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Students as Ground Observers for Satellite Cloud Retrieval Validation

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K-12 Education and outreach portion of CERES: Clouds and the Earth's Radiant Energy System ... Science and Education support from NASA's Earth Science Enterprise. ... – PowerPoint PPT presentation

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Title: Students as Ground Observers for Satellite Cloud Retrieval Validation


1
Students as Ground Observers for Satellite Cloud
Retrieval Validation
Lin H. Chambers, P. Kay Costulis, David F.
Young NASA Langley Research Center, Hampton,
VA Tina M. Rogerson Science Applications
International Corporation, Hampton, VA
  • 13th Conference on Satellite Meteorology
    Oceanography
  • Norfolk, VA
  • Sept. 2004

2
OUTLINE
  • Sources of student data
  • What is the SCOOL Project?
  • Comparisons
  • Proof of Concept
  • New Comparisons
  • Bright Surfaces
  • Conclusions

3
Sources of Student Data
  • The CERES SCOOL Project
  • More than 35,000 complete observations
  • 9,172 now have corresponding CERES data
  • http//scool.larc.nasa.gov
  • The GLOBE Program
  • More than 2.5 M cloud data points
  • http//www.globe.gov

4
What is SCOOL?
  • Began Jan. 1997
  • Students Cloud Observations On-Line
  • K-12 Education and outreach portion of CERES
    Clouds and the Earth's Radiant Energy System
  • 1700 participants in 65 countries
  • Focused on obtaining ground-based cloud
    observations for validation of the CERES data

5
The SCOOL Concept
  • Students provide ground observations for CERES
    overpass
  • Determine satellite overpass time
  • Observe cloud properties
  • Transmit results to NASA
  • Compare to satellite-retrieved properties
  • Data of value to CERES scientists
  • Real-world learning for students

6
Data Collected
Cloud type Contrails Cloud cover Visual
opacity Surface Cover Surface Measurements Comment
s
7
Comparing to Satellite
  • SCOOL Site Matched to 1 degree Satellite Region
  • Observation
  • Times
  • Within
  • 15 Minutes

8
FIRST SCOOL ComparisonCloud Observations Over
Gloucester, VAJanuary 13 17, 1997
9
Initial ComparisonsProof of Concept
  • Measurements in 1998
  • CERES on TRMM only (50 correspondences)
  • Augmented with AVHRR and geostationary data
    (50) Analyzed by hand

10
Cloud Amount Comparison
62 in complete agreement 0 in complete
disagreement
Stats Chi-Squared value of 82 significant to
5e-12
11
Cloud Layer Comparison
12
Interim Conclusions
  • Clearly some useful information
  • Insight into cloud layering
  • Insight into sparse, thin cirrus
  • Educationally a big success

13
New Comparisons - 2004
  • New CERES angular models
  • (see talk by Loeb this afternoon)
  • CERES on TRMM, Terra, Aqua
  • Feb. 1998 to April 2004
  • Production data products

14
Data Available
Max 479 (High School in Pennsylvania) Min 1
(70 schools)
15
Cloud Amount Comparison
54.5 in complete agreement 2 in complete
disagreement
Stats Chi-Squared value of 5636 significant!!!
16
Students Overcast vs. Satellite Clear (48 cases)
  • Spatial Mismatch? gt1/3 are schools located
    less than 0.1 degree from the edge of a lat/long
    grid box.
  • Universal Time? 3 cases with incorrect UT
  • Student/Satellite error? remaining cases have
    no clear explanation. Study needed.
  • Snow 10 cases, yet the satellite still reports
    clear sky.

17
Students Clear vs.Satellite Overcast (143 cases)
  • Spatial mismatch? About 22
  • Universal Time? 10
  • Snow? 18 cases students report snow.
  • Only one satellite retrieval is suspect low
    cloud temperature 2.5K below the surface
    temperature.
  • Satellite/Student error? stratus clear?

18
Cloud Amount Comparison
191 3-class errors (2) - 1/3 easily
explainable 711 2-class errors (8) - need more
study 3271 1-class errors (36) - may be
near-matches
19
First look at 1-class errors
Students say 0-5 cloud Satellite says 5-50
cloud
20 of CERES has 10 lt fc lt 15
24 of CERES has 5 lt fc lt 10
20
Subvisual Cirrus?
  • MODIS vs GLOBE cloud type comparison indicated
    some subvisual cirrus (Stephens and Rogers,
    2004).
  • This CERES/SCOOL dataset
  • 19 cases where ttotlt 3
  • None high cloud only
  • 5 cases where ttot lt 1
  • None high clouds
  • No evidence of subvisual cirrus in this dataset
  • May be due to location of the SCOOL student
    data, over land with few data points in the
    Tropics.

21
Cloud Layer Comparison
22
Effect of Bright Surfaces
  • 1057 reports (11) with snow or ice in ground
    report
  • Data from 1/4 of respondents

Max - 86 (4th grade in NH) Min - 1 (31 schools)
23
Snow Effect on Cloud Amount
Chi-squared 671
24
Snow Effect on Cloud Amount
25
Snow Effect on Cloud Layers
26
Snow Effect on Cloud Layers
27
Conclusions
First major analysis of student ground observer
data to validate cloud retrievals from a
satellite instrument. A few pitfalls are
evident. Useful information can be derived.
28
Future Plans
Inviting SCOOL participants to do detailed
analysis of their correspondences More analysis
to be done (2-class and 1-class errors, cloud
levels, opacity.) Data available via the
Internet for analysis http//asd-www.larc.nasa.go
v/SCOOL/usedata.html
29
Acknowledgments
Science and Education support from NASAs Earth
Science Enterprise. This work would not be
possible without the participation of our
extended network of educators and their students,
and we thank them most sincerely for their
efforts.
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