The CALJET experiment was carried out along the coasts of California and Oregon and up to 1000 km offshore from 1 December 1997 to 31 March 1998. The initial objectives of the experiment were to explore the role of coastal and offshore observations of low-level jets and their mesoscale environment in land-falling winter storms on mesoscale quantitative precipitation and wind forecasting. At the core of the experimental design were two key objectives: 1) to better understand the underlying physical processes that cause heavy rains and strong winds in this region of complex coastal topography, and 2) to explore the impact of possible future observing systems on 0-24 h quantitative precipitation and wind forecasts during the approach and land-fall of oceanic winter storms arriving from the data-sparse eastern Pacific Ocean.
Because a strong El Nino developed after the initial plan was complete, and such conditions are well correlated with very wet winters in California, new objectives were incorporated into the experimental design. These centered on assessing the role of coastal air-sea interactions on the evolution of storms and their resulting rainfall as they crossed and interacted with a strong coastal sea surface temperature anomaly. This was done by adding extensive observations of the oceanic mixed layer, and of air-sea fluxes off the California coast. In addition, offshore data were gathered in more approaching storms to help with real-time weather prediction. This later objective also led to an extension of the special observing period, and to the development of a hybrid targeting strategy based on combining information from an ensemble-based mesoscale targeting technique with the original targeting approach that was based on underlying physical principles and mesoscale adjoint modeling.
The experimental objectives led to the design of an observing system that combined many types of measurements of the ocean and atmosphere, as well as real-time mesoscale numerical modeling, and real-time communication of the experimental data to weather forecasters and operational numerical weather prediction models. In this respect the CALJET team implemented an experimental system that was integrated not only in the sense of observing systems, but also in terms of its combined operational and research objectives. This was accomplished by integrating the following tools:
One of NOAA's P-3 aircraft with GPS dropsondes.
A 20-station coastal network of wind profilers with RASS.
An array of >50 drifting buoys (deployed by NWS for operational and experimental purposes).
Two mobile 3-cm wavelength Doppler radars (Univ. of Oklahoma's Doppler on Wheels).
A special radar and balloon observing network to study the microphysics and dynamics of orographic rain.
Specialized satellite-based feature tracked winds from GOES.
The Coastal Ocean-Atmosphere Prediction System (COAMPS).
The Penn-State/NCAR MM5 mesoscale numerical model.
Real-time communication of data from the P-3 aircraft, wind profilers, drifting buoys, and satellite winds for operational weather forecasting