1. Downscaling sea level rise in the Mediterranean Sea under different future climate change scenarios ( )
Kareem M. Tonbol (Ph.D.)
Assistant Professor
Head of Meteorology & Hydrographic Survey Program
College of Maritime Transport & Technology (CMTT)
Arab Academy for Science, Technology & Maritime Transport (AASTMT)
Workshop, Cecil Hotel Alexandria, Egypt
23-Oct-17

2. Outlines What is the Downscaling? Types of Downscaling.
Why do we need Downscaling?
Methods of Downscaling.
Current Project Objectives.
Methodology For Statistical Downscaling.
Results of Statistical Downscaling.
Workshop, Cecil Hotel Alexandria, Egypt
23-Oct-17

3. What is the Downscaling?
Downscaling: is the general name for a procedure to take information known at large scales (GCMs) to make predictions at local scales.
Typically, GCMs have a resolution of km by km.
Many impacts models require information at scales of 50 km or less.
Because the scale of a Global Circulation Model (GCM) output is coarse -- a grid cell from a typical GCM model run being 2.5 x 2.5 degrees or roughly 250 kilometers square, it is difficult to use GCM output directly in most regional and local-scale environmental modeling.
The origin of downscaling is connected with the early development of numerical weather forecasting, which was first carried out on digital computers in the 1950s.
The term downscaling was probably first used in a study by von Storch, Zorita, and Cubasch (1991).
Workshop, Cecil Hotel Alexandria, Egypt
23-Oct-17

4. What is the Downscaling?
Global Emission Scenarios
General Circulation Model (GCM). { km}
Regional Climate Model (RCM). {up to 3 km}
Downscaling
(Topography – Land Use)
One Way
(Oceanic Model)
Two Way
(Oceanic & Climate Model)
Workshop, Cecil Hotel Alexandria, Egypt
23-Oct-17

5. Types of Downscaling
Temporal Downscaling: Refers to the derivation of fine scale temporal data from coarser-scale temporal information (e.g., daily data from monthly or seasonal information).
Temporal Resolution: The time scale at which a measurement is taken or a value is represented. Daily and monthly resolutions denote one value per day and one value per month, respectively.
Spatial Downscaling: Refers to the methods used to derive climate information at finer spatial resolution from coarser spatial resolution GCM output.
Spatial Resolution: In climate, spatial resolution refers to the size of a grid cell in which km and km are considered to be “fine” and “coarse,” respectively.
Spatial Downscaling: The fundamental basis of spatial downscaling is the assumption that significant relationships exist between local and large-scale climate.
Temporal Downscaling: Its main application is in impact studies when impact models require daily or even more frequent information.
Workshop, Cecil Hotel Alexandria, Egypt
23-Oct-17

6. Why do we need Downscaling?
To respond to the needs of decision makers to plan for climate change
Impacts of a changing climate, and the adaptation strategies to deal with them, need to be addressed at finer, regional scale.
From Global to Regional Scale
Workshop, Cecil Hotel Alexandria, Egypt
23-Oct-17

7. Why do we need Downscaling?
Workshop, Cecil Hotel Alexandria, Egypt
23-Oct-17

8. Why do we need Downscaling?
Bridge mismatch of spatial scale between the scale of GCMs and the resolution needed for impacts assessments, as the GCMs are designed to simulate the large-scale flow of energy and mass, but not to calculate local details.
“Most GCMs neither incorporate nor provide information on scales smaller than a few hundred kilometers. The effective size or scale of the ecosystem on which climatic impacts actually occur is usually much smaller than this. We are therefore faced with the problem of estimating climate changes on a local scale from the essentially large-scale results of a GCM.” Gates (1985)
“One major problem faced in applying GCM projections to regional impact assessments is the coarse spatial scale of the estimates.” Carter et al. (1994)
‘downscaling techniques are commonly used to address the scale mismatch between coarse resolution GCMs … and the local catchment scales required for … hydrologic modeling’ Fowler and Wilby (2007)
One reason is that the earth is described in terms of a grid, and the size of each grid box typically is approximately 100 kilometers. It is currently not possible to use a finer grid, because it would require more computer resources than is presently available.
Workshop, Cecil Hotel Alexandria, Egypt
23-Oct-17

9. Why do we need Downscaling?
Intergovernmental Panel on climate Change (IPCC) fifth assessment report (AR5): The increase in downscaled data sets has not narrowed the uncertainty range. Integrating these data with historical change and process-based understanding remains an important challenge.
Workshop, Cecil Hotel Alexandria, Egypt
23-Oct-17

10. Methods of Downscaling
Statistical:
Statistically relating large scale climate features that GCMs (e.g., 500mb heights) & local climate characteristics (e.g., daily, monthly temperature at a point) provide.
Dynamical:
Physical processes are directly modeled at a finer spatial scale, incorporating the effects of regional topography and land cover, typical scales being 1/2 to 1/16th of a degree.
Statistical: In contrast to the dynamical method, the statistical methods are easy to implement and interpret. They require minimal computing resources but rely heavily on historical climate observations and the assumption that currently observed relationships will carry into the future. However, high quality historical records often are not available in developing countries.
Dynamical: This method has numerous advantages but is computationally intensive and requires large volumes of data as well as a high level of expertise to implement and interpret results, often beyond the capacities of institutions in developing countries.
Workshop, Cecil Hotel Alexandria, Egypt
23-Oct-17

11. Workshop, Cecil Hotel Alexandria, Egypt
23-Oct-17

12. Current Project Objectives
Monitor and analyze the dynamics of SLR over the Mediterranean Sea;
Project different SLR for the four CMIP5 various scenarios over the Mediterranean Sea until the end of the current century with 5 km spatial resolution; and
Project different SLR for the four CMIP5 different scenarios along the Nile Delta coast up to 2100 with 50 m spatial resolution.
Workshop, Cecil Hotel Alexandria, Egypt
23-Oct-17

13. Methodology For Statistical Downscaling
This Statistical downscaling is built on the thermal effect (Rahmstorf (2007), together with the effect of sea level west of Gibraltar (active Mediterranean Atlantic Basin)
Where, h is sea level, t is time, SST is sea surface temperature, SSTo is average SST over the years, Ao= , A1= , A2= This equation describes 70% of sea level changes over the Mediterranean Sea with the level of significance = 94% and standard error = 0.006m.
Workshop, Cecil Hotel Alexandria, Egypt
23-Oct-17

14. Results of Statistical Downscaling
Statistical downscaling over the Mediterranean Sea describe 70% of sea level changes over the Mediterranean Sea with a standard error of m with the use of sea surface temperature and sea level to the west of Gibraltar. The statistical sea level downscaling result shows that the projected sea level over the Mediterranean Sea is expected to increase between 13 cm to 33 cm.
Sea level rise statistical uncertainty over the Mediterranean Sea with respect to the average sea level over the period from
Workshop, Cecil Hotel Alexandria, Egypt
23-Oct-17

15. acknowledgement
This research work is part of a research project sponsored by: IDRC-Canada for establishing Alexandria Research Centre for Adaptation to Climate Change (ARCA) Thank you
Workshop, Cecil Hotel Alexandria, Egypt
23-Oct-17

16. Workshop, Cecil Hotel Alexandria, Egypt
23-Oct-17