Category Archives: Phenomena
A weather radar consists of a transmitter and a receiver. The transmitter emits pulses of radio waves outward in a circular pattern. Precipitation scatters these radio waves.
“Reflectivity” is the amount of transmitted power returned to the radar and measured by its receiver. The intensity of this received signal indicates the intensity of the precipitation.
Measuring the time it takes for the radio wave to leave the radar and return tells us how far away the storm is. The direction the radar is pointing locates the storm. Continue reading
Hunga Tonga erupted on Jan. 15 and lasted 11 hours.
It devastated the region, covering the land in a layer of ash. The eruption blasted a plume of ash and water vapor 34 miles into the atmosphere — into the mesosphere.
The Hunga Tonga plume contained only a very small amount of sulfur dioxide (SO2). Sulfur dioxide from volcanic mega-eruptions that reach high in the atmosphere can have an impact on global temperature. The mega-eruption of Pinatubo in 1991 released enough sulfur dioxide to cool the Earth’s surface for three years. The Tonga eruption will not have that kind of impact. Continue reading
This winter has already delivered some notable disasters, and it is important to carefully consider the anatomy of such high impact weather events in order to, as accurately as possible, understand to what degree an event is attributable to the … Continue reading
On Nov. 7, numerous “holes” appeared to be punched out of a cloud deck across the Upper Midwest.
Punch holes can occur after a plane flies through the cloud if the cloud droplets are supercooled, with their temperatures below freezing. Continue reading
The extreme and persistent drought that has plagued parts of California for several years will be at least slightly remedied by the torrential rains that fell over the weekend over much of the central and northern part of the state.
These rains were associated with a phenomenon called an “atmospheric river.”
Atmospheric rivers are organized flows of deep, moist air from the subtropics and tropics that bring many locations in California a large portion of their annual precipitation. Continue reading