Papers by Martti Heikinheimo
Agricultural and Forest Meteorology, 1999
The NOPEX two concentrated ®eld efforts (CFEs) (June 1994 and April±July 1995) provide high quali... more The NOPEX two concentrated ®eld efforts (CFEs) (June 1994 and April±July 1995) provide high quality data sets for the Boreal environment. The analysis of these data with traditional meteorological and hydrological approaches allow estimations of¯uxes of latent and sensible heat, but these¯ux estimates are not directly comparable due to differences in temporal and spatial scales. The challenge here has been to overcome these dif®culties so that the different estimates can be critically compared and evaluated in a systematical way. Five different approaches for the estimation of the regional¯ux of sensible and/or latent heat over the NOPEX area have been evaluated: (1) Direct aggregation Ð mixed layer evolution method, (2) Weighted averages of (a) aircraft measurements in the boundary layer and of (b) mast measurements, (3) Numerical models (a) ECOMAG Ð a distributed hydrological model and (b) MIUU Ð a mesoscale meteorological model.
1. Summary of major highlights A new verification system became operational in the end of 2008 re... more 1. Summary of major highlights A new verification system became operational in the end of 2008 replacing the previous one with various new features. The technical structure is totally new and enables better options for enhancements and further developments. The new system will allow for direct comparison of direct model output, post-processed model output, and end products based on gird-edited data of the forecasters. Some results are presented here. Monthly and seasonal EPS data have been applied to produce different physical, chemical and biological variables in the Baltic Sea. 2. Use and application of model output ECMWF output are used widely supporting the traditional weather service, and also as input for various applications like limited area NWP modelling (HIRLAM, AROME), dispersion and trajectory models, hydrological models (run by Finland's Environmental Administration), road condition models, and wave models. 2.1 Post-processing of products 2.1.2 Physical adaptation F...
Journal of Atmospheric and Oceanic Technology, 1989
A miniature open-path CO2 and H2O sensor for the simultaneous monitoring of CO2 and water vapor w... more A miniature open-path CO2 and H2O sensor for the simultaneous monitoring of CO2 and water vapor was designed and was used for measuring atmospheric turbulence fluctuations and, in conjunction with a fast-response anemometer, of the transport of these entities above vegetated canopies. The sensor was found to have suitable noise and stability features for the determination of fluxes over a
Agricultural and Forest Meteorology, 1999
In order to improve the accuracy of forecasting near-surface atmospheric variables over a heterog... more In order to improve the accuracy of forecasting near-surface atmospheric variables over a heterogeneous landscape, a framework of subgrid surface types and the ISBA parameterisation scheme for land surfaces have been tested in the operational weather forecast model HIRLAM, using a 5.5 km grid resolution. Surface energy¯uxes measured during a single summer day at six ®xed sites in the NOPEX area, representing agricultural ®elds, boreal forests and lakes, were used for veri®cation.
Weather warnings for high impact weather play a more crucial role than ever. With rising vulnerab... more Weather warnings for high impact weather play a more crucial role than ever. With rising vulnerability impact and damages continue to rise. The meteoalarm platform brought producers of warnings (National Meteorological and Hydrological Services) and their users closer together. The users come in high numbers from the general public, but also from public institutions within Civil Protection, who looks for
Radiosondes releases during the NOPEX-WINTEX experiment carried out in late winter in Northern Fi... more Radiosondes releases during the NOPEX-WINTEX experiment carried out in late winter in Northern Finland were analysed for the determination of the height h of the atmospheric boundary layer. We investigate various possible scaling approaches, based on length scales using micrometeorological turbulence surface measurements and the background atmospheric stratification above h. Under stable conditions, the three previously observed turbulence regimes delineated by values of z/L (L is the Obukhov length) appears as a blueprint for understanding the departures found for the suitability of the Ekman scaling based on L E = u * /f (u * is the friction velocity and f the Coriolis parameter). The length scale L N = u * /N (where N is the Brunt-Väisälä frequency) appears to be a useful scale under most stable conditions, especially in association with L. Under unstable conditions, shear production of turbulence is still significant, so that the three scales L, L N and L E are again relevant and the dimensionless ratios µ N = L N /L and L N /L E = N/f describe well the WINTEX data. Furthermore, in the classical scaling framework, the unstable domain may also be divided into three regimes as reflected by the dependence of u * on instability (z/L).
The influence of the predicted climate warming on soil frost conditions in Finland was studied us... more The influence of the predicted climate warming on soil frost conditions in Finland was studied using a climate scenario based on a Hadley Centre (U.K.) global ocean-atmosphere general circulation model (HadCM2) run. HadCM2 results were dynamically downscaled to the regional level using the regional climate model at the Rossby Centre (Sweden). The future period this study focuses on is the
Theoretical and Applied Climatology, 2001
Polar-orbiting NOAA14 AVHRR (Advanced Very-High-Resolution Radiometer) based estimates of surface... more Polar-orbiting NOAA14 AVHRR (Advanced Very-High-Resolution Radiometer) based estimates of surface re¯ectance, with a spatial resolution of about 1.1 km at nadir, were derived for a single almost cloud-free image of snowcovered, partly-forested boreal terrain in northern Finland. As a part of the WINTEX campaign, comparative measurements of re¯ectance were made along three 30 km¯ight legs with downward and upward-facing broadband pyranometers installed in a C-130 aircraft. After co-location of the satellite sensor pixels and the airborne samples, the two estimates of broadband (0.3±3 mm) surface re¯ectance matched to within 2%, with a standard error of 4.4% (absolute units). The re¯ectance variation obtained by the aircraft along the¯ight legs was well matched by the satellite-based method.
Theoretical and Applied Climatology, 2001
Reasonably simple yet realistic modelling schemes simulating the heat and mass balance within a s... more Reasonably simple yet realistic modelling schemes simulating the heat and mass balance within a snow pack are required to provide the necessary boundary conditions for meteorological and hydrological models. An improvement to a one-layer snow energy balance model (UEB, Tarboton et al., 1995) is proposed to better simulate snow surface and snow pack temperatures and, as a result, snowmelt. The modi®ed scheme is assessed against measured snow data from the WINTEX ®eld campaign during spring 1997 in northern Finland, and compared with results from a complex multi-layer snow energy balance scheme. The results show that separation of a one-layer representation into two snow layers and a soil layer enables a more realistic simulation of soil and snow temperatures as well as of the snow surface temperature. The two-layer and the multi-layer snow schemes yielded comparable results for internal processes in the snow whenever the simulation was carried out under similar boundary forcing. The modi®ed scheme is proposed for use as a sub-scheme in meteorological or hydrological models, or as a tool for simulating spatially-variable snowmelt and the surface energy balance during seasonal snow cover.
Physics and Chemistry of the Earth, Parts A/B/C, 2002
Many agricultural applications are based on meteorological data. For example estimation of surfac... more Many agricultural applications are based on meteorological data. For example estimation of surface moisture, crop yield or forecasting of outbreak of crop diseases or insect pests is largely dependent on meteorological conditions. To ensure that there continuously is a (in spite of changes in meteorological observing network) spatially and temporally adequate amount of meteorological data available a system was taken
Journal of Hydrology, 1998
The interface between land surfaces and the atmosphere is a key area in climate research, where l... more The interface between land surfaces and the atmosphere is a key area in climate research, where lack of basic knowledge prevents us from reducing the considerable uncertainties about predicted changes. Boreal forests play an important, but not well known, role in the global hydrological and biogeochemical cycles. NOPEX (a NOrthern hemisphere climate Processes land surface EXperiment) is devoted to the
Journal of Applied Meteorology, 1999
... Sci.,21, 361385. Möser, W., and E. Raschke, 1983: Mapping global radiation and cloudiness fr... more ... Sci.,21, 361385. Möser, W., and E. Raschke, 1983: Mapping global radiation and cloudiness from METEOSAT image data. Meteor. Rundsch.,36, 3341. Pinker, RT, and J. Ewing, 1985: Modeling surface solar radiation:Model formulation and validation. J. Climate Appl. ...
Boundary-layer Meteorology - BOUND-LAY METEOROL, 1998
The dependency of the latent heat flux on the over-water fetch on lakes surrounded by tall, dense... more The dependency of the latent heat flux on the over-water fetch on lakes surrounded by tall, dense forest was studied by making use of measurements made on two different-sized lakes. The measurements were made during the NOPEX (Northern Hemisphere Climate-Processes Land Surface Experiment) field campaign. It was found that, in the case of a typical Scandinavian lake with a size of less than 10 km2, the latent heat flux will increase as a function of over-water fetch due to the increase of wind speed and in spite of the increased air humidity. This also has implications on area-averaged fluxes: when two lakes having similar shorelines, lake water temperatures and solar radiation conditions are compared, then the evaporation per unit area is smaller from the smaller lake. When the lakes are large, with fetches of several kilometres, then the significance of sheltering is small. If point measurements are used for the estimation of area-averaged latent heat fluxes from lakes with short f...
International Journal of Climatology, 1997
In this study, detailed spatial analyses of the long-term mean global radiation in Finland were m... more In this study, detailed spatial analyses of the long-term mean global radiation in Finland were made using both directly measured and indirectly estimated radiation values. The interpolation on to a 10 km ×10 km grid was done using the kriging interpolation method, which can take external forcing, such as the altitude, into account in the interpolation. The time period used
Hydrological Processes, 2001
Evaporation from a willow short-rotation forest was analysed using a modified version of the Shut... more Evaporation from a willow short-rotation forest was analysed using a modified version of the Shuttleworth-Wallace model. The main modification consisted of a two-layer soil module, which enabled soil surface resistance to be calculated as a function of the wetness of the top soil. Introduction of the threshold value of the leaf area index when scaling up from the leaf to the canopy resistance resulted in improvement to the simulated evaporation. The analysis was concentrated mainly on the 1988 season (May-October) when total evaporation was measured by the energy balance/Bowen ratio method throughout the growing season, covering all stages of canopy development. At the beginning of the 1994 season, soil evaporation were also measured with a ventilated chamber system. The general seasonal dynamics of the evaporation were fairly well simulated with the model. The largest deviation between measured and simulated evaporation occurred in June, when the model underestimated evaporation by about 1 mm day 1 . The model underestimated also in May but not as much as in June. In September and October the performance of the model was very good. For 130 days of the period May-October the cumulated measured evaporation was 364 mm and the simulated evaporation for the same days was 362 mm. It should be pointed out that this result was obtained without calibrating the model against the measured evaporation. The total simulated evaporation for the season was 450 mm with transpiration constituting 298 mm (66%), soil evaporation 102 mm (23%) and interception evaporation 50 mm (11%). The sensitivity analysis showed, in general, that simulated evaporation was most sensitive to changes in resistances when the leaf area index was smallest, i.e. under non-closed canopy conditions. Changes in stomatal resistance, which is one of the most sensitive parameters, with associated changes in canopy transpiration, resulted in a negative feedback effect on soil evaporation. This reduced the total evaporation's sensitivity to stomatal resistance. This type of interaction between canopy and soil or undergrowth fluxes has been observed in other studies as well.
Hydrological Processes, 1999
The objective of this study was to compare two energy balance models to simulate energy exchange,... more The objective of this study was to compare two energy balance models to simulate energy exchange, skin temperature and albedo at the snow surface. Point measurements of vertical snow temperature and density pro®les, snow surface temperature, net radiation and albedo were taken during spring 1997 at a site within a sparse coniferous stand in northern Finland. Standard meteorological measurements were available near the snow site at the SodankylaÈ Meteorological Observatory. The study period included two weeks of measurements of turbulent heat¯uxes with the eddy-correlation method above snow as a part of the NOPEX±WINTEX project``Land-surface-atmosphere interactions in a wintertime boreal landscape''. Two point models with dierent snow process representations were tested and the modelled energy¯uxes at the snow surface were compared. UEB was chosen as a simple model, which derived the surface energy¯uxes but treated the snowpack as one layer. SNTHERM represented a sophisticated model to simulate mass and energy transfer at the snowpack boundaries and within the snow cover. The results showed major dierences in the modelled radiation balance due to dierent albedo procedures implemented in the models. The model comparison using identical radiation input data indicated that SNTHERM had a better overall agreement to the measurements as compared with UEB. Major dierences between the two models were found in the calculation of sensible heat ux and snow surface temperature, which were sensitive to the correction for atmospheric stability and snow thermal conductivity, respectively. The comparison of the SNTHERM results to the eddy-correlation measurements of sensible heat¯ux supported the use of a restricted correction for atmospheric stability. The forest canopy had a notable eect on the short-wave radiation balance, the vertical wind pro®le, and the measured sensible heat¯ux.
Climate Research, 2001
This study was aimed at assessing the potential impacts of climate change on the depth and durati... more This study was aimed at assessing the potential impacts of climate change on the depth and duration of soil frost under snow cover in forests growing at different geographical locations in Finland. Frost simulations using a process-based forest ecosystem model (FinnFor) were made for Scots pine Pinus sylvestris L. stands (height 17 m, stand density 1100 stems ha -1 ) growing on a moraine sandy soil. The climate change forecast used in the computations was based on the global ocean-atmosphere general circulation model HadCM2 that was dynamically downscaled to the regional level. The simulated climate warming during the winter months was about 4 to 5°C by the end of the 21st century. Frost simulations showed that the length of the soil frost period would lessen all over the country. Though winters will be warmer, the associated decrease in snow cover in southern Finland will increase the probability of frozen ground there in the middle of winter compared with the current climate. In central and northern Finland there will be so much snow, even in the future, that the maximum annual soil frost depth will decrease there.
Bulletin of the American Meteorological Society, 2001
The Baltic Sea Experiment (BALTEX) is one of the five continental-scale experiments of the Global... more The Baltic Sea Experiment (BALTEX) is one of the five continental-scale experiments of the Global Energy and Water Cycle Experiment (GEWEX). More than 50 research groups from 14 European countries are participating in this project to measure and model the energy and water cycle over the large drainage basin of the Baltic Sea in northern Europe. BALTEX aims to provide a better understanding of the processes of the climate system and to improve and to validate the water cycle in regional numerical models for weather forecasting and climate studies. A major effort is undertaken to couple interactively the atmosphere with the vegetated continental surfaces and the Baltic Sea including its sea ice. The intensive observational and modeling phase BRIDGE, which is a contribution to the Coordinated Enhanced Observing Period of GEWEX, will provide enhanced datasets for the period October 1999-February 2002 to validate numerical models and satellite products. Major achievements have been obtained in an improved understanding of related exchange processes. For the first time an interactive atmosphere-ocean-land surface model for the Baltic Sea was tested. This paper reports on major activities and some results.
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Papers by Martti Heikinheimo