Improving Representations of Boundary Layer Processes
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Climate Models and Their Evaluation
8 Climate Models and Their Evaluation Coordinating Lead Authors: David A. Randall (USA), Richard A. Wood (UK) Lead Authors: Sandrine Bony (France), Robert Colman (Australia), Thierry Fichefet (Belgium), John Fyfe (Canada), Vladimir Kattsov (Russian Federation), Andrew Pitman (Australia), Jagadish Shukla (USA), Jayaraman Srinivasan (India), Ronald J. Stouffer (USA), Akimasa Sumi (Japan), Karl E. Taylor (USA) Contributing Authors: K. AchutaRao (USA), R. Allan (UK), A. Berger (Belgium), H. Blatter (Switzerland), C. Bonfi ls (USA, France), A. Boone (France, USA), C. Bretherton (USA), A. Broccoli (USA), V. Brovkin (Germany, Russian Federation), W. Cai (Australia), M. Claussen (Germany), P. Dirmeyer (USA), C. Doutriaux (USA, France), H. Drange (Norway), J.-L. Dufresne (France), S. Emori (Japan), P. Forster (UK), A. Frei (USA), A. Ganopolski (Germany), P. Gent (USA), P. Gleckler (USA), H. Goosse (Belgium), R. Graham (UK), J.M. Gregory (UK), R. Gudgel (USA), A. Hall (USA), S. Hallegatte (USA, France), H. Hasumi (Japan), A. Henderson-Sellers (Switzerland), H. Hendon (Australia), K. Hodges (UK), M. Holland (USA), A.A.M. Holtslag (Netherlands), E. Hunke (USA), P. Huybrechts (Belgium), W. Ingram (UK), F. Joos (Switzerland), B. Kirtman (USA), S. Klein (USA), R. Koster (USA), P. Kushner (Canada), J. Lanzante (USA), M. Latif (Germany), N.-C. Lau (USA), M. Meinshausen (Germany), A. Monahan (Canada), J.M. Murphy (UK), T. Osborn (UK), T. Pavlova (Russian Federationi), V. Petoukhov (Germany), T. Phillips (USA), S. Power (Australia), S. Rahmstorf (Germany), S.C.B. Raper (UK), H. Renssen (Netherlands), D. Rind (USA), M. Roberts (UK), A. Rosati (USA), C. Schär (Switzerland), A. Schmittner (USA, Germany), J. Scinocca (Canada), D. Seidov (USA), A.G. -
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15 NOVEMBER 2006 A R O R A A N D B O E R 5875 The Temporal Variability of Soil Moisture and Surface Hydrological Quantities in a Climate Model VIVEK K. ARORA AND GEORGE J. BOER Canadian Centre for Climate Modelling and Analysis, Meteorological Service of Canada, University of Victoria, Victoria, British Columbia, Canada (Manuscript received 4 October 2005, in final form 8 February 2006) ABSTRACT The variance budget of land surface hydrological quantities is analyzed in the second Atmospheric Model Intercomparison Project (AMIP2) simulation made with the Canadian Centre for Climate Modelling and Analysis (CCCma) third-generation general circulation model (AGCM3). The land surface parameteriza- tion in this model is the comparatively sophisticated Canadian Land Surface Scheme (CLASS). Second- order statistics, namely variances and covariances, are evaluated, and simulated variances are compared with observationally based estimates. The soil moisture variance is related to second-order statistics of surface hydrological quantities. The persistence time scale of soil moisture anomalies is also evaluated. Model values of precipitation and evapotranspiration variability compare reasonably well with observa- tionally based and reanalysis estimates. Soil moisture variability is compared with that simulated by the Variable Infiltration Capacity-2 Layer (VIC-2L) hydrological model driven with observed meteorological data. An equation is developed linking the variances and covariances of precipitation, evapotranspiration, and runoff to soil moisture variance via a transfer function. The transfer function is connected to soil moisture persistence in terms of lagged autocorrelation. Soil moisture persistence time scales are shorter in the Tropics and longer at high latitudes as is consistent with the relationship between soil moisture persis- tence and the latitudinal structure of potential evaporation found in earlier studies. -
Global Climate Models and Their Limitations Anthony Lupo (USA) William Kininmonth (Australia) Contributing: J
1 Global Climate Models and Their Limitations Anthony Lupo (USA) William Kininmonth (Australia) Contributing: J. Scott Armstrong (USA), Kesten Green (Australia) 1. Global Climate Models and Their Limitations Key Findings Introduction 1.1 Model Simulation and Forecasting 1.2 Modeling Techniques 1.3 Elements of Climate 1.4 Large Scale Phenomena and Teleconnections Key Findings Confidence in a model is further based on the The IPCC places great confidence in the ability of careful evaluation of its performance, in which model general circulation models (GCMs) to simulate future output is compared against actual observations. A climate and attribute observed climate change to large portion of this chapter, therefore, is devoted to anthropogenic emissions of greenhouse gases. They the evaluation of climate models against real-world claim the “development of climate models has climate and other biospheric data. That evaluation, resulted in more realism in the representation of many summarized in the findings of numerous peer- quantities and aspects of the climate system,” adding, reviewed scientific papers described in the different “it is extremely likely that human activities have subsections of this chapter, reveals the IPCC is caused more than half of the observed increase in overestimating the ability of current state-of-the-art global average surface temperature since the 1950s” GCMs to accurately simulate both past and future (p. 9 and 10 of the Summary for Policy Makers, climate. The IPCC’s stated confidence in the models, Second Order Draft of AR5, dated October 5, 2012). as presented at the beginning of this chapter, is likely This chapter begins with a brief review of the exaggerated. -
Assimila Blank
NERC NERC Strategy for Earth System Modelling: Technical Support Audit Report Version 1.1 December 2009 Contact Details Dr Zofia Stott Assimila Ltd 1 Earley Gate The University of Reading Reading, RG6 6AT Tel: +44 (0)118 966 0554 Mobile: +44 (0)7932 565822 email: [email protected] NERC STRATEGY FOR ESM – AUDIT REPORT VERSION1.1, DECEMBER 2009 Contents 1. BACKGROUND ....................................................................................................................... 4 1.1 Introduction .............................................................................................................. 4 1.2 Context .................................................................................................................... 4 1.3 Scope of the ESM audit ............................................................................................ 4 1.4 Methodology ............................................................................................................ 5 2. Scene setting ........................................................................................................................... 7 2.1 NERC Strategy......................................................................................................... 7 2.2 Definition of Earth system modelling ........................................................................ 8 2.3 Broad categories of activities supported by NERC ................................................. 10 2.4 Structure of the report ........................................................................................... -
A New Method to Retrieve the Diurnal Variability of Planetary Boundary Layer Height from Lidar Under Different Thermodynamic
Remote Sensing of Environment 237 (2020) 111519 Contents lists available at ScienceDirect Remote Sensing of Environment journal homepage: www.elsevier.com/locate/rse A new method to retrieve the diurnal variability of planetary boundary layer T height from lidar under diferent thermodynamic stability conditions ∗ Tianning Sua, Zhanqing Lia, , Ralph Kahnb a Department of Atmospheric and Oceanic Science & ESSIC, University of Maryland, College Park, MD, 20740, USA b Climate and Radiation Laboratory, Earth Science Division, NASA Goddard Space Flight Center, Greenbelt, MD, USA ARTICLE INFO ABSTRACT Keywords: The planetary boundary layer height (PBLH) is an important parameter for understanding the accumulation of Planetary boundary layer height pollutants and the dynamics of the lower atmosphere. Lidar has been used for tracking the evolution of PBLH by Thermodynamic stability using aerosol backscatter as a tracer, assuming aerosol is generally well-mixed in the PBL; however, the validity Lidar of this assumption actually varies with atmospheric stability. This is demonstrated here for stable boundary Aerosols layers (SBL), neutral boundary layers (NBL), and convective boundary layers (CBL) using an 8-year dataset of micropulse lidar (MPL) and radiosonde (RS) measurements at the ARM Southern Great Plains, and MPL at the GSFC site. Due to weak thermal convection and complex aerosol stratifcation, traditional gradient and wavelet methods can have difculty capturing the diurnal PBLH variations in the morning and forenoon, as well as under stable conditions generally. A new method is developed that combines lidar-measured aerosol backscatter with a stability dependent model of PBLH temporal variation (DTDS). The latter helps “recalibrate” the PBLH in the presence of a residual aerosol layer that does not change in harmony with PBL diurnal variation. -
Terrestrial Biosphere Carbon Storage Under Alternative Climate Projections
TERRESTRIAL BIOSPHERE CARBON STORAGE UNDER ALTERNATIVE CLIMATE PROJECTIONS SIBYLL SCHAPHOFF1, WOLFGANG LUCHT1, DIETER GERTEN1, STEPHEN SITCH1, WOLFGANG CRAMER1 and I. COLIN PRENTICE2 1Potsdam Institute for Climate Impact Research, P.O. Box 601203, D-14412 Potsdam, Germany E-mail: [email protected] 2QUEST, Department of Earth Sciences, University of Bristol, Wills Memorial Building, Bristol BS8 1RJ, UK Abstract. This study investigates commonalities and differences in projected land biosphere carbon storage among climate change projections derived from one emission scenario by five different gen- eral circulation models (GCMs). Carbon storage is studied using a global biogeochemical process model of vegetation and soil that includes dynamic treatment of changes in vegetation composition, a recently enhanced version of the Lund-Potsdam-Jena Dynamic Global Vegetation Model (LPJ- DGVM). Uncertainty in future terrestrial carbon storage due to differences in the climate projections is large. Changes by the end of the century range from −106 to +201 PgC, thus, even the sign of the response whether source or sink, is uncertain. Three out of five climate projections produce a land carbon source by the year 2100, one is approximately neutral and one a sink. A regional breakdown shows some robust qualitative features. Large areas of the boreal forest are shown as a future CO2 source, while a sink appears in the arctic. The sign of the response in tropical and sub-tropical ecosys- tems differs among models, due to the large variations in simulated precipitation patterns. The largest uncertainty is in the response of tropical rainforests of South America and Central Africa. 1. Introduction The land biosphere plays a substantial role in the global carbon cycle. -
The Seasonal Cycle of Planetary Boundary Layer Depth
1 The seasonal cycle of planetary boundary layer depth 2 determined using COSMIC radio occultation data 3 4 Ka Man Chan and Robert Wood 5 Department of Atmospheric Science, University of Washington, Seattle WA 6 7 Abstract. 8 The seasonal cycle of planetary boundary layer (PBL) depth is examined globally using 9 observations from the Constellation Observing System for the Meteorology, Ionosphere, and 10 Climate (COSMIC) satellite mission. COSMIC uses GPS Radio Occultation (GPS-RO) to derive 11 the vertical profile of refractivity at high vertical resolution (~100 m). Here, we describe an 12 algorithm to determine PBL top height and thus PBL depth from the maximum vertical gradient 13 of refractivity. PBL top detection is sensitive to hydrolapses at non-polar latitudes but to both 14 hydrolapses and temperature jumps in polar regions. The PBL depths and their seasonal cycles 15 compare favorably with selected radiosonde-derived estimates at Tropical, midlatitude and 16 Antarctic sites, adding confidence that COSMIC can effectively provide estimates of seasonal 17 cycles globally. PBL depth over extratropical land regions peaks during summer consistent with 18 weak static stability and strong surface sensible heating. The subtropics and Tropics exhibit a 19 markedly different cycle that largely follows the seasonal march of the intertropical convergence 20 zone (ITCZ) with the deepest PBLs associated with dry phases, again suggestive that surface 21 sensible heating deepens the PBL and that wet periods exhibit shallower PBLs. 22 Marine PBL depth has a somewhat similar seasonal march to that over continents but is 23 weaker in amplitude and is shifted poleward. -
Chapter 2. Turbulence and the Planetary Boundary Layer
Chapter 2. Turbulence and the Planetary Boundary Layer In the chapter we will first have a qualitative overview of the PBL then learn the concept of Reynolds averaging and derive the Reynolds averaged equations. Making use of the equations, we will discuss several applications of the boundary layer theories, including the development of mixed layer as a pre-conditioner of server convection, the development of Ekman spiral wind profile and the Ekman pumping effect, low-level jet and dryline phenomena. The emphasis is on the applications. What is turbulence, really? Typically a flow is said to be turbulent when it exhibits highly irregular or chaotic, quasi-random motion spanning a continuous spectrum of time and space scales. The definition of turbulence can be, however, application dependent. E.g., cumulus convection can be organized at the relatively small scales, but may appear turbulent in the context of global circulations. Main references: Stull, R. B., 1988: An Introduction to Boundary Layer Meteorology. Kluwer Academic, 666 pp. Chapter 5 of Holton, J. R., 1992: An Introduction to Dynamic Meteorology. Academic Press, New York, 511 pp. 2.1. Planetary boundary layer and its structure The planetary boundary layer (PBL) is defined as the part of the atmosphere that is strongly influenced directly by the presence of the surface of the earth, and responds to surface forcings with a timescale of about an hour or less. 1 PBL is special because: • we live in it • it is where and how most of the solar heating gets into the atmosphere • it is complicated due to the processes of the ground (boundary) • boundary layer is very turbulent • others … (read Stull handout). -
The Planetary Boundary Layer
January 27, 2004 9:4 Elsevier/AID aid CHAPTER 5 The Planetary Boundary Layer The planetary boundary layer is that portion of the atmosphere in which the flow field is strongly influenced directly by interaction with the surface of the earth. Ultimately this interaction depends on molecular viscosity. It is, however, only within a few millimeters of the surface, where vertical shears are very intense, that molecular diffusion is comparable to other terms in the momentum equation. Outside this viscous sublayer molecular diffusion is not important in the boundary layer equations for the mean wind, although it is still important for small-scale tur- bulent eddies. However, viscosity still has an important indirect role; it causes the velocity to vanish at the surface. As a consequence of this no-slip boundary con- dition, even a fairly weak wind will cause a large-velocity shear near the surface, which continually leads to the development of turbulent eddies. These turbulent motions have spatial and temporal variations at scales much smaller than those resolved by the meteorological observing network. Such shear-induced eddies, together with convective eddies caused by surface heating, are very effective in transferring momentum to the surface and transferring heat (latent and sensible) away from the surface at rates many orders of magnitude faster than can be done by molecular processes. The depth of the planetary boundary layer produced by this turbulent transport may range from as little as 30 m in conditions of large 115 January 27, 2004 9:4 Elsevier/AID aid 116 5 the planetary boundary layer static stability to more than 3 km in highly convective conditions. -
Climate Models an Assessment of Strengths and Limitations
Climate Models An Assessment of Strengths and Limitations U.S. Climate Change Science Program Synthesis and Assessment Product 3.1 July 2008 FEDERAL EXECUTIVE TEAM Acting Director, Climate Change Science Program ......................................................William J. Brennan Director, Climate Change Science Program Office.......................................................Peter A. Schultz Lead Agency Principal Representative to CCSP; Associate Director, Department of Energy, Office of Biological and Environmental Research .........................................................................................Anna Palmisano Product Lead; Department of Energy, Office of Biological and Environmental Research ........................................................Anjuli S. Bamzai Synthesis and Assessment Product Advisory Group Chair; Associate Director, EPA National Center for Environmental Assessment.....................................................................................................................Michael W. Slimak Synthesis and Assessment Product Coordinator, Climate Change Science Program Office ......................................................................Fabien J.G. Laurier OTHER AGENCY REPRESENTATIVES National Aeronautics and Space Administration ...........................................................Donald Anderson National Oceanic and Atmospheric Administration ......................................................Brian D. Gross National Science Foundation .........................................................................................Jay -
Biosphere-Atmosphere Interactions Over West Africa. I: Development and Validation of a Coupled Dynamic Model
Q. J. R. Meteorol. Soc. (2000), 126, pp. 1239-1260 Biosphere-atmosphere interactions over West Africa. I: Development and validation of a coupled dynamic model By GUILING WANG' and ELFATM A. B. ELTAHJR Massachusetts Institute of Technology, USA (Received 12 April 1999; revised 7 September 1999) SUMMARY In this study we develop a zonally symmetric, synchronously coupled biosphere-atmosphere model including ecosystem dynamics, and apply this model to study biosphere-atmosphere interactions in the region of West Africa. The atmospheric model is zonally symmetric, and includes representation of atmospheric dynamics, a radiation scheme, a moist convection scheme, a boundary-layer scheme, and a cloud-parametrization scheme. The biospheric model is the Integrated BIosphere Simulator (IBIS), which includes representation of the water, energy, momentum, and carbon balance, vegetation phenology, and vegetation dynamics. We modified the representation of canopy hydrology in IBIS to account for the impact of rainfall subgrid variability. The biospheric model and atmospheric model are separately tested against observations. The synchronously coupled model is then used to simulate the biosphere-atmosphere system of West Africa. A study on the role of biosphere-atmosphere interactions, including ecosystem dynamics, in the climate variability over West Africa using this model will be presented in a companion paper. KEYWORDS: Biosphere-atmosphere interactions Drought Ecosystem dynamics West Africa 1. INTRODUCTION In the past two decades, significant scientific effort has been devoted to the study of the severe persistent drought in West Africa which started in the late 1960s. Among other factors, land-surface feedback triggered by man-made desertification is widely viewed as a possible mechanism for the drought occurrence and its persistence. -
Quantifying the UK's Carbon Dioxide Flux: an Atmospheric Inverse
Quantifying the UK’s Carbon Dioxide Flux: An atmospheric inverse modelling approach using a regional measurement network Emily D. White1, Matthew Rigby1, Mark F. Lunt1,2, T. Luke Smallman2,3, Edward Comyn-Platt4, Alistair J. Manning5, Anita L. Ganesan6, Simon O’Doherty1, Ann R. Stavert1,7, Kieran Stanley1, Mathew 5 Williams2,3, Peter Levy8, Michel Ramonet9, Grant L. Forster10,11, Andrew C. Manning10, Paul I. Palmer2 1School of Chemistry, University of Bristol, Bristol, BS8 1TS, UK 2School of GeoSciences, University of Edinburgh, Edinburgh, EH9 3FF, UK 3National Centre for Earth Observation, Edinburgh, EH9 3FF, UK 4Centre for Ecology and Hydrology, Wallingford, OX10 8BB, UK 10 5Hadley Centre, Met. Office, Exeter, EX1 3PB, UK 6School of Geographical Sciences, University of Bristol, Bristol, BS8 1SS, UK 7Climate Science Centre, CSIRO Oceans and Atmosphere, Aspendale VIC 3195, Australia 8Centre for Ecology and Hydrology (Edinburgh Research Station), Penicuik, E26 0QB, UK 9Laboratoire des Sciences du Climat et de l’Environnement, CEA-CNRS-UVSQ, Gif-sur-Yvette, 91198, France 15 10Centre for Ocean and Atmospheric Sciences, School of Environmental Sciences, University of East Anglia, Norwich, NR4 7TJ, UK 11National Centre for Atmospheric Science, School of Environmental Sciences, University of East Anglia, Norwich, NR4 7TJ, UK Correspondence to: Emily White ([email protected]), Matthew Rigby ([email protected]) 20 Abstract. We present a method to derive atmospheric-observation-based estimates of carbon dioxide (CO2) fluxes at the national scale, demonstrated using data from a network of surface tall tower sites across the UK and Ireland over the period 2013-2014. The inversion is carried out using simulations from a Lagrangian chemical transport model and an innovative hierarchical Bayesian Markov chain Monte Carlo (MCMC) framework, which addresses some of the traditional problems faced by inverse modelling studies, such as subjectivity in the specification of model and prior uncertainties.