Hossein Nahavandchi
| hossein.nahavandchi@ntnu.no | |
| Position | Professor |
| Unit | Department of Civil and Transport Engineering |
My Research/Teaching Interests:
Current Research: Greenland Ice-mass balance from satellite gravity observations
Satellite gravity missions have been providing valuable information regarding Earth's gravity field. The Gravity Recovery and Climate Experiment (GRACE) satellite mission provides temporal variations of Earth's gravity with a period of around one month. GRACE measures changes in Earth's gravity field caused by regional shifts in the Earh's mass, including ice sheets, oceans and water stored in the soil and in underground aquifers. The GRACE twin satellites launched in March 2002 and jointly implemented by the NASA and German Aerospace Center (DLR). We have been using GRACE data to estimate the rate of ice mass variability over Greenland. GRACE offers the best available method for measuring the total mass balance of the Greenland ice sheets. The Figure below shows monthly ice mass changes summed over the entire Greenland ice sheet, between April 2002 and February 2010, estimated in Gigatonne from three GRACE data sets released by GFZ (Potsdam), JPL (California) and CSR (Texas). Note that this plot shows deviation from the average ice mass over the 2002 to 2010 period. It does not mean that the ice sheet was gaining ice before 2006 but that ice mass was above the 2002 to 2010 average. The ice mass was below the 2002 to 2010 avergage after 2006. The trend of the best fitting straigh line for CSR data is -163±20 Gigatonne per year.The results indicate that the ice-mass loss rate has been increasing in the time period between 2002 and 2010.
Current Research: Ocean circulation in North Atlantic and the Arctic sea from satellite altimetry observations
The Ocean plays a key role in determining the global climate. To develop techniques for pridicting furure climate, one must undrestand the dynamics of the global ocean circulation. A viable approach to observing the global and regional ocean circulations with sufficient resolution is the use of a satellite radar altimeter to measure the Mean Sea Surface (MSS) height. Multiple radar altimetry data from ESA satellites of ENVISAT, ERS-1 and ERS-2 and NASA satellite of GFO were used to determine the NTNU MSS model. NTNU MSS model is used to derive the mean dynamic topography and the ocesn circulation as it is shown in the Figure below. This plot shows the surface currents system in the North Atlantic and the Arctic sea for the time period 1993-2007. Flow of warm water is shown as red arrow and cold water as blue arrow. The Northward flow of warm water in the North Atlantic is partly balanced by southward flow of clod water in the East Greenland. Note that the detalied surface currents are not shown in this picture.
Research Intrests
-
Climate Change Studies
- Polar Research
- Ocean Circulation and Transport
- Satellite Positioning
- Satellite Earth Monitoring (Gravimetry and Altimetry)
Teaching
- TBA4852 Interdisciplinary Teamwork
- TBA4565 Geomatics, Specialization Course
- TBA4560 Geomatics, Specialization Project
- TBA4567 Physical geodesi
- TBA4565 Geometric sattelite geodesy (GPS)
- TTT4234 Space Technology I
- TBA4925 Geomatics, Master Thesis
- BA8200 Advanced Theory of Errors and Adjustment
- BA8202 Advanced Physical Geodesy
- BA8604 Satellite Gravimetry and Altimetry
- BA8605 Advanced Global Positioning System (GPS)
- BA8203 An integrated Earth System Approach to the Study of Ocean Climate
Research Projects
- Arctic and Antarctic Mass balance (Ice loss) from satellite gravity and satellite altimetry measurements
- Ocean Circulation and Transport Between the North Atlantic and Arctic sea (OCTAS)
- New improvments in Geoidal height modeling
- Development of a regional GPS-based model of Ionospheric for Norway
- Arctic geoid for ocean circulation, sea-ice exploration and climate change
Completed PHD thesis
- Trond Arve Haakonsen (Temporal and Spatial analyses of continuous GPS observations)
- Erik Nyrnes (Error analyses and quality control of wellbore directional surveys)
- Ali Soltanpour (Geoid and Geoid-type surface determination)
- Kourosh Ghazavi ( Satellite altimetry derived mean sea surface and its error analysis over OCTAS study area)
Links:
