GTE PEM-TROPICS B EXPEDITION PLAN
The following document provides a description of the scientific objectives, measurements, and implementation plan for phase B of the NASA Pacific Exploratory Mission in the Tropics (PEM-Tropics B) scheduled for March-April 1999. PEM-Tropics A was conducted during August-October, 1996. The PEM-Tropics missions are part of a continuing series of field studies that NASA has conducted over the past decade through its Global Tropospheric Experiment (GTE), a major component of the Tropospheric Chemistry Program within NASA's Earth Science Enterprise Office. Guidance for the GTE field studies has come from ad hoc planning meetings, convened by the Manager of the Tropospheric Chemistry Program. Emerging from the first of these planning meeting in July 1984 was a recommended long-range plan for a series of field studies to be conducted through the NASA Tropospheric Chemistry Program, and, where possible, coordinated with other national and international studies.
The recommended field measurements included studies of tropical forest, Arctic tundra, global distributions, long-range transport, as well as instrument intercomparisons. Since that initial meeting, four other planning meetings have been convened to review and update this long-range plan. The recommendations of these meetings have resulted in field studies of the Amazon Rain Forest and the northern latitude tundra (e.g. Atmospheric Boundary Layer Experiments, ABLE-2 and ABLE-3), evaluation of instrumentation for measurements of odd nitrogen and sulfur species (e.g. Chemical Instrument Test and Evaluation, CITE -2 and -3), measurements over the tropical Atlantic (e.g. Transport and Atmospheric Chemistry near the Equator- Atlantic, TRACE-A) and the current series of studies over the Pacific (e.g. Pacific Exploratory Missions, PEM-West A&B, PEM-Tropics A, and the current PEM-Tropics B). The PEM experiments, along with TRACE-A, are viewed as providing global distributions of key atmospheric species and studying their long-range transport.
The NASA Pacific Exploratory Mission in the central and eastern regions of the tropical Pacific Ocean basin (PEM-Tropics B) scheduled for the March/April 1999 time period will comprise the second of two planned Pacific Exploratory Missions in the central and eastern regions of the tropical Pacific Ocean basin. PEM-Tropics B will be conducted as part of NASA's Global Tropospheric Experiment (GTE). The GTE is an ongoing element of the Tropospheric Chemistry Program, a Research and Analysis (R&A) program within the Science Division of NASA's Office for Earth Science Enterprise.
The long-range goal of the GTE is to contribute substantially to scientific understanding of human impacts on the chemistry of the global troposphere. Changes in chemical composition of the troposphere on a global scale have been well documented during the last two decades and have given rise to considerable concern that these chemical changes in the troposphere, which are expected to increase as population increases and economic activity expands, will lead to changes in the earth's climate. The connection between atmospheric chemical composition change and climate change is a major focus of NASA's Earth Science Enterprise Office.
NASA has important and unique capabilities with which to study possible changes in the chemistry of the troposphere. The GTE has provided a scientific management structure for bringing these capabilities to bear in the most effective manner. The major thrust of the GTE has been to utilize NASA's DC-8 and P-3B aircraft to carry multi-instrument payloads into regions of the global troposphere where natural processes and/or human impacts are believed to be particularly significant in effecting chemical composition changes and/or where the troposphere is still relatively unimpacted. Previous missions conducted by the GTE have provided valuable data in such change-sensitive environments as the Amazon rain forest in Brazil, the tropical South Atlantic Ocean, the Alaskan tundra, the northern Canadian wetlands, and the western Pacific Ocean just off the Asian continent.
In August-October, 1996, the GTE PEM-Tropics A mission utilized both the NASA DC-8 and P-3B aircraft in a coordinated project to study the chemistry of the troposphere over the central and eastern Pacific Ocean with a focus on the tropics. This relatively unexplored region of the troposphere was expected to be and, in many places, was found to be a very clean air region of the world, possibly the cleanest on earth. It proved to be an outstanding "laboratory" for studying the role of nitrogen oxides in tropospheric ozone formation and loss and of sulfur compounds in aerosol formation, problems that have important climate implications. It yielded important new information on chemical changes that are affecting the oxidizing power of the global troposphere and, therefore, the rate at which the global atmosphere can cleanse itself of pollutants emitted into it by human activities. Data from the PEM-Tropics A mission have been released to the public, and in October 1997, the PEM-Tropics A Science Team submitted papers for publication of some key results in a special section of JGR-Atmospheres. Publication of the papers is expected in early 1999.
The tropical South Pacific region, while still quite clean, was found, however, to be experiencing significant burdens of pollutants at elevated altitudes south of the South Pacific Convergence Zone (SPCZ). These pollutants appear, from preliminary analysis, to have originated from biomass burning on landmasses to the west of the impacted areas. A major objective of PEM-Tropics B (see scientific objectives) is to study the tropical Pacific atmosphere during a season when the influence from biomass burning should be significantly less than during the PEM-Tropics A experiment. PEM-Tropics B is presently scheduled to begin instrument integration aboard the DC-8 and P-3B aircraft in mid-January, 1999, with overseas deployment from March through April 1999. The DC-8 and P3-B are based at the NASA Dryden Flight Research Center and the NASA Wallops Flight Facility, respectively.
For global tropospheric chemistry, the Pacific Basin troposphere is a very large chemical reaction vessel. From Peru to Borneo it is 17,700 km in the east-west direction, and from the southern ice shelf to Alaska it is 13,300 km. It covers 35% of the total surface area of the earth and 50% of the ocean surface. Much of the Pacific Basin is remote from continental influence, and hence is expected to be a particularly sensitive indicator of the global-scale impact of human activity on the chemistry of the troposphere.
One of the most important issues in global tropospheric chemistry is the sensitivity of the oxidizing power of the troposphere to human influence. Oxidation by the hydroxyl radical (OH) in the troposphere is the main sink for a number of gases important for climate change and stratospheric O3 depletion, including hydrochlorofluorocarbons, methane, methyl bromide, and methyl chloroform. A decrease in tropospheric OH concentrations would increase the tropospheric concentrations of these gases and increase their fluxes into the stratosphere. It would also reduce the global atmosphere’s ability to cleanse itself of reactive pollutants and maintain its current chemistry.
Concentrations of tropospheric OH are determined by a number of photochemical reactions involving O3, nitrogen oxides (NOx), carbon monoxide (CO), methane (CH4), and non-methane hydrocarbons (NMHCs). Ozone, the primary precursor of OH, is supplied to the troposphere by transport from the stratosphere, and is also produced within the troposphere by photochemical oxidation of methane and NMHCs in the presence of NOx. Anthropogenic emissions of NOx, CH4, NMHCs, and CO could have a large effect on the oxidizing power of the troposphere, directly by affecting OH and indirectly by providing a source of O3. Tropical regions play an especially critical role in determining the global oxidizing power of the atmosphere because of the high UV radiation and humidity, which promote the formation of OH from reactions that follow the photolysis of O3.
Another major issue in global tropospheric chemistry is the role of atmospheric sulfur chemistry in aerosol formation. Sulfate aerosols affect the earth's radiative balance both through direct back scattering of solar radiation and indirectly as cloud condensation nuclei (CCN). CCN, themselves products of aerosol growth processes, are believed to have their origin in nucleation processes involving gas phase H2SO4, the latter species being produced from the oxidation of SO2 by OH. Sulfate and SO2 over the Pacific may originate from a number of sources including, long-range transport of anthropogenic pollution, marine biogenic releases of dimethlysulfide (DMS), and volcanic emissions.
The GTE PEM-Tropics A mission, a two-aircraft mission conducted in 1996, provided the first detailed survey of tropospheric chemistry over the South Pacific Basin. Previous data from this region were sparse, reflecting the difficulty of access. The GAMETAG aircraft missions in 1977 and 1978 provided some early data over the western part of the Basin; they were, however, restricted by the low ceiling and limited endurance of the aircraft used and also by the state-of-the-science of the instruments available at the time. The more recent STRATOZ III and PEM-West A and B missions provided detailed data along the South American and Asian rims of the South Pacific Basin, respectively. Ozonesonde and CO measurements have been made at American Samoa for a number of years. Additional observations have been made from other island sites (e.g. SEAREX) and from ships. Even so, there were virtually no data for the southeast quadrant of the Basin, extending from the international dateline to the South American coast prior to PEM-Tropics A.
PEM-Tropics A. was conducted during August-October 1996. The two aircraft platforms used were the NASA DC-8 and P-3B. They flew over an area extending zonally across the entire Pacific Basin and meridionally from Hawaii to south of New Zealand. Significant coverage of the Walker circulation cell over the Pacific Basin was achieved, including the up welling region over the western equatorial Pacific, the subsiding region offshore of South America, and the connecting atmosphere in between. Much emphasis was placed on vertical profiling to obtain as complete a three-dimensional picture of trace gas concentrations as possible. The PEM-Tropics A mission was very successful. It provided an excellent atmospheric chemical survey of the region that was enhanced by significant breakthroughs in instrumental capability to measure OH, NO at extremely low levels, and many sulfur compounds, some for the first time. PEM-Tropics A also revealed significant influence of biomass burning emissions over the South Pacific. Air trajectory analyses point strongly toward these emissions as having been transported from South America, Africa, and Oceania.
The initial findings from PEM-Tropics A are scheduled to be published in the Journal of Geophysical Research in early 1999. Also, PEM-Tropics A data can be accessed directly from the GTE ftp site (https://www-air.larc.nasa.gov/pub/PEMTROPICSA) or through the GTE Web Site (http://www-gte.larc.nasa.gov) using the "Data Archive" hot link. PEM-Tropics A data can also be accessed from the Langley DAAC Web Site (http://eosweb.larc.nasa.gov) through the "Access Data" then "Data Accessible from the Web" hot links. The GTE ftp and GTE web sites provide data files for individual investigations, on a flight-by-flight basis, while the DAAC site provides a single file of all the data from all investigators, on a flight-by-flight basis. Data from ozonesonde launches at Easter Island; Tahiti; American Samoa; and Lauder, New Zealand; beginning approximately one year prior to the PEM-Tropics A mission, are also available on the GTE ftp and web sites.
PEM-Tropics B will continue investigation of tropospheric chemistry over the north and south tropical Pacific Oceans. It will be an airborne study that will complement the PEM-Tropics A mission. It will be conducted during March-April, 1999, thereby providing an opportunity to investigate different chemical and transport properties of the tropical troposphere. PEM-Tropics B will take place in the southern-tropical wet season, when the influence from biomass burning observed in PEM-Tropics A should be minimal. The study region will range from 1650 E to 800 W longitudes with major deployment sites at Hawaii, Kiritimati (Christmas Island), Tahiti, and Fiji. The NASA DC-8 and P-3B aircraft will be the primary measurement platforms.
As in PEM-Tropics A, the goals of PEM-Tropics B are to improve our understanding of the oxidizing power of the atmosphere and the processes controlling sulfur aerosol formation. Like PEM-Tropics A, it will also continue the effort to establish baseline values for chemical species that are directly coupled to the oxidizing power and aerosol loading of the troposphere. PEM-Tropics B will encompass observations over a wide range of geographical locations within the tropical Pacific (Figure 2.4 and/or http://www-gte.larc.nasa.gov/pem/pemtb_flt.htm) and will sample a wide range of meteorological conditions. These observations will form the basis for defining current baseline values for chemical composition in the tropical Pacific and establish the range of variability in this composition. Supported by transport-chemistry models, they also will be used to improve our understanding of the importance of different source types, and hence, their roles in controlling the oxidizing power and aerosol loading of the tropical troposphere.
Reflecting our current state-of-knowledge of the tropical Pacific, two general objectives are defined for PEM-Tropics B:
A. TO PROVIDE BASELINE DATA FOR CHEMICAL SPECIES THAT DETERMINE THE OXIDIZING POWER AND AEROSOL LOADING OF THE TROPICAL PACIFIC.
B. TO EVALUATE THE CHEMICAL AND DYNAMIC FACTORS CONTROLLING OZONE, OH, AND AEROSOL LEVELS OVER THIS REMOTE REGION.
Within the framework of these general objectives, five specific tasks are identified:
1. QUANTIFY THE FAST PHOTOCHEMICAL PROCESSES CONTROLLING OH CONCENTRATIONS.
Of critical importance to our assessment of changes in the oxidizing power of the troposphere, is an improved understanding of the fast photochemical processes producing and consuming OH, and the cycling of OH with other members of the HOx family. Currently, this understanding is still sketchy, in part because instrumentation for measuring HOx species has only recently come available. Some of the first OH measurements ever recorded at equatorial latitudes were those reported during PEM-Tropics A. A major priority in PEM-Tropics B will be to expand on this initial effort by including both upper and lower tropospheric measurements of OH as well as peroxy radicals. An OH instrument will be part of the payload for both the P-3B and DC-8 aircraft. In addition, observations of the ensemble of species that determine the production, loss, and cycling of HOx will be recorded. The PEM-Tropics B database will thus provide one of the best opportunities yet to quantitatively evaluate current photochemical models over a wide range of tropical conditions.
2. INVESTIGATE THE FACTORS RESPONSIBLE FOR LARGE-SCALE LOW CONCENTRATIONS OF TROPOSPHERIC OZONE OVER THE EQUATORIAL PACIFIC.
Tropospheric ozone column densities over the equatorial Pacific are the lowest in the world, with values as low as one third those found in other regions of the tropics. It has not yet been quantitatively determined what combination of dynamical and chemical factors is responsible for this large-scale depletion. The chemical measurements in PEM-Tropics B will allow direct computation of ozone production and loss rates over the equatorial Pacific and surrounding regions. These data, combined with detailed meteorological information and supported by simulations with chemistry-transport models, will provide a quantitative assessment of the factors contributing to the very low levels of ozone in this region
.
3.STUDY THE ROLE OF THE ITCZ AND SPCZ AS BARRIERS TO ATMOSPHERIC TRANSPORT BETWEEN THE NORTHERN AND SOUTHERN HEMISPHERES AND WITHIN THE SOUTH PACIFIC.
Observations from PEM-Tropics A have shown that the large scale meteorological flow forming the SPCZ (South Pacific Convergence Zone) constitutes an important barrier for transport between the tropical and subtropical latitudes of the western South Pacific. In particular, it was found that the SPCZ represented the northern boundary for the influence of biomass burning advected by westerly winds in the subtropical atmosphere. The unusually low ozone concentrations in the equatorial Pacific troposphere could quite possibly be related to the presence of the SPCZ. PEM-Tropics B will take place at a time of year (March-April) when the SPCZ is particularly strong and thus will include targeted investigations of the SPCZ as a barrier to atmospheric transport. Also, there will be at least six flights crossing the ITCZ (Inter Tropical Convergence Zone) south of Hawaii, making possible a further investigation of the inter hemispheric transport characteristics for this region.
4. INVESTIGATE THE SCAVENGING OF GASES/AEROSOLS AS-SOCIATED WITH DEEP CONVECTION AND GAS-TO-AEROSOL CONVERSION TAKING PLACE IN CONVECTIVE OUTFLOWS.
Deep convection is thought to provide the dominant mechanism for ventilation of the tropical upper troposphere. There is a need to better understand how this mechanism affects oxidants and aerosol concentrations as well as their respective precursors in the upper troposphere. Specific questions relate to the extent of convective influence, the mass fluxes of different species in convection, the scavenging of soluble gases and aerosols in the convective precipitation, and the chemistry and aerosol formation taking place in convective outflows. Several cases of deep convection were identified during some of the tropical flights of the earlier NASA field program PEM-West B; however, instrument limitations at that time prevented a detailed characterization of these events. During PEM-Tropics B coordinated flights of the P-3B and DC-8 aircraft, with augmented instrumentation, will specifically target this issue.
5.ELUCIDATE THE PROCESSES CONTROLLING PHOTOCHEMISTRY AND AEROSOL FORMATION BENEATH THE TRADE WIND INVERSION.
The lower troposphere over the tropical oceans, including the marine boundary layer and the transition layers below the trade-wind inversion, is an important region for chemical loss of ozone and for growth of sulfate aerosols. Aerosol nucleation can also take place as evidenced from low altitude studies conducted during PEM-Tropics A. At this time there is a need to better understand ozone photochemistry and sulfur oxidation in this region, and the role of ocean-atmosphere exchange processes. PEM-Tropics B will provide data on atmospheric composition, aerosol microphysics, and ocean-atmosphere fluxes for a range of marine productivity and meteorological conditions over the tropical Pacific.
Figure 2.4 PEM-Tropics B Operations Sites and Nominal Aircraft Flight Tracks
The PEM-Tropics B Science Team is comprised of the Principal Investigators, Co-mission Scientists and Meteorologists, who were selected in response to NASA Research Announcement NRA-97-MTPE-13. The GTE Program and Project Managers are ex officio members. The Science Team is co-chaired by the Mission Scientists or, in their absence, the Mission Meteorologists. The Mission Meteorologists will also be responsible for meteorological forecasting for the flight operations and for determining the origins and forecasting destinations of the air masses encountered during the flights. The Mission Scientists and Mission Meteorologists have data analyses and reporting responsibilities.
The Science Team is responsible for: science systems operation and performance; detailed flight mission design; identifying systems support requirements; data analyses and reporting; defining data handling, schedules, and protocol procedures (within NASA guidelines); and data submission to the GTE Data Archive.
The Science Team will determine its own methods and protocol for interactions among team members aboard each aircraft to achieve overall mission objectives. The Science Team and the GTE Project Office have developed detailed plans as outlined herein to conduct the PEM-Tropics B Expedition and meet the mission objectives presented in Section 2.0. The Science Team has also established a data management and data protocol plan (Section 6.0) that will promote the timely publication and dissemination (Section 8.0) of scientific results in accordance with data handling policies of the NASA Tropospheric Chemistry Program. These policies generally require that data from GTE experiments be made available to the public after a brief period of exclusive use by Science Teams for validation of the data. As indicated in the PEM Tropics NRA (97-MTPE-13A), a period of six months has been established for PEM-Tropics B for this purpose.
Members of GTE PEM-Tropics B Science Team are listed in Table 3.0.
The objectives of the PEM-Tropics B study are discussed in Section 2.0. To accomplish these objectives, the mission design includes a pre-deployment phase involving ozonesonde launches from five stations in the south Pacific, the field deployment phase utilizing the instrumented NASA DC-8 and P-3B aircraft from four operational sites in the Pacific, and the post deployment analyses and reporting phase. The pre-deployment phase was initiated in January 1997, and continues through October 1999; the field deployment phase is scheduled for March 1, 1999, through April 19, 1999; and the analyses and reporting phase is scheduled for completion with submittal of manuscripts by the investigators for publication TBD.
Tables 4.1-1 and 4.1-2 list the Principal Investigators and measurements aboard the DC-8 and P-3B aircraft respectively, along with a brief description of each investigation, including measurement teachnique and characteristics of the parameters measured. Layout of the instruments aboard each aircraft are shown at the same internet site and in figures 4.1-1 and 4.1-2, which follow. Aircraft characteristics are listed in Appendix C of this document.
Table 4.2 presents the parameters describing meteorological, navigational, and other aircraft parameters or "housekeeping measurements" to be measured aboard the two aircraft. These measurements will be obtained by the DC-8 Data Acquisition and Distribution System (DADS) and the P-3B Project Data System (PDS) and are to be provided to all investigators by the GTE Project Office.
The pre-deployment phase of PEM-Tropics B, consisting of a five station ozonesonde network, was initiated to provide a time history of tropospheric ozone in the PEM-Tropics B study region and to augment the data obtained aboard the aircraft during deployment. Ozonesonde balloons are released from American Samoa; Easter Island (Isla de Pascua); Fiji; Lauder, New Zealand; and Tahiti. Ozonesonde data from other sites (e.g. Christmas Island and Galapagos Island) may also become available. More details of the network are given in Section 5.2.
Table 4.1-1 DC-8 Investigators/Parameters .
Table 4.1-2 P-3B Investigators/Parameters.
Figure 4.1-1 DC-8 Instrument Layout.
Figure 4.1-2 P-3B Instrument Layout.
Origin notes:
1-- aircraft sensor
2-- Project sensor
3-- calculated
(DC-8 listed first and P-3B second)
Overall meteorological support will be provided by investigator teams from the Massachusetts Institute of Technology (MIT) and Florida State University (FSU). The Principal Investigators from these teams also serve as the Co-mission Meteorologists (see Table 3.0) providing forecasting for flight planning during the deployment phase of PEM-Tropics B. Members of these teams will conduct post-mission research and analyses focused on understanding the meteorological setting of PEM-Tropics B, and the meteorological impact on long-range transport of the chemical constituents measured during the expedition. Significant meteorological support will also be provided by Météo France Polynésie Françe (the French meteorological agency in Tahiti).
In addition to the analyses and modeling studies that will be conducted as part of the experimental investigations listed in Tables 4.1-1 and 4.1-2, more focused modeling investigations (Table 4.5) will also be conducted by those Science Team members whose role is listed as "Theoretical Studies" in Table 3.0.
The modeling activities are planned as a part of the "real-time" field activities as well as post-mission analyses. These analyses will incorporate various chemical models focusing on specific science issues as well as meteorological models for real time air mass trajectories. Table 4.5 lists the modeling products for each investigation, along with a brief description of the models.
4.6 Aircraft Measurement Methodology
The combined instrumentation payload aboard the DC-8 and P-3B (see Tables 4.1-1 and 4.1-2) was selected to meet the objectives and tasks (addressed in Section 2.4) of the PEM-Tropics B investigations. Differences in aircraft characteristics and payloads aboard each aircraft suggest differences in the methodology to be employed by the respective P-3B and DC-8 investigator teams in designing flight plans.
The DC-8 payload, for example, includes the DIAL and LASE system, which provides an important capability for characterization of the ozone, aerosol, and water vapor structure above and below the DC-8 flight altitude. Significant additions to the capabilities of the DC-8 payload, over that during PEM-Tropics A, are the measurements of OH and HOx and the LASE instrument for vertical profiles of H2O. Furthermore, the DC-8 aircraft has the capability for longer range and higher altitude coverage than the P-3B aircraft. Because of these important characteristics of the aircraft capability and payload, it is anticipated that the DC-8 flights will tend to emphasize characterization of ozone photochemical precursors concentrations on a very large scale, together with a more detailed air mass characterization based on measurements of both photochemical as well as non-photochemical species.
The P-3B’s characteristics and payload differ from the DC-8’s in several important ways. For example, it operates more efficiently at low altitudes. It will also have instrumentation for making hydroxyl radical measurements as well as systems for measuring several important sulfur compounds. In addition, the P-3B will be instrumented for turbulent air motion measurements (e.g., TAMMS). The hydroxyl and sulfur instrumentation should make possible a more in-depth examination of both the photochemical oxidizing characteristics of the tropical troposphere, and sources and critical transformation processes controlling atmospheric sulfur. The TAMMS system, on the other hand, will offer the capability for boundary layer flux measurements of selected species. Because of these payload and operational characteristics, it is anticipated that the P-3B flights will tend to emphasize process oriented studies associated with sulfur and ozone/hydroxyl photochemistry and include some boundary layer flux investigations.
The locations of the experiments aboard each aircraft are given in Figures 4.1-1 and 4.1-2 and and the GTE homepage (http://www-gte.larc.nasa.gov/). Aircraft characteristics are listed in Appendix C.
Table 4.5 Modeling and Meteorological Analyses
The nominal flight schedule for the DC-8 and P-3B aircraft are given in Table 5.0 and the nominal flight tracks are shown in Figure 2.4. Nominal flight profiles are shown in Appendix D. Layout of the instruments aboard each aircraft are shown in Figures 4.1-1 and 4.1-2 . Aircraft characteristics are listed in Appendix C.
Measurement systems installation and integration aboard the DC-8 will be performed at the NASA Dryden Flight Research Center where systems checkout flights will also be conducted. The same functions will be performed at the NASA Wallops Flight Center for the P-3B. Both aircraft will begin the deployment for PEM-Tropics B with a transit flight from the U.S. West Coast to Hawaii. During the initial phase, the DC-8 will be based at Hilo, Hawaii and the P-3B at Christmas Island (Kiritimati). The two aircraft will conduct three coordinated fights from these bases of operation, after which the DC-8 will transit to Fiji for focused studies around the SPCZ and north west of Fiji. The P-3B will remain at Christmas Island for three additional flights. The P-3B will transit to Western Samoa for exploratory measurements in the ozone trough west of Samoa. Both aircraft will then transit to Tahiti where additional coordinated studies will be conducted. After completion of four local flights from Tahiti, the P-3B will return to the Wallops Flight Facility via Hawaii. The DC-8 will conduct a total of five local flights from Tahiti before returning to Dryden via Easter Island, where it will carry out one local sortie.
5.2 Ozonesonde Network Measurements
Supporting measurements for the PEM-Tropics B mission include ozonesonde releases from Easter Island; Fiji; Tahiti; American Somoa; and Lauder, New Zealand (Figure 2.4). The sondes from Easter Island and Lauder are standard, on-going releases, which have been incorporated into the PEM-Tropics B study per an agreement with each respective station. Tahiti, Fiji, and American Samoa are sites contracted specifically to support the PEM-Tropics B series. NOAA, per an arrangement with NASA, has primary responsibility for the ozonesonde releases from these three sites. Personnel from Météo France, in Tahiti, and University of the South Pacific, in Fiji, are collaborating with both NOAA and NASA for ozonesonde operations. Releases from the five sites are nominally at a rate of 1 per week, beginning about January 1998 through October 1999 for PEM-Tropics B. The release rate at Tahiti, American Samoa, and Fiji will increase to 2 per week during the aircraft deployment phase (early March through mid-April, 1999). The release rate at the other 2 stations will remain at 1 per week. (Note: Ozonesonde operations prior to January 1998 are archived as part of the previous expedition, PEM-Tropics A). The Tahiti, Fiji, and American Samoa sites use EN-SCI Model 5A/T-max sondes, which reach an altitude of 30+ km. Measurements of ozone, temperature, and pressure are recorded to maximum altitude, and humidity is available to 12 km.. Data are available at 250-meter intervals and have an accuracy of about 10%. Data from all stations will be submitted to the GTE data archive, typically within 3 months of acquisition, and may be used by all PEM-Tropics B Science Team members per the PEM-Tropics B Data Protocol (see Sect. 6). Personnel responsible for the ozonesonde network are listed in Table 5.2.
Ozonesonde data may also be available from launches at Galapagos Island and Christmas Island (Kiritimati), which will be conducted by the Sounding of Ozone and Water in the Equatorial Region/Pacific Mission (SOWER/Pacific). This mission, started in March 1998, is a four-year program of coordinated ozone and water vapor soundings from these sites.
Table 5.2 lists the investigator and/or organization responsible for ozonesonde operations at each site as well as the nominal launch rate.
|
SITE |
INVESTIGATOR |
|---|---|
| 1Tahiti | Patrick Simon (Météo France) |
| 1Fiji | Kanayathu Koshy (USP) |
| 1American Samoa | Sam Oltmans (NOAA) |
| 2Lauder, NZ | Greg Bodecker (NIWAR) |
| 2Easter Island | Jorge Carreno (Météo Chile) |
| 3Christmas Island | SOWER/ Pacific |
| 3Galapagos Island | SOWER/ Pacific |
| 4Galapagos Island | SOWER/ Pacific |
|
LAUNCH RATE |
|
| 1,2One per week | Jan. 98 - Oct. 99 |
| 1Two per week | March 99 - April 99 |
| 34-5 Total | March 99 |
| 44-5 Total | 1999 |
5.3 Meteorological Support Measurements
Meteorological support for flight planning and post mission analyses will be provided by a team of meteorologist from the Massachusetts Institute of Technology (MIT), Florida State University (FSU), Météo France (MF), and the GTE Project Office. The Co-Mission Meteorologists from MIT and FSU (see Table 3.0) will, respectively, travel with and provide the specific met support required for P-3B and DC-8 aircraft. Personnel from MF will provide general forecasting support during deployment from Tahiti, as well as the ECMWF gridded data during the entire mission for real-time forecasting and post mission analyses. The GTE project meteorologist initially will travel with the P-3B, and then with the DC-8, supporting the mission meteorologists through the acquisition and the preliminary analysis of meteorological data products.
FSU will serve as the central hub for accessing the primary meteorological data products supporting flight planning during the aircraft deployment. Personal from both MIT and FSU will access the ECMWF gridded data, generating daily met products, which will be stored on the "home base" meteorological PC located at FSU. MIT will generate a set of forecast products to include maps of surface pressure, temperature and winds, the divergent wind component at 1000 hPa, geopotential height and temperature, specific humidity, potential vorticity, vertical motion and streamlines all at various pressure heights. Additionally, personnel from FSU will routinely pull satellite images from various WWW sites and store them on the meteorological PC.
FSU will calculate backward trajectories during the deployment phase using the ECMWF gridded data. Clusters of arrival points will be selected at locations along the anticipated flight tracks of the next several DC-8 and P-3B missions. Ten-day backward trajectories will be computed at various altitudes for each of these arrival points. A portable INMARSAT B satellite-based communication station coupled to the "remote-based" PC, will provide the communication link for a high data rate (56/64 KBPS) PC-to-PC transfer of the met products (e.g. calculated and satellite images) stored on the home based PC located at FSU.
After the deployment phase is completed, FSU will re-compute trajectories, using actual flight information to select the arrival points and levels. The Science Team will be asked to select additional locations/levels that are needed in their individual research analyses. These results will constitute the final trajectory archive located at the GTE Project Office at NASA Langley. Finally, a trajectory climatology will be prepared for the South Pacific Basin, emphasizing locations visited by the two aircraft. These results will also become part of the final archive. Table 5.3 lists the meteorological parameters, which will be used for in-field flight planning, and post-mission data analysis and which will become part of the mission data archive located at the GTE Project Office at NASA Langley.
Météo France will provide additional forecasting support during flight operations from Tahiti, and will provide copies of the daily surface maps generated during the deployment period. Flight planning support will also be available from meteorological stations at each deployment site.
+ Available post mission
Principal Investigator and GTE Project Office responsibilities for data handling, submittal and publication are defined in this Section. The specifics of the data protocol and schedules for data submittal and publications were developed and agreed to by the PEM-Tropics B Science Team.
The purpose of the PEM-Tropics B data protocol is to: (1) encourage an orderly and timely analysis, interpretation, and publication of data obtained during integrated field expeditions in pursuit of the goals of the NASA Tropospheric Chemistry program; (2) foster collaboration among investigator teams; and (3) establish a procedure to produce an integrated expedition archive that will serve as a central repository of data products to be released to the public domain. Participation in this data protocol by investigators from other collaborating investigating teams, if any, will be in accordance with agreements among the respective Science Teams.
Members of the PEM-Tropics B Science Team have agreed to the following general guidelines for the PEM-Tropics B Data protocol:
6.1.1 PEM-Tropics B Data Archive Format
All data submitted to the PEM-Tropics B Preliminary Data Archive and to the Final Data Archive will be in the GTE Format described in Appendix E.
All data and data products submitted for the Preliminary and the Final Data Archive will be submitted to the GTE Data Manager. Submittal to the Preliminary Archive Data will be on 3.5-inch disk. Submittal to the Final Archive will be via FTP.
6.1.3 PEM-Tropics B Data Archive
The PEM-Tropics Archive will consist of all measurements and data products that are acquired or generated as part of the PEM-Tropics B mission. Tables 4.1-1, 4.1-2 and 4.5-1 define the instrumentation and the modeling activities that have been funded as part of the mission. Measurements and products from these investigations will comprise the PEM-Tropics B Data Archive.
During the field deployment phase of PEM-Tropics B, results from measurements acquired during each DC-8 and P-3B-B flight will be submitted to the Data Manager in the standard archive format described in Appendix E, within 24 hours of completion of each flight. The Preliminary Data Archive will be comprised of these field submissions. Use of the Preliminary Archive will be governed by Data Protocol described in Section 6.1.
The Final PEM-Tropics Archive will be comprised of all measurements and data products emerging from the investigations listed in Tables 4.2-1, 4.2-2, and 4.5. Measurements and data products will be submitted to the GTE Project Office in the GTE Format described in Appendix E (published separately) per the data schedule given in Section 8.3.
6.1.4 Data handling and Certification for Release to Archives
Investigators are responsible for acquiring, processing, certifying, and reducing the data from their instruments and providing required data products on schedule. Only certified data shall be submitted to the GTE Data Manager for inclusion in the Final Data Archive.
The GTE Data Manager will verify that all data files submitted to the Preliminary Archive and the Final Archive adheres to the GTE Archive format. Data files submitted to the final archive will be further examined for logical consistency with regard to the time sequence of the data entries, dates, position, etc.. Submissions that do not adhere to the format specification and/or that have logical inconsistencies will be returned to the investigator for correction.
The Preliminary Archive will be available to the PEM-Tropics B Science Team at the conclusion of field deployment phase of the expedition. These data are preliminary and should only be used by members of the PEM-Tropics B Science Team per the restrictions noted in section 6.1.
The Final Archive will be released to the PEM-Tropics B Science Team via FTP per the data schedule in Section 8.3 to provide a period of 3 months for team validation of the measurements prior to release to the Langley DAAC and public.
The GTE Data Manager will produce an expedition archive of certified data for release to the Langley DAAC. The archive will include all final data as submitted by the investigators. Public release of the final archive will be accomplished by submittal of the archive to the Langley DAAC and the web GTE sites.
6.1.6 Data Retrieval from GTE and DAAC Archives
The Global Tropospheric Experiment (GTE) is among the projects supported by the NASA-Langley DAAC. The most current information about the GTE data sets archived can be found on the GTE Home Page, http://www-gte.larc.nasa.gov/ or on the Langley DAAC Home Page, http://eosweb.larc.nasa.gov/; follow "Projects Supported" link.
Please contact the Langley DAAC User Services staff with any questions about supported data sets, ordering instructions, or problems with ordering data:
| Langley DAAC Science, User and Data Support Office |
| NASA-Langley Research Center |
| Mail Stop 157D |
| Hampton, VA 23681-0001 |
| Phone: (757) 864-8656 |
| FAX: (757) 864-8807 |
| E-mail: larc@eos.nasa.gov |
Retrieval of data from the GTE archive is described in Appendix E.
6.1.7 Presentations and Publications
There will be no PEM-Tropics B Science Team member presentations or publications of PEM-Tropics B data except by approval of the PEM-Tropics B Science Team or as defined in Section 6.1. Use of another investigator’s data should be accompanied by an offer for co-authorship and significant participation in the development of any resulting publication and/or presentations.
The GTE Project Office will provide the data acquisition, display, storage, distribution, and archival of housekeeping and ancillary data during the PEM-Tropics B Expedition. Basic aircraft housekeeping data will be recorded and distributed to investigator stations on board the DC-8 aircraft via the Data Acquisition and Distribution System (DADS) as described in Appendix F and to investigator stations on board the P-3B via the Project Distribution System (PDS) as described in Appendix G. The capability for real-time display of selected housekeeping, ancillary, and PI data sets during flight is provided on both aircraft via the respective video distribution system. The PDS and DADS will also provide the capability to record and display selected PI measurements (per agreement of the respective PI). Provisions for input of PI measurements to the PDS or DADS will be in analog format with a range of ± 10 Volts. This data will be used for real-time display purposes. A PI whose data is recorded by the PDS may notify the Project Office within 24 hours after the flight to retain the recorded data for submittal to the Preliminary Archive. Otherwise, the recorded data will be removed and the PI must provide a data file to the Preliminary Archive.
The GTE Project office will also produce preliminary tabular and graphical summaries of the housekeeping and ancillary data for each flight during the expedition. Final data analysis and submittal of the housekeeping and ancillary data in the GTE Archive will be in accordance with the data protocol schedule adopted by the PEM-Tropics B Science Team.
Housekeeping, ancillary, and selected PI measurements will be recorded by DADS (Appendix F) and video cameras. DADS will record and distribute the aircraft navigational and meteorological data from the Navigational Management System (NMS), which combines GPS and ground-based location data. NMS is used by the DC-8 flight crew to incorporate GPS accuracy with flight profiles. In addition DADS creates and distributes a real time track map display with optional wind field data. NOAA polar orbiter AVHRR satellite images captured in flight on the Automatic Picture Transmission system (APT) are available on monitors at investigator stations. DADS updates recorded parameters at 1 Hz and distributes a serial data stream throughout the aircraft at transmission rates of 1200, 9600, and 19.2K baud. Tables F4 and F5 of Appendix F list the parameters and describe the DADS serial data stream format. All data parameters are in engineering units. Units are not included in the data stream. Additional information on the DADS is available in the DC-8 Airborne Laboratory Experimenters Handbook. Table F7 lists the ancillary measurements that are recorded by the DADS and information recorded by video cameras. DADS will provide tabulated data sets that can be selectively viewed on monitors located at PI instrument racks.
The GTE-PDS (Appendix G) is the primary data acquisition, display, and distribution system for housekeeping (Table G-1) and ancillary measurements (Table G-3) on board the P-3B-B aircraft. The PDS system records aircraft navigational and meteorological data, ancillary measurements, and selected PI measurements and distributes a serial data stream of these data at 1 Hz throughout the aircraft at a transmission rate of 19.2K baud. All data parameters are in engineering units. Units are not included in the data stream. The PDS provides tabulated data sets and plots that can be selectively viewed on monitors located at various locations in the aircraft.
6.2.3 Recording Analog Signals
The DADS and PDS systems offer the capability to record analog signals from selected investigator instruments. The recorded data are merged with the housekeeping and ancillary data and displayed during each flight to assist the Mission Scientists in assessing the overall mission status. The measurements listed in Tables 6.2.3 (below) and G-3 (Appendix G) are recorded by PDS for real-time display during flight. The respective PIs have agreed to have the following measurements recorded by the PDS.
Both aircraft will be using GPS signals to generate Universal Time (UT) to be used as the 1 Hz reference for data acquisition.
The DADS and the PDS provide a standard IRIG B signal which may be used by PIs when a timing accuracy better than 1 second is required. The IRIG B signal provides a timing pulse that is accurate to 1 m s.
6.3.2 Data Recording Frequency
The DADS and PDS will record selected PIs signals along with housekeeping and ancillary data at 1 Hz. The mission data will be available to PIs after flight completion in various formats as a field product. These formats include 1-minute average of key parameters, time series and altitude summary plots, and 10-second average of housekeeping and ancillary data (Section 6.5.1).
PI recording systems should operate at a frequency appropriate to the phenomena being measured and data submitted to the final data archive should be at this frequency.
The GTE Project Office is responsible for the acquisition, display, storage, distribution, and archival of housekeeping and ancillary data. DADS and PDS will provide data recorded from the aircraft systems, selected PIs signals, images from cloud videos and the Storm Scope. PIs are responsible for the acquisition, recording, and archiving of their measurements.
The data collected by DADS and PDS will be made available to PIs in visual tabular and graphical format via the video distribution system. Data are also transmitted to PIs via the serial distribution system in ASCII format (Section 6.4.2).
6.4.2 Serial Data System (SDS)
The SDS is supported on the DC-8 by DADS. Serial data parameters are transmitted via the SDS at 1200, 9600, and 19.2K baud rates. A parameter list and description of the serial data block formats for the various baud rates are listed in Appendix F (Tables F2 - F5). Data records are 392 characters in length and in ASCII format.
The SDS is supported on the P-3B by PDS. Serial data parameters are transmitted via the SDS at a 19.2K baud rate. The parameter list and block format is described in Appendix G (Tables G1 and G2). Data records are 392 characters in length and in ASCII format. The data stream is divided into 7 blocks of 56 characters each (Table G2). Each of the 7 blocks begins with a letter identifier (C through I) and ends with an ASCII carriage return and a line feed. Parameters within a block are separated by a space and each block is padded with blanks, when necessary, to occupy the full 56 locations. This structure is similar on both aircraft. Blocks H and I are available for augmenting the data field to include additional parameters by the Project Manager as required.
6.4.3 Video Distribution System (VDS)
The VDS on the P-3B consists of flat-panel LCD monitors. Monitors will be distributed throughout the P-3B to provide visual access to all PIs. There will be four (4) displays available which can be independently selected by the PIs on each monitor. These displays include: (1) the primary alpha-numeric housekeeping data, (2) selected graphical plots, (3) forward cloud camera view, and (4) a quad-view of the stormscope display, nadir and forward cloud camera, and selected graphical data plots.
The VDS on the DC-8 consists of various type monitors located at PI instrument racks. There are several flight displays available which can be selected independently by PIs. These displays include: (1) alpha-numeric data, (2) graphical data, (3) track plot, (4) Weather Satellite APT Receiver, and (5) optional displays (e.g. LIDAR images). Further details are given in Appendix F.
Data products for PEM-Tropics B mission will be comprised of all measurements and/or model-generated parameters from PI or GTE Project measurements. The P-3B PDS and DC-8 DADS will convert all voltage signals to engineering units, where feasible, and display subsets of data to the video display system (Section 6.4.3) on board the aircraft. Table F1 in Appendix F is an example of the tabular data which will displayed on the DC-8 VDS and Figure G2 in Appendix G is the video screen which will be displayed on the P-3B-B VDS.
Distribution of the data products will be in the form of a Preliminary Data Archive and the Final Data Archive. The Preliminary Data Archive will be assembled using the field data products available from PIs and Project measurements within 24 hours after each flight. The Final Data Archive will contain final data submission of all PI measurements, Project measurements, model-generated data products, and meteorological parameters acquired during the field deployment.
The PEM-Tropics B Science Team has committed to a free and open exchange of preliminary data in the field. Each investigator will provide to the GTE Data Manager preliminary data from each flight within 24 hours after flight completion. Preliminary data recorded by the DADS and the PDS will be made available to the Science Team within 24 hours following each flight. The field products provided by investigators and the Project Office are preliminary data. Use of this data shall be in accordance with Section 6.1.(e).
The DC-8 DADS field data products include aircraft position and parameter plots, diskettes containing the archived DADS serial ASCII data stream, and printed copies of the Mission Director’s log files.
The GTE Project Office will produce preliminary mission data summaries for each flight on both aircraft during the expedition and provide copies to each PI group. The mission summaries include the following:
The Project Office will also produce 10-second averages of the housekeeping and ancillary data recorded during each flight, formatted in GTE Data Archive Format, and recorded onto 3.5" floppy disks. These may be copied and used by investigator groups. The original video recordings will be available for viewing in the field. Copies of these video tapes will be distributed upon request post mission.
6.5.2 Data Products Distribution
The DC-8 DADS data (Table F4, Appendix F) will be converted to the GTE Archive Format under the direction of the GTE Data Manager. The resulting data product will be distributed in concert with final meteorological products to the Science Team 60 days following the mission. Data recorded by the GTE PDS on board the P-3B aircraft will also be distributed to the Science Team 60 days following the mission. Parameters to be included in these final data products are identified in the Data Products Tables.
The Project Office serves as a central repository and distribution center for all data products obtained during PEM-Tropics B mission. The mission archive consists of all measurements and/or model products developed as part of the PEM-Tropics B mission. Each investigator is responsible for submitting preliminary field results to the GTE Data Manager, or his designee, within 24 hours after each flight for distribution to the Science Team during the mission. Final validated results from the mission must be submitted to the GTE Data Manager within 60 days following completion of the field deployment phase. The GTE Data Manager is responsible for submitting the PEM-Tropics B data to the Langley Distributed Active Archive Center, which will be the repository for all of the mission data.
The Project Office, with the Co-Mission Meteorologists, will arrange for the acquisition, and subsequent distribution to the Science Team, of meteorological data supporting the mission objectives. These data include meteorological products for flight planning and post mission products to support analysis and publication of results.
Data platforms, measurement techniques, species measured, and modeling activities are described in Section 4.0. Measurements and products included in the archive are listed in Tables 4.1-1, 4.1-2, and 4.5-1. Meteorological data sources are discussed in Section 5.3 and meteorological products to be submitted to the archive are listed in Table 5.3-1. All data products should be submitted in the GTE Data Archive Format (Appendix E published separately). Schedules for submission of data to the archive and distribution of the archive are given in Table 8.3-1.
The final data submitted by the investigators will be scanned by the GTE Project Office to ensure that the data has been submitted in the proper format prior to release to the public domain. Public release of the expedition archive will be to the Langley DAAC (refer to Section 6.1.6).
6.6 Data Analysis/Publication Plan
Early and comprehensive publication of GTE PEM-Tropics B results is a primary objective of the Science Team. Each PI is responsible for producing publication products in support of this objective. All published data must be submitted to the mission archive.
Three data workshops are anticipated following the mission. Data Workshop 1 will provide the first opportunity for participants to discuss and review the complete set of field measurements. Data Workshop 2, following the submittal of model results, will focus on model/measurement results and initiation of outlines for journal papers. Data Workshop 3 will be scheduled at the first workshop and focus on review of draft manuscripts. The schedule for data workshops 1 and 2 are given in Section 8.3.
Oral presentations of selected results by investigators prior to manuscript submission to the selected journal may take place at a conference to be determined by the PEM-Tropics B Science Team. Copies of presentation abstracts shall also be sent to the GTE Project Manager at submittal. Presentation of results at other meetings before manuscript submission must be approved by the Science Team.
Initial publication of results from the PEM-Tropics B Expedition will be in a special issue of an appropriate journal to be determined by the Science Team per the Data Management Schedule (Section 8.3). Copies of papers should be sent to the GTE Project Manager for inclusion in the mission archive.
6.6.4 Collaborating Science Team Usage of Measurements
The protocol for exchange of PEM-Tropics B measurements and data products with other collaborating Science Teams will be governed by agreements between the respective Science Teams and signed by the GTE Project Office and the respective representative of the collaborating Science Team. Collaboration between all such Science Teams requires the approval of the GTE Program Manager.
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