Juho Karhu

Comb-assisted spectroscopic gas thermometry

Touko Uotila, Santeri Larnimaa, Juho Karhu, Markku Vainio

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Comb-assisted spectroscopic gas thermometry

Touko Uotila, Santeri Larnimaa, Juho Karhu, Markku Vainio

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Single-scattering albedo and iterated refractive indices of fresh and aged black and brown carbon particles emitted from burning peat and boreal forest floor surface in chamber experiments

Aki O. Virkkula, Delun Li, Luis Barreira, Anni H. Hartikainen et autres

It has been predicted that boreal forest and peatland fires will increase in the future as the climate warms. It is important for climate models that the optical properties of the aerosols emitted during these fires are well described. Laboratory experiments were …

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This is How Ice Defines Us

Sohvi; id_orcid 0000-0002-9403-4716 Kangasluoma, Juho Karhu

The short documentary explores the role and agency of ice in shaping Arctic futures by following a sailboat journey through the Northwest Passage and an overwintering in Kalaallit Nunaat. The documentary is part of the Planetocene2025 research project which proposes a new …

Comment on ar-2025-38

Joel Kuula, Juho Karhu, Tommi Mikkonen, Aki O. Virkkula et autres

Abstract. This study experimentally investigated the influence of aggregate morphology on soot light absorption. Fresh soot was generated using an inverted-flame burner and compacted through controlled humidification–drying cycles to isolate the effects of structural transformation from those of chemical composition or coating. …

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Review of Kuula et al., ar-2025-38

Joel Kuula, Juho Karhu, Tommi Mikkonen, Aki O. Virkkula et autres

Abstract. This study experimentally investigated the influence of aggregate morphology on soot light absorption. Fresh soot was generated using an inverted-flame burner and compacted through controlled humidification–drying cycles to isolate the effects of structural transformation from those of chemical composition or coating. …

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Experimental investigation of soot morphological transformation and its impact on size-resolved light absorption

Joel Kuula, Juho Karhu, Tommi Mikkonen, Aki O. Virkkula et autres

Abstract. This study experimentally investigated the influence of aggregate morphology on soot light absorption. Fresh soot was generated using an inverted-flame burner and compacted through controlled humidification–drying cycles to isolate the effects of structural transformation from those of chemical composition or coating. …

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Identification of microplastics with cantilever enhanced photoacoustic spectroscopy in infrared region

Sudatta Das, Juho Karhu, Blaž Hrovat, Arto P. Koistinen et autres

Microplastics have become ubiquitous in the environment, posing significant threats to ecosystems and organisms across the globe. Accurate risk assessment of these pollutants hinges on the availability of comprehensive qualitative and quantitative data. This paper demonstrates the potential of photoacoustic spectroscopy (PAS) …

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Cantilever-Enhanced Photoacoustic − Instrument for Field Measurements of Black Carbon

Tommi Mikkonen, Juho Karhu, Joel Kuula, Aki O. Virkkula et autres

Black carbon (BC), an aerosol emitted from biomass combustion and comprised mostly of elemental carbon, is one of the most harmful air pollutants in the world. Due to its ability to easily penetrate the lungs and strongly absorb solar radiation, BC plays …

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Frequency Comb-Based Spectroscopy of 02 for Primary Thermometry

Touko Uotila, Mikhail Roiz, Juho Karhu, Santeri Larnimaa et autres

Rovibrational absorption spectroscopy can be used for primary gas thermometry since absorption line strengths and shapes are affected by the temperature of the absorbing sample [1]. Examples of established spectroscopic thermometry techniques include Doppler-broadening thermometry (DBT), line-strength ratio thermometry (LRT), and rotational-state …

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Field-deployable cantilever-enhanced photoacoustic instrument for aerosol light absorption measurement at three wavelengths

Juho Karhu, Tommi Mikkonen, Joel Kuula, Aki O. Virkkula et autres

We demonstrate a measurement of aerosol absorption at three wavelengths for particles below 1 µm in diameter using a highly sensitive photoacoustic spectrometer. The acoustic signal is detected with a cantilever microphone, which allows for sensitive detection without the need to apply …

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Validation of cantilever-enhanced photoacoustic particle-size-resolved light absorption measurement using nigrosin reference particles and Mie modelling

Joel Kuula, Juho Karhu, Tommi Mikkonen, Patrick Grahn et autres

Particle light absorption enhancement, also known as the lensing effect, is a complex phenomenon where particles undergo optical transformation as they age. This process is influenced by several factors, including particle size. To investigate the lensing effect, this study introduces and validates …

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