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Vertical profiling of aerosol properties with two-wavelength polarization Raman lidar over the Vipava valley
William Eichinger, Klemen Bergant, Griša Močnik, Luka Drinovec, Samo Stamoč, Asta Gregorič, Longlong Wang, 2018, objavljeni povzetek znanstvenega prispevka na konferenci

Opis: Presence of atmospheric aerosols affects the Earth’s radiation budget and thus also atmospheric thermal structure, which in turn affects cloud and planetary boundary layer (PBL) dynamics. We combine in-situ and remote measurements to determine aerosol properties in a representative hot-spot for air pollution in a complex terrain configuration. Vertical profiles of aerosol properties were investigated using a two-wavelength polarization Raman lidar system in the Vipava valley. Using lidar-obtained particle depolarization ratio, lidar ratio and backscatter Ångström exponent (355 nm / 1064 nm), which depend on aerosol shape, size and refractive index, thus the aerosols can be identified and the roles of different aerosol types in the observed atmospheric processes were investigated. In addition, aerosol absorption coefficients were measured in-situ by Aethalometers (AE33, Magee Scientific / Aerosol d.o.o.) on the valley floor and on the adjacent mountain range, 850 m above the lidar site. Our primary goal was to study the variability of aerosol types within and above the Vipava valley, which was performed using the entire lidar dataset from August – December 2017. Primary anthropogenic aerosols within the valley is mainly emitted from two sources: individual domestic heating systems, which mostly use biomass fuel and traffic. Natural aerosols, transported by long-range transport, such as mineral dust and sea salt, were observed both above the PBL and entering into the PBL. Vertical distributions of aerosol properties, in par- ticular the particle depolarization ratio, indicated atmospheric stratification with different aerosol types occupying different height ranges. In the presence of Bora (strong down-slope wind), Kelvin-Helmholtz instabilities were observed between the PBL and the free troposphere. Using aerosol type identification capability of our system, we discovered that this instability was responsible for ejecting aerosols from the PBL up to 2 km into the free troposphere. In addition, we improved the reliability of aerosol identification in vertical profiles using absorption coeffi- cient measured by Aethalometer. Combining it with the aerosol extinction coefficient at 355 nm derived from lidar data, we derived aerosol single scattering albedo (SSA), which is an important parameter for aerosol characterization.
Najdeno v: osebi
Ključne besede: Aerosol, Vipava valley, lidar
Objavljeno: 23.04.2018; Ogledov: 2076; Prenosov: 0
.pdf Polno besedilo (35,82 KB)

Bora wind, Wind speed vertical profile, Logarithmic law, Power law
Klemen Bergant, Samo Stanič, Marija Bervida, 2018, objavljeni znanstveni prispevek na konferenci

Opis: Bora is cold and gusty downslope wind with variable gust frequency and duration, appearing on the lee side of Dinaric Alps. Its flow characteristics are unique and theoretically still not fully described, especially for modeling purposes. We present an analysis of the wind speed vertical profiles at Razdrto, which lies in a gap between the Nanos and Javorniki plateau in southwest Slovenia and is strongly exposed to Bora. An analysis of the vertical wind speed profiles during Bora episodes is based on experimental wind data, provided by Helikopter energija, for six Bora events of different duration, appearing between April 2010 and May 2011. Average wind speed in 10-minute intervals was collected at four different heights (20, 31, 40 and 41.7 m above the ground)at the wind turbine site in Razdrto using cup anemometers. Wind direction data with same temporal resolution was obtained from a single wind vane placed at 40.9 m above the ground. Based on the collected data, the applicability of the empirical power-law and the logarithmic law profiles, commonly used for the description of neutrally stratified atmosphere, was investigated for the case of Bora. The parameters for the power-law and logarithmic law were obtained by fitting the wind speed data using linear regression method and are compared to standard values for that particular type of terrain. The quality of fits was very good with r2 above 0.9, indicating that both power-law and logarithmic law adequately describe mean horizontal Bora wind. The median value of the power-law coefficient was found to be 0.16±0.03, which is consistent with standard value for neutral atmosphere (0.143). The aerodynamic roughness varied from 0.003 m to 0.22 m with the median value of 0.09±0.07, which describes open level country terrain with some trees. The event in November 2010 with large roughness is expected to be due to specific wind direction and surface conditions.
Najdeno v: osebi
Ključne besede: Bora wind, Wind speed vertical profile, Logarithmic law, Power law
Objavljeno: 07.02.2019; Ogledov: 1591; Prenosov: 12
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New Data Policy in South-East Europe
Klemen Bergant, prispevek na konferenci brez natisa

Opis: Conference contribution presents the process of development of a new data policy for the South-East European Multi-Hazard Early Warning Advisory System project (SEE-MHEWS-A Project). The project, led by the World Meteorological Organization, is currently in a demonstration phase. National meteorological and hydrological services (NMHSs) from 17 countries in the South-East Europe are involved in the project. With common SEE-MHEWS Data Policy Agreement the involved NMHSs express their willingness and provide legal framework for the exchange of all available meteorological and hydrological data with a main purpose to improve their meteorological and hydrological forecasts and warnings. The project data policy could be seen as a first step towards the open data policy in the region.
Najdeno v: osebi
Ključne besede: Multi-Hazard Early Warning System, Meteorological and Hydorlogical Warnings, Data Exchnage, Data Policy
Objavljeno: 06.01.2021; Ogledov: 381; Prenosov: 0
.pdf Polno besedilo (285,96 KB)

What else needs to be said on Climate Change and Droughts: Future Chalanges
Klemen Bergant, prispevek na konferenci brez natisa

Opis: Extreme weather events, including droughts, and a failure of climate-change mitigation and adaptation are the most urgent global risks taking into account their likelihood and impact. The economic loss related to extreme weather events is increasing. Observations show that droughts became more frequent and severe in the last decades across the entire Europe, and according to the climate projections the drought risk will continue to increase in 21st century, therefore we need to take action now. Efficient drought monitoring and early warning system is the basic climate change adaptation measure. Different drought monitoring and warning systems are available on local, regional and global level and for efficient management of drought risk we need to connect those tools and integrate them into multi-hazard early warning systems.
Najdeno v: osebi
Ključne besede: climate change, extreme weather events, droughts, monitoring, early warnings
Objavljeno: 07.01.2021; Ogledov: 424; Prenosov: 0
.pdf Polno besedilo (1,12 MB)

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