# Presentation: 258111

## Aerosol Remote Sensingby Ilana Lefkovitz

-  Student Researchers: 2Juan Rodrigez, 2Irving Andino, 1Karol Baldyga
- Faculty Mentor: 1Dr. James Frost
- 1LaGuardia Community College: 31-10 Thomson Avenue, Long Island City, New York 11101
- 2City College: New York, New York

## BACKGROUND

- Aerosols are solid or liquid particles suspended in the atmosphere. They are produced from both anthropogenic and natural sources. In order to truly understand global warming, it is crucial that we evaluate the role aerosols play in climate change. Aerosols are highly varied in size, composition, and lifetime and this makes it extremely hard to quantify their cooling effect, which is comparable in magnitude to the warming effect of greenhouse gases.
- 	Various remote sensing instruments, like the polarimeter and sunphotometer retrieve information about aerosol properties—their refractive index (composition), radius (size), and tau (optical depth, concentration).

**BACKGROUND**

- _Aerosols_

## Aerosols

- This project involves the use of a **hand-held polarimeter**, a **rotating shadowband radiometer, and a CIMEL sunphotometer**. By analyzing the data from all three ground instruments accurate values for the optical depth, the size, and refractive index of the aerosols can be obtained. Such information will be used by scientists to develop better computer models which make predictions about future climate change.

**MY PROJECT**

## Data Analysis

- _Aerosols_

## Aerosols

- _Aerosols_

**CONCLUSIONS**** **
- Both the data from the LaGuardia Community College MFR and the hand-held polarimeter seem to confirm the data from the CIMEL at CCNY, since all instruments measured a tau near .30.
- On July 17, as shown by the CIMEL radius plot, most of the aerosols were comprised of either two sizes: .1 (fine) or 5 (coarse) microns. Since the polarimeter cannot account for these coarse aerosols due to its being monomodal, variations existed in the data for each of the color wavelengths. This is also why an exact refractive index could not be obtained but instead approximated at a range of 1.35-1.45.
_**FUTURE PROJECTS:**_
- Bimodal polarimeter data analysis program
- PDA (new Java program)
- GLORY Mission (comparing our data to the 2008 launched satellite)

## References and Additional Acknowledgements  

- _[http://www.cis.lagcc.cuny.edu/nasa/htm%20files/handheldpolarimeter](http://www.cis.lagcc.cuny.edu/nasa/htm%20files/handheldpolarimeter)_
- _earthobservatory.nasa.gov/Library/Aerosols/ _
- _oea.larc.nasa.gov/PAIS/Aerosols.html_
- _http://aeronet.gsfc.nasa.gov/_
- Brian Cairns

## Aerosols

- Global Warming = Reality

-   Worldwide temperatures have risen     	more than 1 ̊ F over past century
-   Disappearing Glaciers
-   Devastating Natural Disasters (Tsunami, 	Hurricane Katrina)

## Why is our climate being altered?

- _Aerosols_

*Greenhouse Gases*

- More gases like carbon dioxide and methane emitted from **Factories, Power Plants, and Automobiles ***trap* heat in the atmosphere

*Aerosols*

**Solid/Liquid particles suspended in the atmosphere** emitted from both natural and anthropogenic** **sources which:
-  reflect light
- scatter light
- absorb light
- (depending on particle composition)

## Climate Forcings 

- _Aerosols_

**Forcings**: changes in the energy balance of the earth
- (measured in Watts per square meter)
-  positve (GHG forcings)
- negative  (aerosol forcings)

**Response: **results of these forcings and changes in:
- temperature
- wind
- rainfall
-  weather extremes

## Types of Aerosols

- _Aerosols_

***Anthropogenic***

***Natural***

- Volcanoes
-  dust storms
-  forest and grassland fires
-  sea spray

-  burning of fossil fuels (soot, smoke)
-  biomass combustion
-  emissions from cars, power plants
- Consists mainly of **sulfates** and **carbon **based aerosols

##  Types of Aerosols (continued...)

- _Aerosols_

- Sulfates:
-  Reflect sunlight back into space
-  Mo

- Carbon-based aerosols:

-  Absorb light
-  Anthropogenic sources

## Other Properties of Aerosols

- _Aerosols_

**Size**:  from 0.01 microns (smoke particles) to several tens of microns (cloud droplets).

**Lifetime:  **from several days to several years

## Stratospheric

-  Upper part of lower atmosphere
- Direct Climate Forcing
-  Longer life aerosols

-   Lower part of lower atmosphere
-  Indirect climate forcing
- (includes influencing cloud properties and processes)
-  shorter lifespan

- Tropospheric

## Why is Aerosol Research so Important?

- _Aerosols_

- Quantification of Green House Gases = **Certain, Precise**

- Quantification of Aerosols = **??????**

_**Aerosols**_ are highly varied in:
-  size
- composition
- lifetime

-  Aerosol variability makes it extremely hard to quantify aerosols and to accurately measure their _***cooling effect***_* (or warming effect depending on composition)* on the atmosphere in opposition to the warming effect by GHG’s.

-  Aerosols are thought to be the cause of respiratory diseases like asthma

-  Certain chemical reactions are aerosol induced which deplete stratospheric ozone

## What is Polarization?

- Polarization is a measure of the direction of vibration of a light wave

- _Aerosols_

- _Natural Light_: unpolarized, light is moving in all directions
- _Reflected and Scattered Light (as by aerosols)_: polarized, moving in one direction.

- Using Polaroid Sheets

- The polaroid sheets consist of microscopic grills that when rotated, alternate between aligned and nonaligned grills. During alignment, the **maximum amount of light** **(intensity) **comes through, but when the grills totally criss cross each other, no light gets through and there is **minimum intensity**

## How the Hand-Held Polarimeter Works

- The Polaroid

- _Aerosols_

- Baffle

- Infrared cutoff filter

- Red, Blue, or Green filters

- Solar Cell

- Multimeter:
- Converts solar energy to electrical energy

- Lens

- Option of mini multi-spectrometer

## Aerosols

** ****	**The tripod is aimed directly at the sun. A protractor assembly aims the polarimeter at a viewing angle, θ, with respect to the sun.  The Polaroid is then rotated and maximum and minimum (intensity) signals are recorded.  The degree of polarization P is then calculated by
- 	                                                            Imax - Imin
- 		                                         P =  --------------------
- 		                                                   Imax + Imin
- 	This is done for a wide range of viewing (scattering) angles.  A plot of P versus the scattering angle is then made.

- _Aerosols_

- Collecting Data

## Aerosols

- We analyzed the data taken on July 11, a partially sunny, quite hazy day, and saw from the plots that the best fit was an optical depth (tau) of 1.0, a radius of .2, and a refractive index of 1.35 which was consistent with the data from all three color filters (red, blue, green).
- After comparing these results with those of the CIMEL instrument, it was evident that our measurements from the polarimeter were accurate. The optical depth reading for the CIMEL was very close to 1.0.

- _Aerosols_

## Aerosols

- Data Analysis: IDL computer plots from hand-held polarimeter

## Aerosols

- Data Analysis: IDL computer plots from hand-held polarimeter

## Data Analysis: IDL computer plots from hand-held polarimeter

- _Aerosols_

## Aerosols

- _Aerosols_

## Aerosols

- Conclusion:

- _Aerosols_

## Polarimeter Data Analyzer (PDA) 

- _Future Projects_

- Instead of using the **IDL **computer program to evaluate the optical depth (tau), radius, refractive index, wavelength and scattering angle which processes each type of data separately—which is highly inefficient and time consuming, we will soon use a **Java program** designed by Irving Andino of the NASA LaGuardia team which will **lay out all the data at one time**

## The Rotating Shadowband Radiometer at LaGuardia Community College

- _Future Projects_

- This sunphotometer is a new feature at LaGuardia Community College. The student researchers and I are responsible for its installation, testing, and operation.  We hope that soon we will be able to take measurements from the instrument and compare them with the hand-held polarimeter results

## Glory Mission

- Called for launch in 2008, the GLORY satellite designed by GISS will take precise **global** measurements from its polarimeter. We hope, here at LaGuardia, that in the future we can compare the data from the hand-held polarimeter with the data from the GLORY polarimeter.