Ice-nucleating Macromolecules from Alpine Forests as Possible Contributors to Cloud Glaciation Processes

2020 ◽  
Author(s):  
Teresa M. Seifried ◽  
Paul Bieber ◽  
Laura Felgitsch ◽  
Hinrich Grothe
Keyword(s):  
Land Surface ◽  
Global Climate ◽  
Life Time ◽  
Ice Nucleation ◽  
Radiative Properties ◽  
Small Scale ◽  
Emission Rates ◽  
Sampling Systems ◽  
Rain Fall

<p>Ice nucleation in the atmosphere leads to the formation of mixed-phase as well as cirrus clouds in the upper troposphere. Cloud glaciation can either occur homogeneously at temperatures below -38°C or heterogeneously in the presence of ice-nucleating particles (INPs) at temperatures higher than -38°C. Depending on the aggregate state of a cloud, it’s life time and radiative properties vary and thus affect regional and global climate. The influence of biogenic INPs on atmospheric processes as well as the transport of these particles from the land surface to the atmosphere remains elusive. Several plants from boreal and alpine forests are known to contain ice-nucleating macromolecules (INMs) to survive in extreme conditions. However, less is known about chemical characteristics and actual emission rates of such INMs.</p><p>We present here our investigation of surface extracts from different tree tissues (Betula pendula and Pinus sylvestris). We were able to extract INMs from nearly all samples. Furthermore, we analyzed the ability of these INMs to be released during rain fall events in-situ. To investigate possible transport mechanisms of INMs from the canopy of studied tree species to the atmosphere we sampled aerosols with two small scale drones, carrying our self-build sampling systems called DAPSI (Drone-based Aerosol Particles Sampling Impinger/Impactor). Results indicate that birches and pines outline an important source of airborne biogenic INPs.</p>

scholarly journals An Effective Similar-Pixel Reconstruction of the High-Frequency Cloud-Covered Areas of Southwest China

2019 ◽  
Vol 11 (3) ◽  
pp. 336 ◽  
Author(s):  
Wenping Yu ◽  
Junlei Tan ◽  
Mingguo Ma ◽  
Xiaolu Li ◽  
Xiaojun She ◽  
...  
Keyword(s):  
Land Surface ◽  
High Frequency ◽  
Southwest China ◽  
Global Climate ◽  
Average Error ◽  
Balance Theory ◽  
High Temporal Resolution ◽  
Retrieval Accuracy ◽  
Southwest Region

With advantages of multispatial resolutions, a high retrieval accuracy, and a high temporal resolution, the satellite-derived land surface temperature (LST) products are very important LST sources. However, the greatest barrier to their wide application is the invalid values produced by large quantities of cloudy pixels, especially for regions frequently swathed in clouds. In this study, an effective method based on the land energy balance theory and similar pixels (SP) method was developed to reconstruct the LSTs over cloudy pixels for the widely used MODIS LST (MOD11A1). The southwest region of China was selected as the study area, where extreme drought has frequently occurred in recent years in the context of global climate change and which commonly exhibits cloudy and foggy weather. The validation results compared with in situ LSTs showed that the reconstructed LSTs have an average error < 1.00 K (0.57 K at night and -0.14 K during the day) and an RMSE < 3.20 K (1.90 K at night and 3.16 K in the daytime). The experiment testing the SP interpolation indicated that the spatial structure of the LST has a greater effect on the SP performance than the size of the data-missing area, which benefits the LST reconstruction in the area frequently covered by large clouds.

scholarly journals Peatlands and the carbon cycle: from local processes to global implications – a synthesis

2008 ◽  
Vol 5 (5) ◽  
pp. 1475-1491 ◽  
Author(s):  
J. Limpens ◽  
F. Berendse ◽  
C. Blodau ◽  
J. G. Canadell ◽  
C. Freeman ◽  
...  
Keyword(s):  
Climate Change ◽  
Land Surface ◽  
Climate Models ◽  
Global Climate ◽  
Global Climate Models ◽  
Trace Gas ◽  
Future Climate Change ◽  
Small Scale ◽  
Ecosystem Structure ◽  
Positive Feedbacks

Abstract. Peatlands cover only 3% of the Earth's land surface but boreal and subarctic peatlands store about 15–30% of the world's soil carbon (C) as peat. Despite their potential for large positive feedbacks to the climate system through sequestration and emission of greenhouse gases, peatlands are not explicitly included in global climate models and therefore in predictions of future climate change. In April 2007 a symposium was held in Wageningen, the Netherlands, to advance our understanding of peatland C cycling. This paper synthesizes the main findings of the symposium, focusing on (i) small-scale processes, (ii) C fluxes at the landscape scale, and (iii) peatlands in the context of climate change. The main drivers controlling C fluxes are largely scale dependent and most are related to some aspects of hydrology. Despite high spatial and annual variability in Net Ecosystem Exchange (NEE), the differences in cumulative annual NEE are more a function of broad scale geographic location and physical setting than internal factors, suggesting the existence of strong feedbacks. In contrast, trace gas emissions seem mainly controlled by local factors. Key uncertainties remain concerning the existence of perturbation thresholds, the relative strengths of the CO2 and CH4 feedback, the links among peatland surface climate, hydrology, ecosystem structure and function, and trace gas biogeochemistry as well as the similarity of process rates across peatland types and climatic zones. Progress on these research areas can only be realized by stronger co-operation between disciplines that address different spatial and temporal scales.

scholarly journals On the Susceptibility of Cold Tropical Cirrus to Ice Nuclei Abundance

2016 ◽  
Vol 73 (6) ◽  
pp. 2445-2464 ◽  
Author(s):  
Eric J. Jensen ◽  
Rei Ueyama ◽  
Leonhard Pfister ◽  
Thaopaul V. Bui ◽  
R. Paul Lawson ◽  
...  
Keyword(s):  
High Frequency ◽  
Regional Distribution ◽  
Ice Nucleation ◽  
Small Scale ◽  
Height Distribution ◽  
Microphysical Properties ◽  
Ice Nuclei ◽  
High Frequency Waves ◽  
The Impact

Abstract Numerical simulations of cirrus formation in the tropical tropopause layer (TTL) during boreal wintertime are used to evaluate the impact of heterogeneous ice nuclei (IN) abundance on cold cloud microphysical properties and occurrence frequencies. The cirrus model includes homogeneous and heterogeneous ice nucleation, deposition growth/sublimation, and sedimentation. Reanalysis temperature and wind fields with high-frequency waves superimposed are used to force the simulations. The model results are constrained by comparison with in situ and satellite observations of TTL cirrus and relative humidity. Temperature variability driven by high-frequency waves has a dominant influence on TTL cirrus microphysical properties and occurrence frequencies, and inclusion of these waves is required to produce agreement between the simulated and observed abundance of TTL cirrus. With homogeneous freezing only and small-scale gravity waves included in the temperature curtains, the model produces excessive ice concentrations compared with in situ observations. Inclusion of relatively numerous heterogeneous ice nuclei (NIN ≥ 100 L−1) in the simulations improves the agreement with observed ice concentrations. However, when IN contribute significantly to TTL cirrus ice nucleation, the occurrence frequency of large supersaturations with respect to ice is less than indicated by in situ measurements. The model results suggest that the sensitivity of TTL cirrus extinction and ice water content statistics to heterogeneous ice nuclei abundance is relatively weak. The simulated occurrence frequencies of TTL cirrus are quite insensitive to ice nuclei abundance, both in terms of cloud frequency height distribution and regional distribution throughout the tropics.

scholarly journals Incidence of rough and irregular atmospheric ice particles from Small Ice Detector 3 measurements

2013 ◽  
Vol 13 (9) ◽  
pp. 24975-25012 ◽  
Author(s):  
Z. Ulanowski ◽  
P. H. Kaye ◽  
E. Hirst ◽  
R. S. Greenaway ◽  
R. J. Cotton ◽  
...  
Keyword(s):  
Light Scattering ◽  
Large Scale ◽  
Extreme Values ◽  
Mixed Phase ◽  
Radiative Properties ◽  
Small Scale ◽  
In Situ Data ◽  
Ice Particles ◽  
Test Particles

Abstract. The knowledge of properties of ice crystals such as size, shape, concavity and roughness is critical in the context of radiative properties of ice and mixed phase clouds. Limitations of current cloud probes to measure these properties can be circumvented by acquiring two-dimensional light scattering patterns instead of particle images. Such patterns were obtained in situ for the first time using the Small Ice Detector 3 (SID-3) probe during several flights in a variety of mid-latitude mixed phase and cirrus clouds. The patterns are analyzed using several measures of pattern texture, selected to reveal the magnitude of particle roughness or complexity. The retrieved roughness is compared to values obtained from a range of well-characterized test particles in the laboratory. It is found that typical in situ roughness corresponds to that found in the rougher subset of the test particles, and sometimes even extends beyond the most extreme values found in the laboratory. In this study we do not differentiate between small-scale, fine surface roughness and large-scale crystal complexity. Instead, we argue that both can have similar manifestations in terms of light scattering properties and also similar causes. Overall, the in situ data is consistent with ice particles with highly irregular or rough surfaces being dominant. Similar magnitudes of roughness were found in growth and sublimation zones of cirrus. The roughness was found to be negatively correlated with the halo ratio, but not with other thermodynamic or microphysical properties found in situ. Slightly higher roughness was observed in cirrus forming in clean oceanic airmasses than in a continental, polluted one. Overall, the roughness and complexity is expected to lead to increased shortwave cloud reflectivity, in comparison with cirrus composed of more regular, smooth ice crystal shapes. These findings put into question suggestions that climate could be modified through aerosol seeding to reduce cirrus cover and optical depth, as the seeding may result in decreased shortwave reflectivity.

scholarly journals Cloud-scale ice supersaturated regions spatially correlate with high water vapor heterogeneities

2013 ◽  
Vol 13 (8) ◽  
pp. 22249-22296
Author(s):  
M. Diao ◽  
M. A. Zondlo ◽  
A. J. Heymsfield ◽  
L. M. Avallone ◽  
M. E. Paige ◽  
...  
Keyword(s):  
Water Vapor ◽  
High Water ◽  
Ice Nucleation ◽  
Cloud Formation ◽  
Small Scale ◽  
Cirrus Cloud ◽  
Median Length ◽  
Upper Troposphere ◽  
Earth’S Climate

Abstract. Cirrus clouds have large yet uncertain impacts on the Earth's climate. Ice supersaturation (ISS) – where the relative humidity with respect to ice (RHi) is greater than 100% – is the prerequisite condition of ice nucleation. Here we use 1 Hz (~230 m) in situ aircraft-based observations from 87° N–67° S to analyze the spatial characteristics of ice supersaturated regions (ISSRs). The median length of 1-D horizontal ISSR segments is found to be very small (~1 km), which is two orders of magnitude smaller than previously reported. To understand the conditions of these small scale ISSRs, we compare individual ISSRs with their horizontally adjacent subsaturated surroundings and show that 99% and 73% of the ISSRs are moister and colder, respectively. When quantifying the contributions of water vapor (H2O) and temperature (T) individually, the magnitudes of the differences between the maximum RHi values inside ISSRs (RHimax) and the RHi in subsaturated surroundings are largely derived from the H2O spatial variabilities (by 88%) than from those of T (by 9%). These features hold for both ISSRs with and without ice crystals present. Similar analyses for all RHi horizontal variabilities (including ISS and non-ISS) show strong contributions from H2O variabilities at various T, H2O, pressure (P) and various horizontal scales (~1–100 km). Our results provide a new observational constraint on ISSRs on the microscale (~100 m) and point to the importance of understanding how these fine scale features originate and impact cirrus cloud formation and the RHi field in the upper troposphere (UT).

Combining cirrus cloud CALIPSO (IIR-CALIOP) and aircraft measurements with climate modeling to evaluate the spatial and seasonal radiative impact of homogeneous ice nucleation

2021 ◽  
Author(s):  
David L. Mitchell ◽  
John F. Mejia ◽  
Anne Garnier ◽  
Yuta Tomii ◽  
Martina Krämer ◽  
...  
Keyword(s):  
Experimental Design ◽  
Climate Modeling ◽  
Cloud Microphysics ◽  
Ice Nucleation ◽  
Cirrus Clouds ◽  
Radiative Properties ◽  
Cirrus Cloud ◽  
Modeling Studies ◽  
Northern And Southern Hemispheres

&lt;p&gt;Many global climate modeling studies over the last decade have attempted to evaluate the relative contributions of homo- and heterogeneous ice nucleation (henceforth hom and het) in cirrus clouds, and the radiative contribution of hom relative to het.&amp;#160; There is likely a spatial and seasonal dependence here.&amp;#160; Since the microphysical and radiative properties of hom- and het-dominated cirrus clouds are likely very different, the outcome of such studies may be important to climate science.&amp;#160; But since the physics determining the competition between hom and het is very complex, involving poorly constrained variables, results from such modeling studies have often contradicted each other.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;This study takes a different approach by using CALIPSO satellite effective diameter (D&lt;sub&gt;e&lt;/sub&gt;) retrievals from cirrus clouds, validated by recent in situ measurements (obtained from 24 field campaigns consisting of 150 flights), to constrain the cloud microphysics module (i.e., version 2 of the Morrison-Gettelman scheme or MG2) in the Whole Atmosphere Community Climate Model version 6 (WACCM6). [As a side-note, the ice particle number concentration N was calculated from the retrieved D&lt;sub&gt;e&lt;/sub&gt; and the in situ climatological ice water content and shown to be consistent with N retrievals based on a CloudSat-CALIPSO lidar-radar method]. The MG2 cirrus cloud ice particle size distribution was constrained to conform with these D&lt;sub&gt;e&lt;/sub&gt; retrievals that depend on temperature (T), latitude, season and land fraction (land vs. ocean).&amp;#160; The treatment of ice particle fall speeds was also revised.&amp;#160; Two 40-year WACCM6 simulations were differenced to obtain the radiative contribution of hom; one based on the retrieved D&lt;sub&gt;e&lt;/sub&gt; and one based on retrieved D&lt;sub&gt;e&lt;/sub&gt; corresponding to het conditions (where retrieved N was minimal).&amp;#160; The experimental design assumes hom-affected cirrus occur only outside the &amp;#177; 30 &amp;#176;latitude zone since cirrus within this zone exhibited the lowest N and were thus used to produce the D&lt;sub&gt;e&lt;/sub&gt; &amp;#8211; T look-up tables corresponding to het conditions.&amp;#160; These D&lt;sub&gt;e&lt;/sub&gt; &amp;#8211; T relationships for het conditions were applied to the entire planet in one simulation (labeled HET) while the other simulation (labeled CALCAL for CALIPSO-calibrated) is based on the actual D&lt;sub&gt;e&lt;/sub&gt; retrievals.&amp;#160; CALCAL &amp;#8211; HET differences in the cloud radiative effect (CRE) reveal the estimated CRE effect due to hom.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;The results show CALCAL &amp;#8211; HET CRE differences of 2.4 and 2.5 W m&lt;sup&gt;-2&lt;/sup&gt; in the northern and southern hemispheres, respectively.&amp;#160; These CRE differences are largely due to cirrus-induced changes in mixed phase clouds.&amp;#160; However, top-of-model (TOM) CALCAL &amp;#8211; HET differences in total net forcing did not match these CRE differences due to mid-level increases in relative humidity in HET relative to CALCAL, so that these TOM differences were 1.8 and 2.0 W m&lt;sup&gt;-2&lt;/sup&gt; in the northern and southern hemispheres, respectively.&amp;#160; Radiative contributions from hom were minimal during the summer months (JJA) since shortwave and longwave cloud forcing tends to cancel then.&amp;#160; Other studies show this is true for the tropics (reinforcing the realism of our experimental design from a radiation purview).&amp;#160; During non-summer months, the TOM CALCAL &amp;#8211; HET difference in total net forcing was 2.4 W m&lt;sup&gt;-2&lt;/sup&gt; in both hemispheres.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;

scholarly journals Cloud-scale ice-supersaturated regions spatially correlate with high water vapor heterogeneities

2014 ◽  
Vol 14 (5) ◽  
pp. 2639-2656 ◽  
Author(s):  
M. Diao ◽  
M. A. Zondlo ◽  
A. J. Heymsfield ◽  
L. M. Avallone ◽  
M. E. Paige ◽  
...  
Keyword(s):  
Water Vapor ◽  
High Water ◽  
Ice Nucleation ◽  
Cloud Formation ◽  
Small Scale ◽  
Cirrus Cloud ◽  
Median Length ◽  
Upper Troposphere ◽  
Earth’S Climate

Abstract. Cirrus clouds have large yet uncertain impacts on Earth's climate. Ice supersaturation (ISS) – where the relative humidity with respect to ice (RHi) is greater than 100% – is the prerequisite condition of ice nucleation. Here we use 1 Hz (~230 m) in situ, aircraft-based observations from 87° N to 67° S to analyze the spatial characteristics of ice-supersaturated regions (ISSRs). The median length of 1-D horizontal ISSR segments is found to be very small (~1 km), which is 2 orders of magnitude smaller than previously reported. To understand the conditions of these small-scale ISSRs, we compare individual ISSRs with their horizontally adjacent subsaturated surroundings and show that 99% and 73% of the ISSRs are moister and colder, respectively. When quantifying the contributions of water vapor (H2O) and temperature (T) individually, the magnitudes of the differences between the maximum RHi values inside ISSRs (RHimax) and the RHi in subsaturated surroundings are largely derived from the H2O spatial variabilities (by 88%) than from those of T (by 9%). These features hold for both ISSRs with and without ice crystals present. Similar analyses for all RHi horizontal variabilities (including ISS and non-ISS) show strong contributions from H2O variabilities at various T, H2O, pressure (P) and various horizontal scales (~1–100 km). Our results provide a new observational constraint on ISSRs on the microscale (~100 m) and point to the importance of understanding how these fine-scale features originate and impact cirrus cloud formation and the RHi field in the upper troposphere (UT).

Effects of Aquifer Heterogeneity and Geochemical Variation on Petroleum-Hydrocarbon Biodegradation at a Gasoline Spill Site

2014 ◽  
Vol 1079-1080 ◽  
pp. 584-588 ◽  
Author(s):  
Po Jen Lien ◽  
Hsiao Jung Ho ◽  
Tzu Hsin Lee ◽  
Wen Liang Lai ◽  
Chih Ming Kao
Keyword(s):  
Land Surface ◽  
Petroleum Hydrocarbon ◽  
Microbial Population ◽  
Three Dimensional ◽  
Reduction Process ◽  
Hydrocarbon Biodegradation ◽  
Chemical Extraction ◽  
Small Scale ◽  
Spill Site

In subsurface environment, small-scale heterogeneities usually cause the reduction of the applicability of in situ remedial techniques. Biogeochemical heterogeneities and preferential groundwater flow paths create complex hydrogeologic conditions at most contaminated sites. A thorough understanding of the resulting three-dimensional distribution of contaminants is a necessity prior to determining a need for remediation. In this study, a gasoline spill site was selected to examine the effects of aquifer heterogeneities and geochemical variations on petroleum hydrocarbon biodegradation via different oxidation-reduction process. At this site, two multilevel sampling wells were installed to delineate the lateral (5 m) and vertical (0.5 m) distribution of contaminant concentrations and different biogeochemical parameters. Two 5-cm (I.D.) continuous soil cores [from 4 to 8 m below land surface (bls)] were collected within the gasoline plume to evaluate the distribution of the microbial population in soils. Results show that high microbial activities were observed in soil samples based on the following evidences: (1) high petroleum hydrocarbon degradation rate, and (2) high microbial biomass. Each soil section was used for chemical extraction, microbial enumeration, and grain size distribution. Results show that the soil sections with more permeable sediment materials corresponded with higher biomass (total anaerobes > 2 x 106cells/g) and significant contaminant degradation. However, those sections with less permeable sediments contained lower microbial population. Results indicate that the subsurface microorganisms were distributed unevenly in the aquifer, and some regions were devoid of microorganisms and biodegradation activities. Spatial distribution of microorganisms, soil materials, and biogeochemical characteristics in the subsurface soils control the extent and kinetics of contaminant biodegradation. Thus, using blended aquifer materials for measurement of in situ biodegradation rates may not achieve representative results.

Hyperresolution Land Surface Modeling in the Context of SMAP Cal–Val

2015 ◽  
Vol 17 (1) ◽  
pp. 345-352 ◽  
Author(s):  
Camille Garnaud ◽  
Stéphane Bélair ◽  
Aaron Berg ◽  
Tracy Rowlandson
Keyword(s):  
Soil Moisture ◽  
Soil Temperature ◽  
Land Surface ◽  
Large Scale ◽  
Initial Conditions ◽  
Surface Condition ◽  
Soil Conditions ◽  
Small Scale ◽  
In Situ Observations

Abstract This study explores the performance of Environment Canada’s Surface Prediction System (SPS) in comparison to in situ observations from the Brightwater Creek soil moisture observation network with respect to soil moisture and soil temperature. To do so, SPS is run at hyperresolution (100 m) over a small domain in southern Saskatchewan (Canada) during the summer of 2014. It is shown that with initial conditions and surface condition forcings based on observations, SPS can simulate soil moisture and soil temperature evolution over time with high accuracy (mean bias of 0.01 m3 m−3 and −0.52°C, respectively). However, the modeled spatial variability is generally much weaker than observed. This is likely related to the model’s use of uniform soil texture, the lack of small-scale orography, as well as a predefined crop growth cycle in SPS. Nonetheless, the spatial averages of simulated soil conditions over the domain are very similar to those observed, suggesting that both are representative of large-scale conditions. Thus, in the context of the National Aeronautics and Space Administration’s (NASA) Soil Moisture Active Passive (SMAP) project, this study shows that both simulated and in situ observations can be upscaled to allow future comparison with upcoming satellite data.

scholarly journals Cirrus Clouds

2017 ◽  
Vol 58 ◽  
pp. 2.1-2.26 ◽  
Author(s):  
Andrew J. Heymsfield ◽  
Martina Krämer ◽  
Anna Luebke ◽  
Phil Brown ◽  
Daniel J. Cziczo ◽  
...  
Keyword(s):  
General Circulation ◽  
General Circulation Models ◽  
Ice Nucleation ◽  
In Situ Measurements ◽  
Cirrus Clouds ◽  
Ice Crystals ◽  
Radiative Properties ◽  
Formation Mechanisms ◽  
Wide Range

Abstract The goal of this chapter is to synthesize information about what is now known about one of the three main types of clouds, cirrus, and to identify areas where more knowledge is needed. Cirrus clouds, composed of ice particles, form in the upper troposphere, where temperatures are generally below −30°C. Satellite observations show that the maximum-occurrence frequency of cirrus is near the tropics, with a large latitudinal movement seasonally. In situ measurements obtained over a wide range of cirrus types, formation mechanisms, temperatures, and geographical locations indicate that the ice water content and particle size generally decrease with decreasing temperature, whereas the ice particle concentration is nearly constant or increases slightly with decreasing temperature. High ice concentrations, sometimes observed in strong updrafts, result from homogeneous nucleation. The satellite-based and in situ measurements indicate that cirrus ice crystals typically differ from the simple, idealized geometry for smooth hexagonal shapes, indicating complexity and/or surface roughness. Their shapes significantly impact cirrus radiative properties and feedbacks to climate. Cirrus clouds, one of the most uncertain components of general circulation models (GCM), pose one of the greatest challenges in predicting the rate and geographical pattern of climate change. Improved measurements of the properties and size distributions and surface structure of small ice crystals (about 20 μm) and identifying the dominant ice nucleation process (heterogeneous versus homogeneous ice nucleation) under different cloud dynamical forcings will lead to a better representation of their properties in GCM and in modeling their current and future effects on climate.

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