STREX

The Storm Transfer and Response Experiment (STREX) was an air-sea interaction research program that was carried out in the Gulf of Alaska to investigate characteristics of the boundary layers of the atmosphere and ocean in middle-latitude storms. Observations were made by ships, aircraft, satellites, and buoys in ten (10) storms. The field phase of STREX was carried out during November and December 1980 by meteorologists from the United States and Canada. STREX was organized as a federation of essentially independent efforts by more than 30 Principal Investigators (PI)s responsible for their own projects, who have agreed to collaborate in data analysis. Major responsibilities for STREX planning and management were carried by scientists representing the Canadian Atmospheric Environment Service (AES) and Institute of Ocean Sciences (IOS), the National Oceanic and Atmospheric Administration (NOAA)’s Pacific Marine Environmental Laboratories (PMEL), and the University of Washington (UW). Other institutions represented by PIs included the: National Aeronautics and Space Administration (NASA)’s Jet Propulsion Laboratory; Langley Research Center; National Center for Atmospheric Research (NCAR); Naval Postgraduate School (NPGS); Office of Weather Research and Modification; and NOAA’s Research Flight Facility; Oregon State University; University of Toronto; and University of Wisconsin.

Scientific Objectives: 

The objectives of STREX were to extend the understanding of the following aspects of Pacific storms: (1) the characteristic spatial distributions of the vertical fluxes of momentum, heat, and water vapor in the atmospheric boundary layer; (2) the scales on which transfer occurs from the boundary layer to the lower troposphere; (3) the characteristic spatial distribution of latent heat release in these storms; and (4) the effects of storms on the upper mixed layer of the ocean.

Observations: 

Aircraft Program -  For the 10 storms chosen for intensive observations, research aircraft carried out a variety of observations. In 9 of these 10 storms, an Air Force Reserve C-130 (920 Weather Recon Group) flew a prescribed track to provide soundings spaced at intervals of about 300 km. On each flight, approximately 9 dropsondes were deployed from a height of 300 mb. Two of the nine dropsondes were scheduled to coincide in time with the soundings taken from the two ships at 3-h intervals. In each of the nine storms, a NOAA P-3 flew a prescribed mission that included dropsondes deployed from 500 mb; multiple penetrations of clouds and fronts; and boundary layer flights to measure vertical fluxes, ocean surface properties, and other quantities. The NOAA P-3 also deployed airborne expendable bathythermographs (AXBT). In four storms, the NCAR Electra was used to make boundary-layer measurements (horizontal distribution of fluxes of momentum, heat, and water vapor, liquid water content cloud physics parameters, radiation) and to observe ocean surface properties (sea surface temperature). The Electra operated out of McChord Air Force Base in Washington State. The NASA C-130 flew at 850 mb in four storms, making microwave and radar observations of the sea surface. The Electra flew comparison flights with the P-3 and the NASA C-130. Flight plans of all aircraft were coordinated carefully.

Shipboard Meteorological Program - The Canadian weathership CCGS Vancouver and the NOAA ship USS Oceanographer were the primary observing platforms for extensive meteorological and oceanographic observational programs during STREX. The Vancouver was stationed at its normal position at 150°N, 145°W, while the Oceanographer was positioned near 50°N, 141 °W. Both ships made standard surface meteorological observations and upper-air soundings. Throughout the STREX period, radiosondes were launched at six-hour intervals, and during selected intensive periods, the frequency was increased to every three hours. Approximately 200 radiosondes were released from each ship.

Oceanographic Program - Observations were carried out from three ships: the CCGS Vancouver, USS Oceanographer, and CSS Parizeau. The most important task was to obtain temperature and salinity profiles to depths of about 300 m as time series. The upper ocean temperature structure also was determined by three moored thermistor chains on a 20 km grid near the Oceanographer. Expendable temperature velocity probes (XTVP) were deployed from the Oceanographer to delineate the inertial current. In order to establish spatial variability, the Oceanographer made three grid surveys with 50 km spacing during the six-week period. The Vancouver also made four grid surveys with 50 km spacing. Horizontal variations of the upper ocean temperature structure also were observed using AXBTs in the 3° by 3° area centered midway between the two ships. Observations were made at intervals of 1/2° to 1°. 

Drifting Buoy Program - A total of 23 satellite-tracked drifting buoys were used in STREX. The buoys were basically of the two types deployed by the U.S. and Canada during the First GARP Global Experiment; however, several new sensors and modifications were introduced. Seven of the buoys were air dropped by the U.S. Coast Guard, while the rest were deployed from the Canadian research vessel CSS Parizeau. The objectives of the program were a) to evaluate the usefulness of satellite-tracked expendable drifting buoys; b) to provide additional surface pressure and sea surface temperature observations to permit a more detailed description of the weather systems encountered during STREX than would be possible from the normal ship and moored buoy reports; c) to provide some information on ocean currents and their response to the passage of storms; and d) to test and evaluate new anemometers, thermistor chains, and variations on drogues and drogue attachments.

Satellite Program - Imagery data from the polar orbiting NOAA-6/TIROS-N and the GOES-West satellites were provided to the STREX Operations Center in near real-time, and were vital for mission selection and forecasting. GOES-West also was used to relay the ship NAVAID sounding data to the Colorado State University ground station for processing at NCAR, and the NOAA 6/TIROS-N Data Collection and Platform Location System was used to relay drifting buoy data to Edmonton for processing. Full-resolution visible and infrared geostationary imagery of the STREX region were archived by the Space Science and Engineering Center (SSEC) at the University of Wisconsin, while full-resolution Advanced Very High  Resolution Radiometer (AVHRR) and TIROS Operational Vertical Sounder (TOVS) data from the polar orbiting satellite were archived by NOAA-EDIS Satellite Services Division in Washington, D.C. 

Data: 

Data archiving and communication among participants were facilitated by the STREX Data Center located at the University of Washington.

Further information and details on STREX can be found at: 

Fleagle, R.G., M. Miyake, J.F. Garrett, and G.A. McBean, 1982: Storm Transfer and Response Experiment. Bull. Amer. Meteor. Soc., 63, 6–14, https://doi.org/10.1175/1520-0477(1982)063<0006:STARE>2.0.CO;2