Changes In Lapse Rate Research Articles

Non-linear climate feedback analysis in an atmospheric general circulation model

A method is described for evaluating the ‘partial derivatives’ of globally averaged top-of-atmosphere (TOA) radiation changes with respect to basic climate model physical parameters. This method is used to analyse feedbacks in the Australian Bureau of Meteorology Research Centre general circulation model. The parameters considered are surface temperature, water vapour, lapse rate and cloud cover. The climate forcing which produces the changes is a globally uniform sea surface temperature (SST) perturbation. The first and second order differentials of model parameters with respect to the forcing (i.e. SST changes) are estimated from quadratic least square fitting. Except for total cloud cover, variables are found to be strong functions of global SST. Strongly non-linear variations of lapse rate and high cloud amount and height appear to relate to the non-linear response in penetrative convection. Globally averaged TOA radiation differentials with respect to model parameters are also evaluated. With the exception of total cloud contributions, a high correlation is generally found to exist, on the global mean level, between TOA radiation and the respective parameter perturbations. The largest non-linear terms contributing to radiative changes are those due to lapse rate and high cloud. The contributions of linear and non-linear terms to the overall radiative response from a 4 K SST perturbation are assessed. Significant non-linear responses are found to be associated with lapse rate, water vapour and cloud changes. Although the exact magnitude of these responses is likely to be a function of the particular model as well as the imposed SST perturbation pattern, the present experiments flag these as processes which cannot properly be understood from linear theory in the evaluation of climate change sensitivity.

Relative influence of lapse rate and water vapor on the greenhouse effect

Observational data are employed in a radiative transfer model to simulate the mean variation in normalized greenhouse effect (NGE) between January and July. This is performed at a variety of locations, and the mean local rate of change in NGE with surface temperature is determined. The result is 1.5 times larger than the variation of NGE with surface temperature obtained by spatially correlating the aggregated data. This disagreement is ascribed to systematic differences between the two approaches and is interpreted as indicating the significant role that large‐scale circulations as well as surface temperatures have on determining local thermal and humidity structures. The separate effects of water vapor and lapse rate variations are estimated, by simulating the January‐July changes in NGE with each process in turn held constant: beyond the tropics the lapse rate feedback is found to dominate over the water vapor feedback, particularly over land; in the inter‐tropics, lapse rate variations account for about a third of the change in greenhouse trapping, contributing substantially to the “super‐greenhouse effect.” Utilizing a radiative‐convective model, the possible effects on climate change of both lapse rate changes and water vapor feedback are compared: a global mean model climate is perturbed by a doubling of atmospheric carbon dioxide and equilibrium surface temperatures obtained for a variety lapse rates. If, under conditions of climate change, the global mean lapse rate varies with surface temperature in the same manner as in the present‐day mean seasonal cycle (increasing the lapse rate magnitude by 6%), then the lapse rate feedback amplifies the modeled water vapor feedback by 40%; conversely, a 12% reduction in the magnitude of the lapse rate completely nullifies the water vapor feedback.

Use of MST radars to probe the mesoscale structure of the tropopause

Profiles of the power scattered at vertical incidence by an MST radar have been compared with temperature profiles measured by radiosondes launched nearby. The results are consistent with a standard scattering model for low and medium scattered power, but deviate from the model at high power. Tropopause heights have been derived from the radar data by two methods: the maximum power and maximum power gradient. The two criteria appear to be equally effective as predictors of the tropopause, despite the theoretical expectation that the latter should be superior. Radiosonde tropopauses which were highly indefinite (no marked change in lapse rate between troposphere and stratosphere) were associated with a shallower minimum than normal in the radar power profile in the upper troposphere. This ability to detect highly indefinite tropopauses shows that an MST radar may be used to monitor continuously the structure of the thermal tropopause. DOI: 10.1034/j.1600-0870.1995.00118.x

Relationship between clear‐sky atmospheric greenhouse effect and deep convection during the Central Equatorial Pacific Experiment: Model calculations and satellite observations

This study investigates the relation between tropical convection and the atmospheric greenhouse effect using data collected during the Central Equatorial Pacific Experiment (CEPEX). We present calculations of total clear‐sky greenhouse effect and its partitioning between the lower, middle, and upper troposphere using high‐quality balloon soundings of temperature and humidity as input to a radiative transfer model. The soundings were taken from a ship every 6 hours from March 7 to 20, 1993, in the central Pacific. We examine the influence on atmospheric greenhouse effect due to changes in humidity and lapse rate and investigate the relationship between atmospheric greenhouse effect, water vapor, and deep convection. Our observations indicate that periods of active or suppressed convection with timescales of the order of days can produce large spatial gradients in clear‐sky atmospheric greenhouse trapping in warm, climatologically convective regions. While the sea surface temperature (SST) decreased by 2 K from west to east, temperatures above 850 mbar showed considerably less variation. Accordingly, lapse rate changes occurred primarily in the boundary layer and such changes account for 80% of the gradient in boundary layer greenhouse effect. The column‐integrated water vapor content from the surface to 850 mbar was nearly constant in each of the regimes. Conversely, large variations in column‐integrated water vapor above 850 mbar and particularly above 500 mbar account for nearly all the gradient in the greenhouse effect in the middle and upper troposphere. Coincident outgoing longwave radiation (OLR) analyses derived from satellite observations show active deep convection in areas with high clear‐sky greenhouse trapping and upper level moisture and generally clear, suppressed conditions elsewhere. In addition, the surface net flux and outgoing flux emitted to space decreased with increased SST. The reduced cooling of the ocean‐atmosphere system is consistent with a supergreenhouse effect operating in regions of deep convection.

Infrared flux parameterizations derived from climate changes in a three‐dimensional climate model

Output from four experiments with the Goddard Institute for Space Studies climate model, simulating climates ranging from ice age conditions to Mesozoic conditions, are used to test whether simple parameterizations of infrared (IR) emissions to space can be applied to annual average climate changes. The possible predictors of IR emissions examined are zonally averaged surface temperature, fractional cloud cover, average cloud top height, tropospheric lapse rate, and atmospheric moisture content. First, parameterizations are derived from latitudinal variations simulated by the model for the current climate. The simplest such parameterization, with IR emissions being a linear function of surface temperature alone, predicts the simulated climate changes in IR emissions, with errors of about 35%. Inclusion of additional regression terms derived from latitudinal variations in the current climate does not improve the prediction of changes in IR emissions. However, by deriving regressions from one climate change and applying them to the other changes, we demonstrate that adding a term describing lapse rate changes reduces the error in the predicted IR flux changes to between 25 and 30%. The lapse rate changes approximately follow the change in moist adiabatic lapse rate in the tropics and the change in the critical lapse rate for baroclinic adjustment in middle latitudes, unless the climate change is so large as to cause a qualitative change in the dynamical regimes. Only a very slight further reduction in the remaining error in the predicted changes in IR emissions was achieved by including an additional predictor, and there was no clear‐cut best choice for the additional predictor.

Stability effects on aerosol size and height distributions

The usual description of the vertical distribution of aerosol concentrations assumes neutral atmospheric stratification. This work examines the influence of atmospheric stability on vertical aerosol concentration profile. A model is developed to describe the aerosol transport in the atmospheric surface layer. The model describes a balance between upward aerosol flux due to atmospheric turbulence and downward flux due to gravitational deposition. Monin-Obukhov similarity theory describes the turbulent profiles of wind, temperature and specific humidity. An approximate equilibrium expression relates particle size to ambient relative humidity. To isolate the role of transport and growth, we first use the model to describe the surface layer concentration of inert particles unaffected by relative humidity. The calculations show that growth phenomena must be included to correctly describe aerosol concentrations in the presence of relative humidity gradients. Complete calculations of aerosols concentrations, including growth effects, show that the concentration of large particles (radius greater than 5 ?m) can vary by an order of magnitude depending on stability. With light winds, the stability effect on large aerosols substantially affects the slope of the expected aerosol size distribution. With strong winds the aerosol distribution is not affected by changes in temperature and humidity lapse rates, but instead is governed by wind-shear-produced turbulent mixing. DOI: 10.1111/j.2153-3490.1980.tb00951.x

Stability effects on aerosol size and height distributions

The usual description of the vertical distribution of aerosol concentrations assumes neutral atmospheric stratification. This work examines the influence of atmospheric stability on vertical aerosol concentration profile. A model is developed to describe the aerosol transport in the atmospheric surface layer. The model describes a balance between upward aerosol flux due to atmospheric turbulence and downward flux due to gravitational deposition. Monin-Obukhov similarity theory describes the turbulent profiles of wind, temperature and specific humidity. An approximate equilibrium expression relates particle size to ambient relative humidity. To isolate the role of transport and growth, we first use the model to describe the surface layer concentration of inert particles unaffected by relative humidity. The calculations show that growth phenomena must be included to correctly describe aerosol concentrations in the presence of relative humidity gradients. Complete calculations of aerosols concentrations, including growth effects, show that the concentration of large particles (radius greater than 5 ?m) can vary by an order of magnitude depending on stability. With light winds, the stability effect on large aerosols substantially affects the slope of the expected aerosol size distribution. With strong winds the aerosol distribution is not affected by changes in temperature and humidity lapse rates, but instead is governed by wind-shear-produced turbulent mixing. DOI: 10.1111/j.2153-3490.1980.tb00951.x

Atmospheric Lapse Rate Regimes and Their Parameterization

Abstract Lapse rates, moist adiabatic lapse rates and the critical lapse rate for baroclinic adjustment are calculated and compared for the mean annual, January and July states in the Northern Hemisphere. In the troposphere above the planetary boundary layer zonal mean lapse rates are within 20% of the moist adiabatic lapse rate from the equator up to about 30°N in January and 50°N in July, but are appreciably more stable in higher latitudes. The latitudinal distribution of tropospheric mean lapse rates clearly delineates two regimes in the atmosphere—a low-latitude regime where the lapse rates are essentially moist adiabatic, and a high-latitude regime where the lapse rates are essentially the critical lapse rate for baroclinic adjustment. The dividing point between the two regimes shifts from 28°N in January to 47°N in July, and the transition is less sharp in July than in January. The absence of appreciable seasonal changes in lapse rates in midlatitudes can be attributed to counterbalancing seasonal c...

Climate Change: An Appraisal of Atmospheric Feedback Mechanisms Employing Zonal Climatology

The sensitivity of the earth's surface temperature to factors which can induce long-term climate change, such as a variation in solar constant, is estimated by employing two readily observable climate changes. One is the latitudinal change in annual mean climate, for which an interpretation of climatological data suggests that cloud amount is not a significant climate feedback mechanism, irrespective of how cloud amount might depend upon surface temperature, since there are compensating changes in both the solar and infrared optical properties of the atmosphere. It is further indicated that all other atmospheric feedback mechanisms, resulting, for example, from temperature-induced changes in water vapor amount, cloud altitude and lapse rate, collectively double the sensitivity of global surface temperature to a change in solar constant. The same conclusion is reached by considering a second type of climate change, that associated with seasonal variations for a given latitude zone. The seasonal interpretation further suggests that cloud amount feedback is unimportant zonally as well as globally. Application of the seasonal data required a correction for what appears to be an important seasonal feedback mechanism. This is attributed to a variability in cloud albedo due to seasonal changes in solar zenith angle. No attempt was made to individually interpret the collective feedback mechanisms which contribute to the doubling in surface temperature sensitivity. It is suggested, however, that the conventional assumption of fixed relative humidity for describing feedback due to water vapor amount might not be as applicable as is generally believed. Climate models which additionally include ice-albedo feedback are discussed within the framework of the present results.

Radar Measurement of Small Scale Turbulence and Thermal Stability in the Lower Atmosphere

Preliminary research results indicate that microwave, pulsed radar can be used to monitor the strength of temperature inversions and the magnitude of small scale turbulent eddies in the atmosphere at low altitudes. This is accomplished by the use of special video analysis equipment which monitors the amplitude and fluctuations of reflected signals from stable, stationary objects in the vicinity of the radar. Long and short period fluctuations are observed on the order of 103 to 10-1 minutes. The long period fluctuations appear to be manifestations of slow changes in the temperature lapse rate; and the short period ones of small scale turbulence in the lower atmosphere. The average strength of reflected signals increases as the lapse rate of temperature decreases in the lower atmosphere. Although atmospheric moisture content enters into the radio refractive index, apparently the highest average signal strengths are associated with ground-based or low altitude temperature inversions. Suitable radars present...

The Impact of Lapse Rates on Life Insurance Prices

The purpose of this paper is to measure the effect of changes in lapse rates on the price of life insurance protection to policyholders. The magnitude of the changes in lapse rates to be considered is determined by reference to data on lapse rates in various companies. Then, the impact of changes in lapse rates is compared to the impact of changes in mortality rates. The conclusions are that lapse rates have a substantial effect on price, and that consideration should be given to the use of expected lapse experience in the classification of life insurance applicants. The discontinuation of life insurance Joseph M. Belth, Ph.D., C.L.U., C.P.C.U., is Associate Professor of Insurance in the Graduate School of Business at Indiana University. He is author of Participating Life Insurance Sold by Stock Companies (1965), for which he received the 1966 Elizur Wright Award of the American Risk and Insurance Association, The Retail Price Structure in American Life Insurance (1966), and A Report on Life Insurance (1967). Dr. Belth is a frequent contributor to this Journal and serves as its Communications Editor. He has received four N.A.I.I. awards for papers published in this Journal. This paper was first presented on September 1, 1966, at the Fourth Annual Risk Theory Seminar of the American Risk and Insurance Association. The author wishes to acknowledge the financial support provided to the Risk Theory Seminar by the Cooperative League of the United States of America, including the following companies: Desjardins Mutual Life Insurance Company, Mutual Service Insurance Company, Cooperators Insurance Association, Co-operative Insurance Services, Ltd., La Societe d'Assurance des Caisses Populaires, Nationwide Insurance Company, and League Life Insurance Company. The author also wishes to acknowledge the asistance of Cheyeh Lin, then a doctoral candidate in Indiana University's Graduate School of Business and presently Assistant Professor of Finance at the University of Cincinnati, who handled a considerable portion of the data processing and tabulation of the results. The author alone, however, assumes full responsibility for the views expressed in the paper and for any errors that may remain. The computer used was the CDC 3600 in Indiana University's Research Computing Center. policies by policyholders prior to maturity or death is recognized as an important factor in the prices that life insurance companies charge their policyholders. For example, the tendency of increased lapse rates to increase the level of life insurance prices is generally cited as one of the primary reasons for discouraging the replacement of existing policies.' Nevertheless, the lapsation problem is usually referred to only in general terms, and, as far as the author has been able to determine, no specific analysis of the impact of lapse rates on prices has ever been published. The purpose of this paper, therefore, is to attempt to measure the effect of changes in lapse rates on the price of life insur-

Vertical distribution of atmospheric ozone and its relation to synoptic meteorological conditions

Results from an analysis of data obtained by means of the chemiluminescent ozone sonde in a series of observations at various stations in North America indicate that the vertical distribution of ozone is closely related to the thermal properties of the air masses through which the sounding is taken. Significant changes in temperature lapse rate or in the wind field frequently are associated with correspondingly significant changes in partial pressure of ozone. When the tropical high-level tropopause overlaps the extratropical tropopause, the ozone sounding frequently appears to be a composite of the upper part of a typical tropical sounding and the lower part of a typical middle-latitude sounding extending through the extratropical tropopause. Preliminary results are presented showing a comparison of the seasonal variation of the ratio Q1/Q2 of the amount of ozone in a lower layer of the atmosphere (300 to 100 mb) to that in an upper layer (100 to 40 mb) with the seasonal variation of the tropical-extratropical tropopause structure as indicated by monthly mean temperature soundings. It is shown that for selected stations at different latitudes the variation in the ratio Q1/Q2 is related to the variation in thickness of the layer of polar stratospheric air that intrudes into the subtropical troposphere.

Lapse rate change due to advection at lower levels and occurrence of pre-monsoon thunderstorms

Using the method of vertical wind shear vector difference, the change in lapse rate brought about by advection alone (upto a height of 5000-7000 ft) was estimated for Calcutta from the upper wind data of 0200 GMT ascent for every day, spread over a period of one month of the usual peak activity of nor'westers which (violent thunderstorms). This change applied to the morning tephigram is found to provide a moderately successful tool for prediction of local afternoon thunderstorms. The percentage of success for the period studied is nearly 80 per cent.

The Stratification of the Atmosphere1 (I)

A suitable nomenclature for atmospheric strata as well as a clear definition of the boundaries is proposed. The necessity of such a new classification is stressed. The atmosphere is divided into an inner and an outer atmosphere; from the latter particles may escape. The inner atmosphere is divided into three spheres—troposphere, stratosphere, and ionosphere—with each sphere in turn being subdivided into 3 or 4 layers. The new classification is based upon the thermal structure of the atmosphere.' Boundaries of each layer are fixed by a sudden change of lapse rate. The bottom layer, the ground layer, the advection layer, and the tropopause layer are subdivisions of the troposphere. The advantages gained by defining a separate tropopause layer as part of the troposphere are discussed in detail. Its upper boundary is assumed to be situated at 12 km over temperate latitudes. The stratosphere, consisting of an isothermal layer, a warm layer, and an upper mixing layer, extends from 12 to 80 km. The atmosphere between 80 and 800 km is occupied by the ionosphere, the subdivisions of which are the E-layer, the Flayer and the atomic layer. Above that height the exosphere exists.

A STUDY OF THE EFFECTS OF DIVERGENCE AND ADVECTION ON LAPSE RATE

Abstract The local twelve-hour change of temperature lapse rate from 5,000 to 10,000 feet is computed in 50 cases as a function of horizontal velocity divergence and vertical variation of horizontal temperature advection, and the result compared with the observed change of lapse rate. The divergence is measured from charts of horizontal velocity components; the vertical variation of horizontal temperature advection is measured by the rate of flow across the isotherms at two different levels and, as an alternate method, by the hodograph. The standard errors of estimate for these two methods are, respectively, 2.2 and 4.4 C km−1. The reliability of the measurements of divergence is studied by comparing the measured values with values computed from the difference between observed change of lapse rate and vertical variation of advection. The correlation coefficient relating these two methods is + 0.60 when advection is measured on constant level charts and + 0.40 when advection is measured by the hodograph.