University Instruction in Observational Techniques: Survey Responses

A 1987 survey of the atmospheric and oceanic science community on university instruction in instrumentation and observations revealed that an apparent imbalance existed between observational and theoretical/numerical components of the atmospheric sciences. The committee analyzing the survey results identified several factors contributing to the perceived imbalance. From a follow—up survey conducted of the same community in 1997 to assess the level of change over 10 years, it is found that some progress has been achieved over this period, but that more can be done. Rather than try to implement all of the recommendations from analysis of the initial survey, it is suggested that attention be focused on seven items that build on partial successes over the last 10 years and that offer likelihood of success in the near future

Climatology of Superadiabatic Conditions for a Rural Area

Temperature measurements taken over a 6-year period from a 32 m tower are used to study the climatology of low-level superadiabatic conditions in a rural area. Plots of monthly distributions of event commencement times and durations display a high degree of symmetry compared to the distributions for inversions previously published. This climatology can be used to better identify periods when spores, pollens, insects, smoke or agricultural chemicals introduced at the surface will quickly become available for long-range transport by the upper level winds

Will Climate Change Impact the Sustainability of Iowa Farms?

Overheads from the 2011 Shivvers Memorial Lecture Series

Concurrent variations of water vapor and temperature corresponding to the interannual variation of precipitation in the North American Regional Reanalysis

The concurrent variation patterns of water vapor and temperature corresponding to the interannual variation of winter precipitation and the roles of change in atmospheric circulation are studied with the North American Regional Reanalysis. A very tight positive relationship between precipitation and relative humidity at interannual time scale is found from the large spatially sampled data set. On the basis of this relationship, the concurrent variations of water vapor and temperature between the wettest and the driest years are categorized into three patterns. The distribution of the patterns shows that more winter precipitation of wetter years corresponds to more water vapor but not lower temperature (moistening pattern) in high latitudes, lower temperature but not more water vapor (cooling pattern) in midlatitudes, and both more water vapor and lower temperature (moistening-cooling pattern) in low latitudes. The characteristics and roles of change in atmospheric circulation from the driest years to the wettest years are analyzed for two selected areas. It is found that, around the selected cooling pattern (moistening pattern) area, the field of wind difference between the wettest years and the driest years is divergent (convergent). Dominated by this, the fields of differences in both heat flux and water vapor flux are divergent (convergent). This leads to the decreases (increases) of the heating and moistening rates and, thus, the characteristics of the cooling pattern (moistening pattern) area with cooling and drying (warming and moistening) from the driest years to the wettest years. This study suggests that, for interannual prediction of precipitation, temperature, in addition to water vapor, should also be considered

Numerical Simulations of Shelterbelt Effects on Wind Direction

A neutral boundary layer nonhydrostatic numerical model is used to determine the characteristics of shelterbelt effects on mean wind direction and to study the processing causing wind rotation when air passes through a shelterbelt. The model uses a turbulence scheme that includes prognostic equations for turbulence kinetic energy and a master length scale proposed by Mellor and Yamada. The simulated results are in quantitative agreement with Nord\u27s field measurements. The spatial variation of wind rotation and its dependence on incident angle and shelterbelt porosity is analysed. Dynamic processes of the wind rotation and its interactions with drag force and pressure perturbation are also discussed. It is concluded that shear of wind direction should be considered, along with shear of speed, in determining turbulent fluxes in the vicinity of a shelterbelt

An Observational Study of Sea- and Land-Breeze Circulation in an Area of Complex Coastal Heating

The diurnal evolution of the three-dimensional structure of a mesoscale circulation system frequently occurring in the area of Kennedy Span Center-Cape Canaveral has been studied using the data from the Kennedy Space Center Atmospheric Boundary Layer Experiment (KABLE). The case was chosen from the spring intensive data-collection period when the greatest daytime temperature difference between land and water (sea and inland rivers) occurs and the local circulations are most intense. The daytime flow structure was determined primarily by the mesoscale pressure-gradient form created by the temperature contrast between land and water. A strong sea-breeze circulation, the dominant feature of the daytime flow field, was modified by a local inland river breeze known as the Indian River breeze, in that divergent flow over the river enhanced the sea-breeze convergence on the seaward side and generated additional convergence on the landward side of the river. The rivers near the coastline also modified the initial flow field by enhancing convergence in the surrounding areas and speeding up the movement of the sea-breeze front. The nighttime flow structure was dominated by a large-scale land breeze that was relatively uniform over the area and became quasi-stationary after midnight. The nonuniformity of the wind-vector rotation rate suggests that mesoscale forcing significantly modifies the Coriolis-induced oscillation. No clear convergence patterns associated with the rivers were observed at night. Detailed characteristics over a diurnal cycle of the sea-land breeze and of the river breeze onset time, strength, depth, propagation speed and both landward and seaward extension, are documented in this study. Some boundary-layer characteristics needed for predicting diffusion of pollutants released from coastal launch pads, including atmospheric stability, depth of the thermal internal boundary layer, and turbulent mixing are also discussed

The Effects of Large-Scale Winds on the Sea–Land-Breeze Circulations in an Area of Complex Coastal Heating

A three-dimensional mesoscale numerical model has been used to examine the effects of large-scale background winds on the characteristics of the sea-land-breeze circulations over an area with an irregular coastline and complex surface-heating patterns at Kennedy Space Center/Cape Canaveral in Florida. A series of numerical experiments was performed in which the large-scale winds were varied in both speed and direction. The surface heating was based on measured surface-temperature variation from the Kennedy Space Center Atmospheric Boundary Layer Experiment (KABLE) during the spring season when the land-sea temperature gradient reaches its maximum. The results from the simulations compared reasonably well with data available from KABLE. The results show that an onshore large-scale flow produces weaker sea-breeze perturbations compared to those generated by an offshore flow. However, the coastal rivers and lagoons create intense surface convergence with strong vertical motion on the seaward side of the river by the merging of the onshore flow with the offshore river breezes, and such strong vertical motion can last for several hours. The disturbances caused by the inland water bodies are significant in the sea-breeze phase but are very minor in the land-breeze phase. An onshore synoptic wind causes an earlier onset of the sea breeze, but delays the onset of the land breeze, and a strong onshore flow of more than 5 m s−1 does not allow the land breeze to develop at all. The maximum offshore wind speed and vertical motion at night are less sensitive to the magnitude of surface cooling than to the large-scale flow and daytime surface heating, which together determine the initial flow at the beginning of the land-breeze phase. The results also show that the magnitude, the sense of rotation, and the diurnal variation of the dominant forces governing the wind-vector rotation change as the orientation of the synoptic wind direction changes. The rate of rotation in the sea-breeze phase is dominated mainly by the balance between the mesoscale pressure gradient and friction; at night, the Coriolis effect also contributes significantly to the balance of forces in the land-breeze phase