The seasonal cycle of biogenic ice-nucleating particles in a boreal forest environment

2020 ◽  
Author(s):  
Julia Schneider ◽  
Kristina Höhler ◽  
Paavo Heikkilä ◽  
Jorma Keskinen ◽  
Barbara Bertozzi ◽  
...  
Keyword(s):  
Boreal Forest ◽  
Seasonal Cycle ◽  
Field Measurements ◽  
Climate Projections ◽  
Research Station ◽  
Forest Environment ◽  
Institute Of Technology ◽  
The University ◽  
Karlsruhe Institute

<p>By triggering the formation of cloud ice crystals in the atmosphere, ice-nucleating particles (INP) strongly influence cloud properties, cloud life cycle and precipitation. Describing the abundance of atmospheric INPs in weather forecasts and climate projections remains challenging, as the global distribution and variability of INPs depend on a variety of different aerosol types and sources. Although widespread field measurements have been conducted, neither short-term variability nor long-term seasonal cycles have yet been well characterized by continuous measurements. In 2018, the University of Helsinki and the Karlsruhe Institute of Technology (KIT) initiated a field campaign HyICE to perform comprehensive long-term INP measurements in the Finnish boreal forest. The campaign took place in Hyytiälä, Southern Finland at the University of Helsinki SMEARII research station (Hari and Kulmala, 2005). KIT provided the INSEKT (Ice Nucleation Spectrometer of the Karlsruhe Institute of Technology) to analyse the INP content of ambient aerosols sampled on filters. INSEKT is able to measure INP concentrations in the immersion-freezing mode at temperatures between 273 K and 248 K. The measurements started in March 2018 and ended in May 2019, which provides a unique continuous long-term time series of INP concentrations for over more than one year with a time resolution of about one to three days. This long-term observation record is used to examine systematic seasonal trends in the INP concentrations and to find meteorological and aerosol related parameters to describe the observed trends and variabilities. These findings will enable to find new parameterizations of atmospheric INP concentrations, as current parameterizations do not reproduce the observed seasonal cycle yet. In addition to INP concentration measurements, heat treatment tests of the aerosol samples have been conducted providing additional indications about the INP types dominating the INP population in the boreal forest, also in dependence on the season. Finally, this contribution will summarize and discuss major findings and implications from the HyICE long-term INP observation.</p><p> </p><p>Hari and Kulmala (2005), Boreal Environ Res. 14, 315-322.</p>

scholarly journals The seasonal cycle of ice-nucleating particles linked to the abundance of biogenic aerosol in boreal forests

2020 ◽  
Author(s):  
Julia Schneider ◽  
Kristina Höhler ◽  
Paavo Heikkilä ◽  
Jorma Keskinen ◽  
Barbara Bertozzi ◽  
...  
Keyword(s):  
Seasonal Variation ◽  
Boreal Forest ◽  
Seasonal Cycle ◽  
Weather Forecasting ◽  
Late Summer ◽  
Active Surface ◽  
Ambient Air ◽  
Ice Nucleation ◽  
Forest Environment ◽  
New Findings

Abstract. Ice-nucleating particles (INPs) trigger the formation of cloud ice crystals in the atmosphere. Therefore, they strongly influence cloud microphysical and optical properties, as well as precipitation and the life cycle of clouds. Improving weather forecasting and climate projection requires an appropriate formulation of atmospheric INP concentrations. This remains challenging, as the global INP distribution and variability depend on a variety of aerosol types and sources, and neither their short-term variability nor their long-term seasonal cycles are well covered by continuous measurements. Here, we provide the first year-long set of observations with a pronounced INP seasonal cycle in a boreal forest environment. Besides the observed seasonal cycle in INP concentrations with a minimum in wintertime and maxima in early and late summer, we also provide indications for a seasonal variation in the prevalent INP type. We show that the seasonal dependency of INP concentrations and prevalent INP types is most likely driven by the abundance of biogenic aerosol. As current parameterizations do not reproduce this variability, we suggest a new parameterization approach, which considers the seasonal variation of INP concentrations. For this, we use the ambient air temperature as a proxy for the season which affects the source strength of biogenic emissions and by that the INP abundance over the boreal forest areas. Furthermore, we provide new INP parameterizations based on the Ice Nucleation Active Surface Site (INAS) approach, which specifically describes the ice nucleation activity of boreal aerosols particles prevalent in different seasons. Our results characterize the boreal forest as an important but variable INP source and provide new perspectives to describe these new findings in atmospheric models.

Chicago

First Woman ◽  
2020 ◽  
pp. 28-47
Author(s):  
James Rodger Fleming
Keyword(s):  
Weather Forecasting ◽  
Single Mother ◽  
Advanced Training ◽  
Introductory Courses ◽  
Illinois Institute ◽  
War Effort ◽  
Institute Of Technology ◽  
The University ◽  
The Tropics

At age 17, Joanne attended the University of Chicago and enrolled in a number of introductory courses, including astrophysics and psychology. In 1942, at the end of her sophomore year, she met Carl-Gustav Rossby and joined the war effort, working to train aviation cadets for weather forecasting. She pursued advanced training in meteorology, but the all-male Chicago faculty opposed her at every step. Her interest in the tropics was piqued by a class she took with Herbert Riel, and the two began a long-term and fruitful collaboration. Her marriage to meteorologist Victor Starr was short-lived. As a single mother, she earned her PhD while working at the Illinois Institute of Technology.

scholarly journals Measurements of LoRaWAN Technology in Urban Scenarios: A Data Descriptor

Data ◽  
2021 ◽  
Vol 6 (6) ◽  
pp. 62
Author(s):  
Pavel Masek ◽  
Martin Stusek  ◽  
Ekaterina Svertoka  ◽  
Jan Pospisil ◽  
Radim Burget ◽  
...  
Keyword(s):  
Signal To Noise Ratio ◽  
Field Measurements ◽  
Area Network ◽  
Wide Area Network ◽  
Received Signal Strength Indicator ◽  
Transceiver Module ◽  
The University ◽  
Long Term Behavior ◽  
The City

This work is a data descriptor paper for measurements related to various operational aspects of LoRaWAN communication technology collected in Brno, Czech Republic. This paper also provides data characterizing the long-term behavior of the LoRaWAN channel collected during the two-month measurement campaign. It covers two measurement locations, one at the university premises, and the second situated near the city center. The dataset’s primary goal is to provide the researchers lacking LoRaWAN devices with an opportunity to compare and analyze the information obtained from 303 different outdoor test locations transmitting to up to 20 gateways operating in the 868 MHz band in a varying metropolitan landscape. To collect the data, we developed a prototype equipped with a Microchip RN2483 Low-Power Wide-Area Network (LPWAN) LoRaWAN technology transceiver module for the field measurements. As an example of data utilization, we showed the Signal-to-noise Ratio (SNR) and Received Signal Strength Indicator (RSSI) in relation to the closest gateway distance.

scholarly journals Estimates of the organic aerosol volatility in a boreal forest using two independent methods

2017 ◽  
Vol 17 (6) ◽  
pp. 4387-4399 ◽  
Author(s):  
Juan Hong ◽  
Mikko Äijälä ◽  
Silja A. K. Häme ◽  
Liqing Hao ◽  
Jonathan Duplissy ◽  
...  
Keyword(s):  
Boreal Forest ◽  
Organic Aerosols ◽  
Field Measurements ◽  
Accommodation Coefficient ◽  
Vaporization Enthalpy ◽  
Particle Phase ◽  
Forest Environment ◽  
Aerosol Mass ◽  
Mass Accommodation Coefficient ◽  
Mass Fractions

Abstract. The volatility distribution of secondary organic aerosols that formed and had undergone aging – i.e., the particle mass fractions of semi-volatile, low-volatility and extremely low volatility organic compounds in the particle phase – was characterized in a boreal forest environment of Hyytiälä, southern Finland. This was done by interpreting field measurements using a volatility tandem differential mobility analyzer (VTDMA) with a kinetic evaporation model. The field measurements were performed during April and May 2014. On average, 40 % of the organics in particles were semi-volatile, 34 % were low-volatility organics and 26 % were extremely low volatility organics. The model was, however, very sensitive to the vaporization enthalpies assumed for the organics (ΔHVAP). The best agreement between the observed and modeled temperature dependence of the evaporation was obtained when effective vaporization enthalpy values of 80 kJ mol−1 were assumed. There are several potential reasons for the low effective enthalpy value, including molecular decomposition or dissociation that might occur in the particle phase upon heating, mixture effects and compound-dependent uncertainties in the mass accommodation coefficient. In addition to the VTDMA-based analysis, semi-volatile and low-volatility organic mass fractions were independently determined by applying positive matrix factorization (PMF) to high-resolution aerosol mass spectrometer (HR-AMS) data. The factor separation was based on the oxygenation levels of organics, specifically the relative abundance of mass ions at m∕z 43 (f43) and m∕z 44 (f44). The mass fractions of these two organic groups were compared against the VTDMA-based results. In general, the best agreement between the VTDMA results and the PMF-derived mass fractions of organics was obtained when ΔHVAP =  80 kJ mol−1 was set for all organic groups in the model, with a linear correlation coefficient of around 0.4. However, this still indicates that only about 16 % (R2) of the variation can be explained by the linear regression between the results from these two methods. The prospect of determining of extremely low volatility organic aerosols (ELVOAs) from AMS data using the PMF analysis should be assessed in future studies.

scholarly journals The seasonal cycle of ice-nucleating particles linked to the abundance of biogenic aerosol in boreal forests

2021 ◽  
Vol 21 (5) ◽  
pp. 3899-3918
Author(s):  
Julia Schneider ◽  
Kristina Höhler ◽  
Paavo Heikkilä ◽  
Jorma Keskinen ◽  
Barbara Bertozzi ◽  
...  
Keyword(s):  
Seasonal Variation ◽  
Boreal Forest ◽  
Seasonal Cycle ◽  
Weather Forecasting ◽  
Late Summer ◽  
Active Surface ◽  
Ambient Air ◽  
Ice Nucleation ◽  
Forest Environment ◽  
New Findings

Abstract. Ice-nucleating particles (INPs) trigger the formation of cloud ice crystals in the atmosphere. Therefore, they strongly influence cloud microphysical and optical properties and precipitation and the life cycle of clouds. Improving weather forecasting and climate projection requires an appropriate formulation of atmospheric INP concentrations. This remains challenging as the global INP distribution and variability depend on a variety of aerosol types and sources, and neither their short-term variability nor their long-term seasonal cycles are well covered by continuous measurements. Here, we provide the first year-long set of observations with a pronounced INP seasonal cycle in a boreal forest environment. Besides the observed seasonal cycle in INP concentrations with a minimum in wintertime and maxima in early and late summer, we also provide indications for a seasonal variation in the prevalent INP type. We show that the seasonal dependency of INP concentrations and prevalent INP types is most likely driven by the abundance of biogenic aerosol. As current parameterizations do not reproduce this variability, we suggest a new mechanistic description for boreal forest environments which considers the seasonal variation in INP concentrations. For this, we use the ambient air temperature measured close to the ground at 4.2 m height as a proxy for the season, which appears to affect the source strength of biogenic emissions and, thus, the INP abundance over the boreal forest. Furthermore, we provide new INP parameterizations based on the Ice Nucleation Active Surface Site (INAS) approach, which specifically describes the ice nucleation activity of boreal aerosols particles prevalent in different seasons. Our results characterize the boreal forest as an important but variable INP source and provide new perspectives to describe these new findings in atmospheric models.

scholarly journals Estimates of the organic aerosol volatility in a boreal forest using two independent methods

2016 ◽  
Author(s):  
Juan Hong ◽  
Mikko Äijälä ◽  
Silja A. K. Häme ◽  
Liqing Hao ◽  
Jonathan Duplissy ◽  
...  
Keyword(s):  
Boreal Forest ◽  
Organic Aerosols ◽  
Field Measurements ◽  
Accommodation Coefficient ◽  
Vaporization Enthalpy ◽  
Forest Environment ◽  
Aerosol Mass ◽  
Mass Accommodation Coefficient ◽  
Volatile Organic ◽  
Mass Fractions

Abstract. Volatility distribution of secondary organic aerosols, i.e. the particle mass fractions of semi-volatile, low-volatility and extremely low-volatility organic compounds was characterized in a boreal forest environment of Hyytiälä, Southern Finland. This was done by interpreting field measurements using a Volatility Tandem Differential Mobility Analyzer (VTDMA) with a kinetic evaporation model. The field measurements were performed during April and May of 2014. On average, 40 % of organics in particles was semi-volatile; 34 % low-volatility organics and 26 % extremely low-volatility organics. The model was, however, very sensitive towards the vaporization enthalpies assumed for the organics (ΔHVAP). The best agreement between the observed and modeled temperature-dependence of the evaporation was obtained when effective vaporization enthalpy values of 80 kJ/mol were assumed. The low effective enthalpy value might result from several potential reasons, including molecular decomposition or dissociation that might occur in the particle phase upon heating, mixture effects and compound-dependent uncertainties in the mass accommodation coefficient. In addition to the VTDMA-based analysis, semi-volatile and low-volatile organic mass fractions were independently determined by applying Positive Matrix Factorization (PMF) to High-Resolution Aerosol Mass Spectrometer (HR-AMS) data. The factor separation was based on the oxygenation levels of organics, specifically the relative abundance of mass ions at m/z 43 (f43) and m/z 44 (f44). The mass fractions of these two organic groups were compared against the VTDMA-based results. In general, the agreement between the VTDMA results and the PMF-derived mass fractions of organics was reasonable with a linear correlation coefficient of around 0.4 with ΔHVAP = 80 kJ/mol set for all organic groups. The prospect of determining of extremely low volatile organic aerosols (ELVOA) from AMS data using the PMF analysis should be assessed in future studies.

From Volunteering to Academic Programming: A Case Example

2016 ◽  
Vol 1 (17) ◽  
pp. 7-11 ◽  
Author(s):  
Cindy Gill ◽  
Sneha Bharadwaj ◽  
Nancy Quick ◽  
Sarah Wainscott ◽  
Paula Chance
Keyword(s):  
Special Needs ◽  
Cultural Relevance ◽  
Master's Program ◽  
Speech Language Pathology ◽  
Community Based ◽  
Charitable Organization ◽  
Language Pathology ◽  
The University

A speech-language pathology master's program that grew out of a partnership between the University of Zambia and a U.S.-based charitable organization, Connective Link Among Special needs Programs (CLASP) International, has just been completed in Zambia. The review of this program is outlined according to the suggested principles for community-based partnerships, a framework which may help evaluate cultural relevance and sustainability in long-term volunteer efforts (Israel, Schulz, Parker, & Becker, 1998).

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