Fysikaaliset menetelmät metsien kaukokartoituksessa

Tieteen tori: Tavoitteena metsien monet hyödy

Spectral contribution of understory to forest reflectance in a boreal site : an analysis of EO-1 Hyperion data

Boreal forests exhibit strong seasonal dynamics in their reflectance spectra during the short, snow-free growing period. This short communication paper reports an analysis of the seasonality of boreal forest spectra from the end of snowmelt until the time of maximal leaf area. We apply a forest reflectance model (FRT) to estimate the seasonal contribution of understow vegetation to forest reflectance from a time series of three Earth Observing 1 (EO-1) Hyperion images acquired in May, June and July. The reflectance simulations are based on detailed seasonal series of leaf area index and understory spectra measurements carried out in ten stands at the Hyytiala Forestry Field Station in Finland. Our results show that the contribution of understory to boreal forest reflectance is high in the visible domain, but it drops at the red edge and stays relatively low and constant in near infrared (NIR). Throughout the growing season, the contribution of the understory remains approximately the same in the NIR domain, whereas larger changes can be observed in the visible domain. (C) 2015 The Authors. Published by Elsevier Inc.Peer reviewe

Scaling PRI between coniferous canopy structures

Peer reviewe

On the angular dependency of canopy gap fractions in pine, spruce and birch stands

The angular profiles of canopy gap fraction curves are influenced by canopy structure, and are commonly expected to vary with stand- and crown-level variables such as tree pattern, crown shape and leaf orientation. In this study, measurements of canopy structure, gap fractions and effective LA! in 986 plots of Scots pine, Norway spruce and Silver birch stands in Finland were used to assess how similar the angular canopy gap fraction profiles are for common boreal tree species. The profiles were characterized with help of the shape function psi(theta), defined as the normalized value of the canopy light extinction coefficient at zenith angle (theta). Variation in psi(theta) would be induced not only by a non-spherical leaf orientation, but also by differences in the directional clumping indices, such as could result from species-specific differences in crown shape. Our results showed that there is wide variation in the shape of psi in the individual plots of the three different species. The species-specific mean curves psi(theta), however, showed relatively small variation with theta, except for a sudden drop at large zenith angles, and the shape of the curves was similar for the different tree species. Results indicate that differences in crown shape of the study species do not significantly affect the angular profiles of canopy gap fraction. (C) 2015 The Authors. Published by Elsevier B.V.Peer reviewe

Storm water modelling and flood risk assessment in Turku harbor catchment

Kaupunkirakenteen tiivistyminen ja läpäisevien pintojen määrän ja laadun muuttuminen vaikuttavat kaupunkihydrologiaan ja lisäävät tarvetta hallita hulevesiä tulvavahinkojen välttämiseksi. Hulevesien hallinta on tullut osaksi kaupunkisuunnittelua ja sen huomiointiin kaavoituksessa ohjataan Suomessa myös lainsäädännöllä. Hulevedet nähdään yhä useammin mahdollisuutena ja osana kaupunkiympäristöä, sen sijaan että ne nähtäisiin haittana. Hulevesiä suositellaan pidättämään ja imeyttämään niiden syntypaikalla sen sijaan että ne johdettaisiin viemäriin. Tämän työn tavoitteena oli mallintaa Turun sataman valuma-alueen hulevesiverkostoa rankkasadetilanteessa ja arvioida eri skenaarioiden avulla alueen tulvariskiä. Lisäksi mallinnuksen avulla tutkittiin, millaisia vaikutuksia viherkatoilla voisi olla alueen hulevesiin. Turussa hulevesien hallinta on mukana suunnittelussa, kun keskustan ja sataman aluetta kaavoitetaan. Turun sataman valuma-alueelle tyypillistä on sen tasaisuus. Hulevesiverkoston kapasiteettia rajoittavat osittain merenpinnan alapuolella sijaitseva verkoston alaosa sekä verkostoon liittyvä jätevedenpuhdistamon purkuputki. Skenaarioiden avulla tutkittiin maaperän johtavuuden vaikutusta, merivesitulvaa sekä tilannetta, jossa jätevedenpuhdistamon purkuvesiä ei enää johdeta hulevesiverkostoon. Lisäksi mallinnettiin eripaksuisia viherkattoja eri alkukosteuksilla 100 %:lle ja 10 %:lle valuma-alueen katoista. Mallinnus tehtiin SWMM5-ohjelmalla. Mallin rakennuksessa käytettiin vastikään kehitettyä GisToSWMM5-ohjelmaa. Mallinnus tehtiin vuoden 2012 elo- ja lokakuun rankkasadetapahtumille, jotka aiheuttivat Turussa hulevesitulvia ja vahinkoja. Tulosten perusteella jätevedenpuhdistamon purkuvesien poistaminen hulevesiverkostosta ei rankkasateella välttämättä vähentäisi merkittävästi verkoston tulvintaa, vaikka kokonaisvalunta vähenisikin huomattavasti. Merivesi rajoittaa hulevesiverkoston kapasiteettia rannikolla, mikä lisää myös hulevesitulvariskiä ylempänä verkostossa. Viherkatoilla puolestaan voidaan vaikuttaa hulevesien pidätykseen ja sadejakson ensimmäiseen virtaamahuippuun madaltavasti.Denser cities and changes in the amount and quality of pervious surfaces have an impact on the urban hydrology and increase the need to manage storm water to avoid flood damages. Storm water management has become a part of city planning and also the Finnish law requires storm water issues to be included in new city plans. Storm water is increasingly seen as an integral part of the city environment, rather than a problem that needs to be removed. Storm water is recommended to be retained and infiltrated on site instead of directing it to the sewage network. The aim of this study was to model the storm water drainage network in Turku harbor catchment during a heavy rain and assess the flood risk of the area with the help of different scenarios. The impact of green roofs on the storm water quantity in the area was also modelled. In Turku storm water management is addressed in planning new developments in the city center and the harbor area. The harbor catchment is typically very flat. Factors limiting the capacity of the drainage network are the situation of lower part of the network below the sea level and the connection between wastewater treatment plant’s discharge pipe and the network. Different scenarios were constructed for studying the impact of the hydraulic conductivity of soil, coastal flood, and conveying the wastewater treatment plant discharge directly to the sea with a new pipeline. In addition, the impact of green roofs with different thicknesses and initial moisture contents was modelled using 100 % and 10 % coverage of the catchment roof area. Modelling was carried out with SWMM5 using heavy rain events from August and October 2012, which had caused storm water flood damage in the study area. The model parametrizations were created with the aid of the recently developed GisToSWMM5 program. According to the modelling results redirecting the wastewater discharge would not necessarily decrease significantly flooding in the although the total discharge would decrease. Sea level limits the capacity of the drainage network on the coast, which increases the risk of storm water floods also in the upper parts of the network. Green roofs increase the water retention capacity lowering especially the first flow peak

DSCOVR EPIC vegetation earth system data record: product analysis and scientific exploration

The NASA's Earth Polychromatic Imaging Camera (EPIC) onboard NOAA's Deep Space Climate Observatory (DSCOVR) mission was launched on February 11, 2015 to the Sun-Earth Lagrangian L1 point where it began to collect radiance data of the entire sunlit Earth every 65 to 110 min in June 2015. It provides imageries in near backscattering directions at ten ultraviolet to near infrared narrow spectral bands. The DSCOVR EPIC science product suite includes vegetation Earth System Data Record (VESDR) that provides leaf area index (LAI) and diurnal courses of normalized difference vegetation index (NDVI), sunlit LAI (SLAI), fraction of incident photosynthetically active radiation (FPAR) and directional area scattering function (DASF). The parameters at 10 km sinusoidal grid and 65 to 110 minute temporal frequency generated from the upstream DSCOVR EPIC BRF product were released on June-07-2018 and are available from the NASA Langley Atmospheric Science Data Center. This poster provides an overview of the EPIC VESDR research. This includes a description of the algorithm and its performance, details of the product, its initial quality assessment and obtaining new information on the 3D canopy structure for use in ecological models through novel combinations of the VESDR parameters.Accepted manuscrip

Photon recollision probability in heterogeneous forest canopies: : compatibility with a hybrid GO model

Peer reviewe

Seasonal changes in canopy leaf area index and MODIS vegetation products for a boreal forest site in central Finland

Peer reviewe

Shoot scattering phase function for Scots pine and its effect on canopy reflectance

Spectral and directional reflectance properties of coniferous forests are known to differ from those of broadleaf forests. Many reasons have been proposed for this, including differences in the optical properties of leaves and shoots, the latter being considered the basic unit in radiative transfer modeling of a coniferous canopy. Unfortunately, very little empirical data is available on the spectrodirectional scattering properties of shoots. Here, we present results of angular measurements (using an ASD FieldSpec 3 spectroradiometer mounted on LAGOS) of ten Scots pine shoots in the spectral range 400--2000 nm. The shoots were found to scatter anisotropically with most of the radiation reflected back into the hemisphere where the radiation source was positioned. To describe the measured directional scattering pattern, we propose a phase function consisting of isotropic and Lambertian scattering components. Next, we used the proposed scattering phase function in a Monte Carlo radiative transfer model. Angular reflectance of a modeled horizontally homogeneous shoot canopy has, due to shoot scattering anisotropy, an enhanced “dark spot” as compared with a canopy composed of isotropic scatterers and a quantitatively similar leaf canopy.Peer reviewe