Pub Date : 2010-11-04DOI: 10.1109/BALTIC.2010.5621653
M. Valentin, T. Helzel, V. Mariette, N. Thomas
The HF-Coastal Radar “WERA” is a shore based remote sensing system to monitor ocean surface currents, waves and wind direction. This very reliable long range and high resolution monitoring system based on short radio wave radar technology. Due to the outstanding accuracy WERA can provide very valuable data to be assimilated into hydrographic models. In case of accidents in a distance of up to 200 km off the coast the real-time ocean surface current data can help Search and Rescue (SAR) operators. Presently, SAR tools are based on hydro-dynamical and atmospheric models to provide hindcast and forecast situations. Even if these oceanic numerical models are efficient to produce instantaneous maps of currents, the accuracy of derived Lagrangian trajectories often is not sufficient for search and rescue purposes. To improve these numerical models by means of realtime data it is essential that the quality of the assimilated data is very high and reliable. For this reason long term comparisons with buoy data for ground truthing and statistical analysis were carried out for more than two years. The resulting data availability (98,7 %) is outstanding and the data quality is as good as buoy data.
{"title":"Coastal Radar WERA, a tool for Search and Rescue and oil spill management","authors":"M. Valentin, T. Helzel, V. Mariette, N. Thomas","doi":"10.1109/BALTIC.2010.5621653","DOIUrl":"https://doi.org/10.1109/BALTIC.2010.5621653","url":null,"abstract":"The HF-Coastal Radar “WERA” is a shore based remote sensing system to monitor ocean surface currents, waves and wind direction. This very reliable long range and high resolution monitoring system based on short radio wave radar technology. Due to the outstanding accuracy WERA can provide very valuable data to be assimilated into hydrographic models. In case of accidents in a distance of up to 200 km off the coast the real-time ocean surface current data can help Search and Rescue (SAR) operators. Presently, SAR tools are based on hydro-dynamical and atmospheric models to provide hindcast and forecast situations. Even if these oceanic numerical models are efficient to produce instantaneous maps of currents, the accuracy of derived Lagrangian trajectories often is not sufficient for search and rescue purposes. To improve these numerical models by means of realtime data it is essential that the quality of the assimilated data is very high and reliable. For this reason long term comparisons with buoy data for ground truthing and statistical analysis were carried out for more than two years. The resulting data availability (98,7 %) is outstanding and the data quality is as good as buoy data.","PeriodicalId":287473,"journal":{"name":"2010 IEEE/OES Baltic International Symposium (BALTIC)","volume":"30 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2010-11-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126590967","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2010-11-04DOI: 10.1109/BALTIC.2010.5621654
L. Kelpšaitė, I. Dailidienė
Changes of the wind and wave regime at the south eastern coast of the Baltic proper, Lithuanian coast, during last decades can be interpreted, as one of the cause of the changes in the sediment transport at study area. Main changes in the predominant wave direction were noticed in the different years that clarify changes in the annual wave activities. Noticed features estimated from field observations and geomorphic features showed that waves approaching from the south-west direction are the major driver for the coastal processes and cause predominant sediment transport along the Lithuanian coast from the south to north. Wave activity is the major driver of coastal processes along the eastern coast of the Baltic Sea and in many sections of its sub-basins. The Lithuanian sea coast is almost straight and exposed to the wind and wave impact. Changes in the wave regime at the eastern coast of the Baltic proper may cause considerable changes in the coastal processes. Variations in the wind wave dynamics may occur at the main wave parameters, such as wave height and period. Changes in the wave approaching direction also may be significant in the short time period. In this study we analyzed changes of the wave regimes at the south-eastern part of the Baltic proper, Lithuanian coast during last decades. Result show that this research can be interpreted, as one of the cause of the changes in the sediment transport regime at study area. Wave prorogation direction mainly depends on the prevalent wind direction. It should be noted that the intensity of coastal circulation has increased during the research period. Changes in the wind direction induce more repetitive west wave direction. The most frequent wave approach direction was indicated as south-west. The second most frequent direction of wind directions and wave approach directions is either from west. These directions also correspond with the typical direction of strongest winds and have one of the longest fetches in the South-eastern Baltic at the Lithuanian coast. This analysis partly explains changes in the abrasion processes at the Lithuanian coast of the Baltic proper. That allows us to continue further studies of changes in wave's regime in the study area, because of the important practical and economical consequences.
{"title":"Wind and wind waves regime climatical changes at the SE Baltic Sea coast","authors":"L. Kelpšaitė, I. Dailidienė","doi":"10.1109/BALTIC.2010.5621654","DOIUrl":"https://doi.org/10.1109/BALTIC.2010.5621654","url":null,"abstract":"Changes of the wind and wave regime at the south eastern coast of the Baltic proper, Lithuanian coast, during last decades can be interpreted, as one of the cause of the changes in the sediment transport at study area. Main changes in the predominant wave direction were noticed in the different years that clarify changes in the annual wave activities. Noticed features estimated from field observations and geomorphic features showed that waves approaching from the south-west direction are the major driver for the coastal processes and cause predominant sediment transport along the Lithuanian coast from the south to north. Wave activity is the major driver of coastal processes along the eastern coast of the Baltic Sea and in many sections of its sub-basins. The Lithuanian sea coast is almost straight and exposed to the wind and wave impact. Changes in the wave regime at the eastern coast of the Baltic proper may cause considerable changes in the coastal processes. Variations in the wind wave dynamics may occur at the main wave parameters, such as wave height and period. Changes in the wave approaching direction also may be significant in the short time period. In this study we analyzed changes of the wave regimes at the south-eastern part of the Baltic proper, Lithuanian coast during last decades. Result show that this research can be interpreted, as one of the cause of the changes in the sediment transport regime at study area. Wave prorogation direction mainly depends on the prevalent wind direction. It should be noted that the intensity of coastal circulation has increased during the research period. Changes in the wind direction induce more repetitive west wave direction. The most frequent wave approach direction was indicated as south-west. The second most frequent direction of wind directions and wave approach directions is either from west. These directions also correspond with the typical direction of strongest winds and have one of the longest fetches in the South-eastern Baltic at the Lithuanian coast. This analysis partly explains changes in the abrasion processes at the Lithuanian coast of the Baltic proper. That allows us to continue further studies of changes in wave's regime in the study area, because of the important practical and economical consequences.","PeriodicalId":287473,"journal":{"name":"2010 IEEE/OES Baltic International Symposium (BALTIC)","volume":"14 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2010-11-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131110281","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2010-11-04DOI: 10.1109/BALTIC.2010.5621651
D. Vaičiūtė, I. Olenina, Rima Kavolyte, I. Dailidienė, R. Pilkaitytė
The national water quality monitoring in the Lithuanian Baltic Sea waters has started fifty years ago. Consistently implemented long-term monitoring programs are critical for detecting changes in water environment in frame of rapidly changing climate and increasing anthropogenic activity on costal waters. Nevertheless, conventional sampling methods cannot produce enough data about spatial and temporal distribution of phytoplankton blooms, outflow hypertrophic waters of the Curonian Lagoon in the Sea. Satellite based remote sensing provides critical ecological information on global, regional and local scales. However, before the direct use of satellite products for the monitoring and scientific applications, Earth observation data should be validated with in situ measurements for the particular research area.
{"title":"Validation of MERIS chlorophyll a products in the Lithuanian Baltic Sea case 2 coastal waters","authors":"D. Vaičiūtė, I. Olenina, Rima Kavolyte, I. Dailidienė, R. Pilkaitytė","doi":"10.1109/BALTIC.2010.5621651","DOIUrl":"https://doi.org/10.1109/BALTIC.2010.5621651","url":null,"abstract":"The national water quality monitoring in the Lithuanian Baltic Sea waters has started fifty years ago. Consistently implemented long-term monitoring programs are critical for detecting changes in water environment in frame of rapidly changing climate and increasing anthropogenic activity on costal waters. Nevertheless, conventional sampling methods cannot produce enough data about spatial and temporal distribution of phytoplankton blooms, outflow hypertrophic waters of the Curonian Lagoon in the Sea. Satellite based remote sensing provides critical ecological information on global, regional and local scales. However, before the direct use of satellite products for the monitoring and scientific applications, Earth observation data should be validated with in situ measurements for the particular research area.","PeriodicalId":287473,"journal":{"name":"2010 IEEE/OES Baltic International Symposium (BALTIC)","volume":"10 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2010-11-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116969030","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2010-11-04DOI: 10.1109/BALTIC.2010.5621640
A. Williams
Current measurements under ice face some challenges not present when measuring current in open water and water free of ice. There is the problem of getting the current meter through a hole in the ice, which limits the horizontal dimensions of the instrument package such as fins that might provide directional stability in open water. Then there is the issue of damage to the sensor from contact with ice in the hole, a problem that is generally less threatening in open water, so for ice deployments protection against this may be required. The small chunks of ice in the hole may interfere with the measurement, certainly a major concern with mechanical sensors, but also an issue with acoustic sensors. Finally, a mooring anchored to the moving ice surface must be tracked for recovery if data are to be only recorded internally. If the data are to be telemetered ashore there must be a data connection to the surface through the mooring line.
{"title":"Current measurements under ice","authors":"A. Williams","doi":"10.1109/BALTIC.2010.5621640","DOIUrl":"https://doi.org/10.1109/BALTIC.2010.5621640","url":null,"abstract":"Current measurements under ice face some challenges not present when measuring current in open water and water free of ice. There is the problem of getting the current meter through a hole in the ice, which limits the horizontal dimensions of the instrument package such as fins that might provide directional stability in open water. Then there is the issue of damage to the sensor from contact with ice in the hole, a problem that is generally less threatening in open water, so for ice deployments protection against this may be required. The small chunks of ice in the hole may interfere with the measurement, certainly a major concern with mechanical sensors, but also an issue with acoustic sensors. Finally, a mooring anchored to the moving ice surface must be tracked for recovery if data are to be only recorded internally. If the data are to be telemetered ashore there must be a data connection to the surface through the mooring line.","PeriodicalId":287473,"journal":{"name":"2010 IEEE/OES Baltic International Symposium (BALTIC)","volume":"31 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2010-11-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117002299","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2010-11-04DOI: 10.1109/BALTIC.2010.5621641
I. Maljutenko, J. Laanemets, U. Raudsepp
Gulf of Finland is described as water body with very complex hydrography. Discharge of the largest river Neva in the eastern part of Gulf is the main cause for horizontal salinity gradient. Buoyancy driven mean cyclonic circulation varies with short term wind forced currents. The 10-year (1997–2006) simulation was done with the General Estuarine Transport Model. The horizontal resolution of the model grid was 0.5 nautical miles and 25 sigma layers in the vertical direction. The model reproduced overall seasonal cycle of temperature and salinity stratification with high inter-annual variability. Annual evolution of temperature stratification followed prevailing meteorological conditions of different years. The years with extreme meteorological conditions are well resolved by the model: the warmest (2002) and coldest (1998) summer and likewise the warm ice free winters 2000/2001 and 2001/2002. Model resolves mesoscale phenomena. Average mean surface circulation showed more persistent surface currents near the southern coast of the Gulf.
{"title":"Long-term high-resolution hydrodynamical model simulation in the Gulf of Finland","authors":"I. Maljutenko, J. Laanemets, U. Raudsepp","doi":"10.1109/BALTIC.2010.5621641","DOIUrl":"https://doi.org/10.1109/BALTIC.2010.5621641","url":null,"abstract":"Gulf of Finland is described as water body with very complex hydrography. Discharge of the largest river Neva in the eastern part of Gulf is the main cause for horizontal salinity gradient. Buoyancy driven mean cyclonic circulation varies with short term wind forced currents. The 10-year (1997–2006) simulation was done with the General Estuarine Transport Model. The horizontal resolution of the model grid was 0.5 nautical miles and 25 sigma layers in the vertical direction. The model reproduced overall seasonal cycle of temperature and salinity stratification with high inter-annual variability. Annual evolution of temperature stratification followed prevailing meteorological conditions of different years. The years with extreme meteorological conditions are well resolved by the model: the warmest (2002) and coldest (1998) summer and likewise the warm ice free winters 2000/2001 and 2001/2002. Model resolves mesoscale phenomena. Average mean surface circulation showed more persistent surface currents near the southern coast of the Gulf.","PeriodicalId":287473,"journal":{"name":"2010 IEEE/OES Baltic International Symposium (BALTIC)","volume":"21 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2010-11-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117006300","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2010-11-04DOI: 10.1109/BALTIC.2010.5621656
P. Lagemaa, I. Suhhova, M. Nõmm, J. Pavelson, J. Elken
Current modeling results from two operational models (Baltic-wide HIROMB-BS01 with 1 nautical mile resolution and subregional HIROMB-EST with 0.5 mile resolution) were compared with ADCP measurements at four sites of different topographic and hydrographic background in the Gulf of Finland. Both models predict a reasonable match with the observed subsurface currents in most of the cases, although there are no data to carry out the assimilation of mesoscale oceanographic features. The correlations of the modeled currents with the observed counterparts yield quite often the values above 0.5, both in the low-frequency and high-frequency range. In general, the models tend to generate less current variability (smaller standard deviations) than observed. There is also some site-specific bias of mean currents. Near-bottom and coastal currents are highly constrained by the topography. High current speeds (above 20 cm/s) were measured in the deep layers of the rough-bottom area around a small island. Such currents were in general well simulated by the 0.5 nm model, only slightly biased by the dominating direction. The modeled near-bottom currents are simply transformable into more realistic results if the correct topography is taken into account. Both the observations and the subregional model results revealed similar halocline-intensified EOF modes of vertical current structure, the amplitudes of which were correlated quite well.
{"title":"Comparison of current simulations by the state-of-the-art operational models in the Gulf of Finland with ADCP measurements","authors":"P. Lagemaa, I. Suhhova, M. Nõmm, J. Pavelson, J. Elken","doi":"10.1109/BALTIC.2010.5621656","DOIUrl":"https://doi.org/10.1109/BALTIC.2010.5621656","url":null,"abstract":"Current modeling results from two operational models (Baltic-wide HIROMB-BS01 with 1 nautical mile resolution and subregional HIROMB-EST with 0.5 mile resolution) were compared with ADCP measurements at four sites of different topographic and hydrographic background in the Gulf of Finland. Both models predict a reasonable match with the observed subsurface currents in most of the cases, although there are no data to carry out the assimilation of mesoscale oceanographic features. The correlations of the modeled currents with the observed counterparts yield quite often the values above 0.5, both in the low-frequency and high-frequency range. In general, the models tend to generate less current variability (smaller standard deviations) than observed. There is also some site-specific bias of mean currents. Near-bottom and coastal currents are highly constrained by the topography. High current speeds (above 20 cm/s) were measured in the deep layers of the rough-bottom area around a small island. Such currents were in general well simulated by the 0.5 nm model, only slightly biased by the dominating direction. The modeled near-bottom currents are simply transformable into more realistic results if the correct topography is taken into account. Both the observations and the subregional model results revealed similar halocline-intensified EOF modes of vertical current structure, the amplitudes of which were correlated quite well.","PeriodicalId":287473,"journal":{"name":"2010 IEEE/OES Baltic International Symposium (BALTIC)","volume":"51 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2010-11-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132202167","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2010-11-04DOI: 10.1109/BALTIC.2010.5621637
E. Soosaar, L. Sipelgas, U. Raudsepp
Optical satellite remote sensing (MODIS and MERIS) enables to obtain ice coverage imagery during cloud free days. In the mid-latitudes cloud free days occur rather seldom during a single ice season. This reduces the value of optical satellite imagery products meant for operational purposes. In climate research, long time series of ice extent are relevant for providing information on the necessity of ice breaking services. Everyday ice breaking on shipping routes requires information about ice types and ice thickness. While the extent of ice and also some ice types are attainable from satellite remote sensing, a simple ice model can be used for the calculation of ice thickness in the case of fast ice. In this study satellite remote sensing is used for the calculation of ice extent and the identification of ice types in the Gulf of Riga. MODIS reflectance data with spatial resolution of 250 m were used for the analyses of ice cover extent in the period of 2000–2005. The winters of 2000/2001 and 2001/2002 were mild, the maximum ice extent was less than 2000 km2 and the ice season lasted from January till the end of March. The winter of 2002/2003 was quite severe and the Gulf of Riga was fully covered with ice (up to 16000 km2). Pa¨rnu Bay is the area where fast ice forms every year and ice breaking is performed to keep Pa¨rnu harbor operational. A simple combined ice model is therefore applied to Pa¨rnu Bay. Ice modeling is performed when normal and severe winter temperatures occur. The length of ice period is compared with the satellite data from MODIS and visual observations as well. Ice thickness in its turn is compared with the in situ measurements made during these winters. Air temperature, water temperature, wind speed, humidity and solar radiation are the data used in our model calculations. Modeling periods last from December 1 to April 30 in 2002/2003 and 2003/2004 (data from Pa¨rnu Sadam AS). A combined model is used to simulate ice thickness [5]. Initial ice formation and melting when water has access to ice surface is considered to take place both on the top and at the bottom of the existing ice layer. In numerical simulation we have used an equation based on heat fluxes between the atmosphere and the ocean. When fast ice has been formed, it is assumed that water does not have access to the surface of ice any more and ice formation takes place only at the bottom of the existing ice. And therefore an equation based on the difference between water and air temperature is used. Simulated ice thickness agrees well with direct measurements made during severe and normal winters. Simulated snow thickness has been overestimated in comparison with the measurements. The model does not take into account the snow carried away by winds and also the snow that has been compressed (the forming of the so-called snow ice).
光学卫星遥感(MODIS和MERIS)能够在无云的日子里获得冰覆盖的图像。在中纬度地区，在一个冰期无云的日子很少发生。这降低了用于业务目的的光学卫星图像产品的价值。在气候研究中，冰面积的长时间序列对提供破冰服务的必要性具有重要意义。每天在航线上破冰需要了解冰的种类和厚度。虽然可以从卫星遥感获得冰的范围和一些冰的类型，但在快速冰的情况下，可以使用一个简单的冰模型来计算冰的厚度。在本研究中，利用卫星遥感计算了里加湾的冰范围和冰类型的识别。利用空间分辨率为250 m的MODIS反射率数据对2000-2005年的冰盖覆盖范围进行了分析。2000/2001年和2001/2002年冬季气候温和，最大冰面积小于2000 km2，冰期为1 ~ 3月底。2002/2003年的冬天相当严寒，里加湾完全被冰覆盖(面积达16000平方公里)。帕恩奴湾是每年快速结冰的地方，为了保持帕恩奴港的运作，必须进行破冰。因此，一个简单的组合冰模型适用于帕诺尔湾。当正常和严寒的冬季温度发生时，执行冰模型。冰期长度与MODIS卫星资料和目视观测资料进行了比较。冰的厚度反过来又与这些冬季的实地测量结果进行比较。气温、水温、风速、湿度和太阳辐射是我们模型计算中使用的数据。2002/2003年和2003/2004年的模型周期为12月1日至4月30日(数据来自Pa¨rnu Sadam AS)。采用组合模型模拟冰厚[5]。当水进入冰表面时，最初的冰形成和融化被认为发生在现有冰层的顶部和底部。在数值模拟中，我们使用了一个基于大气和海洋之间热流的方程。当快速冰形成时，人们假定水不再能够接触到冰的表面，而冰的形成只发生在现有冰的底部。因此，一个基于水和空气温度之差的方程被使用。模拟的冰厚与在严寒和正常冬季进行的直接测量结果吻合得很好。与实际测量值相比，模拟雪厚被高估了。该模型没有考虑到被风带走的雪和被压缩的雪(所谓的雪冰的形成)。
{"title":"Simple model calculations of the ice thickness for complementing satellite remote sensing of ice extent","authors":"E. Soosaar, L. Sipelgas, U. Raudsepp","doi":"10.1109/BALTIC.2010.5621637","DOIUrl":"https://doi.org/10.1109/BALTIC.2010.5621637","url":null,"abstract":"Optical satellite remote sensing (MODIS and MERIS) enables to obtain ice coverage imagery during cloud free days. In the mid-latitudes cloud free days occur rather seldom during a single ice season. This reduces the value of optical satellite imagery products meant for operational purposes. In climate research, long time series of ice extent are relevant for providing information on the necessity of ice breaking services. Everyday ice breaking on shipping routes requires information about ice types and ice thickness. While the extent of ice and also some ice types are attainable from satellite remote sensing, a simple ice model can be used for the calculation of ice thickness in the case of fast ice. In this study satellite remote sensing is used for the calculation of ice extent and the identification of ice types in the Gulf of Riga. MODIS reflectance data with spatial resolution of 250 m were used for the analyses of ice cover extent in the period of 2000–2005. The winters of 2000/2001 and 2001/2002 were mild, the maximum ice extent was less than 2000 km2 and the ice season lasted from January till the end of March. The winter of 2002/2003 was quite severe and the Gulf of Riga was fully covered with ice (up to 16000 km2). Pa¨rnu Bay is the area where fast ice forms every year and ice breaking is performed to keep Pa¨rnu harbor operational. A simple combined ice model is therefore applied to Pa¨rnu Bay. Ice modeling is performed when normal and severe winter temperatures occur. The length of ice period is compared with the satellite data from MODIS and visual observations as well. Ice thickness in its turn is compared with the in situ measurements made during these winters. Air temperature, water temperature, wind speed, humidity and solar radiation are the data used in our model calculations. Modeling periods last from December 1 to April 30 in 2002/2003 and 2003/2004 (data from Pa¨rnu Sadam AS). A combined model is used to simulate ice thickness [5]. Initial ice formation and melting when water has access to ice surface is considered to take place both on the top and at the bottom of the existing ice layer. In numerical simulation we have used an equation based on heat fluxes between the atmosphere and the ocean. When fast ice has been formed, it is assumed that water does not have access to the surface of ice any more and ice formation takes place only at the bottom of the existing ice. And therefore an equation based on the difference between water and air temperature is used. Simulated ice thickness agrees well with direct measurements made during severe and normal winters. Simulated snow thickness has been overestimated in comparison with the measurements. The model does not take into account the snow carried away by winds and also the snow that has been compressed (the forming of the so-called snow ice).","PeriodicalId":287473,"journal":{"name":"2010 IEEE/OES Baltic International Symposium (BALTIC)","volume":"25 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2010-11-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123875114","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2010-11-04DOI: 10.1109/BALTIC.2010.5621643
A. Stips, M. Lilover
The aim of the present study is to assess changes in the Baltic Sea climate based on different available meteorological data sources (ERA40 and ERA-INTERIM) and various published Baltic Sea climate indices. This regional assessment will be presented in relation to global climate change and assessments available from the literature. The climate of the Baltic Sea which is located between 50N and 70N is mainly influenced by the competition of westerly humid air flow and easterly continental type air masses and is therefore highly variable. We are investigating air temperature, wind speed, cloud cover, solar radiation and precipitation. Comparisons to climate indices of general relevance as the Baltic ice cover will be conducted. Using regression analysis we could confirm the following basic trends, increase in air temperature, increase in precipitation, increase in cloudiness. The increase in air temperature in the Baltic Sea area (0.02K/year) is much more rapid then the warming trend for the global air temperature (0.005K/year). The increase in cloudiness has resulted in an effective reduction of incoming solar radiation therefore the accelerated warming is not a result of increased solar radiation, but likely due to an increased net long wave radiation input. Further it has to be mentioned that not all available data sets confirmed the trend in cloudiness, ERA40 data show a nonsignificant decrease instead. No clear trend in the wind velocities could be detected, but wind velocities from ERA40 reanalysis project show an insignificant increase in wind speeds. Results from model runs with the GETM model (General Estuarine Transport Model, http://getm.eu) show sea surface warming consistent with the increase in heat flux forcing and with satellite observations. The warmer sea surface without an adequate warming in the deeper parts results in a much stronger vertical density stratification and consequently to reduced vertical mixing. A more thorough inspection of the available regional and global data provides some reasonable doubt concerning the application of least square regression analysis to the available time series. Indeed it can be shown by a test based on the F statistics that most of the analyzed time series cannot be considered as stationary and therefore drawing simple regression lines trough these datasets is statistically incorrect. Testing for structural breakpoints in these time series reveals for many investigated parameters and also for many tested climate indices the existence of such breakpoints in the 70–80ties of the last century. Therefore it has to be concluded that the simple trend estimation for many climate parameters is statistically incorrect. Instead for statistical investigations it has to be assumed that there exist either 2 different climate states with either 2 different means or alternatively with 2 different trends which have to be estimated separately.
{"title":"Yet another assessment of climate change in the Baltic Sea area: Breakpoints in climate time series","authors":"A. Stips, M. Lilover","doi":"10.1109/BALTIC.2010.5621643","DOIUrl":"https://doi.org/10.1109/BALTIC.2010.5621643","url":null,"abstract":"The aim of the present study is to assess changes in the Baltic Sea climate based on different available meteorological data sources (ERA40 and ERA-INTERIM) and various published Baltic Sea climate indices. This regional assessment will be presented in relation to global climate change and assessments available from the literature. The climate of the Baltic Sea which is located between 50N and 70N is mainly influenced by the competition of westerly humid air flow and easterly continental type air masses and is therefore highly variable. We are investigating air temperature, wind speed, cloud cover, solar radiation and precipitation. Comparisons to climate indices of general relevance as the Baltic ice cover will be conducted. Using regression analysis we could confirm the following basic trends, increase in air temperature, increase in precipitation, increase in cloudiness. The increase in air temperature in the Baltic Sea area (0.02K/year) is much more rapid then the warming trend for the global air temperature (0.005K/year). The increase in cloudiness has resulted in an effective reduction of incoming solar radiation therefore the accelerated warming is not a result of increased solar radiation, but likely due to an increased net long wave radiation input. Further it has to be mentioned that not all available data sets confirmed the trend in cloudiness, ERA40 data show a nonsignificant decrease instead. No clear trend in the wind velocities could be detected, but wind velocities from ERA40 reanalysis project show an insignificant increase in wind speeds. Results from model runs with the GETM model (General Estuarine Transport Model, http://getm.eu) show sea surface warming consistent with the increase in heat flux forcing and with satellite observations. The warmer sea surface without an adequate warming in the deeper parts results in a much stronger vertical density stratification and consequently to reduced vertical mixing. A more thorough inspection of the available regional and global data provides some reasonable doubt concerning the application of least square regression analysis to the available time series. Indeed it can be shown by a test based on the F statistics that most of the analyzed time series cannot be considered as stationary and therefore drawing simple regression lines trough these datasets is statistically incorrect. Testing for structural breakpoints in these time series reveals for many investigated parameters and also for many tested climate indices the existence of such breakpoints in the 70–80ties of the last century. Therefore it has to be concluded that the simple trend estimation for many climate parameters is statistically incorrect. Instead for statistical investigations it has to be assumed that there exist either 2 different climate states with either 2 different means or alternatively with 2 different trends which have to be estimated separately.","PeriodicalId":287473,"journal":{"name":"2010 IEEE/OES Baltic International Symposium (BALTIC)","volume":"37 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2010-11-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114559832","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2010-11-04DOI: 10.1109/BALTIC.2010.5621625
V. Alari, U. Raudsepp, A. Erm
The aim of this study is to assess the applicability of the pressure wave gauge to measure wind waves at transitional water depths. In this study, a rather uncommon method is proposed to check the validity of the linear wave theory. Namely, we compare the wave induced near-bed velocities measured directly with the Acoustic Doppler Velocimeter (ADV) to those calculated from wave gauge measurements. A subsurface mooring station equipped with an ADV and a pressure wave gauge was deployed in Keibu Bay, a small coastal environment in the southern Gulf of Finland, at a depth of 7 m in June 2010. Among long period oscillations, i.e. currents, the ADV allowed measuring wind wave induced orbital velocities. The ADV was set to measure orbital velocities 27 cm above the bottom at 2 Hz, while the pressure sensor of the wave gauge was 5 m from the bottom and measured pressure at 4 Hz continuously. After removing turbulent velocity from the ADV measurements, the combined horizontal spectrum was calculated and the bottom orbital speed was derived. The surface elevation spectra were estimated from the pressure measurements and the near-bed orbital speed was calculated from the wave spectra. The measurement campaign was characterized by diverse wave activity. It presents growing wind seas, fetch limited, swell and mixed sea states. The maximum significant wave height was 1.12 m. The wave data obtained were examined for their region of validity in the framework of Stokes' and Airy's wave theories. 80 % of data were in the range of Stokes' wave theory. The comparison of the ADV measured near-bed orbital speed and the data derived from wave gauge measurements showed remarkable agreement. The correlation coefficient was 0.98 and the root-mean-square error for orbital speed was 1.2 cm/s. During the largest wave event, the measured near-bed orbital speed reached 25.8 cm/s over a 5-minute period, and the calculated speed was 25.2 cm/s. In conclusion, the pressure data measured in coastal seas can be transformed into surface waves via the linear wave theory.
{"title":"Comparison of ADV measured near-bed orbital speed and latter derived from wave gauge measurements at intermediate water depths","authors":"V. Alari, U. Raudsepp, A. Erm","doi":"10.1109/BALTIC.2010.5621625","DOIUrl":"https://doi.org/10.1109/BALTIC.2010.5621625","url":null,"abstract":"The aim of this study is to assess the applicability of the pressure wave gauge to measure wind waves at transitional water depths. In this study, a rather uncommon method is proposed to check the validity of the linear wave theory. Namely, we compare the wave induced near-bed velocities measured directly with the Acoustic Doppler Velocimeter (ADV) to those calculated from wave gauge measurements. A subsurface mooring station equipped with an ADV and a pressure wave gauge was deployed in Keibu Bay, a small coastal environment in the southern Gulf of Finland, at a depth of 7 m in June 2010. Among long period oscillations, i.e. currents, the ADV allowed measuring wind wave induced orbital velocities. The ADV was set to measure orbital velocities 27 cm above the bottom at 2 Hz, while the pressure sensor of the wave gauge was 5 m from the bottom and measured pressure at 4 Hz continuously. After removing turbulent velocity from the ADV measurements, the combined horizontal spectrum was calculated and the bottom orbital speed was derived. The surface elevation spectra were estimated from the pressure measurements and the near-bed orbital speed was calculated from the wave spectra. The measurement campaign was characterized by diverse wave activity. It presents growing wind seas, fetch limited, swell and mixed sea states. The maximum significant wave height was 1.12 m. The wave data obtained were examined for their region of validity in the framework of Stokes' and Airy's wave theories. 80 % of data were in the range of Stokes' wave theory. The comparison of the ADV measured near-bed orbital speed and the data derived from wave gauge measurements showed remarkable agreement. The correlation coefficient was 0.98 and the root-mean-square error for orbital speed was 1.2 cm/s. During the largest wave event, the measured near-bed orbital speed reached 25.8 cm/s over a 5-minute period, and the calculated speed was 25.2 cm/s. In conclusion, the pressure data measured in coastal seas can be transformed into surface waves via the linear wave theory.","PeriodicalId":287473,"journal":{"name":"2010 IEEE/OES Baltic International Symposium (BALTIC)","volume":"9 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2010-11-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130580044","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2010-11-04DOI: 10.1109/BALTIC.2010.5621630
A. Erm, V. Alari, F. Buschmann, T. Kõuts, U. Raudsepp, K. Loitjarv
Dependence of near bottom currents and turbidity on wind and wave parameters is analyzed. Measurements campaigns with an acoustic Doppler velocymeter (ADV Field/Hydra, SonTek/YSI) were curried out in two bays in north western Estonia — the first one on Naissaar Shallow in Tallinn Bay (22.12.2009–12.01.2010, water depth 9 m, 37 cm from the bottom) and the second one in Keibu Bay (03.06.2010–26.06.2010, water depth 7m, 27 cm). Near bottom velocities were recorded with frequencies 2 Hz (currents) and 0.2 Hz (wave induced orbital motion). Additionally the water turbidity at the same level as flow measurements was performed using an integrated turbidity meter OBS 3+ (YSI). Wave parameters were recorded using a pressure wave gauge (PTR Group, Tallinn). The ADV measured flows consist of wind induced currents, wave induced orbital motions and turbulence. Maximum of wind induced currents reached meanly 10–15 cm/s at both measurement locations, while the maximum near bed orbital motions peaked over 40 cm/s. Measurements showed that the near bottom velocities in Keibu Bay were in correlation with wind speed, but turbidity values showed a significant increase only in some special weather conditions. From the comparison of ADV, turbidity meter and wave gauge characteristics it followed that turbidity was clearly depending on the wave energy. It means only quite long and high waves inducing bottom orbital velocities (calculated from the wave gauge data) over 20 cm/s were able to resuspend bottom sediments.
{"title":"Near bottom velocity and turbidity measurements in coastal waters of NW Estonia","authors":"A. Erm, V. Alari, F. Buschmann, T. Kõuts, U. Raudsepp, K. Loitjarv","doi":"10.1109/BALTIC.2010.5621630","DOIUrl":"https://doi.org/10.1109/BALTIC.2010.5621630","url":null,"abstract":"Dependence of near bottom currents and turbidity on wind and wave parameters is analyzed. Measurements campaigns with an acoustic Doppler velocymeter (ADV Field/Hydra, SonTek/YSI) were curried out in two bays in north western Estonia — the first one on Naissaar Shallow in Tallinn Bay (22.12.2009–12.01.2010, water depth 9 m, 37 cm from the bottom) and the second one in Keibu Bay (03.06.2010–26.06.2010, water depth 7m, 27 cm). Near bottom velocities were recorded with frequencies 2 Hz (currents) and 0.2 Hz (wave induced orbital motion). Additionally the water turbidity at the same level as flow measurements was performed using an integrated turbidity meter OBS 3+ (YSI). Wave parameters were recorded using a pressure wave gauge (PTR Group, Tallinn). The ADV measured flows consist of wind induced currents, wave induced orbital motions and turbulence. Maximum of wind induced currents reached meanly 10–15 cm/s at both measurement locations, while the maximum near bed orbital motions peaked over 40 cm/s. Measurements showed that the near bottom velocities in Keibu Bay were in correlation with wind speed, but turbidity values showed a significant increase only in some special weather conditions. From the comparison of ADV, turbidity meter and wave gauge characteristics it followed that turbidity was clearly depending on the wave energy. It means only quite long and high waves inducing bottom orbital velocities (calculated from the wave gauge data) over 20 cm/s were able to resuspend bottom sediments.","PeriodicalId":287473,"journal":{"name":"2010 IEEE/OES Baltic International Symposium (BALTIC)","volume":"66 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2010-11-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130261016","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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