U. Hõrrak

Publication List Details

Period

2004 - 2009

Number

53

Co-Authors

Negatively charged nanoparticles produced by splashing of water (2009)

H. Tammet, U. Hõrrak, M. Kulmala

The production of splashing-generated balloelectric intermediate ions was studied by means of mobility spectrometry in the atmosphere during the rain and in a laboratory experiment simulating the...

Atmospheric sub-3 nm particles at high altitudes (2009)

S. Mirme, A. Mirme, A. Minikin, A. Petzold, U. Hõrrak, ...

Formation of new atmospheric aerosol particles is known to occur almost all over the world and the importance of these particles to climate and air quality has been recognized. Recently, it was found...

Atmospheric data over a solar cycle: no connection between galactic cosmic rays and new particle formation (2009)

M. Kulmala, I. Riipinen, T. Nieminen, M. Hulkkonen, L. Sogacheva, H. E. Manninen, ...

Aerosol particles affect the Earth's radiative balance by directly scattering and absorbing solar radiation and, indirectly, through their activation into cloud droplets. Both effects are known with...

Variation and balance of positive air ion concentrations in a boreal forest (2008)

Hõrrak, U., Aalto, P. P., Salm, J., Komsaare, K., Tammet, H., Mäkelä, J. M., ...

Air ions are characterized on the basis of measurements carried out in a boreal forest at the Hyytiälä SMEAR station, Finland, during the BIOFOR III campaign in spring 1999. The air ions were...

Formation and characteristics of ions and charged aerosol particles in a native Australian Eucalypt forest (2008)

Suni, T., Kulmala, M., Hirsikko, A., Bergman, T., Laakso, L., Aalto, P. P., ...

Biogenic aerosol formation is likely to contribute significantly to the global aerosol load. In recent years, new-particle formation has been observed in various ecosystems around the world but...

Variation and balance of positive air ion concentrations in a boreal forest (2008)

Hõrrak, U., Aalto, P. P., Salm, J., Komsaare, K., Tammet, H., Mäkelä, J. M., ...

Air ions are characterized on the basis of measurements carried out in a boreal forest at the Hyytiälä SMEAR station, Finland, during the BIOFOR III campaign in spring 1999. The air ions were...

Formation and characteristics of ions and charged aerosol particles in a native Australian Eucalypt forest (2008)

Suni, T., Kulmala, M., Hirsikko, A., Bergman, T., Laakso, L., Aalto, P. P., ...

Biogenic aerosol formation is likely to contribute significantly to the global aerosol load. In recent years, new-particle formation has been observed in various ecosystems around the world but...

Formation and characteristics of ions and charged aerosol particles in a native Australian Eucalypt forest (2008)

T. Suni, M. Kulmala, A. Hirsikko, T. Bergman, L. Laakso, P. P. Aalto, ...

Biogenic aerosol formation is likely to contribute significantly to the global aerosol load. In recent years, new-particle formation has been observed in various ecosystems around the world but...

Variation and balance of positive air ion concentrations in a boreal forest (2008)

U. Hõrrak, P. P. Aalto, J. Salm, K. Komsaare, H. Tammet, J. M. Mäkelä, ...

Air ions are characterized on the basis of measurements carried out in a boreal forest at the Hyytiälä SMEAR station, Finland, during the BIOFOR III campaign in spring 1999. The air ions were...

Negatively charged nanoparticles produced by splashing of water (2008)

H. Tammet, U. Hõrrak, M. Kulmala

The production of splashing-generated balloelectric intermediate ions was studied by means of mobility spectrometry in the atmosphere during the rain and in a laboratory experiment simulating the...

Identification and classification of the formation of intermediate ions measured in boreal forest (2007)

A. Hirsikko, T. Bergman, L. Laakso, M. Dal Maso, I. Riipinen, U. Hõrrak, ...

We have measured the size distributions of air ions (0.42–7.5 nm in diameter) with the Balanced Scanning Mobility Analyzer in boreal forest, in Southern Finland since spring 2003. The size...

Formation and characteristics of ions and charged aerosol particles in a native Australian Eucalypt forest (2007)

Suni, T., Kulmala, M., Hirsikko, A., Bergman, T., Laakso, L., Aalto, P. P., ...

Biogenic aerosol formation is likely to contribute significantly to the global aerosol load. In recent years, new-particle formation (NPF) has been observed in various ecosystems around the world but...

Characterization of positive air ions in boreal forest air at the Hyytiälä SMEAR station (2007)

Hõrrak, U., Aalto, P. P., Salm, J., Komsaare, K., Tammet, H., Mäkelä, J. M., ...

The behavior of the concentration of positive small (or cluster) air ions and naturally charged nanometer aerosol particles (aerosol ions) has been studied on the basis of measurements carried out in...

Concentrations and fluxes of aerosol particles during the LAPBIAT measurement campaign in Värriö field station (2007)

Ruuskanen, T. M., Kaasik, M., Aalto, P. P., Hõrrak, U., Vana, M., Mårtensson, M., ...

The LAPBIAT measurement campaign took place in the SMEAR I measurement station located in Eastern Lapland in the spring of 2003 between 26 April and 11 May. In this paper we describe the measurement...

Concentrations and fluxes of aerosol particles during the LAPBIAT measurement campaign at Värriö field station (2007)

Ruuskanen, T. M., Kaasik, M., Aalto, P. P., Hõrrak, U., Vana, M., Mårtensson, M., ...

The LAPBIAT measurement campaign took place in the Värriö SMEAR I measurement station located in Eastern Lapland in the spring of 2003 between 26 April and 11 May. In this paper we describe the...

Identification and classification of the formation of intermediate ions measured in boreal forest (2007)

Hirsikko, A., Bergman, T., Laakso, L., Dal Maso, M., Riipinen, I., Hõrrak, U., ...

We have measured the size distributions of air ions (0.42?7.5 nm in diameter) with the Balanced Scanning Mobility Analyzer in boreal forest, in Southern Finland since spring 2003. The size range...

Formation and characteristics of ions and charged aerosol particles in a native Australian Eucalypt forest (2007)

Suni, T., Kulmala, M., Hirsikko, A., Bergman, T., Laakso, L., Aalto, P. P., ...

Biogenic aerosol formation is likely to contribute significantly to the global aerosol load. In recent years, new-particle formation (NPF) has been observed in various ecosystems around the world but...

Characterization of positive air ions in boreal forest air at the Hyytiälä SMEAR station (2007)

Hõrrak, U., Aalto, P. P., Salm, J., Komsaare, K., Tammet, H., Mäkelä, J. M., ...

The behavior of the concentration of positive small (or cluster) air ions and naturally charged nanometer aerosol particles (aerosol ions) has been studied on the basis of measurements carried out in...

Concentrations and fluxes of aerosol particles during the LAPBIAT measurement campaign in Värriö field station (2007)

Ruuskanen, T. M., Kaasik, M., Aalto, P. P., Hõrrak, U., Vana, M., Mårtensson, M., ...

The LAPBIAT measurement campaign took place in the SMEAR I measurement station located in Eastern Lapland in the spring of 2003 between 26 April and 11 May. In this paper we describe the measurement...

Concentrations and fluxes of aerosol particles during the LAPBIAT measurement campaign at Värriö field station (2007)

Ruuskanen, T. M., Kaasik, M., Aalto, P. P., Hõrrak, U., Vana, M., Mårtensson, M., ...

The LAPBIAT measurement campaign took place in the Värriö SMEAR I measurement station located in Eastern Lapland in the spring of 2003 between 26 April and 11 May. In this paper we describe the...

Identification and classification of the formation of intermediate ions measured in boreal forest (2007)

Hirsikko, A., Bergman, T., Laakso, L., Dal Maso, M., Riipinen, I., Hõrrak, U., ...

We have measured the size distributions of air ions (0.42?7.5 nm in diameter) with the Balanced Scanning Mobility Analyzer in boreal forest, in Southern Finland since spring 2003. The size range...

Concentrations and fluxes of aerosol particles during the LAPBIAT measurement campaign at Värriö field station (2007)

T. M. Ruuskanen, M. Kaasik, P. P. Aalto, U. Hõrrak, M. Vana, M. Mårtensson, ...

The LAPBIAT measurement campaign took place in the Värriö SMEAR I measurement station located in Eastern Lapland in the spring of 2003 between 26 April and 11 May. In this paper we describe the...

Concentrations and fluxes of aerosol particles during the LAPBIAT measurement campaign in Värriö field station (2007)

T. M. Ruuskanen, M. Kaasik, P. P. Aalto, U. Hõrrak, M. Vana, M. Mårtensson, ...

The LAPBIAT measurement campaign took place in the SMEAR I measurement station located in Eastern Lapland in the spring of 2003 between 26 April and 11 May. In this paper we describe the measurement...

Characterization of positive air ions in boreal forest air at the Hyytiälä SMEAR station (2007)

U. Hõrrak, P. P. Aalto, J. Salm, K. Komsaare, H. Tammet, J. M. Mäkelä, ...

The behavior of the concentration of positive small (or cluster) air ions and naturally charged nanometer aerosol particles (aerosol ions) has been studied on the basis of measurements carried out in...

Formation and characteristics of ions and charged aerosol particles in a native Australian Eucalypt forest (2007)

T. Suni, M. Kulmala, A. Hirsikko, T. Bergman, L. Laakso, P. P. Aalto, ...

Biogenic aerosol formation is likely to contribute significantly to the global aerosol load. In recent years, new-particle formation (NPF) has been observed in various ecosystems around the world but...

Factors of air ion balance in a coniferous forest according to measurements in Hyytiälä, Finland (2006)

H. Tammet, U. Hõrrak, L. Laakso, M. Kulmala

A new mathematical model describing air ion balance was developed and tested. It has improved approximations and includes dry deposition of ions onto the forest canopy. The model leads to an explicit...

Identification and classification of the formation of intermediate ions measured in boreal forest (2006)

Hirsikko, A., Bergman, T., Laakso, L., Dal Maso, M., Riipinen, I., Hõrrak, U., ...

We have measured the size distributions of air ions (0.42?7.5 nm in diameter) with the Balanced Scanning Mobility Analyzer in boreal forest, in Southern Finland since spring 2003. The size range...

Factors of air ion balance in a coniferous forest according to measurements in Hyytiälä, Finland (2006)

Tammet, H., Hõrrak, U., Laakso, L., Kulmala, M.

A new theoretical model includes dry deposition of ions onto the forest canopy and takes into account different parameters of positive and negative ions. Explicit algebraic solution of the air ion...

Factors of air ion balance in a coniferous forest according to measurements in Hyytiälä, Finland (2006)

Tammet, H., Hõrrak, U., Laakso, L., Kulmala, M.

A new mathematical model describing air ion balance was developed and tested. It has improved approximations and includes dry deposition of ions onto the forest canopy. The model leads to an explicit...

Identification and classification of the formation of intermediate ions measured in boreal forest (2006)

Hirsikko, A., Bergman, T., Laakso, L., Dal Maso, M., Riipinen, I., Hõrrak, U., ...

We have measured the size distributions of air ions (0.42?7.5 nm in diameter) with the Balanced Scanning Mobility Analyzer in boreal forest, in Southern Finland since spring 2003. The size range...

Factors of air ion balance in a coniferous forest according to measurements in Hyytiälä, Finland (2006)

Tammet, H., Hõrrak, U., Laakso, L., Kulmala, M.

A new theoretical model includes dry deposition of ions onto the forest canopy and takes into account different parameters of positive and negative ions. Explicit algebraic solution of the air ion...

Factors of air ion balance in a coniferous forest according to measurements in Hyytiälä, Finland (2006)

Tammet, H., Hõrrak, U., Laakso, L., Kulmala, M.

A new mathematical model describing air ion balance was developed and tested. It has improved approximations and includes dry deposition of ions onto the forest canopy. The model leads to an explicit...

Characterization of air ions in boreal forest air during BIOFOR III campaign (2005)

Hõrrak, U., Aalto, P. P., Salm, J., Mäkelä, J. M., Laakso, L., Laakso, L., ...

The behavior of the concentration of positive small (or cluster) air ions and naturally charged nanometer aerosol particles (aerosol ions) has been studied on the basis of measurements carried out in...

Characterization of air ions in boreal forest air during BIOFOR III campaign (2005)

Hõrrak, U., Aalto, P. P., Salm, J., Mäkelä, J. M., Laakso, L., Laakso, L., ...

The behavior of the concentration of positive small (or cluster) air ions and naturally charged nanometer aerosol particles (aerosol ions) has been studied on the basis of measurements carried out in...

Characterization of air ions in boreal forest air during BIOFOR III campaign (2005)

U. Hõrrak, P. P. Aalto, J. Salm, J. M. Mäkelä, L. Laakso, L. Laakso, ...

The behavior of the concentration of positive small (or cluster) air ions and naturally charged nanometer aerosol particles (aerosol ions) has been studied on the basis of measurements carried out in...

Ion production rate in a boreal forest based on ion, particle and radiation measurements (2004)

L. Laakso, T. Petäjä, M. Kulmala, J. Paatero, U. Hõrrak, ...

In this study the ion production rates in a boreal forest were studied based on two different methods: 1) cluster ion and particle concentration measurements, 2) external radiation and radon...

Kinetic nucleation and ions in boreal forest particle formation events (2004)

L. Laakso, T. Anttila, P. P. Aalto, M. Kulmala, U. Hõrrak, ...

In order to gain a more comprehensive picture on different mechanisms behind atmospheric particle formation, measurement results from QUEST 2-campaign are analyzed with an aid of an aerosol dynamic...

Initial steps of aerosol growth (2004)

M. Kulmala, L. Laakso, I. Riipinen, M. Dal Maso, T. Anttila, ...

The formation and growth of atmospheric aerosols depend on several steps, namely nucleation, initial steps of growth and subsequent – mainly condensational – growth. This work focuses on...

Initial steps of aerosol growth (2004)

Kulmala, O., Laakso, L., Lehtinen, K. E. J., Riipinen, I., Dal Maso, M., Anttila, T., ...

The formation and growth of atmospheric aerosols depend on several steps, namely nucleation, initial steps of growth and subsequent ? mainly condensational ? growth. This work focuses on the initial...

Ion production rate in a boreal forest based on ion, particle and radiation measurements (2004)

Laakso, L., Petäjä, T., Lehtinen, K. E. J., Kulmala, M., Paatero, J., Hõrrak, U., ...

In this study the ion production rates in a boreal forest are studied based on two different methods: 1) cluster ion and particle concentration measurements, 2) external radiation and radon...

Kinetic nucleation and ions in boreal particle formation events (2004)

Laakso, L., Anttila, T., Lehtinen, K. E. J., Aalto, P. P., Kulmala, M., Hõrrak, U., ...

In order to gain a more comprehensive picture on different mechanisms behind atmospheric particle formation, measurement results from QUEST 2-campaign are analyzed with an aid of an aerosol dynamic...

Initial steps of aerosol growth (2004)

Kulmala, M., Laakso, L., Lehtinen, K. E. J., Riipinen, I., Dal Maso, M., Anttila, T., ...

The formation and growth of atmospheric aerosols depend on several steps, namely nucleation, initial steps of growth and subsequent ? mainly condensational ? growth. This work focuses on the initial...

Kinetic nucleation and ions in boreal forest particle formation events (2004)

Laakso, L., Anttila, T., Lehtinen, K. E. J., Aalto, P. P., Kulmala, M., Hõrrak, U., ...

In order to gain a more comprehensive picture on different mechanisms behind atmospheric particle formation, measurement results from QUEST 2-campaign are analyzed with an aid of an aerosol dynamic...

Ion production rate in a boreal forest based on ion, particle and radiation measurements (2004)

Laakso, L., Petäjä, T., Lehtinen, K. E. J., Kulmala, M., Paatero, J., Hõrrak, U., ...

In this study the ion production rates in a boreal forest were studied based on two different methods: 1) cluster ion and particle concentration measurements, 2) external radiation and radon...

Initial steps of aerosol growth (2004)

Kulmala, O., Laakso, L., Lehtinen, K. E. J., Riipinen, I., Dal Maso, M., Anttila, T., ...

The formation and growth of atmospheric aerosols depend on several steps, namely nucleation, initial steps of growth and subsequent ? mainly condensational ? growth. This work focuses on the initial...

Ion production rate in a boreal forest based on ion, particle and radiation measurements (2004)

Laakso, L., Petäjä, T., Lehtinen, K. E. J., Kulmala, M., Paatero, J., Hõrrak, U., ...

In this study the ion production rates in a boreal forest are studied based on two different methods: 1) cluster ion and particle concentration measurements, 2) external radiation and radon...

Kinetic nucleation and ions in boreal particle formation events (2004)

Laakso, L., Anttila, T., Lehtinen, K. E. J., Aalto, P. P., Kulmala, M., Hõrrak, U., ...

In order to gain a more comprehensive picture on different mechanisms behind atmospheric particle formation, measurement results from QUEST 2-campaign are analyzed with an aid of an aerosol dynamic...

Initial steps of aerosol growth (2004)

Kulmala, M., Laakso, L., Lehtinen, K. E. J., Riipinen, I., Dal Maso, M., Anttila, T., ...

The formation and growth of atmospheric aerosols depend on several steps, namely nucleation, initial steps of growth and subsequent ? mainly condensational ? growth. This work focuses on the initial...

Kinetic nucleation and ions in boreal forest particle formation events (2004)

Laakso, L., Anttila, T., Lehtinen, K. E. J., Aalto, P. P., Kulmala, M., Hõrrak, U., ...

In order to gain a more comprehensive picture on different mechanisms behind atmospheric particle formation, measurement results from QUEST 2-campaign are analyzed with an aid of an aerosol dynamic...

Ion production rate in a boreal forest based on ion, particle and radiation measurements (2004)

Laakso, L., Petäjä, T., Lehtinen, K. E. J., Kulmala, M., Paatero, J., Hõrrak, U., ...

In this study the ion production rates in a boreal forest were studied based on two different methods: 1) cluster ion and particle concentration measurements, 2) external radiation and radon...

Kinetic nucleation and ions in boreal particle formation events (2004)

L. Laakso, T. Anttila, P. P. Aalto, M. Kulmala, U. Hõrrak, ...

In order to gain a more comprehensive picture on different mechanisms behind atmospheric particle formation, measurement results from QUEST 2-campaign are analyzed with an aid of an aerosol dynamic...

Ion production rate in a boreal forest based on ion, particle and radiation measurements (2004)

L. Laakso, T. Petäjä, M. Kulmala, J. Paatero, U. Hõrrak, ...

In this study the ion production rates in a boreal forest are studied based on two different methods: 1) cluster ion and particle concentration measurements, 2) external radiation and radon...

Initial steps of aerosol growth (2004)

O. Kulmala, L. Laakso, I. Riipinen, M. Dal Maso, T. Anttila, ...

The formation and growth of atmospheric aerosols depend on several steps, namely nucleation, initial steps of growth and subsequent – mainly condensational – growth. This work focuses on...