Robert H. Aron

Availability of chilling temperatures in California

Abstract Deciduous plants require chilling temperatures in winter in order to have normal renewed growth in spring. Since only limited California records of hourly temperatures exist, the more extensive records of maximum and minimum temperature, average relative humidity, and wet bulb temperature were used to derive empirical equations for estimating the extent of chilling occurring under various conditions. The average occurrence of chilling temperatures throughout California was then mapped for several periods. It was found to vary with height in a manner that differed slightly between the Sacramento and San Joaquin valleys. The effects of various environmental conditions are also discussed. High temperatures and solar radiation are shown to decrease, and clouds, shade and wind to increase the effectiveness of chilling temperatures.

Clarification of Selected Misconceptions in Physical Geography

Abstract A number of student misconceptions commonly surface in introductory physical geography classes. They often seem to have a life of their own and persist from one generation to the next. The repetition of and a reluctance to discard such erroneous notions result in their perpetuation. In addition to locational misplacements, misconceptions are also common in the oceanographic, atmospheric, and geomorphic realms. Appropriate correction and explanation is offered, where possible, to clarify problem situations. Exposure of these myths can serve as a useful pedagogical tool.

Gender-Related Knowledge Variations within Geography.

In a survey of students from junior high through the undergraduate college level, males consistently out-performed females on a test covering map skills and physical, human, and regional aspects of geography. The gender gap was consistent across all four subfields. It widened with increased education and was significant even after accounting for numerous personal information items that might have explained the difference. This consistent performance difference involving the broad spectrum of geographic knowledge argues against explaining the gender gap as symptomatic of differences in a single underlying factor such as map skills or spatial abilities. Knowledge-based and nonknowledge-based explanations for the gender difference are discussed.

Statistical Forecasting Models:I. Carbon Monoxide Concentrations in the Los Angeles Basin

The body of information presented in this paper is directed to those individuals constructing models for forecasting carbon monoxide concentrations and/or wishing to know which parameters were found most closely associated with CO concentrations. Models for forecasting daily maximum CO concentrations throughout the Los Angeles area were derived using least squares. The parameters that proved most significant within the models derivedfor forecasting daily maximum CO concentrations were the preceding days CO concentrations, pressure differences between nearby stations, the height of the 500 mb level, temperatures at the surface, 1000 mb and/or 950 mb, days of the week, the length of daylight, and potential solar radiation. These models are currently being employed by the South Coast Air Quality Management District with good results.

Mixing height—an inconsistent indicator of potential air pollution concentrations

Abstract The correlation between mixing height and air pollution levels was found to be inconsistent. Mixing height had a lower correlation to the maximum oxidant concentration than other parameters such as temperatures at different heights, the previous days oxidant concentration, height and temperature of the inversion base and top, geopotential heights and pressure gradient. Mixing height also had a lower correlation with the maximum CO concentration than other parameters, including the inversion base height, the previous days CO concentration, temperatures at different heights, pressure gradients and geopotential heights. Low correlations between mixing height and air pollution levels may be because: 1. (1) there is a greater variation in mixing height in time and space than is generally thought; 2. (2) the standard calculation of mixing height does not give an accurate estimation of the height to which pollutants are dispersed or 3. (3) air pollutants may have had insufficient time to disperse to the mixing height. When empirically derived statistical models are used to predict air pollution levels, failure to include mixing height as a potential predictor will probably not degrade the quality of the model.

The Persistence of Selected Geographic Misperceptions: A Survey of Junior High through Undergraduate College Students.

Abstract The degree to which students misperceive the relative locations of continents, states, and ocean sizes was assessed. In order to test suspected geographic misperceptions, identical questionnaires were given to more than 700 students from the junior high school through upper undergraduate levels, including future teachers. Misperception rates as a function of class level, gender, and expressed student interests were tested using Chi Square. Geographic misperceptions were found to persist across all measured educational levels. Upper level undergraduate geography and earth science students had the best overall score. Junior high school students scored better than students entering both general elementary and science-related teacher preparation classes. Junior high males did significantly better than females. This gender difference decreased in high school and was virtually absent at the university level. No significant differences in misperceptions were found between students with different subject...

Underprediction of Female Performance from Standardized Knowledge Tests: A Further Example from the Knowledge of Geography Test

It has been documented that some tests ofbackground knowledge underpredict the performance offemale students in college. This study explored whetherthe underprediction phenomenon would also be found for a test that tapped four subfields ofgeography. Students (primarily White, N = 315) enrolledin nine geography classes at a comprehensive, midwesternuniversity completed the Knowledge of Geography (KOG) test during the first week of the semester andconsented to release their first exam grades, finalgrades, and ACT scores. Replicating a previous study(Henrie, Aron, Nelson, & Poole, 1997), there were gender differences favoring males across allfour subfields of the KOG test. KOG test scorescorrelated with grades, but males and females achievedcomparable course grades despite the lower performance of females on the KOG test. Examples illustratehow small differences between predicted and actualgrades can translate into large gender discrepancieswhenever minimum scores from tests that underpredict the performance of a subgroup are used toqualify students for educationalopportunities.

The Effect of Low Plant Cover on the Surface Air Layer

Vegetation occupies the space between the earth’s surface and the atmosphere. A plant cover not only takes up space, but forms a transition zone, because the individual plant parts, such as leaves, needles, twigs, and branches, behave like solid ground, absorbing and emitting radiation, evaporating, and playing their part in the exchange of energy with the surrounding air. However, the air is still able to circulate within the plant cover more or less freely. Thus vegetation forms a new component part of the air layer near the ground.

The Influence of Topography on the Microclimate

In Chapter II, the microclimate of a level surface without vegetation was considered. Then in Chapters V and VI, this assumption was abandoned, and the interactions of vegetation and microclimate were studied. Now the assumption that the ground is level will also be abandoned, and the influences exerted on microclimate by the topographic variations of the terrain will be investigated.

The distribution of the most favorable temperatures for citrus flower induction in Israel

In this study the distribution of optimum temperatures for the induction of citrus blossoms in Israel has been determined. The number of flowers that form on citrus plants grown in the subtropics is known to be affected by the temperatures to which the plants are exposed. However, too few records of hourly temperatures exist in Israel to make an estimate of the occurrence and/or distribution of temperatures beneficial for citrus flower induction, although maximum and minimum temperatures are widely recorded. Thus, a model derived from the hourly records could be applied to the stations recording only maximum and minimum temperatures. The average optimum temperature was mapped for citrus flower induction throughout Israel.