Update on LMWG Proposed Hydrologic Improvements to CLM Overview of proposed hydrology schemes (3) CAM/CLM and offline CLM simulations – Follow the water

Update on LMWG Proposed Hydrologic Improvements to CLM

•Overview of proposed hydrology schemes (3)

•CAM/CLM and offline CLM simulations – Follow the water

•Preliminary conclusions

•Validation against tower fluxes

Project Objectives: Wetter soils, increased transpiration/photosynthesis, improved partitioning of evapotranspiration and representation of land-atmosphere feedbacks, particularly in the tropics (Amazon)

CLM Hydrology Project Simulations

Hyd_con (released CAM3/CLM3)

Hyd_sunsha (Two-leaf canopy model)

P. Thornton, TSS/NCAR

Hyd_plaw_plsc (Surface Datasets (PFTs, LAI, Soil Albedo))

P. Lawrence, CU/CIRES

Hyd_dlptmcsD. Lawrence, P. Thornton/NCAR

Hyd_nliZ.L. Yang, G.Y.

Niu/UTA

Hyd_bd_nlaiR. Dickinson/GIT

Hydrology

Canopy Water

Evaporation

Interception

Melt

Sublimation

ThroughfallStemflow

Infiltration Surface Runoff

Evaporation

Transpiration

Precipitation

RedistributionOcean

Soil Water

Snow

Dra

inag

e

Summary of Hyd_dlptmcs (NCAR)Interception (decrease) – Reduce fraction of potential intercepted water by ¼.

Transpiration (increase) –Soil moisture stress as in LSM (linear function between optimum and dry soil moisture).

Soil Evaporation (decrease) – Reduce soil-canopy air space conductance.

Surface Runoff (decrease) – Saturated fraction runoff unchanged. Runoff over non-saturated fraction controlled by enhancement factor based on root fraction in top 3 layers (macropores).

Soil Water Dynamics (increase) – Remove exponential decrease in hydraulic conductivity. Depends only on sand content of each layer.

Drainage (increase) – Eliminate saturated and non-saturated fraction drainage. Free drainage from layer 10 controlled by hydraulic conductivity.

Note that Infiltration is a residual of surface water flux - evaporation - surface runoff.

Hydrology

Canopy Water

Evaporation

Interception

Melt

Sublimation

ThroughfallStemflow


Evaporation

Transpiration

Precipitation

RedistributionOcean

Soil Water

Snow

Dra

inag

e

Summary of Hyd_bd_nlai (GIT)

Interception (decrease) – Limit storage capacity and Limit storage capacity and leaf wet fraction by fractional area of liquid leaf wet fraction by fractional area of liquid precipitation (convective rain falls over 10% of precipitation (convective rain falls over 10% of gridcell).gridcell).

Surface Runoff (decrease) – Saturated fraction runoff is exponential function of existing water table scale height. No non-saturated fraction runoff.

Soil Water Dynamics (increase) – Remove exponential decrease in hydraulic conductivity. Depends only on sand content of each layer.

Drainage (increase) – Eliminate saturated and non-saturated fraction drainage. No flux boundary condition at bottom layer. Base flow consists of weighted contributions of freely draining soil and that impeded by coupling to water table and applied to bottom layer . Water table depth based on lowest saturated layer and soil matric potential.

Hydrology

Canopy Water

Evaporation

Interception

Melt

Sublimation

ThroughfallStemflow


Evaporation

Transpiration

Precipitation

RedistributionOcean

Soil Water

Snow

Dra

inag

e

Summary of Hyd_nli

Interception (decrease) – Reduce fraction of potential intercepted water by fractional area of precipitation (convective precip falls over 10% of gridcell)(convective precip falls over 10% of gridcell). Leaf wet fraction unchanged. Applied to convective snow as well.

Surface Runoff (decrease) – Saturated fraction runoff is exponential function of water table depth. Max saturated runoff provided by topographic index.

Soil Water Dynamics (increase) – Exponential decrease in hydraulic conductivity but enhanced by factor of seven.

Drainage (increase) – Eliminate saturated and non-saturated fraction drainage. No flux boundary condition at bottom layer. Excessive water above saturation added to above unsaturated layer. Base flow based on maximum baseflow parameter and exponential function of water table depth and applied to all layers.

CAM3/CLMx - Follow the water

Ocean

Hydrology

Canopy Water

Evaporation

Interception

Melt

Sublimation

ThroughfallStemflow


Evaporation

Transpiration

Precipitation

Redistribution

Soil Water

Snow

Dra

inag

e


Hydrology

Canopy Water

Evaporation

Interception

Melt

Sublimation

ThroughfallStemflow


Evaporation

Transpiration

Precipitation

Redistribution

Soil Water

Snow

Dra

inag

e


Hydrology

Canopy Water

Evaporation

Interception

Melt

Sublimation

ThroughfallStemflow


Evaporation

Transpiration

Precipitation

Redistribution

Soil Water

Snow

Dra

inag

e


Hydrology

Canopy Water

Evaporation

Interception

Melt

Sublimation

ThroughfallStemflow


Evaporation

Transpiration

Precipitation

Redistribution

Soil Water

Snow

Dra

inag

e


Hydrology

Canopy Water

Evaporation

Interception

Melt

Sublimation

ThroughfallStemflow


Evaporation

Transpiration

Precipitation

Redistribution

Soil Water

Snow

Dra

inag

e


Hydrology

Canopy Water

Evaporation

Interception

Melt

Sublimation

ThroughfallStemflow


Evaporation

Transpiration

Precipitation

Redistribution

Soil Water

Snow

Dra

inag

e


Hydrology

Canopy Water

Evaporation

Interception

Melt

Sublimation

ThroughfallStemflow


Evaporation

Transpiration

Precipitation

Redistribution

Soil Water

Snow

Dra

inag

e


Hydrology

Canopy Water

Evaporation

Interception

Melt

Sublimation

ThroughfallStemflow


Evaporation

Transpiration

Precipitation

Redistribution

Soil Water

Snow

Dra

inag

e


Hydrology

Canopy Water

Evaporation

Interception

Melt

Sublimation

ThroughfallStemflow


Evaporation

Transpiration

Precipitation

Redistribution

Soil Water

Snow

Dra

inag

e


Hydrology

Canopy Water

Evaporation

Interception

Melt

Sublimation

ThroughfallStemflow


Evaporation

Transpiration

Precipitation

Redistribution

Soil Water

Snow

Dra

inag

e


Hydrology

Canopy Water

Evaporation

Interception

Melt

Sublimation

ThroughfallStemflow


Evaporation

Transpiration

Precipitation

Redistribution

Soil Water

Snow

Dra

inag

e

CAM3/CLMx Global Land Annual Average

Photosynthesis

65

100115

158142 143

120

-101030507090

110130150170190

Pg

Partitioning of Evapotranspiration

010203040506070

%

Transpiration Ground Evap Canopy Evap

Partitioning of Runoff

00.10.20.30.40.50.60.7

Su

rfac

e R

un

off

Rat

io

0.7

0.75

0.8

0.85

0.9

To

tal R

un

off

(m

m/d

ay)

Surface Runoff Ratio Total Runoff

Hydrologic Cycle

0.5

1

1.5

2

2.5

Hyd_c

on

Hyd_s

unsh

a

Hyd_p

law_p

lsc

Hyd_d

lptm

cs

Hyd_n

li

Hyd_b

d_nlai Obs

mm

/da

y

Precipitation Evapotranspiration Runoff

CAM3/CLMx

River Discharge to Ocean

Offline CLM (“Examining the simulated hydrology under biased

forcings makes no sense”)

Atmospheric forcing courtesy of T.Qian/A. Dai - NCAR

CAM3/CLMx

Discharge for World’s Top 10 RiversOffline CLM

CAM/CLMx Climate Changes


CAM3/CLMx

CAM3/CLMx Volumetric Soil Moisture

Conclusions• All schemes (in combination with sun/shade model and new surface datasets) offer

substantial improvements in producing wetter soils, increasing transpiration and photosynthesis, and improving the partitioning of evapotranspiration.

• Hyd_dlptmcs and Hyd_bd_nlai are most similar in terms of partitioning of evapotranspiration and surface runoff ratio. Globally, Hyd_nli has less transpiration and canopy evaporation, more ground evaporation, lower surface runoff ratio than the other two schemes.

• All schemes produce reasonable river discharge to ocean compared to observations.

• In the Amazon, all schemes improve temperature and precipitation biases and hydrologic cycle.

• In general, the three schemes produce similar but small changes in climate. The most notable exceptions to this are:

– All schemes produce cooling in Arabian Peninsula and India in DJF (undesirable) with Hyd_nli resulting in the largest cooling

– Increase in wet season precipitation in the Amazon in all schemes (desirable) and an enhanced seasonal cycle in the Congo (undesirable).

– In JJA, all schemes produce cooling in Europe and near Caspian/Black seas, most of U.S., and Amazon (desirable). All schemes increase positive bias in precipitation in Arabian Peninsula and southern India (undesirable).

Conclusions

• All schemes require minimal software engineering for implementation and only small changes to documentation (tech note)

• All schemes have free parameters that could be “tuned”.

• Final optimal scheme will likely consist of some combination of desirable aspects of each scheme. How to determine this requires more testing against observations and a deeper understanding of why each scheme performs as it does.

EXTRA SLIDES

Hydrology

Canopy Water

Evaporation

Interception

Melt

Sublimation

ThroughfallStemflow


Evaporation

Transpiration

Precipitation

RedistributionOcean

Soil Water

Snow

Dra

inag

e

Summary of Hyd_con (CAM3/CLM3)Interception – Fraction of potential intercepted water is an exponential function of leaf and stem area.

Transpiration – Soil moisture stress is a non-linear function of root distribution and soil water potential.

Soil Evaporation – Soil-canopy air space conductance is a weighted function of bare soil and dense canopy conductances where weights depend on leaf and stem area.

Surface Runoff – Sum of runoff from saturated and unsaturated fractions which are determined from a water table scale height (conceptual TOPMODEL).

Soil Water Dynamics – Exponential decrease in hydraulic conductivity.

Drainage (increase) – Sum of drainage from saturated and non-saturated fractions plus drainage from layer 10 controlled by hydraulic conductivity.

Note that Infiltration is a residual of surface water flux - evaporation - surface runoff.

ABRACOS CLMx (solid line), Observed (dashed line) Latent Heat Flux (Aug 8-Oct 4, 1992) Broadleaf evergreen tropical forest

Hyd_con Hyd_dlptmcs Hyd_nli Hyd_bd_nlai

ABRACOS CLMx

• Atmospheric forcing– Magnitude of wind (m s-1)

– Specific humidity (kg kg-1) (or relative humidity or dewpoint temperature)

– Pressure (Pa)

– Air temperature (K)

– Incident longwave radiation (W m-2) (or derived from vapor pressure and temp)

– Precipitation (mm s-1)

– Incident direct and diffuse visible and near-infrared solar radiation (W m -2) (or total solar radiation)

– Netcdf format, ½ hour resolution preferred

• Surface characteristics– Plant functional types and abundance

– Soil color

– Soil texture (vertical profile of %sand/%clay)

– Monthly LAI and SAI

– Monthly canopy top and bottom heights

CLM Forcing and Validation Requirements – Tower Flux Sites

• Validation– Radiative fluxes (m s-1)

– Turbulent fluxes (including CO2)

– Soil temperature and soil moisture

– Runoff

CLM Forcing and Validation Requirements – Tower Flux Sites

• FIFE (grassland prairie in Kansas)

• BOREAS (old aspen, old black spruce in Canadian boreal forest)

• Cabauw (grassland in the Netherlands)

• Valdai (grassland in Russia)

• ABRACOS (rainforest in Brazil)

• Tucson (semi-arid desert)

• Other possibilities– LBA (primary rainforest, pasture)

– FLUXNET (various ecosystems)

– Hapex-Mobilhy (soybean field in France)

Tower Flux Site Forcing and Validation Data In-house

Interception

•Hyd_con

•Hyd_dlptmcs

•Hyd_nli

•Hyd_bd_nlai

1 exp 0.5intr rain snoq q q L S

0.25 1 exp 0.5intr rain snoq q q L S

1 exp 0.5intr P rain snoq f q q L S

, , , ,

, , , ,10

rain C sno C rain L sno L

P

rain C sno C rain L sno L

q q q qf

q q q q

, ,

, ,10

rain C rain L

P

rain C rain L

q qf

q q

,maxcan PW f p L S

2 3

1canwet

P

Wf

f p L S

1 sun shawet P b

dry sun shab s b s

f f r L Lr

L r r r r

,maxcanW p L S

2 3

1canwet

Wf

p L S

sun shadry b

dry sun shab s b s

f r L Lr

L r r r r

wet P dryr f f r wet dryr f r

Transpiration (Soil Moisture Stress)

•Hyd_con

•Hyd_dlptmcs

t i ii

w r max

max ,

ii

sat i

w

, ,, ,

, ,

1, 0liq i dry ii liq i dry i

opt i dry i

w

Soil Evaporation

•Hyd_con

•Hyd_dlptmcs

1ah aw

s av

r rC U

, , 1s s bare s denseC C W C W

L SW e

, 0.004s denseC

2 L SW e

, 0.0025s denseC

Surface Runoff

•Hyd_con

•Hyd_dlptmcs

•Hyd_nli

•Hyd_bd_nlai

4

,0 ,01 sover sat liq sat liqq f q f w q

,min 1,expsat fact w scalehf w z 10

, ,101

w scaleh z h i iz f z s z

4 16

,0 ,01rI

sover sat liq sat liqq f q f w q

3

1r iI r

,0over sat liqq f q

1exp 0.6 nli

sat fact wf w zz

, ,0expover w scaleh liqq a z q

0.36factw

0.5z

0.4a

Soil Water Dynamics (hydraulic conductivity)

•Hyd_con

•Hyd_dlptmcs

•Hyd_nli

•Hyd_bd_nlai

0.884 0.0153 % ,, 0.0070556 10 exp

sand h isat h i

iz

k zz

0.5z

2 3

, , 1

, ,

, , 1

0.5

0.5

iB

liq i liq i

h i sat h i

sat i sat i

k z k z

0.884 0.0153 %

, 0.0070556 10sand

sat h iik z

0.884 0.0153 % ,,

10.0070556 10 exp exp

sand h isat h i

iz

k zz z

0.884 0.0153 %

, 0.0070556 10sand

sat h iik z

Drainage

•Hyd_con

•Hyd_dlptmcs

•Hyd_nli

•Hyd_bd_nlai

,10

, , ,10 ,10,10

excess deficithliq liq

drai drai wet drai dry h liqliq

k zw wq q q k z

t t

, ,expdrai wet sat b w scalehq f l z

12 3, 1 B

drai dry sat D bq f k w

0.04Dk 51 10bl

,10

,10 ,10,10

excess deficithliq liq

drai h liqliq

k zw wq k z

t t

,1,max

1exp

excess deficitliq liqnli

drai sb w

w wq R z

z t t

4,max 1 10sbR

, ,

10.5 0.5

excess deficitliq liq

drai

drai free drai watert

w wq

t tq q

, ,10drai free hq k z

4 3, max 2 10 ,3 10 exp bd

drai watert wq z

0.5z

,

, , , 9

,6

6 9i h i

liq i drai wet drai dry

i h ii

z k zw t q q i

z k z

,

, 10

,1

1 10i h i

liq i drai

i h ii

z k zw tq i

z k z

,10

, ,

10.5 0.5liq

drai free drai watert

w t

q q

Drainage



CCSM Hyd_dlptmcs Climate Changes

CCSM Hyd_dlptmcs Climate Changes

CAM3/CLMx

Hydrology

Canopy Water

Evaporation

Interception

Sublimation

ThroughfallStemflow


Evaporation

Transpiration

Precipitation

Redistribution

Soil Water

Snow

Dra

inag

e

Mean Annual Cycle of River Flow for Amazon and Congo

CAM3/CLMx Offline CLM

Documents

Update on LMWG Proposed Hydrologic Improvements to CLM Overview of proposed hydrology schemes (3) CAM/CLM and offline CLM simulations – Follow the water