Weichun Fong

Bio: Weichun Fong is an academic researcher from University of Colorado Boulder. The author has contributed to research in topics: Lidar & Thermosphere. The author has an hindex of 12, co-authored 19 publications receiving 453 citations. Previous affiliations of Weichun Fong include Cooperative Institute for Research in Environmental Sciences.

Lidar observations of neutral Fe layers and fast gravity waves in the thermosphere (110–155 km) at McMurdo (77.8°S, 166.7°E), Antarctica

Abstract: [1] We report the first lidar observations of neutral Fe layers with gravity wave signatures in the thermosphere from 110–155 km at McMurdo, Antarctica in May 2011. The thermospheric Fe densities are low, ranging from ∼200 cm−3 at 120 km to ∼20 cm−3 at 150 km. The measured temperatures from 115–135 km are considerably warmer than MSIS and appear to be related to Joule heating enhanced by aurora. The observed waves originate in the lower atmosphere and show periods of 1.5–2 h through 77–155 km. The vertical wavelength increases from ∼13 km at 115 km to ∼70 km at 150 km altitude. These wave characteristics are strikingly similar to the traveling ionospheric disturbances caused by internal gravity waves. The thermospheric Fe layers are likely formed through the neutralization of vertically converged Fe+ layers that descend in height following the gravity wave downward phase progression.

Inertia‐gravity waves in Antarctica: A case study using simultaneous lidar and radar measurements at McMurdo/Scott Base (77.8°S, 166.7°E)

Abstract: [1] This study presents the first coincident observation of inertia-gravity waves (IGWs) by lidar and radar in the Antarctic mesopause region This is also the first known observation of two simultaneous IGWs at the same location An Fe Boltzmann lidar at Arrival Heights (778°S, 1667°E) provides high-resolution temperature data, and a co-located MF radar provides wind data On 29 June 2011, coherent wave structures are observed in both the Fe lidar temperature and MF radar winds Two dominant waves are determined from the temperature data with apparent periods of 77 ± 02 and 50 ± 01 h and vertical wavelengths of 22 ± 2 and 23 ± 2 km, respectively The simultaneous measurements of temperature and wind allow the intrinsic wave properties to be derived from hodograph analyses unambiguously The analysis shows that the longer-period wave propagates northward with an azimuth of θ = 11° ± 5° clockwise from north This wave has a horizontal wavelength of λh = 22 ± 02 × 103 km and an intrinsic period of τI = 79 ± 03 h The intrinsic horizontal phase speed (CIh) for this wave is 80 ± 4 m/s, while the horizontal and vertical group velocities (Cgh and Cgz) are 48 ± 3 m/s and 05 ± 01 m/s, respectively The shorter-period wave has τI = 45 ± 03 h and θ = 100° ± 4° with λh = 11 ± 01 × 103 km and CIh = 68 ± 5 m/s Its group velocities are Cgh = 58 ± 5 m/s and Cgz = 11 ± 01 m/s Therefore, both waves propagate with very shallow elevation angles from the horizon (ϕ = 06° ± 01° and ϕ = 11° ± 01° for the longer- and shorter-period waves, respectively) but originate from different sources Our analysis suggests that the longer-period IGW most likely originates from the stratosphere in a region of unbalanced flow

Lidar observations of persistent gravity waves with periods of 3–10 h in the Antarctic middle and upper atmosphere at McMurdo (77.83°S, 166.67°E)

Abstract: Persistent, dominant, and large-amplitude gravity waves with 3–10 h periods and vertical wavelengths ~20–30 km are observed in temperatures from the stratosphere to lower thermosphere with an Fe Boltzmann lidar at McMurdo, Antarctica. These waves exhibit characteristics of inertia-gravity waves in case studies, yet they are extremely persistent and have been present during every lidar observation. We characterize these 3–10 h waves in the mesosphere and lower thermosphere using lidar temperature data in June from 2011 to 2015. A new method is applied to identify the major wave events from every lidar run longer than 12 h. A continuous 65 h lidar run on 28–30 June 2014 exhibits a 7.5 h wave spanning ~60 h, and 6.5 h and 3.4 h waves spanning 40 and 45 h, respectively. Over the course of 5 years, 323 h of data in June reveal that the major wave periods occur in several groups centered from ~3.5 to 7.5 h, with vertical phase speeds of 0.8–2 m/s. These 3–10 h waves possess more than half of the spectral energy for ~93% of the time. A rigorous prewhitening, postcoloring technique is introduced for frequency power spectra investigation. The resulting spectral slopes are unusually steep (−2.7) below ~100 km but gradually become shallower with increasing altitude, reaching about −1.6 at 110 km. Two-dimensional fast Fourier transform spectra confirm that these waves have a uniform dominant vertical wavelength of 20–30 km across periods of 3.5–10 h. These statistical features shed light on the wave source and pave the way for future research.

Lidar observations of stratospheric gravity waves from 2011 to 2015 at McMurdo (77.84°S, 166.69°E), Antarctica: 1. Vertical wavelengths, periods, and frequency and vertical wave number spectra

Abstract: Five years of atmospheric temperature data, collected with an Fe Boltzmann lidar by the University of Colorado group from 2011 to 2015 at Arrival Heights, are used to characterize the vertical wavelengths, periods, vertical phase speeds, frequency spectra, and vertical wave number spectra of stratospheric gravity waves from 30 to 50 km altitudes. Over 1000 dominant gravity wave events are identified from the data. The seasonal spectral distributions of vertical wavelengths, periods, and vertical phase speeds in summer, winter, and spring/fall are found obeying a lognormal distribution. Both the downward and upward phase progression gravity waves are observed by the lidar, and the fractions of gravity waves with downward phase progression increase from summer ~59% to winter ~70%.

Vertical evolution of potential energy density and vertical wave number spectrum of Antarctic gravity waves from 35 to 105 km at McMurdo (77.8°S, 166.7°E)

Abstract: We report the first characterization of potential energy densities and vertical wave number spectra of Antarctic gravity waves (GWs) from 35 to 105 km, derived from Fe lidar temperature measurements at McMurdo (77.8°S, 166.7°E) in 2011–2013 winters. For GWs with periods of 2–10 h, the potential energy density per unit volume (Epv) decreases by 2 orders of magnitude from 35 to 105 km, while that per unit mass (Epm) increases from several to hundreds of J/kg. Epm increases with a mean scale height of ~10.4 km in the Rayleigh region (35–65 km) and of ~13.2 km in the Fe region (81–105 km), and of particular interest is the inferred severe dissipation in between (65–81 km). Overall, the vertical evolutions of Epv and Epm indicate considerable wave energy loss from the stratosphere to the lower thermosphere. The vertical wave number spectra exhibit power law forms for vertical wavelengths λz 10 km in 35–60 km. PSDs increase by 1 order of magnitude from the stratosphere to the lower thermosphere. Using higher temporal resolution data to include 0.5–2 h waves increase Epm by ~25–45% and increase PSDs of 2–5 km waves by a factor of 2 and of >10 km waves by less than 50%.

The mesosphere and metals: chemistry and changes.

Abstract: The subject of this review is the atmospheric chemistry of the metals which ablate from meteoroids in the Earth’s upper atmosphere. The major meteoric species are Fe, Mg, Si, and Na, against which two minor species, Ca and K, offer surprising contrasts. These metals exist as layers of atoms between about 80 and 105 km and atomic ions at higher altitudes. Below 85 km they form compounds—oxides, hydroxides, and carbonates—which polymerize into nanometer-sized meteoric smoke particles (MSPs). These particles probably act as condensation nuclei for clouds in the mesosphere and stratosphere and eventually after about 4 years are deposited at the Earth’s surface. The subject of meteoric metal chemistry was reviewed in 19911 and 2003,2 and there were also more focused reviews on laboratory studies of metal reactions in 19943 and 20024 and the atmospheric modeling of metals in 2002.5 The present review will therefore concentrate on the many developments that have taken place in the past decade. On the observational side, these developments include the near-global measurement of the Na, K, Mg, and Mg+ layers from satellite-borne spectrometers and lidar observations of Na and Fe from several Antarctic observatories, the discovery that metal atoms are removed in the vicinity of noctilucent (or polar mesospheric) clouds, the surprising observation of metal atoms up to around 180 km in the thermosphere, the unexpected finding that the ratio of the Na d lines in the terrestrial nightglow is variable, the first observations of the molecular bands of FeO and NiO in the nightglow, the first measurements of the vertical flux of Na atoms in the upper mesosphere, the measurement of MSPs from rockets, incoherent scatter radars, satellites, and aircraft, and measurements of the depositional flux of meteoric smoke in polar ice cores. Laboratory measurements (including the application of quantum chemistry calculations) have addressed several issues: the ion and neutral gas-phase chemistries of compounds containing Fe, Ca, Mg, Si, and K, leading to the first chemically closed reaction schemes for these metals, the uptake of metal atoms on low-temperature ice surfaces and the resulting photoelectric emission, understanding the variable Na d line ratio observations, and the formation of a variety of iron oxide and Fe–Mg–silicate nanoparticles as analogues of meteoric smoke. There have also been significant developments in modeling: a chemical ablation model to predict the evaporation rates of individual elements from a meteoroid, coupling this ablation model with an astronomical model of dust input to generate the meteoric input function (MIF), the inclusion of the MIF together with metal chemistry in a whole atmosphere chemistry climate model to create the first global models of the Na, Fe, Mg, and K layers, an explanation for the 50 year old puzzle of why the Na and K layers exhibit such different seasonal behavior, modeling the growth and transport of MSPs through the mesosphere and stratosphere, the paleoclimate implications of an enhanced cosmic dust input, and the climate implications of the deposition of meteoric Fe into the Southern Ocean. The present review is divided into five sections following this Introduction. Section 2 is a general review of the mesosphere and lower thermosphere from the perspective of understanding the metal layers and the sensitivity of this atmospheric region to solar activity and longer term anthropogenic changes. Section 3 describes the atmospheric chemistry of the meteoric metals and then reviews observations of the metal layers and MSPs. Section 4 deals with laboratory and theoretical studies of gas-phase metal reactions and particle formation under mesospheric conditions. Section 5 is concerned with the development of global models of metal chemistry which describe the input and ablation of cosmic dust, the gas-phase chemistry of metallic species, the formation of MSPs, and transport to the Earth’s surface. Section 6 is then a summary with a discussion of future directions for the field.

Introduction to the SPARC Reanalysis Intercomparison Project (S-RIP)

Abstract: The climate research community uses atmospheric reanalysis data sets to understand a wide range of processes and variability in the atmosphere, yet different reanalyses may give very different results for the same diagnostics. The Stratosphere–troposphere Processes And their Role in Climate (SPARC) Reanalysis Intercomparison Project (S-RIP) is a coordinated activity to compare reanalysis data sets using a variety of key diagnostics. The objectives of this project are to identify differences among reanalyses and understand their underlying causes, to provide guidance on appropriate usage of various reanalysis products in scientific studies, particularly those of relevance to SPARC, and to contribute to future improvements in the reanalysis products by establishing collaborative links between reanalysis centres and data users. The project focuses predominantly on differences among reanalyses, although studies that include operational analyses and studies comparing reanalyses with observations are also included when appropriate. The emphasis is on diagnostics of the upper troposphere, stratosphere, and lower mesosphere. This paper summarizes the motivation and goals of the S-RIP activity and extensively reviews key technical aspects of the reanalysis data sets that are the focus of this activity. The special issue \"The SPARC Reanalysis Intercomparison Project (S-RIP)\" in this journal serves to collect research with relevance to the S-RIP in preparation for the publication of the planned two (interim and full) S-RIP reports.

The deep propagating gravity wave experiment (deepwave): an airborne and ground-based exploration of gravity wave propagation and effects from their sources throughout the lower and middle atmosphere

Abstract: The Deep Propagating Gravity Wave Experiment (DEEPWAVE) was designed to quantify gravity wave (GW) dynamics and effects from orographic and other sources to regions of dissipation at high altitudes. The core DEEPWAVE field phase took place from May through July 2014 using a comprehensive suite of airborne and ground-based instruments providing measurements from Earth’s surface to ∼100 km. Austral winter was chosen to observe deep GW propagation to high altitudes. DEEPWAVE was based on South Island, New Zealand, to provide access to the New Zealand and Tasmanian “hotspots” of GW activity and additional GW sources over the Southern Ocean and Tasman Sea. To observe GWs up to ∼100 km, DEEPWAVE utilized three new instruments built specifically for the National Science Foundation (NSF)/National Center for Atmospheric Research (NCAR) Gulfstream V (GV): a Rayleigh lidar, a sodium resonance lidar, and an advanced mesosphere temperature mapper. These measurements were supplemented by in situ probes, dropson...

Secondary Gravity Waves in the Winter Mesosphere: Results From a High-Resolution Global Circulation Model

Abstract: This study analyzes a new high-resolution general circulation model with regard to secondary gravity waves in the mesosphere during austral winter. The model resolves gravity waves down to horizontal and vertical wavelengths of 165 and 1.5 km, respectively. The resolved mean wave drag agrees well with that from a conventional model with parameterized gravity waves up to the midmesosphere in winter and up to the upper mesosphere in summer. About half of the zonal-mean vertical flux of westward momentum in the southern winter stratosphere is due to orographic gravity waves. The high intermittency of the primary orographic gravity waves gives rise to secondary waves that result in a substantial eastward drag in the winter mesopause region. This induces an additional eastward maximum of the mean zonal wind at z ∼ 100 km. Radar and lidar measurements at polar latitudes and results from other high-resolution global models are consistent with this finding. Hence, secondary gravity waves may play a significant role in the general circulation of the winter mesopause region. Plain Language Summary We present a new gravity-resolving general circulation model that extends into the lower thermosphere. The simulated summer-to-winter-pole circulation in the upper mesosphere is nearly realistic and driven by resolved waves. We find a new phenomenon that results from the generation of secondary gravity waves in the stratosphere and lower mesosphere. The effect is characterized by an eastward gravity drag that causes a secondary eastward wind maximum around the polar winter mesopause. Analysis of the simulated gravity waves shows consistence with other gravity wave resolving models and with observational studies of the austral winter middle atmosphere, including the mesopause region.

Using Satellite Observations to Constrain Parameterizations of Gravity Wave Effects for Global Models

Abstract: Abstract Small-scale gravity waves are common features in atmospheric temperature observations. In satellite observations, these waves have been traditionally difficult to resolve because the footprint or resolution of the measurements precluded their detection or clear identification. Recent advances in satellite instrument resolution coupled to innovative analysis techniques have led in the last decade to some new global datasets describing the temperature variance associated with these waves. Such satellite observations have been considered the best hope for quantifying the global properties of gravity waves needed to constrain parameterizations of their effects for global models. Although global maps of averaged gravity wave temperature variance have now been published from a variety of different instruments on Earth-orbiting platforms these maps have not provided the needed constraints. The present paper first summarizes what has been learned from traditional temporally and spatially averaged analyse...