Jason-1 near real-time applications G.H. Born 1, R.R. Leben 1, One application of altimetry is to observational and modeling D.S. McCollum 1, J.M. Wilczak 2 provide observations over sparsely programs toward operational 1 (CCAR, USA) 2 (NOAA Environmental Technology sampled ocean regions to improve applications of altimeter data in the Laboratory, USA) weather and climate forecasts. region. For example, improved forecasts of severe landfalling winter storms on The very successful TOPEX/ the U.S. West Coast have the Introduction POSEIDON and ERS-1 & 2 potential to prevent serious human altimeter missions flown in the and economic losses. It is likely The human and economic impact 1990s demonstrated the utility of that altimetry-based upper ocean of severe landfalling winter storms altimeter data for near real-time heat content estimates could aid in on the U.S. West Coast are ocean monitoring. One of the the refinement of forecast and comparable, on an annual average, primary objectives of the Jason-1 hindcast simulations of these to earthquakes. Like hurricanes, mission is to build on this success storms by providing improved the prediction of these storms is and initiate an era of operational model input at the ocean boundary. hindered because they develop over oceanography that will continue We have been investigating how the ocean where observations are well into the 2000s. As a part of well altimetry-based heat content sparse. An important operational our Jason-1 research activities we estimates compare with in-situ application of Jason-1 will be to will continue to provide near real- heat content measurements taken provide additional ocean observations time data products for research from airborne expendable to improve forecasts of severe activities and to work toward bathythermographs (AXBTs) off the weather and climate events. operational use of altimeter data California coast. Preliminary studies by the public, industrial and show very good agreement, both in During the NOAA California government sectors. space and time, and we are working Landfalling Jets Experiment closely with the ongoing NOAA (CALJET) in the winter of 1997- 1998, data were collected in regions where additional and/or improved observations could potentially help downstream forecasts. A region of sensitivity, found by an adjoint analysis using the MM5 numerical weather model, was the temperature field in the lower atmosphere 1000 km off the California coast. As a result one of the objectives of CALJET was to determine the sensitivity of landfalling storms to the upper-ocean thermal structure, which is still very much a work in progress. In the winter of 1997- 1998, NOAA P3 aircraft were used to perform airborne expendable bathythermograph (AXBT) surveys in the region to profile the upper ocean temperature in the region. Current research and operational weather models rely on satellite- based sea surface temperature (SST) measurements in combination with climatological SST data sets to infer the upper ocean thermal structure Figure 1: Heat Content Anomaly (HCA) maps for Jan. 20. (a) in-situ AXBT, and heat content. Our goal is to (b) TOPEX, (c) blended TOPEX/ERS, and (d) mesoscale TOPEX/ERS. develop a procedure whereby 19 Figure 2: Time Series of the spatial mean heat content in the analysis region; blue: TOPEX, green: blended TOPEX/ERS, red: mesoscale TOPEX/ERS. altimetry-based heat content in the upper 350 meters of the water estimates can be used to accurately column. The AXBT heat content monitor the upper-ocean heat was computed directly from the content off the West Coast of the temperature profiles. Altimetry- U.S. The ultimate objective is to based heat content estimates were develop a near real-time capability made using a linear relationship for estimating the upper-ocean between changes in the surface thermal structure from altimetry geopotential anomaly and the to use as input into research and underlying heat content variations operational forecast models. using the World Ocean Atlas 1998 (WOA 1998) [Hendricks, 1996; We have made preliminary Chambers, 1997]. The climatological comparisons of altimetry-based mean heat content also was used to upper-ocean heat content estimates reference the heat content determined References with in situ measurements from from AXBTs to a long-term mean. Chambers D.P., B.D. Tapley, the CALJET study. The extended Three altimetry data sets were used R.H. Stewart, 1997: Long-Period heat content time series in the for comparison with the in-situ Ocean Heat Storage Rates and Basin- study region spanning the entire measurements. The first altimetric Scale Heat Fluxes from TOPEX, TOPEX/POSEIDON (T/P) mission J. Geophys. Res., Vol. 102, No. C5, data set was based on TOPEX data pp. 10525-10533. is useful for putting into context alone. The second altimetric data the warmer conditions observed in set was obtained by “blending” Hendricks J.R., 1996: Global Sea Level Rise and Upper Ocean Heat the study region that were TOPEX and ERS-2 altimeter data Storage Estimates From associated with the 1997-1998 with an emphasis on retaining the TOPEX/POSEIDON Satellite El Niño. We found that resolving longer wavelength oceanographic Altimetry, Doctoral Dissertation, the mesoscale oceanographic signals accurately measured by T/P, University of Colorado at Boulder. component of heat content is and the mesoscale signal sampled Lillibridge J., R. Leben, F. Vossepoel, required to adequately monitor the by both the T/P and ERS-2 satellites 1997: Real-Time Altimetry from ERS-2, Proc. 3rd ERS Symp., upper-ocean heat content in the (blended TOPEX/ERS). The third Florence, Italy, March 1997. region. The results from this study data set is an operational data set are being used to help plan additional Ralph M., 2000: The Pacific that is produced by heavily filtering, Landfalling Jets Experiment ocean observations during the NOAA combining TOPEX with ERS-1 and (PACJET) and a Long-Term Effort to Pacific Landfalling Jets Experiment ERS-2 altimetry data with an Improve 0-24 Hour West Coast (PACJET) [Ralph, 2000], a follow- emphasis on retaining only Forecasts, PACJET Program Document, http://www.etl.noaa.gov/programs/ on to CALJET, during the winter of mesoscale structure. pacjet/pacjet.shtml, January 27, 2000. 2000-2001. Sato O.T., P.S. Polito, W.T. Liu, 2000: Importance of Salinity Measurements in the Heat Storage Estimation from Data and Methods TOPEX/POSEIDON, Geophys. Res. Lett., Vol. 27, No. 4, pp. 549-551. Synoptic AXBT surveys were performed from aircraft to collect upper-ocean temperature profiles off the West Coast of the U.S. during the winter of 1997-1998. Three sets Corresponding author: of altimetry-based sea surface height George H. Born anomalies (SSHA), and the AXBT CCAR, Campus Box 431, Boulder, temperature measurements, were Colorado 80309-0431 - USA used to compute the heat content E-mail: [email protected] 20.