modeling daily net shortwave radiation over rugged surfaces using modis atmospheric products
TRANSCRIPT
IGARSS 2011
Modeling Daily Net Shortwave Radiation Over Rugged Surfaces
Using MODIS Atmospheric Products
IGARSS 2011 at Vancouver
28 July 2011
Zhang Hailong, Xin Xiaozhou, Liu Qinhuo
State Key Laboratory of Remote Sensing ScienceInstitute of Remote Sensing Applications
Chinese Academy of Sciences
IGARSS 2011
Outline
• Background
• Data and methodology
• Results and discussion
• Conclusion
IGARSS 2011
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
Background
IGARSS 2011
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
Data and methodology
• NSSR retrieval
• Global solar radiation
W)-(1 W- WN SSR
IGARSS 2011
Data and methodology
• Beam
• Diffuse
• Reflected
• Global downward solar radiation
)sin(hE T(clear) T(cloudy)I R0 dirI
)II (I nAR difI
)1/()( gg sdifdirsref III
wss
wsr
refdifdir IIIW )(
IGARSS 2011
Data and methodology
• 3D effects of cloud
IGARSS 2011
Data and methodology
• Viewing angle correction
O
P
Sensor
C
O’A
B
hViewing position True position
IGARSS 2011
Data and methodology
• Solar angle correction
O
Solar
C
O’A
B
h
shadow position
True position
IGARSS 2011
Results and discussion
• Model validation
(X-axis: observed values; Y-axis: modeled values. Unit: MJ/(m2·d) )
IGARSS 2011
Results and discussion
• Model validation
(X-axis: observed values; Y-axis: modeled values. Unit: MJ/(m2·d) )
IGARSS 2011
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
Results and discussion
• Error analysis spatial resolution gaps between the observed and retriev
ed 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
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