1. The Water, Life and Civilisation project: Meteorology Investigating the climate of the Eastern Mediterranean using regional climate models David Brayshaw, Brian Hoskins, Julia Slingo & Emily Black MedCLIVAR meeting, ICTP, Italy, October 2008
CBRL

2. Talk outline
WLC-Meteorology is part of a broader programme at Reading University:
Describe the WLC project more generally
Present an outline of the Meteorology component
Initial results
Plans for the future

3. Origin of agriculture, 10,000 BC Mesopotamian Civilisation 6500 BC
Ancient civilisations in the Middle East and North East Africa
JORDAN VALLEY
Origin of agriculture, 10,000 BC
First towns, 8500 BC
NILE VALLEY
Egyptian
Civilisation,
3500 BC
EUPHRATES VALLEY
Mesopotamian Civilisation BC
Throughout human history into the present day, and beyond, the scene of economic, social, and political change that is intimately related to the hydrological climate
Aim: To assess the impact of changes in the hydrological climate on past, present and future societies in the semi-arid regions of the Middle East and North Africa, with a case study of the Jordan Valley

4. Hydrological modelling Palaeoenvironmental studies
The five sub-projects and their links
Climate modelling
To describe annual and seasonal changes in climate for the Middle East and North Africa Region, 20,000 BC – AD 2100
Archaeological studies
To understand human history within the Jordan Valley, and MENA region as a whole
Hydrological modelling
To describe the spatial and temporal variations in water flow of the Jordan River system
Palaeoenvironmental studies
To reconstruct prehistoric, historic and modern landscapes of the Jordan Valley
Development studies
To understand current and future demands on water usage and supply

5. The Jordan Valley
Number of sites, particularly going to focus on a couple of sites in S Jordan (parciularly WF16)
Characterised by an extremely dry climate, but ample evidence of early societies in this region (from approx 10,000 years BP). The WF16 system is situated at the bottom of the escarpment leading up to a plain, at end of a wadi that currently seems to be characterised by several winter floods (approx 5 = good year) and a small year-round base flow. Teams have been out to collect records here (and elsewhere in Jordan and the Dead Sea area)

6. Aims of WLC-Meteorology
Produce climate simulations of the Middle East that are of use to the palaeo-science teams in interpreting proxy-records and archaeological evidence over the last 12,000 years
Combine/compare/contrast with regional palaeo-records
Develop understanding of the physical mechanisms involved in such changes
Emily Black working on C21 simulations
SAY SOMETHING ABOUT::::
Palaeo-records often have mixed temperature/precipitation signals and climate interpretations of them ignore regional variations (due to orography, changes in moisture source, etc)
“Validation” of model climate through palaeo-records
vs.
“Interpretation” of palaeo-records using information provided by climate model
Still in early stages of Met component – approx 1-2 years, preseeent early findings and outlines here

7. Palaeo-modelling design
Two sets of integrations:
“Baseline integrations”
Investigating the impact of (relatively) slow changes in GHG, and insolation
“Event scenarios” and sensitivity tests
Atlantic MOC disruption at 8.2kBP
Green/Wet Sahara
Warm West Pacific
Two strands:
A set of “baseline integrations” – investigating the (generally smooth) changes brought about by changes in GHG concentrations and orbit over last 12,000 years
A set of “event scenarios” – investigating the characteristic impacts of certain events or palaeo-climate possibilities that cannot be directly captured by the model
Examples: 8.2kBP, Green/Wet Sahara (find quote for this)
Find a paper to show that GS not got in coupled oav PMIPII models.
What we offer: Not using the most sophisticated OAVcoupled models, but RCM able to provide detail on Med storm track (key supplier of moisture to region) and will attempt to provide a process-based understanding

8. Palaeo-modelling design: The baseline integrations
Climate forcings
Changed to “past” values
Fixed at “modern” values
Solar forcing due to orbital changes
Land surface properties
(fixed at present day)
Green house gas changes
Pre-industrial ocean heat fluxes
Climate models
High res. regional model (~50km)
Low resolution global models (~300km)
Each run is 20 years of data. Includes daily precipitation, 6h diagnostics for several dynamical fields (e.g. U250, T700, MSLP), lots of monthly mean data.
Mention sensitivity tests
Lateral
SST
HadSM3
HadAM3
HadRM3
boundaries
Simulations at:
Pre-industrial, 1kBP, 2kBP, 3kBP, 4kBP, 5kBP, 6kBP, 8kBP, 10kBP, 12kBP

9. Palaeo-modelling design: The “event scenarios”
Palaeorecords indicate spikes and shifts in the regional climate
Profound impact on societies:
For example, increased aridity associated with collapse of Akkadian Empire ~4kBP (Cullen et al., 2000)
Causal mechanisms:
“Natural” variability (which may also change with time)
Specific climate “events” or “shifts”
Model limitations:
Atmosphere only (thermodynamic slab ocean used in global model)
Fixed vegetation scheme
Short run length due to computational cost
Force specific, well known, climate “events” through the surface boundary conditions to examine the extent of the climatic response
Events/shifts possibly caused by volcanoes/breaching of an ice-dam

10. The regional model DJF Mediterranean storm track
ERA-40 ( )
Global model
Regional model
Black line is the 5.0 line
Plot from Kevin Hodge’s webpage
Figures show 2-6 day band-pass filtered standard deviation of meridional wind at 500 hPa

11. The regional model MAM Mediterranean storm track
ERA-40 ( )
Global model
Regional model
Each run is 20 years of data. Includes daily precipitation, 6h diagnostics for several dynamical fields (e.g. U250, T700, MSLP), lots of monthly mean data.
Mention sensitivity tests
Plot from Kevin Hodge’s webpage
Figures show 2-6 day band-pass filtered standard deviation of meridional wind at 500 hPa

12. Using a regional model: Spatial structure Precipitation gradients
Global model (Pre-industrial control run)
ERA-40: January precipitation
Regional model (Preindustrial control run)
Stage of project => prelim analysis only
RCM gets coastal rain structure – important when examining small scale features
Regional model captures strong gradients in target region
Rainfall plots = January precip (mm/day)
BPF plot = RCM rs2kbp00

13. Cross section at 35oN for each time period (anomalies)
Changes over the last 12,000 years Solar forcing and the seasonal cycle
Warmer summer, colder winter
Seasonal forcing bigger than GHG forcing (typically <1Wm-2 from pre-ind)
Also see “later” seasons in recent millenia
Month
Latitude
Orbital parameters change (obliquity, eccentricity, date of perihelion etc)
Impacts upon climate system through changes in incident solar radiation (W m-2)
Month
Cross section at 35oN for each time period (anomalies)
ka BP

14. Changes during the last 12kaBP
Changes in surface air temperature and precipitation in palaeo simulations for the target region
Anomalies expressed w.r.t preindustrial
1 and 2 standard deviations shown
Surface air temperature anomaly
December-February
Precipitation anomaly
October-June
Changes in monthly mean precipitation
Precip mean 0kbp = 0.38mm/day
Precip = ondjfmamj
SurfairT mean 0kBP = 10oC
SurfairT = djf
May be more important to look at seasonal shifts
ALSO NOTE THAT RAIN IN COLD MAY BE MORE EFFECTIVE

15. Changes during the last 2kaBP: Surface air temperature anomalies
Changes in monthly mean precipitation
Precip mean 0kbp = 0.38mm/day
Precip = ondjfmamj
SurfairT mean 0kBP = 10oC
SurfairT = djf
May be more important to look at seasonal shifts
ALSO NOTE THAT RAIN IN COLD MAY BE MORE EFFECTIVE
Changes during the last 2kaBP: Surface air temperature anomalies
Jan-Apr
May-Aug
Sep-Dec
Cooler spring-early summer and warmer late summer/early autumn
Seasons shift, coastal lag 15

16. “Event” modelling: Green Sahara/Wet Sahara
From Nick Drake’s webpage:
SAY MY EVENT MODELS TEND TO BE “EXTREME CASE” SCENARIOS
In early-mid Holocene evidence for large palaeo-lakes in North Africa (e.g. Lake Megachad, Drake and Bristow, 2006).
Dessicated in a relatively abrupt shift ~4-6kyBP
Also evidence of much increased vegetation in the earlier Holocene

17. “Event” modelling: Green Sahara/Wet Sahara
GCMs: Northward shift and intensification of the ITCZ at 6kBP
Connected to stronger NH summer insolation, stronger monsoonal flows and changes in tropical SST gradients (e.g. PMIP2, Braconnot et al 2007)
Amplified by vegetation feedbacks
Figures from Braconnot et al (2007)

18. “Event” modelling: Green Sahara/Wet Sahara
Possible simulations:
Control 6kBP simulation
6kBP + imposed Green Sahara
6kBP + imposed “Wet” Sahara (green and open lakes)
6kBP + enhanced tropical SST gradients
Combined (3)+(4)?
From Nick Drake’s webpage:
Use regional model to examine impact on Mediterranean storm track

19. “Event” modelling: 8.2kBP event
Widespread evidence for a “spike” in palaeorecords around ~8,000 years ago
Cause believed to be bursting of ice dams holding back glacial lake Agassiz in NE America
“Put very simply, a really big flood happened … from Laurentide-dammed lakes … [at] an age of about 8.47ka” (Alley and Agustsdottir, 2005)
Disrupts MOC in North Atlantic
Some relevance to future MOC weakening (“it is very likely that the Atlantic MOC will slow down during the 21st century”, IPCC 4AR)
Summary of climate anomalies associated with 8.2kBP event
From Alley and Agustsdottir (2005)

20. “Event” modelling: MOC shutdown
DJF surface temperature change
(MOC off – MOC on)
MOC shutdown experiments
HadCM3 “hosing” simulation under pre-industrial conditions (Vellinga and Wu, 2008)
Using SST data to tune slab models and repeat experiments using HadSM3/HadRM3
Focus on impacts upon Mediterranean storm track
Sensitivity to background state
8,000 years BP
Pre-industrial conditions
Sea ice
warmer
colder

21. “Event modelling”: MOC shutdown Storm tracks and the mean flow
Control: storm track (BPF MSLP)
Control: 250 hPa
Dramatic changes in mid-latitude storm tracks and jet structure but insufficient resolution to confidently assess the impacts on Mediterranean storm track
Hosed: storm track (BPF MSLP)
Hosed: 250 hPa
For Atlantic storm tracks, see Brayshaw et al (under review, JClim)

22. Other work: Downscaling for hydrology
Comparing with rain-gauge style data
Model simulations
Rain gauge data
Probability of rain:
Markov chains
Pr(Rain|Rain) Pr(Rain|NoRain)
PDF of rain on rain day
Fitted gamma functions/histogram
Mention EB;’s future stuff working
Mention seasonal cycle problems, mention TRACK ideas
Combining with satellite data to do regional statistical downscaling?
Dan’s/Andy’s Dead Sea work?
Mention Andy/Sam’s population work. Mention importance of veg/infiltration?
Statistical model
Synthetic rainfall time series
Hydrology models etc

23. Future work: TRACK diagnostics
Kevin Hodges’ TRACK diagnostics
Track density
Storm intensity
Genesis density
Lysis density
Feature density
Lifetime
Speed
Growth/decay rates
Using Vorticity 500 hPa (3h) and a range of 6h data
See Hoskins and Hodges (2002)
Say about downscaling problems – possibly use track?
Say about finding out a bit more about what these storm are (STJ vs LLBC) different to N Atlantic track

24. Summary
Regional model greatly improves spatial detail in the Eastern Mediterranean
Simulations run for a range of time periods: 2100AD to 12kBP
Future work will focus on physical mechanisms:
Understanding changes in storm track (e.g., using TRACK)
Sensitivity tests (8.2ky event, Green Sahara, Warm West Pacific)
Investigating downscaling, and possibly forward modelling of Oxygen isotopes

25. Contact: Any questions? d.j.brayshaw@reading.ac.uk