Publications by Raymond Pierrehumbert

The advection-diffusion problem for stratospheric flow. Part II: Probability distribution function of tracer gradients


YY Hu, RT Pierrehumbert

The hydrologic cycle in deep-time climate problems.

Nature 419 (2002) 191-198

RT Pierrehumbert

Hydrology refers to the whole panoply of effects the water molecule has on climate and on the land surface during its journey there and back again between ocean and atmosphere. On its way, it is cycled through vapour, cloud water, snow, sea ice and glacier ice, as well as acting as a catalyst for silicate-carbonate weathering reactions governing atmospheric carbon dioxide. Because carbon dioxide affects the hydrologic cycle through temperature, climate is a pas des deux between carbon dioxide and water, with important guest appearances by surface ice cover.

Surface quasigeostrophic turbulence: The study of an active scalar.

Chaos 12 (2002) 439-450

J Sukhatme, RT Pierrehumbert

We study the statistical and geometrical properties of the potential temperature (PT) field in the surface quasigeostrophic (SQG) system of equations. In addition to extracting information in a global sense via tools such as the power spectrum, the g-beta spectrum, and the structure functions we explore the local nature of the PT field by means of the wavelet transform method. The primary indication is that an initially smooth PT field becomes rough (within specified scales), though in a qualitatively sparse fashion. Similarly, initially one-dimensional iso-PT contours (i.e., PT level sets) are seen to acquire a fractal nature. Moreover, the dimensions of the iso-PT contours satisfy existing analytical bounds. The expectation that the roughness will manifest itself in the singular nature of the gradient fields is confirmed via the multifractal nature of the dissipation field. Following earlier work on the subject, the singular and oscillatory nature of the gradient field is investigated by examining the scaling of a probability measure and a sign singular measure, respectively. A physically motivated derivation of the relations between the variety of scaling exponents is presented, the aim being to bring out some of the underlying assumptions which seem to have gone unnoticed in previous presentations. Apart from concentrating on specific properties of the SQG system, a broader theme of the paper is a comparison of the diagnostic inertial range properties of the SQG system with both the two- and three-dimensional Euler equations. (c) 2002 American Institute of Physics.

The advection-diffusion problem for stratospheric flow. Part I: Concentration probability distribution function


Y Hu, RT Pierrehumbert

Impact of ocean dynamics on the simulation of the Neoproterozoic "snowball Earth"


CJ Poulsen, RT Pierrehumbert, RL Jacob

A new approach to stable isotope-based paleoaltimetry: implications for paleoaltimetry and paleohypsometry of the High Himalaya since the Late Miocene


DB Rowley, RT Pierrehumbert, BS Currie

Physical Climate Processes and Feedbacks

in Climate Change 2001: The Scientific Basis Contribution of Working Group I to the Third Assessment Report of the Intergovernmental Panel on Climate Change, Cambridge University Press (2001) 7

T Stocker, RT Pierrehumbert, G Clarke, TN Palmer, K Trenberth, R Lindzen

Climate Change 2001: The Scientific Basis is the most comprehensive and up-to-date scientific assessment of past, present and future climate change.

'Equability' in an unequal world: The early Eocene revisited

GFF 122 (2000) 101-102

PJ Markwick, PJ Valdes, BW Sellwood, RT Pierrehumbert

Lattice models of advection-diffusion.

Chaos (Woodbury, N.Y.) 10 (2000) 61-74

RT Pierrehumbert

We present a synthesis of theoretical results concerning the probability distribution of the concentration of a passive tracer subject to both diffusion and to advection by a spatially smooth time-dependent flow. The freely decaying case is contrasted with the equilibrium case. A computationally efficient model of advection-diffusion on a lattice is introduced, and used to test and probe the limits of the theoretical ideas. It is shown that the probability distribution for the freely decaying case has fat tails, which have slower than exponential decay. The additively forced case has a Gaussian core and exponential tails, in full conformance with prior theoretical expectations. An analysis of the magnitude and implications of temporal fluctuations of the conditional diffusion and dissipation is presented, showing the importance of these fluctuations in governing the shape of the tails. Some results concerning the probability distribution of dissipation, and concerning the spatial scaling properties of concentration fluctuation, are also presented. Though the lattice model is applied only to smooth flow in the present work, it is readily applicable to problems involving rough flow, and to chemically reacting tracers. (c) 2000 American Institute of Physics.

Spatially correlated and inhomogeneous random advection

PHYSICS OF FLUIDS 12 (2000) 822-834

K Ngan, RT Pierrehumbert

Atmospheric pCO<inf>2</inf>sensitivity to the biological pump in the ocean

Global Biogeochemical Cycles 14 (2000) 1219-1230

DE Archer, G Eshel, A Winguth, W Broecker, R Pierrehumbert, M Tobis, R Jacob

In models of the global carbon cycle, the pCO2of the atmosphere is more sensitive to the chemistry of the high-latitude surface ocean than the tropical ocean. Because sea-surface nutrient concentrations are generally high in the high latitudes, pCO2sensitivity to high-latitude forcing also determines pCO2sensitivity to the biological pump globally. We diagnose high-latitude sensitivity of a range of ocean models using atmospheric pCO2above an abiotic ocean; cold high-latitude waters pull abiotic pCO2to low values. Box models are very high-latitude sensitive, while most global circulation models are considerably less so, including a two-dimensional overturning model, two primitive equation models, the Hamburg class of large scale geostrophic (LSG) general circulation models (GCMs), and the MICOM isopycnic GCM. High-latitude forcing becomes more important in a depth-coordinate GCM when lateral diffusion is oriented along isopycnal surfaces, rather than horizontally, following Redi [1982]. In two different GCMs (a primitive equation model and LSG), addition of the Gent and McWilliams [1990] isopycnal thickness diffusion scheme had only minor impact on high-latitude sensitivity. Using a simplified box model, we show that high-latitude sensitivity depends on a high-latitude monopoly on deep water formation. In an attempt to bridge the gap between box models and GCMs, we constructed a simple slab overturning model with an imposed stream function which can be discretized at arbitrary resolution from box model to GCM scale. High-latitude sensitivity is independent of model resolution but very sensitive to vertical diffusion. Diffusion acts to break the high-latitude monopoly, decreasing high-latitude sensitivity. In the isopycnal GCM MICOM, however, high-latitude sensitivity is relatively insensitive to diapycnal diffusion of tracers such as CO2. This would imply that flow pathways in MICOM take the place of vertical diffusion in the slab model. The two nominally most sophisticated ocean models in the comparison are the isopycnal model MICOM and the depth-coordinate GCM with Redi [1982] and Gent and McWilliams [1990] mixing. Unfortunately, these two models disagree in their abiotic CO2behavior; the depth-coordinate isopycnal mixing GCM is high-latitude sensitive, in accord with box models, while MICOM is less so. The rest of the GCMs, which have historically seen the most used in geochemical studies, are even less high-latitude sensitive than MICOM. This discrepancy needs to be resolved. In the meantime, the implication of the MICOM/traditional GCM result would be that box models overestimate high-latitude sensitivity of the real ocean. This would eliminate iron dust fertilization of the ocean as an explanation for the glacial pCO2range of 180-200 uatm [Archer et al., 2000].

Climate change and the tropical Pacific: the sleeping dragon wakes.

Proceedings of the National Academy of Sciences of the United States of America 97 (2000) 1355-1358

RT Pierrehumbert

Subtropical water vapor as a mediator of rapid global climate change

in Mechanisms of Global Climate Change at Millennial Time Scales, American Geophysical Union (1999) 22
Part of a series from Geophysical Monograph Series

RT Pierrehumbert

Mixing of an advected-diffused tracer in the lower stratosphere: probability distribution functions of tracer gradients and differences


YY Hu, RT Pierrehumbert, AMS, AMS

Spatially inhomogeneous random advection


K Ngan, RT Pierrehumbert, AMS, AMS

Huascaran delta O-18 as an indicator of tropical climate during the Last Glacial Maximum


RT Pierrehumbert

Dynamics of a passive tracer in a velocity field of four identical point vortices


S Boatto, RT Pierrehumbert

Subtropical water vapor as a mediator of rapid global climate change

in Geophysical Monograph Series, 112 (1999) 339-361

RT Pierrehumbert

© 1999 by the American Geophysical Union. This article surveys the essential features of atmospheric water vapor dynamics needed to address current issues regarding the possible role of water vapor changes in mediating climate fluctuations on the millennial to Milankovic time scales. The focus is on the subtropics, which afford the most interesting possibilities for significant feedbacks. The observed distribution of water vapor, the amount by which water vapor must change in order to cause a significant temperature change, and the physical factors that determine the water vapor content of the subtropical atmosphere are discussed. It is shown that halving the subtropical relative humidity would lead to a 2.5K cooling of the tropics, while doubling it would lead to a 3K warming. The humidity content of the subtropics could be reduced by enhancing subsidence, reducing transient eddy activity, or contracting the convective region. Further work is needed to determine which, if any, of these changes occur in concert with the observed millennial and longer scale climate fluctions.

On the scattering greenhouse effect of CO2 ice clouds


RT Pierrehumbert, C Erlick

Lateral mixing as a source of subtropical water vapor


RT Pierrehumbert