large scale soil moisture modelling - amazon s3
TRANSCRIPT
LARGE SCALE SOIL
MOISTURE MODELLING
Giuseppe Formetta, Vicky Bell, and Eleanor [email protected] Centre for Ecology and Hydrology, Wallingford, UK
Wednesday 25th January 2017
Satellite Applications Catapult Electron Building, Fermi Avenue, Harwell
Soil Moisture Workshop
WHY SOIL MOISTURE IS IMPORTANT?
Outline
- MOTIVATIONS
- THE JULES MODEL - a “land-surface” model(Thanks to Eleanor Blyth and Alberto Martinez-de la Torre)
- THE GRID-TO-GRID MODEL - a “hydrological”
model(Thanks to Vicky Bell)
WHY SOIL MOISTURE IS IMPORTANT?
Soil availability
Land-useAgriculture
Soil moisture effects many human activities
Floods
WHY SOIL MOISTURE MODELLING?
• Traditional field measurement of soil moisture is
time consuming and expensive
• Soil moisture is not routinely monitored over the
long term like precipitation and discharge
• The remotely sensed soil moisture data has its
own uncertainties; e.g. mismatch in scale
between the in situ measurements; surface
estimates only.
• Increasing computational speeds allow for more
accurate numerical modelling techniques
• Models can tell what will be: evaluating effects of
land-use, climate changes
vs
THE LAND-SURFACE MODEL JULES
JULES is a community model of land surface, vegetation and soil processes led by
CEH and the UK Met Office
~200 users across NERC, Met Office,
universities, overseas,…
>40 NERC proposals since 2008 with
JULES activity
Used by the Met Office weather and
climate models (IPCC)
Will be used in NERC/Met Office UK
Earth System Model (UKESM1)
Applications:
THE LAND-SURFACE MODEL JULES
Energy BudgetPhotosynthesis
Water Budget
Carbon Cycle
Carbon assimilated
from the air, converted
Into leaf, roots and
stem carbon.
CO2 and CH4
release from soil
Water flows between the
atmosphere and the surface
Carbon and water flows
through the stomata
between the surface and
the atmosphere:
photosynthesis, respiration
and transpiration
The snow pack
can have up to 3
layers
Water and heat
flows:
ice formation effect
Energy flows
between the
surface and the
atmosphere:
radiation, heat
and latent heat
modified from: JULES: Best et al, 2011, Clark et al, 2011, GMD. http://JULES.JCHMR.ORG
THE LAND-SURFACE MODEL JULES
Energy BudgetPhotosynthesis
Water Budget
Carbon Cycle
Carbon assimilated
from the air, converted
Into leaf, roots and
stem carbon.
CO2 and CH4
release from soil
Water flows between the
atmosphere and the surface
Carbon and water flows
through the stomata
between the surface and
the atmosphere:
photosynthesis, respiration
and transpiration
The snow pack
can have up to 3
layers
Water and heat
flows:
ice formation effect
Energy flows
between the
surface and the
atmosphere:
radiation, heat
and latent heat
modified from: JULES: Best et al, 2011, Clark et al, 2011, GMD. http://JULES.JCHMR.ORG
Plants grows
and compete
with each
other for light,
changing the
land cover
1. Incoming moisture is split into runoff and water absorbed.
Runoff is diverted in rivers.
2. There is a constant redistribution of water within the soil column
as it tries to reach a state of equilibrium. This is determined
using the Darcy’s law:
𝑞 = 𝐾𝜕Ψ
𝜕𝑧+ 1
3. At the bottom of the soil layers (3m), water is taken out at a rate
assuming only gravitational effects – free drainage.
4. This drainage joins the surface runoff in rivers.
THE LAND-SURFACE MODEL JULES
Model INPUT
Soil moisture and runoff component
• Incoming solar radiation
• Relative humidity
• Atmospheric pressure
• Air temperature
• Precipitation
• Wind speed
Model soil moisture OUTPUT
10 cm35 cm
100 cm
300 cm
• Averaged soil moisture
typically at 4 depths
THE LAND-SURFACE MODEL JULESSoil moisture content for all UK at 1km
resolution: mean for the 1961-2012 period
Plot scale soil moisture content
evolution in time for different layers.
Available at http://earth2observe.github.io/water-
resource-reanalysis-v1/results/table_sma.html
0-10 cm
depth
100-300
cm depth
Standard deviation of the soil moisture content anomalies at
global scale at ~50km resolution for the 2002-2012
CHESS (1km resolution)
driving data available thought
the CEH webpage
The Grid-to-Grid hydrological model
Energy BudgetPhotosynthesis
Water Budget
Carbon Cycle
Carbon assimilated from
the air, converted Into leaf,
roots and stem carbon.
CO2 and CH4
release from soil
Water flows between the surface and the
atmosphere: precipitation
Carbon and water flows
through the stomata
between the surface and
the atmosphere:
photosynthesis, respiration
and transpiration
The snow pack can
have up to 2 layers
Surface and sub-surface runoff
routed laterally to estimate
downstream rive flows
Energy flows
between the
surface and the
atmosphere:
radiation, heat and
latent heat
Dry snow
Wet snow
Unsaturated zone
Saturated zone
The Grid-to-Grid hydrological model
River
Soil column
depth, L s0
Percolation,
QP
Lateral
drainage,
QD
Groundwater
flow (sub-
surface runoff),
QG
Subsurface
flow
Saturation-
excess surface
runoff, q
• A spatially distributed grid-based model
• Driven by gridded rainfall and potential evaporation data
• Estimates naturalised river flows on a 1km grid at 15 min t-step
• Gridded spatial datasets of landscape properties (soil, land-cover, topography, geology) reduces the need for calibrating model parameters
Bell et al. (2009). Journal of Hydrology, 377 (3-4), 335-350
Data available on request:
• daily/monthly/annual 1km grids of depth averaged soil moisture
• monthly grids should be freely available soon.
The Grid-to-Grid applications
• Flood forecasting - used countrywide for operational flood forecasting and warning for the EA and SEPA
• Models national river flows 24/7, forecasts out to 5 days
• Surface water flooding
• Estimating projected future change in UK river flows (collaboration with Met Office Hadley Centre)
• Seasonal forecasting of river flows and subsurface water storage: http://www.hydoutuk.net/
• Sensitivity to rainfall map used in EA/FFC’s Flood Outlook (used by operational flood managers)
Flood forecasting with G2G
Soil moisture (%)Soil moisture (%)
Applications: Sensitivity to rainfall map
This map uses the G2G estimates of subsurface storage to highlight areas where water storage, s, is below or above the monthly mean (smean),
and by how much (mm)
This map highlights areas where the ground is WET relative to the
long term – now used by EA/FFC in their fortnightly “Flood Outlook”
Soil moisture
Collaboration with EA and Met Office
Bell VA, Davies HN, Kay AL, Marsh TJ, Brookshaw A, Jenkins A. 2013. Developing a large-scale
water-balance approach to seasonal forecasting: application to the 2012 drought in Britain.
Hydrological Processes, 27(20), 3003–3012.
Applications: seasonal hydrological forecasts
• The most recent end of month G2G sub-surface storage estimate is used as the initial condition for a water-balance forecast of the next 1- and 3-months sub-surface storage using Met Office GloSea5 rainfall forecast ensemble members and climatological PE as input (Bell et al. 2013).
• Corresponding ensembles of regional river flow estimates for the next 1- and 3-months ahead can be estimated using the water balance (WB) hydrological model using historical and spatial information from the G2G.
Present day
G2G run WB model run for 1-3 months ahead
Observed rain+ PE Ensemble forecast monthly rain + mean PE
Bell, V. A., Davies, H. N., Kay, A. L., Brookshaw, A. &
A.A, Scaife. A national-scale seasonal hydrological
forecast system: Development and evaluation over
Britain, HESS (2017, in preparation)
To summarise….
Land Surface Models (e.g. JULES)Self-consistent representation of energy and evaporationModels many processes (Temperature, CO2, snow etc.)Complex formulation, slow, can lack accuracyLimited assessment against observations
Hydrological Models (e.g. Grid-to-Grid, PDM)Required to be fast and accurateRealistic representation of river flow processesGood for modelling floods & droughts in river basinsAssessed against observations
Groundwat
er storage
Surface
storageDirect
runoff
Probability-
distributed soil
moisture
storage
Surface
runoff
Baseflow
Recharg
e
P
E
S1
qs
qb
S3
S2
q
Groundwat
er storage
Surface
storageDirect
runoff
Probability-
distributed soil
moisture
storage
Surface
runoff
Baseflow
Recharg
e
P
E
S1
qs
qb
S3
S2
q
Often used for research into large scale feedbacks
Often used for civil engineering applications e.g. flood forecasting
To summarize….
Land Surface Models (e.g. JULES)Self-consistent representation of energy and evaporationModels many processes (Temperature, CO2, snow etc.)Complex formulation, slow, can lack accuracyLimited assessment against observations
Hydrological Models (e.g. Grid-to-Grid, PDM)Required to be fast and accurateRealistic representation of river flow processesGood for modelling floods & droughts in river basinsAssessed against observations
Groundwat
er storage
Surface
storageDirect
runoff
Probability-
distributed soil
moisture
storage
Surface
runoff
Baseflow
Recharg
e
P
E
S1
qs
qb
S3
S2
q
Groundwat
er storage
Surface
storageDirect
runoff
Probability-
distributed soil
moisture
storage
Surface
runoff
Baseflow
Recharg
e
P
E
S1
qs
qb
S3
S2
q
Often used for research into large scale feedbacks
hydrology
evaporation
Often used for civil engineering applications e.g. flood forecasting