New research from NASA has concluded that tropical cyclones like Gaston produce rain differently than another class of storms called "extra-tropical" cyclones. According to the study, making a proper distinction between these systems by looking at both raindrop size and abundance may be a key to assisting weather forecasters in estimating rainfall intensity. By doing so, forecasters can reduce the surprise factor of flash flooding and the unfortunate loss of property and life.
Ali Tokay, a research scientist from the Joint Center for Earth Systems Technology (JCET) at the University of Maryland Baltimore County, Baltimore, and NASA's Goddard Space Flight Center, Greenbelt, Md., compared the rain measurements collected in tropical storms and hurricanes during the past three Atlantic hurricane seasons with measurements after these storms transitioned to being extra-tropical. Tokay's study appeared in the May issue of the American Meteorological Society's Monthly Weather Review.
When a tropical cyclone -- the generic name for tropical depressions, tropical storms and hurricanes -- merges with a mid-latitude frontal storm system, measurable changes to the raindrop size and abundance occur as the system transitions to become extra-tropical. Extra-tropical cyclones also form outside the tropics without being part of a tropical system, and tend to form over land rather than over the open ocean. This category of storm can produce anything from a cloudy sky to a thunderstorm as it develops between weather fronts, the boundaries separating air masses of different densities.
Tokay looked at raindrop size, rain intensity, and the area in which rain falls in both tropical cyclones and extra-tropical cyclones using ground-based rain-measuring instruments called disdrometers. These instruments measure the range of raindrop sizes in a storm and the intensity of the rainfall. The disdrometer is an important part of the ground-based rain measuring instruments that are used to validate rainfall seen from satellites including the Tropical Rainfall Measuring Mission (TRMM), a joint mission with NASA and the Japanese Space Agency. He concluded that tropical cyclones that form over water tend to rain harder and have a greater amount of smaller drops before they transition to being extra-tropical with raindrops of larger size and mass.
"Torrents of rainfall from tropical storms are not surprising since the systems are large and move slowly. It is also true that slow moving frontal systems associated with an extra-tropical cyclone can result in abundant rainfall at a site," said Tokay. "What is less known is that the distribution of raindrops within a volume of air between the two systems differs substantially even though weather radar may measure the same returned power which is known as reflectivity." This is why disdrometer measurements of raindrop size are needed.
"Both rain intensity and reflectivity are integral products of raindrop size distribution, but they are mathematically related to different powers of the drop size," said Tokay. Weather radars cannot measure the range of raindrop sizes. As a result, rainfall estimates from weather radars must employ the use of equations that make assumptions about raindrop size. These assumptions can result in underestimation of rain intensity, and the possibility of deadly flooding.
In the study, Tokay uses disdrometer data from various sites around the U.S. and abroad. Most of the data were collected at NASA's Wallops Flight Facility, Wallops Island, Va., where Paul Bashor of Computer Sciences Corporation, Wallops Island, Va. maintains several types of disdrometers. The data from two tropical storms were collected at Orlando, Fla., and Lafayette, La. through collaborative efforts with Takis Kasparis at the University of Central Florida's Orlando campus, and Emad Habib of the University of Louisiana at Lafayette.
Lynn Chandler | EurekAlert!
In times of climate change: What a lake’s colour can tell about its condition
21.09.2017 | Leibniz-Institut für Gewässerökologie und Binnenfischerei (IGB)
Did marine sponges trigger the ‘Cambrian explosion’ through ‘ecosystem engineering’?
21.09.2017 | Helmholtz-Zentrum Potsdam - Deutsches GeoForschungsZentrum GFZ
Plants and algae use the enzyme Rubisco to fix carbon dioxide, removing it from the atmosphere and converting it into biomass. Algae have figured out a way to increase the efficiency of carbon fixation. They gather most of their Rubisco into a ball-shaped microcompartment called the pyrenoid, which they flood with a high local concentration of carbon dioxide. A team of scientists at Princeton University, the Carnegie Institution for Science, Stanford University and the Max Plank Institute of Biochemistry have unravelled the mysteries of how the pyrenoid is assembled. These insights can help to engineer crops that remove more carbon dioxide from the atmosphere while producing more food.
A warming planet
Our brains house extremely complex neuronal circuits, whose detailed structures are still largely unknown. This is especially true for the so-called cerebral cortex of mammals, where among other things vision, thoughts or spatial orientation are being computed. Here the rules by which nerve cells are connected to each other are only partly understood. A team of scientists around Moritz Helmstaedter at the Frankfiurt Max Planck Institute for Brain Research and Helene Schmidt (Humboldt University in Berlin) have now discovered a surprisingly precise nerve cell connectivity pattern in the part of the cerebral cortex that is responsible for orienting the individual animal or human in space.
The researchers report online in Nature (Schmidt et al., 2017. Axonal synapse sorting in medial entorhinal cortex, DOI: 10.1038/nature24005) that synapses in...
Whispering gallery mode (WGM) resonators are used to make tiny micro-lasers, sensors, switches, routers and other devices. These tiny structures rely on a...
Using ultrafast flashes of laser and x-ray radiation, scientists at the Max Planck Institute of Quantum Optics (Garching, Germany) took snapshots of the briefest electron motion inside a solid material to date. The electron motion lasted only 750 billionths of the billionth of a second before it fainted, setting a new record of human capability to capture ultrafast processes inside solids!
When x-rays shine onto solid materials or large molecules, an electron is pushed away from its original place near the nucleus of the atom, leaving a hole...
For the first time, physicists have successfully imaged spiral magnetic ordering in a multiferroic material. These materials are considered highly promising candidates for future data storage media. The researchers were able to prove their findings using unique quantum sensors that were developed at Basel University and that can analyze electromagnetic fields on the nanometer scale. The results – obtained by scientists from the University of Basel’s Department of Physics, the Swiss Nanoscience Institute, the University of Montpellier and several laboratories from University Paris-Saclay – were recently published in the journal Nature.
Multiferroics are materials that simultaneously react to electric and magnetic fields. These two properties are rarely found together, and their combined...
19.09.2017 | Event News
12.09.2017 | Event News
06.09.2017 | Event News
22.09.2017 | Life Sciences
22.09.2017 | Medical Engineering
22.09.2017 | Physics and Astronomy