METEOROLOGY CLASS #1 LT LAZARUK AND WO2 LUCAS LAMOUREUX

METEOROLOGY CLASS #1 LT LAZARUK AND WO2 LUCAS LAMOUREUX

CLASS #1 OVERVIEW WHAT WILL YOU BE LEARNING AN INTRODUCTION THE ATMOSPHERE CLOUDS STABILITY TEMPERATURE & HUMIDITY

INTRODUCTION

PART 1 INTRODUCTION IN THE INTRODUCTION SECTION THE FOLLOWING WILL BE COVERED: UNDERSTANDING THE HEMISPHERE'S ATMOSPHERIC BALANCE

UNDERSTANDING THE HEMISPHERES MOST (IF NOT ALL) THE MATERIAL IN METEOROLOGY WILL BE LIMITED TO THE NORTHERN HEMISPHERE. AS A GLIDER PILOT OR PRIVATE PILOT, IT IS UNLIKELY YOU WILL FLY IN THE SOUTHERN HEMISPHERE. HOWEVER MOST OF THE TOPICS WE DISCUSS WILL BE THE INVERSE FOR THE SOUTHERN HEMISPHERE (I.E. THE OPPOSITE)

ATMOSPHERIC BALANCE BEFORE BEGINNING, WE MUST DISCUSS THE IDEA OR CONCEPT OF ATMOSPHERIC BALANCE. WHENEVER THE ATMOSPHERE IS OUT OF BALANCE IT WILL ALWAYS ACT TO RE-BALANCE ITSELF! THESE PROCESSES OF RE-BALANCING ARE RESPONSIBLE FOR CREATING WEATHER.

SUMMARY OF INTRODUCTION THIS STUDY OF WEATHER LIMITED TO NORTHERN HEMISPHERE UNBALANCED ATMOSPHERE CREATES WEATHER

THE ATMOSPHERE

PART 2 THE ATMOSPHERE IN THE SECTION OF THE ATMOSPHERE THE FOLLOWING TOPICS WILL BE COVERED: OUR ATMOSPHERE AND ITS COMPOSITION DIVISIONS OF THE ATMOSPHERE (MAINLY SELF-STUDY) PROPERTIES OF THE ATMOSPHERE (MAINLY SELF-STUDY) ICAO STANDARD ATMOSPHERE

OUR ATMOSPHERE THE ATMOSPHERE IS A MIXTURE OF GASES NITROGEN 78% OXYGEN 21% OTHER GASES 1% FROM A WEATHER STANDPOINT WATER VAPOUR IS THE MOST IMPORTANT COMPONENT OF THE ATMOSPHERE BUT WHY? Nitrogen Oxygen Other Gases

PROPERTIES OF THE ATMOSPHERE THE 3 PROPERTIES OF THE ATMOSPHERE MOBILITY CAPACITY FOR EXPANSION CAPACITY FOR COMPRESSION CAPACITY FOR EXPANSION IS THE MOST IMPORTANT PROPERTY BUT WHY? THE PROPERTIES OF THE ATMOSPHERE IS MAINLY A SELF STUDY TOPIC.

DIVISIONS OF THE ATMOSPHERE THE ATMOSPHERE IS DIVIDED INTO DISTINCT LAYERS THAT SURROUND THE EARTH: REMEMBER! THE SUN MELTS THE EARTH THE LAYERS OF THE ATMOSPHERE ARE MAINLY A SELF-STUDY TOPIC.

THE TROPOSPHERE SELF-STUDY TOPIC LOWEST LAYER OF THE ATMOSPHERE THICKNESS VARIES WITH LATITUDE APPROX. 28,000 FT OVER POLES APPROX. 54,000 FT OVER EQUATOR MOST WEATHER OCCURS THIS LAYER HINT WATER VAPOUR PRESSURE, TEMPERATURE AND DENSITY DECREASE WITH HEIGHT UPPER BOUNDARY IS CALLED THE TROPOPAUSE; TEMPERATURE CAN IS APPROXIMATELY -56 DEGREES CELCIUS

THE STRATOSPHERE SELF-STUDY TOPIC HARDLY NO WATER VAPOUR PRESENT OZONE LAYER EXISTS IN THE STRATOSPHERE PRESSURE DECREASES WITH HEIGHT, BUT TEMPERATURE RISES FROM APPROXIMATELY -56 CELSIUS TO 0 CELSIUS WHY? OZONE LAYER ABSORBS SOME OF THE SUN S RAYS UPPER BOUNDARY IS CALLED THE STRATOPAUSE

THE MESOSPHERE SELF-STUDY TOPIC SIGNIFICANT DECREASE IN TEMPERATURE

THE THERMOSPHERE SELF-STUDY TOPIC RELATIVELY A SIGNIFICANT INCREASE IN TEMPERATURE OVER 100 KM ABOVE THE SURFACE OF THE EARTH THERE ARE FEW AIR MOLECULES IN THIS LAYER

THE EXOSPHERE SELF-STUDY TOPIC KNOWN AS A TRANSITION LAYER TO SPACE TEMPERATURE CONTINUES TO RISE OVER 3,000 CELSIUS PRESSURE DECREASES TO ALMOST PERFECT VACUUM AIR BECOMES THINNER AND THINNER WITH HEIGHT AROUND 150 KM ABOVE THE EARTH, SATELLITES NO LONGER NEED AERODYNAMIC LIFT TO STAY ALOFT

ICAO STANDARD ATMOSPHERE THIS IS AN IMPORTANT TOPIC TO REMEMBER THINK OF THIS AS THE IDEAL OR PERFECT FOR THE NORTHERN HEMISPHERE, THE ICAO ATMOSPHERE IS DEFINED AS BELOW: AIR IS A PERFECTLY DRY GAS MSL IS 29.92 HG (INCHES OF MERCURY) MSL TEMPERATURE IS 15C STANDARD LAPSE RATE IS 1.98 / 1000 FEET

CLOUDS

PART 3 CLOUDS THE FOLLOWING WILL BE COVERED IN THIS SECTION: CLOUD FORMATION CLASSIFICATION OF CLOUDS CLOUD NOMENCLATURE DEFINING THE SKY USING OKATAS THE NAMES OF CLOUDS ARE MAINLY A SELF-STUDY TOPIC.

CLOUD FORMATION THERE ARE TWO WAYS CLOUDS CAN FORM: CUMULIFORM (PUFFY AND VERTICALLY TENDING) VERTICALLY UNSTABLE BAD TURBULENCE BUT GOOD RELATIVE VISIBILITIES STRATOFORM (HORIZONTAL LAYERS) HORIZONTALLY STABLE SMOOTH BUT BAD RELATIVE VISIBILITIES

CUMULIFORM CLOUDS CLOUD TYPE #1 CUMULIFORM CLOUDS ARE BIG, PUFFY CLOUDS THAT DEVELOP UPWARDS INTO THE SKY THEY ARE UNSTABLE, TURBULENT CLOUDS THAT HAVE GOOD RELATIVE VISIBILITIES. WHY? BECAUSE OF THE INSTABILITY WITHIN THIS CLOUD INSIDE THESE CLOUDS, STRONG VERTICAL UP/DOWN DRAFTS PUSH THE CLOUD UPWARD, EXTENDING IT UP INTO THE ATMOSPHERE. THESE VERTICAL UPDRAFTS ALSO CREATE STRONG TURBULENCE WITHIN THE CLOUD. CAN YOU IMAGINE flying THROUGH THIS CLOUD? THESE VERTICAL UPDRAFTS ALSO MIX AROUND AND PUSH ALL OF THE IMPURITIES WITHIN THE CLOUD UP AND OUT OF THE PILOT S VIEW SO THERE IS LESS OF THESE IMPURITIES IN ANY ONE AREA. THIS RESULTS IN BETTER VISIBILITIES INSIDE THIS CLOUD TYPE.

STRATOFORM CLOUDS ARE LAYER-TYPE CLOUDS THAT DEVELOP IN HORIZONTAL LAYERS. THEY ARE STABLE, SMOOTH CLOUDS THAT HAVE POOR RELATIVE VISIBILITIES. WHY? BECAUSE THEY ARE VERY STABLE. THERE ARE NO UP/DOWN DRAFTS INSIDE THESE CLOUDS SO THEY TEND TO DEVELOP IN HORIZONTAL STABLE LAYERS. WHEN flying THROUGH, BECAUSE THESE CLOUDS ARE SO STABLE, IT IS A VERY SMOOTH RIDE. NOW BECAUSE THERE ARE NO UP/DOWN DRAFTS, ALL THE IMPURITIES IN THE CLOUD JUST SETTLE INTO A HORIZONTAL LAYER MEANING THAT THERE IS A GREATER CONCENTRATION OF THEM IN ANY GIVEN SPOT. THUS THE VISIBILITY IS RELATIVELY POORER.

THE HOW-TO GUIDE CLOUD FORMATION WHEN A WARM, MOIST PARCEL OF AIR STARTS RISING BECAUSE IT S LESS DENSE THAN THE OTHER AIR AROUND, IT BEGINS TO COOL (TEMPERATURE DECREASES AS WE GAIN ALTITUDE). AS THE RISING WARM AIR BEGINS TO COOL, IT STARTS TO EXPAND. (ATMOSPHERIC PROPERTY: CAPACITY FOR EXPANSION) WHEN THE RISING AIR COOLS ENOUGH (SO IT IS THE SAME TEMPERATURE AS THE SURROUNDING AIR), IT WILL STOP RISING. THIS IMAGINARY BOUNDARY WHERE THE RISING WARM AIR STOPS RISING IS CALLED THE CONDENSATION LEVEL. THE CONDENSATION LEVEL (IN MOST CASES) IS THE CLOUD BASE BECAUSE AT THIS LEVEL, THE AIR HAS STOPPED RISING AND BEGUN TO COOL AND CONDENSE TO FORM THE BASE LAYER OF THE CLOUD.. AS THE AIR PARCEL CONTINUES COOLING AND EXPANDING, IT CONDENSES INTO WATER DROPLETS (THINK OF STEAM COOLING OFF ON YOUR HAND AND CONDENSING INTO A LIQUID).

CLOUD FORMATION CONTINUED SO WHAT BRINGS ALL THESE WATER DROPLETS TOGETHER TO ACTUALLY FORM A CLOUD? WELL, WE NEED SOMETHING CALLED CONDENSATION NUCLEI TO SPONGE TOGETHER ALL THESE WATER DROPLETS THINK ABOUT WHAT HAPPENS WHEN YOU DROP A SPONGE IN A SINK FULL OF WATER (LIQUID DROPLETS). CONDENSATION NUCLEI ACT LIKE A BIG SPONGE IN THE AIR. THE CONDENSED LIQUID DROPLETS ARE SPONGED TOGETHER BY THE CONDENSATION NUCLEI TO FORM A CLOUD. EXAMPLES OF CONDENSATION NUCEI: DUST, SMOKE, SULFUR, SMOG, POLLUTANTS DEPENDING ON THE AMOUNT OF INSTABILITY AND MOISTURE IN THIS NEWLY CREATED CLOUD, THE ATMOSPHERE IS CAPABLE OF PRODUCING A WIDE RANGE OF CLOUDS FROM LOW RAIN CLOUDS TO VIOLENT STORMS.

CLASSIFICATION OF CLOUDS RECALL: CLOUDS CAN BE GROUPED ACCORDING TO HOW THEY FORM (CUMULIFORM OR STRATOFORM) DEPENDING ON WHERE A CLOUD FORMS AND ITS COMPOSITION, WE CAN FURTHER CLASSIFY CLOUDS INTO 4 DISTINCT CLOUD FAMILIES: HIGH CLOUDS MIDDLE CLOUDS LOW CLOUDS CLOUDS OF VERTICAL DEVELOPMENT

THE 4 CLOUD FAMILIES HIGH CLOUDS BASES RANGE FROM 16,500 FT TO 45,000 FT COMPOSED OF MAINLY ICE CRYSTALS MIDDLE CLOUDS BASES RANGING FROM 6,500 FT TO 23,000 FT COMPOSED OF ICE CRYSTALS AND WATER DROPLETS (SOME SUPER COOLED) LOW CLOUDS SUPER COOLED WATER DROPLETS STAY IN LIQUID FOR BETWEEN 0C AND -15C. AS SOON AS THEY CONTACT A SURFACE THEY IMMEDIATELY FREEZE. WHY MAY THIS HAVE IMPORTANCE? BASES RANGING FROM 0 FT TO 6,500 FT COMPOSED OF MAINLY WATER DROPLETS (SOME SUPER COOLED)

THE 4 FAMILIES CONTINUED CLOUDS OF VERTICAL DEVELOPMENT THESE ARE ALWAYS CUMULIFORM CLOUDS BASES RANGE FROM 1,500 FT TO 45,000 FT COMPOSED OF ICE CRYSTALS, WATER DROPLETS AND SUPER COOLED WATER DROPLETS BEWARE: THESE CUMULIFORM CLOUDS MAY BE EMBEDDED (HIDING) WITHIN INNOCENT LOOKING STRATOFORM CLOUDS YOU COULD BE FLYING IN STABLE STRATOFORM CLOUDS AND WITHOUT WARNING, ENCOUNTER SEVERE TURBULENCE.

CLOUD NOMENCLATURE THERE ARE TWO PARTS TO MOST CLOUD NAMES: THE FIRST PART OF THE NAME: LOCATION AND HEIGHT HIGH CLOUDS CIRRO MIDDLE CLOUDS ALTO LOW CLOUDS STRATO THE SECOND PART OF THE NAME: CHARACTERISTICS CUMULIFORM (UNSTABLE) CLOUDS CUMULUS STRATOFORM (STABLE) CLOUDS STRATUS

CLOUD NAME EXAMPLE LET S TRY AN EXAMPLE CIRROCUMULUS CIRRO - THIS CLOUD IS PART OF THE HIGH CLOUD FAMILY CUMULUS - THIS CLOUD IS VERTICALLY UNSTABLE BUT OFFERS RELATIVELY GOOD VISIBILITY.

WELL-KNOWN CLOUDS HERE IS A LIST OF ALL KNOWN CLOUDS WITHIN THEIR RESPECTIVE CLOUD FAMILIES HIGH CLOUDS CIRRUS* CIRROSTRATUS CIRROCUMULUS MIDDLE CLOUDS ALTOSTRATUS ALTOCUMULUS ALTOCUMULUS CASTELLANUS LOW CLOUDS STRATUS* (A.K.A FOG) NIMBOSTRATUS* (THE TERM NIMBO MEANS RAIN CLOUD ) STRATOCUMULUS CLOUDS OF VERTICAL DEVELOPMENT CUMULUS* TOWERING CUMULUS CUMULONIMBUS* (COMMONLY REFERRED TO AS CB OR STORM CLOUDS) *INDICATES CLOUDS WHOSE NAMES DO NOT FOLLOW TRADITIONAL NOMENCLATURE RULES.

OKTAS WE WILL USE A MEASURING SYSTEM CALLED OKTAS TO MESSURE HOW MUCH OF THE SKY IS ACTUALLY COVERED BY CLOUDS THERE ARE FIVE DIFFERENT SKY CONDITIONS THAT ARE MEASURED USING OKTAS OKATAS ARE THE METHOD IN WHICH WE CLASSIFY CLOUD COVERAGE IN METAR S AND TAF S

OKTAS CONTINUED WE WILL DIVIDE THE SKY INTO 8 SEGMENTS WHICH WE WILL CALL OKTAS AS MORE OF THESE SEGMENTS BECOME COVERED WITH CLOUD, THE SKY BECOMES CLOUDIER AND THE NUMBER OF OKTAS OF CLOUD IN THE SKY INCREASE. A CLOUDLESS SKY WOULD MEAN THAT THERE ARE 0 OKTAS OF CLOUD COVERING THE SKY. AN OVERCAST SKY WOULD MEAN THAT THE SKY IS COMPLETELY COVERED BY CLOUD THUS 8 OKTAS OF THE SKY IS COVERED IN CLOUD.

OKTAS CONTINUED 2 THE FOLLOWING OKTAS ARE ASSOCIATED WITH EACH SKY CONDITION NUMBER OF OKTAS ABRREVIATION NAME OF COVERAGE MEANING 0 SKC SKY CLEAR 0/8 SKY COVERED 1 2 FEW FEW CLOUDS 1/8 TO 2/8 SKY COVERED 3 4 SCT SCATTED 3/8 TO 4/8 SKY COVERED 5 7 BKN BROKEN 5/8 TO 7/8 SKY COVERED 8 OVC OVERCAST 8/8 SKY COVERED

VFR PILOTS AND OKTAS VFR PILOTS CANNOT FLY IN CLOUDS! BUT HOW MUCH CLOUD IS TOO MUCH? PIOTS CAN ACTUALLY FLY THROUGH CLOUDS SO LONG AS THE CLOUDS ARE BELOW A BROKEN CONDITION. THIS MEANS THAT IF THERE IS A SCATTERED LAYER OF CLOUDS AT 2,000 FT, A VFR PILOT MAY FLY ABOVE THAT LAYER OF CLOUD HOWEVER, IF THERE IS A BROKEN LAYER OF CLOUD AT 2,000 FT, A VFR PILOT MUST REMAIN UNDERNEATH THAT CLOUD

ATMOSPHERIC STABILITY

PART 4 ATMOSPHERIC STABILITY IN THIS SECTION THE FOLLOWING WILL BE COVERED DEFINITION OF STABILITY WEATHER AND STABILITY THE 5 ATMOSPHERIC LIFTING AGENTS

STABILITY AIR TENDS TO MOVE IN A HORIZONTAL FASHION, BUT SOMETIMES THERE ARE DISTURBANCES THAT MAY CAUSE VERTICAL UPDRAFTS AND DOWNDRAFTS TO DEVELOP. STABLE AIR WILL RESIST THESE DISTURBANCES AND REMAIN IN A HORIZONTAL LAYER. IF A MASS OF STABLE AIR IS DISTURBED BY A LIFTING AGENT, STABLE AIR WILL RETURN TO ITS ORIGINAL LEVEL. (LIFTING AGENTS WILL BE DISCUSSED IN ANOTHER POWER POINT) UNSTABLE AIR WILL MOVE MORE VERTICALLY AND NOT RESIST THESE DISTURBANCES. IF A MASS OF UNSTABLE AIR IS DISTURBED BY A LIFTING AGENT, UNSTABLE AIR WILL BEGIN TO RISE MORE VIOLENTLY AND QUICKLY.

FLIGHT CHARACTERISTICS & STABILITY!!!THE FOLLOWING COMPARISONS ARE RELATIVE TO ONE ANOTHER!!! STABLE AIR (ASSOCIATED WITH STRATOFORM CLOUDS) POOR VISIBILITY SMOOTH FLYING CONDITIONS STEADY PRECIPITATION (CHARACTERISTIC OF STRATOFORM CLOUDS) UNSTABLE AIR (ASSOCIATED WITH CUMULUS-TYPE CLOUDS) RELATIVELY GOOD VISIBILITY TURBULENT FLYING CONDITIONS SHOWERY PRECIPITATION (CHARACTERISTIC OF CUMULIFORM CLOUDS)

THE 5 LIFTING AGENTS SO WHAT EXACTLY CAUSES AIR TO RISE IN THE ATMOSPHERE? THERE ARE 5 SPECIFIC LIFTING FORCES (AGENTS) THAT FORCE AIR TO RISE: CONVECTION OROGRAPHIC LIFT FRONTAL LIFT MECHANICAL TURBULENCE CONVERGENCE

CONVECTION PERHAPS THE MOST COMMON CONDITION THAT EXPLAINS WHY AIR RISES IS CONVECTION. RECALL: WARM AIR RISES AND COLD AIR SINKS. WHEN WARM AIR RISES, THIS CREATES AN IMBALANCE. SO COOLER AIR MUST COME BACK DOWN TO REPLACE THE RISING WARM AIR THAT HAS LEFT THE EARTH S SURFACE. THE RESULT IS A CONVECTIVE CYCLE WHERE AIR RISES (BECAUSE IT IS WARMER) AND THEN SINKS (BECAUSE IT IS COLDER AND BECAUSE IT HAS TO REPLACE WHAT HAS BEEN TAKEN FROM THE EARTH S SURFACE) THIS IS PRECISELY WHAT CONVECTION IS AND IS ONE LIFTING AGENT THAT FORCES AIR TO RISE

OROGRAPHIC LIFT SUPPOSE: YOU HAVE A MOUNTAIN RANGE AND AN AIR MASS AT THE BOTTOM OF THE MOUNTAIN RANGE IF THERE IS A WIND BLOWING (EXERTING A FORCE) ON THE AIR MASS, THE AIR MASS WILL BE FORCED UP THE MOUNTAIN RANGE... FORCING IT UP INTO THE ATMOSPHERE! THIS FORCE (LIFTING AGENT) CALLED OROGRAPHIC LIFT IS THE SECOND WAY IN WHICH AN AIR MASS CAN BE MADE TO RISE IN THE ATMOSPHERE

FRONTAL LIFT SUPPOSE: THERE ARE TWO AIR MASSES APPROACHING EACH OTHER AND ONE OF THE AIR MASSES IS COLDER (DENSER) THAN THE OTHER. THE COLDER (DENSER) AIR MASS WILL BE FORCED UNDER THE WARMER (LESS DENSE) AIR MASS. THIS LIFTING AGENT THAT IS FORCING WARM AIR ALOFT IS CALLED FRONTAL LIFT BECAUSE WHEN 2 AIR MASSES INTERACT WITH ONE ANOTHER, A FRONT IS CREATED THUS IT MAKES SENSE TO CALL THIS LIFTING FORCE, FRONTAL LIFT. WE WILL DISCUSS THE FORMATION OF FRONTS LATER.

MECHANICAL TURBULENCE RECALL: MECHANICAL TURBULENCE IS CREATED WHEN WIND COMES INTO CONTACT WITH BUILDINGS, MOUNTAINS, ETC... FRICTION BETWEEN THE AIR AND THE GROUND DISRUPTS THE LOWER LEVELS OF AIR INTO A SERIES OF EDDIES (LITTLE TURBULENT POCKETS OF AIR). THESE EDDIES ARE USUALLY CONfiNED TO THE LOWER LEVELS OF THE ATMOSPHERE BUT MAY EXTEND HIGHER IF THE AIR IS UNSTABLE THESE TURBULENT EDDIES CAN SPREAD THROUGHOUT THE ATMOSPHERE, CARRYING AIR WITH THEM... THIS LIFTING AGENT IS CALLED MECHANICAL TURBULENCE

CONVERGENCE PRESSURE (WIND) FLOWS INWARDS TO A LOW PRESSURE SYSTEM WE HAVEN T LEARNED THIS YET. WHAT DO YOU THINK HAPPENS TO THE EXCESS PRESSURE FLOWING INTO THE LOW PRESSURE SYSTEM? IT MUST GO SOMEWHERE! IT CAN T REALLY GO DOWN INTO THE EARTH AND CAN T GO SIDE-TO-SIDE SO THE EXCESS AIR IS FORCED UPWARD AND ANY AIR MASSES DIRECTLY ABOVE THE CONVERGING LOW PRESSURE SYSTEM WILL THUS BE FORCED UPWARD AS WELL THIS LIFTING AGENT IS THUS CALLED CONVERGENCE.

TEMPERATURE AND HUMIDITY

PART 5 TEMPERATURE AND HUMIDITY THE FOLLOWING WILL BE COVERED IN THIS SECTION: CHANGES OF STATE RELATIVE HUMIDITY DEW POINT LAPSE RATE

CONDENSATION CHANGES OF STATE VAPOUR IS COOLED THEN BECOMES LIQUID SUBLIMATION VAPOUR IS COOLED RAPIDLY THEN BECOMES SOLID EVAPORATION LIQUID IS HEATED AND BECOMES VAPOUR MELTING SOLID BECOMES LIQUID FREEZING LIQUID BECOMES SOLID

RELATIVE HUMIDITY DEFINED AS THE PERCENTAGE OF WATER VAPOUR IN THE AIR SATURATED OR WET AIR HAS 100% RELATIVE HUMIDITY COMPLETELY DRY AIR HAS 0% RELATIVE HUMIDITY FOR EXAMPLE: IF THE RELATIVE HUMIDITY IS 50%, HALF OF ANY GIVEN PARCEL OF AIR WOULD BE SATURATED. SINCE THE ATMOSPHERE IS MADE UP OF MANY PARCEL S OF AIR, 50% HUMIDITY IMPLIES THAT HALF THE ATMOSPHERE IS SATURATED.

CHANGING THE RELATIVE HUMIDITY RECALL: WHAT HAPPENS WHEN WE HEAT AN AIR MOLECULE? DOES IT GROW IN SIZE? IF YOU HEAT A MASS OF AIR AND THE AMOUNT OF WATER VAPOUR DOES NOT CHANGE, THE RELATIVE HUMIDITY WILL DECREASE. AS YOU HEAT UP A PARCEL OF AIR, IT WILL EXPAND THUS INCREASING THE SIZE OF THE PARCEL OF AIR AS THE SIZE OF THE PARCEL OF AIR INCREASES AND IF THE WATER VAPOUR CONTENT DOES NOT CHANGE, THERE IS MORE ROOM FOR THE SAME AMOUNT OF WATER VAPOUR INSIDE AND THUS THE % OF WATER VAPOUR IN THE LARGER PARCEL OF AIR DECREASES... THUS THE RELATIVE HUMIDITY DECREASES. WHEN YOU COOL A PARCEL OF AIR, THE RELATIVE HUMIDITY WILL INCREASE THINK ABOUT IT!

TEMPERATURE TEMPERATURE IS HOW HOT OR COLD IT IS OUTSIDE (YES WE UNDERSTAND THERE IS A PHYSICS DEFINITION FOR TEMPERATURE, BUT FOR METEOROLOGY THAT IS ALL YOU NEED TO KNOW) AN ISOTHERM JOINS PLACES (LOCATIONS) OF EQUAL TEMPERATURE THE RELATIONSHIP BETWEEN TEMPERATURE AND DENSITY AS THE TEMPERATURE INCREASE, AIR MOLECULES WILL START MOVING APART AND THE DENSITY ( CLOSENESS OF THE MOLECULES) DECREASES. AS THE TEMPERATURE DECREASES. AIR MOLECULES SLOW DOWN AND COME CLOSER TOGETHER DENSITY INCREASES.

DEW POINT RECALL: AIR MUST BE COOLED SO THAT THE WATER VAPOR IN THE AIR CAN CONDENSE AND CHANGE INTO WATER DROPLETS DEW POINT IS THE TEMPERATURE AT WHICH AIR MUST BE COOLED IN ORDER FOR CONDENSATION TO OCCUR (TO FORM CLOUDS) A PARCEL OF AIR CAN BE COOLED WHEN: THE ATMOSPHERE COOLS DOWN AT NIGHT WHEN THE PARCEL OF AIR RISES UP IN THE ATMOSPHERE AND COOLS WITH HEIGHT THE SPREAD IS THE DIFFERENCE BETWEEN THE TEMPERATURE ON THE GROUND AND THE DEW POINT IF THE SPREAD IS SMALL, CLOUDS WILL LIKELY FORM IF THE SPREAD IS LARGE, CLOUDS WILL NOT LIKELY FORM

DEW POINT CONTINUED FOR EXAMPLE: IF THE SURFACE TEMPERATURE IS 10C AND THE DEW POINT IS -3C --> THE SPREAD IS 13C. THIS MEANS THAT THE ATMOSPHERE OR AIR MASS MUST COOL BY 13C BEFORE CLOUDS CAN FORM. IN THIS CASE, A 13C SPREAD IS CONSIDERED A LARGE SPREAD... CLOUDS WILL LIKELY NOT FORM IF THE SPREAD IS SAY 2C, CLOUDS WILL LIKELY FORM BECAUSE THE ATMOSPHERE ONLY HAS TO COOL BY 2C IN ORDER FOR AN AIR MASS TO CONDENSE AND FORM CLOUDS

LAPSE RATE RECALL: AS YOU RISE UP IN THE TROPOSPHERE, THE TEMPERATURE DECREASES THE RATE AT WHICH THE TEMPERATURE DROPS AS YOU GAIN ALTITUDE IS CALLED THE LAPSE RATE THERE ARE DIFFERENT STANDARD LAPSE RATES GIVEN FOR DIFFERENT ATMOSPHERIC CONDITIONS: ICAO STANDARD LAPSE RATE -> 1.98C / 1000FT WET ADIABATIC LAPSE RATE -> 1.5C / 1000FT DRY ADIABATIC LAPSE RATE -> 3C / 1000FT THESE ARE STANDARD NUMBERS USED FOR CALCULATIONS... NOT THE ACTUAL RATES FOR ANY GIVEN DAY

LAPSE RATE AND STABILITY LAPSE RATE CAN TELL US A LOT ABOUT THE STABILITY OF THE AIR A STEEP LAPSE RATE INDICATES UNSTABLE AIR WHILE A SHALLOW LAPSE RATE INDICATES STABLE AIR BUT HOW? WHEN THE TEMPERATURE CHANGES SIGNIfiCANTLY WITH HEIGHT, THE LAPSE RATE IS STEEP. (EX OF A STEEP LAPSE RATE: 8C/ 1,000 FT MEANS THAT FOR EVERY 1,000 FEET YOU GO UP, THE TEMP DECREASES BY 8C!) FOR THE TEMPERATURE TO CHANGE SIGNIfiCANTLY WITH HEIGHT (A STEEP LAPSE RATE), WE NEED THERE TO BE COLD AIR ALOFT... SO THE TEMPERATURE DECREASES FROM WARM TO COLD QUICKLY! SINCE COLD AIR SINKS (MORE DENSE), THE COLD AIR ALOFT WILL SINK TOWARDS EARTH THOUGH THE WARM AIR THAT IS BELOW WILL BE WARMER THAN THIS NEW COOLER AIR THAT HAS JUST SUNK DOWN. THE WARM AIR WILL BE FORCED TO RISE UP. THIS CREATES VERTICAL AIR MOVEMENTS LIKE A GIANT MIXING MACHINE OF AIR THUS MAKING THE AIR UNSTABLE! AND SO A STEEP LAPSE RATE = UNSTABLE AIR!

LAPSE RATE AND STABILITY CONTINUED WHEN THE TEMPERATURE CHANGES SLOWLY WITH HEIGHT, THE LAPSE RATE IS SHALLOW WHEN THE TEMPERATURE CHANGES SLOWLY WITH HEIGHT, IT MEANS THAT THERE IS WARM AIR ALOFT... TEMPERATURE IS NOT CHANGING VERY QUICKLY BECAUSE THE DIFFERENCE IN TEMPERATURE ON THE GROUND AND UP HIGH IS SMALL (HENCE WARM AIR IS ALOFT). SINCE WARM AIR DOES NOT TEND TO RISE WITHIN ALREADY WARM AIR, NOTHING HAPPENS IN TERMS OF RISING AIR AND SO THE AIR MASS IS RELATIVELY STABLE... AND SO SHALLOW LAPSE RATE = STABLE AIR! WE CAN THEREFORE CONCLUDE: IF WE CHANGE OR MODIFY THE LAPSE RATE, THEN THE STABILITY OF THE AIR WILL ALSO CHANGE. BECAUSE THE LAPSE RATE IS NOT UNIFORM THROUGHOUT THE ATMOSPHERE, THE STABILITY OF THE ATMOSPHERE CAN VARY THROUGHOUT THE ATMOSPHERE AS A RESULT

DETERMINING CLOUD BASES AS A FUTURE CANADIAN VFR (VISUAL flight RULES) PILOT, YOU WILL BE CONCERNED ABOUT CLOUDS AND WHERE THEY WILL BE ALONG YOUR ROUTE OF TRAVEL. IN REALITY, A PILOT MAY NOT ALWAYS HAVE ACCESS TO CLOUD INFORMATION BUT IF THEY HAVE THE CURRENT TEMPERATURE AND DEW POINT FOR THE AREA THEY ARE flying INTO, HE CAN EASILY APPROXIMATE THE CLOUD BASES AND PLAN HIS flight ACCORDINGLY ALL A PILOT NEEDS IS THE SURFACE TEMPERATURE AND THE DEW POINT AND THEN WITH THIS INFORMATION, HE CAN APPROXIMATE THE CLOUD BASES ALONG HIS flight PATH AN EXAMPLE IS ON THE NEXT PAGE...

AN EXAMPLE A PILOT IS flying AT 2,000 FEET ON A HUMID DAY AND WANTS TO KNOW IF THEY WILL ENCOUNTER CLOUDS ALONG THEIR flight PATH. THE PILOT HAS THE FOLLOWING INFORMATION: CURRENT SURFACE TEMPERATURE IS 10C REPORTED DEW POINT IN THE AREA IS 4C WHAT ELSE DOES S/HE KNOW FROM THIS INFORMATION? THE SPREAD IS 6C IT S A HUMID DAY (LOTS OF MOISTURE) SO HE WILL USE THE WET ADIABATIC LAPSE RATE OF 1.5C / 1000 FEET

ANSWER TO PREVIOUS EXAMPLE IF THE AIR MUST COOL BY 6C BEFORE CONDENSATION CAN OCCUR (BEFORE CLOUDS CAN FORM), AND AIR COOLS AT 1.5C EVERY 1,000 FEET UPWARDS, THEN IT MAKES SENSE THAT THE LOWEST CLOUD BASES WILL BE FORMING AT 4,000 FEET... HERE S WHY: ON THE GROUND, THE TEMPERATURE IS 10C. AT 1,000 FEET, THE TEMPERATURE IS 8.5C (SUBTRACTED 1.5C) AT 2,000 FEET, THE TEMPERATURE IS 7C (SUBTRACTED 1.5C) AT 3,000 FEET, THE TEMPERATURE IS 5.5C (SUBTRACTED 1.5C) AT 4,000 FEET, THE TEMPERATURE IS 4C (SUBTRACTED A final 1.5C AND WE VE REACHED THE DEW POINT) SINCE THE CLOUDS (AND THEIR BASES) WILL BEGIN FORMING AT 4,000 FEET AND THE PILOT IS flying AT 2,000 FEET, THERE WILL CLEARLY BE NO CONflICT AND THEY WILL REMAIN VFR!

QUESTIONS?

READING/SELF-STUDY FOR NOTES #1 LAYERS OF THE ATMOSPHERE PROPERTIES OF THE ATMOSPHERE CLOUD NAMES