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NASA NTRS2006

Variational Assimilation of Global Microwave Rainfall Retrievals: Physical and Dynamical Impact on GEOS Analyses and Forecasts

Global microwave rainfall retrievals from a 5-satellite constellation, including TMI from TRMM, SSWI from DMSP F13, F14 and F15, and AMSR-E from EOS-AQUA, are assimilated into the NASA Goddard Earth Observing System (GEOS) Data Assimilation System (DAS) using a 1-D variational continuous assimilation (VCA) algorithm. The physical and dynamical impact of rainfall assimilation on GEOS analyses and forecasts is examined at various temporal and spatial scales. This study demonstrates that the 1-D VCA algorithm, which was originally developed and evaluated for rainfall assimilations over tropical oceans, can effectively assimilate satellite microwave rainfall retrievals and improve GEOS analyses over both the Tropics and the extratropics where the atmospheric processes are dominated by different large-scale dynamics and moist physics, and also over the land, where rainfall estimates from passive microwave radiometers are believed to be less accurate. Results show that rainfall assimilation renders the GEOS analysis physically and dynamically more consistent with the observed precipitation at the monthly-mean and 6-hour time scales. Over regions where the model precipitation tends to misbehave in distinctly different rainy regimes, the 1-D VCA algorithm, by compensating for errors in the model s moist time-tendency in a 6-h analysis window, is able to bring the rainfall analysis closer to the observed. The radiation and cloud fields also tend to be in better agreement with independent satellite observations in the rainfall-assimilation m especially over regions where rainfall analyses indicate large improvements. Assimilation experiments with and without rainfall data for a midlatitude frontal system clearly indicates that the GEOS analysis is improved through changes in the thermodynamic and dynamic fields that respond to the rainfall assimilation. The synoptic structures of temperature, moisture, winds, divergence, and vertical motion, as well as vorticity are more realistically captured across the front. Short-term forecasts using initial conditions assimilated with rainfall data also show slight improvements. 1

Lin, Xin↗
NASA NTRS2006

Arcing in Leo and Geo Simulated Environments: Comparative Analysis

Comprehensive tests of two solar array samples in simulated Low Earth Orbit (LEO) and Geosynchronous Orbit (GEO) environments have demonstrated that the arc inception voltage was 2-3 times lower in the LEO plasma than in the GEO vacuum. Arc current pulse wave forms are also essentially different in these environments. Moreover, the wide variations of pulse forms do not allow introducing the definition of a "standard arc wave form" even in GEO conditions. Visual inspection of the samples after testing in a GEO environment revealed considerable damage on coverglass surfaces and interconnects. These harmful consequences can be explained by the discharge energy being one order of magnitude higher in vacuum than in background plasma. The tests also revealed a potential danger of powerful electrostatic discharges that could be initiated on the solar array surface of a satellite in GEO during the ignition of an arcjet thruster.

Vayner, Boris V.↗
NASA NTRS2007

Applied Astronomy: An Optical Survey for Space Debris at GEO

A viewgraph is presented to discuss space debris at Geosynchronous Earth Orbit (GEO). The topics include: 1) Syncom1 launched February 14, 1963 Failed on orbit insertion 1st piece of GEO debris!; 2) Example of recent GEO payload: XM-2 Rock satellite for direct broadcast radio; 3) MODEST Michigan Orbital DEbrisSurvey Telescope the telescope formerly known as the Curtis-Schmidt; 4) GEO Debris Survey; 5) Examples of Detections; 6) Brightness Variations Common; 7) Observed Angular Rates; 8) Two Populations at GEO; 9) High Area-to-Mass Ratio Material (A/M); 10) Examples of MLI; 11) Examples of MLI Release in LEO; 12) Liou & Weaver (2005) models; 13) ESA 1-m Telescope Survey; 14) Two Telescopes March 2007 Survey and Follow-up; 15) Final Eccentricity; and 16) How control Space Debris?

Seitzer, Patrick↗
NASA NTRS2007

Initial Verification of GEOS-4 Aerosols Using CALIPSO and MODIS: Scene Classification

A-train sensors such as MODIS and MISR provide column aerosol properties, and in the process a means of estimating aerosol type (e.g. smoke vs. dust). Correct classification of aerosol type is important because retrievals are often dependent upon selection of the right aerosol model. In addition, aerosol scene classification helps place the retrieved products in context for comparisons and analysis with aerosol transport models. The recent addition of CALIPSO to the A-train now provides a means of classifying aerosol distribution with altitude. CALIPSO level 1 products include profiles of attenuated backscatter at 532 and 1064 nm, and depolarization at 532 nm. Backscatter intensity, wavelength ratio, and depolarization provide information on the vertical profile of aerosol concentration, size, and shape. Thus similar estimates of aerosol type using MODIS or MISR are possible with CALIPSO, and the combination of data from all sensors provides a means of 3D aerosol scene classification. The NASA Goddard Earth Observing System general circulation model and data assimilation system (GEOS-4) provides global 3D aerosol mass for sulfate, sea salt, dust, and black and organic carbon. A GEOS-4 aerosol scene classification algorithm has been developed to provide estimates of aerosol mixtures along the flight track for NASA's Geoscience Laser Altimeter System (GLAS) satellite lidar. GLAS launched in 2003 and did not have the benefit of depolarization measurements or other sensors from the A-train. Aerosol typing from GLAS data alone was not possible, and the GEOS-4 aerosol classifier has been used to identify aerosol type and improve the retrieval of GLAS products. Here we compare 3D aerosol scene classification using CALIPSO and MODIS with the GEOS-4 aerosol classifier. Dust, smoke, and pollution examples will be discussed in the context of providing an initial verification of the 3D GEOS-4 aerosol products. Prior model verification has only been attempted with surface mass comparisons and column optical depth from AERONET and MODIS.

Welton, Ellsworth J.↗
NASA NTRS2008

Optical Studies of Orbital Debris at GEO Using Two Telescopes

Beginning in March, 2007, optical observations of debris at geosynchronous orbit (GEO) were commenced using two telescopes simultaneously at the Cerro Tololo Inter-American Observatory (CTIO) in Chile. The University of Michigan's 0.6/0.9-m Schmidt telescope MODEST (for Michigan Orbital DEbris Survey Telescope) was used in survey mode to find objects that potentially could be at GEO. Because GEO objects only appear in this telescope's field of view for an average of 5 minutes, a full six-parameter orbit can not be determined. Interrupting the survey for follow-up observations leads to incompleteness in the survey results. Instead, as objects are detected on MODEST, initial predictions assuming a circular orbit are done for where the object will be for the next hour, and the objects are reacquired as quickly as possible on the CTIO 0.9-m telescope. This second telescope then follows-up during the first night and, if possible, over several more nights to obtain the maximum time arc possible, and the best six parameter orbit. Our goal is to obtain an initial orbit for all detected objects fainter than R = 15th in order to estimate the orbital distribution of objects selected on the basis of two observational criteria: magnitude and angular rate. Objects fainter than 15th are largely uncataloged and have a completely different angular rate distribution than brighter objects. Combining the information obtained for both faint and bright objects yields a more complete picture of the debris environment rather than just concentrating on the faint debris. One objective is to estimate what fraction of objects selected on the basis of angular rate are not at GEO. A second objective is to obtain magnitudes and colors in standard astronomical filters (BVRI) for comparison with reflectance spectra of likely spacecraft materials. This paper reports on results from two 14 night runs with both telescopes: in March and November 2007: (1) A significant fraction of objects fainter than R = 15th have eccentric orbits (e > 0.1) (2) Virtually all objects selected on the basis of angular rate are in the GEO and GTO regimes. (3) Calibrated magnitudes and colors in BVRI were obtained for many objects fainter than R = 15th magnitude. This work is supported by NASA's Orbital Debris Program Office, Johnson Space Center, Houston, Texas, USA.

Seitzer, P.↗
NASA NTRS2009

Reflectance Spectra Comparison of Orbital Debris, Intact Spacecraft, and Intact Rocket Bodies in the GEO Regime

A key objective of NASA s Orbital Debris program office at Johnson Space Center (JSC) is to characterize the debris environment by way of assessing the physical properties (type, mass, density, and size) of objects in orbit. Knowledge of the geosynchronous orbit (GEO) debris environment in particular can be used to determine the hazard probability at specific GEO altitudes and aid predictions of the future environment. To calculate an optical size from an intensity measurement of an object in the GEO regime, a 0.175 albedo is assumed currently. However, identification of specific material type or types could improve albedo accuracy and yield a more accurate size estimate for the debris piece. Using spectroscopy, it is possible to determine the surface materials of space objects. The study described herein used the NASA Infrared Telescope Facility (IRTF) to record spectral data in the 0.6 to 2.5 micron regime on eight catalogued space objects. For comparison, all of the objects observed were in GEO or near-GEO. The eight objects consisted of two intact spacecraft, three rocket bodies, and three catalogued debris pieces. Two of the debris pieces stemmed from Titan 3C transtage breakup and the third is from COSMOS 2054. The reflectance spectra of the Titan 3C pieces share similar slopes (increasing with wavelength) and lack any strong absorption features. The COSMOS debris spectra is flat and has no absorption features. In contrast, the intact spacecraft show classic absorption features due to solar panels with a strong band gap feature near 1 micron. The two spacecraft are spin-stabilized objects and therefore have solar panels surrounding the outer surface. Two of the three rocket bodies are inertial upper stage (IUS) rocket bodies and have similar looking spectra. The slopes flatten out near 1.5 microns with absorption features in the near-infrared that are similar to that of white paint. The third rocket body has a similar flattening of slope but with fewer features of white paint - indicating that the surface paint on the SL-12 may be different than the IUS. This study shows that the surface materials of debris appear different spectrally than intact rocket bodies and spacecraft and therefore are not believed to be solar panel material or pristine white paint. Further investigation is necessary in order to eliminate materials as possible choices for the debris pieces.

Barker, Ed↗
NASA NTRS2012

Visible Light Spectroscopy of GEO Debris

Our goal is to understand the physical characteristics of debris at geosynchronous orbit (GEO). Our approach is to compare the observed reflectance as a function of wavelength with laboratory measurements of typical spacecraft surfaces to understand what the materials are likely to be. Because debris could be irregular in shape and tumbling at an unknown rate, rapid simultaneous measurements over a range of wavelengths are required. Acquiring spectra of optically faint objects with short exposure times to minimize these effects requires a large telescope. We describe optical spectroscopy obtained during 12-14 March 2012 with the IMACS imaging spectrograph on the 6.5-m 'Walter Baade' Magellan telescope at Las Campanas Observatory in Chile. When used in f/2 imaging mode for acquisition, this instrument has a field of view of 30 arc-minutes in diameter. After acquisition and centering of a GEO object, a 2.5 arc-second wide slit and a grism are moved into the beam for spectroscopy. We used a 200 l/mm grism blazed at 660 nm for wavelength coverage in the 500-900 nm region. Typical exposure times for spectra were 15-30 seconds. Spectra were obtained for five objects in the GEO regime listed as debris in the US Space Command public catalog, and one high area to mass ratio GEO object. In addition spectra were obtained of three cataloged IDCSP (Initial Defense Communications Satellite Program) satellites with known initial properties just below the GEO regime. All spectra were calibrated using white dwarf flux standards and solar analog stars. We will describe our experiences using Magellan, a telescope never used previously for orbital debris spectroscopy, and our initial results.

Seitzer, Patrick↗
NASA NTRS2012

The Impact of Horizontal and Temporal Resolution on Convection and Precipitation with High-Resolution GEOS-5

Using a high-resolution non-hydrostatic version of GEOS-5 with the cubed-sphere finite-volume dynamical core, the impact of spatial and temporal resolution on cloud properties will be evaluated. There are indications from examining convective cluster development in high resolution GEOS-5 forecasts that the temporal resolution within the model may playas significant a role as horizontal resolution. Comparing modeled convective cloud clusters versus satellite observations of brightness temperature, we have found that improved. temporal resolution in GEOS-S accounts for a significant portion of the improvements in the statistical distribution of convective cloud clusters. Using satellite simulators in GEOS-S we will compare the cloud optical properties of GEOS-S at various spatial and temporal resolutions with those observed from MODIS. The potential impact of these results on tropical cyclone formation and intensity will be examined as well.

Putman, William P.↗
NASA NTRS2012

Constraining Middle Atmospheric Moisture in GEOS-5 Using EOS-MLS Observations

Middle atmospheric water vapor plays an important role in climate and atmospheric chemistry. In the middle atmosphere, water vapor, after ozone and carbon dioxide, is an important radiatively active gas that impacts climate forcing and the energy balance. It is also the source of the hydroxyl radical (OH) whose abundances affect ozone and other constituents. The abundance of water vapor in the middle atmosphere is determined by upward transport of dehydrated air through the tropical tropopause layer, by the middle atmospheric circulation, production by the photolysis of methane (CH4), and other physical and chemical processes in the stratosphere and mesosphere. The Modern-Era Retrospective analysis for Research and Applications (MERRA) reanalysis with GEOS-5 did not assimilate any moisture observations in the middle atmosphere. The plan is to use such observations, available sporadically from research satellites, in future GEOS-5 reanalyses. An overview will be provided of the progress to date with assimilating the EOS-Aura Microwave Limb Sounder (MLS) moisture retrievals, alongside ozone and temperature, into GEOS-5. Initial results demonstrate that the MLS observations can significantly improve the middle atmospheric moisture field in GEOS-5, although this result depends on introducing a physically meaningful representation of background error covariances for middle atmospheric moisture into the system. High-resolution features in the new moisture field will be examined, and their relationships with ozone, in a two-year assimilation experiment with GEOS-5. Discussion will focus on how Aura MLS moisture observations benefit the analyses.

Jin, Jianjun↗
NASA NTRS2012

Impacts of Assimilating MLS Temperature on the Upper Stratosphere in GEOS-5

Standard configurations of the GEOS-5 data assimilation system use nadir infrared and microwave sounders that provide deep-layer constraints on the thermal structure in the stratosphere. In the upper stratosphere, this information is currently provided by the Advanced Microwave Sounding Units (AMSU-As) on NOAA s polar-orbiting satellites. The highest peaking AMSU-A channel (14) peaks near 2.5hPa. Evaluation of the upper stratosphere reveals substantial biases in the temperature, cased in part by biases in the underlying GCM, and difficulties in representing the stratopause structure under disturbed conditions. This work demonstrates, unsurprisingly, that the assimilation into GEOS-5 of temperature profiles derived from EOS-Aura MLS leads to a substantially better representation of the stratopause structure from a climatological perspective and for disturbed events. Future plans with GEOS-5 include a reanalysis that includes numerous "research" datasets alongside the operational NOAA datasets that were used in MERRA. As preparation for this reanalysis, the present study examines how assimilating the MLS observations impact the error statistics for the AMSU-A instruments. Discussion will address the issue of bias correction for the AMSU-A Channel 14 radiances, which is presently turned off in GEOS-5 because of the absence of accurate temperature observations that can anchor the GEOS-5 analyses. The issue of what can be done in periods when no limb-sounder data are available will also be addressed.

Pawson, S.↗
NASA NTRS2012

The Impact of Satellite Atmospheric Motion Vectors in the GMAO GEOS-5 Global Data Assimilation System

The impact of satellite-derived atmospheric motion vectors (AMVs) on numerical weather forecasts is examined using the GEOS-5 global atmospheric data assimilation system. Cycling data assimilation experiments, including twice-daily 5-day forecasts, are conducted for two 6-week periods during the 2010 Atlantic hurricane season and 2010-2011Northern Hemisphere winter season. Results from a control experiment that includes all AMVs and other data types assimilated operationally in GEOS-5 are compared with those from an experiment in which the GEOS-5 AMVs (only) are replaced by ones produced by the U. S. Navy?s NAVDAS-AR atmospheric data assimilation system. The Navy AMVs are assimilated in their entirety as well as in various subset combinations. The primary objective of these experiments is to determine whether aspects of the NAVDAS-AR data selection and quality control procedure, especially the use of carefully averaged ("super-ob?) wind vectors and large volume of AMVs, explain the typically larger beneficial impact of these data in the Navy system as compared with most other forecast systems. Adjoint-based observation impact calculations are assessed and compared with traditional metrics such as forecast geopotential height anomaly correlations and observation-minus-forecast departures. Results so far indicate that that the greater number of NRL AMVs is primarily responsible for their larger impact, although superobing also appears to be beneficial. Map views show that the impact obtained from assimilation of the NRL AMVs is more uniformly beneficial, perhaps due to the averaging of individual observations in creating the super-obs. While the NRL AMVs have a much larger impact in GEOS-5 than do the control AMVs, their impact is still smaller than in the Navy forecast system, suggesting that the mix of observations may play an important role in modulating the impact of any one data type. At the same time, reducing the number of satellite radiances assimilated in GEOS-5 does not significantly alter the impact of the AMVs

Gelaro, R. D.↗
NASA NTRS2012

Observations of GEO Debris with the Magellan 6.5-m Telescopes

Optical observations of geosynchronous orbit (GEO) debris are important to address two questions: 1. What is the distribution function of objects at GEO as a function of brightness? With some assumptions, this can be used to infer a size distribution. 2. Can we determine what the likely composition of individual GEO debris pieces is from studies of the spectral reflectance of these objects? In this paper we report on optical observations with the 6.5-m Magellan telescopes at Las Campanas Observatory in Chile that attempt to answer both questions. Imaging observations over a 0.5 degree diameter field-of-view have detected a significant population of optically faint debris candidates with R > 19th magnitude, corresponding to a size smaller than 20 cm assuming an albedo of 0.175. Many of these objects show brightness variations larger than a factor of 2, suggesting either irregular shapes or albedo variations or both. The object detection rate (per square degree per hour) shows an increase over the rate measured in the 0.6-m MODEST observations, implying an increase in the population at optically fainter levels. Assuming that the albedo distribution is the same for both samples, this corresponds to an increase in the population of smaller size debris. To study the second issue, calibrated reflectance spectroscopy has been obtained of a sample of GEO and near GEO objects with orbits in the public U.S. Space Surveillance Network catalog. With a 6.5-m telescope, the exposures times are short (30 seconds or less), and provide simultaneous wavelength coverage from 4500 to 8000 Angstroms. If the observed objects are tumbling, then simultaneous coverage and short exposure times are essential for a realistic assessment of the object fs spectral signature. We will compare the calibrated spectra with lab-based measurements of simple spacecraft surfaces composed of a single material.

Seitzer, Patrick↗
NASA NTRS2013

Development of Two-Moment Cloud Microphysics for Liquid and Ice Within the NASA Goddard Earth Observing System Model (GEOS-5)

This work presents the development of a two-moment cloud microphysics scheme within the version 5 of the NASA Goddard Earth Observing System (GEOS-5). The scheme includes the implementation of a comprehensive stratiform microphysics module, a new cloud coverage scheme that allows ice supersaturation and a new microphysics module embedded within the moist convection parameterization of GEOS-5. Comprehensive physically-based descriptions of ice nucleation, including homogeneous and heterogeneous freezing, and liquid droplet activation are implemented to describe the formation of cloud particles in stratiform clouds and convective cumulus. The effect of preexisting ice crystals on the formation of cirrus clouds is also accounted for. A new parameterization of the subgrid scale vertical velocity distribution accounting for turbulence and gravity wave motion is developed. The implementation of the new microphysics significantly improves the representation of liquid water and ice in GEOS-5. Evaluation of the model shows agreement of the simulated droplet and ice crystal effective and volumetric radius with satellite retrievals and in situ observations. The simulated global distribution of supersaturation is also in agreement with observations. It was found that when using the new microphysics the fraction of condensate that remains as liquid follows a sigmoidal increase with temperature which differs from the linear increase assumed in most models and is in better agreement with available observations. The performance of the new microphysics in reproducing the observed total cloud fraction, longwave and shortwave cloud forcing, and total precipitation is similar to the operational version of GEOS-5 and in agreement with satellite retrievals. However the new microphysics tends to underestimate the coverage of persistent low level stratocumulus. Sensitivity studies showed that the simulated cloud properties are robust to moderate variation in cloud microphysical parameters. However significant sensitivity in ice cloud properties was found to variation in the dispersion of the ice crystal size distribution and the critical size for ice autoconversion. The implementation of the new microphysics leads to a more realistic representation of cloud processes in GEOS-5 and allows the linkage of cloud properties to aerosol emissions.

Aerosol-Cloud Interactions↗
NASA NTRS2017

The Small Size Debris Population at GEO from Optical Observations

We have observed the geosynchronous orbit (GEO) debris population at sizes smaller than 10 cm using optical observations with the 6.5-m Magellan telescope 'Walter Baade' at the Las Campanas Observatory in Chile. The IMACS f/2 imaging camera with a 0.5-degree diameter field of view has been used in small area surveys of the GEO regime to study the population of optically faint GEO debris. The goal is to estimate the population of GEO debris that is fainter than can be studied with 1-meter class telescopes. A significant population of objects fainter than R = 19th magnitude has been found. These objects have observed with angular rates consistent with circular orbits and orbital inclinations up to 15 degrees at GEO. A sizeable number of these objects have significant brightness variations ("flashes") during the 5-second exposure, which suggest rapid changes in the albedo-projected size product.

Seitzer, Patrick↗
NASA NTRS2019

File Specification for GEOS-CF Products

The NASA Global Earth Observing System (GEOS) model has been expanded to provide global near-real-time forecasts of atmospheric composition at a horizontal resolution of 0.25 degrees (about 25 km). This GEOS Composition Forecast (GEOS-CF) system combines the GEOS weather analysis and forecasting system with the state-of-the-science GEOS-Chem chemistry module (Bey et al., 2001; Keller et al., 2014; Long et al., 2015) to provide detailed chemical analysis of a wide range of air pollutants including ozone, carbon monoxide, nitrogen oxides, and fine particulate matter (PM2.5).

Knowland, Katherine E.↗
NASA NTRS2019

Integrating Remote Sensing Observations with NASA's GEOS-5 Modeling Framework in Support of Retrospective Analyses and Seasonal Prediction of Biosphere-Atmosphere CO2 Flux

The absorption of nearly half of all anthropogenic carbon dioxide (CO2) emissions by terrestrial and marine ecosystems has played a critical role in mitigating climate change. However, a persistent lack of understanding of these uptake processes impedes attribution, and thereby introduces large uncertainties into projections of the trajectory of carbon and climate in coming decades. A better understanding and quantification of the seasonal and interannual variability of carbon flux between the atmosphere and ocean and terrestrial biospheres is critically needed to improve predictions from Earth system models. We propose to bring together a diverse suite of remote sensing observations, mechanistic models, and NASA's Goddard Earth Observing System, version 5 (GEOS-5) model to address two objective 1) quantify the processes controlling the temporal variability of biosphere-atmosphere CO2 flux on seasonal and interannual timescales from 1989 to 2018 and 2) evaluating the predictability of the components of carbon flux on seasonal timescales. Because GEOS-5 has been developed to incorporate a variety of Earth system observations and includes a complete and physically consistent depiction of the atmosphere, land, and ocean carbon cycles, it represents a unique and ideal synthesis framework for this effort. By expanding the realism of processes that could be included in GEOS-5 seasonal forecasts, this effort supports NASA's goals toward an integrated Earth system modeling and prediction framework.We propose to integrate a number of observations into the GEOS-5 modeling system to refine retrospective estimates of both terrestrial and marine carbon flux and to test hypotheses regarding the effects of climate drivers on terrestrial carbon flux. This will include assimilating several satellite ocean color products in the NASA Ocean Biogeochemistry Model (NOBM) to improve the representation of ocean biology. We will also utilize remote sensing datasets to increase the temporal resolution of global land-use change estimates and fire emissions to better constrain the temporal variability of the terrestrial carbon cycle. This information will be incorporated into two NASA terrestrial biosphere models Catchment-CN, a dynamic vegetation model that is integrated within GEOS-5 and the Ecosystem Demography (ED) model, a core modeling resource supporting the Global Ecosystem Dynamics Investigation (GEDI) mission to map biomass. Fluxes will be evaluated through 1) comparison to top-down flux estimates inferred from surface CO2 observations and 2) comparison against available aircraft and satellite observations.By combining predictions of net ecosystem exchange and air-sea CO2 flux from land and ocean models with statistical predictions of land use change, fire, and fossil fuel emissions, we propose to create the first dynamical CO2 forecast on seasonal timescales. Because of the experimental nature of this endeavor, an important project objective will be to evaluate the limits to the predictability of different carbon cycle processes over lead times of 1-12 months using different satellite and surface data streams.

Ott, Lesley↗
NASA NTRS2020

OMI Measurements of Bromine Monoxide and Implications for Missing Sources of Polar Bromine in GEOS-Chem

The OMI satellite instrument provides total column measurements of bromine monoxide (BrO) with daily global coverage. Reactive bromine compounds (Br and BrO) catalytically destroy ozone in both the stratosphere and troposphere. The current emission scheme of brominated source gases in the GEOS-Chem chemical transport model well represents the stratospheric burden of bromine. However, halogen research in GEOS-Chem has largely focused on the influence of halogens on the tropospheric oxidative capacity. In the troposphere, the distribution of brominated compounds is more variable and significant uncertainties remain in the chemical processes governing the sources and sinks of reactive bromine compounds. In this study, we use GEOS-Chem simulated stratospheric columns of BrO to separate the tropospheric signal of BrO from the OMI total column measurements. The resulting tropospheric BrO columns are used to identify seasonal and regional anomalies in tropospheric BrO not currently represented in GEOS-Chem. In particular, periods of elevated tropospheric BrO during polar spring are observable by OMI, and past studies have connected these so-called "bromine explosion" events to near complete removal of surface ozone. Due to significant uncertainties in the springtime polar source of reactive bromine, many global models, including GEOS-Chem, do not simulate these tropospheric ozone depletion events. Consequently, OMI-based tropospheric columns of BrO are useful tool for investigating the impact of bromine explosion events on tropospheric ozone depletion episodes as well as background air quality.

Wales, Pamela↗
NASA NTRS2020

Toward Coupled Data Assimilation in NASA’s GEOS: Developments in the Ocean Context

The Global Modeling & Assimilation Office (GMAO) at NASA GSFC produces analyses and predictions of the Earth system using various configurations of the Goddard Earth Observing System (GEOS) model and assimilation system. The current sub-seasonal-to-seasonal prediction system (GEOS-S2S) is based on a coupled atmosphere-ocean-land-ice configuration of GEOS which includes the Modular Ocean Model version 5 (MOM5) run at approximately 50-km resolution and a de-coupled OI-based ocean analysis that uses an initialization of MOM5 forced by the MERRA-2 reanalysis. GMAO will soon implement an updated GEOS-S2S system that will run at 25-km resolution and adopt aspects of the hybrid four-dimensional ensemble-variational (H4DEnVar) system already running in the production-version atmospheric analysis system, including a Local Ensemble Transform Kalman Filter (LETKF) to provide initial conditions for the oceanic state. This presentation will focus on developments to sustain the GMAO's systems on longer time horizons, where more radical transformations will be required to adapt to advanced computing environments, higher resolution and more diverse model components, and new observations for the Earth system. Results will describe progress toward a version of the GEOS coupled system that will be based around the Joint Effort for Data assimilation Integration (JEDI) framework being developed within Joint Center for Satellite Data Assimilation (JCSDA) and include an updated ocean model, MOM6. Discussion will focus specifically on the use of a Unified Forward Operator (UFO) for simulating observations and the Object Oriented Prediction System (OOPS) for providing the state estimate. These features are being developed as a multi-agency effort under the auspices of the JCSDA and are being adopted in the GMAO for all its applications of coupled data assimilation including S2S, numerical weather prediction, and reanalysis.

Mahajan, Rahul↗