Ch03 Temperature.pptVIP

* * Cycles of Air Temperatures Cycles of Air Temperatures Annual temperature variations: Highest and lowest mean temperatures do not coincide with maximum or minimum incoming solar radiation. In the northern hemisphere, August has the highest mean temperature, while June has the highest incoming solar radiation. World Distribution of Temperature Temperature Measurement Mechanical thermometers: Liquid in glass Maximum thermometer—mercury Minimum thermometer—alcohol Thermograph—bimetal strip Electrical thermometers: Thermistor—electrically resistant at different temperatures Very fast Temperature Measurement Instrument shelters: White box Louvered sides Over grass 1.5 m above ground Temperature Scales Fixed points: Ice point Ice melts 32oF, 0o C, 273 K Steam point Water boils 212o F, 100o C, 373 K Temperature Scales Fahrenheit 1715 Celsius 1742 Kelvin Absolute, no negatives Temperature Scales Heat Stress and Wind Chill: Indices of Human Discomfort Apparent temperature is the temperature a person perceives. Heat stress is caused by high temperature and high humidity. Sweat does not evaporate from body. Feels hotter Heat stress index Heat Stress and Wind Chill: Indices of Human Discomfort Heat Stress and Wind Chill: Indices of Human Discomfort Wind chill is the cooling power of moving air. Evaporates moisture Cools body Feels colder Wind chill chart Heat Stress and Wind Chill: Indices of Human Discomfort End Chapter 3 （一）大气热力学第一定律 对于单位质量的理想气体（热力学系统），从外界吸收的热量dQ等于其内能增量dE与气体膨胀对外所做工dW之和。 大气的增温与冷却 dQ p, T, V dQ = CvdT + PdV 故 dE=CVdT dE A dW p dW=PA△L=PdV 或 因此，气温变化有两种过程：一是与外界热量交换引起，称为非绝热变化(Diabatic) ；二是由外界压力变化引起，称为绝热变化(Adiabatic)。 附录 （二）气温的非绝热变化过程 辐射Radiation：近地面大气对太阳短波辐射直接吸收很少，主要吸收地面有效辐射。 热传导Conduction：空气与下垫面、相邻空气层之间，通过分子热运动进行的热量交换，又称感热交换/Sensible Heat Transfer (H)。 对流/平流Advection/Convection：空气垂直运动/水平运动所引起的热量输送。 湍流Turbulence：空气与下垫面、相邻空气层之间，通过空气不规则运动（湍流）进行的热量交换。 蒸发和凝结Evaporation/Condendation：下垫面上水分（主要是海洋）蒸发时吸收其热量，这部分热量以潜热形式随水汽向上输送，在高空当水汽凝结时，潜热释放，从而大气间接地