Broadband radiative flux measurements
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Broadband radiative flux measurements
Background
The purpose of this study is twofold. It focus on validation of remote sensing estimates of radiative fluxes at the surface and on time series analysis of the heat exchange at OWS Mike.
Broadband radiative flux measurements collected at several stations in the North Sea, Norwegian, Barents and Greenland Seas is being used to validate EUMETSAT Ocean and Sea Ice SAF radiative flux products. These products are routinely produced on passage and daily basis (see http://saf.met.no/ for details). However, validation data over ocean and in northern areas have been virually non existent. Thus the radiative flux measurements performed by iAOOS-Norway and IPY-THORPEX as well as by external activities (e.g. http://www.noc.soton.ac.uk/ooc/CRUISES/HiWASE/index.php) herein will be used for validation of these products. The measurements will also be used for tuning of the algorithms. At OWS MIKE measurements providing a full surface energy budget including both radiative and turbulent hear fluxes were proposed by the project, but due to administrative and technical problems these have not been implemented. Fortunately Margaret Yelland and Robin Pascal at University of Southampton are doing similar measurements at OWS Mike and has provided access to these. These observations will be used for validation of bulk parameterisations for the time period with collocated direct measurements. The most reliable bulk parameterisations will be used for generation of time series of the surface energy budget at OWS MIKE since 1948. This timeseries will be compared with timeseries of changes in the heat content at OWS MIKE and any changes in the heat advection inferred.
The Norwegian Meteorological Institute (METNO) operates meteorological stations at the islands Bjørnøya, Hopen and Jan Mayen. These stations are staffed to perform operational meteorological observations. IPY funding received through IPY-THORPEX and iAOOS-Norway have made it possible to mount equipment for broadband radiative flux measurements with direct tranmission of results to the main office in Oslo. To achieve regularity throughout the project period some essential parts of the equipment will be duplicated and kept in reserve at the stations.
More information on the implementations at various locations, as well as external data (OWS Mike/Polarfront and Ekofisk) used within the project is provided below. Information on the collocated meteorological observations will be added.
Stations with broadband radiative flux measurements
The stations that are being used within this project is shown in the figure above. They are all briefly described below along with real time data illustrations where possible:
Ekofisk
University of Bergen (NO) is doing broadband radiative measurements at the Ekofisk oil rig. The instruments are collocated with the radiosonde station and is kindly made available to iAOOS-Norway. Contact persons are Jan Asle Olseth and Tor deLange.
OWS Mike
University of Southampton (UK) is doing broadband radiative measurements at the weather ship OWS MIKE as well as measurements of turbulent heat fluxes. Data are kindly made available to iAOOS-Norway by Margaret Yelland and Robin Pascal. For more information please visit http://www.noc.soton.ac.uk/ooc/CRUISES/HiWASE/index.php. As of March 2009 it is decided that the weather ship will be removed in January 2010. How to continue scientific observations at this location is being examined but that is beyond scope for this project.
Bjørnøya (Bear Island)
METNO have mounted equipment to measure surface broadband raditive fluxes at Bear Island. The instruments are located at the meteorological station and data are transmitted in real time to the main office in Oslo. Please contact Øystein Godøy for further information. The first version of this dataset is published within the DOKIPY IPY database in Norway. The figure below shows updated (every 3 hour) surface downward shortwave and longwave irradiances at Bjørnøya for 2008 and 2009 as minute and monthly values. The equipment at Bjørnøya had a visit of a hungry or curious polar bear in January 2009, this resulted in missing observations while the equipment was fixed. At Bjørnøya spare parts are available for most of the equipment to ensure the continous operationa required to achieve reliable time series. The spare parts inventory will be updated in 2009. Experience have shown that the set up have been vulnerable e.g. to curious or hungry polar bears and measures have been taken to compensate this, including plug and play spare parts. The instrumentation at Bjørnøya is co-funded through iAOOS-Norway and IPY-THORPEX.
The meteorological station and the radiative fluxes instrumentation at Bjørnøya is shown below. Photos by Hans Arne Vassbotn (METNO).
Jan Mayen
METNO have mounted equipment to measure surface broadband raditive fluxes at Jan Mayen. The instruments are located at the meteorological station and data are transmitted in real time to the main office in Oslo. Please contact Øystein Godøy for further information. The first version of this dataset is published within the DOKIPY IPY database in Norway. The figure below shows updated (every 3 hour) surface downward shortwave and longwave irradiances at Jan Mayen for 2008 and 2009 as minute and monthly values. At Jan Mayen the spare parts inventory is currently not complete. This will be done in 2009. The main challenge at Jan Mayen is the volcanic sand at the island and how this will affect the instruments. Due to this problem, the instruments were mounted on a building where the roof functions as a spoiler, hoping that this reduces the most estreme wear on the domes. The set up will be evaluated mid 2009 to define the spare parts required for continous operation over the winter. The instrumentation at Jan Mayen is all funded through iAOOS-Norway.
The radiative fluxes equipment at Jan Mayen is shown below. Photos by Camilla Weum Stjern (top), then at METNO, currently at UiO, Idar Hersvik (bottom left) and Dag Fjeld (bottom right), both at METNO. The crew manning Jan Mayen have a web page, http://www.jan-mayen.no/,describing activities at the island.
Hopen
In November 2009, instrumentation to observe broadband radiative fluxes were mounted at the meteorological station operated by METNO at Hopen. data are transmitted in real time to the main office in Oslo. Please contact Øystein Godøy for further information. The figure below shows updated (every 3 hour) surface downward shortwave and longwave irradiances. Irregularities must be expected in 2009 and the first dataset is expected to be published early 2010 using the same format and channels as for Bjørnøya and Jan Mayen. The instrumentation at Hopen is all funded through iAOOS-Norway.
The radiative fluxes equipment at Hopen is shown below. Photos from Wikipedia (no credit given, top) and Jens Helge Halvorsen (bottom), METNO.
EUMETSAT OSISAF products
EUMETSAT Ocean and Sea Ice SAF radiative flux products are available from http://saf.met.no/. These products estimated from satellite measurements are being compared with in situ observations in the Arctic. A sample remote sensing product is shown below with the positions of in situ observations being examined overlayed.
More information
More information about the project can be found at http://www.iaoos.no/.