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Byung-Ju Sohn
and
Franklin R. Robertson

Despite the general agreement that clouds cool the earth–atmosphere, there are substantial differences in estimated magnitudes of the annual global mean of cloud radiative forcing. Recent estimates of globally averaged net cloud radiative forcing range from −2 to −27 W m−2. The reasons for these differences have not been clarified in spite of the important role of clouds in maintaining global heat balance. Here, three estimation methods [Earth Radiation Budget Experiment (ERBE), Regression I, and Regression II] are compared using the same data source and analysis period.

Intercomparison has been done for the time period of February and March 1985 over which major satellite radiation budget and cloudiness datasets (ERBE radiation budget, Nimbus-7, and ISCCP cloudiness) are contemporaneous. The global averages of five sets of net cloud radiative forcing by three independent methods agree to within 3.5 W m−2; four of five cases agree to within 1 W m−2. This suggests that differences in published global mean values of net cloud radiative forcing are mainly due to different data sources and analysis periods and a best estimated annual mean among all previous estimates appears to be the ERBE measurement, that is, −17.3 W m−2. In contrast to the close agreement in the net cloud radiative forcing estimates, both longwave and shortwave cloud radiative forcing show more dependence on the chosen method and dataset. The bias of regression-retrieved values between Nimbus-7 and ISCCP cloud climatology is largely attributed to the difference in total cloudiness between two climatologies whereas the discrepancies between the ERBE and regression method appear to be, in part, due to the conceptually different definition of clear-sky flux.

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Brian A. Tinsley

cloud cover, as will be discussed in the sections “The global atmospheric electric circuit linking ionosphere and troposphere,” “Space charge in clouds,” “Electro-anti-scavenging,” and “Electro-scavenging.” Also, the modulation of the GCR flux can change the rate of ion-mediated nucleation of condensation nuclei in the lower stratosphere. By changing the latitude distribution of tropospheric cloud cover, latitude gradients of temperature are set up by infrared radiative forcing below the clouds and

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Jakob Zscheischler
and
Flavio Lehner

simulations typically consist of many (up to 100 per model) equally plausible simulations with transient forcing by slightly perturbing the initial conditions. Despite potentially much larger sample sizes, a general challenge in event attribution persists, namely, how to evaluate whether counterfactual simulations represent extreme events well. Notwithstanding the above challenges, some examples for multivariate event attribution exist. Kiriliouk and Naveau (2020) present a theoretical extension to

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Gijs de Boer
,
Gillian Young McCusker
,
Georgia Sotiropoulou
,
Yvette Gramlich
,
Jo Browse
, and
Jean-Christophe Raut

this conference, though it was a topic that came up during this session. Presentations covered a variety of environmental topics, including interactions between sea ice concentration and cloud life cycle in the context of the seasonal cycle and the influence of external forcers such as volcanic eruptions on cloud lifetime and radiative response. Additionally, there was a presentation discussing numerical simulations to evaluate air mass transformations during the advection of air from lower

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James R. Blankenship
and
Richard C. Savage

Experience with the operational application of the U.S. Air Force Weather Service's Data Acquisition and Processing Program (DAPP) has shown that satellite imagery requires many different processing and enhancement techniques in order to be fully utilized. Modern imaging scanners provide more information than can be adequately revealed with conventional “cloud pictures”; the value of imagery can be greatly increased by enhancement modes directed toward specific applications. Although complete utilization demands computer processing, much of the information content can be made available to the meteorological analyst by application of electro-optical enhancement techniques. This paper illustrates some of those electro-optical enhancement techniques, both for those who may wish to better understand DAPP and for those who wish to adapt these enhancement techniques to their own applications.

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Woodrow C. Jacobs
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James P. Jenrette

Practical procedures for forecasting areas of overcast skies and precipitation are presented. The forecast thickness field is relabeled as a forecast maximum precipitable water field. A forecast actual precepitable water field is then graphically subtracted from this field to derive a forecast saturation chart. The forecast saturation chart is then adjusted with the forecast vertical-motion field. Isopleths of critical values on the adjusted saturation chart outline forecast areas of overcast skies and areas of probable precipitation.

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James P. Jenrette

An objective method of forecasting Gulf stratus clouds at Bryan Air Base, Texas in the summer season is developed using the scatter-diagram technique. The parameters used are (1) resultant wind direction, (2) resultant pressure-gradient magnitude, (3) Houston temperature-dew-point spread, (4) Bryan dew point, and (5) Bryan temperature-dew-point spread. Based on one year of independent data and four years of dependent data, the skill scores are 0.55 and 0.70 respectively.

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William K. Widger Jr.
and
C. N. Touart

The meteorological data which can be expected from artificial satellites of relatively sophisticated types are discussed, as are the problems associated with the observing and handling of such data. The deductions which seem possible from such data and a simplified example of how they might be used are presented. An appraisal of the probable meteorological value of such data is included.

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David Atlas
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