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JULIAN ADEM

Abstract

Satellite observations of outgoing long-wave radiation and albedo presented by Winston are used to test a highly simplified radiation model. Computations with the model are consistent with the satellite observations and show that the outgoing long-wave radiation is inversely correlated to the albedo and cloudiness on a broad scale. However, the satellite values of albedo are much smaller than the computed values.

In order to lower the computed values of albedo so as to agree with the satellite ones, we would have to assume that the absorption of short-wave radiation by the water vapor, dust, ozone, and clouds in the atmosphere is equal roughly to twice the values estimated by London.

Assuming that the satellite values are correct, the discrepancies in outgoing long-wave radiation are probably due to the crudeness in the values of the effective atmospheric radiation temperature used in the model which are not well known and which can, therefore, be determined from the satellite values of outgoing long-wave radiation and cloudiness.

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JULIAN ADEM

Abstract

The author's thermal model for monthly and seasonal numerical prediction of temperatures is generalized, so that besides radiation other forms of heating (or the anomalies of heating) are generated within the model. This is done by expressing such heating as a linear function of variables predicted in the model.

The anomalies directly incorporated are those in the storages of thermal energy which are introduced by prescribing in the previous interval the temperature of the surface water in the oceans and the temperature of the midtroposphere, as well as the anomalies in the short-wave radiation absorbed by the surface; which in turn are introduced by prescribing the albedo (snow cover) at the end of the previous interval.

The numerical experiments show that important anomalies of the evaporation at the surface, of the vertical turbulent transport of sensible heat from the surface, of the condensation of water vapor in the clouds, and of the cloudiness are introduced by the anomalies of the computed temperature fields. Furthermore, these induced anomalies of the heating functions and of the cloudiness in turn introduce changes in the anomalies of the temperature fields.

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JULIÁN ADEM

Abstract

The mean relative humidity in the troposphere is expressed as a linear function of the total cloudiness, and the specific humidity as a function of temperature and cloudiness. A formula for the total precipitable water as a function of the cloudiness, the surface temperature, and the 500-mb. temperature is given. Computations of the total precipitable water over the Northern Hemisphere with the derived formula, using monthly averages, show good agreement with the estimates made by Starr, Peixoto, and Crisi.

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JULIAN ADEM

Abstract

By means of adequate parameterizations, the advection of heat by the mean wind and that by ocean currents are incorporated in a thermodynamic model for long-range weather prediction.

Numerical experiments with the revised model for a single case (January 1968) show that nonnegligible anomalies of wind and ocean currents are generated. These introduce important changes in the predicted surface temperature and in the 700-mb temperature anomalies. Furthermore, the predicted monthly anomalies of temperature are in good agreement with the observations and are better than those obtained when advection by mean wind is neglected.

An evaluation of the predictions by the model of the anomalies of the mean monthly surface air temperature for the whole year 1969 over the conterminous United States is presented; and it is shown that, for this period, the skill improves considerably when advection by the mean wind is included.

Normal temperatures are computed using normal observed geostrophic mean winds in the midtroposphere and climatological seasonal values of ocean currents.

For January, the effect of introducing advection by the prescribed observed normal geostrophic wind is to move toward the east the midcontinental troughs and midoceanic ridges that were obtained without advection. The resultant temperature distribution for the Northern Hemisphere at 700 mb is in remarkably good agreement with the observed values.

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JULIAN ADEM

Abstract

The three-dimensional fields of horizontal wind, vertical wind, pressure, and density are expressed as functions of the temperature, the density, and the lapse rate at a given height. Computations with the formulas for monthly values are carried out and compared with observations. It is found, in agreement with other authors, that at a height of about 8 km. there exists a constant density surface. This allows us to express the horizontal wind as a function of the temperature and the lapse rate.

A kinematic method to compute the vertical wind is given. The numerical computations show that the use of a geostrophic wind is a good working method for the computations of vertical wind when one deals with average states over periods of a month.

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JULIAN ADEM

Abstract

By considering the conservation of energy and the balance of radiation in the troposphere, in the cloud layer, and in the surface of the earth, we obtain a system of six equations containing six unknowns. The variables are the temperatures and the excesses of radiation in the troposphere, in the cloud layer, and in the surface of the earth. The equations contain as parameters the insolation, the cloudiness, the heat given off by the oceans and the continents to the atmosphere, and the initial temperature distributions. The model contains only meridional turbulent transport in the troposphere. Computations for both hemispheres and for the four seasons, as well as for the annual case, are carried out, obtaining a remarkable agreement with observations.

The meridional transport is accomplished by the cyclones and anticyclones of the middle latitudes with an austausch coefficient of the order of magnitude of 5×1010 cm.2 sec.−1.

The energy received from the surface of the earth by the atmosphere is very important for the maintenance and prediction of temperatures.

In the seasonal and in the annual cases there is no substantial storage of energy in the troposphere and a balance almost exists among the excess of radiation, the energy transported meridionally by turbulence, and the heat given off by the oceans and the continents. Therefore the prediction of the seasonal temperatures does not depend strongly on the initial temperatures in the troposphere itself.

In the annual case there also exists a balance in the upper layer of continents and oceans between the excess of radiation and the heat given off to the atmosphere. However in the seasonal case there exists a large storage of energy in the oceans and no such balance exists. Therefore, the mean seasonal temperature in the troposphere depends very strongly on the temperature in the oceans and we need to prescribe the temperature in the oceans at the early part of the season to predict the mean tropospheric temperature for the whole season.

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JULIAN ADEM

Abstract

The equations of conservation of thermal energy in the troposphere and at the surface of the earth are used as the basis for predicting the temperature of the troposphere-ocean-continent system for periods of time as long as a month or a season.

Computations of the normal temperature for January in the mid-troposphere and at the surface of the earth are carried out, and the results agree well with observations.

Using as data the temperature in the oceans and in the mid-troposphere in December 1962 and the abnormal snow cover of December 31, 1962, a numerical temperature prediction is carried out for January 1963, obtaining good agreement with observations.

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JULIAN ADEM
and
WARREN J. JACOB

Abstract

The results of a 1-yr. experiment in numerical prediction of monthly mean temperatures using a time-averaged thermodynamic model are presented.

For the 12-mo. period from December 1965 to November 1966 the statistical evaluation of the prediction of anomalies of the mean monthly surface temperature over North America shows skill higher than persistence for each season, except for summer.

Similarly, the evaluation of the predictions of month-to-month changes in ocean surface temperature anomalies also shows skill substantially higher than that of a prediction based on the tendency to return to normal.

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Julian Adem
and
William L. Donn

A long-range forecasting technique, based on a physical model that emphasizes thermodynamics, is applied to the prediction of anomalies of temperature and precipitation for the Northern Hemisphere. Monthly forecasts are initialized with the sea surface temperature, 700 mb temperature and surface albedo, including variable snow-ice conditions. Application to the hot spell and drought in the summer of 1980 for the contiguous United States shows very encouraging skill when verified for the standard 100-station NOAA grid.

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