Presentation is loading. Please wait.

Presentation is loading. Please wait.

Comparison of Satellite-Derived and In-Situ Observations of Ice and Snow Surface Temperatures over Greenland Dorothy K. Hall, Jason E. Box, Kimberly A.

Similar presentations


Presentation on theme: "Comparison of Satellite-Derived and In-Situ Observations of Ice and Snow Surface Temperatures over Greenland Dorothy K. Hall, Jason E. Box, Kimberly A."— Presentation transcript:

1 Comparison of Satellite-Derived and In-Situ Observations of Ice and Snow Surface Temperatures over Greenland Dorothy K. Hall, Jason E. Box, Kimberly A. Casey, Simon J. Hook, Christopher A. Shuman and Konrad Steffen Code NASA GSFC Assessing the accuracy of standard Earth Observing System (EOS) land-surface temperature (LST) products from MODIS, ASTER and ETM+ over the Greenland Ice Sheet. The RMS error of the satellite LST products is generally ~0.5  C. Figure 1: Greenland Climate Network (GC-Net) automatic weather station (AWS) location map of Greenland (Steffen and Box, 2001). Figure 2: Comparison between MODIS- derived LST and AWS-derived air temperature. Figure 3: Comparison of MODIS and ASTER LSTs. Figure 4: Comparison of MODIS and ETM+ LSTs. Hydrospheric and Biospheric Sciences Laboratory

2 Name: Dorothy K. Hall Phone: References: Hall et al., J.E. Box, K.A. Casey, S.J. Hook, C.A. Shuman and K. Steffen, in press: Comparison of Satellite-Derived and In-Situ Observations of Ice and Snow Surface Temperatures over Greenland, Remote Sensing of Environment. Hall, D.K., Williams, R.S., Jr., Luthcke, S.B. & DiGirolamo, N.E. (2008). Greenland Ice Sheet surface temperature, melt and mass loss: 2000 – 2006, Journal of Glaciology, 54(184): Steffen, K. & Box, J. (2001). Surface climatology of the Greenland ice sheet: Greenland climate network , Journal of Geophysical Research, 106(D24):33,951-33,964. Wan, Z., Zhang, Y., Zhang, Q. & Li, Z.-L. (2002). Validation of the land-surface temperature products retrieved from Terra Moderate Resolution Imaging Spectroradiometer data. Remote Sensing of Environment, 83: Data Source: MODIS, ASTER and ETM+ LST products. Figures are from Hall et al. (in press). Technical Description of Image: Figure 1: Greenland Climate Network (GC-Net) automatic weather station (AWS) location map of Greenland (Steffen and Box, 2001). Figure 2: Comparison between MODIS-derived LST and AWS-derived air temperature. Excluded are cases when downward solar irradiance exceeded 240 Wm-2 while wind speed was <4 m sec-1. Also excluded are cases when AWS air temperatures were above the melting point. The solid line is the 1:1 line. The dashed line is the best-fit line. Figure 3: Comparison of MODIS and ASTER LSTs. The solid line is the 1:1 line. The dashed line is the best-fit line. Figure 4: Comparison of MODIS and ETM+ LSTs. The solid line is the 1:1 line. The dashed line is the best-fit line Scientific Significance: The cryospheric community can have confidence in the EOS LST products from the MODIS, ASTER and ETM+ as employed over pure snow and ice targets; they are accurate to ~±0.5  C. This research shows that these instruments provide accurate LSTs over the same target at the same time of day, same date, even though they operate in different parts of the EM spectrum and the algorithms used to derive the LSTs are different. The LST data from the standard products, in particular MODIS, can be used with confidence as part of a climate-data record of ice-sheet LST (see Hall et al., 2008). Hydrospheric and Biospheric Sciences Laboratory

3 Synthetic Aperture Microwave Radiometry at L-band for Remote Sensing of Soil Moisture and Ocean Salinity Aperture synthesis is an interferometric technique for achieving high spatial resolution using an array of small antennas. It is being developed to meet the requirements for future L-band sensors to monitor soil moisture and salinity in the coastal oceans. L-band missions such as Aquarius and SMAP will demonstrate remote sensing of ocean salinity and soil moisture from space, but the future will require higher spatial resolution. Aircraft experiments with 2D-STAR will demonstrate new technology to meet this need. Fig 1: Example Image during SMEX-03 Fig 2: Retrieved Soil Moisture vs. Measured David LeVine, Code 614.6, NASA GSFC Hydrospheric and Biospheric Sciences Laboratory

4 Name: David M. Le Vine, NASA/GSFC Phone: References: D. M. Le Vine, T. J. Jackson, and M. Haken, “Initial images of the synthetic aperture radiometer 2D-STAR,” IEEE Trans. Geosci. Remote Sens., vol. 45, no. 11, pp , November, D. Ryu, T. J. Jackson, R. Bindlish, and D. M. Le Vine, “L-band microwave observations over land surface using a two-dimensional synthetic aperture radiometer,” Geophys. Res. Let., vol. 34, p. L14401, DOI: /2007GL N. Skou and D. M. Le Vine, Microwave Radiometer Systems. Norwood, MA: Artech House, 2006, chapters, 8 and 15. Data Sources: This technology development has been a joint effort involving NASA-GSFC (Instrument Sciences Branch), the University of Massachusetts (Department of Electrical Engineering), the USDA-Agricultural Research Service (soil moisture experiments) and ProSensing, Inc (private contractor and partner in implementing the hardware). The data shown here was collected during SMEX-03 and SMEX-04, experiments conducted to improve understanding of remote sensing of soil moisture and test the technology of aperture synthesis. Experiments with earlier versions of the technology have been conducted over oceans to demonstrate remote sensing of salinity. Technical Description of Images: Figure 1: Example L:-band image of brightness temperature during the soil moisture experiment, SMEX-03. The top image is a Landsat false color image of the experiment site. The location is near Huntsville, Alabama (upper left corner of the image). The lower image is brightness temperature obtained by 2D-STAR. The four east-west flight lines are evident in the image. The instrument was mounted aboard the NASA P-3B. (Le Vine, Jackson and Haken, 2007) Figure 2: Comparison of soil moisture derived from the 2D-STAR L-band images with the soil moisture sampled on the ground. The average retrieved surface soil moisture was compared with the regional mean of the soil moisture data collected concurrently with the 2D-STAR flights. Even though there was a wide variation in soil moisture, land cover and topography, the surface soil moisture sensed by the 2D-STAR was closely correlated with ground- based soil moisture data (Ryu et al, 2007). Scientific Significance: Soil moisture and ocean salinity are important parameters for understanding the global water cycle and for understanding climate and climate change. Soil moisture is a boundary condition important for understanding energy exchange at the surface. It is also of importance in agriculture for assessing productivity and crop stress and in hydrology for modeling runoff and predicting floods. Salinity, together with temperature, determines buoyancy and is critical to understanding the density driven ocean circulation. The thermohaline circulation drives large amounts of heat and water around the oceans and is important for understanding climate. Monitoring soil moisture and ocean salinity from space are optimally done at L-band (1.4 GHz). But long wavelengths mean large antennas in space and this has hindered deployment of sensors in space and limits the spatial resolution available for future applications to the coastal oceans and hydrology at the watershed scale. Aperture synthesis is an emerging technology designed to overcome this limitation. It uses the correlation between pairs of small antennas to achieve the spatial resolution equivalent of a large scanning antenna (Skou and Le Vine, 2006). Hydrospheric and Biospheric Sciences Laboratory


Download ppt "Comparison of Satellite-Derived and In-Situ Observations of Ice and Snow Surface Temperatures over Greenland Dorothy K. Hall, Jason E. Box, Kimberly A."

Similar presentations


Ads by Google