EG 1204 Earth Systems an introduction Meteorology and

EG 1204: Earth Systems: an introduction Meteorology and Climate Dr Mark Cresswell Structure of the atmosphere & ocea

Topics we will cover • • Introduction to lecture series & basic Astronomy Composition of the atmosphere Vertical structure of the atmosphere Relationships between pressure, temperature and height • Introduction to the oceans • Structure of the oceans • Characteristics of oceans and circulation

Suggested References #1 Text Books: • Ahrens, C. Donald. (2000) Meteorology today : an introduction to weather, climate, and the environment. • Harvey, Danny. (2000) Climate and global environmental change • Burroughs, William James. (2001) Climate change : a multidisciplinary approach. • Climate change 2001 : The scientific basis / edited by J. T. Houghton • Mc. Guffie K and Henderson-Sellers A. (1997). A climate modelling primer. Published by John Wiley, England.

Suggested References #2 Scientific Journals: • Quarterly Journal of the Royal Meteorological Society • Monthly Weather Review • Meteorological Applications • Journal of Climatology

Suggested References #3 Internet: • KNMI climate explorer: – http: //climexp. knmi. nl • Royal Meteorological Society: – http: //www. royal-met-soc. org. uk/ • The Met. Office: – http: //www. meto. gov. uk/ • NOAA-ENSO: – http: //nsipp. gsfc. nasa. gov/enso/

General Points • The atmosphere behaves like a fluid • The atmosphere is a mixture of different gases, aerosols and particles • The atmosphere remains around the earth as an envelope because of gravity • Much of the observed motion in the atmosphere results from solar radiation

Basic Astronomy • For most of the Earth, energy varies on daily (diurnal) and seasonal (annual) time-scales. • Changes from daytime to night and progression through the four seasons depends on the configuration of the Earth-Sun orbit

Basic Astronomy • The Earth completes a single rotation about its axis in approx 24 hours (23. 9345 hours!) - this period is known as a day

Basic Astronomy • The Earth completes a single revolution around the Sun in approx 365 days (365. 256 days) - period is known as a year

Basic Astronomy • Axis about which the earth rotates tilts Spring Summer Winter Autumn

Composition of the atmosphere

Vertical structure of the atmosphere • Weight is the mass of an object multiplied by the acceleration of gravity Weight = mass x gravity • An object’s mass is the quantity of matter in the object

Vertical structure of the atmosphere • The density of air is determined by the mass of molecules and the amount of space between them Density = mass/volume • Density tells us how much matter is in a given space (or volume)

Vertical structure of the atmosphere • Each time an air molecule bounces against an object it gives a tiny push • This small pushing force divided by the area on which it pushes is called pressure Pressure = force/area

Vertical structure of the atmosphere • In meteorology we discuss air pressure in units of hectopascals (h. Pa) (previously called millibars mb) • The average atmospheric pressure at the Earth surface is 1013. 25 h. Pa • We can sense sudden changes in pressure when our ears ‘pop’ such as that experienced in old aircraft

Relationship between pressure and height • As we climb in elevation (up a mountain or in a hot air balloon) fewer air molecules are above us: atmospheric pressure always decreases with increasing height

Relationship between temperature and height

Introduction to the Oceans • The oceans occupy 71% of the earth’s surface • Over 60% of global ocean surface is in the southern hemisphere • Three quarters of the ocean area is between 3, 000 and 6, 000 metres deep

Structure of the Oceans • The thermocline is a layer characterised by decreasing temperature and increasing density with depth • The thermocline is stratified and inhibits vertical mixing

Structure of the Oceans • Below thermocline layer is the deep layer of cold, dense water • Deep layer motion is mostly driven by density variations due to salinity change