Jose P. Peixoto

The Atmospheric Branch Of The Hydrological Cycle And Climate

Based on daily observations from about 1000 rawinsonde stations, tables and global distributions of the various water vapour fields are presented for mean annual, winter and summer conditions covering the 10-year period, May 1963 through April 1973. The fields include horizontal maps of precipitable water, of total zonal, meridional and vertical transports by eddy and mean circulations, as well as meridional profiles and zonal mean cross-sections of these quantities.

Global Angular Momentum and Energy Balance Requirements from Observations

Publisher Summary This chapter presents an overview of global angular momentum and energy balance requirements deduced through observations. The structure of the basic circulation, the temperature, humidity, and kinetic energy fields, both regarding their long-term mean values and their day-to-day and seasonal variability characteristics, are discussed. Following this, the three-dimensional structure of the transports by the transient eddy, stationary eddy, and mean meridional circulations are explained. The chapter describes how the source regions of incoming solar radiation and the sink regions of outgoing terrestrial radiation are distributed over the globe, and how the atmosphere and oceans respond to these forcing factors. It also explores what happens to the solar energy once it has entered the atmosphere. The storage and transport of energy in the atmosphere is analyzed, followed by a discussion on the amount of energy that flows into the underlying surface. The storage and transport of energy in the oceans is also discussed..

Entropy budget of the atmosphere

The balance equations for the entropy in the atmosphere are presented and discussed. Using observed energy fluxes and atmospheric temperatures, we present estimates of the various terms in the global mean entropy budget. The largest boundary fluxes of entropy are associated with the emission of longwave radiation. The fluxes of entropy associated with turbulent and molecular diffusion are found to be much smaller. On the planetary scale the mean outgoing flux of entropy at the top of the atmosphere is found to be about 22 times larger than the mean incoming flux of entropy through solar radiation. The rates of entropy production and destruction by the various irreversible processes that occur in the atmosphere are also computed. The entropy production terms involved in the release of latent heat and the absorption of solar radiation are, by far, the largest sources of entropy for the atmosphere, whereas the production of entropy associated with the absorption of longwave radiation is an order of magnitude smaller. The destruction is mainly accomplished through cooling by outgoing longwave radiation. The contributions of the sensible heat fluxes and friction are relatively small. Regional contributions to the total entropy generation in the atmosphere are studied by considering an equatorial region bounded by two latitudinal walls at 15oN and 15oS and a polar region poleward of 70oN. The rates of entropy generation by the various diabatic processes are highest in the equatorial region; part of the generated entropy is exported to higher latitudes. Most natural phenomena occurring in the climate system are characterized by great irreversibility. For example, the turbulent motion in the planetary boundary layer does not spontaneously develop into the large-scale organized flow of the general circulation; a cloud cannot be reconstituted from the same water it lost previously through precipitation; rivers do not flow backward from the sea to their headwaters; and ocean water does not decompose spontaneously into oxygen and hydrogen. We will analyze the entropy budget of the atmosphere since it is important for the study of the thermodynamical behavior of the climatic system and, in particular, for atmospheric phenomena. The second law for an isolated system,

Estimates of the energy cycle of the oceans

A new formulation of the general problem of the large-scale energetics for the global oceans is presented and analyzed. Using a variety of ocean surface observations, some of the terms in the energy balance equations, such as the time rates of change, the generation rates of available gravitational potential energy G(P) and kinetic energy G(K), and the conversion rate from available gravitational potential energy into kinetic energy C(P, K), are estimated for annual and seasonal mean conditions. An attempt is also made to measure the uncertainty of these terms in order to assess the reliability of the results. The interseasonal variability is analyzed showing that the winter hemisphere represents the most active region of the globe. Using the data and some reasonable assumptions, pictures of the energy cycle in the global oceans for yearly and seasonal conditions are constructed. The hemispheric and global dissipation rates of available gravitational potential energy D(P) and of kinetic energy D(K) are estimated as residuals, assuming that the contribution from the internal energy C(I, K) is only a minor factor. After analyzing the general consistency of the picture of the energy cycle for the oceans, the conclusion is reached that the G(P) and G(K) terms are about equally important terms needed to describe and understand the structure and dynamics of the global ocean circulation.

On the meridional flux of water vapor in the northern hemisphere

SummaryIn this paper data are presented concerning the zonal transport of water vapor at several levels in the atmosphere for winter, for summer and for the calendar year of 1950, over the northern hemisphere. Vertical integrals and zonal averages are included in the discussion.

THE AUTOREGRESSIVE MODEL OF CLIMATOLOGICAL TIME SERIES: AN APPLICATION TO THE LONGEST TIME SERIES IN PORTUGAL

The autoregressive model is extremely useful for the representation of many geophysical time series. The present paper deals, in the first place, with the analysis of sets of meteorological observations (temperature and precipitation) made sequentially in time, from 1856 to 1994, at equidistant time intervals Δt = 1 year. The best fitting is an autoregressive model of order 45. A thorough discussion of the temperature observation time series is presented, showing two main salient features: an approximately 0ċ6°C secular trend during the past century and a definite warming in the 1980s and early 1990s. The estimated values of temperature and precipitation are compared with the observed data series.

Modes of Variability in Annual Hemispheric Water Vapor and Transport Fields

Abstract The variability of annually averaged water vapor and water vapor transport fields over the Northern Hemisphere during the fifteen year period 1958–1973 is studied by means of empirical orthogonal function (EOF) analysis. Examined are vertically integrated values of the moisture quantities at a set of 91 stations chosen to cover the hemisphere as uniformly as possible. Analyses of the zonal and meridional transports are performed separately, but in addition a version of the EOF analysis is performed in which the two are treated as components of a single vector. All resulting modes are examined in light of statistical significance criteria established through a form of Monte Carlo testing. The first mode in moisture variability appears to be highly significant, and it is dominated by opposite behavior in the held over Africa and over the western equatorial Pacific. Its time series reflects a sharp change in regime during the period studied. The significant mode of variability in the zonal transport...

Harmonic analysis of the mean northern hemisphere water vapor distribution for the year 1950

SummaryHarmonic analyses along latitudes 30°, 45° and 60° of the mean northern hemisphere water vapor field are presented. The seasonal variations of these spectra are investigated and the relative contributions of the various scales of mean eddies to the meridional transport of water vapor are calculated. Of special interest is the finding that perturbations of wave number 2, corresponding to the great continents and oceans, are dominant at all three latitudes and of primary importance in effecting the northward transport of water vapor.

Seasonal variability in the pole-to-pole modes of water vapor transport during the IGY

SummaryAnalyses of the global fields of moisture transport have been decomposed into their transient eddy, standing eddy and mean cell components for each of two semester seasons during the IGY. Maps of the vertically integrated transient eddy fluxes in both the zonal and meridional directions are presented. Further consideration is given to the zonally averaged fields of moisture transport by the different modes. In the zonal direction, the influence of the mean cellular mode is dominant. In the meridional direction, the transient eddies play a significant role in the seasonal water balance of mid-latitudes, whereas the mean meridional circulation is the determining mode in the tropics. Standing eddy contributions are generally small. Differences in the water vapor fluxes associated with each mode from one season to the next are depicted and related to baroclinic effects and monsoonal behavior where they occur.ZusammenfassungDurch Analysen der globalen Felder des Feuchtetransportes wurde dieser in seine Anteile von wandernden Wirbeln, stationären Wirbeln und mittlerer Zirkulation für jedes von zwei Halbjahren im Internationalen Geophysikalischen Jahr aufgegliedert. Es werden Karten des vertikal integrierten Flusses auf Grund wandernder Wirbel in zonaler und in vertikaler Richtung vorgelegt. Ferner werden Betrachtungen über die zonal gemittelten Felder des durch die verschiedenen Arten bewirkten Feuchtetransportes angestellt. In zonaler Richtung ist der Einfluß der mittleren zellularen Zirkulation vorherrschend. In meridionaler Richtung spielen die wandernden Wirbel eine bedeutende Rolle im jahreszeitlichen Wasserhaushalt der mittleren Breiten, während die mittlere meridionale Zirkulation die bestimmende Art in den Tropen darstellt. Die Beiträge stationärer Wirbel sind im allgemeinen klein. Die Unterschiede des mit jeder Art verbundenen Wasserdampfflusses von einer Jahreszeit zur anderen werden beschrieben und mit baroklinen Auswirkungen und mit monsunalem Verhalten, wo solches auftritt, in Beziehung gebracht.

The role of the atmosphere in the water cycle

The hydrological cycle is a consequence of the conservation of water substance in the climatic system in its three phases and must be regarded in toto with the aerial and terrestrial branches.