Black Research Program: General Approach Characterization, dynamical diagnosis, and validation of

the life cycles of extratropical meteorological phenomena

¨ Characterization: Assess statistics, structure & evolution

Dynamical Diagnosis: Use dynamical theory to develop mathematical diagnostic tools that are then applied to phenomenological life cycles to test mechanistic hypotheses

Validation: Validate life cycle characteristics and dynamical mechanisms in climate models and various reanalysis datasets

Nature of Research: Computational analysis of large multi-dimensional datasets (observations & climate simulations)

¨ Datasets: Reanalysis datasets & climate simulation output

Jet Streams in the Extratropical Atmosphere

Strong, narrow and quasi-horizontal “rivers of air” Typically located in upper troposphere or stratosphere Thousands of km long; hundreds of km wide; few km deep

Jet Stream Overview

Tropospheric Jet Stream Structure: Mid-Winter

300 hPa winds (vectors - wind direction; shading - windspeed)

Multi-Year Average (Jan 15) Daily Snapshot (Jan 15, 2006)

[Units: m/s]

Jet Stream Overview

Tropospheric Jet Stream Structure: Mid-Summer

300 hPa winds (vectors - wind direction; shading - windspeed)

Multi-Year Average (July 15) Daily Snapshot (July 15, 2006)

[Units: m/s]

Black Research Program: Phenomena Weather regimes, annular modes, anomalous temperature

events, cyclones, seasonal transitions, strat-trop coupling

• Northern Annular Mode: variability in polar vortex strength• Polar Annular Mode: variability in polar vortex position

Black Research Program: Phenomena Weather regimes, annular modes, anomalous temperature

events, cyclones, seasonal transitions, strat-trop coupling

• Synoptic and dynamic studies of cold air outbreaks• Physical mechanisms and low frequency modulation

Phenomena: Winter Cold Air Outbreaks in Southeast Weather regimes, annular modes, anomalous temperature

events, cyclones, seasonal transitions, strat-trop coupling

♥ No significant

trend in thefrequency of coldair outbreaks

♣ Past 2 winters(09/10 & 10/11)rank in the top 5 among the last 60 years (!)

Phenomena: Winter Warm Waves in Southeast Weather regimes, annular modes, anomalous temperature

events, cyclones, seasonal transitions, strat-trop coupling

♥ StatisticallySignificantdownward trendin warm waves

♣ Very low valuesduring last twowinter seasons(09/10 & 10/11)

Phenomena: Recent Cold Winters & Arctic Oscillation Weather regimes, annular modes, anomalous temperature

events, cyclones, seasonal transitions, strat-trop coupling

• Robust cold air outbreaks continue to be observed• Strongly modulated by annular mode (weak jet stream)

Average surface air temperature anomalies 12/15 – 01/14

1/07/2004

Winters of 2009/10 & 2010/11: Unusual Behavior!

Composite Surface Wind Anomalies →

(NOAA/ESRL)

Composite Surface AirTemperatureAnomalies →

(NOAA/ESRL)

Phenomena: Spring Onset in the Arctic Weather regimes, annular modes, anomalous temperature

events, cyclones, seasonal transitions, strat-trop coupling

♥ Temperature changeat high latitudes israther abrupt

♣ Temperature changeappears linked to alarge-scale circulationchange over the North Atlantic

Jet Stream Overview

Phenomena: Spring Onset in the Arctic

Atmospheric Changes between March 1 and May 1

Lower Tropospheric Heights Precipitation Rate