Frequently Asked Questions about the ASOS Exposure Documentation Effort

What is the ASOS Exposure Documentation Effort?

It's a project to take photos of the area surrounding coastal and inland ASOS sites in areas subject to hurricanes. The photos will help document station exposure and identify obstacles that could reduce the winds at the site.

How can this benefit the operational forecaster?

It's sometimes difficult for forecasters to be familiar with the surroundings of ASOS stations they work with and validate against within their county warning areas. The ASOS exposure documentation effort will produce photos of the surroundings of each site.

These photos and other information (for each of the identified ASOS sites) would be contained on a web page at NCDC and the local office (if desired). If a forecaster sees something unusual in the observations, a mouse click can bring up the station 's web page to see if there are any obstacles affecting the wind from that direction.

The digital cameras provided for this task will become a resource for the local office. The cameras will be useful for many tasks including storm damage surveys, spotter training, and miscellaneous photos for local office web pages.

Why is this information important for hurricane forecast operations and research?

Hurricane Andrew taught us that nearby trees, buildings and other obstacles to the wind can cause large differences (as much as a factor of 2) in the winds experienced at stations. During a storm event these differences add variability to the wind fi eld and might be misinterpreted as being associated with a mesoscale weather feature.

During tropical cyclone episodes, anemometer site documentation information of coastal and inland observing stations will make it possible for Hurricane Research Division (HRD) and National Hurricane Center (NHC) meteorologists to correct wind observations for the influence of upstream roughness elements. Roughness numbers can be assessed for each wind direction sector based on photography. This is then put into a look up table to allow "on the fly" correction of winds to an "open terrain" exposure typical of an ideal airport runway. This will facilitate real-time analyses of hurricane and tropical storm wind fields during and after landfall. Otherwise it can take several months to reconstruct a wind field since site visits are required to document station exposures.

An "open terrain" analysis of the wind field removes small scale variability and better represents the convective, synoptic and mesoscale features of the storm.

This type of analysis is also consistent with the wind loading provisions in building codes, making it easier convert maximum sustained winds to peak gusts to see if the design winds in an area were exceeded.

What happens after we send the information to NCDC?

NCDC will archive the information and place it on a web site for public access. In addition to the documentation information, NCDC will provide topographic maps showing the location of the station relative to more distant terrain features.

How will NCDC use the information?

The information will help document the ASOS site for anyone who uses data from the site. In addition to providing information on wind exposure, the photos will allow NCDC to document types of temperature and precipitation sensors at each station, and validate the station position and anemometer height.

Who is the Hurricane Research Division (HRD) ?

HRD is a division of one of NOAA's Environmental Research Laboratories, the Atlantic Oceanographic and Meteorological Laboratory, under the Oceanic and Atmospheric Research line office. Formerly known as the National Hurricane Research Laboratory, HR D is NOAA's primary center for applied and basic research on tropical meteorology and hurricanes. HRD has a history of working closely with NHC and local weather service offices affected by landfalling hurricanes. For more information on HRD please brow se our web site. Hurricane Research Division

Is this a duplication of effort?

Documentation does exist for ASOS stations but there is not enough information on the surroundings of the stations to allow wind correction as a function of direction. Sometimes there is uncertainty of the actual location and height of the wind mast a nd types of sensors. Sometimes information on site exposures is not readily available to the forecaster or researcher.

Who is paying for this documentation?

The U.S. Weather Research Program has provided support for this project as part of the Hurricane Research Division's "Tropical Cyclone Winds at Landfall" proposal. These funds include a bulk purchase of digital cameras. Funding is also provided to the NCDC to maintain the documentation and place it on their web site.

Do the cameras have to be returned after the documentation?

No, the equipment may be used permanently within the NWS office for what ever purpose deemed necessary.

How often should the documentation be done?

Site documentation photos would probably be updated every 5-10 years to keep current with station upgrades and land use changes surrounding the station.

What is the deadline for completion of documentation?

Although no hard deadline has been set, it is important to try to complete all documentations before the beginning of the next hurricane season. Documentation should be completed by June 1, 1999.

How long will a site documentation take? Is any special training needed?

Once familiar with the camera features and operation, no special training is needed other than the ability to obtain a GPS fix, read a compass, take a picture with a "point and shoot" type camera, measure the height of the wind instrument on th e mast, and estimate or measure the distance to major obstacles to the flow.

A recent (7-24-97) site visit to the non-commissioned Tamiami Airport site (TMB) with the Miami NWS Office DAPM and El tech was completed in about 20 min. This included taking the mast down to measure the anemometer height, taking a GPS location fix, and photographing the upstream exposure every 45 degrees. The images were downloaded and enhanced on a PC back at the MIA NWS office in another 30 min. With a laptop computer the images could be enhanced in the field if desired.

Can an Apple Macintosh Computer be used for this?

The Nikon camera comes with software and cables for the Macintosh in addition to the PC. These's no reason why you can't use a Macintosh to do this as long as it is networked and has the JAVA virtual machine.

What about Coastal-Marine Automated Stations? Are they being documented?

Yes, the Tropical Cyclone WInds at Landfall Project also includes funds for documentation of C-MAN stations (NDBC) along the hurricane threatened coastline. In addition selected C-MAN stations will have enhanced time series wind recording capabilities.

What NWS Offices are Included?

Below are the offices identified to be located in areas that could experience inland or coastal affects of hurricanes and tropical storm winds. The Office is followed by a rough estimate of the number of ASOS stations within its' jurisdiction.

Portland ME 16
Burlington VT 7
Boston MA 25
Brookhaven/N.Y.City NY 20
Albany NY 5
Binghampton NY 6
State College PA 11
Philadelphia PA 15
Baltimore/Wash DC/Dulles 11
Roanoke VA 4
Wakefield/Norfolk VA 12
Raleigh Durham NC 8
Wilmington NC 4
Moorehead City NC 8
Columbia SC 5
Charleston SC 4
Greenville/Spartanburg SC 6
Atlanta 9
Tallahassee FL 9
Jacksonville FL 8
Tampa FL 10
Melbourne FL 9
Miami FL 10
Mobile AL 11
Birmingham AL 10
Jackson MS 9
Lake Charles LA 7
New Orleans LA 10
Shreveport LA 3
Houston, TX 9
Austin/San Antonio TX 9
Corpus Christi TX 10
Brownsville TX 4
Honolulu HI 9
Guam 2
San Juan PR 4*
*Includes U.S. VI sites

Contacts and Suggestions:

Acknowledgements:

Special thanks to Suzanne Melisano, MIA DAPM for all her assistance .
Rainer Dombrowsky, Mac Mclaughlin, John McNulty, Steve Rinard, Joe Golden, Dick Marshall, Jerry Jarrell, Mark DeMaria, Al Wissman, and Lou Uccellini for their support.

Tropical Cylone Winds at Landfall
Principal Investigator:
Mark D. Powell (HRD)

mark.powell@noaa.gov

NCDC:
Ned Guttman nguttman@ncdc.noaa.gov
David Bowman dbowman@ncdc.noaa.gov

Related Links: