Geography 311 – Climatology Geography Major Global Environmental Change Cluster Questions to think about: What is climate? How is climate different from weather? Are they related? What controls the climate? Does climate change – do we care? Can climate be predicted? Why is it so darn wet? Why is central Europe (or Wisconsin) flooding? Weather and Climate Meteorology and Climatology Elements & Controls Elements Temperature Precipitation Solar Radiation Wind Speed and Direction Atmospheric Pressure Humidity Visibility Climate Controls Latitude Earth-Sun Relationships Major pressure and wind systems Marine vs. Continental Setting Proximity Relative to prevailing winds Topography Elevation: normal lapse rate Topographic barriers Do you want to be a Meteorologist or a Climatologist ?? Meteorology Physics and Math Current state of the atmosphere – and short-term future Data-collection via radiosondes and satellites Solve equations of motion Be a TV Star like Matt - KGW Tools of the Meteorologist Radiosonde…. Do you want to be a Meteorologist or a Climatologist ?? Climatology Geography and Environmental Sciences Long-term state of the atmosphere – averages and measures of variability Data-collection: Cooperative climatological network Statistical analysis and mapping Impacts on human activity Be a College Prof like Dan Climate Regions Isotherms - temperature Annual Precipitation Long-term Trends Government Agencies Meteorology: National Weather Service Mission: Protect Human Life and Property Portland Weather Service Office Seattle Weather Service Office Datastreme – 0nline Meteorology Course Unisys Weather Page Climatology: National Climate Data Center (NOAA) Mission: Archive and provide historical data Western Regional Climate Center Oregon Climate Service (Note: First Web Assignment) A Few Basics: Planetary Energy Balance Energy In = Energy Out S (1 ) R 4 R T 2 2 4 T 18o C But the observed Ts is about 15° C (Ts – surface temperature) What’s Missing? Vertical structure of the Atmosphere and the composition of the atmosphere. The “greenhouse effect” Energy storage and transport The “general circulation” of the atmosphere and oceans Hence: The Climate System The General Circulation Solar heating is greater than longwave cooling in the tropics: energy accumulates there, both in the atmosphere and the oceans Longwave cooling is greater than solar heating near the poles: energy is lost there, by thermal radiation to outer space The “job” of the atmosphere and the oceans is to transport energy from where it accumulates to where it can be lost (poleward and upward) This job is difficult because of the Coriolis force – yet it is Coriolis that turns North/South (meridional) transport into East/West (Zonal) winds. How is Energy Transported to its “escape zones?” Both atmospheric and ocean transport are crucial Buoyancy-driven convection drives vertical transport Latent heat is at least as important as sensible heat Atmospheric Circulation in a nutshell Hot air rises (rains a lot) in the tropics Air cools and sinks in the subtropics (deserts) Poleward-flow is deflected by the Coriolis force into westerly jet streams in the temperate zone Jet streams are unstable to small perturbations, leading to huge eddies (storms and fronts) that finish the job Ocean Currents midlatitude “gyres” W-E flow in tropics circumpolar current How are these known? Effects on poleward energy transport? Climate vs. Weather (as related to predictability) “Climate is what you expect … weather is what you get!” Climate is an “envelope of possibilities” within which the weather bounces around. Climate is determined by the properties of the Earth system itself (the boundary conditions), whereas weather depends very sensitively on the evolution of the system from one moment to the next. Predictability “If they can’t predict the weather, how can they possibly hope to predict the climate?” Weather forecasts are only useful for a few days, maybe a week at best Forecasting is limited by modeling skill and inadequate observations, but even if these were perfect, the limit of predictability would be about 2 weeks This limit is a property of the atmosphere itself, not a failure of our science! Give the weather folks a break! Limits to Predictability The dynamical equations governing the motions of the atmosphere and oceans are strongly nonlinear. This makes them very sensitively dependent on their initial conditions. Errors in the initial conditions, no matter how trivial or on how small a spatial scale, quickly grow in magnitude and propagate to larger spatial scales. Butterfly analogy of Lorenz (1963): Predictability Times Boundary-layer eddy: Cumulonimbus clouds: Mid-latitude cyclone: Big standing waves: El Niño: Deep ocean circulation: 10 minutes 1 hour 3 days 10 days 100 days 50 years(?) Forecasting (time-frames) Can’t forecast the weather in Portland on the day of the Geog 311 final exam in December: (Snow? Sunshine? -10 C? +20 C?) Can we forecast that tomorrow will be colder than it is today? Can “forecast” with complete confidence that –100 C < Tmax < +100 C Why? Boundary conditions – aka External Controls! Solar constant Atmospheric composition Tilt of Earth’s axis, latitude, etc Slow vs. Fast Climate Components Some parts of the Earth system are slower to respond to changes than the atmosphere (e.g., ocean temperatures, soil moisture). Such slow processes give the climate “memory”. If processes that control these “slow” processes are known, they may be predicted. The statistics of the weather respond in systematic and predictable ways to changes in boundary forcing. Boston (45 N. ) Zimbabwe (20 S.) Seasonal Forecasting In the past 10 years, we’ve learned a lot about the processes that control tropical Pacific sea-surface temperatures (El Niño and La Niña). Once these processes get started, we can predict their evolution with some skill. Weather anomalies associated with these events are then forecast several months in advance. Works much better in some places than others (not too reliable at Fort Collins, Colorado; but more so in Portland, Oregon). Why? Climate Modeling Weather and ocean circulation are governed by a set of reasonably well-known deterministic equations (like F = ma). The governing equations of climate are in general not known. Climate modeling is for the most part a “brute force” activity that involves running “weather” forecast models for a very long time with perturbed or slowly changing boundary conditions. The initial conditions of a climate simulation are forgotten in a few simulated weeks. The statistics of the simulated weather are the output of interest, the simulated climate. Examples of Climate Simulations Ice-Age simulations require only a knowledge of boundary conditions: Orbital geometry Sea-surface temperatures Ice orography The atmosphere quickly adjusts to the changed conditions, and an ice-age climate develops. Simulations of global warming involve perturbed boundary conditions too (atmospheric composition and radiative properties). Ocean response is critical, and must be predicted, not prescribed. GUIDING PRINCIPLE FOR INFORMED CLIMATE DECISION: Humans can take actions to reduce climate change and its impacts. CLIMATE LITERACY: The Essential Principles of Climate Science • The Sun is the primary source of energy for Earths climate system. • Climate is regulated by complex interactions among components of the Earth system. • Life on Earth depends on, is shaped by, and affects climate. • Climate varies over space and time through both natural and man-made processes. • Our understanding of the climate system is improved through observations, theoretical studies, and modeling. • Human activities are impacting the climate system. • Climate change will have consequences for the Earth system and human lives.