Relative Humidity and Dew Point Temp Practice



Research Earth Science AgendaFebruary 9, Thursday:A Day2nd block: NEW SEATING CHART – Find your seat (Promethean)Take out your agendas from Feb 3 & 7Any more weather station model practice activities? pass it forwardWARM-UPS:Quick review of Rel Humidity and Dew Point temperature(DP%20&%20RH)/ESRT%20page%2012%20index.htm Differentiate between Relative AND Specific HumidityDiscuss conditions that result in HIGH relative humidity and LOW relative humidityExplain WHY air holding 10 grams of water vapor at 80 degrees F has a LOWER relative humidity than air holding 10 grams of water vapor at 50 degrees F. Describe the significance of the dew point temperatureWhy do meteorologists use dew point as a more accurate measure to predict precipitation?DESCRIBE how to use a sling psychrometer – BE SPECIFIC! Your description should enable a student to accurately measure relative humidity and understand the purpose of EACH thermometer.OBJECTIVES:METEOROLOGY: Water in the atmosphereCheck the following: LAB: Measuring Relative Humidity and Dew Point CAREFULLY FOLLOW ALL INSTRUCTIONS AND BE SURE TO ACCURATELY RECORD ALL TEMPERATURES!AFTER YOU COLLECT ALL DATA, take out your Relative Humidity and Dew Point temperature HW – we will go over theseHOMEWORK:Review all notes on water in the atmosphere BE SURE YOU ALSO KNOW THE FOLLOWING:The N. Hemisphere has more land than waterThe S. Hemisphere has more water than landHow does this affect Global Temperatures?Air moves from HIGH to LOW pressure – creates breezes and windsEffect of Earth’s rotation?Coriolis EffectGlobal Winds form from global pressure belts (air moves from high to low pressure)Temperature and humidity (moisture) determine air density and air pressureElevation/altitude also affects air pressureComplete the Relative Humidity and Dew Point Temperature LabBEGIN THE WATER IN THE ATMOSPHERE TEST REVIEWQUIZ CORRECTIONS – SAME FORMAT – WRITE OUT THE COMPLETE QUESTION AND CORRECT ANSWER for all missed responses. INCLUDE diagramsRelative Humidity and Dew Point Temp PracticeName:_______________________BLOCK:_________Dew Point Temp Worksheet Complete the chart below using the Rel. Humidity and Dew Point Temp. Tables. Note the Wet Bulb Depression is the difference between the wet-bulb and dry-bulb thermometers.Air Temp(C)Wet Bulb Temp(C)Diff. betw. wet and dry bulb(C)Dew Point Temperature(C)1181322826314848450-36-11-127151081410Relative Humidity WorksheetComplete the chart below using the Tables on page 704 of your Earth Science Reference Tables.Air Temp(C)Wet Bulb Temp(C)Wet Bulb Depression(C)Relative Humidity(%)12416228183201744-151916615107232180-362293567818000For questions #1-10, refer to the graph below, which shows the hourly surface temperature, dew point, and relative humidity for a twenty-four hour period during the month of May. The lowest air temperature occurred at what time? The highest relative humidity reading occurred at what time?The highest air temperature occurred at about what time?The lowest relative humidity occurred at about what time?According to the graph, what happens to the relative humidity as the air temperature increases?At what time(s) did the air temperature equal the dew point?What was the relative humidity (%) when the air temperature equaled the dew point?Condensation (water coming out of the air) is most likely to occur at approximately what time?At approximately what time was the rate of evaporation highest?The greatest change in air temperature occurred during the period from: A) midnight to 6AM C) noon to 6PM B) 6AM to noon D) 6PM to midnight____________________________________________________________________________________________________Use the following tables for your calculations. You may also use pg. 704 in your text bookSling Psychrometer Lab ActivityTwo instruments used to measure humidity are the Sling Psychrometer and Hair Hygrometer. The Sling Psychrometer works on the principle that evaporation is a cooling process (evaporation causes cooling). The sling Psychrometer has 2 thermometers – a wet bulb and a dry bulb thermometer. The wet-bulb has a wet wick around the end. The dry-bulb is a regular thermometer. You gently rotate (sling) the psychrometer in the air. The dry-bulb thermometer is measuring the air temperature. The wet-bulb is measuring evaporation. As water evaporates from the wick, the temperature of the thermometer decreases (evaporation causes cooling). The drier the air (less moisture), the greater the decrease in temperature and the greater the difference between the wet and dry bulb temperatures. For moist air, less evaporation occurs and there is little change in the wet-bulb temperature and less of a difference between wet and dry bulb temperatures. IF there is NO difference between the 2 temperatures, the air is saturated (air is holding all the moisture it is capable of holding at that temperature). Therefore, there is no evaporation taking place.The Hair Hygrometer works on the principle that hair expands when wet and shrinks when dry. The needle goes up with higher humidity (more water vapor in the air) and goes down with lower humidity (drier air). Sling Psychrometer LAB ActivityWrite a Purpose and Hypothesis for this lab.WRITE a BRIEF BACKGROUND (explaining all the concepts used in the lab)You will be CALCULATING the relative humidity AND dew point temperature from your dataYOU MUST show all calculations!!Procedures:Lightly wet the wick on the thermometer of your sling psychrometer.Using your data table, record the initial temperatures of BOTH thermometers starting with the wet-bulb temperature. Gently sling your psychrometer for approx. ONE minute.Check the wet bulb temperature FIRST, followed by the dry-bulb temperature. If the temperature has changed, be sure to make a note of this.Continue slinging your psychrometer and checking the temperatures (approx. 30 sec intervals) UNTIL the wet-bulb temperature stops decreasing.NOTE: If the wet-bulb temperature begins to INCREAS (rise), you went “too far”. All the water had evaporated so the thermometer is simply recording the air temperature.SUBTRACT the final wet and dry bulb temperatures.Use the Relative Humidity Chart (dry bulb temperature and the difference between the wet and dry-bulb temperatures) and record the relative humidity as a %. NAME:DATE:Class Period:INSTRUCTION SHEET & FORMAL LAB REPORT:Finding Dew Point & Relative HumidityINSTRUCTIONS:You will be using a sling psychrometer It is not necessary that the temperatures on both thermometers of the psychrometer be identical. BUT, this may introduce a small error in your findings.Procedures for using the Sling Psychrometer:Be sure the wet bulb thermometer is WETRecord the initial temperatures in your “Field Data Tables”Gently twirl the psychrometer for approx. 1 minuteRecord BOTH temperatures BEGINNING with the WET-BULBGently twirl the psychrometer for an additional 30 – 45 secs (approx.)Record the temperatures (always record WET-BULB 1st)Twirl the psychrometer for approx. 20 secondsRecord both temperaturesTwirl for approx. 10 secondsRecordContinue twirling for 10 second intervals until the wet-bulb temperature stops falling:IF the wet-bulb temperature increases, you twirled the instrument for too long a time.Use the last wet-bulb temperature. that showed a decreaseRecord these on your data sheet found in the lab.Determine the Dew Point Temperature & Relative Humidity using the reference tables on pg.704 of your text book or the tables on your agendaRecord on your lab data sheet. SHOW calculations or make note of how you found the final relative humidity and dew point temperatureANALYSIS:Why SHOULD you run the experiment SEVERAL TIMES and average the results?Why was the wet-bulb temperature always less than the dry bulb temperature?Could the wet- & dry- bulb temperatures be the same? EXPLAIN:Could the wet-bulb be higher than the dry-bulb temperature? EXPLAIN:Explain the relationship between difference in the wet- & dry-bulb temperatures and % of moisture in the airWhat units are used for dew point temperature? For Relative Humidity?The sling psychrometer works on the principle that …Explain WHY warm air can hold more water vapor than cooler air. Field DATA TABLESInitial Temperature1st Check2nd Check3rdCheckFinal TemperatureWet-Bulb TemperatureDry-Bulb TemperatureDifference (dry – wet)Relative HumidityDew Point TemperatureCALCULATIONS/EXPLANATION of final dew point temperature and relative humidity STUDY GUIDE FOR METEOROLOGY CUMULATIVE TESTMeteorology Vocabulary:AnemometerSling psychrometer/Hair hygrometerWeather vane BarometerThermometerIsobars (steep and gentle pressure gradients)High and low pressure areas on a mapIsothermsRelative HumiditySpecific humidityDew pointGreenhouse EffectFossil fuels and effect on Earth’s atmosphereInsolation and effect of angle of sun on Earth’s surfaceHeating of Land vs. WaterLand & Sea Breeze DiagramGraph interpretations – heating of land vs. waterAir Pressure & WindsMovement from high to low pressureHigh and Low pressure areasDirection of Winds Weak vs. gentle pressure-gradientsSinking vs. rising air – temperature & density dependent and effect on air pressureAreas on Earth where pressure is always low (why) and high (why)Earth’s rotation and effect on winds – GLOBAL WINDS AND PRESSURE BELTS (know the diagram)!Coriolis effectDirection of deflection (turning) in Northern and Southern hemispheresRelative Humidity & Dew point temperaturesHow to calculate AND INTERPRETAir Masses, Clouds, and FrontsDefinition of air massTypes of air masses – locationsAssociated temperature and humidityTypes of FrontsSymbolsDirection of movementAssociated weather and clouds (STORMS)Hurricanes and TornadoesConditions for formationLocation of formation ................
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