Thursday, 26 January 2012: 2:00 PM
The Goddard Satellite-Based Surface Turbulent Fluxes (GSSTF) Datasets: Updates, Improvements and Applications (invited)
Room 256 (New Orleans Convention Center )
Accurate ocean surface turbulent flux measurements are crucial to understanding the global water and energy cycle changes. As a major component of the global oceanic fresh water flux, the oceanic evaporation is particularly useful for predicting oceanic circulation and transport. Remote sensing is a valuable tool for global monitoring of these flux measurements. The GSSTF algorithm was thus developed and applied to remote sensing research and applications. The early version GSSTF2 (a global 1°x1° daily dataset of July 1987-December 2000) was widely used by the scientific community for global energy and water cycle research, and regional and short period data analysis since its official release in 2001. In a recently funded project by the NASA/Making Earth System data records for Use in Research Environments (MEaSUREs) Program, a new version GSSTF2b (a global 1°x1° daily dataset of July 1987-December 2008) using the improved and upgraded input datasets that included the updated Special Sensor Microwave Imagers (SSM/I) V6 product (e.g., brightness temperature [TB]) and the NCEP-DOE Reanalysis II product (e.g., sea surface/skin temperature) was therefore produced and distributed in October 2010. GSSTF2b was found to generally agree better with the sounding observations than GSSTF2 did in all three components of fluxes, i.e., latent heat flux (LHF), sensible heat flux (SHF), and wind stress (WST). In a recent intercomparison study led by one of the GSSTF2b/GSSTF2 users, GSSTF2b was also found performed well, especially in LHF and SHF, among the eleven accessed global oceanic surface turbulent fluxes datasets that include six reanalysis, four satellite-derived, and one combined. Certain foremost climate and weather scenarios such as the ENSO and the Monsoon activities can also be genuinely demonstrated by the GSSTF2b fluxes.
However, we recently realized that the gradually increasing temporal trend shown in the globally averaged LHF of GSSTF2b, especially post 2000~2001, was somewhat related to a similar trend found in the SSM/I TB that was used to retrieve the bottom layer precipitable water (WB), then the specific humidity (Qa), and subsequently LHF. We further found that the TB trend was mainly due to the therefore found temporal variations (decreasing) of Earth incidence angle of the individual SSM/I satellites. We are currently nearly completing a further improved version GSSTF2c using the newly corrected TB's. Not only the temporal trends of the related parameters (i.e., WB, Qa, and LHF) of GSSTF2c are thus reduced, these parameters retrieved based on the respective satellites are also merging toward optimal magnitudes. We are currently about to start the production for an even newer version of GSSTF product, i.e., GSSTF3 with an upgraded spatial resolution (i.e., 0.25°x0.25°) by also applying the corrected TB's that were just used for producing GSSTF2c. The major improvements of the subsequently developed GSSTF datasets, as well as the scientific applications of the data will be discussed in more details at the meeting.