Class #32: Friday, November 131 Weather Forecasting (conclusion) Climate types of the present

Class #32: Friday, November 132 The Comeback of Analog Forecasts ENSO has characteristic weather patterns that are statistically more common in El Niño, La Niño, and neutral conditions. Some of the uncertainty of numerical weather forecasts (the 6 th type of forecasts) can be assessed using a type of analog forecast.

Class #32: Friday, November 133 A New Method of Forecasting Spectral models view the atmosphere as having a number of waves of different wavelengths and amplitudes (wave heights). Spectral models are faster than grid point models. Spectral models are used for mid and long range forecasts.

Class #32: Friday, November 134 Another New Forecasting Method: Ensemble Forecasting Involves running the same forecasting model many times, using very slightly different conditions. Is a research tool, because it is too slow to show in real time Slight changes in initial conditions can produce very different forecasts 50 in test ensemble that follows Resembles the old analog method

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8 Climate Is to weather what a friend’s personality is to his/her mood Sums up the weather’s long-term behavior Is the collective state of the atmosphere for a given place over a specified interval of time

Class #32: Friday, November 139 Climate is defined by Location –Globe, continent, region, city –Chapter 14: regional and global scale Time: a specified interval –30 year average is normal –100 years or longer for history of climate Averages and extremes of variables –Chapter 14: temperature and precipitation

Class #32: Friday, November 1310 Controls on climate Similar to controls on temperature in Chapter 3 Latitude: solar energy input Elevation: air temperature, snow vs. rain Topography: moist vs. dry, temperature, distribution of cloud patterns, solar energy reaching the surface

Class #32: Friday, November 1311 Controls on Climate (continued) Proximity to large bodies of water –Thermal properties of water (absorption, heat capacity, transparency, mixing) moderate temperature downwind Prevailing atmospheric circulation –Intertropical Convergence Zone (ITCZ) –Subtropical Highs

Class #32: Friday, November 1312 Classifying Climate Hard to do –No clear boundaries –Complex natural systems How it is done –Important to life: hot or cold; moist or dry –Most common system: based on vegetation Köppen climate classification scheme based on vegetation and temperature

Class #32: Friday, November 1313 Köppen (KEPP-in) Scheme Modified by Trewartha and Horn Related to geography and global circulation Uses letters (1, 2 or 3) in Chapter 14 Has many other subdivisions within the categories shown in our book Has 6 major groups: A, B, C, D, E, H

Class #32: Friday, November 1314 The 6 major climate groups A: Tropical moist B: Dry (can be subtropical or mid latitude) C: Moist with mild winters (mid latitude) D: Moist with severe winters (mid latitude) E: Polar (high latitude) H: Highland (rapid climate change with elevation) 2 nd letter: usually latitude (except B) 3 rd letter: differences in temperature

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Class #32: Friday, November 1318 Tropical Humid Climates: Af, Aw, Am All tropical (A) climates are humid Letter “f” means no dry season, rain year round, usually closest to the equator Letter “m” means “monsoonal”, with a short dry season and a very rainy season Letter “w” means “winter dry season” except no real winter in tropics, just cool

Class #32: Friday, November 1319 Tropical humid climates (continued) Af –Closest to the equator –Smallest annual range of temperature – inches of rain per month –Most thunderstorms in afternoon –Linked to ITCZ –Tropical rain forests Am –Seasonal onshore winds during summer monsoon –Climates with most yearly precipitation –Jungle vegetation

Class #32: Friday, November 1320 Tropical moist climates (continued) Aw –Farthest A climate from the equator –Often border Af –Tropical wet and dry –Wet summers, dry, cooler winters –Linked to the seasonal migration of the ITCZ –Vegetation is savannah or tropical grasslands with scattered deciduous trees, as in the grasslands of Africa.

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Class #32: Friday, November 1322 Dry (B) climates Potential evaporation minus precipitation is greater than 0. More land of this climate type than any other Lubbock has a B climate Descending branch of the Hadley circulation near the subtropical highs or Rain shadow of a mountain range

Class #32: Friday, November 1323 Dry climate subtypes 2 nd letter –“S” for steppe or semi-arid (like Lubbock) –“W” for true desert (extremely dry) 3 rd letter –“h” for low-latitude, hot (yearly average temperature >= 64ºF) –“k” for mid latitude, cool (yearly average temperature <64ºF)

Class #32: Friday, November 1324 Dry climate subtypes (continued) BWh Extremely dry and hot; can have large sand dunes; Sahara, Arabian peninsula, central Australia, most extreme B climate BSk Least extreme B climate; midlatitude steppe, often high plateau, Lubbock, Denver, San Diego; often rain shadow BSh Much of Mexico, lower latitude, subtropical steppe BWk Central Asia, very dry, midlatitude rain shadow, continental interior

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