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NASA NTRS1999

Modeling the QBO and SAO Driven by Gravity Waves

Hines' Doppler spread parameterization (DSP) for small scale gravity waves (GW) is applied in a global scale numerical spectral model (NSM) to describe the semi-annual and quasi-biennial oscillations (SAO and QBO) as well as the long term interannual variations that are driven by wave mean flow interactions. This model has been successful in simulating the salient features observed near the equator at altitudes above 20 km, including the QBO extension into the upper mesosphere inferred from UARS measurements. The model has now been extended to describe also the mean zonal and meridional circulations of the upper troposphere and lower stratosphere that affect the equatorial QBO and its global scale extension. This is accomplished in part through tuning of the GW parameterization, and preliminary results lead to the following conclusions: (1) To reproduce the upwelling at equatorial latitudes associated with the Brewer/Dobson circulation that in part is modulated in the model by the vertical component of the Coriolis force, the eddy diffusivity in the lower stratosphere had to be enhanced and the related GW spectrum modified to bring it in closer agreement with the form recommended for the DSP. (2) To compensate for the required increase in the diffusivity, the observed QBO requires a larger GW source that is closer to the middle of the range recommended for the DSP. (3) Through global scale momentum redistribution, the above developments are conducive to extending the QBO and SAO oscillations to higher latitudes. Multi-year interannual oscillations are generated through wave filtering by the solar driven annual oscillation in the zonal circulation. (4) In a 3D version of the model, wave momentum is absorbed and dissipated by tides and planetary waves. Thus, a somewhat larger GW source is required to generate realistic amplitudes for the QBO and SAO.

Mayr, H. G.↗
NASA NTRS1998

Transport Between the Tropical and Midlatitude Lower Statosphere: Implications for Ozone Response to High-Speed Civil Transport Emissions

Several recent studies have quantified the air exchange rate between the tropics and midlatitudes in the lower stratosphere using airborne and satellite measurements of chemical species. It is found that the midlatitude air is mixed into the tropical lower stratosphere with a replacement timescale of 13.5 months (with 20% uncertainty) for the region from the tropopause to 21 km and at least 18 months for the region of 20-28 km. These estimates are used to adjust the horizontal eddy diffusion coefficients, K(sub yy), in a two-dimensional chemistry transport model. The value of K(sub yy) previously used to simulate the subtropical barrier, 0.03 x 10(exp 6) sq m/s, generates an exchange time of about 4 years, and the model without subtropical barrier (K(sub yy) = 0.3 x 10(exp 6) sq m/s) has an exchange time of 5 months. Adjusting the K(sub yy) to 0.13 x 10(exp 6) sq m/s from the tropopause to 21 km and 0.07 x 10(exp 6) sq m/s above 21 km produces the exchange timescales which match the estimates deduced from the measurements. The subtropical barrier prevents the engine emissions of the high-speed civil transport (HSCT) aircraft from being transported into the tropics and subsequently lifted into the upper atmosphere or mixed into the southern hemisphere. The model results show that the calculated ozone response to HSCT aircraft emissions using the K(sob yy) adjusted to observed mixing rates is substantially smaller than that simulated without the subtropical barrier.

Shia, R.-L.↗
NASA NTRS2000

Vertical Distributions of PH3 in Saturn from Observations of Its 1-0 and 3-2 Rotational Lines

Far-infrared Fourier-transform spectrometer measurements of the 1-0 and 3-2 PH3 transitions in Saturn's disk near 267 and 800 GHz (8.9 and 26.7/cm), respectively, were analyzed simultaneously to derive a global mean profile for the PH3 vertical mixing ratio between 100 and 600 mbar total pressure. The far-infrared spectrum is relatively free from spectral interlopers, suffers minimal absorption or scattering by atmospheric particulates, and contains intrinsically weak PH3 lines that are sensitive to a range of atmospheric depths. The combined spectra are inconsistent with a uniform tropospheric mixing ratio, even with a stratospheric cut-off. They are consistent with a volume mixing ratio of PH3 that drops from 1.2 x 10(exp -5) at 645 mbar pressure to a value of 4.1 x 10(exp -7) at 150 mbar pressure, a decrease that is linear is log abundance vs log pressure. The mixing ratio could drop even more quickly at atmospheric pressures below 150 mbar and still be consistent with the data. The mixing ratio may well remain constant with depth for pressures above 630 mbar. The maximum PH3 mixing ratio in this model is consistent with a [P]/[H] ratio in the deep atmosphere that is about a factor of 10 higher than solar composition. Such a model is consistent with rapid mixing up to the radiative-convective boundary and transport by, for example, vertical waves just above this boundary. In the best fitting model, the eddy diffusion coefficient is approximately 10(exp 4) sq cm near 630 mbar, and it must increase with altitude. The predominant PH3 loss mechanisms are direct photolysis by UV radiation and scavenging by H atoms produced by the photolysis.

Orton, G. S.↗
NASA NTRS2000

Interannual Variability in the Equatorial Stratosphere: Comparison of 2D Model Simulations with Satellite Constituent Data

Satellite observations from UARS and TOMS have provided unique data sets for studying seasonal and interannual stratospheric constituent variability during the 1990's. The corresponding meteorological variability is also well represented by the partly satellite-based UKMO assimilation winds and temperatures. In this study, we use the UKMO meteorological fields to derive zonal mean transport components (residual circulation, horizontal eddy diffusion) for each year, 1992-1998. These fields are then used in our GSFC two-dimensional chemistry and transport model to simulate the year to year changes in ozone and long lived tracers in the equatorial stratosphere due to interannual dynamical variability. The resulting model simulation of ozone and CH4 compares reasonably well with UARS data in reproducing a dominant QBO signal in the lower stratosphere, and a dominant semiannual signature in the upper stratosphere which appears to be modulated by the lower stratospheric QBO. The model also compares well with TOMS data in simulating the phase of the QBO in total ozone, although the model QBO amplitude is somewhat underestimated relative to TOMS. These comparisons illustrate that the general zonal mean transport characteristics in the equatorial stratosphere can be reasonably well simulated using an empirically-based residual circulation.

Fleming, Eric L.↗
NASA NTRS2000

Photochemical Modeling of CH3 Abundances in the Outer Solar System

Recent measurements of methyl radicals (CH3) in the upper atmospheres of Saturn and Neptune by the Infrared Space Observatory (ISO) provide new constraints to photochemical models of hydrocarbon chemistry in the outer solar system. The derived column abundances of CH3 on Saturn above 10 mbar and Neptune above the 0.2 mbar pressure level are (2.5 - 6.0) x 10(exp 13) / sq cm and (0.7 - 2.8) x 10(exp 13) / sq cm, respectively. We use the updated Caltech/Jet Propulsion Laboratory photochemical model, which incorporates hydrocarbon photochemistry, vertical molecular and bulk atmospheric eddy diffusion, and realistic radiative transfer modeling, to study the CH3 abundances in the upper atmosphere of the giant planets and Titan. We identify the key reactions that control the concentrations of CH3 in the model, such as the three-body recombination reaction, CH3 + CH3 + M yields C2H6 + M. We evaluate and extrapolate the three-body rate constant of this reaction to the low-temperature limit (1.8 x 10(exp -16) T(sup -3.75) e(sup -300/T), T < 300 K) and compare methyl radical abundances in five atmospheres: Jupiter, Saturn, Uranus, Neptune, and Titan. The sensitivity of our models to the rate coefficients for the reactions H + CH3 + M yields CH4 + M, H + C2H3 yields C2H2 + H2, (sup 1)CH2 + H2 yields CH3 + H, and H + C2H5 yields 2CH3, the branching ratios of CH4 photolysis, vertical mixing in the five atmospheres, and Lyman alpha photon enhancement at the orbit of Neptune have all been tested. The results of our model CH3 abundances for both Saturn (5.1 x 10(exp 13) / sq cm) and Neptune (2.2 x 10(exp 13) / sq cm) show good agreement with ISO Short Wavelength Spectrometer measurements. Using the same chemical reaction set, our calculations also successfully generate vertical profiles of stable hydrocarbons consistent with Voyager and ground-based measurements in these outer solar system atmospheres. Predictions of CH3 column concentrations (for p <= 0.2 mbar) in the atmospheres of Jupiter (3.3 x 10(exp 13) /sq cm), Uranus (2.5 x 10(exp 12) / sq cm), and Titan (1.9 x 10(exp 15) / sq cm) may be checked by future observations.

Lee, Anthony Y. T.↗
NASA NTRS1997

Vertical Transport Processes for Inert and Scavenged Species: TRACE-A Measurements

The TRACE-A mission of the NASA DC-8 aircraft made a large-scale survey of the tropical and subtropical atmosphere in September and October of 1992. Both In-situ measurements of CO (G. Sachsen NASA Langley) and aerosol size (J. Browell group, NASA Langley) provide excellent data sets with which to constrain vertical transport by planetary boundary layer mixing and deep-cloud cumulus convection. Lidar profiles of aerosol-induced scattering and ozone (also by Bremen) are somewhat require more subtle interpretation as tracers, but the vertical information on layering largely compensates for these complexities. The reason this DC-8 dataset is so useful is that very large areas of biomass burning over Africa and South America provide surface sources of appropriate sizes with which to characterize vertical and horizontal motions; the major limitation of our source description is that biomass burning patterns move considerably every few days, and daily burning inventories are a matter of concurrent, intensive research. We use the Penn State / NCAR MM5 model in an assimilation mode on the synoptic and intercontinental scale, and assess the success it shows in vertical transport descriptions. We find that the general level of emissions suggested by the climatological approach (Will. Has, U. of Montana) appears to be approximately correct, possibly a bit low, for this October, 1992, time period. Vertical transport in planetary boundary layer mixing to 5.5 kin was observed and reproduced in our simulations. Furthermore we find evidence that Blackader "transilient" or matrix-transport scheme is needed, but may require some adaptation in our tracer model: CO seems to exhibit very high values at the top of the planetary boundary layer, a process that stretches the eddy-diffusion parameterization. We will report on progress in improving the deep convective transport of carbon monoxide: the Grail scheme as we used it at 100 kin resolution did not transport enough material to the upper troposphere. We expect to be able to attribute this to either parameterization reasons (inadequacy of this parameterization at the large 100km scale) or other reasons. Nevertheless, the qualitative nature of deep transport by clouds shows up well in the simulations. As for scavengable species, the simulations predict tens of micrograms per standard cubic meter of smoke aerosol in the boundary layer. In a straightforward illustration of our simple bulk-mass scavenging parameterization, to one or two micrograms per standard cubic meter of smoke aerosol in the free troposphere just above the source regions: very high concentrations for the free troposphere. We expect to report on comparisons of these predictions to a variety of observations.

Chatfield, Robert B.↗
NASA NTRS1996

Haze Formation is an Important Sink for HCN on Titan

Titan's organic haze is potentially an important sink of photochemically produced carbon and nitrogen compounds. An assortment of microphysical haze models all suggest that the haze production rate is 10(exp -14) gm per square centimeter per second, within a factor of two. Spectral analysis of laboratory tholins compared to Titan's geometric albedo spectrum suggest that the laboratory material is a good analog to Titan's haze. The laboratory material has an elemental composition given approximately by C4H4N, with an uncertainty in the C/N ratio of a factor of two. Thus, the haze represents a sink for C of 4 x 10(exp 8) per square centimeter per second, and a sink for N of 1 x 10(exp 8) per square centimeter per second. The C sink is small compared to condensation of hydrocarbons but the sink for N is comparable to the total production rate of HCN. Because estimates of the eddy diffusion profile on Titan have been based on the HCN profile, inclusion of this additional sink for N will affect estimates for all transport processes in Titan's atmosphere.

McKay, Christopher P.↗
NASA NTRS1997

The Properties and Effects of Titan's Organic Haze

Titan's organic haze is the the dominant absorber of solar energy in Titan's atmosphere, creating an anti-greenhouse effect. Its variation over time may have had important implications for Titan's surface temperature. The haze is potentially an important sink of photochemically produced carbon and nitrogen compounds. Laboratory simulations and microphysical models suggest that the haze is a sink for C of 4 x 10(exp 8)/ sq cm s, and a sink for N of 1 x 10(exp 8)sq cm s. The C sink is small compared to condensation of hydrocarbons but the sink for N is comparable to the total production rate of HCN. Because estimates of the eddy diffusion profile on Titan have been based on the HCN profile, inclusion of this additional sink for N will affect estimates for all transport processes in Titan's atmosphere.

McKay, Christopher P.↗
NASA NTRS1959

Analysis of Turbulent Flow and Heat Transfer in Noncircular Passages

Previous work on turbulent heat transfer and flow in tubes was generalized and applied to flow in non-circular passages of equilateral triangular and square cross section. Expressions for eddy diffusivity that had been verified for flow and heat transfer in tubes were assumed to apply in general along lines normal to a wall. Velocity distributions, wall shear-stress distributions, and friction factors, as well as wall heat-transfer distributions, wall temperature distributions, and average heat-transfer coefficients were calculated. In addition, results from a previous analysis for axial flow between rods were compared with new experimental data. For calculating wall temperature distributions, uniform heat generation in the passage wall and uniform heat transfer at the outer surface were assumed. The application of the results is restricted to moderately small peripheral wall temperature variations. Calculations were made for Reynolds numbers from 20,000 to 900,000 and Prandtl numbers from 0.73 to 300. Results show that velocities, shear stresses, and heat transfer in the region near the corner were lower than average values and were zero at the corner. Friction factors and average Nusselt numbers were lower than in a tube.

Taylor, Maynard F.↗
NASA NTRS2010

Meridional Distribution of CH3C2H and C4H2 in Saturn's Stratosphere from CIRS/Cassini Limb and Nadir Observations

Limb and nadir spectra acquired by Cassini/CIRS (Composite InfraRed Spectrometer) are analyzed in order to derive, for the first time, the meridional variations of diacetylene (C4H2) and methylacetylene (CH3C2H) mixing ratios in Saturn's stratosphere, from 5 hPa up to 0.05 hPa and 80 deg S to 45 deg N. We find that the C4H2 and CH3C2H meridional distributions mimic that of acetylene (C2H2), exhibiting small-scale variations that are not present in photochemical model predictions. The most striking feature of the meridional distribution of both molecules is an asymmetry between mid-southern and mid-northern latitudes. The mid-southern latitudes are found depleted in hydrocarbons relative to their northern counterparts. In contrast, photochemical models predict similar abundances at north and south mid-latitudes. We favor a dynamical explanation for this asymmetry, with upwelling in the south and downwelling in the north, the latter coinciding with the region undergoing ring shadowing. The depletion in hydrocarbons at mid-southern latitudes could also result from chemical reactions with oxygen-bearing molecules. Poleward of 60 deg S, at 0.1 and 0.05 hPa, we find that the CH3C2H and C4H2 abundances increase dramatically. This behavior is in sharp contradiction with photochemical model predictions, which exhibit a strong decrease towards the south pole. Several processes could explain our observations, such as subsidence, a large vertical eddy diffusion coefficient at high altitudes, auroral chemistry that enhances CH3C2H and C4H2 production, or shielding from photolysis by aerosols or molecules produced from auroral chemistry. However, problems remain with all these hypotheses, including the lack of similar behavior at lower altitudes. Our derived mean mixing ratios at 0.5 hPa of (2.4 +/- 0.3) 10(exp -10) for C4H2 and of (1.1 +/- 0.3) 10(exp -9) for CH3C2H are compatible with the analysis of global-average ISO observations performed by Moses et al. Finally, we provide values for the ratios [CH3C2H]/[C2H2] and [C4H2]/[C2H2] that can constrain the coupled chemistry of these hydrocarbons.

Guerlet, Sandrine↗
NASA NTRS2014

The Atmospheres of Directly Imaged Planets: Where Has All the Methane Gone?

Methane and ammonia both first appear at lower effective temperatures in brown dwarf atmospheres than equilibrium chemistry models would suggest. This has traditionally been understood as a consequence of vertical mixing timescales being shorter than chemical equilibration timescales in brown dwarf photospheres. Indeed the eddy diffusivity, a variable accounting for the vigor of vertical mixing, has become a standard part of the description of brown dwarf atmosphere models, along with Teff and log g. While some models have suggested that methane is less favored at lower gravity, the almost complete absence of methane in the atmospheres of directly imaged planets, such as those orbiting HR 8799, even at effective temperatures where methane is readily apparent in brown dwarf spectra, has been puzzling. To better understand the paucity of methane in low gravity atmospheres we have revisited the problem of methane chemistry and mixing. We employed a 1-D atmospheric chemistry code augmented with an updated and complete network of the chemical reactions that link CO to CH4. We find the methane abundance at altitudes at or above the effective photosphere is a strong function of surface gravity because higher g shifts the p-T structure to higher pressures (i.e., a given optical depth is proportional to p/g, a relation mitigated somewhat by pressure broadening). Thus quenching in more massive brown dwarfs occurs at a lower temperature and higher pressure, both favoring CH4. We predict that in the lowest mass young giant planets, methane will appear very late, at effective temperatures as low as 600 K rather than the 1200 K seen among field brown dwarfs. This methane deficiency has important implications for the interpretation of spectra as well as methane-based planetary companion searches, such as the NICI survey. The GPI and SPHERE surveys will test these ideas and probe atmospheric chemistry and composition in an entire new range of parameter space. A caveat is that these calculations presume that the C to O ratio is comfortably less than one; the behavior is quite different if C and O are equally abundant, and of course CH4 is always present if C exceeds O.

young giant planets↗
NASA NTRS2018

Precipitating Electron Energy Flux and Characteristic Energies in Jupiter's Main Auroral Region as Measured by Juno/JEDI

The relationship between electron energy flux and the characteristic energy of electron distributions in the main auroral loss cone bridges the gap between predictions made by theory and measurements just recently available from Juno. For decades such relationships have been inferred from remote sensing observations of the Jovian aurora, primarily from the Hubble Space Telescope, and also more recently from Hisaki. However, to infer these quantities, remote sensing techniques had to assume properties of the Jovian atmospheric structure - leading to uncertainties in their profile. Juno's arrival and subsequent auroral passes have allowed us to obtain these relationships unambiguously for the first time, when the spacecraft passes through the auroral acceleration region. Using Juno /Jupiter Energetic particle Detector Instrument (JEDI), an energetic particle instrument, we present these relationships for the 30-kiloelectronvolts to 1-megaelectronvolts electron population. Observations presented here show that the electron energy flux in the loss cone is a nonlinear function of the characteristic or mean electron energy and supports both the predictions from Knight (1973, https://doi.org/10.1016/0032-0633(73)90093-7) and magnetohydrodynamic turbulence acceleration theories (e.g., Saur et al., 2003, https://doi.org/10.1029/2002GL015761). Finally, we compare the in situ analyses of Juno with remote Hisaki observations and use them to help constrain Jupiter's atmospheric profile. We find a possible solution that provides the best agreement between these data sets is an atmospheric profile that more efficiently transports the hydrocarbons to higher altitudes. If this is correct, it supports the previously published idea (e.g., Parkinson et al., 2006, https://doi.org/10.1029/2005JE002539) that precipitating electrons increase the hydrocarbon eddy diffusion coefficients in the auroral regions.

Auroral↗
NASA NTRS2019

Planetary Boundary Layer Height from AIRS, MERRA-2, and GPS Radio Occultation Data Products at NASA GES DISC, and Insights from Their Profiles Intercomparison

The NASA Goddard Earth Sciences Data and Information Services Center (GES DISC) provides archive and distribution services for several data products in the Planetary Boundary Layer (PBL) category. As a new variable added to the Atmospheric Infrared Sounder (AIRS) Version 6 support product, the PBL height from AIRS is derived based on the gradients of the retrieved relative humidity profile, and provides the atmospheric pressure at the top of the PBL over the ocean. The GES DISC also hosts the Modern-Era Retrospective analysis for Research and Applications-2 (MERRA-2) product generated by the Goddard Earth Observing System Model Version 5 (GEOS-5) data assimilation system. The PBL height from MERRA-2 is based on the total eddy diffusion coefficient of heat. The monthly PBL height has been made available in the Giovanni system (Giovanni is a Web-based application developed by the GES DISC providing a simple and intuitive way to visualize, analyze, and access vast amounts of Earth science remote sensing data). Recently, the GES DISC began serving the global PBL height climatology product derived from the COSMIC/FORMOSAT-3 and TerraSAR-X Global Positioning System (GPS) radio occultation (RO) measurements from June 2006 to December 2015. In a previous study, we presented the monthly PBL height data from AIRS and MERRA-2 and demonstrated the GES DISC services which support data intercomparison, such as access, plotting, sub-setting, regridding, and generation of a multi-year monthly mean. We also provided intercomparison results, and found that different PBL height definitions contributed to significant differences of PBL height values between AIRS and MERRA-2. In this work, we present the 10-year seasonal climatologies from the AIRS, MERRA-2 and GPS-RO. We also used the cross section and vertical profile services in Giovanni to display and analyze the vertical atmosphere structure over regions where the PBL height derived from the AIRS and MERRA-2 are quite different. The examination of the AIRS and MERRA-2 three-dimensional data found that the relative humidity profiles had larger differences than the temperature profiles. The MERRA-2 gives more details than the AIRS for the vertical distribution of the humidity.

Ding, Feng↗
NASA NTRS2022

Persistent Layers of Enhanced Gravity Wave Dissipation in the Upper Mesosphere Revealed From SABER Observations

Dissipation of gravity waves (GWs) and resultant momentum flux deposition and eddy diffusion significantly influence the atmospheric structure and circulation. Using the temperature profiles measured by the SABER instrument (2002–2021), we derive the global GW action and its scale height (HAm). Comparing to the background scale height (H), we identify a persistent layer of enhanced GW dissipation (HAm/H > 2) in the upper mesosphere. The enhanced dissipation is primarily centered at 80–85 km with a vertical range of ∼8–20 km. At middle and high latitudes, the enhanced dissipation extends down to ∼60 km and is located above the eastward (westward) wind peak in winter (summer). At low latitudes, enhanced dissipation occurs around the wind reversals. The possible mechanisms of enhanced dissipation include wave refraction, wind filtering, and reduced static stability. The persistent layer of enhanced dissipation identified here provide observational evidence for GW dissipation constrains in models.

gravity waves↗
NASA NTRS1991

Gravity wave-driven fluctuations in OH nightglow from an extended, dissipative emission region

The paper theoretically examines the modification of the characteristics of OH nightglow from an extended emission region by eddy momentum and eddy thermal diffusivities. The reactions that account for OH decay are presented with the additional modifications demonstrating the importance of the upper limit of vertical integration of the extended source. When the vertical wavelengths are smaller than the thickness of the main OH emission region, oscillations cause the effects, particularly at long wavelengths. Eddy diffusion increases the vertical wavelength, and therefore the interference effects related to a finite range of vertical integration can be reduced by accounting for eddy diffusion. It is determined that the effects of eddy momentum and thermal diffusivities are important elements of gravity wave dynamics and should be considered when calculating OH emission perturbations and related variables.

Schubert, G.↗
NASA NTRSDate not supplied

Development of a Unified SHOC-EDMF PBL Parameterization in the NASA GEOS Model

We present results from a novel extension of the boundary layer parameterization in the NASA Goddard Earth Observing System (GEOS) model. An Eddy Diffusivity-Mass Flux (EDMF) multi-plume updraft scheme was previously implemented in GEOS. Here we replace the K-profile eddy diffusivity scheme of Lock et. al. (2000) with the Simplified Higher Order Closure (SHOC). The scheme prognoses turbulent kinetic energy, and derives buoyancy flux, cloud fraction and condensate from a trivariate double-gaussian joint PDF. The original SHOC scheme is modified in two significant respects: (i) contributions from the EDMF updrafts are included in estimates of all higher order moments used to determine the PDF; and (ii) the second and third moments of total water are made prognostic variables, with source terms associated with EDMF updrafts. The predicted higher order moments as well as updraft and environmental properties are compared with large eddy simulations in several case studies.

SHOC-EDMF↗
NASA NTRSDate not supplied

A Unified SHOC-MF Boundary Layer Parameterization in the NASA Goddard Earth Observing System Model

We present results from a novel extension of the boundary layer parameterization in the NASA Goddard Earth Observing System (GEOS) model. An Eddy Diffusivity-Mass Flux (EDMF) multi-plume updraft scheme was previously implemented in GEOS. Here we replace the K-profile eddy diffusivity scheme of Lock et. al. (2000) with the Simplified Higher Order Closure (SHOC; Bogenschutz and Krueger, 2013). The scheme prognoses turbulent kinetic energy, and derives buoyancy flux, cloud fraction and condensate from a trivariate double-gaussian joint PDF. The original SHOC scheme is modified in two significant respects: (i) contributions from the EDMF updrafts are included in estimates of all higher order moments used to determine the PDF; and (ii) the second and third moments of total water are made prognostic variables, with source terms associated with EDMF updrafts. The predicted higher order moments as well as updraft and environmental properties are compared with large eddy simulations in several case studies. Results indicate that many higher order moments are underestimated when the mass flux contribution is neglected.

Nathan Arnold↗
NASA NTRSDate not supplied

A Unified SHOC-MF Boundary Layer Parameterization in the NASA Goddard Earth Observing System Model

We present results from a novel extension of the boundary layer parameterization in the NASA Goddard Earth Observing System (GEOS) model. An Eddy Diffusivity-Mass Flux (EDMF) multi-plume updraft scheme was previously implemented in GEOS. Here we replace the K-profile eddy diffusivity scheme of Lock et. al. (2000) with the Simplified Higher Order Closure (SHOC; Bogenschutz and Krueger, 2013). The scheme prognoses turbulent kinetic energy, and derives buoyancy flux, cloud fraction and condensate from a trivariate double-gaussian joint PDF. The original SHOC scheme is modified in two significant respects: (i) contributions from the EDMF updrafts are included in estimates of all higher order moments used to determine the PDF; and (ii) the second and third moments of total water are made prognostic variables, with source terms associated with EDMF updrafts. The predicted higher order moments as well as updraft and environmental properties are compared with large eddy simulations in several case studies. Results indicate that many higher order moments are underestimated when the mass flux contribution is neglected.

Nathan Arnold↗