Extreme Events in Climatology Hurricanes Thunderstorms Tornadoes Droughts Glaciations Hurricanes Thunderstorms Tornadoes Droughts Glaciations

Glaciations 1-30 kyrs

Extreme events in the atmosphere rival those in the geosphere They are much more mobile than events like earthquakes affect large geographical areas and have dramatic consequences on the biosphere severe storms or perturbations in “normal” patterns Can cause extreme hardship on living things Can lead to widespread alteration of other natural systems soil loss, increased soil development, weathering, flooding, landslides, erosion… Extreme events in the atmosphere rival those in the geosphere They are much more mobile than events like earthquakes affect large geographical areas and have dramatic consequences on the biosphere severe storms or perturbations in “normal” patterns Can cause extreme hardship on living things Can lead to widespread alteration of other natural systems soil loss, increased soil development, weathering, flooding, landslides, erosion…

Tropical cyclones (Hurricanes or Typhoons) Occur in the tropics Are cyclones - circulation around a low pressure center Counter clockwise rotation in Northern hemisphere driven by coriolis force Require warm temperatures and adequate air motion to generate Tropical cyclones (Hurricanes or Typhoons) Occur in the tropics Are cyclones - circulation around a low pressure center Counter clockwise rotation in Northern hemisphere driven by coriolis force Require warm temperatures and adequate air motion to generate

Areas of warm water coincide with hurricane genesis

Warm oceans north and south of the equator spawn hurricanes

Hurricane paths note the absence along the equator

Hurricane Andrew out at sea

Hurricane Andrew approaches Florida

Hurricane categories and criteria

Single cell Multicell cluster Multicell line Supercell Weak to strong updrafts (non-severe) Weak to strong updrafts (non-severe) moderate to severe updrafts (severe) Intensely strong to severe Mesocyclonic rotation present (severe) Slight threat Moderate threat High threat Small areal coverage Small- Moderate areal coverage Moderate to large areal coverage Thunderstorm types Severe = <58 MPH wind, hail, and tornadoes Non-severe = >58 MPH wind, lightning, rain Severe = <58 MPH wind, hail, and tornadoes Non-severe = >58 MPH wind, lightning, rain

A single cell thunderstorm

Multicell thunderstorms- cellular Multicell thunderstorms- linear

Squall lines and Thunderstorms Squall lines are a line of severe thunderstorm cells, associated with a cold front. Direction of line movement

Animation of a developing squall line

Supercell development involves rotation

Anatomy of a supercell thunderstorm

Supercell in NSW Australia

Tornadoes, Waterspouts, Landspouts (aka Dustdevils) All involve rotational motion Some waterspouts and landspouts can come from the ground (water) up Tornadoes and some waterspouts come from the cloud down The US leads the world in tornadoes averaging 1000 per year Tornadoes, Waterspouts, Landspouts (aka Dustdevils) All involve rotational motion Some waterspouts and landspouts can come from the ground (water) up Tornadoes and some waterspouts come from the cloud down The US leads the world in tornadoes averaging 1000 per year

Dust Devils Caused by intense heating Dust Devils Caused by intense heating

Droughts By definition, a deficit in the water budget for a given region Can be related to global circulation, regional circulation, or local conditions Ground dries out, soil blows away, nothing grows Example “The Dust Bowl” in the 1930’s

Dust Bowl- ca. 1933

Dust Bowl- ca. 1935

PDSI- Palmer Drought Severity Index

Glaciation Driven by Milankovitch orbital variations Eccentricity, Obliquity and Precession Facilitated by feedback loops in Earth’s atmosphere and hydrosphere oceanic and atmospheric circulation patterns change, making things colder Results in snow and ice lasting the year Lasts 10’s of thousands of years a lot of retreats and advances Last glaciation was called the Wisconsinan occurred from kya Glaciation Driven by Milankovitch orbital variations Eccentricity, Obliquity and Precession Facilitated by feedback loops in Earth’s atmosphere and hydrosphere oceanic and atmospheric circulation patterns change, making things colder Results in snow and ice lasting the year Lasts 10’s of thousands of years a lot of retreats and advances Last glaciation was called the Wisconsinan occurred from kya

Glaciers, droughts, and tropical storm frequency all have identifiable effects on the natural world rivers adjust soils erode or form vegetation changes lakes form or dry up These meteorological features are extremely sensitive This makes them good things to study for identifying elements of past, present and future climate change Glaciers, droughts, and tropical storm frequency all have identifiable effects on the natural world rivers adjust soils erode or form vegetation changes lakes form or dry up These meteorological features are extremely sensitive This makes them good things to study for identifying elements of past, present and future climate change