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Norton D. Strommen
and
Jay R. Harman

Abstract

A shift in the area of maximum lake-effect snowfafl—toward Lake Michigan from an early season inland location between November and January and a return inland by March—over western lower Michigan was investigated for the period from November 1965 through March 1971. The seasonal pattern for all areas of western lower Michigan was similar, but the inland displacement of early- and late-season snowfall was nearly twice as great in the northwest section.

Lake-snow days were identified and daily maps analyzed to determine the axis of maximum snowfall the displacement from the lakeshore was measured along three traverses, one each in southwest, west-central and northwest lower Michigan. Temperature differences between the lake water and air at the 850 mb level and geostrophic winds at the surface, 850, 700 and 500 mb levels were calculated over mid-Lake Michigan, and observed winds for Green Bay, Wisc., and Flint, Mich., were determined for each lake-snow day.

The degree of inland displacement of lake-effect snow was strongly related to wind speed at the surface and the 850 mb level. At a given wind speed, a greater lake surface −850 mb temperature contrast was associated with snowfall nearer the lakeshore, and wind speed upstream at Green Bay was more closely correlated with lake-snow patterns than was the wind speed downstream at Flint.

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WERNER SCHWERDTFEGER
and
NORTON D. STROMMEN

Abstract

No Abstract Available.

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WERNER SCHWERDTFEGER
and
NORTON D. STROMMEN

Abstract

No Abstract Available.

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WERNER SCHWERDTFEGER
and
NORTON D. STROMMEN

Abstract

Hourly aerological soundings released at Bedford, Mass. in April 1960, together with all available conventional synoptic observations, are used for a detailed analysis of a cold front south of the center of a northeastward-moving depression. It is shown that in this case the dynamically important change from one air mass to another throughout the entire troposphere occurred several hours after the passage of a weak surface cold front. The major cooling over Bedford presented itself in a nearly vertical column from about 500 m. above the ground to heights of around 8 km., with the main decrease of temperature at the surface occurring during the following two hours.

It is suggested that this case is not an exceptional one, but that it rather may reflect the typical structure of a strong cold air invasion near the center of a depression in which the horizontal wind component normal to the front increases with height. Under such conditions an analysis according to the classical Norwegian scheme, with the wedge-shaped cold air mass, would be unrealistic.

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Jerry D. Hill
,
Norton D. Strommen
,
Clarence M. Sakamoto
, and
Sharon K. Leduc

Abstract

The development of a critical world food situation during the early 1970's was the background leading to the Large Area Crop Inventory Experiment (LACIE). The need was to develop a capability for timely monitoring of crops on a global scale. Three U.S. Government agencies, NASA, NOAA and USDA, undertook the task of developing technology to extract the crop-related information available from the global weather-reporting network and the Landsat satellite. This paper describes the overall LACIE technical approach to make a quasi-operational application of existing research results and the accomplishments of this cooperative experiment in utilizing the weather information.

Using available agrometeorological data, techniques were implemented to estimate crop development, assess relative crop vigor and estimate yield for wheat, the crop of principal interest to the experiment. Global weather data were utilized in preparing timely yield estimates for selected areas of the U.S. Great Plains, the U.S.S.R. and Canada. Additionally, wheat yield models were developed and pilot tested for Brazil, Australia, India and Argentina. The results of the work show that heading dates for wheat in North America can be predicted with an average absolute error of about 5 days for winter wheat and 4 days for spring wheat. Independent tests of wheat yield models over a 10-year period for the U.S. Great Plains produced a root-mean-square error of 1.12 quintals per hectare (q ha−1) while similar tests in the U.S.S.R. produced an error of 1.31 q ha−1. Research designed to improve the initial capability is described as is the rationale for further evolution of a capability to monitor global climate and assess its impact on world food supplies.

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Raymond P. Motha
,
Sharon K. Leduc
,
Louis T. Steyaert
,
Clarence M. Sakamoto
, and
Norton D. Strommen

Abstract

A regional precipitation analysis from a total of 813 recording stations in 11 West African countries for the drought period 1968–75 is presented. Results illustrate the severity and extent of meteorological drought which prevailed throughout the region and reached greatest magnitude in 1973. In that year, the critical 300–400 mm zone of annual rainfall was at least 200 km south of its normal position resulting in major crop failures in several sub-Saharan countries.

In Nigeria, 50-year records of rainfall from 28 stations were examined to study both temporal and spatial distributions. In the northern Sahelian zone of Nigeria, two prolonged drought periods were observed (i.e., 1940’s and 1968–76). This detailed analysis further demonstrated the strong relationship between rainfall in the Sahelian region and the position of the Intertropical Convergence Zone (ITCZ). However, there were years during which widespread below-normal rainfall occur-red throughout most of Nigeria which supports previous studies linking large-scale tropical circulation features to rainfall in the Sahel.

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