Dynamic Power Spectral Analysis of Solar Measurements from Photospheric, Chromospheric, and Coronal Sources

An important aspect in the power spectral analysis of solar variability is the quasistationary and quasiperiodic nature of solar periodicities. In other words, the frequency, phase, and amplitude of solar periodicities vary on time scales ranging from active region lifetimes to solar cycle time scales. Here, researchers employ a dynamic, or running, power spectral density analysis to determine many periodicities and their time-varying nature in the projected area of active sunspot groups (S sub act). The Solar Maximum Mission/Active Cavity Radiometer Irradiance Monitor (SMM/ACRIM) total solar irradiance (S), the Nimbus-7 MgII center-to-wing ratio (R (MgII sub c/w)), the Ottawa 10.7 cm flux (F sub 10.7), and the GOES background x ray flux (X sub b) for the maximum, descending, and minimum portions of solar cycle 21 (i.e., 1980 to 1986) are used. The technique dramatically illustrates several previously unrecognized periodicities. For example, a relatively stable period at about 51 days has been found in those indices which are related to emerging magnetic fields. The majority of solar periodicities, particularly around 27, 150 and 300 days, are quasiperiodic because they vary in amplitude and frequency throughout the solar cycle. Finally, it is shown that there are clear differences between the power spectral densities of solar measurements from photospheric, chromospheric, and coronal sources

Disasters and climate change: analyses and methods for projecting future losses from extreme weather

Vellinga, P. [Promotor]Aerts, J.C.J.H. [Promotor

Have disaster losses increased due to anthropogenic climate change?

A number of studies were conducted to demonstrate the best way to assess the potential influence of climate change on disaster losses was to analyze future projections in place of historical data. These studies showed that increases in exposure and wealth were the most important drivers for growing disaster losses. Most of these studies also showed that disaster losses remained constant after normalization, including losses from earthquakes They found that increases after normalization did not fully correct for wealth and population increases, or they identified other sources of exposure increases or vulnerability changes or changing environmental conditions. The analysis of these disaster loss studies showed that economic losses from various weather-related natural hazards, such as storms, tropical cyclones, floods, and small-scale weather events had increased around the globe

Irrigation and water resources in the 1990's

Presented at Irrigation and water resources in the 1990's: proceedings from the 1992 national conference held on October 5-7, 1992 in Phoenix, Arizona.Includes bibliographical references.Since planning for droughts must be done in wet cycles, storing surplus surface water behind dams or in aquifers is essential. Underground storage is enhanced by increasing the infiltration of water into the soil, using in-channel and off-channel spreading systems and basins. In-channel spreading is achieved with low dams or weirs that increase the width and depth of streams, or by constructing T- or L-dikes in the streambed to spread the water over the entire width of the bed. Off-channel systems are mostly specially constructed infiltration basins or old gravel pits. Contrary to what may intuitively be expected, shallow basins tend to give higher infiltration rates than deep basins because there is less compaction of clogging layers that accumulate on the bottom due to suspended solids and biological activity. This is demonstrated with a soils engineering analysis and with field data. Artificial recharge can also be important in temporary storage of water, for example, in connection with seasonal changes in the use of sewage effluent for irrigation or in the demand for drinking water. For the latter, such aquifer storage and recovery generally is much less expensive than building water treatment plants with enough peaking capacity or surface storage. Artificial recharge also can play a role in the reuse of wastewater because it provides treatment benefits, gives seasonal storage, and improves the aesthetics of water reuse by breaking up the pipe-to-pipe connection of direct reuse