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At least 703 records · Page 39
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NASA NTRS1998

Multiple GISS AGCM Hindcasts and MSU Versions of 1979-1998

Multiple realizations of the 1979-1998 time period have been simulated by the Goddard Institute for Space Studies Atmospheric General Circulation Model (GISS AGCM) to explore its responsiveness to accumulated forcings, particularly over sensitive agricultural regions. A microwave radiative transfer postprocessor has produced the AGCM's lower tropospheric, tropospheric and lower stratospheric brightness temperature (Tb) time series for correlations with the various Microwave Sounding Unit (MSU) time series available. MSU maps of monthly means and anomalies were also used to assess the AGCM's mean annual cycle and regional variability. Seven realizations by the AGCM were forced by observed sea surface temperatures (sst) through 1992 to gather rough standard deviations associated with internal model variability. Subsequent runs hindcast January 1979 through April 1998 with an accumulation of forcings: observed ssts, greenhouse gases, stratospheric volcanic aerosols. stratospheric and tropospheric ozone and tropospheric sulfate and black carbon aerosols. The goal of narrowing gaps between AGCM and MSU time series was complicated by MSU time series, by Tb simulation concerns and by unforced climatic variability in the AGCM and in the real world. Lower stratospheric Tb correlations between the AGCM and MSU for 1979-1998 reached as high as 0.91 +/-0.16 globally with sst, greenhouse gases, volcanic aerosol, stratospheric ozone forcings and tropospheric aerosols. Mid-tropospheric Tb correlations reached as high as 0.66 +/-.04 globally and 0.84 +/-.02 in the tropics. Oceanic lower tropospheric Tb correlations similarly reached 0.61 +/-.06 globally and 0.79 +/-.02 in the tropics. Of the sensitive agricultural areas considered, Nordeste in northeastern Brazil was simulated best with mid-tropospheric Tb correlations up to 0.75 +/- .03. The two other agricultural regions, in Africa and in the northern mid-latitudes, suffered from higher levels of non-sst variability. Zimbabwe had a maximum mid-tropospheric correlation of 0.54 +/- 0.11 while the U.S. Cornbelt had only 0.25 +/- .10. Precipitation and surface temperature performance are also examined over these regions. Correlations of MSU and AGCM time series mostly improved with addition of explicit atmospheric forcings in zonal bands but not in agricultural regional bins each encompassing only six AGCM gridcells.

Shah, Kathryn Pierce↗
NASA NTRS1999

Remote Sensing of smoke and its Direct Radiative Forcing in South America

Smoke aerosol, organic and black carbon particles suspended in the air, can absorb and reflect solar radiation to space, i.e., direct radiative forcing. Depending on the ratio of scattering to absorption, and the surface spectral properties, the net smoke effect can be warming or cooling of the climate system. Data from the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) flown on the ER-2 at altitude of 20km, and of the AERONET ground based sun/sky radiometers are used to assess the smoke aerosol optical thickness over the land and the direct radiative forcing at the top of the atmosphere and at ground level, respectively. The data are collected during the Smoke, Clouds, and Radiation - Brazil (SCAR-B) experiment. In contrast to model results of the smoke effect, we show using the AVIRIS data, that even though the surface albedo is high (0.17 - average on the solar spectrum) and the smoke single scattering albedo is low (0.88), smoke does increase the instantaneous reflectance of sunlight to space by 30-40 W/m2 for an increase in the smoke optical thickness of 0.5. The AERONET data are used to derive, simultaneously, the effect of smoke on the downward radiation. Models using spectrally averaged smoke optical properties and averaged surface reflectance, predicted very small smoke forcing. The reason is that smoke is mainly opaque in short wavelengths (e.g.<0.7 micron) while the surface is mainly bright in longer wavelengths (>0.7 micron). Modeling the effect of smoke on climate forcing cannot be done using the spectrally average properties. It requires the knowledge of the smoke and surface spectral properties.

Kaufman, Yoram J.↗
NASA NTRS1999

The CEOS International Directory Network: Progress and Plans, Spring, 1999

The Global Change Master Directory (GCMD) serves as the software development hub for the Committee on Earth observation Satellites' (CEOS) International Directory Network (IDN). The GCMD has upgraded the software for the IDN nodes as Version 7 of the GCMD: MD7-Oracle and MD7-Isite, as well as three other MD7 experimental interfaces. The contribution by DLR representatives (Germany) of the DLR Thesaurus will be demonstrated as an educational tool for use with MD7-Isite. The software will be installed at twelve nodes around the world: Brazil, Argentina, the Netherlands, Canada, France, Germany, Italy, Japan, Australia, New Zealand, Switzerland, and several sites in the United States. Representing NASA for the International Directory Network and the CEOS Data Access Subgroup, NASA's contribution to this international interoperability effort will be updated. Discussion will include interoperability with the CEOS Interoperability Protocol (CIP), features of the latest version of the software, including upgraded capabilities for distributed input by the IDN nodes, installation logistics, "mirroring", population objectives, and future plans.

Olsen, Lola M.↗
NASA NTRS1999

Remote Sensing of Tropical Tropospheric Ozone: Validation on the R/V R. H. Brown and the SHADOZ (Southern Hemisphere Additional Ozonesondes) Project

This talk will give background on tropical tropospheric ozone studies in the field and from space from the TOMS (Total Ozone Mapping Spectrometer) satellite instrument. Background will be given on why tropospheric ozone in the tropics is of interest to people studying global change and its role in measurements on the R/V R H Brown 1999 Aerosols cruise. The new modified-residual method (Hudson and Thompson, 1998; Thompson and Hudson, 1999) for determining column depth of tropospheric ozone from TOMS will be described. Examples of modified-residual TTO (tropical tropospheric ozone) maps will be shown. These include Earth-Probe TOMS maps of ozone from the 1997 Indonesian fires as well as 14 years of twice-monthly maps from which seasonal and trends behavior can be deduced. The need for validation data for TTO maps has led to establishment of the NASA/NOAA-sponsored SHADOZ network in which 9 tropical nations are participating (Ascension Is., Brazil, Kenya, Indonesia, Fiji, Tahiti, Galapagos, Am. Samoa, Reunion Is. [France]). Some of the R/V Brown ozonesonde data, collected from daily launches on board the ship, from mid-January through mid-february 1999, will be shown.

Thompson, Anne↗
NASA NTRS1998

Tropical Tropospheric Ozone From Nimbus 7 and Earth-Probe Toms: Validation, ENSO Signals and Trends

The well-known wave-one pattern seen in tropical total ozone has been used to develop a modified-residual (MR) method for retrieving time-averaged stratospheric ozone and tropospheric ozone column amount from TOMS (Total Ozone Mapping Spectrometer) over the 14 complete years of Nimbus 7 observations (1979-1992) and from Earth-Probe (1996-present) and ADEOS/TOMS (1996-1997). Nine- to sixteen-day averaged tropical tropospheric ozone (TTO) maps show a seasonality expected from dynamical and chemical influences. Validation of the TTO time-series is presently limited to Atlantic sounding stations, notably Ascension Island, Natal, Brazil, and Brazzaville, Congo. Stratospheric column ozone, which is also derived from the modified-residual method, compares well with sondes and with stratospheric ozone column derived from other satellites.

Thompson, Anne M.↗
NASA NTRS1999

TRMM Field Campaigns: Objectives and Status Report

The Tropical Rainfall Measuring Mission (TRMM) satellite has been sending valuable data since launch in November 1997. Some of the key goals of the joint NASA (US) and NASDA (Japan) mission are: (1) to estimate the four-dimensional diabatic heating in the tropical and subtropical atmosphere, (2) understand the role of latent heating in driving tropical and extratropical circulations, (3) obtain monthly area-averaged estimates of rainfall over the data-sparse oceans, and (4) estimate the relative contribution of convective and stratiform precipitation over different regions during different seasons. The overarching scientific objective is to understand and improve estimates of rainfall and latent heating profiles throughout the global tropics. This requires observations for fundamental understanding of cloud dynamics and microphysics, as well as for validation, testing assumptions and error estimates of cloud-resolving models, forward radiative transfer models, algorithms used to estimate rainfall statistics and vertical structure of precipitation from surface-based radar, and from satellites. Field experiments designed to contribute to this understanding have been conducted in Texas and the South China Sea in spring of 1998, Florida in summer of 1998, and interior Brazil in (boreal) winter 1999. In summer 1999, a major oceanic campaign will be based at Kwajalein Atoll. Some early results will be highlighted, noting some significant contrasts between oceanic and continental convective systems.

Zipser, Edward I.↗
NASA NTRS1999

The Guara Campaign: Rocket-Radar Investigations of the Earth's Upper Atmosphere at the Magnetic and Geographic Equators

The Guara Campaign consisted of a series of sounding rockets that were launched from August to October, 1994 at a new launch facility at Alcantara, Brazil, which is within one degree of the Earth's magnetic equator. The campaign was based on focused scientific experiments designed to investigate the electrodynamics and irregularities in the ionosphere and mesosphere at the Earth's magnetic equator and to study their relationship with neutral upper atmosphere motions. In all, 13 large sounding rockets and 20 small meteorological rockets were launched as part of four different experiment groups designed to investigate: (1) the daytime equatorial electrojet, (2) very high altitude Spread-F processes, (3) sunset electrodynamics, and (4) middle atmosphere-thermosphere coupling at the equator. The instrumentation on the sounding rockets varied with each investigation, but primarily included experiments to measure electric fields, currents, plasma densities,- neutral winds, neutral densities and temperatures, and ionospheric instabilities. All of the experiments utilized ground-based scientific instruments including a VHF backscatter radar interferometer, magnetometers, ionosondes, and scintillation receivers. An overview of each investigation is provided, along with a description of the launch site and the ground-based experiments. Scientific highlights of the campaign are provided.

Pfaff, Robert F., Jr.↗
NASA NTRS1999

The Importance of Meteorological Measurement for the Scientific Study of the Mesosphere

The rocket-borne falling sphere technique has been providing temperature and wind measurements to 90 km. For example, the High Resolution Doppler Imager (HRDI) experiment on the Upper Atmosphere Research Satellite (UARS) and during the GUARA Campaign. The measurement of temperature and wind using the falling sphere method is well known, but will be briefly reviewed. The vertical resolution of the data is examined at different geographical locations and seasons. Time/height sections characterizing the temperature and wind structure will be presented for low (Alcantara, Brazil), middle (Wallops Island and Barking Sands, Hawaii), and high latitudes (ARR and ESRANGE). We address radar quality required, data smoothing, and expected measurement accuracy. Special emphasis will be given to the data gathered during the GUARA campaign, especially small- and large-scale motions including transports of momentum and heat. In the GUARA campaign, the combined Use of small meteorological payloads to measure large scale temperature and wind variations coupled with measurements of small scale turbulence from the larger rockets provided clear cut evidence of gravity wave breaking in the 85 to 90 km region.

Schmidlin, F. J.↗
NASA NTRS1999

The Role of Boundary Layer Aerosol in the Vertical Development of Precipitation and Electrification: Another Look at the Contrast Between Lightning over Land and Over Ocean

Comparisons are made between the cloud condensation nuclei (CCN) concentration in the boundary layer and radar/electrical observations of the vertical development of precipitation and lightning in both the 'break period' and 'monsoon' regimes in tropical Brazil. The initial radar echoes and the maximum flash rates are found to be higher when the CCN concentration is higher, characteristic of the 'break period' conditions. One possible explanation for both observations is the survival of cloud droplets against coalescence and their attainment of the mixed phase region aloft.

Williams, E.↗
NASA NTRS1996

Dual-Frequency Interferometric SAR Observations of a Tropical Rain-Forest

Repeat-pass, interferometric, radar observations of tropical rain-forest collected by the Shuttle Imaging Radar C (SIR-C) in the state of Rondonia, Brazil, reveal signal coherence is destroyed at C-band (5.6-cm) in the forest, whereas L-band (24-cm) radar signals remain strongly coherent over the entire landscape. At L-band, the rms difference in inferred topographic height between the forest and adjacent clearings is 5 m, equivalent to the height noise. Atmospheric delays are large, however, forming kilometer-sized anomalies with a 1.2-cm rms one way. Radar interferometric studies of the humid tropics must therefore be conducted at long radar wavelengths, with kilometric base-lines or with two antennas operating simultaneously.

Rigot, E.↗
NASA NTRS1999

The Importance of Meteorological Measurements for the Scientific Study of the Mesosphere

The rocket-borne falling sphere technique has been providing temperature and wind measurements to 90 km. For example, the HRDI experiment on the Upper Atmosphere Research Satellite (UARS) and during the GUARA Campaign. The measurement of temperature and wind using the falling sphere method is well known, but will be briefly reviewed. The vertical resolution of the data is examined at different geographical locations and seasons. Time/height sections characterizing the temperature and wind structure will be presented for low (Alcantara, Brazil), middle (Wallops Island and Barking Sands, Hawaii), and high latitudes (ARR and ESRANGE). We address radar quality required, data smoothing, and expected measurement accuracy. Special emphasis will be given to the data gathered during the GUARA campaign, especially small- and large-scale motions including transports of momentum and heat. In the GUARA campaign, the combined use of small meteorological payloads to measure large scale temperature and wind variations coupled with measurements of small scale turbulence from the larger rockets provided clear cut evidence of gravity wave breaking in the 85 to 90 km region.

Schmidlin, F. J.↗
NASA NTRS1999

NASA's Earth Observations Program: Past, Present and Future

A presentation will be given at the Annual National Awards and President's Invited Lecture. The event is sponsored by the Associated Scientific and Technical Societies, an organization which serves the interests of 40,000 scientists and engineers all over South Africa. A general presentation will be given on the topic of NASA's Earth Observation Program and will be supplemented with visualizations using the NASA/NOAA Earth Science Electronic theater. Included will be space observations with an eye on southern Africa, including Etosha National Park, Namibia, Okavanga Delta, Botswana, Victoria Falls, Zimbabwe, and Cape Town, the Highveld around Johannesburg, Blyde River Canyon, and the Lowveld of Kruger National Park in South Africa; also included will be some AVHRR imagery of fire occurrence during the dry season, mostly the Miombo woodland of Zambia, Angola, Malawi, and northern Mozambique, supplemented with SeaWiFS imagery for VI, aerosols, clouds, AVHRR fire time series, Landsat TM (and possibly ETM+, if available), and other global data sets. Would also like to include some Terra animations from SVS, including perhaps the launch sequence. The presentation would conclude with some of the ER-2 MAS imagery from Brazil that highlights the capability that we plan to bring to Africa in August 2000.

King, Michael D.↗
NASA NTRS2000

A Regional-Scale Assessment of Satellite Derived Precipitable Water Vapor Across The Amazon Basin

Atmospheric water vapor is widely recognized as a key climate variable, linking an assortment of poorly understood and complex processes. It is a major element of the hydrological cycle and provides a mechanism for energy exchange among many of the Earth system components. Reducing uncertainty in our current knowledge of water vapor and its role in the climate system requires accurate measurement, improved modeling techniques, and long-term prediction. Satellites have the potential to satisfy these criteria, as well as provide high resolution measurements that are not available from conventional sources. The focus of this paper is to examine the temporal and mesoscale variations of satellite derived precipitable water vapor (PW) across the Amazon Basin. This region is pivotal in the functioning of the global climate system through its abundant release of latent heat associated with heavy precipitation events. In addition, anthropogenic deforestation and biomass burning activities in recent decades are altering the conditions of the atmosphere, especially in the planetary boundary layer. A physical split-window (PSW) algorithm estimates PW using images from the GOES satellites along with the NCEP/NCAR Reanalysis data that provides the first guess information. Retrievals are made at a three-hourly time step during daylight hours in the Amazon Basin and surrounding areas for the months of June and October in 1988 (dry year) and 1995 (wet year). Spatially continuous fields are generated 5 times daily at 12Z, 15Z, 18Z, 21Z, and 00Z. These fields are then averaged to create monthly and 3 hourly monthly grids. Overall, the PSW estimates PW reasonable well in the Amazon with MAE ranging from 3.0 - 9.0 mm and MAE/observed mean around 20% in comparison to radiosonde observations. The distribution of PW generally mimics that of precipitation. Maximum values (42 - 52 mm) are located in the Northwest whereas minimum values (18 - 27 mm) are found along Brazil's East coast. Aside from the East coast, PW has a stronger north-south gradient than that of rainfall. As for the temporal variation of PW, June (1988 and 1995) experiences a peak about 1400 local time, corresponding to a maximum in air temperature. In contrast, October (1988 and 1995) experiences a maximum early in the day, 1100 local time, with a gradual decrease toward nighttime.

DeLiberty, Tracy↗
NASA NTRS1998

Advances in Understanding Decadal Climate Variability

Recently, a joint Brazil-France-U.S. program, known as PIRATA (Pilot Research moored Array in the Tropical Atlantic), was proposed to begin the deployment of moored measurement platforms in the tropical Atlantic in order to enhance the existing observational data base and subsequent understanding of the processes by which the ocean and atmosphere couple in key regions of the tropical Atlantic Ocean. Empirical studies have suggested that there are strong relationships between tropical Atlantic upper ocean variability, SST, ocean-atmosphere coupling and regional climate variability. During the early 1980's a coordinated set of surface wind, subsurface thermal structure, and subsurface current observations were obtained as part of the U.S.-France SEQUAL- FOCAL process experiment designed to observe the seasonal response of the tropical Atlantic Ocean to surface forcing. Since that time, however, the observational data base for the tropical Atlantic Ocean has disintegrated to a few shiptracks measuring ocean temperatures and a small collection of tide gauge stations measuring sea level. A more comprehensive set of observations, modeling and empirical studies is now in order to make progress on understanding the regional climate variability. The proposed PIRATA program will use mooring platforms similar to the tropical Pacific Ocean TAO array to measure surface fluxes of momentum and heat and the corresponding changes in the upper ocean thermal structure. It is anticipated that the oceanic data from this monitoring array will also be used in a predictive mode for initialization studies of regional coupled climate models. Of particular interest are zonal and meridional modes of ocean-atmosphere variability within the tropical Atlantic basin that have significant impacts on the regional climate of the bordering continents.

Busalaacchi, Antonio J.↗
NASA NTRS1999

ER-2 Observations of Precipitation Systems During TRMM-LBA

The NASA ER-2 performed numerous flights over precipitation systems in Rondonia, Brazil. The ER-2 carried a payload including the ER-2 Doppler Radar (EDOP), the Advanced Microwave Precipitation Radiometer (AMPR), the Lightning Instrument Package, and other instruments. This presentation will overview the types of data sets collected during TRMM-LBA (Tropical Rainfall Measuring Mission Satellite-Large Scale Biosphere Atmosphere Experiment in Amazonia) with particular emphasis on EDOP measurements. Numerous cases of convection ranging from weak to very intense, were overflown by the ER-2. Two TRMM overpasses were coincident with ER-2 flights which allowed for intercomparisons between the Precipitation Radiometer (PR), EDOP, and the S-POL (S-band Polarimetric Radar) and TOGA (Tropical Oceans and Global Atmosphere) ground-based radars. Preliminary results from this comparison will be presented as well as initial selection of case studies and efforts involving vertical motions in convection.

Heymsfield, Gerald↗
NASA NTRS1999

SHADOZ (Southern Hemisphere ADditional OZonesondes): A New Ozonesonde Data Set for the Earth Science Community

In the past several years, new tropical tropospheric ozone data products have been developed from TOMS and other satellites. Global chemical-transport models have been developed for interpretation of satellite data and to predict future ozone levels in the troposphere and stratosphere. However, the lack of ozone profile measurements for validation and evaluation of these data sets and models is critical in regions like the tropics. In 1998 NASA/Goddard Space Flight Center, in partnership with NOAA/CMDL (Climate Monitoring and Diagnostics Lab) and other nations, began a 2-year project to collect weekly ozonesonde measurements at southern hemisphere tropical sites and make the data available to the scientific community at a single electronic location: http://code9lQ.gsfc.nasa.gov/Data services/Shadoz/shadoz hmpq2.htmi A summary of data from the SHADOZ sites will be presented: Ascension Island, Fiji, Tahiti, Galapagos, American Samoa, Natal (Brazil), Reunion Island, Watukosek (Java), Nairobi and Irene, South Africa. SHADOZ is designed to meet other needs: (1) Provide the first climatology of tropical ozone along the equatorial zone for the wave-one pattern in total ozone; (2) Supplement field project observations. (3) Guide algorithm development for future satellite instruments; (4) Train scientists and educators in southern hemisphere tropical locations. From time to time, intensive tropical campaigns are making data available to SHADOZ. Data from the first half of 1999 will include INDOEX (Indian Ocean Experiment), SOWER (Stratospheric Ozone and Water in the Equatorial Region) at Christmas Island (2N, 157W), and a cruise from Norfolk, Virginia to Cape Town and Mauritius on NOAA's RN 'Ronald H Brown.'

Witte, J. C.↗
NASA NTRS1999

Remote Sensing of Smoke and its Direct Radiative Forcing in South-America

Smoke aerosol, organic and black carbon particles suspended in the air, are capable to absorb and reflect solar radiation to space - direct radiative forcing. Depending on the ratio of scattering to absorption, and on the surface spectral properties, the net smoke effect can be warming or cooling of the climate system. Data from the AVIRIS spectrometer flown on the ER-2 at altitude of 20 km, and of the AERONET ground based sun/sky radiometers are used to assess the smoke aerosol optical thickness over the land and the direct radiative forcing at the top of the atmosphere and at ground level, respectively. The data are collected during the SCAR-B experiment in Brazil. In contrast to model results of the smoke effect, we show using the AVIRIS data, that even though the surface albedo is high (0.17 - average on the solar spectrum) and the smoke single scattering albedo is low (0.88), smoke does increase the instantaneous reflectance of sunlight to space by 30-40 W/m(exp 2) for an increase in the smoke optical thickness of 0.5. The AERONET data are used to derive, simultaneously, the effect of smoke on the downward radiation. Models using spectrally averaged smoke optical properties and averaged surface reflectance, predicted very small smoke forcing. The reason is that smoke is mainly opaque in short wavelengths (e.g.< 0.7 micron) while the surface is mainly bright in longer wavelengths (> 0.7 micron). Modeling the effect of smoke on climate forcing cannot be done using the spectrally average properties. It requires the knowledge of the smoke and surface spectral properties.

Kaufman, Yoram↗
NASA NTRS2000

STS-99 Crew Activities Report / Flight Day 09 Highlights

The primary objective of the STS-99 mission was to complete high resolution mapping of large sections of the Earth's surface using the Shuttle Radar Topography Mission (SRTM), a specially modified radar system. This radar system produced unrivaled 3-D images of the Earth's Surface. The mission was launched at 12:31 on February 11, 2000 onboard the space shuttle Endeavour, and led by Commander Kevin Kregel. The crew was Pilot Dominic L. Pudwill Gorie and Mission Specialists Janet L. Kavandi, Janice E. Voss, Mamoru Mohri from the National Space Development Agency (Japanese Space Agency), and Gerhard P. J. Thiele from DARA (German Space Agency). This tape shows the activities of the ninth day of the mission. The announcement of the decision to extend the SRTM for 9 hours is made to the crew. This means that almost all (i.e., 99.9 %) of the target area of the Earth will be imaged, at least once. Some shots of the 200 foot long mast where the outboard antennas are located are shown. Mamoru Mohri is shown changing a data tape, while he explains the rationale for recording rather than transmitting the data. Gerhard Thiele speaks to the German press. At the end of this tape are images generated from the SRTM. There are views of Oahu, Molokai, Lanai and west Maui, Hawaii; Dallas, Texas; Salalah, Oman; and Tasmania, Australia. Animations showing the topography around Hokkaido, Japan and Brazil are also shown.

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