Atmospheric Moisture, Precipitation, and Clouds PDF

10/28/24 ATMOSPHERIC MOISTURE, PRECIPITATION, AND CLOUDS, CHAPTER 7 1 CONCEPTS IMPORTANT FOR UNDERSTANDING WEATHER HYDROLOGIC CYCLE HUMIDITY STABILITY ADIABATIC PROCESSES CLOUDS...

10/28/24 ATMOSPHERIC MOISTURE, PRECIPITATION, AND CLOUDS, CHAPTER 7 1 CONCEPTS IMPORTANT FOR UNDERSTANDING WEATHER HYDROLOGIC CYCLE HUMIDITY STABILITY ADIABATIC PROCESSES CLOUDS FOG 2 1  10/28/24 WATER ON EARTH Figure 7.3 Not much overall in atmosphere 3 GLOBAL WATER Transpiration km3 See Figure 7.4 4 2  10/28/24 GLOBAL WATER Transpiration km3 See Figure 7.4 5 GLOBAL WATER Transpiration km3 See Figure 7.4 6 3  10/28/24 GLOBAL WATER Transpiration km3 See Figure 7.4 7 GLOBAL WATER Transpiration km3 See Figure 7.4 8 4  10/28/24 GLOBAL WATER Transpiration km3 See Figure 7.4 9 GLOBAL WATER Transpiration km3 See Figure 7.4 10 5  10/28/24 GLOBAL WATER Transpiration km3 See Figure 7.4 11 HUMIDITY DEFINITION TEMPERATURE AND HUMIDITY MAXIMUM HUMIDITY RELATIVE HUMIDITY SATURATED AIR UNSATURATED AIR DEW POINT TEMPERATURE 12 6  10/28/24 MORNING DEW 13 CONDENSATION EXAMPLES RH increases to 100% 14 7  10/28/24 HUMIDITY DEFINITION TEMPERATURE AND HUMIDITY RELATIVE HUMIDITY DEW POINT TEMPERATURE ABSOLUTE HUMIDITY (g/m3) SPECIFIC HUMIDITY (g/kg) MEASURING HUMIDITY 15 MEASURING HUMIDITY (TRADITIONAL) Modern hygrometers use electrical resistance, optical properties, or weight of water Sling psychrometer Hair hygrometer 16 8  10/28/24 RELATIVE HUMIDITY AND TEMPERATURE THROUGHOUT A TYPICAL DAY Temperature RH NOON 17 RELATIVE HUMIDITY MAPS REAL TIME 18 9  10/28/24 STABILITY: MOVEMENT OF AIR PARCELS AIR PARCEL: BODY OF AIR WITH PARTICULAR TEMPERATURE AND HUMIDITY CHARACTERISTICS WILL IT RISE OR FALL? 19 WHY THINK ABOUT STABILITY? CONVECTIONAL HEATING TRIGGERS UPDRAFT AIR MAY NOT RISE STABILITY: TENDENCY OF A PARCEL OF AIR TO EITHER REMAIN AS IT IS OR CHANGE ITS INITIAL POSITION BY RISING OR FALLING AIR PARCEL CAN BE STABLE UNSTABLE 20 10  10/28/24 WHAT DETERMINES STABILITY? ONLY RISE IF WARMER WHEN AN AIR PARCEL THAN SURROUNDING AIR RISES (OR SINKS) IT NORMAL LAPSE RATE OR COOLS (OR WARMS) ENVIRONMENTAL LAPSE CALLED ADIABATIC RATE (6.4 ºC/1000 M OR HEATING (OR ADIABATIC 3.5 ºF/1000 FT) COOLING) THIS RATE VARIES 21 ADIABATIC PROCESSES: COOLING AND HEATING Compression (warming) Expansion (cooling) See Figure 7.15 22 11  10/28/24 ADIABATIC RATES DRY ADIABATIC LAPSE MOIST ADIABATIC LAPSE RATE (DALR) RATE (MALR) RATE AT WHICH RATE AT WHICH “UNSATURATED” AIR “SATURATED” AIR COOLS COOLS (OR WARMS) (OR WARMS) 10 ºC/1000 M OR 5.5 »5-6 ºC/1000 M OR 3.3 ºF/1000 FT ºF/1000 FT 23 EXAMPLES OF ADIABATIC PROCESSES UNSTABLE CONDITIONALLY UNSTABLE STABLE LCL (DEW POINT TEMP, RH = 100%) 24 12  10/28/24 ADIABATIC RATE CAN CHANGE Figure 7.16 25 DETERMINING STABILITY DEPENDS UPON ENVIRONMENTAL LAPSE RATE 26 13  10/28/24 CONDENSATION PROCESS OCCURS WHEN AIR IS SATURATED CLOUDS FOG REQUIRES CONDENSATION NUCLEI (2 mm) SMOKE, POLLUTION, DUST WATER DROPLETS GROW AROUND NUCLEI 27 CONDENSATION PROCESSES COLLISION-COALESCENCE BERGERON PROCESS PROCESS COLDER/TALLER CLOUDS WARMER CLOUDS WATER IN ALL THREE PHASES NOT COMMON ELSEWHERE ICE CRYSTALS FORM PRIMARILY IN TROPICS ATTRACT NEARBY SUPERCOOLED CLOUD DROPLETS COLLIDE AND WATER DROPLETS GROW (UP TO 5 mm) UNTIL ICE CRYSTALS INCREASE IN SIZE THEY FALL DUE TO WEIGHT MAY MELT ON WAY TO GROUND AND FORM RAIN 28 14  10/28/24 VIRGA 29 30 15  10/28/24 TYPES OF CLOUDS AND FOG SEE PAGES 160-164 31 CLOUDS DEFINITION THREE BASIC FORMS OF CLOUDS STRATIFORM CUMULIFORM CIRROFORM FURTHER CLASSIFIED BASED ON ELEVATION CIRRO – STRATO (NIMBO) ALTO – CUMULO 32 16  10/28/24 CIRRUS CLOUDS 33 CIRROCUMULUS CLOUDS 34 17  10/28/24 ALTOCUMULUS CLOUDS 35 ALTOSTRATUS CLOUDS 36 18  10/28/24 NIMBOSTRATUS 37 STRATOCUMULUS 38 19  10/28/24 STRATUS 39 CUMULUS 40 20  10/28/24 CUMULONIMBUS 41 CUMULUS CLOUDS OVER AFRICA 42 21  10/28/24 FIELD OF CUMULONIMBUS Over Gulf of Mexico- hazy surface conditions 43 CUMULUS CLOUD STREETS B.C. Maldives 44 22  10/28/24 FOG ADVECTION FOG EVAPORATION FOG (SEA SMOKE) UPSLOPE FOG VALLEY FOG RADIATION FOG 46 ADVECTION FOG Warm air Cold water 47 23  10/28/24 EVAPORATION FOG Cold air Warm water 48 UPSLOPE FOG air rm Wa 49 24  10/28/24 VALLEY FOG Cold air 50 VALLEY FOG (SCHMON TOWER) 51 25  10/28/24 VALLEY FOG (CENTRAL VALLEY, CA) 52 RADIATION FOG 53 26