species. Throughfall and precipitation intensities (mm/hr) expressed very strong linear relationship (adjusted coefficients of determination were from 0.80 to 0.95) for the entire range of observed rainfall intensities. For Cornus the ratio of throughfall to precipitation intensity was close to 0.93:1, for Itea it was 0.82:1. The ratios were lesser for Hydrangea (0.65:1), and especially for Prunus (0.48:1). Therefore we show that reduced by the canopy, throughfall intensity results in the bulk of precipitation depth intercepted during the rain events. In contrast, the amount of water stored on the canopy and evaporated between and after rain events contributes minimally to interception. Simulations of potential evaporation based on the Penman-Monteith method showed a large underestimation of evaporation from the wet canopies during the rain events. Approaches other than energy balance models of potential evaporation from a still water surface are being discussed in order to explain large evaporation from within a wet isolated canopy.

Variability, drivers, and effects of atmospheric nitrogen inputs across an urban area: Emerging patterns among human activities, the atmosphere, and soils.

PubMed

Decina, Stephen M; Templer, Pamela H; Hutyra, Lucy R; Gately, Conor K; Rao, Preeti

2017-12-31

Atmospheric deposition of nitrogen (N) is a major input of N to the biosphere and is elevated beyond preindustrial levels throughout many ecosystems. Deposition monitoring networks in the United States generally avoid urban areas in order to capture regional patterns of N deposition, and studies measuring N deposition in cities usually include only one or two urban sites in an urban-rural comparison or as an anchor along an urban-to-rural gradient. Describing patterns and drivers of atmospheric N inputs is crucial for understanding the effects of N deposition; however, little is known about the variability and drivers of atmospheric N inputs or their effects on soil biogeochemistry within urban ecosystems. We measured rates of canopy throughfall N as a measure of atmospheric N inputs, as well as soil net N mineralization and nitrification, soil solution N, and soil respiration at 15 sites across the greater Boston, Massachusetts area. Rates of throughfall N are 8.70±0.68kgNha -1 yr -1 , vary 3.5-fold across sites, and are positively correlated with rates of local vehicle N emissions. Ammonium (NH 4 + ) composes 69.9±2.2% of inorganic throughfall N inputs and is highest in late spring, suggesting a contribution from local fertilizer inputs. Soil solution NO 3 - is positively correlated with throughfall NO 3 - inputs. In contrast, soil solution NH 4 + , net N mineralization, nitrification, and soil respiration are not correlated with rates of throughfall N inputs. Rather, these processes are correlated with soil properties such as soil organic matter. Our results demonstrate high variability in rates of urban throughfall N inputs, correlation of throughfall N inputs with local vehicle N emissions, and a decoupling of urban soil biogeochemistry and throughfall N inputs. Copyright © 2017 Elsevier B.V. All rights reserved.

Soil moisture depletion under simulated drought in the Amazon: impacts on deep root uptake.

PubMed

Markewitz, Daniel; Devine, Scott; Davidson, Eric A; Brando, Paulo; Nepstad, Daniel C

2010-08-01

*Deep root water uptake in tropical Amazonian forests has been a major discovery during the last 15 yr. However, the effects of extended droughts, which may increase with climate change, on deep soil moisture utilization remain uncertain. *The current study utilized a 1999-2005 record of volumetric water content (VWC) under a throughfall exclusion experiment to calibrate a one-dimensional model of the hydrologic system to estimate VWC, and to quantify the rate of root uptake through 11.5 m of soil. *Simulations with root uptake compensation had a relative root mean square error (RRMSE) of 11% at 0-40 cm and < 5% at 350-1150 cm. The simulated contribution of deep root uptake under the control was c. 20% of water demand from 250 to 550 cm and c. 10% from 550 to 1150 cm. Furthermore, in years 2 (2001) and 3 (2002) of throughfall exclusion, deep root uptake increased as soil moisture was available but then declined to near zero in deep layers in 2003 and 2004. *Deep root uptake was limited despite high VWC (i.e. > 0.30 cm(3) cm(-3)). This limitation may partly be attributable to high residual water contents (theta(r)) in these high-clay (70-90%) soils or due to high soil-to-root resistance. The ability of deep roots and soils to contribute increasing amounts of water with extended drought will be limited.

Modeling the effects of throughfall reduction on soil water content in a Brazilian Oxisol under a moist tropical forest

NASA Astrophysics Data System (ADS)

Belk, Elizabeth L.; Markewitz, Daniel; Rasmussen, Todd C.; Carvalho, Eduardo J. Maklouf; Nepstad, Daniel C.; Davidson, Eric A.

2007-08-01

Access to water reserves in deep soil during drought periods determines whether or not the tropical moist forests of Amazonia will be buffered from the deleterious effects of water deficits. Changing climatic conditions are predicted to increase periods of drought in Amazonian forests and may lead to increased tree mortality, changes in forest composition, or greater susceptibility to fire. A throughfall reduction experiment has been established in the Tapajós National Forest of east-central Amazonia (Brazil) to test the potential effects of severe water stress during prolonged droughts. Using time domain reflectometry observations of water contents from this experiment, we have developed a dynamic, one-dimensional, vertical flow model to enhance our understanding of hydrologic processes within these tall-stature forests on well-drained, upland, deep Oxisols and to simulate changes in the distribution of soil water. Simulations using 960 days of data accurately captured mild soil water depletion near the surface after the first treatment year and decreasing soil moisture at depth during the second treatment year. The model is sensitive to the water retention and unsaturated flow equation parameters, specifically the van Genuchten parameters θs, θr, and n, but less sensitive to Ks and α. The low root-mean-square error between observed and predicted volumetric soil water content suggests that this vertical flow model captures the most important hydrologic processes in the upper landscape position of this study site. The model indicates that present rates of evapotranspiration within the exclusion plot have been sustained at the expense of soil water storage.

Impacts of Alien Tree Invasion on Evapotranspiration in Tropical Montane Cloud Forest in Hawai'i

NASA Astrophysics Data System (ADS)

Giambelluca, T. W.; Asner, G. P.; Martin, R. E.; Nullet, M. M.; Huang, M.; Delay, J. K.; Mudd, R. G.; Takahashi, M.

2007-12-01

Hawaiian tropical montane cloud forests (TMCFs) are ecologically and hydrologically valuable zones. TMCFs in Hawai'i serve as refugia for the remaining intact native terrestrial plant and animal ecosystems, and are major sources of hydrologic input to surface water and groundwater systems. Invasion of alien tree species, with obvious effects on the ecological integrity of TMCFs, also threatens to impact the hydrological services these forests provide. Much speculation has been made about the hydrological effects of replacing native forest tree species with alien trees in Hawai'i, but until now no measurements have been made to test these assertions. We established two study sites, each equipped with eddy covariance and other micrometeorological instrumentation, one within native Metrosideros polymorpha forest and the other at a site heavily invaded by Psidium cattleianum, in the cloud forest zone of Hawai'i Volcanoes National Park. We are conducting measurements of stand-level evapotranspiration, transpiration (using sapflow techniques), energy balance, throughfall, stemflow, and soil moisture at each site. Preliminary analysis of these measurements shows that the fraction of available energy used for evapotranspiration (ET Fraction) at the native site is much higher for wet canopy conditions. The ET Fraction at the native site has an annual cycle corresponding to the annual cycle in leaf area. Deviations from the annual cycle are more closely related to variations in canopy wetness than to variations in soil moisture. Overall, ET as a function of available energy is 27% higher at the invaded site than the native site. The difference in ET between the two sites is especially pronounced during dry canopy periods, during which the ET Fraction is 53% higher at the invaded site than the native site. Sapflow measurements using heat balance collars show that leaf-area-specific transpiration is much greater in invasive P. cattleianum trees than in remnant native M. polymorpha trees at the invaded site. These results indicate that the P. cattleianum invasion is altering the hydrological cycle of the TMCF where it is found, with potential significant negative consequences for island water supply.

Broad-spectrum monitoring strategies for predicting occult precipitation contribution to water balance in a coastal watershed in California: Ground-truthing, areal monitoring and isotopic analysis of fog in the San Francisco Bay region

NASA Astrophysics Data System (ADS)

Koohafkan, M.; Thompson, S. E.; Leonardson, R.; Dufour, A.

2013-12-01

We showcase a fog monitoring study designed to quantitatively estimate the contribution of summer fog events to the water balance of a coastal watershed managed by the San Francisco Public Utilities Commission. Two decades of research now clearly show that fog and occult precipitation can be major contributors to the water balance of watersheds worldwide. Monitoring, understanding and predicting occult precipitation is therefore as hydrologically compelling as forecasting precipitation or evaporation, particularly in the face of climate variability. We combine ground-based monitoring and collection strategies with remote sensing technologies, time-lapse imagery, and isotope analysis to trace the ';signature' of fog in physical and ecological processes. Spatial coverage and duration of fog events in the watershed is monitored using time-lapse cameras and leaf wetness sensors strategically positioned to provide estimates of the fog bank extent and cloud base elevation, and this fine-scale data is used to estimate transpiration suppression by fog and is examined in the context of regional climate through the use of satellite imagery. Soil moisture sensors, throughfall collectors and advective fog collectors deployed throughout the watershed provide quantitative estimates of fog drip contribution to soil moisture and plants. Fog incidence records and streamflow monitoring provide daily estimates of fog contribution to streamflow. Isotope analysis of soil water, fog drip, stream water and vegetation samples are used to probe for evidence of direct root and leaf uptake of fog drip by plants. Using this diversity of fog monitoring methods, we develop an empirical framework for the inclusion of fog processes in water balance models.

Tree species' responses to throughfall removal experiments superimposed on a natural drought event in two contrasting humid temperate forests in New Hampshire, USA

NASA Astrophysics Data System (ADS)

Jennings, Katie; McIntire, Cameron; Coble, Adam; Vandeboncoeur, Matthew; Rustad, Lindsay; Templer, Pamela; Absbjornsen, Heidi

2017-04-01

Climate change is likely to affect Northeastern U.S. forests through the increased frequency and severity of drought events. However, our understanding of how these humid temperate forests will respond to moderate to extreme droughts is limited. Given the important role that these forests play in providing ecosystem services and in supplying forest products, enhancing our knowledge about the impacts of drought is critical to guiding forest management and climate change adaptation efforts. We conducted 50% throughfall removal experiments at two contrasting sites in the Northeastern US (Hubbard Brook Experimental Forest and Thompson Farm, NH, USA), which were superimposed on the severe natural drought occurring in August-September 2016. Preliminary analysis suggests that the two sites respond differently to simulated drought. Pinus strobus trees at Thompson Farm reduced their transpiration rates in response to both the natural and experimental drought, particularly evident during a 5-day period at the height of the drought were transpiration nearly ceased. Both P. strobus and Quercus rubra trees increased their water use efficiency in response to reduced soil water availability, with Q. rubra allowing its midday water potential to reach more negative values, consistent with its more drought tolerant strategy compared to P. strobus. In contrast, we did not detect any significant differences in tree transpiration rates or growth in the dominant tree species, Acer rubrum, in response to the experimental drought treatment at Hubbard Brook. However, both soil respiration and fine root biomass production were lower in the drought treatment plots relative to the control plots at Hubbard Brook. We plan to continue these throughfall removal experiments for at least two more years to better understand the implications of future drought in these humid temperate forests and identify differences in species' physiological adaptations and threshold responses.

Fogwater deposition modeling for terrestrial ecosystems: A review of developments and measurements

NASA Astrophysics Data System (ADS)

Katata, Genki

2014-07-01

Recent progress in modeling fogwater (and low cloud water) deposition over terrestrial ecosystems during fogwater droplet interception by vegetative surfaces is reviewed. Several types of models and parameterizations for fogwater deposition are discussed with comparing assumptions, input parameter requirements, and modeled processes. The relationships among deposition velocity of fogwater (Vd) in model results, wind speed, and plant species structures associated with literature values are gathered for model validation. Quantitative comparisons between model results and observations in forest environments revealed differences as large as 2 orders of magnitude, which are likely caused by uncertainties in measurement techniques over heterogeneous landscapes. Results from the literature review show that Vd values ranged from 2.1 to 8.0 cm s-1 for short vegetation, whereas Vd = 7.7-92 cm s-1 and 0-20 cm s-1 for forests measured by throughfall-based methods and the eddy covariance method, respectively. This review also discusses the current understanding of the impacts of fogwater deposition on atmosphere-land interactions and over complex terrain based on results from numerical studies. Lastly, future research priorities in innovative modeling and observational approaches for model validation are outlined.

Hydro-chemical cycle of forest ecosystem in the Norikura Highlands

NASA Astrophysics Data System (ADS)

Muramoto, Michiko; Nara, Maiko; Asari, Tomoko; Suzuki, Keisuke

Because of precipitation serves as a major vehicle of nutrient input into the forest ecosystem, the accurate measurement of its volume and ion concentration is of prime importance in an evaluation of any bio-geochemical cycle. Therefore, chemistry of the precipitation and throughfall of forest ecosystem was investigated in the Norikura Highlands. The investigation period was from January, 2003 to October, 2006. The throughfall volume in growing season and dormant season were 86 % and 93 % of the precipitation volume. Throughfall pH increased with increasing K+ concentration showed that H+ was held within the canopy by cation exchange reaction. And the concentration level of K+, Mg2+ and Ca2+ in the throughfall was much higher than that in the precipitation. It was the cause of canopy leaching. In growing season, proportions of canopy leaching of K+, Mg2+ and Ca2+ were 95 %, 70 % and 43 % of the throughfall deposition respectively. At Coniferous site, the flux of dry deposition was higher in dormant season than growing season. It is suggested that aerosol of the atmosphere and leaf area might be influenced.

Mercury fluxes in a natural forested Amazonian catchment (Serra do Navio, Amapá State, Brazil).

PubMed

Fostier, A H; Forti, M C; Guimarães, J R; Melfi, A J; Boulet, R; Espirito Santo, C M; Krug, F J

2000-10-09

Mercury (Hg total) fluxes were calculated for rainwater, throughfall and stream water in a small catchment located in the northeastern region of the Brazilian Amazon (Serra do Navio, Amapá State), whose upper part is covered by a natural rainforest and lower part was altered due to deforestation and activities related to manganese mining. The catchment area is 200 km from the nearest gold mining (garimpo). Minimum and maximum Hg concentrations were measured monthly from October 1996 to September 1997 and were 3.5-23.4 ng l(-1) for rainwater, 16.5-82.7 ng l(-1) for throughfall (March-August 1997) and 1.2-6.1 and 4.2-18.8 ng l(-1) for stream water, in natural and disturbed areas, respectively. In the natural area, the inputs were 18.2 microg m 2 year(-1) in rainwater and 72 microg m(-2) year(-1) in throughfall. This enrichment was attributed to dry deposition. The stream output of 2.9 microg m(-2) year(-1) indicates that Hg is being recycled within the forest as other chemical species or is being retained by the soil system, as confirmed by the cumulative Hg burden in the 0-10 cm surface layer, which was 36480 microg m(-2). When the disturbed area of the catchment was included, the stream output was 9.3 microg m(-2), clearly indicating the impact of the deforestation of the lower part of the basin on the release of mercury. The Hg burden in the disturbed area was 7560 microg m(-2) for the 0-10 cm surface layer.

Decreased summer drought affects plant productivity and soil carbon dynamics in Mediterranean woodland

NASA Astrophysics Data System (ADS)

Cotrufo, M. F.; Alberti, G.; Inglima, I.; Marjanović, H.; Lecain, D.; Zaldei, A.; Peressotti, A.; Miglietta, F.

2011-06-01

Precipitation patterns are expected to change in the Mediterranean region within the next decades, with projected decreases in total rainfall and increases in extreme events. We manipulated precipitation patterns in a Mediterranean woodland, dominated by Arbutus unedo L., to study the effects of changing precipitation regimes on above-ground net primary production (ANPP) and soil C dynamics, specifically plant-derived C input to soil and soil respiration (SR). Experimental plots were exposed to either a 20 % reduction of throughfall or to water addition targeted at maintaining soil water content above a minimum of 10 % v/v. Treatments were compared to control plots which received ambient precipitation. The throughfall manipulation experiment started in 2004 and we report data up to the 2009 growing season. Enhanced soil moisture during summer months highly stimulated annual stem primary production, litter fall, SR and net annual plant-derived C input to soil which on average increased by 130 %, 26 %, 50 % and 220 %, respectively, as compared to control. In contrast, the 20 % reduction in throughfall (equivalent to 10 % reduction of precipitation) did not significantly change soil moisture at the site, and therefore did not significantly affect ANPP or SR. We conclude that minor changes (around 10 % reduction) in precipitation amount are not likely to significantly affect ANPP or soil C dynamics in Mediterranean woodland. However, if summer rain increases, C cycling will significantly accelerate but soil C stocks are not likely to be changed in the short-term. More studies involving modelling of long term C dynamics are needed to predict if the estimated increases in soil C input under wet conditions is going to be sustained and if labile C is being substituted to stable C, with a negative effect on long term soil C stocks.

Hydrologic and geochemical factors affecting the chemistry of small headwater streams in response to acidic deposition on Catoctin Mountain, north-central Maryland

USGS Publications Warehouse

Rice, Karen C.; Bricker, Owen P.

1996-01-01

Hydrologic and water-quality data were collected at a precipitation-collection station and from two small watersheds on Catoctin Mountain, north- central Maryland, as part of an investigation of episodic acidification and its effects on streamwater quality. Data were collected from June 1990 through December 1993. Descriptions of the water shed instrumentation, data-collection techniques, and laboratory methods used to conduct the studies are included. Data that were collected on precipitation, throughfall, soil water, ground water, and streamwater during base flow and stormflow indicate that the streams undergo episodic acidification during storms. Both streams showed decreases in pH to less than 5.0 standard units during stormflow. The acid-neutralizing capacity (ANC) of both streams decreased during stormflow, and the ANC of one of the streams, Bear Branch, became negative. The chemistries of the different types of waters that were sampled indicate that shallow subsurface water with minimal residence time in the watersheds is routed to the streams to become stormflow and is the cause of the episodic acidification observed. Three-component hydrograph separations were performed on the data collected during several storms in each watershed. The hydrograph separations of all of the storms indicate that throughfall contributed 0 to 50 percent of the stormflow, soil water contributed 0 to 80 percent, and ground water contributed 20 to 90 percent. The results of the hydrograph separations indicate that, in general, the watershed with higher hydraulic gradients tends to have shallower and shorter flow paths than the watershed with lower hydraulic gradients.

Effect of summer throughfall exclusion, summer drought, and winter snow cover on methane fluxes in a temperate forest soil

USGS Publications Warehouse

Borken, W.; Davidson, E.A.; Savage, K.; Sundquist, E.T.; Steudler, P.

2006-01-01

Soil moisture strongly controls the uptake of atmospheric methane by limiting the diffusion of methane into the soil, resulting in a negative correlation between soil moisture and methane uptake rates under most non-drought conditions. However, little is known about the effect of water stress on methane uptake in temperate forests during severe droughts. We simulated extreme summer droughts by exclusion of 168 mm (2001) and 344 mm (2002) throughfall using three translucent roofs in a mixed deciduous forest at the Harvard Forest, Massachusetts, USA. The treatment significantly increased CH4 uptake during the first weeks of throughfall exclusion in 2001 and during most of the 2002 treatment period. Low summertime CH4 uptake rates were found only briefly in both control and exclusion plots during a natural late summer drought, when water contents below 0.15 g cm-3 may have caused water stress of methanotrophs in the A horizon. Because these soils are well drained, the exclusion treatment had little effect on A horizon water content between wetting events, and the effect of water stress was smaller and more brief than was the overall treatment effect on methane diffusion. Methane consumption rates were highest in the A horizon and showed a parabolic relationship between gravimetric water content and CH4 consumption, with maximum rate at 0.23 g H2O g-1 soil. On average, about 74% of atmospheric CH4 was consumed in the top 4-5 cm of the mineral soil. By contrast, little or no CH4 consumption occurred in the O horizon. Snow cover significantly reduced the uptake rate from December to March. Removal of snow enhanced CH4 uptake by about 700-1000%, resulting in uptake rates similar to those measured during the growing season. Soil temperatures had little effect on CH4 uptake as long as the mineral soil was not frozen, indicating strong substrate limitation of methanotrophs throughout the year. Our results suggest that the extension of snow periods may affect the annual rate of CH4 oxidation and that summer droughts may increase the soil CH4 sink of temperate forest soils. ?? 2005 Elsevier Ltd. All rights reserved.

Throughfall and fog deposition of nitrogen and sulfur at an N-limited and N-saturated site in the San Bernardino Mountains, southern California

Treesearch

Mark E. Fenn; Mark A. Poth; Susan L. Schilling; David B. Grainger

2000-01-01

Inorganic nitrogen (N) and sulfur (S) deposition in bulk throughfall and fog were determined at two sites located at opposite ends (42 km apart) of a pollution gradient in the San Bernardino Mountains. Plot-level averages for total annual N and S deposition in throughfall in 1996 were 18.8 and 2.9 kg·ha–1, respectively, at Camp Paivika (CP) and 2...

Apportionment of rainfall in central Himalayan forests (India)

NASA Astrophysics Data System (ADS)

Pathak, P. C.; Pandey, A. N.; Singh, J. S.

1985-02-01

The apportionment of rainfall into throughfall, stemflow and interception in certain forests of Kumaun Himalaya was assessed during the 1981 and 1982 monsoon seasons. Stemflow accounted for 0.28-0.89%, throughfall 74.7-91.5% and interception 8.1-25.0% of gross rainfall. The absolute values of throughfall, stemflow and interception were influenced by tree species. Overland flow was low for all forests, indicating that the latter are subsurface flow systems and, consequently, are specially susceptible to deforestation.

Soil CO2 Efflux and Its Components Responded Differently to Throughfall Exclusion and Fertilization in a Loblolly Pine (Pinus taeda) Plantation

NASA Astrophysics Data System (ADS)

Yang, J.; Luedtke, C.; Akers, K.; McGuire, M.; Aubrey, D. P.; Teskey, R. O.

2014-12-01

Soil CO2 efflux (RS) is an important component of forest ecosystem carbon budgets and net ecosystem CO2 exchange, but little is known about how RS and its components respond to decreasing soil moisture and changes in soil fertility. The experiment design was a 2 X 2 factorial combination of fertilization (2 levels) and precipitation (throughfall exclusion, 2 levels) replicated in four blocks. We measured RS along with soil temperature (Ts) and soil moisture (WS) from 2012 to 2014 in a loblolly pine plantation in Washington, GA. The autotrophic (RA) and heterotrophic (RH) components of soil CO2 efflux were separated using trenched plots. Our objectives were to (1) quantify impacts of throughfall exclusion and fertilization on RS and its components (RA, RH).and (2) determine soil CO2efflux and its components individually response to environmental factors and biological factors in throughfall exclusion and fertilization treatments. Annual mean RS was 2.11, 1.73, 2.09 and 1.92 for treatments of control, fertilization, throughfall exclusion and combination of fertilization and throughfall exclusion, respectively, from 2012 to 2013. The apparent Q10 for RS was 2.26, 2.25, 2.12 and 2.35 in the four treatments, respectively. There were no significant differences in RS among treatments except between the Ws treatments. However, there was slight reduction in RS and RA in fertilization and the fertilization plus throughfall exclusion treatment. In all treaments, Ts explained more than 80% of variation in RS. The contribution of CO2-derived from ectomycorrhizal hyphae was less than 15%. RS and RH was better predicted by TS in the dormant season than the growing season, indicating that additional factors such as root growth and photosynthesis became more important contributors to RS during the growing season. Fertilization slightly decreased RS mainly from a decrease in RH. Throughfall exclusion increased the contribution of RA to RS. We concluded that soil moisture had more effect on RS and its components than changes in fertility.

Detecting spatial structures in throughfall data: the effect of extent, sample size, sampling design, and variogram estimation method

NASA Astrophysics Data System (ADS)

Voss, Sebastian; Zimmermann, Beate; Zimmermann, Alexander

2016-04-01

In the last three decades, an increasing number of studies analyzed spatial patterns in throughfall to investigate the consequences of rainfall redistribution for biogeochemical and hydrological processes in forests. In the majority of cases, variograms were used to characterize the spatial properties of the throughfall data. The estimation of the variogram from sample data requires an appropriate sampling scheme: most importantly, a large sample and an appropriate layout of sampling locations that often has to serve both variogram estimation and geostatistical prediction. While some recommendations on these aspects exist, they focus on Gaussian data and high ratios of the variogram range to the extent of the study area. However, many hydrological data, and throughfall data in particular, do not follow a Gaussian distribution. In this study, we examined the effect of extent, sample size, sampling design, and calculation methods on variogram estimation of throughfall data. For our investigation, we first generated non-Gaussian random fields based on throughfall data with heavy outliers. Subsequently, we sampled the fields with three extents (plots with edge lengths of 25 m, 50 m, and 100 m), four common sampling designs (two grid-based layouts, transect and random sampling), and five sample sizes (50, 100, 150, 200, 400). We then estimated the variogram parameters by method-of-moments and residual maximum likelihood. Our key findings are threefold. First, the choice of the extent has a substantial influence on the estimation of the variogram. A comparatively small ratio of the extent to the correlation length is beneficial for variogram estimation. Second, a combination of a minimum sample size of 150, a design that ensures the sampling of small distances and variogram estimation by residual maximum likelihood offers a good compromise between accuracy and efficiency. Third, studies relying on method-of-moments based variogram estimation may have to employ at least 200 sampling points for reliable variogram estimates. These suggested sample sizes exceed the numbers recommended by studies dealing with Gaussian data by up to 100 %. Given that most previous throughfall studies relied on method-of-moments variogram estimation and sample sizes << 200, our current knowledge about throughfall spatial variability stands on shaky ground.

Hydrological and nutrient fluxes in the soil-atmosphere interface in Brazilian semiarid

NASA Astrophysics Data System (ADS)

Leal, Karinne; Borma, Laura; Forti, Cristina

2014-05-01

Semiarids are water stress regions caused by the association of high potential evapotranspiration, high temperatures (in summer) and generally low rainfall. Although unfavorable climatic conditions, semiarid regions represent about 14% global population and has been suffering land transformation, such as replacement by pastures and croplands. Crescent demand for agricultural and forests products in Brazilian semiarid has taken Caatinga deforestations, typical vegetation of that area that covers about 10% of Brazilian territory, with consequences in hydrology and biogeochemistry. The effect of these disruptions are poorly understood. The aim of this research is to characterize the differences in transfers of water and nutrients, in soil-atmosphere interface, between a typical Caatinga vegetation and pasture. Two field campaigns were made to sample and measure the water from rainfall, throughfall, stemflow, runoff and soil water. The collections were conducted during the rainy season, extended from April to August in 2012 and 2013, in São João, a county in the semiarid region of Pernambuco State, in the northeast of Brazil. The samples are being analyzed in order to determine their major cations and anions concentrations, total dissolved carbon (TDC), total organic carbon (TOC), total nitrogen (TN), alkalinity and pH. The observed precipitation represented about 40% and 50% of the historical average precipitation, in 2012 and 2013, respectively. This observations highlight the severe drought experienced in the region, mainly in the first year of sampling. The throughfall represented about 35% of the rainfall in 2012, and about 25% in 2013. In semiarid vegetations the average throughfall is about 49%, with variation coefficient of ±32%, so the observed data are consistent with those reported in the literature. These observations suggests that in drier years the vegetation holds more moisture than in wetter years. However, these data must be correlated with others parameters that influence the relationship between rainfall and troughfall, such as intensity and duration of the rain, wind speed and air humidity before the rainfall. The runoff was an order of magnitude lower in 2012 than in 2013. The chemical analyzes are still being processed. Key-words: Caatinga, carbon, nitrogen, land transformation.

Evidence for the Activation of Shallow Preferential Flow Paths in a Tropical Panama Watershed Using Germanium and Silicon

NASA Astrophysics Data System (ADS)

Gardner, Christopher B.; Litt, Guy F.; Lyons, W. Berry; Ogden, Fred L.

2017-10-01

In humid tropical watersheds, the hydrologic flow paths taken by rain event waters and how they interact with groundwater and soil matrix water to form streamflow are poorly understood. Preferential flow paths (PFPs) confound storm infiltration processes, especially in the humid tropics where PFPs are common. This work applies germanium (Ge) and silicon (Si) as natural flow path tracers in conjunction with water stable isotopes and electrical conductivity to examine the rapid delivery of shallow soil water, the activation of PFPs, and event water partitioning in an experimental catchment in central Panama. We employed a three-component mixing model for hydrograph separation using the following end-member waters: (i) base flow (high [Si], low [Ge], and low Ge/Si ratio), (ii) dilute canopy throughfall (low [Si] and low [Ge]), and (iii) shallow (<15 cm) soil matrix water (low [Si], high [Ge], and high Ge/Si ratio). These three end-members bounded all observed Ge/Si streamflow ratios. During small rain events (<˜24 mm), base flow and dilute canopy throughfall components dominated stormflow. During larger precipitation events (>˜35 mm), we detected the third shallow soil water component with an elevated [Ge] and Ge/Si ratio. This component reached its maximum during the hydrograph's receding limb coincident with the maximum event fraction, and increased proportionally to the total storm rainfall exceeding ˜35 mm. Only shallow (<15 cm) soil matrix water exhibited elevated Ge concentrations and high Ge/Si ratios. This third component represents rapidly delivered soil matrix water combined with shallow lateral PFP activation through which event waters interact with soil minerals.

Interactive effects of fertilization and throughfall exclusion on the physiological responses and whole-tree carbon uptake of mature loblolly pine

Treesearch

Zhenmin Tang; Mary A. Sword Sayer; Jim L. Chambers; James P. Barnett

2004-01-01

Few studies have examined the combined effects of nutrition and water exclusion on the canopy physiology of mature loblolly pine (Pinus taeda L.). Understanding the impacts of forest management on plantation productivity requires extensive research on the relationship between silvicultural treatments and environmental constraints to growth. We...

Modelling rainfall interception by a lowland tropical rain forest in northeastern Puerto Rico

NASA Astrophysics Data System (ADS)

Schellekens, J.; Scatena, F. N.; Bruijnzeel, L. A.; Wickel, A. J.

1999-12-01

Recent surveys of tropical forest water use suggest that rainfall interception by the canopy is largest in wet maritime locations. To investigate the underlying processes at one such location—the Luquillo Experimental Forest in eastern Puerto Rico—66 days of detailed throughfall and above-canopy climatic data were collected in 1996 and analysed using the Rutter and Gash models of rainfall interception. Throughfall occurred on 80% of the days distributed over 80 rainfall events. Measured interception loss was 50% of gross precipitation. When Penman-Monteith based estimates for the wet canopy evaporation rate (0.11 mm h -1 on average) and a canopy storage of 1.15 mm were used, both models severely underestimated measured interception loss. A detailed analysis of four storms using the Rutter model showed that optimizing the model for the wet canopy evaporation component yielded much better results than increasing the canopy storage capacity. However, the Rutter model failed to properly estimate throughfall amounts during an exceptionally large event. The analytical model, on the other hand, was capable of representing interception during the extreme event, but once again optimizing wet canopy evaporation rates produced a much better fit than optimizing the canopy storage capacity. As such, the present results support the idea that it is primarily a high rate of evaporation from a wet canopy that is responsible for the observed high interception losses.

Rainfall partitioning and related hydrochemical fluxes in a diverse and in a mono specific (Phenakospermum guyannense) secondary vegetation stand in eastern Amazonia.

PubMed

Hölscher, D; Sá, T D A; Möller, R F; Denich, M; Fölster, H

1998-04-01

Rainfall partitioning into throughfall and stemflow was studied in a diverse and in a mono specific stand of secondary vegetation in Eastern Amazonia. The nutrient concentrations in the water were analysed in order to quantify the related hydrochemical fluxes. Secondary vegetation forms the fallow in the local shifting cultivation system and is usually dominated by shrubs and trees. Phenakospermum guyannense (Strelitziaceae), a banana-like herb, is one of the predominant non-woody species. The study was conducted during an 18-month period in a 2.5-year-old relatively species-rich stand and a 10-year-old stand dominated by P. guyannense. In a year with 1956 mm of rainfall 65% (1281 mm) of this quantity reached the soil as throughfall in the diverse stand and 38% (743 mm) in the mono specific stand. Stemflow was estimated to be 23% and 41% respectively. P. guyannense and Banara guianensis (Flacourtiaceae), a tree species, were causing these high funnelling effects. In the young diverse stand B. guianensis had a stemflow of more than 200 l year -1 and P. guyannense had a median flux of 77 l year -1 per pseudostem. In the older stand the taller plants of P.␣guyannense collected 644 l year -1 per pseudostem on the median. The reason for these high values could be the banana-like growth form of P. guyannense and the crown morphology of B. guianensis, which has inclined branches. The low proportion of throughfall and the high stemflow values differ from all previous studies in Amazonian primary forests. The proximity to the Atlantic Ocean strongly influenced the nutrient fluxes via rainfall at our study site. This becomes obvious from the high Na and Cl fluxes with rainfall (19.7 kg Na ha -1 year -1 , 37.2 kg Cl ha -1 year -1 ) which were approximately equal to the Na and Cl fluxes with the sum of throughfall and stemflow for both stands. K fluxes in throughfall and stemflow in both stands were higher than in rainfall by a factor of 8. The high K enrichment during the crown passage is assumed to be caused by a␣high K concentration in the leaf tissue resulting in enhanced leaching from the leaves. In months with low␣rainfall the concentrations of Ca, Mg, S and Cl in throughfall of the diverse stand were significantly higher than in months with high rainfall. This was mainly due to vegetation burns in the dry period, which resulted in ash deposition on the canopy and subsequent wash-off and solution of ash particles.

Tropical land-cover change alters biogeochemical inputs to ecosystems in a Mexican montane landscape.

PubMed

Ponette-González, A G; Weathers, K C; Curran, L M

2010-10-01

In tropical regions, the effects of land-cover change on nutrient and pollutant inputs to ecosystems remain poorly documented and may be pronounced, especially in montane areas exposed to elevated atmospheric deposition. We examined atmospheric deposition and canopy interactions of sulfate-sulfur (SO4(2-)-S), chloride (Cl-), and nitrate-nitrogen (NO(3-)-N) in three extensive tropical montane land-cover types: clearings, forest, and coffee agroforest. Bulk and fog deposition to clearings was measured as well as throughfall (water that falls through plant canopies) ion fluxes in seven forest and five coffee sites. Sampling was conducted from 2005 to 2008 across two regions in the Sierra Madre Oriental, Veracruz, Mexico. Annual throughfall fluxes to forest and coffee sites ranged over 6-27 kg SO4(2-)-S/ha, 12-69 kg Cl-/ha, and 2-6 kg NO(3-)-N/ha. Sulfate-S in forest and coffee throughfall was higher or similar to bulk S deposition measured in clearings. Throughfall Cl- inputs, however, were consistently higher than Cl- amounts deposited to cleared areas, with net Cl- fluxes enhanced in evergreen coffee relative to semi-deciduous forest plots. Compared to bulk nitrate-N deposition, forest and coffee canopies retained 1-4 kg NO(3-)-N/ha annually, reducing NO(3-)-N inputs to soils. Overall, throughfall fluxes were similar to values reported for Neotropical sites influenced by anthropogenic emissions, while bulk S and N deposition were nine- and eightfold greater, respectively, than background wet deposition rates for remote tropical areas. Our results demonstrate that land-cover type significantly alters the magnitude and spatial distribution of atmospheric inputs to tropical ecosystems, primarily through canopy-induced changes in fog and dry deposition. However, we found that land cover interacts with topography and climate in significant ways to produce spatially heterogeneous patterns of anion fluxes, and that these factors can converge to create deposition hotspots. For land managers, this finding suggests that there is potential to identify species and ecosystems at risk of excess and increasing deposition in montane watersheds undergoing rapid transformation. Our data further indicate that montane ecosystems are vulnerable to air pollution impacts in this and similar tropical regions downwind of urban, industrial, and agricultural emission sources.

In situ 13CO2 pulse labelling of field-grown eucalypt trees revealed the effects of potassium nutrition and throughfall exclusion on phloem transport of photosynthetic carbon.

PubMed

Epron, Daniel; Cabral, Osvaldo Machado Rodrigues; Laclau, Jean-Paul; Dannoura, Masako; Packer, Ana Paula; Plain, Caroline; Battie-Laclau, Patricia; Moreira, Marcelo Zacharias; Trivelin, Paulo Cesar Ocheuze; Bouillet, Jean-Pierre; Gérant, Dominique; Nouvellon, Yann

2016-01-01

Potassium (K) is an important limiting factor of tree growth, but little is known of the effects of K supply on the long-distance transport of photosynthetic carbon (C) in the phloem and of the interaction between K fertilization and drought. We pulse-labelled 2-year-old Eucalyptus grandis L. trees grown in a field trial combining K fertilization (+K and -K) and throughfall exclusion (+W and -W), and we estimated the velocity of C transfer by comparing time lags between the uptake of (13)CO2 and its recovery in trunk CO2 efflux recorded at different heights. We also analysed the dynamics of the labelled photosynthates recovered in the foliage and in the phloem sap (inner bark extract). The mean residence time of labelled C in the foliage was short (21-31 h). The time series of (13)C in excess in the foliage was affected by the level of fertilization, whereas the effect of throughfall exclusion was not significant. The velocity of C transfer in the trunk (0.20-0.82 m h(-1)) was twice as high in +K trees than in -K trees, with no significant effect of throughfall exclusion except for one +K -W tree labelled in the middle of the drought season that was exposed to a more pronounced water stress (midday leaf water potential of -2.2 MPa). Our results suggest that besides reductions in photosynthetic C supply and in C demand by sink organs, the lower velocity under K deficiency is due to a lower cross-sectional area of the sieve tubes, whereas an increase in phloem sap viscosity is more likely limiting phloem transport under drought. In all treatments, 10 times less (13)C was recovered in inner bark extracts at the bottom of the trunk when compared with the base of the crown, suggesting that a large part of the labelled assimilates has been exported out of the phloem and replaced by unlabelled C. This supports the 'leakage-retrieval mechanism' that may play a role in maintaining the pressure gradient between source and sink organs required to sustain high velocity of phloem transport in tall trees. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Effects of experimental throughfall reduction and soil warming on fine root biomass and its decomposition in a warm temperate oak forest.

PubMed

Liu, Yanchun; Liu, Shirong; Wan, Shiqiang; Wang, Jingxin; Wang, Hui; Liu, Kuan

2017-01-01

Fine root dynamics play a critical role in regulating carbon (C) cycling in terrestrial ecosystems. Examining responses of fine root biomass and its decomposition to altered precipitation pattern and climate warming is crucial to understand terrestrial C dynamics and its feedback to climate change. Fine root biomass and its decomposition rate were investigated in a warm temperate oak forest through a field manipulation experiment with throughfall reduction and soil warming conducted. Throughfall reduction significantly interacted with soil warming in affecting fine root biomass and its decomposition. Throughfall reduction substantially increased fine root biomass and its decomposition in unheated plots, but negative effects occurred in warmed plots. Soil warming significantly enhanced fine root biomass and its decomposition under ambient precipitation, but the opposite effects exhibited under throughfall reduction. Different responses in fine root biomass among different treatments could be largely attributed to soil total nitrogen (N), while fine root decomposition rate was more depended on microbial biomass C and N. Our observations indicate that decreased precipitation may offset the positive effect of soil warming on fine root biomass and decomposition. Copyright © 2016 Elsevier B.V. All rights reserved.

Fitting rainfall interception models to forest ecosystems of Mexico

NASA Astrophysics Data System (ADS)

Návar, José

2017-05-01

Models that accurately predict forest interception are essential both for water balance studies and for assessing watershed responses to changes in land use and the long-term climate variability. This paper compares the performance of four rainfall interception models-the sparse Gash (1995), Rutter et al. (1975), Liu (1997) and two new models (NvMxa and NvMxb)-using data from four spatially extensive, structurally diverse forest ecosystems in Mexico. Ninety-eight case studies measuring interception in tropical dry (25), arid/semi-arid (29), temperate (26), and tropical montane cloud forests (18) were compiled and analyzed. Coefficients derived from raw data or published statistical relationships were used as model input to evaluate multi-storm forest interception at the case study scale. On average empirical data showed that, tropical montane cloud, temperate, arid/semi-arid and tropical dry forests intercepted 14%, 18%, 22% and 26% of total precipitation, respectively. The models performed well in predicting interception, with mean deviations between measured and modeled interception as a function of total precipitation (ME) generally <5.8% and Nash-Sutcliffe efficiency E estimators >0.66. Model fitting precision was dependent on the forest ecosystem. Arid/semi-arid forests exhibited the smallest, while tropical montane cloud forest displayed the largest ME deviations. Improved agreement between measured and modeled data requires modification of in-storm evaporation rate in the Liu; the canopy storage in the sparse Gash model; and the throughfall coefficient in the Rutter and the NvMx models. This research concludes on recommending the wide application of rainfall interception models with some caution as they provide mixed results. The extensive forest interception data source, the fitting and testing of four models, the introduction of a new model, and the availability of coefficient values for all four forest ecosystems are an important source of information and a benchmark for future investigations in this area of hydrology.

Removal of Polycyclic Aromatic Hydrocarbons from Precipitation in an Urban Forest of Guangzhou, South China.

PubMed

Chen, Bufeng; Pei, Nancai; Huang, Junbiao; Liu, Shuguang; Zhang, Na; Xiao, Yihua; Pan, Yongjun

2015-08-01

Polycyclic aromatic hydrocarbon (PAH) concentrations and fluxes were measured monthly in situ from rain events in an urban forest in the megapolitan city Guangzhou, China, to investigate impacts of forest canopy and soils on PAHs. Mean Σ9-PAH concentrations were 107.5, 101.6, 106.3, 107.1 and 42.4 ng L(-1) in precipitation, throughfall, seepage water at the 30 and 60 cm soil depth, and runoff, respectively, indicating a great decrease in the form of runoff. Meanwhile, annual fluxes of total PAHs decreased from precipitation (205.9 µg m(-2) year(-1)), to throughfall (156.3 µg m(-2) year(-1)), and to seepage water (65.3 µg m(-2) year(-1) at 30-cm soil depth and 7.5 µg m(-2) year(-1) at 60-cm soil depth), but increased in runoff (34.1 µg m(-2) year(-1)). When compared to precipitation, PAH fluxes decreased by 83.4% in runoff, with 29% contributed by forest canopy and 71% by soils. Soil biodegradation explained 18.2% of PAH reduction by the surface soil layer and 34.6% by the middle soil layer.

A methodology for investigating interdependencies between measured throughfall, meteorological variables and canopy structure on a small catchment.

NASA Astrophysics Data System (ADS)

Maurer, Thomas; Gustavos Trujillo Siliézar, Carlos; Oeser, Anne; Pohle, Ina; Hinz, Christoph

2016-04-01

In evolving initial landscapes, vegetation development depends on a variety of feedback effects. One of the less understood feedback loops is the interaction between throughfall and plant canopy development. The amount of throughfall is governed by the characteristics of the vegetation canopy, whereas vegetation pattern evolution may in turn depend on the spatio-temporal distribution of throughfall. Meteorological factors that may influence throughfall, while at the same time interacting with the canopy, are e.g. wind speed, wind direction and rainfall intensity. Our objective is to investigate how throughfall, vegetation canopy and meteorological variables interact in an exemplary eco-hydrological system in its initial development phase, in which the canopy is very heterogeneous and rapidly changing. For that purpose, we developed a methodological approach combining field methods, raster image analysis and multivariate statistics. The research area for this study is the Hühnerwasser ('Chicken Creek') catchment in Lower Lusatia, Brandenburg, Germany, where after eight years of succession, the spatial distribution of plant species is highly heterogeneous, leading to increasingly differentiated throughfall patterns. The constructed 6-ha catchment offers ideal conditions for our study due to the rapidly changing vegetation structure and the availability of complementary monitoring data. Throughfall data were obtained by 50 tipping bucket rain gauges arranged in two transects and connected via a wireless sensor network that cover the predominant vegetation types on the catchment (locust copses, dense sallow thorn bushes and reeds, base herbaceous and medium-rise small-reed vegetation, and open areas covered by moss and lichens). The spatial configuration of the vegetation canopy for each measurement site was described via digital image analysis of hemispheric photographs of the canopy using the ArcGIS Spatial Analyst, GapLight and ImageJ software. Meteorological data from two on-site weather stations (wind direction, wind speed, air temperature, air humidity, insolation, soil temperature, precipitation) were provided by the 'Research Platform Chicken Creek' (https://www.tu-cottbus.de/projekte/en/oekosysteme/startseite.html). Data were combined and multivariate statistical analysis (PCA, cluster analysis, regression trees) were conducted using the R-software to i) obtain statistical indices describing the relevant characteristics of the data and ii) to identify the determining factors for throughfall intensity. The methodology is currently tested and results will be presented. Preliminary evaluation of the image analysis approach showed only marginal, systematic deviation of results for the different software tools applied, which makes the developed workflow a viable tool for canopy characterization. Results from this study will have a broad spectrum of possible applications, for instance the development / calibration of rainfall interception models, the incorporation into eco-hydrological models, or to test the fault tolerance of wireless rainfall sensor networks.

Spatial and Temporal Patterns of Throughfall Amounts and Solutes in a Tropical Montane Forest - Comparisons with Findings From Lowland Rain Forests

NASA Astrophysics Data System (ADS)

Zimmermann, A.

2007-05-01

The diverse tree species composition, irregular shaped tree crowns and a multi-layered forest structure affect the redistribution of rainfall in lower montane rain forests. In addition, abundant epiphyte biomass and associated canopy humus influence spatial patterns of throughfall. The spatial variability of throughfall amounts controls spatial patterns of solute concentrations and deposition. Moreover, the living and dead biomass interacts with the rainwater during the passage through the canopy and creates a chemical variability of its own. Since spatial and temporal patterns are intimately linked, the analysis of temporal solute concentration dynamics is an important step to understand the emerging spatial patterns. I hypothesized that: (1) the spatial variability of volumes and chemical composition of throughfall is particularly high compared with other forests because of the high biodiversity and epiphytism, (2) the temporal stability of the spatial pattern is high because of stable structures in the canopy (e.g. large epiphytes) that show only minor changes during the short term observation period, and (3) the element concentrations decrease with increasing rainfall because of exhausting element pools in the canopy. The study area at 1950 m above sea level is located in the south Ecuadorian Andes far away from anthropogenic emission sources and marine influences. Rain and throughfall were collected from August to October 2005 on an event and within-event basis for five precipitation periods and analyzed for pH, K, Na, Ca, Mg, NH4+, Cl-, NO3-, PO43-, TN, TP and TOC. Throughfall amounts and most of the solutes showed a high spatial variability, thereby the variability of H+, K, Ca, Mg, Cl- and NO3- exceeded those from a Brazilian tropical rain forest. The temporal persistence of the spatial patterns was high for throughfall amounts and varied depending on the solute. Highly persistent time stability patterns were detected for K, Mg and TOC concentrations. Time stability patterns of solute deposition were somewhat weaker than for concentrations for most of the solutes. Epiphytes strongly affected time stability patterns in that collectors situated below thick moss mats or arboreal bromeliads were in large part responsible for the extreme persistence with low throughfall amounts and high ion concentrations (H+ showed low concentrations). Rainfall solute concentrations were low compared with a variety of other tropical lowland and montane forest sites and showed a small temporal variability during the study period for both between and within-event dynamics, respectively. Throughfall solute concentrations were more within the range when compared with other sites and showed highly variable within-event dynamics. For most of the solutes, within-event concentrations did not reach low, constant concentrations in later event stages, rather concentrations fluctuated (e.g. Cl-) or increased (e.g. K and TOC). The within-event throughfall solute concentration dynamics in this lower montane rain forest contrast to recent observations from lowland tropical rain forests in Panama and Brazil. The observed within-event patterns are attributed (1) to the influence of epiphytes and associated canopy humus, and (2) to low rainfall intensities.

Atmospheric Inputs of Mercury and Organic Carbon into a Forested Upland/Bog Watershed

Treesearch

Randall K. Kolka; E.A. Nater; D.F. Grigal; E.S. Verry

1999-01-01

Inputs of mercury (Hg) and dissolved organic carbon (DOC) in throughfall and stemflow waters were measured for an upland/bog watershed in northern Minnesota, and were compared to the deposition in a nearby opening to determine the influence of tree canopies on Hg and DOC deposition. Twice as much Hg and seven times as much DOC was deposited in the forested watershed...

Overstory vegetation influence nitrogen and dissolved organic carbon flux from the atmosphere to the forest floor: Boreal Plain, Canada

Treesearch

David E. Pelster; Randall K. Kolka; Ellie E. Prepas

2009-01-01

Nitrate, ammonium, total dissolved nitrogen (TDN), dissolved organic nitrogen (DON) and dissolved organic carbon (DOC) concentrations and flux were measured for one year in bulk deposition and throughfall from three stand types (upland deciduous, upland conifer and wetland conifer) on the Boreal Plain, Canada. Annual (November 2006 to October 2007 water year) flux...

Soil and hydrological responses to wild pig (Sus scofa) exclusion from native and strawberry guava (Psidium cattleianum)-invaded tropical montane wet forests

Treesearch

Ayron M. Strauch; Gregory L. Bruland; Richard A. MacKenzie; Christian P. Giardina

2016-01-01

The structure and function of many ecosystems are threatened by non-native, invasive plant and animal species. Globally, invasive trees alter interception, evapotranspiration, water use, and throughfall, while wild pigs (Sus scofa) have been introduced and now invade widely ranging ecosystems, with impacts to soil and groundcover, and as a...

Long term changes in atmospheric N and S throughfall deposition and effects on soil solution chemistry in a Scots pine forest in the Netherlands.

PubMed

Boxman, Andries W; Peters, Roy C J H; Roelofs, Jan G M

2008-12-01

In a Scots pine forest the throughfall deposition and the chemical composition of the soil solution was monitored since 1984. (Inter)national legislation measures led to a reduction of the deposition of nitrogen and sulphur. The deposition of sulphur has decreased by approximately 65%. The total mineral-nitrogen deposition has decreased by ca. 25%, which is mainly due to a reduction in ammonium-N deposition (-40%), since nitrate-N deposition has increased (+50%). The nitrogen concentration in the upper mineral soil solution at 10 cm depth has decreased, leading to an improved nutritional balance, which may result in improved tree vitality. In the drainage water at 90 cm depth the fluxes of NO3(-) and SO4(2-) have decreased, resulting in a reduced leeching of accompanying base cations, thus preserving nutrients in the ecosystem. It may take still several years, however, before this will meet the prerequisite of a sustainable ecosystem.

Comparison of forest edge effects on throughfall deposition in different forest types.

PubMed

Wuyts, Karen; De Schrijver, An; Staelens, Jeroen; Gielis, Leen; Vandenbruwane, Jeroen; Verheyen, Kris

2008-12-01

This study examined the influence of distance to the forest edge, forest type, and time on Cl-, SO4(2-), NO3(-), and NH4+ throughfall deposition in forest edges. The forests were dominated by pedunculate oak, silver birch, or Corsican/Austrian pine, and were situated in two regions of Flanders (Belgium). Along transects, throughfall deposition was monitored at distances of 0-128 m from the forest edge. A repeated-measures analysis demonstrated that time, forest type, and distance to the forest edge significantly influenced throughfall deposition of the ions studied. The effect of distance to the forest edge depended significantly on forest type in the deposition of Cl-, SO4(2-), and NO3(-): the edge effect was significantly greater in pine stands than in deciduous birch and oak stands. This finding supports the possibility of converting pine plantations into oak or birch forests in order to mitigate the input of nitrogen and potentially acidifying deposition.

The temporal response to drought in a Mediterranean evergreen tree: comparing a regional precipitation gradient and a throughfall exclusion experiment.

PubMed

Martin-Stpaul, Nicolas K; Limousin, Jean-Marc; Vogt-Schilb, Hélène; Rodríguez-Calcerrada, Jesus; Rambal, Serge; Longepierre, Damien; Misson, Laurent

2013-08-01

Like many midlatitude ecosystems, Mediterranean forests will suffer longer and more intense droughts with the ongoing climate change. The responses to drought in long-lived trees differ depending on the time scale considered, and short-term responses are currently better understood than longer term acclimation. We assessed the temporal changes in trees facing a chronic reduction in water availability by comparing leaf-scale physiological traits, branch-scale hydraulic traits, and stand-scale biomass partitioning in the evergreen Quercus ilex across a regional precipitation gradient (long-term changes) and in a partial throughfall exclusion experiment (TEE, medium term changes). At the leaf scale, gas exchange, mass per unit area and nitrogen concentration showed homeostatic responses to drought as they did not change among the sites of the precipitation gradient or in the experimental treatments of the TEE. A similar homeostatic response was observed for the xylem vulnerability to cavitation at the branch scale. In contrast, the ratio of leaf area over sapwood area (LA/SA) in young branches exhibited a transient response to drought because it decreased in response to the TEE the first 4 years of treatment, but did not change among the sites of the gradient. At the stand scale, leaf area index (LAI) decreased, and the ratios of stem SA to LAI and of fine root area to LAI both increased in trees subjected to throughfall exclusion and from the wettest to the driest site of the gradient. Taken together, these results suggest that acclimation to chronic drought in long-lived Q. ilex is mediated by changes in hydraulic allometry that shift progressively from low (branch) to high (stand) organizational levels, and act to maintain the leaf water potential within the range of xylem hydraulic function and leaf photosynthetic assimilation. © 2013 John Wiley & Sons Ltd.

STEMFLOW CONTRIBUTION TO THE 'FERTILE ISLAND' EFFECT IN CREOSOTEBUSH, LARREA TRIDENTATA

EPA Science Inventory

Stemflow, throughfall and bulk precipitation were collected on six creosotebushes (Larrea tridentata) during 18 events in the summer rainy season in the northern Chihuahuan Desert. The average stemflow was 16.8 +-1.9%; throughfall average 64.7 +-3.2%. The concentration of all ion...

Acid-base chemistry of dissolved organic matter in aqueous leaf extracts: Application to organic acids in throughfall. [Chrysolepis sempervirens; Pinus monticola; Salix orestera

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brown, A.D.; Sposito, G.

Elemental composition data were obtained for bulk precipitation and throughfall samples and for aqueous extracts of leaves of three woody plant species common in the subalpine Sierras Nevada range, California: chinquapin (Chrysolepis sempervirens Hjelmqvist), western white pine (Pinus monticola Dougl.), and willow (Salix orestera Schneider). The acid-base equilibria of the extracts were characterized by potentiometric titration and proton formation functions were computed. The latter then were modeled assuming four classes of quasiparticle acidic functional groups, yielding negative logarithms of conditional protonation constants in the range 4.8 to 5.0, 6.1 to 6.6, 7.4 to 7.7, and 9.1 to 9.4. The relativemore » concentration of a given acidic functional group class varied markedly among the three woody species, but the conditional protonation constants were very similar. The model parameters, along with dissolved organic C concentration and pH values, were used to estimate net anion deficits in throughfall samples collected from the same sites as the leaf samples. On average, the calculated charge concentration of free organic anions in the western white pine extract matched the throughfall anion deficit, whereas the deficits in the chinquapin and willow throughfall samples were not accounted for by free anion concentrations. Metal complexation and in situ, species-dependent leaf surfaces processes may account for these latter differences.« less

Throughfall chemistry beneath Quercus rubra: atmospheric, foliar, and soil chemistry considerations

Treesearch

Theodor D. Leininger; W.E. Winner

1988-01-01

Concentrations of inorganic ions were measured in bulk rainfall and bulk throughfall collected beneath northern red oak (Quercus rubra L.) trees growing in fertile, limestone-derived soil and less fertile sandstone/shale-derived soil. Rainfall passing through the crowns at both sites was enriched with SO2-4...

Modelling rainfall interception by a lowland tropical rain forest in northeastern Puerto Rico

Treesearch

J. Schellekensa; F.N. Scatenab; L.A. Bruijnzeela; A.J. \\t Wickela

1999-01-01

Recent surveys of tropical forest water use suggest that rainfall interception by the canopy is largest in wet maritime locations. To investigate the underlying processes at one such location—the Luquillo Experimental Forest in eastern Puerto Rico—66 days of detailed throughfall and above-canopy climatic data were collected in 1996 and analysed using the Rutter and...

Seasonal and spatial variability of rainfall redistribution under Scots pine and Downy oak forests in Mediterranean conditions

NASA Astrophysics Data System (ADS)

Garcia-Estringana, Pablo; Latron, Jérôme; Molina, Antonio J.; Llorens, Pilar

2013-04-01

The large degree of temporal and spatial variability of throughfall input patterns may lead to significant changes in the volume of water that reach the soil in each location, and beyond in the hydrological response of forested hillslopes. To explore the role of vegetation in the temporal and spatial redistribution of rainfall in Mediterranean climatic conditions two contrasted stands were monitored. One is a Downy oak forest (Quercus pubescens) and the other is a Scots pine forest (Pinus sylvestris), both are located in the Vallcebre research catchments (NE Spain, 42° 12'N, 1° 49'E). These plots are representative of Mediterranean mountain areas with spontaneous afforestation by Scots pine as a consequence of the abandonment of agricultural terraces, formerly covered by Downy oaks. The monitoring design of each plot consists of a set of 20 automatic rain recorders and 40 automatic soil moisture probes located below the canopy. 100 hemispheric photographs of the canopy were used to place the instruments at representative locations (in terms of canopy cover) within the plot. Bulk rainfall, stemflow and meteorological conditions above the forest cover are also automatically recorded. Canopy cover as well as biometric characteristics of the plots are also regularly measured. This work presents the first results describing the variability of throughfall beneath each forest stand and compares the persistence of temporal patterns among stands, and for the oaks stand among the leafed and the leafless period. Furthermore, canopy structure, rainfall characteristics and meteorological conditions of rainfall events are evaluated as main drivers of throughfall redistribution.

Chemistry of through-fall and stem-flow leachate following rainfall simulation over pinyon and juniper

USDA-ARS?s Scientific Manuscript database

We hypothesized that leachate from pinyon and juniper canopies, following rainfall events, may contribute sizable levels of solutes and C to the soil surface. We quantified solutes and dissolved carbon in stem-flow (SF) and through-fall (TF) following replicated rainfall simulation events in a pinyo...

Interception loss, throughfall and stemflow in a maritime pine stand. II. An application of Gash's analytical model of interception

NASA Astrophysics Data System (ADS)

Loustau, D.; Berbigier, P.; Granier, A.

1992-10-01

Interception, throughfall and stemflow were determined in an 18-year-old maritime pine stand for a period of 30 months. This involved 71 rainfall events, each corresponding either to a single storm or to several storms. Gash's analytical model of interception was used to estimate the sensitivity of interception to canopy structure and climatic parameters. The seasonal cumulative interception loss corresponded to 12.6-21.0% of the amount of rainfall, whereas throughfall and stemflow accounted for 77-83% and 1-6%, respectively. On a seasonal basis, simulated data fitted the measured data satisfactorily ( r2 = 0.75). The rainfall partitioning between interception, throughfall and stemflow was shown to be sensitive to (1) the rainfall regime, i.e. the relative importance of light storms to total rainfall, (2) the climatic parameters, rainfall rate and average evaporation rate during storms, and (3) the canopy structure parameters of the model. The low interception rate of the canopy was attributed primarily to the low leaf area index of the stand.

Kinetic energy of throughfall in a highly diverse forest ecosystem in the humid subtropics

NASA Astrophysics Data System (ADS)

Geißler, Christian; Kühn, Peter; Scholten, Thomas

2010-05-01

After decades of research it is generally accepted that vegetation is a key factor in controlling soil erosion. Therefore, in ecosystems where erosion is a serious problem, afforestation is a common measure against erosion. Most of the studies in the last decades focused on agricultural systems and less attention was paid to natural systems. To understand the mechanisms preventing soil erosion in natural systems the processes have to be studied in detail and gradually. The first step and central research question is on how the canopies of the tree layer alter the properties of rainfall and generate throughfall. Kinetic energy is a widely used parameter to estimate the erosion potential of open field rainfall and throughfall. In the past, numerous studies have shown that vegetation of a certain height enhances the kinetic energy under the canopy (Chapman 1948, Mosley 1982, Vis 1986, Hall & Calder 1993, Nanko et al. 2006, Nanko et al. 2008) in relation to open field rainfall. This is mainly due to a shift in the drop size distribution to less but larger drops possessing a higher amount of kinetic energy. In vital forest ecosystems lower vegetation (shrubs, herbs) as well as a continuous litter layer protects the forest soil from the impact of large drops. The influence of biodiversity, specific forest stands or single species in this process system is still in discussion. In the present study calibrated splash cups (after Ellison 1947, Geißler et al. under review) have been used to detect differences in kinetic energy on the scale of specific species and on the scale of forest stands of contrasting age and biodiversity in a natural forest ecosystem. The splash cups have been calibrated experimentally using a laser disdrometer. The results show that the kinetic energy of throughfall produced by the tree layer increases with the age of the specific forest stand. The average throughfall kinetic energy (J m-2) is about 2.6 times higher in forests than under open field conditions. Most of the energy is supposed to be absorbed by shrubs, herbs and the litter layer. For some species in the shrub and herb layer throughfall drops are crucial for seed dispersal (Nakanishi 2002). A higher kinetic energy of throughfall should be advantageous for seed dispersal and probably support biodiversity. Further, it is shown that the variability of kinetic energy in forests varies among the age of the forest stand which can be related to the forest structure. In our case there is a high variability in young forests (< 30 years) due to selective logging (some older trees were left out) and gaps in the tree layer. Old forests (> 80 years) also have a high variability in kinetic energy. There, external influences like snow and wind break result in a fragmentary tree layer which allows less erosive rainfall to reach the forest floor. Medium aged forests are more homogenous regarding canopy closure or tree heights. Generally, the variability of kinetic energy in forests is increasing with the amount of rainfall. Moreover, it is shown that the kinetic energy of throughfall is species specific. For the investigated tree species the values range between 24.41 J m-2 mm-1 (Daphniphyllum oldhamii) and 33.24 J m-2 mm-1 (Schima superba) while the concurrent rainfall in the open field has an average kinetic energy of 6.75 J m-2 mm-1. Leaf size and canopy architecture are supposed to be two of the controlling variables for specific species. These results give implications for afforestation measures and are important input variables for modeling of erosion processes. Chapman, G., 1948. Size of raindrops and their striking force at the soil surface in a Red Pine plantation. Transactions - American Geophysical Union, 29: 664-670. Ellison, W.D., 1947. Soil Erosion Studies - Part II. Agricultural Engineering, 28: 197-201. Geißler, C., Kühn, P., Böhnke, M., Bruelheide, H., Shi, X., Scholten, T., under review: Measuring splash erosion potential under vegetation using sand-filled splash cups. Hall, R.L., Calder, I.R., 1993. Drop size modification by forest canopies: measurements using a disdrometer. Journal of Geophysical Research (D10), 98: 18465-18470. Mosley, M.P., 1982. The effect of a New Zealand beech forest canopy on the kinetic energy of water drops and on surface erosion. Earth Surface Processes and Landforms, 7: 103-107. Nakanishi, H., 2002. Splash dispersal by raindrops. Ecological research, 17: 663-671. Nanko, K., Hotta, N., Suzuki, M., 2006. Evaluating the influence of canopy species and meteorological factors on throughfall drop size distribution. Journal of Hydrology, 329: 422-431. Nanko, K., Mizugaki, S., Onda, Y., 2008. Estimation of soil splash detachment rates on the forest floor of an unmanaged Japanese cypress plantation based on field measurements of throughfall drop sizes and velocities. Catena, 72: 348-361. Vis, M., 1986. Interception, drop size distribution and rainfall kinetic energy in four Columbian forest ecosystems. Earth Surface Processes and Landforms, 11: 591-603.

The effects of decreased water availability on loblolly pine (Pinus taeda L.) productivity and the interaction between fertilizer and drought

Treesearch

Adam O. Maggard; Rodney E. Will; Duncan S. Wilson; Cassandra R. Meek

2016-01-01

As part of the regional PINEMAP (Pine Integrated Network: Education, Mitigation, and Adaptation project) funded by the NIFA - USDA, we established a factorial study in McCurtain County, OK near Broken Bow. This study examined the effects of fertilization and ~30 percent reduction in throughfall on an seven-yearold loblolly pine (Pinus taeda L.) plantation. The...

Sampling throughfall and stemflow in young loblolly pine plantations

Treesearch

S.J. Zarnoch; D.A. Abrahamson; P.M. Dougherty

2002-01-01

Throughfall and stemflow estimates were obtained on a rain-event basis for small (0.09-hectare) plots established in a young loblolly pine (Pinus taeda L.) plantation in North Carolina. The plots were exposed to specific fertilization and irrigation treatments, which resulted in a wide range of basal areas and leaf area indices. Coefficients of variation were also...

Spatial patterns of Armillaria populations in the walker branch watershed throughfall displacement experiment, Tennessee,USA.

Treesearch

Johann N. Bruhn; James A. Brenneman; James J., Jr. Wetteroff; Jeanne D. Mihail; Theodor D. Leininger

1997-01-01

Species in the white-rot fungal genus Armillaria vary in parasitic aggressiveness as root and butt rot pathogens of trees. Armillaria genets (individuals) were mapped in the Throughfall Displacement Experiment (TDE) using mushrooms and rhizomorphs collected in 1994 and 1995. Initiated in July 1993, the TDE consists of three 80 x 80...

Wet and dry deposition in the AOSR collected by ion exchange resin samplers

Treesearch

Mark Fenn

2015-01-01

Atmospheric deposition of nitrogen (N), sulfur (S), and base cations was measured across the network of jack pine sites in the Athabasca Oil Sands Region using ion exchange resin (IER) collectors. Deposition was measured in forest clearings (bulk deposition) and under jack pine canopies (throughfall). As noted previously for other pollutants, throughfall deposition of...

High frequency and large deposition of acid fog on high elevation forest.

PubMed

Igawa, Manabu; Matsumura, Ko; Okochi, Hiroshi

2002-01-01

We have collected and analyzed fogwater on the mountainside of Mt. Oyama (1252 m) in the Tanzawa Mountains of Japan and observed the fog event frequency from the base of the mountain with a video camera. The fog event frequency increased with elevation and was observed to be present 46% of the year at the summit. The water deposition via throughfall increased with elevation because of the increase in fogwater interception and was about twice that via rain at the summit, where the air pollutant deposition via throughfall was several times that via rainwater. The dry deposition and the deposition via fogwater were dominant factors in the total ion deposition at high elevation sites. In a fog event, nitric acid, the major acid component on the mountain, is formed during the transport of the air mass from the base of the mountain along the mountainside, where gases including nitric acid deposit and are scavenged by fogwater. Therefore, high acidity caused by nitric acid and relatively low ion strength are observed in the fogwater at high elevation sites.

Properties of dissolved and total organic matter in throughfall, stemflow and forest floor leachate of Central European forests

NASA Astrophysics Data System (ADS)

Bischoff, S.; Schwarz, M. T.; Siemens, J.; Thieme, L.; Wilcke, W.; Michalzik, B.

2014-10-01

For the first time, we investigated the composition of dissolved organic matter (DOM) compared to total OM (TOM, consisting of DOM and particulate OM, POM) in throughfall, stemflow and forest floor leachate of beech and spruce forests using solid state 13C nuclear magnetic resonance spectroscopy. We hypothesized that the composition and properties of OM in forest ecosystem water samples differed between DOM and TOM and between the two tree species. Under beech, a contribution of phyllosphere-derived fresh POM was echoed in structural differences. Compared with DOM, TOM exhibited higher relative intensities for the alkyl C region, representing aliphatic C from less decomposed organic material, and lower relative intensities for lignin-derived and aromatic C of the aryl C region, resulting in lower aromaticity indices and reduced humification intensities. Since differences in the structural composition of DOM and TOM were less pronounced under spruce than under beech, we suspect a~tree species-related effect on the origin of OM composition and resulting properties (e.g. recalcitrance, allelopathic potential).

A simple tool for estimating throughfall nitrogen deposition in forests of western North America using lichens

Treesearch

Heather T. Root; Linda H. Geiser; Mark E. Fenn; Sarah Jovan; Martin A. Hutten; Suraj Ahuja; Karen Dillman; David Schirokauer; Shanti Berryman; Jill A. McMurray

2013-01-01

Anthropogenic nitrogen (N) deposition has had substantial impacts on forests of North America. Managers seek to monitor deposition to identify areas of concern and establish critical loads, which define the amount of deposition that can be tolerated by ecosystems without causing substantial harm. We present a new monitoring approach that estimates throughfall inorganic...

Seasonal sulfate deposition and export patterns for a small Appalachian watershed

Treesearch

Pamela J. Edwards; James D. Gregory; H. Lee Allen

1999-01-01

Sulfate deposition and exports from 1988–92 were analyzed for a small headwater catchment in north-centralWest Virginia.Annual sulfate inputs, estimated by applying throughfall-adjusted ratios to bulk deposition values, and outputs were approximately equal for the five years. Annual mean throughfall-adjusted deposition and export loads were 55.78 and 55.48 kg ha

Rates and Implications of Rainfall Interception in a Coastal Redwood Forest

Treesearch

Leslie M. Reid; Jack Lewis

2007-01-01

Throughfall was measured for a year at five-min intervals in 11 collectors randomly located on two plots in a second-growth redwood forest at the Caspar Creek Experimental Watersheds. Monitoring at one plot continued two more years, during which stemflow from 24 trees was also measured. Comparison of throughfall and stemflow to rainfall measured in adjacent clearings...

Summar throughfall and winter deposition in the San Bernardino mountains in southern California

Treesearch

Mark E. Fenn; Andrzej Bytnerowicz

1997-01-01

Summer throughfall and year-round precipitation chemistry were studied for three years at Barton Flats (BF), a low to moderate pollution site in the San Bernardino Mountains (SBM) in southern California. Winter fog plus dry deposition, and bulk deposition were also measured during one season at three sites traversing an atmospheric deposition gradient in the SBM....

Summer throughfall and winter deposition in the San Bernardino mountains in southern California

Treesearch

M. E. Fenn; A. Bytnerowicz

1997-01-01

Summer throughfall and year-round precipitation chemistry were studied for three years at Barton Flats (BF), a low to moderate pollution site in the San Bernardino Mountains (SBM) in southern California. Winter fog plus dry deposition, and bulk deposition were also measured during one season at three sites traversing an atmospheric deposition gradient in the SBM....

Long-term effects of rainforest disturbance on the nutrient composition of throughfall, organic layer percolate and soil solution at Mt. Kilimanjaro.

PubMed

Schrumpf, Marion; Axmacher, Jan C; Zech, Wolfgang; Lehmann, Johannes; Lyaruu, Herbert V C

2007-04-15

At the lower parts of the forest belt at Mt. Kilimanjaro, selective logging has led to a mosaic of mature forest, old secondary forests ( approximately 60 years), and old clearings ( approximately 10 years) covered by shrub vegetation. These variations in the vegetation are reflected by differences in nutrient leaching from the canopy and in both amount and quality of litter reaching the ground, thereby also influencing mineralization rates and the composition of seepage water in litter percolate and soil solution. The aim of this study was to investigate how above- and belowground nutrient dynamics vary between regeneration stages, and if forest regeneration at the clearings is hampered by a deterioration of abiotic site conditions. K, Mg, Ca, Na and N compounds were analysed in rainfall, throughfall, organic layer percolate and the soil solution to a depth of 1.00 m at three clearings, three secondary forest and four mature forest sites. Element fluxes via throughfall showed only small variations among regeneration stages except for K and NO(3)-N. With 57-83 kg ha(-1) a(-1)and 2.6-4.1 kg ha(-1) a(-1) respectively, K and NO(3)-N fluxes via throughfall were significantly higher at the clearings than at the mature forest sites (32-37 and 0.7-1.0 kg ha(-1) a(-1) for K and NO(3)-N). In organic layer percolate and in soil solution at 0.15-m soil depth, concentrations of K, Mg, Ca and N were highest at the clearings. In the organic layer percolate, median K concentrations were e.g. 7.4 mg l(-1) for the clearings but only 1.4 mg l(-1) for the mature forests, and for NO(3)-N, median concentrations were 3.1 mg l(-1) for the clearings but only 0.92 mg l(-1) for the mature forest sites. Still, differences in annual means between clearings and mature forests were not always significant due to a high variability within the clearings. With the exception of NO(3)-N, belowground nutrient concentrations in secondary forests ranged between concentrations in mature forests and clearings. Vegetation type-specific differences decreased with increasing soil depths in the soil solution. Overall, the opening of the forest led to a higher spatial and seasonal variation of nutrient concentrations in the seepage water. These results suggest differences in both mineralization rates and in nutrient budgeting at different regeneration stages. Since nutrient availability was highest at the clearings and no compaction of the soil was observed, deterioration of soil properties did not seem to be the main reason for the impeded regeneration on the clearings.

Element budgets of two contrasting catchments in the Black Forest (Federal Republic of Germany)

NASA Astrophysics Data System (ADS)

Feger, K. H.; Brahmer, G.; Zöttl, H. W.

1990-08-01

Rainfall and throughfall inputs of all major cations and anions, via open-field bulk precipitation and canopy throughfall, are compared with streamwater outputs in two forested catchments at higher altitudes of the Black Forest. The sites differ considerably in terms of bedrock geology, soil type, soilwater characteristics, topography, and forest management history. Deposition at both sites is almost equal and, in contrast to other forest areas in Central Europe, of a low-to-moderate level. Dry deposition does not seem to play an important role. Distinct differences in the elemental output emerge owing to the differing site conditions. At Villingen, deposited nitrogen is almost totally retained, whereas at Schluchsee, nitrogen output and input are of the same order of magnitude. This is consistent with the different nitrogen nutrition level of the stands, microbial turnover in the soil, and former management practices (change of tree species, excessive nutrient export). Sulphur is not retained in either of the catchments. At Schluchsee, sulphur export exceeds input from canopy throughfall by a factor of 2.5. The higher output rates, both of nitrogen and sulphur at Schluchsee, are due to the much higher microbial mineralization of organic matter as shown by previous incubation tests. Differences in cation and proton export are mainly caused by a different drainage pattern. In contrast to the Schluchsee catchment, where vertical water pathways prevail, the streamwater solute output at Villingen is dominated by a shallow subsurface runoff. Atmospheric deposition is a contributing, but not the dominant, factor in the biogeochemical cycling at these sites. Hence, a generally applicable quantitative definition of 'critical loads', especially for nitrogen, is illusory and the use of such numbers will be misleading.

Canopy structural alterations to nitrogen functions of the soil microbial community in a Quercus virginiana forest

NASA Astrophysics Data System (ADS)

Moore, L. D.; Van Stan, J. T., II; Rosier, C. L.; Gay, T. E.; Wu, T.

2014-12-01

Forest canopy structure controls the timing, amount and chemical character of precipitation supply to soils through interception and drainage along crown surfaces. Yet, few studies have examined forest canopy structural connections to soil microbial communities (SMCs), and none have measured how this affects SMC N functions. The maritime Quercus virginiana Mill. (southern live oak) forests of St Catherine's Island, GA, USA provide an ideal opportunity to examine canopy structural alterations to SMCs and their functioning, as their throughfall varies substantially across space due to dense Tillandsia usneoides L. (spanish moss) mats bestrewn throughout. To examine the impact of throughfall variability on SMC N functions, we examined points along the canopy coverage continuum: large canopy gaps (0%), bare canopy (50-60%), and canopy of heavy T. usneoides coverage (>=85%). Five sites beneath each of the canopy cover types were monitored for throughfall water/ions and soil leachates chemistry for one storm each month over the growing period (7 months, Mar-2014 to Sep-2014) to compare with soil chemistry and SMC communities sampled every two months throughout that same period (Mar, May, Jul, Sep). DGGE and QPCR analysis of the N functioning genes (NFGs) to characterize the ammonia oxidizing bacterial (AOB-amoA), archaea (AOA-amoA), and ammonification (chiA) communities were used to determine the nitrification and decomposition potential of these microbial communities. PRS™-probes (Western Ag Innovations Inc., Saskatoon, Canada) were then used to determine the availability of NO3-N and NH4+N in the soils over a 6-week period to evaluate whether the differing NFG abundance and community structures resulted in altered N cycling.

Monitoring nitrogen deposition in throughfall using ion exchange resin columns: a field test in the San Bernardino Mountains

Treesearch

Mark E. Fenn; Mark A. Poth

2004-01-01

Conventional throughfall collection methods are labor intensive and analytically expensive to implement at broad scales. This study was conducted to test an alternative approach requiring infrequent sample collection and a greatly reduced number of chemical analyses. The major objective of the study was to determine the feasibility of using ion exchange resin (IER) to...

Throughfall in a Puerto Rican lower montane rain forest: A comparison of sampling strategies

Treesearch

F. Holwerda; F.N. Scatena; L.A. Bruijnzeel

2006-01-01

During a one-year period, the variability of throughfall and the standard errors of the means associated with different gauge arrangements were studied in a lower montane rain forest in Puerto Rico. The following gauge arrangements were used: (1) 60 fixed gauges, (2) 30 fixed gauges, and (3) 30 roving gauges. Stemflow was measured on 22 trees of four different species...

Precipitation nutrients in the open and under two forests in Minnesota

Treesearch

Elon S. Verry; D.R. Timmons

1977-01-01

Concentrations of N, P, K, Ca, Mg, and Na were measured in rain and snow in the open, and in throughfall and stemflow under black spruce and aspen forests in north-central Minnesota. Concentrations of total P in rain and black spruce throughfall were inversely related to storm size. Annual precipitation nutrient inputs to the forest floor were calculated for each site...

Detecting spatial structures in throughfall data: The effect of extent, sample size, sampling design, and variogram estimation method

NASA Astrophysics Data System (ADS)

Voss, Sebastian; Zimmermann, Beate; Zimmermann, Alexander

2016-09-01

In the last decades, an increasing number of studies analyzed spatial patterns in throughfall by means of variograms. The estimation of the variogram from sample data requires an appropriate sampling scheme: most importantly, a large sample and a layout of sampling locations that often has to serve both variogram estimation and geostatistical prediction. While some recommendations on these aspects exist, they focus on Gaussian data and high ratios of the variogram range to the extent of the study area. However, many hydrological data, and throughfall data in particular, do not follow a Gaussian distribution. In this study, we examined the effect of extent, sample size, sampling design, and calculation method on variogram estimation of throughfall data. For our investigation, we first generated non-Gaussian random fields based on throughfall data with large outliers. Subsequently, we sampled the fields with three extents (plots with edge lengths of 25 m, 50 m, and 100 m), four common sampling designs (two grid-based layouts, transect and random sampling) and five sample sizes (50, 100, 150, 200, 400). We then estimated the variogram parameters by method-of-moments (non-robust and robust estimators) and residual maximum likelihood. Our key findings are threefold. First, the choice of the extent has a substantial influence on the estimation of the variogram. A comparatively small ratio of the extent to the correlation length is beneficial for variogram estimation. Second, a combination of a minimum sample size of 150, a design that ensures the sampling of small distances and variogram estimation by residual maximum likelihood offers a good compromise between accuracy and efficiency. Third, studies relying on method-of-moments based variogram estimation may have to employ at least 200 sampling points for reliable variogram estimates. These suggested sample sizes exceed the number recommended by studies dealing with Gaussian data by up to 100 %. Given that most previous throughfall studies relied on method-of-moments variogram estimation and sample sizes ≪200, currently available data are prone to large uncertainties.

Deposition pattern and throughfall fluxes in secondary cool temperate forest, South Korea

NASA Astrophysics Data System (ADS)

Kumar Gautam, Mukesh; Lee, Kwang-Sik; Song, Byeong-Yeol

2017-07-01

Chemistry and deposition fluxes in the rainfall and throughfall of red pine (Pinus densiflora), black locust (Robinia pseudoacacia), and chestnut (Castanea crenata) monocultures, and mixed red pine-black locust-chestnut stands were examined in a nutrient-limited cool temperate forest of central South Korea. Throughfall was enriched in both basic and acidic constituents relative to rainfall, suggesting that both dry deposition and canopy leaching are important sources of throughfall constituents. Net throughfall fluxes (NTFs) of cations and anions significantly differed among four different stands as well as seasonally. Red pine exhibited highest fluxes (TF and NTF) for Ca2+, black locust for K+, mixed stands for Mg2+, and chestnut for Na+. In contrast, NTF of SO42-, NO3-, and NH4+was highest in the red pine, intermediate in the chestnut and mixed stands, and lowest in the black locust. In general, canopy uptake of H+ and NH4+ for all stands was higher in summer than in winter. Dry deposition appears to play a major role in atmospheric deposition to this cool temperate forest, especially in summer. Dry deposition for both cations and anions displayed high spatial variability, even though stands were adjacent to one another and experienced identical atmospheric deposition loads. Canopy leaching of K+ (95-78% of NTF), Mg2+ (92-23% of NTF), and Ca2+ (91-12% of NTF) was highest for the black locust, lowest for chestnut, and intermediate for the red pine and mixed stands. The present study documented significant changes in throughfall chemistry and NTF among different forest stands, which presumably be related with the differences in the canopy characteristics and differences in their scavenging capacity for dry deposition and canopy exchange. Difference in the canopy retention of H+ and base cation leaching suggests that canopy exchange was mainly driven by weak acid excretion and lesser by H+ exchange reaction. Our results indicate that despite a high base cation deposition, a combination of higher input of acidifying constituents, low soil pH, and total acidic deposition approaching South Korean critical loads make regional forest vulnerable to acidification.

Atmospheric Inputs of Nitrogen, Carbon, and Phosphorus across an Urban Area: Unaccounted Fluxes and Canopy Influences

NASA Astrophysics Data System (ADS)

Decina, Stephen M.; Templer, Pamela H.; Hutyra, Lucy R.

2018-02-01

Rates of atmospheric deposition are declining across the United States, yet urban areas remain hotspots of atmospheric deposition. While past studies show elevated rates of inorganic nitrogen (N) deposition in cities, less is known about atmospheric inputs of organic N, organic carbon (C), and organic and inorganic phosphorus (P), all of which can affect ecosystem processes, water quality, and air quality. Further, the effect of the tree canopy on amounts and forms of nutrients reaching urban ground surfaces is not well-characterized. We measured growing season rates of total N, organic C, and total P in bulk atmospheric inputs, throughfall, and soil solution around the greater Boston area. We found that organic N constitutes a third of total N inputs, organic C inputs are comparable to rural inputs, and inorganic P inputs are 1.2 times higher than those in sewage effluent. Atmospheric inputs are enhanced two-to-eight times in late spring and are elevated beneath tree canopies, suggesting that trees augment atmospheric inputs to ground surfaces. Additionally, throughfall inputs may directly enter runoff when trees extend above impervious surfaces, as is the case with 26.1% of Boston's tree canopy. Our results indicate that the urban atmosphere is a significant source of elemental inputs that may impact urban ecosystems and efforts to improve water quality, particularly in terms of P. Further, as cities create policies encouraging tree planting to provide ecosystem services, locating trees above permeable surfaces to reduce runoff nutrient loads may be essential to managing urban biogeochemical cycling and water quality.

Ptaquiloside from bracken in stream water at base flow and during storm events.

PubMed

Clauson-Kaas, Frederik; Ramwell, Carmel; Hansen, Hans Chr B; Strobel, Bjarne W

2016-12-01

The bracken fern (Pteridium spp.) densely populates both open and woodland vegetation types around the globe. Bracken is toxic to livestock when consumed, and a group of potent illudane-type carcinogens have been identified, of which the compound ptaquiloside (PTA) is the most abundant. The highly water soluble PTA has been shown to be leachable from bracken fronds, and present in the soil and water below bracken stands. This has raised concerns over whether the compound might pose a risk to drinking water sources. We investigated PTA concentrations in a small stream draining a bracken-infested catchment at base flow and in response to storm events during a growth season, and included sampling of the bracken canopy throughfall. Streams in other bracken-dominated areas were also sampled at base flow for comparison, and a controlled pulse experiment was conducted in the field to study the in-stream dynamics of PTA. Ptaquiloside concentrations in the stream never exceeded 61 ng L -1 in the base flow samples, but peaked at 2.2 μg L -1 during the studied storm events. The mass of PTA in the stream, per storm event, was 7.5-93 mg from this catchment. A clear temporal connection was observed between rainfall and PTA concentration in the stream, with a reproducible time lag of approx. 1 h from onset of rain to elevated concentrations, and returning rather quickly (about 2 h) to base flow concentration levels. The concentration of PTA behaved similar to an inert tracer (Cl - ) in the pulse experiment over a relative short time scale (minutes-hours) reflecting no PTA sorption, and dispersion and dilution considerably lowered the observed PTA concentrations downstream. Bracken throughfall revealed a potent and lasting source of PTA during rainfall, with concentrations up to 169 μg L -1 , that did not decrease over the course of the event. In the stream, the throughfall contribution to PTA cannot be separated from a possible below-ground input from litter, rhizomes and soil. Catchment-specific factors such as the soil pH, topography, hydrology, and bracken coverage will evidently affect the level of PTA observed in the receiving stream, as well as the distance from bracken, but time since precipitation seems most important. Studying PTA loads and transport in surface streams fed by bracken-infested catchments, simply taking occasional grab samples will not capture the precipitation-linked pulses. The place and time of sampling governs the findings, and including event-based sampling is essential to provide a more complete picture of PTA loads to surface water. Copyright © 2016 Elsevier Ltd. All rights reserved.

Atmospheric deposition and canopy exchange processes in alpine forest ecosystems (northern Italy)

NASA Astrophysics Data System (ADS)

Balestrini, Raffaella; Tagliaferri, Antonio

Throughfall and bulk precipitation chemistry were studied for five years (June 1994-May 1999) at two high elevation forest sites (Val Gerola and Val Masino) which were known to differ in terms of tree health, as assessed by live crown condition. The ion concentration of bulk precipitation samples did not differ significantly between sites, except for Mg 2+, while the throughfall concentrations differed in the measured values of H +, N-NO 3-, Cl -, Na +, K +, DOC and weak organic acids. The results of the application of the canopy exchange model indicated a higher contribution from the dry deposition of N-NO 3-, N-NH 4+ and H + at Val Gerola, where the damage symptoms were more evident. In addition, the canopy leaching of Ca 2+, K + and weak organic acids were 47%, 21% and 27% higher at Val Gerola than at Val Masino. Annual SO 42- deposition fluxes (21.3 kg ha -1 yr -1 at Val Masino and 23.6 kg ha -1 yr -1 at Val Gerola) were similar to those reported for moderately polluted European and U.S. sites. Annual N loads were 13.6 and 13.1 kg ha -1 yr -1 in the bulk input, and 15.0 and 18.0 kg ha -1 yr -1 in throughfall inputs, at Val Masino and Val Gerola, respectively. The contribution of the organic fraction to the total N atmospheric deposition load is significant, constituting 17% of the bulk flux and 40% of the throughfall flux. Measured nitrogen loads exceed the critical nutrient loads by several kg N ha -1 at both stations. In particular the nitrogen throughfall load at Val Gerola was about 3 times higher than the critical values.

Trace metals in bulk precipitation and throughfall in a suburban area of Japan

NASA Astrophysics Data System (ADS)

Hou, H.; Takamatsu, T.; Koshikawa, M. K.; Hosomi, M.

Throughfall and bulk precipitation samples were collected monthly for 1.5 years over bare land and under canopies of Japanese cedar ( Cryptomeria japonica), Japanese red pine ( Pinus densiflora), Japanese cypress ( Chamaecyparis obtusa), and bamboo-leafed oak ( Quercus myrsinaefolia) in a suburban area of Japan. Samples were analyzed for dissolved Al, Mn, Fe, Cu, Zn, Ag, In, Sn, Sb and Bi by ICP-AES and ICP-MS. The metal concentrations were higher in throughfall, especially that of C. japonica, than bulk precipitation. Enrichment ratios (ERs: ratios of metal concentrations in throughfall to those in bulk precipitation) ranged from 2.5 (Zn) to 5.3 (Ag) (3.9 on average), and ERs for slightly soluble metals were generally higher than those for easily soluble metals. Concentrations of Mn, Fe, Cu, and Zn accounted for 99% of the total concentration of heavy metals in rainwater, whereas those of rare metals such as Ag, In, Sn, and Bi totaled <0.23%. Average concentrations of rare metals were 0.002 and 0.010 μg l -1 for Ag, 0.001 and 0.005 μg l -1 for In, 0.062 and 0.21 μg l -1 for Sn, and 0.006 and 0.023 μg l -1 for Bi in bulk precipitation and throughfall, respectively. The metal concentrations in rainwater were negatively correlated to the volume of rainwater, indicating that washout is the main mechanism that incorporates metals into rainwater. From the enrichment factors, that is, (X/Al) rain/(X/Al) crust, metals other than Fe were shown to be more enriched in rainwater than in the Earth's crust, including those present as a result of leaching from soil dust (Mn) and from anthropogenic sources (Cu, Zn, Ag, In, Sn, Sb, and Bi).

Estimating Chemical Exchange between Atmospheric Deposition and Forest Canopy in Guizhou, China.

PubMed

Li, Wei; Gao, Fang; Liao, Xueqin

2013-01-01

To evaluate the effects of atmospheric deposition on forest ecosystems, wet-only precipitation and throughfall samples were collected in two forest types (Masson pine [ Lamb.] forests and mixed conifer and broadleaf forests) in the Longli forest in the Guizhou province of southwestern China for a period of 21 successive months from April 2007 to December 2008. The pH and chemical components of precipitation and throughfall were analyzed. In addition, the canopy budget model was applied to distinguish between in-canopy and atmospheric sources of chemical compounds. Canopy leaching and total potentially acidifying deposition fluxes were calculated. The results showed that the average pH and the concentration of ions in throughfall were higher than those in precipitation, with the exception of the NH concentration. Dry deposition of S and N accumulated more in Masson pine forests than in mixed conifer and broadleaf forests. Canopy leaching was the most significant source of base cations in forest throughfall, which was higher in the mixed forests than in the coniferous forests. Anions in throughfall deposition in Masson pine forests exceeded those in the mixed forests. Higher total potentially acidifying deposition fluxes reflected the more effective amounts of acid delivered to Masson pine forests compared with mixed conifer and broadleaf forests. In addition, acid deposition induced the leaching and loss of nutrient ions such as Mg, K, and Ca. Although the trees of the studied areas have not shown any symptoms of cation loss, a potentially harmful influence was engendered by atmospheric deposition in the two forest types in the Longli area. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

Oxidized Nitrogen in Precipitation, Throughfall, and Streamfall from a Forested Watershed in Oklahoma

USGS Publications Warehouse

Lawrence, Stephen J.; Wigington, Parker J.

1987-01-01

Oxidized nitrogen (nitrite plus nitrate N) concentrations were measured from bulk precipitation, bulk throughfall, and screamflow in a 7. 86 hectare forested watershed in southeastern Oklahoma during the wet season from March through June 1983. Oxidized nitrogen inputs comparable to results of other studies were recorded during the 19 rainstorms sampled. Oxidized nitrogen concentrations appeared to increase after rainfall interacted with the pine and hardwood canopies and were inversely related to both rainfall and throughfall depth. Oxidized N concentrations in streamflow were greatest during the rising limb of storm flow with subsequent decreases during the falling limb of storm hydrographs and lowest during base flow. The oxidized N inputs from bulk precipitation were considerably greater than outputs from streamflow resulting in a net retention of oxidized nitrogen within the watershed during the study period.

Source diagnostics of polycyclic aromatic hydrocarbons in urban road runoff, dust, rain and canopy throughfall.

PubMed

Zhang, Wei; Zhang, Shucai; Wan, Chao; Yue, Dapan; Ye, Youbin; Wang, Xuejun

2008-06-01

Diagnostic ratios and multivariate analysis were utilized to apportion polycyclic aromatic hydrocarbon (PAH) sources for road runoff, road dust, rain and canopy throughfall based on samples collected in an urban area of Beijing, China. Three sampling sites representing vehicle lane, bicycle lane and branch road were selected. For road runoff and road dust, vehicular emission and coal combustion were identified as major sources, and the source contributions varied among the sampling sites. For rain, three principal components were apportioned representing coal/oil combustion (54%), vehicular emission (34%) and coking (12%). For canopy throughfall, vehicular emission (56%), coal combustion (30%) and oil combustion (14%) were identified as major sources. Overall, the PAH's source for road runoff mainly reflected that for road dust. Despite site-specific sources, the findings at the study area provided a general picture of PAHs sources for the road runoff system in urban area of Beijing.

FLASHFlux Info

Atmospheric Science Data Center

2013-05-20

... Surface Emissivity Cloud Area Fraction Cloud Effective Pressure Cloud Effective Temperature Cloud Effective Height Cloud Top Pressure Cloud Base Pressure Cloud Particle Phase Liquid Water Path Ice Water Path Water Particle Radius Ice Particle ...

CERES-MISR Info

Atmospheric Science Data Center

2013-05-20

... Surface Albedo Cloud Area Fraction Cloud Effective Pressure Cloud Effective Temperature Cloud Effective Height Cloud Top Pressure Cloud Base Pressure Cloud Particle Phase Liquid Water Path Ice Water Path Water Particle Radius Ice Particle ...

CERES CRS Info

Atmospheric Science Data Center

2013-05-17

... Flux - Down Cloud Area Fraction Cloud Effective Pressure Cloud Effective Temperature Cloud Effective Height Cloud Top Pressure Cloud Base Pressure Cloud Particle Phase Liquid Water Path Ice Water Path Water Particle Radius Ice Particle ...

CERES SSF Current Info

Atmospheric Science Data Center

2013-05-17

... Surface Albedo Cloud Area Fraction Cloud Effective Pressure Cloud Effective Temperature Cloud Effective Height Cloud Top Pressure Cloud Base Pressure Cloud Particle Phase Liquid Water Path Ice Water Path Water Particle Radius Ice Particle ...

Controls on mercury and methylmercury deposition for two watersheds in Acadia National Park, Maine.

PubMed

Johnson, K B; Haines, T A; Kahl, J S; Norton, S A; Amirbahman, Aria; Sheehan, K D

2007-03-01

Throughfall and bulk precipitation samples were collected for two watersheds at Acadia National Park, Maine, from 3 May to 16 November 2000, to determine which landscape factors affected mercury (Hg) deposition. One of these watersheds, Cadillac Brook, burned in 1947, providing a natural experimental design to study the effects of forest type on deposition to forested watersheds. Sites that face southwest received the highest Hg deposition, which may be due to the interception of cross-continental movement of contaminated air masses. Sites covered with softwood vegetation also received higher Hg deposition than other vegetation types because of the higher scavenging efficiency of the canopy structure. Methyl mercury (MeHg) deposition was not affected by these factors. Hg deposition, as bulk precipitation and throughfall was lower in Cadillac Brook watershed (burned) than in Hadlock Brook watershed (unburned) because of vegetation type and watershed aspect. Hg and MeHg inputs were weighted by season and vegetation type because these two factors had the most influence on deposition. Hg volatilization was not determined. The total Hg deposition via throughfall and bulk precipitation was 9.4 microg/m(2)/year in Cadillac Brook watershed and 10.2 microg/m(2)/year in Hadlock Brook watershed. The total MeHg deposition via throughfall and bulk precipitation was 0.05 microg/m(2)/year in Cadillac Brook watershed and 0.10 microg/m(2)/year in Hadlock Brook watershed.

137Cs dynamics in the forest of Fukushima after the nuclear power plant accident in March 2011

NASA Astrophysics Data System (ADS)

Endo, I.; Ohte, N.; Iseda, K.; Kobayashi, N.; Hirose, A.; Tanoi, K.

2013-12-01

The accident of Fukushima Daiichi nuclear power plant after the earthquake and Tsunami in March 11th 2011, caused large amount of radioactive Cesium (137Cs) emission into the environment. In the region of Fukushima Prefecture, forest dominates more than 70 % of the land area. River water from the forest area is used for food production and also for drinking water. Thus, it is important to understand the dynamics of 137Cs deposited in the forest to predict how the radioactive Cs diffuse and discharge from the forest catchments. We measured 137Cs concentration of the tree body, litter fall, throughfall, and stemflow, in order to clarify how 137Cs deposited on the above ground biomass of the forest are transported to the forest floor. We set forest site at the upstream part of Kami-Oguni River catchment, northern part of Fukushima Prefecture. Three plots (2 deciduous stands and 1 Japanese cedar (Cryptomeria japonica) plantation stand) were set in the forest site. Quercus serrata and C. japonica, which are representative tree species, were chosen at each plot and concentration of 137Cs on the bark, sapwood and heartwood were measured every 2 m from the ground to tree top. From each plot, 137Cs concentration of leaf litter was measured among species. Water samples of throughfall and stemflow were filtered and 137Cs concentration in suspended matter was measured. 137Cs was deposited on the bark of Q. serrata at high concentration (9-18 kBq/kg) but there were no clear relationship between tree height and concentration. 137Cs concentration of the sapwood (41 Bq/kg) was relatively higher than that of the heartwood (5 Bq/kg). It was suggested that 137Cs may be absorbed from bark and/or root. The concentration of 137Cs deposited in leaf litter varied from non-detected level to above 30 kBq/kg. The concentration was higher at evergreen tree than deciduous tree. It is considered that the litter of evergreen tree was derived from leaves on the tree canopy at the time of the accident. Also, though the leaves of deciduous trees had not been emerged at the time of the accident, significant levels of 137Cs on those leaves suggest that 137Cs may have translocated from some part of tree body. The concentration of 137Cs in rain water was below detection level. However, both throughfall and stemflow contained 137Cs at every plot. From these results, it is suggested that 137Cs deposited on the above ground biomass of the forest continues to move to the forest floor by litter fall and rain event.

Integrative measurements focusing on carbon, energy and water fluxes at the forest site 'Hohes Holz' and the grassland 'Grosses Bruch'

NASA Astrophysics Data System (ADS)

Rebmann, Corinna; Claudia, Schütze; Sara, Marañón-Jiménez; Sebastian, Gimper; Matthias, Zink; Luis, Samaniego; Matthias, Cuntz

2017-04-01

The reduction of greenhouse gas (GHG) emissions and the optimization of Carbon sequestration by ecosystems have become priority objectives for current climate change policies. In this context, the long term research project TERENO and the research infrastructure ICOS have been established. The eddy covariance technique allows obtaining an integrative estimate of the ecosystem carbon, water and energy balances at the ecosystem level. The relative contributions of evaporation and transpiration as well as carbon sources and sinks need, however, to be determined separately for thorough process understanding. Two different ecosystem observatories have recently been established in the Magdeburger Börde: a deciduous forest (Hohes Holz) and a meadow (Grosses Bruch). A comprehensive system of instrumentation provides continuous data for the evaluation of energy, water and carbon fluxes at the 1500 ha large forest site, including a 50 m high eddy covariance (EC) tower for micrometeorological investigations in different heights above and below canopy, throughfall and stem flow sensors, a soil moisture and temperature sensor network, soil respiration chambers, sap flow sensors, and ancillary analysis of trees such a dendrometer and leaf area index measurements. Eddy covariance measurements allow the assessment of the carbon (Net Ecosystem Exchange, NEE) and water balance at the ecosystem scale. To better understand the contributing processes we partition water und carbon fluxes of the forest ecosystem by different methods. Tower-based data of NEE are therefore complemented and validated by continuous automatic and manual campaign measurements of soil effluxes and their drivers. Water fluxes into the ecosystem are partitioned by stem flow and throughfall measurements and a distributed soil moisture network. Gap fraction in the forest has a strong influence on the distribution on the water fluxes and is therefore determined on a regular basis. Since the establishment of the flux sites, two abnormally dry years (2015 and 2016) occurred. Fluxes from these years are evaluated in detail here. These data are additionally used to evaluate the drought assessment of the German Drought Monitor (www.ufz.de/droughtmonitor).

Impacts of Wildfire on Interception Losses and Net Precipitation in a Sub-Alpine Rocky Mountain Watershed in Alberta, Canada.

NASA Astrophysics Data System (ADS)

Williams, C.; Silins, U.; Wagner, M. J.; Bladon, K. D.; Martens, A. M.; Anderson, A.; Stone, M.; Emelko, M. B.

2014-12-01

Interception of precipitation in sub-alpine forests is likely to be strongly reduced after wildfire, potentially producing large increases in net precipitation. Objectives of this study were to describe changes in rainfall and snow interception, and net precipitation after the severe 2003 Lost Creek wildfire as part of the Southern Rockies Watershed Project in the south-west Rocky Mountains of Alberta, Canada. Throughfall troughs and stemflow gauges were used to explore relationships between throughfall, stemflow, and net rainfall with variation in gross rainfall in burned and undisturbed stands during the summers of 2006-2008. These relationships were used to scale the effects of the wildfire on net rainfall for the first decade after the wildfire (2004-2013) using a 10 year rainfall record in the watershed. Annual snowpack surveys (5 snow courses in each of burned and reference stands) measured peak snowpack depth, density, and snow water equivalent (SWE) for this same period. Mean annual P was 1140 mm (684-1519 mm) during the first 10 years after the wildfire, with 61% falling as snow. Throughfall and stemflow in the burned forest accounted for 86% and 7% of gross rainfall, respectively, compared with 53% and 0.002% in the unburned stands in the summers of 2006-2008. Scaled rainfall interception relationships (=f(rainfall event size)) indicated annual increases in net rainfall were 192 mm/yr (133-347 mm) for 10 years after the fire. Similarly, mean increases in peak SWE were 134 mm/yr (93-216 mm). Collectively, the mean increase in net precipitation was 325 mm/yr (226-563 mm; 29%) for the first decade after the wildfire. Hydrologic forcing by increased net precipitation may be a particularly important element of wildfire impacts on sub-alpine watersheds. Furthermore, because of the very slow growth rates of sub-alpine forests, increases in net precipitation are likely to persist and affect precipitation-runoff relationships for decades in these environments.

Satellite Remote Sensing of the Liquid Water Sensitivity in Water Clouds

NASA Technical Reports Server (NTRS)

Han, Qing-Yuan; Rossow, William B.; Welch, Ronald; Zeng, Jane; Jansen, James E. (Technical Monitor)

2001-01-01

In estimation of the aerosol indirect effect, cloud liquid water path is considered either constant (Twomey effect) or increasing with enhanced droplet number concentrations (drizzle-suppression effect, or Albrecht effect) if cloud microphysics is the prevailing mechanism during the aerosol-cloud interactions. On the other hand, if cloud thermodynamics and dynamics are considered, the cloud liquid water path may be decreased with increasing droplet number concentration, which is predicted by model calculations and observed in ship-track and urban influence studies. This study is to examine the different responses of cloud liquid water path to changes of cloud droplet number concentration. Satellite data (January, April, July and October 1987) are used to retrieve the cloud liquid water sensitivity, defined as the changes of liquid water path versus changes of column droplet number concentrations. The results of a global survey reveal that 1) in at least one third of the cases the cloud liquid water sensitivity is negative, and the regional and seasonal variations of the negative liquid water sensitivity are consistent with other observations; 2) cloud droplet sizes are always inversely proportional to column droplet number concentrations. Our results suggest that an increase of cloud droplet number concentration leads to reduced cloud droplet size and enhanced evaporation, which weakens the coupling between water clouds and boundary layer in warm zones, decreases water supply from surface and desiccates cloud liquid water. Our results also suggest that the current evaluations of negative aerosol indirect forcing by global climate models (GCM), which are based on Twomey effect or Albrecht effect, may be overestimated.

Development of a New Model for Accurate Prediction of Cloud Water Deposition on Vegetation

NASA Astrophysics Data System (ADS)

Katata, G.; Nagai, H.; Wrzesinsky, T.; Klemm, O.; Eugster, W.; Burkard, R.

2006-12-01

Scarcity of water resources in arid and semi-arid areas is of great concern in the light of population growth and food shortages. Several experiments focusing on cloud (fog) water deposition on the land surface suggest that cloud water plays an important role in water resource in such regions. A one-dimensional vegetation model including the process of cloud water deposition on vegetation has been developed to better predict cloud water deposition on the vegetation. New schemes to calculate capture efficiency of leaf, cloud droplet size distribution, and gravitational flux of cloud water were incorporated in the model. Model calculations were compared with the data acquired at the Norway spruce forest at the Waldstein site, Germany. High performance of the model was confirmed by comparisons of calculated net radiation, sensible and latent heat, and cloud water fluxes over the forest with measurements. The present model provided a better prediction of measured turbulent and gravitational fluxes of cloud water over the canopy than the Lovett model, which is a commonly used cloud water deposition model. Detailed calculations of evapotranspiration and of turbulent exchange of heat and water vapor within the canopy and the modifications are necessary for accurate prediction of cloud water deposition. Numerical experiments to examine the dependence of cloud water deposition on the vegetation species (coniferous and broad-leaved trees, flat and cylindrical grasses) and structures (Leaf Area Index (LAI) and canopy height) are performed using the presented model. The results indicate that the differences of leaf shape and size have a large impact on cloud water deposition. Cloud water deposition also varies with the growth of vegetation and seasonal change of LAI. We found that the coniferous trees whose height and LAI are 24 m and 2.0 m2m-2, respectively, produce the largest amount of cloud water deposition in all combinations of vegetation species and structures in the experiments.

Evaporation components of a boreal forest: variations during the growing season

NASA Astrophysics Data System (ADS)

Grelle, A.; Lundberg, A.; Lindroth, A.; Morén, A.-S.; Cienciala, E.

1997-10-01

To improve the understanding of interactions between the boreal forest and the climate system as a key issue for global climate change, the water budget of a mixed pine and spruce forest in central Sweden was estimated by measurements of the water flux components and the total evaporation flux during the period 16 May-31 October 1995. Total evaporation was measured using eddy correlation and the components were obtained using measurements of precipitation, throughfall, tree transpiration, and forest floor evaporation. On a daily basis, tree transpiration was the dominant evaporation component during the vegetation period. However, it could be efficiently blocked by a wet canopy associated with large interception evaporation. The accumulated total evaporation was 399 mm, transpiration was 243 mm, forest floor evaporation was 56 mm and interception evaporation was 74 mm. The accumulated sum of interception, transpiration, and floor evaporation was 51 mm larger than the actual measured total evaporation. This difference was mainly attributed to the fact that transpiration was measured in a rather dense 50-year-old stand while total evaporation represented the average conditions of older, roughly 100-year-old stands. To compare eddy-correlation measurements with small-scale measurements of evaporation components, a source area analysis was made to select the flux data that give the best representation of the investigated stand. Especially under stable atmospheric conditions the requirements for surface homogeneity were very high and extreme care had to be taken to be aware of the flux source areas. Canopy water storage was determined by two methods: by the water balance of the canopy, which gave a result of 3.3 mm; and by the so-called minimum method based on plots of throughfall versus precipitation, which gave a much lower value of 1.5 mm. Seasonal interception evaporation constituted 30% of the precipitation.

Temporal and spatial variability of Fe and Mn in perched groundwater flowing through weathered argillite underlying a steep forested hillslope

NASA Astrophysics Data System (ADS)

Kim, H.; Bishop, J. K.

2013-12-01

Groundwater flowing through weathered bedrock dictates the runoff chemistry to streams in many catchments yet; its chemical evolution has been rarely documented. In particular, observations of Fe and Mn dynamics in groundwater are extremely challenging due to their high reactivity. To preserve the sample integrity for these elements we have developed a new sampling scheme that is applicable to autosamplers; a gravitational filtration system (GFS). GFS is capable of filtering samples by gravity within 30 minutes after the sampling. The GFS samples showed a good agreement with reference samples, which were collected following the standard sampling method for trace metals (i.e. immediate filtration and acidification). Since October 2011, GFS has been employed to monitor Fe and Mn in perched groundwater that moves through weathered argillite in an intensively instrumented hillslope (Rivendell), in the Angelo Coast Range Reserve. The study site is located at the headwaters of the Eel River, northern California, characterized by a typical coastal Californian Mediterranean climate. We collected groundwater samples at 3 wells along the hillslope (upslope (W10), mid-slope (W3) and near the creek (W1)) with 1-3 day intervals. Additionally, rainwater and throughfall samples were collected at a meadow near the hillslope and at the middle of the hillslope, respectively. The results from our observations indicate that Fe and Mn exhibit distinct spatial and temporal behavior under variable hydrologic conditions. The concentrations of Fe in throughfall vs. rainwater were similar (0.45μM vs. 0.49μM), but Mn in throughfall was 10-fold higher than that in rainwater (1.2 μM vs. 0.1 μM). In the early rainy season, W10's water table was deep (-18m) and Fe and Mn in W10 were 30-150 nM and 1-2 μM, respectively. As the rainy season proceeds, W10's water table rose by 4-6m, indicating the arrival of new water. At this time, Mn in W10 decreased to ~0.1 μM, synchronizing with the water table rise, and remained unchanged throughout the season. In contrast, Fe slowly declined to <10nM for this high water table regime. During the summer recession limb, Fe and Mn concentrations in W10 began to increase. During the dry summer, the concentrations of Fe and Mn at W3 were 2-3μM and 15-20 μM, respectively. At the beginning of the rainy seasons, the W3 water table slowly rose (<1 m) and both Fe and Mn decreased by 10-fold. The concentrations of Fe and Mn decreased to 20-70nM and 0.1 μM, respectively, when W3's water table became highly dynamic and fluctuated about 4 m. At W1, Fe and Mn remained in the 50-100nM and 5-10 μM ranges, respectively; however, the water table was extremely responsive to rainfall inputs. Mn in W1 was briefly diluted to <0.1 μM during large rainstorms and rebounded within several days. In the late summer of 2012, Fe and Mn in W1 increased up to 2-6 μM and 80 μM, respectively. These high-frequency observations of Fe and Mn will provide insight into the biogeochemical cycles of redox sensitive elements in upland terrains, allowing for better quantitative estimation of these elemental fluxes.

The effects of phenoseason and storm characteristics on throughfall solute washoff and leaching dynamics from a temperate deciduous forest canopy.

PubMed

Van Stan, John T; Levia, Delphis F; Inamdar, Shreeram P; Lepori-Bui, Michelle; Mitchell, Myron J

2012-07-15

Seasonal variations in the washoff and leaching dynamics of throughfall ionic fluxes represent a significant process affecting the biogeochemical cycling of forested ecosystems-particularly for temperate deciduous forests with distinct phenological seasons (or "phenoseasons"). Most studies on temperate deciduous forests aggregate seasonal throughfall fluxes to the leafed (growing) and leafless (dormant) periods, yet the phenological conditions controlling seasonality demand finer-scale demarcations that include the transitional phenoseasons (leaf senescence and emergence). To fill these gaps our study examines the washoff and leaching dynamics of Na(+), Mg(2+), K(+), Ca(2+), Cl(-), SO(4)(2-), and NO(3)(-) throughfall derived from bulk and sequentially sampled rain events across leafed, leafless and both transitional phenoseasons over a 3-year period (2008-2010). As throughfall washoff and leached solute fluxes are also closely-coupled to rainfall conditions, we further examine the effects of storm characteristics on phenoseasonal washoff-dominated (Na(+) and Cl(-)) and leaching-dominated (K(+), Ca(2+), Mg(2+)) fluxes through intrastorm event comparison plots and factorial MANOVA. Highly significant differences in leached and washoff solute fluxes were found across meteorological conditions (p<0.001) nested within phenoseasonal divisions (p<0.00001). Phenoseasonal washoff Na(+) and Cl(-) fluxes seemed to be more closely related to leaf area; whereas, leaching flux and canopy exchange of all solutes to correspond more with major phenological changes (when the canopies tend to be most metabolically active). The greatest differences in leached Mg(2+), K(+), Ca(2+), and SO(4)(2-) fluxes were not between the full leafed and leafless phenoseasons (33-80% difference), but between the transitional periods (80 to 200 fold greater during leaf senescence than leaf emergence). Intrastorm average canopy NO(3)(-) leaching, however, ranged from low losses (1 μmol(c)m(-2)h(-1)) to canopy uptake (-2 μmol(c)m(-2)h(-1)) during both transitional phenoseasons. K(+), Ca(2+), Mg(2+) were all markedly more exchangeable during senescence, with Ca(2+) and Mg(2+) being more tightly held by the canopy. Leaching rates and fluxes for all measured solutes were negligible to negative during emergence, except for K(+) and SO(4)(2-). Our results indicate that much of the variance in timing and magnitude of throughfall solute fluxes to forest soils within temperate deciduous ecosystems may be ascribed to phenologically-delineated seasons and storm conditions. Copyright © 2012 Elsevier B.V. All rights reserved.

Entrainment, Drizzle, and Cloud Albedo

NASA Technical Reports Server (NTRS)

Ackerman, A. S.; Kirkpatrick, J. P.; Stevens, D. E.; Toon, O. B.

2004-01-01

Increased aerosol and hence droplet concentrations in polluted clouds are expected to inhibit precipitation and thereby increase cloud water, leading to more reflective clouds that partially offset global warming. Yet polluted clouds are not generally observed to hold more water. Much of the uncertainty regarding the indirect aerosol effect stems from inadequate understanding of such changes in cloud water. Detailed simulations show that the relative humidity of air overlying stratocumulus is a leading factor determining whether cloud water increases or decreases when precipitation is suppressed. When the overlying air is dry, cloud water can decrease as droplet concentrations increase.

Global statistics of liquid water content and effective number density of water clouds over ocean derived from combined CALIPSO and MODIS measurements

NASA Astrophysics Data System (ADS)

Hu, Y.; Vaughan, M.; McClain, C.; Behrenfeld, M.; Maring, H.; Anderson, D.; Sun-Mack, S.; Flittner, D.; Huang, J.; Wielicki, B.; Minnis, P.; Weimer, C.; Trepte, C.; Kuehn, R.

2007-03-01

This study presents an empirical relation that links layer integrated depolarization ratios, the extinction coefficients, and effective radii of water clouds, based on Monte Carlo simulations of CALIPSO lidar observations. Combined with cloud effective radius retrieved from MODIS, cloud liquid water content and effective number density of water clouds are estimated from CALIPSO lidar depolarization measurements in this study. Global statistics of the cloud liquid water content and effective number density are presented.

Characterization of Cloud Water-Content Distribution

NASA Technical Reports Server (NTRS)

Lee, Seungwon

2010-01-01

The development of realistic cloud parameterizations for climate models requires accurate characterizations of subgrid distributions of thermodynamic variables. To this end, a software tool was developed to characterize cloud water-content distributions in climate-model sub-grid scales. This software characterizes distributions of cloud water content with respect to cloud phase, cloud type, precipitation occurrence, and geo-location using CloudSat radar measurements. It uses a statistical method called maximum likelihood estimation to estimate the probability density function of the cloud water content.

Determination of ice water path in ice-over-water cloud systems using combined MODIS and AMSR-E measurements

NASA Astrophysics Data System (ADS)

Huang, Jianping; Minnis, Patrick; Lin, Bing; Yi, Yuhong; Fan, T.-F.; Sun-Mack, Sunny; Ayers, J. K.

2006-11-01

To provide more accurate ice cloud microphysical properties, the multi-layered cloud retrieval system (MCRS) is used to retrieve ice water path (IWP) in ice-over-water cloud systems globally over oceans using combined instrument data from Aqua. The liquid water path (LWP) of lower-layer water clouds is estimated from the Advanced Microwave Scanning Radiometer for EOS (AMSR-E) measurements. The properties of the upper-level ice clouds are then derived from Moderate Resolution Imaging Spectroradiometer (MODIS) measurements by matching simulated radiances from a two-cloud-layer radiative transfer model. The results show that the MCRS can significantly improve the accuracy and reduce the over-estimation of optical depth and IWP retrievals for ice-over-water cloud systems. The mean daytime ice cloud optical depth and IWP for overlapped ice-over-water clouds over oceans from Aqua are 7.6 and 146.4 gm-2, respectively, down from the initial single-layer retrievals of 17.3 and 322.3 gm-2. The mean IWP for actual single-layer clouds is 128.2 gm-2.

Above-Cloud Precipitable Water Retrievals using the MODIS 0.94 micron Band with Applications for Multi-Layer Cloud Detection

NASA Technical Reports Server (NTRS)

Platnick, S.; Wind, G.

2004-01-01

In order to perform satellite retrievals of cloud properties, it is important to account for the effect of the above-cloud atmosphere on the observations. The solar bands used in the operational MODIS Terra and Aqua cloud optical and microphysical algorithms (visible, NIR, and SWIR spectral windows) are primarily affected by water vapor, and to a lesser extent by well-mixed gases. For water vapor, the above-cloud column amount, or precipitable water, provides adequate information for an atmospheric correction; details of the vertical vapor distribution are not typically necessary for the level of correction required. Cloud-top pressure has a secondary effect due to pressure broadening influences. For well- mixed gases, cloud-top pressure is also required for estimates of above-cloud abundances. We present a method for obtaining above-cloud precipitable water over dark Ocean surfaces using the MODIS 0.94 pm vapor absorption band. The retrieval includes an iterative procedure for establishing cloud-top temperature and pressure, and is useful for both single layer water and ice clouds. Knowledge of cloud thermodynamic phase is fundamental in retrieving cloud optical and microphysical properties. However, in cases of optically thin cirrus overlapping lower water clouds, the concept of a single unique phase is ill- defined and depends, at least, on the spectral region of interest. We will present a method for multi-layer and multi-phase cloud detection which uses above-cloud precipitable water retrievals along with several existing MODIS operational cloud products (cloud-top pressure derived from a C02 slicing algorithm, IR and SWIR phase retrievals). Results are catagorized by whether the radiative signature in the MODIS solar bands is primarily that of a water cloud with ice cloud contamination, or visa-versa. Examples in polar and mid-latitude regions will be shown.

Cloud water in windward and leeward mountain forests: The stable isotope signature of orographic cloud water

USGS Publications Warehouse

Scholl, M.A.; Giambelluca, T.W.; Gingerich, S.B.; Nullet, M.A.; Loope, L.L.

2007-01-01

Cloud water can be a significant hydrologic input to mountain forests. Because it is a precipitation source that is vulnerable to climate change, it is important to quantify amounts of cloud water input at watershed and regional scales. During this study, cloud water and rain samples were collected monthly for 2 years at sites on windward and leeward East Maui. The difference in isotopic composition between volume‐weighted average cloud water and rain samples was 1.4‰ δ18O and 12‰ δ2H for the windward site and 2.8‰ δ18O and 25‰ δ2H for the leeward site, with the cloud water samples enriched in 18O and 2H relative to the rain samples. A summary of previous literature shows that fog and/or cloud water is enriched in 18O and 2H compared to rain at many locations around the world; this study documents cloud water and rain isotopic composition resulting from weather patterns common to montane environments in the trade wind latitudes. An end‐member isotopic composition for cloud water was identified for each site and was used in an isotopic mixing model to estimate the proportion of precipitation input from orographic clouds. Orographic cloud water input was 37% of the total precipitation at the windward site and 46% at the leeward site. This represents an estimate of water input to the forest that could be altered by changes in cloud base altitude resulting from global climate change or deforestation.

An examination of the effects of explicit cloud water in the UCLA GCM

NASA Technical Reports Server (NTRS)

Ose, Tomoaki

1993-01-01

The effect of explicit cloud water on the climate simulation by the University of California of Los Angeles GCM is investigated by adding the mixing ratios of cloud ice and cloud liquid water to the prognostic variables of the model. The detrained cloud ice and cloud liquid water are obtained by the microphysical calculation in the Arakawa-Schubert (1974) cumulus scheme. The results are compared with the observations concerned with cloudiness, planetary albedo, OLR, and the dependence of cloud water content on temperature.

Nitrogen deposition in a southern hemisphere biodiversity hotspot within and surrounding Cape Town, South Africa

NASA Astrophysics Data System (ADS)

Angstmann, J. L.; Hall, S.; February, E.; West, A. G.; Allsopp, N.; Bond, W.

2011-12-01

Anthropogenic nitrogen (N) emissions have increased dramatically since the agricultural and industrial revolutions leading to N deposition in the northern hemisphere that is estimated to be an order of magnitude greater than preindustrial fluxes. N deposition rates of 5-15 kg N ha-1 yr-1 in Europe and N. America decrease plant species diversity, increase invasive species, and lead to eutrophication of surface waters. The southern hemisphere is home to over 50% of the world's biodiversity hotspots, including the 90,000 km2 Cape Floristic Region which houses 9,030 vascular plant species, 69% of which are endemic. However, to date, N deposition rates in the southern hemisphere are highly uncertain, with global models of N deposition based upon sparse datasets at best. Many terrestrial systems, such as fynbos shrublands, are adapted to low N availability and exhibit high species diversity and endemism, rendering them susceptible to ecological changes from N deposition. In this research, we quantified the spatial and temporal distribution of wet and dry N deposition across 30 protected fynbos ecosystems within the urban airshed of Cape Town, South Africa. We predicted that 1) total inorganic N deposition varies predictably along the urban-rural gradient (highest near the city centre), 2) N deposition varies seasonally, with higher fluxes in the winter months when atmospheric stability causes a build-up of N gases in and around the city, and 3) total inorganic N deposition will exceed the critical load of 10-15 kg N ha-1 yr-1 for Mediterranean shrublands, past which negative ecosystem effects have been shown to occur. Estimates of N deposition based on NO2 concentrations within the city suggest that total N deposition ranges from 8-13 kg N ha-1 yr-1 . However, we show that N deposition measured by ion-exchange resin collectors is far less than expected, averaging less than 2 kg N ha-1 yr-1 (range 0.5 - 5.5 kg N ha-1 yr-1 ), and is is dominated by NO3-, suggesting combustion sources. Despite low rates compared to northern hemisphere studies, throughfall N fluxes are lower on average than bulk N fluxes, suggesting significant N uptake through the canopy. Preliminary analyses of cloud water + dry deposition show concentrations of N up to an order of magnitude higher than rainfall. These results suggest that dry and cloud water deposition may contribute high N loads to fynbos shrublands, but these areas may be localized to mountain tops near the city center.

The role of event water, a rapid shallow flow component, and catchment size in summer stormflow

USGS Publications Warehouse

Brown, V.A.; McDonnell, Jeffery J.; Burns, Douglas A.; Kendall, C.

1999-01-01

Seven nested headwater catchments (8 to 161 ha) were monitored during five summer rain events to evaluate storm runoff components and the effect of catchment size on water sources. Two-component isotopic hydrograph separation showed that event-water contributions near the time of peakflow ranged from 49% to 62% in the 7 catchments during the highest intensity event. The proportion of event water in stormflow was greater than could be accounted for by direct precipitation onto saturated areas. DOC concentrations in stormflow were strongly correlated with stream 18O composition. Bivariate mixing diagrams indicated that the large event water contributions were likely derived from flow through the soil O-horizon. Results from two-tracer, three-component hydrograph separations showed that the throughfall and O-horizon soil-water components together could account for the estimated contributions of event water to stormflow. End-member mixing analysis confirmed these results. Estimated event-water contributions were inversely related to catchment size, but the relation was significant for only the event with greatest rainfall intensity. Our results suggest that perched, shallow subsurface flow provides a substantial contribution to summer stormflow in these small catchments, but the relative contribution of this component decreases with catchment size.Seven nested headwater catchments (8 to 161 ha) were monitored during five summer rain events to evaluate storm runoff components and the effect of catchment size on water sources. Two-component isotopic hydrograph separation showed that event-water contributions near the time of peakflow ranged from 49% to 62% in the 7 catchments during the highest intensity event. The proportion of event water in stormflow was greater than could be accounted for by direct precipitation onto saturated areas. DOC concentrations in stormflow were strongly correlated with stream 18O composition. Bivariate mixing diagrams indicated that the large event water contributions were likely derived from flow through the soil O-horizon. Results from two-tracer, three-component hydrograph separations showed that the throughfall and O-horizon soil-water components together could account for the estimated contributions of event water to stormflow. End-member mixing analysis confirmed these results. Estimated event-water contributions were inversely related to catchment size, but the relation was significant for only the event with greatest rainfall intensity. Our results suggest that perched, shallow subsurface flow provides a substantial contribution to summer stormflow in these small catchments, but the relative contribution of this component decreases with catchment size.

Technique for assessing vegetation-induced moisture flux, with implications for global climate modeling

NASA Technical Reports Server (NTRS)

Macari, Emir Jose

1990-01-01

The time between storms, the duration of storms, and the storm depths are studied in relation to vegetation controls on the disposition of rainfall. It is proposed that understanding the movement of water between the vegetation and soil (including evapotranspiration and infiltration) will be the gateway for modeling atmospheric flux and improving global climate models. The overall objective goal of the proposed research effort is to develop a field/lab methodology which will provide a better understanding of vegetation induced water movement. Water flow initiated from stem flow of wooded slopes feeds soil water pathways, which in turn feed the deeper ground water system and give rise to stream response. This is balanced by more water inputs via throughfall, where it percolates the soil matrix and allows much greater rates of evapotranspiration and atmospheric/soil moisture flux. This research study seeks to gain an understanding of the effect of vegetation on soil moisture, and the effect of this differential wetting on resulting evapotranspiration and atmospheric flux.

Determination of Ice Water Path in Ice-over-Water Cloud Systems Using Combined MODIS and AMSR-E Measurements

NASA Technical Reports Server (NTRS)

Huang, Jianping; Minnis, Patrick; Lin, Bing; Yi, Yuhong; Fan, T.-F.; Sun-Mack, Sunny; Ayers, J. K.

2006-01-01

To provide more accurate ice cloud properties for evaluating climate models, the updated version of multi-layered cloud retrieval system (MCRS) is used to retrieve ice water path (IWP) in ice-over-water cloud systems over global ocean using combined instrument data from the Aqua satellite. The liquid water path (LWP) of lower layer water clouds is estimated from the Advanced Microwave Scanning Radiometer for EOS (AMSR-E) measurements. With the lower layer LWP known, the properties of the upper-level ice clouds are then derived from Moderate Resolution Imaging Spectroradiometer measurements by matching simulated radiances from a two-cloud layer radiative transfer model. Comparisons with single-layer cirrus systems and surface-based radar retrievals show that the MCRS can significantly improve the accuracy and reduce the over-estimation of optical depth and ice water path retrievals for ice over-water cloud systems. During the period from December 2004 through February 2005, the mean daytime ice cloud optical depth and IWP for overlapped ice-over-water clouds over ocean from Aqua are 7.6 and 146.4 gm(sup -2), respectively, significantly less than the initial single layer retrievals of 17.3 and 322.3 gm(sup -2). The mean IWP for actual single-layer clouds was 128.2 gm(sup -2).

Chemical evaluation of soil-solution in acid forest soils

USGS Publications Warehouse

Lawrence, G.B.; David, M.B.

1996-01-01

Soil-solution chemistry is commonly studied in forests through the use of soil lysimeters.This approach is impractical for regional survey studies, however, because lysimeter installation and operation is expensive and time consuming. To address these problems, a new technique was developed to compare soil-solution chemistry among red spruce stands in New York, Vermont, New Hampshire, Maine. Soil solutions were expelled by positive air pressure from soil that had been placed in a sealed cylinder. Before the air pressure was applied, a solution chemically similar to throughfall was added to the soil to bring it to approximate field capacity. After the solution sample was expelled, the soil was removed from the cylinder and chemically analyzed. The method was tested with homogenized Oa and Bs horizon soils collected from a red spruce stand in the Adirondack Mountains of New York, a red spruce stand in east-central Vermont, and a mixed hardwood stand in the Catskill Mountains of New York. Reproducibility, effects of varying the reaction time between adding throughfall and expelling soil solution (5-65 minutes) and effects of varying the chemical composition of added throughfall, were evaluated. In general, results showed that (i) the method was reproducible (coefficients of variation were generally < 15%), (ii) variations in the length of reaction-time did not affect expelled solution concentrations, and (iii) adding and expelling solution did not cause detectable changes in soil exchange chemistry. Concentrations of expelled solutions varied with the concentrations of added throughfall; the lower the CEC, the more sensitive expelled solution concentrations were to the chemical concentrations of added throughfall. Addition of a tracer (NaBr) showed that the expelled solution was a mixture of added solution and solution that preexisted in the soil. Comparisons of expelled solution concentrations with concentrations of soil solutions collected by zero-tension and tension lysimetry indicated that expelled solution concentrations were higher than those obtained with either type of lysimeter, although there was less difference with tension lysimeters than zero-tension lysimeters. The method used for collection of soil solution should be taken into consideration whenever soil solution data are being interpreted.

Estimates of ion sources in deciduous and coniferous throughfall

USGS Publications Warehouse

Puckett, L.J.

1990-01-01

Estimates of external and internal sources of ions in net throughfall deposition were derived for a deciduous and coniferous canopy by use of multiple regression. The externel source component appears to be dominated by dry deposition of Ca2+, SO2 and NO3- during dormant and growing seasons for the two canopy types. Increases in the leaching rates of K+ and Mg2+ during the growing season reflect the presence of leaves in the deciduous canopy and increased physiological activity in both canopies. Internal leaching rates for SO42- doubled during the growing season presumably caused by increased physiological activity and uptake of SO2 through stomates. Net deposition of SO42- in throughfall during the growing season appears highly dependent on stomatal uptake of SO2. Estimates of SO2 deposition velocities were 0.06 cm s-1 and 0.13 cm s-1 for the deciduous and coniferous canopies, respectively, during the dormant season, and 0.30 cm s-1 and 0.43 cm s-1 for the deciduous and coniferous canopies, respectively, during the growing season. For the ions of major interest with respect to ecosystem effects, namely H+, NO3- and SO42-, precipitation inputs generally outweighed estimates of dry deposition input. However, net throughfall deposition of NO3- and SO42- accounted for 20-47 and 34-50 per cent, respectively, of total deposition of those ions. Error estimates of ion sources were at least 50-100 per cent and the method is subject to several assumptions and limitations.

Water Ice Cloud Opacities and Temperatures Derived from the Viking IRTM Data Set

NASA Technical Reports Server (NTRS)

TamppariL. K.; Zurek, R. W.; Paige, D. A.

1999-01-01

The degree to which water ice clouds play a role in the Mars climate is unknown. Latent heating of water ice clouds is small and since most hazes appeared to be thin (tau less than or = 1) their radiative effects have been neglected. Condensation likely limits the vertical extent of water vapor in the water column and a lowering of the condensation altitude, as seen in the northern spring and summer, could increase the seasonal exchange of water between the atmosphere and the surface. It has been suggested that water ice cloud formation is more frequent and widespread in the aphelic hemisphere (currently the northern). This may limit water to the northern hemisphere through greater exchange with the regolith and through restricted southward transport of water vapor by the Mars Hadley circulation. In addition, it has been suggested that water ice cloud formation also controls the vertical distribution of atmospheric dust in some seasons. This scavenging of dust may Continuing from the IRTM cloud maps, derived cloud opacities and cloud temperatures for several locations and seasons will be presented. Sensitivities to cloud particle sizes, surface temperature, and dust opacity will be discussed.

Amazonian former gold mined soils as a source of methylmercury: evidence from a small scale watershed in French Guiana.

PubMed

Guedron, Stephane; Grimaldi, Michel; Grimaldi, Catherine; Cossa, Daniel; Tisserand, Delphine; Charlet, Laurent

2011-04-01

Total mercury (HgT) and monomethylmercury (MMHg) were investigated in a tropical head watershed (1 km(2)) of French Guiana. The watershed includes a pristine area on the hill slopes and a former gold mined flat in the bottomland. Concentrations of dissolved and particulate HgT and MMHg were measured in rain, throughfall, soil water and at three points along the stream. Samples were taken in-between and during 14 storm events at the beginning and middle of the 2005 and 2006 rainy seasons. Dissolved and particulate HgT concentrations in the stream slightly increased downstream, while dissolved and particulate MMHg concentrations were low at the pristine sub-watershed outlet (median = 0.006 ng L(-1) and 1.84 ng g(-1), respectively) and sharply increased at the gold mined flat outlet (median = 0.056 ng L(-1) and 6.80 ng g(-1), respectively). Oxisols, which are dominant in the pristine area act as a sink of HgT and MMHg from rain and throughfall inputs. Hydromorphic soils in the flat are strongly contaminated with Hg (including Hg(0) droplets) and their structure has been disturbed by former gold-mining processes, leading to multiple stagnant water areas where biogeochemical conditions are favorable for methylation. In the former gold mined flat high dissolved MMHg concentrations (up to 0.8 ng L(-1)) were measured in puddles or suboxic soil pore waters, whereas high dissolved HgT concentrations were found in lower Eh conditions. Iron-reducing bacteria were suggested as the main methylators since highest concentrations for dissolved MMHg were associated with high dissolved ferrous iron concentrations. The connection between saturated areas and stagnant waters with the hydrographic network during rain events leads to the export of dissolved MMHg and HgT in stream waters, especially at the beginning of the rainy season. As both legal and illegal gold-mining continues to expand in French Guiana, an increase in dissolved and particulate MMHg emissions in the hydrographic network is expected. This will enhance MMHg bio-amplification and present a threat to local populations, whose diet relies mainly on fish. Copyright © 2011 Elsevier Ltd. All rights reserved.

Estimation of liquid water cloud height and fraction using simulated AMSU-A and MHS data. [Advanced Microwave Sounding Unit and Microwave Humidity Sounder

NASA Technical Reports Server (NTRS)

Huang, Hung-Lung; Diak, George R.

1992-01-01

The rms retrieval errors in cloud top pressure for fully overcast conditions over both land and water surfaces are shown for AMSU-A oxygen channel pair 3 and 5 and MHS water vapor channel pair 4 and 5. For both pairs, the decrease of retrieval skill from high cloud is evident for almost all liquid water contents. For high cloud and medium cloud, the water vapor pair outperforms the oxygen pair. Retrieval accuracy is the best for high and middle clouds and degrades as the cloud top is lower in the atmosphere.

Limits to the Indirect Aerosol Forcing in Stratocumulus

NASA Technical Reports Server (NTRS)

Ackerman, Andrew; Toon, O.; Stevens, D.; Coakley, J., Jr.

2003-01-01

The indirect radiative forcing of aerosols is poorly constrained by the observational data underlying the simple cloud parameterizations in GCMs. signal of cloud response to increased aerosol concentrations from meteorological noise. Recent satellite observations indicate a significant decrease of cloud water in ship tracks, in contrast to an ensemble of in situ measurements showing no average change in cloud water relative to the surrounding clouds. Both results contradict the expectation of cloud water increasing in polluted clouds. We find through large-eddy simulations of stratocumulus that the trend in the satellite data is likely an artifact of sampling only overcast clouds. The simulations instead show cloud cover increasing with droplet concentrations. The simulations also show that increases in cloud water from suppressing drizzle by increased droplet concentrations are favored at night or at extremely low droplet concentrations. At typical droplet concentrations we find that the Twomey effect on cloud albedo is amplified very little by the secondary indirect effect of drizzle suppression, largely because the absorption of solar radiation by cloud water reduces boundary-layer mixing in the daytime and thereby restricts any possible increase in cloud water from drizzle suppression. The cloud and boundary layer respond to radiative heating variations on a time scale of hours, and on longer time scales respond to imbalances between large-scale horizontal advection and the entrainment of inversion air. We analyze the co-varying response of cloud water, cloud thickness, width of droplet size distributions, and dispersion of the optical depth, as well as the overall response of cloud albedo, to changes in droplet concentrations. We also dissect the underlying physical mechanisms through sensitivity studies. Ship tracks represent an ideal natural laboratory to extricate the

Characteristic Vertical Profiles of Cloud Water Composition in Marine Stratocumulus Clouds and Relationships With Precipitation

NASA Astrophysics Data System (ADS)

MacDonald, Alexander B.; Dadashazar, Hossein; Chuang, Patrick Y.; Crosbie, Ewan; Wang, Hailong; Wang, Zhen; Jonsson, Haflidi H.; Flagan, Richard C.; Seinfeld, John H.; Sorooshian, Armin

2018-04-01

This study uses airborne cloud water composition measurements to characterize the vertical structure of air-equivalent mass concentrations of water-soluble species in marine stratocumulus clouds off the California coast. A total of 385 cloud water samples were collected in the months of July and August between 2011 and 2016 and analyzed for water-soluble ionic and elemental composition. Three characteristic profiles emerge: (i) a reduction of concentration with in-cloud altitude for particulate species directly emitted from sources below cloud without in-cloud sources (e.g., Cl- and Na+), (ii) an increase of concentration with in-cloud altitude (e.g., NO2- and formate), and (iii) species exhibiting a peak in concentration in the middle of cloud (e.g., non-sea-salt SO42-, NO3-, and organic acids). Vertical profiles of rainout parameters such as loss frequency, lifetime, and change in concentration with respect to time show that the scavenging efficiency throughout the cloud depth depends strongly on the thickness of the cloud. Thin clouds exhibit a greater scavenging loss frequency at cloud top, while thick clouds have a greater scavenging loss frequency at cloud base. The implications of these results for treatment of wet scavenging in models are discussed.

Characteristic Vertical Profiles of Cloud Water Composition in Marine Stratocumulus Clouds and Relationships With Precipitation

DOE Office of Scientific and Technical Information (OSTI.GOV)

MacDonald, Alexander B.; Dadashazar, Hossein; Chuang, Patrick Y.

This study uses airborne cloud water composition measurements to characterize the vertical structure of air-equivalent mass concentrations of water-soluble species in marine stratocumulus clouds off the California coast. A total of 385 cloud water samples were collected in the months of July and August between 2011 and 2016 and analyzed for water-soluble ionic and elemental composition. Three characteristic profiles emerge: (i) a reduction of concentration with in-cloud altitude for particulate species directly emitted from sources below cloud without in-cloud sources (e.g., Cl-, Na+); (ii) an increase of concentration with in-cloud altitude (e.g., NO2-, formate); and (iii) species exhibiting a peakmore » in concentration in the middle of cloud (e.g., non-sea salt SO42-, NO3-, organic acids). Vertical profiles of rainout parameters such as loss frequency, lifetime, and change in concentration with respect to time show that the scavenging efficiency throughout the cloud depth depends strongly on the thickness of the cloud. Thin clouds exhibit a greater scavenging loss frequency at cloud top, while thick clouds have a greater scavenging loss frequency at cloud base. The implications of these results for treatment of wet scavenging in models are discussed.« less

Snow precipitation on Mars driven by cloud-induced night-time convection

NASA Astrophysics Data System (ADS)

Spiga, Aymeric; Hinson, David P.; Madeleine, Jean-Baptiste; Navarro, Thomas; Millour, Ehouarn; Forget, François; Montmessin, Franck

2017-09-01

Although it contains less water vapour than Earth's atmosphere, the Martian atmosphere hosts clouds. These clouds, composed of water-ice particles, influence the global transport of water vapour and the seasonal variations of ice deposits. However, the influence of water-ice clouds on local weather is unclear: it is thought that Martian clouds are devoid of moist convective motions, and snow precipitation occurs only by the slow sedimentation of individual particles. Here we present numerical simulations of the meteorology in Martian cloudy regions that demonstrate that localized convective snowstorms can occur on Mars. We show that such snowstorms--or ice microbursts--can explain deep night-time mixing layers detected from orbit and precipitation signatures detected below water-ice clouds by the Phoenix lander. In our simulations, convective snowstorms occur only during the Martian night, and result from atmospheric instability due to radiative cooling of water-ice cloud particles. This triggers strong convective plumes within and below clouds, with fast snow precipitation resulting from the vigorous descending currents. Night-time convection in Martian water-ice clouds and the associated snow precipitation lead to transport of water both above and below the mixing layers, and thus would affect Mars' water cycle past and present, especially under the high-obliquity conditions associated with a more intense water cycle.

Global statistics of liquid water content and effective number concentration of water clouds over ocean derived from combined CALIPSO and MODIS measurements

NASA Astrophysics Data System (ADS)

Hu, Y.; Vaughan, M.; McClain, C.; Behrenfeld, M.; Maring, H.; Anderson, D.; Sun-Mack, S.; Flittner, D.; Huang, J.; Wielicki, B.; Minnis, P.; Weimer, C.; Trepte, C.; Kuehn, R.

2007-06-01

This study presents an empirical relation that links the volume extinction coefficients of water clouds, the layer integrated depolarization ratios measured by lidar, and the effective radii of water clouds derived from collocated passive sensor observations. Based on Monte Carlo simulations of CALIPSO lidar observations, this method combines the cloud effective radius reported by MODIS with the lidar depolarization ratios measured by CALIPSO to estimate both the liquid water content and the effective number concentration of water clouds. The method is applied to collocated CALIPSO and MODIS measurements obtained during July and October of 2006, and January 2007. Global statistics of the cloud liquid water content and effective number concentration are presented.

Biogenic, urban, and wildfire influences on the molecular composition of dissolved organic compounds in cloud water

NASA Astrophysics Data System (ADS)

Cook, Ryan D.; Lin, Ying-Hsuan; Peng, Zhuoyu; Boone, Eric; Chu, Rosalie K.; Dukett, James E.; Gunsch, Matthew J.; Zhang, Wuliang; Tolic, Nikola; Laskin, Alexander; Pratt, Kerri A.

2017-12-01

Organic aerosol formation and transformation occurs within aqueous aerosol and cloud droplets, yet little is known about the composition of high molecular weight organic compounds in cloud water. Cloud water samples collected at Whiteface Mountain, New York, during August-September 2014 were analyzed by ultra-high-resolution mass spectrometry to investigate the molecular composition of dissolved organic carbon, with a focus on sulfur- and nitrogen-containing compounds. Organic molecular composition was evaluated in the context of cloud water inorganic ion concentrations, pH, and total organic carbon concentrations to gain insights into the sources and aqueous-phase processes of the observed high molecular weight organic compounds. Cloud water acidity was positively correlated with the average oxygen : carbon ratio of the organic constituents, suggesting the possibility for aqueous acid-catalyzed (prior to cloud droplet activation or during/after cloud droplet evaporation) and/or radical (within cloud droplets) oxidation processes. Many tracer compounds recently identified in laboratory studies of bulk aqueous-phase reactions were identified in the cloud water. Organosulfate compounds, with both biogenic and anthropogenic volatile organic compound precursors, were detected for cloud water samples influenced by air masses that had traveled over forested and populated areas. Oxidation products of long-chain (C10-12) alkane precursors were detected during urban influence. Influence of Canadian wildfires resulted in increased numbers of identified sulfur-containing compounds and oligomeric species, including those formed through aqueous-phase reactions involving methylglyoxal. Light-absorbing aqueous-phase products of syringol and guaiacol oxidation were observed in the wildfire-influenced samples, and dinitroaromatic compounds were observed in all cloud water samples (wildfire, biogenic, and urban-influenced). Overall, the cloud water molecular composition depended on air mass source influence and reflected aqueous-phase reactions involving biogenic, urban, and biomass burning precursors.

Study on Cloud Water Resources and Precipitation Efficiency Characteristic over China

NASA Astrophysics Data System (ADS)

Zhou, Y., Sr.; Cai, M., Jr.

2017-12-01

The original concept and quantitative assessment method of cloud water resource and its related physical parameters are proposed based on the atmospheric water circulation and precipitation enhancement. A diagnosis method of the three-dimensional (3-D) cloud and cloud water field are proposed , based on cloud observation and atmospheric reanalysis data. Furthermore, using analysis data and precipitation products, Chinese cloud water resources in 2008-2010 are assessed preliminarily. The results show that: 1. Atmospheric water cycle and water balance plays an important part of the climate system. Water substance includes water vapor and hydrometeors, and the water cycle is the process of phase transition of water substances. Water vapor changes its phase into solid or liquid hydrometeors by lifting and condensation, and after that, the hydrometeors grow lager through cloud physical processes and then precipitate to ground, which is the mainly resource of available fresh water .Therefore, it's far from enough to only focus on the amount of water vapor, more attention should be transfered to the hydrometeors (cloud water resources) which is formed by the process of phase transition including lifting and condensation. The core task of rainfall enhancement is to develop the cloud water resources and raise the precipitation efficiency by proper technological measures. 2. Comparing with the water vapor, the hydrometeor content is much smaller. Besides, the horizontal delivery amount also shows two orders of magnitude lower than water vapor. But the update cycle is faster and the precipitation efficiency is higher. The amount of cloud water resources in the atmosphere is determined by the instantaneous quantity, the advection transport, condensation and precipitation from the water balance.The cloud water resources vary a lot in different regions. In southeast China, hydrometeor has the fastest renewal cycle and the highest precipitation efficiency. The total amount of hydrometeor in the northwest China is relatively small, but it still has some development potential due to the low precipitation efficiency. 3. The accuracy of the assessment results can be improved and the estimation error can be reduced by using higher-resolution reanalysis data or combining of observational diagnosis and numerical model.

Boron isotopes at the catchment scale, a new potential tool to infer critical zone processes.

NASA Astrophysics Data System (ADS)

Gaillardet, J.; Noireaux, J.; Braun, J. J.; Riotte, J.; Louvat, P.; Bouchez, J.; Lemarchand, D.; Muddu, S.; Mohan Kumar, M.; Candaudap, F.

2017-12-01

Boron is a mid-mass element that has two isotopes, 10B and 11B. These isotopes are largely fractioned by a number of chemical, biological and physical processes. Boron as a great affinity for clays and is useful for life, making it a double tracer of critical zone processes. This study focuses on the Mule Hole Critical Zone Observatory in South India. This is part of the French Research Infrastructure OZCAR and has benefited from the fruitful Indo-French collaboration (Indo-French Cell for Water Sciences) for more that 15 years. Boron and its isotopes were measured in the different compartment of the CZ in Mule Hole, vegetation, atmosphere, throughfall, soil, soil water, river water and compared to the behavior of other elements. The well constrained hydrology in Mule Hole allowed us to calculate the main fluxes affecting boron in the Critical Zone and came to the first order conclusion that the recycling of boron by vegetation is by far the most important flux within the system, reaching 15-20 times the catchment outlet flux. From an isotopic point of view, the total range of variation is measured between -3 ‰ and 77‰, with a bedrock value at 10‰ in classical delta unit, making boron a well suited tracer for constraining CZ processes. The flux of boron most enriched in heavy boron is the throughfall, showing the importance of biological processes in controlling the boron isotopic composition of the stream. Boron in soils in depleted in the heavy isotope but is enriched in boron compared to the bedrock, a surprising situation that we interpret as the legacy of a previous stage of transient weathering. These results indicate a strong decoupling between the behaviors of boron at the surface of the CZ and at depth.

Decreased summer drought affects plant productivity and soil carbon dynamics in a Mediterranean woodland

NASA Astrophysics Data System (ADS)

Cotrufo, M. F.; Alberti, G.; Inglima, I.; Marjanović, H.; Lecain, D.; Zaldei, A.; Peressotti, A.; Miglietta, F.

2011-09-01

Precipitation patterns are expected to change in the Mediterranean region within the next decades, with projected decreases in total rainfall and increases in extreme events. We manipulated precipitation patterns in a Mediterranean woodland, dominated by Arbutus unedo L., to study the effects of changing precipitation regimes on above-ground net primary production (ANPP) and soil C dynamics, specifically plant-derived C input to soil and soil respiration (SR). Experimental plots were exposed to either a 20 % reduction of throughfall or to water addition targeted at maintaining soil water content above a minimum of 10 % v/v. Treatments were compared to control plots which received ambient precipitation. Enhanced soil moisture during summer months highly stimulated annual stem primary production, litter fall, SR and net annual plant-derived C input to soil which on average increased by 130 %, 26 %, 58 % and 220 %, respectively, as compared to the control. In contrast, the 20 % reduction in throughfall (equivalent to 10 % reduction in precipitation) did not significantly change soil moisture at the site, and therefore did not significantly affect ANPP or SR. We conclude that minor changes (around 10 % reduction) in precipitation amount are not likely to significantly affect ANPP or soil C dynamics in Mediterranean woodlands. However, if summer rain increases, C cycling will significantly accelerate but soil C stocks are not likely to be changed in the short-term. More studies involving modelling of long-term C dynamics are needed to predict if the estimated increases in soil C input under wet conditions is going to be sustained and if labile C is being substituted to stable C, with a negative effect on long-term soil C stocks.

Challenges in Estimating Evapotranspiration of Young Sparse Stands in a Boreal Forest of Eastern-Canada

NASA Astrophysics Data System (ADS)

Hadiwijaya, B.; Nadeau, D.; Pépin, S.

2017-12-01

Forest evapotranspiration is the sum of transpiration, evaporation from intercepted rainfall by the canopy and soil evaporation, each component being governed by distinct time scales and mechanisms. Therefore, to develop a simple, yet realistic, model to estimate evapotranspiration over forested areas, field measurements must capture the full chronological sequence of events taking place following rainfall. This becomes a challenge in the case of young sparse forest stands due to large diversity in canopy covers and leaf area indices, which leads to strong spatial variation in intercepted rainfall by the canopy. Unfortunately, very few studies have focused on transition between the dry and wet canopy conditions. The objectives of this study are to investigate each element of rain interception and intercepted water loss, to characterize water loss partitioning processes based on precipitation rate, elapsed time and time-sequence events. To do this, we conducted a summer field campaign at Forêt Montmorency (47°N, 71°W), in southern Québec, Canada, started from early May until late October. The site is characterized by a humid continental climate, with a mean annual precipitation of 1500 mm. The site is located at the boreal forest region, in the balsam for-white birch ecosystem, whose growing season typically extends from May until October. Six measurement plots were established around two micrometeorological towers located in juvenile and sapling forest stands. Five sap flow probes to measure transpiration and a set of rainfall interception instruments (measuring throughfall, free throughfall and stemflow separately) have been deployed on each plot. Initial results presented will include the estimated evapotranspiration rate and soil evaporation measured using eddy covariance method, transpiration rate and high resolution analysis of rainfall interception.

Satellite-Based Assessment of Possible Dust Aerosols Semi-Direct Effect on Cloud Water Path over East Asia

NASA Technical Reports Server (NTRS)

Huang, Jianping; Lin, Bing; Minnis, Patrick; Wang, Tainhe; Wang, Xin; Hu, Yongxiang; Yi, Yuhong; Ayers, J. Kirk

2006-01-01

The semi-direct effects of dust aerosols are analyzed over eastern Asia using 2 years (June 2002 to June 2004) of data from the Clouds and the Earth s Radiant Energy System (CERES) scanning radiometer and MODerate Resolution Imaging Spectroradiometer (MODIS) on the Aqua satellite, and 18 years (1984 to 2001) of International Satellite Cloud Climatology Project (ISCCP) data. The results show that the water path of dust-contaminated clouds is considerably smaller than that of dust-free clouds. The mean ice water path (IWP) and liquid water path (LWP) of dusty clouds are less than their dust-free counterparts by 23.7% and 49.8%, respectively. The long-term statistical relationship derived from ISCCP also confirms that there is significant negative correlation between dust storm index and ISCCP cloud water path. These results suggest that dust aerosols warm clouds, increase the evaporation of cloud droplets and further reduce cloud water path, the so-called semi-direct effect. The semi-direct effect may play a role in cloud development over arid and semi-arid areas of East Asia and contribute to the reduction of precipitation.

The impact of radiatively active water-ice clouds on Martian mesoscale atmospheric circulations

NASA Astrophysics Data System (ADS)

Spiga, A.; Madeleine, J.-B.; Hinson, D.; Navarro, T.; Forget, F.

2014-04-01

Background and Goals Water ice clouds are a key component of the Martian climate [1]. Understanding the properties of the Martian water ice clouds is crucial to constrain the Red Planet's climate and hydrological cycle both in the present and in the past [2]. In recent years, this statement have become all the more true as it was shown that the radiative effects of water ice clouds is far from being as negligible as hitherto believed; water ice clouds plays instead a key role in the large-scale thermal structure and dynamics of the Martian atmosphere [3, 4, 5]. Nevertheless, the radiative effect of water ice clouds at lower scales than the large synoptic scale (the so-called meso-scales) is still left to be explored. Here we use for the first time mesoscale modeling with radiatively active water ice clouds to address this open question.

Sulphur isotopes as tracers of the influence of a coal-fired power plant on a Scots pine forest in Catalonia (NE Spain)

NASA Astrophysics Data System (ADS)

Puig, R.; Àvila, A.; Soler, A.

Stable sulphur isotopes and major ionic composition were analysed in precipitation and throughfall samples from a Scots pine ( Pinus sylvestris, L.) forest near the Cercs coal-fired power plant (Catalonia, NE Spain). The purpose of the study was to determine the main sources of sulphur deposition on this pine forest. Sulphur isotope measurements from the SO 2 power plant stack emissions were used to identify the isotopic signature of this source. Net throughfall fluxes of sulphur (26.1 kg S ha 1 yr -1) and nitrogen (16.3 kg N ha -1 yr -1) were higher—5-25 times higher for S and 5-15 times for N—at this site than in other forests in Catalonia. Sulphur isotope analysis confirmed that the net throughfall fluxes of sulphur were mostly due to the dry deposition of the SO 2 power plant emissions onto the pine canopies. Two potential atmospheric end-members were distinguished: regional background rainwater (δ 34S=+7.2‰) and power plant emissions (δ 34S=-2.8‰). By applying a two-component sulphur isotope mixing model, we found that during periods of low power plant activity (⩽10 emission h day -1), 62% of the throughfall sulphate could be attributed to the power plant emissions. At higher activity periods (⩾14 emission h day -1), this contribution rose to 73%. Although power plant contribution to bulk deposition was lower in both cases (34% and 45%), the possible influence of sulphate coming with long-range transport events from the polluted areas in the Mediterranean basin (δ 34S≈0‰) was not discarded.

Biochemical basis of osmotic potential for several hardwood species

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shirshac, T.L.; Gebre, G.M.; Tschaplinski, T.J.

1995-06-01

Metabolite concentrations in leaves of several tree species in an upland oak forest were characterized to determine the biochemical basis of species differences in osmotic potential at saturation. Hydrologic treatments at the site included ambient, wet (+33% throughfall precipitation), and dry (-33% throughfall precipitation). All samples collected from the ambient plot in May have been analyzed for free primary amino acids, inorganic ions, soluble carbohydrates, phenolic compounds, and organic acids. In all species, free primary amino acids accounted for less than 1% of the total solute pool. Dogwood had the lowest total solute concentration (687 {mu}mol/g dw), corresponding to themore » highest osmotic potential at saturation (-1.05 MPa). Understory red maple, sugar maple, scarlet oak, white oak, and overstory red maple had increasing total solute concentrations, with chestnut oak having the highest solute concentration (1126 {mu}mol/g dw) and the lowest osmotic potential (-1.76 MPa). Osmotic adjustment to water stress was evident in chestnut oak in the dry treatment throughout the growing season--up to a 0.21 MPa difference in the dry plot relative to the ambient plot in September. The data on carbohydrate concentrations, however, only partially account for the adjustments. Given that inorganic ions constituted almost 50% of the total solute pool in chestnut oak in May, any large solute adjustment would likely result from changes in inorganic ions.« less

Morphological and phenological shoot plasticity in a Mediterranean evergreen oak facing long-term increased drought.

PubMed

Limousin, Jean-Marc; Rambal, Serge; Ourcival, Jean-Marc; Rodríguez-Calcerrada, Jesus; Pérez-Ramos, Ignacio M; Rodríguez-Cortina, Raquel; Misson, Laurent; Joffre, Richard

2012-06-01

Mediterranean trees must adjust their canopy leaf area to the unpredictable timing and severity of summer drought. The impact of increased drought on the canopy dynamics of the evergreen Quercus ilex was studied by measuring shoot growth, leaf production, litterfall, leafing phenology and leaf demography in a mature forest stand submitted to partial throughfall exclusion for 7 years. The leaf area index rapidly declined in the throughfall-exclusion plot and was 19% lower than in the control plot after 7 years of treatment. Consequently, leaf litterfall was significantly lower in the dry treatment. Such a decline in leaf area occurred through a change in branch allometry with a decreased number of ramifications produced and a reduction of the leaf area supported per unit sapwood area of the shoot (LA/SA). The leafing phenology was slightly delayed and the median leaf life span was slightly longer in the dry treatment. The canopy dynamics in both treatments were driven by water availability with a 1-year lag: leaf shedding and production were reduced following dry years; in contrast, leaf turnover was increased following wet years. The drought-induced decrease in leaf area, resulting from both plasticity in shoot development and slower leaf turnover, appeared to be a hydraulic adjustment to limit canopy transpiration and maintain leaf-specific hydraulic conductivity under drier conditions.

Representing Plant Hydraulics in a Global Model: Updates to the Community Land Model

NASA Astrophysics Data System (ADS)

Kennedy, D.; Swenson, S. C.; Oleson, K. W.; Lawrence, D. M.; Fisher, R.; Gentine, P.

2017-12-01

In previous versions, the Community Land Model has used soil moisture to stand in for plant water status, with transpiration and photosynthesis driven directly by soil water potential. This eschews significant literature demonstrating the importance of plant hydraulic traits in the dynamics of water flow through the soil-plant-atmosphere continuum and in the regulation of stomatal aperture. In this study we install a simplified hydraulic framework to represent vegetation water potential and to regulate root water uptake and turbulent fluxes. Plant hydraulics allow for a more explicit representation of plant water status, which improves the physical basis for many processes represented in CLM. This includes root water uptake and the attenuation of photosynthesis and transpiration with drought. Model description is accompanied by results from a point simulation based at the Caxiuanã flux tower site in Eastern Amazonia, covering a throughfall exclusion experiment from 2001-2003. Including plant hydraulics improves the response to drought forcing compared to previous versions of CLM. Parameter sensitivity is examined at the same site and presented in the context of estimating hydraulic parameters in a global model.

Operational implications of a cloud model simulation of space shuttle exhaust clouds in different atmospheric conditions

NASA Technical Reports Server (NTRS)

Zak, J. A.

1989-01-01

A three-dimensional cloud model was used to characterize the dominant influence of the environment on the Space Shuttle exhaust cloud. The model was modified to accept the actual heat and moisture from rocket exhausts and deluge water as initial conditions. An upper-air sounding determined the ambient atmosphere in which the cloud would grow. The model was validated by comparing simulated clouds with observed clouds from four actual Shuttle launches. Results are discussed with operational weather forecasters in mind. The model successfully produced clouds with dimensions, rise, decay, liquid water contents, and vertical motion fields very similar to observed clouds whose dimensions were calculated from 16 mm film frames. Once validated, the model was used in a number of different atmospheric conditions ranging from very unstable to very stable. Wind shear strongly affected the appearance of both the ground cloud and vertical column cloud. The ambient low-level atmospheric moisture governed the amount of cloud water in model clouds. Some dry atmospheres produced little or no cloud water. An empirical forecast technique for Shuttle cloud rise is presented and differences between natural atmospheric convection and exhaust clouds are discussed.

Humus layer is the main locus of secondary SO4 production in boreal forests

NASA Astrophysics Data System (ADS)

Houle, Daniel; Marty, Charles; Duchesne, Louis; Gagnon, Christian

2014-02-01

Identifying the sources of S exported from catchments and the reactivity of the large soil organic S pool is crucial to understand the mid- or long-term response of forested catchments to decreasing atmospheric S deposition and global warming. Sulfur fluxes as well as S and O isotopes of SO4 were measured in precipitation, throughfall, soil solutions and streams at two boreal forest catchments respectively dominated by black spruce (BS) and balsam fir (BF) in Quebec, Canada. Overall, δ34S-SO4 signature showed relatively small variations among various solution types. However, at both sites, δ18O-SO4 in precipitation (averages of 10.5-11.1‰) was decreased by 3.5-3.6‰ in throughfall because of the production of secondary SO4 through oxidation of SO2 deposited on the canopy. Throughfall δ18O-SO4 was decreased by a further 5.4-6.6‰ in the solution leaving the humus layer which was attributed to the production of secondary SO4 under the action of soil microorganisms through the oxidation of organic S during which the S atom acquired O from water and gaseous O2 present in the soil. A mixing equation based on known isotopic signature of each source suggested that ˜67-81% of the S-SO4 leaving the catchments had interacted with the canopy and the humus layer. The stability of δ18O-SO4 in the mineral soil solution and in the stream of both sites, suggests that SO4 does not undergo reduction-oxidation cycles after its passage through the humus layer. Despite its huge size, the organic S reservoir within the mineral soil would be largely inert. Given the chemical nature of SO4 transformation in the canopy, the humus layer would be responsible for nearly 100% of the biological production of secondary SO4 in the whole watershed at both sites. Taking into account the substantial production of dissolved organic S in the humus layer further emphasizes the crucial importance of the latter in the S cycling of boreal forests.

Intra-Urban Variability in Elemental Carbon Deposition to Tree Canopies

NASA Astrophysics Data System (ADS)

Barrett, T. E.; Ponette-González, A.; Rindy, J. E.; Sheesley, R. J.

2017-12-01

Urban areas cover <1% of the earth's land surface, yet they represent globally significant sources of atmospheric elemental carbon (EC). A product of incomplete fossil fuel, biofuel, and biomass combustion, EC is a powerful climate-forcing agent and a significant component of fine particulate matter in urban atmospheres. Thus, understanding the factors that govern EC removal in urban areas could help mitigate climate change, while improving air quality for urban residents. EC particles can be removed from the atmosphere in precipitation (wet and fog deposition) or they can settle directly onto receptor surfaces (dry deposition). Only limited measurements indicate that EC deposition is higher in urban than in rural and remote regions. However, EC deposition likely exhibits considerable intra-urban variability, with tree canopies serving as potentially important sinks for EC on the cityscape. The goal of this research is to quantify spatial variability in total (wet + dry) EC deposition to urban tree canopies in the Dallas-Fort Worth Metroplex. Using a stratified non-random sampling design, 41 oak trees (22 post oak (Quercus stellata) and 19 live oak (Quercus virginiana)) were selected near (<100 m) and far from roads (>100 m) for measurements of throughfall (water that falls from the canopy to the forest floor). Additionally, 16 bulk rainfall samplers were deployed in grassy areas with no canopy cover. Results from one rain event indicate a volume weighted mean concentration of 83 µg EC L-1 in post oak throughfall, 36 µg EC L-1 in live oak throughfall, and 4 µg EC L-1 in bulk rainfall. Total EC deposition to oak tree canopies was 2.0 ± 2.1 (SD) mg m-2 for post oak and 0.7 ± 0.3 mg m-2 for live oak. Bulk rainfall deposition was 0.08 ± 0.1 mg m-2. Our preliminary findings show that trees are effective urban air filters, removing 9-25 times more EC from the atmosphere than rainwater alone. Resolving surface controls on atmospheric EC removal is key to developing and assessing near-term climate and air quality mitigation strategies.

Observed Increase of TTL Temperature and Water Vapor in Polluted Couds over Asia

DOE Office of Scientific and Technical Information (OSTI.GOV)

Su, Hui; Jiang, Jonathan; Liu, Xiaohong

2011-06-01

Aerosols can affect cloud particle size and lifetime, which impacts precipitation, radiation and climate. Previous studies1-4 suggested that reduced ice cloud particle size and fall speed due to the influence of aerosols may increase evaporation of ice crystals and/or cloud radiative heating in the tropical tropopause layer (TTL), leading to higher water vapor abundance in air entering the stratosphere. Observational substantiation of such processes is still lacking. Here, we analyze new observations from multiple NASA satellites to show the imprint of pollution influence on stratospheric water vapor. We focus our analysis on the highly-polluted South and East Asia region duringmore » boreal summer. We find that "polluted" ice clouds have smaller ice effective radius than "clean" clouds. In the TTL, the polluted clouds are associated with warmer temperature and higher specific humidity than the clean clouds. The water vapor difference between the polluted and clean clouds cannot be explained by other meteorological factors, such as updraft and detrainment strength. Therefore, the observed higher water vapor entry value into the stratosphere in the polluted clouds than in the clean clouds is likely a manifestation of aerosol pollution influence on stratospheric water vapor. Given the radiative and chemical importance of stratospheric water vapor, the increasing emission of aerosols over Asia may have profound impacts on stratospheric chemistry and global energy balance and water cycle.« less

Aqueous Processing of Atmospheric Organic Particles in Cloud Water Collected via Aircraft Sampling

DOE Office of Scientific and Technical Information (OSTI.GOV)

Boone, Eric J.; Laskin, Alexander; Laskin, Julia

2015-07-21

Cloud water and below-cloud atmospheric particle samples were collected onboard a research aircraft during the Southern Oxidant and Aerosol Study (SOAS) over a forested region of Alabama in June 2013. The organic molecular composition of the samples was studied to gain insights into the aqueous-phase processing of organic compounds within cloud droplets. High resolution mass spectrometry with nanospray desorption electrospray ionization and direct infusion electrospray ionization were utilized to compare the organic composition of the particle and cloud water samples, respectively. Isoprene and monoterpene-derived organosulfates and oligomers were identified in both the particles and cloud water, showing the significant influencemore » of biogenic volatile organic compound oxidation above the forested region. While the average O:C ratios of the organic compounds were similar between the atmospheric particle and cloud water samples, the chemical composition of these samples was quite different. Specifically, hydrolysis of organosulfates and formation of nitrogen-containing compounds were observed for the cloud water when compared to the atmospheric particle samples, demonstrating that cloud processing changes the composition of organic aerosol.« less

The Coupled Mars Dust and Water Cycles: Understanding How Clouds Affect the Vertical Distribution and Meridional Transport of Dust and Water.

NASA Technical Reports Server (NTRS)

Kahre, M. A.

2015-01-01

The dust and water cycles are crucial to the current Martian climate, and they are coupled through cloud formation. Dust strongly impacts the thermal structure of the atmosphere and thus greatly affects atmospheric circulation, while clouds provide radiative forcing and control the hemispheric exchange of water through the modification of the vertical distributions of water and dust. Recent improvements in the quality and sophistication of both observations and climate models allow for a more comprehensive understanding of how the interaction between the dust and water cycles (through cloud formation) affects the dust and water cycles individually. We focus here on the effects of clouds on the vertical distribution of dust and water, and how those vertical distributions control the net meridional transport of water. For this study, we utilize observations of temperature, dust and water ice from the Mars Climate Sounder (MCS) on the Mars Reconnaissance Orbiter (MRO) combined with the NASA ARC Mars Global Climate Model (MGCM). We demonstrate that the magnitude and nature of the net meridional transport of water between the northern and southern hemispheres during NH summer is sensitive to the vertical structure of the simulated aphelion cloud belt. We further examine how clouds influence the atmospheric thermal structure and thus the vertical structure of the cloud belt. Our goal is to identify and understand the importance of radiative/dynamic feedbacks due to the physical processes involved with cloud formation and evolution on the current climate of Mars.

The Mars Dust and Water Cycles: Investigating the Influence of Clouds on the Vertical Distribution and Meridional Transport of Dust and Water.

NASA Technical Reports Server (NTRS)

Kahre, M. A.; Haberle, R. M.; Hollingsworth, J. L.; Brecht, A. S.; Urata, R.

2015-01-01

The dust and water cycles are critical to the current Martian climate, and they interact with each other through cloud formation. Dust modulates the thermal structure of the atmosphere and thus greatly influences atmospheric circulation. Clouds provide radiative forcing and control the net hemispheric transport of water through the alteration of the vertical distributions of water and dust. Recent advancements in the quality and sophistication of both climate models and observations enable an increased understanding of how the coupling between the dust and water cycles (through cloud formation) impacts the dust and water cycles. We focus here on the effects of clouds on the vertical distributions of dust and water and how those vertical distributions control the net meridional transport of water. We utilize observations of temperature, dust and water ice from the Mars Climate Sounder (MCS) on the Mars Reconnaissance Orbiter (MRO) and the NASA ARC Mars Global Climate Model (MGCM) to show that the magnitude and nature of the hemispheric exchange of water during NH summer is sensitive to the vertical structure of the simulated aphelion cloud belt. Further, we investigate how clouds influence atmospheric temperatures and thus the vertical structure of the cloud belt. Our goal is to isolate and understand the importance of radiative/dynamic feedbacks due to the physical processes involved with cloud formation and evolution on the current climate of Mars.

The Mars Dust and Water Cycles: Investigating the Influence of Clouds on the Vertical Distribution and Meridional Transport of Dust and Water

NASA Astrophysics Data System (ADS)

Kahre, Melinda A.; Haberle, Robert M.; Hollingsworth, Jeffery L.; Brecht, Amanda S.; Urata, Richard A.

2015-11-01

The dust and water cycles are critical to the current Martian climate, and they interact with each other through cloud formation. Dust modulates the thermal structure of the atmosphere and thus greatly influences atmospheric circulation. Clouds provide radiative forcing and control the net hemispheric transport of water through the alteration of the vertical distributions of water and dust. Recent advancements in the quality and sophistication of both climate models and observations enable an increased understanding of how the coupling between the dust and water cycles (through cloud formation) impacts the dust and water cycles. We focus here on the effects of clouds on the vertical distributions of dust and water and how those vertical distributions control the net meridional transport of water. We utilize observations of temperature, dust and water ice from the Mars Climate Sounder (MCS) on the Mars Reconnaissance Orbiter (MRO) and the NASA ARC Mars Global Climate Model (MGCM) to show that the magnitude and nature of the hemispheric exchange of water during NH summer is sensitive to the vertical structure of the simulated aphelion cloud belt. Further, we investigate how clouds influence atmospheric temperatures and thus the vertical structure of the cloud belt. Our goal is to isolate and understand the importance of radiative/dynamic feedbacks due to the physical processes involved with cloud formation and evolution on the current climate of Mars.

Seasonality of stable isotope composition of atmospheric water input at the southern slopes of Mt. Kilimanjaro, Tanzania

USGS Publications Warehouse

Otte, Insa; Detsch, Florian; Gutlein, Adrian; Scholl, Martha A.; Kiese, Ralf; Appelhans, Tim; Nauss, Thomas

2017-01-01

To understand the moisture regime at the southern slopes of Mt. Kilimanjaro, we analysed the isotopic variability of oxygen (δ18O) and hydrogen (δD) of rainfall, throughfall, and fog from a total of 2,140 samples collected weekly over 2 years at 9 study sites along an elevation transect ranging from 950 to 3,880 m above sea level. Precipitation in the Kilimanjaro tropical rainforests consists of a combination of rainfall, throughfall, and fog. We defined local meteoric water lines for all 3 precipitation types individually and the overall precipitation, δDprec = 7.45 (±0.05) × δ18Oprec + 13.61 (±0.20), n = 2,140, R2 = .91, p < .001. We investigated the precipitation-type-specific stable isotope composition and analysed the effects of amount, altitude, and temperature. Aggregated annual mean values revealed isotope composition of rainfall as most depleted and fog water as most enriched in heavy isotopes at the highest elevation research site. We found an altitude effect of δ18Orain = −0.11‰ × 100 m−1, which varied according to precipitation type and season. The relatively weak isotope or altitude gradient may reveal 2 different moisture sources in the research area: (a) local moisture recycling and (b) regional moisture sources. Generally, the seasonality of δ18Orain values follows the bimodal rainfall distribution under the influences of south- and north-easterly trade winds. These seasonal patterns of isotopic composition were linked to different regional moisture sources by analysing Hybrid Single Particle Lagrangian Integrated Trajectory backward trajectories. Seasonality of dexcess values revealed evidence of enhanced moisture recycling after the onset of the rainy seasons. This comprehensive dataset is essential for further research using stable isotopes as a hydrological tracer of sources of precipitation that contribute to water resources of the Kilimanjaro region.

The Effect of Cirrus Clouds on Water Vapor Transport in the Upper Troposphere and Lower Stratosphere

NASA Astrophysics Data System (ADS)

Lei, L.; McCormick, M. P.; Anderson, J.

2017-12-01

Water vapor plays an important role in the Earth's radiation budget and stratospheric chemistry. It is widely accepted that a large percentage of water vapor entering the stratosphere travels through the tropical tropopause and is dehydrated by the cold tropopause temperature. The vertical transport of water vapor is also affected by the radiative effects of cirrus clouds in the tropical tropopause layer. This latter effect of cirrus clouds was investigated in this research. The work focuses on the tropical and mid-latitude region (50N-50S). Water vapor data from the Microwave Limb Sounder (MLS) and cirrus cloud data from the Cloud-Aerosol Lidar and Infrared pathfinder Satellite Observation (CALIPSO) instruments were used to investigate the relationship between the water vapor and the occurrence of cirrus cloud. A 10-degree in longitude by 10-degree in latitude resolution was chosen to bin the MLS and CALIPSO data. The result shows that the maximum water vapor in the upper troposphere (below 146 hPa) is matched very well with the highest frequency of cirrus cloud occurrences. Maximum water vapor in the lower stratosphere (100 hPa) is partly matched with the maximum cirrus cloud occurrence in the summer time. The National Oceanic and Atmospheric Administration Interpolated Outgoing Longwave Radiation data and NCEP-DOE Reanalysis 2 wind data were used also to investigate the relationship between the water vapor entering the stratosphere, deep convection, and wind. Results show that maximum water vapor at 100 hPa coincides with the northern hemisphere summer-time anticyclone. The effects from both single-layer cirrus clouds and cirrus clouds above the anvil top on the water vapor entering the stratosphere were also studied and will be presented.

Determination of Large-Scale Cloud Ice Water Concentration by Combining Surface Radar and Satellite Data in Support of ARM SCM Activities

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Guosheng

2013-03-15

Single-column modeling (SCM) is one of the key elements of Atmospheric Radiation Measurement (ARM) research initiatives for the development and testing of various physical parameterizations to be used in general circulation models (GCMs). The data required for use with an SCM include observed vertical profiles of temperature, water vapor, and condensed water, as well as the large-scale vertical motion and tendencies of temperature, water vapor, and condensed water due to horizontal advection. Surface-based measurements operated at ARM sites and upper-air sounding networks supply most of the required variables for model inputs, but do not provide the horizontal advection term ofmore » condensed water. Since surface cloud radar and microwave radiometer observations at ARM sites are single-point measurements, they can provide the amount of condensed water at the location of observation sites, but not a horizontal distribution of condensed water contents. Consequently, observational data for the large-scale advection tendencies of condensed water have not been available to the ARM cloud modeling community based on surface observations alone. This lack of advection data of water condensate could cause large uncertainties in SCM simulations. Additionally, to evaluate GCMs cloud physical parameterization, we need to compare GCM results with observed cloud water amounts over a scale that is large enough to be comparable to what a GCM grid represents. To this end, the point-measurements at ARM surface sites are again not adequate. Therefore, cloud water observations over a large area are needed. The main goal of this project is to retrieve ice water contents over an area of 10 x 10 deg. surrounding the ARM sites by combining surface and satellite observations. Built on the progress made during previous ARM research, we have conducted the retrievals of 3-dimensional ice water content by combining surface radar/radiometer and satellite measurements, and have produced 3-D cloud ice water contents in support of cloud modeling activities. The approach of the study is to expand a (surface) point measurement to an (satellite) area measurement. That is, the study takes the advantage of the high quality cloud measurements (particularly cloud radar and microwave radiometer measurements) at the point of the ARM sites. We use the cloud ice water characteristics derived from the point measurement to guide/constrain a satellite retrieval algorithm, then use the satellite algorithm to derive the 3-D cloud ice water distributions within an 10° (latitude) x 10° (longitude) area. During the research period, we have developed, validated and improved our cloud ice water retrievals, and have produced and archived at ARM website as a PI-product of the 3-D cloud ice water contents using combined satellite high-frequency microwave and surface radar observations for SGP March 2000 IOP and TWP-ICE 2006 IOP over 10 deg. x 10 deg. area centered at ARM SGP central facility and Darwin sites. We have also worked on validation of the 3-D ice water product by CloudSat data, synergy with visible/infrared cloud ice water retrievals for better results at low ice water conditions, and created a long-term (several years) of ice water climatology in 10 x 10 deg. area of ARM SGP and TWP sites and then compared it with GCMs.« less

Biogenic, urban, and wildfire influences on the molecular composition of dissolved organic compounds in cloud water

DOE PAGES

Cook, Ryan D.; Lin, Ying-Hsuan; Peng, Zhuoyu; ...

2017-12-21

Organic aerosol formation and transformation occurs within aqueous aerosol and cloud droplets, yet little is known about the composition of high molecular weight organic compounds in cloud water. Cloud water samples collected at Whiteface Mountain, New York, during August-September 2014 were analyzed by ultra-high-resolution mass spectrometry to investigate the molecular composition of dissolved organic carbon, with a focus on sulfur- and nitrogen-containing compounds. Organic molecular composition was evaluated in the context of cloud water inorganic ion concentrations, pH, and total organic carbon concentrations to gain insights into the sources and aqueous-phase processes of the observed high molecular weight organic compounds.more » Cloud water acidity was positively correlated with the average oxygen : carbon ratio of the organic constituents, suggesting the possibility for aqueous acid-catalyzed (prior to cloud droplet activation or during/after cloud droplet evaporation) and/or radical (within cloud droplets) oxidation processes. Many tracer compounds recently identified in laboratory studies of bulk aqueous-phase reactions were identified in the cloud water. Organosulfate compounds, with both biogenic and anthropogenic volatile organic compound precursors, were detected for cloud water samples influenced by air masses that had traveled over forested and populated areas. Oxidation products of long-chain (C 10-12) alkane precursors were detected during urban influence. Influence of Canadian wildfires resulted in increased numbers of identified sulfur-containing compounds and oligomeric species, including those formed through aqueous-phase reactions involving methylglyoxal. Light-absorbing aqueous-phase products of syringol and guaiacol oxidation were observed in the wildfire-influenced samples, and dinitroaromatic compounds were observed in all cloud water samples (wildfire, biogenic, and urban-influenced). Overall, the cloud water molecular composition depended on air mass source influence and reflected aqueous-phase reactions involving biogenic, urban, and biomass burning precursors.« less

Biogenic, urban, and wildfire influences on the molecular composition of dissolved organic compounds in cloud water

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cook, Ryan D.; Lin, Ying-Hsuan; Peng, Zhuoyu

Organic aerosol formation and transformation occurs within aqueous aerosol and cloud droplets, yet little is known about the composition of high molecular weight organic compounds in cloud water. Cloud water samples collected at Whiteface Mountain, New York, during August-September 2014 were analyzed by ultra-high-resolution mass spectrometry to investigate the molecular composition of dissolved organic carbon, with a focus on sulfur- and nitrogen-containing compounds. Organic molecular composition was evaluated in the context of cloud water inorganic ion concentrations, pH, and total organic carbon concentrations to gain insights into the sources and aqueous-phase processes of the observed high molecular weight organic compounds.more » Cloud water acidity was positively correlated with the average oxygen : carbon ratio of the organic constituents, suggesting the possibility for aqueous acid-catalyzed (prior to cloud droplet activation or during/after cloud droplet evaporation) and/or radical (within cloud droplets) oxidation processes. Many tracer compounds recently identified in laboratory studies of bulk aqueous-phase reactions were identified in the cloud water. Organosulfate compounds, with both biogenic and anthropogenic volatile organic compound precursors, were detected for cloud water samples influenced by air masses that had traveled over forested and populated areas. Oxidation products of long-chain (C 10-12) alkane precursors were detected during urban influence. Influence of Canadian wildfires resulted in increased numbers of identified sulfur-containing compounds and oligomeric species, including those formed through aqueous-phase reactions involving methylglyoxal. Light-absorbing aqueous-phase products of syringol and guaiacol oxidation were observed in the wildfire-influenced samples, and dinitroaromatic compounds were observed in all cloud water samples (wildfire, biogenic, and urban-influenced). Overall, the cloud water molecular composition depended on air mass source influence and reflected aqueous-phase reactions involving biogenic, urban, and biomass burning precursors.« less

Seasonal and Interannual Variations of Top-of-Atmosphere Irradiance and Cloud Cover over Polar Regions Derived from the CERES Data Set

NASA Technical Reports Server (NTRS)

Kato, Seiji; Loeb, Norman G.; Minnis, Patrick; Francis, Jennifer A.; Charlock, Thomas P.; Rutan, David A.; Clothiaux, Eugene E.; Sun-Mack, Szedung

2006-01-01

The semi-direct effects of dust aerosols are analyzed over eastern Asia using 2 years (June 2002 to June 2004) of data from the Clouds and the Earth s Radiant Energy System (CERES) scanning radiometer and MODerate Resolution Imaging Spectroradiometer (MODIS) on the Aqua satellite, and 18 years (1984 to 2001) of International Satellite Cloud Climatology Project (ISCCP) data. The results show that the water path of dust-contaminated clouds is considerably smaller than that of dust-free clouds. The mean ice water path (IWP) and liquid water path (LWP) of dusty clouds are less than their dust-free counterparts by 23.7% and 49.8%, respectively. The long-term statistical relationship derived from ISCCP also confirms that there is significant negative correlation between dust storm index and ISCCP cloud water path. These results suggest that dust aerosols warm clouds, increase the evaporation of cloud droplets and further reduce cloud water path, the so-called semi-direct effect. The semi-direct effect may play a role in cloud development over arid and semi-arid areas of East Asia and contribute to the reduction of precipitation.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cook, Ryan D.; Lin, Ying-Hsuan; Peng, Zhuoyu

Organic aerosol formation and transformation occurs within aqueous aerosol and cloud droplets, yet little is known about the composition of high molecular weight organic compounds in cloud water. Cloud water samples collected at Whiteface Mountain, New York, during August-September 2014 were analyzed by ultra-high-resolution mass spectrometry to investigate the molecular composition of dissolved organic carbon, with a focus on sulfur- and nitrogen-containing compounds. Organic molecular composition was evaluated in the context of cloud water inorganic ion concentrations, pH, and total organic carbon concentrations to gain insights into the sources and aqueous-phase processes of the observed high molecular weight organic compounds.more » Cloud water acidity was positively correlated with the average oxygen : carbon ratio of the organic constituents, suggesting the possibility for aqueous acid-catalyzed (prior to cloud droplet activation or during/after cloud droplet evaporation) and/or radical (within cloud droplets) oxidation processes. Many tracer compounds recently identified in laboratory studies of bulk aqueous-phase reactions were identified in the cloud water. Organosulfate compounds, with both biogenic and anthropogenic volatile organic compound precursors, were detected for cloud water samples influenced by air masses that had traveled over forested and populated areas. Oxidation products of long-chain (C 10-12) alkane precursors were detected during urban influence. Influence of Canadian wildfires resulted in increased numbers of identified sulfur-containing compounds and oligomeric species, including those formed through aqueous-phase reactions involving methylglyoxal. Light-absorbing aqueous-phase products of syringol and guaiacol oxidation were observed in the wildfire-influenced samples, and dinitroaromatic compounds were observed in all cloud water samples (wildfire, biogenic, and urban-influenced). Overall, the cloud water molecular composition depended on air mass source influence and reflected aqueous-phase reactions involving biogenic, urban, and biomass burning precursors.« less

Explicit prediction of ice clouds in general circulation models

NASA Astrophysics Data System (ADS)

Kohler, Martin

1999-11-01

Although clouds play extremely important roles in the radiation budget and hydrological cycle of the Earth, there are large quantitative uncertainties in our understanding of their generation, maintenance and decay mechanisms, representing major obstacles in the development of reliable prognostic cloud water schemes for General Circulation Models (GCMs). Recognizing their relative neglect in the past, both observationally and theoretically, this work places special focus on ice clouds. A recent version of the UCLA - University of Utah Cloud Resolving Model (CRM) that includes interactive radiation is used to perform idealized experiments to study ice cloud maintenance and decay mechanisms under various conditions in term of: (1) background static stability, (2) background relative humidity, (3) rate of cloud ice addition over a fixed initial time-period and (4) radiation: daytime, nighttime and no-radiation. Radiation is found to have major effects on the life-time of layer-clouds. Optically thick ice clouds decay significantly slower than expected from pure microphysical crystal fall-out (taucld = 0.9--1.4 h as opposed to no-motion taumicro = 0.5--0.7 h). This is explained by the upward turbulent fluxes of water induced by IR destabilization, which partially balance the downward transport of water by snowfall. Solar radiation further slows the ice-water decay by destruction of the inversion above cloud-top and the resulting upward transport of water. Optically thin ice clouds, on the other hand, may exhibit even longer life-times (>1 day) in the presence of radiational cooling. The resulting saturation mixing ratio reduction provides for a constant cloud ice source. These CRM results are used to develop a prognostic cloud water scheme for the UCLA-GCM. The framework is based on the bulk water phase model of Ose (1993). The model predicts cloud liquid water and cloud ice separately, and which is extended to split the ice phase into suspended cloud ice (predicted) and falling snow (diagnosed) components. An empirical parameterization of the effect of upward turbulent water fluxes in cloud layers is obtained from the CRM simulations by (1) identifying the time-scale of conversion of cloud ice to snow as the key parameter, and (2) regressing it onto cloud differential IR heating and environmental static stability. The updated UCLA-GCM achieves close agreement with observations in global mean top of atmosphere fluxes (within 1--4 W/m2). Artificially suppressing the impact of cloud turbulent fluxes reduces the global mean ice water path by a factor of 3 and produces errors in each of solar and IR fluxes at the top of atmosphere of about 5--6 W/m2.

Limits to Cloud Susceptibility

NASA Technical Reports Server (NTRS)

Coakley, James A., Jr.

2002-01-01

1-kilometer AVHRR observations of ship tracks in low-level clouds off the west coast of the U S. were used to determine limits for the degree to which clouds might be altered by increases in anthropogenic aerosols. Hundreds of tracks were analyzed to determine whether the changes in droplet radii, visible optical depths, and cloud top altitudes that result from the influx of particles from underlying ships were consistent with expectations based on simple models for the indirect effect of aerosols. The models predict substantial increases in sunlight reflected by polluted clouds due to the increases in droplet numbers and cloud liquid water that result from the elevated particle concentrations. Contrary to the model predictions, the analysis of ship tracks revealed a 15-20% reduction in liquid water for the polluted clouds. Studies performed with a large-eddy cloud simulation model suggested that the shortfall in cloud liquid water found in the satellite observations might be attributed to the restriction that the 1-kilometer pixels be completely covered by either polluted or unpolluted cloud. The simulation model revealed that a substantial fraction of the indirect effect is caused by a horizontal redistribution of cloud water in the polluted clouds. Cloud-free gaps in polluted clouds fill in with cloud water while the cloud-free gaps in the surrounding unpolluted clouds remain cloud-free. By limiting the analysis to only overcast pixels, the current study failed to account for the gap-filling predicted by the simulation model. This finding and an analysis of the spatial variability of marine stratus suggest new ways to analyze ship tracks to determine the limit to which particle pollution will alter the amount of sunlight reflected by clouds.

Contrasting Cloud Composition Between Coupled and Decoupled Marine Boundary Layer Clouds

NASA Astrophysics Data System (ADS)

WANG, Z.; Mora, M.; Dadashazar, H.; MacDonald, A.; Crosbie, E.; Bates, K. H.; Coggon, M. M.; Craven, J. S.; Xian, P.; Campbell, J. R.; AzadiAghdam, M.; Woods, R. K.; Jonsson, H.; Flagan, R. C.; Seinfeld, J.; Sorooshian, A.

2016-12-01

Marine stratocumulus clouds often become decoupled from the vertical layer immediately above the ocean surface. This study contrasts cloud chemical composition between coupled and decoupled marine stratocumulus clouds. Cloud water and droplet residual particle composition were measured in clouds off the California coast during three airborne experiments in July-August of separate years (E-PEACE 2011, NiCE 2013, BOAS 2015). Decoupled clouds exhibited significantly lower overall mass concentrations in both cloud water and droplet residual particles, consistent with reduced cloud droplet number concentration and sub-cloud aerosol (Dp > 100 nm) number concentration, owing to detachment from surface sources. Non-refractory sub-micrometer aerosol measurements show that coupled clouds exhibit higher sulfate mass fractions in droplet residual particles, owing to more abundant precursor emissions from the ocean and ships. Consequently, decoupled clouds exhibited higher mass fractions of organics, nitrate, and ammonium in droplet residual particles, owing to effects of long-range transport from more distant sources. Total cloud water mass concentration in coupled clouds was dominated by sodium and chloride, and their mass fractions and concentrations exceeded those in decoupled clouds. Conversely, with the exception of sea salt constituents (e.g., Cl, Na, Mg, K), cloud water mass fractions of all species examined were higher in decoupled clouds relative to coupled clouds. These results suggest that an important variable is the extent to which clouds are coupled to the surface layer when interpreting microphysical data relevant to clouds and aerosol particles.

Dependence of marine stratocumulus reflectivities on liquid water paths

NASA Technical Reports Server (NTRS)

Coakley, James A., Jr.; Snider, Jack B.

1990-01-01

Simple parameterizations that relate cloud liquid water content to cloud reflectivity are often used in general circulation climate models to calculate the effect of clouds in the earth's energy budget. Such parameterizations have been developed by Stephens (1978) and by Slingo and Schrecker (1982) and others. Here researchers seek to verify the parametric relationship through the use of simultaneous observations of cloud liquid water content and cloud reflectivity. The column amount of cloud liquid was measured using a microwave radiometer on San Nicolas Island following techniques described by Hogg et al., (1983). Cloud reflectivity was obtained through spatial coherence analysis of Advanced Very High Resolution Radiometer (AVHRR) imagery data (Coakley and Beckner, 1988). They present the dependence of the observed reflectivity on the observed liquid water path. They also compare this empirical relationship with that proposed by Stephens (1978). Researchers found that by taking clouds to be isotropic reflectors, the observed reflectivities and observed column amounts of cloud liquid water are related in a manner that is consistent with simple parameterizations often used in general circulation climate models to determine the effect of clouds on the earth's radiation budget. Attempts to use the results of radiative transfer calculations to correct for the anisotropy of the AVHRR derived reflectivities resulted in a greater scatter of the points about the relationship expected between liquid water path and reflectivity. The anisotropy of the observed reflectivities proved to be small, much smaller than indicated by theory. To critically assess parameterizations, more simultaneous observations of cloud liquid water and cloud reflectivities and better calibration of the AVHRR sensors are needed.

Estimates of cloud water deposition at Mountain Acid Deposition Program sites in the Appalachian Mountains.

PubMed

Baumgardner, Ralph E; Isil, Selma S; Lavery, Thomas F; Rogers, Christopher M; Mohnen, Volker A

2003-03-01

Cloud water deposition was estimated at three high-elevation sites in the Appalachian Mountains of the eastern United States (Whiteface Mountain, NY; Whitetop Mountain, VA; and Clingman's Dome, TN) from 1994 through 1999 as part of the Mountain Acid Deposition Program (MADPro). This paper provides a summary of cloud water chemistry, cloud liquid water content, cloud frequency, estimates of cloud water deposition of sulfur and nitrogen species, and estimates of total deposition of sulfur and nitrogen at these sites. Other cloud studies in the Appalachians and their comparison to MADPro are also summarized. Whiteface Mountain exhibited the lowest mean and median concentrations of sulfur and nitrogen ions in cloud water, while Clingman's Dome exhibited the highest mean and median concentrations. This geographic gradient is partly an effect of the different meteorological conditions experienced at northern versus southern sites in addition to the difference in pollution content of air masses reaching the sites. All sites measured seasonal cloud water deposition rates of SO4(2-) greater than 50 kg/ha and NO3(-) rates of greater than 25 kg/ha. These high-elevation sites experienced additional deposition loading of SO4(2-) and NO3(-) on the order of 6-20 times greater compared with lower elevation Clean Air Status and Trends Network (CASTNet) sites. Approximately 80-90% of this extra loading is from cloud deposition.

Development of GK-2A cloud optical and microphysical properties retrieval algorithm

NASA Astrophysics Data System (ADS)

Yang, Y.; Yum, S. S.; Um, J.

2017-12-01

Cloud and aerosol radiative forcing is known to be one of the the largest uncertainties in climate change prediction. To reduce this uncertainty, remote sensing observation of cloud radiative and microphysical properties have been used since 1970s and the corresponding remote sensing techniques and instruments have been developed. As a part of such effort, Geo-KOMPSAT-2A (Geostationary Korea Multi-Purpose Satellite-2A, GK-2A) will be launched in 2018. On the GK-2A, the Advanced Meteorological Imager (AMI) is primary instrument which have 3 visible, 3 near-infrared, and 10 infrared channels. To retrieve optical and microphysical properties of clouds using AMI measurements, the preliminary version of new cloud retrieval algorithm for GK-2A was developed and several validation tests were conducted. This algorithm retrieves cloud optical thickness (COT), cloud effective radius (CER), liquid water path (LWP), and ice water path (IWP), so we named this algorithm as Daytime Cloud Optical thickness, Effective radius and liquid and ice Water path (DCOEW). The DCOEW uses cloud reflectance at visible and near-infrared channels as input data. An optimal estimation (OE) approach that requires appropriate a-priori values and measurement error information is used to retrieve COT and CER. LWP and IWP are calculated using empirical relationships between COT/CER and cloud water path that were determined previously. To validate retrieved cloud properties, we compared DCOEW output data with other operational satellite data. For COT and CER validation, we used two different data sets. To compare algorithms that use cloud reflectance at visible and near-IR channels as input data, MODIS MYD06 cloud product was selected. For the validation with cloud products that are based on microwave measurements, COT(2B-TAU)/CER(2C-ICE) data retrieved from CloudSat cloud profiling radar (W-band, 94 GHz) was used. For cloud water path validation, AMSR-2 Level-3 Cloud liquid water data was used. Detailed results will be shown at the conference.

Enhancement of Cloud Cover and Suppression of Nocturnal Drizzle in Stratocumulus Polluted by Haze

NASA Technical Reports Server (NTRS)

Ackerman, Andrew S.; Toon, O. B.; Stevens, D. E.; Coakley, J. A., Jr.; Gore, Warren J. (Technical Monitor)

2002-01-01

Recent satellite observations indicate a significant decrease of cloud water in ship tracks, in contrast to an ensemble of in situ ship-track measurements that show no average change in cloud water relative to the surrounding clouds. We find through large-eddy simulations of stratocumulus that the trend in the satellite data is likely an artifact of sampling only overcast clouds. The simulations instead show cloud cover increasing with droplet concentrations. Our simulations also show that increases in cloud water from drizzle suppression (by increasing droplet concentrations) are favored at night or at extremely low droplet concentrations.

Near-Global Survey of Cloud Column Susceptibilities Using ISCCP Data

NASA Technical Reports Server (NTRS)

Han, Qingyuan; Rossow, William B.; Chou, Joyce; Welch, Ronald M.; Hansen, James E. (Technical Monitor)

2000-01-01

A new parameter, cloud column susceptibility, is introduced to study the aerosol indirect effect. There are several advantages of this new parameter in comparison with the traditional cloud susceptibility. First, no assumptions about constant liquid water content and cloud layer thickness are required in calculations so that errors caused by these assumptions can be avoided. Second, no a priori knowledge of liquid water content is necessary in remote sensing, which makes global survey by satellite data possible even though liquid water content may change significantly. Third, this new parameter can deal with variations of cloud geometrical thickness during cloud-aerosol interactions, which are evidenced by Without assuming how cloud droplet size will respond to changes of number concentration, this new parameter describes the aerosol indirect effect more directly. It addresses the question of how cloud albedo changes with increasing column number concentrations of cloud droplets, which is resulted from cloud-aerosol interactions. In this study, two approaches are used to retrieve cloud column susceptibility by satellite data. The results of both approaches show a striking contrast of cloud column susceptibilities between continental and maritime. Between the two approaches, the one that uses no assumption of constant liquid water content leads to smaller, some times even negative, cloud column susceptibilities. This finding suggests that the aerosol indirect effect may be overestimated if the assumption of constant liquid water content is used in model studies.

Entrainment and cloud evaporation deduced from the stable isotope chemistry of clouds during ORACLES

NASA Astrophysics Data System (ADS)

Noone, D.; Henze, D.; Rainwater, B.; Toohey, D. W.

2017-12-01

The magnitude of the influence of biomass burning aerosols on cloud and rain processes is controlled by a series of processes which are difficult to measure directly. A consequence of this limitation is the emergence of significant uncertainty in the representation of cloud-aerosol interactions in models and the resulting cloud radiative forcing. Interaction between cloud and the regional atmosphere causes evaporation, and the rate of evaporation at cloud top is controlled in part by entrainment of air from above which exposes saturated cloud air to drier conditions. Similarly, the size of cloud droplets also controls evaporation rates, which in turn is linked to the abundance of condensation nuclei. To quantify the dependence of cloud properties on biomass burning aerosols the dynamic relationship between evaporation, drop size and entrainment on aerosol state, is evaluated for stratiform clouds in the southeast Atlantic Ocean. These clouds are seasonally exposed to biomass burning plumes from agricultural fires in southern Africa. Measurements of the stable isotope ratios of cloud water and total water are used to deduce the disequilibrium responsible for evaporation within clouds. Disequilibrium is identified by the relationship between hydrogen and oxygen isotope ratios of water vapor and cloud water in and near clouds. To obtain the needed information, a custom-built, dual inlet system was deployed alongside isotopic gas analyzers on the NASA Orion aircraft as part of the Observations of Aerosols above Clouds and their Interactions (ORACLES) campaign. The sampling system obtains both total water and cloud liquid content for the population of droplets above 7 micrometer diameter. The thermodynamic modeling required to convert the observed equilibrium and kinetic isotopic is linked to evaporation and entrainment is described, and the performance of the measurement system is discussed.

A cloud model simulation of space shuttle exhaust clouds in different atmospheric conditions

NASA Technical Reports Server (NTRS)

Chen, C.; Zak, J. A.

1989-01-01

A three-dimensional cloud model was used to characterize the dominant influence of the environment on the Space Shuttle exhaust cloud. The model was modified to accept the actual heat and moisture from rocket exhausts and deluge water as initial conditions. An upper-air sounding determined the ambient atmosphere in which the cloud could grow. The model was validated by comparing simulated clouds with observed clouds from four actual Shuttle launches. The model successfully produced clouds with dimensions, rise, decay, liquid water contents and vertical motion fields very similar to observed clouds whose dimensions were calculated from 16 mm film frames. Once validated, the model was used in a number of different atmospheric conditions ranging from very unstable to very stable. In moist, unstable atmospheres simulated clouds rose to about 3.5 km in the first 4 to 8 minutes then decayed. Liquid water contents ranged from 0.3 to 1.0 g kg-1 mixing ratios and vertical motions were from 2 to 10 ms-1. An inversion served both to reduce entrainment (and erosion) at the top and to prevent continued cloud rise. Even in the most unstable atmospheres, the ground cloud did not rise beyond 4 km and in stable atmospheres with strong low level inversions the cloud could be trapped below 500 m. Wind shear strongly affected the appearance of both the ground cloud and vertical column cloud. The ambient low-level atmospheric moisture governed the amount of cloud water in model clouds. Some dry atmospheres produced little or no cloud water. One case of a simulated TITAN rocket explosion is also discussed.

Instrument for Aircraft-Icing and Cloud-Physics Measurements

NASA Technical Reports Server (NTRS)

Lilie, Lyle; Bouley, Dan; Sivo, Chris

2006-01-01

The figure shows a compact, rugged, simple sensor head that is part of an instrumentation system for making measurements to characterize the severity of aircraft-icing conditions and/or to perform research on cloud physics. The quantities that are calculated from measurement data acquired by this system and that are used to quantify the severity of icing conditions include sizes of cloud water drops, cloud liquid water content (LWC), cloud ice water content (IWC), and cloud total water content (TWC). The sensor head is mounted on the outside of an aircraft, positioned and oriented to intercept the ambient airflow. The sensor head consists of an open housing that is heated in a controlled manner to keep it free of ice and that contains four hot-wire elements. The hot-wire sensing elements have different shapes and sizes and, therefore, exhibit different measurement efficiencies with respect to droplet size and water phase (liquid, frozen, or mixed). Three of the hot-wire sensing elements are oriented across the airflow so as to intercept incoming cloud water. For each of these elements, the LWC or TWC affects the power required to maintain a constant temperature in the presence of cloud water.

Ice Cloud Properties in Ice-Over-Water Cloud Systems Using TRMM VIRS and TMI Data

NASA Technical Reports Server (NTRS)

Minnis, Patrick; Huang, Jianping; Lin, Bing; Yi, Yuhong; Arduini, Robert F.; Fan, Tai-Fang; Ayers, J. Kirk; Mace, Gerald G.

2007-01-01

A multi-layered cloud retrieval system (MCRS) is updated and used to estimate ice water path in maritime ice-over-water clouds using Visible and Infrared Scanner (VIRS) and TRMM Microwave Imager (TMI) measurements from the Tropical Rainfall Measuring Mission spacecraft between January and August 1998. Lookup tables of top-of-atmosphere 0.65- m reflectance are developed for ice-over-water cloud systems using radiative transfer calculations with various combinations of ice-over-water cloud layers. The liquid and ice water paths, LWP and IWP, respectively, are determined with the MCRS using these lookup tables with a combination of microwave (MW), visible (VIS), and infrared (IR) data. LWP, determined directly from the TMI MW data, is used to define the lower-level cloud properties to select the proper lookup table. The properties of the upper-level ice clouds, such as optical depth and effective size, are then derived using the Visible Infrared Solar-infrared Split-window Technique (VISST), which matches the VIRS IR, 3.9- m, and VIS data to the multilayer-cloud lookup table reflectances and a set of emittance parameterizations. Initial comparisons with surface-based radar retrievals suggest that this enhanced MCRS can significantly improve the accuracy and decrease the IWP in overlapped clouds by 42% and 13% compared to using the single-layer VISST and an earlier simplified MW-VIS-IR (MVI) differencing method, respectively, for ice-over-water cloud systems. The tropical distribution of ice-over-water clouds is the same as derived earlier from combined TMI and VIRS data, but the new values of IWP and optical depth are slightly larger than the older MVI values, and exceed those of single-layered layered clouds by 7% and 11%, respectively. The mean IWP from the MCRS is 8-14% greater than that retrieved from radar retrievals of overlapped clouds over two surface sites and the standard deviations of the differences are similar to those for single-layered clouds. Examples of a method for applying the MCRS over land without microwave data yield similar differences with the surface retrievals. By combining the MCRS with other techniques that focus primarily on optically thin cirrus over low water clouds, it will be possible to more fully assess the IWP in all conditions over ocean except for precipitating systems.

Stable water isotopologue ratios in fog and cloud droplets of liquid clouds are not size-dependent

USGS Publications Warehouse

Spiegel, J.K.; Aemisegger, F.; Scholl, M.; Wienhold, F.G.; Collett, J.L.; Lee, T.; van Pinxteren, D.; Mertes, S.; Tilgner, A.; Herrmann, H.; Werner, Roland A.; Buchmann, N.; Eugster, W.

2012-01-01

In this work, we present the first observations of stable water isotopologue ratios in cloud droplets of different sizes collected simultaneously. We address the question whether the isotope ratio of droplets in a liquid cloud varies as a function of droplet size. Samples were collected from a ground intercepted cloud (= fog) during the Hill Cap Cloud Thuringia 2010 campaign (HCCT-2010) using a three-stage Caltech Active Strand Cloud water Collector (CASCC). An instrument test revealed that no artificial isotopic fractionation occurs during sample collection with the CASCC. Furthermore, we could experimentally confirm the hypothesis that the δ values of cloud droplets of the relevant droplet sizes (μm-range) were not significantly different and thus can be assumed to be in isotopic equilibrium immediately with the surrounding water vapor. However, during the dissolution period of the cloud, when the supersaturation inside the cloud decreased and the cloud began to clear, differences in isotope ratios of the different droplet sizes tended to be larger. This is likely to result from the cloud's heterogeneity, implying that larger and smaller cloud droplets have been collected at different moments in time, delivering isotope ratios from different collection times.

Short-range precipitation forecasts using assimilation of simulated satellite water vapor profiles and column cloud liquid water amounts

NASA Technical Reports Server (NTRS)

Wu, Xiaohua; Diak, George R.; Hayden, Cristopher M.; Young, John A.

1995-01-01

These observing system simulation experiments investigate the assimilation of satellite-observed water vapor and cloud liquid water data in the initialization of a limited-area primitive equations model with the goal of improving short-range precipitation forecasts. The assimilation procedure presented includes two aspects: specification of an initial cloud liquid water vertical distribution and diabatic initialization. The satellite data is simulated for the next generation of polar-orbiting satellite instruments, the Advanced Microwave Sounding Unit (AMSU) and the High-Resolution Infrared Sounder (HIRS), which are scheduled to be launched on the NOAA-K satellite in the mid-1990s. Based on cloud-top height and total column cloud liquid water amounts simulated for satellite data a diagnostic method is used to specify an initial cloud water vertical distribution and to modify the initial moisture distribution in cloudy areas. Using a diabatic initialization procedure, the associated latent heating profiles are directly assimilated into the numerical model. The initial heating is estimated by time averaging the latent heat release from convective and large-scale condensation during the early forecast stage after insertion of satellite-observed temperature, water vapor, and cloud water formation. The assimilation of satellite-observed moisture and cloud water, together withy three-mode diabatic initialization, significantly alleviates the model precipitation spinup problem, especially in the first 3 h of the forecast. Experimental forecasts indicate that the impact of satellite-observed temperature and water vapor profiles and cloud water alone in the initialization procedure shortens the spinup time for precipitation rates by 1-2 h and for regeneration of the areal coverage by 3 h. The diabatic initialization further reduces the precipitation spinup time (compared to adiabatic initialization) by 1 h.

Warming ancient Mars with water clouds

NASA Astrophysics Data System (ADS)

Hartwick, V.; Toon, B.

2017-12-01

High clouds in the present day Mars atmosphere nucleate on interplanetary dust particles (IDPs) that burn up on entry into the Mars atmosphere. Clouds form when superstaturated water vapor condenses on suspended aerosols. Radiatively active water ice clouds may play a crucial role in warming the early Mars climate. Urata and Toon (2011) simulate a stable warm paleo-climate for Mars if clouds form high in the atmosphere and if particles are sufficiently large (r > 10 μm). The annual fluence of micrometeoroids at Mars was larger early on in the evolution of our solar system. Additionally, the water vapor budget throughout the middle and high atmosphere was likely heightened . Both factors should contribute to enhanced nucleation and growth of water ice cloud particles at high altitudes. Here, we use the MarsCAM-CARMA general circulation model (GCM) to examine the radiative impact of high altitude water ice clouds on the early Mars climate and as a possible solution to the faint young sun problem for Mars.

Large Scale Ice Water Path and 3-D Ice Water Content

DOE Data Explorer

Liu, Guosheng

2008-01-15

Cloud ice water concentration is one of the most important, yet poorly observed, cloud properties. Developing physical parameterizations used in general circulation models through single-column modeling is one of the key foci of the ARM program. In addition to the vertical profiles of temperature, water vapor and condensed water at the model grids, large-scale horizontal advective tendencies of these variables are also required as forcing terms in the single-column models. Observed horizontal advection of condensed water has not been available because the radar/lidar/radiometer observations at the ARM site are single-point measurement, therefore, do not provide horizontal distribution of condensed water. The intention of this product is to provide large-scale distribution of cloud ice water by merging available surface and satellite measurements. The satellite cloud ice water algorithm uses ARM ground-based measurements as baseline, produces datasets for 3-D cloud ice water distributions in a 10 deg x 10 deg area near ARM site. The approach of the study is to expand a (surface) point measurement to an (satellite) areal measurement. That is, this study takes the advantage of the high quality cloud measurements at the point of ARM site. We use the cloud characteristics derived from the point measurement to guide/constrain satellite retrieval, then use the satellite algorithm to derive the cloud ice water distributions within an area, i.e., 10 deg x 10 deg centered at ARM site.

Clouds vertical properties over the Northern Hemisphere monsoon regions from CloudSat-CALIPSO measurements

NASA Astrophysics Data System (ADS)

Das, Subrata Kumar; Golhait, R. B.; Uma, K. N.

2017-01-01

The CloudSat spaceborne radar and Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) space-borne lidar measurements, provide opportunities to understand the intriguing behavior of the vertical structure of monsoon clouds. The combined CloudSat-CALIPSO data products have been used for the summer season (June-August) of 2006-2010 to present the statistics of cloud macrophysical (such as cloud occurrence frequency, distribution of cloud top and base heights, geometrical thickness and cloud types base on occurrence height), and microphysical (such as ice water content, ice water path, and ice effective radius) properties of the Northern Hemisphere (NH) monsoon region. The monsoon regions considered in this work are the North American (NAM), North African (NAF), Indian (IND), East Asian (EAS), and Western North Pacific (WNP). The total cloud fraction over the IND (mostly multiple-layered cloud) appeared to be more frequent as compared to the other monsoon regions. Three distinctive modes of cloud top height distribution are observed over all the monsoon regions. The high-level cloud fraction is comparatively high over the WNP and IND. The ice water content and ice water path over the IND are maximum compared to the other monsoon regions. We found that the ice water content has little variations over the NAM, NAF, IND, and WNP as compared to their macrophysical properties and thus give an impression that the regional differences in dynamics and thermodynamics properties primarily cause changes in the cloud frequency or coverage and only secondary in the cloud ice properties. The background atmospheric dynamics using wind and relative humidity from the ERA-Interim reanalysis data have also been investigated which helps in understanding the variability of the cloud properties over the different monsoon regions.

Simulating the Current Water Cycle with the NASA Ames Mars Global Climate Model

NASA Astrophysics Data System (ADS)

Kahre, M. A.; Haberle, R. M.; Hollingsworth, J. L.; Brecht, A. S.; Urata, R. A.; Montmessin, F.

2017-12-01

The water cycle is a critical component of the current Mars climate system, and it is now widely recognized that water ice clouds significantly affect the nature of the simulated water cycle. Two processes are key to implementing clouds in a Mars global climate model (GCM): the microphysical processes of formation and dissipation, and their radiative effects on atmospheric heating/cooling rates. Together, these processes alter the thermal structure, change the atmospheric dynamics, and regulate inter-hemispheric transport. We have made considerable progress using the NASA Ames Mars GCM to simulate the current-day water cycle with radiatively active clouds. Cloud fields from our baseline simulation are in generally good agreement with observations. The predicted seasonal extent and peak IR optical depths are consistent MGS/TES observations. Additionally, the thermal response to the clouds in the aphelion cloud belt (ACB) is generally consistent with observations and other climate model predictions. Notably, there is a distinct gap in the predicted clouds over the North Residual Cap (NRC) during local summer, but the clouds reappear in this simulation over the NRC earlier than the observations indicate. Polar clouds are predicted near the seasonal CO2 ice caps, but the column thicknesses of these clouds are generally too thick compared to observations. Our baseline simulation is dry compared to MGS/TES-observed water vapor abundances, particularly in the tropics and subtropics. These areas of disagreement appear to be a consistent with other current water cycle GCMs. Future avenues of investigation will target improving our understanding of what controls the vertical extent of clouds and the apparent seasonal evolution of cloud particle sizes within the ACB.

Implementing a warm cloud microphysics parameterization for convective clouds in NCAR CESM

NASA Astrophysics Data System (ADS)

Shiu, C.; Chen, Y.; Chen, W.; Li, J. F.; Tsai, I.; Chen, J.; Hsu, H.

2013-12-01

Most of cumulus convection schemes use simple empirical approaches to convert cloud liquid mass to rain water or cloud ice to snow e.g. using a constant autoconversion rate and dividing cloud liquid mass into cloud water and ice as function of air temperature (e.g. Zhang and McFarlane scheme in NCAR CAM model). There are few studies trying to use cloud microphysical schemes to better simulate such precipitation processes in the convective schemes of global models (e.g. Lohmann [2008] and Song, Zhang, and Li [2012]). A two-moment warm cloud parameterization (i.e. Chen and Liu [2004]) is implemented into the deep convection scheme of CAM5.2 of CESM model for treatment of conversion of cloud liquid water to rain water. Short-term AMIP type global simulations are conducted to evaluate the possible impacts from the modification of this physical parameterization. Simulated results are further compared to observational results from AMWG diagnostic package and CloudSAT data sets. Several sensitivity tests regarding to changes in cloud top droplet concentration (here as a rough testing for aerosol indirect effects) and changes in detrained cloud size of convective cloud ice are also carried out to understand their possible impacts on the cloud and precipitation simulations.

The Mars Dust Cycle: Investigating the Effects of Radiatively Active Water Ice Clouds on Surface Stresses and Dust Lifting Potential with the NASA Ames Mars General Circulation Model

NASA Technical Reports Server (NTRS)

Kahre, Melinda A.; Hollingsworth, Jeffery

2012-01-01

The dust cycle is a critically important component of Mars' current climate system. Dust is present in the atmosphere of Mars year-round but the dust loading varies with season in a generally repeatable manner. Dust has a significant influence on the thermal structure of the atmosphere and thus greatly affects atmospheric circulation. The dust cycle is the most difficult of the three climate cycles (CO2, water, and dust) to model realistically with general circulation models. Until recently, numerical modeling investigations of the dust cycle have typically not included the effects of couplings to the water cycle through cloud formation. In the Martian atmosphere, dust particles likely provide the seed nuclei for heterogeneous nucleation of water ice clouds. As ice coats atmospheric dust grains, the newly formed cloud particles exhibit different physical and radiative characteristics. Thus, the coupling between the dust and water cycles likely affects the distributions of dust, water vapor and water ice, and thus atmospheric heating and cooling and the resulting circulations. We use the NASA Ames Mars GCM to investigate the effects of radiatively active water ice clouds on surface stress and the potential for dust lifting. The model includes a state-of-the-art water ice cloud microphysics package and a radiative transfer scheme that accounts for the radiative effects of CO2 gas, dust, and water ice clouds. We focus on simulations that are radiatively forced by a prescribed dust map, and we compare simulations that do and do not include radiatively active clouds. Preliminary results suggest that the magnitude and spatial patterns of surface stress (and thus dust lifting potential) are substantial influenced by the radiative effects of water ice clouds.

Isolating the Liquid Cloud Response to Recent Arctic Sea Ice Variability Using Spaceborne Lidar Observations

NASA Astrophysics Data System (ADS)

Morrison, A. L.; Kay, J. E.; Chepfer, H.; Guzman, R.; Yettella, V.

2018-01-01

While the radiative influence of clouds on Arctic sea ice is known, the influence of sea ice cover on Arctic clouds is challenging to detect, separate from atmospheric circulation, and attribute to human activities. Providing observational constraints on the two-way relationship between sea ice cover and Arctic clouds is important for predicting the rate of future sea ice loss. Here we use 8 years of CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations) spaceborne lidar observations from 2008 to 2015 to analyze Arctic cloud profiles over sea ice and over open water. Using a novel surface mask to restrict our analysis to where sea ice concentration varies, we isolate the influence of sea ice cover on Arctic Ocean clouds. The study focuses on clouds containing liquid water because liquid-containing clouds are the most important cloud type for radiative fluxes and therefore for sea ice melt and growth. Summer is the only season with no observed cloud response to sea ice cover variability: liquid cloud profiles are nearly identical over sea ice and over open water. These results suggest that shortwave summer cloud feedbacks do not slow long-term summer sea ice loss. In contrast, more liquid clouds are observed over open water than over sea ice in the winter, spring, and fall in the 8 year mean and in each individual year. Observed fall sea ice loss cannot be explained by natural variability alone, which suggests that observed increases in fall Arctic cloud cover over newly open water are linked to human activities.

Cloud Radiation Forcings and Feedbacks: General Circulation Model Tests and Observational Validation

NASA Technical Reports Server (NTRS)

Lee,Wan-Ho; Iacobellis, Sam F.; Somerville, Richard C. J.

1997-01-01

Using an atmospheric general circulation model (the National Center for Atmospheric Research Community Climate Model: CCM2), the effects on climate sensitivity of several different cloud radiation parameterizations have been investigated. In addition to the original cloud radiation scheme of CCM2, four parameterizations incorporating prognostic cloud water were tested: one version with prescribed cloud radiative properties and three other versions with interactive cloud radiative properties. The authors' numerical experiments employ perpetual July integrations driven by globally constant sea surface temperature forcings of two degrees, both positive and negative. A diagnostic radiation calculation has been applied to investigate the partial contributions of high, middle, and low cloud to the total cloud radiative forcing, as well as the contributions of water vapor, temperature, and cloud to the net climate feedback. The high cloud net radiative forcing is positive, and the middle and low cloud net radiative forcings are negative. The total net cloud forcing is negative in all of the model versions. The effect of interactive cloud radiative properties on global climate sensitivity is significant. The net cloud radiative feedbacks consist of quite different shortwave and longwave components between the schemes with interactive cloud radiative properties and the schemes with specified properties. The increase in cloud water content in the warmer climate leads to optically thicker middle- and low-level clouds and in turn to negative shortwave feedbacks for the interactive radiative schemes, while the decrease in cloud amount simply produces a positive shortwave feedback for the schemes with a specified cloud water path. For the longwave feedbacks, the decrease in high effective cloudiness for the schemes without interactive radiative properties leads to a negative feedback, while for the other cases, the longwave feedback is positive. These cloud radiation parameterizations are empirically validated by using a single-column diagnostic model. together with measurements from the Atmospheric Radiation Measurement program and from the Tropical Ocean Global Atmosphere Combined Ocean-Atmosphere Response Experiment. The inclusion of prognostic cloud water produces a notable improvement in the realism of the parameterizations, as judged by these observations. Furthermore, the observational evidence suggests that deriving cloud radiative properties from cloud water content and microphysical characteristics is a promising route to further improvement.

Profiling of Atmospheric Water Vapor from the SSM/T-2 Radiometric Measurements

NASA Technical Reports Server (NTRS)

Wang, J. R.

2000-01-01

An advantage of using the millimeter-wave measurements for water vapor profiling is the ability to probe beyond a moderate cloud cover. Such a capability has been demonstrated from an airborne MIR (Millimeter-wave Imaging Radiometer) flight over the Pacific Ocean during an intense observation period of TOGA/COARE (Tropical Ocean Global Atmosphere/ Couple Ocean Atmospheric Response Experiment) in early 1993. A Cloud Lidar System (CLS) and MODIS Airborne Simulator (MAS) were on board the same aircraft to identify the presence of clouds and cloud type. The retrieval algorithm not only provides output of a water vapor profile, but also the cloud liquid water and approximate cloud altitude required to satisfy convergence of the retrieval. The validity of these cloud parameters has not been verified previously. In this document, these cloud parameters are compared with those derived from concurrent measurements from the CLS and AMPR (Advanced Microwave Precipitation Radiometer).

Analysis of Meteorological Data Obtained During Flight in a Supercooled Stratiform Cloud of High Liquid-Water Content

NASA Technical Reports Server (NTRS)

Perkins, Porter J.; Kline, Dwight B.

1951-01-01

Flight icing-rate data obtained in a dense and. abnormally deep supercooled stratiform cloud system indicated the existence of liquid-water contents generally exceeding values in amount and extent previously reported over the midwestern sections of the United States. Additional information obtained during descent through a part of the cloud system indicated liquid-water contents that significantly exceeded theoretical values, especially near the middle of the cloud layer.. The growth of cloud droplets to sizes that resulted in sedimentation from the upper portions of the cloud is considered to be a possible cause of the high water contents near the center of the cloud layer. Flight measurements of the vertical temperature distribution in the cloud layer indicated a rate of change of temperature with altitude exceeding that of the moist adiabatic lapse rate. This excessive rate of change is considered to have contributed to the severity of the condition.

Evaluating the feasibility of global climate models to simulate cloud cover effect controlled by Marine Stratocumulus regime transitions

NASA Astrophysics Data System (ADS)

Goren, Tom; Muelmenstaedt, Johannes; Rosenfeld, Daniel; Quaas, Johannes

2017-04-01

Marine stratocumulus clouds (MSC) occur in two main cloud regimes of open and closed cells that differ significantly by their cloud cover. Closed cells gradually get cleansed of high CCN concentrations in a process that involves initiation of drizzle that breaks the full cloud cover into open cells. The drizzle creates downdrafts that organize the convection along converging gust fronts, which in turn produce stronger updrafts that can sustain more cloud water that compensates the depletion of the cloud water by the rain. In addition, having stronger updrafts allow the clouds to grow relatively deep before rain starts to deplete its cloud water. Therefore, lower droplet concentrations and stronger rain would lead to lower cloud fraction, but not necessary also to lower liquid water path (LWP). The fundamental relationships between these key variables derived from global climate model (GCM) simulations are analyzed with respect to observations in order to determine whether the GCM parameterizations can represent well the governing physical mechanisms upon MSC regime transitions. The results are used to evaluate the feasibility of GCM's for estimating aerosol cloud-mediated radiative forcing upon MSC regime transitions, which are responsible for the largest aerosol cloud-mediated radiative forcing.

Global model comparison of heterogeneous ice nucleation parameterizations in mixed phase clouds

NASA Astrophysics Data System (ADS)

Yun, Yuxing; Penner, Joyce E.

2012-04-01

A new aerosol-dependent mixed phase cloud parameterization for deposition/condensation/immersion (DCI) ice nucleation and one for contact freezing are compared to the original formulations in a coupled general circulation model and aerosol transport model. The present-day cloud liquid and ice water fields and cloud radiative forcing are analyzed and compared to observations. The new DCI freezing parameterization changes the spatial distribution of the cloud water field. Significant changes are found in the cloud ice water fraction and in the middle cloud fractions. The new DCI freezing parameterization predicts less ice water path (IWP) than the original formulation, especially in the Southern Hemisphere. The smaller IWP leads to a less efficient Bergeron-Findeisen process resulting in a larger liquid water path, shortwave cloud forcing, and longwave cloud forcing. It is found that contact freezing parameterizations have a greater impact on the cloud water field and radiative forcing than the two DCI freezing parameterizations that we compared. The net solar flux at top of atmosphere and net longwave flux at the top of the atmosphere change by up to 8.73 and 3.52 W m-2, respectively, due to the use of different DCI and contact freezing parameterizations in mixed phase clouds. The total climate forcing from anthropogenic black carbon/organic matter in mixed phase clouds is estimated to be 0.16-0.93 W m-2using the aerosol-dependent parameterizations. A sensitivity test with contact ice nuclei concentration in the original parameterization fit to that recommended by Young (1974) gives results that are closer to the new contact freezing parameterization.

Wet and Occult Ion Deposition To An Elevated Forest Ecosystem In Switzerland

NASA Astrophysics Data System (ADS)

Buetzberger, P.; Burkard, R.; Eugster, W.

Due to much higher ion concentrations in fogwater compared to rainwater, critical deposition levels of nutrients such as sulfate, nitrate or ammonium can be achieved in areas with high fog frequency. From summer 2001 until spring 2002 a measuring campaign of the FINIMSAS project (Fog Interception and Nutrient Inputs to Montane- Subalpine Areas in Switzerland) is being conducted at Laegeren (690m asl) on the Swiss Plateau. Fog frequency was high during our campaign. Similar measurements were carried out in 1986/87 at the exact same location, providing a reference data set for comparison. Because the deposition flux was measured differently during 1986/87, direct compar- isons are only possible for ion concentrations. Preliminary results show a significant decrease of sulfate and ammonium median concentrations of more than 50 % over this 15 year period, whereas nitrate decrease is relatively small. This corresponds well with the large-scale evolution of the air pollutant emissions of SO2 (major decrease) and NOx (relatively small decrease). The strong reduction of ammonium is probably due to the reduced use of fertilizer in the area. Chloride shows the largest decrease which can be attributed to the improvement of filtering technique of waste incinerations. In order to achieve maximum comparability, similar event types (e.g. advection fog vs. radiation fog) with similar meteorological conditions were interpreted individually. Analysis of fog nutrient input with respect to wind direction, wind speed, and origin of air mass will help to understand the influence of local and large-scale emissions on fog water concentrations in Switzerland. Computations based on half-hourly mean wind direction revealed significantly lower fog water input but higher median concentra- tions of all measured components if the dominating wind sector was East. Event-based wind field analyses were also carried out and compared to computed trajectories. In order to assess the influence of fog and rain water nutrient deposition on vegetation and soil, we measured throughfall precipitation close to the forest floor. Whereas fog water showed pH values as low as 3, throughfall water was between pH 6 and 7, indicating an important buffering capacity of this ecosystem mainly due to potassium leaching and probably calcium compounds. High ionic concentrations and low pH values seem to act mostly on the leaves.

4-D cloud properties from passive satellite data and applications to resolve the flight icing threat to aircraft

NASA Astrophysics Data System (ADS)

Smith, William L., Jr.

The threat for aircraft icing in clouds is a significant hazard that routinely impacts aviation operations. Accurate diagnoses and forecasts of aircraft icing conditions requires identifying the location and vertical distribution of clouds with super-cooled liquid water (SLW) droplets, as well as the characteristics of the droplet size distribution. Traditional forecasting methods rely on guidance from numerical models and conventional observations, neither of which currently resolve cloud properties adequately on the optimal scales needed for aviation. Satellite imagers provide measurements over large areas with high spatial resolution that can be interpreted to identify the locations and characteristics of clouds, including features associated with adverse weather and storms. This thesis develops new techniques for interpreting cloud products derived from satellite data to infer the flight icing threat to aircraft in a wide range of cloud conditions. For unobscured low clouds, the icing threat is determined using empirical relationships developed from correlations between satellite imager retrievals of liquid water path and droplet size with icing conditions reported by pilots (PIREPS). For deep ice over water cloud systems, ice and liquid water content profiles are derived by using the imager cloud properties to constrain climatological information on cloud vertical structure and water phase obtained apriori from radar and lidar observations, and from cloud model analyses. Retrievals of the SLW content embedded within overlapping clouds are mapped to the icing threat using guidance from an airfoil modeling study. Compared to PIREPS, the satellite icing detection and intensity accuracies are found to be about 90% and 70%, respectively. Mean differences between the imager IWC retrievals with those from CloudSat and Calipso are less than 30%. This level of closure in the cloud water budget can only be achieved by correcting for errors in the imager retrievals due to the simplifying but poor assumption that deep optically thick clouds are single-phase and vertically homogeneous. When applied to geostationary satellite data, the profiling method provides a real-time characterization of clouds in 4-D. This research should improve the utility of satellite imager data for quantitatively diagnosing and predicting clouds and their effects in weather and climate applications.

Characterization of cumulus cloud fields using trajectories in the center of gravity versus water mass phase space: 1. Cloud tracking and phase space description: CENTER OF GRAVITY VERSUS WATER MASS 1

DOE Office of Scientific and Technical Information (OSTI.GOV)

Heiblum, Reuven H.; Altaratz, Orit; Koren, Ilan

We study the evolution of warm convective cloud fields using large eddy simulations of continental and trade cumulus. Individual clouds are tracked a posteriori from formation to dissipation using a 3D cloud tracking algorithm and results are presented in the phase- space of center of gravity altitude versus cloud liquid water mass (CvM space). The CvM space is shown to contain rich information on cloud field characteristics, cloud morphology, and common cloud development pathways, together facilitating a comprehensive understanding of the cloud field. In this part we show how the meteorological (thermodynamic) conditions that determine the cloud properties are projectedmore » on the CvM phase space and how changes in the initial conditions affect the clouds' trajectories in this space. This part sets the stage for a detailed microphysical analysis that will be shown in part II.« less

Canopy rainfall partitioning across an urbanization gradient in forest structure as characterized by terrestrial LiDAR

NASA Astrophysics Data System (ADS)

Mesta, D. C.; Van Stan, J. T., II; Yankine, S. A.; Cote, J. F.; Jarvis, M. T.; Hildebrandt, A.; Friesen, J.; Maldonado, G.

2017-12-01

As urbanization expands, greater forest area is shifting from natural stand structures to urban stand structures, like forest fragments and landscaped tree rows. Changes in forest canopy structure have been found to drastically alter the amount of rainwater reaching the surface. However, stormwater management models generally treat all forest structures (beyond needle versus broadleaved) similarly. This study examines the rainfall partitioning of Pinus spp. canopies along a natural-to-urban forest gradient and compares these to canopy structural measurements using terrestrial LiDAR. Throughfall and meteorological observations were also used to estimate parameters of the commonly-used Gash interception model. Preliminary findings indicate that as forest structure changed from natural, closed canopy conditions to semi-closed canopy fragments and, ultimately, to exposed urban landscaping tree rows, the interchange between throughfall and rainfall interception also changed. This shift in partitioning between throughfall and rainfall interception may be linked to intuitive parameters, like canopy closure and density, as well as more complex metrics, like the fine-scale patterning of gaps (ie, lacunarity). Thus, results indicate that not all forests of the same species should be treated the same by stormwater models. Rather, their canopy structural characteristics should be used to vary their hydrometeorological interactions.

A physical retrieval of cloud liquid water over the global oceans using special sensor microwave/imager (SSM/I) observations

NASA Astrophysics Data System (ADS)

Greenwald, Thomas J.; Stephens, Graeme L.; Vonder Haar, Thomas H.; Jackson, Darren L.

1993-10-01

A method of remotely sensing integrated cloud liquid water over the oceans using spaceborne passive measurements from the special sensor microwave/imager (SSM/I) is described. The technique is comprised of a simple physical model that uses the 19.35- and 37-GHz channels of the SSM/I. The most comprehensive validation to date of cloud liquid water estimated from satellites is presented. This is accomplished through a comparison to independent ground-based microwave radiometer measurements of liquid water on San Nicolas Island, over the North Sea, and on Kwajalein and Saipan Islands in the western Pacific. In areas of marine stratocumulus clouds off the coast of California a further comparison is made to liquid water inferred from advanced very high resolution radiometer (AVHRR) visible reflectance measurements. The results are also compared qualitatively with near-coincident satellite imagery and with other existing microwave methods in selected regions. These comparisons indicate that the liquid water amounts derived from the simple scheme are consistent with the ground-based measurements for nonprecipitating cloud systems in the subtropics and middle to high latitudes. The comparison in the tropics, however, was less conclusive. Nevertheless, the retrieval method appears to have general applicability over most areas of the global oceans. An observational measure of the minimum uncertainty in the retrievals is determined in a limited number of known cloud-free areas, where the liquid water amounts are found to have a low variability of 0.016 kg m-2. A simple sensitivity and error analysis suggests that the liquid water estimates have a theoretical relative error typically ranging from about 25% to near 40% depending on the atmospheric/surface conditions and on the amount of liquid water present in the cloud. For the global oceans as a whole the average cloud liquid water is determined to be about 0.08 kg m-2. The major conclusion of this paper is that reasonably accurate amounts of cloud liquid water can be retrieved from SSM/I observations for nonprecipitating cloud systems, particularly in areas of persistent stratocumulus clouds, with less accurate retrievals in tropical regions.

The pH and ionic composition of stratiform cloud water

NASA Astrophysics Data System (ADS)

Castillo, Raymond A.; Jiusto, James E.; Mclaren, Eugene

Over 50 cloud water samples were collected during five comprehensive case studies of the water chemistry of stratiform clouds at Whiteface Mountain, New York. The water samples were analyzed for pH, conductivity and ions of sodium, potassium, magnesium, calcium, ammonium, sulfate, chloride and nitrate. Trajectory analyses and cloud condensation nucleus concentrations at 0.5 % confirmed that the air masses in all five of these cases represented continental air that was relatively clean (low aerosol concentration) for the northeystern United States. The major ions related to cloud water pH were found to be sulfate, nitrate, potassium, ammonium and calcium. The results revealed a mean hydrogen ion concentration [ H+] = 0.239 meq ℓ -1 ( σ = ± 0.21) which converts to a mean pH = 3.6 for all collected cloud samples. The low pH values are related to a normal background of nitrate ions found in the rural continental air masses plus sulfate ions largely from the industrial emissions of the midwestern United States. The [NO -3], in two of the three cases presented, demonstrates the importance of the nitrate ions' contribution to the pH of cloud water. A dependent means analysis of 40 events yielded a significant difference (0.04 level of significance), with the mean pH of precipitation (4.2) being greater than the mean pH of cloud water (4.0) for event samples. The ion concentrations indicated that the cloud rainout process contributed from 67 % to almost 100% of the total ion concentration of the precipitation. The washout process, i.e. precipitation scavenging below the cloud base, contributed considerably less than the cloud/rainout process of those total precipitation anions associated with air pollution.

Multilayer Cloud Detection with the MODIS Near-Infrared Water Vapor Absorption Band

NASA Technical Reports Server (NTRS)

Wind, Galina; Platnick, Steven; King, Michael D.; Hubanks, Paul A,; Pavolonis, Michael J.; Heidinger, Andrew K.; Yang, Ping; Baum, Bryan A.

2009-01-01

Data Collection 5 processing for the Moderate Resolution Imaging Spectroradiometer (MODIS) onboard the NASA Earth Observing System EOS Terra and Aqua spacecraft includes an algorithm for detecting multilayered clouds in daytime. The main objective of this algorithm is to detect multilayered cloud scenes, specifically optically thin ice cloud overlying a lower-level water cloud, that presents difficulties for retrieving cloud effective radius using single layer plane-parallel cloud models. The algorithm uses the MODIS 0.94 micron water vapor band along with CO2 bands to obtain two above-cloud precipitable water retrievals, the difference of which, in conjunction with additional tests, provides a map of where multilayered clouds might potentially exist. The presence of a multilayered cloud results in a large difference in retrievals of above-cloud properties between the CO2 and the 0.94 micron methods. In this paper the MODIS multilayered cloud algorithm is described, results of using the algorithm over example scenes are shown, and global statistics for multilayered clouds as observed by MODIS are discussed. A theoretical study of the algorithm behavior for simulated multilayered clouds is also given. Results are compared to two other comparable passive imager methods. A set of standard cloudy atmospheric profiles developed during the course of this investigation is also presented. The results lead to the conclusion that the MODIS multilayer cloud detection algorithm has some skill in identifying multilayered clouds with different thermodynamic phases

Species-Specific Effects on Throughfall Kinetic Energy in Subtropical Forest Plantations Are Related to Leaf Traits and Tree Architecture

PubMed Central

Bruelheide, Helge; Härdtle, Werner; Kröber, Wenzel; Li, Ying; von Oheimb, Goddert

2015-01-01

Soil erosion is a key threat to many ecosystems, especially in subtropical China where high erosion rates occur. While the mechanisms that induce soil erosion on agricultural land are well understood, soil erosion processes in forests have rarely been studied. Throughfall kinetic energy (TKE) is influenced in manifold ways and often determined by the tree’s leaf and architectural traits. We investigated the role of species identity in mono-specific stands on TKE by asking to what extent TKE is species-specific and which leaf and architectural traits account for variation in TKE. We measured TKE of 11 different tree species planted in monocultures in a biodiversity-ecosystem-functioning experiment in subtropical China, using sand-filled splash cups during five natural rainfall events in summer 2013. In addition, 14 leaf and tree architectural traits were measured and linked to TKE. Our results showed that TKE was highly species-specific. Highest TKE was found below Choerospondias axillaris and Sapindus saponaria, while Schima superba showed lowest TKE. These species-specific effects were mediated by leaf habit, leaf area (LA), leaf pinnation, leaf margin, stem diameter at ground level (GD), crown base height (CBH), tree height, number of branches and leaf area index (LAI) as biotic factors and throughfall as abiotic factor. Among these, leaf habit, tree height and LA showed the highest effect sizes on TKE and can be considered as major drivers of TKE. TKE was positively influenced by LA, GD, CBH, tree height, LAI, and throughfall amount while it was negatively influenced by the number of branches. TKE was lower in evergreen, simple leaved and dentate leaved than in deciduous, pinnated or entire leaved species. Our results clearly showed that soil erosion in forest plantations can be mitigated by the appropriate choice of tree species. PMID:26079260

Species-Specific Effects on Throughfall Kinetic Energy in Subtropical Forest Plantations Are Related to Leaf Traits and Tree Architecture.

PubMed

Goebes, Philipp; Bruelheide, Helge; Härdtle, Werner; Kröber, Wenzel; Kühn, Peter; Li, Ying; Seitz, Steffen; von Oheimb, Goddert; Scholten, Thomas

2015-01-01

Soil erosion is a key threat to many ecosystems, especially in subtropical China where high erosion rates occur. While the mechanisms that induce soil erosion on agricultural land are well understood, soil erosion processes in forests have rarely been studied. Throughfall kinetic energy (TKE) is influenced in manifold ways and often determined by the tree's leaf and architectural traits. We investigated the role of species identity in mono-specific stands on TKE by asking to what extent TKE is species-specific and which leaf and architectural traits account for variation in TKE. We measured TKE of 11 different tree species planted in monocultures in a biodiversity-ecosystem-functioning experiment in subtropical China, using sand-filled splash cups during five natural rainfall events in summer 2013. In addition, 14 leaf and tree architectural traits were measured and linked to TKE. Our results showed that TKE was highly species-specific. Highest TKE was found below Choerospondias axillaris and Sapindus saponaria, while Schima superba showed lowest TKE. These species-specific effects were mediated by leaf habit, leaf area (LA), leaf pinnation, leaf margin, stem diameter at ground level (GD), crown base height (CBH), tree height, number of branches and leaf area index (LAI) as biotic factors and throughfall as abiotic factor. Among these, leaf habit, tree height and LA showed the highest effect sizes on TKE and can be considered as major drivers of TKE. TKE was positively influenced by LA, GD, CBH, tree height, LAI, and throughfall amount while it was negatively influenced by the number of branches. TKE was lower in evergreen, simple leaved and dentate leaved than in deciduous, pinnated or entire leaved species. Our results clearly showed that soil erosion in forest plantations can be mitigated by the appropriate choice of tree species.

A method to assess the inter-annual weather-dependent variability in air pollution concentration and deposition based on weather typing

NASA Astrophysics Data System (ADS)

Pleijel, Håkan; Grundström, Maria; Karlsson, Gunilla Pihl; Karlsson, Per Erik; Chen, Deliang

2016-02-01

Annual anomalies in air pollutant concentrations, and deposition (bulk and throughfall) of sulphate, nitrate and ammonium, in the Gothenburg region, south-west Sweden, were correlated with optimized linear combinations of the yearly frequency of Lamb Weather Types (LWTs) to determine the extent to which the year-to-year variation in pollution exposure can be partly explained by weather related variability. Air concentrations of urban NO2, CO, PM10, as well as O3 at both an urban and a rural monitoring site, and the deposition of sulphate, nitrate and ammonium for the period 1997-2010 were included in the analysis. Linear detrending of the time series was performed to estimate trend-independent anomalies. These estimated anomalies were subtracted from observed annual values. Then the statistical significance of temporal trends with and without LWT adjustment was tested. For the pollutants studied, the annual anomaly was well correlated with the annual LWT combination (R2 in the range 0.52-0.90). Some negative (annual average [NO2], ammonia bulk deposition) or positive (average urban [O3]) temporal trends became statistically significant (p < 0.05) when the LWT adjustment was applied. In all the cases but one (NH4 throughfall, for which no temporal trend existed) the significance of temporal trends became stronger with LWT adjustment. For nitrate and ammonium, the LWT based adjustment explained a larger fraction of the inter-annual variation for bulk deposition than for throughfall. This is probably linked to the longer time scale of canopy related dry deposition processes influencing throughfall being explained to a lesser extent by LWTs than the meteorological factors controlling bulk deposition. The proposed novel methodology can be used by authorities responsible for air pollution management, and by researchers studying temporal trends in pollution, to evaluate e.g. the relative importance of changes in emissions and weather variability in annual air pollution exposure.

Contrasting cloud composition between coupled and decoupled marine boundary layer clouds

NASA Astrophysics Data System (ADS)

Wang, Zhen; Mora Ramirez, Marco; Dadashazar, Hossein; MacDonald, Alex B.; Crosbie, Ewan; Bates, Kelvin H.; Coggon, Matthew M.; Craven, Jill S.; Lynch, Peng; Campbell, James R.; Azadi Aghdam, Mojtaba; Woods, Roy K.; Jonsson, Haflidi; Flagan, Richard C.; Seinfeld, John H.; Sorooshian, Armin

2016-10-01

Marine stratocumulus clouds often become decoupled from the vertical layer immediately above the ocean surface. This study contrasts cloud chemical composition between coupled and decoupled marine stratocumulus clouds for dissolved nonwater substances. Cloud water and droplet residual particle composition were measured in clouds off the California coast during three airborne experiments in July-August of separate years (Eastern Pacific Emitted Aerosol Cloud Experiment 2011, Nucleation in California Experiment 2013, and Biological and Oceanic Atmospheric Study 2015). Decoupled clouds exhibited significantly lower air-equivalent mass concentrations in both cloud water and droplet residual particles, consistent with reduced cloud droplet number concentration and subcloud aerosol (Dp > 100 nm) number concentration, owing to detachment from surface sources. Nonrefractory submicrometer aerosol measurements show that coupled clouds exhibit higher sulfate mass fractions in droplet residual particles, owing to more abundant precursor emissions from the ocean and ships. Consequently, decoupled clouds exhibited higher mass fractions of organics, nitrate, and ammonium in droplet residual particles, owing to effects of long-range transport from more distant sources. Sodium and chloride dominated in terms of air-equivalent concentration in cloud water for coupled clouds, and their mass fractions and concentrations exceeded those in decoupled clouds. Conversely, with the exception of sea-salt constituents (e.g., Cl, Na, Mg, and K), cloud water mass fractions of all species examined were higher in decoupled clouds relative to coupled clouds. Satellite and Navy Aerosol Analysis and Prediction System-based reanalysis data are compared with each other, and the airborne data to conclude that limitations in resolving boundary layer processes in a global model prevent it from accurately quantifying observed differences between coupled and decoupled cloud composition.

Controlled generation of large volumes of atmospheric clouds in a ground-based environmental chamber

NASA Technical Reports Server (NTRS)

Hettel, H. J.; Depena, R. G.; Pena, J. A.

1975-01-01

Atmospheric clouds were generated in a 23,000 cubic meter environmental chamber as the first step in a two part study on the effects of contaminants on cloud formation. The generation procedure was modeled on the terrestrial generation mechanism so that naturally occurring microphysics mechanisms were operative in the cloud generation process. Temperature, altitude, liquid water content, and convective updraft velocity could be selected independently over the range of terrestrially realizable clouds. To provide cloud stability, a cotton muslin cylinder 29.3 meters in diameter and 24.2 meters high was erected within the chamber and continuously wetted with water at precisely the same temperature as the cloud. The improved instrumentation which permitted fast, precise, and continual measurements of cloud temperature and liquid water content is described.

Remote Sensing of Water Vapor and Thin Cirrus Clouds using MODIS Near-IR Channels

NASA Technical Reports Server (NTRS)

Gao, Bo-Cai; Kaufman, Yoram J.

2001-01-01

The Moderate Resolution Imaging Spectroradiometer (MODIS), a major facility instrument on board the Terra Spacecraft, was successfully launched into space in December of 1999. MODIS has several near-IR channels within and around the 0.94 micrometer water vapor bands for remote sensing of integrated atmospheric water vapor over land and above clouds. MODIS also has a special near-IR channel centered at 1.375-micron with a width of 30 nm for remote sensing of cirrus clouds. In this paper, we describe briefly the physical principles on remote sensing of water vapor and cirrus clouds using these channels. We also present sample water vapor images and cirrus cloud images obtained from MODIS data.

Determination of effective droplet radius and optical depth of liquid water clouds over a tropical site in northern Thailand using passive microwave soundings, aircraft measurements and spectral irradiance data

NASA Astrophysics Data System (ADS)

Nimnuan, P.; Janjai, S.; Nunez, M.; Pratummasoot, N.; Buntoung, S.; Charuchittipan, D.; Chanyatham, T.; Chantraket, P.; Tantiplubthong, N.

2017-08-01

This paper presents an algorithm for deriving the effective droplet radius and optical depth of liquid water clouds using ground-based measurements, aircraft observations and an adiabatic model of cloud liquid water. The algorithm derives cloud effective radius and cloud optical depth over a tropical site at Omkoi (17.80°N, 98.43°E), Thailand. Monthly averages of cloud optical depth are highest in April (54.5), which is the month with the lowest average cloud effective radius (4.2 μm), both occurring before the start of the rainy season and at the end of the high contamination period. By contrast, the monsoon period extending from May to October brings higher cloud effective radius and lower cloud optical depth to the region on average. At the diurnal scale there is a gradual increase in average cloud optical depth and decrease in cloud effective radius as the day progresses.

Impact of aerosols, dust, water vapor and clouds on fair weather PG and implications for the Carnegie curve

NASA Astrophysics Data System (ADS)

Kourtidis, Konstantinos; Georgoulias, Aristeidis

2017-04-01

We studied the impact of anthropogenic aerosols, fine mode natural aerosols, Saharan dust, atmospheric water vapor, cloud fraction, cloud optical depth and cloud top height on the magnitude of fair weather PG at the rural station of Xanthi. Fair weather PG was measured in situ while the other parameters were obtained from the MODIS instrument onboard the Terra and Aqua satellites. All of the above parameteres were found to impact fair weather PG magnitude. Regarding aerosols, the impact was larger for Saharan dust and fine mode natural aerosols whereas regarding clouds the impact was larger for cloud fraction while less than that of aerosols. Water vapour and ice precipitable water were also found to influence fair weather PG. Since aerosols and water are ubiquitous in the atmosphere and exhibit large spatial and temporal variability, we postulate that our understanding of the Carnegie curve might need revision.

A comparison of Aqua MODIS ice and liquid water cloud physical and optical properties between collection 6 and collection 5.1: Pixel-to-pixel comparisons

NASA Astrophysics Data System (ADS)

Yi, Bingqi; Rapp, Anita D.; Yang, Ping; Baum, Bryan A.; King, Michael D.

2017-04-01

We compare differences in ice and liquid water cloud physical and optical properties between Aqua Moderate Resolution Imaging Spectroradiometer (MODIS) collection 6 (C6) and collection 5.1 (C51). The C6 cloud products changed significantly due to improved calibration, improvements based on comparisons with the Cloud-Aerosol Lidar with Orthogonal Polarization, treatment of subpixel liquid water clouds, introduction of a roughened ice habit for C6 rather than the use of smooth ice particles in C51, and more. The MODIS cloud products form a long-term data set for analysis, modeling, and various purposes. Thus, it is important to understand the impact of the changes. Two cases are considered for C6 to C51 comparisons. Case 1 considers pixels with valid cloud retrievals in both C6 and C51, while case 2 compares all valid cloud retrievals in each collection. One year (2012) of level-2 MODIS cloud products are examined, including cloud effective radius (CER), optical thickness (COT), water path, cloud top pressure (CTP), cloud top temperature, and cloud fraction. Large C6-C51 differences are found in the ice CER (regionally, as large as 15 μm) and COT (decrease in annual average by approximately 25%). Liquid water clouds have higher CTP in marine stratocumulus regions in C6 but lower CTP globally (-5 hPa), and there are 66% more valid pixels in C6 (case 2) due to the treatment of pixels with subpixel clouds. Simulated total cloud radiative signatures from C51 and C6 are compared to Clouds and the Earth's Radiant Energy System Energy Balanced And Filled (EBAF) product. The C6 CREs compare more closely with the EBAF than the C51 counterparts.

Cloud deposition of PAHs at Mount Lushan in southern China.

PubMed

Wang, Ruixia; Wang, Yan; Li, Hongli; Yang, Minmin; Sun, Lei; Wang, Tao; Wang, Wenxing

2015-09-01

Cloud water samples were collected from Mount Lushan, a high alpine area of southern China, and analyzed using GC-MS to investigate the concentration levels, seasonal variations, particle-dissolved phase partitioning, ecological risk of PAHs and its relationship to the atmosphere and rainwater. The average concentration of total (dissolved+particle) PAHs in cloud water was 819.90 ng/L, which ranged from 2.30 ng/L for DbA to 295.38 ng/L for PhA. PhA (33.11%) contributed the most individual PAHs, followed by Flu (28.24%). Distinct seasonal variations in the total PAHs measured in this research had a higher concentration during the spring and a lower concentration during the summer. When cloud events occurred, the concentration of the atmospheric PAHs of the two phases decreased. The contribution from the gaseous phase of total PAHs in the air to the dissolved phase in cloud water was up to 60.43%, but the particulate phase in the air only contributed 39.57% to the total scavenging. The contribution of total PAHs from the atmosphere to clouds is higher in the gaseous phase than in the particulate phase. A comparative study of the concentrations of cloud water and the closest rain water revealed that the PAH concentration in rainwater was 1.80 times less than that of cloud water and that the dominant individual compounds in cloud water and rainwater were PhA and Flu. A total of 81.27% of the PAHs in cloud samples and 72.21% of the PAHs in rain samples remained in the dissolved phase. Ecological risk assessment indicated that PAHs in cloud water in spring and summer caused a certain degree of ecosystem risk and the mean ecosystem risk in spring was higher than that in summer. Copyright © 2015 Elsevier B.V. All rights reserved.

An Algorithm for the Retrieval of Droplet Number Concentration and Geometrical Thickness of Stratiform Marine Boundary Layer Clouds Applied to MODIS Radiometric Observations.

NASA Astrophysics Data System (ADS)

Schüller, Lothar; Bennartz, Ralf; Fischer, Jürgen; Brenguier, Jean-Louis

2005-01-01

Algorithms are now currently used for the retrieval of cloud optical thickness and droplet effective radius from multispectral radiance measurements. This paper extends their application to the retrieval of cloud droplet number concentration, cloud geometrical thickness, and liquid water path in shallow convective clouds, using an algorithm that was previously tested with airborne measurements of cloud radiances and validated against in situ measurements of the same clouds. The retrieval is based on a stratified cloud model of liquid water content and droplet spectrum. Radiance measurements in visible and near-infrared channels of the Moderate Resolution Imaging Spectroradiometer (MODIS), which is operated from the NASA platforms Terra and Aqua, are analyzed. Because of uncertainties in the simulation of the continental surface reflectance, the algorithm is presently limited to the monitoring of the microphysical structure of boundary layer clouds over the ocean. Two MODIS scenes of extended cloud fields over the North Atlantic Ocean trade wind region are processed. A transport and dispersion model (the Hybrid Single-Particle Lagrangian Integrated Trajectory Model, HYSPLIT4) is also used to characterize the origin of the air masses and hence their aerosol regimes. One cloud field formed in an air mass that was advected from southern Europe and North Africa. It shows high values of the droplet concentration when compared with the second cloud system, which developed in a more pristine environment. The more pristine case also exhibits a higher geometrical thickness and, thus, liquid water path, which counterbalances the expected cloud albedo increase of the polluted case. Estimates of cloud liquid water path are then compared with retrievals from the Special Sensor Microwave Imager (SSM/I). SSM/I-derived liquid water paths are in good agreement with the MODIS-derived values.

Analyzing the Effect of Intraseasonal Meteorological Variability and Land Cover on Aerosol-Cloud Interactions During the Amazonian Biomass Burning Season

NASA Technical Reports Server (NTRS)

TenHoeve, J. E.; Remer, L. A.; Jacobson, M. Z.

2010-01-01

High resolution aerosol, cloud, water vapor, and atmospheric profile data from the Moderate Resolution Imaging Spectroradiometer (MODIS) are utilized to examine the impact of aerosols on clouds during the Amazonian biomass burning season in Rondnia, Brazil. It is found that increasing background column water vapor (CWV) throughout this transition season between the Amazon dry and wet seasons exerts a strong effect on cloud properties. As a result, aerosol-cloud correlations should be stratified by column water vapor to achieve a more accurate assessment of the effect of aerosols on clouds. Previous studies ignored the systematic changes to meteorological factors during the transition season, leading to possible misinterpretation of their results. Cloud fraction is shown generally to increase with aerosol optical depth (AOD) for both low and high values of column water vapor, whereas the relationship between cloud optical depth (COD) and AOD exhibits a different relationship. COD increases with AOD until AOD approx. 0.25 due to the first indirect (microphysical) effect. At higher values of AOD, COD is found to decrease with increasing AOD, which may be due to: (1) the inhibition of cloud development by absorbing aerosols (radiative effect) and/or (2) a retrieval artifact in which the measured reflectance in the visible is less than expected from a cloud top either from the darkening of clouds through the addition of carbonaceous biomass burning aerosols or subpixel dark surface contamination in the measured cloud reflectance. If (1) is a contributing mechanism, as we suspect, then a linear relationship between the indirect effect and increasing AOD, assumed in a majority of GCMs, is inaccurate since these models do not include treatment of aerosol absorption in and around clouds. The effect of aerosols on both column water vapor and clouds over varying land surface types is also analyzed. The study finds that the difference in column water vapor between forest and pasture is not correlated with aerosol loading, supporting the assumption that temporal variation of column water vapor is primarily a function of the larger-scale meteorology. However, a difference in the response of cloud fraction to increasing AOD is observed between forest and pasture. This suggests that dissimilarities between other meteorological factors, such as atmospheric stability, are likely to have an impact on aerosol-cloud correlations between different land-cover types.

Automated detection of Martian water ice clouds: the Valles Marineris

NASA Astrophysics Data System (ADS)

Ogohara, Kazunori; Munetomo, Takafumi; Hatanaka, Yuji; Okumura, Susumu

2016-10-01

We need to extract water ice clouds from the large number of Mars images in order to reveal spatial and temporal variations of water ice cloud occurrence and to meteorologically understand climatology of water ice clouds. However, visible images observed by Mars orbiters for several years are too many to visually inspect each of them even though the inspection was limited to one region. Therefore, an automated detection algorithm of Martian water ice clouds is necessary for collecting ice cloud images efficiently. In addition, it may visualize new aspects of spatial and temporal variations of water ice clouds that we have never been aware. We present a method for automatically evaluating the presence of Martian water ice clouds using difference images and cross-correlation distributions calculated from blue band images of the Valles Marineris obtained by the Mars Orbiter Camera onboard the Mars Global Surveyor (MGS/MOC). We derived one subtracted image and one cross-correlation distribution from two reflectance images. The difference between the maximum and the average, variance, kurtosis, and skewness of the subtracted image were calculated. Those of the cross-correlation distribution were also calculated. These eight statistics were used as feature vectors for training Support Vector Machine, and its generalization ability was tested using 10-fold cross-validation. F-measure and accuracy tended to be approximately 0.8 if the maximum in the normalized reflectance and the difference of the maximum and the average in the cross-correlation were chosen as features. In the process of the development of the detection algorithm, we found many cases where the Valles Marineris became clearly brighter than adjacent areas in the blue band. It is at present unclear whether the bright Valles Marineris means the occurrence of water ice clouds inside the Valles Marineris or not. Therefore, subtracted images showing the bright Valles Marineris were excluded from the detection of water ice clouds

Throughfall Displacement Experiment (TDE) Ecosystem Model Intercomparison Project Data Archive

DOE Data Explorer

Hanson, Paul J. [Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (USA); Amthor, Jeffrey S. [Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (USA); Baldocchi, Dennis D. [University of California, Berkeley; Grant, Robert F. [University of Alberta, Canada; Hartley, Anne E. [Ohio State University; Hui, Dafeng [University of Oklahoma; Hunt, Jr., E. Raymond [Agricultural Research Service, U.S. Department of Agriculture; Johnson, Dale W. [University of Nevada, Reno; Kimball, John S. [University of Montana; King, Anthony W. [Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (USA); Luo, Yiqi [University of Oklahoma; McNulty, Steven G. [Southern Global Change Program, U.S. Forest Service, U.S. Department of Agriculture; Sun, Ge [North Carolina State University, Raleigh, NC (USA); Thornton, Peter E. [University of Montana; Wang, Shusen [Geomatics Canada - Canada Centre for Remote Sensing Natural Resources, Canada; Williams, Matthew [University of Edinburgh, United Kingdom; Wilson, Kell B. [National Oceanic and Atmospheric Administration, U.S. Department of Commerce; Wullschleger, Stanley D. [Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (USA)

2002-08-01

This archive provides and documents data from a project whose purpose is to compare the output of various ecosystem models when they are run with the data from the Throughfall Displacement Experiment (TDE) at Walker Branch Watershed, Oak Ridge, Tennessee. The project is not designed to determine which models are "best" for diagnosis (i.e., explaining the current functioning of the system) or prognosis (i.e., predicting the response of the system to future conditions), but, rather, to clarify similarities and differences among the models and their components, so that all models can be improved. Data archive: ftp://cdiac.ornl.gov/ftp/tdemodel/. TDE data archive web site: http://cdiac.ess-dive.lbl.gov/epubs/ndp/ndp078a/ndp078a.html.

Hydrologic, chemical, and isotopic characterization of two small watersheds on Catoctin Mountain, north-central Maryland, U.S.A.

USGS Publications Warehouse

Rice, Karen C.; Bricker, O.P.

1993-01-01

Two small (100 ha) watersheds located on Catoctin Mountain in north-central Maryland were intensively instrumented in 1990 and have been hydrologically, chemically, and isotopically monitored for 3 years. Dissolved concentrations of major ions (Ca2+, Mg2+, Na+, K+, total AI, CI-, NO3-, SO42- , HCO3-, and SiO2) and stable isotopic (D and 18O) values have been analyzed for most types of water (precipitation, throughfall, two depths of soil water, shallow groundwater, and streamwater) that enter, travel through, and exit each watershed. The major objectives of the study were to characterize the chemical and isotopic signatures of all aqueous components of the watersheds and to interpret the causes of the changes in chemical and isotopic compositions of streamwater during storm runoff. This paper describes selected results of the study.

Water ice clouds on Mars: a study of partial cloudiness with a global climate model and MARCI data

NASA Astrophysics Data System (ADS)

Pottier, Alizée; Montmessin, Franck; Forget, François; Wolff, Mike; Navarro, Thomas; Millour, Ehouarn; Madeleine, Jean-Baptiste; Spiga, Aymeric; Bertrand, Tanguy

2015-04-01

There is a large reservoir of water ice on Mars in the polar caps, that sublimates in summer and releases water vapor. Water is then advected in the atmospheric circulation that evolves seasonally. This vapor forms clouds, frost, and can also be adsorbed in the soil. In a global study of the water cycle, water ice clouds play a key part in the martian climate. There is a need to understand better their distribution and radiative effect. The tool used in this study is the global climate model (GCM) of the Laboratoire de Météorologie Dynamique. It is made up of a core that computes fluid dynamics, and a physical part that gathers a number of parametrised processes. It includes tracers and the condensation and sublimation of water in the atmosphere and on the ground, allowing a study of the complete water cycle. To improve the representation of water ice clouds in the model, a new parametrisation of partial cloudiness has been implemented and will be presented. Indeed, model cells are hundreds of kilometers wide, and it is quite unrealistic to suppose that cloud coverage is always uniform in them. Furthermore, the model was quite unstable since the implementation of the radiative effect of clouds, and partial cloudiness had the effect of reducing this instability. In practice, a subgrid temperature distribution is supposed, and the temperature computed in the model is interpreted as its mean. The subgrid scale temperature distribution is simple, and its width is a free parameter. Using this distribution, the fraction of the grid cells under the water vapor condensation temperature is interpreted as the fraction of the cell in which clouds form (or cloud fraction). From these fractions at each height a total partial cloudiness (the clouds as seen from the orbit) is deduced. The radiative transfer is computed twice, for the clear area and for the cloudy one. Observing the water cycle with this new parametrisation, some differences are seen with standard runs. These changes mainly affect the aphelion cloud belt and the polar hoods. Partial cloudiness is compared to higher resolution (one per one degree) runs in which cloudiness diagnostics are done. MARCI data of cloud opacity is also used to verify the predicted water ice cloud distribution and patchiness. The aim is to understand the causes of patchiness and to validate the choice of a subgrid scale temperature distribution. There are seasonal variations, recurring patterns near major topographical features.

Observed correlations between aerosol and cloud properties in an Indian Ocean trade cumulus regime

NASA Astrophysics Data System (ADS)

Pistone, Kristina; Praveen, Puppala S.; Thomas, Rick M.; Ramanathan, Veerabhadran; Wilcox, Eric M.; Bender, Frida A.-M.

2017-04-01

There are multiple factors which affect the micro- and macrophysical properties of clouds, including the atmospheric vertical structure and dominant meteorological conditions in addition to aerosol concentration, all of which may be coupled to one another. In the quest to determine aerosol effects on clouds, these potential relationships must be understood. As bio- and fossil fuel combustion has increased in southeast Asia, corresponding increases in atmospheric aerosol pollution have been seen over the surrounding regions. These emissions notably include black carbon (BC) aerosols, which absorb rather than reflect solar radiation, affecting the atmosphere over the Indian Ocean through direct warming in addition to modifying cloud microphysical properties. The CARDEX (Cloud, Aerosol, Radiative forcing, Dynamics EXperiment) field campaign was conducted during the winter monsoon season (February and March) of 2012 in the northern Indian Ocean, a region dominated by trade cumulus clouds. During CARDEX, small unmanned aircraft were deployed, measuring aerosol, radiation, cloud, water vapor fluxes, and meteorological properties while a surface observatory collected continuous measurements of atmospheric precipitable water vapor (PWV), water vapor fluxes, surface and total-column aerosol, and cloud liquid water path (LWP). We present observations which indicate a positive correlation between aerosol and cloud LWP only when considering cases with low atmospheric water vapor (PWV)

Precipitation formation from orographic cloud seeding.

PubMed

French, Jeffrey R; Friedrich, Katja; Tessendorf, Sarah A; Rauber, Robert M; Geerts, Bart; Rasmussen, Roy M; Xue, Lulin; Kunkel, Melvin L; Blestrud, Derek R

2018-02-06

Throughout the western United States and other semiarid mountainous regions across the globe, water supplies are fed primarily through the melting of snowpack. Growing populations place higher demands on water, while warmer winters and earlier springs reduce its supply. Water managers are tantalized by the prospect of cloud seeding as a way to increase winter snowfall, thereby shifting the balance between water supply and demand. Little direct scientific evidence exists that confirms even the basic physical hypothesis upon which cloud seeding relies. The intent of glaciogenic seeding of orographic clouds is to introduce aerosol into a cloud to alter the natural development of cloud particles and enhance wintertime precipitation in a targeted region. The hypothesized chain of events begins with the introduction of silver iodide aerosol into cloud regions containing supercooled liquid water, leading to the nucleation of ice crystals, followed by ice particle growth to sizes sufficiently large such that snow falls to the ground. Despite numerous experiments spanning several decades, no direct observations of this process exist. Here, measurements from radars and aircraft-mounted cloud physics probes are presented that together show the initiation, growth, and fallout to the mountain surface of ice crystals resulting from glaciogenic seeding. These data, by themselves, do not address the question of cloud seeding efficacy, but rather form a critical set of observations necessary for such investigations. These observations are unambiguous and provide details of the physical chain of events following the introduction of glaciogenic cloud seeding aerosol into supercooled liquid orographic clouds.

A unified parameterization of clouds and turbulence using CLUBB and subcolumns in the Community Atmosphere Model

DOE PAGES

Thayer-Calder, K.; Gettelman, A.; Craig, C.; ...

2015-06-30

Most global climate models parameterize separate cloud types using separate parameterizations. This approach has several disadvantages, including obscure interactions between parameterizations and inaccurate triggering of cumulus parameterizations. Alternatively, a unified cloud parameterization uses one equation set to represent all cloud types. Such cloud types include stratiform liquid and ice cloud, shallow convective cloud, and deep convective cloud. Vital to the success of a unified parameterization is a general interface between clouds and microphysics. One such interface involves drawing Monte Carlo samples of subgrid variability of temperature, water vapor, cloud liquid, and cloud ice, and feeding the sample points into amore » microphysics scheme.This study evaluates a unified cloud parameterization and a Monte Carlo microphysics interface that has been implemented in the Community Atmosphere Model (CAM) version 5.3. Results describing the mean climate and tropical variability from global simulations are presented. The new model shows a degradation in precipitation skill but improvements in short-wave cloud forcing, liquid water path, long-wave cloud forcing, precipitable water, and tropical wave simulation. Also presented are estimations of computational expense and investigation of sensitivity to number of subcolumns.« less

A unified parameterization of clouds and turbulence using CLUBB and subcolumns in the Community Atmosphere Model

DOE PAGES

Thayer-Calder, Katherine; Gettelman, A.; Craig, Cheryl; ...

2015-12-01

Most global climate models parameterize separate cloud types using separate parameterizations.This approach has several disadvantages, including obscure interactions between parameterizations and inaccurate triggering of cumulus parameterizations. Alternatively, a unified cloud parameterization uses one equation set to represent all cloud types. Such cloud types include stratiform liquid and ice cloud, shallow convective cloud, and deep convective cloud. Vital to the success of a unified parameterization is a general interface between clouds and microphysics. One such interface involves drawing Monte Carlo samples of subgrid variability of temperature, water vapor, cloud liquid, and cloud ice, and feeding the sample points into a microphysicsmore » scheme. This study evaluates a unified cloud parameterization and a Monte Carlo microphysics interface that has been implemented in the Community Atmosphere Model (CAM) version 5.3. Results describing the mean climate and tropical variability from global simulations are presented. In conclusion, the new model shows a degradation in precipitation skill but improvements in short-wave cloud forcing, liquid water path, long-wave cloud forcing, perceptible water, and tropical wave simulation. Also presented are estimations of computational expense and investigation of sensitivity to number of subcolumns.« less

In situ observations of Arctic cloud properties across the Beaufort Sea marginal ice zone

NASA Astrophysics Data System (ADS)

Corr, C.; Moore, R.; Winstead, E.; Thornhill, K. L., II; Crosbie, E.; Ziemba, L. D.; Beyersdorf, A. J.; Chen, G.; Martin, R.; Shook, M.; Corbett, J.; Smith, W. L., Jr.; Anderson, B. E.

2016-12-01

Clouds play an important role in Arctic climate. This is particularly true over the Arctic Ocean where feedbacks between clouds and sea-ice impact the surface radiation budget through modifications of sea-ice extent, ice thickness, cloud base height, and cloud cover. This work summarizes measurements of Arctic cloud properties made aboard the NASA C-130 aircraft over the Beaufort Sea during ARISE (Arctic Radiation - IceBridge Sea&Ice Experiment) in September 2014. The influence of surface-type on cloud properties is also investigated. Specifically, liquid water content (LWC), droplet concentrations, and droplet size distributions are compared for clouds sampled over three distinct regimes in the Beaufort Sea: 1) open water, 2) the marginal ice zone, and 3) sea-ice. Regardless of surface type, nearly all clouds intercepted during ARISE were liquid-phase clouds. However, differences in droplet size distributions and concentrations were evident for the surface types; clouds over the MIZ and sea-ice generally had fewer and larger droplets compared to those over open water. The potential implication these results have for understanding cloud-surface albedo climate feedbacks in Arctic are discussed.

Atmospheric chemistry of carboxylic acids: microbial implication versus photochemistry

NASA Astrophysics Data System (ADS)

Vaïtilingom, M.; Charbouillot, T.; Deguillaume, L.; Maisonobe, R.; Parazols, M.; Amato, P.; Sancelme, M.; Delort, A.-M.

2011-02-01

Clouds are multiphasic atmospheric systems in which the dissolved organic compounds, dominated by carboxylic acids, are subject to multiple chemical transformations in the aqueous phase. Among them, solar radiation, by generating hydroxyl radicals (•OH), is considered as the main catalyzer of the reactivity of organic species in clouds. We investigated to which extent the active biomass existing in cloud water represents an alternative route to the chemical reactivity of carboxylic acids. Pure cultures of seventeen bacterial strains (Arthrobacter, Bacillus, Clavibacter, Frigoribacterium, Pseudomonas, Sphingomonas and Rhodococcus), previously isolated from cloud water and representative of the viable community of clouds were first individually incubated in two artificial bulk cloud water solutions at 17 °C and 5 °C. These solutions mimicked the chemical composition of cloud water from "marine" and "continental" air masses, and contained the major carboxylic acids existing in the cloud water (i.e. acetate, formate, succinate and oxalate). The concentrations of these carboxylic compounds were monitored over time and biodegradation rates were determined. In average, they ranged from 2 ×10-19 for succinate to 1 × 10-18 mol cell-1 s-1 for formate at 17 °C and from 4 × 10-20 for succinate to 6 × 10-19 mol cell-1 s-1 for formate at 5 °C, with no significant difference between "marine" and "continental" media. In parallel, irradiation experiments were also conducted in these two artificial media to compare biodegradation and photodegradation of carboxylic compounds. To complete this comparison, the photodegradation rates of carboxylic acids by •OH radicals were calculated from literature data. Inferred estimations suggested a significant participation of microbes to the transformation of carboxylic acids in cloud water, particularly for acetate and succinate (up to 90%). Furthermore, a natural cloud water sample was incubated (including its indigenous microflora); the rates of biodegradation were determined and compared to the photodegradation rates involving •OH radicals. The biodegradation rates in "natural" and "artificial" cloud water were in the same order of magnitude; this confirms the significant role of the active biomass in the aqueous reactivity of clouds.

Temporal evolution of stable water isotopologues in cloud droplets in a hill cap cloud in central Europe (HCCT-2010)

USGS Publications Warehouse

Spiegel, J.K.; Aemisegger, F.; Scholl, M.; Wienhold, F.G.; Collett, J.L.; Lee, T.; van Pinxteren, D.; Mertes, S.; Tilgner, A.; Herrmann, H.; Werner, Roland A.; Buchmann, N.; Eugster, W.

2012-01-01

In this work, we present the first study resolving the temporal evolution of δ2H and δ18O values in cloud droplets during 13 different cloud events. The cloud events were probed on a 937 m high mountain chain in Germany in the framework of the Hill Cap Cloud Thuringia 2010 campaign (HCCT-2010) in September and October 2010. The δ values of cloud droplets ranged from −77‰ to −15‰ (δ2H) and from −12.1‰ to −3.9‰ (δ18O) over the whole campaign. The cloud water line of the measured δ values was δ2H=7.8×δ18O+13×10−3, which is of similar slope, but with higher deuterium excess than other Central European Meteoric Water Lines. Decreasing δ values in the course of the campaign agree with seasonal trends observed in rain in central Europe. The deuterium excess was higher in clouds developing after recent precipitation revealing episodes of regional moisture recycling. The variations in δ values during one cloud event could either result from changes in meteorological conditions during condensation or from variations in the δ values of the water vapor feeding the cloud. To test which of both aspects dominated during the investigated cloud events, we modeled the variation in δ values in cloud water using a closed box model. We could show that the variation in δ values of two cloud events was mainly due to changes in local temperature conditions. For the other eleven cloud events, the variation was most likely caused by changes in the isotopic composition of the advected and entrained vapor. Frontal passages during two of the latter cloud events led to the strongest temporal changes in both δ2H (≈ 6‰ per hour) and δ18O (≈ 0.6‰ per hour). Moreover, a detailed trajectory analysis for the two longest cloud events revealed that variations in the entrained vapor were most likely related to rain out or changes in relative humidity and temperature at the moisture source region or both. This study illustrates the sensitivity of stable isotope composition of cloud water to changes in large scale air mass properties and regional recycling of moisture.

Ice Particle Impact on Cloud Water Content Instrumentation

NASA Technical Reports Server (NTRS)

Emery, Edward F.; Miller, Dean R.; Plaskon, Stephen R.; Strapp, Walter; Lillie, Lyle

2004-01-01

Determining the total amount of water contained in an icing cloud necessitates the measurement of both the liquid droplets and ice particles. One commonly accepted method for measuring cloud water content utilizes a hot wire sensing element, which is maintained at a constant temperature. In this approach, the cloud water content is equated with the power required to keep the sense element at a constant temperature. This method inherently assumes that impinging cloud particles remain on the sensing element surface long enough to be evaporated. In the case of ice particles, this assumption requires that the particles do not bounce off the surface after impact. Recent tests aimed at characterizing ice particle impact on a thermally heated wing section, have raised questions about the validity of this assumption. Ice particles were observed to bounce off the heated wing section a very high percentage of the time. This result could have implications for Total Water Content sensors which are designed to capture ice particles, and thus do not account for bouncing or breakup of ice particles. Based on these results, a test was conducted to investigate ice particle impact on the sensing elements of the following hot-wire cloud water content probes: (1) Nevzorov Total Water Content (TWC)/Liquid Water Content (LWC) probe, (2) Science Engineering Associates TWC probe, and (3) Particle Measuring Systems King probe. Close-up video imaging was used to study ice particle impact on the sensing element of each probe. The measured water content from each probe was also determined for each cloud condition. This paper will present results from this investigation and attempt to evaluate the significance of ice particle impact on hot-wire cloud water content measurements.

First UAV Measurements of Entrainment Layer Fluxes with Coupled Cloud Property Measurements

NASA Astrophysics Data System (ADS)

Thomas, R. M.; Praveen, P. S.; Wilcox, E. M.; Pistone, K.; Bender, F.; Ramanathan, V.

2012-12-01

This study details entrainment flux measurements made from a lightweight unmanned aerial vehicle (UAV) containing turbulent water vapor flux instrumentation (Thomas et al., 2012). The system was flown for 26 flights during the Cloud, Aerosol, Radiative forcing, Dynamics EXperiment (CARDEX) in the Maldives in March 2012 to study interrelationships between entrainment, aerosols, water budget, cloud microphysics and radiative fluxes in a trade wind cumulus cloud regime. A major advantage of using this lightweight, precision autopiloted UAV system with scientific telemetry is the ability to target small-scale features in the boundary layer, such as an entrainment layer, with minimal aircraft induced disruption. Results are presented from two UAVs flown in stacked formation: one UAV situated in-cloud measuring cloud-droplet size distribution spectra and liquid water content, and another co-located 100m above measuring turbulent properties and entrainment latent heat flux (λEE). We also show latent heat flux and turbulence measurements routinely made at the entrainment layer base and altitudes from the surface up to 4kft. Ratios of λEE to corresponding surface tower values (λES) display a bimodal frequency distribution with ranges 0.22-0.53 and 0.79-1.5, with occasional events >7. Reasons for this distribution are discussed drawing upon boundary layer and free tropospheric dynamics and meteorology, turbulence length scales, surface conditions, and cloud interactions. Latent heat flux profiles are combined with in-cloud UAV Liquid Water Content (LWC) data and surface based Liquid Water Path (LWP) and Precipitable Water Vapor (PWV) measurements to produce observationally constrained vertical water budgets, providing insights into diurnal coupling of λEE and λES. Observed λEE, λES, water budgets, and cloud microphysical responses to entrainment are then contextualized with respect to measured aerosol loading profiles and airmass history.

Cloud/climate sensitivity experiments

NASA Technical Reports Server (NTRS)

Roads, J. O.; Vallis, G. K.; Remer, L.

1982-01-01

A study of the relationships between large-scale cloud fields and large scale circulation patterns is presented. The basic tool is a multi-level numerical model comprising conservation equations for temperature, water vapor and cloud water and appropriate parameterizations for evaporation, condensation, precipitation and radiative feedbacks. Incorporating an equation for cloud water in a large-scale model is somewhat novel and allows the formation and advection of clouds to be treated explicitly. The model is run on a two-dimensional, vertical-horizontal grid with constant winds. It is shown that cloud cover increases with decreased eddy vertical velocity, decreased horizontal advection, decreased atmospheric temperature, increased surface temperature, and decreased precipitation efficiency. The cloud field is found to be well correlated with the relative humidity field except at the highest levels. When radiative feedbacks are incorporated and the temperature increased by increasing CO2 content, cloud amounts decrease at upper-levels or equivalently cloud top height falls. This reduces the temperature response, especially at upper levels, compared with an experiment in which cloud cover is fixed.

Modelling rainfall interception by forests: a new method for estimating the canopy storage capacity

NASA Astrophysics Data System (ADS)

Pereira, Fernando; Valente, Fernanda; Nóbrega, Cristina

2015-04-01

Evaporation of rainfall intercepted by forests is usually an important part of a catchment water balance. Recognizing the importance of interception loss, several models of the process have been developed. A key parameter of these models is the canopy storage capacity (S), commonly estimated by the so-called Leyton method. However, this method is somewhat subjective in the selection of the storms used to derive S, which is particularly critical when throughfall is highly variable in space. To overcome these problems, a new method for estimating S was proposed in 2009 by Pereira et al. (Agricultural and Forest Meteorology, 149: 680-688), which uses information from a larger number of storms, is less sensitive to throughfall spatial variability and is consistent with the formulation of the two most widely used rainfall interception models, Gash analytical model and Rutter model. However, this method has a drawback: it does not account for stemflow (Sf). To allow a wider use of this methodology, we propose now a revised version which makes the estimation of S independent of the importance of stemflow. For the application of this new version we only need to establish a linear regression of throughfall vs. gross rainfall using data from all storms large enough to saturate the canopy. Two of the parameters used by the Gash and the Rutter models, pd (the drainage partitioning coefficient) and S, are then derived from the regression coefficients: pd is firstly estimated allowing then the derivation of S but, if Sf is not considered, S can be estimated making pd= 0. This new method was tested using data from a eucalyptus plantation, a maritime pine forest and a traditional olive grove, all located in Central Portugal. For both the eucalyptus and the pine forests pd and S estimated by this new approach were comparable to the values derived in previous studies using the standard procedures. In the case of the traditional olive grove, the estimates obtained by this methodology for pd and S allowed interception loss to be modelled with a normalized averaged error less than 4%. Globally, these results confirm that the method is more robust and certainly less subjective, providing adequate estimates for pd and S which, in turn, are crucial for a good performance of the interception models.

A Diagnostic PDF Cloud Scheme to Improve Subtropical Low Clouds in NCAR Community Atmosphere Model (CAM5)

NASA Astrophysics Data System (ADS)

Qin, Yi; Lin, Yanluan; Xu, Shiming; Ma, Hsi-Yen; Xie, Shaocheng

2018-02-01

Low clouds strongly impact the radiation budget of the climate system, but their simulation in most GCMs has remained a challenge, especially over the subtropical stratocumulus region. Assuming a Gaussian distribution for the subgrid-scale total water and liquid water potential temperature, a new statistical cloud scheme is proposed and tested in NCAR Community Atmospheric Model version 5 (CAM5). The subgrid-scale variance is diagnosed from the turbulent and shallow convective processes in CAM5. The approach is able to maintain the consistency between cloud fraction and cloud condensate and thus alleviates the adjustment needed in the default relative humidity-based cloud fraction scheme. Short-term forecast simulations indicate that low cloud fraction and liquid water content, including their diurnal cycle, are improved due to a proper consideration of subgrid-scale variance over the southeastern Pacific Ocean region. Compared with the default cloud scheme, the new approach produced the mean climate reasonably well with improved shortwave cloud forcing (SWCF) due to more reasonable low cloud fraction and liquid water path over regions with predominant low clouds. Meanwhile, the SWCF bias over the tropical land regions is also alleviated. Furthermore, the simulated marine boundary layer clouds with the new approach extend further offshore and agree better with observations. The new approach is able to obtain the top of atmosphere (TOA) radiation balance with a slightly alleviated double ITCZ problem in preliminary coupled simulations. This study implies that a close coupling of cloud processes with other subgrid-scale physical processes is a promising approach to improve cloud simulations.

Reprint of "How do components of real cloud water affect aqueous pyruvate oxidation?"

NASA Astrophysics Data System (ADS)

Boris, Alexandra J.; Desyaterik, Yury; Collett, Jeffrey L.

2015-01-01

Chemical oxidation of dissolved volatile or semi-volatile organic compounds within fog and cloud droplets in the atmosphere could be a major pathway for secondary organic aerosol (SOA) formation. This proposed pathway consists of: (1) dissolution of organic chemicals from the gas phase into a droplet; (2) reaction with an aqueous phase oxidant to yield low volatility products; and (3) formation of particle phase organic matter as the droplet evaporates. The common approach to simulating aqueous SOA (aqSOA) reactions is photo-oxidation of laboratory standards in pure water. Reactions leading to aqSOA formation should be studied within real cloud and fog water to determine whether additional competing processes might alter apparent rates of reaction as indicated by rates of reactant loss or product formation. To evaluate and identify the origin of any cloud water matrix effects on one example of observed aqSOA production, pyruvate oxidation experiments simulating aqSOA formation were monitored within pure water, real cloud water samples, and an aqueous solution of inorganic salts. Two analysis methods were used: online electrospray ionization high-resolution time-of-flight mass spectrometry (ESI-HR-ToF-MS), and offline anion exchange chromatography (IC) with quantitative conductivity and qualitative ESI-HR-ToF-MS detection. The apparent rate of oxidation of pyruvate was slowed in cloud water matrices: overall measured degradation rates of pyruvate were lower than in pure water. This can be at least partially accounted for by the observed formation of pyruvate from reactions of other cloud water components. Organic constituents of cloud water also compete for oxidants and/or UV light, contributing to the observed slowed degradation rates of pyruvate. The oxidation of pyruvate was not significantly affected by the presence of inorganic anions (nitrate and sulfate) at cloud-relevant concentrations. Future bulk studies of aqSOA formation reactions using simplified simulated cloud solutions and model estimates of generated aqSOA mass should take into account possible generation of, or competition for, oxidant molecules by organic components found in the complex matrices typically associated with real atmospheric water droplets. Additionally, it is likely that some components of real atmospheric waters have not yet been identified as aqSOA precursors, but could be distinguished through further simplified bulk oxidations of known atmospheric water components.

Indian Summer Monsoon Drought 2009: Role of Aerosol and Cloud Microphysics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hazra, Anupam; Taraphdar, Sourav; Halder, Madhuparna

2013-07-01

Cloud dynamics played a fundamental role in defining Indian summer monsoon (ISM) rainfall during drought in 2009. The anomalously negative precipitation was consistent with cloud properties. Although, aerosols inhibited the growth of cloud effective radius in the background of sparse water vapor, their role is secondary. The primary role, however, is played by the interactive feedback between cloud microphysics and dynamics owing to reduced efficient cloud droplet growth, lesser latent heating release and shortage of water content. Cloud microphysical processes were instrumental for the occurrence of ISM drought 2009.

Mars topographic clouds: MAVEN/IUVS observations and LMD MGCM predictions

NASA Astrophysics Data System (ADS)

Schneider, Nicholas M.; Connour, Kyle; Forget, Francois; Deighan, Justin; Jain, Sonal; Vals, Margaux; Wolff, Michael J.; Chaffin, Michael S.; Crismani, Matteo; Stewart, A. Ian F.; McClintock, William E.; Holsclaw, Greg; Lefevre, Franck; Montmessin, Franck; Stiepen, Arnaud; Stevens, Michael H.; Evans, J. Scott; Yelle, Roger; Lo, Daniel; Clarke, John T.; Jakosky, Bruce

2017-10-01

The Imaging Ultraviolet Spectrograph (IUVS) instrument on the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft takes mid-UV spectral images of the Martian atmosphere. From these apoapse disk images, information about clouds and aerosols can be retrieved and comprise the only MAVEN observations of topographic clouds and cloud morphologies. Measuring local time variability of large-scale recurring cloud features is made possible with MAVEN’s ~4.5-hour elliptical orbit, something not possible with sun-synchronous orbits. We have run the LMD MGCM (Mars global circulation model) at 1° x 1° resolution to simulate water ice cloud formation with inputs consistent with observing parameters and Mars seasons. Topographic clouds are observed to form daily during the late mornings of northern hemisphere spring and this phenomenon recurs until late summer (Ls = 160°), after which topographic clouds wane in thickness. By northern fall, most topographic clouds cease to form except over Arsia Mons and Pavonis Mons, where clouds can still be observed. Our data show moderate cloud formation over these regions as late as Ls = 220°, something difficult for the model to replicate. Previous studies have shown that models have trouble simulating equatorial cloud thickness in combination with a realistic amount of water vapor and not-too-thick polar water ice clouds, implying aspects of the water cycle are not fully understood. We present data/model comparisons as well as further refinements on parameter inputs based on IUVS observations.

Mars topographic clouds: MAVEN/IUVS observations and LMD MGCM predictions

NASA Astrophysics Data System (ADS)

Connour, K.; Schneider, N.; Forget, F.; Deighan, J.; Jain, S.; Pottier, A.; Wolff, M. J.; Chaffin, M.; Crismani, M. M. J.; Stewart, I. F.; McClintock, B.; Holsclaw, G.; Lefèvre, F.; Montmessin, F.; Stiepen, A.; Stevens, M. H.; Evans, J. S.; Yelle, R. V.; Lo, D.; Clarke, J. T.; Jakosky, B. M.

2017-12-01

The Imaging Ultraviolet Spectrograph (IUVS) instrument on the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft takes mid-UV spectral images of the Martian atmosphere. From these apoapse disk images, information about clouds and aerosols can be retrieved and comprise the only MAVEN observations of topographic clouds and cloud morphologies. Measuring local time variability of large-scale recurring cloud features is made possible with MAVEN's 4.5-hour elliptical orbit, something not possible with sun-synchronous orbits. We have run the LMD MGCM (Mars global circulation model) at 1° x 1° resolution to simulate water ice cloud formation with inputs consistent with observing parameters and Mars seasons. Topographic clouds are observed to form daily during the late mornings of northern hemisphere spring and this phenomenon recurs until late summer (Ls = 160°), after which topographic clouds wane in thickness. By northern fall, most topographic clouds cease to form except over Arsia Mons and Pavonis Mons, where clouds can still be observed. Our data show moderate cloud formation over these regions as late as Ls = 220°, something difficult for the model to replicate. Previous studies have shown that models have trouble simulating equatorial cloud thickness in combination with a realistic amount of water vapor and not-too-thick polar water ice clouds, implying aspects of the water cycle are not fully understood. We present data/model comparisons as well as further refinements on parameter inputs based on IUVS observations.

Remote Sensing of Radiative and Microphysical Properties of Clouds During TC (sup 4): Results from MAS, MASTER, MODIS, and MISR

NASA Technical Reports Server (NTRS)

King, Michael D.; Platnick, Steven; Wind, Galina; Arnold, G. Thomas; Dominguez, Roseanne T.

2010-01-01

The Moderate Resolution Imaging Spectroradiometer (MODIS) Airborne Simulator (MAS) and MODIS/Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) Airborne Simulator (MASTER) were used to obtain measurements of the bidirectional reflectance and brightness temperature of clouds at 50 discrete wavelengths between 0.47 and 14.2 microns (12.9 microns for MASTER). These observations were obtained from the NASA ER-2 aircraft as part of the Tropical Composition, Cloud and Climate Coupling (TC4) experiment conducted over Central America and surrounding Pacific and Atlantic Oceans between 17 July and 8 August 2007. Multispectral images in eleven distinct bands were used to derive a confidence in clear sky (or alternatively the probability Of cloud) over land and ocean ecosystems. Based on the results of individual tests run as part of the cloud mask, an algorithm was developed to estimate the phase of the clouds (liquid water, ice, or undetermined phase). The cloud optical thickness and effective radius were derived for both liquid water and ice clouds that were detected during each flight, using a nearly identical algorithm to that implemented operationally to process MODIS Cloud data from the Aqua and Terra satellites (Collection 5). This analysis shows that the cloud mask developed for operational use on MODIS, and tested using MAS and MASTER data in TC(sup 4), is quite capable of distinguishing both liquid water and ice clouds during daytime conditions over both land and ocean. The cloud optical thickness and effective radius retrievals use five distinct bands of the MAS (or MASTER), and these results were compared with nearly simultaneous retrievals of marine liquid water clouds from MODIS on the Terra spacecraft. Finally, this MODIS-based algorithm was adapted to Multiangle Imaging SpectroRadiometer (MISR) data to infer the cloud optical thickness Of liquid water clouds from MISR. Results of this analysis are compared and contrasted.

Aircraft millimeter-wave passive sensing of cloud liquid water and water vapor during VOCALS-REx

DOE PAGES

Zuidema, P.; Leon, D.; Pazmany, A.; ...

2012-01-05

Routine liquid water path measurements and water vapor path are valuable for process studies of the cloudy marine boundary layer and for the assessment of large-scale models. The VOCALS Regional Experiment respected this goal by including a small, inexpensive, upwardpointing millimeter-wavelength passive radiometer on the fourteen research flights of the NCAR C-130 plane, the Gband (183 GHz) Vapor Radiometer (GVR). The radiometer permitted above-cloud retrievals of the free-tropospheric water vapor path (WVP). Retrieved free-tropospheric (abovecloud) water vapor paths possessed a strong longitudinal gradient, with off-shore values of one to twomm and nearcoastal values reaching tenmm. The VOCALS-REx free troposphere wasmore » drier than that of previous years. Cloud liquid water paths (LWPs) were retrieved from the sub-cloud and cloudbase aircraft legs through a combination of the GVR, remotely-sensed cloud boundary information, and insitu thermodynamic data. The absolute (between-leg) and relative (within-leg) accuracy of the LWP retrievals at 1 Hz (≈100 m) resolution was estimated at 20 gm -2 and 3 gm -2 respectively for well-mixed conditions, and 25 gm -2 absolute uncertainty for decoupled conditions where the input WVP specification was more uncertain. Retrieved liquid water paths matched adiabatic values derived from coincident cloud thickness measurements exceedingly well. A significant contribution of the GVR dataset was the extended information on the thin clouds, with 62% (28 %) of the retrieved LWPs <100 (40) gm -2. Coastal LWPs values were lower than those offshore. For the four dedicated 20° S flights, the mean (median) coastal LWP was 67 (61) gm -2, increasing to 166 (120) gm -2 1500 km offshore. Finally, the overall LWP cloud fraction from thirteen research flights was 63 %, higher than that of adiabatic LWPs at 40 %, but lower than the lidar-determined cloud cover of 85 %, further testifying to the frequent occurrence of thin clouds.« less

Climatic Implications of the Observed Temperature Dependence of the Liquid Water Path of Low Clouds in the Southern Great Plains

NASA Technical Reports Server (NTRS)

DelGenio, Anthony

1999-01-01

Satellite observations of low-level clouds have challenged the assumption that adiabatic liquid water content combined with constant physical thickness will lead to a negative cloud optics feedback in a decadal climate change. We explore the reasons for the satellite results using four years of surface remote sensing data from the Atmospheric Radiation Measurement Program Cloud and Radiation Testbed site in the Southern Great Plains of the United States. We find that low cloud liquid water path is approximately invariant with temperature in winter but decreases strongly with temperature in summer, consistent with the satellite inferences at this latitude. This behavior occurs because liquid water content shows no detectable temperature dependence while cloud physical thickness decreases with warming. Thinning of clouds with warming is observed on seasonal, synoptic, and diurnal time scales; it is most obvious in the warm sectors of baroclinic waves. Although cloud top is observed to slightly descend with warming, the primary cause of thinning, is the ascent of cloud base due to the reduction in surface relative humidity and the concomitant increase in the lifting condensation level of surface air. Low cloud liquid water path is not observed to be a continuous function of temperature. Rather, the behavior we observe is best explained as a transition in the frequency of occurrence of different boundary layer types. At cold temperatures, a mixture of stratified and convective boundary layers is observed, leading to a broad distribution of liquid water path values, while at warm temperatures, only convective boundary layers with small liquid water paths, some of them decoupled, are observed. Our results, combined with the earlier satellite inferences, imply that the commonly quoted 1.5C lower limit for the equilibrium global climate sensitivity to a doubling of CO2 which is based on models with near-adiabatic liquid water behavior and constant physical thickness, should be revised upward.

Climatic Implications of the Observed Temperature Dependence of the Liquid Water Path of Low Clouds in the Southern Great Plains

NASA Technical Reports Server (NTRS)

DelGenio, Anthony D.; Wolf, Audrey B.

1999-01-01

Satellite observations of low-level clouds have challenged the assumption that adiabatic liquid water content combined with constant physical thickness will lead to a negative cloud optics feedback in a decadal climate change. We explore the reasons for the satellite results using four years of surface remote sensing data from the Atmospheric Radiation Measurement Program Cloud and Radiation Testbed site in the Southern Great Plains of the United States. We find that low cloud liquid water path is approximately invariant with temperature in winter but decreases strongly with temperature in summer, consistent with the satellite inferences at this latitude. This behavior occurs because liquid water content shows no detectable temperature dependence while cloud physical thickness decreases with warming. Thinning of clouds with warming is observed on seasonal, synoptic, and diurnal time scales; it is most obvious in the warm sectors of baroclinic waves. Although cloud top is observed to slightly descend with warming, the primary cause of thinning is the ascent of cloud base due to the reduction in surface relative humidity and the concomitant increase in the lifting condensation level of surface air. Low cloud liquid water path is not observed to be a continuous function of temperature. Rather, the behavior we observe is best explained as a transition in the frequency of occurrence of different boundary layer types: At cold temperatures, a mixture of stratified and convective boundary layers is observed, leading to a broad distribution of liquid water path values, while at warm temperatures, only convective boundary layers with small liquid water paths, some of them decoupled, are observed. Our results, combined with the earlier satellite inferences, imply that the commonly quoted 1.50 C lower limit for the equilibrium global climate sensitivity to a doubling of CO2, which is based on models with near-adiabatic liquid water behavior and constant physical thickness, should be revised upward.

New Insights on Hydro-Climate Feedback Processes over the Tropical Ocean from TRMM

NASA Technical Reports Server (NTRS)

Lau, William K. M.; Wu, H. T.; Li, Xiaofan; Sui, C. H.

2002-01-01

In this paper, we study hydro-climate feedback processes over the tropical oceans, by examining the relationships among large scale circulation and Tropical Rainfall Measuring Mission Microwave Imager-Sea Surface Temperature (TMI-SST), and a range of TRMM rain products including rain rate, cloud liquid water, precipitable water, cloud types and areal coverage, and precipitation efficiency. Results show that for a warm event (1998), the 28C threshold of convective precipitation is quite well defined over the tropical oceans. However, for a cold event (1999), the SST threshold is less well defined, especially over the central and eastern Pacific cold tongue, where stratiform rain occurs at much lower than 28 C. Precipitation rates and cloud liquid water are found to be more closely related to the large scale vertical motion than to the underlying SST. While total columnar water vapor is more strongly dependent on SST. For a large domain, over the eastern Pacific, we find that the areal extent of the cloudy region tends to shrink as the SST increases. Examination of the relationship between cloud liquid water and rain rate suggests that the residence time of cloud liquid water tends to be shorter, associated with higher precipitation efficiency in a warmer climate. It is hypothesized that the reduction in cloudy area may be influenced both by the shift in large scale cloud patterns in response to changes in large scale forcings, and possible increase in the cloud liquid water conversion to rain water in a warmer environment. Results of numerical experiments with the Goddard cloud resolving model to test the hypothesis will be discussed.

Sound, infrasound, and sonic boom absorption by atmospheric clouds.

PubMed

Baudoin, Michaël; Coulouvrat, François; Thomas, Jean-Louis

2011-09-01

This study quantifies the influence of atmospheric clouds on propagation of sound and infrasound, based on an existing model [Gubaidulin and Nigmatulin, Int. J. Multiphase Flow 26, 207-228 (2000)]. Clouds are considered as a dilute and polydisperse suspension of liquid water droplets within a mixture of dry air and water vapor, both considered as perfect gases. The model is limited to low and medium altitude clouds, with a small ice content. Four physical mechanisms are taken into account: viscoinertial effects, heat transfer, water phase changes (evaporation and condensation), and vapor diffusion. Physical properties of atmospheric clouds (altitude, thickness, water content and droplet size distribution) are collected, along with values of the thermodynamical coefficients. Different types of clouds have been selected. Quantitative evaluation shows that, for low audible and infrasound frequencies, absorption within clouds is several orders of magnitude larger than classical absorption. The importance of phase changes and vapor diffusion is outlined. Finally, numerical simulations for nonlinear propagation of sonic booms indicate that, for thick clouds, attenuation can lead to a very large decay of the boom at the ground level. © 2011 Acoustical Society of America

Entrainment, Drizzle, and the Indirect Effect in Stratiform Clouds

NASA Technical Reports Server (NTRS)

Ackerman, Andrew

2005-01-01

Activation of some fraction of increased concentrations of sub-micron soluble aerosol particles lead to enhanced cloud droplet concentrations and hence smaller droplets, increasing their total cross sectional area and thus reflecting solar radiation more efficiently (the Twomey, or first indirect, effect). However, because of competition during condensational growth, droplet distributions tend to broaden as numbers increase, reducing the sensitivity of cloud albedo to droplet concentration on the order of 10%. Also, smaller droplets less effectively produce drizzle through collisions and coalescence, and it is widely expected (and found in large-scale models) that decreased precipitation leads to clouds with more cloud water on average (the so-called cloud lifetime, or second indirect, effect). Much of the uncertainty regarding the overall indirect aerosol effect stems from inadequate understanding of such changes in cloud water. Detailed simulations based on FIRE-I, ASTEX, and DYCOMS-II conditions show that suppression of precipitation from increased droplet concentrations leads to increased cloud water only when sufficient precipitation reaches the surface, a condition favored when the overlying air is-humid or droplet concentrations are very low. Otherwise, aerosol induced suppression of precipitation enhances entrainment of overlying dry air, thereby reducing cloud water and diminishing the indirect climate forcing.

Ground-based remote sensing of thin clouds in the Arctic

NASA Astrophysics Data System (ADS)

Garrett, T. J.; Zhao, C.

2012-11-01

This paper describes a method for using interferometer measurements of downwelling thermal radiation to retrieve the properties of single-layer clouds. Cloud phase is determined from ratios of thermal emission in three "micro-windows" where absorption by water vapor is particularly small. Cloud microphysical and optical properties are retrieved from thermal emission in two micro-windows, constrained by the transmission through clouds of stratospheric ozone emission. Assuming a cloud does not approximate a blackbody, the estimated 95% confidence retrieval errors in effective radius, visible optical depth, number concentration, and water path are, respectively, 10%, 20%, 38% (55% for ice crystals), and 16%. Applied to data from the Atmospheric Radiation Measurement program (ARM) North Slope of Alaska - Adjacent Arctic Ocean (NSA-AAO) site near Barrow, Alaska, retrievals show general agreement with ground-based microwave radiometer measurements of liquid water path. Compared to other retrieval methods, advantages of this technique include its ability to characterize thin clouds year round, that water vapor is not a primary source of retrieval error, and that the retrievals of microphysical properties are only weakly sensitive to retrieved cloud phase. The primary limitation is the inapplicability to thicker clouds that radiate as blackbodies.

Parameterization of Cirrus Cloud Vertical Profiles and Geometrical Thickness Using CALIPSO and CloudSat Data

NASA Astrophysics Data System (ADS)

Khatri, P.; Iwabuchi, H.; Saito, M.

2017-12-01

High-level cirrus clouds, which normally occur over more than 20% of the globe, are known to have profound impacts on energy budget and climate change. The scientific knowledge regarding the vertical structure of such high-level cirrus clouds and their geometrical thickness are relatively poorer compared to low-level water clouds. Knowledge regarding cloud vertical structure is especially important in passive remote sensing of cloud properties using infrared channels or channels strongly influenced by gaseous absorption when clouds are geometrically thick and optically thin. Such information is also very useful for validating cloud resolving numerical models. This study analyzes global scale data of ice clouds identified by Cloud profiling Radar (CPR) onboard CloudSat and Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) onboard CALIPSO to parameterize (i) vertical profiles of ice water content (IWC), cloud-particle effective radius (CER), and ice-particle number concentration for varying ice water path (IWP) values and (ii) the relation of cloud geometrical thickness (CGT) with IWP and CER for varying cloud top temperature (CTT) values. It is found that the maxima in IWC and CER profile shifts towards cloud base with the increase of IWP. Similarly, if the cloud properties remain same, CGT shows an increasing trend with the decrease of CTT. The implementation of such cloud vertical inhomogeneity parameterization in the forward model used in the Integrated Cloud Analysis System ICAS (Iwabuchi et al., 2016) generally shows increase of brightness temperatures in infrared channels compared to vertically homogeneous cloud assumption. The cloud vertical inhomogeneity is found to bring noticeable changes in retrieved cloud properties. Retrieved CER and cloud top height become larger for optically thick cloud. We will show results of comparison of cloud properties retrieved from infrared measurements and active remote sensing.

Liquid Water Cloud Measurements Using the Raman Lidar Technique: Current Understanding and Future Research Needs

NASA Technical Reports Server (NTRS)

Tetsu, Sakai; Whiteman, David N.; Russo, Felicita; Turner, David D.; Veselovskii, Igor; Melfi, S. Harvey; Nagai, Tomohiro; Mano, Yuzo

2013-01-01

This paper describes recent work in the Raman lidar liquid water cloud measurement technique. The range-resolved spectral measurements at the National Aeronautics and Space Administration Goddard Space Flight Center indicate that the Raman backscattering spectra measured in and below low clouds agree well with theoretical spectra for vapor and liquid water. The calibration coefficients of the liquid water measurement for the Raman lidar at the Atmospheric Radiation Measurement Program Southern Great Plains site of the U.S. Department of Energy were determined by comparison with the liquid water path (LWP) obtained with Atmospheric Emitted Radiance Interferometer (AERI) and the liquid water content (LWC) obtained with the millimeter wavelength cloud radar and water vapor radiometer (MMCR-WVR) together. These comparisons were used to estimate the Raman liquid water cross-sectional value. The results indicate a bias consistent with an effective liquid water Raman cross-sectional value that is 28%-46% lower than published, which may be explained by the fact that the difference in the detectors' sensitivity has not been accounted for. The LWP of a thin altostratus cloud showed good qualitative agreement between lidar retrievals and AERI. However, the overall ensemble of comparisons of LWP showed considerable scatter, possibly because of the different fields of view of the instruments, the 350-m distance between the instruments, and the horizontal inhomogeneity of the clouds. The LWC profiles for a thick stratus cloud showed agreement between lidar retrievals andMMCR-WVR between the cloud base and 150m above that where the optical depth was less than 3. Areas requiring further research in this technique are discussed.

How might Australian rainforest cloud interception respond to climate change?

NASA Astrophysics Data System (ADS)

Wallace, Jim; McJannet, Dave

2013-02-01

SummaryThe lower and upper montane rainforests in northern Queensland receive significant amounts of cloud interception that affect both in situ canopy wetness and downstream runoff. Cloud interception contributes 5-30% of the annual water input to the canopy and this increases to 40-70% of the monthly water input during the dry season. This occult water is therefore an important input to the canopy, sustaining the epiphytes, mosses and other species that depend on wet canopy conditions. The potential effect of climate change on cloud interception was examined using the relationship between cloud interception and cloud frequency derived from measurements made at four different rainforest locations. Any given change in cloud frequency produces a greater change in cloud interception and this 'amplification' increases from 1.1 to 1.7 as cloud frequency increases from 5% to 70%. This means that any changes in cloud frequency will have the greatest relative effects at the higher altitude sites where cloud interception is greatest. As cloud frequency is also a major factor affecting canopy wetness, any given change in cloud frequency will therefore have a greater impact on canopy wetness at the higher altitude sites. These changes in wetness duration will augment those due to changes in rainfall and may have important implications for the fauna and flora that depend on wet canopy conditions. We also found that the Australian rainforests may be more efficient (by ˜50% on average) in intercepting cloud water than American coniferous forests, which may be due to differences in canopy structure and exposure at the different sites.

Single-footprint retrievals of temperature, water vapor and cloud properties from AIRS

NASA Astrophysics Data System (ADS)

Irion, Fredrick W.; Kahn, Brian H.; Schreier, Mathias M.; Fetzer, Eric J.; Fishbein, Evan; Fu, Dejian; Kalmus, Peter; Wilson, R. Chris; Wong, Sun; Yue, Qing

2018-02-01

Single-footprint Atmospheric Infrared Sounder spectra are used in an optimal estimation-based algorithm (AIRS-OE) for simultaneous retrieval of atmospheric temperature, water vapor, surface temperature, cloud-top temperature, effective cloud optical depth and effective cloud particle radius. In a departure from currently operational AIRS retrievals (AIRS V6), cloud scattering and absorption are in the radiative transfer forward model and AIRS single-footprint thermal infrared data are used directly rather than cloud-cleared spectra (which are calculated using nine adjacent AIRS infrared footprints). Coincident MODIS cloud data are used for cloud a priori data. Using single-footprint spectra improves the horizontal resolution of the AIRS retrieval from ˜ 45 to ˜ 13.5 km at nadir, but as microwave data are not used, the retrieval is not made at altitudes below thick clouds. An outline of the AIRS-OE retrieval procedure and information content analysis is presented. Initial comparisons of AIRS-OE to AIRS V6 results show increased horizontal detail in the water vapor and relative humidity fields in the free troposphere above the clouds. Initial comparisons of temperature, water vapor and relative humidity profiles with coincident radiosondes show good agreement. Future improvements to the retrieval algorithm, and to the forward model in particular, are discussed.

Climatic Implications of the Observed Temperature Dependence of the Liquid Water Path of Low Clouds

NASA Technical Reports Server (NTRS)

DelGenio, Anthony

1999-01-01

The uncertainty in the global climate sensitivity to an equilibrium doubling of carbon dioxide is often stated to be 1.5-4.5 K, largely due to uncertainties in cloud feedbacks. The lower end of this range is based on the assumption or prediction in some GCMs that cloud liquid water behaves adiabatically, thus implying that cloud optical thickness will increase in a warming climate if the physical thickness of clouds is invariant. Satellite observations of low-level cloud optical thickness and liquid water path have challenged this assumption, however, at low and middle latitudes. We attempt to explain the satellite results using four years of surface remote sensing data from the Atmospheric Radiation Measurements (ARM) Cloud And Radiation Testbed (CART) site in the Southern Great Plains. We find that low cloud liquid water path is insensitive to temperature in winter but strongly decreases with temperature in summer. The latter occurs because surface relative humidity decreases with warming, causing cloud base to rise and clouds to geometrically thin. Meanwhile, inferred liquid water contents hardly vary with temperature, suggesting entrainment depletion. Physically, the temperature dependence appears to represent a transition from higher probabilities of stratified boundary layers at cold temperatures to a higher incidence of convective boundary layers at warm temperatures. The combination of our results and the earlier satellite findings imply that the minimum climate sensitivity should be revised upward from 1.5 K.

Kinetic Energy of Throughfall in Subtropical Forests of SE China – Effects of Tree Canopy Structure, Functional Traits, and Biodiversity

PubMed Central

Geißler, Christian; Nadrowski, Karin; Kühn, Peter; Baruffol, Martin; Bruelheide, Helge; Schmid, Bernhard; Scholten, Thomas

2013-01-01

Throughfall kinetic energy (TKE) plays an important role in soil erosion in forests. We studied TKE as a function of biodiversity, functional diversity as well as structural stand variables in a secondary subtropical broad-leaved forest in the Gutianshan National Nature Reserve (GNNR) in south-east China, a biodiversity hotspot in the northern hemisphere with more than 250 woody species present. Using a mixed model approach we could identify significant effects of all these variables on TKE: TKE increased with rarefied tree species richness and decreased with increasing proportion of needle-leaved species and increasing leaf area index (LAI). Furthermore, for average rainfall amounts TKE was decreasing with tree canopy height whereas for high rainfall amounts this was not the case. The spatial pattern of throughfall was stable across several rain events. The temporal variation of TKE decreased with rainfall intensity and increased with tree diversity. Our results show that more diverse forest stands over the season have to cope with higher cumulative raindrop energy than less diverse stands. However, the kinetic energy (KE) of one single raindrop is less predictable in diverse stands since the variability in KE is higher. This paper is the first to contribute to the understanding of the ecosystem function of soil erosion prevention in diverse subtropical forests. PMID:23457440

Processes affecting the response of sulfate concentrations to clearcutting in a northern hardwood forest, Catskill Mountains, New York, U.S.A.

USGS Publications Warehouse

Welsch, D.L.; Burns, Douglas A.; Murdoch, Peter S.

2004-01-01

The effects of disturbance on the biogeochemical processes that affect the sulfur (S) cycle in forested ecosystems are important, but have been studied in only a few locations. In this investigation, the mechanisms that caused large decreases in stream SO42- concentrations after clearcutting a small forested catchment in the Catskill Mountains of southeastern New York in 1997 were identified through an examination of pH and SO42- concentrations in soil solutions, bulk deposition of SO42- in throughfall collectors, adsorbed SO 42- concentrations in buried soil bags, and spatial variations in SO42- concentrations in shallow groundwater. The load of SO42- -S in stream water during the first 2 years after clearcutting was about 2 kg ha-1.year-1 less than the background value of 8-10 kg ha-1 year-1. The 10 and 19% decrease in net throughfall flux of SO42- -S during the 2nd and 3rd year after the clearcut, respectively, reflects reduced dry deposition of S after removal of the canopy, but this decrease accounts for 0 and 43%, respectively, of the decrease in SO42- load in streamflow for these 2 years. The pH of B-horizon soil water decreased from 4.5 to 4.0 within 8 months after the clearcut, and SO42- concentrations decreased from 45 ??mol L-1 to less than 20 ??mol L-1 during this time. A strong correlation between SO 42- concentrations and pH values (r2=0.71, p<0.01) in B-horizon soil water during the post-harvest period (1997-1999) reflects increased SO42- adsorption in response to soil acidification. Sulfate concentrations in groundwater from 21 spatially distributed wells were inversely related to a topographic index that served as a surrogate for soil wetness; thus, providing additional evidence that SO 42- adsorption was the dominant cause of the decreased SO42- concentrations in the stream after clearcutting. These results are consistent with those from a 1985 whole-tree harvest at the Hubbard Brook Experimental Forest in New Hampshire in which increased SO 42- adsorption resulting from decreased soil pH was the primary cause of decreased SO42- concentrations in stream water.

An Eight-Month Sample of Marine Stratocumulus Cloud Fraction, Albedo, and Integrated Liquid Water.

NASA Astrophysics Data System (ADS)

Fairall, C. W.; Hare, J. E.; Snider, J. B.

1990-08-01

As part of the First International Satellite Cloud Climatology Regional Experiment (FIRE), a surface meteorology and shortwave/longwave irradiance station was operated in a marine stratocumulus regime on the northwest tip of San Nicolas island off the coast of Southern California. Measurements were taken from March through October 1987, including a FIRE Intensive Field Operation (IFO) held in July. Algorithms were developed to use the longwave irradiance data to estimate fractional cloudiness and to use the shortwave irradiance to estimate cloud albedo and integrated cloud liquid water content. Cloud base height is estimated from computations of the lifting condensation level. The algorithms are tested against direct measurements made during the IFO; a 30% adjustment was made to the liquid water parameterization. The algorithms are then applied to the entire database. The stratocumulus clouds over the island are found to have a cloud base height of about 400 m, an integrated liquid water content of 75 gm2, a fractional cloudiness of 0.95, and an albedo of 0.55. Integrated liquid water content rarely exceeds 350 g m2 and albedo rarely exceeds 0.90 for stratocumulus clouds. Over the summer months, the average cloud fraction shows a maximum at sunrise of 0.74 and a minimum at sunset of 0.41. Over the same period, the average cloud albedo shows a maximum of 0.61 at sunrise and a minimum of 0.31 a few hours after local noon (although the estimate is more uncertain because of the extreme solar zenith angle). The use of joint frequency distributions of fractional cloudiness with solar transmittance or cloud base height to classify cloud types appears to be useful.

Ecophysiological importance of cloud immersion in a relic spruce-fir forest at elevational limits, southern Appalachian Mountains, USA.

PubMed

Berry, Z Carter; Smith, William K

2013-11-01

Climate warming predicts changes to the frequency and height of cloud-immersion events in mountain communities. Threatened southern Appalachian spruce-fir forests have been suggested to persist because of frequent periods of cloud immersion. These relic forests exist on only seven mountaintop areas, grow only above ca. 1,500 m elevation (maximum 2,037 m), and harbor the endemic Abies fraseri. To predict future distribution, we examined the ecophysiological effects of cloud immersion on saplings of A. fraseri and Picea rubens at their upper and lower elevational limits. Leaf photosynthesis, conductance, transpiration, xylem water potentials, and general abiotic variables were measured simultaneously on individuals at the top (1,960 m) and bottom (1,510 m) of their elevation limits on numerous clear and cloud-immersed days throughout the growing season. The high elevation sites had 1.5 as many cloud-immersed days (75 % of days) as the low elevation sites (56 % of days). Cloud immersion resulted in higher photosynthesis, leaf conductance, and xylem water potentials, particularly during afternoon measurements. Leaf conductance remained higher throughout the day with corresponding increases in photosynthesis and transpiration, despite low photon flux density levels, leading to an increase in water potentials from morning to afternoon. The endemic A. fraseri had a greater response in carbon gain and water balance in response to cloud immersion. Climate models predict warmer temperatures with a decrease in the frequency of cloud immersion for this region, leading to an environment on these peaks similar to elevations where spruce-fir communities currently do not exist. Because spruce-fir communities may rely on cloud immersion for improved carbon gain and water conservation, an upslope shift is likely if cloud ceilings rise. Their ultimate survival will likely depend on the magnitude of changes in cloud regimes.

Evaluation of ACCESS Model Cloud Properties Over the SouthernOcean Area Using Multiple-satellite ProductsSan Luo1,2 Zhian Sun2, Xiaogu Zheng1, Lawrie Rikus2 and Charmaine Franklin31 College of Global Change and Earth System Science, Beijing Normal University, China 2 Collaboration for Australian Weather and Climate Research3 CSIRO

NASA Astrophysics Data System (ADS)

Luo, S.

2016-12-01

Radiation field and cloud properties over the Southern Ocean area generated by the Australian Community Climate and Earth System Simulator (ACCESS) are evaluated using multiple-satellite products from the Fast Longwave And Shortwave radiative Fluxes (FLASHFlux) project and NASA/GEWEX surface radiation budget (SRB) data. The cloud properties are also evaluated using the observational simulator package COSP, a synthetic brightness temperature model (SBTM) and cloud liquid-water path data (UWisc) from the University of Wisconsin satellite retrievals. All of these evaluations are focused on the Southern Ocean area in an effort to understand the reasons behind the short-wave radiation biases at the surface. It is found that the model overestimates the high-level cloud fraction and frequency of occurrence of small ice-water content and underestimates the middle and low-level cloud fraction and water content. In order to improve the modelled radiation fields over the Southern Ocean area, two main modifications have been made to the physical schemes in the ACCESS model. Firstly the autoconversion rate at which the cloud water is converted into rain and the accretion rate in the warm rain scheme have been modified, which increases the cloud liquid-water content in warm cloud layers. Secondly, the scheme which determines the fraction of supercooled liquid water in mixed-phase clouds in the parametrization of cloud optical properties has been changed to use one derived from CALIPSO data which provides larger liquid cloud fractions and thus higher optical depths than the default scheme. Sensitivity tests of these two schemes in ACCESS climate runs have shown that applying either can lead to a reduction of the solar radiation reaching the surface and reduce the short-wave radiation biases.

MODIS Views Variations in Cloud Types

NASA Technical Reports Server (NTRS)

2002-01-01

This MODIS image, centered over the Great Lakes region in North America, shows a variety of cloud types. The clouds at the top of the image, colored pink, are cold, high-level snow and ice clouds, while the neon green clouds are lower-level water clouds. Because different cloud types reflect and emit radiant energy differently, scientists can use MODIS' unique data set to measure the sizes of cloud particles and distinguish between water, snow, and ice clouds. This scene was acquired on Feb. 24, 2000, and is a red, green, blue composite of bands 1, 6, and 31 (0.66, 1.6, and 11.0 microns, respectively). Image by Liam Gumley, Space Science and Engineering Center, University of Wisconsin-Madison

Contributions of Heterogeneous Ice Nucleation, Large-Scale Circulation, and Shallow Cumulus Detrainment to Cloud Phase Transition in Mixed-Phase Clouds with NCAR CAM5

NASA Astrophysics Data System (ADS)

Liu, X.; Wang, Y.; Zhang, D.; Wang, Z.

2016-12-01

Mixed-phase clouds consisting of both liquid and ice water occur frequently at high-latitudes and in mid-latitude storm track regions. This type of clouds has been shown to play a critical role in the surface energy balance, surface air temperature, and sea ice melting in the Arctic. Cloud phase partitioning between liquid and ice water determines the cloud optical depth of mixed-phase clouds because of distinct optical properties of liquid and ice hydrometeors. The representation and simulation of cloud phase partitioning in state-of-the-art global climate models (GCMs) are associated with large biases. In this study, the cloud phase partition in mixed-phase clouds simulated from the NCAR Community Atmosphere Model version 5 (CAM5) is evaluated against satellite observations. Observation-based supercooled liquid fraction (SLF) is calculated from CloudSat, MODIS and CPR radar detected liquid and ice water paths for clouds with cloud-top temperatures between -40 and 0°C. Sensitivity tests with CAM5 are conducted for different heterogeneous ice nucleation parameterizations with respect to aerosol influence (Wang et al., 2014), different phase transition temperatures for detrained cloud water from shallow convection (Kay et al., 2016), and different CAM5 model configurations (free-run versus nudged winds and temperature, Zhang et al., 2015). A classical nucleation theory-based ice nucleation parameterization in mixed-phase clouds increases the SLF especially at temperatures colder than -20°C, and significantly improves the model agreement with observations in the Arctic. The change of transition temperature for detrained cloud water increases the SLF at higher temperatures and improves the SLF mostly over the Southern Ocean. Even with the improved SLF from the ice nucleation and shallow cumulus detrainment, the low SLF biases in some regions can only be improved through the improved circulation with the nudging technique. Our study highlights the challenges of representations of large-scale moisture transport, cloud microphysics, ice nucleation, and cumulus detrainment in order to improve the mixed-phase transition in GCMs.

Observations of cloud liquid water path over oceans: Optical and microwave remote sensing methods

NASA Technical Reports Server (NTRS)

Lin, Bing; Rossow, William B.

1994-01-01

Published estimates of cloud liquid water path (LWP) from satellite-measured microwave radiation show little agreement, even about the relative magnitudes of LWP in the tropics and midlatitudes. To understand these differences and to obtain more reliable estimate, optical and microwave LWP retrieval methods are compared using the International Satellite Cloud Climatology Project (ISCCP) and special sensor microwave/imager (SSM/I) data. Errors in microwave LWP retrieval associated with uncertainties in surface, atmosphere, and cloud properties are assessed. Sea surface temperature may not produce great LWP errors, if accurate contemporaneous measurements are used in the retrieval. An uncertainty of estimated near-surface wind speed as high as 2 m/s produces uncertainty in LWP of about 5 mg/sq cm. Cloud liquid water temperature has only a small effect on LWP retrievals (rms errors less than 2 mg/sq cm), if errors in the temperature are less than 5 C; however, such errors can produce spurious variations of LWP with latitude and season. Errors in atmospheric column water vapor (CWV) are strongly coupled with errors in LWP (for some retrieval methods) causing errors as large as 30 mg/sq cm. Because microwave radiation is much less sensitive to clouds with small LWP (less than 7 mg/sq cm) than visible wavelength radiation, the microwave results are very sensitive to the process used to separate clear and cloudy conditions. Different cloud detection sensitivities in different microwave retrieval methods bias estimated LWP values. Comparing ISCCP and SSM/I LWPs, we find that the two estimated values are consistent in global, zonal, and regional means for warm, nonprecipitating clouds, which have average LWP values of about 5 mg/sq cm and occur much more frequently than precipitating clouds. Ice water path (IWP) can be roughly estimated from the differences between ISCCP total water path and SSM/I LWP for cold, nonprecipitating clouds. IWP in the winter hemisphere is about 3 times the LWP but only half the LWP in the summer hemisphere. Precipitating clouds contribute significantly to monthly, zonal mean LWP values determined from microwave, especially in the intertropical convergence zone (ITCZ), because they have almost 10 times the liquid water (cloud plus precipitation) of nonprecipitating clouds on average. There are significant differences among microwave LWP estimates associated with the treatment of precipitating clouds.

Hole punch clouds over the Bahamas

NASA Image and Video Library

2017-12-08

In elementary school, students learn that water freezes at 0 degrees Celsius (32 degrees Fahrenheit). That is true most of the time, but there are exceptions to the rule. For instance, water with very few impurities (such as dust or pollution particles, fungal spores, bacteria) can be chilled to much cooler temperatures and still remain liquid—a process known as supercooling. Supercooling may sound exotic, but it occurs pretty routinely in Earth’s atmosphere. Altocumulus clouds, a common type of mid-altitude cloud, are mostly composed of water droplets supercooled to a temperature of about -15 degrees C. Altocumulus clouds with supercooled tops cover about 8 percent of Earth’s surface at any given time. Supercooled water droplets play a key role in the formation of hole-punch and canal clouds, the distinctive clouds shown in these satellite images. Hole-punch clouds usually appear as circular gaps in decks of altocumulus clouds; canal clouds look similar but the gaps are longer and thinner. This true-color image shows hole-punch and canal clouds off the coast of Florida, as observed on December 12, 2014, by the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite. Both types of cloud form when aircraft fly through cloud decks rich with supercooled water droplets and produce aerodynamic contrails. Air expands and cools as it moves around the wings and past the propeller, a process known as adiabatic cooling. Air temperatures over jet wings often cool by as much as 20 degrees Celsius, pushing supercooled water droplets to the point of freezing. As ice crystals form, they absorb nearby water droplets. Since ice crystals are relatively heavy, they tend to sink. This triggers tiny bursts of snow or rain that leave gaps in the cloud cover. Whether a cloud formation becomes a hole-punch or canal depends on the thickness of the cloud layer, the air temperature, and the degree of horizontal wind shear. Both descending and ascending aircraft—including jets and propeller planes—can trigger hole-punch and canal clouds. The nearest major airports in the images above include Miami International, Fort Lauderdale International, Grand Bahama International, and Palm Beach International. Credit: NASA/GSFC/Jeff Schmaltz/MODIS Land Rapid Response Team NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram

A Simple Model of Cirrus Horizontal Inhomogeneity and Cloud Fraction

NASA Technical Reports Server (NTRS)

Smith, Samantha A.; DelGenio, Anthony D.

1998-01-01

A simple model of horizontal inhomogeneity and cloud fraction in cirrus clouds has been formulated on the basis that all internal horizontal inhomogeneity in the ice mixing ratio is due to variations in the cloud depth, which are assumed to be Gaussian. The use of such a model was justified by the observed relationship between the normalized variability of the ice water mixing ratio (and extinction) and the normalized variability of cloud depth. Using radar cloud depth data as input, the model reproduced well the in-cloud ice water mixing ratio histograms obtained from horizontal runs during the FIRE2 cirrus campaign. For totally overcast cases the histograms were almost Gaussian, but changed as cloud fraction decreased to exponential distributions which peaked at the lowest nonzero ice value for cloud fractions below 90%. Cloud fractions predicted by the model were always within 28% of the observed value. The predicted average ice water mixing ratios were within 34% of the observed values. This model could be used in a GCM to produce the ice mixing ratio probability distribution function and to estimate cloud fraction. It only requires basic meteorological parameters, the depth of the saturated layer and the standard deviation of cloud depth as input.

A physically-based retrieval of cloud liquid water from SSM/I measurements

NASA Technical Reports Server (NTRS)

Greenwald, Thomas J.; Stephens, Graeme L.; Vonder Haar, Thomas H.

1992-01-01

A simple physical scheme is proposed for retrieving cloud liquid water over the ice-free global oceans from Special Sensor Microwave/Imager (SSM/I) observations. Details of the microwave retrieval scheme are discussed, and the microwave-derived liquid water amounts are compared with the ground radiometer and AVHRR-derived liquid water for stratocumulus clouds off the coast of California. Global distributions of the liquid water path derived by the method proposed here are presented.

Laser-induced plasma cloud interaction and ice multiplication under cirrus cloud conditions

PubMed Central

Leisner, Thomas; Duft, Denis; Möhler, Ottmar; Saathoff, Harald; Schnaiter, Martin; Henin, Stefano; Stelmaszczyk, Kamil; Petrarca, Massimo; Delagrange, Raphaëlle; Hao, Zuoqiang; Lüder, Johannes; Petit, Yannick; Rohwetter, Philipp; Kasparian, Jérôme; Wolf, Jean-Pierre; Wöste, Ludger

2013-01-01

Potential impacts of lightning-induced plasma on cloud ice formation and precipitation have been a subject of debate for decades. Here, we report on the interaction of laser-generated plasma channels with water and ice clouds observed in a large cloud simulation chamber. Under the conditions of a typical storm cloud, in which ice and supercooled water coexist, no direct influence of the plasma channels on ice formation or precipitation processes could be detected. Under conditions typical for thin cirrus ice clouds, however, the plasma channels induced a surprisingly strong effect of ice multiplication. Within a few minutes, the laser action led to a strong enhancement of the total ice particle number density in the chamber by up to a factor of 100, even though only a 10−9 fraction of the chamber volume was exposed to the plasma channels. The newly formed ice particles quickly reduced the water vapor pressure to ice saturation, thereby increasing the cloud optical thickness by up to three orders of magnitude. A model relying on the complete vaporization of ice particles in the laser filament and the condensation of the resulting water vapor on plasma ions reproduces our experimental findings. This surprising effect might open new perspectives for remote sensing of water vapor and ice in the upper troposphere. PMID:23733936

Laser-induced plasma cloud interaction and ice multiplication under cirrus cloud conditions.

PubMed

Leisner, Thomas; Duft, Denis; Möhler, Ottmar; Saathoff, Harald; Schnaiter, Martin; Henin, Stefano; Stelmaszczyk, Kamil; Petrarca, Massimo; Delagrange, Raphaëlle; Hao, Zuoqiang; Lüder, Johannes; Petit, Yannick; Rohwetter, Philipp; Kasparian, Jérôme; Wolf, Jean-Pierre; Wöste, Ludger

2013-06-18

Potential impacts of lightning-induced plasma on cloud ice formation and precipitation have been a subject of debate for decades. Here, we report on the interaction of laser-generated plasma channels with water and ice clouds observed in a large cloud simulation chamber. Under the conditions of a typical storm cloud, in which ice and supercooled water coexist, no direct influence of the plasma channels on ice formation or precipitation processes could be detected. Under conditions typical for thin cirrus ice clouds, however, the plasma channels induced a surprisingly strong effect of ice multiplication. Within a few minutes, the laser action led to a strong enhancement of the total ice particle number density in the chamber by up to a factor of 100, even though only a 10(-9) fraction of the chamber volume was exposed to the plasma channels. The newly formed ice particles quickly reduced the water vapor pressure to ice saturation, thereby increasing the cloud optical thickness by up to three orders of magnitude. A model relying on the complete vaporization of ice particles in the laser filament and the condensation of the resulting water vapor on plasma ions reproduces our experimental findings. This surprising effect might open new perspectives for remote sensing of water vapor and ice in the upper troposphere.

Assessment of dust aerosol effect on cloud properties over Northwest China using CERES SSF data

NASA Astrophysics Data System (ADS)

Huang, J.; Wang, X.; Wang, T.; Su, J.; Minnis, P.; Lin, B.; Hu, Y.; Yi, Y.

Dust aerosols not only have direct effects on the climate through reflection and absorption of the short and long wave radiation but also modify cloud properties such as the number concentration and size of cloud droplets indirect effect and contribute to diabatic heating in the atmosphere that often enhances cloud evaporation and reduces the cloud water path In this study indirect and semi-direct effects of dust aerosols are analyzed over eastern Asia using two years June 2002 to June 2004 of CERES Clouds and the Earth s Radiant Energy Budget Scanner and MODIS MODerate Resolution Imaging Spectroradiometer Aqua Edition 1B SSF Single Scanner Footprint data sets The statistical analysis shows evidence for both indirect and semi-direct effect of Asia dust aerosols The dust appears to reduce the ice cloud effective particle diameter and increase high cloud amount On average ice cloud effective particle diameters of cirrus clouds under dust polluted conditions dusty cloud are 11 smaller than those derived from ice clouds in dust-free atmospheric environments The water paths of dusty clouds are also considerably smaller than those of dust-free clouds Dust aerosols could warm clouds thereby increasing the evaporation of cloud droplets resulting in reduced cloud water path semi-direct effect The semi-direct effect may be dominated the interaction between dust aerosols and clouds over arid and semi-arid areas and partly contribute to reduced precipitation

Simulations of the effects of water vapor, cloud liquid water, and ice on AMSU moisture channel brightness temperatures

NASA Technical Reports Server (NTRS)

Muller, Bradley M.; Fuelberg, Henry E.; Xiang, Xuwu

1994-01-01

Radiative transfer simulations are performed to determine how water vapor and nonprecipitating cloud liquid water and ice particles within typical midlatitude atmospheres affect brightness temperatures T(sub B)'s of moisture sounding channels used in the Advanced Microwave Sounding Unit (AMSU) and AMSU-like instruments. The purpose is to promote a general understanding of passive top-of-atmosphere T(sub B)'s for window frequencies at 23.8, 89.0, and 157.0 GHz, and water vapor frequencies at 176.31, 180.31, and 182.31 GHz by documenting specific examples. This is accomplished through detailed analyses of T(sub B)'s for idealized atmospheres, mostly representing temperate conditions over land. Cloud effects are considered in terms of five basic properties: droplet size distribution, phase, liquid or ice water content, altitude, and thickness. Effects on T(sub B) of changing surface emissivity also are addressed. The brightness temperature contribution functions are presented as an aid to physically interpreting AMSU T(sub B)'s. Both liquid and ice clouds impact the T(sub B)'s in a variety of ways. The T(sub B)'s at 23.8 and 89 GHz are more strongly affected by altostratus liquid clouds than by cirrus clouds for equivalent water paths. In contrast, channels near 157 and 183 GHz are more strongly affected by ice clouds. Higher clouds have a greater impact on 157- and 183-GHz T(sub B)'s than do lower clouds. Clouds depress T(sub B)'s of the higher-frequency channels by suppressing, but not necessarily obscuring, radiance contributions from below. Thus, T(sub B)'s are less closely associated with cloud-top temperatures than are IR radiometric temperatures. Water vapor alone accounts for up to 89% of the total attenuation by a midtropospheric liquid cloud for channels near 183 GHz. The Rayleigh approximation is found to be adequate for typical droplet size distributions; however, Mie scattering effects from liquid droplets become important for droplet size distribution functions with modal radii greater than 20 micrometers near 157 and 183 GHz, and greater than 30-40 micrometers at 89 GHz. This is due mainly to the relatively small concentrations of droplets much larger than the mode radius. Orographic clouds and tropical cumuli have been observed to contain droplet size distributions with mode radii in the 30-40 micrometers range. Thus, as new instruments bridge the gap between microwave and infrared to frequencies even higher than 183 GHz, radiative transfer modelers are cautioned to explicitly address scattering characteristics of such clouds.

Xylem vulnerability curves of canopy branches of mature trees from Caxiuana and Tapajos National Forests, Para, Brazil

DOE Office of Scientific and Technical Information (OSTI.GOV)

Powell, Thomas; Moorcroft, Paul

Raw data for xylem vulnerability curves measured on upper canopy branches of mature trees from the Caxiuana and Tapajos National Forests, Para, Brazil. Tapajos samples were harvested from km67 transects, which is nearby the decommissioned throughfall-exclusion, drought-experiment plots. Caxiuana samples were harvested from trees growing in the throughfall-exclusion, drought-experiment plots. Data were collected in 2011 and 2012. Dataset includes: date of measurement, site ID, plot ID, tree ID (species, tree tag #), xylem pressure, percent loss of conductivity. Air injection method was used. Data reference: Powell et al. (2017) Differences in xylem cavitation resistance and leaf hydraulic traits explain differencesmore » in drought tolerance among mature Amazon rainforest trees. Global Change Biology.« less

Integration of Satellite-Derived Cloud Phase, Cloud Top Height, and Liquid Water Path into an Operational Aircraft Icing Nowcasting System

NASA Technical Reports Server (NTRS)

Haggerty, Julie; McDonough, Frank; Black, Jennifer; Landott, Scott; Wolff, Cory; Mueller, Steven; Minnis, Patrick; Smith, William, Jr.

2008-01-01

Operational products used by the U.S. Federal Aviation Administration to alert pilots of hazardous icing provide nowcast and short-term forecast estimates of the potential for the presence of supercooled liquid water and supercooled large droplets. The Current Icing Product (CIP) system employs basic satellite-derived information, including a cloud mask and cloud top temperature estimates, together with multiple other data sources to produce a gridded, three-dimensional, hourly depiction of icing probability and severity. Advanced satellite-derived cloud products developed at the NASA Langley Research Center (LaRC) provide a more detailed description of cloud properties (primarily at cloud top) compared to the basic satellite-derived information used currently in CIP. Cloud hydrometeor phase, liquid water path, cloud effective temperature, and cloud top height as estimated by the LaRC algorithms are into the CIP fuzzy logic scheme and a confidence value is determined. Examples of CIP products before and after the integration of the LaRC satellite-derived products will be presented at the conference.

Instrumental neutron activation analysis data for cloud-water particulate samples, Mount Bamboo, Taiwan

USGS Publications Warehouse

Lin, Neng-Huei; Sheu, Guey-Rong; Wetherbee, Gregory A.; Debey, Timothy M.

2013-01-01

Cloud water was sampled on Mount Bamboo in northern Taiwan during March 22-24, 2002. Cloud-water samples were filtered using 0.45-micron filters to remove particulate material from the water samples. Filtered particulates were analyzed by instrumental neutron activation analysis (INAA) at the U.S. Geological Survey National Reactor Facility in Denver, Colorado, in February 2012. INAA elemental composition data for the particulate materials are presented. These data complement analyses of the aqueous portion of the cloud-water samples, which were performed earlier by the Department of Atmospheric Sciences, National Central University, Taiwan. The data are intended for evaluation of atmospheric transport processes and air-pollution sources in Southeast Asia.

The Radiative Effects of Martian Water Ice Clouds on the Local Atmospheric Temperature Profile

NASA Technical Reports Server (NTRS)

Colaprete, Anthony; Toon, Owen B.

2000-01-01

Mars Pathfinder made numerous discoveries, one of which was a deep temperature inversion that extended from about 15 km down to 8 km above the surface. It has been suggested by Haberle et al. (1999. J. Geophys. Res. 104, 8957-8974.) that radiative cooling by a water ice cloud may generate such an inversion. Clouds can strongly affect the local air temperature due to their ability to radiate efficiently in the infrared and due to the low air mass of the martian atmosphere, which allows the temperature to change during the relatively short lifetime of a cloud. We utilize a time-dependent microphysical aerosol model coupled to a radiative--convective model to explore the effects water ice clouds have on the local martian temperature profile. We constrain the dust and water vapor abundance using data from the Viking Missions and Mars Pathfinder. Water t ice clouds with visible optical depths of r > 0.1 form readily in these simulations. These clouds alter the local air temperature directly, through infrared cooling, and indirectly, by redistributing atmospheric dust. With this model we are able to reproduce the temperature inversions observed by Mars Pathfinder and Mars Global t Surveyor 2000 Academic Press

Observed Cloud Properties Above the Northern Indian Ocean During CARDEX 2012

NASA Astrophysics Data System (ADS)

Gao, L.; Wilcox, E. M.

2016-12-01

An analysis of cloud microphysical, macrophysical and radiative properties during the dry winter monsoon season above the northern Indian Ocean is presented. The Cloud Aerosol Radiative Forcing Experiment (CARDEX), conducted from 16 February to 30 March 2012 at the Maldives Climate Observatory on Hanimaadhoo (MCOH), used autonomous unmanned aerial vehicles (UAVs) to measure the aerosol profiles, water vapor flux and cloud properties concurrent with continuous ground measurements of surface aerosol and meteorological variables as well as the total-column precipitable water vapor (PWV) and the cloud liquid water path (LWP). Here we present the cloud properties only for the cases with lower atmospheric water vapor using the criterion that the PWV less than 40 kg/m2. This criterion acts to filter the data to control for the natural meteorological variability in the region according to previous studies. The high polluted case is found to correlate with warmer temperature, higher relative humidity in boundary layer and lower lifted condensation level (LCL). Micro Pulse Lidar (MPL) retrieved cloud base height coincides with calculated LCL height which is lower for high polluted case. Meanwhile satellite retrieved cloud top height didn't show obvious variation indicating cloud deepening which is consistent with the observed greater cloud LWP in high polluted case. Those high polluted clouds are associated with more cloud droplets and smaller effective radius and are generally becoming narrower due to the stronger cloud side evaporation-entrainment effect and becoming deeper due to more moist static energy. Clouds in high polluted condition become brighter with higher albedo which can cause a net shortwave forcing over -40 W/m2 in this region.

Remote Sensing of the Radiative and Microphysical Properties of Clouds during TC4: Results from MAS, MASTER, MODIS, and MISR

NASA Technical Reports Server (NTRS)

King, Michael D.; Platnick, Steven; Wind, Galina; Arnold, George T.; Ackerman, Steven A.; Frey, Richard

2007-01-01

The MODIS Airborne Simulator (MAS) and MODIS/ASTER Airborne Simulator (MASTER) were used to obtain measurements of the bidirectional reflectance and brightness temperature of clouds at 50 discrete wavelengths between 0.47 and 14.3 (12.9 m for MASTER). These observations were obtained from the NASA ER-2 aircraft as part of the Tropical Composition, Clouds and Climate Coupling Experiment (TC4) conducted over Central America and surrounding Pacific and Atlantic Oceans between July 17 and August 8, 2007. Multispectral images in eight distinct bands were used to derive a confidence in clear sky (or alternatively the probability of cloud) over land and ocean ecosystems. Based on the results of individual tests run as part of this cloud mask, an algorithm was developed to estimate the phase of the clouds (liquid water, ice, or undetermined phase). Finally, the cloud optical thickness and effective radius were derived for both liquid water and ice clouds that were detected during each flight, using a nearly identical algorithm as that implemented operationally to process MODIS cloud data from the Aqua and Terra satellites (Collection 5). This analysis shows that the cloud mask developed for operational use on MODIS, and tested using MAS and MASTER date in TC4, is quite capable of distinguishing both liquid water and ice clouds during daytime conditions over both land and ocean. The cloud optical thickness and effective radius retrievals used three distinct bands of the MAS (or MASTER), and these results were compared with nearly simultaneous retrievals of MODIS on the Terra spacecraft. Finally, this MODIS-based algorithm was adapted to MISR data to infer the cloud optical thickness of liquid water clouds from MISR. Results of this analysis will be presented and discussed.

Joint retrievals of cloud and drizzle in marine boundary layer clouds using ground-based radar, lidar and zenith radiances

DOE PAGES

Fielding, M. D.; Chiu, J. C.; Hogan, R. J.; ...

2015-02-16

Active remote sensing of marine boundary-layer clouds is challenging as drizzle drops often dominate the observed radar reflectivity. We present a new method to simultaneously retrieve cloud and drizzle vertical profiles in drizzling boundary-layer cloud using surface-based observations of radar reflectivity, lidar attenuated backscatter, and zenith radiances. Specifically, the vertical structure of droplet size and water content of both cloud and drizzle is characterised throughout the cloud. An ensemble optimal estimation approach provides full error statistics given the uncertainty in the observations. To evaluate the new method, we first perform retrievals using synthetic measurements from large-eddy simulation snapshots of cumulusmore » under stratocumulus, where cloud water path is retrieved with an error of 31 g m −2. The method also performs well in non-drizzling clouds where no assumption of the cloud profile is required. We then apply the method to observations of marine stratocumulus obtained during the Atmospheric Radiation Measurement MAGIC deployment in the northeast Pacific. Here, retrieved cloud water path agrees well with independent 3-channel microwave radiometer retrievals, with a root mean square difference of 10–20 g m −2.« less

Cloud Droplet Size and Liquid Water Path Retrievals From Zenith Radiance Measurements: Examples From the Atmospheric Radiation Measurement Program and the Aerosol Robotic Network

NASA Technical Reports Server (NTRS)

Chiu, J. C.; Marshak, A.; Huang, C.-H.; Varnai, T.; Hogan, R. J.; Giles, D. M.; Holben, B. N.; Knyazikhin, Y.; O'Connor, E. J.; Wiscombe, W. J.

2012-01-01

The ground-based Atmospheric Radiation Measurement Program (ARM) and NASA Aerosol Robotic Network (AERONET) routinely monitor clouds using zenith radiances at visible and near-infrared wavelengths. Using the transmittance calculated from such measurements, we have developed a new retrieval method for cloud effective droplet size and conducted extensive tests for non-precipitating liquid water clouds. The underlying principle is to combine a water-absorbing wavelength (i.e. 1640 nm) with a nonwater-absorbing wavelength for acquiring information on cloud droplet size and optical depth. For simulated stratocumulus clouds with liquid water path less than 300 g/sq m and horizontal resolution of 201m, the retrieval method underestimates the mean effective radius by 0.8 m, with a root-mean-squared error of 1.7 m and a relative deviation of 13 %. For actual observations with a liquid water path less than 450 gm.2 at the ARM Oklahoma site during 2007-2008, our 1.5 min-averaged retrievals are generally larger by around 1 m than those from combined ground-based cloud radar and microwave radiometer at a 5min temporal resolution. We also compared our retrievals to those from combined shortwave flux and microwave observations for relatively homogeneous clouds, showing that the bias between these two retrieval sets is negligible, but the error of 2.6 m and the relative deviation of 22% are larger than those found in our simulation case. Finally, the transmittance-based cloud effective droplet radii agree to better than 11% with satellite observations and have a negative bias of 1 m. Overall, the retrieval method provides reasonable cloud effective radius estimates, which can enhance the cloud products of both ARM and AERONET.

Observed cloud reflectivities and liquid water paths: An update

NASA Technical Reports Server (NTRS)

Coakley, James A., Jr.; Snider, Jack B.

1990-01-01

The FIRE microwave radiometer observations of liquid water path from San Nicolas Island and simultaneous NOAA AVHRR observations of cloud reflectivity were used to test a relationship between cloud liquid water path and cloud reflectivity that is often used in general circulation climate models (Stephens, 1978). The results of attempts to improve the data analysis which was described at the previous FIRE Science Team Workshop and elsewhere (Coakley and Snider, 1989) are reported. The improvements included the analysis of additional satellite passes over San Nicolas and sensitivity studies to estimate the effects on the observed reflectivities due to: (1) nonzero surface reflectivities beneath the clouds; (2) the anisotropy of the reflected radiances observed by the AVHRR; (3) small scale spatial structure in the liquid water path; and (4) adjustments to the calibration of AVHRR.

Impact of Long-Range Transported African Dust Events on Cloud Composition and Physical Properties at a Caribbean Tropical Montane Cloud Forest

NASA Astrophysics Data System (ADS)

Valle-Diaz, C. J.; Torres-Delgado, E.; Lee, T.; Collett, J. L.; Cuadra-Rodriguez, L. A.; Prather, K. A.; Spiegel, J.; Eugster, W.

2012-12-01

We studied the impact of long-range transported African Dust (LRTAD) on cloud composition and properties at the Caribbean tropical montane cloud forest (TMCF) of Pico del Este (PE), as part of the Puerto Rico African Dust and Clouds Study (PRADACS). Here we present results from measurements performed in July 2011. Bulk chemical analysis of cloud water and rainwater showed pH and conductivity higher in the presence of dust. pH and conductivity were also higher for larger cloud droplets (size cut of 17 μm at 50% efficiency) suggesting a higher content of dust in this fraction. The concentration of the water-soluble ions in rainwater was found to be lower than for cloud water. This in turn translates to higher pH and lower conductivity. African dust influence at PE was confirmed by the presence of nss-Ca, Fe, Mg, Na, and Al in cloud/rain water, and inferred by HYSPLIT trajectories and the satellite images from the Saharan Air Layer (SAL). Interstitial single-particle size and chemistry measured using aerosol time-of-flight mass spectrometry revealed mostly sea-salt particles (Na, Cl, Ca) and dust particles (Fe, Ti, Mg, nss-Ca). Anthropogenic influence detected as the presence of EC, a tracer for combustion processes, was found to be fairly small according to ATOFMS measurements. An increase of total organic carbon, total nitrogen, and dissolved organic carbon was observed during LRTAD events. Cloud droplet distributions revealed that LRTAD can lead to more numerous, but smaller cloud droplets (around 8 μm in average) at PE. However, total liquid water content appeared to be unaffected by this shift of droplet sizes. Overall, differences in the studied physicochemical properties of aerosols and clouds during dust and non-dust events were observed. Our results show that during LRTAD events, aerosol-cloud-precipitation interactions are altered at PE. Detailed results will be presented at the meeting.

Shallow cumulus rooted in photosynthesis

NASA Astrophysics Data System (ADS)

Vila-Guerau Arellano, J.; Ouwersloot, H.; Horn, G.; Sikma, M.; Jacobs, C. M.; Baldocchi, D.

2014-12-01

We investigate the interaction between plant evapotranspiration, controlled by photosynthesis (for a low vegetation cover by C3 and C4 grasses), and the moist thermals that are responsible for the formation and development of shallow cumulus clouds (SCu). We perform systematic numerical experiments at fine spatial scales using large-eddy simulations explicitly coupled to a plant-physiology model. To break down the complexity of the vegetation-atmospheric system at the diurnal scales, we design the following experiments with increasing complexity: (a) clouds that are transparent to radiation, (b) clouds that shade the surface from the incoming shortwave radiation and (c) plant stomata whose apertures react with an adjustment in time to cloud perturbations. The shading by SCu leads to a strong spatial variability in photosynthesis and the surface energy balance. As a result, experiment (b) simulates SCu that are characterized by less extreme and less skewed values of the liquid water path and cloud-base height. These findings are corroborated by the calculation of characteristics lengths scales of the thermals and clouds using autocorrelation and spectral analysis methods. We find that experiments (a) and (b) are characterized by similar cloud cover evolution, but different cloud population characteristics. Experiment (b), including cloud shading, is characterized by smaller clouds, but closer to each other. By performing a sensitivity analysis on the exchange of water vapor and carbon dioxide at the canopy level, we show that the larger water-use efficiency of C4 grass leads to two opposing effects that directly influence boundary-layer clouds: the thermals below the clouds are more vigorous and deeper driven by a larger buoyancy surface flux (positive effect), but are characterized by less moisture content (negative effect). We conclude that under the investigated mid-latitude atmospheric and well-watered soil conditions, SCu over C4 grass fields is characterized by larger cloud cover and an enhanced liquid water path compared to C3 grass fields.

Physical attributes of some clouds amid a forest ecosystem's trees

USGS Publications Warehouse

DeFelice, Thomas P.

2002-01-01

Cloud or fog water collected by forest canopies of any elevation could represent significant sources of required moisture and nutrients for forest ecosystems, human consumption, and as an alternative source of water for agriculture and domestic use. The physical characteristics of fogs and other clouds have been well studied, and this information can be useful to water balance or canopy–cloud interaction model verification and to calibration or training of satellite-borne sensors to recognize atmospheric attributes, such as optical thickness, albedo, and cloud properties. These studies have taken place above-canopy or within canopy clearings and rarely amid the canopy. Simultaneous physical and chemical characteristics of clouds amid and above the trees of a mountain forest, located about 3.3 km southwest of Mt. Mitchell, NC, were collected between 13 and 22 June 1993. This paper summarizes the physical characteristics of the cloud portions amid the trees. The characteristic cloud amid the trees (including cloud and precipitation periods) contained 250 droplet/cm3 with a mean diameter of 9.5 μm and liquid water content (LWC) of 0.11 g m−3. The cloud droplets exhibited a bimodal distribution with modes at about 2 and 8 μm and a mean diameter near 5 μm during precipitation-free periods, whereas the concurrent above-canopy cloud droplets had a unimodal distribution with a mode near 6 μm and a mean diameter of 6 μm. The horizontal cloud water flux is nonlinearly related to the rate of collection onto that surface amid the trees, especially for the Atmospheric Sciences Research Center (ASRC) sampling device, whereas it is linear when the forward scattering spectrometer probe (FSSP) are is used. These findings suggest that statements about the effects clouds have on surfaces they encounter, which are based on above-canopy or canopy-clearing data, can be misleading, if not erroneous.

Cold Water Vapor in the Barnard 5 Molecular Cloud

NASA Technical Reports Server (NTRS)

Wirstrom, E. S.; Charnley, S. B.; Persson, C. M.; Buckle, J. V.; Cordiner, M. A.; Takakuwa, S.

2014-01-01

After more than 30 yr of investigations, the nature of gas-grain interactions at low temperatures remains an unresolved issue in astrochemistry. Water ice is the dominant ice found in cold molecular clouds; however, there is only one region where cold ((is) approximately 10 K) water vapor has been detected-L1544. This study aims to shed light on ice desorption mechanisms under cold cloud conditions by expanding the sample. The clumpy distribution of methanol in dark clouds testifies to transient desorption processes at work-likely to also disrupt water ice mantles. Therefore, the Herschel HIFI instrument was used to search for cold water in a small sample of prominent methanol emission peaks. We report detections of the ground-state transition of o-H2O (J = 110-101) at 556.9360 GHz toward two positions in the cold molecular cloud, Barnard 5. The relative abundances of methanol and water gas support a desorption mechanism which disrupts the outer ice mantle layers, rather than causing complete mantle removal.

SAGE II

Atmospheric Science Data Center

2016-02-16

... the spatial distributions of stratospheric aerosols, ozone, nitrogen dioxide, water vapor and cloud occurrence by mapping vertical profiles ... Clouds Clouds in a Clear Sky Clouds in the Balance Stars Clouds Crops Volcanoes and Climate Change ...

Observed reflectivities and liquid water content for marine stratocumulus

NASA Technical Reports Server (NTRS)

Coakley, J. A., Jr.; Snider, J. B.

1989-01-01

Simultaneous observations of cloud liquid water content and cloud reflectivity are used to verify their parametric relationship in a manner consistent with simple parameterizations often used in general-circulation climate models. The column amount of cloud liquid water was measured with a microwave radiometer on San Nicolas Island as described by Hogg et al., (1983). Cloud reflectivity was obtained through spatial coherence analysis of AVHRR imagery data as per Coakley and Baldwin (1984) and Coakley and Beckner (1988). The dependence of the observed reflectivity on the observed liquid water is discussed, and this empirical relationship is compared with the parameterization proposed by Stephens (1978).

Biomass burning drives atmospheric nutrient redistribution within forested peatlands in Borneo

NASA Astrophysics Data System (ADS)

Ponette-González, Alexandra G.; Curran, Lisa M.; Pittman, Alice M.; Carlson, Kimberly M.; Steele, Bethel G.; Ratnasari, Dessy; Mujiman; Weathers, Kathleen C.

2016-08-01

Biomass burning plays a critical role not only in atmospheric emissions, but also in the deposition and redistribution of biologically important nutrients within tropical landscapes. We quantified the influence of fire on biogeochemical fluxes of nitrogen (N), phosphorus (P), and sulfur (S) in a 12 ha forested peatland in West Kalimantan, Indonesia. Total (inorganic + organic) N, {{{{NO}}}3}- -N, {{{{NH}}}4}+ -N, total P, {{{{PO}}}4}3- -P, and {{{{SO}}}4}2- -S fluxes were measured in throughfall and bulk rainfall weekly from July 2013 to September 2014. To identify fire events, we used concentrations of particulate matter (PM10) and MODIS Active Fire Product counts within 20 and 100 km radius buffers surrounding the site. Dominant sources of throughfall nutrient deposition were explored using cluster and back-trajectory analysis. Our findings show that this Bornean peatland receives some of the highest P (7.9 kg {{{{PO}}}4}3- -P ha-1yr-1) and S (42 kg {{{{SO}}}4}2- -S ha-1yr-1) deposition reported globally, and that N deposition (8.7 kg inorganic N ha-1yr-1) exceeds critical load limits suggested for tropical forests. Six major dry periods and associated fire events occurred during the study. Seventy-eight percent of fires within 20 km and 40% within 100 km of the site were detected within oil palm plantation leases (industrial agriculture) on peatlands. These fires had a disproportionate impact on below-canopy nutrient fluxes. Post-fire throughfall events contributed >30% of the total inorganic N ({{{{NO}}}3}- -N + {{{{NH}}}4}+ -N) and {{{{PO}}}4}3- -P flux to peatland soils during the study period. Our results indicate that biomass burning associated with agricultural peat fires is a major source of N, P, and S in throughfall and could rival industrial pollution as an input to these systems during major fire years. Given the sheer magnitude of fluxes reported here, fire-related redistribution of nutrients may have significant fertilizing or acidifying effects on a diversity of nutrient-limited ecosystems.

Effects of cloud size and cloud particles on satellite-observed reflected brightness

NASA Technical Reports Server (NTRS)

Reynolds, D. W.; Mckee, T. B.; Danielson, K. S.

1978-01-01

Satellite observations allowed obtaining data on the visible brightness of cumulus clouds over South Park, Colorado, while aircraft observations were made in cloud to obtain the drop size distributions and liquid water content of the cloud. Attention is focused on evaluating the relationship between cloud brightness, horizontal dimension, and internal microphysical structure. A Monte Carlo cloud model for finite clouds was run using different distributions of drop sizes and numbers, while varying the cloud depth and width to determine how theory would predict what the satellite would view from its given location in space. Comparison of these results to the satellite observed reflectances is presented. Theoretical results are found to be in good agreement with observations. For clouds of optical thickness between 20 and 60, monitoring cloud brightness changes in clouds of uniform depth and variable width gives adequate information about a cloud's liquid water content. A cloud having a 10:1 width to depth ratio is almost reaching its maximum brightness for a specified optical thickness.

ARM Evaluation Product : Droplet Number Concentration Value-Added Product

DOE Data Explorer

Riihimaki, Laura

2014-05-15

Cloud droplet number concentration is an important factor in understanding aerosol-cloud interactions. As aerosol concentration increases, it is expected that droplet number concentration, Nd, will increase and droplet size decrease, for a given liquid water path (Twomey 1977), which will greatly affect cloud albedo as smaller droplets reflect more shortwave radiation. However, the magnitude and variability of these processes under different environmental conditions is still uncertain. McComiskey et al. (2009) have implemented a method, based on Boers and Mitchell (1994), for calculating Nd from ground-based remote sensing measurements of optical depth and liquid water path. They show that the magnitude of the aerosol-cloud interactions (ACI) varies with a range of factors, including the relative value of the cloud liquid water path (LWP), the aerosol size distribution, and the cloud updraft velocity. Estimates of Nd under a range of cloud types and conditions and at a variety of sites are needed to further quantify the impacts of aerosol cloud interactions.

Physics Parameterization for Seasonal Prediction

DTIC Science & Technology

2012-09-30

comparison Project, a joint effort between the Year of Tropical Convection (YOTC) Program and the Global Energy and Water Cycle Experiment (GEWEX) Cloud...unified” representation of the water cycle in the model. One such area is the correspondence between diagnosed cloud cover and prognostic cloud

Ice Clouds in Martian Arctic (Accelerated Movie)

NASA Technical Reports Server (NTRS)

2008-01-01

Clouds scoot across the Martian sky in a movie clip consisting of 10 frames taken by the Surface Stereo Imager on NASA's Phoenix Mars Lander.

This clip accelerates the motion. The camera took these 10 frames over a 10-minute period from 2:52 p.m. to 3:02 p.m. local solar time at the Phoenix site during Sol 94 (Aug. 29), the 94th Martian day since landing.

Particles of water-ice make up these clouds, like ice-crystal cirrus clouds on Earth. Ice hazes have been common at the Phoenix site in recent days.

The camera took these images as part of a campaign by the Phoenix team to see clouds and track winds. The view is toward slightly west of due south, so the clouds are moving westward or west-northwestward.

The clouds are a dramatic visualization of the Martian water cycle. The water vapor comes off the north pole during the peak of summer. The northern-Mars summer has just passed its peak water-vapor abundance at the Phoenix site. The atmospheric water is available to form into clouds, fog and frost, such as the lander has been observing recently.

The Phoenix Mission is led by the University of Arizona, Tucson, on behalf of NASA. Project management of the mission is by NASA's Jet Propulsion Laboratory, Pasadena, Calif. Spacecraft development is by Lockheed Martin Space Systems, Denver.

Responses of Cloud Type Distributions to the Large-Scale Dynamical Circulation: Water Budget-Related Dynamical Phase Space and Dynamical Regimes

NASA Technical Reports Server (NTRS)

Wong, Sun; Del Genio, Anthony; Wang, Tao; Kahn, Brian; Fetzer, Eric J.; L'Ecuyer, Tristan S.

2015-01-01

Goals: Water budget-related dynamical phase space; Connect large-scale dynamical conditions to atmospheric water budget (including precipitation); Connect atmospheric water budget to cloud type distributions.

A Cloudy Day on Mars

NASA Technical Reports Server (NTRS)

2002-01-01

(Released 23 April 2002) The Science This image, centered near 49.7 N and 43.0 W (317.0 E), displays splotchy water ice clouds that obscure the surface. Most of Mars was in a relatively clear period when this image was acquired, which is why many of the other THEMIS images acquired during the same period do not have obvious signs of atmospheric dust or water ice clouds. This image is far enough north to catch the edge of the north polar hood that develops during the northern winter. This is a cap of water ice and CO₂ ice clouds that form over the Martian north pole. Mars has a number of interesting atmospheric phenomena which THEMIS will be able to view in addition to water ice clouds, including dust devils, dust storms, and tracking atmospheric temperatures with the infrared camera. The Story Anyone who's been on an airplane in a storm knows how clouds on Earth can block the view below. The thin water ice clouds on Mars might make things slightly blurry, but at least we can still see the surface. While the surface features may not be as clear in this image, it's actually kind of fascinating to see clouds at work, because we can get a sense of how the north pole on Mars influences the weather and the climate. In this image, the north pole is responsible for the presence of the clouds. Made of water ice and carbon dioxide, these clouds 'mist out' in a atmospheric 'hood' that caps the surface during the northern Martian winter, hiding it from full view of eager observers here on Earth.

Investigating the differences of cirrus cloud properties in nucleation, growth and sublimation regions based on airborne water vapor lidar measurements

NASA Astrophysics Data System (ADS)

Urbanek, Benedikt; Groß, Silke; Wirth, Martin

2017-04-01

Cirrus clouds impose high uncertainties on weather and climate prediction, as knowledge on important processes is still incomplete. For instance it remains unclear how cloud optical, microphysical, and radiative properties change as the cirrus evolves. To gain better understanding of cirrus clouds, their optical and microphysical properties and their changes with cirrus cloud evolution the ML-CIRRUS campaign was conducted in March and April 2014. Measurements with a combined in-situ and remote sensing payload were performed with the German research aircraft HALO based in Oberpfaffenhofen. 16 research flights with altogether 88 flight hours were performed over the North-Atlantic, western and central Europe to probe different cirrus cloud regimes and cirrus clouds at different stages of evolution. One of the key remotes sensing instruments during ML-CIRRUS was the airborne differential absorption and high spectral lidar system WALES. It measures the 2-dimensional distribution of water vapor inside and outside of cirrus clouds as well as the optical properties of the clouds. Bases on these airborne lidar measurements a novel classification scheme to derive the stage of cirrus cloud evolution was developed. It identifies regions of ice nucleation, particle growth by deposition of water vapor, and ice sublimation. This method is used to investigate differences in the distribution and value of optical properties as well as in the distribution of water vapor and relative humidity depending on the stage of evolution of the cloud. We will present the lidar based classification scheme and its application on a wave driven cirrus cloud case, and we will show first results of the dependence of optical cloud properties and relative humidity distributions on the determined stage of evolution.

An energy balance model exploration of the impacts of interactions between surface albedo, cloud cover and water vapor on polar amplification

NASA Astrophysics Data System (ADS)

Södergren, A. Helena; McDonald, Adrian J.; Bodeker, Gregory E.

2017-11-01

We examine the effects of non-linear interactions between surface albedo, water vapor and cloud cover (referred to as climate variables) on amplified warming of the polar regions, using a new energy balance model. Our simulations show that the sum of the contributions to surface temperature changes due to any variable considered in isolation is smaller than the temperature changes from coupled feedback simulations. This non-linearity is strongest when all three climate variables are allowed to interact. Surface albedo appears to be the strongest driver of this non-linear behavior, followed by water vapor and clouds. This is because increases in longwave radiation absorbed by the surface, related to increases in water vapor and clouds, and increases in surface absorbed shortwave radiation caused by a decrease in surface albedo, amplify each other. Furthermore, our results corroborate previous findings that while increases in cloud cover and water vapor, along with the greenhouse effect itself, warm the polar regions, water vapor also significantly warms equatorial regions, which reduces polar amplification. Changes in surface albedo drive large changes in absorption of incoming shortwave radiation, thereby enhancing surface warming. Unlike high latitudes, surface albedo change at low latitudes are more constrained. Interactions between surface albedo, water vapor and clouds drive larger increases in temperatures in the polar regions compared to low latitudes. This is in spite of the fact that, due to a forcing, cloud cover increases at high latitudes and decreases in low latitudes, and that water vapor significantly enhances warming at low latitudes.

The Chemistry and Excitation of Water in Molecular Clouds

NASA Technical Reports Server (NTRS)

Hollenbach, David

2003-01-01

We model the chemistry and thermal balance of opaque molecular clouds exposed to an external flux of ultraviolet photons. We include the processes of gas phase and grain surface chemical reactions; in particular we examine closely the freezing of atoms and molecules onto grain surfaces and the desorption of molecules from grain surfaces as a function of depth into a molecular cloud. We find that on the surface of a molecular cloud the gas phase water abundances are low because of photodissociation, and the grain phase water (ice) abundance is low because of photodesorption of water from the grain surfaces. Deeper into the cloud, at A(sub v) less than or approximately 2-8 depending on the strength of the external ultraviolet flux, the gas phase water abundance increases with depth as the photodissociation rates decline due to dust attenuation of the ultraviolet field. However, beyond A(sub v) less than or approximately 2-8 the gas phase water abundance declines because the water freezes as water ice on the grains, and photodesorption is no longer effective in clearing the ice. A peak water abundance of about 10(exp -6) to 10(exp -7) occurs at about A(sub v) approximately 2-8, relatively independent of the gas density and the ultraviolet field. We show that such a model matches very closely the observations of the Submillimeter Wave Astronomical Satellite (SWAS), a NASA Small Explorer Mission. The model elucidates several mechanisms that have been recently invoked to understand gas phase chemistry in clouds, including-the freeze-out of molecules onto grain surface, the desorption of these molecules from the surfaces, and the abundance gradients of molecules as functions of depth into molecular clouds.

Worldwide data sets constrain the water vapor uptake coefficient in cloud formation

PubMed Central

Raatikainen, Tomi; Nenes, Athanasios; Seinfeld, John H.; Morales, Ricardo; Moore, Richard H.; Lathem, Terry L.; Lance, Sara; Padró, Luz T.; Lin, Jack J.; Cerully, Kate M.; Bougiatioti, Aikaterini; Cozic, Julie; Ruehl, Christopher R.; Chuang, Patrick Y.; Anderson, Bruce E.; Flagan, Richard C.; Jonsson, Haflidi; Mihalopoulos, Nikos; Smith, James N.

2013-01-01

Cloud droplet formation depends on the condensation of water vapor on ambient aerosols, the rate of which is strongly affected by the kinetics of water uptake as expressed by the condensation (or mass accommodation) coefficient, αc. Estimates of αc for droplet growth from activation of ambient particles vary considerably and represent a critical source of uncertainty in estimates of global cloud droplet distributions and the aerosol indirect forcing of climate. We present an analysis of 10 globally relevant data sets of cloud condensation nuclei to constrain the value of αc for ambient aerosol. We find that rapid activation kinetics (αc > 0.1) is uniformly prevalent. This finding resolves a long-standing issue in cloud physics, as the uncertainty in water vapor accommodation on droplets is considerably less than previously thought. PMID:23431189

Worldwide data sets constrain the water vapor uptake coefficient in cloud formation.

PubMed

Raatikainen, Tomi; Nenes, Athanasios; Seinfeld, John H; Morales, Ricardo; Moore, Richard H; Lathem, Terry L; Lance, Sara; Padró, Luz T; Lin, Jack J; Cerully, Kate M; Bougiatioti, Aikaterini; Cozic, Julie; Ruehl, Christopher R; Chuang, Patrick Y; Anderson, Bruce E; Flagan, Richard C; Jonsson, Haflidi; Mihalopoulos, Nikos; Smith, James N

2013-03-05

Cloud droplet formation depends on the condensation of water vapor on ambient aerosols, the rate of which is strongly affected by the kinetics of water uptake as expressed by the condensation (or mass accommodation) coefficient, αc. Estimates of αc for droplet growth from activation of ambient particles vary considerably and represent a critical source of uncertainty in estimates of global cloud droplet distributions and the aerosol indirect forcing of climate. We present an analysis of 10 globally relevant data sets of cloud condensation nuclei to constrain the value of αc for ambient aerosol. We find that rapid activation kinetics (αc > 0.1) is uniformly prevalent. This finding resolves a long-standing issue in cloud physics, as the uncertainty in water vapor accommodation on droplets is considerably less than previously thought.

Spectral Dependence of MODIS Cloud Droplet Effective Radius Retrievals for Marine Boundary Layer Clouds

NASA Technical Reports Server (NTRS)

Zhang, Zhibo; Platnick, Steven E.; Ackerman, Andrew S.; Cho, Hyoun-Myoung

2014-01-01

Low-level warm marine boundary layer (MBL) clouds cover large regions of Earth's surface. They have a significant role in Earth's radiative energy balance and hydrological cycle. Despite the fundamental role of low-level warm water clouds in climate, our understanding of these clouds is still limited. In particular, connections between their properties (e.g. cloud fraction, cloud water path, and cloud droplet size) and environmental factors such as aerosol loading and meteorological conditions continue to be uncertain or unknown. Modeling these clouds in climate models remains a challenging problem. As a result, the influence of aerosols on these clouds in the past and future, and the potential impacts of these clouds on global warming remain open questions leading to substantial uncertainty in climate projections. To improve our understanding of these clouds, we need continuous observations of cloud properties on both a global scale and over a long enough timescale for climate studies. At present, satellite-based remote sensing is the only means of providing such observations.

Observing Ice in Clouds from Space

NASA Technical Reports Server (NTRS)

Ackerman, S.; Star, D. O'C.; Skofronick-Jackson, G.; Evans, F.; Wang, J. R.; Norris, P.; daSilva, A.; Soden, B.

2006-01-01

There are many satellite observations of cloud top properties and the liquid and rain content of clouds, however, we do not yet quantitatively understand the processes that control the water budget of the upper troposphere where ice is the predominant phase, and how these processes are linked to precipitation processes and the radiative energy budget. The ice in clouds in the upper troposphere either melts into rain or is detrained, and persists, as cirrus clouds affecting the hydrological and energy cycle, respectively. Fully modeling the Earth's climate and improving weather and climate forecasts requires accurate satellite measurements of various cloud properties at the temporal and spatial scales of cloud processes. These properties include cloud horizontal and vertical structure, cloud water content and some measure of particle sizes and shapes. The uncertainty in knowledge of these ice characteristics is reflected in the large discrepancies in model simulations of the upper tropospheric water budget. Model simulations are sensitive to the partition of ice between precipitation and outflow processes, i.e., to the parameterization of ice clouds and ice processes. One barrier to achieving accurate global ice cloud properties is the lack of adequate observations at millimeter and submillimeter wavelengths (183-874 GHz). Recent advances in instrumentation have allowed for the development and implementation of an airborne submillimeter-wave radiometer. The brightness temperatures at these frequencies are especially sensitive to cirrus ice particle sizes (because they are comparable to the wavelength). This allows for more accurate ice water path estimates when multiple channels are used to probe into the cloud layers. Further, submillimeter wavelengths offer simplicity in the retrieval algorithms because they do not probe into the liquid and near surface portions of clouds, thus requiring only one term of the radiative transfer equation (ice scattering) to relate brightness temperatures to ice. The next step is a satellite mission designed to acquire global Earth radiance measurements in the submillimeter-wave region, thus bridging the measurement gap between microwave sounders and shorter-wavelength infrared and visible sensors. This presentation provides scientific justification and an approach to measuring ice water path and particle size from a satellite platform that spans a range encompassing both the hydrologically active and radiatively active components of cloud systems.

Modelling and intepreting the isotopic composition of water vapour in convective updrafts

NASA Astrophysics Data System (ADS)

Bolot, M.; Legras, B.; Moyer, E. J.

2012-08-01

The isotopic compositions of water vapour and its condensates have long been used as tracers of the global hydrological cycle, but may also be useful for understanding processes within individual convective clouds. We review here the representation of processes that alter water isotopic compositions during processing of air in convective updrafts and present a unified model for water vapour isotopic evolution within undiluted deep convective cores, with a special focus on the out-of-equilibrium conditions of mixed phase zones where metastable liquid water and ice coexist. We use our model to show that a combination of water isotopologue measurements can constrain critical convective parameters including degree of supersaturation, supercooled water content and glaciation temperature. Important isotopic processes in updrafts include kinetic effects that are a consequence of diffusive growth or decay of cloud particles within a supersaturated or subsaturated environment; isotopic re-equilibration between vapour and supercooled droplets, which buffers isotopic distillation; and differing mechanisms of glaciation (droplet freezing vs. the Wegener-Bergeron-Findeisen process). As all of these processes are related to updraft strength, droplet size distribution and the retention of supercooled water, isotopic measurements can serve as a probe of in-cloud conditions of importance to convective processes. We study the sensitivity of the profile of water vapour isotopic composition to differing model assumptions and show how measurements of isotopic composition at cloud base and cloud top alone may be sufficient to retrieve key cloud parameters.

Modelling and interpreting the isotopic composition of water vapour in convective updrafts

NASA Astrophysics Data System (ADS)

Bolot, M.; Legras, B.; Moyer, E. J.

2013-08-01

The isotopic compositions of water vapour and its condensates have long been used as tracers of the global hydrological cycle, but may also be useful for understanding processes within individual convective clouds. We review here the representation of processes that alter water isotopic compositions during processing of air in convective updrafts and present a unified model for water vapour isotopic evolution within undiluted deep convective cores, with a special focus on the out-of-equilibrium conditions of mixed-phase zones where metastable liquid water and ice coexist. We use our model to show that a combination of water isotopologue measurements can constrain critical convective parameters, including degree of supersaturation, supercooled water content and glaciation temperature. Important isotopic processes in updrafts include kinetic effects that are a consequence of diffusive growth or decay of cloud particles within a supersaturated or subsaturated environment; isotopic re-equilibration between vapour and supercooled droplets, which buffers isotopic distillation; and differing mechanisms of glaciation (droplet freezing vs. the Wegener-Bergeron-Findeisen process). As all of these processes are related to updraft strength, particle size distribution and the retention of supercooled water, isotopic measurements can serve as a probe of in-cloud conditions of importance to convective processes. We study the sensitivity of the profile of water vapour isotopic composition to differing model assumptions and show how measurements of isotopic composition at cloud base and cloud top alone may be sufficient to retrieve key cloud parameters.

STS-55 Earth observation of the Timor Sea

NASA Technical Reports Server (NTRS)

1993-01-01

STS-55 Earth observation taken from Columbia, Orbiter Vehicle (OV) 102, shows the Timor Sea along the south coast of Timor. The sunglint pattern shows a sharp boundary in sea surface temperature, with cooler water along the coast and warmer water offshore. The sunglint brightness reveals water surface roughness with bright indicating smooth water and dark representing rough water. Cooler water is smoother because it acts to stabilize the atmospheric boundary layer, while the warm water acts to destabilize the atmosphere. Another indication of water temperature is the cloud pattern. Advection within the atmosphere as a result of warming at the sea surface forms low-level clouds with the small, popcorn-like appearance seen in upper right corner of the photograph. The cool water, on the other hand, is relatively free of the popcorn-like clouds. The distribution of the clouds indicates that the wind is blowing toward the upper right corner of the photograph. Also note the line of low-level

The role of water ice clouds in the Martian hydrologic cycle

NASA Technical Reports Server (NTRS)

James, Philip B.

1990-01-01

A one-dimensional model for the seasonal cycle of water on Mars has been used to investigate the direction of the net annual transport of water on the planet and to study the possible role of water ice clouds, which are included as an independent phase in addition to ground ice and water vapor, in the cycle. The calculated seasonal and spatial patterns of occurrence of water ice clouds are qualitatively similar to the observed polar hoods, suggesting that these polar clouds are, in fact, an important component of water cycle. A residual dry ice in the south acts as a cold trap which, in the absence of sources other than the caps, will ultimately attract the water ice from the north cap; however, in the presence of a source of water in northern midlatitudes during spring, it is possible that the observed distribution of vapor and ice can be in a steady state even if a residual CO2 cap is a permanent feature of the system.

The Effect of Clouds on Water Vapor Profiling from the Millimeter-Wave Radiometric Measurements

NASA Technical Reports Server (NTRS)

Wang, J. R.; Spinhirne, J. D.; Racette, P.; Chang, L. A.; Hart, W.

1997-01-01

Simultaneous measurements with the millimeter-wave imaging radiometer (MIR), cloud lidar system (CLS), and the MODIS airborne simulator (MAS) were made aboard the NASA ER-2 aircraft over the western Pacific Ocean on 17-18 January 1993. These measurements were used to study the effects of clouds on water vapor profile retrievals based on millimeter-wave radiometer measurements. The CLS backscatter measurements (at 0.532 and 1.064 am) provided information on the heights and a detailed structure of cloud layers; the types of clouds could be positively identified. All 12 MAS channels (0.6-13 Am) essentially respond to all types of clouds, while the six MIR channels (89-220 GHz) show little sensitivity to cirrus clouds. The radiances from the 12-/Am and 0.875-gm channels of the MAS and the 89-GHz channel of the MIR were used to gauge the performance of the retrieval of water vapor profiles from the MIR observations under cloudy conditions. It was found that, for cirrus and absorptive (liquid) clouds, better than 80% of the retrieval was convergent when one of the three criteria was satisfied; that is, the radiance at 0.875 Am is less than 100 W/cm.sr, or the brightness at 12 Am is greater than 260 K, or brightness at 89 GHz is less than 270 K (equivalent to cloud liquid water of less than 0.04 g/cm). The range of these radiances for convergent retrieval increases markedly when the condition for convergent retrieval was somewhat relaxed. The algorithm of water vapor profiling from the MIR measurements could not perform adequately over the areas of storm-related clouds that scatter radiation at millimeter wavelengths.

Testing cloud microphysics parameterizations in NCAR CAM5 with ISDAC and M-PACE observations

NASA Astrophysics Data System (ADS)

Liu, Xiaohong; Xie, Shaocheng; Boyle, James; Klein, Stephen A.; Shi, Xiangjun; Wang, Zhien; Lin, Wuyin; Ghan, Steven J.; Earle, Michael; Liu, Peter S. K.; Zelenyuk, Alla

2011-01-01

Arctic clouds simulated by the National Center for Atmospheric Research (NCAR) Community Atmospheric Model version 5 (CAM5) are evaluated with observations from the U.S. Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) Indirect and Semi-Direct Aerosol Campaign (ISDAC) and Mixed-Phase Arctic Cloud Experiment (M-PACE), which were conducted at its North Slope of Alaska site in April 2008 and October 2004, respectively. Model forecasts for the Arctic spring and fall seasons performed under the Cloud-Associated Parameterizations Testbed framework generally reproduce the spatial distributions of cloud fraction for single-layer boundary-layer mixed-phase stratocumulus and multilayer or deep frontal clouds. However, for low-level stratocumulus, the model significantly underestimates the observed cloud liquid water content in both seasons. As a result, CAM5 significantly underestimates the surface downward longwave radiative fluxes by 20-40 W m-2. Introducing a new ice nucleation parameterization slightly improves the model performance for low-level mixed-phase clouds by increasing cloud liquid water content through the reduction of the conversion rate from cloud liquid to ice by the Wegener-Bergeron-Findeisen process. The CAM5 single-column model testing shows that changing the instantaneous freezing temperature of rain to form snow from -5°C to -40°C causes a large increase in modeled cloud liquid water content through the slowing down of cloud liquid and rain-related processes (e.g., autoconversion of cloud liquid to rain). The underestimation of aerosol concentrations in CAM5 in the Arctic also plays an important role in the low bias of cloud liquid water in the single-layer mixed-phase clouds. In addition, numerical issues related to the coupling of model physics and time stepping in CAM5 are responsible for the model biases and will be explored in future studies.

Sensitivity of a cloud parameterization package in the National Center for Atmospheric Research Community Climate Model

NASA Astrophysics Data System (ADS)

Kao, C.-Y. J.; Smith, W. S.

1999-05-01

A physically based cloud parameterization package, which includes the Arakawa-Schubert (AS) scheme for subgrid-scale convective clouds and the Sundqvist (SUN) scheme for nonconvective grid-scale layered clouds (hereafter referred to as the SUNAS cloud package), is incorporated into the National Center for Atmospheric Research (NCAR) Community Climate Model, Version 2 (CCM2). The AS scheme is used for a more reasonable heating distribution due to convective clouds and their associated precipitation. The SUN scheme allows for the prognostic computation of cloud water so that the cloud optical properties are more physically determined for shortwave and longwave radiation calculations. In addition, the formation of anvil-like clouds from deep convective systems is able to be simulated with the SUNAS package. A 10-year simulation spanning the period from 1980 to 1989 is conducted, and the effect of the cloud package on the January climate is assessed by comparing it with various available data sets and the National Center for Environmental Protection/NCAR reanalysis. Strengths and deficiencies of both the SUN and AS methods are identified and discussed. The AS scheme improves some aspects of the model dynamics and precipitation, especially with respect to the Pacific North America (PNA) pattern. CCM2's tendency to produce a westward bias of the 500 mbar stationary wave (time-averaged zonal anomalies) in the PNA sector is remedied apparently because of a less "locked-in" heating pattern in the tropics. The additional degree of freedom added by the prognostic calculation of cloud water in the SUN scheme produces interesting results in the modeled cloud and radiation fields compared with data. In general, too little cloud water forms in the tropics, while excessive cloud cover and cloud liquid water are simulated in midlatitudes. This results in a somewhat degraded simulation of the radiation budget. The overall simulated precipitation by the SUNAS package is, however, substantially improved over the original CCM2.

Forest health status in Europe.

PubMed

Lorenz, Martin; Mues, Volker

2007-03-21

Forest health status in Europe is assessed by the International Cooperative Programme on Assessment and Monitoring of Air Pollution Effects on Forests (ICP Forests). Established by the Convention on Long-Range Transboundary Air Pollution (CLRTAP) under the United Nations Economic Commission for Europe (UNECE), the ICP Forests has been monitoring forest condition in close cooperation with the European Commission (EC) for 20 years. The present paper describes the latest results of the deposition measurements on permanent monitoring plots and of the extensive defoliation sample survey. The findings reveal marked spatial patterns in bulk and throughfall depositions of nitrate (N-NO3(-)), ammonium (N-NH4(+)), and sulfate (S-SO4(2-)), as well as an obvious decrease in bulk and throughfall deposition of sulfate. Latest analyses of defoliation data confirm previous results, indicating a high correlation with weather extremes.

Atmospheric mercury in Changbai Mountain area, northeastern China II. The distribution of reactive gaseous mercury and particulate mercury and mercury deposition fluxes.

PubMed

Wan, Qi; Feng, Xinbin; Lu, Julia; Zheng, Wei; Song, Xinjie; Li, Ping; Han, Shijie; Xu, Hao

2009-08-01

Reactive gaseous mercury (RGM) and particulate mercury (Hgp) concentrations in ambient air from a remote site at Changbai Mountain area in northeastern China were intermittently monitored from August 2005 to July 2006 totaling 93 days representing fall, winter-spring and summer season, respectively. Rainwater and snow samples were collected during a whole year, and total mercury (THg) in rain samples were used to calculate wet depositional flux. A throughfall method and a model method were used to estimate dry depositional flux. Results showed mean concentrations of RGM and Hgp are 65 and 77 pg m(-3). Compared to background concentrations of atmospheric mercury species in Northern Hemisphere, RGM and Hgp are significantly elevated in Changbai area. Large values for standard deviation indicated fast reactivity and a low residence time for these mercury species. Seasonal variability is also important, with lower mercury levels in summer compared to other seasons, which is attributed to scavenging by rainfall and low local mercury emissions in summer. THg concentrations ranged from 11.5 to 15.9 ng L(-1) in rainwater samples and 14.9-18.6 ng L(-1) in throughfall samples. Wet depositional flux in Changbai area is calculated to be 8.4 microg m(-2) a(-1), and dry deposition flux is estimated to be 16.5 microg m(-2) a(-1) according to a throughfall method and 20.2 microg m(-2) a(-1) using a model method.

The impact of pollutants from a major northern highway on an adjacent hardwood forest.

PubMed

Watmough, S A; Rabinowitz, T; Baker, S

2017-02-01

Emissions of pollutants from highways can exert multiple stresses on adjacent ecosystems. In this study air concentrations of NO 2 and throughfall deposition of inorganic N (NO 3 - and NH 4 + ), SO 4 2- , Cl - , base cations and several metals were measured in all four seasons along a 1.5km hardwood forest gradient extending away from a major highway (Highway 401) in southern Ontario, Canada. Soil and lichen chemistry and herbaceous plant and epiphytic lichen species composition were measured within the hardwood forest to evaluate impacts of these pollutants. Air concentrations of NO 2 and deposition of inorganic N, Cl - , base cations and Cu and Zn in throughfall were significantly elevated within 100m of the road compared with the more distant sites. Concentrations of several pollutants including N (and δ 15 N), Na + , Al and Fe in epiphytic lichen tissue decreased with distance from the highway, and epiphytic lichen richness was lower at sites within 100m of the road. Despite high throughfall inputs of >15kgNha -1 y -1 and 100kgNa + ha -1 y -1 within 33m of the highway, for example, there was no significant difference in soil chemistry amongst sites. Plant community composition at sites within 80m of the highway differed from sites located further from the road, but it is unclear whether differences were due to highway emissions or were a result of natural forest edge effects. Copyright © 2016 Elsevier B.V. All rights reserved.

Joint retrievals of cloud and drizzle in marine boundary layer clouds using ground-based radar, lidar and zenith radiances

DOE PAGES

Fielding, M. D.; Chiu, J. C.; Hogan, R. J.; ...

2015-07-02

Active remote sensing of marine boundary-layer clouds is challenging as drizzle drops often dominate the observed radar reflectivity. We present a new method to simultaneously retrieve cloud and drizzle vertical profiles in drizzling boundary-layer clouds using surface-based observations of radar reflectivity, lidar attenuated backscatter, and zenith radiances under conditions when precipitation does not reach the surface. Specifically, the vertical structure of droplet size and water content of both cloud and drizzle is characterised throughout the cloud. An ensemble optimal estimation approach provides full error statistics given the uncertainty in the observations. To evaluate the new method, we first perform retrievalsmore » using synthetic measurements from large-eddy simulation snapshots of cumulus under stratocumulus, where cloud water path is retrieved with an error of 31 g m -2. The method also performs well in non-drizzling clouds where no assumption of the cloud profile is required. We then apply the method to observations of marine stratocumulus obtained during the Atmospheric Radiation Measurement MAGIC deployment in the Northeast Pacific. Here, retrieved cloud water path agrees well with independent three-channel microwave radiometer retrievals, with a root mean square difference of 10–20 g m -2.« less

Re-evaluating the Cloud Lifetime Effect: Does Precipitation Suppression Always Lead to an Increased Cloud Extent in Warm Clouds?

NASA Astrophysics Data System (ADS)

Douglas, A.; L'Ecuyer, T.

2017-12-01

Aerosol influences on cloud lifetime remain a poorly understood pathway of aerosol-cloud-radiation interaction with large margins of error according to the fifth IPCC report. Increases in cloud lifetime are attributed to changes in cloud extent due to the suppression of precipitation by increased aerosol concentrations. The dependence of changes in cloud fraction and probability of precipitation on aerosol perturbations for controlled cloud regimes will be investigated using A-Train measurements. CloudSat, MODIS, and AMSR-E measurements from 2006 to 2010 are sorted into regimes established using stability to describe local meteorology, and relative humidity and liquid water path to describe cloud morphology. Holding the thermodynamic and meteorological environments constant allows variations in precipitation and cloud extent owing to regime-specific cloud lifetime effects to be attributed to aerosol perturbations. The relationship between precipitation suppression, cloud extent, and liquid water path will be analyzed. The cloud lifetime effect will be constrained using regimes in the hopes of improving our understanding of precipitation-aerosol interactions.

Moisture structure of tropical cloud systems as inferred from SSM/I

NASA Technical Reports Server (NTRS)

Robertson, Franklin R.

1989-01-01

The structure of tropical cloud systems was examined using data obtained by the Special Sensor Microwave/Imager on vertically-integrated vapor, ice, and liquid water (including precipitable water) in a cloud cluster associated with a Pacific easterly wave. The cloud cluster provided a sample of the varying signatures of bulk microphysical processes in organized tropical convection. Composition techniques were used to interpret this variability and its significance in terms of the response of convection to its thermodynamic environment. The relative intensities of the ice and liquid-water signatures should provide insight on the relative contribution of stratiform vs convective rain and the characteristics of the water budgets of mesoscale convective systems.

Comparison of global cloud liquid water path derived from microwave measurements with CERES-MODIS

NASA Astrophysics Data System (ADS)

Yi, Y.; Minnis, P.; Huang, J.; Lin, B.; Ayers, K.; Sun-Mack, S.; Fan, A.

Cloud liquid water path LWP is a crucial parameter for climate studies due to the link that it provides between the atmospheric hydrological and radiative budgets Satellite-based visible infrared techniques such as the Visible Infrared Solar Split-Window Technique VISST can retrieve LWP for water clouds assumes single-layer over a variety of surfaces If the water clouds are overlapped by ice clouds the LWP of the underlying clouds can not be retrieved by such techniques However microwave techniques may be used to retrieve the LWP underneath ice clouds due to the microwave s insensitivity to cloud ice particles LWP is typically retrieved from satellite-observed microwave radiances only over ocean due to variations of land surface temperature and emissivity Recently Deeter and Vivekanandan 2006 developed a new technique for retrieving LWP over land In order to overcome the sensitivity to land surface temperature and emissivity their technique is based on a parameterization of microwave polarization-difference signals In this study a similar regression-based technique for retrieving LWP over land and ocean using Advanced Microwave Scanning Radiometer - EOS AMSR-E measurements is developed Furthermore the microwave surface emissivities are also derived using clear-sky fields of view based on the Clouds and Earth s Radiant Energy System Moderate-resolution Imaging Spectroradiometer CERES-MODIS cloud mask These emissivities are used in an alternate form of the technique The results are evaluated using independent measurements such

Relationship between cloud-to-ground discharge and penetrative clouds: A multi-channel satellite application

NASA Astrophysics Data System (ADS)

Machado, Luiz A. T.; Lima, Wagner F. A.; Pinto, Osmar; Morales, Carlos A.

This work presents a relationship between atmospheric cloud-to-ground discharges and penetrative convective clouds. It combines Infrared and Water Vapor channels from the GOES-12 geostationary satellite with cloud-to-ground discharge data from the Brazilian Integrated Lightning Detection Network (RINDAT) during the period from January to February 2005. The difference between water vapor and infrared brightness temperature is a tracer penetrating clouds. Due to the water vapor channel's strong absorption, this difference is positive only during overshooting cases, when convective clouds penetrate the stratosphere. From this difference and the cloud-to-ground, discharge measured on the ground by RINDAT, it was possible to adjust exponential curves that relate the brightness temperature difference from these two channels to the probability of occurrence of cloud-to-ground discharges, with a very large coefficient of determination. If WV-IR brightness temperature difference is greater than - 15 K there is a large potential for cloud-to-ground discharge activity. As this difference increases the cloud-to-ground discharge probably increases, for example: if this difference is equal to zero, the probability of having at least one cloud-to-ground discharge is 10.9%, 7.0% for two, 4.4% for four, 2.7% for eight and 1.5% for sixteen cloud-to-ground discharges. Through this process, was developed a scheme that estimates the probability of occurrence of cloud-to-ground discharge over all the continental region of South America.

Cloud Microphysics Budget in the Tropical Deep Convective Regime

NASA Technical Reports Server (NTRS)

Li, Xiao-Fan; Sui, C.-H.; Lau, K.-M.; Einaudi, Franco (Technical Monitor)

2001-01-01

Cloud microphysics budgets in the tropical deep convective regime are analyzed based on a 2-D cloud resolving simulation. The model is forced by the large-scale vertical velocity and zonal wind and large-scale horizontal advections derived from TOGA COARE for a 20-day period. The role of cloud microphysics is first examined by analyzing mass-weighted mean heat budget and column-integrated moisture budget. Hourly budgets show that local changes of mass-weighted mean temperature and column-integrated moisture are mainly determined by the residuals between vertical thermal advection and latent heat of condensation and between vertical moisture advection and condensation respectively. Thus, atmospheric thermodynamics depends on how cloud microphysical processes are parameterized. Cloud microphysics budgets are then analyzed for raining conditions. For cloud-vapor exchange between cloud system and its embedded environment, rainfall and evaporation of raindrop are compensated by the condensation and deposition of supersaturated vapor. Inside the cloud system, the condensation of supersaturated vapor balances conversion from cloud water to raindrop, snow, and graupel through collection and accretion processes. The deposition of supersaturated vapor balances conversion from cloud ice to snow through conversion and riming processes. The conversion and riming of cloud ice and the accretion of cloud water balance conversion from snow to graupel through accretion process. Finally, the collection of cloud water and the melting of graupel increase raindrop to compensate the loss of raindrop due to rainfall and the evaporation of raindrop.

Impacts of solar-absorbing aerosol layers on the transition of stratocumulus to trade cumulus clouds

DOE PAGES

Zhou, Xiaoli; Ackerman, Andrew S.; Fridlind, Ann M.; ...

2017-10-26

Here, the effects of an initially overlying layer of solar-absorbing aerosol on the transition of stratocumulus to trade cumulus clouds are examined using large-eddy simulations. For lightly drizzling cloud the transition is generally hastened, resulting mainly from increased cloud droplet number concentration ( N c) induced by entrained aerosol. The increased N c slows sedimentation of cloud droplets and shortens their relaxation time for diffusional growth, both of which accelerate entrainment of overlying air and thereby stratocumulus breakup. However, the decrease in albedo from cloud breakup is more than offset by redistributing cloud water over a greater number of droplets,more » such that the diurnal-average shortwave forcing at the top of the atmosphere is negative. The negative radiative forcing is enhanced by sizable longwave contributions, which result from the greater cloud breakup and a reduced boundary layer height associated with aerosol heating. A perturbation of moisture instead of aerosol aloft leads to a greater liquid water path and a more gradual transition. Adding absorbing aerosol to that atmosphere results in substantial reductions in liquid water path (LWP) and cloud cover that lead to positive shortwave and negative longwave forcings on average canceling each other. Only for heavily drizzling clouds is the breakup delayed, as inhibition of precipitation overcomes cloud water loss from enhanced entrainment. Considering these simulations as an imperfect proxy for biomass burning plumes influencing Namibian stratocumulus, we expect regional indirect plus semi-direct forcings to be substantially negative to negligible at the top of the atmosphere, with its magnitude sensitive to background and perturbation properties.« less

Impacts of solar-absorbing aerosol layers on the transition of stratocumulus to trade cumulus clouds

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhou, Xiaoli; Ackerman, Andrew S.; Fridlind, Ann M.

Here, the effects of an initially overlying layer of solar-absorbing aerosol on the transition of stratocumulus to trade cumulus clouds are examined using large-eddy simulations. For lightly drizzling cloud the transition is generally hastened, resulting mainly from increased cloud droplet number concentration ( N c) induced by entrained aerosol. The increased N c slows sedimentation of cloud droplets and shortens their relaxation time for diffusional growth, both of which accelerate entrainment of overlying air and thereby stratocumulus breakup. However, the decrease in albedo from cloud breakup is more than offset by redistributing cloud water over a greater number of droplets,more » such that the diurnal-average shortwave forcing at the top of the atmosphere is negative. The negative radiative forcing is enhanced by sizable longwave contributions, which result from the greater cloud breakup and a reduced boundary layer height associated with aerosol heating. A perturbation of moisture instead of aerosol aloft leads to a greater liquid water path and a more gradual transition. Adding absorbing aerosol to that atmosphere results in substantial reductions in liquid water path (LWP) and cloud cover that lead to positive shortwave and negative longwave forcings on average canceling each other. Only for heavily drizzling clouds is the breakup delayed, as inhibition of precipitation overcomes cloud water loss from enhanced entrainment. Considering these simulations as an imperfect proxy for biomass burning plumes influencing Namibian stratocumulus, we expect regional indirect plus semi-direct forcings to be substantially negative to negligible at the top of the atmosphere, with its magnitude sensitive to background and perturbation properties.« less

Impacts of solar-absorbing aerosol layers on the transition of stratocumulus to trade cumulus clouds

NASA Astrophysics Data System (ADS)

Zhou, Xiaoli; Ackerman, Andrew S.; Fridlind, Ann M.; Wood, Robert; Kollias, Pavlos

2017-10-01

The effects of an initially overlying layer of solar-absorbing aerosol on the transition of stratocumulus to trade cumulus clouds are examined using large-eddy simulations. For lightly drizzling cloud the transition is generally hastened, resulting mainly from increased cloud droplet number concentration (Nc) induced by entrained aerosol. The increased Nc slows sedimentation of cloud droplets and shortens their relaxation time for diffusional growth, both of which accelerate entrainment of overlying air and thereby stratocumulus breakup. However, the decrease in albedo from cloud breakup is more than offset by redistributing cloud water over a greater number of droplets, such that the diurnal-average shortwave forcing at the top of the atmosphere is negative. The negative radiative forcing is enhanced by sizable longwave contributions, which result from the greater cloud breakup and a reduced boundary layer height associated with aerosol heating. A perturbation of moisture instead of aerosol aloft leads to a greater liquid water path and a more gradual transition. Adding absorbing aerosol to that atmosphere results in substantial reductions in liquid water path (LWP) and cloud cover that lead to positive shortwave and negative longwave forcings on average canceling each other. Only for heavily drizzling clouds is the breakup delayed, as inhibition of precipitation overcomes cloud water loss from enhanced entrainment. Considering these simulations as an imperfect proxy for biomass burning plumes influencing Namibian stratocumulus, we expect regional indirect plus semi-direct forcings to be substantially negative to negligible at the top of the atmosphere, with its magnitude sensitive to background and perturbation properties.

Seasonal Differences in Tropical Western Pacific Cloud Ice, Water Vapor and Aerosols Observed From Space During ATTREX-III and POSIDON

NASA Astrophysics Data System (ADS)

Avery, M. A.; Rosenlof, K. H.; Vaughan, M.; Getzewich, B. J.; Thornberry, T. D.; Gao, R. S.; Rollins, A. W.; Woods, S.; Yorks, J. E.; Jensen, E. J.

2017-12-01

Recent aircraft missions sampling the tropical tropopause layer (TTL) in the tropical Western Pacific have provided a wealth of detailed cloud microphysical and associated aerosol, water vapor and temperature data for understanding processes that regulate stratospheric composition and hydration. This presentation seeks to provide a regional context for these measurements by comparing and contrasting active space-based observations from these time periods (Feb-Mar 2014 for ATTREX-III and Oct 2016 for POSIDON), primarily from the Clouds and Aerosol Lidar with Orthogonal Polarization (CALIOP), with the addition of Cloud Profiling Radar (CPR) and the Cloud-Aerosol Transport System (CATS) where these data sets are available. While the ATTREX III and POSIDON aircraft field missions both took place from Guam in the Western Pacific, there were striking differences between the amount, geographical distribution and properties of cirrus clouds and aerosols in the Tropical TTL. In addition to cloud and aerosol amount and location, we present geometric properties, including cloud top heights, transparent cloud and aerosol layer thicknesses and location of the 532 nm backscatter centroid, which is roughly equivalent to the layer vertical center of mass. We also present differences in the distribution of cirrus cloud extinction coefficients and ice water content, and aerosol optical depths, as detected from space, and compare these with in situ measurements and with temperature and water vapor distributions from the Microwave Limb Sounder (MLS). We find that there is more intense convection reaching the tropical tropopause during the POSIDON mission, and consequently more associated cloud ice observed during POSIDON than during ATTREX-III.

Impacts of Solar-Absorbing Aerosol Layers on the Transition of Stratocumulus to Trade Cumulus Clouds

NASA Technical Reports Server (NTRS)

Zhou, Xiaoli; Ackerman, Andrew S.; Fridlind, Ann M.; Wood, Robert; Kollias, Pavlos

2017-01-01

The effects of an initially overlying layer of solar-absorbing aerosol on the transition of stratocumulus to trade cumulus clouds are examined using large-eddy simulations. For lightly drizzling cloud the transition is generally hastened, resulting mainly from increased cloud droplet number concentration (Nc) induced by entrained aerosol. The increased Nc slows sedimentation of cloud droplets and shortens their relaxation time for diffusional growth, both of which accelerate entrainment of overlying air and thereby stratocumulus breakup. However, the decrease in albedo from cloud breakup is more than offset by redistributing cloud water over a greater number of droplets, such that the diurnal-average shortwave forcing at the top of the atmosphere is negative. The negative radiative forcing is enhanced by sizable longwave contributions, which result from the greater cloud breakup and a reduced boundary layer height associated with aerosol heating. A perturbation of moisture instead of aerosol aloft leads to a greater liquid water path and a more gradual transition. Adding absorbing aerosol to that atmosphere results in substantial reductions in liquid water path (LWP) and cloud cover that lead to positive short-wave and negative longwave forcings on average canceling each other. Only for heavily drizzling clouds is the breakup delayed, as inhibition of precipitation overcomes cloud water loss from enhanced entrainment. Considering these simulations as an imperfect proxy for biomass burning plumes influencing Namibian stratocumulus, we expect regional indirect plus semi-direct forcings to be substantially negative to negligible at the top of the atmosphere, with its magnitude sensitive to background and perturbation properties.

ARC-1989-AC89-0114-324

NASA Image and Video Library

1989-02-28

Arctic Ozone Expedition Stavanger Norway These clouds in the polar regions north of Stravanger, Norway are representative of what are called 'Type 1' and Type 2' polar stratospheric clouds. Type 1 are seen in the lower portion and consist of cloud particles comprised of nitrogen trihydrates. Seen edge-on as in this view, they appear as a thin dark orange or brown layer. Multiple layering can be seen. The Type 2 clouds are above and consist mostly of water molecules frozen as ice. The size of the particles in Type 2 clouds, the water-ice clouds, are much larger than the particle size of the Type 1 clouds - which are on the order of the wavelength of light.

An upper limit to the abundance of lightning-produced amino acids in the Jovian water clouds

NASA Astrophysics Data System (ADS)

Bar-Nun, A.; Noy, N.; Podolak, M.

1984-08-01

The effect of excess hydrogen on the synthesis of amino acids by high-temperature shock waves in a hydrogen/methane/ammonia/water vapor mixture was studied experimentally. The energy efficiency results, together with the best estimate of the lightning energy dissipation rate on Jupiter from the Voyage data, were used to calculate an upper limit to the rate of amino acid production by lightning in Jovian water clouds. Using reasonable values for the eddy diffusion coefficients within and below the water clouds, the column abundance of lightning-produced amino acids in the clouds was estimated to be 6.2 x 10 to the -6th cm-am. Hence, concentration of amino acids in water droplets would be 8 x 10 to the -8th mole/liter.

Insights into Aqueous-phase processing through Comparison of the Organic Chemical Composition of Atmospheric Particles and Cloud Water in the Southeast United States

NASA Astrophysics Data System (ADS)

Boone, E.; Laskin, J.; Laskin, A.; Wirth, C.; Shepson, P. B.; Stirm, B. H.; Pratt, K.

2014-12-01

Organic compounds comprise a significant mass fraction of submicron atmospheric particles with considerable contribution from secondary organic aerosol (SOA), a large fraction of which is formed from the oxidation of biogenic volatile organic compounds. Aqueous-phase reactions in particles and cloud droplets are suggested to increase SOA mass and change the chemical composition the particles following cloud evaporation. Aqueous-phase processing may also explain discrepancies between measurements and models. To gain a better understanding of these processes, cloud water and below-cloud atmospheric particles were collected onboard a research aircraft during the Southeast Oxidants and Aerosol Study (SOAS) over Alabama in June 2013. Nanospray desorption electrospray ionization (nano-DESI) and direct electrospray ionization (ESI) coupled with high resolution mass spectrometry were utilized to compare the organic molecular composition of the particle and cloud water samples, respectively. Several hundred unique compounds have been identified in the particle and cloud water samples, allowing possible aqueous-phase reactions to be examined. Hydrolysis of organosulfate compounds, aqueous-phase formation of nitrogen-containing compounds, and possible fragmentation of oligomeric compounds will be discussed, with comparisons to previous laboratory studies. This study provides insights into aqueous-phase reactions in ambient cloud droplets.

The relationships among cloud microphysics, chemistry, and precipitation rate in cold mountain clouds

NASA Astrophysics Data System (ADS)

Borys, Randolph D.; Lowenthal, Douglas H.; Mitchell, David L.

A study was conducted to examine the relationships among air pollutant loadings, cloud microphysics, and snowfall rates in cold mountain clouds. It was hypothesized that variations in pollutant loadings would be reflected in shifts in the cloud droplet size distribution. A field program was conducted at Storm Peak Laboratory (SPL) at an elevation of 3210 m MSL in northwestern Colorado. Cold precipitating clouds were sampled during January, 1995. Cloud water was collected and analyzed for major ion and trace element chemistry. Cloud droplet concentrations and size were measured continuously using a PMS FSSP-100. The results indicate a direct relationship between clear-air equivalent (CAE) sulfate concentrations in cloud water and cloud droplet concentrations, an indirect relationship between droplet number and droplet size, a direct relationship between droplet size and snowfall rate, and an indirect relationship between CAE sulfate concentration and snowfall rate.

Exploring the potential of the cosmic-ray neutron method to measure interception storage dynamics

NASA Astrophysics Data System (ADS)

Jakobi, Jannis; Bogena, Heye; Huisman, Johan Alexander; Diekkrüger, Bernd; Vereecken, Harry

2017-04-01

Cosmic-ray neutron soil moisture probes are an emerging technology that relies on the negative correlation between near-surface fast neutron counts and soil moisture content. Hydrogen atoms in the soil, which are mainly present as water, moderate the secondary neutrons on the way back to the surface. Any application of this method needs to consider the sensitivity of the neutron counts to additional sources of hydrogen (e.g. above- and below-ground biomass, humidity of the lower atmosphere, lattice water of the soil minerals, organic matter and water in the litter layer, intercepted water in the canopy, and soil organic matter). In this study, we analyzed the effects of canopy-intercepted water on the cosmic-ray neutron counts. For this, an arable field cropped with sugar beet was instrumented with several cosmic-ray neutron probes and a wireless sensor network with more than 140 in-situ soil moisture sensors. Additionally rainfall interception was estimated using a new approach coupling throughfall measurements and leaf wetness sensors. The derived interception storage was used to correct for interception effects on cosmic ray neutrons to enhance soil water content prediction. Furthermore, the potential for a simultaneous prediction of above- and below-ground biomass, soil moisture and interception was tested.

The use of marine cloud water samples as a diagnostic tool for aqueous chemistry, cloud microphysical processes and dynamics

NASA Astrophysics Data System (ADS)

Crosbie, E.; Ziemba, L. D.; Moore, R.; Shook, M.; Jordan, C.; Thornhill, K. L., II; Winstead, E.; Shingler, T.; Brown, M.; MacDonald, A. B.; Dadashazar, H.; Sorooshian, A.; Weiss-Penzias, P. S.; Anderson, B.

2017-12-01

Clouds play several roles in the Earth's climate system. In addition to their clear significance to the hydrological cycle, they strongly modulate the shortwave and longwave radiative balance of the atmosphere, with subsequent feedback on the atmospheric circulation. Furthermore, clouds act as a conduit for the fate and emergence of important trace chemical species and are the predominant removal mechanism for atmospheric aerosols. Marine boundary layer clouds cover large swaths of the global oceans. Because of their global significance, they have attracted significant attention into understanding how changes in aerosols are translated into changes in cloud macro- and microphysical properties. The circular nature of the influence of clouds-on-aerosols and aerosols-on-clouds has been used to explain the chaotic patterns often seen in marine clouds, however, this feedback also presents a substantial hurdle in resolving the uncertain role of anthropogenic aerosols on climate. Here we discuss ways in which the chemical constituents found in cloud water can offer insight into the physical and chemical processes inherent in marine clouds, through the use of aircraft measurements. We focus on observational data from cloud water samples collected during flights conducted over the remote North Atlantic and along coastal California across multiple campaigns. We explore topics related to aqueous processing, wet scavenging and source apportionment.

Plasticity in leaf-level water relations of tropical rainforest trees in response to experimental drought.

PubMed

Binks, Oliver; Meir, Patrick; Rowland, Lucy; da Costa, Antonio Carlos Lola; Vasconcelos, Steel Silva; de Oliveira, Alex Antonio Ribeiro; Ferreira, Leandro; Christoffersen, Bradley; Nardini, Andrea; Mencuccini, Maurizio

2016-07-01

The tropics are predicted to become warmer and drier, and understanding the sensitivity of tree species to drought is important for characterizing the risk to forests of climate change. This study makes use of a long-term drought experiment in the Amazon rainforest to evaluate the role of leaf-level water relations, leaf anatomy and their plasticity in response to drought in six tree genera. The variables (osmotic potential at full turgor, turgor loss point, capacitance, elastic modulus, relative water content and saturated water content) were compared between seasons and between plots (control and through-fall exclusion) enabling a comparison between short- and long-term plasticity in traits. Leaf anatomical traits were correlated with water relation parameters to determine whether water relations differed among tissues. The key findings were: osmotic adjustment occurred in response to the long-term drought treatment; species resistant to drought stress showed less osmotic adjustment than drought-sensitive species; and water relation traits were correlated with tissue properties, especially the thickness of the abaxial epidermis and the spongy mesophyll. These findings demonstrate that cell-level water relation traits can acclimate to long-term water stress, and highlight the limitations of extrapolating the results of short-term studies to temporal scales associated with climate change. © 2016 The Authors. New Phytologist © 2016 New Phytologist Trust.

High-resolution mapping of Martian water ice clouds using Mars Express OMEGA observations - Derivation of the diurnal cloud life cycle

NASA Astrophysics Data System (ADS)

Szantai, Andre; Audouard, Joachim; Madeleine, Jean-Baptiste; Forget, Francois; Pottier, Alizée; Millour, Ehouarn; Gondet, Brigitte; Langevin, Yves; Bibring, Jean-Pierre

2016-10-01

The mapping in space and time of water ice clouds can help to explain the Martian water cycle and atmospheric circulation. For this purpose, an ice cloud index (ICI) corresponding to the depth of a water ice absorption band at 3.4 microns is derived from a series of OMEGA images (spectels) covering 5 Martian years. The ICI values for the corresponding pixels are then binned on a high-resolution regular grid (1° longitude x 1° latitude x 5° Ls x 1 h local time) and averaged. Inside each bin, the cloud cover is calculated by dividing the number of pixels considered as cloudy (after comparison to a threshold) to the number of all (valid) pixelsWe compare the maps of clouds obtained around local time 14:00 with collocated TES cloud observations (which were only obtained around this time of the day). A good agreement is found.Averaged ICI compared to the water ice column variable from the Martian Climate Database (MCD) show a correct correlation (~0.5) , which increases when values limited to the tropics only are compared.The number of gridpoints containing ICI values is small ( ~1%), but by taking several neighbor gridpoints and over longer periods, we can observe a cloud life cycle during daytime. An example in the the tropics, around the northern summer solstice, shows a decrease of cloudiness in the morning followed by an increase in the afternoon.

A New Approach for Checking and Complementing CALIPSO Lidar Calibration

NASA Technical Reports Server (NTRS)

Josset, Damien B.; Vaughan, Mark A.; Hu, Yongxiang; Avery, Melody A.; Powell, Kathleen A.; Hunt, William H.; Winker, David M.; Pelon, Jacques; Trepte, Charles R.; Lucker, Patricia L.;

Impact of aerosols on ice crystal size

NASA Astrophysics Data System (ADS)

Zhao, Bin; Liou, Kuo-Nan; Gu, Yu; Jiang, Jonathan H.; Li, Qinbin; Fu, Rong; Huang, Lei; Liu, Xiaohong; Shi, Xiangjun; Su, Hui; He, Cenlin

2018-01-01

The interactions between aerosols and ice clouds represent one of the largest uncertainties in global radiative forcing from pre-industrial time to the present. In particular, the impact of aerosols on ice crystal effective radius (Rei), which is a key parameter determining ice clouds' net radiative effect, is highly uncertain due to limited and conflicting observational evidence. Here we investigate the effects of aerosols on Rei under different meteorological conditions using 9-year satellite observations. We find that the responses of Rei to aerosol loadings are modulated by water vapor amount in conjunction with several other meteorological parameters. While there is a significant negative correlation between Rei and aerosol loading in moist conditions, consistent with the "Twomey effect" for liquid clouds, a strong positive correlation between the two occurs in dry conditions. Simulations based on a cloud parcel model suggest that water vapor modulates the relative importance of different ice nucleation modes, leading to the opposite aerosol impacts between moist and dry conditions. When ice clouds are decomposed into those generated from deep convection and formed in situ, the water vapor modulation remains in effect for both ice cloud types, although the sensitivities of Rei to aerosols differ noticeably between them due to distinct formation mechanisms. The water vapor modulation can largely explain the difference in the responses of Rei to aerosol loadings in various seasons. A proper representation of the water vapor modulation is essential for an accurate estimate of aerosol-cloud radiative forcing produced by ice clouds.

The CREW intercomparison of SEVIRI cloud retrievals

NASA Astrophysics Data System (ADS)

Hamann, U.; Walther, A.; Bennartz, R.; Thoss, A.; Meirink, J. M.; Roebeling, R.

2012-12-01

About 70% of the earth's surface is covered with clouds. They strongly influence the radiation balance and the water cycle of the earth. Hence the detailed monitoring of cloud properties - such as cloud fraction, cloud top temperature, cloud particle size, and cloud water path - is important to understand the role of clouds in the weather and the climate system. The remote sensing with passive sensors is an essential mean for the global observation of the cloud parameters, but is nevertheless challenging. This presentation focuses on the inter-comparison and validation of cloud physical properties retrievals from the Spinning Enhanced Visible and InfraRed Imager (SEVIRI) onboard METEOSAT. For this study we use retrievals from 12 state-of-art algorithms (Eumetsat, KNMI, NASA Langley, NASA Goddard, University Madison/Wisconsin, DWD, DLR, Meteo-France, KMI, FU Berlin, UK MetOffice) that are made available through the common database of the CREW (Cloud Retrieval Evaluation Working) group. Cloud detection, cloud top phase, height, and temperature, as well as optical properties and water path are validated with CLOUDSAT, CALIPSO, MISR, and AMSR-E measurements. Special emphasis is given to challenging retrieval conditions. Semi-transparent clouds over the earth's surface or another cloud layer modify the measured brightness temperature and increase the retrieval uncertainty. The consideration of the three-dimensional radiative effects is especially important for large viewing angles and broken cloud fields. Aerosols might be misclassified as cloud and may increase the retrieval uncertainty, too. Due to the availability of the high number of sophisticated retrieval datasets, the advantages of different retrieval approaches can be examined and suggestions for future retrieval developments can be made. We like to thank Eumetsat for sponsoring the CREW project including this work.nstitutes that participate in the CREW project.

Cloud Response to Arctic Sea Ice Loss and Implications for Feedbacks in the CESM1 Climate Model

NASA Astrophysics Data System (ADS)

Morrison, A.; Kay, J. E.; Chepfer, H.; Guzman, R.; Bonazzola, M.

2017-12-01

Clouds have the potential to accelerate or slow the rate of Arctic sea ice loss through their radiative influence on the surface. Cloud feedbacks can therefore play into Arctic warming as clouds respond to changes in sea ice cover. As the Arctic moves toward an ice-free state, understanding how cloud - sea ice relationships change in response to sea ice loss is critical for predicting the future climate trajectory. From satellite observations we know the effect of present-day sea ice cover on clouds, but how will clouds respond to sea ice loss as the Arctic transitions to a seasonally open water state? In this study we use a lidar simulator to first evaluate cloud - sea ice relationships in the Community Earth System Model (CESM1) against present-day observations (2006-2015). In the current climate, the cloud response to sea ice is well-represented in CESM1: we see no summer cloud response to changes in sea ice cover, but more fall clouds over open water than over sea ice. Since CESM1 is credible for the current Arctic climate, we next assess if our process-based understanding of Arctic cloud feedbacks related to sea ice loss is relevant for understanding future Arctic clouds. In the future Arctic, summer cloud structure continues to be insensitive to surface conditions. As the Arctic warms in the fall, however, the boundary layer deepens and cloud fraction increases over open ocean during each consecutive decade from 2020 - 2100. This study will also explore seasonal changes in cloud properties such as opacity and liquid water path. Results thus far suggest that a positive fall cloud - sea ice feedback exists in the present-day and future Arctic climate.

Estimates of the aerosol indirect effect over the Baltic Sea region derived from 12 years of MODIS observations

NASA Astrophysics Data System (ADS)

Saponaro, Giulia; Kolmonen, Pekka; Sogacheva, Larisa; Rodriguez, Edith; Virtanen, Timo; de Leeuw, Gerrit

2017-02-01

Retrieved from the Moderate Resolution Imaging Spectroradiometer (MODIS) on-board the Aqua satellite, 12 years (2003-2014) of aerosol and cloud properties were used to statistically quantify aerosol-cloud interaction (ACI) over the Baltic Sea region, including the relatively clean Fennoscandia and the more polluted central-eastern Europe. These areas allowed us to study the effects of different aerosol types and concentrations on macro- and microphysical properties of clouds: cloud effective radius (CER), cloud fraction (CF), cloud optical thickness (COT), cloud liquid water path (LWP) and cloud-top height (CTH). Aerosol properties used are aerosol optical depth (AOD), Ångström exponent (AE) and aerosol index (AI). The study was limited to low-level water clouds in the summer. The vertical distributions of the relationships between cloud properties and aerosols show an effect of aerosols on low-level water clouds. CF, COT, LWP and CTH tend to increase with aerosol loading, indicating changes in the cloud structure, while the effective radius of cloud droplets decreases. The ACI is larger at relatively low cloud-top levels, between 900 and 700 hPa. Most of the studied cloud variables were unaffected by the lower-tropospheric stability (LTS), except for the cloud fraction. The spatial distribution of aerosol and cloud parameters and ACI, here defined as the change in CER as a function of aerosol concentration for a fixed LWP, shows positive and statistically significant ACI over the Baltic Sea and Fennoscandia, with the former having the largest values. Small negative ACI values are observed in central-eastern Europe, suggesting that large aerosol concentrations saturate the ACI.

Forest on the edge: Seasonal cloud forest in Oman creates its own ecological niche

NASA Astrophysics Data System (ADS)

Hildebrandt, Anke; Eltahir, Elfatih A. B.

2006-06-01

Cloud forests usually grow in the moist tropics where water is not a limiting factor to plant growth. Here, for the first time, we describe the hydrology of a water limited seasonal cloud forest in the Dhofar mountains of Oman. This ecosystem is under significant stress from camels feeding on tree canopies. The Dhofar forests are the remnants of a moist vegetation belt, which once spread across the Arabian Peninsula. According to our investigation the process of cloud immersion during the summer season creates within this desert a niche for moist woodland vegetation. Woodland vegetation survives in this ecosystem, sustained through enhanced capture of cloud water by their canopies (horizontal precipitation). Degraded land lacks this additional water source, which inhibits re-establishment of trees. Our modeling results suggest that cattle feeding may lead to irreversible destruction of one of the most diverse ecosystems in Arabia.

Representation of Arctic mixed-phase clouds and the Wegener-Bergeron-Findeisen process in climate models: Perspectives from a cloud-resolving study

NASA Astrophysics Data System (ADS)

Fan, Jiwen; Ghan, Steven; Ovchinnikov, Mikhail; Liu, Xiaohong; Rasch, Philip J.; Korolev, Alexei

2011-01-01

Two types of Arctic mixed-phase clouds observed during the ISDAC and M-PACE field campaigns are simulated using a 3-dimensional cloud-resolving model (CRM) with size-resolved cloud microphysics. The modeled cloud properties agree reasonably well with aircraft measurements and surface-based retrievals. Cloud properties such as the probability density function (PDF) of vertical velocity (w), cloud liquid and ice, regimes of cloud particle growth, including the Wegener-Bergeron-Findeisen (WBF) process, and the relationships among properties/processes in mixed-phase clouds are examined to gain insights for improving their representation in General Circulation Models (GCMs). The PDF of the simulated w is well represented by a Gaussian function, validating, at least for arctic clouds, the subgrid treatment used in GCMs. The PDFs of liquid and ice water contents can be approximated by Gamma functions, and a Gaussian function can describe the total water distribution, but a fixed variance assumption should be avoided in both cases. The CRM results support the assumption frequently used in GCMs that mixed phase clouds maintain water vapor near liquid saturation. Thus, ice continues to grow throughout the stratiform cloud but the WBF process occurs in about 50% of cloud volume where liquid and ice co-exist, predominantly in downdrafts. In updrafts, liquid and ice particles grow simultaneously. The relationship between the ice depositional growth rate and cloud ice strongly depends on the capacitance of ice particles. The simplified size-independent capacitance of ice particles used in GCMs could lead to large deviations in ice depositional growth.

Organic acids in cloud water and rainwater at a mountain site in acid rain areas of South China.

PubMed

Sun, Xiao; Wang, Yan; Li, Haiyan; Yang, Xueqiao; Sun, Lei; Wang, Xinfeng; Wang, Tao; Wang, Wenxing

2016-05-01

To investigate the chemical characteristics of organic acids and to identify their source, cloud water and rainwater samples were collected at Mount Lu, a mountain site located in the acid rain-affected area of south China, from August to September of 2011 and March to May of 2012. The volume-weighted mean (VWM) concentration of organic acids in cloud water was 38.42 μeq/L, ranging from 7.45 to 111.46 μeq/L, contributing to 2.50 % of acidity. In rainwater samples, organic acid concentrations varied from 12.39 to 68.97 μeq/L (VWM of 33.39 μeq/L). Organic acids contributed significant acidity to rainwater, with a value of 17.66 %. Formic acid, acetic acid, and oxalic acid were the most common organic acids in both cloud water and rainwater. Organic acids had an obviously higher concentration in summer than in spring in cloud water, whereas there was much less discrimination in rainwater between the two seasons. The contribution of organic acids to acidity was lower during summer than during spring in both cloud water (2.20 % in summer vs 2.83 % in spring) and rainwater (12.24 % in summer vs 19.89 % in spring). The formic-to-acetic acid ratio (F/A) showed that organic acids were dominated by primary emissions in 71.31 % of the cloud water samples and whole rainwater samples. Positive matrix factorization (PMF) analysis determined four factors as the sources of organic acids in cloud water, including biogenic emissions (61.8 %), anthropogenic emissions (15.28 %), marine emissions (15.07 %) and soil emissions (7.85 %). The findings from this study imply an indispensable role of organic acids in wet deposition, but organic acids may have a limited capacity to increase ecological risks in local environments.

Dependence of stratocumulus-topped boundary-layer entrainment on cloud-water sedimentation: Impact on global aerosol indirect effect in GISS ModelE3 single column model and global simulations

NASA Astrophysics Data System (ADS)

Ackerman, A. S.; Kelley, M.; Cheng, Y.; Fridlind, A. M.; Del Genio, A. D.; Bauer, S.

2017-12-01

Reduction in cloud-water sedimentation induced by increasing droplet concentrations has been shown in large-eddy simulations (LES) and direct numerical simulation (DNS) to enhance boundary-layer entrainment, thereby reducing cloud liquid water path and offsetting the Twomey effect when the overlying air is sufficiently dry, which is typical. Among recent upgrades to ModelE3, the latest version of the NASA Goddard Institute for Space Studies (GISS) general circulation model (GCM), are a two-moment stratiform cloud microphysics treatment with prognostic precipitation and a moist turbulence scheme that includes an option in its entrainment closure of a simple parameterization for the effect of cloud-water sedimentation. Single column model (SCM) simulations are compared to LES results for a stratocumulus case study and show that invoking the sedimentation-entrainment parameterization option indeed reduces the dependence of cloud liquid water path on increasing aerosol concentrations. Impacts of variations of the SCM configuration and the sedimentation-entrainment parameterization will be explored. Its impact on global aerosol indirect forcing in the framework of idealized atmospheric GCM simulations will also be assessed.

Balloon borne Antarctic frost point measurements and their impact on polar stratospheric cloud theories

NASA Technical Reports Server (NTRS)

Rosen, James M.; Hofmann, D. J.; Carpenter, J. R.; Harder, J. W.; Oltmans, S. J.

1988-01-01

The first balloon-borne frost point measurements over Antarctica were made during September and October, 1987 as part of the NOZE 2 effort at McMurdo. The results indicate water vapor mixing ratios on the order of 2 ppmv in the 15 to 20 km region which is somewhat smaller than the typical values currently being used significantly smaller than the typical values currently being used in polar stratospheric cloud (PSC) theories. The observed water vapor mixing ratio would correspond to saturated conditions for what is thought to be the lowest stratospheric temperatures encountered over the Antarctic. Through the use of available lidar observations there appears to be significant evidence that some PSCs form at temperatures higher than the local frost point (with respect to water) in the 10 to 20 km region thus supporting the nitric acid theory of PSC composition. Clouds near 15 km and below appear to form in regions saturated with respect to water and thus are probably mostly ice water clouds although they could contain relatively small amounts of other constituents. Photographic evidence suggests that the clouds forming above the frost point probably have an appearance quite different from the lower altitude iridescent, colored nacreous clouds.

A Method for Obtaining High Frequency, Global, IR-Based Convective Cloud Tops for Studies of the TTL

NASA Technical Reports Server (NTRS)

Pfister, Leonhard; Ueyama, Rei; Jensen, Eric; Schoeberl, Mark

2017-01-01

Models of varying complexity that simulate water vapor and clouds in the Tropical Tropopause Layer (TTL) show that including convection directly is essential to properly simulating the water vapor and cloud distribution. In boreal winter, for example, simulations without convection yield a water vapor distribution that is too uniform with longitude, as well as minimal cloud distributions. Two things are important for convective simulations. First, it is important to get the convective cloud top potential temperature correctly, since unrealistically high values (reaching above the cold point tropopause too frequently) will cause excessive hydration of the stratosphere. Second, one must capture the time variation as well, since hydration by convection depends on the local relative humidity (temperature), which has substantial variation on synoptic time scales in the TTL. This paper describes a method for obtaining high frequency (3-hourly) global convective cloud top distributions which can be used in trajectory models. The method uses rainfall thresholds, standard IR brightness temperatures, meteorological temperature analyses, and physically realistic and documented corrections IR brightness temperature corrections to derive cloud top altitudes and potential temperatures. The cloud top altitudes compare well with combined CLOUDSAT and CALIPSO data, both in time-averaged overall vertical and horizontal distributions and in individual cases (correlations of .65-.7). An important finding is that there is significant uncertainty (nearly .5 km) in evaluating the statistical distribution of convective cloud tops even using lidar. Deep convection whose tops are in regions of high relative humidity (such as much of the TTL), will cause clouds to form above the actual convection. It is often difficult to distinguish these clouds from the actual convective cloud due to the uncertainties of evaluating ice water content from lidar measurements. Comparison with models show that calculated cloud top altitudes are generally higher than those calculated by global analyses (e.g., MERRA). Interannual variability in the distribution of convective cloud top altitudes is also investigated.

Impacts of cloud immersion on microclimate, photosynthesis and water relations of Abies fraseri (Pursh.) Poiret in a temperate mountain cloud forest.

PubMed

Reinhardt, Keith; Smith, William K

2008-11-01

The red spruce-Fraser fir ecosystem [Picea rubens Sarg.-Abies fraseri (Pursh) Poir.] of the southern Appalachian mountains, USA, is a temperate zone cloud forest immersed in clouds for 30-40% of a typical summer day, and experiencing immersion on about 65% of all days annually. We compared the microclimate, photosynthetic gas exchange, and water relations of Fraser fir trees in open areas during cloud-immersed, low-cloud, or sunny periods. In contrast to sunny periods, cloud immersion reduced instantaneous sunlight irradiance by 10-50%, and midday atmospheric vapor pressure deficit (VPD) was 85% lower. Needle surfaces were wet for up to 16 h per day during cloud-immersed days compared to <1 h for clear days. Shoot-level light-saturated photosynthesis (A (sat)) on both cloud-immersed (16.0 micromol m(-2) s(-1)) and low-cloud (17.9 micromol m(-2) s(-1)) days was greater than A (sat) on sunny days (14.4 micromol m(-2) s(-1)). Daily mean A was lowest on cloud-immersed days due to reduced sunlight levels, while leaf conductance (g) was significantly higher, with a mean value of 0.30 mol m(-2) s(-1). These g values were greater than commonly reported for conifer tree species with needle-like leaves, and declined exponentially with increasing leaf-to-air VPD. Daily mean transpiration (E) on immersed days was 43 and 20% lower compared to sunny and low-cloud days, respectively. As a result, daily mean water use efficiency (A/E) was lowest on cloud-immersed days due to light limitation of A, and high humidity resulted in greater uncoupling of A from g. Thus, substantial differences in photosynthetic CO2 uptake, and corresponding water relations, were strongly associated with cloud conditions that occur over substantial periods of the summer growth season.

Radiative consequences of low-temperature infrared refractive indices for supercooled water clouds

NASA Astrophysics Data System (ADS)

Rowe, P. M.; Neshyba, S.; Walden, V. P.

2013-07-01

Simulations of cloud radiative properties for climate modeling and remote sensing rely on accurate knowledge of the complex refractive index (CRI) of water. Although conventional algorithms employ a temperature independent assumption (TIA), recent infrared measurements of supercooled water have demonstrated that the CRI becomes increasingly ice-like at lower temperatures. Here, we assess biases that result from ignoring this temperature dependence. We show that TIA-based cloud retrievals introduce spurious ice into pure, supercooled clouds, or underestimate cloud thickness and droplet size. TIA-based downwelling radiative fluxes are lower than those for the temperature-dependent CRI by as much as 1.7 W m-2 (in cold regions), while top-of-atmosphere fluxes are higher by as much as 3.4 W m-2 (in warm regions). Proper accounting of the temperature dependence of the CRI, therefore, leads to significantly greater local greenhouse warming due to supercooled clouds than previously predicted. The current experimental uncertainty in the CRI at low temperatures must be reduced to properly account for supercooled clouds in both climate models and cloud property retrievals.

Radiative consequences of low-temperature infrared refractive indices for supercooled water clouds

NASA Astrophysics Data System (ADS)

Rowe, P. M.; Neshyba, S.; Walden, V. P.

2013-12-01

Simulations of cloud radiative properties for climate modeling and remote sensing rely on accurate knowledge of the complex refractive index (CRI) of water. Although conventional algorithms employ a temperature-independent assumption (TIA), recent infrared measurements of supercooled water have demonstrated that the CRI becomes increasingly ice-like at lower temperatures. Here, we assess biases that result from ignoring this temperature dependence. We show that TIA-based cloud retrievals introduce spurious ice into pure, supercooled clouds, or underestimate cloud optical thickness and droplet size. TIA-based downwelling radiative fluxes are lower than those for the temperature-dependent CRI by as much as 1.7 W m-2 (in cold regions), while top-of-atmosphere fluxes are higher by as much as 3.4 W m-2 (in warm regions). Proper accounting of the temperature dependence of the CRI, therefore, leads to significantly greater local greenhouse warming due to supercooled clouds than previously predicted. The current experimental uncertainty in the CRI at low temperatures must be reduced to account for supercooled clouds properly in both climate models and cloud-property retrievals.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chitra Sivaraman, PNNL

Cloud droplet number concentration is an important factor in understanding aerosol-cloud interactions. As aerosol concentration increases, it is expected that droplet number concentration (Nd) will increase and droplet size will decrease, for a given liquid water path. This will greatly affect cloud albedo as smaller droplets reflect more shortwave radiation; however, the magnitude and variability of these processes under different environmental conditions is still uncertain.McComiskey et al. (2009) have implemented a method, based onBoers and Mitchell (1994), for calculating Nd from ground-based remote sensing measurements of optical depth and liquid water path. They show that the magnitude of the aerosol-cloudmore » interactions (ACI) varies with a range of factors, including the relative value of the cloud liquid water path (LWP), the aerosol size distribution, and the cloud updraft velocity. Estimates of Nd under a range of cloud types and conditions and at a variety of sites are needed to further quantify the impacts of aerosol cloud interactions. In order to provide data sets for studying aerosol-cloud interactions, the McComiskey et al. (2009) method was implemented as the Droplet Number Concentration (NDROP) value-added product (VAP).« less

Entrainment, Drizzle, and Stratocumulus Cloud Albedo

NASA Technical Reports Server (NTRS)

Ackerman, A. S.; Kirkpatrick, M. P.; Stevens, D. E.; Toon, O. B.

2004-01-01

Globally averaged cloud changes from GCMs on average show a doubling of the Twomey effect, which is the change in cloud albedo with respect to changes in droplet concentrations for fixed cloud water and droplet dispersion. In contrast, ship-track measurements show a much more modest amplification of the Twomey effect, suggesting that the GCMs are exaggerating the indirect aerosol effect. We have run large-eddy simulations with bin microphysics of marine stratocumulus from multiple field campaigns, and find that the large-eddy simulations are in much better agreement with the ship-track measurements. The inversion strength over N. Pacific stratocumulus (as measured during DYCOMS-II) is generally much stronger than over N. Atlantic stratocumulus (as measured during ASTEX), and we have found that the response of cloud water to increasing droplet concentration changes sign as the inversion strengthens. For the different environmental conditions, we will show the overall response of cloud albedo to droplet concentrations, and decompose the response into its contributing factors of changes in cloud water, droplet dispersion, and horizontal inhomogeneity.

Parameterization of bulk condensation in numerical cloud models

NASA Technical Reports Server (NTRS)

Kogan, Yefim L.; Martin, William J.

1994-01-01

The accuracy of the moist saturation adjustment scheme has been evaluated using a three-dimensional explicit microphysical cloud model. It was found that the error in saturation adjustment depends strongly on the Cloud Condensation Nucleii (CCN) concentration in the ambient atmosphere. The scheme provides rather accurate results in the case where a sufficiently large number of CCN (on the order of several hundred per cubic centimeter) is available. However, under conditions typical of marine stratocumulus cloud layers with low CCN concentration, the error in the amounts of condensed water vapor and released latent heat may be as large as 40%-50%. A revision of the saturation adjustment scheme is devised that employs the CCN concentration, dynamical supersaturation, and cloud water content as additional variables in the calculation of the condensation rate. The revised condensation model reduced the error in maximum updraft and cloud water content in the climatically significant case of marine stratocumulus cloud layers by an order of magnitude.

Microphysical Properties and Water Budget for Summer Convective Clouds over the Tibetan Plateau

NASA Astrophysics Data System (ADS)

Guo, X.; Tang, J.; Chang, Y.

2017-12-01

During the Third Tibetan Plateau Atmospheric Scientific Experiment (TIPEX-III), the clouds and precipitation processes over the Tibetan Plateau have been intensively investigated. On basis of field campaign, the cloud microphysical structure, water transformation and budget properties for typical convective precipitation processes in the summer season of 2014 over the plateau are studied using mesoscale numerical prediction model (WRF) combined with observational data collected during the experiment. The results indicate that WRF model could reproduce the general characteristics of diurnal variation of clouds and precipitation process over the plateau, however, the temporal and spatial distribution and intensity of cloud bands and precipitation simulated by WRF model still had large differences with those observed. Ice process played a critical role in the development of summer convective clouds and precipitation over the plateau. The surface precipitation was primarily formed by the melting process of graupel particles. Although the warm cloud microphysical process had small direct contribution on the surface precipitation, it had an important contribution in the formation of graupel embryos. High amount of supercooled cloud water content and graupel particles could be found in the clouds. The formation and growth of snow particles relied on the conversion of ice crystal and the aggregation with ice crystal over 12 km (-40°), but the formation of snow particles below 12 km (-40°)was dependent on the conversion of Bergeron process of ice crystals and its growth resulted from riming process with supercooled cloud water. The accretion process of supercooled raindrops by ice crystal and snow particles contributed to the production of graupel embryos and their growth mainly relied on the riming process with supercooled cloud water and aggregation process with snow particles. The mean daily conversion rate from vapor to precipitation was as high as 27.27%, which is close to Yangtze River downstream, and is higher than the regions of northern and northwestern China. The contribution of daily mean surface evaporation to precipitation was 10.92%, indicating that the 90% rainfall was from the conversion of water vapor outside the plateau.

When is an INP not an INP?

NASA Astrophysics Data System (ADS)

Simpson, Emma; Connolly, Paul; McFiggans, Gordon

2016-04-01

Processes such as precipitation and radiation depend on the concentration and size of different hydrometeors within clouds therefore it is important to accurately predict them in weather and climate models. A large fraction of clouds present in our atmosphere are mixed phase; contain both liquid and ice particles. The number of drops and ice crystals present in mixed phase clouds strongly depends on the size distribution of aerosols. Cloud condensation nuclei (CCN), a subset of atmospheric aerosol particles, are required for liquid drops to form in the atmosphere. These particles are ubiquitous in the atmosphere. To nucleate ice particles in mixed phase clouds ice nucleating particles (INP) are required. These particles are rarer than CCN. Here we investigate the case where CCN and INPs are in direct competition with each other for water vapour within a cloud. Focusing on the immersion and condensation modes of freezing (where an INP must be immersed within a liquid drop before it can freeze) we show that the presence of CCN can suppress the formation of ice. CCN are more hydrophilic than IN and as such are better able to compete for water vapour than, typically insoluble, INPs. Therefore water is more likely to condense onto a CCN than INP, leaving the INP without enough condensed water on it to be able to freeze in the immersion or condensation mode. The magnitude of this suppression effect strongly depends on a currently unconstrained quantity. Here we refer to this quantity as the critical mass of condensed water required for freezing, Mwc. Mwc is the threshold amount of water that must be condensed onto a INP before it can freeze in the immersion or condensation mode. Using the detailed cloud parcel model, Aerosol-Cloud-Precipiation-Interaction Model (ACPIM), developed at the University of Manchester we show that if only a small amount of water is required for freezing there is little suppression effect and if a large amount of water is required there is a large suppression effect. In this poster possible ways to constrain Mwc are discussed as well as conditions where the suppression effect is likely to be greatest. Key Words: Clouds, aerosol, CCN, IN, modelling

Assessment of Global Cloud Datasets from Satellites: Project and Database Initiated by the GEWEX Radiation Panel

NASA Technical Reports Server (NTRS)

Stubenrauch, C. J.; Rossow, W. B.; Kinne, S.; Ackerman, S.; Cesana, G.; Chepfer, H.; Getzewich, B.; Di Girolamo, L.; Guignard, A.; Heidinger, A.;

Parametric behaviors of CLUBB in simulations of low clouds in the Community Atmosphere Model (CAM)

DOE PAGES

Guo, Zhun; Wang, Minghuai; Qian, Yun; ...

2015-07-03

In this study, we investigate the sensitivity of simulated low clouds to 14 selected tunable parameters of Cloud Layers Unified By Binormals (CLUBB), a higher order closure (HOC) scheme, and 4 parameters of the Zhang-McFarlane (ZM) deep convection scheme in the Community Atmosphere Model version 5 (CAM5). A quasi-Monte Carlo (QMC) sampling approach is adopted to effectively explore the high-dimensional parameter space and a generalized linear model is applied to study the responses of simulated cloud fields to tunable parameters. Our results show that the variance in simulated low-cloud properties (cloud fraction and liquid water path) can be explained bymore » the selected tunable parameters in two different ways: macrophysics itself and its interaction with microphysics. First, the parameters related to dynamic and thermodynamic turbulent structure and double Gaussians closure are found to be the most influential parameters for simulating low clouds. The spatial distributions of the parameter contributions show clear cloud-regime dependence. Second, because of the coupling between cloud macrophysics and cloud microphysics, the coefficient of the dissipation term in the total water variance equation is influential. This parameter affects the variance of in-cloud cloud water, which further influences microphysical process rates, such as autoconversion, and eventually low-cloud fraction. Furthermore, this study improves understanding of HOC behavior associated with parameter uncertainties and provides valuable insights for the interaction of macrophysics and microphysics.« less

GEWEX cloud assessment: A review

NASA Astrophysics Data System (ADS)

Stubenrauch, Claudia; Rossow, William B.; Kinne, Stefan; Ackerman, Steve; Cesana, Gregory; Chepfer, Hélène; Di Girolamo, Larry; Getzewich, Brian; Guignard, Anthony; Heidinger, Andy; Maddux, Brent; Menzel, Paul; Minnis, Patrick; Pearl, Cindy; Platnick, Steven; Poulsen, Caroline; Riedi, Jérôme; Sayer, Andrew; Sun-Mack, Sunny; Walther, Andi; Winker, Dave; Zeng, Shen; Zhao, Guangyu

2013-05-01

Clouds cover about 70% of the Earth's surface and play a dominant role in the energy and water cycle of our planet. Only satellite observations provide a continuous survey of the state of the atmosphere over the entire globe and across the wide range of spatial and temporal scales that comprise weather and climate variability. Satellite cloud data records now exceed more than 25 years; however, climatologies compiled from different satellite datasets can exhibit systematic biases. Questions therefore arise as to the accuracy and limitations of the various sensors. The Global Energy and Water cycle Experiment (GEWEX) Cloud Assessment, initiated in 2005 by the GEWEX Radiation Panel, provides the first coordinated intercomparison of publicly available, global cloud products (gridded, monthly statistics) retrieved from measurements of multi-spectral imagers (some with multi-angle view and polarization capabilities), IR sounders and lidar. Cloud properties under study include cloud amount, cloud height (in terms of pressure, temperature or altitude), cloud radiative properties (optical depth or emissivity), cloud thermodynamic phase and bulk microphysical properties (effective particle size and water path). Differences in average cloud properties, especially in the amount of high-level clouds, are mostly explained by the inherent instrument measurement capability for detecting and/or identifying optically thin cirrus, especially when overlying low-level clouds. The study of long-term variations with these datasets requires consideration of many factors. The monthly, gridded database presented here facilitates further assessments, climate studies, and the evaluation of climate models.

Testing ice microphysics parameterizations in the NCAR Community Atmospheric Model Version 3 using Tropical Warm Pool-International Cloud Experiment data

DOE PAGES

Wang, Weiguo; Liu, Xiaohong; Xie, Shaocheng; ...

2009-07-23

Here, cloud properties have been simulated with a new double-moment microphysics scheme under the framework of the single-column version of NCAR Community Atmospheric Model version 3 (CAM3). For comparison, the same simulation was made with the standard single-moment microphysics scheme of CAM3. Results from both simulations compared favorably with observations during the Tropical Warm Pool–International Cloud Experiment by the U.S. Department of Energy Atmospheric Radiation Measurement Program in terms of the temporal variation and vertical distribution of cloud fraction and cloud condensate. Major differences between the two simulations are in the magnitude and distribution of ice water content within themore » mixed-phase cloud during the monsoon period, though the total frozen water (snow plus ice) contents are similar. The ice mass content in the mixed-phase cloud from the new scheme is larger than that from the standard scheme, and ice water content extends 2 km further downward, which is in better agreement with observations. The dependence of the frozen water mass fraction on temperature from the new scheme is also in better agreement with available observations. Outgoing longwave radiation (OLR) at the top of the atmosphere (TOA) from the simulation with the new scheme is, in general, larger than that with the standard scheme, while the surface downward longwave radiation is similar. Sensitivity tests suggest that different treatments of the ice crystal effective radius contribute significantly to the difference in the calculations of TOA OLR, in addition to cloud water path. Numerical experiments show that cloud properties in the new scheme can respond reasonably to changes in the concentration of aerosols and emphasize the importance of correctly simulating aerosol effects in climate models for aerosol-cloud interactions. Further evaluation, especially for ice cloud properties based on in-situ data, is needed.« less

Cloud Coverage Enhancement and Nocturnal Drizzle Suppression in Stratocumulus by Aerosols

NASA Technical Reports Server (NTRS)

Ackerman, Andrew S.; Toon, Owen B.; Stevens, David E.; Coakley, James A., Jr.; Gore, Warren J. (Technical Monitor)

2002-01-01

Recent satellite observations of ship tracks surprisingly indicate that cloud water decreases with increasing droplet concentrations. However, we find by analyzing detailed simulations of stratocumulus that the reported trend is likely an artifact of sampling, only overcast clouds. The simulations instead show cloud coverage increasing with droplet concentrations, accounting for 25% of cloud albedo increase at moderate droplet concentrations. Our simulations also show that increases in cloud water from drizzle suppression (by increasing droplet concentrations) are favored only at night or at extremely low droplet concentrations, suggesting that the indirect aerosol forcing is overestimated in climate change projections by many general circulation models.

Final Report fir DE-SC0005507 (A1618): The Development of an Improved Cloud Microphysical Product for Model and Remote Sensing Evaluation using RACORO Observations

DOE Office of Scientific and Technical Information (OSTI.GOV)

McFarquhar, Greg M.

2012-09-21

We proposed to analyze data collected during the Routine Aerial Facilities (AAF) Clouds with Low Optical Water Depths (CLOWD) Optical Radiative Observations (RACORO) in order to develop an integrated product of cloud microphysical properties (number concentration of drops in different size bins, total liquid drop concentration integrated over all bin sizes, liquid water content LWC, extinction of liquid clouds, effective radius of water drops, and radar reflectivity factor) that could be used to evaluate large-eddy simulations (LES), general circulation models (GCMs) and ground-based remote sensing retrievals, and to develop cloud parameterizations with the end goal of improving the modeling ofmore » cloud processes and properties and their impact on atmospheric radiation. We have completed the development of this microphysical database. We investigated the differences in the size distributions measured by the Cloud and Aerosol Spectrometer (CAS) and the Forward Scattering Probe (FSSP), between the one dimensional cloud imaging probe (1DC) and the two-dimensional cloud imaging probe (2DC), and between the bulk LWCs measured by the Gerber probe against those derived from the size resolved probes.« less

Characteristics of bacterial community in cloud water at Mt Tai: similarity and disparity under polluted and non-polluted cloud episodes

NASA Astrophysics Data System (ADS)

Wei, Min; Xu, Caihong; Chen, Jianmin; Zhu, Chao; Li, Jiarong; Lv, Ganglin

2017-04-01

Bacteria are widely distributed in atmospheric aerosols and are indispensable components of clouds, playing an important role in the atmospheric hydrological cycle. However, limited information is available about the bacterial community structure and function, especially for the increasing air pollution in the North China Plain. Here, we present a comprehensive characterization of bacterial community composition, function, variation, and environmental influence for cloud water collected at Mt Tai from 24 July to 23 August 2014. Using Miseq 16S rRNA gene sequencing, the highly diverse bacterial community in cloud water and the predominant phyla of Proteobacteria, Bacteroidetes, Cyanobacteria, and Firmicutes were investigated. Bacteria that survive at low temperature, radiation, and poor nutrient conditions were found in cloud water, suggesting adaption to an extreme environment. The bacterial gene functions predicted from the 16S rRNA gene using the Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt) suggested that the pathways related to metabolism and disease infections were significantly correlated with the predominant genera. The abundant genera Acinetobacter, Stenotrophomonas, Pseudomonas, and Empedobacter originated from a wide range of habitats including cloud condensation nuclei and ice nuclei active species, opportunistic pathogens, and functional species, demonstrating the importance of ecology and health in cloud water. Cluster analysis including hierarchical cluster (Hcluster) and principal coordinate analysis (PCoA) indicated a significant disparity between polluted and non-polluted samples. Linear discriminant analysis effect size (LEfSe) demonstrated that potential pathogens were enriched in the polluted cloud samples, whereas the diverse ecological function groups were significant in the non-polluted samples. Discrepant community structure determined by redundancy analysis (RDA) indicated that the major ions in cloud water and PM2. 5 in the atmosphere have a negative impact on bacteria, playing a vital role in shaping microbial community structure. The major ions might provide nutrition to bacteria and directly influence the bacterial community, whereas PM2. 5 in air has an indirect impact on bacterial community structure. During wet deposition, soluble particulate matter was dissolved in water droplets resulting in elevated concentration in cloud water. PM2. 5 was possibly associated with different origins and pathways of air mass as determined using source tracking by the backward trajectory, mainly related to long-range transport. This work enhanced our understanding of the characteristics of bacterial ecology in the atmospheric aqueous phase, highlighting the potential influence of environmental variables on the bacterial community in cloud processes. It may provide fundamental information of the bacterial community response in cloud water under increasing pollution. However, due to the limited sample size (13 samples) collected at the summit of Mt Tai, these issues need in-depth discussion. Further studies based on an annual series of field observation experiments and laboratory simulations will continue to track these issues.

Cloud Water Content Sensor for Sounding Balloons and Small UAVs

NASA Technical Reports Server (NTRS)

Bognar, John A.

2009-01-01

A lightweight, battery-powered sensor was developed for measuring cloud water content, which is the amount of liquid or solid water present in a cloud, generally expressed as grams of water per cubic meter. This sensor has near-zero power consumption and can be flown on standard sounding balloons and small, unmanned aerial vehicles (UAVs). The amount of solid or liquid water is important to the study of atmospheric processes and behavior. Previous sensing techniques relied on strongly heating the incoming air, which requires a major energy input that cannot be achieved on sounding balloons or small UAVs.

Cloud Properties Derived from Surface-Based Near-Infrared Spectral Transmission

NASA Technical Reports Server (NTRS)

Pilewskie, Peter; Twomey, S.; Gore, Warren J. Y. (Technical Monitor)

1996-01-01

Surface based near-infrared cloud spectral transmission measurements from a recent precipitation/cloud physics field study are used to determine cloud physical properties and relate them to other remote sensing and in situ measurements. Asymptotic formulae provide an effective means of closely approximating the qualitative and quantitative behavior of transmission computed by more laborious detailed methods. Relationships derived from asymptotic formulae are applied to measured transmission spectra to test objectively the internal consistency of data sets acquired during the field program and they confirmed the quality of the measurements. These relationships appear to be very useful in themselves, not merely as a quality control measure, but also a potentially valuable remote-sensing technique in its own right. Additional benefits from this analysis have been the separation of condensed water (cloud) transmission and water vapor transmission and the development of a method to derive cloud liquid water content.

Cirrus clouds. I - A cirrus cloud model. II - Numerical experiments on the formation and maintenance of cirrus

NASA Technical Reports Server (NTRS)

Starr, D. OC.; Cox, S. K.

1985-01-01

A simplified cirrus cloud model is presented which may be used to investigate the role of various physical processes in the life cycle of a cirrus cloud. The model is a two-dimensional, time-dependent, Eulerian numerical model where the focus is on cloud-scale processes. Parametrizations are developed to account for phase changes of water, radiative processes, and the effects of microphysical structure on the vertical flux of ice water. The results of a simulation of a thin cirrostratus cloud are given. The results of numerical experiments performed with the model are described in order to demonstrate the important role of cloud-scale processes in determining the cloud properties maintained in response to larger scale forcing. The effects of microphysical composition and radiative processes are considered, as well as their interaction with thermodynamic and dynamic processes within the cloud. It is shown that cirrus clouds operate in an entirely different manner than liquid phase stratiform clouds.

Aerosol effect on cloud droplet size as monitored from surface-based remote sensing over East China Sea region

NASA Astrophysics Data System (ADS)

Pandithurai, G.; Takamura, T.; Yamaguchi, J.; Miyagi, K.; Takano, T.; Ishizaka, Y.; Dipu, S.; Shimizu, A.

2009-07-01

The effect of increased aerosol concentrations on the low-level, non-precipitating, ice-free stratus clouds is examined using a suite of surface-based remote sensing systems. Cloud droplet effective radius and liquid water path are retrieved using cloud radar and microwave radiometer. Collocated measurements of aerosol scattering coefficient, size distribution and cloud condensation nuclei (CCN) concentrations were used to examine the response of cloud droplet size and optical thickness to increased CCN proxies. During the episodic events of increase in aerosol accumulation-mode volume distribution, the decrease in droplet size and increase in cloud optical thickness is observed. The indirect effect estimates are made for both droplet effective radius and cloud optical thickness for different liquid water path ranges and they range 0.02-0.18 and 0.005-0.154, respectively. Data are also categorized into thin and thick clouds based on cloud geometric thickness (Δz) and estimates show IE values are relatively higher for thicker clouds.

Microwave Ground-Based Retrievals of Liquid Water Path in Drizzling Clouds: Challenges and Possibilities

NASA Astrophysics Data System (ADS)

Cadeddu, M. P.; Marchand, R.; Orlandi, E.; Turner, D. D.; Mech, M.

2016-12-01

The retrieval of liquid water path (LWP) during drizzle and rain from ground-based microwave radiometers presents several challenges that have not been entirely solved. Ground-based microwave radiometers have been traditionally used to retrieve cloud LWP assuming non-precipitating conditions. Yet retrieval of liquid water path under light rain and possibly the partition of total liquid water path among cloud and rain are very important to study cloud properties because the presence of drizzle affects for example the cloud's lifetime. Improving the LWP retrieval during drizzle and possibly partitioning cloud and rain LWP is therefore highly desirable. In precipitating clouds the raindrop's size is of the same order of magnitude of the wavelength sampled by the instrument and the effects of hydrometeor's scattering can't be neglected. In this paper we model the effect of scattering hydrometeors on radiometric brightness temperatures commonly used in LWP retrievals and develop a physical retrieval to derive precipitable water vapor (PWV), total LWP, and the fraction of cloud and rain liquid water (Cf) from microwave brightness temperatures at three commonly used frequencies. The retrieval is first applied to a set of synthetic measurements and is then used to retrieve PWV, LWP, and Cf in two drizzling cases at the Atmospheric Radiation Measurement (ARM) Program Eastern North Atlantic (ENA) site. Results show that there is useful information in the microwave brightness temperatures that can be used to reduce LWP retrieval uncertainty during light rain and can open the path for a better integration of active and passive sensors. The effect of raindrops on the radiometer's lens is examined with the help of a digital camera and experimental data. A possible way to account for raindrop deposition on the instrument's lens is suggested.

Using Long-term Satellite Observations to Identify Sensitive Regimes and Active Regions of Aerosol Indirect Effects for Liquid Clouds over Global Oceans

DOE PAGES

Zhao, Xuepeng; Liu, Yangang; Yu, Fangquan; ...

2017-11-16

Long-term (1981-2011) satellite climate data records (CDRs) of clouds and aerosols are used to investigate the aerosol-cloud interaction of marine water cloud from a climatology perspective. Our focus is on identifying the regimes and regions where the aerosol indirect effect (AIE) are evident in long-term averages over the global oceans through analyzing the correlation features between aerosol loading and the key cloud variables including cloud droplet effective radius (CDER), cloud optical depth (COD), cloud water path (CWP), cloud top height (CTH), and cloud top temperature (CTT). An aerosol optical thickness (AOT) range of 0.13 < AOT < 0.3 is identifiedmore » as the sensitive regime of the conventional first AIE where CDER is more susceptible to AOT than the other cloud variables. The first AIE that manifests as the change of long-term averaged CDER appears only in limited oceanic regions. The signature of aerosol invigoration of water clouds as revealed by the increase of cloud cover fraction (CCF) and CTH with increasing AOT at the middle/high latitudes of both hemispheres is identified for a pristine atmosphere (AOT < 0.08). Aerosol invigoration signature is also revealed by the concurrent increase of CDER, COD, and CWP with increasing AOT for a polluted marine atmosphere (AOT > 0.3) in the tropical convergence zones. The regions where the second AIE is likely to manifest in the CCF change are limited to several oceanic areas with high CCF of the warm water clouds near the western coasts of continents. The second AIE signature as represented by the reduction of the precipitation efficiency with increasing AOT is more likely to be observed in the AOT regime of 0.08 < AOT < 0.4. The corresponding AIE active regions manifested themselves as the decline of the precipitation efficiency are mainly limited to the oceanic areas downwind of continental aerosols. Furthermore, the sensitive regime of the conventional AIE identified in this observational study is likely associated with the transitional regime from the aerosol-limited regime to the updraft-limited regime identified for aerosol-cloud interaction in cloud model simulations.« less

Using Long-Term Satellite Observations to Identify Sensitive Regimes and Active Regions of Aerosol Indirect Effects for Liquid Clouds Over Global Oceans

NASA Astrophysics Data System (ADS)

Zhao, Xuepeng; Liu, Yangang; Yu, Fangquan; Heidinger, Andrew K.

2018-01-01

Long-term (1981-2011) satellite climate data records of clouds and aerosols are used to investigate the aerosol-cloud interaction of marine water cloud from a climatology perspective. Our focus is on identifying the regimes and regions where the aerosol indirect effects (AIEs) are evident in long-term averages over the global oceans through analyzing the correlation features between aerosol loading and the key cloud variables including cloud droplet effective radius (CDER), cloud optical depth (COD), cloud water path (CWP), cloud top height (CTH), and cloud top temperature (CTT). An aerosol optical thickness (AOT) range of 0.13 < AOT < 0.3 is identified as the sensitive regime of the conventional first AIE where CDER is more susceptible to AOT than the other cloud variables. The first AIE that manifests as the change of long-term averaged CDER appears only in limited oceanic regions. The signature of aerosol invigoration of water clouds as revealed by the increase of cloud cover fraction (CCF) and CTH with increasing AOT at the middle/high latitudes of both hemispheres is identified for a pristine atmosphere (AOT < 0.08). Aerosol invigoration signature is also revealed by the concurrent increase of CDER, COD, and CWP with increasing AOT for a polluted marine atmosphere (AOT > 0.3) in the tropical convergence zones. The regions where the second AIE is likely to manifest in the CCF change are limited to several oceanic areas with high CCF of the warm water clouds near the western coasts of continents. The second AIE signature as represented by the reduction of the precipitation efficiency with increasing AOT is more likely to be observed in the AOT regime of 0.08 < AOT < 0.4. The corresponding AIE active regions manifested themselves as the decline of the precipitation efficiency are mainly limited to the oceanic areas downwind of continental aerosols. The sensitive regime of the conventional AIE identified in this observational study is likely associated with the transitional regime from the aerosol-limited regime to the updraft-limited regime identified for aerosol-cloud interaction in cloud model simulations.

Using Long-Term Satellite Observations to Identify Sensitive Regimes and Active Regions of Aerosol Indirect Effects for Liquid Clouds Over Global Oceans.

PubMed

Zhao, Xuepeng; Liu, Yangang; Yu, Fangquan; Heidinger, Andrew K

2018-01-16

Long-term (1981-2011) satellite climate data records of clouds and aerosols are used to investigate the aerosol-cloud interaction of marine water cloud from a climatology perspective. Our focus is on identifying the regimes and regions where the aerosol indirect effects (AIEs) are evident in long-term averages over the global oceans through analyzing the correlation features between aerosol loading and the key cloud variables including cloud droplet effective radius (CDER), cloud optical depth (COD), cloud water path (CWP), cloud top height (CTH), and cloud top temperature (CTT). An aerosol optical thickness (AOT) range of 0.13 < AOT < 0.3 is identified as the sensitive regime of the conventional first AIE where CDER is more susceptible to AOT than the other cloud variables. The first AIE that manifests as the change of long-term averaged CDER appears only in limited oceanic regions. The signature of aerosol invigoration of water clouds as revealed by the increase of cloud cover fraction (CCF) and CTH with increasing AOT at the middle/high latitudes of both hemispheres is identified for a pristine atmosphere (AOT < 0.08). Aerosol invigoration signature is also revealed by the concurrent increase of CDER, COD, and CWP with increasing AOT for a polluted marine atmosphere (AOT > 0.3) in the tropical convergence zones. The regions where the second AIE is likely to manifest in the CCF change are limited to several oceanic areas with high CCF of the warm water clouds near the western coasts of continents. The second AIE signature as represented by the reduction of the precipitation efficiency with increasing AOT is more likely to be observed in the AOT regime of 0.08 < AOT < 0.4. The corresponding AIE active regions manifested themselves as the decline of the precipitation efficiency are mainly limited to the oceanic areas downwind of continental aerosols. The sensitive regime of the conventional AIE identified in this observational study is likely associated with the transitional regime from the aerosol-limited regime to the updraft-limited regime identified for aerosol-cloud interaction in cloud model simulations.

Using Long-term Satellite Observations to Identify Sensitive Regimes and Active Regions of Aerosol Indirect Effects for Liquid Clouds over Global Oceans

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhao, Xuepeng; Liu, Yangang; Yu, Fangquan

Long-term (1981-2011) satellite climate data records (CDRs) of clouds and aerosols are used to investigate the aerosol-cloud interaction of marine water cloud from a climatology perspective. Our focus is on identifying the regimes and regions where the aerosol indirect effect (AIE) are evident in long-term averages over the global oceans through analyzing the correlation features between aerosol loading and the key cloud variables including cloud droplet effective radius (CDER), cloud optical depth (COD), cloud water path (CWP), cloud top height (CTH), and cloud top temperature (CTT). An aerosol optical thickness (AOT) range of 0.13 < AOT < 0.3 is identifiedmore » as the sensitive regime of the conventional first AIE where CDER is more susceptible to AOT than the other cloud variables. The first AIE that manifests as the change of long-term averaged CDER appears only in limited oceanic regions. The signature of aerosol invigoration of water clouds as revealed by the increase of cloud cover fraction (CCF) and CTH with increasing AOT at the middle/high latitudes of both hemispheres is identified for a pristine atmosphere (AOT < 0.08). Aerosol invigoration signature is also revealed by the concurrent increase of CDER, COD, and CWP with increasing AOT for a polluted marine atmosphere (AOT > 0.3) in the tropical convergence zones. The regions where the second AIE is likely to manifest in the CCF change are limited to several oceanic areas with high CCF of the warm water clouds near the western coasts of continents. The second AIE signature as represented by the reduction of the precipitation efficiency with increasing AOT is more likely to be observed in the AOT regime of 0.08 < AOT < 0.4. The corresponding AIE active regions manifested themselves as the decline of the precipitation efficiency are mainly limited to the oceanic areas downwind of continental aerosols. Furthermore, the sensitive regime of the conventional AIE identified in this observational study is likely associated with the transitional regime from the aerosol-limited regime to the updraft-limited regime identified for aerosol-cloud interaction in cloud model simulations.« less

Interactions Between Atmospheric Aerosols and Marine Boundary Layer Clouds on Regional and Global Scales

NASA Astrophysics Data System (ADS)

Wang, Zhen

Airborne aerosols are crucial atmospheric constituents that are involved in global climate change and human life qualities. Understanding the nature and magnitude of aerosol-cloud-precipitation interactions is critical in model predictions for atmospheric radiation budget and the water cycle. The interactions depend on a variety of factors including aerosol physicochemical complexity, cloud types, meteorological and thermodynamic regimes and data processing techniques. This PhD work is an effort to quantify the relationships among aerosol, clouds, and precipitation on both global and regional scales by using satellite retrievals and aircraft measurements. The first study examines spatial distributions of conversion rate of cloud water to rainwater in warm maritime clouds over the globe by using NASA A-Train satellite data. This study compares the time scale of the onset of precipitation with different aerosol categories defined by values of aerosol optical depth, fine mode fraction, and Angstrom Exponent. The results indicate that conversion time scales are actually quite sensitive to lower tropospheric static stability (LTSS) and cloud liquid water path (LWP), in addition to aerosol type. Analysis shows that tropical Pacific Ocean is dominated by the highest average conversion rate while subtropical warm cloud regions (far northeastern Pacific Ocean, far southeastern Pacific Ocean, Western Africa coastal area) exhibit the opposite result. Conversion times are mostly shorter for lower LTSS regimes. When LTSS condition is fixed, higher conversion rates coincide with higher LWP and lower aerosol index categories. After a general global view of physical property quantifications, the rest of the presented PhD studies is focused on regional airborne observations, especially bulk cloud water chemistry and aerosol aqueous-phase reactions during the summertime off the California coast. Local air mass origins are categorized into three distinct types (ocean, ships, and land) with their influences on cloud water composition examined and implications of wet deposition discussed. Chemical analysis of cloud water samples indicates a wide pH range between 2.92 and 7.58, with an average as 4.46. The highest pH values were observed north of San Francisco, coincident with the strongest land mass influence (e.g. Si, B, and Cs). Conversely, the lowest pH values were observed south of San Francisco where there is heavy ship traffic, resulting in the highest concentrations of sulfate, nitrate, V, Fe, Al, P, Cd, Ti, Sb, P, and Mn. The acidic cloud environment with influences from various air mass types can affect the California coastal aquatic ecosystem since it can promote the conversion of micronutrients to more soluble forms. Beyond characterization of how regional air mass sources affect cloud water composition, aircraft cloud water collection provides precious information on tracking cloud processing with specific species such as oxalic acid, which is the most abundant dicarboxylic acid in tropospheric aerosols. Particular attention is given to explore relationship between detected metals with oxalate aqueous-phase production mechanisms. A number of case flights show that oxalate concentrations drop by nearly an order of magnitude relative to samples in the same vicinity with similar environmental and cloud physical conditions. Such a unique feature was consistent with an inverse relationship between oxalate and Fe. In order to examine the hypothesis that oxalate decreasing is potentially related to existing of Fe, chemistry box model simulations were conducted. The prediction results show that the loss of oxalate due to the photolysis of iron oxalato complexes is likely a significant oxalate sink in the study region due to the ubiquity of oxalate precursors, clouds, and metal emissions from ships, the ocean, and continental sources.

The Characteristics of Ice Cloud Properties in China Derived from DARDAR data

NASA Astrophysics Data System (ADS)

Lin, T.; Zheng, Y.

2017-12-01

Ice clouds play an important role in modulating the Earth radiation budget and global hydrological cycle.Thus,study the properties of ice clouds has the vital significance on the interaction between the atmospheric models,cloud,radiation and climate .The world has explore the combination of two or several kinds of sensor data to solve the complementary strengths and error reduction to improve accuracy of ice cloud at the present , but for China ,has be lack of research on combination sensor data to analysis properties of ice cloud.To reach a wider range of ice cloud, a combination of the CloudSat radar and the CALIPSO lidar is used to derive ice cloud properties. These products include the radar/lidar product (DARDAR) developed at the University of Reading.The China probability distribution of ice cloud occurrence frequency, ice water path, ice water content and ice cloud effective radius were presented based on DARDAR data from 2012 to 2016,the distribution and vertical sturctures was discussed.The results indicate that the ice cloud occurrence frequency distribution takes on ascend trend in the last 4 years and has obvious seasonal variation, the high concentration area in the northeastern part of the Tibetan Plateau,ice cloud occurrence frequency is relatively high in northwest area.the increased of ice cloud occurrence frequency play an integral role of the climate warming in these four years; the general trend for the ice water path is southeast area bigger than northwest area, in winter the IWP is the smallest, biggest in summer; the IWC is the biggest in summer, and the vertical height distribution higher than other seasons; ice cloud effective radius and ice water content had similar trend..There were slight declines in ice cloud effective radius with increase height of China,in the summer ice effective radius is generally larger.The ice cloud impact Earth radiation via their albedo an greenhouse effects, that is, cooling the Earth by reflecting solar incident radiation and at the same time.Thus,thorough research of the characteristics of ice cloud properties can explain the complicated relationship between ice cloud and global warming,and this kind of data analysis can comprehend the climate effect of mainland China .

Ice Cloud Formation and Dehydration in the Tropical Tropopause Layer

NASA Technical Reports Server (NTRS)

Jensen, Eric; Gore, Warren J. (Technical Monitor)

2002-01-01

Stratospheric water vapor is important not only for its greenhouse forcing, but also because it plays a significant role in stratospheric chemistry. Several recent studies have focused on the potential for dehydration due to ice cloud formation in air rising slowly through the tropical tropopause layer (TTL). Holton and Gettelman showed that temperature variations associated with horizontal transport of air in the TTL can drive ice cloud formation and dehydration, and Gettelman et al. recently examined the cloud formation and dehydration along kinematic trajectories using simple assumptions about the cloud properties. In this study, a Lagrangian, one-dimensional cloud model has been used to further investigate cloud formation and dehydration as air is transported horizontally and vertically through the TTL. Time-height curtains of temperature are extracted from meteorological analyses. The model tracks the growth, advection, and sedimentation of individual cloud particles. The regional distribution of clouds simulated in the model is comparable to the subvisible cirrus distribution indicated by SAGE II. The simulated cloud properties and cloud frequencies depend strongly on the assumed supersaturation threshold for ice nucleation. The clouds typically do not dehydrate the air along trajectories down to the temperature minimum saturation mixing ratio. Rather the water vapor mixing ratio crossing the tropopause along trajectories is 10-50% larger than the saturation mixing ratio. I will also discuss the impacts of Kelvin waves and gravity waves on cloud properties and dehydration efficiency. These simulations can be used to determine whether observed lower stratospheric water vapor mixing ratios can be explained by dehydration associated with in situ TTL cloud formation alone.

Effects of radiation and turbulence on the diabatic heating and water budget of the stratiform region of a tropical cloud cluster

NASA Technical Reports Server (NTRS)

Churchill, Dean D.; Houze, Robert A., Jr.

1991-01-01

A twi-dimensional kinematic model has been used to diagnose the thermodynamic, water vapor, and hydrometeor fields of the stratiform clouds associated with a mesoscale tropical cloud cluster. The model incorporates ice- and water-cloud microphysics, visible and infrared radiation, and convective adjustment. It is intended to determine the relative contributions of radiation, mycrophysics, and turbulence to diabatic heating, and the effects that radiation has on the water budget of the cluster in the absence of dynamical interactions. The model has been initialized with thermodynamic fields and wind velocities diagnosed from a GATE tropical squall line. It is found that radiation does not directly affect the water budget of the stratiform region, and any radiative effect on hydrometeors must involve interaction with dynamics.

Evolution of trace elements in the planetary boundary layer in southern China: Effects of dust storms and aerosol-cloud interactions

NASA Astrophysics Data System (ADS)

Li, Tao; Wang, Yan; Zhou, Jie; Wang, Tao; Ding, Aijun; Nie, Wei; Xue, Likun; Wang, Xinfeng; Wang, Wenxing

2017-03-01

Aerosols and cloud water were analyzed at a mountaintop in the planetary boundary layer in southern China during March-May 2009, when two Asian dust storms occurred, to investigate the effects of aerosol-cloud interactions (ACIs) on chemical evolution of atmospheric trace elements. Fe, Al, and Zn predominated in both coarse and fine aerosols, followed by high concentrations of toxic Pb, As, and Cd. Most of these aerosol trace elements, which were affected by dust storms, exhibited various increases in concentrations but consistent decreases in solubility. Zn, Fe, Al, and Pb were the most abundant trace elements in cloud water. The trace element concentrations exhibited logarithmic inverse relationships with the cloud liquid water content and were found highly pH dependent with minimum concentrations at the threshold of pH 5.0. The calculation of Visual MINTEQ model showed that 80.7-96.3% of Fe(II), Zn(II), Pb(II), and Cu(II) existed in divalent free ions, while 71.7% of Fe(III) and 71.5% of Al(III) were complexed by oxalate and fluoride, respectively. ACIs could markedly change the speciation distributions of trace elements in cloud water by pH modification. The in-cloud scavenging of aerosol trace elements likely reached a peak after the first 2-3 h of cloud processing, with scavenging ratios between 0.12 for Cr and 0.57 for Pb. The increases of the trace element solubility (4-33%) were determined in both in-cloud aerosols and postcloud aerosols. These results indicated the significant importance of aerosol-cloud interactions to the evolution of trace elements during the first several cloud condensation/evaporation cycles.

West Antarctica as a Natural Laboratory for Single- and Mixed-Phase Cloud Microphysics

NASA Astrophysics Data System (ADS)

Wilson, A.; Scott, R. C.; Lubin, D.

2016-12-01

As part of the ARM West Antarctic Radiation Experiment (AWARE), a micropulse lidar (MPL) and a shortwave spectroradiometer were deployed to the West Antarctic Ice Sheet (WAIS) Divide Ice Camp during December 2015 and January 2016. Contrasting meteorological conditions gave rise to several distinct episodes of mixed-phase clouds, liquid water clouds, and entirely glaciated clouds. These phases were readily distinguished in the polarization signature from the MPL. The spectroradiometer measured downwelling hemispheric irradiance in the wavelength interval 0.35-2.2 microns, with 3-nanometer resolution at visible and 10-nanometer resolution at near-infrared wavelengths. Under overcast sky conditions, this measured irradiance is sensitive to total cloud optical depth for wavelengths shorter than 1.1 microns, and is sensitive at both cloud phase and effective particle size in the 1.6-micron window. For single-phase clouds, the spectral irradiance in the 1.6-micron window shows marked contrasts between liquid and ice water. For mixed phase clouds, this spectral dependence of the 1.6-micron irradiance is consistent with the prevailing phase, but in all cases the irradiance is small than that under a liquid water cloud having the same total optical depth. Radiative transfer retrievals of effective particle size from the 1.6-micron irradiance data reveal liquid water effective radii typically 2 microns smaller than found in the spring and summertime high Arctic. Most of the clouds sampled here were within 2 km of the surface, and there are comprehensive ancillary data including sondes four times daily, additional microwave radiometer data, and broadband radiometry. This AWARE data set from WAIS Divide provides a unique opportunity for testing and improving cloud microphysical parameterizations in extreme cold and pristine conditions.

The Effect of Environmental Conditions on Tropical Deep Convective Systems Observed from the TRMM Satellite

NASA Technical Reports Server (NTRS)

Lin, Bing; Wielicki, Bruce A.; Minnis, Patrick; Chambers, Lin H.; Xu, Kuan-Man; Hu, Yongxiang; Fan, Tai-Fang

2005-01-01

This study uses measurements of radiation and cloud properties taken between January and August 1998 by three Tropical Rainfall Measuring Mission (TRMM) instruments, the Clouds and the Earth's Radiant Energy System (CERES) scanner, the TRMM Microwave Imager (TMI), and the Visible and InfraRed Scanner (VIRS), to evaluate the variations of tropical deep convective systems (DCS) with sea surface temperature (SST) and precipitation. This study finds that DCS precipitation efficiency increases with SST at a rate of approx. 2%/K. Despite increasing rainfall efficiency, the cloud areal coverage rises with SST at a rate of about 7%/K in the warm tropical seas. There, the boundary layer moisture supply for deep convection and the moisture transported to the upper troposphere for cirrus-anvil cloud formation increase by approx. 6.3%/K and approx. 4.0%/K, respectively. The changes in cloud formation efficiency, along with the increased transport of moisture available for cloud formation, likely contribute to the large rate of increasing DCS areal coverage. Although no direct observations are available, the increase of cloud formation efficiency with rising SST is deduced indirectly from measurements of changes in the ratio of DCS ice water path and boundary layer water vapor amount with SST. Besides the cloud areal coverage, DCS cluster effective sizes also increase with precipitation. Furthermore, other cloud properties, such as cloud total water and ice water paths, increase with SST. These changes in DCS properties will produce a negative radiative feedback for the earth's climate system due to strong reflection of shortwave radiation by the DCS. These results significantly differ from some previous hypothesized dehydration scenarios for warmer climates, and have great potential in testing current cloud-system resolving models and convective parameterizations of general circulation models.

Statistical retrieval of thin liquid cloud microphysical properties using ground-based infrared and microwave observations

NASA Astrophysics Data System (ADS)

Marke, Tobias; Ebell, Kerstin; Löhnert, Ulrich; Turner, David D.

2016-12-01

In this article, liquid water cloud microphysical properties are retrieved by a combination of microwave and infrared ground-based observations. Clouds containing liquid water are frequently occurring in most climate regimes and play a significant role in terms of interaction with radiation. Small perturbations in the amount of liquid water contained in the cloud can cause large variations in the radiative fluxes. This effect is enhanced for thin clouds (liquid water path, LWP <100 g/m2), which makes accurate retrieval information of the cloud properties crucial. Due to large relative errors in retrieving low LWP values from observations in the microwave domain and a high sensitivity for infrared methods when the LWP is low, a synergistic retrieval based on a neural network approach is built to estimate both LWP and cloud effective radius (reff). These statistical retrievals can be applied without high computational demand but imply constraints like prior information on cloud phase and cloud layering. The neural network retrievals are able to retrieve LWP and reff for thin clouds with a mean relative error of 9% and 17%, respectively. This is demonstrated using synthetic observations of a microwave radiometer (MWR) and a spectrally highly resolved infrared interferometer. The accuracy and robustness of the synergistic retrievals is confirmed by a low bias in a radiative closure study for the downwelling shortwave flux, even for marginally invalid scenes. Also, broadband infrared radiance observations, in combination with the MWR, have the potential to retrieve LWP with a higher accuracy than a MWR-only retrieval.

Aerosol effects on cloud water amounts were successfully simulated by a global cloud-system resolving model.

PubMed

Sato, Yousuke; Goto, Daisuke; Michibata, Takuro; Suzuki, Kentaroh; Takemura, Toshihiko; Tomita, Hirofumi; Nakajima, Teruyuki

2018-03-07

Aerosols affect climate by modifying cloud properties through their role as cloud condensation nuclei or ice nuclei, called aerosol-cloud interactions. In most global climate models (GCMs), the aerosol-cloud interactions are represented by empirical parameterisations, in which the mass of cloud liquid water (LWP) is assumed to increase monotonically with increasing aerosol loading. Recent satellite observations, however, have yielded contradictory results: LWP can decrease with increasing aerosol loading. This difference implies that GCMs overestimate the aerosol effect, but the reasons for the difference are not obvious. Here, we reproduce satellite-observed LWP responses using a global simulation with explicit representations of cloud microphysics, instead of the parameterisations. Our analyses reveal that the decrease in LWP originates from the response of evaporation and condensation processes to aerosol perturbations, which are not represented in GCMs. The explicit representation of cloud microphysics in global scale modelling reduces the uncertainty of climate prediction.

Tree species related functional properties of dissolved and total organic matter in throughfall, stemflow and forest floor solutions

NASA Astrophysics Data System (ADS)

Michalzik, Beate; Bischoff, Sebastian; Schwarz, Martin; Siemens, Jan; Thieme, Lisa; Wilcke, Wolfgang

2016-04-01

The amount and chemical nature of water-bound organic matter is a prerequisite for advancing our understanding of the C and nutrient cycling and associated ecosystem processes. While many investigations have addressed the nature and dynamics of DOM in terrestrial ecosystems, only a few have investigated the dynamics and composition of water-bound total OM (TOM) including the particulate organic matter fraction (POM; 0.45 μm < POM < 500 μm). Since water-bound element and nutrient concentrations are conventionally measured after 0.45 μm-filtration, the exclusion of the POM fraction results in misleading inferences and budgeting gaps of nutrient and energy fluxes in terrestrial ecosystems. Furthermore, tree species differ in leaf composition (e.g. nutrient, polyphenols content) and leaf litter quality, which in turn affect a variety of ecosystem processes. Nevertheless, the composition and amount of DOM and TOM derived from living plant material via throughfall (TF), stemflow (SF) and its compositional fate traversing the forest floor (FF) are insufficiently understood. In particular we asked: How do tree species and forest types affect the amount of dissolved and particulate C and N in TF and FF solutions and thus the input into the mineral soil? Do functional properties (e.g. aromaticity) of DOM and TOM differ in TF, SF and FF solutions collected in beech and spruce stands and among different beech stands across Germany? To monitor (mineral) soil input fluxes of DOM and POM in different spruce and beech forests, we fortnightly sampled TF and FF solution over three years (2010-2012) in the "Hainich-Dün-Exploratory", Thuringia, Central Germany, which forms part of the DFG SPP 1374 "Exploratories for Large-scale and Long-term Functional Biodiversity Research". To characterize chemical properties of DOM and TOM, we applied solid-state 13C NMR spectroscopy to TF, SF and FF solutions from three European beech regions across Germany and from Norway spruce sites of the Hainich-Dün-Exploratory. Fluxes of POC and PN were highly variable between years and added significantly to the annual budgets of DOC and DN in TF and FF solutions especially in beech forests. The non-consideration of these particle-bound element fluxes remarkable underestimates the TOC input to the soil by 30 to 40% and those of TN by 10 to 20%. We therefore emphasize the imperative to include POC and PN fluxes into C and N budgeting of forest ecosystems. 13C NMR spectroscopy revealed remarkable tree-species related differences in the composition of DOM and TOM. Compared to DOM, TOM generally showed higher intensities for the alkyl C region and lower ones for lignin-derived and aromatic C of the aryl C region resulting in lower aromaticity indices and a diminished degree of humification. Differences in the structural composition of DOM and TOM under beech lessened in the order: throughfall > stemflow > forest floor leachate. Compared to spruce, TF DOM under beech concordantly showed the highest intensities of aromatic and phenolic C and lowest ones of alkyl-C. Phenolic compounds are known for their allelopathic potential successfully impairing competing plants and hence altering ecosystem structure and functions - mechanisms being still imperfectly understood.

Sensitivity of single column model simulations of Arctic springtime clouds to different cloud cover and mixed phase cloud parameterizations

NASA Astrophysics Data System (ADS)

Zhang, Junhua; Lohmann, Ulrike

2003-08-01

The single column model of the Canadian Centre for Climate Modeling and Analysis (CCCma) climate model is used to simulate Arctic spring cloud properties observed during the Surface Heat Budget of the Arctic Ocean (SHEBA) experiment. The model is driven by the rawinsonde observations constrained European Center for Medium-Range Weather Forecasts (ECMWF) reanalysis data. Five cloud parameterizations, including three statistical and two explicit schemes, are compared and the sensitivity to mixed phase cloud parameterizations is studied. Using the original mixed phase cloud parameterization of the model, the statistical cloud schemes produce more cloud cover, cloud water, and precipitation than the explicit schemes and in general agree better with observations. The mixed phase cloud parameterization from ECMWF decreases the initial saturation specific humidity threshold of cloud formation. This improves the simulated cloud cover in the explicit schemes and reduces the difference between the different cloud schemes. On the other hand, because the ECMWF mixed phase cloud scheme does not consider the Bergeron-Findeisen process, less ice crystals are formed. This leads to a higher liquid water path and less precipitation than what was observed.

Ground-based remote sensing of thin clouds in the Arctic

NASA Astrophysics Data System (ADS)

Garrett, T. J.; Zhao, C.

2013-05-01

This paper describes a method for using interferometer measurements of downwelling thermal radiation to retrieve the properties of single-layer clouds. Cloud phase is determined from ratios of thermal emission in three "micro-windows" at 862.5 cm-1, 935.8 cm-1, and 988.4 cm-1 where absorption by water vapour is particularly small. Cloud microphysical and optical properties are retrieved from thermal emission in the first two of these micro-windows, constrained by the transmission through clouds of primarily stratospheric ozone emission at 1040 cm-1. Assuming a cloud does not approximate a blackbody, the estimated 95% confidence retrieval errors in effective radius re, visible optical depth τ, number concentration N, and water path WP are, respectively, 10%, 20%, 38% (55% for ice crystals), and 16%. Applied to data from the Atmospheric Radiation Measurement programme (ARM) North Slope of Alaska - Adjacent Arctic Ocean (NSA-AAO) site near Barrow, Alaska, retrievals show general agreement with both ground-based microwave radiometer measurements of liquid water path and a method that uses combined shortwave and microwave measurements to retrieve re, τ and N. Compared to other retrieval methods, advantages of this technique include its ability to characterise thin clouds year round, that water vapour is not a primary source of retrieval error, and that the retrievals of microphysical properties are only weakly sensitive to retrieved cloud phase. The primary limitation is the inapplicability to thicker clouds that radiate as blackbodies and that it relies on a fairly comprehensive suite of ground based measurements.

The potential influence of Asian and African mineral dust on ice, mixed-phase and liquid water clouds

NASA Astrophysics Data System (ADS)

Wiacek, A.; Peter, T.; Lohmann, U.

2010-02-01

This modelling study explores the availability of mineral dust particles as ice nuclei for interactions with ice, mixed-phase and liquid water clouds, also tracking the particles' history of cloud-processing. We performed 61 320 one-week forward trajectory calculations originating near the surface of major dust emitting regions in Africa and Asia using high-resolution meteorological analysis fields for the year 2007. Without explicitly modelling dust emission and deposition processes, dust-bearing trajectories were assumed to be those coinciding with known dust emission seasons. We found that dust emissions from Asian deserts lead to a higher potential for interactions with high clouds, despite being the climatologically much smaller dust emission source. This is due to Asian regions experiencing significantly more ascent than African regions, with strongest ascent in the Asian Taklimakan desert at ~25%, ~40% and 10% of trajectories ascending to 300 hPa in spring, summer and fall, respectively. The specific humidity at each trajectory's starting point was transported in a Lagrangian manner and relative humidities with respect to water and ice were calculated in 6-h steps downstream, allowing us to estimate the formation of liquid, mixed-phase and ice clouds. Practically none of the simulated air parcels reached regions where homogeneous ice nucleation can take place (T≲-40 °C) along trajectories that have not experienced water saturation first. By far the largest fraction of cloud forming trajectories entered conditions of mixed-phase clouds, where mineral dust will potentially exert the biggest influence. The majority of trajectories also passed through regions supersaturated with respect to ice but subsaturated with respect to water, where "warm" (T≳-40 °C) ice clouds may form prior to supercooled water or mixed-phase clouds. The importance of "warm" ice clouds and the general influence of dust in the mixed-phase cloud region are highly uncertain due to considerable scatter in recent laboratory data from ice nucleation experiments, which we briefly review in this work. For "classical" cirrus-forming temperatures, our results show that only mineral dust IN that underwent mixed-phase cloud-processing previously are likely to be relevant, and, therefore, we recommend further systematic studies of immersion mode ice nucleation on mineral dust suspended in atmospherically relevant coatings.

Illuminating hydrological processes at the soil-vegetation-atmosphere interface with water stable isotopes

NASA Astrophysics Data System (ADS)

Sprenger, Matthias; Leistert, Hannes; Gimbel, Katharina; Weiler, Markus

2016-09-01

Water stable isotopes (18O and 2H) are widely used as ideal tracers to track water through the soil and to separate evaporation from transpiration. Due to the technical developments in the last two decades, soil water stable isotope data have become easier to collect. Thus, the application of isotope methods in soils is growing rapidly. Studies that make use of soil water stable isotopes often have a multidisciplinary character since an interplay of processes that take place in the vadose zone has to be considered. In this review, we provide an overview of the hydrological processes that alter the soil water stable isotopic composition and present studies utilizing pore water stable isotopes. The processes that are discussed include the water input as precipitation or throughfall, the output as evaporation, transpiration, or recharge, and specific flow and transport processes. Based on the review and supported by additional data and modeling results, we pose a different view on the recently proposed two water world hypothesis. As an alternative to two distinct pools of soil water, where one pool is enriched in heavy isotopes and used by the vegetation and the other pool does not undergo isotopic fractionation and becomes recharge, the water gets successively mixed with newly introduced rainwater during the percolation process. This way, water initially isotopically enriched in the topsoil loses the fractionation signal with increasing infiltration depth, leading to unfractionated isotopic signals in the groundwater.

Effects of forest structure on hydrological processes in China

NASA Astrophysics Data System (ADS)

Sun, Jiamei; Yu, Xinxiao; Wang, Henian; Jia, Guodong; Zhao, Yang; Tu, Zhihua; Deng, Wenping; Jia, Jianbo; Chen, Jungang

2018-06-01

There are serious concerns between forest and water quantity, Chinese extensive land area makes the relationship more complicated, thus, the effects of forest structure on hydrological processes in China were not fully comprehended. In this research, forest's hydrological functions, including rainfall partitioning, litter interception, evapotranspiration (ET), were analyzed in China. The results showed that throughfall was the largest proportion of gross precipitation with fraction between 69.3 ± 8.8% and 84.4 ± 5.6%. Then was canopy interception which varied from 14.6 ± 1.4% to 29.1 ± 3.3%. Throughfall was correlated with gross precipitation, canopy thickness and canopy density. Canopy interception was correlated with gross precipitation, LAI, canopy density, biomass, mixed degree, uniform angle index, aggregation index. Stemflow accounted for only 1.2 ± 0.32% of gross precipitation, with the greatest fraction of 2.1 ± 0.2% in XBH site and the least fraction of 0.3 ± 0.1% in DB site. Gross precipitation was the main factor in determining stemflow. DB site had the greatest litter interception (7.7 ± 0.8 mm) and HB site had the least (0.9 ± 0.3 mm). Litter interception had closer correlation with undecomposed litter mass (0.66) than total litter mass (0.46). Path-coefficient analysis showed that stand density, Shannon-Wiener index, litter mass, size ratio had greater impact on litter interception than other factors. ET was mainly influenced by precipitation, and it also correlated with LAI, canopy density and biomass. In north China, ET percentage (the ratio of ET and precipitation) was 82.7-109.5%, while it decreased to 63.1-88.5% in south China, ET demand in XBS site was larger than precipitation. ET percentage increased with increasing latitude and elevation, decreased with increasing temperature.

Northern Forest DroughtNet: A New Framework to Understand Impacts of Precipitation Change on the Northern Forest Ecosystem

NASA Astrophysics Data System (ADS)

Asbjornsen, H.; Rustad, L.; Templer, P. H.; Jennings, K.; Phillips, R.; Smith, M.

2014-12-01

Recent trends and projections for future change for the U.S. northern forests suggest that the region's climate is becoming warmer, wetter, and, ironically, drier, with more precipitation occurring as large events, separated by longer periods with no precipitation. However, to date, precipitation manipulation experiments conducted in forest ecosystems represent only ~5% of all such experiments worldwide, and our understanding of how the mesic-adapted northern forest will respond to greater frequency and intensity of drought in the future is especially poor. Several important challenges have hampered previous research efforts to conduct forest drought experiments and draw robust conclusions, including difficulties in reducing water uptake by deep and lateral tree roots, logistical and financial constraints to establishing and maintaining large-scale field experiments, and the lack of standardized approaches for determining the appropriate precipitation manipulation treatment (e.g., amount and timing of throughfall displacement), designing and constructing the throughfall displacement infrastructure, identifying key response variables, and collecting and analyzing the field data. The overarching goal of this project is to establish a regional research coordination network - Northern Forest DroughtNet - to investigate the impacts of changes in the amount and distribution of precipitation on the hydrology, biogeochemistry, and carbon (C) cycling dynamics of northern temperate forests. Specific objectives include the development of a standard prototype for conducting precipitation manipulation studies in forest ecosystems (in collaboration with the international DroughtNet-RCN) and the implementation of this prototype drought experiment at the Hubbard Brook Experimental Forest. Here, we present the advances made thus far towards achieving the objectives of Northern Forest DroughtNet, plans for future work, and an invitation to the larger scientific community interested in precipitation manipulation experiments in forest ecosystems to participate in the network.

Change in hydraulic properties and leaf traits of a tall rainforest tree species subjected to long-term throughfall exclusion in the perhumid tropics

NASA Astrophysics Data System (ADS)

Schuldt, B.; Leuschner, C.; Horna, V.; Moser, G.; Köhler, M.; Barus, H.

2010-11-01

In a throughfall displacement experiment on Sulawesi, Indonesia, three 0.16 ha stands of a premontane perhumid rainforest were exposed to a two-year soil desiccation period that reduced the soil moisture in the upper soil layers beyond the conventional wilting point. About 25 variables, including leaf morphological and chemical traits, stem diameter growth and hydraulic properties of the xylem in the trunk and terminal twigs, were investigated in trees of the tall-growing tree species Castanopsis acuminatissima (Fagaceae) by comparing desiccated roof plots with nearby control plots. We tested the hypotheses that this tall and productive species is particularly sensitive to drought, and the exposed upper sun canopy is more affected than the shade canopy. Hydraulic conductivity in the xylem of terminal twigs normalised to vessel lumen area was reduced by 25%, leaf area-specific conductivity by 10-33% during the desiccation treatment. Surprisingly, the leaves present at the end of the drought treatment were significantly larger, but not smaller in the roof plots, though reduced in number (about 30% less leaves per unit of twig sapwood area), which points to a drought effect on the leaf bud formation while the remaining leaves may have profited from a surplus of water. Mean vessel diameter and axial conductivity in the outermost xylem of the trunk were significantly reduced and wood density increased, while annual stem diameter increment decreased by 26%. In contradiction to our hypotheses, (i) we found no signs of major damage to the C. acuminatissima trees nor to any other drought sensitivity of tall trees, and (ii) the exposed upper canopy was not more drought susceptible than the shade canopy.

Spatio-Temporal Variability of Gross Rainfall, Throughfall and Stemflow in a Non-native Hawaiian Forest

NASA Astrophysics Data System (ADS)

Fares, A.; Safeeq, M.; Fares, S.

2011-12-01

Information on partitioning of gross rainfall in non-native trees in Hawaiian forests is limited. In this study, measurements of gross rainfall (PG), throughfall (TF), and stemflow (SF) were made at three locations in the upper Mākaha valley watershed to perform canopy water balance and parameterize Gash analytical model. The three selected locations are dominated by Strawberry guava (Psidium cattleianum), Christmas berry (Schinus terebinthifolius), Java plum (Syzygium cumini), and Coffee (Coffea Arabica) trees. Mean TF expressed as percentage of PG was the lowest (43.32%) under Strawberry guava and the highest (56.47%) under a mixture of Christmas berry, Strawberry guava, and Java plum. However, measured SF was the highest (33.9%) for Strawberry guava and lowest (3.6%) under the mixture of Christmas berry, Strawberry guava, and Java plum. The highest SF under Strawberry guava can be attributed to its smooth bark and steep branching and could have been the reason behind lowest TF. The mean observed interception losses varied between 23% under Strawberry guava and 45% for the site dominated by Coffee. Estimated mean free TF coefficients varied from 0.34 to 0.44, while the mean canopy storage capacity varied from 0.89 to 1.94 mm. The mean SF partitioning coefficient ranged from 0.05 to 0.37. The estimated canopy storage and trunk storage (P't) varied from 4.6 to 5.7 mm and 1.47 to 3.72 mm, respectively. Trees with nearly vertical branches and smooth bark (i.e. Strawberry Guava) resulted in smaller value of trunk storage. The analytical Gash's model for rainfall interception was successfully applied and its simulated results agreed reasonably well with observed data.

Parameterizing Size Distribution in Ice Clouds

DOE Office of Scientific and Technical Information (OSTI.GOV)

DeSlover, Daniel; Mitchell, David L.

2009-09-25

PARAMETERIZING SIZE DISTRIBUTIONS IN ICE CLOUDS David L. Mitchell and Daniel H. DeSlover ABSTRACT An outstanding problem that contributes considerable uncertainty to Global Climate Model (GCM) predictions of future climate is the characterization of ice particle sizes in cirrus clouds. Recent parameterizations of ice cloud effective diameter differ by a factor of three, which, for overcast conditions, often translate to changes in outgoing longwave radiation (OLR) of 55 W m-2 or more. Much of this uncertainty in cirrus particle sizes is related to the problem of ice particle shattering during in situ sampling of the ice particle size distribution (PSD).more » Ice particles often shatter into many smaller ice fragments upon collision with the rim of the probe inlet tube. These small ice artifacts are counted as real ice crystals, resulting in anomalously high concentrations of small ice crystals (D < 100 µm) and underestimates of the mean and effective size of the PSD. Half of the cirrus cloud optical depth calculated from these in situ measurements can be due to this shattering phenomenon. Another challenge is the determination of ice and liquid water amounts in mixed phase clouds. Mixed phase clouds in the Arctic contain mostly liquid water, and the presence of ice is important for determining their lifecycle. Colder high clouds between -20 and -36 oC may also be mixed phase but in this case their condensate is mostly ice with low levels of liquid water. Rather than affecting their lifecycle, the presence of liquid dramatically affects the cloud optical properties, which affects cloud-climate feedback processes in GCMs. This project has made advancements in solving both of these problems. Regarding the first problem, PSD in ice clouds are uncertain due to the inability to reliably measure the concentrations of the smallest crystals (D < 100 µm), known as the “small mode”. Rather than using in situ probe measurements aboard aircraft, we employed a treatment of ice cloud optical properties formulated in terms of PSD parameters in combination with remote measurements of thermal radiances to characterize the small mode. This is possible since the absorption efficiency (Qabs) of small mode crystals is larger at 12 µm wavelength relative to 11 µm wavelength due to the process of wave resonance or photon tunneling more active at 12 µm. This makes the 12/11 µm absorption optical depth ratio (or equivalently the 12/11 µm Qabs ratio) a means for detecting the relative concentration of small ice particles in cirrus. Using this principle, this project tested and developed PSD schemes that can help characterize cirrus clouds at each of the three ARM sites: SGP, NSA and TWP. This was the main effort of this project. These PSD schemes and ice sedimentation velocities predicted from them have been used to test the new cirrus microphysics parameterization in the GCM known as the Community Climate Systems Model (CCSM) as part of an ongoing collaboration with NCAR. Regarding the second problem, we developed and did preliminary testing on a passive thermal method for retrieving the total water path (TWP) of Arctic mixed phase clouds where TWPs are often in the range of 20 to 130 g m-2 (difficult for microwave radiometers to accurately measure). We also developed a new radar method for retrieving the cloud ice water content (IWC), which can be vertically integrated to yield the ice water path (IWP). These techniques were combined to determine the IWP and liquid water path (LWP) in Arctic clouds, and hence the fraction of ice and liquid water. We have tested this approach using a case study from the ARM field campaign called M-PACE (Mixed-Phase Arctic Cloud Experiment). This research led to a new satellite remote sensing method that appears promising for detecting low levels of liquid water in high clouds typically between -20 and -36 oC. We hope to develop this method in future research.« less

MISR RICO Products

Atmospheric Science Data Center

2016-11-25

... microphysics of the transition to a mature rainshaft, organization of trade wind clouds, water budget of trade wind cumulus, and the ... (MISR) mission objectives involve providing accurate information on cloud cover, cloud-track winds, stereo-derived cloud-top ...

Cirrus cloud retrieval with MSG/SEVIRI using artificial neural networks

NASA Astrophysics Data System (ADS)

Strandgren, Johan; Bugliaro, Luca; Sehnke, Frank; Schröder, Leon

2017-09-01

Cirrus clouds play an important role in climate as they tend to warm the Earth-atmosphere system. Nevertheless their physical properties remain one of the largest sources of uncertainty in atmospheric research. To better understand the physical processes of cirrus clouds and their climate impact, enhanced satellite observations are necessary. In this paper we present a new algorithm, CiPS (Cirrus Properties from SEVIRI), that detects cirrus clouds and retrieves the corresponding cloud top height, ice optical thickness and ice water path using the SEVIRI imager aboard the geostationary Meteosat Second Generation satellites. CiPS utilises a set of artificial neural networks trained with SEVIRI thermal observations, CALIOP backscatter products, the ECMWF surface temperature and auxiliary data. CiPS detects 71 and 95 % of all cirrus clouds with an optical thickness of 0.1 and 1.0, respectively, that are retrieved by CALIOP. Among the cirrus-free pixels, CiPS classifies 96 % correctly. With respect to CALIOP, the cloud top height retrieved by CiPS has a mean absolute percentage error of 10 % or less for cirrus clouds with a top height greater than 8 km. For the ice optical thickness, CiPS has a mean absolute percentage error of 50 % or less for cirrus clouds with an optical thickness between 0.35 and 1.8 and of 100 % or less for cirrus clouds with an optical thickness down to 0.07 with respect to the optical thickness retrieved by CALIOP. The ice water path retrieved by CiPS shows a similar performance, with mean absolute percentage errors of 100 % or less for cirrus clouds with an ice water path down to 1.7 g m-2. Since the training reference data from CALIOP only include ice water path and optical thickness for comparably thin clouds, CiPS also retrieves an opacity flag, which tells us whether a retrieved cirrus is likely to be too thick for CiPS to accurately derive the ice water path and optical thickness. By retrieving CALIOP-like cirrus properties with the large spatial coverage and high temporal resolution of SEVIRI during both day and night, CiPS is a powerful tool for analysing the temporal evolution of cirrus clouds including their optical and physical properties. To demonstrate this, the life cycle of a thin cirrus cloud is analysed.

Synoptic Traveling Weather Systems on Mars: Effects of Radiatively-Active Water Ice Clouds

NASA Astrophysics Data System (ADS)

Hollingsworth, Jeffery L.; Kahre, Melinda A.; Haberle, Robert; Atsuki Urata, Richard

2016-10-01

Atmospheric aerosols on Mars are critical in determining the nature of its thermal structure, its large-scale circulation, and hence the overall climate of the planet. We conduct multi-annual simulations with the latest version of the NASA Ames Mars global climate model (GCM), gcm2.3+, that includes a modernized radiative-transfer package and complex water-ice cloud microphysics package which permit radiative effects and interactions of suspended atmospheric aerosols (e.g., water ice clouds, water vapor, dust, and mutual interactions) to influence the net diabatic heating. Results indicate that radiatively active water ice clouds profoundly affect the seasonal and annual mean climate. The mean thermal structure and balanced circulation patterns are strongly modified near the surface and aloft. Warming of the subtropical atmosphere at altitude and cooling of the high latitude atmosphere at low levels takes place, which increases the mean pole-to-equator temperature contrast (i.e., "baroclinicity"). With radiatively active water ice clouds (RAC) compared to radiatively inert water ice clouds (nonRAC), significant changes in the intensity of the mean state and forced stationary Rossby modes occur, both of which affect the vigor and intensity of traveling, synoptic period weather systems. Such weather systems not only act as key agents in the transport of heat and momentum beyond the extent of the Hadley circulation, but also the transport of trace species such as water vapor, water ice-clouds, dust and others. The northern hemisphere (NH) forced Rossby waves and resultant wave train are augmented in the RAC case: the modes are more intense and the wave train is shifted equatorward. Significant changes also occur within the subtropics and tropics. The Rossby wave train sets up, combined with the traveling synoptic-period weather systems (i.e., cyclones and anticyclones), the geographic extent of storm zones (or storm tracks) within the NH. A variety of circulation features will be presented which indicate contrasts between the RAC and nonRAC cases, and which highlight key effects radiatively-active clouds have on physical and dynamical processes active in the current climate of Mars.

Synoptic Traveling Weather Systems on Mars: Effects of Radiatively-Active Water Ice Clouds

NASA Technical Reports Server (NTRS)

Hollingsworth, Jeffery; Kahre, Melinda; Haberle, Robert; Urata, Richard

2017-01-01

Atmospheric aerosols on Mars are critical in determining the nature of its thermal structure, its large-scale circulation, and hence the overall climate of the planet. We conduct multi-annual simulations with the latest version of the NASA Ames Mars global climate model (GCM), gcm2.3+, that includes a modernized radiative-transfer package and complex water-ice cloud microphysics package which permit radiative effects and interactions of suspended atmospheric aerosols (e.g., water ice clouds, water vapor, dust, and mutual interactions) to influence the net diabatic heating. Results indicate that radiatively active water ice clouds profoundly affect the seasonal and annual mean climate. The mean thermal structure and balanced circulation patterns are strongly modified near the surface and aloft. Warming of the subtropical atmosphere at altitude and cooling of the high latitude atmosphere at low levels takes place, which increases the mean pole-to-equator temperature contrast (i.e., "baroclinicity"). With radiatively active water ice clouds (RAC) compared to radiatively inert water ice clouds (nonRAC), significant changes in the intensity of the mean state and forced stationary Rossby modes occur, both of which affect the vigor and intensity of traveling, synoptic period weather systems. Such weather systems not only act as key agents in the transport of heat and momentum beyond the extent of the Hadley circulation, but also the transport of trace species such as water vapor, water ice-clouds, dust and others. The northern hemisphere (NH) forced Rossby waves and resultant wave train are augmented in the RAC case: the modes are more intense and the wave train is shifted equatorward. Significant changes also occur within the subtropics and tropics. The Rossby wave train sets up, combined with the traveling synoptic period weather systems (i.e., cyclones and anticyclones), the geographic extent of storm zones (or storm tracks) within the NH. A variety of circulation features will be presented which indicate contrasts between the RAC and nonRAC cases, and which highlight key effects radiatively-active clouds have on physical and dynamical processes active in the current climate of Mars.

Synoptic Traveling Weather Systems on Mars: Effects of Radiatively-Active Water Ice Clouds

NASA Technical Reports Server (NTRS)

Hollingsworth, Jeffery; Kahre, Melinda; Haberle, Robert; Urata, Richard

2017-01-01

Atmospheric aerosols on Mars are critical in determining the nature of its thermal structure, its large-scale circulation, and hence the overall climate of the planet. We conduct multi-annual simulations with the latest version of the NASA Ames Mars global climate model (GCM), gcm2.3+, that includes a modernized radiative-transfer package and complex water-ice cloud microphysics package which permit radiative effects and interactions of suspended atmospheric aerosols (e.g., water ice clouds, water vapor, dust, and mutual interactions) to influence the net diabatic heating. Results indicate that radiatively active water ice clouds profoundly affect the seasonal and annual mean climate. The mean thermal structure and balanced circulation patterns are strongly modified near the surface and aloft. Warming of the subtropical atmosphere at altitude and cooling of the high latitude atmosphere at low levels takes place, which increases the mean pole-to-equator temperature contrast (i.e., "baroclinicity"). With radiatively active water ice clouds (RAC) compared to radiatively inert water ice clouds (nonRAC), significant changes in the intensity of the mean state and forced stationary Rossby modes occur, both of which affect the vigor and intensity of traveling, synoptic period weather systems.Such weather systems not only act as key agents in the transport of heat and momentum beyond the extent of the Hadley circulation, but also the transport of trace species such as water vapor, water ice-clouds, dust and others. The northern hemisphere (NH) forced Rossby waves and resultant wave train are augmented in the RAC case: the modes are more intense and the wave train is shifted equatorward. Significant changes also occur within the subtropics and tropics. The Rossby wave train sets up, combined with the traveling synoptic period weather systems (i.e., cyclones and anticyclones), the geographic extent of storm zones (or storm tracks) within the NH. A variety of circulation features will be presented which indicate contrasts between the RAC and nonRAC cases, and which highlight key effects radiatively-active clouds have on physical and dynamical processes active in the current climate of Mars.

Aircraft Natural/Artificial Icing

DTIC Science & Technology

2009-02-12

LWC are 0.1 to 0.8 g/m3 for stratiform clouds and 0.2 to 2.5 g/m3 for cumuliform clouds. The drop size distribution in the cloud is usually...cloud hydrometeor size distributions from 0.5 to 50 um, particle shape (discrimination between water and ice), particle optical properties (refractive...index), precipitation size distributions from 25 um to 1550 um, liquid water content from 0.01 to 3 gm-3 and aircraft velocity and atmospheric

Combining multiple isotopes and metagenomic to delineate the role of tree canopy nitrification in European forests along nitrogen deposition and climate gradients

NASA Astrophysics Data System (ADS)

Guerrieri, R.; Avila, A.; Barceló, A.; Elustondo, D.; Hellstein, S.; Magnani, F.; Mattana, S.; Matteucci, G.; Merilä, P.; Michalski, G. M.; Nicolas, M.; Vanguelova, E.; Verstraeten, A.; Waldner, P.; Watanabe, M.; Penuelas, J.; Mencuccini, M.

2017-12-01

Forest canopies influence our climate through carbon, water and energy exchanges with the atmosphere. However, less investigated is whether and how tree canopies change the chemical composition of precipitation, with important implications on forest nutrient cycling. Recently, we provided for the first time isotopic evidence that biological nitrification in tree canopies was responsible for significant changes in the amount of nitrate from rainfall to throughfall across two UK forests at high nitrogen (N) deposition [1]. This finding strongly suggested that bacteria and/or Archaea species of the phyllosphere are responsible for transforming atmospheric N before it reaches the soil. Despite microbial epiphytes representing an important component of tree canopies, attention has been mostly directed to their role as pathogens, while we still do not know whether and how they affect nutrient cycling. Our study aims to 1) characterize microbial communities harboured in tree canopies for two of the most dominant species in Europe (Fagus sylvatica L. and Pinus sylvestris L.) using metagenomic techniques, 2) quantify the functional genes related to nitrification but also to denitrification and N fixation, and 3) estimate the contribution of NO3 derived from biological canopy nitrification vs. atmospheric NO3 input by using δ15N, δ18O and δ17O of NO3in forest water. We considered i) twelve sites included in the EU ICP long term intensive forest monitoring network, chosen along a climate and nitrogen deposition gradient, spanning from Fennoscandia to the Mediterranean and ii) a manipulation experiment where N mist treatments were carried out either to the soil or over tree canopies. We will present preliminary results regarding microbial diversity in the phyllosphere, water (rainfall and throughfall) and soil samples over the gradient. Furthermore, we will report differences between the two investigated tree species for the phyllosphere core microbiome in terms of relative abundance of bacterial and Archaea classes and those species related to N cycling. Finally we will assess whether there are differences among tree species and sites in the number of functional genes related to N cycling and how they are related to the N deposition and/or climate. [1] Guerrieri et al. 2015 Global Change and Biology 21 (12): 4613-4626.

NASA Glenn Icing Research Tunnel: 2014 Cloud Calibration Procedure and Results

NASA Technical Reports Server (NTRS)

Van Zante, Judith F.; Ide, Robert F.; Steen, Laura E.; Acosta, Waldo J.

2014-01-01

The results of the December 2013 to February 2014 Icing Research Tunnel full icing cloud calibration are presented. The calibration steps included establishing a uniform cloud and conducting drop size and liquid water content calibrations. The goal of the calibration was to develop a uniform cloud, and to generate a transfer function from the inputs of air speed, spray bar atomizing air pressure and water pressure to the outputs of median volumetric drop diameter and liquid water content. This was done for both 14 CFR Parts 25 and 29, Appendix C ('typical' icing) and soon-to-be released Appendix O (supercooled large drop) conditions.

NASA Glenn Icing Research Tunnel: Upgrade and Cloud Calibration

NASA Technical Reports Server (NTRS)

VanZante, Judith Foss; Ide, Robert F.; Steen, Laura E.

2012-01-01

In 2011, NASA Glenn s Icing Research Tunnel underwent a major modification to it s refrigeration plant and heat exchanger. This paper presents the results of the subsequent full cloud calibration. Details of the calibration procedure and results are presented herein. The steps include developing a nozzle transfer map, establishing a uniform cloud, conducting a drop sizing calibration and finally a liquid water content calibration. The goal of the calibration is to develop a uniform cloud, and to build a transfer map from the inputs of air speed, spray bar atomizing air pressure and water pressure to the output of median volumetric droplet diameter and liquid water content.

NASA Glenn Icing Research Tunnel: 2012 Cloud Calibration Procedure and Results

NASA Technical Reports Server (NTRS)

VanZante, Judith Foss; Ide, Robert F.; Steen, Laura E.

2012-01-01

In 2011, NASA Glenn s Icing Research Tunnel underwent a major modification to it s refrigeration plant and heat exchanger. This paper presents the results of the subsequent full cloud calibration. Details of the calibration procedure and results are presented herein. The steps include developing a nozzle transfer map, establishing a uniform cloud, conducting a drop sizing calibration and finally a liquid water content calibration. The goal of the calibration is to develop a uniform cloud, and to build a transfer map from the inputs of air speed, spray bar atomizing air pressure and water pressure to the output of median volumetric droplet diameter and liquid water content.

View of cold water eddies in Falkland Current off southern Argentina

NASA Image and Video Library

1973-12-14

SL4-137-3608 (14 Dec. 1973) --- A view of cold water eddies in the Falkland Current off the South Atlantic coast of southern Argentina as seen from the Skylab space station in Earth orbit. This picture was taken by one of the Skylab 4 crewmen using a hand-held 70mm Hasselblad camera. This land area (left corner) extends south along the coast from Puerto Deseado (center left border) for about 50 miles. Within the ocean, several light blue areas are visible and represent the occurrence of plankton with the Falkland Current. Over the ocean, the cold water eddies are identified by the circular cloud-free areas within the cloud street pattern and bordered by cumulus cloud buildup (white). The cloud streets indicate the wind is from the southwest and do not form over eddies because energy form the atmosphere is absorbed by the cold ocean water. On the downwind side of the eddies, cumulus clouds tend to form as the cold moist air flows over the warmer water. Similar cloud and eddy features have been observed by the Skylab 4 crewmen in the Yucatan Current off Yucatan Peninsula and in some parts of the South Pacific. Studies are underway by Dr. George Maul, NOAA, and Dr. Robert Stevenson, ONR, to determine the significance of the cold water eddies to ocean dynamics. Photo credit: NASA

An Oil-Stream Photomicrographic Aeroscope for Obtaining Cloud Liquid-Water Content and Droplet Size Distributions in Flight

NASA Technical Reports Server (NTRS)

Hacker, Paul T.

1956-01-01

An airborne cloud aeroscope by which droplet size, size distribution, and liquid-water content of clouds can be determined has been developed and tested in flight and in wind tunnels with water sprays. In this aeroscope the cloud droplets are continuously captured in a stream of oil, which Is then photographed by a photomicrographic camera. The droplet size and size distribution can be determined directly from the photographs. With the droplet size distribution known, the liquid-water content of the cloud can be computed from the geometry of the aeroscope, the airspeed, and the oil-flow rate. The aeroscope has the following features: Data are obtained semi-automatically, and permanent data are taken in the form of photographs. A single picture usually contains a sufficient number of droplets to establish the droplet size distribution. Cloud droplets are continuously captured in the stream of oil, but pictures are taken at Intervals. The aeroscope can be operated in icing and non-icing conditions. Because of mixing of oil in the instrument, the droplet-distribution patterns and liquid-water content values from a single picture are exponentially weighted average values over a path length of about 3/4 mile at 150 miles per hour. The liquid-water contents, volume-median diameters, and distribution patterns obtained on test flights and in the Lewis icing tunnel are similar to previously published data.

Evaluating The Indirect Effect of Cirrus Clouds

NASA Astrophysics Data System (ADS)

Dobbie, S.; Jonas, P. R.

What effect would an increase in nucleating aerosols have on the radiative and cloud properties? What error would be incurred by evaluating the indirect effect by taking an evolved cloud and fixing the integrated water content and vary the number of ice crystals? These questions will be addressed in this work. We will use the UK LES cloud resolving model to perform a sensitivity study for cirrus clouds to the indirect effect, and will evaluate approximate methods in the process. In this work, we will initialize the base (no increase of aerosol) cirrus clouds so that the double moment scheme is constrained to agree with observations through the ef- fective radius. Effective radius is calculated using the local concentration and the ice water content. We then perform a sensitivity experiment to investigate the dependence of the average IWC, effective size, and radiative properties (including heating rates) to variations in the nucleation rate. Conclusions will be draw as to the possible ef- fect of changes in aerosol amounts on cirrus. We will determine how sensitive the cloud and radiative properties are to various aerosol increases. We will also discuss the applicability of the Meyer et al. (1992) nucleation formulae for our simulations. It is important to stress that in this work we only change the nucleation rate for the newly forming cloud. By doing this, we are not fixing the total water content and redistributing the water amongst increased ice crystals. We increase the number of aerosols available to be nucleated and allow the model to evolve the size distributions. In this way, there is competition for the water vapour, the ice particles are evolved dynamically with different fall speeds, the conversion rates to other hydrometers (such as aggregates) are affected, and the heating rates are different due to the different size distributions that evolve. We will look at how the water content, the distribution of water, and the radiative properties are affected by the indirect effect.

Validation of Nimbus-7 cloud and SMMR data

NASA Technical Reports Server (NTRS)

Hwang, P. H.; Yeh, H. Y. M.; Macmillan, D. S.; Long, C. S.

1986-01-01

The relationship between cloud amount, water content (WC), and liquid water content (LWC) is studied. Nimbus-7 cloud data and LWC and WC data derived from the SMMR for July 1979 are analyzed and compared. The SMMR sea surface temperature (SST) data are also compared to Air Force SST data. The comparisons reveal that Nimbus-7 cloud data and the SMMR WC and LWC data correlate well, and there is also good agreement between the SMMR SST and the Air Force data. The data demonstrate that there is a relation between the WC, LWC, and cloud amount data.

Two-channel microwave radiometer for observations of total column precipitable water vapor and cloud liquid water path

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liljegren, J.C.

1994-01-01

The Atmospheric Radiation Measurement (ARM) Program is focused on improving the treatment of radiation transfer in models of the atmospheric general circulation, as well as on improving parameterizations of cloud properties and formation processes in these models (USDOE, 1990). To help achieve these objectives, ARM is deploying several two-channel, microwave radiometers at the Cloud and Radiation Testbed (CART) site in Oklahoma for the purpose of obtaining long time series observations of total precipitable water vapor (PWV) and cloud liquid water path (LWP). The performance of the WVR-1100 microwave radiometer deployed by ARM at the Oklahoma CART site central facility tomore » provide time series measurements precipitable water vapor (PWV) and liquid water path (LWP) has been presented. The instrument has proven to be durable and reliable in continuous field operation since June, 1992. The accuracy of the PWV has been demonstrated to achieve the limiting accuracy of the statistical retrieval under clear sky conditions, degrading with increasing LWP. Improvements are planned to address moisture accumulation on the Teflon window, as well as to identity the presence of clouds with LWP at or below the retrieval uncertainty.« less

Dynamic chemistry in the perched groundwater flowing through weathered bedrock underling a steep forested hillslope, north California

NASA Astrophysics Data System (ADS)

Kim, H.; Rempe, D. M.; Bishop, J. K.; Dietrich, W.; Fung, I.; Wood, T. J.

2012-12-01

The spatial and temporal pattern of groundwater chemistry in the seasonally perched groundwater systems that develop in the weathered bedrock zone under hillslopes have rarely been documented, yet chemical evolution of water here dictates the runoff chemistry to streams in many places. Here we exploit an intensively instrumented hillslope to document water well chemistry at three wells and adjacent stream. We have been sampling groundwater at daily frequency since October 2008 on a forested hillslope, "Rivendell", at the Angelo Coast Range Reserve located at the headwaters of the Eel River, California. The site is typical of California's coastal Mediterranean climate. The groundwater samples have been collected from a depth near the boundary between the weathered and fresh bedrock at three locations along the hillslope: Well 1 (bottom of hillslope), Well 3 (mid-slope), and Well 10 (near the ridge). Bulk rainwater and throughfall samples were collected at a meadow across the hillslope and at the middle of the slope, respectively, as well. Near the ridge (Well 10), during the first significant rainstorms of 2009 (133mm/42.5hours) and 2010 (220mm/42hours), when the water table changed only 0.32m and 0.66m, respectively, the concentration of Ca, Mg, and Na started to increase rapidly compared to the dry season (e.g. 2-6 μM vs 0.02-0.2μM [Mg]/day). However, during these same storms, K concentration sharply increased to 50-60 μM and decreased to 20-30μM, synchronizing with the water table responses. Throughfalls of these storms had at least 10 fold lower Ca, Mg, and Na concentrations than the well water while they had 10 fold higher K compared to the pre-event groundwater values. When the total seasonal cumulative rainfall exceeds 600 mm, the Well 10 solute concentration was diluted nearly 3 fold (e.g. [Mg] 0.3 mM vs. 0.1 mM) and the water table was raised significantly (2-6 meters). Throughout the rainy season, Well10 retained its diluted chemistry signature and on average the water table remained elevated as subsequent rainstorms repeatedly recharged the system. Well10 solute concentration slowly increased at the end of the rainy season when the water table fell. In contrast, at the foot of the hill slope, even though the water table was responsive to each rainfall event, its water chemistry developed a strong dilution signatures only during the intense rainstorms (total rainfall > 70mm); the solute concentration decreased (e.g. [Mg] = 0.1mM) during the rising limb of the well hydrograph and recovered back to its pre-event value (e.g. [Mg] = 0.3mM) during the falling limb of the well hydrograph. During small storms, the solute concentration of Well 1 either did not change or slightly increased. Mid-slope showed similar behavior to Well 1. The Well 3 solute concentration was diluted about 3 fold (e.g. [Mg] 0.3mM to 0.1mM) as the water table rose and increased as the water table receded. However unlike Well 1, the water chemistry of Well 3 did not recover to its pre-event composition at any point during the rainy season and the recovery rate was slower than that of Well 1. These water chemistry observations provide insight into the dynamics of water movement within the fractured, weathered bedrock zone, and point to both vertical and lateral mixing processes that influence the chemical evolution of waters.

Effect of the secondary organic aerosol coatings on black carbon water uptake, cloud condensation nuclei activity, and particle collapse

EPA Science Inventory

The ability of black carbon aerosols to absorb water and act as a cloud condensation nuclei (CCN) directly controls their lifetime in the atmosphere as well as their impact on cloud formation, thus impacting the earth’s climate. Black carbon emitted from most combustion pro...

Unveiling aerosol-cloud interactions - Part 2: Minimising the effects of aerosol swelling and wet scavenging in ECHAM6-HAM2 for comparison to satellite data

NASA Astrophysics Data System (ADS)

Neubauer, David; Christensen, Matthew W.; Poulsen, Caroline A.; Lohmann, Ulrike

2017-11-01

Aerosol-cloud interactions (ACIs) are uncertain and the estimates of the ACI effective radiative forcing (ERFaci) magnitude show a large variability. Within the Aerosol_cci project the susceptibility of cloud properties to changes in aerosol properties is derived from the high-resolution AATSR (Advanced Along-Track Scanning Radiometer) data set using the Cloud-Aerosol Pairing Algorithm (CAPA) (as described in our companion paper) and compared to susceptibilities from the global aerosol climate model ECHAM6-HAM2 and MODIS-CERES (Moderate Resolution Imaging Spectroradiometer - Clouds and the Earth's Radiant Energy System) data. For ECHAM6-HAM2 the dry aerosol is analysed to mimic the effect of CAPA. Furthermore the analysis is done for different environmental regimes. The aerosol-liquid water path relationship in ECHAM6-HAM2 is systematically stronger than in AATSR-CAPA data and cannot be explained by an overestimation of autoconversion when using diagnostic precipitation but rather by aerosol swelling in regions where humidity is high and clouds are present. When aerosol water is removed from the analysis in ECHAM6-HAM2 the strength of the susceptibilities of liquid water path, cloud droplet number concentration and cloud albedo as well as ERFaci agree much better with those of AATSR-CAPA or MODIS-CERES. When comparing satellite-derived to model-derived susceptibilities, this study finds it more appropriate to use dry aerosol in the computation of model susceptibilities. We further find that the statistical relationships inferred from different satellite sensors (AATSR-CAPA vs. MODIS-CERES) as well as from ECHAM6-HAM2 are not always of the same sign for the tested environmental conditions. In particular the susceptibility of the liquid water path is negative in non-raining scenes for MODIS-CERES but positive for AATSR-CAPA and ECHAM6-HAM2. Feedback processes like cloud-top entrainment that are missing or not well represented in the model are therefore not well constrained by satellite observations. In addition to aerosol swelling, wet scavenging and aerosol processing have an impact on liquid water path, cloud albedo and cloud droplet number susceptibilities. Aerosol processing leads to negative liquid water path susceptibilities to changes in aerosol index (AI) in ECHAM6-HAM2, likely due to aerosol-size changes by aerosol processing. Our results indicate that for statistical analysis of aerosol-cloud interactions the unwanted effects of aerosol swelling, wet scavenging and aerosol processing need to be minimised when computing susceptibilities of cloud variables to changes in aerosol.

Remote Sensing of Energy Distribution Characteristics over the Tibet

NASA Astrophysics Data System (ADS)

Shi, J.; Husi, L.; Wang, T.

2017-12-01

The overall objective of our study is to quantify the spatiotemporal characteristics and changes of typical factors dominating water and energy cycles in the Tibet region. Especially, we focus on variables of clouds optical & microphysical parameters, surface shortwave and longwave radiation. Clouds play a key role in the Tibetan region's water and energy cycles. They seriously impact the precipitation, temperature and surface energy distribution. Considering that proper cloud products with relatively higher spatial and temporal sampling and with satisfactory accuracy are serious lacking in the Tibet region, except cloud optical thickness, cloud effective radius and liquid/ice water content, the cloud coverage dynamics at hourly scales also analyzed jointly based on measurements of Himawari-8, and MODIS. Surface radiation, as an important energy source in perturbating the Tibet's evapotranspiration, snow and glacier melting, is a controlling factor in energy balance in the Tibet region. All currently available radiation products in this area are not suitable for regional scale study of water and energy exchange and snow/glacier melting due to their coarse resolution and low accuracies because of cloud and topography. A strategy for deriving land surface upward and downward radiation by fusing optical and microwave remote sensing data is proposed. At the same time, the big topographic effect on the surface radiation are also modelled and analyzed over the Tibet region.

Optically Thin Liquid Water Clouds: Their Importance and Our Challenge

NASA Technical Reports Server (NTRS)

Turner, D. D.; Vogelmann, A. M.; Austin, R. T.; Barnard, J. C.; Cady-Pereira, K.; Chiu, J. C.; Clough, S. A.; Flynn, C.; Khaiyer, M. M.; Liljegren, J.;

Clouds Aerosols Internal Affaires: Increasing Cloud Fraction and Enhancing the Convection

NASA Technical Reports Server (NTRS)

Koren, Ilan; Kaufman, Yoram; Remer, Lorraine; Rosenfeld, Danny; Rudich, Yinon

2004-01-01

Clouds developing in a polluted environment have more numerous, smaller cloud droplets that can increase the cloud lifetime and liquid water content. Such changes in the cloud droplet properties may suppress low precipitation allowing development of a stronger convection and higher freezing level. Delaying the washout of the cloud water (and aerosol), and the stronger convection will result in higher clouds with longer life time and larger anvils. We show these effects by using large statistics of the new, 1km resolution data from MODIS on the Terra satellite. We isolate the aerosol effects from meteorology by regression and showing that aerosol microphysical effects increases cloud fraction by average of 30 presents for all cloud types and increases convective cloud top pressure by average of 35mb. We analyze the aerosol cloud interaction separately for high pressure trade wind cloud systems and separately for deep convective cloud systems. The resultant aerosol radiative effect on climate for the high pressure cloud system is: -10 to -13 W/sq m at the top of the atmosphere (TOA) and -11 to -14 W/sq m at the surface. For deeper convective clouds the forcing is: -4 to -5 W/sq m at the TOA and -6 to -7 W/sq m at the surface.

Observational Evidence of Changes in Water Vapor, Clouds, and Radiation at the ARM SGP Site

NASA Technical Reports Server (NTRS)

Dong, Xiquan; Xi, Baike; Minnus, Patrick

2006-01-01

Characterizing water vapor and cloud effects on the surface radiation budget is critical for understanding the current climate because water vapor is the most important greenhouse gas in the atmosphere and clouds are one of the largest sources of uncertainty in predicting potential future climate change. Several studies have shown that insolation over land declined until 1990 then increased until the present. Using 8 years of surface data, we observed the increasing trend of insolation from 1997 to 2000, but detected a significant decrease from 2001 to 2004. The variation of cloud fraction mirrors that of insolation with an overall increase of 1 percent per year. Under clear-sky conditions, water vapor changes have a greater impact on longwave flux than on insolation.

Phase transformation of mixed-phase clouds

NASA Astrophysics Data System (ADS)

Korolev, Alexei; Isaac, George

2003-01-01

The glaciation time of a mixed-phase cloud due to the Wegener-Bergeron-Findeisen mechanism is calculated using an adiabatic one-dimensional numerical model for the cases of zero, ascending, descending and oscillating vertical velocities. The characteristic values of the glaciation time are obtained for different concentrations of ice particles and liquid-water content. Steady state is not possible for the ice-water content/total water content ratio in a uniformly vertically moving mixed-phase parcel. The vertical oscillation of a cloud parcel may result in a periodic evaporation and activation of liquid droplets in the presence of ice particles during infinite time. After a certain time, the average ice-water content and liquid-water content reach a steady state. This phenomenon may explain the existence of long-lived mixed-phase stratiform layers. The obtained results are important for understanding the mechanisms of formation and life cycle of mixed-phase clouds.

NASA Glenn Icing Research Tunnel: 2014 and 2015 Cloud Calibration Procedures and Results

NASA Technical Reports Server (NTRS)

Steen, Laura E.; Ide, Robert F.; Van Zante, Judith F.; Acosta, Waldo J.

2015-01-01

This report summarizes the current status of the NASA Glenn Research Center (GRC) Icing Research Tunnel cloud calibration: specifically, the cloud uniformity, liquid water content, and drop-size calibration results from both the January-February 2014 full cloud calibration and the January 2015 interim cloud calibration. Some aspects of the cloud have remained the same as what was reported for the 2014 full calibration, including the cloud uniformity from the Standard nozzles, the drop-size equations for Standard and Mod1 nozzles, and the liquid water content for large-drop conditions. Overall, the tests performed in January 2015 showed good repeatability to 2014, but there is new information to report as well. There have been minor updates to the Mod1 cloud uniformity on the north side of the test section. Also, successful testing with the OAP-230Y has allowed the IRT to re-expand its operating envelopes for large-drop conditions to a maximum median volumetric diameter of 270 microns. Lastly, improvements to the collection-efficiency correction for the SEA multi-wire have resulted in new calibration equations for Standard- and Mod1-nozzle liquid water content.

Super-cooled liquid water topped sub-arctic clouds and precipitation - investigation based on combination of ground-based in-situ and remote-sensing observations

NASA Astrophysics Data System (ADS)

Hirsikko, Anne; Brus, David; O'Connor, Ewan J.; Filioglou, Maria; Komppula, Mika; Romakkaniemi, Sami

2017-04-01

In the high and mid latitudes super-cooled liquid water layers are frequently observed on top of clouds. These layers are difficult to forecast with numerical weather prediction models, even though, they have strong influence on atmospheric radiative properties, cloud microphysical properties, and subsequently, precipitation. This work investigates properties of super-cooled liquid water layer topped sub-arctic clouds and precipitation observed with ground-based in-situ (cloud probes) and remote-sensing (a cloud radar, Doppler and multi-wavelength lidars) instrumentation during two-month long Pallas Cloud Experiment (PaCE 2015) in autumn 2015. Analysis is based on standard Cloudnet scheme supplemented with new retrieval products of the specific clouds and their properties. Combination of two scales of observation provides new information on properties of clouds and precipitation in the sub-arctic Pallas region. Current status of results will be presented during the conference. The authors acknowledge financial support by the Academy of Finland (Centre of Excellence Programme, grant no 272041; and ICINA project, grant no 285068), the ACTRIS2 - European Union's Horizon 2020 research and innovation programme under grant agreement No 654109, the KONE foundation, and the EU FP7 project BACCHUS (grant no 603445).

Radiocesium migration in the litter layer of different forest types in Fukushima, Japan.

PubMed

Kurihara, Momo; Onda, Yuichi; Kato, Hiroaki; Loffredo, Nicolas; Yasutaka, Tetsuo; Coppin, Frederic

2018-07-01

Cesium-137 ( 137 Cs) migration in the litter layer consists of various processes, such as input via throughfall, output via litter decomposition, and input from deeper layers via soil organism activity. We conducted litter bag experiments over 2 years (December 2014-November 2016) to quantify the inputs and outputs of 137 Cs in the litter layer in a Japanese cedar plantation (Cryptomeria japonica) and a mixed broadleaf forest dominated by Quercus serrata located 40 km northwest of the Fukushima Dai-ichi Nuclear Power Plant. The experiments included four conditions, combining contaminated and non-contaminated litter and deeper layer material, and the inputs and outputs were estimated from the combination of 137 Cs increases and decreases in the litter layer under each condition. The 137 Cs dynamics differed between the two forests. In the C. japonica forest, some 137 Cs input via throughfall remained in the litter layer, and downward 137 Cs flux passed through the litter layer was 0.42 (/year).Upward flux of 137 Cs from the deeper layer was very restricted, < 0.017 (/year). In the broadleaf forest, migration of 137 Cs in throughfall into deeper layers was restricted, downward 137 Cs flux was less than 0.003 (/year).Upward input of 137 Cs from the deeper layer was prominent, 0.037 (/year). 137 Cs output via litter decomposition was observed in both forests. The flux in the C. japonica forest was slower than that in the broadleaf forest, 0.12 and 0.15 (/year), respectively. Copyright © 2018 Elsevier Ltd. All rights reserved.

Preparatory studies of zero-g cloud drop coalescence experiment

NASA Technical Reports Server (NTRS)

Telford, J. W.; Keck, T. S.

1979-01-01

Experiments to be performed in a weightless environment in order to study collision and coalescence processes of cloud droplets are described. Rain formation in warm clouds, formation of larger cloud drops, ice and water collision processes, and precipitation in supercooled clouds are among the topics covered.

Polar clouds and radiation in satellite observations, reanalyses, and climate models

NASA Astrophysics Data System (ADS)

Lenaerts, Jan T. M.; Van Tricht, Kristof; Lhermitte, Stef; L'Ecuyer, Tristan S.

2017-04-01

Clouds play a pivotal role in the surface energy budget of the polar regions. Here we use two largely independent data sets of cloud and surface downwelling radiation observations derived by satellite remote sensing (2007-2010) to evaluate simulated clouds and radiation over both polar ice sheets and oceans in state-of-the-art atmospheric reanalyses (ERA-Interim and Modern Era Retrospective-Analysis for Research and Applications-2) and the Coupled Model Intercomparison Project Phase 5 (CMIP5) climate model ensemble. First, we show that, compared to Clouds and the Earth's Radiant Energy System-Energy Balanced and Filled, CloudSat-CALIPSO better represents cloud liquid and ice water path over high latitudes, owing to its recent explicit determination of cloud phase that will be part of its new R05 release. The reanalyses and climate models disagree widely on the amount of cloud liquid and ice in the polar regions. Compared to the observations, we find significant but inconsistent biases in the model simulations of cloud liquid and ice water, as well as in the downwelling radiation components. The CMIP5 models display a wide range of cloud characteristics of the polar regions, especially with regard to cloud liquid water, limiting the representativeness of the multimodel mean. A few CMIP5 models (CNRM, GISS, GFDL, and IPSL_CM5b) clearly outperform the others, which enhances credibility in their projected future cloud and radiation changes over high latitudes. Given the rapid changes in polar regions and global feedbacks involved, future climate model developments should target improved representation of polar clouds. To that end, remote sensing observations are crucial, in spite of large remaining observational uncertainties, which is evidenced by the substantial differences between the two data sets.

Characterization of cumulus cloud fields using trajectories in the center of gravity versus water mass phase space: 2. Aerosol effects on warm convective clouds: Center of Gravity Versus Water Mass 2

DOE Office of Scientific and Technical Information (OSTI.GOV)

Heiblum, Reuven H.; Altaratz, Orit; Koren, Ilan

2016-06-07

In Part I of this work a 3D cloud tracking algorithm and phase-space of center of gravity altitude versus cloud liquid water mass (CvM space) were introduced and described in detail. We showed how new physical insight can be gained by following cloud trajectories in the CvM space. Here, this approach is used to investigate aerosol effects on cloud fields of warm cumuli. We show a clear effect of the aerosol loading on the shape and size of CvM clusters. We also find fundamental differences in the CvM space between simulations using bin versus bulk microphysical schemes, with the binmore » scheme precipitation expressing much higher sensitivity to changes in aerosol concentrations. Using the bin microphysical scheme, we find that the increase in cloud center of gravity altitude with increase in aerosol concentrations occurs for a wide range of cloud sizes. This is attributed to reduced sedimentation, increased buoyancy and vertical velocities, and increased environmental instability, all of which are tightly coupled to inhibition of precipitation processes and subsequent feedbacks of clouds on their environment. Many of the physical processes shown here are consistent with processes typically associated with cloud invigoration.« less

Raman Lidar Measurements During the International H2O Project. 2; Instrument Comparisons and Case Studies

NASA Technical Reports Server (NTRS)

Whiteman, D. N.; Demoz, B.; DiGirolamo, P.; Corner, J.; Veselovskii, I.; Evans, K.; Wang, Z.; Sabatino, D.; Schwemmer, G.; Gentry, B.

2005-01-01

The NASA/GSFC Scanning Raman Lidar (SRL) participated in the International H2O Project (IHOP) that occurred in May and June, 2002 in the midwestern part of the U. S. The SRL system configuration and methods of data analysis were described in part I of this paper. In this second part, comparisons of SRL water vapor measurements and those of chilled mirror radiosonde and LASE airborne water vapor lidar are performed. Two case studies are presented; one for daytime and one for nighttime. The daytime case study is of a convectively driven boundary layer event and is used to characterize the SRL water vapor random error characteristics. The nighttime case study is of a thunderstorm-generated cirrus cloud case that is studied in it s meteorological context. Upper tropospheric humidification due to precipitation from the cirrus cloud is quantified as is the cirrus cloud ice water content and particle depolarization ratio. These detailed cirrus cloud measurements are being used in a cirrus cloud modeling study.

Surface fractal dimension, water adsorption efficiency, and cloud nucleation activity of insoluble aerosol.

PubMed

Laaksonen, Ari; Malila, Jussi; Nenes, Athanasios; Hung, Hui-Ming; Chen, Jen-Ping

2016-05-03

Surface porosity affects the ability of a substance to adsorb gases. The surface fractal dimension D is a measure that indicates the amount that a surface fills a space, and can thereby be used to characterize the surface porosity. Here we propose a new method for determining D, based on measuring both the water vapour adsorption isotherm of a given substance, and its ability to act as a cloud condensation nucleus when introduced to humidified air in aerosol form. We show that our method agrees well with previous methods based on measurement of nitrogen adsorption. Besides proving the usefulness of the new method for general surface characterization of materials, our results show that the surface fractal dimension is an important determinant in cloud drop formation on water insoluble particles. We suggest that a closure can be obtained between experimental critical supersaturation for cloud drop activation and that calculated based on water adsorption data, if the latter is corrected using the surface fractal dimension of the insoluble cloud nucleus.

Surface fractal dimension, water adsorption efficiency, and cloud nucleation activity of insoluble aerosol

NASA Astrophysics Data System (ADS)

Laaksonen, Ari; Malila, Jussi; Nenes, Athanasios; Hung, Hui-Ming; Chen, Jen-Ping

2016-05-01

Surface porosity affects the ability of a substance to adsorb gases. The surface fractal dimension D is a measure that indicates the amount that a surface fills a space, and can thereby be used to characterize the surface porosity. Here we propose a new method for determining D, based on measuring both the water vapour adsorption isotherm of a given substance, and its ability to act as a cloud condensation nucleus when introduced to humidified air in aerosol form. We show that our method agrees well with previous methods based on measurement of nitrogen adsorption. Besides proving the usefulness of the new method for general surface characterization of materials, our results show that the surface fractal dimension is an important determinant in cloud drop formation on water insoluble particles. We suggest that a closure can be obtained between experimental critical supersaturation for cloud drop activation and that calculated based on water adsorption data, if the latter is corrected using the surface fractal dimension of the insoluble cloud nucleus.

NASA Experiment on Tropospheric-Stratospheric Water Vapor Transport in the Intertropical Convergence Zone

NASA Technical Reports Server (NTRS)

Page, William A.

1982-01-01

The following six papers report preliminary results obtained from a field experiment designed to study the role of tropical cumulo-nimbus clouds in the transfer of water vapor from the troposphere to the stratosphere over the region of Panama. The measurements were made utilizing special NOAA enhanced IR satellite images, radiosonde-ozonesondes and a NASA U-2 aircraft carrying. nine experiments. The experiments were provided by a group of NASA, NOAA, industry, and university scientists. Measurements included atmospheric humidity, air and cloud top temperatures, atmospheric tracer constituents, cloud particle characteristics and cloud morphology. The aircraft made a total of eleven flights from August 30 through September 18, 1980, from Howard Air Force Base, Panama; the pilots obtained horizontal and vertical profiles in and near convectively active regions and flew around and over cumulo-nimbus towers and through the extended anvils in the stratosphere. Cumulo-nimbus clouds in the tropics appear to play an important role in upward water vapor transport and may represent the principal source influencing the stratospheric water vapor budget. The clouds provide strong vertical circulation in the troposphere, mixing surface air and its trace materials (water vapor, CFM's sulfur compounds, etc.) quickly up to the tropopause. It is usually assumed that large scale mean motions or eddy scale motions transport the trace materials through the tropopause and into the stratosphere where they are further dispersed and react with other stratospheric constituents. The important step between the troposphere and stratosphere for water vapor appears to depend upon the processes occurring at or near the tropopause at the tops of the cumulo-nimbus towers. Several processes have been sugested: (1) The highest towers penetrate the tropopause and carry water in the form of small ice particles directly into the stratosphere. (2) Water vapor from the tops of the cumulonimbus clouds is transported somehow through the tropopause, the vapor pressure being controlled by the temperature at the tops of the clouds; the dryness of the stratosphere could be explained if most of the transport occurs in connection with very high clouds in regions with very high and cold tropopause. (3) Cumulo-nimbus anvils act as terrestrial-radiation shields allowing the ice particle temperatures near cloud tops to cool radiatively below the supersaturation point; this cooling would cause a vapor deposition on the ice particles which will settle out and thus act as water scavengers. The experiment was designed to collect information on these detailed physical processes near and above the tropopause in order to assess their importance and the role they play in controlling stratospheric water vapor humidity.

Radiative Susceptibility of Cloudy Atmospheres to Droplet Number Perturbations: 1. Theoretical Analysis and Examples from MODIS

NASA Technical Reports Server (NTRS)

Platnick, Steven; Oreopoulos, Lazaros

2008-01-01

Theoretical and satellite-based assessments of the sensitivity of broadband shortwave radiative fluxes in cloudy atmospheres to small perturbations in the cloud droplet number concentration (N) of liquid water clouds under constant water conditions are performed. Two approaches to study this sensitivity are adopted: absolute increases in N, for which the radiative response is referred to as absolute cloud susceptibility, and relative increases in N or relative cloud susceptibility. Estimating the former is more challenging as it requires an assumed value for either cloud liquid water content or geometrical thickness; both susceptibilities require an assumed relationship between the droplet volume and effective radius. Expanding upon previous susceptibility studies, present radiative calculations include the effect of AN perturbations on droplet asymmetry parameter and single-scattering albedo, in addition to extinction. Absolute cloud susceptibility has a strong nonlinear dependence on the droplet effective radius as expected, while relative cloud susceptibility is primarily dependent on optical thickness. Molecular absorption and reflecting surfaces both reduce the relative contribution of the cloud to the top-of-atmosphere (TOA) flux and therefore also reduce the TOA albedo susceptibility. Transmittance susceptibilities are negative with absolute values similar to albedo susceptibility, while atmospheric absorptance susceptibilities are about an order of magnitude smaller than albedo susceptibilities and can be either positive or negative. Observation-based susceptibility calculations are derived from MODIS pixel-level retrievals of liquid water cloud optical thickness, effective radius, and cloud top temperature; two data granule examples are shown. Susceptibility quantifies the aerosol indirect effect sensitivity in a way that can be easily computed from model fields. As such, susceptibilities derived from MODIS observations provide a higher-order test of model cloud properties used for indirect effect studies. MODIS-derived global distributions of cloud susceptibility and radiative forcing calculations are presented in a companion paper.

Liquid water content variation with altitude in clouds over Europe

NASA Astrophysics Data System (ADS)

Andreea, Boscornea; Sabina, Stefan

2013-04-01

Cloud water content is one of the most fundamental measurements in cloud physics. Knowledge of the vertical variability of cloud microphysical characteristics is important for a variety of reasons. The profile of liquid water content (LWC) partially governs the radiative transfer for cloudy atmospheres, LWC profiles improves our understanding of processes acting to form and maintain cloud systems and may lead to improvements in the representation of clouds in numerical models. Presently, in situ airborne measurements provide the most accurate information about cloud microphysical characteristics. This information can be used for verification of both numerical models and cloud remote sensing techniques. The aim of this paper was to analyze the liquid water content (LWC) measurements in clouds, in time of the aircraft flights. The aircraft and its platform ATMOSLAB - Airborne Laboratory for Environmental Atmospheric Research is property of the National Institute for Aerospace Research "Elie Carafoli" (INCAS), Bucharest, Romania. The airborne laboratory equipped for special research missions is based on a Hawker Beechcraft - King Air C90 GTx aircraft and is equipped with a sensors system CAPS - Cloud, Aerosol and Precipitation Spectrometer (30 bins, 0.51-50 m). The processed and analyzed measurements are acquired during 4 flights from Romania (Bucharest, 44°25'57″N 26°06'14″E) to Germany (Berlin 52°30'2″N 13°23'56″E) above the same region of Europe. The flight path was starting from Bucharest to the western part of Romania above Hungary, Austria at a cruse altitude between 6000-8500 m, and after 5 hours reaching Berlin. In total we acquired data during approximately 20 flight hours and we presented the vertical and horizontal LWC variations for different cloud types. The LWC values are similar for each type of cloud to values from literature. The vertical LWC profiles in the atmosphere measured during takeoff and landing of the aircraft have shown their dependence of the meteorological parameters.

Liquid Water Oceans in Ice Giants

NASA Technical Reports Server (NTRS)

Wiktorowicz, Sloane J.; Ingersoll, Andrew P.

2007-01-01

Aptly named, ice giants such as Uranus and Neptune contain significant amounts of water. While this water cannot be present near the cloud tops, it must be abundant in the deep interior. We investigate the likelihood of a liquid water ocean existing in the hydrogen-rich region between the cloud tops and deep interior. Starting from an assumed temperature at a given upper tropospheric pressure (the photosphere), we follow a moist adiabat downward. The mixing ratio of water to hydrogen in the gas phase is small in the photosphere and increases with depth. The mixing ratio in the condensed phase is near unity in the photosphere and decreases with depth; this gives two possible outcomes. If at some pressure level the mixing ratio of water in the gas phase is equal to that in the deep interior, then that level is the cloud base. The gas below the cloud base has constant mixing ratio. Alternately, if the mixing ratio of water in the condensed phase reaches that in the deep interior, then the surface of a liquid ocean will occur. Below this ocean surface, the mixing ratio of water will be constant. A cloud base occurs when the photospheric temperature is high. For a family of ice giants with different photospheric temperatures, the cooler ice giants will have warmer cloud bases. For an ice giant with a cool enough photospheric temperature, the cloud base will exist at the critical temperature. For still cooler ice giants, ocean surfaces will result. A high mixing ratio of water in the deep interior favors a liquid ocean. We find that Neptune is both too warm (photospheric temperature too high) and too dry (mixing ratio of water in the deep interior too low) for liquid oceans to exist at present. To have a liquid ocean, Neptune s deep interior water to gas ratio would have to be higher than current models allow, and the density at 19 kbar would have to be approx. equal to 0.8 g/cu cm. Such a high density is inconsistent with gravitational data obtained during the Voyager flyby. In our model, Neptune s water cloud base occurs around 660 K and 11 kbar, and the density there is consistent with Voyager gravitational data. As Neptune cools, the probability of a liquid ocean increases. Extrasolar "hot Neptunes," which presumably migrate inward toward their parent stars, cannot harbor liquid water oceans unless they have lost almost all of the hydrogen and helium from their deep interiors.

Observed Aerosol Influence on Ice Water Content of Arctic Mixed-Phase Clouds

NASA Astrophysics Data System (ADS)

Norgren, M.; de Boer, G.; Shupe, M.

2016-12-01

The response of ice water content (IWC) in Arctic mixed-phase stratocumulus to atmospheric aerosols is observed. IWC retrievals from ground based radars operated by the Atmospheric Radiation Measurement (ARM) program in Barrow, Alaska are used to construct composite profiles of cloud IWC from a 9-year radar record starting in January of 2000. The IWC profiles for high (polluted) and low (clean) aerosol loadings are compared. Generally, we find that clean clouds exhibit statistically significant higher levels of IWC than do polluted clouds by a factor of 2-4 at cloud base. For springtime clouds, with a maximum relative humidity with respect to ice (RHI) above 110% in the cloud layer, the IWC at cloud base was a factor of 3.25 times higher in clean clouds than it was in polluted clouds. We infer that the aerosol loading of the cloud environment alters the liquid drop size distribution within the cloud, with larger drops being more frequent in clean clouds. Larger cloud drops promote riming within the cloud layer, which is one explanation for the higher IWC levels in clean clouds. The drop size distribution may also be a significant control of ice nucleation events within mixed-phase clouds. Whether the high IWC levels in clean clouds are due to increased riming or nucleation events is unclear at this time.

Triggering a Wet Climate on Mars: The Role of Outflow Channels in Martian Water Cycles

NASA Astrophysics Data System (ADS)

Santiago, D.; Asphaug, E. I.; Colaprete, A.

2011-12-01

The triggering of a robust water cycle on Mars has been hypothesized to be caused by gigantic flooding events evidenced by outflow channels. Here we use the Ames Mars General Circulation Model (MGCM) to study how these presumably abrupt eruptions of water (Carr,1996) affected the climate of Mars. We model where the water ultimately went as part of a transient hydrologic cycle. Chryse Planitia, east of Tharsis, has evidence for multiple water outflow channels. One of the largest channels is Ares Valles, which was carved by floods with estimated water volumes of order 10^5 km^2 (Andrews-Hanna, 2007 & Carr, 1996). Outflow discharge rate estimates range from 10^6 to 10^7 m^3/seconds or greater (Andrews-Hanna & Phillips, 2007, Harrison & Grimm, 2008). Studies suggest that outflow channels formed with smaller, successive floods instead of a single large flood (Wilson, et al.,2004). Warner et al. (2009) suggest up to six outflow events for the formation of Ares Valles, while estimates for another large outflow, Kasei Valles, might have been flooded by over two thousand floods with a total water volume of 5.5 x 10^5 km^3 (Harrison & Grimm, 2008). By adding water to the surface of Mars at the given outflow rate, as an expanding one-layer lake, we are able to study quantitatively how these outflow events influenced Mars climate, particularly the hydrologic cycle. In particular: Could sudden introductions of large amounts of water on the Martian surface lead to a new equilibrated water cycle? Can we tie certain fluvial surface features to transient or sustained water cycles? What are the roles of water vapor and water ice clouds to sudden changes in the water cycle on Mars? How are radiative feedbacks involved with this? What is the ultimate fate of the outflow water? This work uses the NASA Ames MGCM version 2.1 and other schemes that are part of the NASA Ames MGCM suite of tools. Various versions of the MGCM developed at Ames have been used extensively to examine dust and volatile distributions on Mars (e.g., Kahre et al., 2006, 2008). The MGCM 2.1 currently has a well-developed water ice cloud formation scheme (Montmessin et al., 2002, 2004a), which includes calculation of cloud particle concentrations, nucleation, growth, and gravitational sedimentation. For examining the effect of a large water outflow on the climate of Mars, we include water tracers, with an advanced cloud particle scheme Preliminary results suggest that water may have been transported globally for years post-outflow. Post-outflow water cloud formation increases dramatically, with water ice clouds and water vapor potentially transporting water globally. The global mass of water vapor and of water ice clouds increases substantially, with the post-outflow patterns settling into annual cycles, with increasing water entering the atmosphere from the surface over time. Future work will examine the radiative effects of the water vapor and water ice clouds, and the longer-term persistence of a new hydrological or climate regime Detailed comparisons of post-outflow precipitation locations with fluvial features on Mars will be done.

Meteorological Analysis of Icing Conditions Encountered in Low-Altitude Stratiform Clouds

NASA Technical Reports Server (NTRS)

Kline, D. B.; Walker, J. A.

1951-01-01

Liquid-water content, droplet size, and temperature data measured during 22 flights in predominatly stratiform clouds through the 1948-49 and the 1949-50 winters are presented. Several icing encounters were of greater severity than those previously measured over the same geographical area, but were within the limits of similar measurements obtained over different terrain within the United States. An analysis of meteorological conditions existing during the 74 flights conducted for four winters indicated an inverse relation of liquid-water concentration to maximum horizontal extent of icing clouds. Data on the vertical extent of supercooled clouds are also presented. Icing conditions were most likely to occur in the southwest and northwest quadrants of a cyclone area, and least likely to occur in the southeast and northeast quadrants where convergent air flow and lifting over the associated warm frontal surface usually cause precipitation. Additional data indicated that, icing conditions were usually encountered in nonprecipitating clouds existing at subfreezing temperatures and were unlikely over areas where most weather observing stations reported the existence of precipitation. Measurements of liquid-water content obtained during 12 flights near the time and location of radiosonde observations were compared with theoretical values. The average liquid-water content of a cloud layer, as measured by the multicylinder technique, seldom exceeded two-thirds of that which could be released by adiabatic lifting. Local areas near the cloud tops equaled or occasionally exceeded the calculated maximum quantity of liquid water.

Sensitivity analysis of upwelling thermal radiance in presence of clouds

NASA Technical Reports Server (NTRS)

Subramanian, S. V.; Tiwari, S. N.; Suttles, J. T.

1981-01-01

Total upwelling radiance at the top of the atmosphere is evaluated theoretically in the presence of clouds. The influence of cloud heights, thicknesses and different cloud covers on the upwelling radiance is also investigated. The characteristics of the two cloud types considered in this study closely correspond to altocumulus and cirrus with the cloud emissivity as a function of its liquid water (or ice) content. For calculation of the integrated transmittance of atmospheric gases such as, H2O, CO2, O3, and N2O, the Quasi Random Band (QRB) model approach is adopted. Results are obtained in three different spectral ranges and are compared with the clearsky radiance results. It is found that the difference between the clearsky and cloudy radiance increases with increasing cloud height and liquid water content. This difference also decreases as the surface temperature approaches the value of the cloud top temperature.

CloudSat First Image of a Warm Front Storm Over the Norwegian Sea

NASA Technical Reports Server (NTRS)

2006-01-01

[figure removed for brevity, see original site] Figure 1

CloudSat's first image, of a warm front storm over the Norwegian Sea, was obtained on May 20, 2006. In this horizontal cross-section of clouds, warm air is seen rising over colder air as the satellite travels from right to left. The red colors are indicative of highly reflective particles such as water droplets (or rain) or larger ice crystals (or snow), while the blue indicates thinner clouds (such as cirrus). The flat green/blue lines across the bottom represent the ground signal. The vertical scale on the CloudSat Cloud Profiling Radar image is approximately 30 kilometers (19 miles). The blue line below the Cloud Profiling Radar image indicates that the data were taken over water. The inset image shows the CloudSat track relative to a Moderate Resolution Imaging Spectroradiometer (MODIS) infrared image taken at nearly the same time.

CloudSat Image of a Polar Night Storm Near Antarctica

NASA Technical Reports Server (NTRS)

2006-01-01

[figure removed for brevity, see original site] Figure 1

CloudSat image of a horizontal cross-section of a polar night storm near Antarctica. Until now, clouds have been hard to observe in polar regions using remote sensing, particularly during the polar winter or night season. The red colors are indicative of highly reflective particles such as water (rain) or ice crystals, while the blue indicates thinner clouds (such as cirrus). The flat green/blue lines across the bottom represent the ground signal. The vertical scale on the CloudSat Cloud Profiling Radar image is approximately 30 kilometers (19 miles). The blue line below the Cloud Profiling Radar image indicates that the data were taken over water; the brown line below the image indicates the relative elevation of the land surface. The inset image shows the CloudSat track relative to a Moderate Resolution Imaging Spectroradiometer (MODIS) infrared image taken at nearly the same time.

A scheme for parameterizing ice cloud water content in general circulation models

NASA Technical Reports Server (NTRS)

Heymsfield, Andrew J.; Donner, Leo J.

1989-01-01

A method for specifying ice water content in GCMs is developed, based on theory and in-cloud measurements. A theoretical development of the conceptual precipitation model is given and the aircraft flights used to characterize the ice mass distribution in deep ice clouds is discussed. Ice water content values derived from the theoretical parameterization are compared with the measured values. The results demonstrate that a simple parameterization for atmospheric ice content can account for ice contents observed in several synoptic contexts.

Design, Evaluation and GCM-Performance of a New Parameterization for Microphysics of Clouds with Relaxed Arakawa-Schubert Scheme (McRas)

NASA Technical Reports Server (NTRS)

Sud, Y. C.; Walker, G. K.

1998-01-01

A prognostic cloud scheme named McRAS (Microphysics of clouds with Relaxed Arakawa-Schubert Scheme) was developed with the aim of improving cloud-microphysics, and cloud-radiation interactions in GCMs. McRAS distinguishes convective, stratiform, and boundary-layer clouds. The convective clouds merge into stratiform clouds on an hourly time-scale, while the boundary-layer clouds do so instantly. The cloud condensate transforms into precipitation following the auto-conversion relations of Sundqvist that contain a parametric adaptation for the Bergeron-Findeisen process of ice crystal growth and collection of cloud condensate by precipitation. All clouds convect, advect, and diffuse both horizontally and vertically with a fully active cloud-microphysics throughout its life-cycle, while the optical properties of clouds are derived from the statistical distribution of hydrometeors and idealized cloud geometry. An evaluation of McRAS in a single column model (SCM) with the GATE Phase III data has shown that McRAS can simulate the observed temperature, humidity, and precipitation without discernible systematic errors. An evaluation with the ARM-CART SCM data in a cloud model intercomparison exercise shows reasonable but not an outstanding accurate simulation. Such a discrepancy is common to almost all models and is related, in part, to the input data quality. McRAS was implemented in the GEOS II GCM. A 50 month integration that was initialized with the ECMWF analysis of observations for January 1, 1987 and forced with the observed sea-surface temperatures and sea-ice distribution and vegetation properties (biomes, and soils), with prognostic soil moisture, snow-cover, and hydrology showed a very realistic simulation of cloud process, incloud water and ice, and cloud-radiative forcing (CRF). The simulated ITCZ showed a realistic time-mean structure and seasonal cycle, while the simulated CRF showed sensitivity to vertical distribution of cloud water which can be easily altered by the choice of time constant and incloud critical cloud water amount regulators for auto-conversion. The CRF and its feedbacks also have a profound effect on the ITCZ. Even though somewhat weaker than observed, the McRAS-GCM simulation produces robust 30-60 day oscillations in the 200 hPa velocity potential. Two ensembles of 4-summer (July, August, September) simulations, one each for 1987 and 1988 show that the McRAS-GCM simulates realistic and statistically significant precipitation differences over India, Central America, and tropical Africa. Several seasonal simulations were performed with McRAS-GEOS II GCM for the summer (June-July- August) and winter (December-January-February) periods to determine how the simulated clouds and CRFs would be affected by: i) advection of clouds; ii) cloud top entrainment instability, iii) cloud water inhomogeneity correction, and (iv) cloud production and dissipation in different cloud-processes. The results show that each of these processes contributes to the simulated cloud-fraction and CRF.

Cloud properties inferred from 8-12 micron data

NASA Technical Reports Server (NTRS)

Strabala, Kathleen I.; Ackerman, Steven A.; Menzel, W. Paul

1994-01-01

A trispectral combination of observations at 8-, 11-, and 12-micron bands is suggested for detecting cloud and cloud properties in the infrared. Atmospheric ice and water vapor absorption peak in opposite halves of the window region so that positive 8-minus-11-micron brightness temperature differences indicate cloud, while near-zero or negative differences indicate clear regions. The absorption coefficient for water increases more between 11 and 12 microns than between 8 and 11 microns, while for ice, the reverse is true. Cloud phases is determined by a scatter diagram of 8-minus-11-micron versus 11-minus-12-micron brightness temperature differences; ice cloud shows a slope greater than 1 and water cloud less than 1. The trispectral brightness temperature method was tested upon high-resolution interferometer data resulting in clear-cloud and cloud-phase delineation. Simulations using differing 8-micron bandwidths revealed no significant degradation of cloud property detection. Thus, the 8-micron bandwidth for future satellites can be selected based on the requirements of other applications, such as surface characterization studies. Application of the technique to current polar-orbiting High-Resolution Infrared Sounder (HIRS)-Advanced Very High Resolution Radiometer (AVHRR) datasets is constrained by the nonuniformity of the cloud scenes sensed within the large HIRS field of view. Analysis of MAS (MODIS Airborne Simulator) high-spatial resolution (500 m) data with all three 8-, 11-, and 12-micron bands revealed sharp delineation of differing cloud and background scenes, from which a simple automated threshold technique was developed. Cloud phase, clear-sky, and qualitative differences in cloud emissivity and cloud height were identified on a case study segment from 24 November 1991, consistent with the scene. More rigorous techniques would allow further cloud parameter clarification. The opportunities for global cloud delineation with the Moderate-Resolution Imaging Spectrometer (MODIS) appear excellent. The spectral selection, the spatial resolution, and the global coverage are all well suited for significant advances.

Surface tension and quasi-emulsion of cavitation bubble cloud.

PubMed

Bai, Lixin; Chen, Xiaoguang; Zhu, Gang; Xu, Weilin; Lin, Weijun; Wu, Pengfei; Li, Chao; Xu, Delong; Yan, Jiuchun

2017-03-01

A quasi-emulsion phenomenon of cavitation structure in a thin liquid layer (the thin liquid layer is trapped between a radiating surface and a hard reflector) is investigated experimentally with high-speed photography. The transformation from cloud-in-water (c/w) emulsion to water-in-cloud (w/c) emulsion is related to the increase of cavitation bubble cloud. The acoustic field in the thin liquid layer is analyzed. It is found that the liquid region has higher acoustic pressure than the cloud region. The bubbles are pushed from liquid region to cloud region by the primary Bjerknes forces. The rate of change of CSF increased with the increase of CSF. The cavitation bubbles on the surface of cavitation cloud are attracted by the cavitation bubbles inside the cloud due to secondary Bjerknes forces. The existence of surface tension on the interface of liquid region and cloud region is proved. The formation mechanism of disc-shaped liquid region and cloud region are analysed by surface tension and incompressibility of cavitation bubble cloud. Copyright © 2016 Elsevier B.V. All rights reserved.

Cloud Microphysics Parameterization in a Shallow Cumulus Cloud Simulated by a Largrangian Cloud Model

NASA Astrophysics Data System (ADS)

Oh, D.; Noh, Y.; Hoffmann, F.; Raasch, S.

2017-12-01

Lagrangian cloud model (LCM) is a fundamentally new approach of cloud simulation, in which the flow field is simulated by large eddy simulation and droplets are treated as Lagrangian particles undergoing cloud microphysics. LCM enables us to investigate raindrop formation and examine the parameterization of cloud microphysics directly by tracking the history of individual Lagrangian droplets simulated by LCM. Analysis of the magnitude of raindrop formation and the background physical conditions at the moment at which every Lagrangian droplet grows from cloud droplets to raindrops in a shallow cumulus cloud reveals how and under which condition raindrops are formed. It also provides information how autoconversion and accretion appear and evolve within a cloud, and how they are affected by various factors such as cloud water mixing ratio, rain water mixing ratio, aerosol concentration, drop size distribution, and dissipation rate. Based on these results, the parameterizations of autoconversion and accretion, such as Kessler (1969), Tripoli and Cotton (1980), Beheng (1994), and Kharioutdonov and Kogan (2000), are examined, and the modifications to improve the parameterizations are proposed.

A satellite observation test bed for cloud parameterization development

NASA Astrophysics Data System (ADS)

Lebsock, M. D.; Suselj, K.

2015-12-01

We present an observational test-bed of cloud and precipitation properties derived from CloudSat, CALIPSO, and the the A-Train. The focus of the test-bed is on marine boundary layer clouds including stratocumulus and cumulus and the transition between these cloud regimes. Test-bed properties include the cloud cover and three dimensional cloud fraction along with the cloud water path and precipitation water content, and associated radiative fluxes. We also include the subgrid scale distribution of cloud and precipitation, and radiaitive quantities, which must be diagnosed by a model parameterization. The test-bed further includes meterological variables from the Modern Era Retrospective-analysis for Research and Applications (MERRA). MERRA variables provide the initialization and forcing datasets to run a parameterization in Single Column Model (SCM) mode. We show comparisons of an Eddy-Diffusivity/Mass-FLux (EDMF) parameterization coupled to micorphsycis and macrophysics packages run in SCM mode with observed clouds. Comparsions are performed regionally in areas of climatological subsidence as well stratified by dynamical and thermodynamical variables. Comparisons demonstrate the ability of the EDMF model to capture the observed transitions between subtropical stratocumulus and cumulus cloud regimes.

Observations of the Global Characteristics and Regional Radiative Effects of Marine Cloud Liquid Water

NASA Technical Reports Server (NTRS)

Greenwald, Thomas J.; Stephens, Graeme L.; Christopher, Sundar A.; Vonder Harr, Thomas H.

1995-01-01

The large-scale spatial distribution and temporal variability of cloud liquid water path (LWP) over the world's oceans and the relationship of cloud LWP to temperature and the radiation budget are investigated using recent satellite measurements from the Special Sensor Microwave/Imager (SSM/I), the Earth Radiation Budget Experiment (ERBE), and the International Satellite Cloud Climatology Project (ISCCP). Observations of cloud liquid water on a 2.5 deg x 2.5 deg and are used over a 53-month period beginning July 1987 and ending in December 1991. The highest values of cloud liquid water (greater than 0.13 kg/sq m) occur largely along principal routes of northern midlatitude storms and in areas dominated by tropical convection. The zonally averaged structure is distinctly trimodal, where maxima appear in the midlatitudes and near the equator. The average marine cloud LWP over the globe is estimated to be about 0.113 kg/sq m. Its highest seasonal variability is typically between 15% and 25% of the annual mean but in certain locations can exceed 30%. Comparisons of cloud LWP to temperature for low clouds during JJA and DJF of 1990 show significant positive correlations at colder temperatures and negative correlations at warmer temperatures. The correlations also exhibit strong seasonal and regional variation. Coincident and collocated observations of cloud LWP from the SSM/I and albedo measurements from the Earth Radiation Budget Satellite (ERBS) and the NOAA-10 satellite are compared for low clouds in the North Pacific and North Atlantic. The observed albedo-LWP relationships correspond reasonably well with theory, where the average cloud effective radius (r(sub e)) is 11.1 microns and the standard deviation is 5.2 microns. The large variability in the inferred values of r(sub e) suggests that other factors may be important in the albedo-LWP relationships. In terms of the effect of the LWP on the net cloud forcing, the authors find that a 0.05 kg/sq m increase in LWP (for LWP less than 0.2 kg/sq m) results in a -25 W/sq m change in the net cloud forcing at a solar zenith angle of 75 deg.

Cloud computing geospatial application for water resources based on free and open source software and open standards - a prototype

NASA Astrophysics Data System (ADS)

Delipetrev, Blagoj

2016-04-01

Presently, most of the existing software is desktop-based, designed to work on a single computer, which represents a major limitation in many ways, starting from limited computer processing, storage power, accessibility, availability, etc. The only feasible solution lies in the web and cloud. This abstract presents research and development of a cloud computing geospatial application for water resources based on free and open source software and open standards using hybrid deployment model of public - private cloud, running on two separate virtual machines (VMs). The first one (VM1) is running on Amazon web services (AWS) and the second one (VM2) is running on a Xen cloud platform. The presented cloud application is developed using free and open source software, open standards and prototype code. The cloud application presents a framework how to develop specialized cloud geospatial application that needs only a web browser to be used. This cloud application is the ultimate collaboration geospatial platform because multiple users across the globe with internet connection and browser can jointly model geospatial objects, enter attribute data and information, execute algorithms, and visualize results. The presented cloud application is: available all the time, accessible from everywhere, it is scalable, works in a distributed computer environment, it creates a real-time multiuser collaboration platform, the programing languages code and components are interoperable, and it is flexible in including additional components. The cloud geospatial application is implemented as a specialized water resources application with three web services for 1) data infrastructure (DI), 2) support for water resources modelling (WRM), 3) user management. The web services are running on two VMs that are communicating over the internet providing services to users. The application was tested on the Zletovica river basin case study with concurrent multiple users. The application is a state-of-the-art cloud geospatial collaboration platform. The presented solution is a prototype and can be used as a foundation for developing of any specialized cloud geospatial applications. Further research will be focused on distributing the cloud application on additional VMs, testing the scalability and availability of services.

The first observed cloud echoes and microphysical parameter retrievals by China's 94-GHz cloud radar

NASA Astrophysics Data System (ADS)

Wu, Juxiu; Wei, Ming; Hang, Xin; Zhou, Jie; Zhang, Peichang; Li, Nan

2014-06-01

By using the cloud echoes first successfully observed by China's indigenous 94-GHz SKY cloud radar, the macrostructure and microphysical properties of drizzling stratocumulus clouds in Anhui Province on 8 June 2013 are analyzed, and the detection capability of this cloud radar is discussed. The results are as follows. (1) The cloud radar is able to observe the time-varying macroscopic and microphysical parameters of clouds, and it can reveal the microscopic structure and small-scale changes of clouds. (2) The velocity spectral width of cloud droplets is small, but the spectral width of the cloud containing both cloud droplets and drizzle is large. When the spectral width is more than 0.4 m s-1, the radar reflectivity factor is larger (over -10 dBZ). (3) The radar's sensitivity is comparatively higher because the minimum radar reflectivity factor is about -35 dBZ in this experiment, which exceeds the threshold for detecting the linear depolarized ratio (LDR) of stratocumulus (commonly -11 to -14 dBZ; decreases with increasing turbulence). (4) After distinguishing of cloud droplets from drizzle, cloud liquid water content and particle effective radius are retrieved. The liquid water content of drizzle is lower than that of cloud droplets at the same radar reflectivity factor.

A Solar Reflectance Method for Retrieving Cloud Optical Thickness and Droplet Size Over Snow and Ice Surfaces

NASA Technical Reports Server (NTRS)

Platnick, S.; Li, J. Y.; King, M. D.; Gerber, H.; Hobbs, P. V.

1999-01-01

Cloud optical thickness and effective radius retrievals from solar reflectance measurements are traditionally implemented using a combination of spectral channels that are absorbing and non-absorbing for water particles. Reflectances in non-absorbing channels (e.g., 0.67, 0.86, 1.2 micron spectral window bands) are largely dependent on cloud optical thickness, while longer wavelength absorbing channels (1.6, 2. 1, and 3.7 micron window bands) provide cloud particle size information. Cloud retrievals over ice and snow surfaces present serious difficulties. At the shorter wavelengths, ice is bright and highly variable, both characteristics acting to significantly increase cloud retrieval uncertainty. In contrast, reflectances at the longer wavelengths are relatively small and may be comparable to that of dark open water. A modification to the traditional cloud retrieval technique is devised. The new algorithm uses only a combination of absorbing spectral channels for which the snow/ice albedo is relatively small. Using this approach, retrievals have been made with the MODIS Airborne Simulator (MAS) imager flown aboard the NASA ER-2 from May - June 1998 during the Arctic FIRE-ACE field deployment. Data from several coordinated ER-2 and University of Washington CV-580 in situ aircraft observations of liquid water stratus clouds are examined. MAS retrievals of optical thickness, droplet effective radius, and liquid water path are shown to be in good agreement with the in situ measurements. The initial success of the technique has implications for future operational satellite cloud retrieval algorithms in polar and wintertime regions.

Hydrologic exchanges and baldcypress water use on deltaic hummocks, Louisiana, USA

USGS Publications Warehouse

Hsueh, Yu-Hsin; Chambers, Jim L.; Krauss, Ken W.; Allen, Scott T.; Keim, Richard F.

2016-01-01

Coastal forested hummocks support clusters of trees in the saltwater–freshwater transition zone. To examine how hummocks support trees in mesohaline sites that are beyond physiological limits of the trees, we used salinity and stable isotopes (2H and 18O) of water as tracers to understand water fluxes in hummocks and uptake by baldcypress (Taxodium distichum (L.) Rich.), which is the most abundant tree species in coastal freshwater forests of the southeastern U.S. Hummocks were always partially submerged and were completely submerged 1 to 8% of the time during the two studied growing seasons, in association with high water in the estuary. Salinity, δ18O, and δ2H varied more in the shallow open water than in groundwater. Surface water and shallow groundwater were similar to throughfall in isotopic composition, which suggested dominance by rainfall. Salinity of groundwater in hummocks increased with depth, was higher than in swales, and fluctuated little over time. Isotopic composition of xylem water in baldcypress was similar to the vadose zone and unlike other measured sources, indicating that trees preferentially use unsaturated hummock tops as refugia from higher salinity and saturated soil in swales and the lower portions of hummocks. Sustained upward gradients of salinity from groundwater to surface water and vadose water, and low variation in groundwater salinity and isotopic composition, suggested long residence time, limited exchange with surface water, and that the shallow subsurface of hummocks is characterized by episodic salinization and slow dilution.

4-D Cloud Water Content Fields Derived from Operational Satellite Data

NASA Technical Reports Server (NTRS)

Smith, William L., Jr.; Minnis, Patrick

2010-01-01

In order to improve operational safety and efficiency, the transportation industry, including aviation, has an urgent need for accurate diagnoses and predictions of clouds and associated weather conditions. Adverse weather accounts for 70% of all air traffic delays within the U.S. National Airspace System. The Federal Aviation Administration has determined that as much as two thirds of weather-related delays are potentially avoidable with better weather information and roughly 20% of all aviation accidents are weather related. Thus, it is recognized that an important factor in meeting the goals of the Next Generation Transportation System (NexGen) vision is the improved integration of weather information. The concept of a 4-D weather cube is being developed to address that need by integrating observed and forecasted weather information into a shared 4-D database, providing an integrated and nationally consistent weather picture for a variety of users and to support operational decision support systems. Weather analyses and forecasts derived using Numerical Weather Prediction (NWP) models are a critical tool that forecasters rely on for guidance and also an important element in current and future decision support systems. For example, the Rapid Update Cycle (RUC) and the recently implemented Rapid Refresh (RR) Weather Research and Forecast (WRF) models provide high frequency forecasts and are key elements of the FAA Aviation Weather Research Program. Because clouds play a crucial role in the dynamics and thermodynamics of the atmosphere, they must be adequately accounted for in NWP models. The RUC, for example, cycles at full resolution five cloud microphysical species (cloud water, cloud ice, rain, snow, and graupel) and has the capability of updating these fields from observations. In order to improve the models initial state and subsequent forecasts, cloud top altitude (or temperature, T(sub c)) derived from operational satellite data, surface observations of cloud base altitude, radar reflectivity, and lightning data are used to help build and remove clouds in the models assimilation system. Despite this advance and the many recent advances made in our understanding of cloud physical processes and radiative effects, many problems remain in adequately representing clouds in models. While the assimilation of cloud top information derived from operational satellite data has merit, other information is available that has not yet been exploited. For example, the vertically integrated cloud water content (CWC) or cloud water path (CWP) and cloud geometric thickness (delta Z) are standard products being derived routinely from operational satellite data. These and other cloud products have been validated under a variety of conditions. Since the uncertainties have generally been found to be less than those found in model analyses and forecasts, the satellite products should be suitable for data assimilation, provided an appropriate strategy can be developed that links the satellite-derived cloud parameters with cloud parameters specified in the model. In this paper, we briefly outline such a strategy and describe a methodology to retrieve cloud water content profiles from operational satellite data. Initial results and future plans are presented. It is expected that the direct assimilation of this new product will provide the most accurate depiction of the vertical distribution of cloud water ever produced at the high spatial and temporal resolution needed for short term weather analyses and forecasts.

Sensitivity of Stratocumulus Optical Depths to Droplet Concentrations: Satellite Observations and Large-Eddy Simulations

NASA Technical Reports Server (NTRS)

Ackerman, A. S.; Stevens, D. E.; Toon, O. B.; Coakley, J. A., Jr.; Gore, Warren J. (Technical Monitor)

2002-01-01

A number of observations and simulations have shown that increased droplet concentrations in ship tracks increase their total cross-sectional area, thereby enhancing cloud albedo and providing a negative (cooling) radiative forcing at the surface and the top of the atmosphere. In some cases cloud water has been found to be enhanced in ship tracks, which has been attributed to suppression of drizzle and implies an enhanced susceptibility of cloud albedo to droplet concentrations. However, observations from aircraft and satellite indicate that on average cloud water is instead reduced in daytime ship tracks. Such a reduction in liquid water may be attributable to cloud-burning caused by solar heating by soot within the ship exhaust, or by increased precipitation resulting from giant nuclei in the ship exhaust. We will summarize the observational evidence and present results from large-eddy simulations that evaluate these mechanisms. Along the way we will present our insights into the interpretation of satellite retrievals of cloud microphysical properties.

Detection of single and multilayer clouds in an artificial neural network approach

NASA Astrophysics Data System (ADS)

Sun-Mack, Sunny; Minnis, Patrick; Smith, William L.; Hong, Gang; Chen, Yan

2017-10-01

Determining whether a scene observed with a satellite imager is composed of a thin cirrus over a water cloud or thick cirrus contiguous with underlying layers of ice and water clouds is often difficult because of similarities in the observed radiance values. In this paper an artificial neural network (ANN) algorithm, employing several Aqua MODIS infrared channels and the retrieved total cloud visible optical depth, is trained to detect multilayer ice-over-water cloud systems as identified by matched April 2009 CloudSat and CALIPSO (CC) data. The CC lidar and radar profiles provide the vertical structure that serves as output truth for a multilayer ANN, or MLANN, algorithm. Applying the trained MLANN to independent July 2008 MODIS data resulted in a combined ML and single layer hit rate of 75% (72%) for nonpolar regions during the day (night). The results are comparable to or more accurate than currently available methods. Areas of improvement are identified and will be addressed in future versions of the MLANN.

On the relationships among cloud cover, mixed-phase partitioning, and planetary albedo in GCMs

DOE PAGES

McCoy, Daniel T.; Tan, Ivy; Hartmann, Dennis L.; ...

2016-05-06

In this study, it is shown that CMIP5 global climate models (GCMs) that convert supercooled water to ice at relatively warm temperatures tend to have a greater mean-state cloud fraction and more negative cloud feedback in the middle and high latitude Southern Hemisphere. We investigate possible reasons for these relationships by analyzing the mixed-phase parameterizations in 26 GCMs. The atmospheric temperature where ice and liquid are equally prevalent (T5050) is used to characterize the mixed-phase parameterization in each GCM. Liquid clouds have a higher albedo than ice clouds, so, all else being equal, models with more supercooled liquid water wouldmore » also have a higher planetary albedo. The lower cloud fraction in these models compensates the higher cloud reflectivity and results in clouds that reflect shortwave radiation (SW) in reasonable agreement with observations, but gives clouds that are too bright and too few. The temperature at which supercooled liquid can remain unfrozen is strongly anti-correlated with cloud fraction in the climate mean state across the model ensemble, but we know of no robust physical mechanism to explain this behavior, especially because this anti-correlation extends through the subtropics. A set of perturbed physics simulations with the Community Atmospheric Model Version 4 (CAM4) shows that, if its temperature-dependent phase partitioning is varied and the critical relative humidity for cloud formation in each model run is also tuned to bring reflected SW into agreement with observations, then cloud fraction increases and liquid water path (LWP) decreases with T5050, as in the CMIP5 ensemble.« less

Reconciling the aerosol-liquid water path relationship in the ECHAM6-HAM GCM and the Aerosol_cci/Cloud_cci (A)ATSR dataset by minimizing the effect of aerosol swelling

NASA Astrophysics Data System (ADS)

Neubauer, D.; Christensen, M.; Lohmann, U.; Poulsen, C. A.

2016-12-01

Studies using present day variability to assess statistical relationships between aerosol and cloud properties find different strengths of these relationships between satellite data and general circulation model (GCM) data. This discrepancy can be explained by structural uncertainties due to differences in the analysis/observational scale and the process scale or spurious relationships between aerosol and cloud properties. Such spurious relationships are the growth of aerosol particles in the humid environment surrounding clouds, misclassification of partly cloudy satellite pixels as cloud free pixels, brightening of aerosol particles by sunlight reflected at cloud edges, or effects of clouds on aerosol like processing of aerosol particles in clouds by nucleation or impact scavenging and subsequent growth by heterogeneous chemistry and release by cloud droplet evaporation or wet scavenging of aerosol particles. To minimize the effects of spatial aggregation and spurious relationships we apply a new nearest neighbour approach to high resolution (A)ATSR datasets from the Aerosol_cci and Cloud_cci projects of the Climate Change Initiative (CCI) programme of ESA. For the ECHAM6-HAM GCM we quantify the impact of using dry aerosol (without aerosol water) in the analysis to mimic the effect of the nearest neighbour approach. The aerosol-liquid water path relationship in ECHAM6-HAM is systematically stronger than in (A)ATSR data and cannot be explained by an overestimation of autoconversion when using diagnostic precipitation but rather by aerosol swelling in regions where humidity is high and clouds are present. When aerosol water is removed from the analysis in ECHAM6-HAM the strength of the aerosol-liquid water path relationship agrees much better with the ones of (A)ATSR or MODIS. We further find that while the observed relationships of different satellite sensors ((A)ATSR vs. MODIS) are not always consistent for tested environmental conditions the relationships in ECHAM6-HAM are missing a strong dependence on environmental conditions which is critical for bridging the gap between satellite and model estimates of aerosol indirect forcing.

Two space scatterer formalism calculation of bulk parameters of thunderclouds

NASA Technical Reports Server (NTRS)

Phanord, Dieudonne D.

1994-01-01

In a previous study, we used a modified two-space scatterer formalism of Twersky to establish for a cloud modeled as a statistically homogeneous distribution of spherical water droplets, the dispersion relations that determine its bulk propagation numbers and bulk indexes of refraction in terms of the vector equivalent scattering amplitude and the dyadic scattering amplitude of the single water droplet in isolation. The results were specialized to the forward direction of scattering while demanding that the scatterers preserve the incident polarization. We apply this approach to obtain specific numerical values for the macroscopic parameters of the cloud. We work with a cloud of density rho = 100 cm(exp -3), a wavelength lambda = 0.7774 microns, and with spherical water droplets of common radius alpha = 10 microns. In addition, the scattering medium is divided into three parts, the medium outside the cloud, moist air (the medium inside the cloud but outside the droplets), and the medium inside the spherical water droplets. The results of this report are applicable to a cloud of any geometry since the boundary does not interfere with the calculations. Also, it is important to notice the plane wave nature of the incidence wave in the moist atmosphere.

Using Long‐Term Satellite Observations to Identify Sensitive Regimes and Active Regions of Aerosol Indirect Effects for Liquid Clouds Over Global Oceans

PubMed Central

Liu, Yangang; Yu, Fangquan; Heidinger, Andrew K.

2018-01-01

Abstract Long‐term (1981–2011) satellite climate data records of clouds and aerosols are used to investigate the aerosol‐cloud interaction of marine water cloud from a climatology perspective. Our focus is on identifying the regimes and regions where the aerosol indirect effects (AIEs) are evident in long‐term averages over the global oceans through analyzing the correlation features between aerosol loading and the key cloud variables including cloud droplet effective radius (CDER), cloud optical depth (COD), cloud water path (CWP), cloud top height (CTH), and cloud top temperature (CTT). An aerosol optical thickness (AOT) range of 0.13 < AOT < 0.3 is identified as the sensitive regime of the conventional first AIE where CDER is more susceptible to AOT than the other cloud variables. The first AIE that manifests as the change of long‐term averaged CDER appears only in limited oceanic regions. The signature of aerosol invigoration of water clouds as revealed by the increase of cloud cover fraction (CCF) and CTH with increasing AOT at the middle/high latitudes of both hemispheres is identified for a pristine atmosphere (AOT < 0.08). Aerosol invigoration signature is also revealed by the concurrent increase of CDER, COD, and CWP with increasing AOT for a polluted marine atmosphere (AOT > 0.3) in the tropical convergence zones. The regions where the second AIE is likely to manifest in the CCF change are limited to several oceanic areas with high CCF of the warm water clouds near the western coasts of continents. The second AIE signature as represented by the reduction of the precipitation efficiency with increasing AOT is more likely to be observed in the AOT regime of 0.08 < AOT < 0.4. The corresponding AIE active regions manifested themselves as the decline of the precipitation efficiency are mainly limited to the oceanic areas downwind of continental aerosols. The sensitive regime of the conventional AIE identified in this observational study is likely associated with the transitional regime from the aerosol‐limited regime to the updraft‐limited regime identified for aerosol‐cloud interaction in cloud model simulations. PMID:29527427

Entrainment in Laboratory Simulations of Cumulus Cloud Flows

NASA Astrophysics Data System (ADS)

Narasimha, R.; Diwan, S.; Subrahmanyam, D.; Sreenivas, K. R.; Bhat, G. S.

2010-12-01

A variety of cumulus cloud flows, including congestus (both shallow bubble and tall tower types), mediocris and fractus have been generated in a water tank by simulating the release of latent heat in real clouds. The simulation is achieved through ohmic heating, injected volumetrically into the flow by applying suitable voltages between diametral cross-sections of starting jets and plumes of electrically conducting fluid (acidified water). Dynamical similarity between atmospheric and laboratory cloud flows is achieved by duplicating values of an appropriate non-dimensional heat release number. Velocity measurements, made by laser instrumentation, show that the Taylor entrainment coefficient generally increases just above the level of commencement of heat injection (corresponding to condensation level in the real cloud). Subsequently the coefficient reaches a maximum before declining to the very low values that characterize tall cumulus towers. The experiments also simulate the protected core of real clouds. Cumulus Congestus : Atmospheric cloud (left), simulated laboratory cloud (right). Panels below show respectively total heat injected and vertical profile of heating in the laboratory cloud.