DOCSLIB.ORG

Influence of the North Atlantic Oscillation on Winter Equivalent Temperature

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Influence of the North Atlantic Oscillation on Winter Equivalent Temperature INFLUENCE OF THE NORTH ATLANTIC OSCILLATION ON WINTER EQUIVALENT TEMPERATURE J. Florencio Pérez (1), Luis Gimeno (1), Pedro Ribera (1), David Gallego (2), Ricardo García (2) and Emiliano Hernández (2) (1) Universidade de Vigo (2) Universidad Complutense de Madrid Introduction Data Analysis Overview Increases in both troposphere temperature and We utilized temperature and humidity data WINTER TEMPERATURE water vapor concentrations are among the expected at 850 hPa level for the 41 yr from 1958 to WINTER AVERAGE EQUIVALENT climate changes due to variations in greenhouse gas 1998 from the National Centers for TEMPERATURE 1958-1998 TREND 1958-1998 concentrations (Kattenberg et al., 1995). However Environmental Prediction–National Center for both increments could be due to changes in the frecuencies of natural atmospheric circulation Atmospheric Research (NCEP–NCAR) regimes (Wallace et al. 1995; Corti et al. 1999). reanalysis. Changes in the long-wave patterns, dominant We calculated daily values of equivalent airmass types, strength or position of climatological “centers of action” should have important influences temperature for every grid point according to on local humidity and temperatures regimes. It is the expression in figure-1. The monthly, known that the recent upward trend in the NAO seasonal and annual means were constructed accounts for much of the observed regional warming from daily means. Seasons were defined as in Europe and cooling over the northwest Atlantic Winter (January, February and March), Hurrell (1995, 1996). However our knowledge about Spring (April, May and June), Summer (July, the influence of NAO on humidity distribution is very August and September) and Fall (October, limited. In the three recent global humidity November and December). climatologies (Peixoto and Oort 1996, Ross and In the Northern Hemisphere, a positive trend in the Elliot, 1996 and Randel et al., 1996) nothing is said The distribution shows a very zonal pattern. temperature is observed over most Europe and about the rol that NAO can play on humidity For every season and for annual values, Absolute maxima are located over continental anomalies from the period 1958-1998 were North America, and over the Atlantic in the 30ºN- distribution. regions. One of them over the African calculated. Anomalies field was then used to 50ºN band. A negative trend is observed over In a recent study about distribution and trends in calculate: equatorial region, and other two in mid Iceland, Greenland and the Northeastern coast of US surface humidity and temperature (Gaffen and lattitudes, one over Africa and the other over Canada, including Hudson Bay. To the south, over Ross, 1999), both increments were found. They were consistent and also consistent with apparent ·Composites for the 41 years Australia. the Northern Hemisphere South Atlantic and over temperature, a measurement of human comfort that Rossby waves are easily detectable in most of North Africa, the Middle East and Central combine temperature and humidity, but it was not ·41-year trends patterns. northen hemisphere mid and high lattitudes. In Asia, a negative trend in the temperature is detected any influence of large-scale dynamics on the southern hemisphere those waves are not detected. Finally, over the Pacific, from 30ºN to the interannual humidity variations. Neither ENSO nor ·Composites for those years when NAO was NAO was significatively correlated with specific so marked. north, a negative trend is detected as well. in a more positive or in a more negative Absolute minimum values are detected over humidity anomalies. However this study was limited phases. To determine these years we use the In the Southern Hemisphere, a very consistent to US. The largest influence of changes of circulation Greenland. positive trend is detected over most of the regions due to NAO are produced over Europe. 41 winter values of NAO index as the normalized pressure difference between south of 30ºS. The only negative observable trend The objective of this study is to analyze the Ponta Delgada (Azores) and Reykjavik is detected at very high lattitudes and from 0ºE- influence on NAO on the pair temperature-humidity (Iceland) and 41 years mean +1SD and 41 150ºE. at an hemispheric scale. A way of quantifing both magnitudes in a single variable consists of using years mean –1SD as thresholds. Seven years were chosen as in positive NAO phase and equivalent temperature (Te), calculated in this study at 850 hPa for the period 1958-1998. other seven as in negative. ·Regression of equivalent temperature on the EQUIVALENT TEMPERATURE TREND 1958-1998 winter NAO index. In the Northern Hemisphere Te shows a very negative trend over Greenland, the Sahara, Middle East, and Southeastern Asia is detected. Positive trends are observed over Northwestern Canada, and from the The equivalent Temperaturature is the temperature Figure 1 central United States to well into the Atlantic. that an air parcel would have if water vapor were European western coast and most of central and condensed out at constant preassure, the latent heat northern Asia also exhibit a positive trend. released being used to heat the air. é æ L w öù T = T ê1+ ç ÷ú In the Southern Hemisphere a positive trend is The mixing rate (w) has been calculated from e ç ÷ detected over the Atlantic and Pacific oceans at about ê è c pd T øú temperature and relative humidity. ë û 30ºS, and over most of the Indian ocean. Over the Te: equivalent temperature Antarctica, in a region similar to that observed for the L: latent heat w: mixing ratio temperature, a negative trend is detected. Cpd: dry air specific heat T: temperature NAO Influence on Equivalent Temperature CORRELATIONS BETWEEN NAO AND T e COMPOSITE OF Te ANOMALIES FOR POSITIVE NAO YEARS In this plot the correlation coefficients locate those regions mostly influenced by this phenomenum. Very In positive NAO years a high negative T anomaly is high negative values are observed over Greenland and e observed over Greenland and the central Sahara, while the Northeastern Canadian coast, and over the central positive anomalies are observed over a long belt that Sahara. Additional negative values are detected over goes from near Alaska to New England, and from there west Australia and a small region in the Antarctica. crosses the Atlantic Ocean and intensifies the positive Maximum positive correlations are detected over anomaly over Europe and throghout most of central and European western coast, mid-east USA, eastern China northern Asia. and the south-eastern coast of South Africa. COMPOSITE OF T ANOMALIES FOR NEGATIVE NAO YEARS e DIFFERENCE BETWEEN Te FOR POSITIVE AND NEGATIVE NAO YEARS The negative NAO composites of Te show a pattern very In this map the highest absolute values locate those similar to that of the positive NAO, but as a negative regions where the amplitude of the oscillations image. The highest positive anomalies are detected over originated by NAO reaches its maximum amplitude. Greenland and the central Sahara, and the lowest These regions are: Greenland, the Sahara, Europe negative values over northwestaern America, Europe and most of Siberia and the western Canada. and cenrtal Siberia. All these regions are located in mid and high latitudes in the Northern Hemisphere. This implies an almost hemispheric-wide influence of NAO. References: ADDITION OF Te FOR POSITIVE AND NEGATIVE NAO YEARS ·Corti, S., F. Molteni, and T. N. Palmer, 1999: Signature of recent climate change in frequencies of natural atmospheric circulation regimes. Nature, 398, 799-802. As it was expected, the range of the values obtained are ·Gaffen D.J. and R.J. Ross, 1999: Climatology and Trends of U.S. Surface Humidity and Temperature. Journal of Climate, 12, 811-828. relatively low compared the the difference. This field is ·Hurrell, J. W., 1995: Decadal trends in the North Atlantic Oscillation regional temperatures and precipitation. Science, 269, 676-679. representative of the out of phase phenomena related to ·Hurrell, J. W., 1996: Influence of variations in extratropical wintertime teleconnections on Northern Hemisphere temperatures. Geophysical the North Atlantic Oscillation. There is not a very clear Research Letters, 23, 665--668. ·Kattenberg, A. et al, 1995: Climate models- Projections of future climate. Climate Change 1995: The Science of Climate Change, J.T. Houghton, distribution pattern. Ery low values are obtained to the L.G. Meira Filho, B.A. Callendar, N. Harris, A. Kattenberg, and K. Maskell, Eds, Cambridge University Press, 285-357. west of Greenland. And the highest positive values over ·Peixoto, J.P., and A.H. Oort, 1996: The climatology of relative humidity in the atmosphere. Journal of Climate, 9, 3443-3463. the Bering Strait and in the north of China. ·Randel, D.L., T.H. Vonder Haar, M.A. Ringerund, G.L Stephens, T.J. Greenwald, and C.L. Combs, 1996: A new global water vapor dataset. Bull. Amer. Meteor. Soc. 77, 1233-1246. ·Ross, R.J., and W.P. Elliot, 1996: Tropospheric precipitable water: A radiosonde-based climatology. NOAA Tech. Memo. ERL-ARL-219, 132 pp, Springfield, VA. ·Wallace, J. M., Y. Zhang, and J. A. Renwick, 1995: Dynamic contribution to hemispheric mean temperature trends. Science, 270, 780--783..
Load more

Recommended publications
  • Physiological Equivalent Temperature Index Applied
    The seventh International Conference on Urban Climate, 29 June - 3 July 2009, Yokohama, Japan PHYSIOLOGICAL EQUIVALENT TEMPERATURE INDEX APPLIED TO WIND TUNNEL EROSION TECHNIQUE PICTURES FOR THE ASSESSMENT OF PEDESTRIAN THERMAL COMFORT Alessandra Rodrigues Prata-Shimomura; Leonardo Marques Monteiro; Anésia Barros Frota * *Laboratório de Conforto Ambiental e Eficiência Energética, Faculdade de Arquitetura e Urbanismo, Universidade de São Paulo - LABAUT/FAUUSP, São Paulo, Brazil Abstract The goal of this research was to verify the influence of the effect of the wind on the pedestrians and the applicability of an index of environmental comfort for external spaces, according to data of wind tunnel simulations. The simulations were performed for the case study of Moema, an upper middle class verticalized residential neighbourhood in Sao Paulo, Brazil. The index used was the Physiological Equivalent Temperature (PET), established specifically for the evaluation of subtropical climates such as the one from the study area. Figures obtained from wind tunnel simulations, using erosion techniques, were used to visualize the field of speed in the level of pedestrian, describing the areas affected by the action of different wind speeds The index was applied on the erosion technique pictures, defining the areas of greater and lesser influence in terms of the effect of wind on the climatic conditions of the site. As a result, one may verify the assessment of the area under study, observing the conditions of comfort and discomfort in light of changes in the values of wind speed. Key words: thermal comfort indices, urban external spaces, wind tunnel simulation 1. INTRODUCTION The metropolitan region of São Paulo has 20 million inhabitants, 11 million of which live within the capital’s boundaries, making it the largest urban agglomeration of South America (Brandão, 2007).
    [Show full text]
  • Basic Features on a Skew-T Chart
    Skew-T Analysis and Stability Indices to Diagnose Severe Thunderstorm Potential Mteor 417 – Iowa State University – Week 6 Bill Gallus Basic features on a skew-T chart Moist adiabat isotherm Mixing ratio line isobar Dry adiabat Parameters that can be determined on a skew-T chart • Mixing ratio (w)– read from dew point curve • Saturation mixing ratio (ws) – read from Temp curve • Rel. Humidity = w/ws More parameters • Vapor pressure (e) – go from dew point up an isotherm to 622mb and read off the mixing ratio (but treat it as mb instead of g/kg) • Saturation vapor pressure (es)– same as above but start at temperature instead of dew point • Wet Bulb Temperature (Tw)– lift air to saturation (take temperature up dry adiabat and dew point up mixing ratio line until they meet). Then go down a moist adiabat to the starting level • Wet Bulb Potential Temperature (θw) – same as Wet Bulb Temperature but keep descending moist adiabat to 1000 mb More parameters • Potential Temperature (θ) – go down dry adiabat from temperature to 1000 mb • Equivalent Temperature (TE) – lift air to saturation and keep lifting to upper troposphere where dry adiabats and moist adiabats become parallel. Then descend a dry adiabat to the starting level. • Equivalent Potential Temperature (θE) – same as above but descend to 1000 mb. Meaning of some parameters • Wet bulb temperature is the temperature air would be cooled to if if water was evaporated into it. Can be useful for forecasting rain/snow changeover if air is dry when precipitation starts as rain. Can also give
    [Show full text]
  • Modeling of Heat Stress in Sows—Part 1: Establishment of the Prediction Model for the Equivalent Temperature Index of the Sows
    animals Article Modeling of Heat Stress in Sows—Part 1: Establishment of the Prediction Model for the Equivalent Temperature Index of the Sows Mengbing Cao 1,2, Chao Zong 1,2,*, Xiaoshuai Wang 3, Guanghui Teng 1,2, Yanrong Zhuang 1,2 and Kaidong Lei 1,2 1 College of Water Resources and Civil Engineering, China Agricultural University, Beijing 100083, China; [email protected] (M.C.); [email protected] (G.T.); [email protected] (Y.Z.); [email protected] (K.L.) 2 Key Laboratory of Agricultural Engineering in Structure and Environment, Ministry of Agriculture and Rural Affairs, Beijing 100083, China 3 College of Biosystems Engineering and Food Science, Zhejiang University, No. 866 Yuhangtang Road, Hangzhou 310058, China; [email protected] * Correspondence: [email protected] Simple Summary: Sows are susceptible to heat stress. Various indicators can be found in the literature assessing the level of heat stress in pigs, but none of them is specific to assess the sows’ thermal condition. Moreover, previous thermal indices have been developed by considering only partial environment parameters, and the interaction between the index and the animal’s physiological response are not always included. Therefore, this study aims to develop and assess a new thermal index specified for sows, called equivalent temperature index for sows (ETIS), with a comprehensive consideration of the influencing factors. An experiment was conducted, and the experimental Citation: Cao, M.; Zong, C.; Wang, data was applied for model development and validation. The equivalent temperatures have been X.; Teng, G.; Zhuang, Y.; Lei, K. transformed on the basis of equal effects of air velocity, relative humidity, floor heat conduction and Modeling of Heat Stress in indoor radiation on the thermal index, and used for the ETIS combination.
    [Show full text]
  • The Basis of Wind Chill RANDALL J
    ARCTIC VOL. 48, NO. 4 (DECEMBER 1995) P. 372– 382 The Basis of Wind Chill RANDALL J. OSCZEVSKI1 (Received 21 June 1994; accepted in revised form 16 August 1995) ABSTRACT. The practical success of the wind chill index has often been vaguely attributed to the effect of wind on heat transfer from bare skin, usually the face. To test this theory, facial heat loss and the wind chill index were compared. The effect of wind speed on heat transfer from a thermal model of a head was investigated in a wind tunnel. When the thermal model was facing the wind, wind speed affected the heat transfer from its face in much the same manner as it would affect the heat transfer from a small cylinder, such as that used in the original wind chill experiments carried out in Antarctica fifty years ago. A mathematical model of heat transfer from the face was developed and compared to other models of wind chill. Skin temperatures calculated from the model were consistent with observations of frostbite and discomfort at a range of wind speeds and temperatures. The wind chill index was shown to be several times larger than the calculated heat transfer, but roughly proportional to it. Wind chill equivalent temperatures were recalculated on the basis of facial cooling. An equivalent temperature increment was derived to account for the effect of bright sunshine. Key words: bioclimatology, cold injuries, cold weather, convective heat transfer, face cooling, frostbite, heat loss, survival, wind chill RÉSUMÉ. La popularité de l’indice de refroidissement du vent a souvent été expliquée par le fait qu’on peut la relier plus ou moins à l’effet du vent sur le transfert thermique à partir de la peau nue, le plus souvent celle du visage.
    [Show full text]
  • Bulletin American Meteorological Society
    BULLETIN OF THE AMERICAN METEOROLOGICAL SOCIETY Entered as second class matter at the Post Office, Worcester, Massachusetts, under Act of Aug. 24, 1912. Issued monthly except July and August. Annual subscription, $3.00; single copies of this issue, 35c. Address all communications to ROBERT G. STONE, Editor Blue Hill Observatory, Harvard University Milton, Mass., U. S. A. Vol. 20 OCTOBER, 1939 No. 8 A Diagram for Obtaining in a Simple Manner Different Humidity Elements and its Use in Daily Synoptic Work DR. W. BLEEKER Subdirector, Royal Netherlands Meteorological Institute, De Bilt, Holland 1. DEFINITIONS AND SYMBOLS 2. CONSTRUCTION OF THE DIAGRAM T — Temperature. The relations between the tempera- Te — Equivalent temperature, the ture, T, the equivalent temperature, temperature which the air Te, and the wet-bulb temperature, Tw, would assume if all water va- are given by pour were condensed at con- (cp+tfcpw) (T-Tw)=Lw M), (1) stant pressure and the heat of condensation used to increase cP (Te-Tw) = Lw Xw, (2) the temperature of the air (von cP (T-Te)+xcPw (T-Tw) = -LwX. (3) Cpw Bezold, 1905). Since = about 2 and x seldom Tw = theoretical wet-bulb tempera- cP ture, the lowest temperature to exceeds 0.025 we may write: which the air can be cooled un- der constant pressure by evap- T-Tw - —— (x-xw), (la) cP orating water into the air -Lw (Normand, 1921; Brunt, 1934). Te-T w = ( Xe — X w ) , (2a) fw equals the temperature of a well-ventilated wet-bulb ther- T-Te = (X - Xe), (3a) mometer (Assmann-psychrome- Cp ter.
    [Show full text]
  • Lecture Ch. 6 Condensed (Liquid) Water How Does Saturation Occur? Cloud in a Jar Demonstration Saturation of Moist Air Saturatio
    Lecture Ch. 6 Condensed (Liquid) Water • Saturation of moist air • Ch. 4: Will H2O condense? • Relationship between humidity and dewpoint – Clausius-Clapeyron describes esat(T) – Clausius-Clapeyron equation • Ch. 5: What will H2O condense on? • Dewpoint – Kohler describes droplet formation – Temperature • Ch. 6: How much H2O will condense? – Depression – Dew point temperature provides metric • Isobaric cooling • Ch. 7: How does condensed H2O affect stability? • Moist adiabatic ascent of air – Conditional stability is affected by moist adiabats • Equivalent temperature • Ch. 8: What happens to condensed H2O? • Aerological diagrams – Precipitation processes Curry and Webster, Ch. 6 Cloud in a Jar Demonstration How does saturation occur? • By increasing water vapor – Evaporation of water at surface – Evaporation of falling rain http://www.youtube.com/ • By cooling watch?v=XH_M4jItiKw – Isobaric – Radiative cooling of rising air • By mixing of two unsaturated air parcels http://groups.physics.umn.edu/demo/old_page/demo_gifs/4B70_20.GIF Curry and Webster, Ch. 6 Saturation of Moist Air Saturation of Moist Air • Dew point temperature • Clausius-Clapeyron equation at dew point R T v = v v p dp L = lv dT p R T 2 € v Llv dln p = 2 dT RvT dln p L = lv dT R T 2 Curry and Webster, Ch. 6 v € 1 Clausius Clapeyron Dewpoint and Humidity • Recall by integration between two temperatures • Integrating from ambient to saturation! we had • Dew point depression (T-TD) 1.0 T=2C INCORRECT! T=24C Figure is wrong. T=46C 0.8 0.6 0.4 Relative Humidity 0.2 0.0 0 5 10 15 20 Dewpoint Depression (T-Td) Start with measured Equivalent Potential Temperature T and Td with altitude, then overlay ws(T).
    [Show full text]
  • Cooling Load Calculations and Principles
    Cooling Load Calculations and Principles Course No: M06-004 Credit: 6 PDH A. Bhatia Continuing Education and Development, Inc. 22 Stonewall Court Woodcliff Lake, NJ 07677 P: (877) 322-5800 [email protected] HVAC COOLING LOAD CALCULATIONS AND PRINCIPLES TABLE OF CONTENTS 1.0 OBJECTIVE..................................................................................................................................................................................... 2 2.0 TERMINOLOGY ............................................................................................................................................................................. 2 3.0 SIZING YOUR AIR-CONDITIONING SYSTEM .......................................................................................................................... 4 3.1 HEATING LOAD V/S COOLING LOAD CALCULATIONS........................................................................................5 4.0 HEAT FLOW RATES...................................................................................................................................................................... 5 4.1 SPACE HEAT GAIN........................................................................................................................................................6 4.2 SPACE HEAT GAIN V/S COOLING LOAD (HEAT STORAGE EFFECT) .................................................................7 4.3 SPACE COOLING V/S COOLING LOAD (COIL)........................................................................................................8
    [Show full text]
  • Implementation and Comparison of a Suite of Heat Stress Metrics Within the Community Land Model Version 4.5
    Geosci. Model Dev., 8, 151–170, 2015 www.geosci-model-dev.net/8/151/2015/ doi:10.5194/gmd-8-151-2015 © Author(s) 2015. CC Attribution 3.0 License. Implementation and comparison of a suite of heat stress metrics within the Community Land Model version 4.5 J. R. Buzan1,2, K. Oleson3, and M. Huber1,2 1Department of Earth Sciences, University of New Hampshire, Durham, New Hampshire, USA 2Earth Systems Research Center, Institute for the Study of Earth, Ocean, and Space, University of New Hampshire, Durham, New Hampshire, USA 3National Center for Atmospheric Research, Boulder, Colorado, USA Correspondence to: J. R. Buzan ([email protected]) Received: 21 June 2014 – Published in Geosci. Model Dev. Discuss.: 8 August 2014 Revised: 2 December 2014 – Accepted: 23 December 2014 – Published: 5 February 2015 Abstract. We implement and analyze 13 different metrics culation and the improved wet bulb calculation are ±1.5 ◦C. (4 moist thermodynamic quantities and 9 heat stress metrics) These differences are important due to human responses in the Community Land Model (CLM4.5), the land surface to heat stress being nonlinear. Furthermore, we show heat component of the Community Earth System Model (CESM). stress has unique regional characteristics. Some metrics have We call these routines the HumanIndexMod. We limit the al- a strong dependency on regionally extreme moisture, while gorithms of the HumanIndexMod to meteorological inputs of others have a strong dependency on regionally extreme tem- temperature, moisture, and pressure for their calculation. All perature. metrics assume no direct sunlight exposure. The goal of this project is to implement a common framework for calculating operationally used heat stress metrics, in climate models, of- fline output, and locally sourced weather data sets, with the 1 Introduction intent that the HumanIndexMod may be used with the broad- est of applications.
    [Show full text]
  • Wind Chill Temperature Chart
    Excerpt from “The New Wind Chill Equivalent Temperature Chart by Randall Osczevsi and Maurice Bluestein A new formula for expressing the combined effect of wind and low temperature on the cooling of exposed skin was introduced in North America in November 2001. This formula is largely based on established engineering correlations of wind speed and convective heat transfer. The formulation it replaced was based on the results of an impromptu experiment that Paul Siple and Charles Passel carried out during the United States Antarctic Expedition, 1939-41. Although the resources available on the expedition limited the sophistication of their experiment, it became the best-known result of a century of Antarctic research. Siple and Passel (1945) simply measured the time it took to freeze water in a small plastic bottle suspended from a post on the roof of the expedition building. From these observations, they derived the Wind Chill Index (WCI), a three- or four-digit number representing the rate of heat loss of the cylinder per unit surface area. ……. The 2001 calculation is for a person moving through the air at walking speed. For the reference still-air condition, the calculation assumes a minimum air speed of 1.34 m s_1, which is the average walking speed of American pedestrians, young and old, crossing intersections in studies of traffic light timing (Knoblauch et al. 1995). When there is wind, it is assumed that the adult is walking into the wind (worst case) and so the walking speed is added to the wind speed at face level when calculating the WCT.
    [Show full text]
  • Wind Chill Equivalent Temperature (WCET) Climatology and Scenarios for Schiphol Airport
    Wind chill equivalent temperature (WCET) Climatology and scenarios for Schiphol Airport Geert Groen, Climate services KNMI 9th October 2009 Abstract This report presents the background, climatology and scenarios of the windchill equivalent temperature (WCET) for Schiphol Airport. The WCET-information is recommended during cold winter events for working conditions outside. KNMI will start using a new method for the calculation of WCET in the winter 2009-2010, this method was established in 2000/2001 in Joint Action Group on Temperature Indices (JAG/TI). Contents 1 Introduction 1 2 Three methods for WCET-calculation 3 2.1 Siple en Passel . .3 2.2 Steadman . .4 2.3 JAG/TI . .4 2.4 Sunshine . .5 3 Table JAG/TI and comparison of three methods 6 3.1 Table method JAG/TI . .6 3.2 Comparison of Siple-Passel, Steadman and JAG/TI at -15°C....7 4 Climatology and scenarios 8 4.1 Climatology WCET . .8 4.2 Scenarios . .9 4.3 Scenarios WCET . 10 5 Inventory thresholds for advisory 12 5.1 Advisory and tresholds in Canada . 13 5.2 TNO research on dexterity . 15 5.3 GGD-advisory . 16 5.4 Suggestions for WCET advisory for Airport Schiphol . 16 2 Chapter 1 Introduction On a winter day with wind blowing in your face, the wind makes it feel colder due to extra loss of body heat. This colder feeling is called windchill. The windchill equivalent temperate WCET (Dutch: gevoelstemperatuur) indicates the equiva- lent temperature on a colder day without wind with the same loss of body heat. The dierence between the (measured) actual air temperature and the (calculated) wind- chill equivalent temperature quanties the inuence of wind on heat loss.
    [Show full text]
  • 5011-REG.Pdf
    REGULATION: 5011-REG Page 1 ELEMENTARY RECESS WEATHER GUIDELINES Recess shall be scheduled outdoors whenever possible. When weather conditions are questionable, principals shall refer to the following guidelines to determine the appropriateness of outdoor recess. A. Temperature. Cold weather injuries such as hypothermia and frostbite and heat-related injuries such as dehydration, heat exhaustion, or heat stroke can be minimized or prevented by following these precautions. Please remember that young children are more sensitive to hot or cold temperatures. When in doubt, the building principal will make the final determination for students to participate in an outdoor activity. B. Heat Index. The heat index is a number that combines air temperature and relative humidity in an attempt to determine the human-perceived equivalent temperature (what the temperature feels like outside). 1. If the heat index is less than 95 degrees, proceed with intense to moderate activities and monitor students carefully. 2. If the heat index is between 95-99 degrees, proceed with moderate to light activities; provide water breaks every 30 minutes; and, continue to monitor students carefully. Re-check heat index hourly. 3. If the heat index is greater than 100 degrees, no outdoor activities are permitted. 4. Be sure that students always have opportunities to hydrate themselves during and after activities. Water should never be withheld if requested by a student when exercising. C. Wind Chill. Wind chill is a number that combines air temperature and wind in an attempt to determine the human-perceived equivalent temperature (what the temperature feels like outside). 1. If the windchill is between 32 and 39 degrees, students should have appropriate outdoor attire to stay warm and dry during recess.
    [Show full text]
  • Lecture Outline
    LECTURE OUTLINE 1. Ways of reaching saturation • Isobaric processes • Isobaric cooling (dew point temperature) • Isobaric and adiabatic cooling by evaporation of water (wet bulb temperature) Temperatura wilgotnego termometru) • Adiabatic and isobaric mixing 1 /26 WAYS OF REACHING SATURATION FORMATION AND DISSIPATION OF CLOUDS For simplicity, we assume that clouds form in the atmosphere when the water vapor reaches the saturation value, and f=100% (in reality this value should be greater than 100%). r f = v r p,T s ( ) An increase of relative humidity can be accomplished by: § increasing the amount of water vapor in the air (i.e. increasing rv); evaporation of water from a surface or via evaporation of rain falling through unsaturated air, § cooling of the air (decrease of rs(p,T)); isobaric cooling (e.g. radiative), adiabatic cooling of rising air, § mixing of two unsaturated parcels of air. 2 /26 THE COMBINED FIRST AND SECOND LAWS WILL BE APPLIED TO THE IDEALIZED THERMODYNAMIC REFERENCE PROCESSES ASSOCIATED WITH PHASE CHANGE OF WATER: 1. isobaric cooling 2. adiabatic isobaric processes 3. adiabatic and isobaric mixing 4. adiabatic expansion 3 /26 TEXTBOOKS • Salby, Chapter 5 • C&W, Chapter 4 • R&Y, Chapter 2 4 /26 ISOBARIC PROCESSES LEADING TO SATURATION THE AIR WITH WATER VAPOR 1. Isobaric cooling (p=const, rv=const) § Dew point temperature § Isobaric cooling with condensation (p=const, rt=const) 2. Isobaric and adiabatic cooling/heating by evaporation/condensation of water Izobaryczne i adiabatyczne ochładzanie poprzez odparowanie wody (p=const, a source of water vapor / water) § Wet bulb temperature § Equivalent temperature 3. Isobaric and adiabatic mixing (p=const, rt=const) 5 /26 ISOBARIC COOLING 6 /26 If vertical movement in the atmosphere is insignificant and a departure from the initial state is small, processes can be seen as isobaric processes.
    [Show full text]