1. David Hein Thursday, 13 March 2008
The PRECIS regional climate modelling system Providing REgional Climates for Impacts Studies
David Hein
Thursday, 13 March 2008
© Crown copyright Met Office

2. What is a Regional Climate Model?
Comprehensive physical high resolution (~50km) climate model
Covers a limited area of the Earth’s surface
Usually includes the atmosphere and land surface components of the climate system
Contains representations of the key processes within the climate system (e.g., cloud, radiation, rainfall, soil hydrology).
A Regional Climate Model (RCM) is a high resolution climate model that covers a limited area of the globe, typically 5,000 km x 5,000 km. RCMs are based on physical laws represented by mathematical equations that are solved using a three-dimensional grid. The typical horizontal resolution of an RCM is 50 km. Hence RCMs are comprehensive physical models, usually including the atmosphere and land surface components of the climate system, and containing representations of the important processes within the climate system (e.g., cloud, radiation, rainfall, soil hydrology). Many of these physical processes take place on much smaller spatial scales than the model grid and cannot be modelled and resolved explicitly. Their effects are taken into account using parametrizations by which the process is represented by relationships between the area or time averaged effect of such sub-grid scale process and the large scale flow.
© Crown copyright 2007

3. RCMs simulate current climate more realistically
Where terrain is flat for thousands of kilometres and away from coasts, the coarse resolution of a GCM may not matter. However, most land areas have mountains, coastlines etc. on scales of a hundred kilometres or less, and RCMs can take account of the effects of much smaller scale terrain than GCMs. The diagram shows simulated and observed winter precipitation over Great Britain. The observations clearly show enhanced rainfall over the mountains of the western part of the country, particularly the north west. This is missing from the GCM simulation, which shows only a broad north –south difference. In contrast to the GCM, the 50 km RCM represents the observed rainfall pattern much more closely.
Patterns of present-day winter precipitation
over Great Britain
© Crown copyright 2007

4. Boundary conditions
Limited area models are driven at the boundaries by GCMs or analyses data.
The nested regional climate modelling technique consists of using initial conditions, time-dependent lateral meteorological conditions and surface boundary conditions to drive high-resolution RCMs. The driving data is derived from GCMs (or analyses of observations) and can include GHG and aerosol forcing. A variation of this technique is to also force the large scale component of the RCM solution throughout the entire domain.
To date, this technique has been used only in one-way mode, i.e. with no feedback from the RCM simulation to the driving GCM. The basic strategy is thus to use the global model to simulate the response of the global circulation to large scale forcings and the RCM to a) account for sub-GCM grid scale forcings (e.g. complex topographical features and land cover inhomogeneity) in a physically-based way; and b) enhance the simulation of atmospheric circulations and climatic variables at fine spatial scales.
© Crown copyright 2007

5. What is PRECIS? Providing REgional Climates for Impact Studies
Regional climate modelling (RCM) system that can be applied to any area of the globe
Generates detailed climate change projections
PRECIS is a regional climate modelling system developed at the Hadley Centre that can run on a PC and comprises:
An RCM that can be applied easily to any area of the globe to generate detailed climate change predictions,
A simple user interface to allow the user to set up and run the RCM, and
A visualisation and data processing package to allow display and manipulation of RCM output.
© Crown copyright 2007

6. The Components of PRECIS
PC version of the Hadley Centre’s HadRM3P Regional Climate Model
resolution 50km (25km for small areas)
runs on the free Linux operating system
User interface to set up RCM experiments
Data processing and display software
Boundary conditions
Training course and materials
Technical Support
In addition to the main software components, the first three items listed here, there are three other important components. The first is the set of boundary conditions which is needed to run the PRECIS RCM and is derived from an archive of global data at the Hadley Centre. The second is this training course and associated materials which provide the background to make most appropriate and best use PRECIS. The third is the PRECIS website which is a source of these and other materials, hosts an interface to request boundary data and provides a forum for requesting advice and sharing experiences with PRECIS.
© Crown copyright 2007

7. Training course and supporting material
Training in the use of PRECIS focuses on:
Background science, including uncertainties
Interpretation of PRECIS results by regional experts
Construction of regional climate change scenarios
Building capacity in countries/regions using PRECIS
PRECIS is supplied with:
a handbook covering the background science, system description and the uses and limitations of PRECIS
a technical manual explaining technical details about the system and how install and to use it
Training workshops will be held to explain to users of PRECIS relevant scientific background so that they understand the components of PRECIS and how to make best use of it. It will explain the potential usefulness and also the limitations of the data PRECIS can provide and how they can be used to construct climate change scenarios. It will also give examples of using PRECIS data in impacts studies. An important aspect of the workshop will be obtaining feedback from users on what they are hoping to use PRECIS for and to encourage and facilitate collaboration between users of PRECIS.
As reference material for users, much of the content of the workshop will be supplied to users (in addition to the workshop presentations) in a workbook, covering the scientific aspects, and a technical manual, covering the installation and use of PRECIS.
© Crown copyright 2007

8. PRECIS Workshops and Projects
Over 200 trained users from over 60 countries
Extensive regional networks in developing countries across the globe
Projects (Belize – CCCCC, India – IITM, China – CAAS, Cuba –INSMET, Brazil – CPTEC, Uganda – START)
International networks (UNFCCC, UNDP-NCSP, UNDP-CRMI)
Strengthened scientific capacities in developing countries for participation in international projects (AMMA, WAMME, )
In summary, PRECIS can provide climate scenarios for any region, allowing for an estimate of uncertainty from different emissions and due to climate variability (though this is only a small part of the total uncertainty in climate scenarios).
The output from PRECIS includes a comprehensive set of data from the atmosphere and land surface, which represent grid-box mean quantities, with a maximum time resolution of one hour.
© Crown copyright 2007

9. Regional focal points and data distribution centres
Africa
African Cent. for Met. Appl. to Dev. (ACMAD, Niger)
Ghana Meteorological Agency (GMA)
University of Cape Town (ENGEO)
Asia
Malaysian Met. Dept. (MMD)
Indian Inst. of Trop. Met.
Chinese Acad. of Agric. Sci. (CAAS)
South America
CPTEC - Brazil
CIMA – Argentina
Caribbean and Central America
Caribbean Com. Clim. Ch. Cent. (CCCCC) (Belize)
Cuban Inst. of Met. (INSMET)
Euro-Asia
Turkish Meteorological Agency (TMA)
PRECIS user network
© Crown copyright 2007

10. Application over India
Annual cycle of all-India rainfall & temperature
Spatio-temporal cycles of current climates well simulated.
Generally temp. and precip. reasonably simulated but large biases in some months (3 – 4oC)
No major shifts in spatio-temporal cycles of future climates.
Projected changes in (a) summer monsoon rainfall (%) and (b) annual mean surface air temperature (ºC) for the period relative to baseline under the A2 scenario.
© Crown copyright 2007

11. Validation over other south Asian countries
Monsoon rainfall over Bangladesh
Trends in maximum temperature over Bangladesh
Estimation of extreme monsoon precipitation over
the Jhelum River basin (Pakistan) in September 1990
High performance in estimating monsoon events over spatio-temporal scales
Provides reliable hydro-climate estimates for hydrological modelling in the Jhelum basin
© Crown copyright 2007

12. A climate change projection for Central America and the Caribbean
Mean surface pressure for 2080:A2
Mean surface pressure for 2080:A2
Appreciable changes in pressure and temperature patterns in the region.
More detailed representation over Cuba (and neighbouring island states) show consistent changes in pressure systems and other climate variables
Mean surface temperature for 2080:A2
© Crown copyright 2007

13. Impacts on crop yield over China under A2 scenario
Key findings
Plots of impacts on crop yield
CO2 fertilisation could reduce yield of rice, maize and wheat up to 37 % within 20 to 80 years
Higher order of CO2 may increase yield and reduce negative impacts of climate change
Extent of these changes are uncertain but would depend on water and nutrient availability, land management practices and biotechnology
Generally, increasing warming tends to increase yield of cotton
© Crown copyright 2007

14. Summary: PRECIS
PRECIS provides a means for generating an accurate and consistent set of high resolution regional climates
PRECIS provides an affordable system of tools for developing countries to generate their own regional climate scenarios
Can be set up by the user over any area of the globe
Used for vulnerability and adaptation studies and climate research
Much success in its application in impacts studies
The PRECIS RCM is currently configured to run at 50 and 25km though the computational expense of using higher resolution means it is only appropriate for small areas or short simulations. PRECIS is supplied on two DVD-ROMs which includes over three years of sample boundary conditions for initial testing of the system. In standard configuration PRECIS is used for a region which is typically 5000 square kilometres though smaller or larger regions can be used if appropriate. It can be used for any region of the globe and thus is applicable in countries and regions which currently have no modelling capability thus enabling them to produce their own scenarios of climate change which can then be used in vulnerability and adaptation studies.
© Crown copyright 2007