Researchers

Eric D'Asaro

Senior Principal Oceanographer

OPD Department

APL-UW

Professor, Oceanography

Craig Lee

Senior Principal Oceanographer

OPD Department

APL-UW

Professor, Oceanography

Ren-Chieh Lien

Senior Principal Oceanographer

OPD Department

APL-UW

Affiliate Professor, Oceanography

Rosalinda Mrvaljevic

Temporary Staff Helper

OPD Department

APL-UW

Luc Rainville

Principal Oceanographer

OPD Department

APL-UW

Affiliate Assistant Professor, Oceanography

Tom Sanford

Senior Principal Oceanographer Emeritus

OPD Department

APL-UW

Professor Emeritus, Oceanography

Funding

ONR

Atmosphere-Ocean Interactions in the Extreme

ITOP: Impact of Typhoons on the Ocean in the Pacific

We fly out in front of the typhoons with the C130s, drop oceanographic instruments into the sea, and then the typhoon runs over the instruments.

"The typhoon comes along and the typhoon starts mixing up the ocean. The warm ocean water that energizes typhoons is only a thin layer on top of a deep, cold ocean. The typhoon’s winds and waves mix these layers, churning the cold water to the surface. After the storm runs over the array of instruments you can see this cold wake has formed and it’s a pretty dramatic feature. It is about 26.5 degrees ... so about 2.5 to 3 degrees cooler than the sea surface temperature was before."

Observation Strategy

Typhoon Fanapi, which struck Tawain in September 2010, was studied intensively by reconnaissance aircraft, air-deployed floats, autonomous gliders, research vessels, and moorings that had been emplaced in the storm's path by U.S. and Taiwanese researchers. These instruments and platforms enabled continuous atmosphere and ocean observations throughout the typhoon's life cycle.

Wake Persistence

ITOP is International Collaboration

Upper left: Sea surface temperature (SST) 2–3 days after the passage of Typhoon Fanapi (max. winds 105 kts, track shown in blue). Various floats and drifters were deployed ahead of the storm at 10/00Z near the 18/00Z forecast storm position. The first 3 days of tracks indicated; the pink line indicates the track of an EM-APEX float, the data of which is shown in the lower panel.

Upper right: SST 9–10 days after the passage of Typhoon Fanapi. Ten days of float and drifter tracks indicated. The surface expression of the wake has faded and has been wrapped around an eddy, as emphasized by the drifter tracks.

Lower: Time series of temperature of the upper 150 m of ocean as measured by the EM-APEX float (pink track). The mixed layer (A) is shallow and warm a day before the passage of Typhoon Fanapi. Intense mixing during the typhonn passage forms a wake (B) by entraining cold subsurface water. Warming of the sea surface (C) begins immediately after the wake is formed. However, a subsurface lens (D) of relatively cold water forms, perhaps enhanced by deep mixing, and remains at least 10 days (E) after the typhoon passage. Thus, though the surface expression is weakened, the cold ribbon seen in the satellite image in the upper right indicates the location of the capped wake.

The western Pacific Ocean has the highest frequency and concentration of tropical cyclones. The U.S. Office of Naval Research and the Taiwan National Science Council fielded research programs here to study the interactions between typhoons and the ocean. Experiments were designed to take in situ oceanic observations on the paths of typhoons across a range of oceanic and atmospheric conditions.

The ITOP program culminated in an intensive observation period in August–October 2010 and resulted in the largest set of oceanographic and atmospheric data ever taken within and immediately following tropical cyclones.

The ITOP project website is hosted by the Earth Observatory Laboratory of the National Center for Atmospheric Research. Learn more about ITOP science objectives, experiment execution, and early results.

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