# Presentation: 489263

## How do aerosols affect air quality, the human environment, and natural ecosystems?

- For AeroCenter Update, March 8, 2008 (Year of the Rat)

- Many others

- and

## Aerosol affects air quality – Emission, transport, and amount of surface particulate matter 

## PM air quality

- Aerosol particles, also called particulate matter (PM) in air quality terms, exert health and environmental problems when in high concentrations

| EPA Standards for PM air quality: |  |  |  |
| --- | --- | --- | --- |
| Air Quality | Color Scale | PM2.5 | PM10 |
|  |  | (μg m-3) | (μg m-3) |
| Good | Green | 0 – 15 | 0 – 54 |
| Moderate | Yellow | 16 – 40 | 55 – 154  |
| Unhealthy for sensitive groups | Orange | 41 – 65 | 155 – 254  |
| Unhealthy | Red | 66 – 150 | 255 – 354 |
| Very unhealthy | Purple | 151 – 250 | 355 – 424 |
| Hazardous | Maroon | 251 – 500 | 425 – 604 |

## Sources of PM:

- Local/Regional:
- Power plants, automobiles, fires, dust, and other natural sources (trees, volcanoes)
- Transboundary transport from outside:
- Pollutants, smoke, and dust generated from other regions that can be transported into region of interest
- The extent of impact of long-range transport and regional emissions on air quality depends on the amount emitted locally and the vertical locations of PM from outside regions

## Sources and transport from observations and models

**Sources and transport from observations and models**

- From: Yoram Kaufman

## What can satellite data tell us about the long range transport of pollution beyond pretty pictures? 

**A Satellite-based assessment of trans-Pacific transport of pollution aerosol**
- Hongbin Yu, Lorraine Remer, Mian Chin, Huisheng Bian, Richard Kleidman, Thomas Diehl, JGR in press, 2008
- (Kaufman special issue)

## Anthropogenic (pollution + smoke) AOD over oceans derived from MODIS

**Yoram Kaufman’s formula:**

**Anthropogenic (pollution + smoke) AOD over oceans derived from MODIS**

- Whereτ, τa and τm are total, anthropogenic, and maritime aerosol optical thickness
- fτ, fd, fm, fa are fractions of fine mode, dust, maritime, and anthropogenic aerosol optical thicknesses
- τa is derived using a modified/ improved Kaufman method
- Using vertical information from GLAS and CALIPSO, RH data from AIRS, and mass extinction efficiency from field measurements to convert τa to mass flux

- From: Hongbin Yu (Yu et al., 2008)

## Measurement-based estimate of transpacific transport of anthropogenic aerosols

- Using aerosol products from multiple satellite sensors (MODIS, GLAS, CALIPSO, AIRS) and from field measurements
- _~ 18 Tg/year_ pollution aerosol is exported from East Asia (and its upwind regions) to NW Pacific
- _~ 4.5 Tg/year_ (25%) reaches the west coast of North America
- This imported amount is about _15%_ of the total anthropogenic emissions in U.S. and Canada
- GOCART and GMI model simulations show similar magnitudes with satellite-based estimate, which is the total column amount

- Export

- Import

- From: Hongbin Yu (Yu et al., 2008)

## The above study is an estimate of total column flux – how does this transport affect the surface air quality? 

**Intercontinental transport of pollution and dust aerosols: Implications for regional air quality**
- (A modeling study)
- Mian Chin, Thomas Diehl, Paul Ginoux, William Malm, ACP 2007

## The impact is critically dependent on vertical extent of transported aerosol plume

- Leaving Asia

- Entering N. Am.

- Asian pollution:
- Max in at surface leaving Asia
- Max above surface (1.5 – 4 km) entering North America
- Requiring downward mixing to send stuff to North American surface

- European pollution:
- Contributing 10 – 50% in the “Asian outflow”!

**GOCART model study**

- Ratio of imported to locally emitted athropogenic fine mode PM at surface:
-     - From _14%_ in NW to _3%_ in SE U.S.

## Other studies showing the importance of aerosol vertical profiles to map the column amount to surface PM:

**Using GEOS-CHEM model to map MISR data to surface PM2.5** – Y. Liu, Kourtakis, R. Kahn, et al, JAWMA 2007
**3-D Air Quality System project** – R. M. Hoff, K. McCann, H. Zhang, A. Prados, and J. Engel-Cox
**Using Giovanni tool to map MODIS AOD to surface PM2.5** – A. Prados and Greg Leptoukh

## MISR & GEOS-Chem – Mapping near-surface pollution(Liu, Krukakis, Kahn et al., 2007)

**MISR & GEOS-Chem – Mapping near-surface pollution**(Liu, Krukakis, Kahn et al., 2007)

- MISR provides _total-column AOT_ over land to constrain model
- MISR also gives _particle shape_ to separate dust & spherical particles --> much better result
- GEOS-CHEM provides aerosol _vertical distribution + detailed spherical-particle chemical speciation_

## 3-D Air Quality System (R. Hoff et al.)

- Integrate NASA satellite sensor and lidar data into EPA’s air quality data systems
- Provide greater accessibility and usability of satellite and lidar data to users of these systems
- Enable monitoring in horizontal and vertical dimensions for forecasting and retrospective analysis

- MODIS 10x10 granule
- AOD product

- Remapped MODIS 12x12 CMAQ
- Gridded AOD product

- Calipso and UMBC Lidar data mapped to EPA PM sites

## Assessing U.S Air Quality with Giovanni (Ana Prados and Greg Leptoukh)

**Assessing U.S Air Quality with Giovanni **(Ana Prados and Greg Leptoukh)

- Data sets: MODIS Terra and Aqua AOD, EPA PM2.5, CALIOP, OMI NO2 and Aerosol Index
- Services: include AOD/PM2.5 correlation maps and scatter plots, and image loops for examining long range transport of pollutants

-  Level-3 MODIS AOD

- EPA PM2.5 (ug/m3)

- May 22nd, 2007: Smoke over north Carolina. High AOD and low PM2.5 (r=0.54). There is also haze in the southeast
- Improved correlation over this region when excluding smoke areas (r=0.80)

- Giovanni data sets and tools help provide a more complete understanding of the origin, evolution, and vertical distribution of aerosol pollution over the continental U.S.

## Remarks on aerosol impact on air quality

- Key quantities: Vertical distribution; composition; and particle size
- Current satellite data have limited information on these quantities
- There are innovative methods to estimate the transport and “retrieve” surface PM from current satellite observations but with large uncertainties
- Future satellite mission should focus on improving capabilities on observing the key quantities with adequate spatial coverage and accuracy

## Aerosol affects human environment – Global dimming/brightening

## Multi-decadal change of solar radiation reaching the surface

- Solar radiation reaching the surface (Ssfc) is the primary energy source for life, and any change of this radiation could substantially affect the climate, hydrological cycle, and ecosystems
- Surface water evaporation
- Soil moisture
- Crop yield
- CO2 uptake

## Multi-decadal change of solar radiation reaching the surface – global dimming/brightening

- From: David Streets (Streets et al., 2004, 2006)

- Total

- Other regions

- East Asia

- Former USSR

- Eastern Europe

- OECD Europe

- U.S.A.

- Long-term observations of Ssfc have shown a decline in solar radiation up to 1990 at several different regions of the world (dimming)
- Recent measurements have indicated an increase of Ssfc since about 1990 over many regions of the world (brightening)
- Anthropogenic emission change mirrors the change of Ssfc, suggesting possible roles of aerosols
- Many other factors can also contribute to the Ssfc change, such as clouds
- Global or regional or local?

## Long-term variations of AOD (1979 – 2006)(Preliminary GOCART results)

**Long-term variations of AOD (1979 – 2006)**(Preliminary GOCART results)

- Using time-varying anthropogenic emission 1979 - 2006 from David Streets
- Compiling volcanic, biomass burning, aircraft/ship emissions (T. Diehl)
- Calculating dust and sea-salt emissions as a function of wind speed and surface conditions

- Global ocean avg AOD, 60S – 60N

- Global land avg AOD, 60S – 60N

- Figure from: Thomas Diehl

## What is the relationship between aerosol emission, AOD, and Ssfc? (Preliminary GOCART results – annual avg)

## Remarks on aerosol impact on surface radiation

- Key quantities: direct and diffuse SW solar radiation at the surface, under both cloudy and clear skies, and aerosol amount and optical properties
- Current satellite retrieval of surface radiation (e.g. from ISCCP or CERES) suffers from difficulties in specify aerosol amount and optical properties
- Current surface radiation networks are limited for adequate global assessment
- Long-term monitoring of surface radiation and aerosols from ground-based network is needed
- Better retrieval of surface radiation from space requires much better knowledge of aerosol properties

## Aerosol affects natural ecosystem – Dust and ocean productivity 

## Connection between dust and ocean biology

- Iron supply is a limiting factor on phytoplankton growth over vast areas of the ocean
- Deposition of dust transported from deserts is believed to be the main source of iron to the open ocean
- However, dust-marine productivity connection depends on the amount of soluble iron, Fe(II)

- Global iron and dust connections

- From: Jickells et al., Science 2005

## Phytoplankton activity is very sensitive to changes in nutrient availability (particularly in the Southern Ocean)

- Soiree Experiment, Edward et al, Nature 2000)

- Artificially seeded Fe in the Southern Ocean

- Visible chlorophyll enhancement afterwards

**Dust as a Tracer of Climate Change in Antarctica and as modulator of Phytoplankton Activity**** **

**Notes:**
Figure on the left shows an increase of dust deposition and Ts in Antartica
Figure on the right shows that deposition of Fe in the Souther Ocean Waters can trigger a phytoplankton bloom visible from satellite.

## Global distributions of Chl. and aerosol

- Satellite retrieves both ocean Chl. (e.g. MODIS and SeaWiFS) and dust aerosols (e.g. MODIS coarse mode, MISR non-spherical), which can be potentially used to link dust to ocean productivity
- But absorbing aerosols (dust, smoke) remain problematic in ocean color data processing

- January 2001

- Chlorophyll Concentration

- From: W.E. Esaias

- Aerosol Optical Thickness

- April 2001

- From: C. McClain

## A combination of MODIS and OMI observations shows dust traveling a long way in the South Atlantic

- Gassó & Stein, GRL 2007

- Observation of dust in the SO is very difficult because:
- Very cloudy --- > very few clear sky retrievals ----- > sampling problem
- Dust activity is episodic and in pulses.
- Only a combination of satellite retrievals and surface (ship) can help to understand dust transport and detection in the SO as this example shows.

**Notes:**
Observation of dust in the SO is very difficult because:
Very cloudy --- > very few clear sky retrievals ----- > sampling problem
Dust activity nowadays is episodic

Only a combination of satellite retrievals can help to understand dust transport and detection in the SO as this example shows.

## Dust deposition over Atlantic Ocean derived from Terra + Aqua MODIS

- Obtain dust AOD τd:
- Estimate vertical profiles using “virtual lidar” – correlations with the NCEP winds
- Convert dust AOD to mass
- Using wind speed and Terra/Aqua dust mass differences to estimate the dust mass transport
- Derive dust deposition

**Kaufman et al. 2005 estimated:**
- 240 ± 80 Tg of dust are transported annually from Africa to Atlantic
- 50 Tg fertilize the Amazon Basin
- 50 Tg reach the Caribbean
- 20 Tg return to Africa and Europe

**Yoram Kaufman’s method:**

- Estimated dust flux, Kaufman et al., JGR 2005

## Remarks on aerosol impact on ocean biology

- Key quantities: dust aerosol amount and deposition, soluble iron, ocean phytoplankton/chlorolphyll
- Current satellite retrievals of ocean color requires accurately accounting for aerosol “interference”
- It is very difficult to observed dust when clouds present
- It is even more difficult to know if iron from dust is active
- Future satellite observation should have a better capability to detect dust even in cloudy conditions with adequate spatial coverage
- Although dust deposition cannot be directly observed by satellites, it can be derived with higher temporal satellite coverage (several times/day) to see aerosol moving and change