Overview II: Importance of the atmospheric boundary layer

Review of last lecture The mission of meteorology is to understand and predict weather- and climate-related disasters (e.g. tornados, hurricanes, El Nino and global warming). 3 scales: weather, climate, climate change The modern climatology (meteorology) was born in the 1940s (a very young science!), but has been growing very fast! Now we have a global observational network with many satellites, ships, radars and surface stations, as well as very comprehensive prediction models running on the world ’ s largest computers.

The current status of weather and climate predictions Weather prediction: Generally good within one week, not good beyond 10 days. The skill depends on season and location. Tropical cyclone (hurricane, typhoon) prediction: good in track, but bad in intensity Climate prediction: Seasonal prediction generally good within 6 months, but not good beyond. Skill depends on season. Climate projection: All models project global warming in the 21st century, but with a 3-fold difference in magnitude.

Why is it so difficult to understand and predict weather and climate?

Problem I: Different parts of the world are strongly connected to each other (The “Teleconnection Problem”) Global atmospheric flow

Example 1: Global impacts of El Nino

Example 2: Global impacts of the mini El Nino (Madden-Julian Oscillation)

Factors affecting US weather and climate El NinoMadden-Julian Oscillation Amazon Arctic N. Atlantic Atlantic/ Sahel

Any location is affected by all the other locations, and in turn is affecting all the other locations

Problem II: Different components of the earth system (atmosphere, land, ocean, ice, clouds, etc) are strongly interacting with each other (The “Feedback Problem”)

Example I: Melting of Arctic sea ice

Video: Ice Albedo feedback

Example 2: Generation of hurricanes Heat from the ocean

Example 3: Generation of El Nino (Lin 2007, Journal of Climate)

Problem III: The earth system composes of both very big objects (such as the whole Pacific Ocean) and very small objects (such as the cloud droplets), making it very difficult to draw them on the same page (The “Subgrid-Scale Problem”)

Vertical Structure of the Atmosphere Definition of the atmospheric boundary layer (ABL) : "that part of the troposphere that is directly influenced by the presence of the earth's surface and responds to surface forcings with a time scale of about an hour or less.” Scale: variable, typically between 100 m - 3 km deep

Importance of ABL: (1) Interface between atmosphere and ocean/ land/ice - flux transfer and feedback

Importance of ABL: (2) The human beings are living in the ABL and changing the climate system Release of greenhouse gases Release of pollutants (aerosols) Change of land cover (deforestation and afforestation)

Importance of ABL: (3) A basic subgrid-scale process

Some Great Weather/Climate Scientists

Prof. Lonnie Thompson – OSU Father of Tropical Glaciology Spent an enormous amount of time above 5500 m Discovered solid record for Earth’s climate history Grown up in West Virginia Did three part-time jobs in high school to make a living Worked for many years with low salary Went back to the Himalayas after heart transplant

Prof. Robert Cess SUNY at Stony Brook World’s leading expert on climate change and Earth’s energy budget Organized the first international team for supercomputer prediction of global climate change, and many NASA and DOE projects Was not even an AMS Fellow when received the Charney Award Finished his Ph.D. in 3 years while doing a full-time job and taking care of his first child Hobby: Collectible cars

The young generation Video: Prof. Dargan Frierson and Elizabeth Maroon sing The World of Daisies (lyrics by Prof. Mike Wallace) in ATM S 111: Global Warming

Importance of hobbies Research is a slow walk: Relax and have fun Research is an Art: Intuition and taste

Summary The current status of weather and climate predictions: (1) weather prediction good to 10 days, (2) tropical cyclone prediction good in track but not in intensity, (3) climate prediction good to two seasons, (4) climate change projections have a 3-fold difference in magnitude. The main reasons of the difficulties in weather and climate predictions: (1) Teleconnection problem, (2) Feedback problem, and (3) Subgrid-scale problem. Importance of the ABL: (1) interface between atmosphere and ocean/land/ice - flux transfer and feedback, (2) the human beings are living in the ABL and change the environment, (3) a basic subgrid-scale process Some great climate scientists. Importance of hobbies.