National Aeronautics and Space Administration

Wallops Flight Facility

Coastal Storms

COASTAL STORMS AND REGIONAL PRECIPITATION

To the millions of citizens living in Coastal Regions the most dramatic changes are usually caused by Storms. Whether caused by the fortunately rare land falling Hurricane or wintertime Nor’easters, the aftermath is immediately visible and the damage can often be severe. Less appreciated but no less damaging are other phenomena such as the occasional major winter snowstorms that develop off the Atlantic coast, bringing major metropolitan cities to a halt. These are often not forecasted. As in other regions too much or too little precipitation can have far reaching consequences. Rivers flood. Runoff from fields increases the nutrient burden of bays and estuaries. Salinity levels in nursery areas for fish and shellfish change and affect their survival or reproductive success. Pollutants can be washed out of the atmosphere and accumulated in coastal waters. NASA has a goal of understanding global precipitation. This is needed to understand the energy balance of the earth and the hydrological cycle. Satellites designed to meet these global goals also measure local precipitation. And measuring and understanding the effects of local storms and regional precipitation are critical to develop the policies that will protect coastal populations and property.

Figure 1. Hurricane

Present Activities:

Global Precipitation (TRMM)

Wallops has been involved in the calibration and validation of the Tropical Rain Measurement mission (TRMM) satellite almost from the creation of the Ground Validation Science team. Recently, we had assumed management of all the Ground Validation operations. Although the TRMM satellite is confined to an orbit that just skirts the Wallops area, the techniques and instruments we have developed were tested and evaluated at Wallops. A state of the art multiple parameter portable radar (NPOL) was recently built and used to support the Convection and Moisture Experiment (CAMEX-4) last summer in Florida. TRMM data from Hurricane Bonnie is shown in Figure 1. The NPOL radar will be returning to Key West Florida for the 2002 Hurricane season. NPOL will be able to measure the heavy precipitation in the rain bands and also through the use of horizontally and vertically polarized radar beams provide information on the nature of the hydrometeors inside the storms clouds.

NPOL will also be used in July to support a major NASA experiment to study tropical cirrus clouds (CRYSTAL FACE). Data from NPOL will document the extent and lifecycle of convective systems that produce most of the cirrus clouds NPOL will also be the control center to coordinate the operations of six highly instrumented aircraft involved in the experiment.

Figure 2. NPOL Antenna

Figure 2 shows the innovative flat antenna of the NPOL radar being installed on top of the sea containers used as its base. This highly transportable radar can be shipped in four sea containers to almost any where in the world, set up and operated requiring only minimal site preparation and a source of diesel fuel.

Figure 3. RHI of Convective

A sample of the NPOL data is shown in Figure 3. The image is a vertical scan showing a strong convective cell (the red color) with the thunderstorm anvil to the left and a second cell forming behind it. Storms of this size typically produce damaging hail, strong winds and can trigger tornados. If the system is slow moving, local flooding usually results.

Precipitation Calibration Laboratory

For more than ten years, Wallops has been involved in developing, using, and calibrating instruments to measure characteristics of precipitation. We have developed extensive facilities to calibrate and test rain gauges and disdrometers. These include a large rain simulation facility where rain rates from a mist all the way up to the heaviest rain rates found in nature can be produced. Three outdoor instrumentation pads; located at Wallops, the Kennedy Space Center and at Darwin, Australia, have been used for long-term intercomparisons of all types of rain gauges and disdrometers for more than ten years. And a unique microwave attenuation system, several using antennas installed on two towers a mile apart on Wallops Island, is designed to measure rainfall detecting the amount the signal is attenuated as is passes from one tower to the other. Several different microwave frequencies are used to improve the estimates. In addition, Dr. Larry Bliven’s Rain-Sea laboratory has a drop tower, which is used to calibrate disdrometers as well as to study the effects of rain on the surface of the ocean. (The rain roughen surface creates problems with satellite measurements.)

Educational Outreach

Two of the students selected for the first Goddard Coastal Zone Research Fellowship will be working with the NPOL radar this summer during the CRYSTAL-FACE and TRMM Key West Evaluation Experiments. These students will have the opportunity to work with the latest technology in radar meteorology as beginning graduate students instead of waiting until they get their first postdoctoral position.

Future/Planned Activities:

Global Precipitation (GPM)

With the launch of the Global Precipitation Measurement Mission, the satellite measurements will cover most of the globe. Wallops will become a regional validation center. In addition to the facilities mentioned above, the 60-foot antennas of the SPANDAR and UHF radars will bring unprecedented sensitivity, range and resolution to measuring properties of coastal storms in support of the satellite measurements. The local network of rain gauges and disdrometers will be extended to cover the entire Eastern Shore. The NPOL radar will be located 30 km from Wallops to provide not only dual polarization measurements but also dual Doppler measurements to provide a 3 dimensional picture of the kinematics of coastal storm systems.

Educational Outreach

The addition of major land based radar systems will greatly increase the opportunities for high school and college students to get hands on experience for collecting and analyzing radar data.

Collaborators:

Lead Investigator: John Gerlach