1. Zhang Hailong, Xin Xiaozhou, Liu Qinhuo
IGARSS 2011 at Vancouver
Modeling Daily Net Shortwave Radiation Over Rugged Surfaces Using MODIS Atmospheric Products
28 July 2011
Zhang Hailong, Xin Xiaozhou, Liu Qinhuo
State Key Laboratory of Remote Sensing Science
Institute of Remote Sensing Applications
Chinese Academy of Sciences
IGARSS 2011

2. Outline Background Data and methodology Results and discussion
Conclusion
IGARSS 2011

3. Background
NSSR (Net Surface Shortwave Radiation ) controls the total energy exchange between the atmosphere and the land surface.
NSSR is not measured in most regular meteorological sites.
NSSR products (ISCCP/GEWEX/CERES) have fine temporal resolution but coarse spatial resolutions.
IGARSS 2011

4. Background
IGARSS 2011

5. Data and methodology Data for model input and validation DATA
Description
MOD09A1
Surface reflectance
MOD03/MYD03
Geolocation data set
MOD05/MYD05
Total precipitable water
MOD06/MYD06
Cloud optical thickness; cloud fraction
DEM
NSSR observations
Model validation
IGARSS 2011

6. Data and methodology
NSSR retrieval
Global solar radiation
IGARSS 2011

7. Data and methodology Beam Diffuse Reflected
Global downward solar radiation
IGARSS 2011

8. Data and methodology
3D effects of cloud
IGARSS 2011

9. Data and methodology Viewing angle correction Viewing position
Sensor C O’ A B h
Viewing position
True position
IGARSS 2011

10. Data and methodology Solar angle correction True position
shadow position O’ O B
IGARSS 2011

11. Results and discussion
Model validation
(X-axis: observed values; Y-axis: modeled values. Unit: MJ/(m2·d) )
IGARSS 2011

12. Results and discussion
Model validation
(X-axis: observed values; Y-axis: modeled values. Unit: MJ/(m2·d) )
IGARSS 2011

13. Results and discussion
Model validation
Erjinaqi
Beijing
Kunming
Lhasa
MBE(%)
4.53
4.21
-7.09
4.63
RMSE(%)
15.31
19.20
24.71
19.39 R2
0.93
0.87
0.78
0.71
Horizontal surface
rugged surface
IGARSS 2011

14. Results and discussion
Error analysis
spatial resolution gaps between the observed and retrieved data.
coarse spatio-temporal resolution of the MODIS atmospheric products
Errors from the data sources: The maximum uncertainty of the MODIS cloud-detection algorithm is 200% (Houborg, 2007)
IGARSS 2011

15. Conclusion
Terrain is a main factor of NSSR attenuation under clear sky
Cloud plays a greater role than terrain under cloudy sky
moderately maps of NSSR on rugged surface can be produced using MODIS data
The geostationary satellites holds great promise for accurate estimation of NSSR
IGARSS 2011

16. Thank You
IGARSS 2011