Boundary layer Evolution Through Harmonization of Aerosol measurements at Ny-Ålesund research stations

Indice Progetti
Acronimo
BETHA-NyÅ
Area di ricerca
Atmospheric sciences
Tematica specifica di ricerca
Regione di interesse
Gruvebadet Svalbard
Sito web progetto
PI
Elena Barbaro
Istituzione PI
Istituto di Scienze Polari - CNR
Sito web istituzionale
https://www.isp.cnr.it/index.php/it/
Altre Istituzioni e soggetti coinvolti
University of Florence; Università degli Studi di Genova; Università degli Studi di Perugia; National Institute for Nuclear Physics (INFN)
Consistenza del team ricerca
Stato progetto
In corso
Il progetto

The Arctic is experiencing the most dramatic impact of t he present climate change, amplifying and driving changes elsewhere in the Earth system. This “Arctic Amplification” is due to peculiar feedbacks between climate forcings and environmental responses, especially involving large changes in surface albedo, over land, sea and long-range transport patterns of air pollutants. A detailed knowledge of the atmospheric processes at different scales can help to define the main causes of “Arctic Amplification”. In this scenario, vertical structure of the Arctic Boundary Layer (ABL) is a key element that can influence aerosol size distribution, chemical composition and its Svalbard is Norway’s northernmost region, and the archipelago is one of the northernmost land-areas in the world. In this archipelago is Ny-Ålesund, a small research town hosting several national and international institutions and their long-term research programmes and projects. This site is a perfect opportunity to investigate ABL thanks to the availability of these three essential facilities in the same place: Gruvebadet (GVB) atmospheric observatory, Zeppelin (ZEP) station and Amundsen-Nobile Climate Change Tower (CCT).
GVB (78.918°N, 11.895°E; 61 m above sea level) is located 800 m south-west of the Ny-Ålesund and it is managed by ISP-CNR. It is an atmospheric laboratory dedicated to the chemical and physical monitoring of atmospheric aerosol begun in 2010 and is still ongoing; the sampling was normally performed from March to October for each year, but since winter 2018/2019, all-year-round samplings have started. Moreover, several campaigns were performed using a tethered balloon equipped also with an optical particle counter (OPC) and meteorological sensors to investigate size-segregated particle samples at ground level and in the free atmosphere and to provide aerosol profiles in and above the boundary layer.
The ZEP observatory (78.908°N, 11.881°E; 474 m above sea level) is located at the top of the Zeppelin mountain, about 3 km from the coast of the fjord and 1 km from GVB. It is owned and managed by the Norwegian Polar Institute and is part of the Global Atmospheric Watch network. Compared to stations closer to sea level, the ZEP station is less affected by local anthropogenic aerosol and pollution sources and by local air flow phenomena such as katabatic winds.
The CCT was installed at the end of 2009 about 2 km west of Ny-Ålesund on the southern coast of Kongsfjorden. The tower is 34-m high and the main sensors are sonic anemometers and low-frequency thermo-hygrometers and anemometers. CCT was conceived to provide a scientific platform for atmospheric monitoring activities in an orographically complex area, to complement other researches, and to host new experiments and instruments devoted to the study of the ABL dynamics, in different atmospheric conditions.
Aerosol plays a relevant role on climate by scattering and absorbing the solar radiation and by influencing cloud formation (i.e. cloud condensation nuclei). Aerosol particles are transported from the middle latitude influencing the composition of Arctic atmosphere, with consequent effects on cloud formation, albedo or sea ice. Several aspects remain poorly known, representing the challenge of the recent aerosol research. For example, organic compounds have notable consequences for atmospheric chemistry and cloud formation, but limited information about the sources of key compound classes such as sugars were produced. On the other hand, the positive forcing of black carbon (BC) is well known because it enhances light absorption processes in the atmosphere, especially in the Arctic, and after its deposition over the glaciers, where triggers and accelerates melting processes. However, the dynamics of BC entertainment in the ABL are still a poorly understood process and may have a wide variability depending on local conditions.
The key challenge of BETHA-NyÅ is to set up an inter-comparison aerosols measurement experiment between GVB and ZEP stations to understand the ABL dynamic effects on the aerosol composition in the Arctic region. The composition data obtained at the two stations will be integrated with meteorological information obtained at CCT and through radiosondes. The sampling alignment in a long-term scenario will be crucial to obtain statistical significant conclusions about the impact of ABL on the atmospheric composition in the Arctic.

 

 

 

Immagini

  • Gruvebadet

  • Motivazione, importanza della ricerca

    Ny-Ålesund is the only Arctic site for aerosol study having two sampling sites, ZEP and GVB, located really close to each other but at different altitudes above sea level. This peculiarity is unique in the polar region and makes possible the study of the influence of the Arctic Boundary Layer (ABL) on aerosol properties. To obtain this information it is necessary (1) to collect measurements at high temporal resolution of chemical markers for local and long range transported aerosol, (2) to harmonize the sampling and analytical procedures between the two sites, (3) to obtain meteorological observations to model the height of ABL and study its structure. By the comparison of measurements and theory, the evolution of ABL along one year of measurements will be achieved. The multidisciplinary character of the project is therefore evident with participation of different expertises including chemistry, atmospheric physics and atmospheric modelling.
    One of the main recommendations reported in the last SESS report 2020 is the data harmonization as well as development of long-term monitoring. The priority is to promote better coordination of observations at existing sites, in order to overcome the lack of common protocols to measure different parameters at different stations. This project transposes this recommendation by sustaining sampling campaigns where the comparability of measurements is the main aim. Common cut-off and/or the use of multiple size classes, temporal resolutions, sampling material, extraction and analysis procedures will be set at the GVB station in order to obtain comparable data with the ZEP measurements. The harmonization will also be performed on several chemical markers, such as BC, EC/OC, major ions, trace
    elements, sugars, and mineralogy of single particles.

    Obiettivi della proposta

    The overall project goal is to investigate the Arctic Boundary Layer (ABL) through the harmonization and synchronization of aerosol measurements performed at GVB and ZEP stations. These sites provide the perfect opportunity because GVB is representative of ground and marine level concentrations, while ZEP is considered to be above the local inversion layer most of the time. The differences in concentration levels and seasonal/interannual trends observed at the two sites can help to better understand the impact of local- and long range sources. Moreover, existing long-time datasets are present from 1993 at ZEP and from 2010 at GVB. Meteorological data obtained by CCT will be integrated to better understand the impact of local sources and long-range transport on ABL.
    To this purpose, we aim to reach several objectives (Os):
    O1 Harmonization of protocols for each measurement, co nsidering the different aspects such as sampling, analytical method, and timing.
    This aim will be obtained also with an inter-comparison between the stations.
    O2 Extension of “harmonized” results in the existing multi-years dataset in bo th stations to obtain an ABL evaluation with a statistical value.
    O3 Imp roving the knowledge of sources, combining all multi-years measurements and applying different source apportionment approaches.
    O4 Use a mu ltidisciplinary approach considering meteorological experimental and theoretical physical expertises to better define ABL characteristics.

    Attività svolta e risultati raggiunti

    The BETHA-NyÅ research will be divided into three work packages (WP), organized in severa l Tasks (T) where the roles of each research unit (RU) are indicated.

    WP1. Harmonization of aerosol measurements at GVB and ZEP stations

    T1.1 Definition of a common protocol for ions, BC, EC/OC, trace elements and sugars between GVB and ZEP (UNIFI, ISP, UNIGE, INFN)
    The main measurements performed at GVB and ZEP stations are major ions, BC, EC/OC, trace elements and sugars. The information about ZEP measurements are available on SIOS data access portal, but the international collaboration (see attached letters) will guarantee the sharing of information. Different Ts are mandatory because each marker has different problems of harmonization needing different approaches.

    T1.2 One year-all campaign with a common protocol for major ions (UNIFI)
    To analyze the ions (Na, NH4, K, Mg, Ca, Cl, NO3, SO4), samples are daily collected routinely all year round at the ZEP station since 1993 following the standard given by EMEP. The same daily determination starts at GVB in 2010, also measuring methanesulfonate (MS) and oxalate (Ox). This task aims to obtain the same sampling and analytical procedure and possibly to extend the measurements of MS and Ox to ZEP.

    T1.3 One year-all campaign with a common protocol for trace elements (UNIGE)
    Since 1994, ZEP has performed the determination of several trace elements (As, C d, Cr, Co, Cu, Pb, Mn, Ni, V, Zn) in aerosol samples. The same elements are also measured at GVB in PM10 since 2010, at 4-days resolution. In BETHA-NyÅ, we will harmonize the analytical procedures, especially about the time coverage, resolution, synchronization, cut-off, sample preparation and analysis, following the EMEP manual.

    T1.4 One year-all campaign with a common protocol for EC/OC and sugars (INFN, ISP)
    At ZEP station, the measurements of EC/OC and sugars are performed on the same high volume (HV) samples since 2017; At GVB, samples for EC/OC and sugars are collected since 2010 using a low volume (LV) sampler and a cascade impactor HV sampler, respectively. In BETHA-NyÅ, we define a new HV sampling protocol for EC/OC and sugars, according to the ZEP sampling resolution and cut-off. EC/OC are analyzed in GVB samples according to the NIOSH-870 thermal protocol, while EUSAAR is used on ZEP samples. For this reason, the intercomparison exercise will allow us to evaluate the comparability of both procedures (sampling + analytical methods) and to continue the historical data series. Moreover, in BETHA-NyÅ, the analytical protocol for sugars will be implemented with 3 compounds analyzed at ZEP station.

    T1.5 One all-year campaign with a common protocol for eBC measurements (ISP)
    eBC concentration is derived from light absorption coefficient measurements performed with a Multi Angle Absorption Photometer (MAAP) and an aethalometer at ZEP and with a Particle Soot Absorption Photometer (PSAP) at GVB. BETHA-NyÅ will optimize the eBC measurement protocol (and correction algorithm) at GVB through the comparison of one year of data collected with different instruments at the same site and with similar instruments at the two sites.

    T1.6 Inter-comparison exercises to extend the evaluation to the existing dataset (UNIFI, UNIGE, INFN, ISP)
    Thanks to international collaboration (see attached letters), ZEP samples will be analyzed using the same protocols used at GVB to compare the results and to evaluate the comparability of measurements.

    T1.7 SEM analysis on selected filter samples for both GVB and ZEP sites in order to extend the comparison to the single particle mineralogy (UNIPG).


    WP2. Source apportionment - definition of sources and processes though innovative modelling approaches

    T2.1 Completion of dataset of aerosol measurements at GVB from 2010 (all RUs)
    During 10 years of activity, several samples have been collected at GVB. BETHA-NyÅ wants to complete the analysis from 2010 to include all data in a unique portal. In particular, these measurements included water soluble organic compounds, water soluble organic matter, organic nitrogen and rare earth elements.

    T2.2 Source apportionment based on multi-time resolution receptor modelling (INFN)
    Advanced receptor modelling (such as Positive Matrix Factorization, PMF, with multi-time implementation using multilinear engine, ME-2) will be applied on the datasets to identify and to characterize the different aerosol sources in terms of chemical profiles and absolute contributions. A multi-time approach is mandatory due to the different time-resolution of the samplings.

    T2.3 Source contributions to carbonaceous PM10 aerosol using quasi Monte Carlo approach (ISP)
    The atmospheric concentration of organic markers and EC/OC will be used to perform carbonaceous aerosol sources apportionment. Several organic molecules investigated at GVB are markers of specific natural and anthropogenic sources. With this purpose, multivariable statistical tools, including Monte Carlo approach, will be employed to apportion OC and EC among local and long-range sources.

    T2.4 Source apportionment back-trajectory-based (UNIPG)
    In order to identify the source areas contributing to aerosols concentrations, extensive medium or high meteo and time resolution backtrajectories will be computed. Then, integrating results from source apportionment analysis with back-trajectory analysis will be used to carry out a Potential Source Contribution Function (PSCF) study. The final outcome of the PSCF method is the ranking of the surrounding geographic regions based on the likelihood of their contribution to specific aerosol sources .


    WP3. Definition of the impact of Arctic Boundary Layer on the aerosol composition integrating meteorological observations and aerosol measurements collected at different levels of the atmospheric column.

    T3.1 Machine learning approach to identify the impact of meteorological variables on aerosol composition (ISP with the support of all RUs)
    Generalized additive models will be used to describe long term trends of primary aerosol components at GVB and ZEP identified by WP2, as a function of predictive variables, including meteorological variables describing the synoptic scale circulation and local meteorology. This approach will allow us to describe the variability of primary aerosols as a combination of different predictive variables, without assuming a linear relationship between them. In addition, the model robustness will be tested with a bootstrapping technique.

    T3.2 Use of meteorological and micrometeorological observations taken at the CCT and through radiosondes (ISP) to evaluate the height of the ABL, the stability of the atmosphere and the depositional processes.

    All this information can lead to a more comprehensive understanding of which are the factors influencing the distribution of aerosol particles along the vertical column

     

    Prodotti