A Note on Reviving the Goddard Satellite-Based Surface Turbulent Fluxes （GSSTF） Dataset

Accurate sea surface flux measurements are crucial forunderstanding the global water and energy cycles. The oceanicevaporation, which is a major component of the global oceanic freshwater flux, is useful for predicting oceanic circulation andtransport. The global Goddard Satellite-based Surface TurbulentFluxes Version-2 (GSSTF2; July 1987--December 2000) dateset that wasofficially released in 2001 has been widely used by scientificcommunity for global energy and water cycle research, and regionaland short period data analyses. We have recently been funded by NASAto resume processing the GSSTF dataset with an objective ofcontinually producing a uniform dataset of sea surface turbulentfluxes, derived from remote sensing data. The dataset is to bereprocessed and brought up-to-date (GSSTF2b) using improved inputdatasets such as a recently upgraded NCEP/DOE sea surfacetemperature reanalysis, and an upgraded surface wind and microwavebrightness temperature V6 dataset (Version 6) from the SpecialSensor Microwave Imager (SSM/I) produced by Remote Sensing Systems(RSS). A second new product (GSSTF3) is further proposed with afiner temporal (12-h) and spatial (0.25^ox0.25^o)resolution. GSSTF2b (July 1987--December 2008) and GSSTF3 (July1999--December 2009) will be released for the research community touse by late 2009 and early 2011, respectively.     

The energy balance experiment EBEX-2000. Part II: Intercomparison of eddy-covariance sensors and post-field data processing methods

The eddy-covariance method is the primary way of measuring turbulent fluxes directly. Many investigators have found that these flux measurements often do not satisfy a fundamental criterion—closure of the surface energy balance. This study investigates to what extent the eddy-covariance measurement technology can be made responsible for this deficiency, in particular the effects of instrumentation or of the post-field data processing. Therefore, current eddy-covariance sensors and several post-field data processing methods were compared. The differences in methodology resulted in deviations of 10% for the sensible heat flux and of 15% for the latent heat flux for an averaging time of 30 min. These disparities were mostly due to different sensor separation corrections and a linear detrending of the data. The impact of different instrumentation on the resulting heat flux estimates was significantly higher. Large deviations from the reference system of up to 50% were found for some sensor combinations. However, very good measurement quality was found for a CSAT3 sonic together with a KH20 krypton hygrometer and also for a UW sonic together with a KH20. If these systems are well calibrated and maintained, an accuracy of better than 5% can be achieved for 30-min values of sensible and latent heat flux measurements. The results from the sonic anemometers Gill Solent-HS, ATI-K, Metek USA-1, and R.M. Young 81000 showed more or less larger deviations from the reference system. The LI-COR LI-7500 open-path H₂O/CO₂ gas analyser in the test was one of the first serial numbers of this sensor type and had technical problems regarding direct solar radiation sensitivity and signal delay. These problems are known by the manufacturer and improvements of the sensor have since been made. The National Center for Atmospheric Research is supported by the National Science Foundation.     

Momentum and Turbulent Kinetic Energy Budgets Within the Park Avenue Street Canyon During the Joint Urban 2003 Field Campaign

Very few attempts have so far been made to quantify the momentum and turbulent kinetic energy (TKE) budgets within real urban canopies. In this study, sonic anemometer data obtained during the Joint Urban 2003 field campaign in Oklahoma City, U.S.A. were used for calculating the momentum and TKE budgets within a real-world urban street canyon. Sonic anemometers were deployed on multiple towers in the lower half of the canyon. Gradients in all three principal directions were included in the analyses. The storage and buoyancy terms were found to have negligible contributions to both the momentum and TKE budgets. The momentum budgets were generally found to be more complex than a simple balance of two physical processes. The horizontal terms were found to have significant and sometimes dominant contributions to the momentum and TKE budgets.