# Presentation: 473117

## MODIS Global Snow and Sea Ice Cover Maps, and Validation Status

***MODIS Global Snow and Sea Ice Cover Maps, and Validation Status***
***Dorothy K. Hall ******1***
***George A. Riggs******2***
***Vincent V. Salomonson******1***
***                                                                       ***
***1******NASA/Goddard Space Flight Center***
***2******SSAI***
***December 18, 2001***

## Other team members and recent collaborators:

**Igor Appel**
**Jon Barton**
**Klaus Bayr**
**Carl Benson**
**Kimberly Casey**
**Al Chang **
**Janet Chien**
**Nick DiGiromalo**
**	**
**	**

**Other team members and recent collaborators:**

**Jim Foster **
**Richard Kelly**
**Andrew Klein**
**Shusun Li**
**Glen Liston**
**Anne Nolin**
**Hugh Powell **
**J.C. Shi****	**
**	**

## Outline

**Product availability**
**Improving the snow algorithm using thermal mask      and various cloud-mask tests**
**Direct-readout snow maps**
**Validation status of products**
**Outreach**
**	**
**	**

***Outline***

## MODIS Snow Data Products  (available through NSIDC)

***MODIS Snow Data Products  (available through NSIDC)***
**Global, daily and 8-day composite 500-m resolution snow maps **
**Global 8-day composite Climate-Modeling Grid (CMG) products at 5-km resolution in production**
**Global daily CMG will be available soon**
**Snow albedo (spring 2002)**
**Level 2 and Level 3 sea ice products available (includes IST)**

## Eight-Day Composite Global Climate Modeling Grid Snow Map (5.6-km resolution, 1/20 )                                                                    

***      ******With Fractional Snow Cover 40-100%                November 16 - 23, 2000***

***o***

**Can be downloaded from: http://snowmelt.gsfc.nasa.gov/MODIS_Snow/modis.html**

**Notes:**
We have been producing these in-house and making them available on our Web site for downloading.
Daily CMGs will be available through NSIDC.  First time that snow/cloud discrimination has been able to be done in an automated algorithm, though cloud mask is conservative, results are excellent for composite products such as this one.

## Algorithm Enhancements

***Algorithm Enhancements***
**Thermal mask - done**
**Cloud tests – in progress**

## 14 November 2000 16:00 MODIS L2 Snow ProductDetail of Southern Florida and the Bahamas 

- 14 November 2000 16:00 MODIS L2 Snow ProductDetail of Southern Florida and the Bahamas

- Before Thermal Mask

- After Thermal Mask

**Errors of commission are now very low, e.g., <0.05% in non-snow-covered areas such as Australia in the summer**

**Notes:**
This slide shows the remarkable amount of snow eliminated from the region boxed in the previous slide.

## Eastern Himalayas, October 23, 2001

**Eastern Himalayas, October 23, 2001**

**Snow**

**Notes:**
(Day 296, 04:25 UTC)

## Lesotho (southern Africa) September 1,2001 

**Lesotho (southern Africa) September 1,2001 **

**MOD02HKM**

**MOD10_L2**

- Bands 1,4,3

**Snow Map**

**Notes:**
08:25 UTC

## Snow in Lesotho

- Image courtesy of
- http://rapidfire.sci.gsfc.nasa.gov

**Snow in Lesotho**
- Sept 01, 2001
- 08:25 UTC

## Zoom showing natural-color image on left and MODIS snow map on right

**Zoom showing natural-color image on left and MODIS snow map on right**

**Snow mapped as cloud**

**Snow**

## Snow in the central U.S. and southern Canada – November 27-28, 2001

- Left - MOD35_L2 cloud spectral tests of bit19 (pink) [BT11 - BT3.7] and bit21 (purple) [R0.87/R0.66], cloud in both (yellow).  Black is snow or non-snow-covered land. Right – MODIS  false-color image.

**Snow in the central U.S. and southern Canada – November 27-28, 2001**

-       MOD02HKM Bands 1,4,6

**Snow**

**Notes:**
Shows where these two spectral tests agree or don’t agree.  Combining these two spectral tests makes a pretty good cloud mask.  But we need to test it under a variety of cloud types in order to be sure that it will be more appropriate for snow mapping than the most conservative mask that we’re using now.  Just use of  bit 19 alone doesn’t pick up all clouds, and some of those clouds are then mapped as snow (usually high, cold clouds with ice crystals). 29 November 2001 1750 UTC
Image of MOD02HKM Bands 1,4,6 on the right.  This combination displays snow in yellow and clouds in white.  
South central US to south central Canada imaged.  
Snow cover from storms that swept across the northern and southern plains, 27-28 November is visible. 

## SNOW MAPPING IS IMPROVED BY SELECTIVE USE OF MOD35_L2 DATA

- Snow algorithm with cloud mask composed of MOD35_L2 bits 19 (pink) and 21 (light purple).
- Pixels changed from snow in cloudless run to cloud in this run are shown in dark purple.  25% of snow pixels were changed (correctly) to cloud.
- Compared to MOD10_L2 this snow map has:
-      45% more snow cover
-      35% less cloud obscuration
**Very small error of false snow on clouds remains.**

**Non-snow-covered land**

**Snow**

**Notes:**
This is the snow alg. run without the cloud mask; we read the two bits (bits 19 & 21) from the cloud mask and overlay them onto the snow map.  

## Zoom showing natural-color image on left and MODIS snow map on right

**Zoom showing natural-color image on left and MODIS snow map on right**

**Snow mapped as cloud**

**Snow**

**Cloud spectral test (bit 21) is causing snow to be mapped as cloud (right).**

##  Direct Readout

** *****Direct Readout***

**Space Science and Engineering Center, (SSEC) University of Wisconsin-Madison**
**NOAA/NESDIS - “Rapid Response”**

## MODIS 250-m resolution image (below) and 500-m resolution snow map (right) derived from MODIS direct-readout data showing result of major snowstorm in southern Canada and North Dakota that occurred on October 24, 2001

***MODIS 250-m resolution image (below) and 500-m resolution snow map (right) derived from MODIS direct-readout data showing result of major snowstorm in southern Canada and North Dakota that occurred on October 24, 2001***

**October 26, 2001**

**University of Wisconsin - Madison Space Science and Engineering Center**

**MODIS 250 m resolution image of snow bands laid down across Southern Saskatchewan and Manitoba in Canada and North Dakota in the United States. As much as a foot of snow fell over the eastern portion of North Dakota from a strong early fall snow storm on Wednesday, October 24. The cities of Fargo and Grand Forks are evident in the image as gridded lighter blocks along the North Dakota/Minnesota border. The snow band in Canada fell from a storm earlier in the week. **

**Grand Forks, ND**

**Snow map**

## Uinta Mountains (northeastern Utah)

**Sub images from the SSEC direct broadcast station**

**1,4,3**

**1,4,6**

***Uinta Mountains (northeastern Utah)***
***October 10, 2001***

**snow map**

## Ad-Hoc Advisory Committee on the MODIS Snow and Ice Products

***Ad-Hoc Advisory Committee on the MODIS Snow and Ice Products***
***October 31, 2001***

**Committee Members:**
**Don Cline/NOHRSC**
**Jeff Key/NOAA – University of Wisconsin**
**Bruce Ramsay/NOAA**
**Dave Robinson/Rutgers University, CHAIR**
**Greg Scharfen/NSIDC**
**Marc Stieglitz/Columbia University**

**Notes:**
Something to think about:  do we really need, or is it meaningful to have FSC for the 500-m resolution 8-day composite snow products?

## Ad-Hoc Advisory Committee on the MODIS Snow and Ice Products

***Ad-Hoc Advisory Committee on the MODIS Snow and Ice Products***
***October 31, 2001***

**Some recommendations:**
**Complete evaluation of snow products so that they can be considered to be validated**
**Validate sea ice products**
**Work with cloud mask tests to identify optimum tests for use with the snow and sea ice maps**
**Provide daily CMG snow maps at ~5-km resolution**
**Provide a fractional snow-cover algorithm for the 500-m resolution snow products**
**Release snow albedo product for beta testing**
**Integrate passive-MW and MODIS algorithms in the Aqua era to improve snow mapping in cloudy areas**

**Notes:**
Something to think about:  do we really need, or is it meaningful to have FSC for the 500-m resolution 8-day composite snow products?

## In-House Validation Activities

***In-House Validation Activities***
**Snow**
**North America - 2000-01 winter time series**
**MODIS snow maps compare well, but show more snow cover than do the NOAA operational snow maps (maximum snow cover)**
**Comparisons with Landsat ETM+ data indicate that we are mapping snow cover that other maps often miss because of the more frequent coverage of the MODIS sensor**
**Sea Ice**
**IST results are reasonable (Li and Key) but serious cloud mask issues over sea ice remain (Key)**
**2001-02 winter**
**Validation efforts will concentrate on CMG product in N.A. and Europe (Scandinavia with J.-G. Winther and R. Solberg)**
**Sea ice maps will be compared with NOAA maps and Landsat images**

## 	           1	 2	3	4	 5	 6	 7	8	

- 	           **1****	**** 2****	****3****	****4****	**** 5****	**** 6****	**** 7****	****8****	**
**        ****MODIS        0.24            0.92         2.13         2.32         1.56         1.79         1.98         2.99****	**
**        ****NOHRSC     0.04            0.53         1.76         1.98         1.38         1.57        1.99          2.78                 ****	**
**        ****Difference  **
**           ****(MODIS-NOHRSC)****  0.20            0.39         0.37         0.34          0.18         0.22        (0.01)       0.21**

- ***Period 1: October 23-30, 2000; period 2: October 31-November 7, 2000; period 3: November 8-15, 2000; **
**period 4:November 16-23, 2000; period 5: November 24-December 1, 2000; period 6: December 2-9, 2000;  **
**period 7: December 10-17, 2000; and period 8: December 18-25, 2000.**
**+Exact numbers would change slightly if watershed boundaries were removed from the NOHRSC maps.**

***Snow-covered area in millions km******2****** for each 8-day composite snow-cover map, exclusive of cloud cover from MODIS and NOHRSC maps.  Numbers in red refer to the 8-day periods*******+***

## When will the snow and ice products be validated?

***When will the snow and ice products be validated?***
**Snow maps - May 2002**** – two papers on this topic will be completed before summer: ESC and PIERS; ESC paper will show errors in different vegetation types in N.A. and Scandinavia**
**Sea ice maps – July 2002**

## Education and Outreach

**Snow video entitled, “Observations of Global Snow Cover from the Ground and Space”**
**New educational Web site based on the snow video**
**Ten Web-based activities that focus on EOS data**
**Numerous presentations to students and teachers**
**Posters**

***Education and Outreach***