Direct Observations of Aerosol Effects on Carbon and Water Cycles Over Different Landscapes

1
Direct Observations of Aerosol Effects on Carbon
and Water Cycles Over Different Landscapes

• Hsin-I Chang
• Ph D student
• Department of Atmospheric Sciences
• Email hchang05_at_purdue.edu
• Advisor Dr. Dev Niyogi
• Department of Atmospheric Sciences/Agronomy
• Email climate_at_purdue.edu
• Purdue University

2

Collaborators
Kiran Alapaty, UNC Chapel Hill, currently with
National Science Foundation Fitz Booker, USDA/
ARS, Air Quality-Plant Growth and Development
Unit, NC Fei Chen, National Center for
Atmospheric Research, Boulder Ken Davis,
Department of Meteorology, Penn State University,
University Park, PA Lianhong Gu, Oak Ridge
National Laboratory, TN Brent Holben, GSFC, NASA,
Greenbelt, MD Teddy Holt, N. C. State Univ and
Naval Research Laboratory, Monterey, CA Tilden
Meyers, ATDD/NOAA, Oak Ridge, TN Walter C.
Oechel, San Diego State University Roger A.
Pielke Sr. and Toshi Matsui Colorado State
UniversityRandy Wells, Department of Crop
Science, N. C. State University, Raleigh, NC
Kell Wilson, ATDD/NOAA, Oak Ridge, TN Yongkang
Xue, Department of Geography, UCLA, Los Angeles,
CA
3
Outline

• Introduction
• Importance and Hypothesis
• Data and Methodology
• Results and Discussion
• Summary
• Future Work

4

• - AEROSOLS AFFECT THE RADIATIVE FEEDBACK OF THE
  ENVIRONMENT
• Majority of the studies have focused on the
  temperature effects gtwhether aerosols cause
  cooling or warming effect in the regional climate.

• In this study we propose that
• Aerosols also have a significant biogeochemical
  feedback on the regional landscapes, and should
  be considered in both carbon and water cycle
  studies

5
Why would aerosols affect biogeochemical pathways?
Total solar radiation (Diffuse Direct) solar
radiation For increased Cloud Cover or Increased
Aerosol Loading, Diffuse Component Increases gt
changes the DDR (Diffuse to Direct Radiation
Ratio)
Hypothesis Increase in DDR will impact the
Terrestrial Carbon and Water Cycles through
Transpiration and Photosynthesis changes
(Transpiration is the most efficient means of
water loss from land surface Photosynthesis is
the dominant mechanism for terrestrial carbon
cycle)
6
Data Need simultaneous observations of carbon
and water vapor fluxes, radiation (including
DDR), and aerosol loading.

• Carbon, Water vapor flux and plant information
  Ameriflux
• Radiation (including DDR) information from
  Ameriflux or NOAA Surface Radiation (SURFRAD)
  sites
• Aerosol loading information from NASA Aerosol
  Robotic Network (AERONET)

7
Study sites

• Six sites available across the U.S. that have
  information on the required variables for our
  study (AOD,diffuse radiation and latent heat
  flux).

Willow Creek, WI Lost Creek, WI (mixed
forest,00,01)
Bondville, IL (agriculture, C3 / C4, 98-02)
Ponca, OK (wheat 98,99)
Walker Branch, TN (mixed forest 2000)
Barrow, AK (grassland 99)
8
Hypothesis to be tested from the observational
analysis

• Increase in the aerosol loading could increase
  CO2 and latent heat flux at field scales
• This would indicate a more vigorous terrestrial
  carbon cycle because of aerosol interactions
• This would also indicate potential for changes in
  the terrestrial water cycle because of aerosol
  loading

9
Does DDR Change Cause Changes in the CO2 Flux at
Field Scale?

• Walker Branch Forest Site
• CO2 flux into the vegetation (due to
  photosynthesis) increases with increasing
  radiation
• For a given radiation, CO2 flux is larger for
  higher DDR
• Rg-total radiation
• Rd-diffuse radiation

negative values indicate CO2 sink (into the
vegetation)
10
Effect of DDR on field scale CO2 Flux
Does DDR Change Cause Changes in the CO2 Flux at
Field Scale?
Yes!
Increase in DDR appears to increase the observed
CO2 flux in the field measurements.
Changes in CO2 flux Normalized for changes in
global Radiation versus Diffuse Fraction
11
Do clouds affect CO2 flux at Field Scale?

• Yes, clouds appear to affect field scale CO2
  fluxes significantly.
• CO2 flux into the vegetation (due to
  photosynthesis) is larger for cloudy conditions

12
Do Aerosols affect field scale CO2 Flux?

• Increase in AOD (no cloud conditions) causes
  increase in DDR (diffuse fraction)
• CO2 flux into the vegetation (due to
  photosynthesis) is larger for higher AOD
  conditions
• Aerosol loading appears to cause field scale
  changes in the CO2 flux

13
Forests
Are these results true for different landscapes?

Croplands
Grasslands
For Forests and Croplands, aerosol loading has a
positive effect on CO2 flux, where there shows a
CO2 flux source at Grassland sites.
14
Hypothesis for LHF-aerosol relation

• At high vegetation LAI (leaf area index)
• LHF is mainly due to transpiration
• with increasing aerosols,diffuse radiation
  increases and air / leaf temperature decreases,
• gt increase in transpiration and thereby
  increase LHF

• At low vegetation LAI
• LHF is mainly due to evaporation
• with increasing aerosols,diffuse radiation
  increases, and air / leaf temperature decreases,
• gt reduce the evaporation and therefore LHF
  decreases.

15
Clustering AOD-LHF relation into different
landscapes.
Forest site
Cropland
Grassland (LHF values opposite in sign)
Latent heat flux appears to generally decrease
with increasing Aerosol Optical Depths for most
of the studied sites.
16
Observed data analyses
Walker Branch (Forest site)
Low LAI case (LAI lt 2.5) LHF decrease with
aerosol loading
High LAI case (LAI gt3) LHF increase with aerosol
loading
17
However, analyzed results vary for different
landscapes
Bondville (soy bean site(C3))
Low LAI case
High LAI case
For higher LAI, the AOD ve dependence seems to
be decreasing
18
Summary for water cycle study

• Forest
• - High LAI LHF increase with AOD
• - Low LAI LHF decrease with AOD
• need to consider Leaf effect for the flux
  change.
• Corn LHF decrease with AOD Leaf area changes
  have more influence on LHF compare to Air
  Temperature and Soil Moisture.
• Soybean LHF decrease with AOD analyses found
  that Soil Moisture may have influence on the
  decreasing trend of Latent Heat Flux- without
  Soil Moisture effect, LHF increase with aerosol
  loading.
• Grassland LHF increase with AOD not considering
  leaf effect. (Soil Moisture data not available)

19
Conclusions

• Aerosols affect land surface processes
• Results confirmed for different canopy conditions
  (mixed forests, corns, soybeans, winter wheat and
  grasslands).
• CO2 sink increases with increasing aerosol
  loading over forests and croplands (both C3 and
  C4)
• CO2 source increases with increasing aerosol
  loading over grasslands
• Water Vapor Flux generally decreases with
  increasing aerosol loading
• Exceptions were one grassland, and high LAI
  forest sites

20
Design of experiments

• Design configuration Need to design confounding
• Environmental Confounding
• (1) crop site USDA Raleigh, Purdue AG Center
• (2) forest site ChEAS (?)
• Radiation decreases in quantity, changing quality
  and spectral changes and higher DDR.
• Changes in temperature will change in VPD,
  evaporation/transpiration, soil moisture,
  emmisivity and albedo, etc.
• Experiments
• (1) for crops use high/low diffuse radiation
  shed change soil moisture stress and stress from
  temperature and humidity gt need to design
  special chambers.
• (2) for forest repeat similar experiments for
  crops and need to examine vertical profiles gt
  responses in different vertical levels may be
  important.

21
Related work
LI6400 CO2 / H2O Flux system

• Analysis for AOD LHF effects is still underway.
  (need to consider interaction terms such as LAI,
  soil moisture)

Leaf and Canopy scale measurements of CO2 and
Water Vapor Flux for plants grown under different
soil moisture conditions at USDA Facility in
Raleigh.
22
Related work

• Effect of Diffuse Radiation (Clouds and Aerosols)
  on Plant Scale Response
• Modeling of the plant scale response for changes
  in Diffuse Radiation
• (with Dr. Booker and Dr. Wells)

Potted plants were grown in 2 sheds with
different diffuse radiation screens and CO2 / H2O
Exchange Measured
23
Direct and diffuse radiation shed
24
Ongoing and Future work

• Regional Analysis of DDR Changes on Latent Heat
  Fluxes using satellite (MODIS) dataset.

• Continue on GEM-RAMS Modeling System for
  isolating the effects of different variables in
  understanding the aerosol feedbacks on the land
  surface response.

25
Thank you
26
Bondville (corn site(C4))
High LAI case LHF increase with aerosol loading
up to certain level.
Low LAI case
27
AOD-LHF relation after accounting for both leaf
and air temperature effects
soy bean site
corn site
Compare with previous slides, Latent heat fluxes
still decrease with aerosol loading without leaf
and temperature effects.
28
Accounting for Soil Moisture effect
Corn Site
Soybean Site

• For both high and low SM conditions, LHF
  decreases with aerosol loading for agricultural
  sites (not shown).
• With no Soil Moisture effect, Latent Heat Flux
  increases with aerosol at Soybean site.

29
Glazing material treatment effects on average
photosynthetic photon flux density (PPDF) at
upper canopy height between 0800-1600 h (EST)
during the experimental period. The ratio of
diffuse PPFD radiation to total PPDF radiation is
also shown. Values are means SE. Values
followed by a different letter were statistically
significantly different (P 0.05).
Glazing Material
Parameter Ambient Clear Diffusing
PPFD (µmol m-2 s-1) 958 6 a 840 6 b 755 5 c
Diffuse Total 0.389 0.002 a 0.415 0.002 b

30
Soybean biomass and yield responses to growth
under Clear and Diffusing glazing materials (mean
SE). Plants were harvested for determination
of biomass (Biomass) at 88 days after planting
(DAP), and for determination of seed yield
(Yield) at 153 DAP. Values in parenthesis
indicate percent change from the Clear treatment.
Statistics P 0.1 ().
Glazing Material
Harvest Parameter Clear Diffusing
Biomass
Height (cm) 55.6 1.4 56.1 1.4
Branch number (plant-1) 17.3 1.4 18.0 1.4
Leaf dry mass (g plant-1) 45.4 3.0 52.0 3.0
Main stem dry mass (g plant-1) 19.2 1.5 19.8 1.5
Branch dry mass (g plant-1) 51.7 3.9 63.0 3.9 (22)
Pod dry mass (g plant-1) 67.3 8.0 75.4 8.0
Root mass (g plant-1) 30.1 2.6 28.8 2.6
Total dry mass (g plant-1) 213.7 15.2 239.0 15.2
Main stem leaf area (m2 plant-1) 0.19 0.01 0.20 0.01
Branch leaf area (m2 plant-1) 1.21 0.08 1.41 0.08 (16)
Total leaf area (m2 plant-1) 1.40 0.08 1.61 0.08 (15)

Yield
Pod number (plant-1) 397 32 394 32
Seed mass (g plant-1) 173 15 179 15
Mass per seed (g) 0.20 0.01 0.19 0.01
Stem mass (g plant-1) 43 4 49 4

31
Net photosynthesis (A) of upper canopy leaves and
whole-plants treated with either Clear or
Diffusing glazing materials (mean SE). Net
photosynthesis of upper canopy leaves on four
plants per treatment was measured weekly between
48 and 105 DAP (seven occasions). In addition,
whole-plant A of three sets of three plants was
measured on 56 DAP. Treatment effects on A were
not statistically significant.
Glazing Material
Clear Diffusing

Upper canopy leaves (µmol m-2 s-1) 28.4 3.3 26.4 2.6

Whole-plant (µmol plant s-1) 14.7 2.3 17.9 0.7