Abstract

Fieldwork was conducted in 2009–11 with Native American agriculturalists and traditionalists in southwestern Oklahoma on the form and use of their weather and climate knowledge: how it is constituted, how it is used in agricultural decision-making, and the extent to which their own weather knowledge is valued in light of other forms of weather information available. Conversations rekindled memories of knowledge imparted and stories told by previous generations and illuminated observational signs some still rely upon. Conversations also revealed that while the agriculturalists and traditionalists are acculturated into contemporary society, they still hold tightly to culturally important ways of knowing about and being in the world and are keen observers of their local environments. Given the contemporary relevance of climate change and its impacts on Indigenous peoples, this paper focuses on their observations and thoughts about climate variability: Have you noticed changes? What impacts do these changes have on you, including both on your agricultural activities and your trusted observational signs? What do you think about the public discourse on climate change? According to most, a changing climate is a real phenomenon perceived at the local scale and is impacting their ability to observe relied-upon indicators, and has caused them to make changes in their agricultural endeavors. The knowledge professed by those in this study can be placed within the larger context of Indigenous environmental knowledge formation, as it follows closely with that discovered through archival research and that described by other inquiries from around the world.

Abstract

In September 1950, U.S. Senator Robert S. Kerr (D-Oklahoma) wrote to Indian leaders across the United States in order to “make some determination with regard to whether or not we are going to have an early winter and whether or not we may expect a hard winter.” Even though he had access to U.S. Weather Bureau predictions and other scientific data, Kerr and his administrative assistant, Ben Dwight, a member of the Choctaw Nation and its onetime Principal Chief, wrote that they “would like to know what some of the Indians in the various sections of the nation think about our coming winter probabilities.” Kerr and Dwight indicated they had a “high regard for the old Indian ways of determining such things—because they are practical and have always been able to make some very accurate predictions.” From 33 letters sent to tribes in 1950 (including 9 to tribes in Oklahoma) 3 responses were known to have been received; a follow-up letter-writing campaign in October 1951 was more fruitful, producing 8 known responses. This paper examines the tribal responses and explores the life and possible motivations of Senator Kerr, an influential man on the U.S. political stage during 1949–63, in seeking this information. This research is part of a broader field investigation that seeks to understand how Native Americans in Oklahoma conceptualize weather and climate, including traditional ways, and how their knowledge is helping to inform new efforts to farm sustainably and create food sovereignty.

Abstract

This study investigates the relation between tropospheric static stability and central North American growing season (May–August) rainfall for the highly contrasting years of 1975. 1976, and 1979. It uses two extensive sets of meteorological data (individual rawinsonde soundings for 38 stations; hourly rainfall totals for 854–944 locations) for the region extending from the Rocky to the Appalachian Mountains and from the Gulf Coast to approximately 55°N in Canada. The major objectives are to: (i) ascertain which of the many available methods of parameterizing static stability are most strongly related to the above (predominantly convective) rainfall; and (ii) quantify the rainfall variance fraction explained by static stability alone, as opposed to other atmospheric processes/conditions. Forty static stability indices and related thermodynamic parameters (SSITPs) are treated.

The results pertaining to objective (i) are definitive and those concerning (ii) are encouraging. The SSITPs that correlate most strongly with rainfall amount consistently include the lifting condensation level (LCL) (near-regionwide) and the convective condensation level (CCL) (western U.S. Great Plains) for the afternoon half-day, and K-type and SWEAT indices (eastern United States) and the CCL and convective temperature (U.S. Great Plains) for the morning half-day. In contrast, the SSITPs developed for forecasting severe thunderstorms and tornadoes correlate poorly with rainfall amount. Except on the U.S. Great Plains, the maximum SSITP-rainfall amount correlation magnitudes tend to be larger for the afternoon half-day (average of 0.47–0.49) than the morning half-day (0.37–0.39). Particularly high maximum afternoon SSITP-rainfall amount correlation magnitudes were obtained for the eastern United States (0.50–0.70); earlier work of this type seldom yielded correlation magnitudes above 0.32. For the SSITPs that correlate most strongly with rainfall amount on a regionwide basis (ICL variant for afternoon; modified-K index for morning), we also document the considerable spatial and intraseasonal variability of the thresholds beyond which the probability of rainfall exceeds that of no rainfall.

Abstract

A diagnostic study of the budget of zonal and eddy components of available potential and kinetic energy is presented for the large-scale basic (time-averaged) state of the atmosphere for Phases 1, 2 and 3 of GATE. The Final Validated Data Set (FVDS) is applied to a modified set of approximate-form energy equations that were originally developed by Lorenz (1955). Geopotential height, temperature, relative humidity, and wind direction and speed were subjectively analyzed at mandatory pressure levels for an area bounded by 20°N, 10°E, 10°S and 40°W. Gridpoint values were extracted at intervals of 2° latitude and longitude. Since basic state data were used, an eddy content or an exchange involving an eddy content represents only the standing eddy component of energy.

Results indicate that zonal kinetic energy (KZ) is the most abundant content and is maximum in the region of the upper tropospheric easterly jet. Both KZ and zonal available potential energy (AZ) decrease from phase-to-phase, whereas the eddy contents, AE and KE, remain nearly constant in time. The dominant energy conversion CA is front AZ to AE in all phases, indicating that the eddy transport of sensible heat is from warmer latitudes to colder latitudes. The CE conversion is from AE to KE during Phases 1 and 3 and is negligible in Phase 2. The conversion between KZ and KE (CK) is negligible in all phases, while the conversion between AZ and KZ (CZ) is small and oscillates. Boundary transports show that only the flux of KZ (BKZ) is significant. The east-west transport in the upper troposphere dominates and is responsible for an import of energy into the region. Generations of AZ and AE were not computed, but residuals imply that AZ is generated by diabatic processes during all phases while AE is destroyed. Residuals also suggest that KE and KZ are destroyed by frictional dissipation.

Finally, we find that our standing eddy contents AE and KE are comparable in magnitude to the eddy energy contents given by Norquist et at. (1977) for a composite of GATE Phase 3 westward propagating wave disturbances. A comparison also is made between the present results and those for June, July, August for the global region bounded by 15°N and 15°S (Kidson et al., 1969). It appears that the stationary wave component in the GATE area makes an important contribution to certain terms in the global scale energy budget, although the global standing eddies encompass different (larger) scales than those in the present study.

Abstract

Sub-Saharan West Africa (10°–20°N) receives rainfall from westward-propagating disturbance lines that have their base within and receive most of their moisture from the low-level, wedge-shaped, southwest monsoonal flow off the tropical Atlantic. This paper builds on earlier research to further identify the tropical Atlantic surface atmospheric and oceanic patterns that accompany drought in sub-Saharan West Africa. Patterns for the four driest years since 1940 (1972, 1977, 1983, 1984) are compared with counterparts for the wettest of the last 20 years (1975) and 60-year (1911–70) average fields.

The key results for the rainy season (July-September) of three of the four severe sub-Saharan drought years (1972, 1977, 1984) duplicate those obtained earlier. They include (i) a distinctive basinwide sea surface temperature (SST) anomaly pattern (positive departure to the south of ∼10°N; negative departures between 10°–25°N); (ii) a concomitant southward displacement (relative to the 1911–70 mean) of the zone of maximum SST by 250–500 km; (iii) the North (South) Atlantic subtropical high extending farther (less) equaterward than in the 60-year mean; and (iv) associated southward displacements (by 200–350 km) of the near-equatorial pressure trough, wind direction discontinuity between Northern and Southern hemisphere tmdm and zones of maximum rainfall frequency and total cloud amount. These results offer further evidence that very deficient sub-Saharan rainy seasons tend to coincide with the southwesterly surface monmonal flow not extending as far north along the West African coast as in the 60-year mean and, by extension, a reduced northward penetration of the monsoon wedge into West Africa. Also consistent with earlier findings is that only the SST patterns of the aforementioned results show evidence of evolving during preceding seasons. This further underlines the potential for tropical Atlantic SST to provide the basis for the prediction of sub-Saharan rainy season quality several months in advance.

These results were not characteristic of the other extremely deficient sub-Saharan rainy season investigated (1983) or the nondrought rainy season studied for comparative purposes (1975), During July-September 1983, the SST departures were positive over much of the tropical Atlantic, and most of the aforementioned near-equatorial atmospheric-oceanic features were in close to their 1911–70 average positions. The latter was also true of July-September 1975, when the SST anomaly pattern was rather fragmented.

An outline of the concept of the North Atlantic Oscillation (NAO), along with some of its history is presented. This is followed by a brief presentation of the results and implications of an encouraging new application of the NAO to a regional climate problem—the interannual variation of Moroccan winter-semester precipitation. That precipitation is shown to be inversely related to the concurrent state of the NAO, and the relationship is relatively strong by the standards of recent research into the mechanisms of tropical and subtropical precipitation fluctuations. It is suggested that the NAO is of particular significance for the important issue of the long-range prediction of Moroccan (and probably also Spanish, Portuguese, and Algerian) winter precipitation, and that further research on this subject is warranted. Several specific recommendations in the latter regard are made.

Abstract

The procedure to calculate the active layer depth of the upper ocean, as proposed by Van den Dool and Horel (DH), was applied to the Atlantic Ocean from 20°S to 70°N. In this method, the observed climatological annual cycle in SST is employed to invert a simple linear energy balance. The results for the Atlantic are similar to those for the Pacific Ocean in several ways. The active layer is considerably shallower than the annual mean mixed layer (which is calculated from in situ sea temperature profiles). Just as for the Pacific, however, the patterns of active and mixed layer depth show a remarkable spatial match.

Using Bunker's datasets for SST and heat transfer over the Atlantic Ocean, the forcing used in the energy balance equation was made increasingly more realistic, from (i) astronomical solar radiation, through (ii) empirical estimates of absorbed solar radiation including the modifying effect of clouds to (iii) the complete empirically determined net ocean surface heat gain. No matter what forcing was used, the calculated active layer is always much shallower than the mixed layer depth. The best pattern match was found using the simplest forcing of all—the astronomical solar forcing.

Increasingly, atmospheric models are being coupled to an oceanic slab in which the SST evolves in response to local heat gains and losses. The key question is how deep that slab should be. Our study implies that, in order to match the observed annual cycle in SST, the oceanic stab should be quite shallow, and certainly shallower than the mixed layer depth. The shallowness of the active layer implies that ocean heat transport contributes to the forcing of the annual cycle in SST in the midlatitudes of the Atlantic Ocean.

Abstract

Residents of the Oklahoma City metropolitan area are frequently threatened by tornadoes. Previous research indicates that perceptions of tornado threat affect behavioral choices when severe weather threatens and, as such, are important to study. In this paper, we examine the potential influence of tornado climatology on risk perception. Residents across central Oklahoma were surveyed about their perceptions of tornado proneness for their home location, and this was compared with the local tornado climatology. Mapping and programming tools were then used to identify relationships between respondents’ perceptions and actual tornado events. Research found that some dimensions of the climatology, such as tornado frequency, nearness, and intensity, have complex effects on risk perception. In particular, tornadoes that were intense, close, and recent had the strongest positive influence on risk perception, but weaker tornadoes appeared to produce an “inoculating” effect. Additional factors were influential, including sharp spatial discontinuities between neighboring places that were not tied to any obvious physical feature or the tornado climatology. Respondents holding lower perceptions of risk also reported lower rates of intention to prepare during tornado watches. By studying place-based perceptions, this research aims to provide a scientific basis for improved communication efforts before and during tornado events and for identifying vulnerable populations.