# Presentation: 707784

## Remote Sensing of Cloud Optical and Microphysical Properties

**Using MODIS Data**

**                                  **
**Bryan A. Baum**
- NASA Langley Research Center
- M. D. King
- NASA Goddard Space Flight Center
- S. Platnick, M. Gray, E. Moody, P. Hubanks
**     ****Topics**:
-        - Retrieval of cloud optical/microphysical properties
-         - Global and regional analyses
-         - Status

***MODIS Science Team Meeting***
***July, 2002***

- MODIS Direct Broadcast, 8 July 2001
- Quebec Forest Fires

## Cloud Clearing

- Based on multispectral threshold tests from 17 spectral bands ranging from 0.55-13.93 μm (including new 1.38 μm band)
- Consists of 48 bits of information for each pixel, including results of individual tests and the processing path used
- bits 1 & 2 give combined results (confident clear, probably clear, probably cloudy, cloudy)
-  Cloud mask is input to rest of atmosphere, land, and ocean algorithms
- Recent improvements for Version 4 (and upcoming reprocessing effort)
- - semi-arid land (less uncertain in clear-sky regions)
- - sunglint (better discrimination between low clouds and clear sky)
- Provided at both 0.25 km and 1 km spatial resolution

## Operational Cloud Products

**18 July 2001**

- Platnick et al, 2002: The MODIS cloud products: Algorithms and examples from Terra. Submitted to *IEEE Transactions on Geoscience and Remote Sensing (TGARSS)*

## Cloud Temperature

- 18 July 2001

## Infrared Cloud Phase

- 18 July 2001

## Multilayered Clouds 

- Multilayered Clouds

## Daytime Multilayered Cloud Detection

- Scatterplot for 200 x 200 pixel array
- Pixels are analyzed multiple times
- (except around edges of granule) by
- staggering the array over the scene

- Number of times a pixel was classified as being multilayered

- Pixel number across scan line

- Scan line number

- Nasiri and Baum, 2002: Daytime Multilayered Cloud
- Detection using MODIS Data. In preparation.

**ice**

**water**

**multilayered**

**clear**

**18 July 2001**

## Retrieval of Optical Thickness and Particle Size(M. D. King and S. Platnick)

- The reflection function of a near-infrared absorbing band (e.g., 2.14 μm) is primarily a function of effective radius
- clouds with small drops (or ice crystals) reflect more than those with large particles
- For optically thick clouds, there is a near orthogonality in the retrieval of c and re using a visible and near-infrared band

- Liquid Water Clouds - ocean surface

- Retrieval of Optical Thickness and Particle Size(M. D. King and S. Platnick)

## Cloud Optical & Microphysical Properties Retrieval Example

- Liquid Water Clouds - ocean surface

- Liquid Water Clouds - ice surface

## Cloud Optical Thickness

- 18 July 2001

## Cloud Particle Size

- 18 July 2001

## Recent Improvements for Collection 4 Code Delivery

- New high resolution surface albedo map based on MOD43.
- New cloud phase decision algorithm that merges results from the
-    IR (8.5 and 11 m) and decision tree (based on cloud mask) approaches.
- Serious algorithm problems solved (polar retrievals, use of pre-calculated
-    cloud property libraries).
- Large reduction in number of unsuccessful retrievals.

## MOD12 (IGBP ecosystem classification) + USGS water + tundra

- Ecosystem Map(A. H. Strahler, C. B. Schaaf, et al. – Boston University)

**Notes:**
For the time being we’re using ecosystem as a surrogate for surface albedo.

## Surface Albedo Surface albedo = ecosystem + MOD43 (Strahler, Schaaf et al.) aggregation

**Notes:**
For the time being we’re using ecosystem as a surrogate for surface albedo.

## Cloud Optical Thickness in the Arctic:Provisional Production Code (edition 3)

**c

- 0

- 5

- 10

- 20

- 15

- June 2, 2001

## Cloud Optical Thickness in the Arctic:Provisional Production Code (new correction)

**c

- 0

- 5

- 10

- 20

- 15

- June 2, 2001

## Cloud Effective Radius in the Arctic:Provisional Production Code (edition 3)

- Cloud Effective Radius in the Arctic:Provisional Production Code (edition 3)

- re(μm)

- 4

- 10

- 22

- 40

- 34

- 16

- 28

- June 2, 2001

## Cloud Effective Radius in the Arctic:Provisional Production Code (new correction)

- re(μm)

- 4

- 10

- 22

- 40

- 34

- 16

- 28

- June 2, 2001

## Global Cloud Retrievals

- What follows are comparisons between identical Terra and Aqua cloud parameters for July 4, 2002.

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##  Summary of Cloud Optical and Microphysical Property Products

- Comparison of prelimary Aqua products to Terra products shows remarkable consistency and is thus encouraging.
- Many improvements have been implemented for retrievals of cloud optical thickness and particle size. Major improvements include:
- 	- polar regions
- 	- cloud phase
- 	- fewer unsuccessful retrievals
- 	- use of MOD43 to improve characterization of multispectral surface reflectances
***Highest priorities are***
***	****1. Mixed-phase clouds*
*	**2. Multilayered clouds*
*	**3. Better cloud phase discrimination*

## Cloud Particle Size Comparison

**Cloud Particle Size Comparison**

- Difference in particle effective radius (microns) relative to a retrieval using the 2.1 m band.
- In general, the left panel shows similar sized or smaller liquid water radii when using the 1.6 m
- band in place of the 2.1 m band, in contrast to larger radii with the 3.7 m band.