DOCSLIB.ORG

Water in the Atmospherebjorn Stevens and Sandrine Bony

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Water in the Atmospherebjorn Stevens and Sandrine Bony Water in the atmosphereBjorn Stevens and Sandrine Bony Much of what we know, and even more of what we don’t know, about Earth’s climate and its propensity to change is rooted in the interplay between water, air circulation, and temperature. very schoolchild learns about the role of how you look at it, being suspended in the atmos- the atmosphere in Earth’s water cycle. But phere is an exceedingly unlikely state for a water few get the chance to learn about water’s molecule to find itself in; but while in that state, E role in determining the properties of the water makes a world of difference. atmosphere. Water determines not only how the Sun’s energy is partitioned through the at- An absorption virtuoso mosphere and across Earth’s surface but also the Water stands out because of its physical and radia- character of the large- scale circulations, which that tive properties. As figure 1 shows, it is a small mol- energy drives. Recognition of the fundamental in- ecule with a large appetite for IR radiation. The fluence of water even predates formal scientific water molecule is endowed with a plethora of rota- thinking. In the Judeo-Christian creation myth, for tional absorption modes, which result from the tum- instance, one of the creator’s first tasks, after sepa- bling of its strong electric dipole around three small rating darkness from light, was to separate water and disparate moments of inertia. These modes con- from water to create the sky. tribute to a rich set of spectral lines that stretch from the near-IR into the microwave. Some of them arise That water assumes such a defining place in the because the rotational modes ornament three vibra- sky is remarkable given that it only accounts for tional modes that form the fundamental rotational– 0.25% of the total mass of the atmosphere. That’s the vibrational (ro- vibrational) bands. One, λ = 6.3 μm, equivalent of a liquid layer only 2.5 cm deep, barely 2 is associated with H-O-H bending; the other two, λ enough to make a global puddle, distributed 1 and λ3, associated with symmetric and asymmetric through the atmosphere almost entirely (99.5%) in stretching, are located near 2.7 μm and overlap with the form of vapor. By way of comparison, the global an overtone of the bending mode. ocean, if spread uniformly over Earth’s surface, would have an average depth of about 2.8 km. Fresh Bjorn Stevens directs the Max Planck Institute for Meteorology in Hamburg, water on Earth’s terrestrial surface—ice sheets, lakes, Germany, and Sandrine Bony is a CNRS senior scientist at the Laboratoire de rivers, wetlands, and soils—is 2000 to 3000 times Météorologie Dynamique in Paris. more abundant than atmospheric water. No matter ERIK CHRISTENSEN, PORKERI www.physicstoday.org June 2013 Physics Today 29 Downloaded 31 May 2013 to 136.172.75.107. This article is copyrighted as indicated in the abstract. Reuse of AIP content is subject to the terms at: http://www.physicstoday.org/about_us/terms Water Such a surfeit of absorption lines also endows strong greenhouse effect and a strong planetary the water molecule with a potent continuum absorp- albedo, despite containing only about 0.5% of the at- tion. Debate continues about the relative contribu- mosphere’s water.2 As only a small fraction of that tions to that continuum from the overlap of the water is distributed in large, precipitating hydro - wings of different spectral lines and from the tran- meteors such as rain and snow, which have relatively sient production of molecular clusters of water small surface-to-volume ratios, precipitating water dimers during collisions in the vapor (see PHYSICS is far less important for Earth’s radiative budget than TODAY, April 2013, page 18). Whatever the cause, the water vapor or suspended condensate. continuum absorption is an important manifestation of water vapor’s unusual effectiveness at interacting Thermodynamics and phase changes with radiation throughout the thermal IR.1 This ef- Because water cycles through vapor and condensate fectiveness is felt also in the near-IR and makes water phases in the atmosphere, the laws of thermodynam- vapor the most important absorber of solar radiation ics place important constraints on the coupling be- in the lower atmosphere. Other molecules found in tween water vapor and air temperature. Through the atmosphere also have strong, or well-placed, the Clapeyron equation, the second law of thermo - absorption features in the IR. But when it comes to dynamics dictates how the saturation vapor pressure interacting with the full spectrum of IR radiation, es depends on temperature T and fundamentally con- including overtones at shorter wavelengths, none strains the humidity structure of the atmosphere. The approaches the virtuosity of the water molecule. equation can be expressed as (See the article by Raymond Pierrehumbert, PHYSICS TODAY, January 2011, page 33.) β delns = dT ln . Condensed water, which atmospheric physi- T (1) cists refer to collectively as hydrometeors, can take various forms, such as the simple crystals, droplets, The factor β is roughly equal to the ratio of the en- snowflakes, graupel, and hail illustrated in figure 1. thalpy of vaporization—the energy required to The extent to which they scatter electromagnetic ra- transform water from liquid to gas at constant pres- diation depends on their refractive index and their sure—to the water vapor gas constant. Its value size relative to the radiation’s wavelength: Shorter (about 5400 K) expresses the strength of the effect of waves are preferentially scattered, longer waves are temperature variations on saturation vapor pres- absorbed. Because the typical size of cloud droplets sure. Because of water’s unusually large enthalpy of (and to a lesser extent cloud ice) is commensurate vaporization, β is a factor of two or three larger than with the shorter wavelengths of the thermal IR, that of other common condensable vapors such as clouds are effective at absorbing energy at these and carbon dioxide, methane, and ammonia. longer wavelengths. The large vaporization enthalpy also implies They are much less effective in doing so at the that at typical surface temperatures, es approximately 10- to 100-fold shorter wavelengths found in the doubles for every 10-K rise in temperature. If the solar part of the spectrum, where the radiation is in- vapor pressure e rises above es—for instance, as a stead scattered. As a result, clouds exhibit both a result of expansional cooling or a radiant loss of a Suspension Precipitation Crystals Snowflakes Graupel and hail Water molecule Figure 1. Hydrometeors (a), the condensed forms of water in the Drizzle atmosphere, come in several Cloud droplets Raindrops sizes. They mostly scatter visible light but absorb over a broad −3 −2 −1 0 1 2 3 4 10 10 10 10 10 10 10 10 range of the IR. (b) The near- b DIAMETER (μm) and thermal-IR regions of the spectrum excite the molecule Visible Near-IR Thermal IR and produce its rotational– vibrational (or ro-vibrational) Ro-vibrational Rotational and rotational bands. Specific 100 λ λ λ lines 1, 2, and 3 mark the Ro-vibrational symmetric stretching mode, TY overtones 1 bending mode, and asymmetric VE LINE stretching mode, respectively. INTENSI RELATI 0.01 λ λ λ 0.4 1.0 3 1 4.0 2 10.0 40.0 WAVELENGTH λ (μm) 30 June 2013 Physics Today www.physicstoday.org Downloaded 31 May 2013 to 136.172.75.107. This article is copyrighted as indicated in the abstract. Reuse of AIP content is subject to the terms at: http://www.physicstoday.org/about_us/terms a b 103 energy—condensate will gen- erally form to maintain the ambient vapor pressure near (Pa) its saturation value. For short- e 102 lived and dilute condensate clouds, the condensate largely follows the atmospheric flow until it evaporates again as the 101 temperature rises or the vapor pressure falls—for instance, through mixing with drier air. VAPOR PRESSURE, 0 For clouds that are suffi- 10 ciently long- lived or conden- sate laden, larger hydromete- 200 220 240 260 280 300 ors such as rain or snow form TEMPERATURE (K) and rapidly precipitate from Figure 2. The atmospheric vapor pressure (a) the atmosphere. as a function of temperature is bounded by The first law of thermo- the atmosphere’s vapor pressure when saturated with water (solid line). The data are shown dynamics dictates how tem- as the median (dot) and range (error bar) of 228 monthly values at different isobaric levels— perature changes for adia- 900 hPa (green), 700 hPa (blue), 500 hPa (orange), and 300 hPa (red). (Data are provided by batic displacements of air the European Centre for Medium-Range Weather Forecasts.) (b) Based on satellite measure- parcels and thus fundamen- ments of radiation emitted at 6.2 μm, this map reveals the relative humidity of the middle tally constrains the thermal and upper troposphere. It also reveals how closely humidity levels are tied to atmospheric structure of the atmosphere. circulation patterns: Pronounced dry regions (dark) show large- scale descending motions of Because air has mass, its pres- air concentrated in the subtropics. Clouds, regions of complete saturation, are visible as sure decreases with altitude. white features. (Image from Meteosat.) So as a parcel of air ascends, it expands and cools adiabatically; likewise, descend- vapor phase, making saturated air quite dry. So ing air warms. The adiabatic temperature change that relatively dry regions of the atmosphere are in- accompanies such vertical displacements is deter- dicative of descending currents, which adiabati- mined by γ*, the adiabatic temperature lapse rate.
Load more

Recommended publications
  • ALBEDO ENHANCEMENT by STRATOSPHERIC SULFUR INJECTIONS: a CONTRIBUTION to RESOLVE a POLICY DILEMMA? an Editorial Essay
    ALBEDO ENHANCEMENT BY STRATOSPHERIC SULFUR INJECTIONS: A CONTRIBUTION TO RESOLVE A POLICY DILEMMA? An Editorial Essay Fossil fuel burning releases about 25 Pg of CO2 per year into the atmosphere, which leads to global warming (Prentice et al., 2001). However, it also emits 55 Tg S as SO2 per year (Stern, 2005), about half of which is converted to sub-micrometer size sulfate particles, the remainder being dry deposited. Recent research has shown that the warming of earth by the increasing concentrations of CO2 and other greenhouse gases is partially countered by some backscattering to space of solar radiation by the sulfate particles, which act as cloud condensation nuclei and thereby influ- ence the micro-physical and optical properties of clouds, affecting regional precip- itation patterns, and increasing cloud albedo (e.g., Rosenfeld, 2000; Ramanathan et al., 2001; Ramaswamy et al., 2001). Anthropogenically enhanced sulfate particle concentrations thus cool the planet, offsetting an uncertain fraction of the anthro- pogenic increase in greenhouse gas warming. However, this fortunate coincidence is “bought” at a substantial price. According to the World Health Organization, the pollution particles affect health and lead to more than 500,000 premature deaths per year worldwide (Nel, 2005). Through acid precipitation and deposition, SO2 and sulfates also cause various kinds of ecological damage. This creates a dilemma for environmental policy makers, because the required emission reductions of SO2, and also anthropogenic organics (except black carbon), as dictated by health and ecological considerations, add to global warming and associated negative conse- quences, such as sea level rise, caused by the greenhouse gases.
    [Show full text]
  • Assessing Urban Heat Island Mitigation Using Green Roofs: a Hardware Scale Modeling Approach
    ASSESSING URBAN HEAT ISLAND MITIGATION USING GREEN ROOFS: A HARDWARE SCALE MODELING APPROACH By William C. Pompeii II A Thesis Submitted to the Department of Geography and Earth Science and the Graduate Council in partial fulfillment of the requirements for the degree of Master of Science in Geoenvironmental Studies SHIPPENSBURG UNIVERSITY Shippensburg, Pennsylvania May, 2010 DEPARTMENT OF GEOGRAPHY AND EARTH SCIENCE SHIPPENSBURG UNIVESITY Upon the recommendation of the chairperson of the department of Geography and Earth Science this thesis is hereby accepted in partial fulfillment of the requirements for the degree of Master of Science in Geoenvironmental Studies Thesis Committee __________________________________________________ ________________ Committee Chairperson Date Dr. Timothy W. Hawkins __________________________________________________ ________________ Committee Member Date Dr. Claire Jantz __________________________________________________ ________________ Committee Member Date Dr. George Pomeroy Table of Contents List of Figures iii List of Tables v ABSTRACT vi Chapter 1: Introduction 1 1.1 Statement of Problem 1 Chapter 2: Review of Literature 3 2.1 Background 3 2.1.1 Urban Heat Island 3 2.2 Green Roofs 6 2.2.1 Origin and Types 6 2.2.2 Benefits of Green Roofs 7 2.3 Chicago-A Case Study City 9 2.3.1 Green Roof Case Study-Chicago City Hall Building 13 2.4 Methods of Study the Urban Heat Island and Benefits of Green Roof Mitigation 15 2.4.1. Urban Heat Island Methods-Dataloggers 15 2.4.2 Green Roof effects on Urban Heat Island
    [Show full text]
  • Radiative Cooling New Opportunities & Enabling Technologies
    Radiative Cooling New Opportunities & Enabling Technologies Aaswath P. Raman, Ph.D. [email protected] Research Associate, Fan Group, Ginzton Laboratory ARPA-E Alternative Power Plant Cooling Workshop, May 12, 2014 1 An opportunity to tap an underutilized resource Use the cold of outer space to cold outer space! (-80°C ! -270°C)! radiatively pump heat from the ground through sky access New: Possible at all hours of the day through photonic design of thermally emissive layers Heat Atmosphere Thermal Meaningful cooling power that EM Waves scales with area: analogies to PV Radiative Cooling Surface! 2 I. INTRODUCTION Radiative cooling is a technique that exploits a natural transparency window for electro- magnetic waves in the Earths atmosphere to transport heat from terrestrial objects into cold space. As a result, objects with the appropriate radiative properties can passively cool them- selves down to temperatures well below the ambient. The atmospheric transparency window is found in the 8-13µm wavelength range, as shown in Fig. 1, and fortuitously overlaps with the blackbody spectralAtmospheric radiance corresponding to typical terrestrialtransmittance temperatures (0-50C), thus enabling objects at these temperatures to emit more power than they absorb. 1 Atmospheric Transmission Radiative cooling is enabled by 0◦C blackbody 50◦C blackbody an atmospheric transparency 0.5 window between 8 – 13 μm 0 7 9 11 13 15 Blackbody spectrum of typical λ [µm] Earth temperature objects overlap with window FIG. 1. Atmopheric Transmissioncold in the outer zenith space direction! vs. wavelength; normalized blackbody spectral radiance of a 0◦C and a(upper 50◦C blackbody atmosphere) emitter ! Varies with cloud cover, Prior work in radiative cooling has almost entirely focused on nighttime cooling,geographic where location and one aims to maximize emission in the atmospheric transparency window, without having to contend with solar radiation.
    [Show full text]
  • Concentrated Radiative Cooling Arxiv:2010.02426V1 [Physics.App
    Concentrated Radiative Cooling Joseph Peoples,1 Yu-Wei Hung,2 Xiangyu Li,1 Daniel Gallagher,1 Nathan Fruehe,1 Anil Yuksel,3 James Braun,1 Travis Horton,2 Xiulin Ruan1∗ 1School of Mechanical Engineering, Purdue University, West Lafayette, IN 47907, USA, 2School of Civil Engineering, Purdue University, West Lafayette, IN 47907, USA, 3IBM Corporation, Austin, TX, 78758, USA ∗To whom correspondence should be addressed; E-mail: [email protected]. A fundamental limit of current radiative cooling systems is that only the top surface facing deep-space can provide the radiative cooling effect, while the bottom surface cannot. Here, we propose and experimentally demonstrate a concept of \concentrated radia- tive cooling" by nesting a radiative cooling system in a mid-infrared reflective trough, so that the lower surface, which does not con- tribute to radiative cooling in previous systems, can radiate heat to deep-space via the reflective trough. Field experiments show that the temperature drop of a radiative cooling pipe with the trough arXiv:2010.02426v1 [physics.app-ph] 6 Oct 2020 is more than double that of the standalone radiative cooling pipe. Furthermore, by integrating the concentrated radiative cooling sys- tem as a preconditioner in an air conditioning system, we predict electricity savings of > 75% in Phoenix, AZ, and > 80% in Reno, NV, for a single-story commercial building. 1 Introduction In 2018, 9.3% of the total generated electricity in the United States went to space cooling and refrigeration of commercial buildings, equating to 164.7 million metric tons of carbon dioxide emission, just for commercial cooling (1).
    [Show full text]
  • The Application of Passive Radiative Cooling in Greenhouses
    sustainability Article The Application of Passive Radiative Cooling in Greenhouses Chia-Hsin Liu 1, Chyung Ay 2, Chun-Yu Tsai 3 and Maw-Tien Lee 1,* 1 Department of Applied Chemistry, National Chia Yi University, Chiayi 60004, Taiwan; [email protected] 2 Department of Biomechatronic Engineering, National Chia Yi University, Chiayi 60004, Taiwan; [email protected] 3 Program of Agriculture Science, National Chiayi University, Chiayi 60004, Taiwan; [email protected] * Correspondence: [email protected]; Tel.: +886-5-2717691 Received: 31 October 2019; Accepted: 24 November 2019; Published: 27 November 2019 Abstract: At present, greenhouses are used to grow a variety of crops around the world. However, with the change of climate, the increasingly harsh weather makes it more and more disadvantageous for people to work inside, and plants are difficult to grow. Previous research has illustrated that radiative cooling can be realized by using certain nonmetal oxide particles created for emission in an infrared atmospheric transparency window, which is an environmentally friendly cooling method due to reducing energy consumption. Polyethylene (PE)-based formulations with a UV stabilizer and nonmetal oxide particles (NOP) were first granulated and then formed a monolayer film by co-injection molding. The experimental results show that due to passive radiative cooling, under the environmental conditions of 35 ◦C, and only considering the natural convection heat transfer, the net cooling power of the greenhouse film developed in this study is 28 W m 2 higher than that of · − the conventional PE film. The temperature inside the simulated greenhouse cladded with the new greenhouse covering was on average 2.2 ◦C less than that of the greenhouse with the conventional PE film.
    [Show full text]
  • Urban Heat Islands
    11 Urban Heat Islands 11.1 Introduction .............................................................................................................................143 11.2 Principles ...................................................................................................................................144 Urban Scales • Conceptual Framework • Heat Island Types, Characteristics, and Underlying Processes • Heat Island Controls 11.3 Methods of Analysis ................................................................................................................151 Observations • Models 11.4 Impacts and Applications ...................................................................................................... 154 Solutions to Mitigate Urban Heat Islands • Human Comfort and Health • Forecasting Urban Weather and Climate and Developing UHI Mitigation Strategies • The Urban Heat Island and Global Climate Warming 11.5 Major Challenges .....................................................................................................................157 M. Roth Science • Observations National University of Singapore References .............................................................................................................................................158 11.1 Introduction heat-related illness and mortality, air pollution, energy demand for air conditioning, and indirectly greenhouse gas emissions. For millions of people living in cities, increased temperatures Heat waves, for example, which heat islands can
    [Show full text]
  • Implementation of Passive Radiative Cooling Technology in Buildings: a Review
    buildings Review Implementation of Passive Radiative Cooling Technology in Buildings: A Review Suhendri , Mingke Hu * , Yuehong Su * , Jo Darkwa and Saffa Riffat Department of Architecture and Built Environment, University of Nottingham, Nottingham NG7 2RD, UK; [email protected] (S.); [email protected] (J.D.); saffa.riff[email protected] (S.R.) * Correspondence: [email protected] (M.H.); [email protected] (Y.S.) Received: 29 October 2020; Accepted: 21 November 2020; Published: 26 November 2020 Abstract: Radiative cooling (RC) is attracting more interest from building engineers and architects. Using the sky as the heat sink, a radiative cooling material can be passively cooled by emitting heat to the sky. As a result of the development of material technology, RC research has been revived, with the aim of increasing the materials’ cooling power as well as finding reliable ways to utilize it in cooling for buildings. This review identifies some issues in the current implementation of RC technologies in buildings from an architectural point of view. Besides the technical performance of the RC technologies, some architectural aspects, such as integration with architectural features, aesthetic requirements, as well as fully passive implementations of RC, also need to be considered for building application. In addition, performance evaluation of a building-integrated RC system should begin to account for its benefit to the occupant’s health and comfort alongside the technical performance. In conclusion, this review on RC implementation in buildings provides a meaningful discussion in regard to the direction of the research. Keywords: radiative cooling; architectural application; combination; passive design architecture 1.
    [Show full text]
  • Significance of Aerosol Radiative Effect in Energy Balance Control on Global Precipitation Change
    View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Central Archive at the University of Reading Significance of aerosol radiative effect in energy balance control on global precipitation change Article Published Version Creative Commons: Attribution 4.0 (CC-BY) Open Access Suzuki, K., Stephens, G. L. and Golaz, J.-C. (2017) Significance of aerosol radiative effect in energy balance control on global precipitation change. Atmospheric Science Letters, 18 (10). pp. 389-395. ISSN 1530-261X doi: https://doi.org/10.1002/asl.780 Available at http://centaur.reading.ac.uk/72369/ It is advisable to refer to the publisher's version if you intend to cite from the work. To link to this article DOI: http://dx.doi.org/10.1002/asl.780 Publisher: John Wiley & Sons All outputs in CentAUR are protected by Intellectual Property Rights law, including copyright law. Copyright and IPR is retained by the creators or other copyright holders. Terms and conditions for use of this material are defined in the End User Agreement . www.reading.ac.uk/centaur CentAUR Central Archive at the University of Reading Reading's research outputs online ATMOSPHERIC SCIENCE LETTERS Atmos. Sci. Let. 18: 389–395 (2017) Published online in Wiley Online Library (wileyonlinelibrary.com) DOI: 10.1002/asl.780 Significance of aerosol radiative effect in energy balance control on global precipitation change Kentaroh Suzuki,1* Graeme L. Stephens2,3 and Jean-Christophe Golaz4 1Atmosphere and Ocean Research Institute, University of Tokyo, Kashiwa, Japan 2Jet Propulsion Laboratory, California Institute of Technology, Pasadena, USA 3Department of Meteorology, University of Reading, Reading, UK 4Lawrence Livermore National Laboratory, Livermore, CA, USA *Correspondence to: Abstract K.
    [Show full text]
  • Full Daytime Sub-Ambient Radiative Cooling with High Figure of Merit in Commercial-Like Paints
    The work below was included in a provisional patent application filed on October 3, 2018 and a non-provisional international patent application (PCT/US2019/054566) filed on October 3, 2019 and published on April 9, 2020.1 Full Daytime Sub-ambient Radiative Cooling with High Figure of Merit in Commercial-like Paints 1,2 1,2 1,3 1 1,4,5 1,2,* Xiangyu Li, Joseph Peoples, Zhifeng Huang, Zixuan Zhao, Jun Qiu and Xiulin Ruan 1 School of Mechanical Engineering, Purdue University, West Lafayette, IN, USA. 2 Birck Nanotechnology Center, Purdue University, West Lafayette, IN, USA. 3 School of Power and Mechanical Engineering, Wuhan University, Wuhan, China. 4 School of Energy Science and Engineering, Harbin Institute of Technology, Harbin, China. 5 State Key Laboratory for Digital Manufacturing Equipment and Technology, Huazhong University of Science and Technology, Wuhan, China. *Correspondence: [email protected] SUMMARY Radiative cooling is a passive cooling technology by reflecting sunlight and emitting radiation in the atmospheric sky window. Although highly desired, full daytime sub-ambient radiative cooling in commercial-like single-layer particle- matrix paints is yet to be achieved. In this work, we have demonstrated full daytime sub-ambient radiative cooling in CaCO3-acrylic paint by adopting large bandgap fillers, a high particle concentration and a broad size distribution. Our paint shows the highest solar reflectance of 95.5% among paints and a high sky- window emissivity of 0.94. Field tests show cooling power exceeding 37 W/m2 and lower surface temperature more than 1.7˚C below ambient at noon. A figure of merit RC is proposed to compare the cooling performance under different weather conditions.
    [Show full text]
  • For the Mitigation of Urban Heat Island and Urban Noise Island
    TOPICAL REVIEW • OPEN ACCESS Recent citations For the mitigation of urban heat island and urban - A Mobile Vehicle-Based Methodology for Dynamic Microclimate Analysis noise island: two simultaneous sides of urban Ioannis Kousis et al discomfort - More Than Just Concrete: Acoustically Efficient Porous Concrete with Different Aggregate Shape and Gradation To cite this article: I Kousis and A L Pisello 2020 Environ. Res. Lett. 15 103004 Louena Shtrepi et al - Intra-urban microclimate investigation in urban heat island through a novel mobile monitoring system Ioannis Kousis et al View the article online for updates and enhancements. This content was downloaded from IP address 170.106.33.22 on 30/09/2021 at 21:30 Environ. Res. Lett. 15 (2020) 103004 https://doi.org/10.1088/1748-9326/abaa0d Environmental Research Letters TOPICAL REVIEW For the mitigation of urban heat island and urban noise island: OPEN ACCESS two simultaneous sides of urban discomfort RECEIVED 13 May 2020 I Kousis1 and A L Pisello1,2 REVISED 1 CIRIAF - Interuniversity Research Center, University of Perugia. Via G. Duranti 67—06125—Perugia Italy 22 July 2020 2 Department of Engineering—University of Perugia. Via G. Duranti 97—06125—Perugia Italy ACCEPTED FOR PUBLICATION 28 July 2020 E-mail: [email protected] PUBLISHED Keywords: UHI mitigation, urban noise mitigation, urban discomfort, energy efficiency, cool materials, sound absorption, solar reflection 28 September 2020 Original Content from this work may be used Abstract under the terms of the Creative Commons Urban environment well-being has become a crucial public issue to face, given the huge Attribution 4.0 licence.
    [Show full text]
  • The Role of Cloud Heating Within the Atmosphere on the High Cloud Amount and Top-Of-Atmosphere Cloud Radiative Effect Bryce E
    JAMES, VOL. ???, XXXX, DOI:10.1002/, The role of cloud heating within the atmosphere on the high cloud amount and top-of-atmosphere cloud radiative effect Bryce E. Harrop,1 Dennis L. Hartmann,1 Key Points. ◦ ACRE both enhances high cloud amount through direct destabilization of the cloud layer and reduces high cloud amount by stabilizing the troposphere to deep convection ◦ ACRE produces more high, optically thin clouds relative to high, optically thick clouds, increases TOA CRE Abstract. The effect of cloud radiation interactions on cloud properties is examined in the context of a limited domain cloud resolving model. The atmospheric cloud radia- tive effect (ACRE) influences the areal extent of tropical high clouds in two distinct ways. The first is through direct radiative destabilization of the elevated cloud layers, mostly as a result of radiation heating the cloud bottom and cooling the cloud top. The sec- ond effect is radiative stabilization, whereby cloud radiative heating of the atmospheric column stabilizes the atmosphere to deep convection. In limited area domain simulations, the stabilizing effect is the dominant role of the cloud radiative heating, thus reducing the cloud cover in simulations where ACRE is included compared to those where it is removed. Cloud radiative heating increases cloud amount, decreases cloud optical depth, and increases cloud top pressure. The combination of these effect increases the top-of- atmosphere cloud radiative effect. In mock-Walker circulation experiments, the decrease in high cloud amount owing to radiative stabilization tends to cancel out the increase in high cloud amount owing to the destabilization within the cloud layer.
    [Show full text]
  • Radiative Cooling and Thermoregulation in the Earth's Glow
    Manuscript - Radiative Cooling and Thermoregulation in the Earth’s Glow- Mandal et. al. Radiative Cooling and Thermoregulation in the Earth’s Glow Jyotirmoy Mandal, 1* Sagar Mandal,2 John Brewer,1 Arvind Ramachandran,3 Aaswath Pattabhi Raman1* 1 Department of Materials Science and Engineering, University of California, Los Angeles, California, USA 2 Independent Researcher, 523 Broadway E, Seattle, Washington, USA 3 Department of Civil, Environmental and Sustainable Engineering, Arizona State University, Tempe, Arizona, USA Contact: Jyotirmoy Mandal ([email protected]) and Aaswath Raman ([email protected]) Abstract Passive radiative cooling involves a net radiative heat loss to the cold outer space through the atmospheric transmission window in the long-wave infrared (LWIR) wavelengths. Due to its passive nature and net cooling effect, it is a promising alternative or complement to electrical cooling. For efficient radiative cooling, an unimpeded view of the sky is ideal, with prior work thus focused on roofs and sky-facing surfaces. However, much of the surface area of typical buildings are vertically oriented, with ≳50% of their field of view subtended by terrestrial features. Under sunlight, these features become warm and thermally irradiate vertical facades of buildings. Since building facades are made of materials that are broadband emitters and absorbers of thermal radiation, this heating effect can dramatically counter heat loss to the sky, diminishing or even reversing the radiative cooling process. We show that selective LWIR emitters on vertical building facades can experience higher cooling than achievable by using conventional broadband thermal emitters. They achieve this enhancement by exploiting the differential transmittance of the atmosphere towards the sky and between terrestrial objects.
    [Show full text]