Martti Toikka - Academia.edu (original) (raw)

Papers by Martti Toikka

12th Canadian Symposium on Remote Sensing Geoscience and Remote Sensing Symposium,, 1989

12th Canadian Symposium on Remote Sensing Geoscience and Remote Sensing Symposium,, 1989

10th Annual International Symposium on Geoscience and Remote Sensing, 1990

[Proceedings] IGARSS'91 Remote Sensing: Global Monitoring for Earth Management, 1991

The Surface and Atmospheric Airborne Microwave Experiment (SAAMEX) was held in Finland on 14-21 M... more The Surface and Atmospheric Airborne Microwave Experiment (SAAMEX) was held in Finland on 14-21 March 1990. The institutes providing airborne microwave sensors for the campaign were the British Meteorological Office (BMO) and the Helsinki University of Technology (HUT). The three main targets were sea ice, snow, and forest canopies. Ground truth measurements were made by several Finnish research institutes.

International Journal of Remote Sensing, 1992

A helicopter-borne 8-channel ranging scatterometer HUTSCAT (Helsinki University of Technology Sca... more A helicopter-borne 8-channel ranging scatterometer HUTSCAT (Helsinki University of Technology Scatterometer) was used to investigate the backscattering behaviour of low-salinity sea ice at 5-4GHz and 9-8 GHz. The measurements were conducted during the BEPERS-88 Sea Ice Campaign in the Gulf of Bothnia, 6-12 March 1988. The backscattering properties of several sea ice types were examined at the two frequencies, using HH,

Atmospheric Chemistry and Physics, 2008

The relevance of snow for climate studies is based on its physical properties, such as high surfa... more The relevance of snow for climate studies is based on its physical properties, such as high surface reflectivity. Surface ultraviolet (UV) albedo is an essential parameter for various applications based on radiative transfer modeling. Here, new continuous measurements of the local UV albedo of natural Arctic snow were made at Sodankylä (67 • 22 N, 26 • 39 E, 179 m a.s.l.) during the spring of 2007. The data were logged at 1-min intervals. The accumulation of snow was up to 68 cm. The surface layer thickness varied from 0.5 to 35 cm with the snow grain size between 0.2 and 2.5 mm. The midday erythemally weighted UV albedo ranged from 0.6 to 0.8 in the accumulation period, and from 0.5 to 0.7 during melting. During the snow melt period, under cases of an almost clear sky and variable cloudiness, an unexpected diurnal decrease of 0.05 in albedo soon after midday, and recovery thereafter, was detected. This diurnal decrease in albedo was found to be asymmetric with respect to solar midday, thus indicating a change in the properties of the snow. Independent UV albedo results with two different types of instruments confirm these findings. The measured temperature of the snow surface was below 0 • C on the following mornings. Hence, the reversible diurnal change, evident for ∼1-2 h, could be explained by the daily metamorphosis of the surface of the snowpack, in which the temperature of the surface increases, melting some of the snow to liquid water, after which the surface freezes again.

International Geoscience and Remote Sensing Symposium, 'Remote Sensing: Moving Toward the 21st Century'., 1988

Eos, Transactions American Geophysical Union, 1989

SAE Technical Paper Series, 1994

SAE Technical Paper Series, 1989

International Geoscience and Remote Sensing Symposium, 'Remote Sensing: Moving Toward the 21st Century'., 1988

International Geoscience and Remote Sensing Symposium, 'Remote Sensing: Moving Toward the 21st Century'., 1988

A waveguide transmission system was used t o measurt the d i e l e c t r i c properties o f sea i... more A waveguide transmission system was used t o measurt the d i e l e c t r i c properties o f sea i c e during the BEPERS-87 (Bothnian Experiment i n Preparation f o r ERS-1) Campaign i n the Gulf o f Bothnia, March 31 A p r i l 3, 1987. The temperature range o f the icb samples was -6.0 t o -0.3OC and the s a l i n i t y range Key words: D i e l e c t r i c constant, sea ice. 0.0 t o 1.0 o/oo.

Atmospheric Chemistry and Physics Discussions, 2008

The relevance of snow for climate studies is based on its physical properties, such as high surfa... more The relevance of snow for climate studies is based on its physical properties, such as high surface reflectivity. Surface ultraviolet (UV) albedo is an essential parameter for various applications based on radiative transfer modeling. Here, new continuous measurements of the local UV albedo of natural Arctic snow were made at Sodankylä 5 (67.37

Atmospheric Chemistry and Physics, 2008

The relevance of snow for climate studies is based on its physical properties, such as high surfa... more The relevance of snow for climate studies is based on its physical properties, such as high surface reflectivity. Surface ultraviolet (UV) albedo is an essential parameter for various applications based on radiative transfer modeling. Here, new continuous measurements of the local UV albedo of natural Arctic snow were made at Sodankylä (67 • 22 N, 26 • 39 E, 179 m a.s.l.) during the spring of 2007. The data were logged at 1-min intervals. The accumulation of snow was up to 68 cm. The surface layer thickness varied from 0.5 to 35 cm with the snow grain size between 0.2 and 2.5 mm. The midday erythemally weighted UV albedo ranged from 0.6 to 0.8 in the accumulation period, and from 0.5 to 0.7 during melting. During the snow melt period, under cases of an almost clear sky and variable cloudiness, an unexpected diurnal decrease of 0.05 in albedo soon after midday, and recovery thereafter, was detected. This diurnal decrease in albedo was found to be asymmetric with respect to solar midday, thus indicating a change in the properties of the snow. Independent UV albedo results with two different types of instruments confirm these findings. The measured temperature of the snow surface was below 0 • C on the following mornings. Hence, the reversible diurnal change, evident for ∼1-2 h, could be explained by the daily metamorphosis of the surface of the snowpack, in which the temperature of the surface increases, melting some of the snow to liquid water, after which the surface freezes again.

1995 International Geoscience and Remote Sensing Symposium, IGARSS '95. Quantitative Remote Sensing for Science and Applications, 1995

Data from three sensors, ESA ERS-1 SAR, the Helsinki University of Technology (HUT) airbome scatt... more Data from three sensors, ESA ERS-1 SAR, the Helsinki University of Technology (HUT) airbome scatterometer HUTSCAT and the HUT airborne microwave radiometer, were used to investigate remote sensing of snow. A test site, located in Sodankyla, northern Finland, was used from the fall of 1991 through the spring of 1993 for data collection. Six airbome campaigns, covering snowfree (frozen and thawed soil), dry snow and wet snow conditions were carried out. A total of 21 ERS-1 S A R images was acquired. The two main goals of the investigation were (1) to determine the effect of various land use categories to the capability of microwave sensors to provide snow information and (2) to study combined use of radar and microwave radiometer in snow mapping.

18th European Microwave Conference, 1988, 1988

A helicopter-borne dual-frequency FM-CW scatterometer for remote sensing is described. The scatte... more A helicopter-borne dual-frequency FM-CW scatterometer for remote sensing is described. The scatterometer can measure the radar backscatter from a target with a range resolution of one meter. This is accomplished by preforming the Fast Fourier Transform to the received time-domain signal. The measurement is made simultaneously at eight channels (VV, HH, HV, and VH modes of polarization at 5.4 GHz and 9.8 GHz).

… Remote Sensing: An …, 1989

A helicopter-borne dual-frequency FM-CW scatterometer (HUTSCAT, Helsinki University of Technology... more A helicopter-borne dual-frequency FM-CW scatterometer (HUTSCAT, Helsinki University of Technology SCATterometer) is described. The HUTSCAT measures the backscattering properties of a target with a range resolution of 65 cm. The real-time ranging capability is obtained by performing the Fast Fourier Transform (FlT) to the received time-domain signal. The measurement is made simultaneously at eight channels (VV, HH, HV, and VH modes of polarization at 5.4 GHz and 9.8 GHz). The scatterometer measures the radar return spectrum for eight channels in 16.6 ms which corresponds to an along-track distance of 0.33 m for the helicopter speed of 20 m/s. The radar system has been designed for remote sensing of forests, sea ice, and snow. The most potential application is the estimation of forest stand characteristics, to be discussed in Part I1 of this paper.

12th Canadian Symposium on Remote Sensing Geoscience and Remote Sensing Symposium,, 1989

12th Canadian Symposium on Remote Sensing Geoscience and Remote Sensing Symposium,, 1989

10th Annual International Symposium on Geoscience and Remote Sensing, 1990

[Proceedings] IGARSS'91 Remote Sensing: Global Monitoring for Earth Management, 1991

The Surface and Atmospheric Airborne Microwave Experiment (SAAMEX) was held in Finland on 14-21 M... more The Surface and Atmospheric Airborne Microwave Experiment (SAAMEX) was held in Finland on 14-21 March 1990. The institutes providing airborne microwave sensors for the campaign were the British Meteorological Office (BMO) and the Helsinki University of Technology (HUT). The three main targets were sea ice, snow, and forest canopies. Ground truth measurements were made by several Finnish research institutes.

International Journal of Remote Sensing, 1992

A helicopter-borne 8-channel ranging scatterometer HUTSCAT (Helsinki University of Technology Sca... more A helicopter-borne 8-channel ranging scatterometer HUTSCAT (Helsinki University of Technology Scatterometer) was used to investigate the backscattering behaviour of low-salinity sea ice at 5-4GHz and 9-8 GHz. The measurements were conducted during the BEPERS-88 Sea Ice Campaign in the Gulf of Bothnia, 6-12 March 1988. The backscattering properties of several sea ice types were examined at the two frequencies, using HH,

Atmospheric Chemistry and Physics, 2008

The relevance of snow for climate studies is based on its physical properties, such as high surfa... more The relevance of snow for climate studies is based on its physical properties, such as high surface reflectivity. Surface ultraviolet (UV) albedo is an essential parameter for various applications based on radiative transfer modeling. Here, new continuous measurements of the local UV albedo of natural Arctic snow were made at Sodankylä (67 • 22 N, 26 • 39 E, 179 m a.s.l.) during the spring of 2007. The data were logged at 1-min intervals. The accumulation of snow was up to 68 cm. The surface layer thickness varied from 0.5 to 35 cm with the snow grain size between 0.2 and 2.5 mm. The midday erythemally weighted UV albedo ranged from 0.6 to 0.8 in the accumulation period, and from 0.5 to 0.7 during melting. During the snow melt period, under cases of an almost clear sky and variable cloudiness, an unexpected diurnal decrease of 0.05 in albedo soon after midday, and recovery thereafter, was detected. This diurnal decrease in albedo was found to be asymmetric with respect to solar midday, thus indicating a change in the properties of the snow. Independent UV albedo results with two different types of instruments confirm these findings. The measured temperature of the snow surface was below 0 • C on the following mornings. Hence, the reversible diurnal change, evident for ∼1-2 h, could be explained by the daily metamorphosis of the surface of the snowpack, in which the temperature of the surface increases, melting some of the snow to liquid water, after which the surface freezes again.

International Geoscience and Remote Sensing Symposium, 'Remote Sensing: Moving Toward the 21st Century'., 1988

Eos, Transactions American Geophysical Union, 1989

SAE Technical Paper Series, 1994

SAE Technical Paper Series, 1989

International Geoscience and Remote Sensing Symposium, 'Remote Sensing: Moving Toward the 21st Century'., 1988

International Geoscience and Remote Sensing Symposium, 'Remote Sensing: Moving Toward the 21st Century'., 1988

A waveguide transmission system was used t o measurt the d i e l e c t r i c properties o f sea i... more A waveguide transmission system was used t o measurt the d i e l e c t r i c properties o f sea i c e during the BEPERS-87 (Bothnian Experiment i n Preparation f o r ERS-1) Campaign i n the Gulf o f Bothnia, March 31 A p r i l 3, 1987. The temperature range o f the icb samples was -6.0 t o -0.3OC and the s a l i n i t y range Key words: D i e l e c t r i c constant, sea ice. 0.0 t o 1.0 o/oo.

Atmospheric Chemistry and Physics Discussions, 2008

The relevance of snow for climate studies is based on its physical properties, such as high surfa... more The relevance of snow for climate studies is based on its physical properties, such as high surface reflectivity. Surface ultraviolet (UV) albedo is an essential parameter for various applications based on radiative transfer modeling. Here, new continuous measurements of the local UV albedo of natural Arctic snow were made at Sodankylä 5 (67.37

Atmospheric Chemistry and Physics, 2008

The relevance of snow for climate studies is based on its physical properties, such as high surfa... more The relevance of snow for climate studies is based on its physical properties, such as high surface reflectivity. Surface ultraviolet (UV) albedo is an essential parameter for various applications based on radiative transfer modeling. Here, new continuous measurements of the local UV albedo of natural Arctic snow were made at Sodankylä (67 • 22 N, 26 • 39 E, 179 m a.s.l.) during the spring of 2007. The data were logged at 1-min intervals. The accumulation of snow was up to 68 cm. The surface layer thickness varied from 0.5 to 35 cm with the snow grain size between 0.2 and 2.5 mm. The midday erythemally weighted UV albedo ranged from 0.6 to 0.8 in the accumulation period, and from 0.5 to 0.7 during melting. During the snow melt period, under cases of an almost clear sky and variable cloudiness, an unexpected diurnal decrease of 0.05 in albedo soon after midday, and recovery thereafter, was detected. This diurnal decrease in albedo was found to be asymmetric with respect to solar midday, thus indicating a change in the properties of the snow. Independent UV albedo results with two different types of instruments confirm these findings. The measured temperature of the snow surface was below 0 • C on the following mornings. Hence, the reversible diurnal change, evident for ∼1-2 h, could be explained by the daily metamorphosis of the surface of the snowpack, in which the temperature of the surface increases, melting some of the snow to liquid water, after which the surface freezes again.

1995 International Geoscience and Remote Sensing Symposium, IGARSS '95. Quantitative Remote Sensing for Science and Applications, 1995

Data from three sensors, ESA ERS-1 SAR, the Helsinki University of Technology (HUT) airbome scatt... more Data from three sensors, ESA ERS-1 SAR, the Helsinki University of Technology (HUT) airbome scatterometer HUTSCAT and the HUT airborne microwave radiometer, were used to investigate remote sensing of snow. A test site, located in Sodankyla, northern Finland, was used from the fall of 1991 through the spring of 1993 for data collection. Six airbome campaigns, covering snowfree (frozen and thawed soil), dry snow and wet snow conditions were carried out. A total of 21 ERS-1 S A R images was acquired. The two main goals of the investigation were (1) to determine the effect of various land use categories to the capability of microwave sensors to provide snow information and (2) to study combined use of radar and microwave radiometer in snow mapping.

18th European Microwave Conference, 1988, 1988

A helicopter-borne dual-frequency FM-CW scatterometer for remote sensing is described. The scatte... more A helicopter-borne dual-frequency FM-CW scatterometer for remote sensing is described. The scatterometer can measure the radar backscatter from a target with a range resolution of one meter. This is accomplished by preforming the Fast Fourier Transform to the received time-domain signal. The measurement is made simultaneously at eight channels (VV, HH, HV, and VH modes of polarization at 5.4 GHz and 9.8 GHz).

… Remote Sensing: An …, 1989

A helicopter-borne dual-frequency FM-CW scatterometer (HUTSCAT, Helsinki University of Technology... more A helicopter-borne dual-frequency FM-CW scatterometer (HUTSCAT, Helsinki University of Technology SCATterometer) is described. The HUTSCAT measures the backscattering properties of a target with a range resolution of 65 cm. The real-time ranging capability is obtained by performing the Fast Fourier Transform (FlT) to the received time-domain signal. The measurement is made simultaneously at eight channels (VV, HH, HV, and VH modes of polarization at 5.4 GHz and 9.8 GHz). The scatterometer measures the radar return spectrum for eight channels in 16.6 ms which corresponds to an along-track distance of 0.33 m for the helicopter speed of 20 m/s. The radar system has been designed for remote sensing of forests, sea ice, and snow. The most potential application is the estimation of forest stand characteristics, to be discussed in Part I1 of this paper.