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Robert F. Dale
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Robert F. Dale and Robert H. Shaw

An upward bias exists in probabilities of 0 or trace weekly total precipitation since small amounts often occur undetected and are recorded as 0 or trace at climatological stations where observations are made only once a day. Exact evaluation and correction of this bias is difficult, but individual estimates of 1-week P(0,T) for substations in the north-central region of the United States can be multiplied by a factor of 0.8 to reduce them to more reasonable values. Although the opportunity for low precipitation bias decreases with increasing length of period, significant bias still persists in the 2- and 3-week estimates in the western part of the north-central region during the winter season. Since the probability of measurable precipitation is 1–P(0,T), the P(0,T) bias is carried into the precipitation probabilities, but compensating biases in the gamma-distribution parameter estimates apparently contain most of the bias in the 0.01 to 0.09-inch interval.

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Robert F. Dale and Robert H. Shaw

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The average seasonal march and frequency of soil moisture in the corn root zone at Ames, Iowa, during a 30-yr period was estimated for a well-drained 5-ft soil profile holding 9 inches of available water at field capacity. Average seasonal marches of soil moisture in the top 5 ft were also prepared from simulated water balance computations for soils with three different available field capacities (6, 9 and 12 inches) and, for each capacity, three different 1 April soil moisture profiles (20, 60 and 100 per cent of available field capacity) from which to begin the moisture budget calculations. The average seasonal march and frequencies of evaporation from a Weather Bureau Class A evaporation pan and from corn with soil moisture not limiting were estimated. Using an experimentally derived atmospheric-soil moisture stress relation for corn, the climatology of potential evapotranspiration from corn was expressed as the soil moisture necessary in the corn root zone to prevent moisture stress in corn on any day of the season. The estimation of moisture stress in corn showed at least some stress days to occur in every one of the 30 years and an average of 40 non-stress days in the critical 63-day period for corn six weeks before silking to three weeks after silking.

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Thomas Q. Carney and Robert F. Dale

Objective methods in which climatology is considered are needed in the design of flight instruction programs. Weather conditions less than the minimum (LM) thresholds designated for Minimum Instructional Visual Flight Rules (MIVFR) were defined as those with <3 mi visibility, <1500 ft ceilings, and/or with surface wind speeds >25 kt. The climatology of the LM conditions for four two-hour flight periods during the spring, fall, and summer semesters at Purdue University was generated. The negative binomial distribution was used to develop the expected LM probability deciles, which, for a fixed level of controllable resources, were used to predict the maximum number of students that should be enrolled in each semester. In the general aviation flight technology program at Purdue University, it was found that with present class enrollments in Visual Flight Rules (VFR) flight training, all students could be expected to complete their scheduled flying hours during a semester, without considerable makeup flight instruction outside the normal class hours, in less than half of the years.

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William L. Nelson and Robert F. Dale

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Reliable crop-weather-technology models are needed for yield prediction and for the determination of climatic risks in crop production. Accurate and timely information on crop yields would help both industry and government anticipate and more efficiently allocate food supply and create a more stable grain price for individual farm planning. Critical analyses of several multiple regression models for predicting county average corn (Zea mays L.) yields with weather information in Indiana showed that yield predictions are very sensitive to the trend variable(s) used to account for technology and also to the specific period of record used to estimate the regression parameters. Models using a function of year as the variable to represent technology trend showed great fluctuation in their parameter estimates and in their yield predictions from year to year. Predicted yields with average weather fluctuated up to 22 bushels per acre from one year to the next in the 1970's as each additional year was added to the fitted model. The use of nitrogen applied to corn land as a technology marker in the regression model reduced the variability in the estimates of the technology and weather coefficients and improved the yield predictions. The identification of the principle environmental factors with a single derived Energy-Crop Growth (ECG) index facilitates the search for other technological and management variables to interpret better the weather-technology interaction in corn production.

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Robert C. Landis and Dale F. Leipper

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Radio-transmitted synoptic data are used to determine the change brought about in the thermal structure of the Atlantic Ocean by the passage of hurricane Betsy in 1965. Such data for sea surface temperature and bathythermograph observations are regularly available from selected areas. Although they are not highly accurate and their interpretation is difficult, they could be more widely utilized in synoptic oceanography, as in this example and in oceanographic forecasting. The data for Betsy indicate thermal changes in the sea similar to those described previously for hurricane Hilda where research data were used. They give evidence of upwelling from 200 ft near the storm track, a 4F sea surface temperature decrease, and downwelling farther away from the track.

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Lawrence A. Schaal and Robert F. Dale

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Historical changes in time of once daily maximum and minimum temperature observations at cooperative climatological stations from 1905 to 1975 have introduced a systematic bias in mean temperatures. Unless corrected, this bias may be interpreted incorrectly as climatic “cooling” and may also affect the assessment of agricultural production potential and fossil fuel needs. Maximum and minimum temperature data for two years from the National Weather Service station at Indianapolis International Airport were used to evaluate the differences between mean temperatures obtained by terminating the 24 h period at the midnight observation and the mean temperatures obtained by terminating the 24 h period at 0700 and 1900 hours, typical observation times for AM and PM observing stations. The greatest mean temperature bias occurs in March when a 1900 observation day yields a monthly mean temperature 1.3°F above a midnight observation, and a 0700 observational day gives a −1.3°F bias. Since the number of AM observing stations in Indiana have increased from 10% of the total number of temperature stations in 1925 to 55% in 1975, the March mean temperature shows a decrease of 1.2°F in the last 40 years, solely because of the change in substation observational times. Unless the time of observation bias is considered, the mixture of AM and PM observations complicates interpretation of areal temperature anomaly patterns. This bias is accumulated in monthly, seasonal or annual values of the mean temperature-derived variables-heating degree days, cooling degree days and growing degree days—and may provide misleading information for applications in industry and agriculture.

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Jeffrey A. Andresen, Robert F. Dale, Jerald J. Fletcher, and Paul V. Preckel

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Weather conditions significantly affect corn yields. while weather remains as the major uncontrolled variable in crop production, an understanding of the influence of weather on yields can aid in early and accurate assessment of the impact of weather and climate on crop yields and allow for timely agricultural extension advisories to help reduce farm management costs and improve marketing, decisions. Based on data for four representative countries in Indiana from 1960 to 1984 (excluding 1970 because of the disastrous southern corn leaf blight), a model was developed to estimate corn (Zea mays L.) yields as a function of several composite soil–crop–weather variables and a technology-trend marker, applied nitrogen fertilizer (N). The model was tested by predicting corn yields for 15 other counties. A daily energy-crop growth (ECG) variable in which different weights were used for the three crop-weather variables which make up the daily ECG—solar radiation intercepted by the canopy, a temperature function, and the ratio of actual to potential evapotranspiration—performed better than when the ECG components were weighted equally. The summation of the weighted daily ECG over a relatively short period (36 days spanning silk) was found to provide the best index for predicting county average corn yield. Numerical estimation results indicate that the ratio of actual to potential evapotranspiration (ET/PET) is much more important than the other two ECG factors in estimating county average corn yield in Indiana.

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atmospheric sciences and problems of society

A series of statements on the relevance of the scientific and technological areas of AMS STAC Committees to national and international problems

Earl G. Droessler, John S. Perry, Lance F. Bosart, Robert F. Dale, Walter A. Lyons, Robert E. Dickinson, Floyd C. Elder, Harold W. Baynton, J. A. Weinman, V. E. Derr, and William R. Bandeen
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Interaction Between the Atmosphere and the Oceans

Report of the Joint Panel on Air-Sea Interaction

George S. Benton, Robert G. Fleagle, Dale F. Leipper, R. B. Montgomery, Norris Rakestraw, William S. Richardson, Herbert Riehl, and James Snodgrass
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