Weather Processes and Systems Part I Principles of Earth Science 15a Read 15a Introduction 15 2 Weather Processes up to Air Masses Ch VIII Atmosphere and Weather Watch 8 5 The making of a cloud How did clouds get their names Cloud spotting guide National Weather Service How Clouds Form https www weather gov jetstream formation What is Weather Weather is the short term day to day condition of the atmosphere What is Climate Climate is the long term avg of weather conditions What is Meteorology Meteorology is the scientific study of the atmosphere including its physical characteristics and motions Meteor heavenly or of the atmosphere Humidity the amount of water vapor present in the air Dependent on the air temperature Relative Humidity at a specific temperature Relative Humidity Instrument to Measure Humidity Hygrometer Uses human hair that either gains or loses water in the air connected to a gauge Sling Psychrometer 2 Thermometers side side dry wet High Humidity little water evaporates from wick Low Humidity more water evaporates from wick Atmospheric Stability Parcel body of air that has specific temp and humidity Two opposing forces determine the vertical position Buoyant Force upward Parcel of lower density than surrounding air is buoyant so it rises a rising parcel expands as external pressure decreases Gravitational Force downward Parcel of higher density than surrounding air is not buoyant so it descends under the force of gravity a falling parcel compresses as external pressure increases Figure 1 Ascent profile of subjects and study locations during the expedition to Mount Everest Nepal Values of PB indicate the mean barometric pressure at each laboratory for the duration of the study 1 kPa 10 millibars Adiabatic Process Ascending rising parcel of air cools by expansion responding to the reduced air pressure at higher altitudes Descending falling parcel heats by compression Temperature changes in ascending and descending air parcels are Adiabatic Meaning they occur as a result of expansion or compression W o any significant heat exchange between the surrounding env and the vertically moving parcel of air Dry Adiabatic Rate Dry Adiabatic Lapse Rate Rising air parcel not yet been cooled to saturation Dry Adiabatic Lapse Rate 10 C per 1000 m 5 5 F per 1000 ft Parcel of air is raised 1 km its temperature will drop by 10 C Dry rate no condensation during this process Moist Adiabatic Rate Rising air cools less rapidly because condensation releases latent heat energy Moist Adiabatic Lapse Rate ranges between 4 and 9 C per 1000 m 2 2 4 9 F per 1000 ft depends on the temperature pressure moisture content Usually use 5 C per 1000 m To Get Rain Moisture in the atmosphere Need thick layer Condensation nuclei Something for water vapor to hold on to so gravity can pull it down Dust most common Smoke Pollen Salts Coalesced water vapor but very small droplets Cloud consists of water droplets ice particles or a mixture of both These form on tiny condensation nuclei which are normally minute specks of sea salt or dust Cloud drops condense on small particulates called cloud condensation nuclei Cirrus High thin wispy clouds drawn out into streaks Composed of ice crystals they form when moisture is present high in the air Lenticular or lens shaped cloud forms as moist air flows up and over a mountain peak or range Cumulus clouds are puffy fair weather cumulus clouds Altocumulus clouds are midlevel clouds arranged in lines or groups http weather ou edu smglenn clouds html Cloud Types Identification Name That Cloud R Ruggiero Fog Cloud on the ground Visibility less than 1km 3300 ft Means air temp and dew point temp at ground level are almost the same saturated conditions Radiation Fog Advection Fog Review Weather vs Climate Humidity Relative Humidity Instruments to measure humidity atmospheric stability adiabatic process DAR MAR How does rain form How do clouds form What are some basic types of clouds What weather do some clouds indicate are expected Where would you expect Advection Fog Where would you expect Radiation Fog Any Questions