Mesospheric Temperature Climatology and Comparisons Above the Rocky Mountains

A Rayleigh-scatter lidar has been operated by the Center for Atmospheric and Space Sciences (CASS) at Utah State University (USU) since 1993. The lidar measures atmospheric temperatures between 45 and 90 km which are important for understanding the physics and chemistry of the middle atmosphere. The temperature profiles were used to create a multi-year temperature climatology. This climatology was used for comparisons with the temperature climatology from the Purple Crow Lidar at the University of Western Ontario, and nightly temperature profiles from the SABER instrument on board the TIMED satellite

Rayleigh-Scatter Lidar Observations at USU\u27s Atmospheric Lidar Observatory (Logan,UT) - Temperature Climatology, Temperature Comparisons with MSIS, and Noctilucent Clouds

The Earth\u27s atmosphere is typically characterized by its temperature structure, which naturally divides the atmosphere into several discrete regions. They are in order of increasing altitude the troposphere, stratosphere, mesosphere, and thermosphere. The first layer and a large portion of the second layer of the Earth\u27s atmosphere are routinely measured via weather balloons that are launched twice daily around the globe. Satellites and their development have motivated the study of the thermosphere. It is the middle region of the Earth atmosphere, which is mainly composed of the mesosphere that lacks routine in situ measurements. Routine observations are therefore carried out via remote sensing. Ground-based instruments typically provide high resolution measurements of the atmosphere over a single point on the globe and space-based instrument capture a global picture at lower resolution. A Rayleigh-scatter lidar has been in operation at Utah State University ( 41 . 7°N III .8°N) starting in September 1993. Observations have continued from that point until the present when funding and observing conditions have permitted. Under normal observational conditions the backscattered photons are proportional to the atmospheric density. These relative density profiles can be used to derive absolute temperature profiles over much of the middle atmosphere. The resulting II years of temperature profiles have been combined into a single composite year which contains - 900 nights and - 5000 hours of observations. This climatology was compared to the mid-latitude climatology from the French lidar group at Haute Provence and relatively good agreement was obtained. It was also compared to the NRL MSIS empirical model to explore the model\u27s validity at mid-latitudes. Some significant differences were found. The coldest atmospheric temperatures are found at the mesopause near the summer solstice. Small ice crystals formed in this region and can grow to form noctilucent clouds (NLC) which are the highest naturally occurring clouds in the atmosphere. Previously, NLC observations have been limited to the region poleward of so• but NLCs have been observed with the ALO lidar on two occasions. Their formation has been attributed to atmospheric dynamics, a large amplitude wave, rather than a general cooling of the atmosphere

MESOSPHERIC TEMPERATURE CLIMATOLOGY ABOVE UTAH STATE UNIVERSITY

A Rayleigh-scatter lidar has been in operation at Utah State University (41.7o N, 111.8 ° W) starting in September 1993 until the present (October 2003). The return profiles from the atmosphere have been analyzed to provide temperature measurements of the middle atmosphere from 45 to 90 km. Various methods of averaging were used to construct a temperature climatology of the region based on these observations. The data analysis algorithm has been critically analyzed to find possible sources of error, and has been compared to an independently derived technique. The resulting temperatures have been compared to other mid-latitude lidars with good agreement. Comparisons were made with temperatures from other ground-based instruments at Bear Lake Observatory. Additional comparisons were carried out with two satellite-based instruments, WINDII and SABER. The comparison of individual nights with the SABER instrument produced surprisingly good agreement considering the difference in the two methds. With the basic analysis of the temperature climatology completed in this work, an outline is given for future research and upgrades to the facility

Atmospheric Lidar Observatory (ALO) Ten-Year Mesospheric Temperature Climatology

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

Mid-Latitude Climatologies of Mesospheric Temperature and Geophysical Temperature Variability Determined with the Rayleigh-Scatter Lidar at ALO-USU

From 1993-2004, 839 nights were observed with the Rayleigh-scatter lidar at Utah State University’s Atmospheric Lidar Observatory. They were reduced to obtain nighttime mesospheric temperatures between 45 and ~90 km, which were then combined to derive composite annual climatologies of mid-latitude temperatures and geophysical temperature variability. At 45 km, near the stratopause, there is a ~250 K temperature minimum in mid-winter and a 273 K maximum in mid-May. The variability behaves oppositely, being 7-10 K in winter and 2.5 K in summer. At 85 km, there is a 215 K temperature maximum at the end of December and a 170 K mesopause minimum in early June. In contrast, the variability is roughly constant at ~20 K. At both low and high altitudes, the temperatures change much more rapidly in spring than in fall. The transition between these opposite temperature behaviors is 65 km. Distinctive temperature structures occur in all regions. In mid-winter, between 45 and 50 km, a 6 K warm region appears, most likely from occasional sudden stratospheric warmings. Above that, a “cold valley” extends to 70 km, which may be related to the bottom side of intermittent inversion layers. Both regions have increased variability. Near 85 km, there is a very rapid heating event of 25 K/month in August with high variability. In October, a temperature minimum, a “cold island”, occurs from 78–86 km with low variability, indicating a regular feature. These USU results are compared extensively to those from other mid-latitude lidars in Canada and France

Middle Atmosphere Temperature Results from a New, High-powered, Large-Aperture Rayleigh Lidar

In June–July 2012, observations were carried out using the recently upgraded, large-aperture, Rayleigh-scatter lidar system located at the Atmospheric Lidar Observatory (ALO) on the campus of Utah State University, in Logan, UT (41.7 N, 111.8 W). This time period was significant because it enabled us to observe the annual temperature minimum in the upper mesosphere-lower thermosphere region. The data collected during the campaign were analyzed for temperatures between ~70–109 km. The results above ~95 km are the first obtained with a Rayleigh-scatter lidar, extending the technique well into the lower thermosphere. A great deal of variability from night-to-night is evident in these temperature profiles and in the mesopause altitude. The profiles also show considerable wave activity from large amplitude waves. The temperatures are compared to those from the MSISe90 model and from the 11-year ALO temperature climatology. This new capability for the ALO Rayleigh lidar, like any new observational capability, opens the potential for new discoveries in this hard-to-observe region

Planetary Waves and Tides Found using Lomb-Scargle Periodogram Analysis of Rayleigh-Scatter Data above Utah State University

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)

Rayleigh Scatter Lidar Observations of the Midlatitude Mesosphere’s Response to Sudden Stratospheric Warmings

The original Rayleigh-scatter lidar that operated at the Atmospheric Lidar Observatory (ALO; 41.7°N, 111.8°W) in the Center for Atmospheric and Space Sciences (CASS) on the campus of Utah State University (USU) collected a very dense set of temperature data for 11 years, from 1993 through 2004. The temperatures derived from these data extended over the mesosphere, from 45 to 90 km. This work will focus on the extensive Rayleigh lidar observations made during the seven major SSW events that occurred between 1993 and 2004. In order to determine the characteristics of the midlatitude mesospheric temperatures during SSWs, comparisons were made between the temperature profile on an individual night during a SSW event and the climatological (11-year average) temperature profile for that night. An overall disturbance pattern was observed in the mesospheric temperatures during these SSWs. It included coolings (sometimes very significant) in the upper mesosphere and warmings in the lower mesosphere

Searching for Troposphere-Mesosphere Connections Using the ALO-USU Rayleigh-Scatter Lidar

The paucity of whole-atmosphere data introduces significant challenges that hinder the study of atmospheric couplings. The mesosphere in particular is a low-information void between the lower and upper atmosphere, which may prevent us from a complete realization of vertical interactions. The Rayleighscatter lidar at Utah State University’s Atmospheric Lidar Observatory (ALO-USU; 41.74° N, 111.81° W), operated with little interruption from 1993 to 2004, providing a valuable temporal and spatial (45 – 90 km) resource in this realm. When studied alongside a multitude of other atmospheric data sources, possible unforeseen connections or insights may result. In this study, an adaptive fit is applied to near-stratopause temperature data from the lidar and several assimilative models to identify simultaneous abnormal changes. A possible connection with tropospheric events is investigated as an example of future efforts that can be made to synthesize similar environmental figures where available