Posters Copyright (c) 2013 Utah State University All rights reserved. http://digitalcommons.usu.edu/atmlidar_post Recent documents in Posters en-us Sun, 27 Jan 2013 01:54:31 PST 3600 Early Observations of the Middle Atmosphere Above USU With the World’s Most Sensitive Lidar http://digitalcommons.usu.edu/atmlidar_post/18 http://digitalcommons.usu.edu/atmlidar_post/18 Sun, 11 Sep 2011 07:47:46 PDT Extensive measurements have been made of the upper atmosphere by satellites and the lower atmosphere is measured twice daily by weather balloons. In contrast, the middle atmosphere is a difficult area to measure and therefore has been much less extensively studied. We are currently upgrading an old lidar system to a new system that will be 70 times more sensitive, making this the most sensitive lidar of its kind in the world. The upgrade consists of combining the outputs of 18 and 24 watt Nd:YAG lasers; implementing an optical chain to detect backscattered light using an existing large, four-mirror telescope; four optical fibers; an optical system and mechanical chopper; photomultiplier tubes; a data-acquisition system; and an aircraft detection radar. Moving to this new system will allow us to extend Rayleigh-scatter observations from 90 to 110 km in the mesosphere and lower thermosphere, significantly higher than was possible with the original system. Alternatively, it will enable significantly greater precision or better time resolution for observations in the previous altitude range. After finishing the upgrade, we will use software previously designed for this system to perform the reduction and analysis of the first data to obtain relative density fluctuations and absolute temperatures.

]]> Lance W. Petersen et al. Wavelength Control for a Potassium Resonance Lidar http://digitalcommons.usu.edu/atmlidar_post/17 http://digitalcommons.usu.edu/atmlidar_post/17 Sun, 11 Sep 2011 06:48:41 PDT An important ground-based way to measure temperatures and winds in the transition region between the upper mesosphere and lower thermosphere (80 to 105 km) is with a resonance-scatter lidar. An alexandrite laser, with a wavelength in the near infrared at 770 nm, is being added to the Atmospheric Lidar Observatory to make this type of observation of potassium. These observations will complement those that have been made for many years with the green Rayleigh-scatter lidar. For these resonance-scatter observations it is necessary to accurately and precisely control the laser wavelength. The intent is to carefully step across the 4 pm (2 GHz) wide potassium spectrum (Figure 1). The width of the spectrum has to be determined within 6.0 fm (3.0 MHz ) to obtain a temperature precision of ±5 K. The Doppler shift of the spectrum has to be determined within 5.1 fm (2.6 MHz) to obtain a wind-speed precision of ±2 m/s. This project is a step in that direction. It involves developing a method, based around a scanning Fabry-Perot interferometer (FPI), to control a CW seed laser that, in turn, controls the alexandrite laser.

]]> Everett E. A. et al. Another Noctilucent Cloud at 41.7ºN http://digitalcommons.usu.edu/atmlidar_post/16 http://digitalcommons.usu.edu/atmlidar_post/16 Sat, 27 Aug 2011 06:46:11 PDT On June 23, 1995, a noctilucent cloud (NLC) was detected with the Rayleigh-scatter lidar at the Atmospheric Lidar Observatory (ALO) on the campus of Utah State University (USU) located in Logan, UT (41.7° N 111.8° W). This observation preceded, by four years, the one from 1999 that was previously reported [Wickwar et al., 2002]. These are both important because of their occurrence significantly equatorward of 50° latitude. The NLC was observed for 45 minutes shortly after local midnight. This was well past the twilight period when NLCs are visible to the naked eye. Several parameters of the NLC were measured by the lidar and are similar to those from the NLC observations in 1999. This NLC was approximately 1.5 km higher. Temperatures were measured in the surrounding region and, because of wave activity, were found to be significantly cooler than the climatological mean.

]]> Joshua P. Herron et al. Comparisons of Long-term Trends and Variability in the Middle Atmosphere http://digitalcommons.usu.edu/atmlidar_post/15 http://digitalcommons.usu.edu/atmlidar_post/15 Sat, 27 Aug 2011 06:36:13 PDT Rayleigh Lidar is routinely used to measure temperatures in the middle atmosphere from 45 to 90 km. It is well adapted for nightly observation, provides excellent vertical temperature resolution, and does not need external calibration. The USU Rayleigh Lidar (41.74°N 111.81°W) dataset spans more than ten years from September 1993 to July 2003 with 62 monthly profiles (about 5 years of data) spread over that period.

With many sources of variation in the atmosphere, all temperature effects cannot be detected. The largest source, and the easiest to measure, is the seasonal variation. In addition there are semiannual variation, secular trends, solar cycle effects, and many others.

]]> Troy Wynn et al. Comparisons of Long-Term Trends and Variability in the Middle Atmosphere http://digitalcommons.usu.edu/atmlidar_post/14 http://digitalcommons.usu.edu/atmlidar_post/14 Sat, 27 Aug 2011 06:27:40 PDT The USU Rayleigh Lidar (41.74°N 111.81°W) has been regularly used to measure temperatures in the middle atmosphere from 45 to 90 km. It is well suited for nightly observation; provides excellent vertical temperature resolution; and does not need external calibration. It began operation in August 1993 and a dataset spanning more than ten years has been collected. The analysis here includes 593 nightly temperature profiles from September 1993 through July 2003.

With many sources of variation in the atmosphere, all temperature effects cannot be easily detected. The largest source of temperature variation, and the easiest to measure, is the annual variation. Other effects, such as the semiannual variation, solar cycle radiation, and secular trends are also important but more difficult to detect at every altitude. Our model includes these effects, some of which are significant at some altitudes while others are not. The linear model used in this analysis included variables for the annual and semiannual variations, solar effects, average temperature, and secular trend. The MgII index, averaged over 81 days, was used as a solar proxy instead of F10.7 because it yielded a marginally better fit.

]]> Troy Wynn et al. Prediction of saturation effects on potassium lidar returns http://digitalcommons.usu.edu/atmlidar_post/13 http://digitalcommons.usu.edu/atmlidar_post/13 Sat, 27 Aug 2011 06:13:25 PDT The Atmospheric Lidar Observatory, on the Utah State University campus, will add a potassium lidar to its existing Rayleigh scatter system in the near future. The current system accurately measures temperatures from 40 km to 85 km in altitude.

Beginning at 80 km, a potassium layer forms due to the disintegration of meteors as they enter earth’s atmosphere. ALO plans to probe this layer using an alexandrite laser scanning a wavelength region near 770 nm, where potassium absorbs light. When the light is re-emitted, it can be measured in the same manner as scattered light in a Rayleigh lidar.

Usually, the return signal is proportional to the number density of potassium atoms. However, if the laser light is too powerful, the potassium layer will become saturated and the return signal will be weaker than it should be.

]]> Joel R. Drake et al. Simulating The Doppler-Free Fluorescence Spectrum For The Potassium D1 Transitions http://digitalcommons.usu.edu/atmlidar_post/12 http://digitalcommons.usu.edu/atmlidar_post/12 Sat, 27 Aug 2011 05:40:05 PDT Radiation theory (absorption, spontaneous emission, and stimulated emission) is applied to Potassium (39K and 41K) to examine details of the D1 lines, Figure 1, in the near IR at 770 nm. When examining the resonance fluorescence from two counter-propagation laser beams in a K cell, Figure 2, three prominent “Doppler-free” features—dips at the D1a and D1b resonances and spikes at their crossover frequencies—stand out superposed on the fluorescence background. They are examined with a detailed simulation, Figures 3 and 4, and compared to observations, Figure 5. Parametric studies of the Doppler-free features, Figures 6–8, indicate how to maximize their prominence, and thus their importance as frequency references for laboratory and atmospheric observations.

]]> Paul G. Johnson et al. Results from the Middle Atmosphere with the Rayleigh-Scatter Lidar at USU’s Atmospheric Lidar Observatory http://digitalcommons.usu.edu/atmlidar_post/11 http://digitalcommons.usu.edu/atmlidar_post/11 Fri, 26 Aug 2011 20:40:05 PDT Vincent B. Wickwar et al. An Earlier Lidar Observation of a Noctilucent Cloud above Logan, Utah (41.7°N) http://digitalcommons.usu.edu/atmlidar_post/10 http://digitalcommons.usu.edu/atmlidar_post/10 Fri, 26 Aug 2011 20:09:57 PDT The Atmospheric Lidar Observatory (ALO) Rayleigh-scatter lidar has been operated for 11 years on the Utah State University (USU) campus (41.7o N 111.8o W). During the morning of 22 June 1995 a noctilucent cloud (NLC) was observed with the lidar well away from the twilight periods when NLCs are visible. It lasted for approximately one hour. This observation and a second in 1999 [Wickwar et al., 2002] are very significant because they show the penetration of NLCs equatorward of 50°, which may have important implications for global change. Temperature profiles calculated at hourly intervals were at least 20 K cooler than the 11-year June climatological average for ALO near the NLC altitude. These cool temperatures arose, in part, because of a major temperature oscillation.

]]> Joshua P. Herron et al. Mesospheric Mid-latitude Density Climatology above Utah State University http://digitalcommons.usu.edu/atmlidar_post/9 http://digitalcommons.usu.edu/atmlidar_post/9 Fri, 26 Aug 2011 19:56:32 PDT Lidars have been used extensively to derive temperatures, but not absolute densities, in the mesospheric region of the atmosphere. We used observations since 1993 with the Rayleigh- scatter lidar at the Atmospheric Lidar Observatory (ALO) at Utah State University (41.7oN, 111.8oW) to create an absolute density climatology between 45 and ~95 km. The observations provide profiles of relative density to which an absolute scale is attached by normalizing the profiles at 45 km to the densities in the MSISe00 empirical model. We examine the density variations on several time scales—during the climatological year, from year to year, and over several weeks. We also compare the densities to those in the MSISe00 model.

]]> Eric M. Lundell et al. Planetary Waves and Tides Found using Lomb-Scargle Periodogram Analysis of Rayleigh-Scatter Data above Utah State University http://digitalcommons.usu.edu/atmlidar_post/8 http://digitalcommons.usu.edu/atmlidar_post/8 Fri, 26 Aug 2011 17:52:41 PDT Because of the significant gaps in nighttime-only data, traditional Fourier techniques are difficult to use to identify tides and short-period planetary waves (PWs). The Lomb-Scargle per- iodogram is a method that was developed by as- tronomers to identify oscillations in nighttime-only and otherwise incomplete data. For the same rea- sons, it is also a powerful tool for aeronomers. The Lomb-Scargle technique is described with particular emphasis on its application to nighttime- only lidar data. Because of the gaps in the data, attention is also placed on techniques used to identify aliasing in the Lomb-Scargle periodo- grams. The method is applied to mesospheric temperatures from the Rayleigh-scatter lidar at the Atmospheric Lidar Observatory (ALO; 41.7°N, 111.8°W) at Utah State University (USU).

]]> Karen L. Nelson et al. Rayleigh-Lidar Determinations of the Vertical Wavelength of Mesospheric Gravity Wave http://digitalcommons.usu.edu/atmlidar_post/7 http://digitalcommons.usu.edu/atmlidar_post/7 Fri, 26 Aug 2011 17:17:31 PDT Atmospheric structures have been observed in the Rayleigh lidar data acquired between 1993 and 2004 at Utah State University (USU). The observations pertain to the density and temperature in the mesosphere between 45 and 90 km altitude. The structures referred to arise from monochromatic Atmospheric Gravity Waves (AGWs). Previous analysis of these data have searched for and found a spectrum with a peak in the vertical wavelength 12–16 km. It has been suggested by other researchers using other types of data that there may be another peak in the spectrum at shorter wavelengths. For this study the lidar data were re- analyzed to search for such waves. To do this, the altitude resolution was reduced from 3 km to 600 m. This enabled the shortest wavelength AGW that can be examined to be reduced from 6 km to ~1.2 km, thereby significantly extending the spectrum investigated. Two additional peaks in the spectrum were found at 1.25–1.75 and 3.0–4.0 km.

]]> Joe R. Slansky et al. Large-Amplitude Temperature Waves in the Upper Atmosphere http://digitalcommons.usu.edu/atmlidar_post/6 http://digitalcommons.usu.edu/atmlidar_post/6 Fri, 26 Aug 2011 16:16:19 PDT Recent LIDAR research at USU found a noctilucent cloud (NLC) near the minimum of a large-amplitude temperature wave in the upper mesosphere. Such a large-amplitude wave had not been seen previously. Initial analysis suggested that this wave might be related to the diurnal tide, but greatly amplified. This research set out to learn whether these waves are a common feature. Large waves or temperature “bumps” exceeding 10 K were found in more than half the observations. A later stage will be to see if they are linked to the tides.

]]> Jarron Lembke et al. Rayleigh-Lidar Observations of Mesospheric Instabilities http://digitalcommons.usu.edu/atmlidar_post/5 http://digitalcommons.usu.edu/atmlidar_post/5 Fri, 26 Aug 2011 16:02:38 PDT From 1993 to 2004 the Utah State University Rayleigh lidar, known as the USU green laser, collected 900 nights of data from the mesosphere (45-90 km). From these observations profiles of relative neutral densities and absolute temperatures were derived. Usually, the atmosphere is horizontally stratified with a balance between gravitational and pressure forces. When this balance is perturbed, it leads to the generation of buoyancy or “gravity” waves. An example of these is clear air turbulence, which can have dramatic effects on airplanes. As these waves propagate upward, the decrease in atmospheric density and conservation of energy combine to give rise to a large increase in amplitude. These growing waves can become large enough that they “break,” giving up their energy to the surrounding atmosphere. The common analogy used here is that of ocean waves in which the waves break near shore. One manifestation of this in the atmosphere is the occurrence of an instability, the convective instability. With this instability detected in the lidar data on several nights, it has become the focus of this work. It is characterized by the buoyancy frequency, the Brunt-Väisälä frequency, becoming zero or imaginary.

]]> Gabriel C. Taylor et al. Atmospheric Lidar Observatory (ALO) Ten-Year Mesospheric Temperature Climatology http://digitalcommons.usu.edu/atmlidar_post/4 http://digitalcommons.usu.edu/atmlidar_post/4 Fri, 26 Aug 2011 15:51:04 PDT The Rayleigh-scatter lidar at the Atmospheric Lidar Observatory (ALO) on the Utah State University (USU) (41.7°N, 111.8°W) campus has been in operation since 1993. The temperature database now contains over ten years of Rayleigh-scatter temperatures. A multi-year temperature climatology has been calculated from these observations along with the RMS and interannual variability. These temperatures and the climatology are currently being used in a number of mesospheric studies, including mesospheric inversion layers, tides, planetary waves, cyclical variations, trends, longitudinal comparisons, and validation studies.

]]> Joshua P. Herron et al. Mesospheric Atmospheric Gravity Wave Properties Derived from Rayleigh-Scatter Lidar Observations above Logan, Utah http://digitalcommons.usu.edu/atmlidar_post/3 http://digitalcommons.usu.edu/atmlidar_post/3 Fri, 26 Aug 2011 14:15:03 PDT Approximately 900 nights of observations with a Rayleigh-scatter lidar at Utah State University’s Atmospheric Lidar Observatory (41.7°N, 111.8°W, 1.47 km above sea level), spanning the 11-year period from late 1993 through 2004, have been reduced to derive nighttime temperature and relative density profiles between 45 and 90 km. Of these, 150 profiles that extend to 90 km or above were used in this work, which is based mainly on relative density data with 3-km altitude resolution and 1-hour temporal resolution. This is, we believe, the first comprehensive study of monochromatic gravity waves using Rayleigh-Scatter lidar observations extending through the entire mesosphere at mid-latitudes. The variations of relative density perturbations were used to identify the presence of monochromatic gravity waves. These waves have a clear downward phase progression (i.e., upward energy propagation) with the most prevalent vertical phase velocity (c ) of 0.6 ms-1 (2.2 km/hr). The most dominant vertical wavelengths (λ ) are between 12 and 16 km. The z z values of Brunt-Väisälä frequency, N (rad/sec), the maximum gravity wave frequency, were calculated by using seasonally averaged nightly temperature and temperature derivative profiles. Using the gravity wave dispersion relation and the values of c , λ , and N, other gravity wave parameters such as wave period (T ), horizontal z z p wavelength (λx), horizontal phase velocity (cx), and horizontal distance to the source region (X) were calculated. There appears to be a seasonal dependence in cz, Tp, λx, and X but not in λz and cx. Values of cz maximized in summer whereas Tp, λx, and X maximized in winter.

]]> Durga Kafle Rayleigh-Lidar Observations of Mesospheric Mid-latitude Density Climatology above Utah State University http://digitalcommons.usu.edu/atmlidar_post/2 http://digitalcommons.usu.edu/atmlidar_post/2 Fri, 26 Aug 2011 14:13:06 PDT Data from Rayleigh lidars have been used extensively to derive temperatures in the mesospheric region of the atmosphere. However, these data have not been used extensively in a similar way to derive neutral densities. We report on one such mid-latitude, density climatology between 45 and ~90 km, based on nearly 600 good nights of observations carried out since 1993 at the Atmospheric Lidar Observatory (ALO) at Utah State University (41.7°N 111.8°W). They produce relative density profiles that are then normalized at 45 km to an empirical model, in this case the MSISe00 model. Despite this normalization, significant differences are found between the observations and the model starting as low as 50 km. For instance, the lower mesosphere is denser than the model in summer and less dense in winter. In contrast, the upper mesosphere is denser near the equinoxes and less dense at other times. Differences between the climatology and the model reach ±11%. The normalized observations show a large seasonal variation, with the summer densities in the 65-75 km region being approximately 55% greater than the winter densities. At both lower and higher altitudes, the seasonal variation is less.

]]> Eric M. Lundell et al. The World's Most Sensitive Rayleigh-Scatter Lidar http://digitalcommons.usu.edu/atmlidar_post/1 http://digitalcommons.usu.edu/atmlidar_post/1 Mon, 15 Aug 2011 10:26:29 PDT Leda Sox et al.